U.S. patent application number 10/823428 was filed with the patent office on 2005-11-17 for coating for wall construction.
Invention is credited to Bingaman, Andrew B., Colbert, Elizabeth, Domenech, Marc, Hedman, Goran, O'Connor, Kenneth B..
Application Number | 20050252128 10/823428 |
Document ID | / |
Family ID | 35308056 |
Filed Date | 2005-11-17 |
United States Patent
Application |
20050252128 |
Kind Code |
A1 |
Colbert, Elizabeth ; et
al. |
November 17, 2005 |
Coating for wall construction
Abstract
A coating for wall construction is provided whereby a level 5
finish may be obtained without the need for a finishing coat or
final skim coat. The coating may be applied to drywall elements
prior to installation and is compatible with jointing materials
such that a substantially homogeneous surface may be obtained after
the drywall elements are assembled with jointing material and the
jointing material is dried. The coating formulation includes a
noncellulosic thickener, a binder, a mineral filler and water. A
method for the construction of interior walls and a construction
assembly for interior walls is further provided.
Inventors: |
Colbert, Elizabeth; (Newark,
DE) ; Bingaman, Andrew B.; (Dillsburg, PA) ;
Domenech, Marc; (La Roque Sur Pernes, FR) ; O'Connor,
Kenneth B.; (Ashburn, VA) ; Hedman, Goran;
(Rochefort du Gard, FR) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC
(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Family ID: |
35308056 |
Appl. No.: |
10/823428 |
Filed: |
April 13, 2004 |
Current U.S.
Class: |
52/344 |
Current CPC
Class: |
B32B 13/08 20130101;
E04F 13/04 20130101 |
Class at
Publication: |
052/344 |
International
Class: |
E04F 013/04 |
Claims
What is claimed is:
1. A coating formulation for drywall application comprising water,
a binder, a filler comprising at least about 60% by weight
CaCO.sub.3, and a noncellulosic thickener.
2. The coating formulation of claim 1, further comprising a
dispersant.
3. The coating formulation of claim 2, further comprising about 0.1
to about 20% by weight anti-cracking agent and about 0.1 to about
5% by weight workability agent.
4. The coating formulation of claim 3, wherein the anti-cracking
agent is mica and the workability agent is clay.
5. The coating formulation of claim 3, wherein the binder is
present in an amount of about 0.5 to about 15% by weight, the
dispersant is present in an amount of about 0.5 to about 15% by
weight and the thickener is present in an amount of about 0.05 to
about 50% by weight.
6. The coating formulation of claim 2, wherein the binder is a
latex binder.
7. The coating formulation of claim 6, wherein the binder is an
acrylic latex binder.
8. The coating formulation of claim 7, wherein the acrylic latex is
present in an amount of about 0.5 to about 15% by weight, the
dispersant is present in an amount of about 0.5 to about 15% by
weight and the thickener is present in an amount of about 0.05 to
about 50% by weight.
9. The coating formulation of claim 2, wherein the dispersant
comprises a sodium polyacrylate.
10. The coating formulation of claim 1, wherein the thickener
comprises a copolymer of an acrylic acid and an acrylic ester.
11. The coating formulation of claim 1, wherein the filler
comprises at least about 75% by weight CaCO.sub.3.
12. The coating formulation of claim 3, wherein the filler
comprises at least about 75% by weight CaCO.sub.3.
13. The coating formulation of claim 1, wherein the filler further
comprises magnesium carbonate, dolomite, gypsum, anhydrite, or
mixtures thereof.
14. A coating formulation for drywall application comprising: about
0.5 to about 15% by weight of a latex binder, about 40 to about 70%
by weight of a filler comprising at least about 60% by weight
CaCO.sub.3, about 0.5 to about 15% by weight of a dispersant, about
0.05 to about 50% by weight of a noncellulosic thickener, and water
in an amount sufficient to provide a viscosity for the formulation
of about 300 to about 450 cps.
15. The coating formulation of claim 14, further comprising about
0.1 to about 20% by weight anti-cracking agent and about 0.1 to
about 5% by weight workability agent.
