U.S. patent application number 11/742547 was filed with the patent office on 2008-10-30 for high impact polymer interlayers.
Invention is credited to Wenjie Chen, Aristotelis Karagiannis.
Application Number | 20080268270 11/742547 |
Document ID | / |
Family ID | 39887358 |
Filed Date | 2008-10-30 |
United States Patent
Application |
20080268270 |
Kind Code |
A1 |
Chen; Wenjie ; et
al. |
October 30, 2008 |
HIGH IMPACT POLYMER INTERLAYERS
Abstract
The present invention provides multiple poly(vinyl butyral)
layer interlayers that can be used in multiple layer glass panel
type applications that require a high level of impact protection,
for example in hurricane protection applications or in bullet proof
glass applications. This effect is achieved by forming a poly(vinyl
butyral) interlayer that has a relatively stiff poly(vinyl butyral)
inner layer disposed between two relatively soft outer poly(vinyl
butyral) layers, where the stiffness difference is achieved by a
plasticizer differential that is achieved at least in substantial
part by a residual hydroxyl content difference among the poly(vinyl
butyral) layers.
Inventors: |
Chen; Wenjie; (Amherst,
MA) ; Karagiannis; Aristotelis; (Amherst,
MA) |
Correspondence
Address: |
BRENC LAW;ANDREW BRENC
P.O. BOX 155
ALBION
PA
16401-0155
US
|
Family ID: |
39887358 |
Appl. No.: |
11/742547 |
Filed: |
April 30, 2007 |
Current U.S.
Class: |
428/516 ;
524/515; 525/191 |
Current CPC
Class: |
B32B 27/42 20130101;
B32B 27/22 20130101; C08K 5/0016 20130101; B32B 17/10761 20130101;
B29C 48/08 20190201; B32B 27/40 20130101; Y10T 428/31913 20150401;
C08L 29/14 20130101; B32B 27/306 20130101; B32B 27/30 20130101;
B29C 48/18 20190201; B32B 27/304 20130101; B32B 2605/00 20130101;
B32B 27/08 20130101; C08K 5/0016 20130101; B32B 2419/00
20130101 |
Class at
Publication: |
428/516 ;
524/515; 525/191 |
International
Class: |
B22F 3/00 20060101
B22F003/00; C08K 5/00 20060101 C08K005/00 |
Claims
1. A multiple layer polymer interlayer comprising: a first polymer
layer comprising poly(vinyl butyral); a second polymer layer
comprising poly(vinyl butyral); a third polymer layer comprising
poly(vinyl butyral); wherein said second polymer layer is disposed
between said first polymer layer and said third polymer layer;
wherein the amount of plasticizer in said plasticized thermoplastic
polymer of said first polymer layer is at least 2 phr greater than
the amount of plasticizer in said plasticized thermoplastic polymer
of said second polymer layer; wherein the amount of plasticizer in
said plasticized thermoplastic polymer of said third polymer layer
is at least 2 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer; and
wherein said second polymer layer has a residual hydroxyl content
by weight that is at least 0.5% greater than the residual hydroxyl
content by weight in each of said plasticized thermoplastic polymer
of said first polymer layer and said plasticized thermoplastic
polymer of said third polymer layer.
2. (canceled)
3. The polymer interlayer of claim 1, wherein said second polymer
layer has a residual hydroxyl content by weight that is at least
2.0% greater than the residual hydroxyl content by weight in each
of said plasticized thermoplastic polymer of said first polymer
layer and said plasticized thermoplastic polymer of said third
polymer layer.
4. The polymer interlayer of claim 1, wherein the tensile break
stress of said second polymer layer is greater than 180 kilograms
per square centimeter, the tensile break stress of said first
polymer layer and said third polymer layer is less than 230
kilograms per square centimeter, and wherein the tensile break
stress of said second polymer layer is more than 15 kilograms per
square centimeter greater than the tensile break stress of said
first polymer layer and said third polymer layer.
5. The polymer interlayer of claim 1, wherein the tensile break
stress of said second polymer layer is more than 15 kilograms per
square centimeter greater than the tensile break stress of said
first polymer layer and said third polymer layer.
6. The polymer interlayer of claim 1, wherein the amount of
plasticizer in said plasticized thermoplastic polymer of said first
polymer layer is at least 5 phr greater than the amount of
plasticizer in said plasticized thermoplastic polymer of said
second polymer layer; and, wherein the amount of plasticizer in
said plasticized thermoplastic polymer of said third polymer layer
is at least 5 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer.
7. A multiple layer glazing panel comprising: a rigid glazing
substrate; a multiple layer interlayer comprising: a first polymer
layer comprising poly(vinyl butyral); a second polymer layer
comprising poly(vinyl butyral); a third polymer layer comprising
poly(vinyl butyral); wherein said second polymer layer is disposed
between said first polymer layer and said third polymer layer;
wherein the amount of plasticizer in said plasticized thermoplastic
polymer of said first polymer layer is at least 2 phr greater than
the amount of plasticizer in said plasticized thermoplastic polymer
of said second polymer layer; wherein the amount of plasticizer in
said plasticized thermoplastic polymer of said third polymer layer
is at least 2 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer;
wherein said second polymer layer has a residual hydroxyl content
by weight that is at least 0.5% greater than the residual hydroxyl
content by weight in each of said plasticized thermoplastic polymer
of said first polymer layer and said plasticized thermoplastic
polymer of said third polymer layer: and, wherein said interlayer
is disposed in contact with said rigid glazing substrate.
