U.S. patent number [Application Number ] was granted by the patent office on 0000-00-00 for united states patent: re34357 ( 1.
Full text is not available for this patent. Click on "Images"
button above to view full patent.
United States Patent |
RE34,357 |
|
**Please see images for:
( Certificate of Correction ) ** |
Issue Date: |
August 24,
1993 |
Current U.S.
Class: |
428/47;
428/219 |
Current CPC
Class: |
D06N
3/06 (20130101); D06N 7/006 (20130101); D06N
7/0047 (20130101); Y10T 428/163 (20150115) |
Current International
Class: |
D06N
7/00 (20060101); D06N 3/06 (20060101); D06N
3/00 (20060101); B32B 003/14 () |
Field of
Search: |
;428/47,219,246 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1525018 |
|
Sep 1978 |
|
GB |
|
2012618 |
|
Aug 1979 |
|
GB |
|
2018618 |
|
Oct 1979 |
|
GB |
|
2019253 |
|
Oct 1979 |
|
GB |
|
Other References
Kerr, A. D.; "A Model Study for Vertical Track Buckling"; High
Speed Ground Transportation Journal; vol. VII, No. 3-1973. .
Humpreys, E. A., et al.; "Properties Analysis of Laminates";
Engineering Materials Handbook; vol. 1; Composites; pp. 218-235,
351-368..
|
Primary Examiner: Lesmes; George F.
Parent Case Text
This application is a continuation-in-part of our copending
application Ser. No. 508,884 filed June 29, 1983, now abandoned,
which is a continuation-in-part of application Ser. No. 400,437
filed July 26, 1982, now abandoned, which is a continuation-in-part
of our copending application Ser. No. 335,190 filed Dec. 28, 1981,
now abandoned.
Claims
We claim:
1. A process for providing a resilient loose-lay floor structure,
said process comprising the steps of
selecting a target critical buckle strain for said floor structure,
said critical buckle strain being greater than the subfloor
dimensional change of a target subfloor,
selecting an approximate basis weight for said floor structure,
said basis weight being within the range of from about 2 to about
10 pounds per square yard,
plotting a contour curve of the selected critical buckle strain for
said selected basis weight by varying the bending stiffness values
from about 0 to about 9 inch-pounds and by varying the relaxed
compressive stiffness values from about 0 to about 10,000 pounds
per inch of width,
determining from said contour curve the range defined by the
minimum and maximum relaxed compressive stiffness values
corresponding to bending stiffness values of about 0.1 and about 9
inch-pounds, respectively,
selecting a matrix material and at least two layers of reinforcing
material such that the sum of the relaxed compressive stiffness
values for said materials falls within the determined range, said
matrix material and said reinforcing materials being selected such
that the sum of the relaxed compressive stiffness values for said
reinforcing materials is not less than the sum of the relaxed
compressive stiffness values for said matrix material,
determining from said contour curve the bending stiffness value
applicable to the sum of the relaxed compressive stiffness values
for said reinforcing materials and said matrix material, and
disposing said layers of reinforcing material in said matrix
material such that the measured bending stiffness of the resultant
floor structure corresponds to the determined bending stiffness, at
least one reinforcing layer being approximately above the neutral
bending plane of said resultant floor structure and at least one
reinforcing layer being approximately below said neutral bending
plane, whereby the critical buckle strain of said resultant floor
structure is approximately equivalent to the target critical buckle
strain and is greater than the strain expected to be caused by said
subfloor dimensional change.
2. The invention as set forth in claim 1 hereof wherein said
minimum relaxed compressive stiffness value determined from said
contour curve corresponds to a minimum bending stiffness value of 1
inch-pound, said floor structure being intended for use over a
subfloor having a subfloor dimensional change of not less than
0.0015.
3. The invention as set forth in claim 2 hereof wherein said
minimum bending stiffness value is 3 inch-pounds and said subfloor
dimensional change is not less than 0.0030.
4. The invention as set forth in claims 1, 2 or 3 hereof wherein
the bending stiffness value required for said floor structure is
determined by constructing a test floor structure comprising said
matrix material and said reinforcing materials, measuring the
relaxed compressive stiffness thereof, and determining from said
curve the bending stiffness which corresponds to said measured
relaxed compressive stiffness, said test structure having a basis
weight essentially equivalent to the selected basis weight.
5. The invention as set forth in claim 4 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5 to
1.
6. The invention as set forth in claim 5 hereof wherein said ratio
is at least 10 to 1.
7. A process for making a resilient loose-lay floor structure, said
process comprising the steps of
selecting a subfloor dimensional change value corresponding to a
target subfloor,
selecting a matrix material and at least one reinforcing material,
said matrix material and said reinforcing material being selected
such that the sum of the relaxed compressive stiffness values for
all reinforcing materials used in said structure is not less than
the relaxed compressive stiffness value for said matrix material,
and the basis weight of said floor structure is from about 2 to
about 10 pounds per square yard,
constructing a test structure by disposing at least two layers of
reinforcing material within said matrix material such that the
bending stiffness of said test structure is from about 0.1 to about
9 inch-pounds, at least one layer of reinforcing material being
approximately above the neutral bending plane of said test
structure and at least one layer of reinforcing material being
approximately below said neutral bending plane,
modifying the relaxed compressive stiffness value of at least one
of said reinforcing layers as necessary to provide a critical
buckle strain for said test structure which is greater than said
subfloor dimensional change value, and
constructing said loose-lay floor structure corresponding to said
test structure, whereby the critical buckle strain of said
loose-lay floor structure is greater than the strain expected to be
caused by said subfloor dimensional change.
8. The invention as set forth in claim 7 hereof wherein said
bending stiffness is from about 1 to about 9 inch-pounds, said
subfloor having a subfloor dimensional change of not less than
0.0015.
9. The invention as set forth in claim 8 hereof wherein said
bending stiffness is from about 3 to about 9 inch-pounds and said
subfloor dimensional change is not less than 0.0030.
10. The invention as set forth in claim 7 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5:1.
11. The invention as set forth in claim 10 hereof wherein said
ratio is at least 10:1.
12. The invention as set forth in claim 8 hereof wherein the ratio
of the sum of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5:1.
13. The invention as set forth in claim 12 hereof wherein said
ratio is at least 10:1.
14. The invention as set forth in claim 9 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5:1.
15. The invention as set forth in claim 14 hereof wherein said
ratio is at least 10:1.
16. The invention as set forth in claims 7, 8, 9, 10, 11, 12, 13,
14, or 15 hereof wherein said layers of reinforcing material have
the same composition.
17. The invention as set forth in claims 7, 8, 9, 10, 11, 12, 13,
14, or 15, hereof wherein said layers of reinforcing material have
different compositions.
18. The invention as set forth in claims 7, 8, 9, 10, 11, 12, 13,
14 or 15 hereof wherein each of said layers of reinforcing material
is disposed within said matrix material in a substantially planar
fashion.
19. The invention as set forth in claims 7, 8, 9, 10, 11, 12, 13,
14 or 15 hereof wherein a substantial portion of at least one of
said reinforcing layers does not lie in the plane thereof.
20. The invention as set forth in claims 7, 8, 9, 10, 11, 12, 13,
14 or 15 hereof wherein the relaxed compressive stiffness of at
least one of said reinforcing layers has been modified.
21. The invention as set forth in claim 20 hereof wherein said
modification has been accomplished in situ.
22. A process for providing a resilient loose-lay floor structure,
said process comprising the steps of
selecting a floor structure having a basis weight of from about 2
to about 10 pounds per square yard and having at least two layers
of reinforcing material disposed within a matrix material, at least
one layer of reinforcing material being approximately above the
neutral bending plane of said floor structure and at least one
layer of reinforcing material being approximately below aaid
neutral bending plane, said structure being unsuitable for use as a
loose-lay floor structure over subfloors having a target subfloor
dimensional change because it has a bending stiffness which is in
excess of about 9 inch-pounds, or a critical buckle strain which is
not greater than said subfloor dimensional change value, or both,
and
modifying at least one of said reinforcing layers by external means
such that the bending stiffness of the resultant flooring structure
is within the range of from about 0.1 to about 9 inch-pounds and
the critical buckle strain of said resultant flooring structure is
greater than said subfloor dimensional change.
23. The invention as set forth in claim 22 hereof wherein the
bending stiffness of said resultant flooring structure is within
the range of from about 1 to about 9 inch-pounds, said ascertained
subfloor dimensional change being not less than 0.0015.
24. The invention as set forth in claim 23 hereof wherein said
bending stiffness is from about 3 to about 9 inch-pounds and said
ascertained subfloor dimensional change is not less than
0.0030.
25. The invention as set forth in claims 22, .[.38 or 39.].
.Iadd.23 or 24 .Iaddend.hereof wherein said layers of reinforcing
material have the same composition.
26. The invention as set forth in claims 22, .[.38 or 39.].
.Iadd.23 or 24 .Iaddend.hereof wherein said layers of reinforcing
material have different compositions.
27. The invention as set forth in claims 22, .[.38, or 39.].
.Iadd.23 or 24 .Iaddend.hereof wherein each of said layers of
reinforcing material is disposed within said matrix material in a
substantially planar fashion.
28. The invention as set forth in claims 22, .[.38 or 39.].
.Iadd.23 or 24 .Iaddend.hereof wherein a substantial portion of at
least one of said reinforcing layers does not lie in the plane
thereof.
29. A process for preparing a flooring structure comprising a
single reinforcing layer, said process comprising the steps of
selecting a flooring structure comprising a single reinforcing
layer, the critical buckle strain of said structure being less than
the subfloor dimensional change of a target subfloor, and
modifying said flooring structure in situ such that the critical
buckle strain becomes greater than said subfloor dimensional
change, whereby said structure will be suitable to accommodate the
subfloor movement of a subfloor having said target subfloor
dimensional change.
30. The invention as set forth in claim 29 hereof comprising the
additional steps of
selecting a target critical buckle strain, said critical buckle
strain being greater than said subfloor dimensional change;
measuring the relaxed compressive stiffness, the bending stiffness
and the basis weight of said selected flooring structure;
plotting a contour curve of the target critical buckle strain for
said selected flooring structure by varying the bending stiffness
values from about 0 to about 9 inch-pounds and by varying the
relaxed compressive stiffness values from about 0 to about 10,000
pounds per inch of width;
determining from said contour curve the target relaxed compressive
stiffness which will be required for said modified flooring
structure; and
modifying said selected flooring structure in situ such that the
resulting modified flooring structure has a relaxed compressive
stiffness value which is the same as or less than the target
relaxed compressive stiffness.
31. The invention as set forth in claim 30 hereof wherein said
reinforcing layer is a glass reinforcing layer.
32. The invention as set forth in claims 29, .[.45 or 46.].
.Iadd.30 or 31 .Iaddend.hereof wherein said reinforcing layer has a
basis weight of from about 15 to about 160 grams per square
meter.
33. The invention as set forth in claim 32 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
34. The invention as set forth in claims 29, .[.45 or 46.].
.Iadd.30 or 31 .Iaddend.hereof wherein said modification is
achieved using a continuous modification pattern.
35. The invention as set forth in claims 29, .[.45 or 46.].
.Iadd.30 or 31 .Iaddend.hereof wherein said modification is
achieved using a modified continuous pattern.
36. The invention as set forth in claims 29, 45 or 46 hereof
wherein said modification is achieved using a discontinuous
modification pattern.
37. The invention as set forth in claims 29, 45 or 46 hereof
wherein said modification is achieved using a discontinuous
modification pattern in combination with a continuous or a modified
continuous pattern.
38. The invention as set forth in claims 29, 45 or 46 hereof
wherein said structure has a structural stability of not more than
about 0.5%.
39. A process for adhering a surface covering to a subsurface, said
process comprising the steps of
(a) selecting a surface covering, the critical buckle strain of
said covering being less than the subsurface dimensional change of
a target subsurface;
(b) selecting a target critical buckle strain which is greater than
the subsurface dimensional change;
(c) measuring the relaxed compressive stiffness, the bending
stiffness and the basis weight of said selected covering;
(d) calculating the adhered basis weight for a surface covering
having the measured bending stiffness, the measured relaxed
compressive stiffness, and a critical buckle strain that is equal
to the target critical buckle strain;
(e) calculating the minimum adhesive strength which will be
necessary to adhere said surface covering to said subsurface in a
manner which will prevent buckling;
(f) selecting a suitable adhesive, and
(g) adhering said surface covering to said subsurface, whereby said
surface covering will accommodate the subsurface movement of said
subsurface without buckling.
40. The invention as set forth in claim 39 hereof wherein said
surface covering comprises at least one reinforcing layer.
41. The invention as set forth in claim 40 hereof wherein said
reinforcing layer is a glass reinforcing layer.
42. The invention as set forth in claims 40 or 41 hereof wherein
each said reinforcing layer has a basis weight of from about 15 to
about 160 grams per square meter.
43. The invention as set forth in claim 42 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
44. A process for modifying a surface covering comprising at least
one reinforcing layer, said process comprising the steps of
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change of a
target subsurface;
(b) selecting an adhesive having a determined adhesive
strength;
(c) measuring the basis weight, the bending stiffness and the
relaxed compressive stiffness of said selected covering;
(d) selecting a target critical buckle strain which is greater than
said subfloor dimensional change;
(e) calculating the adhered basis weight which would be obtained if
said selected covering were adhered to said subsurface using said
adhesive;
(f) calculating the relaxed compressive stiffness for a modified
surface covering having the measured bending stiffness, the
calculated adhered basis weight, and a critical buckle strain which
is equal to the target critical buckle strain, and
(g) modifying said covering in situ such that it has a relaxed
compressive stiffness value which is not greater than the
calculated relaxed compressive stiffness value, whereby said
modified structure is capable of being adhered to said subsurface
using said adhesive such that it will accommodate the subsurface
novement of said subsurface without buckling.
45. The invention as set forth in claim 44 hereof wherein said
reinforcing layer is a glass reinforcing layer.
46. The invention as set forth in claim 44 or 45 hereof wherein
said reinforcing layer has a basis weight of from about 15 to about
160 grams per square meter.
47. The invention as set forth in claim 46 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
48. The invention as set forth in claims 44 or 45 hereof wherein
said modification is achieved using a continuous modification
pattern.
49. The invention as set forth in claims 44 or 45 hereof wherein
said modification is achieved using a modified continuous
pattern.
50. The invention as set forth in claims 44 or 45 hereof wherein
said modification is achieved using a discontinuous modification
pattern.
51. The invention as set forth in claims 44 or 45 hereof wherein
said modification is achieved using a discontinuous modification
pattern in combination with a continuous or a modified continuous
pattern.
52. The invention as set forth in claims 44 or 45 hereof wherein
said structure has a structural stability of not more than about
0.5%.
53. A process for modifying a surface covering comprising at least
one reinforcing layer, said process comprising the steps of
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change of a
target subsurface;
(b) modifying said covering in situ such that the critical buckle
strain of the modified covering is greater than the initially
measured critical buckle strain, but less than the critical buckle
strain which would equal or exceed the subsurface dimensional
change;
(c) selecting a target critical buckle strain which is greater than
the subsurface dimensional change;
(d) measuring the bending stiffness, relaxed compressive stiffness
and basis weight of said modified covering;
(e) calculating the adhered basis weight for a covering having the
measured bending stiffness, the measured relaxed compressive
stiffness, and a critical buckle strain that is equal to the target
critical buckle strain; and
(f) calculating the minimum adhesive strength necessary to adhere
said modified covering to said target subsurface, whereby when said
modified covering is adhered to said target subsurface using a
suitable adhesive having an adhesive strength at least as great as
said calculated adhesive strength, said modified covering will be
suitable to accommodate the subsurface movement of said target
subsurface without buckling.
54. The invention as set forth in claim 53 hereof wherein said
reinforcing layer is a glass reinforcing layer.
55. The invention as set forth in claims 53 or 54 hereof wherein
said reinforcing layer has a basis weight of from about 15 to about
160 grams per square meter.
56. The invention as set forth in claims 53 or 54 hereof wherein
said weight is from about 20 to about 80 grams per square
meter.
57. The invention as set forth in claims 53 or 54 hereof wherein
said modification is achieved using a continuous modification
pattern.
58. The invention as set forth in claims 53 or 54 hereof wherein
said modification is achieved using a modified continuous
pattern.
59. The invention as set forth in claims 53 or 54 hereof wherein
said modification is achieved using a discontinuous modification
pattern.
60. The invention as set forth in claims 53 or 54 hereof wherein
said modification is achieved using a discontinuous modification
pattern in combination with a continuous or a modified continuous
pattern.
61. The invention as set forth in claims 53 or 54 hereof wherein
said structure has a structural stability of not more than about
0.5%.
62. A process for preparing a flooring structure comprising a
single reinforcing layer, said process comprising the steps of
selecting a matrix material for said structure, said matrix
material being capable of providing a desired basis weight for said
structure,
selecting a reinforcing layer, said layer having regions of
differential relaxed compressive/tensile stiffness such that, when
said structure is formed from said material and said layer, said
structure will have a critical buckle strain greater than the
subfloor dimensional change of a target subfloor, and
embedding said reinforcing layer in said matrix material, whereby
said structure will be suitable to accommodate the subfloor
movement of said subfloor without buckling when said structure is
disposed on said subfloor.
63. The invention as set forth in claim 62 hereof wherein said
reinforcing layer is a glass reinforcing layer.
64. The invention as set forth in claim 63 hereof wherein said
layer is non-woven.
65. The invention as set forth in claims 62, 63 or 64 hereof
wherein said reinforcing layer comprises regions wherein said layer
is physically interrupted.
66. The invention as set forth in claims 62, 63 or 64 hereof
wherein said reinforcing layer comprises regions wherein said layer
is chemically nodified.
67. The invention as set forth in claim 66 hereof wherein said
chemically modified regions comprise at least one selectively
applied binder.
68. The invention as set forth in claim 62 hereof wherein said
regions of differential relaxed compressive/tensile stiffness are
provided by selectively varying the regional fiber content of said
layer.