16. The coating formulation of claim 15, wherein the anti-cracking
agent is mica and the workability agent is clay.
17. The coating formulation of claim 15, wherein the dispersant
comprises a sodium polyacrylate.
18. The coating formulation of claim 14, wherein the formulation
comprises about 1.0 to about 4.0% by weight of a latex binder,
about 45 to about 65% by weight of a filler comprising at least
about 75% by weight CaCO.sub.3, about 2.0 to about 9.0% by weight
of a dispersant, about 0.1 to about 5.0% by weight of a
noncellulosic thickener
19. The coating formulation of claim 14, wherein the latex binder
comprises an acrylic latex binder.
20. The coating formulation of claim 14, wherein the thickener
comprises a copolymer of an acrylic acid and an acrylic ester.
21. The coating formulation of claim 14, wherein the filler
comprises at least about 75% by weight CaCO.sub.3.
22. The coating formulation of claim 15, wherein the filler
comprises at least about 75% by weight CaCO.sub.3.
23. The coating formulation of claim 14, wherein the filler further
comprises magnesium carbonate, dolomite, gypsum, anhydrite, or
mixtures thereof.
24. A construction assembly for interior walls, comprising: skim
coated drywall elements comprising drywall elements having at least
one skim coat deposited on the drywall elements, the skim coat
formed from a coating formulation comprising water, a binder, a
filler comprising at least about 60% by weight CaCO.sub.3, and a
noncellulosic thickener; and at least one jointing material
jointing the skim coated drywall elements to form a substantially
plane outer surface.
25. The construction assembly of claim 24, wherein the at least one
jointing material and the at least one skim coat form, in the dry
state, a substantially homogeneous outer surface on the
substantially plane outer surface.
26. The construction assembly of claim 24, wherein the drywall
elements are flat, prefabricated elements.
27. The construction assembly of claim 26, wherein the flat,
prefabricated elements are gypsum wallboard.
28. The construction assembly of claim 24, wherein the skim coat
when dry has a thickness of between about 5 and about 60 mil.
29. The construction assembly of claim 25, wherein the
substantially homogeneous outer surface comprises a level 5
finish.
30. The construction assembly of claim 24, wherein the skim coat is
formed from a coating formulation further comprising about 0.1 to
about 20% by weight anti-cracking agent and about 0.1 to about 5%
by weight workability agent.
31. The construction assembly of claim 30, wherein the
anti-cracking agent is mica and the workability agent is clay.
32. The construction assembly of claim 30, wherein the coating
formulation further comprises a dispersant.
33. The construction assembly of claim 32, wherein the binder is
present in an amount of about 0.5 to about 15% by weight, the
dispersant is present in an amount of about 0.5 to about 15% by
weight and the thickener is present in an amount of about 0.05 to
about 50% by weight.
34. The construction assembly of claim 32, wherein the binder is an
acrylic latex binder.
35. The construction assembly of claim 34, wherein the acrylic
latex binder is present in an amount of about 0.5 to about 15% by
weight, the dispersant is present in an amount of about 0.5 to
about 15% by weight and the thickener is present in an amount of
about 0.05 to about 50% by weight.
36. The construction assembly of claim 32, wherein the dispersant
comprises a sodium polyacrylate.
37. The construction assembly of claim 24, wherein the thickener
comprises a copolymer of an acrylic acid and an acrylic ester.
38. A method for the construction of interior walls comprising:
assembling skim coated prefabricated drywall elements, wherein the
skim coated prefabricated drywall elements have a coating layer
formed from a coating formulation comprising water, a binder, a
filler comprising at least about 60% by weight CaCO.sub.3, and a
noncellulosic thickener, and are formed of at least one skim coat
deposited on the prefabricated drywall elements by a coating
device; jointing adjacent prefabricated drywall elements with a
jointing material to form joints; and drying the jointing
material.
39. The method of claim 38, wherein the jointing material and the
at least one skim coat form, in the dry state, a substantially
homogeneous outer surface for the entire surface formed from the
jointing material and skim coated prefabricated drywall
elements.
