Note: Descriptions are shown in the official language in which they were submitted.
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- 1 - 06-12-(1089)~
PLASTICIZ~D PULYVINYL BUTYRAL INl'ERLAYERS
-
PROCESS FOR FORMING SAME AND PLASTICIZER
BLEND THEREFOR
BACKGROUND OF INVENTION
This invention relates to polyvinyl butyral
(PVB) sheet plasticized with fatty acid esters and
more paxticularly with a fatty acid ester blend which
provides the sheet with improved penetration resist-
ance without significant loss in its resistance to
stress cracking polycarbonate or polyacrylate when in
contact therewith as an interlayer in a laminated
glass assembly.
In recent years sociologists and psycholo-
gists have started a movement toward prisons without
bars. Thick layers of impact resistant polycarbonate
initially used in such applications were quite early
determined to be inadequate since the polycarbonate
could be burned or scratched or dissolved or fractured
when heated or abused. Moreover, when exposed to the
elements the polycarbonate turned yellow, lost its
strength and was susceptable to crazing. Based on
this early work a need was defined for a material for
security applications which was strong, chemically
impervious, and scratch and fracture resistant over a
wide range of ambient conditions.
Thereafter laminates of one or more layers
of glass with one or more layers of polycarbonate
were proposed which in use were mounted with the glass
layer on the outside exposed to the elements and the
polycarbonate either forming the innermost surface or
positioned inboard of a glass layer forming such
innermost surface. ~owever, with these laminates an
interlayer between the glass and polycarbonate is
necessary since polycarbonate will not adequately
adhere to glass.
Thermoplastic polyurethane layers have been
used to laminate polycarbonate to glass but polyure-
thanes are costly and usually require treatment of
8941
-2- 06-12-(10~9)~
the glass with a primer coating before lamination.
Moreover, such polyurethanes are difficult to process
into laminates because their low melting temperatures
dictate the need for a batch type deairing operation
with long exposure to vacuum for complete air removal.
Commercially available grades of PVB sheet are not
acceptable as an interlayer to adhere polycarbonate to
glass because the plasticizer in the PVB crazes the
polycarbonate. To solve this a special barrier
coating, as disclosed in U. S. 4,243,719, was proposed
between the polycarbonate and PVB to keep the plasti-
cizer in the PVB away from the polycarbonate. The PVB
is still necessary since the coating will not adhere
to the glass and the PVB assists in absorbing energy
on impacting. Such a coating must be pinhole-free for
obvious reasons and moreover is costly in that it
represents an additional layer in an already multi
layered laminate which could be avoided if a plasti-
cizer for PVB were available which did not craze the
polycarbonate.
Sulfonamide and phosphate plasticizers for
PVB which do not attack polycarbonate are disclosed in
U. S. 3,539,442 and 3,406,086 respectively but PV~
containing such plasticizers can only be difficultly
extruded in forming sheet since they tend to decompose
at extrusion conditions and degrade the PVB.
: Certain esters which in natural form can be
the major c~nstituents of castor oil are proposed
in U. S. 4,128,694 as plasticizers for P~B which
neither craze polycarbonate or polyacrylate nor
deteriorate during extrusion of plasticized PVB.
However, such interlayers exhibit relatively high
glass transition temperatures (Tg~ at the usual
plasticizer loadings and marginal peel adhesion to
polycarbonate which means the impact properties at low
performance temperatures are also marginal. This has
0~ .
94~
precluded the use of such interlayers in security glass
applications exposed to cold climates.
A need, therefore, exists in the art for a
plasticized PVB sheet having the properties of those
disclosed in U. S. 4,128,694, but which has a lo~ Tg and
higher peel adhesion and therefore improved low
temperature performance properties when present as a
functional PVB interlayer in a security glass laminate.
Eligher peel adhesion (i.e. equal to or greater than 10
newtons per cm) is needed to maintain laminate integrity
during and after laminate impacting. However, very high
peel adhesion (i.e~ equal to or greater than 30 newtons
per cm) can produce laminate failure due to breakthrough
when the laminate is impacted. On the other hand, very
low peel adhesion (i.e. less than 10 newtons per cm) can
produce delamination on impacting, e.g. along the
laminate edges.