69. The invention as set forth in claims 62 or 63 hereof wherein
said structure has a structural stability of not more than about
0.5%.
70. A process for preparing a flooring structure comprising a
single reinforcing layer, said process comprising the steps of
selecting a target critical buckle strain for said structure, said
target critical buckle strain being greater than the subfloor
dimensional change of a target subfloor,
selecting a reinforcing layer and a matrix material such that a
floor covering having a desired basis weight can be produced,
determining the critical buckle strain for a floor covering
constructed from said layer and said material,
imparting regions of differential relaxed compressive/tensile
stiffness to said reinforcing layer, whereby when a structure is
prepared from said modified layer and said matrix material, said
structure will have a critical buckle strain which is not less than
said target critical buckle strain, and
constructing said flooring structure, whereby said structure will
be suitable to accommodate the subfloor movement of said subfloor
without buckling when said structure is disposed on said
subfloor.
71. The invention as set forth in claim 70 hereof wherein said
reinforcing layer is a glass reinforcing layer.
72. The invention as set forth in claim 71 hereof wherein said
layer is non-woven.
73. The invention as set forth in claims 70, 71 or 72 hereof
wherein said regions have reduced the relaxed compressive/tensile
stiffness of said reinforcing layer.
74. The invention as set forth in claim 73 hereof wherein said
reinforcing layer comprises regions wherein said layer is
physically interrupted.
75. The invention as set forth in claim 73 hereof wherein said
reinforcing layer comprises regions wherein said layer is
chemically modified.
76. The invention as set forth in claims 70, 71 or 72 wherein said
regions have increased the relaxed compressive/tensile stiffness of
said reinforcing layer.
77. The invention as set forth in claim 76 hereof wherein said
reinforcing layer comprises regions wherein said layer is
chemically modified.
78. The invention as set forth in claim 77 hereof wherein said
chemically modified regions comprise at least one selectively
applied binder.
79. The invention as set forth in claim 70 hereof wherein said
regions of differential relaxed compressive/tensile stiffness are
provided by selectively varying the regional fiber content of said
layer.
80. The invention as set forth in claim 70, 71 or 72 hereof wherein
said structure has a structural stability of not more than about
0.5%.
81. A resilient loose-lay floor structure, said floor structure
having a basis weight of from about 2 to about 10 pounds per square
yard and comprising a matrix material and at least two layers of
reinforcing material disposed within said matrix material, at least
one of said layers being approximately above the neutral bending
plane of said loose-lay floor structure and at least one of said
layers being approximately below said neutral bending plane, the
sum of the relaxed compressive stiffness values for said
reinforcing materials being not less than the relaxed compressive
stiffness value for said matrix material, said floor structure
having a bending stiffness of from about 0.1 to about 9 inch-pounds
and a critical buckle strain greater than the strain expected to be
caused by a target subfloor dimensional change.
82. The invention as set forth in claim 81 hereof wherein said
bending stiffness is from about 1 to about 9 inch-pounds, said
subfloor having a subfloor dimensional change of not less than
0.0015.
83. The invention as set forth in claim 82 hereof wherein said
bending stiffness is from about 3 to about 9 inch-pounds and said
subfloor dimensional change is not less than 0.0030.
84. The invention as set forth in claim 81 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5 to
1.
85. The invention as set forth in claim 84 hereof wherein said
ratio is at least 10 to 1.
86. The invention as set forth in claim 82 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5:1.
87. The invention as set forth in claim 86 hereof wherein said
ratio is at least 10:1.
88. The invention as set forth in claim 83 hereof wherein the ratio
of the sums of said relaxed compressive stiffness values for said
reinforcing materials and said matrix material is at least 5:1.
89. The invention as set forth in claim 88 hereof wherein said
ratio is at least 10:1.
90. The invention as set forth in claims 81, 82, 83, 84, 85, 86,
87, 88 or 89 hereof wherein said layers of reinforcing material
have the same composition.
91. The invention as set forth in claims 81 82, 83, 84, 85, 86, 87,
88 or 89 hereof wherein said layers of reinforcing material have
different compositions.
92. The invention as set forth in claims 81, 82, 83, 84, 85, 86,
87, 88 or 89 wherein each of said layers of reinforcing material is
disposed within said matrix material in a substantially planar
fashion.
93. The invention as set forth in claims 81, 82, 83, 84, 85, 86,
87, 88 or 89 hereof wherein a substantial portion of at least one
of said reinforcing layers does not lie in the same plane.
94. The invention as set forth in claims 81, 82, 83, 84, 85, 86,
87, 88 or 89 hereof wherein the relaxed compressive stiffness of at
least one of said reinforcing layers has been modified.
95. The invention as set forth in claim 94, hereof wherein said
modification has been accomplished in situ.
96. A modified flooring structure comprising a single reinforcing
layer, said structure having been produced by modifying in situ a
flooring structure having a critical buckle strain which was less
than the subfloor dimensional change of a target subfloor, said
modified flooring structure having a critical buckle strain which
is greater than said subfloor dimensional change, whereby said
modified flooring structure is suitable to accommodate the subfloor
movement of said target subfloor.
97. The invention as set forth in claim 96 hereof wherein said in
situ modification was achieved by
selecting a target critical buckle strain, said critical buckle
strain being greater than said subfloor dimensional change;
determining the relaxed compressive stiffness, the bending
stiffness and the basis weight of said flooring structure;
plotting a contour curve of the target critical buckle strain for
said flooring structure by varying the bending stiffness values
from about 0 to about 9 inch-pounds and by varying the relaxed
compressive stiffness values from about 0 to about 10,000 pounds
per inch of width;
determining from said contour curve the relaxed compressive
stiffness required for said modified flooring structure; and
modifying said flooring structure in situ such that the resulting
modified flooring structure has a relaxed compressive stiffness
value which is the same as or less than the target relaxed
compressive stiffness.
98. The invention as set forth in claim 97, hereof wherein said
reinforcing layer is a glass reinforcing layer.
99. The invention as set forth in claims 96, 97 or 98 hereof
wherein said reinforcing layer has a basis weight of from about 15
to about 160 grams per square meter.
100. The invention as set forth in claim 99 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
101. The invention as set forth in claims 96, 97 or 98 hereof
wherein said structure comprises a reinforcing layer having a
continuous modification pattern.
102. The invention as set forth in claims 96, 97 or 98 hereof
wherein said structure comprises a reinforcing layer having a
modified continuous pattern.
103. The invention as set forth in claims 96, 97 or 98 hereof
wherein said structure comprises a reinforcing layer having a
discontinuous modification pattern.
104. The invention as set forth in claims 96, 97 or 98 hereof
wherein said structure comprises a reinforcing layer having a
discontinuous modification pattern in combination with a continuous
or a modified continuous pattern.
105. The invention as set forth in claims 96, 97 or 98 hereof
wherein said structure has a structural stability of not more than
about 0.5%.
106. A surface covering which is suitable to be adhered with an
adhesive to a target subsurface without buckling, said surface
covering comprising
(a) a matrix material, and
(b) at least one reinforcing layer disposed therein which has been
modified in situ such that .Iadd.prior to modification, said
surface covering and the selected adhesive provide an adhered
critical buckle strain less than the subsurface dimensional change,
and after modification said surface covering has a critical buckle
strain which is less change, and after modification .Iaddend.said
surface covering the subsurface dimensional change of said target
subsurface, the difference between said critical buckle strain and
said subsurface dimensional change being such that the adhesive
strength of a selected adhesive in combination with the basis
weight of said surface covering will be sufficient to provide an
adhesive bond having a strength which is not less than the adhered
basis weight calculated for said surface covering, whereby said
surface covering is suitable to be adhered with said adhesive to
said subsurface without buckling.
107. The invention as set forth in claim 106 hereof wherein said
surface covering is produced by
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change;
(b) selecting an adhesive having a determined adhesive
strength;
(c) measuring the basis weight, the bending stiffness and the
relaxed compressive stiffness of said selected covering;
(d) selecting a target critical buckle strain which is greater than
the subsurface dimensional change;
(e) calculating the adhered basis weight which would be obtained if
said selected covering were adhered to said subsurface using said
adhesive;
(f) calculating the relaxed compressive stiffness for a modified
surface covering having the measured bending stiffness, the
calculated adhered basis weight, and a critical buckle strain which
is equal to the target critical buckle strain, and
(g) modifying said covering in situ such that it has a relaxed
compressive stiffness value which is not greater than the
calculated relaxed compressive stiffness value.
108. The invention as set forth in claim 106 hereof wherein said
surface covering is obtained by
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change;
(b) modifying said covering in situ such that the critical buckle
strain of the modified covering is greater than the initially
measured critical buckle strain, but less than the critical buckle
strain which would equal or exceed the subsurface dimensional
change;
(c) selecting a target critical buckle strain which is greater than
the subsurface dimensional change;
(d) measuring the bending stiffness, relaxed compressive stiffness
and basis weight of said modified covering;
(e) calculating the adhered basis weight for a covering having the
measured bending stiffness, the measured relaxed compressive
stiffness, and a critical buckle strain that is equal to the target
critical buckle strain; and
(f) calculating the minimum adhesive strength necessary to adhere
said modified covering to said subsurface.
109. The invention as set forth in claim 106 hereof wherein said
reinforcing layer is a glass reinforcing layer.
110. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said reinforcing layer has a basis weight of from
about 15 to about 160 grams per square meter.
111. The invention as set forth in claim 110 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
112. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said modification is achieved using a continuous
modification pattern.
113. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said modification is achieved using a modified
continuous pattern.
114. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said modification is achieved using a discontinuous
modification pattern.
115. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said modification is achieved using a discontinuous
modification pattern in combination with a continuous or a modified
continuous pattern.
116. The invention as set forth in claims 106, 107, 108 or 109
hereof wherein said structure has a structural stability of not
more than about 0.5%.
117. A composite structure comprising a surface covering, a
subsurface and an adhesive which adheres said surface covering and
said subsurface together, said surface covering comprising
(a) a matrix material, and
(b) at least one reinforcing layer disposed therein which has been
modified in situ, the critical buckle strain of said surface
covering being less than the subsurface dimensional change of said
subsurface, the difference between said critical buckle strain and
said subsurface dimensional change being such that the adhesive
strength of said adhesive in combination with the basis weight of
said surface covering provides an adhesive bond having a strength
which is not less than the adhered basis weight calculated for said
surface covering.
118. The invention as set forth in claim 117 hereof wherein said
composite structure is obtained by
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change;
(b) selecting an adhesive having a determined adhesive
strength;
(c) measuring the basis weight, the bending stiffness and the
relaxed compressive stiffness of said selected covering;
(d) selecting a target critical buckle strain which is greater than
the subfloor dimensional change;
(e) calculating the adhered basis weight which would be obtained if
said selected covering were adhered to said subsurface using said
adhesive;
(f) calculating the relaxed compressive stiffness for a modified
surface covering having the measured bending stiffness, the
calculated adhered basis weight, and a critical buckle strain which
is equal to the target critical buckle strain;
(g) modifying said covering in situ such that it has a relaxed
compressive stiffness value which is not greater than the
calculated relaxed compressive stiffness value; and
(h) adhering said surface covering to said subsurface using said
selected adhesive.
119. The invention as set forth in claim 117 hereof wherein said
composite structure is obtained by
(a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change;
(b) modifying said covering in situ such that the critical buckle
strain of the modified covering is greater than the initially
measured critical buckle strain, but less than the critical buckle
strain which would equal or exceed the subsurface dimensional
change;
(c) selecting a target critical buckle strain which is greater than
the subsurface dimensional change;
(d) measuring the bending stiffness, relaxed compressive stiffness
and basis weight of said modified covering;
(e) calculating the adhered basis weight for a covering having the
measured bending stiffness, the measured relaxed compressive
stiffness, and a critical buckle strain which is equal to the
target critical buckle strain;
(f) calculating the minimum adhesive strength necessary to adhere
said modified covering to said subsurface;
(g) selecting an adhesive having an adhesive strength which is at
least as great as said calculated adhesive strength; and
(h) adhering said surface covering to said subsurface using said
selected adhesive.
120. The invention as set forth in claim 117 hereof wherein said
reinforcing layer is a glass reinforcing layer.
121. The invention as set forth in claims 117, 118, 119 or 120
hereof wherein said reinforcing layer has a basis weight of from
about 15 to about 160 grams per square meter.
122. The invention as set forth in claim 121 hereof wherein said
basis weight is from about 20 to about 80 grams per square
meter.
123. The invention as set forth in claim 117, 118, 119 or 120
hereof wherein said modification is achieved using a continuous
modification pattern.
124. The invention as set forth in claims 117, 118, 119 or 120
hereof wherein said modification is achieved using a modified
continuous pattern.
125. The invention as set forth in claims 117, 118, 119 or 120
hereof wherein said modification is achieved using a discontinuous
modification pattern.
126. The invention as set forth in claims 117, 118, 119 or 120
hereof wherein said modification is achieved using a discontinuous
modification pattern in combination with a continuous or a modified
continuous pattern.
127. The invention as set forth in claims 117, .[.99, 100 or 101.].
.Iadd.118, 119 or 120 .Iaddend.hereof wherein said structure has a
structural stability of not more than about 0.5%.
128. A flooring structure, said structure comprising
a matrix material, and
a single reinforcing layer embedded within said matrix material,
said layer comprising regions of differential relaxed
compressive/tensile stiffness .Iadd.wherein said reinforcing layer
comprises regions in which said layer is physically interrupted or
chemically modified .Iaddend.such that said structure has a
critical buckle strain in excess of the subfloor dimensional change
of a target subfloor, said structure being suitable to accommodate
the movement of said subfloor without buckling when disposed over
said subfloor.
129. The invention as set forth in claim 128 hereof wherein said
reinforcing layer is a glass reinforcing layer.
130. The invention as set forth in claim 129 hereof wherein said
layer is non-woven. .[.131. The invention as set forth in claim
128, 129 or 130 hereof wherein said reinforcing layer comprises
regions wherein said layer is physically interrupted..]. .[.132.
The invention as set forth in claims 128, 129 or 130 hereof wherein
said reinforcing layer comprises regions
wherein said layer is chemically modified..]. 133. The invention as
set forth in .[.claim 132.]. .Iadd.claims 128, 129 or 130
.Iaddend.hereof wherein said chemically modified regions comprise
at least one selectively
applied binder. 134. The invention as set forth in claim 128 hereof
wherein said regions of differential relaxed compressive/tensile
stiffness are provided by selectively varying the regional fiber
content of said
layer. 135. The invention as set forth in claims 128 or 129 hereof
wherein said structure has a structural stability of not more than
about 0.5%.
Description
The present invention relates to loose-lay and adhered surface
coverings, and more particularly to loose-lay and adhered surface
coverings which will be suitable for use over stable or unstable
subsurfaces.
BACKGROUND OF THE INVENTION
Decorative floor coverings comprising resilient material have been
in use for many years. Usually these floor coverings have been
fastened to subfloors with adhesives; however, the installation of
such coverings is time consuming and expensive. Therefore, it is
desirable to place the floor coverings on subfloors without the use
of adhesives; i.e., to loosely lay the covering on the subfloor. In
such circumstances, the weight of the loose-lay floor covering
itself tends to hold it in place, although it may also be pinned to
the subfloor by furniture, appliances, and other objects which rest
upon it.
Loose lay floor coverings should have the following
characteristics; namely, they should not curl or dome; they should
not shirk or grow with time or under the influence of environmental
change; they should stay in place under the influence of a rolling
load; and they should withstand or accommodate the movement of
subfloors without buckling. The latter problem creates special
difficulties because subfloors range from those which are
dimensionally stable (e.g. concrete) to those which are
dimensionally unstable (e.g. particleboard). Other problems are
also encountered depending on the type of subfloor over which the
loose-lay floor is placed. Thus, the flooring industry has
dedicated a considerable amount of time and effort to develop a
loose-lay flooring which will have the aforementioned
characteristics.
PRIOR ART
Various references are found in the prior art pertaining to loose
lay flooring. U.S. Pat. No. 3,821,059 discloses segmentally
accommodating loose-lay flooring comprising a plurality of rigid
elements that distribute stresses within the flooring matrix such
that they appear as a series of small distortions. U.S. Pat. No.
3,364,058 discloses a composite floor comprising a base support, a
release coat, a waterproofing coat, a wear coat, and a top layer,
said composite floor being designed to avoid damage caused by the
movement of the subflooring. U.S. Pat. No. 4,066,813 discloses a
method for reducing growth properties of resilient flooring having
a fibrous cellulosic backing by incorporating a small amount of a
growth inhibitor. In addition, a variety of patents address the
problem of stress relief by inclusion of a series of deformable
geometric configurations into structural matrices. Examples of such
are U.S. Pat. Nos. 4,146,666; 4,049,855; 4,035,536; and 4,020,205.
Nevertheless, none of the prior art references adequately teach how
to construct a flooring material which may be loosely laid over the
surface of a stable or unstable subfloor.
Accordingly, one objective of the present invention is to provide
processes for designing and constructing a loose-lay floor
structure which will accommodate the movement of an unstable
subfloor without buckling.
Another objective of the present invention is to provide processes
for designing and constructing a loose-lay floor structure which
will accommodate the movement of any type of subfloor without
buckling, doming and curling, and which will not move under a
rolling load.
Yet another objective of the present invention is to provide a
process by which a flooring material having predictable subfloor
accommodation characteristics may be designed.
Still another objective of the present invention is to provide
floor structures which will have the aforementioned attributes.
Still yet another objective of the present invention is to provide
methods by which products comprising one or more reinforcing layers
may be modified in situ to provide buckling characteristics which
allow the products to be used as loose-lay or adhered surface
coverings.
These and other advantages of the present invention will become
apparent from the detailed description of the preferred embodiments
which follow.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A and 1B illustrate a diagram of a computer program which
may be used to calculate the contour curves of the present
invention.
FIG. 2 illustrates the contour curve of Example 1.
FIG. 3 illustrates the contour curve of Example 2.
FIG. 4 illustrates a structure as set forth in Example 2.
FIG. 5 illustrates a structure as set forth in Example 2.