40. The method of claim 39, wherein the substantially homogeneous
outer surface comprises a level 5 finish.
41. The method of claim 38, wherein the skim coat when dry has a
thickness of between about 5 and about 60 mil.
42. The method of claim 38, wherein the skim coat is deposited on
the prefabricated drywall elements by spraying during
prefabrication of the drywall elements.
43. The method of claim 38, wherein the skim coat is deposited
after assembly of the skim coated prefabricated drywall
elements.
44. The method of claim 38, wherein the coating formulation further
comprises about 0.1 to about 20% by weight mica and about 0.1 to
about 5% by weight clay.
45. The method of claim 38, wherein coating formulation further
comprises a dispersant.
46. The method of claim 45, wherein the binder is an acrylic latex
binder.
47. The method of claim 46, wherein the acrylic latex binder is
present in an amount of about 0.5 to about 15% by weight, the
dispersant is present in an amount of about 0.5 to about 15% by
weight and the thickener is present in an amount of about 0.05 to
about 50% by weight.
48. The method of claim 45, wherein the dispersant is a sodium
polyacrylate.
49. The method of claim 45, wherein the thickener comprises a
copolymer of an acrylic acid and an acrylic ester.
50. The method of claim 38, wherein the prefabricated drywall
elements are gypsum wallboard.
51. A flat, prefabricated drywall element comprising a core of
plaster or gypsum having at least one sheet of lining paper and a
coating layer formed of at least one skim coat deposited on the
lining paper, the skim coat formed from a coating formulation
comprising water, a binder, a filler comprising at least about 60%
by weight CaCO.sub.3, and a noncellulosic thickener.
52. The flat, prefabricated drywall element of claim 51, wherein
the coating formulation further comprises a dispersant.
53. The flat, prefabricated drywall element of claim 51, wherein
the binder is an acrylic latex binder.
Description
FIELD OF THE INVENTION
[0001] A coating and coating formulation for improved drywall
installation are provided. A method for constructing interior walls
including applying the coating and a construction assembly formed
with the use of the coating are further provided.
BACKGROUND
[0002] Interior walls typically are installed by use of flat,
prefabricated boards which are assembled with the use of jointing
material such as joint compounds, sealing coats, joint coats and/or
joint-pointing coats. The prefabricated elements can be gypsum
fiberboards, cement fiberboards, gypsum wallboards or plaster
boards and the like. The flat, prefabricated boards typically
include at least one sheet of lining paper, at least one outer
layer of which has a visible outer face ready to be decorated.
Generally, in the construction of interior walls, flat
prefabricated elements, or drywall elements, are fastened to wall
frames by, for example, nails or screws, and the joints taped or
plastered with a jointing material. The prefabricated elements are
assembled together, optionally with a jointing material and the
joints are finished with a sealing coat, joint coat and/or
joint-pointing coat, so as to obtain an overall visible outer
surface which is relatively uniform or plane, including in the
region of the joints.
[0003] After the interior assembly work has been completed, the
preparation generally involves covering the overall surface
obtained, i.e., the lining of the flat prefabricated elements plus
the joints, with one or more layers of a paint or priming or
finishing coat. The overall visible outer surface of the flat,
prefabricated boards typically needs to be prepared, before
receiving any surface decoration, such as by application of one or
more layers of a film covering of the paint or lacquer type or a
wallpaper. This preparation is necessitated especially by the shade
or color differences existing between the visible outer surface of
the flat prefabricated elements, for example plasterboards, and the
visible outer surface of the joints.
[0004] The preparation operation represents an appreciable
additional cost, for example in a complete process for the
construction of a building. And, in some cases, it is still
insufficient for obtaining an overall decorated surface of uniform
appearance, particularly in view of the physico-mechanical
differences prevailing between the joints and the flat
prefabricated elements.