SUMMARY OF THE INVENTION
In accordance with one particular aspect of
the present invention, there is provided, in a PVB sheet
plasticized with a multiester of an alcohol having 2 to
4 hydroxyl groups and a C16 to C20 unsaturated fatty
acid having a hydroxyl group attached to the acid
molecule, the improvement which comprises, in
combination with such multiester, a monoester of a
glycol and such C16 to C20 unsaturated fatty acid, the
amount of the combination of multiester and monoester
being from about 10 to about 55 parts per hundred parts
of the PVB resin, and wherein the ratio of monoester to
multiester is between about 1:1 to about 5:1.
In accordance with another particular aspect
of the present invention, there is provided, in a
process for the preparation of PVB sheet by blending
polyvinylbutyral with a plasticizer which is a
multiester of an alcohol having 2 to 4 hydroxyl groups
and a C16 to C20 unsaturated fatty acid having a
~? ~?
-- 4
hydroxyl group attached to the acid molecule and
extruding the blend to form a sheet, the improvement
which comprises adding to the blend a monoester of a
glycol and the C16 to C20 unsaturated fatty acid, the
amount of the combination of multiester and monoester
being from about 10 to about 55 parts per hundred parts
of the PVB resin, and wherein the ratio of monoester to
multiester is between about 1:1 to about 5:1.
In accordance with a still further aspect of
the present invention, there is provided a plasticizer
blend for polyvinyl butyral comprising a monoester of a
glycol and a C16 to C20 unsaturated fatty acid having a
hydroxyl group attached to the acid molecule and a
multiester of an alcohol having 2 to ~ hydroxyl groups
and the unsaturated fatty acid, the amount of the
combination of multiester and monoester being from about
10 to about 55 parts per hundred parts of the PVs resin,
and wherein the ratio of monoester to multiester is
between about 1:1 to about 5:1.
The monoester is preferably propylene 1,2
glycol partially esterified with ricinoleic acid.
DESCRIPTION OF PREFERRED EMBODIMENTS
U. S. No. 4,128,69~ discloses a plasticizer
for PVB resin in the form of a specific fatty acid
multiester of an alcohol having 2 to 4 hydroxyl groups
and a C16 to C20 unsaturated fatty acid having a
hydroxyl group attached to the acid molecule. The term
"multiester" as used herein means an ester formed by
esterifying more than one hydroxyl group o such an
alcohol with such an acid~ Such plastici~er in a PVB
interlayer does not attack polycarbonate or polyacrylate
when present in a multiple panel safety or security
glass laminate assembly. In the present invention, a
monoester species of such specific fatty acid multiester
is combined with ~he latter to form a plasticizer blend
for PVB which unexpectedly lowers
L~ ~,
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the Tg of PVB plasticized therewith and incrementally
improves the PVs interlayer penetration resistance and
peel adhesion to polycarbonate ovex that obtained
using the fatty acid multiester alone. Performance
with polyacrylate is predicted to be similar. The
plasticizer blend of the present invention, therefore,
comprises a multiester component te.g. a triester~
combined with a monoester glycol component, each
component being derivable from the same class of
unsaturated fatty acidsO
The preferred multiester component of the
plasticizer blend of the present invention is con-
tained in castor oil which is a triglyceride ester of
fatty acids. It comprlses a mi~ture of esters of
glycerol with the following acids, (the figure in
parentheses being the approximate weight percent of
esters formed from that acid): ricinoleic acid
(89.5%), oleic acid (3~0%), linoleic acid (4.2~),
stearic acid 1% and dihydroxy-stearic acid. Approxi-
mately 63.6% of the ricinoleate is triester, (glyceroltriricinoleate) 31.1~ diester and 5.1% the monoester.
The latter level of monoester in castor oil is insuf-
ficient in itself to provide the improvement of the
present invention. Other multiesters found useful
wherein one molecule of the esterifying acid has
reacted with each available hydroxyl of the alcohol
are those based on triethylene glycol, trimethylol
propane and pentaerythritol.
The unsaturated fatty acid monoester found
synergistically effective as an additional plasticizer
in combination with the preferred castor oil in PVB
sheet in property improving combination in a blend
with the multiester referred to above is a monoester of
a glycol and a C16 to C20 unsaturated fatty acid
having a hydroxyl group attached to the acid molecule.