FIG. 6 illustrates a structure as set forth in Example 3.
FIG. 7 illustrates a structure as set forth in Example 3.
FIG. 8 illustrates a structure as set forth in Example 4.
FIG. 9 illustrates the contour curve of Example 4.
FIG. 10 illustrates the contour curve of Example 7.
FIG. 11 illustrates the contour curve of Example 8.
FIG. 12 illustrates one example of a continuous modification
pattern.
FIG. 13 illustrates one example of a modified continuous
pattern.
FIG. 14 illustrates one example of a discontinuous pattern.
FIG. 15 illustrates the contour curve applicable to Examples
9-13.
FIGS. 16A and 16B illustrate a diagram of a modified computer
program, comparable to FIGS. 1A and 1B, which may be used to
calculate the adhered basis weight and/or strain according to the
present invention.
FIG. 17 illustrates a test strip having differential regions of
relaxed compressive/tensile stiffness.
SUMMARY OF THE INVENTION
The present invention concerns loose-lay floor structures
comprising at least two layers of reinforcing material and
processes to design and produce them. Loose-lay floors may be
designed which will be suitable for use over stable subfloors, or
which will accommodate the movement of very unstable subfloors.
Flooring constructed according to this invention will have the
ability to resist buckling, curling and doming, and will resist
moving under a rolling load. A process is also provided for
modifying structures comprising a single reinforcing layer in situ
so as to convert structures with unacceptable buckling
characteristics into structures with acceptable buckling
characteristics. As an alternative, the reinforcing layer may be
premodified such that, when used to provide a surface covering, the
covering will have acceptable buckling characteristics. In
appropriate circumstances, surface coverings of the present
invention may also be adhered to subsurfaces, and processes are
described wherein the required adhesive capacity of an adhesive can
be calculated.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In one embodiment, the present invention relates to a process for
designing a resilient loose-lay floor structure for use over
subflooring having an ascertainable subfloor dimensional change.
Said process comprises the steps of selecting a target critical
buckle strain for said floor structure, said critical buckle strain
being greater than the subfloor dimensional change; selecting an
approximate basis weight for said floor structure, said basis
weight being within the range of from about 2 to about 10 pounds
per square yard; plotting a contour curve of the selected critical
buckle strain for said selected basis weight by varying the bending
stiffness values from about 0 to about 9 inch-pounds and by varying
the relaxed compressive stiffness values from about 0 to about
10,000 pounds per inch of width; determining from said contour
curve the range defined by the minimum and maximum relaxed
compressive stiffness values corresponding to bending stiffness
values of about 0.1 and about 9 inch-pounds, respectively;
selecting a matrix material and at least two layers of reinforcing
material such that the sum of the relaxed compressive stiffness
values for said materials falls within the determined range, said
matrix material and said reinforcing materials being selected such
that the sum of the relaxed compressive stiffness values for said
reinforcing materials is not less than the sum of the relaxed
compressive stiffness values for said matrix material; and
determining from said contour curve the bending stiffness value
applicable to the sum of the relaxed compressive stiffness values
for said reinforcing materials and said matrix material, whereby,
when said layers of reinforcing material are disposed within said
matrix material such that the measured bending stiffness of the
resultant floor structure corresponds to the determined bending
stiffness, at least one reinforcing layer being approximately above
the neutral bending plane of said resultant floor structure and at
least one reinforcing layer being approximately below said neutral
bending plane, the critical buckle strain for said resultant floor
structure will be approximately equivalent to the target critical
buckle strain and will be greater than the strain expected to be
caused by the subfloor dimensional change.
In a second embodiment, the present invention relates to a process
for making a resilient loose-lay floor structure for use over a
subfloor having an ascertainable subfloor dimensional change. Said
process comprises the steps of selecting a matrix material and at
least one reinforcing material, and disposing at least two layers
of reinforcing material within said matrix material such that the
bending stiffness of said loose-lay floor structure is from about
0.1 to about 9 inch-pounds, at least one layer of reinforcing
material being approximately above the neutral bending plane of
said loose-lay floor structure and at least one layer of
reinforcing material being approximately below said neutral bending
plane, said matrix material and said reinforcing materials being
selected such that the sum of the relaxed compressive stiffness
values for said reinforcing materials is not less than the relaxed
compressive stiffness value for said matrix material and the basis
weight of said floor structure is from about 2 to about 10 pounds
per square yard, whereby the critical buckle strain of said
loose-lay floor structure is greater than the strain expected to be
caused by the subfloor dimensional change.
In a third embodiment, the present invention relates to a resilient
loose-lay floor structure for use over a subfloor having an
ascertainable subfloor dimensional change. Said floor structure has
a basis weight of from about 2 to about 10 pounds per square yard
and comprises a matrix material and at least two layers of
reinforcing material disposed within said matrix material, at least
one of said layers being approximately above the neutral bending
plane of said loose-lay floor structure and at least one of said
layers being approximately below said neutral bending plane. The
sum of the relaxed compressive stiffness values for said
reinforcing materials is not less than the sum of the relaxed
compressive stiffness values for said matrix materials. Said floor
structure has a bending stiffness of from about 0.1 to about 9
inch-pounds and a critical buckle strain greater than the strain
expected to be caused by the subfloor dimensional change.
In a fourth embodiment, the present invention comprises a process
for treating a potential resilient loose-lay floor structure having
a basis weight of from about 2 to about 10 pounds per square yard
and having at least two layers of reinforcing material disposed
within a matrix material, at least one layer of reinforcing
material being approximately above the neutral bending plane of
said floor structure and at least one layer of reinforcing material
being approximately below said neutral bending plane, said
structure being unsuitable for use as a loose-lay floor structure
over a subfloor having an ascertained subfloor dimensional change
because it has a bending stiffness which is in excess of about 9
inch-pounds, or a critical buckle strain which is not greater than
the asertained subfloor dimensional change, or both, said process
comprising the modification of at least one of said reinforcing
layers by external means such that the bending stiffness of the
resultant flooring structure is within the range of from about 0.1
to about 9 inch-pounds and the critical buckle strain of said
resultant flooring structure is greater than said ascertained
subfloor dimensional change.
In a fifth embodiment, the present invention comprises a process
for preparing a flooring structure comprising a single reinforcing
layer, said structure being suitable to accommodate the subfloor
movement of a subfloor having an ascertainable subfloor dimensional
change, said process comprising the steps of selecting a flooring
structure comprising a single encapsulated glass reinforcing layer,
the critical buckle strain of said structure being less than the
subfloor dimensional change, and modifying said flooring structure
in situ such that the critical buckle strain becomes greater than
said subfloor dimensional change.
In a sixth embodiment, the present invention comprises a flooring
structure comprising a single reinforcing layer, said structure
having been modified in situ such that its critical buckle strain
is greater than the subfloor dimensional change of the subfloor
over which said structure will be used.
In a seventh embodiment, the present invention comprises a process
for adhering a surface covering to a subsurface having an
ascertainable subsurface dimensional change such that said surface
covering will accommodate subsurface movement without buckling,
said process comprising the steps of (a) selecting a surface
covering, the critical buckle strain of the selected covering being
less than the subsurface dimensional change; (b) selecting a target
critical buckle strain which is greater than the subsurface
dimensional change; (c) measuring the relaxed compressive
stiffness, the bending stiffness, and the basis weight of said
selected covering; (d) calculating tne adhered basis weight for a
surface covering having the measured bending stiffness, the
measured relaxed compressive stiffness, and a critical buckle
strain which is equal to the target critical buckle strain; (e)
calculating the minimum adhesive strength which will be necessary
to adhere said surface covering to said subsurface in a manner
which will prevent buckling; (f) selecting a suitable adhesive, and
(g) adhering said surface covering to said subsurface.
In an eighth embodiment, the present invention comprises a process
for modifying a surface covering comprising at least one
reinforcing layer whereby it can be adhered without buckling to a
subsurface having an ascertainable subsurface dimensional change,
said process comprising the steps of (a) selecting a surface
covering comprising at least one reinforcing layer, the critical
buckle strain of said selected covering being less than the
subsurface dimensional change; (b) selecting an adhesive having a
determined adhesive strength; (c) measuring the basis weight, the
bending stiffness and the relaxed compressive stiffness of said
selected covering; (d) selecting a target critical buckle strain
which is greater than the subfloor dimensional change; (e)
calculating the adhered basis weight which would be obtained if
said selected covering were adhered to said subsurface using said
adhesive; (f) calculating the relaxed compressive stiffness for a
modified surface covering having the measured bending stiffness,
the calculated adhered basis weight, and a critical buckle strain
which is equal to the target critical buckle strain, and (g)
modifying said covering in situ such that it has a relaxed
compressive stiffness which is not greater than the calculated
relaxed compressive stiffness value, whereby when the modified
surface covering is adhered to said subsurface using said adhesive,
it will accommodate subsurface movement without buckling.
In a ninth embodiment, the present invention comprises a process
for modifying a surface covering comprising at least one
reinforcing layer, the modified covering being suitable to
accommodate the subsurface movement of a subsurface having an
ascertainable subsurface dimensional change when said modified
covering is adhered to said subsurface, said process comprising the
steps of (a) selecting a surface covering comprising at least one
reinforcing layer, the critical buckle strain of said selected
covering being less than the subsurface dimensional change; (b)
modifying said covering in situ such that the critical buckle
strain of the modified covering is greater than the initially
measured critical buckle strain, but less than the critical buckle
strain which would equal or exceed the subsurface dimensional
change; (c) selecting a target critical buckle strain which is
greater than the subsurface dimensional change; (d) measuring the
bending stiffness, relaxed compressive stiffhess and basis weight
of said modified covering; (e) calculating the adhered basis weight
for a covering having the measured bending stiffness, the measured
relaxed compressive stiffness, and a critical buckle strain that is
equal to the target critical buckle strain; and (f) calculating the
minimum adhesive strength necessary to adhere said modified
covering to said subsurface, whereby when a suitable adhesive
having an adhesive strength at least as great as said calculated
adhesive strength is selected, said modified structure can be
adhered to said subsurface in a manner which will prevent
buckling.
In a tenth embodiment, the present invention relates to a surface
covering which is suitable to be adhered with an adhesive to a
subsurface without buckling, said surface covering comprising (a) a
matrix material, and (b) at least one reinforcing layer disposed
therein which has been modified in situ such that said surface
covering has a critical buckle strain which is less than the
subsurface dimensional change of said subsurface, the difference
between said buckle strain and said subsurface dimensional change
being such that the adhesive strength of a selected adhesive in
combination with the basis weight of said surface covering will be
sufficient to provide an adhesive bond having a strength which is
not less than the adhered basis weight calculated for said surface
covering.
In an eleventh embodiment, the present invention relates to a
composite structure comprising a surface covering, a subsurface and
an adhesive which adheres said surface covering and said subsurface
together, said surface covering comprising (a) a matrix material,
and (b) at least one reinforcing layer disposed therein which has
been modified in situ, the critical buckle strain of said surface
covering being less than the subsurface dimensional change of said
subsurface, the difference between said critical buckle strain and
said subsurface dimensional change being such that the adhesive
strength of said adhesive in combination with the basis weight of
said surface covering provides an adhesive bond having a strength
which is not less than the adhered basis weight calculated for said
surface covering.
In a twelfth embodiment, the present invention relates to a
flooring structure, said structure comprising a matrix material,
and a single reinforcing layer embedded within said matrix
material, said layer comprising regions of differential relaxed
compressive/tensile stiffness such that said structure has a
critical buckle strain in excess of the subfloor dimensional change
of a subfloor having an ascertainable subfloor dimensional change,
said structure being suitable to accommodate the movement of said
subfloor.
In a thirteenth embodiment, the present invention relates to a
process for preparing a flooring structure comprising a single
reinforcing layer, said structure being suitable to accommodate the
subfloor movement of a subfloor having an ascertainable subfloor
dimensional change, said process comprising the steps of selecting
a matrix material for said structure, said matrix material being
capable of providing a desired basis weight for said structure,
selecting a reinforcing layer, said layer having regions of
differential relaxed compressive/tensile stiffness such that, when
said structure is formed from said material and said layer, said
structure will have a critical buckle strain greater than said
subfloor dimensional change, and embedding said reinforcing layer
in said matrix material.
In a fourteenth embodiment, the present invention relates to a
process for preparing a flooring structure comprising a single
reinforcing layer, said structure being suitable to accommodate the
subfloor movement of a subfloor having an ascertainable subfloor
dimensional change, said process comprising the steps of selecting
a target critical buckle strain for said structure, said target
critical buckle strain being greater than the subfloor dimensional
change, selecting a reinforcing layer and a matrix material such
that a floor covering having a desired basis weight can be
produced, determining the critical buckle strain for a floor
covering constructed from said layer and said material, imparting
regions of differential relaxed compressive/tensile stiffness to
said reinforcing layer, whereby when a structure is prepared from
said modified layer and said matrix material, said structure will
have a critical buckle strain which is not less than said target
critical buckle strain, and constructing said flooring
structure.
As used herein, "loose-lay floor structure" is a floor structure
which will lie tlat on a stable or unstable subfloor, which will
resist doming, curling, buckling, or movement under a rolling load,
which preferably has a low structural stability value as defined
hereinbelow, and which need not be held in place using
adhesives.
As used herein, "accommodating floor structure" is a loose-lay
floor structure which will accommodate or alter its size and shape
to match that of an unstable subfloor.
As used herein, "subfloor dimensional change" is a measure of the
change in length of a subflooring material under the conditions of
its environment. This change is expressed herein as change per unit
length.
As used herein, "critical buckle strain" is the strain at which a
loose-lay floor structure that is compressed in a planar fashion
will buckle.
As used herein, "relaxed compressive stiffness" is the approximate
compressing force per inch of width divided by the induced strain,
the value of said relaxed compressive stiffness being projected to
a 1000-hour load relaxation and the compressive force being applied
in a planar fashion, the measurement being taken in the linear
portion of the stress-strain curve.
As used herein, "relaxed tensile stiffness" is the approximate
stretching force per inch of width divided by the induced strain,
the value of said relaxed tensile stiffness being projected to a
1000-hour load relaxation and the stretching force being applied in
a planar fashion, the measurement being taken in the linear portion
of the stress-strain curve.
As used herein, "basis weight" is the weight in pounds per square
yard of a loose-lay flooring material.
As used herein, "matrix material" comprises all components of a
loose-lay flooring material, excluding the reinforcing
material.
As used herein, "bending stiffness" is the resistance to bending
demonstrated by a loose-lay flooring material as measured in
inch-pounds using a cantilever beam or equivalent method.
As used herein, "bending resistance" is a material parameter used
in the theoretical derivation of the potential energy expression,
and characterizes the resistance of the flooring material to
bending.
As used herein, "structural stability" is a measure of the change
in length in percent of a flooring sample which has been heated at
180.degree. F. for six hours and reconditioned at 73.4.degree. F.
and 50% relative humidity for one hour.
As used herein, the "neutral bending plane" of a strip of material,
the ends of which are being subjected to a downward bending force,
is an imaginary plane within said material above which the material
is under tension and below which it is under compression.
As used herein, "in situ" (in conjunction with one or more layers
of reinforcing material) refers to a disposition of the reinforcing
material in the final structure, in a partially completed
structure, or in a prestructure which later becomes an integral
part of the final structure.
Loose-lay flooring should be expected to maintain within acceptable
limits the shape and dimensions of the room in which it is placed,
and it should not shrink from the walls leaving unsightly gaps.
This requirement applies regardless of the nature of the subfloor.
Therefore, a desirable trait for a flooring material, whether
loose-lay or adhered, is that it have a structural stability under
normal conditions of not more than 0.5% and preferably not more
than 0.1%.
If the subflooring on which the loose-lay floor structure is to be
placed is stable, the characteristics which must be demonstrated by
the loose-lay floor are less stringent than for unstable subfloors
since minimal dimensional changes of the subflooring result in
minimal planar compressions of the floor structure. Nevertheless,
problems can still be encountered which relate to doming and
curling, and to movement under a rolling load.
Conversely, unstable subfloors such as particleboard dramatically
increase the requirements for a loose-lay flooring because such
subfloors tend to expand and contract depending on the temperature
and relative humidity conditions within the structure in which the
subfloor resides. During winter months, dry furnace-heated air
tends to shrink unstable subfloors, whereas during humid summer
months such subfloors tend to expand. A loose-lay floor structure
that is laid over such a subsurface at its maximum expanded
position and is pinned, attached or otherwise restricted by heavy
objects such as appliances experiences a variety of stresses when
the subfloor changes its dimensions. A loose-lay flooring structure
constructed according to the prior art and having the required
structural stability is often unable to accommodate these stresses,
thus leading to doming, buckling or curling of the flooring.
Surprisingly, we have discovered that loose-lay floor structures
comprising at least two layers of reinforcing material may be
constructed which will meet all of the aformentioned criteria. As a
general rule, loose-lay floor structures with superior
accommodation characteristics result when the basis weight and the
bending stiffness are increased and the compressive stiffness is
lowered. Accordingly, by following processes as set forth
hereinbelow, loose-lay flooring can be constructed which will have
predictable characteristics when applied over a subfloor having an
ascertainable subfloor dimensional change.
One factor which must be considered at the outset is the amount of
variation which can be expected from a given subfloor. For example,
subfloor shrinkage can be expected to place a strain on the
loose-lay floor structure when it is compressed in a planar fashion
by the movement of the subfloor. If a flooring structure is
constructed with a critical buckle strain equivalent to the
expected subfloor dimensional change and the flooring is compressed
by the maximum expected shrinkage of the subfloor, it will buckle.
Thus, the critical buckle strain of tne floor structure must be
greater than the expected strain which will result from maximum
subfloor movement. A loose-lay floor structure will experience the
maximum compressive strain if it has been installed on subflooring
which is in its maximum expanded condition; therefore, it should be
designed to withstand this strain without buckling.