SUMMARY
[0005] A coating formulation for drywall application is provided
which simplifies the installation of interior walls by
substantially eliminating the need for a final skim coat on the
drywall. In one embodiment, the coating formulation comprises
water, a binder, a filler comprising at least about 60% by weight
CaCO.sub.3, and a noncellulosic thickener. The coating formulation
may be applied to drywall elements during manufacture of
prefabricated drywall elements or may be applied upon installation
of the drywall elements for interior walls.
[0006] In a further embodiment, a coating formulation for drywall
application is provided comprising about 0.5 to about 15% by weight
of a latex binder, about 40 to about 70% by weight of a filler
comprising at least about 60% by weight CaCO.sub.3, about 0.5 to
about 15% by weight of a dispersant, about 0.05 to about 50% by
weight of a noncellulosic thickener, and water in an amount
sufficient to provide a viscosity for the formulation of about 300
to about 450 cps.
[0007] A construction assembly for interior walls is further
provided comprising skim coated drywall elements comprising drywall
elements having at least one skim coat deposited on the drywall
elements, the skim coat formed from a coating formulation
comprising water, a binder, a filler comprising at least about 60%
by weight CaCO.sub.3, and a noncellulosic thickener; and at least
one jointing material jointing the skim coated drywall elements to
form a substantially plane outer surface. Preferably, the jointing
material and the drywall elements having a skim coat form, in the
dry state, a substantially homogeneous outer surface for the entire
surface formed of the jointing material and skim coated drywall
elements.
[0008] A method for the construction of interior walls is further
provided comprising assembling skim coated prefabricated drywall
elements, wherein the skim coated prefabricated drywall elements
have a coating layer formed from a coating formulation comprising
water, a binder, a filler comprising at least about 60% by weight
CaCO.sub.3, and a noncellulosic thickener and are formed of at
least one skim coat deposited on the prefabricated drywall elements
by a coating device, jointing adjacent prefabricated drywall
elements with a jointing material to form joints, and drying the
jointing material. Preferably, the jointing material and the at
least one skim coat form, in the dry state, a substantially
homogeneous outer surface for the entire surface formed of the
jointing material and skim coated prefabricated drywall
elements.
[0009] A flat prefabricated drywall element is further provided
comprising a core of plaster or gypsum having at least one sheet of
lining paper and a coating layer formed of at least one skim coat
deposited on the lining paper, the skim coat formed from a coating
formulation comprising water, a binder, a filler comprising at
least about 60% by weight CaCO.sub.3, and a noncellulosic
thickener.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] The coating provided affords improved drywall installation
efficiency and improvements in texture, absorption characteristics,
sanding characteristics, processing characteristics and final
performance characteristics. The coated drywall product produced
using the coating formulations and methods disclosed preferably
provides a final surface for the drywall that substantially equals
a level 5 skim-coated finish. The drywall finish levels as used
herein refer to the Levels of Gypsum Board Finish of GA 214-96:
Recommended Levels of Gypsum Board Finish published in 1996. A
level 5 finish is typically recommended for areas where severe
lighting conditions exist and areas that are to receive gloss,
semi-gloss, enamel or non-textured flat paints.
[0011] As used herein, the term "drywall" means any wall structure
especially for interior application, wherein the wall structure may
be prefabricated or not prefabricated material and includes gypsum
fiberboards, cement fiberboards, cement wallboards, plasterboards
and the like. Drywall elements typically are made of a gypsum or
plaster core sandwiched or faced in paper or cardboard and produced
like sheets which may be fastened to wall frames such as with nails
or screws. The drywall has a surface usually placed outwardly in an
interior construction such that there is a visible outer surface or
face ready to be decorated.
[0012] Conventionally, one of the sheets of paper used for making
drywall elements has a dark color which can vary between a gray
color and a chestnut color, since it is composed of cellulose
fibers which have not undergone any particular purifying treatment.
Traditionally, this so-called grey paper is obtained from
unbleached chemical pulp and/or from mechanical pulp, and/or from
thermomechanical pulp and/or from semi-chemical pulp. By mechanical
pulp, it is usually meant a pulp obtained entirely by mechanical
means from various raw materials, essentially wood, which can be
provided by salvaged products originating from wood, such as old
cardboard boxes, trimmings of kraft paper and/or old newspapers.
