U.S. patent application number 11/335959 was filed with the patent office on 2006-11-23 for glass/polyvinylbutyral laminates having directional surface patterns and a process for preparing same.
Invention is credited to Chul Won Choi, Sang Gyu Lee.
Application Number | 20060263608 11/335959 |
Document ID | / |
Family ID | 46323663 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060263608 |
Kind Code |
A1 |
Choi; Chul Won ; et
al. |
November 23, 2006 |
Glass/polyvinylbutyral laminates having directional surface
patterns and a process for preparing same
Abstract
De-airing of PVB/glass laminates can be improved, while haze in
the pre-press is minimized and sleep time reduced as a result using
a PVB sheet having a roughened surface with directionality. A
roughened surface with a washboard pattern that is useful in this
regard can be obtained by varying certain conditions of a
melt-fracture extrusion process.
Inventors: |
Choi; Chul Won; (Ulsan,
KR) ; Lee; Sang Gyu; (Kyungki-do, KR) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY;LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
46323663 |
Appl. No.: |
11/335959 |
Filed: |
January 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10204128 |
Aug 14, 2002 |
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11335959 |
Jan 20, 2006 |
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Current U.S.
Class: |
428/426 ;
428/141 |
Current CPC
Class: |
B32B 2307/538 20130101;
B32B 27/42 20130101; C08K 5/103 20130101; B32B 2605/08 20130101;
Y10T 428/24355 20150115; C08L 29/14 20130101; B32B 2250/40
20130101; B32B 2605/006 20130101; B32B 17/10761 20130101; B32B
27/30 20130101; B29C 48/08 20190201; B32B 2250/03 20130101; B32B
3/26 20130101; C08K 5/103 20130101; B32B 17/10577 20130101 |
Class at
Publication: |
428/426 ;
428/141 |
International
Class: |
B32B 17/10 20060101
B32B017/10; B32B 25/04 20060101 B32B025/04 |
Claims
1. A polyvinyl butyral (PVB) sheet having a roughened directional
surface pattern having substantially uninterrupted channels in the
cross-web direction, wherein the directional pattern is created
using a melt fracture extrusion process without the use of an
embossing tool.
2. The sheet of claim 1 having a washboard surface pattern.
3. The sheet of claim 2 having an R.sub.z of greater than about
30.
4. The sheet of claim 3 having an R.sub.z of greater than 35.
5. The sheet of claim 4 having an R.sub.z of greater than about
40.
6. The sheet of claim 5 having an R.sub.z of from about 35 to about
100.
7. A polyvinyl butyral sheet having a herringbone surface pattern
created using a melt fracture extrusion process without the use of
an embossing tool.
8. The sheet of claim 7 having an R.sub.z of less than about
35.
9. The sheet of claim 8 having an R.sub.z of less than about
30.
10. The sheet of claim 7 having an R.sub.z of from about 15 to
about 35.
11. The sheet of claim 10 having an R.sub.z of from about 20 to
about 30.
12. A process for creating a directional pattern on a surface of a
polyvinyl butyral sheet comprising the step: extruding molten PVB
using a melt fracture extrusion process, wherein the pattern can be
varied by varying the extrusion process parameters and wherein an
embossing tool is not used.
13. The process of claim 12 wherein a washboard pattern is created
using a die pressure of greater than about 58 kg/cm.sup.2.
14. The process of claim 12 wherein a herringbone pattern is
created using a die pressure of less than about 37 kg/cm.sup.2.
15. A laminate comprising a polyvinyl butyral interlayer, wherein
the interlayer is obtained from a polyvinyl butyral sheet having a
roughened directional surface pattern created by extrusion of the
sheet using a melt fracture process.
16. The laminate of claim 15 wherein the directional surface
pattern on the PVB is a washboard pattern obtained using a die
pressure of greater than about 58 kg/cm.sup.2.
17. The laminate of claim 15 wherein the directional surface
pattern of the PVB sheet is a herringbone pattern obtained using a
die pressure of less than about 37 kg/cm.sup.2.
18. The laminate of claim 15 wherein at least one layer is glass
adhered to the PVB layer.
19. The laminate of claim 18 wherein the PVB is adhered to at least
two layers of glass.