8. (canceled)
9. The panel of claim 7, wherein said second polymer layer has a
residual hydroxyl content by weight that is at least 2.0% greater
than the residual hydroxyl content by weight in each of said
plasticized thermoplastic polymer of said first polymer layer and
said plasticized thermoplastic polymer of said third polymer
layer.
10. The panel of claim 7, wherein the tensile break stress of said
second polymer layer is greater than 180 kilograms per square
centimeter, the tensile break stress of said first polymer layer
and said third polymer layer is less than 230 kilograms per square
centimeter, and wherein the tensile break stress of said second
polymer layer is more than 15 kilograms per square centimeter
greater than the tensile break stress of said first polymer layer
and said third polymer layer.
11. The panel of claim 7, wherein the tensile break stress of said
second polymer layer is more than 15 kilograms per square
centimeter greater than the tensile break stress of said first
polymer layer and said third polymer layer.
12. The panel of claim 7, wherein the amount of plasticizer in said
plasticized thermoplastic polymer of said first polymer layer is at
least 5 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer;
and, wherein the amount of plasticizer in said plasticized
thermoplastic polymer of said third polymer layer is at least 5 phr
greater than the amount of plasticizer in said plasticized
thermoplastic polymer of said second polymer layer.
13. A method of making a multiple layer interlayer, comprising:
forming a first polymer melt, a second polymer melt, and a third
polymer melt, wherein the difference in phr of the plasticizer
concentrations between any of said first polymer melt, said second
polymer melt, and said third polymer melt is 2 phr or less;
coextruding said first polymer melt, said second polymer melt, and
said third polymer melt to form said interlayer having a first
polymer layer, a second polymer layer, and a third polymer layer,
with said second polymer layer disposed between said first polymer
layer and said third polymer layer, thereby causing a migration of
plasticizer from said second polymer layer into both said first
polymer layer and said third polymer layer; wherein said second
polymer layer has a residual hydroxyl content by weight that is at
least 0.5% greater than the residual hydroxyl content by weight in
said plasticized thermoplastic polymer of said first polymer layer
and said plasticized thermoplastic polymer of said third polymer
layer.
14. The method of claim 13, wherein said second polymer layer has a
residual hydroxyl content by weight that is at least 0.5% greater
than the residual hydroxyl content by weight in each of said
plasticized thermoplastic polymer of said first polymer layer and
said plasticized thermoplastic polymer of said third polymer
layer.
15. The method of claim 13, wherein said second polymer layer has a
residual hydroxyl content by weight that is at least 2.0% greater
than the residual hydroxyl content by weight in each of said
plasticized thermoplastic polymer of said first polymer layer and
said plasticized thermoplastic polymer of said third polymer
layer.
16. The method of claim 13, wherein the tensile break stress of
said second polymer layer is greater than 180 kilograms per square
centimeter, the tensile break stress of said first polymer layer
and said third polymer layer is less than 230 kilograms per square
centimeter, and wherein the tensile break stress of said second
polymer layer is more than 15 kilograms per square centimeter
greater than the tensile break stress of said first polymer layer
and said third polymer layer.
17. The method of claim 13, wherein the tensile break stress of
said second polymer layer is more than 15 kilograms per square
centimeter greater than the tensile break stress of said first
polymer layer and said third polymer layer.
18. The method of claim 13, wherein the amount of plasticizer in
said plasticized thermoplastic polymer of said first polymer layer
is at least 5 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer;
and, wherein the amount of plasticizer in said plasticized
thermoplastic polymer of said third polymer layer is at least 5 phr
greater than the amount of plasticizer in said plasticized
thermoplastic polymer of said second polymer layer.
19. A method of making a multiple layer interlayer, comprising:
forming a first polymer melt, a second polymer melt, and a third
polymer melt; coextruding said first polymer melt, said second
polymer melt, and said third polymer melt to form said interlayer
having a first polymer layer, a second polymer layer, and a third
polymer layer, with said second polymer layer disposed between said
first polymer layer and said third polymer layer; wherein the
amount of plasticizer in said plasticized thermoplastic polymer of
said first polymer layer is at least 2 phr greater than the amount
of plasticizer in said plasticized thermoplastic polymer of said
second polymer layer; and, wherein the amount of plasticizer in
said plasticized thermoplastic polymer of said third polymer layer
is at least 2 phr greater than the amount of plasticizer in said
plasticized thermoplastic polymer of said second polymer layer.
Description
FIELD OF THE INVENTION
[0001] The present invention is in the field of polymer interlayers
and multiple layer glass panels comprising polymer interlayers,
and, more specifically, the present invention is in the field of
polymer interlayers comprising multiple thermoplastic layers.
BACKGROUND
[0002] Poly(vinyl butyral) (PVB) is commonly used in the
manufacture of polymer layers that can be used as interlayers in
light-transmitting laminates such as safety glass or polymeric
laminates. Safety glass often refers to a transparent laminate
comprising a poly(vinyl butyral) layer disposed between two layers
of glass. Safety glass often is used to provide a transparent
barrier in architectural and automotive openings. Its main function
is to absorb energy, such as that caused by a blow from an object,
without allowing penetration through the opening or the dispersion
of shards of glass, thus minimizing damage or injury to the objects
or persons within an enclosed area. Safety glass also can be used
to provide other beneficial effects, such as to attenuate acoustic
noise, reduce UV and/or IR light transmission, and/or enhance the
appearance and aesthetic appeal of window openings.
[0003] Safety glass is particularly desirable in architectural
glazing applications that are intended for use in areas prone to
hurricane activity. During hurricanes, wind-borne debris will be
present. To protect a building during hurricane from being damaged,
windows and doors, typically the weakest link in a building's
envelope, must be safeguarded from penetration by wind-borne
debris, and they must also remain in the place through the
remainder of the storm. Therefore, an interlayer that can safeguard
a window against significant impacts and remain in the opening
during cyclical wind loading even if the glass is cracked is
particularly desirable.