The preferred monoester is propylene glycol 1,~
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-6- 06-12-(1089)A
monoricinoleate. Though not certain of the reason, it
appears that the unreacted hydroxyl group immediately
ad~acent the acid linkage in the monoester plays an
important function in the plasticizer blend insofar as
5 improving the peel adhesion to polycarbonate or
polyacrylate of PVB interlayer plasticized there-
with, as well as the penetration resistance of glass
laminates made up of layers of these materials.
The acids that may be used to form the
10 multiester and monoester plasticizer components of the
blend of the present invention have from 16 to 20 car-
bon atoms and include in addition to ricinoleic acid,
(12-hyroxyoleic acid) other hydroxy-oleic acids with
the hydroxyl group located other than on the "12" car-
bon atom such as 6~, 8-, 14-, or 16-hydroxy-oleic acid,
12-hydroxyelaidic acid and acids with the same em-
pirical formula with the hydroxyl located on other
than the "12" atom. Also included are the corres-
ponding variations of 12-hydroxy-hexodec-9-enoic
acid and 12-hydroxy-eicos-9-enoic acid.
A single acid may provide all the esterify-
ing acid groups but usually a mixture of unsaturated
esterifying acids, are used, provided that the ester-
ifying acids together provide at least one unsatura-
tion and one hydroxyl group per molecule of plasti-
cizer.
The amount of plasticizer blend to be used
in the laminate interlayer of the invention should be
from 10 to 55 parts per hundred parts of P~TB resin
(phr). The preferred amount is 20 to 50 phr and
particularly preferred is 30 to 40 phr.
The weight proportion of monoester to
multiester in the plasticizex blend should be between
about 1:1 to about 5:1. When castor oil is used as
the multiester, allowance may optionally be made for
the minor level of monoester therein in determining
:,
~5~3g~1
-7- 06-12-~1089)A
the total amount of monoester to be used in the blend.
It is preferred that the monoester be present as the
major constituent of the plasticizer blend, i.e.
present in amount greater than the multiester. The
most preferred proportion of monoester to multiester
is 2:1.
The monoesters of the present invention are
commercially available from CasChem Inc., Bayonne, New
Jersey, 07002 under the registered trademark Flexricin.
The various grades of each used in the Examples
following are identified in the footnotes to Table 1.
In general, the polyvinyl acetal resins
employed may be considered to be made up, on a weight
basis, of from 5 to 25 percent hydroxyl groups, cal-
culated as polyvinyl alcohol, O to 4 percent acetategroups, calculated as polyvinyl acetate, and the bal-
ance substantially acetal. When the acetal is buty-
raldehyde acetal, the polyvinyl acetal resin will
preferably contain, on a weight hasis, ~rom 10 to 25
percent hydroxyl groups, calculated as polyvinyl
alcohol and from 0 to lO percent acetate groups,
calculated as polyvinyl acetate, the balance being
substantially butyraldehyde acetal.
The polycarbonate component may be any
suitable sheet of polycarbonate such as disclosed in
U. S. Patent Nos. 3,028,365 and 3,117,Ql9 and is
preferably prepared by reacting di(monohydroxyaryl)-
alkanes with derivati~es of carbonic acid such as
phosgene and bischloro-carbonic acid esters of di-
(monohydroxy-aryl)-alkanes. Commercial polycarbonate
sheeting is available from General Electric Company
under the trademark Lexan.
Where the resin sheet is a polyacrylate
this may be as an ester of a lower aliphatic alcohol,
such as butyl-, propyl-, ethyl-, or methyl alcohol
and acrylic-, methacrylic-, ethacrylic, propacrylic-
5~39~
-8- 06-12-(1089)A
or butacrylic- acid. By far the most convenient is
polymethyl methacrylate.
The plasticized interlayer of the invention
can be used to make a simple laminate with the inter-
layer in contact on at least one surface with apolycarbonate or a polyacrylate sheet. Vsually one of
the surfaces of the interlayer will be in contact~
with a different material such as glass.
For security glass it is usual to provide
multiple layers, such as four or more, comprising
plasticized interlayers and polycarbonate or poly-
acrylate layers and glass layers laminated together to
form laminates of from 1/2 inch up to several inches
in thickness. For such purposes the construction
usually comprises glass/interlayer/polycarbonate or
polyacrylate/interlayer/glass units multiplied as
appropriate.