20. The laminate of claim 15 wherein at least one layer of an
additional polymer is included in addition to the PVB.
21. An article obtained from a laminate of claim 15.
22. The article of claim 21 wherein the article is a windshield, or
automotive side-glass.
23. The article of claim 21 wherein the article is a window, shelf,
or architectural glass.
24. The process of claim 13 wherein the lip steam pressure is below
about 10 kg/cm.sup.2 (9.8 MPa).
25. The process of claim 14 wherein the lip steam pressure is below
15 kg/cm.sup.2 (9.8 MPa).
Description
[0001] This application is a continuation-in-part of U.S.
application Ser. No. 10/204,128, filed Aug. 14, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to glass laminates. The
present invention particularly relates to laminates of glass and
polyvinylbutyral, and a process of preparing same.
[0004] 2. Description of Related Art
[0005] Glass laminates that include plasticized polyvinyl butyral
(PVB) interlayers can be used in various applications, including
use in automotive safety glass applications such as windshields and
side glass; in architectural applications such as windows, doors
and/or building panels; and in various other applications such as
in display cases, as shelving, and the like.
[0006] Glass/PVB laminates can be prepared by conventional methods.
Typically, a laminate can be prepared by first positioning a sheet
of PVB between two pieces of glass to obtain an assembly, and
trimming the excess PVB interlayer. A "pre-press" is obtained from
the assembly by removing air trapped between the glass and the
interlayer, and then sealing the edges. A conventional method for
edge sealing requires placing the assembly inside of a rubber bag
and removing the air from the bag by applying vacuum. The rubber
bag and contents can then be passed through a furnace wherein the
temperature is increased to about 135.degree. C. in order to obtain
the pre-press. A pre-press so obtained can be heated in an
autoclave wherein heat and pressure are applied, residual air is
dissolved in the PVB interlayer, and bonding occurs between the
interlayer and the surface being laminated.
[0007] An interlayer having a smooth surface can present problems
during the assembly and de-airing steps of a lamination process if
a vacuum bag system is used to make the pre-press. In the assembly
step, the smooth pattern allows the interlayer to tack too easily
to the glass, making placement of the interlayer difficult. In the
de-airing step, a smooth pattern can lead to a laminate having
trapped air, and flaws in the laminate can result therefrom. It is
known that interlayers having a rough surface can facilitate
de-airing. Rough surface patterns can be generated by conventional
methods, including use of an embossing tool to impart a
reproducible pattern on the surface of the interlayer material. It
is also conventional to generate a randomly irregular surface
pattern by a melt-fracture process, which can provide channels by
which air can escape during the lamination process.
[0008] In a typical windshield laminating process, the PVB
interlayer is first subjected to a shaping step wherein the PVB
interlayer is differentially stretched such that the shaped
interlayer better conforms to the curvature of the vehicle for
which the windshield is designed. In the shaping step, the PVB roll
is unwound, and the interlayer is heated to approximately
100.degree. C. and then passed over one or more cones which are
smooth, and then chilled to approximately 10.degree. C. for
storage, and then cut into blanks slightly larger than the size of
the windshield. Stresses incurred in the shaping process are
partially relaxed as the blanks are conditioned at 10.degree. C.
During the shaping step, some of the pattern roughness is pressed
out temporarily, but will recover according to stress relaxation
kinetics well known in the art of polymer rheology.
[0009] For interlayers with surface patterns generated in a
melt-fracture process, haze in a pre-press can be a problem,
especially if the interlayer material is used within twelve hours
of being shaped for lamination in a vacuum bag pre-pressing system.
Pre-presses with less than 15% light transmission are typically
rejected. Use of an embossing tool can be effective in resolving
the de-airing and pre-press clarity concerns, but is more costly
and more work intensive than use of a melt fracture process. An
embossing process is inflexible relative to the melt fracture
process, with respect to producing different patterns on the same
equipment.