[0004] Attempts to create such an interlayer for hurricane
protection have usually involved balancing the benefit to high
impact resistance obtained from using a relatively softer and lower
glass adhesion polymeric interlayer with the benefit of high
cyclical wind loading resistance after glass cracking which is
obtained from using a stiffer and high glass adhesion polymeric
interlayer.
[0005] If an interlayer is too soft or adhesion to glass is too
low, then the interlayer will not have the strength to resist high
wind loading after an impact. On the other hand, if the interlayer
is too stiff and adhesion to glass is too high, then the interlayer
will not have a high level of impact resistance--i.e., the
interlayer will have low penetration resistance.
[0006] Therefore, further improved interlayer compositions are
needed to provide multiple layer safety glass that has high impact
resistance and high cyclical wind-loading resistance for, among
other things, hurricane protection.
SUMMARY OF THE INVENTION
[0007] The present invention provides multiple poly(vinyl butyral)
layer interlayers that can be used in multiple layer glass panel
type applications that require a high level of impact protection,
for example in hurricane protection applications or in bullet proof
glass applications. This effect is achieved by forming a poly(vinyl
butyral) interlayer that has a relatively stiff poly(vinyl butyral)
inner layer disposed between two relatively soft outer poly(vinyl
butyral) layers, where the stiffness difference is achieved by a
plasticizer differential that is achieved at least in substantial
part by a residual hydroxyl content difference among the poly(vinyl
butyral) layers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 represents a schematic cross sectional view of a
multiple manifold coextrusion device of the present invention.
[0009] FIG. 2 is a graph showing the results of a ball drop impact
test for three sample interlayer embodiments of the present
invention and a control interlayer.
DETAILED DESCRIPTION
[0010] According to the present invention, it has now been
surprisingly discovered that superior impact resistance and high
stiffness characteristics can be imparted on multiple layer glazing
panels by incorporating a multiple layer interlayer into the
panels, where the interlayer comprises three poly(vinyl butyral)
layers having different plasticizer concentrations that are stably
achieved by formulating the poly(vinyl butyral) layers with
different levels of residual hydroxyl content.
[0011] The composition of the poly(vinyl butyral) layers is such
that net migration of plasticizer from one poly(vinyl butyral)
layer to another is negligible or zero, thereby maintaining the
plasticizer differential.
[0012] As used herein, "plasticizer content" can be measured as
parts per hundred resin parts (phr), on a weight per weight basis.
For example, if 30 grams of plasticizer is added to 100 grams of
polymer resin, then the plasticizer content of the resulting
plasticized polymer would be 30 phr. As used herein throughout,
when the plasticizer content of a polymer layer is given, the
plasticizer content of that particular layer is determined with
reference to the phr of the plasticizer in the melt that was used
to produce that particular layer.
[0013] For layers of unknown plasticizer content, the plasticizer
content can be determined via a wet chemical method in which an
appropriate solvent, or a mixture of solvents, is used to extract
the plasticizer out of the layer. By knowing the weight of the
sample layer and the weight of the extracted layer, the plasticizer
content in phr can be calculated. In the case of a multiple polymer
layer interlayer, individual polymer layers can be physically
separated from one another before the plasticizer content in each
of the polymer layers is measured.
[0014] In various embodiments of the present invention, a multiple
layer interlayer that imparts superior impact resistance and high
stiffness characteristics on multiple layer glass panels comprises
three polymer layers having different stiffness. The stiffness of
the two skin layers can be the same or different.
[0015] As used herein, an "interlayer" is any thermoplastic
construct that can be used in multiple layer glass applications,
such as safety glass in windshields and architectural windows, and
a "multiple layer" interlayer is any interlayer that is formed by
combining, usually through laminating processes or coextrusion, two
or more individual layers into a single interlayer.
[0016] In various embodiments of the present invention, a multiple
layer interlayer comprises three polymer layers disposed in contact
with each other, wherein each polymer layer comprises a
thermoplastic polymer, as detailed elsewhere herein.
[0017] In preferred embodiments of the present invention, three
layer interlayers of the present invention have two outer
poly(vinyl butyral) layers and an inner poly(vinyl butyral) layer,
with the outer layers having relatively high plasticizer content
and low residual hydroxyl content (as detailed elsewhere herein),
and the inner layer having a relatively low plasticizer content and
high residual hydroxyl content.
[0018] For a given type of plasticizer, the compatibility of that
plasticizer in poly(vinyl butyral) is largely determined by the
residual hydroxyl content or vinyl acetate content. Typically,
poly(vinyl butyral) with a greater residual hydroxyl content or
vinyl acetate content will have different compatibility or capacity
with the given plasticizer from poly(vinyl butyral) with a lower
residual hydroxyl content and vinyl acetate content. These
properties can be used to select the hydroxyl or vinyl acetate
content of each poly(vinyl butyral) polymer and formulate each of
the polymer layers to allow for the proper plasticizer loading and
to stably maintain the difference in plasticizer content between
the polymer layers.
[0019] In various embodiments of the present invention, the
plasticizer content of the outer layers are each at least 2 phr, 5
phr, 8 phr, 10 phr, 12 phr, 15 phr, 18 phr, 20 phr, or 25 phr
greater than the plasticizer content of the inner polymer layer.
The outer layers can have, for example, 10-75 phr plasticizer,
while the inner layer can have, for example, 0-50 phr plasticizer.
As noted above, the plasticizer difference between the layers is
maintained in the final laminate or coextruded interlayer due to
the difference in residual hydroxyl content or vinyl acetate
content.