Three significant parameters will affect the tendency of the
loose-lay floor structure to buckle. These are the basis weight,
bending stiffness and the relaxed compressive stiffness, which were
defined above. The basis weight of ordinarily used resilient
flooring material usually varies from about 2 to about 10 pounds
per square yard. As a general rule, the greater the instability of
the subfloor, the greater the basis weight will have to be to
prevent buckling because the added weight of the flooring requires
an increased compressing force to induce buckling.
A second parameter is the bending stiffness of the loose-lay
flooring, the bending stiffness being a measure of the ease with
which the flooring will bend and buckle. Resilient sheet flooring
material will normally range in stiffness from very flexible (i.e.,
having a bending stiffness of ca 0.1 inch-pounds) to fairly stiff
(i.e., having a bending stiffness of ca 9 inch-pounds). Sheet
flooring will rarely have a bending stiffness exceeding the latter
value because it must be transported on rolls. Should the bending
stiffness be greater than 9, problems can be encountered with
cracking, bending, and folding when the flooring is wound on small
diameter rolls.
The third parameter is the relaxed compressive stiffness which will
be discussed in more detail below.
The essence of the present invention is that if one skilled in the
art knows the amount of subfloor dimensional change that will
occur, that person can design and construct a loose-lay floor
structure which will have a critical buckle strain that is greater
than the strain which will be exerted on the loose-lay flooring by
the subfloor. Preferably, the loose-lay floor structure will also
have a suitable structural stability. Using mathematical formulas
derived from the theory of buckling, one or more critical buckle
strain contour curves can be generated for selected basis weights
by varying the relaxed compressive stiffness values and the bending
stiffness values or, alternatively, the bending resistance values.
For convenience, the curves displayed herein illustrate plots of
bending stiffness versus relaxed compressive stiffness for constant
basis weight and constant critical buckle strain values. By
determining a range of applicable compressive stiffness values from
the curve, appropriate matrix materials and reinforcing materials
can be selected. A bending stiffness value for the floor structure
can then be determined for these materials and a suitable floor
structure can be constructed by appropriately disposing at least
two layers of reinforcing material within said matrix material.
The relaxed compressive stiffness of the loose-lay floor structure
will approximate the sum of the relaxed compressive stiffness
values for the components of said flooring. Thus, by obtaining the
relaxed compressive stiffness values for materials which may
comprise the matrix material and the reinforcing layers, at least
two of the latter to be disposed within the matrix material,
appropriate materials can be selected such that the sum of the
respective relaxed compressive stiffness values falls approximately
within the range of relaxed compressive stiffness values indicated
by the curve. The actual relaxed compressive stiffness value may
then be determined by constructing a test floor structure and,
using this value, the target bending stiffness value may be
determined from the curve. Alternatively, the sum of the relaxed
compressive (tensile) stiffness values may be used to theoretically
predict the required bending stiffness. It must be recognized that
results which are theoretically calculated for a flooring structure
will depend to a certain extent on experimentally measured values
as well as on other variables which are less predictable;
therefore, some variation from the theoretically predicted results
can be expected. For that reason, this latter approach is less
satisfactory.
Once the desired bending stiffness has been determined, the
reinforcing layers may be disposed within the matrix material such
that a bending stiffness essentially equivalent to the desired
bending stiffness is obtained. The loose-lay floor structure thus
obtained should have a critical buckle strain capable of
withstanding the strain which will be imposed on it by the
subfloor.
Stiffness is a well-known characteristic which may be determined in
a variety of ways. Standard tests are well known in the art. For
example, ANSI/ASTM D 747, also known as the Olsen Stiffness Test,
describes a standard method for determining the stiffness of
plastics using a cantilever beam. For purposes of the present
invention, satisfactory values may be obtained using a 1-inch span
and measuring the bending moment values at a bend angle of
20.degree.. As used herein, the bending moment determined by the
Olsen Stiffness Test is equivalent to the bending stiffness.
More difficulty is encountered in obtaining relaxed compressive
stiffness data for materials which may be used to construct the
loose-lay floor structure. Such measurements may readily be made by
conventional means for the matrix material, taking into account the
relaxation of the material under stress with time. The resulting
relaxed compressive stiffness values projected to 1000-hour
relaxation by means well known in the art should be used to
practice the present invention.
Conversely, reinforcing materials, which may be of thin,
light-weight construction, usually do not lend themselves to such
measurements. Therefore, the information can be estimated by
measuring the relaxed tensile stiffness of the material, also
taking into account the relaxation of the material under stress
with time. For preferred materials, the relaxed tensile stiffness,
when properly measured, will be of approximately the same magnitude
as the relaxed compressive stiffness. Accordingly, relaxed tensile
stiffness values may be substituted for relaxed compressive
stiffness values.
The contour curves referred to above may be derived by conventional
mathematical means. Theoretical models for determining buckling
characteristics are well known in the art. For example, A. D. Kerr
has published, among others, a paper concerning vertical track
buckling in High Speed Ground Transportation Journal, 7, 351
(1973). Loose-lay floor structures are similarly amenable to such
theoretical studies. Accordingly, the potential energy, .pi., of a
sheet flooring structure after buckling may be calculated from the
following formula. ##EQU1## where C=bending resistance
.theta.=angle of lift-off of the buckle
Q=basis weight
K=relaxed compressive (or tensile) stiffness
L.sub.o =one half the length of the buckled area prior to
application of the strain that caused the buckle
E=the compressive strain applied to create the buckle
The bending resistance, C, may be calculated from the bending
stiffness measured according to the Olsen Stiffness Test, using the
following equation ##EQU2## where M.sub.w =the measured bending
stiffness
S=the span used in the test
b=the width of the test specimen
.phi.=the angle in radians at which the measurement was taken
The critical buckle strain may be calculated mathematically by
applying the principle of minimum potential energy. Bending
stiffness values, M.sub.w, are converted to bending resistance
values, C. Upon setting the derivatives of .pi. with respect to
.theta., and of .pi. with respect to L.sub.o, equal to zero,
assigning values for E and Q, and varying C and K within known
limits, solutions can be obtained where E becomes the critical
buckle strain. For example, this may be accomplished by using the
Newton-Rathson Method of solving non-linear simultaneous equations.
The solutions obtained by varying these bending resistance and
relaxed compressive (tensile) stiffness values within known ranges
yields tables of points of critical buckle strain. From these, one
or more contour curves of constant critical buckle strain can be
plotted for use as hereinafter described. As noted above, the
contour curves illustrated herein are plotted in terms of bending
stiffness, M.sub.w, and relaxed compressive stiffness, K, rather
than in terms of bending resistance, C, and K. The values of C used
for calculation are converted from M.sub.w values. A flow chart for
a computer program which may be used to generate this information
is illustrated in FIGS. 1A and 1B, which must be read together. Of
course it will be appreciated that parameters which are
ascertainable by reference to various curves may also be determined
by purely mathematical means. The use of such mathematical means to
derive the information required to practice the present invention
is a matter of choice to the artisan. Accordingly, language in the
specification and in the claims which refers to the plotting of
curves and the like will also be deemed to include such
mathematical alternatives.
In practicing the present invention, loose-lay flooring may be
constructed for use over a particular subfloor having an
ascertained or ascertainable subfloor dimensional change, or it can
be constructed for use over subflooring having an expected subfloor
dimensional change. As used herein, the expression "having an
ascertainable (or ascertained) subfloor dimensional change" will be
considered to encompass all of these alternatives. In any event,
the objective will be to construct a loose-lay floor structure
which has a critical buckle strain that is sufficient to
accommodate the expected subfloor dimensional change. At one
extreme are very stable subfloors, such as concrete, for which the
subfloor dimensional change (and hence the critical buckle strain)
would be minimal. At the other extreme are very unstable subfloors,
such as particleboard, for which the maximum subfloor dimensional
change value (and hence the critical buckle strain) should be about
0.003.
Once the desired critical buckle strain of the flooring is known,
an approximate basis weight for the flooring material can be
selected. Any suitable resilient flooring material can be used,
including polyvinyl chloride resin, acrylic resin, vinyl acetate
resin, vinyl chloride-vinyl acetate copolymers, and the like.
Furthermore, the flooring material may also comprise wear layers,
decorative layers and the like. Structures comprising these
materials usually have a basis weight of from about 2 to about 10
pounds per square yard, although lighter or heavier weights may be
desired in certain circumstances. Since the basis weight is not
critical when a loose-lay flooring is to be placed over a stable
subfloor, basis weights for such usage will preferably vary from
about 2 to about 5 pounds per square yard to conserve cost.
Conversely, for unstable subfloors, basis weights of from about 5
to about 10 pounds per square yard will be preferred. Nevertheless,
these values are provided merely as approximations and are not
intended to limit the scope of the invention.
Next, using the selected basis weight, a contour curve of the
desired critical buckle strain is plotted from data points obtained
by varying the bending stiffness values over a range of from about
0 to about 9 inch-pounds, and by varying the relaxed compressive
stiffness values over a range of from about 0 to about 10,000
pounds per inch of width.
As previously noted, the bending stiffness of resilient flooring
material is usually limited by practical considerations to be
within the range of from about 0.1 to about 9 inch-pounds. However,
as the subfloor dimensional change increases, higher bending
stiffness values will be preferred. Thus, over an unstable subfloor
having a subfloor dimensional change of 0.0015, where greater
accommodation of subfloor movement is required from the floor
structure, higher values such as from about 1 to about 9
inch-pounds are preferred. For subfloors having a subfloor
dimensional change of 0.0025 or more, a bending stiffness of from
about 2 to about 9 inch-pounds is preferred, and, for subfloors
having a subfloor dimensional change of 0.0030 or more, a bending
stiffness of about 3 to about 9 inch-pounds is preferred.
The actual relaxed compressive stiffness range which will be
applicable to the floor structure will be discernible from the
contour curve and, once this range is known, matrix materials and
at least two layers of reinforcing materials can be selected such
that the sum of the relaxed compressive (or tensile) stiffness
values for these materials falls within the indicated range. The
sum of these values also gives, from the curve, the target bending
stiffness for the floor structure. Thus, the reinforcing material
can be disposed within the matrix material such that the target
bending stiffness is achieved.
The reinforcing material will comprise fibrous materials, many of
which are conventionally used in the art. Examples of such
materials are fibrous mats comprising glass, polyester, rayon,
nylon and the like, or combinations thereof. Very lightweight
materials on the order of 0.5 ounce per square yard are preferred
when constructing structures comprising two or more reinforcing
layers and where little or no in situ modification is employed.
Reinforcing materials used in loose-lay flooring should have a
relaxed compressive stiffness which is as uniform as possible in
all directions. Woven materials tend to have directional strength
depending on whether the material is compressed or stretched in a
machine direction or across machine direction. Such directional
strength variation is minimized with non-woven materials;
therefore, non-woven materials are preferred.
Specialized reinforcing materials having unique characteristics may
also be used. One such non-woven material is a glass mat comprising
a binder which dissolves or softens in the presence of plasticizers
found in typical matrix materials. Although the use of such
material makes the prediction of relaxed compressive stiffness
values much more difficult, there are also advantages. For example,
reinforcing materials containing soluble binders are often heavier
in nature and easier to handle in a production environment than
materials which do not contain such binders. Thus, they may be used
where handleability is a problem, but where it is also desirable to
produce a floor structure having a reduced relaxed compressive
stiffness.
In the usual situation, the majority of the relaxed compressive
(tensile) stiffness of the total flooring will be provided by the
reinforcing material. The matrix material, being a resilient
plastic, is usually not dimensionally stable and in most situations
will stretch or compress quite easily. The reinforcing material,
however, does not readily compress or stretch. Preferably, the
relaxed compressive stiffness of the reinforcing material will be
about 5 times that of the matrix material and more preferably about
10 times that of the matrix material. Suitable flooring can be made
with reinforcing material and matrix material having similar
relaxed compressive stiffness values. However, the sum of the
relaxed compressive stiffness values for the reinforcing materials
should not be less than the sum of the relaxed compressive
stiffness values for the matrix materials.
The bending stiffness of a loose-lay floor structure constructed
according to the present invention will vary depending on how the
reinforcing layers are disposed within the matrix material. In most
instances it will be desirable to have the reinforcing material
disposed within the matrix material in a substantially planar
fashion. However, as set forth below, it may be preferable in
certain circumstances to dispose the reinforcing material in a
non-planar fashion. Preferably, two reinforcing layers will be
used, although suitable loose-lay flooring can be produced using
single reinforcing layers or more than two reinforcing layers. The
use of single layers is discussed in more detail below.
As a general rule, the greater the separation of the two layers,
the greater the bending stiffness. Thus, if one reinforcing layer
is disposed near the top surface of the matrix material and one is
disposed near the bottom surface, the bending stiffness will be
greater than if both reinforcing layers are disposed near the
neutral bending plane of the composite material.
Combinations of reinforcing materials may also be used. Rather than
using two layers of the same reinforcing material in a matrix
material, a lighter reinforcing layer can be used in combination
with a heavier reinforcing layer. The heavier reinforcing can be
placed closer to the neutral bending plane, but it will still
produce a bending stiffness comparable to that of a lighter weight
reinforcing material disposed closer to the surface of the matrix
material. Nevertheless when using heavier material, care must be
taken not to exceed the desired relaxed compressive stiffness of
the final product.
The use of such combinations can have great importance as, for
example, where the surface of the matrix material is embossed, or
where a wear layer is applied. If a lighter-weight reinforcment is
placed near the surface of a matrix, embossing will tend to deform
the reinforcement so that it is no longer planar, thus reducing its
contribution to the relaxed compressive stiffness of the flooring
structure. However, if a somewhat heavier reinforcment is used,
that reinforcment could be disposed further away from the surface
of the matrix, thereby diminishing the effects of the embossing.
Similarly, if a wear layer with high compressive stiffness is to be
applied, the neutral bending plane will be higher up in the
composite structure than it would be when such a layer was not a
component of the original matrix material. In such a situation, it
might be necessary to place a lighter weight reinforcing material
in the wear layer in order to achieve an adequate bending stiffness
and relaxed compressive stiffness. Nevertheless, this problem may
likewise be avoided by disposing a heavier reinforcing layer in the
matrix material.
Other alternatives are also available to modify the characteristics
of a flooring structure. For example, a reinforcing material has
its greatest relaxed compressive/tensile stiffness when it is in a
planar configuration. If the reinforcing layer is disposed in a
matrix material in a non-planar fashion, or if it is modified such
that a substantial portion of the reinforcing layer does not lie in
the same plane, the relaxed compressive/tensile stiffness will be
reduced. The former may be achieved by disposing the reinforcing
within the matrix in a wavy or wrinkled manner; however,
modification may be achieved in a variety of ways. For example, the
reinforcing may be deformed from a planar configuration by
embossing or other similar treatment.
Another means of reducing relaxed compressive/tensile stiffness of
a reinforcing material is by modifying the material in a manner
which does not affect planarity. For example, such modifications
would include means such as perforating, cutting, punching holes,
and the like, or by folding to break the fibers and then again
flattening the reinforcing material. The same effect may also be
achieved through the use of softenable binders, as referred to
above.
In addition to modifications by which the relaxed
compressive/tensile stiffness of a reinforcing material is
decreased, techniques may be employed by which this parameter is
increased. Reinforcing layers usually contain binders which provide
added strength, and the binders are normally applied in a uniform
manner either while the layer is being formed, or after it is
formed; however, it is not necessary that binders be applied
uniformly. For example, binders or saturants may be applied in a
selected pattern such that the fibers of a web are attached
together in a different manner in different regions of the web. The
same effect may also be obtained if a binder is uniformly applied,
but cured only in a selected pattern. As another possibility, a web
in which the fibers are held together with binder, but which
nevertheless has a low relaxed compressive stiffness, may be
selectively treated with a saturant to fill the interstitial spaces
in certain areas, thereby increasing the relaxed compressive
stiffness.
Changes in relaxed compressive/tensile stiffness may also be
achieved by varying the regional fiber content of a reinforcing
layer. For example, layers comprising one or more fiber types may
be provided with differential regions of relaxed
compressive/tensile stiffness by selectively varying the mass per
unit volume of the layer; i.e., by varying the mat density. Such
changes may be achieved by maintaining a uniform mat thickness
while varying the openness of the reinforcing. Nevertheless, these
stiffness changes may also be achieved by using layers of uniform
density but selectively varying the thickness of the layer. Of
course, it will also be apparent that the latter result may be
achieved by changing the thickness of the layer through the
selective application of a second fiber type to an existing mat.
From this it follows that different fiber types could be
selectively applied in a pattern of abutting regions to create
desired changes in relaxed compressive/tensile stiffness.
From the foregoing, it will be apparent that all manner of physical
or chemical modifications may be employed, alone or in combination,
to increase and/or decrease the relaxed compressive stiffness
values of a reinforcing material. In essence, these modifications
impart regions of differential relaxed compressive/tensile
stiffness to the reinforcing layer. As a result of these regional
variations, the layer exhibits an average relaxed
compressive/tensile stiffness such that, when the modified layer
resides in a flooring structure, the flooring structure will have a
critical buckle strain which is greater than the subfloor
dimensional change of the subfloor over which the flooring
structure is used or intended to be used. This average relaxed
compressive/tensile stiffness will, of necessity, be less than the
regions of highest relaxed compressive/tensile stiffness found
within the layer.
These modifications may be achieved as a matter of foresight or
hindsight. Thus, a reinforcing material having a high or a low
relaxed compressive stiffness value may be pretreated in such
fashion that the relaxed compressive stiffness is increased or
reduced to a satisfactory value, after which it may be disposed
within the matrix material. Alternatively, the flooring structure
may be constructed and the relaxed compressive stiffness and/or the
bending stiffness measured. Adjustments can then be made by
modifying one or more of the reinforcing layers in situ. In this
way, flooring structures which might not otherwise be suitable for
use over a given subfloor may be treated so as to impart the
necessary bending stiffness and/or relaxed compressive stiffness
values. It will also be apparent that, in view of the teachings
herein, artisans may produce, or arrange to have suppliers produce,
reinforcing materials which contain appropriate regions of
differential relaxed compressive/tensile stiffness such that the
layers may be utilized with no modification or minimal modification
to provide flooring structures having desired performance
characteristics.