[0010] While use of rough patterns obtained by a melt-fracture
process could improve the effectiveness of de-airing by vacuum,
rough patterns generated by melt fracture require more energy to
melt down in the heating step. This could render the pre-press
hazier than if it had been made from a smoother interlayer. In a
conventional process for making flat laminates, a glass/PVB/glass
assembly is typically heated to the point where the PVB attains a
temperature of abut 50-90.degree. C. At this temperature, the
entire assembly is passed through a set of nip rolls, and the nip
rolls exert pressure that squeezes out the interstitial air and
also seals the edges of the pre-press. Pre-presses that use
conventional PVB with a roughened surface obtained by a melt
fracture process tend to be hazy if R.sub.z is above 30
micrometers.
[0011] It is desirable to obtain an interlayer material with a
surface rough enough to minimize haze in a pre-press, yet maintain
a desirable balance of physical properties of the interlayer,
without requiring the capital investment, loss of yield, loss of
flexibility, or possible contamination that can result from use of
an embossing tool. Therefore it can be desirable to obtain such a
rough surface without use of an embossing tool.
SUMMARY OF THE INVENTION
[0012] In one aspect, the present invention is a plasticized
polyvinyl butyral sheet having a directional surface pattern
created using a melt fracture process during extrusion of the
sheet.
[0013] In another aspect, the present invention is a plasticized
polyvinyl butyral sheet having a washboard surface pattern created
using a melt fracture process during extrusion of the sheet.
[0014] In another aspect, the present invention is a plasticized
polyvinyl butyral sheet having a herringbone surface pattern
created using a melt fracture process during extrusion of the
sheet.
[0015] In another aspect, the present invention is a process for
creating a directional pattern on a surface of a plasticized
polyvinyl butyral sheet using a melt fracture process during
extrusion of the sheet.
[0016] In still another aspect, the present invention is a laminate
comprising a plasticized polyvinyl butyral interlayer, wherein the
interlayer is obtained from a polyvinyl butyral sheet having a
directional surface pattern created using a melt fracture process
during extrusion of the sheet.
DETAILED DESCRIPTION
[0017] In one embodiment, the present invention is a plasticized
polyvinyl butyral (PVB) sheet having a roughened surface wherein
the surface has directionality imparted by a melt fracture
extrusion process. PVB sheeting of the present invention is
plasticized. Conventional plasticizers known in the art of
preparing PVB sheets can be used in the practice of the present
invention. Such plasticizers include, but are not limited to:
triethylene glycol-di-2-ethyl butyrate; triethylene
glycol-di-2-ethyl hexanoate; and dibutyl sebacate.
[0018] The roughness of the surface of a PVB sheet of the present
invention is such that haze in a glass/PVB pre-press is low even if
the PVB is used within 12 hours after it is stretched. Surface
roughness can be measured by conventional methods, and can be
expressed by the term R.sub.z. In a washboard PVB sheet of the
present invention R.sub.z is greater than about 30 micrometers, as
determined by ISO R468. Preferably a washboard pattern of the
present invention has a roughness of greater than about 35, more
preferably greater than about 40 and most preferably from about 35
to about 100. In a herringbone pattern of the present invention,
the R.sub.z is less than about 35, preferably less than about 30,
more preferably from about 15 to about 35, and most preferably from
about 20 to about 30 micrometers. In a PVB sheet of the present
invention, the rough surface has a directional pattern, and the
rough directional pattern is obtained without use of an embossing
tool.
[0019] In another embodiment, the present invention is a laminate
comprising at least one layer of PVB and at least one layer of
glass, wherein the PVB layer is obtained by an extrusion process
wherein a roughened PVB surface having directionality is obtained
without use of an embossing tool. The laminate is prepared
according to conventional methods, wherein an assembly comprising
at least one layer of PVB of the present invention is heated, and
then de-aired under vacuum and at elevated temperature to form a
pre-press. Alternatively, the laminate can be prepared by heating
the assembly in an oven and then passing it through one or more
pairs of nip rolls. The pre-press can be autoclaved according to
conventional methods and conditions to yield a finished laminate
article.
[0020] In still another embodiment, the present invention is a
process for preparing a PVB sheet having a roughened surface having
directionality imparted using a melt fracture extrusion process,
without the aid of an embossing tool. Directionality, as the term
is used herein, refers to the tendency of a roughened pattern of
the present invention to have an ordered, repetitive pattern that
gives the appearance of an embossed pattern. However, such a
pattern is obtained without using an embossing tool. As such,
problems associated with use of an embossing tool are eliminated.