The laminates produced using the plasticized
interlayer of the invention may be treated to reduce
light transmission by tinting one or more of the com-
ponent layers or by supplying a metallized surface to
one or more of the layers. The treatment can be such
as to produce a uniform reduction in light transmission
over the whole sheet or perhaps in the form of a band
or other form of localized effect.
Laminates formed according to the present
invention are broadly useful in any application re-
quiring a safety glass assembly such as in vehicular
windshields, but are especially useful in security ap-
plications such as prisons without bars and installa-
tions requiring a somewhat lesser degree of security
such as bank windows, cashier booths, jewelry counters
and the like. Applications in which the laminates of
the inventisn can be used are disclosed in U. S.
~5 4,243,719, col. 10, line 3 through col. 12, line 36.
85~
-9- 06-12-tlO89)A
In addition to the plasticizers, the inter-
layers of the present invention may contain other
additives such as dyes, ultraviolet light stabiliz-
ers, salts to control adhesion and antioxidants ~nd
may, if desired, be treated with additives to improve
laminating efficiency.
The invention is further described with
reference to the following examples which are for
illustration only and are not intended to imply any
limitation or restriction on the invention.
EXAMPLES 1 - 9
Laminates of uncoated, general purpose high
impact, glazing grade, polycarbonate (Lexan~ 9030) and
PVB sheet were made using various plasticizers accord-
ing to the following procedure.
The PVB used contained 18 weight percent
hydroxyl groups (measured as polyvinyl alcohol) and
had a solution viscosity o~ .23-.~5 ~a.s as determined
by Kinemetic Viscometer, Cannon Fenske type (ASTM
D-4445). The plasticizer(s) was added to the PVB
resin and mixed either manually or with a low inten-
sity laboratory mixer and allowed to sit overnight to
promote absorption of the plasticizer by the resin. A
sigma blade mixer with steam for heating passing
through the mixer jacket was then used for about ten
minutes to melt and mix the resin and plasticizer and
form molten crumbs of plasticized PVB.
The crumbs o~ plasticized PVB were deposited
in a ~rame and pressed into blocks 35.5 cm by 40.6 cm
of about 5 cm thickness. Slices of plasticized
interlayer of about O.75 mm thickness were cut from
these blocks and separated from each other via inter-
posed plastic fllm, conditioned for about one hour at
20 to 35% relative humidity to control moisture level
therein at 0.4 to 0.5 weight %.
3_ ~ 5 ~3 9 L~
-10- 06-12-(1089)A
Initially washed polycarbonate (0.32 cm to
0.62 cm thickness) sheets and layers of commercially
available float glass were u-sed in assembling each
laminate as follows: a slice of plasticized inter-
layer was placed on either side of the polycarbonate
layer and then a layer of glass placed against each
layer of interlayer. The loosely assembled laminRte
was pre-compressed at about 4.576 MPa (45.7 kg/cm2)
at temperatures of 100C.-215C. in conventional
10 manner usin~ a heated press, then air-autoclaved at
93~., .343 MPa (3.5 kg/cm2) for one hour, 10 min.,
followed hy 135C. and 1.274 MPa (13 kg/cm2) for
one hour after which the temperature was reduced to
38C. for 20 min. whereupon the pressure was reduced
15 to end the cycle.
Other laminates for peel adhesion testing
were prepared using standard laminating techniques
familiar to those in the art except that an adhesive
coated aluminum foil was substituted for one of the
20 glass layers and the glass and interlayer on the
other side of the polycarbonate was eliminated.
Values for the various properties presented
in Table 1 following were determined according to the
following procedures.
The glass transition temperature (Tg) of
plasticized PVB was measured using a Rheometric
Mechanical Spectrometer which is a rectangular torsion
test conducted in a nitrogen atmosphere at a constant
frequency ~l-hertz) and temperature.
Compatability of plasticizer and PVB resin
as determined by the extent of exudation of the
plasticizer from the resin after melt mixing was
visually noted by the absence or presence and level
of free plasticizer either on the surface of the
35 plasticized resin or in the bowl of the sigma mixer.