The type of reinforcing material which is used and the modification
(if any) which is performed on it may, in many circumstances,
depend on the machinery which is used to handle it during
processing. As explained above, where two reinforcing layers are
used and where little or no in situ modification is employed,
lightweight materials on the order of 0.5 ounce per square yard are
often preferred. Nevertheless, lighter gauge reinforcing layers or
premodified reinforcing layers may not have the strength to
withstand normal processing conditions. For these reasons, it is
often preferred to use a relatively heavy material (perhaps on the
order of 2 ounces per square yard or more) and to modify the
material in situ. Nevertheless, the use of lighter gauge or
premodified materials is within the range of skills possessed by an
ordinary artisan and is considered to be within the scope of the
present invention.
This technique is also applicable to flooring structures comprising
single reinforcing layers. A number of such structures have been
described in the prior art. For example, U.K. Pat. No. 1,525,018
discloses structures comprising glass reinforcing layers, the
density of the glass being about 80 to about 160 grams per square
meter. Similarly, U.K. Patent Application Nos. 2,012,618A,
2,018,618A and 2,019,253A refer to fibrous tissues having a density
of about 10 to about 60 grams per square meter. Related structures
comprising encapsulated glass are also described in U.S. Pat. Nos.
4,242,380 and 3,980,511. Furthermore, structures comprising nylon,
polyester and other woven and non-woven materials are likewise
known in the art.
When single heavy gauge reinforcing (e.g., 2 ounces per square
yard) is used to provide adequate dimensional stability, such
structures can fail when placed over unstable subfloors. Applicants
have discovered that premodification of a reinforcing layer or in
situ modification of the layer (or combinations thereof) may be
used to advantage when preparing these structures. For example,
flooring structures comprising a single layer of glass reinforcing
were physically cut in various patterns, such as those illustrated
in FIGS. 12-14. FIG. 12 illustrates a pattern of square cuts which
were deep enough to pierce the reinforcing layer, the structure
otherwise being left intact. This pattern is referred to as a
continuous modification pattern because there is still a continuum
of reinforcing available within the flooring structure; e.g.,
longitudinally along lines A--A and transversely along lines B--B
of FIG. 12. A modified continuous pattern is illustrated in FIG.
13, the linear nature of the continuum of reinforcing being
substantially disrupted.
A different type of cutting pattern referred to as a discontinuous
pattern is illustrated in FIG. 14. In this instance, the cutting is
accomplished in both longitudinal and transverse directions so that
no continuum of reinforcing remains. It is understood, however,
that the patterns disclosed herein are provided merely by way of
illustration, and that other geometric designs and patterns will
also provide suitable results. The selection of a particular
pattern may depend on artistic preferences, as well as on
structural requirements. Accordingly, the design or pattern which
is selected will be largely a matter of choice to the artisan.
In situ modifications may also be accomplished by embossing-type
techniques in which the application of external forces disrupts the
integrity of the reinforcing layer, or, as previously described, by
chemical modifications which impart differential regions of relaxed
compressive stiffness. The physical modifications may readily be
achieved even though the layer is already embedded in a completed
structure, a partially completed structure, or even in a
prestructure (such as a mat or web embedded in a plastisol) which
is later made an integral part of the final structure; however,
chemical modifications are more difficult to achieve on structures
of this type. All such techniques are included within the
definition of "modifications" as hereinbefore described.
To practice the in situ modification invention on an existing
structure comprising a single reinforcing layer, essentially the
same sequence of events as described earlier for more complex
structures should preferably be employed. First, the instability of
an actual or proposed subfloor should be considered and a desired
target critical buckle strain should be selected for the end
product whereby this critical buckle strain is greater than the
subfloor dimensional change. The basis weight of the existing
structure can then be measured and one or more curves of constant
critical buckle strain can be generated by setting E equal to the
desired critical buckle strain, Q equal to the basis weight and
varying the bending stiffness, Mw, and the relaxed compressive
stiffness, K, as hereinbefore described. The bending stiffness and
the relaxed compressive stiffness of the existing structure can
then be measured.
The measured relaxed compressive stiffness in most instances, and
especially where the existing structure contains a very heavy or
very light reinforcing material, will not be relatable to the curve
corresponding to the target critical buckle strain. However, the
measured bending stiffness can be used in conjunction with the
curve to determine the relaxed compressive stiffness which should
be demonstrated by the desired end product. Thus, if the existing
structure is modified in situ so that the resulting structure has a
relaxed compressive stiffness which approximates that determined
from the curve, the critical buckle strain of this resulting
product should be such that the structure can be used over the
intended subfloor. It has been found that, by applying such
techniques to structures which have unsuitable buckling
characteristics, structures are produced which have extremely good
performance characteristics.
Where a premodified reinforcing layer is used, the procedure will
be slightly different because the layer will not be modified in
situ. The target critical buckle strain will be selected in the
usual manner based on the subfloor dimensional change, and the
basis weight can then be selected, usually in the range of 2-10
pounds per square yard. The values for E and Q are determined based
on the selected materials, and curves of constant critical buckle
strain are constructed as defined above. By constructing a
structure having the selected basis weight from the matrix material
and the reinforcing layer, the bending stiffness of the ultimate
structure can be estimated; however, as indicated below, the
estimated and the actual value will be essentially the same. Once
this value is known, the required relaxed compressive stiffness for
the reinforcing material can be determined from the curve and the
reinforcing layer can be modified as necessary.
Another aspect of the modification procedure is the effect that
modification has on the structural stability of the resulting
structure. It was explained above that a structural stability of
not more than 0.5% was preferred, but that a structural stability
of not more than about 0.1% was most preferred. The reason is that,
if a flooring structure is placed in a doorway, next to a wall, or
next to another piece of loose-lay flooring, it is undesirable for
the structure to shrink or grow because unsightly gaps or buckles
can appear. Neverthelss, if the structure is used as an area
covering, structural stability may be an insignificant factor
because the growth or shrinkage may not be noticeable. Accordingly,
the importance of structural stability will depend on the intended
use of the structure.
Modification can have a significant effect on structural stability.
For example, if a reinforcing layer has a high relaxed compressive
stiffness, it will impart good structural stability to a structure
in which it is used, but it may also impart too low a critical
buckle strain to the structure. Thus, the structure may not be
capable of accommodating subfloor movement. Modification may be
required in order to decrease the relaxed compressive/tensile
stiffness and thus increase the critical buckle strain to a level
in excess of the subfloor dimensional change. In effecting this
increase in critical buckle strain, the environment in which the
flooring structure will be used should be considered. For example,
if an area cover is intended, the modification may be extensive
such that the critical buckle strain is far in excess of the
subfloor dimensional change. Should that occur, the structural
stability of the structure would be quite high so that growth or
shrinkage in excess of 0.5% might occur after installation.
Nevertheless, because of the intended use, this level of
instability would probably be unimportant.
Conversely, if significant growth or shrinkage would be
undesirable, care should be taken in modifying or premodifying the
reinforcing layer. A guide to the artisan in such circumstances is
that the critical buckle strain of the structure in which the
modified layer is used should be only slightly in excess of the
subfloor dimensional change.
Although in situ modification or premodification can cause
substantial increases or reductions of the relaxed compressive
stiffness values, the bending stiffness values for singly
reinforced structures are relatively unaffected in most instances.
Thus, the initially determined bending stiffness may be used to
predict the required relaxed compressive stiffness from the curve.
In those uncommon instances where the bending stiffness shows a
significant change, the necessary relaxed compressive stiffness
value may be determined from the curve using the bending stiffness
value for the modified structure.
Surprisingly, we have also discovered that the present invention is
applicable to a variety of surface coverings such as sheet
flooring, floor tile, wall tile, ceiling tile, and the like,
wherein these surface coverings are adhered to subsurfaces using an
adhesive. The same basic principles which apply to loose-lay
flooring also apply to adhered surface coverings; however, certain
of the definitions previously set forth herein should be expanded
in scope. For example, the subsurface dimensional change as used
hereafter is analogous to the subfloor dimensional change; an
accomodating surface covering is one which will accommodate or
alter its size and shape to match that of an unstable subsurface,
even when it is adhered to the subsurface; etc.
One major modification in terminology concerns the basis weight. In
the case of loose-lay flooring, the flooring is held to the
subsurface by its own weight. In a ceiling tile, however, the tile
would tend to be separated from the ceiling subsurface by its
weight; i.e., gravity would tend to make it fall. This
gravitational pull is offset by the adhesive; thus, for purposes of
this application of the invention, the adhesive strength of an
adhesive should be considered concurrently with the effect of
gravity on the basis weight.
Several possible aspects of this are envisaged. For example, if a
floor covering is considered, the adhesive strength will be
enhanced by the gravitational effect on the covering; if a ceiling
covering is considered, the gravitational effect will detract from
the adhesive strength; and if a wall covering is considered, the
adhesive strength will be relatively unaffected because the
gravitational pull will tend to shear in a direction perpendicular
to the adhesive strength, a situation which may be ignored for
purposes of the present invention.
For convenience, the term "adhered basis weight" will be used
herein to describe the calculated value which is the minimum
strength necessary to adhere a surface covering to a subsurface.
This value is a composite of the adhesive strength of an adhesive
and the actual basis weight of a material but, in actual practice,
the adhered basis weight usually will be due almost entirely to the
adhesive. For example, a typical floor covering may have a basis
weight of two to three pounds per square yard, whereas a typical
adhesive may have an adhesive strength of two to three pounds per
square inch. Accordingly, in many instances the basis weight of the
surface covering will be quite small in comparison to the adhesive
strength. As will be more fully explained below, the adhered basis
weight may be calculated by substituting appropriate values for
relaxed compressive stiffness, bending stiffness, and target
critical buckle strain into the standard equation, or it may be
determined by adding the actual basis weight to, or substracting it
from, the adhesive strength.
Other aspects of adhesives which should be considered are their
interactions with the surface coverings, the subsurfaces, and the
environment in which they are used. Adhesives are often formulated
for specific uses. Therefore, for purposes of the present
invention, it is assumed that the artisan has the skill to select
an adhesive which will show long-term compatibility with the
surface covering, the subsurface, and the environment in which it
is used. It must be emphasized, however, that the accurate
measurement of adhesive strength is very important and, for that
reason, the directions for use provided by the manufacturer of the
adhesive should be precisely followed. Furthermore, the application
should be made in the same way for the test and for field
installation; e.g., if the directions specify that an adhesive
should be applied in a particular manner with a trowel having
specified groove dimensions, the application of the adhesive should
be performed exactly in that manner both for the test and when the
surface covering is installed over a subsurface. If the
installation is not performed in the same way, the predictions
obtained according to the present invention may, in many instances,
be invalid.
An adhesive which is used to adhere two surfaces together has,
after appropriate aging, an initial adherence strength; however, an
adhesive bond usually diminishes in strength under load with time
and, thus, it may eventually rupture. Because of the potential for
a decrease in adhesive strength with time, it has been found that
the adhesive strength which should be used when practicing the
present invention is the adhesive strength under load in a given
environment. This value is defined as the approximate force per
square inch (or per square yard) at which the adhesive will fail.
It preferably is calculated using the bending stiffness, relaxed
compressive stiffness and actual basis weight of a given surface
covering in combination with the "adhered critical buckle strain."
This latter term may be defined as the strain at which a surface
covering that is adhered to a subsurface with a given adhesive will
buckle when compressed in a planar fashion. For the reasons set
forth herein, an adhered critical buckle strain value is usually
applicable only to the surface covering/adhesive/subsurface system
for which it is measured.
Although adhesive strength may be determined in a number of
different ways, the adhesive strength of an adhesive may be
conveniently determined for a given surface covering/subsurface
system by preparing test strips of surface coverings adhered to
subsurface materials which have been conditioned at high relative
humidity and temperature (e.g., 80.degree.-100.degree. F.). When
the adhered systems are subjected to drying conditions at low
relative humidity, a strain is induced in the surface covering
material. The tendency to buckle caused by the compressive strain
which is introduced into the surface covering by subsurface
shrinkage is usually compensated for by the adhesive; however, in
many situations the adhesive eventually fails and the surface
covering buckles. The strain at which this occurs is the adhered
critical buckle strain of the system, and it is a measurable value.
Consequently, it may be used to calculate the adhesive strength as
illustrated in the examples. In appropriate circumstances, the
adhesive strength value may also be projected mathematically or
graphically from other adhesive strength data.
Three types of rupture are possible, namely, rupture of the
adhesive itself, which is a loss of cohesive strength; rupture of
the bond between the adhesive and the test subsurface; and rupture
of the bond between the test surface backing and the adhesive. A
determination of the type of rupture is not a feature of the
present invention; however, it is information which is often useful
to the artisan.
Because, in this aspect of the invention, the surface coverings are
adhered to a subsurface with an adhesive, several of the
calculation limits suggested for loose-lay flooring no longer
apply. For example, floor tile and wall tile normally would not be
rolled, and the sugested bending stiffness upper limit of ca 9
inch-pounds for loose-lay flooring would not be applicable to tile.
Bending stiffness values in excess of 20 inch-pounds have been
measured for flooring tiles; however, by extending the bending
stiffness limits used in the calculations, suitable adhesive
strengths have been determined. From this it will be apparent that
the suggested ranges used in the calculations may be expanded as
necessary to be compatible with the materials under consideration,
and that the extensions of these ranges will not adversely affect
the calculated results.
In practicing the present invention, a number of alternatives are
possible, as suggested by the following hypothetical situations:
(1) a situation where the surface covering is used as is, and the
minimum strength of the adhesive is calculated to ensure firm
adherence; (2) a situation where an adhesive is selected and the
surface covering is then modified to provide at least minimal
performance characteristics in combination with the adhesive; and
(3) a situation where a surface covering is selected and modified,
and the minimum adhesive requirement is determined so that an
appropriate adhesive can be selected. Of course, these situations
are provided by way of illustration, and not by way of
limitation.
In the first-described hypothetical situation, no modification
occurs to the surface covering and it is adhered to the subsurface
by using an adhesive having appropriate strength. In the past, the
selection of an appropriate adhesive was quite difficult to
achieve. As explained above, although an adhesive may initially
perform suitably in a given environment, the adhesive may fail
under load with time. This may be due to a number of factors, such
as changes in the adhesive or adhesive strength caused by the
environment (e.g., dampness), or to the buckling tendencies of
certain surface coverings when placed over unstable subsurfaces.
For these reasons, actual testing of adhered surface
covering/subsurface systems will preferably be conducted as
previously described during which the climate is changed from
humid, summer-like to dry, winter-like conditions. These
determinations can be made even for adhesives which change
substantially with time, provided that the manner of change can be
quantified, and in addition, the present invention will also permit
one skilled in the art to find other alternatives of a suitable
adhesive cannot be found.
To practice this first-described aspect of the invention, it is
first necessary to estimate what subsurface dimensional change is
anticipated, and then to assess the performance characteristics of
the surface covering by measuring its bending stiffness, basis
weight and relaxed tensile stiffness. The critical buckle strain of
the covering is then calculated in the usual manner. If the
critical buckle strain is greater than the subsurface dimensional
change, the situation falls within the scope of the loose-lay
flooring situation previously described; i.e., no adhesive would be
necessary unless the surface covering were to be used as a ceiling
or a wall covering. However, if it is less than the subsurface
dimensional change, the necessary minimum adhesive strength can be
calculated. This may be done by selecting a target critical buckle
strain in excess of the subsurface dimensional change; then, using
this target value and the measured bending stiffness and relaxed
compressive stiffness values, the adhered basis weight of the
structure is calculated.
As applied to this hypothetical situation, the adhered basis weight
is a value which incorporates two parameters, the actual basis
weight of the surface covering and the minimum required adhesive
strength of the adhesive. For example, if the structure is a
ceiling tile, the basis weight of the tile would act counter to the
adhesive; thus, the minimum adhesive strength required for the
adhesive would be the calculated adhered basis weight plus the
actual basis weight. Conversely, if the structure is a floor
structure, the basis weight would act in concert with the adhesive;
thus, the minimum adhesive strength would be the calculated adhered
basis weight less the actual basis weight. As an added
consideration, it should also be recognized that the calculated
adhesive strength is that which is necessary to minimally overcome
the factors which would tend to cause the surface covering to
separate from the subsurface. Accordingly, in this, as well as
other situations, it may be advisable to select an adhesive having
a greater-than-required adhesive strength so as to overcome
unforeseen factors such as detrimental environmental effects, loss
of strength due to plasticizer migration, and the like.
In the second hypothetical situation, the surface covering and the
adhesive are selected, and the adhesive strength is determined as
previously described. The bending stiffness, basis weight and
relaxed compressive stiffness are measured for the unmodified
surface covering, and an appropriate target critical buckle strain,
in excess of the subsurface dimensional change, is selected. The
adhered basis weight is determined depending on the intended use by
combining the basis weight and the strength of the adhesive in an
appropriate manner, as referred to above. The desired relaxed
compressive stiffness can then be calculated using these data. From
this information, the surface covering is modified in situ as
previously described to give, ideally, a structure having the
calculated relaxed compressive stiffness. Of course, safety factors
may be included in these calculations, as previously suggested.
The third hypothetical situation set forth above relates to a
comparable situation, except that the modification is achieved
first and then the minimum adhesive strength is determined by
making the necessary calculations.
The manner in which the in situ modifications may be achieved was
referred to earlier; however, it is emphasized that modifications
may be performed in a variety of ways. For example, modification
may be performed on intact coverings or on partially constructed
coverings which are later converted to surface coverings having
defined characteristics. Based on practical performance criteria,
it appears to be preferred to modify the structure and then apply
the back coat because the back coat usually seals the structure.
This is especially true where seepage into an open structure might
occur. Of course, the required degree of modification may also be
determined by estimating the characteristics of individual
components or combinations of individual components, or it may be
achieved by evaluating composite structures and then
back-calculating the characteristics which will be needed in future
structures.
The present invention has the advantage of providing a relatively
reliable way to predict the characteristics of loose-lay flooring
structures and adhered surface coverings, and it also provides
guidelines by which the various parameters may be modified so as to
predictably alter the characteristics of such structures and
surface coverings.