Thermomechanical pulp means a pulp obtained by thermal treatment
followed by a mechanical treatment of the raw material. By
semi-chemical pulp is meant a pulp obtained by eliminating some of
the non-cellulose components from the raw material by means of
chemical treatment and requiring a subsequent mechanical treatment
in order to disperse the fibers.
[0013] The other sheet of a drywall element has a visible face,
called a lining face, which may be of a color generally lighter
than the gray sheet. To obtain this lighter color, the layer or
layers of this face are based on chemical pulp, if appropriately
bleached, composed of recycled and/or new cellulose fibers, and/or
on mechanical pulp, if appropriately bleached. By chemical pulp is
meant a pulp obtained by eliminating a very large proportion of the
non-cellulose components from the raw material by chemical
treatment, for example, by cooking in the presence of suitable
chemical agents, such as soda or bisulfites. When this chemical
treatment is completed by bleaching, a large part of the colored
substances is eliminated, as well as the substances which risk
decomposing by ageing and giving unpleasant yellow shades
associated with the presence of, for example, lignin. The coating
provided preferably is applied to this face of the drywall;
however, the coating may be applied to any type of paper or outer
surface utilized in the manufacture of drywall, including printed
paper and the like.
[0014] Generally, the coating is applied to all or a portion of the
surface of the drywall either during prefabrication of the drywall
elements or boards or after installation in the interior of a
structure. The coating has a composition compatible with jointing
material and is applied as a skim coat or film coat of relatively
low thickness on the visible surface of the drywall. One or more
coats may be applied. The coating preferably provides a
substantially homogeneous appearance to the drywall even after the
joints are prepared as is known in the art. The characteristics of
the coating are such that the coating and other materials utilized
in the installation of drywall preferably compatibly provide a
substantially homogeneous appearance, especially when viewed
visually during installation. The drywall installation is
simplified since one or more layers of primer or paint or finishing
coats are not required to complete the preparation of the wall for
decoration. Specifically, in preferred embodiments, when the
coating is applied to drywall, an additional skim coat or finishing
coat is not required to obtain a level 5 finish.
[0015] Any commercially available jointing material may be used to
complete the construction of the interior surface of the interior
structure installed with coated drywall. The coating provides a
smoothing of the texture of the drywall such that the fibers
typically seen under primer or paint after installation of the
drywall are substantially covered. Moreover, the coating changes
the characteristics of the drywall to provide a surface with an
absorbance closer to the absorbance of the jointing material
surface when dry, which surface is thus visually substantially
uniform. The coating also provides a durable surface such that the
sanding on the jointing material does not easily remove or damage
the coating surface. Thus, the coating preferably provides a
durable surface with sufficiently smooth texture and absorbance to
be substantially compatible with the jointing material.
[0016] In one embodiment, the jointing material also comprises a
system including water, binder, thickener, dispersant, and filler,
particularly CaCO.sub.3, in amounts resulting in a material with
properties suitable for a jointing material and which provides a
substantially similar surface to the coating as to texture and
absorbance, enabling the coating and jointing material when dry to
preferably provide a level 5 finish without application of a skim
or final coat. Thus, a final skim coat may be eliminated from the
preparation of the wall, saving time and money when constructing
interior walls. Preferably, the jointing material used is as
disclosed in the copending application entitled "A System Using a
Drywall Board and a Jointing Compound", filed on even date herewith
and coassigned with the present application, incorporated herein by
reference in its entirety. In other preferred embodiments, the
jointing material may be as disclosed in U.S. Patent Application
Publication Nos. 2003/0153651 and 2003/0084633, both of which are
hereby incorporated by reference in their entireties.
[0017] After the coating and jointing material has been applied to
drywall, the jointing material jointing the skim coated drywall
elements and the skim coated drywall elements form a substantially
plane outer surface comprising a surface of the jointing material
and a surface of the skim coated drywall elements. This surface may
then be decorated as is known in the art by application of a paint
or wallpaper covering.