[0020] As used herein, residual hydroxyl content (as vinyl hydroxyl
content or poly(vinyl alcohol) (PVOH) content) refers to the amount
of hydroxyl groups remaining as side groups on the polymer chains
after processing is complete. For example, poly(vinyl butyral) can
be manufactured by hydrolyzing poly(vinyl acetate) to poly(vinyl
alcohol), and then reacting the poly(vinyl alcohol) with
butyraldehyde to form poly(vinyl butyral). In the process of
hydrolyzing the poly(vinyl acetate), typically not all of the
acetate side groups are converted to hydroxyl groups. Further,
reaction with butyraldehyde typically will not result in all
hydroxyl groups being converted to acetal groups. Consequently, in
any finished poly(vinyl butyral), there will typically be residual
acetate groups (as vinyl acetate groups) and residual hydroxyl
groups (as vinyl alcohol groups) as side groups on the polymer
chain. As used herein, residual hydroxyl content is measured on a
weight percent basis per ASTM 1396.
[0021] In various embodiments of the present invention, the
residual hydroxyl content of the inner polymer layer can be at
least 0.5%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 3.0%, 4.0%, 5.0%, 7.5%,
or at least 10% greater than the residual hydroxyl content of the
two outer polymer layers. This difference is calculated by
subtracting the residual hydroxyl content of the layer with the
lower residual hydroxyl content from the residual hydroxyl content
of the layer with the greater residual hydroxyl content. For
example, if the middle polymer layer has a residual hydroxyl
content of 20%, and an outer polymer layer has a residual hydroxyl
content of 17%, then the residual hydroxyl content of the middle
layer is 3% greater than the residual hydroxyl content of the outer
layer.
[0022] As is known in the art, residual hydroxyl content in
poly(vinyl butyral) resin can be controlled by controlling
butyraldehyde concentration, reaction times, and other variables in
the manufacturing process. In various embodiments, the residual
hydroxyl content of the layers is as follows: middle layer less
than 30% and outer layers less than 28%; middle layer less than 25%
and outer layers less than 23%; middle layer less than 23% and
outer layers less than 21%; middle layer less than 21% and outer
layers less than 19%; middle layer less than 21% and outer layer
less than 17%; middle layer less than 21% and out layer less than
15%; middle layer less than 21% and out layer less than 12%; middle
layer less than 20% and outer layers less than 17%; middle layer
less than 18% and outer layers less than 15%; and middle layer less
than 15% and outer layers less than 12%. In any of these
embodiments, any suitable values given in the paragraph, above, for
the difference in hydroxyl content between the layers can be
used.
[0023] As used herein, tensile break stress, or tensile strength,
of a polymer layer is defined and measured according to the method
described in JIS K6771. In various embodiments of the present
invention, the polymer layers have a tensile break stress according
to the following, wherein the middle polymer layer in the following
list is the polymer layer with the lower plasticizer content:
middle polymer layer greater than 135 kilograms per square
centimeter and outer polymer layers less than 120 kilograms per
square centimeter; middle polymer layer greater than 150 kilograms
per square centimeter and outer polymer layers less than 135
kilograms per square centimeter; middle polymer layer greater than
165 kilograms per square centimeter and outer polymer layers less
than 150 kilograms per square centimeter; middle polymer layer
greater than 180 kilograms per square centimeter and outer polymer
layers less than 165 kilograms per square centimeter; or middle
polymer layer greater than 350 kilograms per square centimeter and
outer polymer layer less than 100 kilograms per square centimeter;
or in general the two polymer layers differ in tensile break stress
by at least 15 kilograms per square centimeter. In yet other
embodiments, the tensile break stress of the middle polymer layer
is greater than 230 kilograms per square centimeter, and the
tensile break stress of the outer polymer layers is less than 230
kilograms per square centimeter.
[0024] In various embodiments of the present invention, two
adjacent polymer layers of the present invention have the differing
plasticizer content and residual hydroxyl content, as described
above, and each further has a residual acetate content of less than
5 mole %, less than 4 mole %, less than 3 mole %, less than 2 mole
%, or less than 1 mole %. These residual acetate concentrations can
be combined with the residual hydroxyl contents given above, in any
combination, to form polymer layers of the present invention having
the described differences in plasticizer content and residual
hydroxyl content while having little to no residual acetate
content.
[0025] In the three layer embodiments of the present invention, the
outer two layers can have the same or different compositions. For
example, one outer polymer layer can have a 10 phr plasticizer
difference with the middle polymer layer, while the second outer
polymer layer can have a 20 phr plasticizer difference with the
middle polymer layer. Such a difference would be useful, for
example and without limitation, in embodiments in which the two
rigid glazing substrates between which the multiple layer
interlayer is being laminated are different or have different
surface treatments.
[0026] In addition to the three layer embodiments described herein,
further embodiments include interlayers having more than three
layers. For example, any of the three polymer layers in the three
layer embodiment can be substituted with multiple thinner polymer
layers that together have the approximate thickness of the single
polymer layer. Such a construction would be desirable, for example
and without limitation, if a modifying agent, such as an
ultraviolet light absorber, was required in only a thin cross
section of the interlayer. In addition to polymer layers, polymer
films, as described below, can also be added, as desired. For
example, a polymer film can be added between the middle polymer
layer and an outer polymer layer in the three layer embodiment to
provide a desired function, such as infrared blocking. Interlayers
of the present invention can have, for example, 4, 5, 6, or up to
10 individual layers.