The following examples will be illustrative to demonstrate, but not
to limit, the advantages of the present invention.
EXAMPLES
Structures Comprising At Least Two Reinforcing Layers
Example 1
This example illustrates a process for designing a loose-lay
flooring structure for use over a subfloor having a subfloor
dimensional change of 0.001. The target critical buckle strain for
the desired flooring structure is selected to be 0.0016 and the
basis weight of the flooring structure is selected to be 4.6 pounds
per square yard. Accordingly, for purposes of calculation, E is
assigned the value of the target critical buckle strain (0.0016)
and Q is assigned the basis weight (4.6 pounds square yards). By
using the assigned values in the equations set forth in the
specification, varying the bending resistance, C, such that the
bending stiffness, M.sub.w, is varied between 0 and 9 inch-pounds,
varying the relaxed compressive stiffness, K, from 0 to 10,000
pounds per inch of width, and solving the resulting equations, a
series of points of constant critical buckle strain corresponding
to the varied values of M.sub.w and K are obtained (FIG. 2). From
the curve, the relaxed compressive stiffness corresponding to the
bending stiffness value of 0.1 inch-pound is 200 pounds per inch of
width (ppiow) and that corresponding to 9 inch-pounds is 930
ppiow.
A reinforcing material from International Paper Co., Identification
No. IP042081-2, is selected for evaluation. This material is a
nonwoven mat comprised of 50% glass and 50% polyester fiber and
having a weight of 0.524 ounce per square yard. The relaxed tensile
stiffness of this material is measured as follows: A sample 2
inches wide and 12 inches in length is cut and clamped in the jaws
of an Instron Tensile Tester such that the jaws are separated by a
distance of 8 inches. The jaws are then moved apart at a rate of
0.02 inch per minute until the sample has elongated by 0.3%; i.e.,
the strain on the sample is 0.003. Jaw movement is stopped and the
load on the sample is monitored for 90 minutes. The load decay
curve is then extrapolated to 1,000 hours by means well known in
the art, giving a relaxed tensile stiffness of 227 ppiow.
A PVC plastisol matrix material is prepared having the following
formula:
______________________________________ Component Parts by Weight
______________________________________ PVC Homopolymer resin (MWt =
106,000) 100 Primary plasticizer 45 Secondary plasticizer 15
Organotin stabilizer 2 Silica gel thickener 1
______________________________________
The relaxed tensile stiffness value measured using the Instron
Tensile Tester is 74 ppiow. Therefore, the ratio of the ppiow
values for the two reinforcing layers to that of the matrix
material is 454:74 or 6.1:1.
The sum of the relaxed compressive stiffness values for the two
layers of reinforcing material and the matrix material is 528 ppiow
and, from the curve, the bending stiffness corresponding to this
ppiow value is 1.65 inch-pounds. Accordingly, a flooring structure
having a basis weight of 4.6 pounds per square yard should have a
critical buckle strain greater than 0.001 when constructed from the
above materials such that the bending stiffness is 1.65
inch-pounds, one reinforcing layer being disposed above the neutral
bending plane of the resulting floor structure and the other
reinforcing layer being disposed below said neutral bending
plane.
To verify this, a flooring structure is constructed for testing
using a high velocity air impingement oven and a reverse roll
coater. A layer of vinyl matrix material 0.01 inch thick is applied
to a release carrier. A layer of the reinforcing material is laid
on the matrix material and allowed to saturate, after which the
composite material is gelled in an oven at 275.degree. F. for two
minutes. After cooling, a second layer of matrix material 0.07 inch
thick is applied to the surface of the gelled sample and this
composite structure is gelled in the oven at 275.degree. F. for two
minutes. A third layer of matrix material 0.01 inch thick is
applied to the gelled substrate and a second layer of reinforcing
material is placed in the wet plastisol and allowed to saturate.
After saturation of the mat, the composite structure is gelled in
an oven at 275.degree. F. for two minutes and then fused at
380.degree. F. for 2.5 minutes. After cooling, the fused composite
structure is pressed between platens having a temperature of
320.degree. F. to consolidate the gauge to 0.08 inch. Pressure is
maintained for 30 seconds to give a material with a basis weight of
4.58 pounds per square yard and bending stiffness, measured
according to ANSI/ASTM D 747, of 1.65 inch-pounds.
To verify its suitability, a sample is placed in an environmental
test chamber on a piece of particle board having a subfloor
dimensional change of 0.001. The particleboard is at its maximum
expanded position and the sample is affixed thereto such that, when
the sample-on-subfloor combination is subjected to a 1,000-hour
simulated, summer-winter seasonal change, the floor sample is
subjected to the strain imposed by the movement of the subfloor.
The ability of the floor structure to accommodate the imposed
strain without buckling demonstrates that it has a critical buckle
strain in excess of 0.001. Verification may also be achieved by
using the measured basis weight, bending stiffness, and relaxed
compressive stiffness values of the resulting floor structure and
then calculating the critical buckle strain mathematically.
EXAMPLE 2
This example illustrates the construction of a flooring structure
whereby an intermediate test structure is employed.
A foamable polyvinyl chloride plastisol matrix material having the
following composition and a viscosity of 10,000 cps is prepared by
means well known in the art.
______________________________________ Parts by Ingredient Weight
______________________________________ Dispersion Grade 36.00 PVC
Homopolymer Resin, MWt 105,000 Dispersion Grade 36.00 PVC
Homopolymer Resin, MWt 80,400 Blending Grade 28.00 PVC Homopolymer
Resin MWt 81,100 Epoxy-type plasticizer 1.00 Dioctyl phthalate
50.00 Blowing agent activator 0.20 Stabilizer 0.15 Azodicarbonamide
blowing agent 0.66 Feldspar filler 18.00
______________________________________
The following structure is prepared for use over a subfloor having
an expected subfloor dimensional change of 0.0015. The target
critical buckle strain for this floor structure is selected to be
0.0018.
The expected subfloor dimensional change of 0.0015 indicates that
the subfloor is of medium stability. Therefore, a basis weight of
4.1 pounds per square yard is selected for the sample. Using these
data, a contour plot is prepared as set forth in Example 1 wherein
E is 0.0018, Q is 4.1 pounds per square yard, and M.sub.w and K are
varied between 0 and 9 inch-pounds and 0 and 10,000 ppiow,
respectively. From the plot obtained (FIG. 3), the range of relaxed
compressive stiffness values corresponding to bending stiffness
values of 0.1 and 9 inch-pounds is determined to be 150 to 750
pounds per inch of width.
A 50% glass fiber/50% polyester fiber reinforcing material having a
basis weight of 0.524 ounce per square yard is selected, as is the
matrix material described above. The relaxed tensile stiffness
value for the foamed matrix is 42 pounds per inch of width whereas
the value for the reinforcing material is 227 pounds per inch of
width. Accordingly, because two reinforcing layers are used, the
total of the relaxed tensile stiffness values is calculated to be
496 pounds per inch of width, as follows:
______________________________________ Relaxed Tensile Stiffness
Component (pounds per inch of width)
______________________________________ Matrix material 42 First
reinforcing layer (R.sub.1) 227 Second reinforcing layer (R.sub.2)
227 496 ______________________________________
This value is within the range of 150 to 750 pounds per inch of
width determined from the curve. Furthermore, the sum of 454 pounds
per inch of width for the two reinforcements is approximately 10
times greater than the value of 42 measured for the matrix
material, which is a desirable relationship.
The actual relaxed compressive stiffness of the composite structure
is determined experimentally by constructing a test structure
according to the following procedure. A layer of matrix material
0.027 inch thick is coated on a release carrier and one layer of
the reinforcing material is placed in an approximately planar
fashion on top of the wet surface. The reinforcing layer is allowed
to saturate and the material is gelled at 280.degree. F. for 1.5
minutes. After cooling, a second layer of plastisol matrix material
essentially comprising the central portion of the eventual
composite structure is coated at a thickness of 0.029 inch on the
gelled substrate. A second layer of reinforcing material is placed
in the wet plastisol and allowed to saturate, after which the
material is gelled at 280.degree. F. for 1.5 minutes. After the
composite has cooled, a third coating of plastisol 0.02 inch thick
is placed on the gelled surface. This composite is gelled at
280.degree. F. for 1.5 minutes to give a structure having a
thickness of 0.076 inch. When fused at 420.degree. F., the blowing
agent is activated and the structure is expanded to a final
thickness of 0.117 inch. This structure is illustrated in FIG. 4 in
which R.sub.1 and R.sub.2 are the reinforcing layers and S.sub.1
and S.sub.2 are the lower and upper surfaces, respectively. The
relaxed compressive stiffness value of this structure is measured
to be 538 pounds per inch of width as compared to the predicted
relaxed tensile stiffness value of 496 pounds per inch of
width.
Referring again to FIG. 3, the relaxed compressive stiffness value
of 538 pounds per inch of width indicates that the bending
stiffness of the finally constructed sample should be 3.3
inch-pounds. However, the bending stiffness of the test structure
is measured to be 0.81 inch-pounds. This value is substantially
below the desired value; therefore, a second composite is
constructed. In this sample, represented by FIG. 5, the reinforcing
layers are separated by a greater distance in order to increase the
bending stiffness.
The procedure followed is essentially the same as that set forth
above. A layer of matrix material is coated to a thickness of 0.01
inch on a release carrier and one layer of reinforcing material,
R.sub.1, is placed in an approximately planar fashion on top of the
coated surface. When saturation is complete, the material is gelled
at 280.degree. F. for 1 minute. After cooling, a layer of matrix
material 0.050 inch thick is coated on the gelled material and
gelled by heating at 280.degree. F. for 2 minutes. A third coating
of plastisol 0.015 inch thick is then placed on the gelled surface
and a second layer of reinforcing material, R.sub.2, is placed in
the wet plastisol. After saturation is complete, the material is
gelled to give a composite structure having a thickness of 0.075
inch. The resulting structure is then fused at 420.degree. F. to
activate the blowing agent and expand the final structure to a
thickness between S.sub.1 and S.sub.2 of 0.117 inch. The bending
stiffness of this structure is measured to be 3.29 inch-pounds.
As noted above, this structure is intended for use over the
subfloor having an expected subfloor dimensional change of 0.0015.
To verify its suitability, a sample is placed on such a subfloor at
its maximum expanded position and affixed to it. When the floor
sample-on-subfloor combination is subjected to a simulated,
1000-hour, summer-winter seasonal change as set forth in Example 1,
no buckling occurs, thus indicating that it has a critical buckle
strain of greater than 0.0015.
The structural stability of this floor structure is determined by
measuring the length of a sample, heating it at 180.degree. F. for
six hours, reconditioning it at 73.4.degree. F. and 50% relative
humidity for one hour, and then remeasuring the length. The percent
change in length (the structure stability) is found to be -0.02%.
This is a desirable value which indicates that the floor structure
is dimensionally stable.
Example 3
The following additional structures are prepared to illustrate the
variations in bending stiffness caused by changing the position of
the reinforcing materials within the matrix. The structure of FIG.
6 is prepared in a single step process essentially as described in
Example 2 except that a single layer of plastisol 0.075 inch thick
is placed on the release carrier. Upon expansion, a thickness of
0.118 inch between surfaces S.sub.1 and S.sub.2 is obtained, and a
bending stiffness of 0.20 inch-pounds is measured for this
structure.
A structure similar to that of FIG. 5 is prepared except that a
Manville glass fiber mat having a basis weight of 20 grams per
square meter (ca. 0.6 ounce per square yard) is employed for
R.sub.1 and R.sub.2. When expanded to a thickness of 0.118, the
structure has a bending stiffness of 5.66 inch-pounds.
The structure of FIG. 7 is prepared in the manner used to prepare
the structure of FIG. 5 (Example 2), except that the material is
not heated to expand the plastisol. The resulting unfoamed matrix
has a thickness of 0.077 inch and the separation between R.sub.1
and R.sub.2 is 0.054 inch. The bending stiffness of this structure
is 1.49 inch-pounds, which is substantially less than the value of
3.29 inch-pounds obtained for the structure of FIG. 5.
When the results obtained for these structures are compared,
several generalities can be made. First, extremely low bending
stiffness values are obtained in the absence of the two reinforcing
layers. Secondly, comparing FIGS. 4 and 5, bending stiffness is
increased when the distance between the reinforcing layers R.sub.1
and R.sub.2 is increased. The same result is also obtained when a
relatively lighter weight reinforcing material is replaced by a
heavier material. Finally, referring to FIGS. 5 and 7, bending
stiffness may also be varied by controlling the amount of expansion
of the matrix material.
Example 4
A structure similar to that of FIG. 5 of Example 2 is prepared, the
difference being that a clear PVC plastisol wear layer, W, is added
to the surface of the structure. This structure is illustrated in
FIG. 8 and is also designed for use over a subfloor having a
subfloor dimensional change of 0.0015; therefore, a target critical
buckle strain of 0.0018 is also chosen for this sample. The basis
weight for the sample, due to the increase in weight attributable
to the wear layer, is 4.7 pounds per square yard.
The contour curve generated for these parameters as set forth in
Example 1 is illustrated in FIG. 9. From this curve, it is seen
that a range of relaxed compressive stiffness values of 160 to 790
is possible over a bending stiffness range of 0.1 to 9 inch-pounds.
Using the relaxed tensile stiffness value of 227 for the
reinforcing layer, 42 for the matrix material and a measured value
of 10 for the 0.01-inch thick wear layer, the sum of the relaxed
tensile stiffness values for the proposed structure is predicted to
be 506 pounds per inch of width. A test structure is constructed
essentially as set forth in Example 2, except that the wear layer
is included. The 1,000-hour relaxed compressive stiffness value for
this structure is 572 pounds per inch of width. The curve of FIG. 9
indicates that the bending stiffness value corresponding to this
relaxed compressive stiffness value is 3.4 inch-pounds. This value
is comparable to that obtained for the structure illustrated by
FIG. 5; therefore, the structure of FIG. 8 is prepared in which
reinforcing layer R.sub.1 is disposed approximately 0.01 inch above
surface S.sub.1 and reinforcing layer R.sub.2 is disposed 0.01
below surface S.sub.2. The bending stiffness for this structure is
shown to be 3.40 inch-pounds. When this structure is tested as
described in Example 1, no buckling occurs, indicating that it is
suitable for use over a subfloor having a subfloor dimensional
change of 0.0015. Furthermore, the structural stability, measured
as set forth in Example 2, is -0.06%, indicating that the structure
is dimensionally stable.
Example 5
A sample identical to that prepared in Example 4 is constructed
except that the side containing the wear layer is mechanically
embossed to a depth of 0.005 inch. The relaxed compressive
stiffness measured for this structure is 546 pounds per inch of
width as compared to 572 pounds per inch of width for the
unembossed structure. No buckling occurs when this structure is
tested in the usual manner, thus indicating that it is also
suitable for use over a subfloor having an expected subfloor
dimensional change of 0.0015. The structural stability, determined
as previously described, is -0.04%.
Example 6
This example illustrates the use of reinforcing materials having a
dissolvable binder whereby the character of the reinforcing
material changes in situ.
A flooring structure for use over a subfloor having a subfloor
dimensional change of 0.002 is desired. Accordingly, a target
critical buckle strain of 0.0026 is selected, as is a basis weight
for the flooring structure of 6.0 pounds per square yard. Using
these values for E and Q, respectively, and varying the relaxed
compressive stiffness K between 0 and 10,000 ppiow and the bending
stiffness M.sub.w between 0 and 9 inch-pounds, a countour curve is
constructed as previously set forth. From the curve (not shown),
the range of applicable relaxed compressive stiffness values is
seen to be 135 to 600 ppiow. The matrix material used in Example 2,
but containing in addition 34 parts by weight of butyl benzyl
phthalate plastisizer, and having a relaxed tensile stiffness of 30
pounds per inch of width is selected for use with reinforcing
material SAF 50/2 obtained from Manville Corporation. The
reinforcing material has a measured relaxed tensile stiffness of
352 ppiow; thus, the expected relaxed compressive stiffness of a
structure comprising two such reinforcing layers and the indicated
matrix material should be 734 ppiow. It is known, however, that the
reinforcing material will lose a portion of its stiffness
contribution when placed in a vinyl matrix, apparently due to
softening of the reinforcing material's binder in the presence of
the plastisizer present in the plastisol.
A test structure comprising two layers of reinforcing material in
the matrix material is constructed as follows: A layer of the
plastisol described above, containing butyl benzyl phthalate to
facilitate softening of the binder, is coated on a chrome steel
plate at a thickness of 0.015 inch and one layer of SAF 50/2
reinforcing material is placed in the wet plastisol. When the
reinforcement is saturated, the material is gelled at 400.degree.
F. for one minute and cooled. Thereafter, a layer of plastisol
approximately 0.045 inch thick is placed on the gelled material and
gelled by heating at 400.degree. F. for 1.5 minutes. A third layer
of plastisol 0.015 inch thick is applied to the gelled surface and
a second layer of SAF 50/2 reinforcement is placed in the wet
plastisol and allowed to saturate. The sample is then heated at
420.degree. F. for 3.5 minutes to fuse the product. The resulting
structure has a thickness of 0.130 inch and a measured basis weight
of 6.0 pounds per square yard. The relaxed compressive stiffness
value for this structure is measured to be 567 pounds per inch of
width, which is significantly lower than the sum estimated above
for this structure. From the curve, the bending stiffness
corresponding to the relaxed compressive stiffness value of 567
pounds per inch of width is 7.5 inch-pounds. The measured bending
stiffness for the structure is determined to be 7.47
inch-pounds.
The above values are within the expected range of values.
Accordingly, a sample is subjected to a 1,000-hour summer-winter
heating season test, as previously illustrated, in order to
determine its suitability. No buckling is observed; therefore, the
sample is suitable for use over a subfloor having a subfloor
dimensional change of 0.002. The structural stability is determined
to be +0.06%.
Example 7
This example illustrates that reinforcing material disposed within
a flooring structure may be modified by external means such that
the relaxed compressive stiffness of the reinforcing material and
hence the relaxed compressive stiffness and the bending stiffness
of the flooring structure are reduced.