[0018] The coating typically is a drying type coating and the
coating formulation comprises water, mineral filler, binder and
thickener. The coating preferably also includes a dispersant. The
water is provided in an amount effective to provide a suitable
viscosity to the coating formulation such that the coating
formulation may be applied by any desirable means to the drywall
material.
[0019] The mineral filler may be any of the fillers known in the
art for use in surface coating compositions or a combination
thereof. Preferably, the mineral filler is of light color,
preferably white with a grain size or particle size distribution
wherein the D50 of the particles is between about 5 and about 35
.mu.m, as determined by light scattering techniques. Too large a
grain size of the filler gives rise to overall surface defects,
such as a reflection of light radiation on the surface of the coat
which is different from that on the surface of the drywall,
bringing about differences in tone and brightness of the shade. Too
large a grain size also gives rise to differences in physical
appearance which are associated with the differences in roughness
between the board and the coating.
[0020] Preferably, the mineral filler comprises more than about 60%
calcium carbonate, more preferably more than about 75%, and most
preferably, greater than about 90% calcium carbonate. Other fillers
may also be used in lesser amounts, such as magnesium carbonate,
dolomite, gypsum, anhydrite and the like. By way of example, a
calcium carbonate filler such as Pulpro 15 from OMYA may be used.
The mineral filler represents about 40 to about 70% of the total
weight of the coating formulation. Preferably, the mineral filler
represents about 45 to about 65% of the total weight of the coating
formulation.
[0021] The coating formulation further may comprise a dispersant.
The dispersant provides cohesion for the formulation, holding the
components of the formulation in suspension even where the
viscosity of the coating formulation is relatively low for a
coating material. The dispersant may include any dispersant or
mixtures thereof which function as desired, preferably any
polyacrylate or polymeric acrylic salt or mixtures thereof, more
preferably a salt of polyacrylate such as a sodium polyacrylate. By
way of example, Acumer.RTM. 9300 or Acumer.RTM. 9400 produced by
Rohm and Haas Company may be used.
[0022] The dispersant preferably represents about 0.5 to about
15.0% of the total weight of the coating formulation. More
preferably, the dispersant represents about 2.0 to about 9.0% of
the total weight of the coating formulation.
[0023] The coating formulation also comprises an organic binder
dispersible in aqueous phase, in a proportion of between about 0.5
and about 15.0%, and preferably between about 1.0 and about 4.0%,
of the total weight of the coating formulation. The binder
preferably imparts sufficient flexibility to the coat to withstand
mechanical stresses, and has both an adhesive capacity for
obtaining a good bond on the overall surface and good resistance to
attacks of ultraviolet light. In addition, the binder typically
will function to harden the surface of the coating after
application.
[0024] The binder in the coating formulation preferably will be a
latex binder or mixtures of such binders. In a preferred
embodiment, the binder is an acrylic latex binder. By way of
example, an acrylic latex such as AC-630 from Rohm and Haas Company
may be used.
[0025] The coating formulation further comprises a thickening agent
which provides an increase in viscosity and functions to aid in
holding the components of the coating formulation in suspension.
The thickening agent preferably is primarily a noncellulosic
thickener or a mixture of noncellulosic thickeners. In some
embodiments, other thickeners known in the art such as cellulosic
thickeners may be included in the formulation as part of a mixture
of thickening agents. By way of example, noncellulosic thickeners
generally identified as alkali soluble emulsions or hydrophobically
modified alkali soluble emulsions may be used. More preferably, the
thickener is a polymeric noncellulosic thickener such as a
polyacrylate, especially a copolymer of an acrylic acid and an
acrylic ester. In a most preferred embodiment, the thickener is a
copolymer of acrylate and methacrylic acid. By way of example,
ASE-60, a polyacrylate of the alkali soluble emulsion category, or
TT-615, a polyacrylate of the hydrophobically modified alkali
soluble emulsion category, both from Rohm and Haas Company, may be
used.