[0027] Other conventional layers, as are known in the art, can be
incorporated into the interlayers of the present invention. For
example, polymer films (described in detail elsewhere herein) such
as polyesters like poly(ethylene terephthalate) having a metallized
layer, an infrared reflecting stack, or other performance layer
deposited thereon, can be included between any two layers of
polymer layers of the present invention. In general, additional
layers of thermoplastics, such as poly(vinyl butyral), polyester
films, primer layers, and hardcoat layers can be added to the
multiple layer interlayers of the present invention according to
the desired result and the particular application.
[0028] In addition to methods of manufacturing multiple layer
interlayers of the present invention and multiple layer glazings
comprising those interlayers in which the interlayers have been
produced by combining individual layers that already have the
desired differences in plasticizer content, methods of the present
invention also include the technique of combining layers having
plasticizer contents that are the same or closer together than in
the final product. For example, a prelaminate can be formed having
outer polymer layers with 30 phr plasticizer and an inner polymer
layer with 30 phr plasticizer, with the inner polymer layer having
a higher residual hydroxyl content than the outer polymer layers,
as detailed elsewhere herein. The prelaminate, which has not been
completely laminated, will be easier to handle than would be the
case if the outer layers had a higher plasticizer content. After
final lamination, plasticizer will migrate from the inner polymer
layer to the outer polymer layers until an equilibrium is reached,
at which point the desired plasticizer differential will have been
reached. In various embodiments of this method of the present
invention, plasticizer content of the inner polymer layer, relative
to the outer polymer layers, at the time of lamination of the
layers can be the same, with a subsequent migration in plasticizer
content resulting in the desired differential. In various
embodiments, the plasticizer content, in terms of phr, of the inner
layer can decrease up to 5% or up to 10% of its initial value
because of migration of plasticizer between the layers after
lamination.
[0029] The present invention also includes methods of manufacturing
an interlayer, comprising the steps of forming a first polymer
layer, a second polymer layer, and a third polymer layer, wherein
the three polymer layers have compositions according to the three
layer embodiments as described elsewhere herein, and laminating the
three polymer layers together to form the interlayer.
[0030] The present invention also includes methods of manufacturing
a multiple layer glazing, comprising laminating any of the
interlayers of the present invention between two rigid, transparent
panels, as are known in the art, such as glass or acrylic
layers.
[0031] The present invention also includes multiple layer glass
panels, such as windshields and architectural windows and doors,
comprising a multiple layer interlayer of the present
invention.
[0032] Also included are multiple layer glazing panels having
plastics, such as acrylics, or other suitable materials in place of
the glass panels.
Polymer Film
[0033] As used herein, a "polymer film" means a relatively thin and
rigid polymer layer that functions as a performance enhancing
layer. Polymer films differ from polymer layers, as used herein, in
that polymer films do not themselves provide the necessary
penetration resistance and glass retention properties to a multiple
layer glazing structure, but rather provide performance
improvements, such as infrared absorption character. Poly(ethylene
terephthalate) is most commonly used as a polymer film.
[0034] In various embodiments, the polymer film layer has a
thickness of 0.013 mm to 0.20 mm, preferably 0.025 mm to 0.1 mm, or
0.04 to 0.06 mm. The polymer film layer can optionally be surface
treated or coated to improve one or more properties, such as
adhesion or infrared radiation reflection. These functional
performance layers include, for example, a multi-layer stack for
reflecting infra-red solar radiation and transmitting visible light
when exposed to sunlight. This multi-layer stack is known in the
art (see, for example, WO 88/01230 and U.S. Pat. No. 4,799,745) and
can comprise, for example, one or more Angstroms-thick metal layers
and one or more (for example two) sequentially deposited, optically
cooperating dielectric layers. As is also known, (see, for example,
U.S. Pat. Nos. 4,017,661 and 4,786,783), the metal layer(s) may
optionally be electrically resistance heated for defrosting or
defogging of any associated glass layers.
[0035] An additional type of polymer film that can be used with the
present invention, which is described in U.S. Pat. No. 6,797,396,
comprises a multitude of nonmetallic layers that function to
reflect infrared radiation without creating interference that can
be caused by metallic layers.
[0036] The polymer film layer, in some embodiments, is optically
transparent (i.e. objects adjacent one side of the layer can be
comfortably seen by the eye of a particular observer looking
through the layer from the other side), and usually has a greater,
in some embodiments significantly greater, tensile modulus
regardless of composition than that of any adjacent polymer layer.
In various embodiments, the polymer film layer comprises a
thermoplastic material. Among thermoplastic materials having
suitable properties are nylons, polyurethanes, acrylics,
polycarbonates, polyolefins such as polypropylene, cellulose
acetates and triacetates, vinyl chloride polymers and copolymers
and the like. In various embodiments, the polymer film layer
comprises materials such as re-stretched thermoplastic films having
the noted properties, which include polyesters, for example
poly(ethylene terephthalate) and copoly(ethylene terephthalate)
(PETG). In various embodiments, poly(ethylene terephthalate) is
used, and, in various embodiments, the poly(ethylene terephthalate)
has been biaxially stretched to improve strength, and has been heat
stabilized to provide low shrinkage characteristics when subjected
to elevated temperatures (e.g. less than 2% shrinkage in both
directions after 30 minutes at 150.degree. C.).
[0037] Various coating and surface treatment techniques for
poly(ethylene terephthalate) film that can be used with the present
invention are disclosed in published European Application No.
0157030. Polymer films of the present invention can also include a
hardcoat and/or and antifog layer, as are known in the art.
Polymer Layer
[0038] As used herein, a "polymer layer" means any thermoplastic
polymer composition formed by any suitable method into a thin layer
that is suitable alone, or in stacks of more than one layer, for
use as an interlayer that provides adequate penetration resistance
and glass retention properties to laminated glazing panels.