Problems associated with use of an embossing tool include, for
example, surface defects and material loss caused by adhesion of
the sheet material to the tool. A directional surface pattern of
the present invention provides ordered channels that are formed by
a continuous alignment of the troughs of roughened surface to
provide substantially uninterrupted channels for airflow.
Uninterrupted channels in a surface pattern can provide the benefit
of more efficient "de-airing" in a lamination process than a
surface pattern having a random array of peaks and valleys. An
extruded sheet of the present invention, viewed on a 3-dimensional
axis wherein the height and depth of the surface pattern is shown
on the y-axis, the sheet length as it is extruded from the extruder
is shown on the x-axis, and the depth of the sheet in the cross-web
direction is represented on the z-axis, has channels that run in
the cross-web direction and that are substantially uninterrupted by
the random occurrence of a raised portion of the surface blocking
the channel. The present invention provides a process for obtaining
a non-random pattern having substantially uninterrupted channels in
the cross-web direction without use of an embossing tool.
[0021] The process comprises varying certain conditions and
parameters in the extrusion process of PVB sheeting material. To
prepare conventional PVB sheeting material, typically parameters
can be varied to control surface pattern. Some parameters that can
be varied are die body temperature and die gap, sheet caliper, lip
stream pressure, lip gap, air gap, content of plasticizer,
temperature of polymer, throughput of molten polymer per unit die
width, and temperature of quench water. Other parameters can be
varied as well. The directional patterns of the present invention
can be obtained in the process of the present invention by varying
the die pressure.
[0022] Under certain die pressure operating conditions, a washboard
pattern is one type of directional pattern that can be obtained on
the PVB surface. By "washboard pattern" it is meant a regular
pattern having substantially uninterrupted channels wherein the
troughs, or surface depressions, of an extruded sheet are aligned
in the cross-web direction to form substantially straight lines.
The lines can run parallel to the front edge of the extruded sheet,
or can be at an angle of from about 1.degree. to about 45.degree..
For example, a washboard pattern can be obtained by operating at a
die pressure of greater than 58 kg/cm.sup.2 (5.69 MPa). A washboard
pattern or surface, as the term is used herein, describes a surface
having alternately high (1) and low (2) areas of elevation that
form ridges (3), similar to the surface of a washboard. The ridges
on a PVB surface of the present invention can be nearly parallel to
the cross-web direction of the sheeting as it is extruded, the
cross-web direction being the direction perpendicular to that of
the extrusion. Under certain other conditions of die pressure, a
herringbone pattern can be obtained on the PVB surface. A
herringbone pattern is a second type of directional surface pattern
that can be obtained in the process of the present invention by
varying process conditions. By "herringbone pattern" it is meant a
regular pattern having substantially uninterrupted channels wherein
the troughs, or surface depressions, of an extruded sheet are
aligned in the cross-web direction to form channels that appear to
regularly change direction up and down in an alternating pattern,
passing through a mid-line, and creating the appearance of
"zig-zag" channels. For example, a herringbone pattern can be
obtained by varying die pressure such that the pressure is below 37
kg/cm.sup.2 (3.63 MPa). The herringbone and washboard patterns are
shown in FIG. 1 and FIG. 2, respectively. Other patterns can be
obtained by varying process conditions, but the directional
patterns of the present invention are controlled primarily by the
die pressure.
[0023] Throughput (rate of polymer through the die) can be in the
range of from about 600 to about 1000 kg per hr per meter,
depending on the equipment being used.
EXAMPLES
[0024] The Examples and comparative examples herein are included
for illustrative purposes only, and are not intended to limit the
scope of the present invention.
[0025] In Examples 1-25, 100 parts of dry PVB flake of nominally
18-23% by weight of un-butyralated vinyl alcohol groups were mixed
with 35-40 parts of tetraethylene glycol di-n-heptanoate
plasticizer and one or more light stabilizers marketed under the
tradename "Tinuvin" by Ciba-Geigy Co. and an antioxidant which were
pre-mixed in the plasticizer continuously in a twin-screw extruder.