[0026] The thickener generally is used in a proportion of about
0.05 to about 50%, and preferably of about 0.1 to about 5.0%, of
the total weight of the coating formulation.
[0027] In addition to the water, mineral filler, dispersant, binder
and thickener, at least one workability agent may be included in
the composition of the coating formulation, especially a clay, in
the proportion of about 0.1 to about 5.0%, and preferably of about
1.0 to about 2.0%, of the total weight of the coating formulation.
The workability agent is preferably one or more silicate
derivatives and, more preferably, a clay of the attapulgite type,
such as M8214 from Engelhard.
[0028] An anti-cracking material or agent may also be desirable in
the coating formulations. Such materials are known in the art and
may include materials such as mica. By way of example, MW 200 from
Oglebay Norton may be used. The anti-cracking agent may represent
about 0.1 to about 20% of the total weight of the coating
formulation. Preferably, the anti-cracking agent will represent
about 1.0 to about 2.0% of the total weight of the coating
formulation.
[0029] Other components, such as biocides, anti-foaming agents,
preservatives, water treatment agents and pigments may also be
incorporated in the composition of the coating formulation in the
conventional way. For example, a water treatment agent may be
needed to adjust the pH of the coating formulation depending on the
water used or the ultimate use of the formulation. Such water
treatment agent may be bicarbonate, which may be used in certain
embodiments to ensure the pH is above about 8. Preservatives are
known in the art and include such materials as
hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine. By way of example,
Troysan 165 from Troy Corporation may be used. The additional
components such as biocides, anti-foaming agents, preservatives,
water treatment agents and pigments are typically used in
relatively minor amounts, generally less than about 1.0% of the of
the total weight of the coating formulation.
[0030] The coating formulation, by way of example, may be prepared
by combining a first fraction of water with the binder and
dispersant and mixing the combination. If a water treatment agent
such as bicarbonate is to be added, such agent may be included in
the first mixing step. The viscosity of the formulation should be
kept as high as possible for as long as possible in order to
effectively optimize the mixing process.
[0031] After sufficiently mixing the binder and dispersant with the
first fraction of water, the mineral filler such as calcium
carbonate is added, followed by the mica and the clay. If a
preservative is to be used, the preservative may be added in this
step, along with other optional components known to those of skill
in the art. The coating formulation is further mixed prior to
addition of the thickener. The remaining water preferably is added
last; however, if the coating formulation mixture after addition of
the mineral filler has a high viscosity, e.g., the coating
formulation mixture is too thick, some water may be added prior to
adding the thickener. Any water remaining may be added after
addition of the thickener.
[0032] Typically, the viscosity of the formulation will be about
250 to about 1200 cps, more preferably about 300 to about 450 cps,
as measured by a Brookfield viscometer at room temperature. By way
of example, the viscosity may be measured for the coating
formulation using T-bar spindle number S91 with 100 rpm. The
viscosity of a jointing material may be measured, for example,
using T-bar spindle number S94 with 2.5 rpm. The viscosity may be
adjusted by any means known in the art to provide a coating
formulation suitable for the desired application.
[0033] The coating formulation preferably is used on prefabricated
drywall elements, preferably flat prefabricated elements such as
gypsum fiberboards, cement fiberboards, gypsum wallboards, plaster
boards and the like.
[0034] The coating formulation preferably is applied as a skim
coat, or film coat of relatively low thickness on the outer surface
of drywall made from prefabricated elements. The coat may be
applied before or after the drywall is sent through a drier.
Preferably, however, the coat will be applied prior to the drier so
that the coat may be dried as the core is dried.
[0035] The skim coat may be applied, by way of example, in the
plant by, for instance, roll coating, curtain coating, vacuum
coating, spraying or the like, via a coating device, on the
prefabricated element so that the skim-coated prefabricated element
is delivered to the assembly site already with a skim coat on it.
Alternatively, the coating formulation may be supplied to the user
for application to the drywall or boards after the drywall or
boards are placed into position during interior construction. The
skim coat from the coating formulation provides a substantially
uniform or plane surface with the joint compound used to install
the drywall or boards upon which the skim coat is placed.