Plasticized poly(vinyl butyral) is most commonly used to form
polymer layers.
[0039] The polymer layer can comprise any suitable polymer, and, in
a preferred embodiment, the polymer layer comprises poly(vinyl
butyral). In any of the embodiments of the present invention given
herein that comprise poly(vinyl butyral) as the polymeric component
of the polymer layer, another embodiment is included in which the
polymer component consists of or consists essentially of poly(vinyl
butyral). In these embodiments, any of the variations in additives
disclosed herein can be used with the polymer layer having a
polymer consisting of or consisting essentially of poly(vinyl
butyral).
[0040] In one embodiment, the polymer layer comprises a polymer
based on partially acetalized poly(vinyl alcohol)s. In another
embodiment, the polymer layer comprises a polymer selected from the
group consisting of poly(vinyl butyral), polyurethane, polyvinyl
chloride, poly(ethylene vinyl acetate), combinations thereof, and
the like. In other embodiments, the polymer layer comprises
plasticized poly(vinyl butyral). In further embodiments the polymer
layer comprises poly(vinyl butyral) and one or more other polymers.
Other polymers having a proper plasticizing capacity can also be
used. In any of the sections herein in which preferred ranges,
values, and/or methods are given specifically for poly(vinyl
butyral) (for example, and without limitation, for plasticizers,
component percentages, thicknesses, and characteristic-enhancing
additives), those ranges also apply, where applicable, to the other
polymers and polymer blends disclosed herein as useful as
components in polymer layers.
[0041] For embodiments comprising poly(vinyl butyral), the
poly(vinyl butyral) can be produced by known acetalization
processes that involve reacting poly(vinyl alcohol) with
butyraldehyde in the presence of an acid catalyst, followed by
neutralization of the catalyst, separation, stabilization, and
drying of the resin, with the understanding that in various
embodiments, residual hydroxyl content will be controlled, as
described elsewhere herein.
[0042] In various embodiments, the polymer layer comprises
poly(vinyl butyral) having a molecular weight greater than 30,000,
40,000, 50,000, 55,000, 60,000, 65,000, 70,000, 120,000, 250,000,
or 350,000 grams per mole (g/mole or Daltons). Small quantities of
a dialdehyde or trialdehyde can also be added during the
acetalization step to increase molecular weight to greater than 350
Daltons (see, for example, U.S. Pat. Nos. 4,874,814; 4,814,529; and
4,654,179). As used herein, the term "molecular weight" means the
weight average molecular weight.
[0043] If additional, conventional polymer layers are used in
addition to any of the embodiments described above as having
residual hydroxyl and plasticizer content differences, those
additional, conventional polymer layers can comprise 20 to 60, 25
to 60, 20 to 80, or 10 to 70 parts plasticizer per one hundred
parts of resin (phr). Of course other quantities can be used as is
appropriate for the particular application. In some embodiments,
the plasticizer has a hydrocarbon segment of fewer than 20, fewer
than 15, fewer than 12, or fewer than 10 carbon atoms.
[0044] Any suitable plasticizers can be added to the polymer resins
of the present invention in order to form the polymer layers.
Plasticizers used in the polymer layers of the present invention
can include esters of a polybasic acid or a polyhydric alcohol,
among others. Suitable plasticizers include, for example,
triethylene glycol di-(2-ethylbutyrate), triethylene glycol
di-(2-ethylhexanoate), triethylene glycol diheptanoate,
tetraethylene glycol diheptanoate, dihexyl adipate, dioctyl
adipate, hexyl cyclohexyladipate, mixtures of heptyl and nonyl
adipates, diisononyl adipate, heptylnonyl adipate, dibutyl
sebacate, polymeric plasticizers such as the oil-modified sebacic
alkyds, and mixtures of phosphates and adipates such as disclosed
in U.S. Pat. No. 3,841,890 and adipates such as disclosed in U.S.
Pat. No. 4,144,217, and mixtures and combinations of the foregoing.
Other plasticizers that can be used are mixed adipates made from
C.sub.4 to C.sub.9 alkyl alcohols and cyclo C.sub.4 to C.sub.10
alcohols, as disclosed in U.S. Pat. No. 5,013,779, and C.sub.6 to
C.sub.8 adipate esters, such as hexyl adipate. In preferred
embodiments, the plasticizer is triethylene glycol
di-(2-ethylhexanoate).
[0045] Adhesion control agents (ACAs) can also be included in the
polymer layers of the present invention to impart the desired
adhesiveness. These agents can be incorporated into the outer
layers in a three polymer layer embodiment, for example. Any of the
ACAs disclosed in U.S. Pat. No. 5,728,472 can be used.
Additionally, residual sodium acetate and/or potassium acetate can
be adjusted by varying the amount of the associated hydroxide used
in acid neutralization. In various embodiments, polymer layers of
the present invention comprise, in addition to sodium acetate,
magnesium bis(2-ethyl butyrate)(chemical abstracts number
79992-76-0). The magnesium salt can be included in an amount
effective to control adhesion of the polymer layer to glass.
[0046] Additives may be incorporated into the polymer layer to
enhance its performance in a final product. Such additives include,
but are not limited to, plasticizers, dyes, pigments, stabilizers
(e.g., ultraviolet stabilizers), antioxidants, flame retardants,
other IR absorbers, anti-block agents, combinations of the
foregoing additives, and the like, as are known in the art.
[0047] Agents that selectively absorb light in the visible or near
infrared spectrum can be added to any of the appropriate polymer
layers. Agents that can be used include dyes and pigments such as
indium tin oxide, antimony tin oxide, or lanthanum hexaboride
(LaB.sub.6).