A flooring structure is desired for use over a subfloor having a
subfloor dimensional change of 0.001; therefore, a target critical
buckle strain of 0.0015 is selected, as is a basis weight of 3.0
pounds per square yard. A contour curve is plotted in the usual
manner and, from the curve (FIG. 10), the range of applicable
relaxed compressive stiffness values is found to be 155 to 770
ppiow.
The following materials are selected to construct the flooring
structure.
______________________________________ Relaxed Tensile Basis
Stiffness Weight Component (ppiow) (lbs/sq. yd.)
______________________________________ Manville Reinforcement 512
0.04 SH-20/1 Manville Reinforcement 761 0.11 SH-50/10 PVC Plastisol
30 2.85 ______________________________________
Using these materials, a flooring structure is constructed with the
heavier reinforcement near the backing. A coating of plastisol
0.015 inch thick is placed on a suitable release carrier and a
layer of SH-50/10 reinforcement is placed in the plastisol and
allowed to saturate. After saturation of this reinforcement, the
material is gelled for one minute at 280.degree. F. On the gelled
substrate is placed a second coating of the same plastisol
composition at a thickness of 0.032 inch. A layer of SH-20/1
reinforcement is placed on the top surface of the plastisol,
allowed to saturate, and then fused at 425.degree. F. to expand the
structure to a final thickness of 0.115 inch. Upon cooling and
separating the structure from the release carrier, a basis weight
of 3.0 pounds per square yard is obtained. The structure
demonstrates a relaxed compressive stiffness of 1303 pounds per
inch of width and a bending stiffness of 5.50 inch-pounds. From the
above cited range, it is obvious that the relaxed compressive
stiffness of 1303 ppiow is too high, and that this structure will
not exhibit the target critical buckle strain.
To reduce the relaxed compressive stiffness of this flooring
structure, a sample is inverted and placed in a press such that the
surface adjacent the SH-50/10 reinforcement is on top. Over this
structure is placed a section of plastic material having a
prismatic textured face with a pattern depth of approximately 0.05
inch. Pressure is applied to the flooring structure and the plastic
such that the prismatic surface is pressed into the flooring
structure to the depth of the prism pattern, thereby disrupting the
character of the SH-50/10 reinforcing layer. The relaxed
compressive stiffness of the modified sample of flooring structure
is 547 pounds per inch of width and the bending stiffness is 3.21
inch-pounds. The critical buckle strain for this structure is seen
to be 0.0015 from the curve, thus indicating that it is suitable
for use over a subfloor having a subfloor dimensional change of
0.001. Furthermore, the structural stability is determined to be
-0.06%, indicating that the structure is dimensionally stable.
Example 8
This example illustrates the construction of a flooring structure
comprising a wear layer, a decorative layer, a foamed plastisol,
and reinforcing materials.
A particleboard subflooring having a subfloor dimensional change of
0.0025 is selected for use. Therefore, a target critical buckle
strain of 0.0036 is selected for the flooring structure, as is a
basis weight of 6.9 pounds per square yard. A contour curve is
constructed in the usual manner and, from the curve (FIG. 11), the
applicable compressive stiffness range is seen to be 90 to 420
ppiow.
The following components are used to construct this flooring
structure.
______________________________________ Relaxed Tensile Basis
Component Stiffness Weight Thickness Component (ppiow) (lbs/sq.
yd.) (inch) ______________________________________ PVC wear layer
10 0.56 0.01 Decorative layer 36 3.27 0.052 PVC foam layer 35 3.00
0.10 International Paper 227 0.03275 0.007 Reinforcement IP042081-2
______________________________________
The foamable plastisol composition of Example 2 is coated on a
release carrier at a thickness of 0.01 inch and the non-woven
reinforcing layer from Example 1 is placed on the surface of the
plastisol and allowed to saturate. The material is then gelled at
280.degree. F. for one minute and cooled to room temperature. A
second layer of plastisol 0.035 inch thick is applied to the
surface of the gelled layer, heated at 425.degree. F. to expand the
foamable plastisol to a thickness of 0.10 inch and cooled to room
temperature. The basis weight of this composite material is 3.0
pounds per square yard.
Onto the cool structure is placed a coating of a urethane adhesive
composition 0.002 inch thick and the coating is then heated at
250.degree. F. to evaporate the solvent. The urethane adhesive
comprises 20% by weight urethane block copolymer, 80% by weight
methyl ethyl ketone and 20% by weight silica gel thickener.
A decorative binder/chip layer is prepared by dicing a filled PVC
composition into fine particles and mixing the resulting chips with
a binder composition to form a particulate material suitable for
deposition using a stencil. The chip composition is as follows:
______________________________________ Component Parts by Weight
______________________________________ Extrusion grade PVC
homopolymer 100 Primary phthalate plasticizer 32.5 Epoxy-type
plasticizer 7.5 Zinc stearate 0.7 Limestone filler 328
______________________________________
The binder/chip composition is prepared by blending 1,225 parts by
weight of the chip composition with 250 parts of
solution-polymerized PVC resin, 123 parts primary plasticizer, 79.5
parts epoxy-type plasticizer and 4.5 parts of stabilizer. Mixing is
accomplished using a Hobart Mixer with a wire whip attachment, the
mixing time being approximately five minutes.
The previously prepared 0.10-inch thick foam sample on release
carrier is perforated with a pin roll which punches holes through
the entire structure at a spacing of approximately 1/8 inch. The
decorative binder/chip composition is stenciled onto the perforated
foam surface forming a layer of approximately 0.085 inch thick, the
basis weight of this layer being 3.27 pounds per square yard. A
second reinforcing layer identical to that used above is placed on
the surface of the stenciled layer and the preformed PVC wear layer
on a release carrier comprising an adhesive is placed on the chip
layer such that the adhesive layer is in contact with the upper
reinforcing layer. The entire structure is placed in a flat press
with the upper platen heated to 295.degree. F. and the lower platen
being water cooled. The press is closed, exerting a mimimum
pressure for eight seconds in order to consolidate the decorative
stenciled layer from a thickness of 0.085 inch to a thickness of
0.052 inch. The press is then opened and an embossing plate
preheated to 275.degree. F. is inserted into the press. The press
is closed for eight seconds, applying sufficient pressure to cause
embossing of the structure to a depth of 0.016 inch. The composite
sample is then removed from the press and cooled to room
temperature, after which the top and bottom carrier layers are
removed.
The relaxed compressive stiffness of this composite structure is
measured to be 358 pounds per inch of width. For this measured
value a bending stiffness of 5.5 is seen to be necessary by
reference to the contour curve. The value measure for this
structure is found to be 5.50 inch pounds; thus, no modification of
the structure is required.
To evaluate the sample it is placed in an environmental test
chamber for 1,000 hours where it is subjected to a summer-winter
environmental change as described above. No buckling is observed;
therefore, the test result indicates that the structure is suitable
for use over a subfloor having a subfloor dimensional change of
0.0025.
Structures Comprising a Single Reinforcing Layer
The following examples illustrate modification techniques by which
singly reinforced flooring structures may be modified in situ.
A foam structure comprising a single reinforcing layer and having a
total thickness of 0.096 inch is prepared using the foamable
plastisol described in Example 2. A layer of plastisol
approximately 15 mils thick is applied to a release carrier and a
non-woven glass fiber mat having a basis weight of 35 grams per
square meter (Identification No. SH 35/6 from Manville Corporation)
is embedded in the wet plastisol. The plastisol containing the
embedded glass mat is then gelled at 280.degree. F. for one minute.
Upon cooling, a layer of plastisol 32 mils thick is placed on the
gelled surface and the composite structure is fused at 430.degree.
F. for 2.5 minutes. The resulting structure has a basis weight of
2.8 pounds per square yard. The bending stiffness is measured to be
0.330 inch-pounds and the relaxed compressive stiffness is measured
to be 1074 ppiow, both measurements being made as hereinbefore
described.
To illustrate the applicability of this process, a curve is
generated by arbitrarily selecting a subfloor dimensional change of
0.0013 and then selecting a target critical buckle strain of
0.0015. By assigning E the value 0.0015 and Q the value of 2.8
pounds per square yard, and then varying the bending stiffness, Mw,
between 0 and 9 inch-pounds while varying the relaxed compressive
stiffness, K, between 0 and 10,000 ppiow, a curve of constant
critical buckle strain is generated (FIG. 15). From the curve, it
is seen that for a structure having a bending stiffness of 0.330
inch-pounds, a relaxed compressive stiffness of 245 ppiow would be
required. Thus, if the measured relaxed compressive stiffness
values are greater than 245 ppiow, the modified structures would
not meet the target critical buckle strains whereas, if the
measured relaxed compressive stiffness values are equal to or less
than this figure, acceptable critical buckle strain values would be
obtained.
The utility of this approach may be seen from Examples 9-13 in
which the above control sample is modified in various ways. A
comparison of the modified ppiow values indicates whether the
modification would be sufficient to give a product with a suitable
critical buckle strain.
Example 9
This example illustrates a series of in situ modifications
performed in a continuous pattern according to the design
illustrated in FIG. 12. In all instances, the squares are cut in
the indicated dimensions and the mortar line (the distance between
the cut squares) is formed in the indicated dimension. The column
entitled Square Area indicates the percentage of the total area
which has been isolated from the continuum of reinforcing by
cutting. The measured bending stiffness values and relaxed
compressive stiffness values are indicated for each modification.
The acceptability of each modification provide a suitable critical
buckle strain is also indicated.
It is noted that regardless of the severity of the modification,
the bending stiffness values tend to vary only slightly from the
originally measured value. This is true in virtually all instances
and indicates that the target relaxed compressive stiffness value
which is originally estimated from the curve using the measured
bending stiffness value will also remain essentially the same.
__________________________________________________________________________
Dimension Dimension Square Measured Relaxed Modification Bending of
Square of Mortar Area Compressive Stiffness y = yes Stiffness
Sample No. (inch) (inch) % (Lbs/in of width) n = no (In.-Lbs.)
__________________________________________________________________________
A 1/2 1/2 25 569 n .301 B 1/4 45 401 n .303 C 1/8 64 168 y .288 D
1/16 81 117 y .272 E 3/4 3/4 27.5 579 n .324 F 1/2 36 511 n .348 G
1/4 56 295 n .329 H 1/8 74 202 y .313 I 1 1 25 540 n .342 J 3/4 36
545 n .343 K 1/2 49 378 n .322 L 1/4 64 312 n .327 M 1/8 81 200 y
.313
__________________________________________________________________________
Example 10
This example illustrates a series of discontinuous pattern examples
cut as illustrated in FIG. 14.
______________________________________ Measured Distance Relaxed
Separating Compressive Acceptable Lines of Stiffness Modification
Bending Sample Cutting (Lbs/in of y = yes Stiffness No. (inch)
width) n = no (In.-Lbs.) ______________________________________ A
1/4 64 y .298 B 1/2 153 y .326 C 3/4 202 y .318 D 1 202 y .330
______________________________________
Example 11
This example illustrates the mechanical punching of a sample to
internally disrupt the reinforcing layer. A wire grid consisting of
wire having a diameter of 0.025 inch, the wires being disposed 1/2
inch apart, is pressed into the sample using a flat press and
sufficient pressure to cause disruption of the reinforcing layer.
Disruption is verified by taking a portion of the sample and
dissolving the plastic material in tetrahydrofuran. Although the
reinforcing layer is not completely separated into square elements,
only a few fibers remain to connect the elements together. The
relaxed compressive stiffness is 214 pounds per inch of width.
These results indicate that the sample is not as significantly
modified as a hand cut example (such as Example 10), but it is
modified sufficiently to be acceptable.
Example 12
This example illustrates external mechanical modification using the
prismatic surface described in Example 7. This surface is pressed
into the sample to a depth of about 0.030" and a piece of the
sample is dissolved in tetrahydrofuran to remove the polymeric
material. Examination of the remaining glass fabric shows that it
has been deformed or dented, but not cut, by the external
modification. The relaxed compressive stiffness is found to be 524
ppiow which indicates that the sample will not have a suitable
critical buckle strain. When compared to the unmodified control
structure, a drop in the relaxed compressive stiffness of the
sample of about 50% is noted. This illustrates how samples may be
internally modified by compression without causing actual
separation of the reinforcing layers. This observation has
significance because it indicates that encapsulated glass
structures may be physically modified in situ without adversely
affecting the structural integrity of a product.
Example 13
This example illustrates a modified continuous pattern prepared
according to the design illustrated in FIG. 13. The pattern is
symmetrical and distances C--C, D--D and E--E are all 1/4 inch. The
relaxed compressive stiffness measured for this structure is 287
ppiow, indicating that its critical buckle strain has been
dramatically improved, although it has not been improved enough for
this structure to meet the target critical buckle strain of 0.0015.
Nevertheless, this result is quite favorable, especially when
compared to the results obtained for structures which have been
modified by other means.
As an example, the isolated square area of this sample is 41%. The
isolated square area of a sample cut according to example 9B is
45%, yet the relaxed compressive stiffness values are 401 ppiow for
that sample and 287 ppiow for the present sample. Thus, in this
instance, the modified continuous pattern is superior.
Structures Which are Adhered Using an Adhesive
Example 14
This example illustrates a process for adhering a surface covering
to a subsurface wherein the esurface covering is unmodified and the
adhesive is evaluated according to the present invention to ensure
that it has adequate adhesive strength.
Four plastisol compositions were prepared having the formulations
listed below. The molecular weights of the resins are determinable
from the specific viscosities (in parentheses) which were measured
according to ASTM D-1243.
______________________________________ Parts by Ingredient Weight
______________________________________ Plastisol A PVC homopolymer
resin, dispersion grade (0.38) 66 PVC homopolymer resin, extender
grade (0.35) 34 Monomeric plasticizer 62 Azobisdicarbonamide
blowing agent 0.8 Blowing agent activator 0.6 Stabilizer 0.7
Limestone filler 50 Plastisol B PVC homopolymer resin, dispersion
grade (0.38) 66 PVC homopolymer resin, extender grade (0.35) 34
Monomeric plasticizer 62 Azobisdicarbonamide blowing agent 1.5
Blowing agent activator 0.6 Stabilizer 0.7 Limestone filler 50
Plastisol C PVC homopolymer resin, dispersion grade (0.58) 60 PVC
homopolymer resin, extender grade (0.35) 40 Monomeric plasticizer
62 Stabilizer 1.5 Pigment 3 Limestone filler 50 Plastisol D PVC
homopolymer resin, dispersion grade (0.60) 30 PVC homopolymer
resin, dispersion grade (0.42) 70 Monomeric plasticizer 45
Viscosity diluent 5 Stabilizer 1
______________________________________
A surface covering was prepared as follows: A roll of #F7155 glass
reinforcing material (mat), commercially available from Manville
Corporation and having a basis weight of 55 grams per square meter,
was used as a reinforcing layer. The glass reinforcing mat was
passed through a knife coater where plastisol A was deposited so as
to saturate the mat. The knife coater was adjusted to provide a
gelled saturated glass layer having a thickness of 0.018 inch. The
structure was passed around a heated drum with the plastisol-coated
surface contacting the drum face. As a result of this procedure,
which was conducted at a drum temperature of 285.degree. F., the
plastisol was gelled.
A layer of plastisol B 0.005 inch thick was applied to the smooth
drum-finished surface by reverse roll coating and the coated mat
was gelled by heating in an oven at 280.degree. F. The structure
was then fed through a rotogravure printer to deposit a decorative
image on the surface of the gelled plastisol B.
After the decorative printing step, a clear layer of plastisol D
was applied over the printed surface to provide a protective
surface 0.01-inch thick. The coated structure was passed through a
fusion oven preheated to 380.degree. F. to: (1) fuse the plastisol
layer D, (2) expand the gelled layer of foamable plastisol B to
about three times its applied thickness, and (3) expand the gelled,
saturated glass layer to about twice its gelled thickness. After
exiting from the oven, the fused structure was mechanically
embossed to create depressed areas of about 0.01 inch in depth into
the decorated surface covering. The structure was then completed by
applying about 0.008 inch of plastisol C to the back of the
embossed surface covering and fusing the plastisol around a drum
heated at 325.degree. F. for approximately 15 to 20 seconds.
Finally, the completed structure was cooled and fed to a windup
device. The measured thicknesses of the various layers of the final
structure were as follows:
______________________________________ Layer Thickness (inch)
______________________________________ wear surface - plastisol D
0.0104 foam formulation - plastisol B 0.0188 foam formulation -
plastisol A 0.0305 back coat - plastisol formulation C 0.0088 Total
thickness 0.0685 ______________________________________
The characteristics of this surface covering, measured as
previously described, were as follows:
______________________________________ relaxed compressive
stiffness 1274 ppiow bending stiffness 0.52 inch-pounds basis
weight 2.7 pounds per sq. yd.
______________________________________
Using these data, the critical buckle strain expected for this
flooring was calculated to be 0.0005.
This material was intended for installation over a subsurface
having a subsurface dimensional change of 0.003; accordingly, a
target critical buckle strain of 0.0035 was selected for use in the
calculation. For this purpose, the computer program previously used
was modified to calculate the adhered basis weight, the general
modification being illustrated in FIGS. 16A and 16B. In addition,
the upper basis weight limit was extended to about 150 pounds per
square yard from the value of 10 pounds per square yard previously
used for calculating loose-lay flooring parameters. The measured
values for the relaxed compressive stiffness and the bending
stiffness, and the desired target critical buckle strain of 0.0035
were substituted into the equation and the adhered basis weight was
calculated to be 145.4 pounds per square yard.
Because this material was intended for use as a floor covering, the
actual basis weight of the material (2.7 pounds per square yard)
would assist in holding the surface covering to the subsurface.
Accordingly, the minimum adhesive force necessary to adhere the
surface covering to the subsurface was calculated by subtracting
2.7 pounds per square yard from the calculated adhered basis weight
of 145.4 pounds per square yard, giving a value of 142.7 pounds per
square yard. It is noted that if the surface covering had been
intended for use as a ceiling tile, the basis weight would have
detracted from the adhesive strength and the minimum adhesive
strength would have been obtained by adding the actual basis weight
to the adhered basis weight.