The melt was forced through a slot die and formed a sheeting of
0.76 mm nominal thickness. In addition, agents for modifying
surface energy of the bulk interlayer and usual adjuvants such as
antioxidants, colorants and ultraviolet absorbers which do not
adversely affect the functioning of the surface energy modifying
agent and adhesion control agent can be included in the PVB
composition. The melt at the die is at approximately
200-220.degree. C. The lips of the die are heated by injecting
pressurized steam into cavities therein. The lip temperature is
controlled by the pressure of the steam injected. One of the die
lips is adjustable so that as it opens, the back-pressure in the
die is decreased and vice versa. The position of this lip is
computer-controlled, and a desired back-pressure in the die (die
pressure) is used as input.
[0026] PVB sheeting having washboard or herringbone pattern was
prepared on conventional extrusion equipment by varying the
condition of die pressure. The same equipment was used for all of
the examples. The conditions and results are given in the Table
below. TABLE-US-00001 TABLE Washboard (W) or Lip Steam Ex.
Herringbone (H) or Die Pressure Pressure R.sub.z (average) No.
Random (R) (kg/cm.sup.2) (kg/cm.sup.2) (micrometers) 1 W 58.8 6.5
62.8 2 H 35.5 6.5 24.4 3 H 35.5 6.5 24.7 4 H 33.5 6.5 29.0 5 H 31.5
6.5 27.2 6 H 29.2 6.5 24.4 7 H 33.6 6.5 28.1 8 H 33.4 6.5 27.6 9 H
33.8 15 26.7 10 H 34.1 15 26.6 11 H 36.0 15 24.3 12 R 62.9 15 47.9
13 R 63.0 10 75.2 14 W 62.8 6.5 80.0 15 W 58.2 6.5 54.5 16 W 58.4
6.5 63.9 17 W 59.3 6.5 60.5 18 W 58.5 6.5 65.1 19 W 58.7 6.5 60.2
20 W 58.6 6.5 65.1 21 W 58.7 6.5 66.5 22 W 60.3 6.5 73.3 23 W 60.0
6.5 70.9 24 W 58.4 6.5 59.8 25 W 60.1 6.5 81.9
Comparative Example 26
[0027] Twenty full size windshields were prepared using a PVB
interlayer commercially available from DuPont under the trade name
Butacite.RTM. BE-1120 with a random surface pattern generated by
melt fracture. The die pressure used was 62.9 kg/cm.sup.2 (61.7
MPa), lip steam pressure was 15 kg/cm.sup.2 (14.7 MPa). The
roughness in terms of R.sub.z was 47.9 micrometers, but there was
no directionality. The interlayer was shaped using typical shaping
equipment, and the shaped interlayer was allowed to recover at
about 15.degree. C. for 4 hours. The pre-presses were prepared
using a commercial vacuum-bag system with approximately 5 minutes
of vacuum at ambient temperature, and 10 minutes inside an oven in
which the PVB temperature gradually rose to about 100.degree. C. at
the end of that period. Ten of the pre-presses were very hazy, and
were judged to be unusable (50% yield).
Comparative Example 27
[0028] Another twenty full size windshields were made of the same
interlayer as in Comparative Example 26 except that the shaped
interlayers had 8 hours of recovery after shaping. Five of the
pre-presses were judged unusable (75% yield). This example shows
that longer recovery time improves pre-press yield.
Example 28
[0029] Twenty windshields were prepared using the procedure in
Comparative Example 26, except that the interlayer had washboard
pattern, and Rz was 62.8 micrometer. It was made with die pressure
of 58.8 kg/cm2 (57.7 MPa) and lip steam pressure of 6.5 kg/cm.sup.2
(6.4 MPa). The interlayer had 4 hours of recovery time after
shaping before it was assembled. One of the twenty pre-presses was
judged unusable (95% yield). The pre-press yield was much higher
than that in Comparative Example 26 although the sheeting was
rougher, leading one skilled in the art to suspect that the
pre-press would be hazier.
Example 29
[0030] Twenty windshields were prepared as in Example 28, except
that the interlayer had 8 hours of recovery time after shaping
before it was assembled. None of the twenty windshields was judged
unusable (100% yield).
* * * * *