[0048] Any suitable method can be used to produce the polymer
layers and the multiple layer interlayers of the present invention.
Details of suitable processes for making poly(vinyl butyral) are
known to those skilled in the art (see, for example, U.S. Pat. Nos.
2,282,057 and 2,282,026). In one embodiment, the solvent method
described in Vinyl Acetal Polymers, in Encyclopedia of Polymer
Science & Technology, 3.sup.rd edition, Volume 8, pages
381-399, by B. E. Wade (2003) can be used. In another embodiment,
the aqueous method described therein can be used. Poly(vinyl
butyral) is commercially available in various forms from, for
example, Solutia Inc., St. Louis, Mo. as Butvar.TM. resin.
[0049] As used herein, "resin" refers to the polymeric (for example
poly(vinyl butyral)) component that is removed from the mixture
that results from the acid catalysis and subsequent neutralization
of the polymeric precursors. Resin will generally have other
components in addition to the polymer, for example poly(vinyl
butyral), such as acetates, salts, and alcohols. As used herein,
"melt" refers to a mixture of resin with a plasticizer and,
optionally, other additives.
[0050] One exemplary method of forming a poly(vinyl butyral) layer
comprises extruding molten poly(vinyl butyral) comprising resin,
plasticizer, and additives and then forcing the melt through a
sheet die (for example, a die having an opening that is
substantially greater in one dimension than in a perpendicular
dimension). Another exemplary method of forming a poly(vinyl
butyral) layer comprises casting a melt from a die onto a roller,
solidifying the resin, and subsequently removing the solidified
resin as a sheet. In either embodiment, the surface texture at
either or both sides of the layer may be controlled by adjusting
the surfaces of the die opening to control melt fracture or by
providing texture at the roller surface. Other techniques for
controlling the layer texture include varying parameters of the
materials (for example, the water content of the resin and/or the
plasticizer, the melt temperature, molecular weight distribution of
the poly(vinyl butyral), or combinations of the foregoing
parameters). Furthermore, the layer can be configured to include
spaced projections that define a temporary surface irregularity to
facilitate the de-airing of the layer during lamination processes
after which the elevated temperatures and pressures of the
laminating process cause the projections to melt into the layer,
thereby resulting in a smooth finish.
[0051] Manufacture of the interlayers of the present invention can
be by any suitable process, for example, by lamination of
individual layers or through coextrusion.
[0052] Lamination of individual layers can be performed by
combining separately produced layers and then applying sufficient
heat and pressure to tack the layers together to form a
"prelaminate," thereby allowing the handling of the layers as a
unit, with final adhesion occurring later when the interlayer is
laminated between rigid glazing substrates. Alternatively,
individual layers can be assembled and positioned between rigid
glazing substrates without any prior tacking, and the complete
multiple layer glazing can be laminated in a single step.
[0053] The preferred method of producing interlayers of the present
invention is through the simultaneous coextrusion of multiple, for
example three, polymer layers. For the purposes of the present
invention, coextrusion of multiple melts results in multiple
polymer layers being formed together as one interlayer.
[0054] Multiple layer interlayers of the present invention are
preferably coextruded using a multiple manifold coextrusion device
such as the one shown in FIG. 1. As shown in schematic cross
sectional view generally at 10, an extrusion device has a first die
manifold 12, a second die manifold 14, and a third die manifold 16.
The device shown in FIG. 1 operates by simultaneously extruding
polymer melts from each manifold (12, 14, 16) toward the extrusion
opening 20, where the multiple layer interlayer is extruded as a
composite of three individual polymer layers. Layer thickness can
be varied by adjusting the distance between the die lips at the
extrusion opening 20.
[0055] As used herein, a "polymer layer" includes layers that are
produced individually and layers that are coextruded. For example,
an interlayer that is produced by coextruding three melts will have
three individual "polymer layers" just as will an interlayer that
is produced by laminating three individually produced polymer
layers into a single interlayer.
[0056] In various embodiments, the interlayers of the present
invention can have total thicknesses of 0.1 to 3 millimeters, 0.2
to 2.5 millimeters, 0.25 to 1.75 millimeters, and 0.3 to 1.5
millimeters (mm). The individual polymer layers of a multiple layer
interlayer can have, for example, approximately equal thicknesses
that, when added together, result in the total thickness ranges
given above. Of course, in other embodiments, the thicknesses of
the layers can be different, and can still add to the total
thicknesses given above.
[0057] The parameters for the polymer layer described above apply
as well to any layer in a multiple layer construct of the present
invention that is a poly(vinyl butyral) type layer.
[0058] The following paragraphs describe various techniques that
can be used to improve and/or measure the characteristics of the
polymer layer.
[0059] The clarity of a polymer layer, and particularly a
poly(vinyl butyral) layer, can be determined by measuring the haze
value, which is a quantification of the amount of light scattered
away from the direction of the incident beam in passing through the
layer. The percent haze can be measured according to the following
technique. An apparatus for measuring the amount of haze, a
Hazemeter, Model D25, which is available from Hunter Associates
(Reston, Va.), can be used in accordance with ASTM D1003-61
(Re-approved 1977)-Procedure A, using Illuminant C, at an observer
angle of 2 degrees. In various embodiments of the present
invention, percent haze is less than 5%, less than 3%, and less
than 1%.
[0060] The visible transmittance can be quantified using a
UV-Vis-NIR spectrophotometer such as the Lambda 900 made by Perkin
Elmer Corp. by methods described in international standard ISO
9050:1990. In various embodiments, the transmittance through a
polymer layer of the present invention is at least 60%, at least
70%, or at least 80%.