[0036] The coating formulation preferably is applied using a
spraying device, which is operated under standard conditions for
coating a product onto a board. The dimensions, rotating speed,
feeding, temperature, and any other operating conditions are within
the skill of a person of ordinary skill in the art. In a preferred
embodiment, the coating is applied by a system as disclosed in the
copending application entitled "Coating Spray Apparatus and Method
of Using Same", filed on even date herewith and coassigned with the
present application, incorporated by reference herein in its
entirety.
[0037] By way of example, drywall material such as gypsum wallboard
is prepared according to standard practices, including depositing a
calcined gypsum slurry between two sheets. Methods of producing
gypsum board, including coated gypsum board, are described for
example in copending, coassigned U.S. patent application Ser. No.
10/625,624, filed Jul. 24, 2003, incorporated herein by reference
in its entirety. The coating formulation may be applied after the
gypsum sets but prior to the gypsum being completely dry.
Thereafter, the gypsum wallboard is dried in conventional driers
which dries both the coating and the gypsum. It has been discovered
that the coating is sufficiently permeable to allow moisture in the
gypsum to be satisfactorily eliminated through the paper and the
coating thereon. An impermeable substance applied to the paper
cover sheet of the gypsum wallboard when the core is still wet may
cause the paper sheet to separate or delaminate from the core as
moisture is driven off in the drier. The coating formulation
provided, however, may be advantageously applied during manufacture
of the drywall without substantially negatively affecting the
drying characteristics of the core material or time required for
drying the core material.
[0038] The final thickness of the coat from the coating
formulation, as determined when dry, is generally between about 5
and about 60 mil, preferably between about 10 and about 15 mil.
[0039] Embodiments of the invention will now be more fully
explained by the following examples. However, the scope of the
invention is not intended to be limited to these examples.
EXAMPLE 1
[0040] A coating formulation according to an embodiment as set
forth in Table 1 was prepared as follows:
[0041] To the first part of the water, bicarbonate, binder, and
dispersant were added and mixed. The calcium carbonate was then
added and mixed, followed by the mica, clay and preservative, which
were also mixed. The thickener then was added and mixed into the
formulation. The remaining water was added after the thickener was
mixed into the formulation.
1TABLE 1 Material Name Pounds Dry Solids % Water 294.68 21.8
Bicarbonate 0.42 100 0.03 AC-630 resin, binder (acrylic latex)
25.79 50 1.91 Acumer 9400, dispersant (sodium 27.09 42.5 2.00
polyacrylate) Calcium carbonate 711.28 100 57.06 Mica 26.43 100
1.96 Clay 19.32 100 1.43 ASE-60, thickener (copolymer acrylic acid,
1.62 28 0.12 acrylic ester) Water 185.00 13.6 Total Pounds 1351.63
Weight solids (%) 61.40 % Dispersant - total formulation 2.00 %
thickener - total formulation 0.12 % binder - total formulation
1.91
EXAMPLE 2
[0042] A coating formulation according to Table 2 was prepared
according to the procedures of Example 1.
2TABLE 2 Material Name Pounds Dry Solids % Water 297.56 21.80
Bicarbonate 0.43 100 0.03 AC-630 resin, binder (acrylic latex)
26.25 50 1.92 Acumer 9300, dispersant (sodium 27.38 45 2.00
polyacrylate) Calcium carbonate 784.89 100 57.51 Mica 26.90 100
1.97 Clay 19.66 100 1.44 TT-615, thickener (copolymer acrylic acid,
1.64 30 0.12 acrylic ester) Water 180.00 13.19 Total Pounds 1364.71
Weight solids (%) 61.90 % Dispersant - total formulation 2.00 %
thickener - total formulation 0.12 % binder - total formulation
1.92
[0043] While the preferred aspects of the invention have been
disclosed in detail, it will be apparent to one skilled in the art
that various changes and modifications can be made without
departing from the spirit and scope thereof.
* * * * *