Penetra~ion resistance of the glass-poly-
carbonate-plasticized interlayer laminates was
~58~
-11- 06-12-(1089)A
measured by dropping a 2270 gm steel ball five times
from 2.4m onto the laminate which had been pre-con-
ditioned for two hours at the temperature at which
the test was run. The lntegrity of the sample inso-
far as the extent, i~ any, of delamination along theglass cracks between the polycarbonate and interlayer
was visually noted after five drops. The term "good
integrity" as used in ~able l following means that
some portion of the laminate, such as the edge area,
had all components adhered together after testing.
Clarity of the autoclaved laminate as de-
termined by haze level was visually noted~
Stress cracking of the polycarbonate by the
plasticizer(s~ used in the interlayer was determined
at 23C. and 70C. In this test the stress
applied to polycarbonate specimens was increment-
ally increased to 13.8 MPa while a patch saturated
with the plasticizer fluid was applied at the point
of maximum stress and the stress noted at which
cracking occurred. More specifically, injection
molded polycarbonate coupons in the form of beams
about 2.5~ cm wide were loaded for a specified time,
e.g. lO minutes, and then the patch saturated with
the test plasticizer was applied to the point of
maximum stress for an additional time depending on
the temperature-i.e. 72 hours at 23C and 8 hours at
70C.
Peel adhes~on-two parallel grooves 4 cm
apart were formed leng-thwise through the aluminum foil
and interlayer. The polycar~onate at one end of the
laminate a few cms in from the end was scored and
broken perpendicular to the grooves. The outside
edge of the aluminum foil and interlayer on each side
of the 4 cm strip was cut at the polycarbonate break.
The foil, interlayer and cut polycarbonate were then
clamped in the test grips of an Instron tensile tester
~ ,
,..
,
-12- 06-12-(1089~A
..
and the force required to separate the foil and
interlayer from the polycarbonate along the grooves
measured at room temperature. A range of 10 to 30
newtons/cm is desired to provide the optimum balance
of impact and delamination resistance in the laminate.
The results obtained are set forth in the
following Table 1.
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-13- 06-12- ( 1089) A
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-16- 06-12-(1089)A
Stress crack performance of the glycerol
triricinoleate/ethylene glycol monoricinoleate blend
of Example 7 is predicted to be equivalent to that
obtained with the blend of Example 2 containing
propylene glycol monoricinoleate.
The foregoing data indicates that when the
multiester i5 the sole or principal plasticizer in the
plasticized interlayer (Example 1) in accordance with
U. S. 4,128,694, though stress crack resistance of the
polycarbonate i5 good, the tendency to delaminate is
high and therefore the penetration resistance is poor
because of the relatively high value of Tg and low
peel adhe~ion. When the lower molecular weight glycol
monoester (Examples 3 and 6) was used alone, Tg was
reduced and pentration r~sistance was improved, but
at the expense of stress crack resistance of the
polycarbonate at high temperature. However, when only
a relatively minor amount (12.5-15 parts) of the
multiester was added to the monoester, (Examples 2,
and 7) acceptable stress crack resistance was obtained
~nd peel adhesion was significantly increased with
respect to the propylene glycol monoricinoleate
species of Example 2 without a reduction in Tg and in
penetration resistance. This significant increase in
peel adhesion and failure of Tg to increase with the
addition of the multiester constituent to the mono-
ester constituent was unexpected. The blend contain-
ing a monoester of an alcohol having more than two
hydroxyl groups, i.e. the pentaerythritol monoricin-
oleate species of Example 5 and the glycerol monori-
cinoleate species of Example 9, which are outside the
scope of this invention, were deficient in color (Ex-
ample 5) and compatibility (Example 9).
Though the plasticized PVB sheet of the
invention can be formed by slicing from blocks as
disclosed in the foregoing Examples, it is preferably
~ . ,
~5~39~
-17- 06-12-(1089)A
formed by extrusion mixing and sheet formation of the
interlayer in a slot die.
The monoester glycol component of the
plasticizer blend of the invention may comprise blends
of monoesters, such as a blend of individual ethylene
and propylene glycol monoester constituents.
While certain specific embodiments of the
invention have been described with particularity
herein, it will be recognized -that various modifica-
tions thereof will occur to those skilled in theart~ The scope of the invention, therefore, is to be
limited solely by the scope of the following claims.
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