[0061] Pummel adhesion can be measured according to the following
technique, and where "pummel" is referred to herein to quantify
adhesion of a polymer layer to glass, the following technique is
used to determine pummel. Two-ply glass laminate samples are
prepared with standard autoclave lamination conditions. The
laminates are cooled to about -18.degree. C. (0.degree. F.) and
manually pummeled with a hammer to break the glass. All broken
glass that is not adhered to the poly(vinyl butyral) layer is then
removed, and the amount of glass left adhered to the poly(vinyl
butyral) layer is visually compared with a set of standards. The
standards correspond to a scale in which varying degrees of glass
remain adhered to the poly(vinyl butyral) layer. In particular, at
a pummel standard of zero, no glass is left adhered to the
poly(vinyl butyral) layer. At a pummel standard of 10, 100% of the
glass remains adhered to the poly(vinyl butyral) layer. Poly(vinyl
butyral) layers of the present invention can have, for example, a
pummel value of between 2 and 10.
[0062] Tensile break stress can be determined for a polymer layer
according to the procedure described in JIS K6771.
[0063] Impact testing is carried out using a staircase method "ball
drop" test to determine the impact resistance of the laminated
glass panel comprising the interlayer. A 2,268 gram steel ball is
dropped vertically onto a horizontally positioned, 30.5
cm.times.30.5 cm size of the sample panel to be tested. Impact
performance is measured as the Mean Break Height (MBH), which is
calculated as the ball drop height at which 50% of the samples
would hold the ball and 50% would allow penetration.
[0064] Flexural Modulus is determined according to ASTM D790.
EXAMPLES
Impact Resistance:
[0065] Examples of the poly(vinyl butyral) multiple layer
interlayers having improved impact resistance are listed in Table
1. The impact resistance, shown as the Mean Break Height (MBH) in
the unit of meters, is illustrated in FIG. 2.
[0066] For the three Samples given in Table 1, each sample
interlayer has a total thickness of 0.64 millimeters (25 mil)
comprising a first layer and a third layer each having 16% residual
hydroxyl content and a thickness of 0.10 millimeters (4 mils) with
a second layer having 18.5% residual hydroxyl content and a
thickness of 0.43 millimeters (17 mils) between and in contact with
the first layer and the third layer.
[0067] Table 1 provides the phr of the plasticizer triethylene
glycol di-(2-ethylhexanoate) (3GEH) formulated with the resin.
TABLE-US-00001 TABLE 1 phr of plasticizer Sample Layer 1 Layer 2
Layer 3 1 32 22 32 2 25 22 25 3 32 27 32
[0068] As shown in FIG. 2, the tested multiple layer interlayer
embodiments of the present invention demonstrate a higher impact
performance at 0.64 millimeter total layer thickness (25 mil),
compared with a conventional, single layer interlayer having a
thickness of 0.76 millimeters (30 mil).
[0069] The stiffness of two sample multiple layer interlayers of
the present invention are measured as the Flexural Modulus of a
laminated glass panel comprising the sample interlayers. The same
thickness of glass is used for both samples and the comparative
interlayer, which is 3 millimeters in the present invention.
Results are shown in Table 2.
[0070] For the two Samples given in Table 2, each sample three
layer interlayer has the thicknesses and residual hydroxyl content
given in the table, with the first and third outer layers of each
having 25 phr of plasticizer triethylene glycol
di-(2-ethylhexanoate) (3GEH) formulated with the resin, and the
second, inner layer of each having 18 phr of that same plasticizer
formulated with the resin. The "Comp" interlayer is a Saflex
"Storm" product that is commercially available from Solutia
Inc.
TABLE-US-00002 TABLE 2 Total Layer Thickness millimeters (mils)
Flexural Thickness Layer 1 Layer 2 Layer 3 Modulus millimeters (16%
(18.5% (16% 10.sup.10 Pa Sample (mils) PVOH) PVOH) PVOH) (10.sup.6
PSI) 4 1.88 (74) 0.38 (15) 1.12 (44) 0.38 (15) 4.54 (6.59) 5 1.32
(52) 0.38 (15) 0.56 (22) 0.38 (15) 4.63 (6.72) Comp Total thickness
of 2.0 millimeters (77 mil) 2.32 (3.36)
[0071] The multiple layer interlayer embodiments of the present
invention shown in Table 2 demonstrate a higher stiffness than a
conventional control sample, where "Pa" is Pascal and "PSI" is
pounds per square inch.
[0072] By virtue of the present invention, it is now possible to
provide multiple layer interlayers that have superior impact
resistance and high stiffness, and that are readily incorporated
into multiple layer constructs, such as laminated glass panels for
architectural windows.
[0073] While the invention has been described with reference to
exemplary embodiments, it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiments disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
[0074] It will further be understood that any of the ranges,
values, or characteristics given for any single component of the
present invention can be used interchangeably with any ranges,
values, or characteristics given for any of the other components of
the invention, where compatible, to form an embodiment having
defined values for each of the components, as given herein
throughout. For example, a polymer layer can be formed comprising
residual acetate content in any of the ranges given in addition to
any of the ranges given for plasticizer, where appropriate, to form
many permutations that are within the scope of the present
invention but that would be cumbersome to list.
[0075] Any figure reference numbers given within the abstract or
any claims are for illustrative purposes only and should not be
construed to limit the claimed invention to any one particular
embodiment shown in any figure.
[0076] Figures are not drawn to scale unless otherwise
indicated.
[0077] Each reference, including journal articles, patents,
applications, and books, referred to herein is hereby incorporated
by reference in its entirety.
* * * * *