Three adhesive candidates were selected for testing. Adhesives
would normally be selected for long-term use in a given
environment; therefore, in addition to strength, they would also be
selected on the basis of their long-term compatibility with the
particle board and with the fused PVC backcoat which were used to
construct the surface covering/subsurface system. When considered
on that basis, the three adhesive candidates normally would not
have been selected because their long-term compatibility with these
materials is unsatisfactory. However, because the purpose of this
example was to illustrate the ability of the present invention to
differentiate between adhesives on the basis of strength, and
because the incompatibility problems were of little consequence
during the term of the test, the incompatibility problems were
disregarded.
The selected adhesives were Armstrong's commercial adhesives, S-750
and S-242, and an Armstrong experimental adhesive, referred to
herein as EXP. The adhesive strength of each of these adhesives was
measured in relation to the surface covering materials (the test
vinyl backing and the test particle board) because no single
adhesive strength value is applicable to an adhesive; i.e., the
adhesive strength of an adhesive often varies depending on the
materials with which it is used.
These adhesives were tested in the following manner. Commercial
particle board sheets (4 ft..times.8 ft..times.1/2") were
conditioned at 100.degree. F. and 80% relative humidity (RH) for
about two weeks until the length of the boards (measured daily)
remained essentially unchanged for three days. Conditioning was
then discontinued and the temperature and humidity were changed to
essentially ambient conditions (72.degree. F. and 50% RH). Pieces
of the test surface covering 14 in. wide and 8 ft. in length were
prepared, and duplicate samples for each adhesive were adhered to
the particle board sheets. The ends of the test strips were stapled
to the sheets so that the strips would be subjected to a
representative compressive stress during the test. The length of
each sheet (L.sub.s) was measured at this time.
After the adhesive bond had aged under ambient conditions for one
week, the conditions were adjusted to 20% RH and 70.degree. F. The
samples were then monitored as the particle board sheets dried out
and contracted, thus placing a compressive force on the eight-foot
span of the samples. When the surface covering samples buckled,
indicating failure of the adhesive bond, the amount of sheet
shrinkage for the particle board was measured by subtracting the
sheet length at failure (L.sub.f) from the sheet length at the time
the samples were adhered to the sheets (L.sub.s). The strain at
failure was determined according to the equation ##EQU3## For the
purpose of this aspect of the invention, the strain at failure is
referred to as the adhered critical buckle strain, which was
defined earlier.
It was noted that all three adhesives failed differently during the
test: The S-750 adhesive lost its cohesive strength and left
adhesive residue on both surfaces; the S-242 adhesive remained on
the particle board leaving the backing essentially free of adhesive
residue; and the EXP adhesive remained on the surface of the
backing and left essentially no residue on the particle board.
An average adhered critical buckle strain was determined for each
system. By inserting this average value, and the relaxed
compressive stiffness and bending stiffness values for the test
surface covering (above), into the equation, the adhered basis
weight for each system was calculated using the computer program
illustrated in FIGS. 16A and 16B. Because the test surface was a
floor covering, the actual basis weight was subtracted from each
value to give the following adhesive strengths:
EXP =13.0 lb./yd..sup.2
S-750=129.6 lb./yd..sup.2
S-242=180.5 lb./yd..sup.2
These values indicated that the S-750 and EXP adhesives would not
perform satisfactorily because their adhesive strengths were less
than the minimum strength as determined from the earlier
calculation (142.7 pounds per square yard). The third adhesive,
S-242, had an adhesive strength which was in excess of the
calculated value, indicating that it would be suitable to adhere
the test surface covering to the particle board subsurface.
To test the validity of this determination, particle board sheets
were conditioned in an environmental test chamber at 80% RH and
72.degree. F. for four weeks, after which a 12 ft..times.10 ft.
subsurface was built over a plywood support surface according to
standard NPA installation directions. A 12 ft..times.10 ft. piece
of surface covering was then adhered to the subsurface using the
S-242 adhesive. It is emphasized that the adhesive was applied
exactly as it was for the above-described strip test, and exactly
according to the application directions.
After the adhesive had aged, a six-week drying cycle was commenced
to induce the particle board to shrink by its subsurface
dimensional change factor of 0.003. Although certain minor
deficiencies were noted during the test, these were not
attributable to the present invention, and the installation was
deemed to have performed satisfactorily. As an example of one
deficiency, surface coverings of the type illustrated in this
Example 14 are commonly affected by the presence of bubbles, or air
pockets, between the surface covering and the subsurface. These
pockets prevent adequate adhesion in certain small areas which
eventually result in the presence of noticeable bubbles or
blisters. These defects are attributable to the manner in which the
test materials are installed and/or to a lack of initial adhesion,
and are not attributable to the invention itself.
Example 15
This example will illustrate the situation where an adhesive is
selected and a selected surface covering is modified so that it
will be suitable for use with the adhesive when adhered to a given
subsurface.
A surface covering was prepared essentially as described in Example
14, except that the glass mat was modified in situ after the
embossing step, before the backing coat (plastisol C) was
applied.
This surface covering was selected for use over a particle board
subsurface having a subsurface dimensional change of 0.0015. The
EXP adhesive was selected and the adhesive strength of this
adhesive was determined as described in Example 14 to be 13.0
pounds per square yard.
The basis weight, bending stiffness and relaxed compressive
stiffness were measured for the selected surface covering to give
the following values:
______________________________________ relaxed compressive
stiffness 1,274 ppiow basis weight 2.6 pounds per sq. yd. bending
stiffness 0.63 inch pounds
______________________________________
From these data, the unmodified surface covering was calculated to
have a critical buckle strain of 0.0005. A target critical buckle
strain of 0.002 was selected for use over the subsurface having an
expected subsurface dimensional change of 0.0015.
The surface covering in this example was also intended for use as a
floor covering. Accordingly, the adhered basis weight was
calculated by adding the adhesive strength of 13.0 pounds per
square yard for the adhesive and the actual basis weight (2.6
pounds per square yard) of the surface covering, giving a value of
15.6 pounds per square yard.
For this example, the computer program illustrated in FIGS. 1A and
1B was used to calculate the relaxed compressive stiffness, except
that the upper limit for the basis weight was expanded such that it
was in excess of the calculated adhered basis weight of 15.6 pounds
per square yard. The measured bending stiffness, the adhered basis
weight, and the target critical buckle strain were substituted into
the equation to provide a calculated relaxed compressive stiffness
value of 648 ppiow. Accordingly, modification of the surface
covering was required in order to reduce the relaxed compressive
stiffness from the initially measured value of 1,274 ppiow to a
value less than or equal to 648 ppiow.
The surface covering was modified by cutting 1-inch diamond-shaped
elements into the reinforcing layer from the back of the surface
covering. The partial structure, was fed upside down at room
temperature through a pair of pinch rolls, the upper roll being an
embossing roll especially designed to perforate the glass
reinforcement and the lower roll being a smooth steel back-up roll.
The roll pressure was adjustable such that modification could be
varied from slight modification at low pressure to substantial
modification at higher pressure. For purposes of the present test,
the nip pressure was adjusted to 120 pounds per lineal inch.
The upper embossing roll was designed with a pattern comparable to
that shown in FIG. 12; however, the pattern was angled at 45
degrees to the machine direction to create a diamond-shaped element
pattern. The raised portions of the embossing roll were 0.045 inch
high and 0.025 inch wide.
After the material had passed through the nip, a test piece was
placed in tetrahydrofuran solvent to dissolve the polymeric
material and recover the modified glass mat. Visual inspection of
the mat showed that the 1-inch diamond elements were almost
completely separated from the continuum of glass, but a few strands
still held the elements in place. The structure was completed as
described in Example 14 through application of plastisol coat C.
The relaxed compressive stiffness of the completed, modified
structure was found to be 623 ppiow.
To evaluate the effect of this modification, the surface covering
was installed over the selected particle board subsurface in the
manner described in Example 14 and the adhered system was subjected
to a six-week cycle during which the particle board shrank by about
a factor of 0.0015, the expected subfloor dimensional change value.
The installation performed satisfactorily and there was no evidence
of buckling.
Example 16
This example will illustrate the modification of a surface
covering, followed by selection of an appropriate adhesive which is
compatible with the characteristics of the modified covering.
A surface covering was partially prepared, modified, and then
completed as described in Example 15. The following physical
properties were measured for the modified structure:
______________________________________ relaxed compressive
stiffness 520 ppiow bending stiffness 0.58 inch-pounds basis weight
2.6 pounds per sq. yd. ______________________________________
Using these data, a critical buckle strain of 0.001 was obtained
for the in situ modified structure. A target critical buckle strain
of 0.0035 was selected for use in the calculation based on a
proposed particle board subfloor having a subfloor dimensional
change of 0.003.
The modified computer program illustrated in FIGS. 16A and 16B was
used to calculate the adhered basis weight by inserting the
measured relaxed compressive stiffness and bending stiffness
values, and the target critical buckle strain of 0.0035, into the
equation. The adhered basis weight was calculated to be 35.8 pounds
per square yard. This surface covering was also intended for use as
a floor covering. Accordingly, the measured basis weight of 2.6
pounds per square yard was subtracted from the calculated adhered
basis weight of 35.8 pounds per square yard in order to give a
required minimum adhesive strength of 33.2 pounds per square yard
for the adhesive.
The adhesive strengths for each of the three adhesives used in
Example 14 were also applicable in this example because the
materials which were being adhered together were identical.
Accordingly, the above calculation indicates that two of the three
adhesives (S-242 and S-750) would be suitable to adhere the
modified structure in this example to the intended subsurface.
A 10 ft..times.12 ft. surface covering sample was adhered to a
particle board subsurface using the S-750 adhesive and tested as
described above for six weeks under simulated environmental test
conditions which would induce a subfloor dimensional change of
0.003. Satisfactory performance was found and there was no
indication of buckling.
Examples Illustrating Increases and Reductions of Relaxed
Compressive/Tensile Stiffness Values
Example 17
This example will illustrate a physical modification of a
reinforcing layer such that the relaxed tensile stiffness of the
layer was increased. A 15-inch wide roll of polyester non-woven mat
from International Paper Co. (Experimental No. 031781-2) having a
basis weight of 0.5 ounce per square yard was selected for use. In
this and subsequent examples, the following procedure was used to
measure the relaxed tensile stiffness.
Specimens were cut in 2-inch.times.12-inch dimensions, the 12-inch
dimension being in the machine direction of the non-woven mat. Each
specimen was placed in the jaws of an Instron Tensile Tester such
that the distance between the jaws was 8 inches. A tensile force
was then placed on the sample to elongate it by 0.3%. The initial
(peak) force was recorded and a curve of force decay was plotted
for 90 minutes, after which the decay curves were mathematically
extrapolated to 1,000 hours. The 1,000-hour values (in ppiow) were
divided by the induced strain of 0.003 to provide the relaxed
tensile stiffness. Control values were obtained by measuring the
relaxed tensile stiffness of an untreated mat (17a), and also of
the mat after heating in an oven at 380.degree. F. for 1.5 minutes
(the conditions which were used to heat-cure the treated sample).
The latter sample was designated 17b.
The treated sample (17c) was prepared by applying a pattern of
plastisol to the mat at a level of about 125 grams per square yard,
permitting the sample to stand for one hour, and then fusing the
plastisol as indicated above. The plastisol used was Plastisol D of
Example 14, and the pattern of application was essentially as
illustrated in FIG. 12 where the squares are 1 inch on edge and the
mortar lines, as indicated by lines A--A and B--B, are 1/4-inch
wide. Lines A--A were oriented in the machine direction whereas
lines B--B were oriented in an across machine direction. FIG. 17
illustrates the appearance of the treated sample wherein arrows
E--E indicate the lines along which the Instron jaws were
fastened.
The following data were obtained for these samples:
______________________________________ Initial (Peak) Force Relaxed
at 0.3% Extrapolated Tensile Exam- Elongation Relaxation Stiffness
ple Description (ppiow) (ppiow) (ppiow)
______________________________________ 17a Control 0.423 0.327 109
17b Heated Control 0.177 0.082 27.3 17c Treated Sample 0.782 0.275
91.7 ______________________________________
These results indicate that the treated sample had a relaxed
tensile stiffness which was increased relative to the heated
control, but which was lower than the value obtained for the
unheated control. The latter value is a relatively meaningless
number, however, because, under conventional processing conditions
used for the selected plastisol, the untreated mat would be altered
by heating and would therefore have the performance characteristics
of the heated control.
Example 18
This example will illustrate a process where the relaxed tensile
stiffness of a mat is first increased, and then decreased. A layer
of Plastisol D from Example 14 was coated at a thickness of ca 0.01
inch onto a release surface and a sheet of the polyester mat of
Example 17 was placed in the plastisol and allowed to saturate for
5 minutes. The saturated mat was then heated as described in
Example 17, cooled and the release paper was removed. The
approximate level of application of fused Plastisol D was about 286
grams per square yard. A sample (18a) was then prepared for testing
as described in Example 17.
A second sample was prepared in the same manner except that the
level of application was about 305 grams per square yard. The
pattern of Example 17 was drawn by pencil on the surface of the
fused mat, and the 1-inch squares were cut from the mat. A sample
(18b) was prepared for testing. The measured results for the two
samples are as follows, and they indicate that the relaxed tensile
stiffness of the control mat was first increased, and then
decreased.
______________________________________ Initial (Peak) Force Relaxed
at 0.3% Extrapolated Tensile Exam- Elongation Relaxation Stiffness
ple Description (ppiow) (ppiow) (ppiow)
______________________________________ 17b Heated Control 0.177
0.082 27.3 18a Fused Mat 0.914 0.456 152 18b Fused, 0.193 0.121
40.3 Modified Mat ______________________________________
Example 19
This example will illustrate the preparation of a sample having an
increased relaxed tensile stiffness value through the use of a
cross-linkable plastisol saturant comprising 300 parts by weight of
Plastisol D, 60 parts by weight of trimethylolpropane
trimethacrylate, and 4 parts by weight of tertiary-butyl
perbenzoate activator. A polyester mat as described in Example 17
was placed in the plastisol and allowed to saturate using the
procedure described in Example 18. After the 5-minute saturation
time had elapsed, the sample was placed in an oven at a temperature
of 275.degree. F. for 5 minutes. This heating exposure gelled the
plastisol, but did not decompose the activator. After gelling was
complete, the sample was removed from the oven and cooled.
The pattern of Example 17 was drawn onto the surface of the gelled
mat and an inhibitor composition comprising 88 parts by weight of
solvent (70% nitroethane, 25% isopropyl acetate and 5% diacetone
alcohol), 5 parts by weight of isopropyl alcohol and 12 parts by
weight of hydroquinone was painted onto the 1-inch square regions
of the pattern using a paint brush. The painted sample was allowed
to air-dry for two hours and was then placed in a 380.degree. F.
oven for 1.5 minutes to fuse and cross-link the structure. After
cooling to room temperature, the sample was separated from the
carrier and visually evaluated. The inhibitor-treated regions were
observed to be off-white in color whereas the mortar lines appeared
brown. The total weight of the applied materials was approximately
232 grams per square yard.
A test sample (19) was cut from the above material and examined in
the usual manner to give the following results:
______________________________________ Initial (Peak) Force Relaxed
at 0.3% Extrapolated Tensile Exam- Elongation Relaxation Stiffness
ple Description (ppiow) (ppiow) (ppiow)
______________________________________ 17b Heated Control 0.177
0.082 27.3 19 Cross-Linked 1.000 0.398 133 Sample
______________________________________
Example 20
This example will illustrate the preparation of a structure which
was usable as a loose-lay area installation; i.e., its structural
stability was such that it should not have been loose-laid in areas
along walls or doors where shrinkage would be unsightly.
A non-woven glass fiber mat, designated SH35/6 from Glaswerk
Schuller GmbH, was selected for use. Onto the surface of this mat
was drawn a pattern similar to that illustrated in FIG. 12 wherein
the squares were 0.8-inch on edge and the mortar lines, as
indicated by lines A--A and B--B of FIG. 12, were approximately
0.33-inch in width. Lines A--A were oriented in the machine
direction whereas lines B--B were oriented in an across machine
direction. After drawing the pattern, the square regions were
physically cut from the sheet and removed.
The area structure was prepared by placing a 0.02-inch thick
coating of a foamable plastisol (Plastisol B from Example 14) on a
release paper using a knife applicator. The plastisol was then
gelled for 2 minutes in an oven at 275.degree. F. After cooling to
room temperature, a second coating of Plastisol B was applied at a
level of 0.01-inch over the first coating and the pre-modified
reinforcing layer was placed in the wet plastisol and allowed to
saturate for several minutes. The composite material was then
gelled by placing the sample in an oven at 275.degree. F. for 2
minutes. After cooling to room temperature, a third coating of
Platisol B was applied as a top layer at a thickness of about
0.02-inch and gelled by placing the structure in an oven at
275.degree. F. for about 5 minutes. The resulting structure had a
thickness of approximately 0.05-inch.
A coating of Plastisol D was applied to the cooled surface of the
gelled substrate at a level of 0.01-inch and the sample was placed
in a fusion oven for about 2.5 minutes at 390.degree. F., after
which the oven was opened and the sample was turned 180 degrees.
Heating was then continued for an additional 2 minutes. After
cooling to room temperature, the sample was separated from the
release carrier and its physical parameters were measured. The
thickness of the sheet was found to be about 0.14 inches, the basis
weight was measured to be 3.4 pounds per square yard and the
relaxed compressive/tensile stiffness was found to be 57 ppiow. The
bending stiffness of the sample was determined to be 0.26
inch-pounds and the critical buckle strain was calculated to be
0.0034. Upon subjecting the sample to a structural stability test
as earlier described, a shrinkage of 0.165 inch or 1.38 percent was
observed. This structure was suitable for use as an area cover.
Our invention is not restricted solely to the descriptions and
illustrations provided above, but encompasses all modifications
envisaged by the following claims.
* * * * *