Canadian Patents Database / Patent 1135923 Summary

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(12) Patent: (11) CA 1135923
(21) Application Number: 329280
(54) English Title: PROCESS FOR LAMINATING THERMOPLASTIC RESIN REINFORCED WITH FIBER GLASS
(54) French Title: METHODE DE FABRICATION DE PANNEAUX DE RESINE THERMOPLASTIQUE ARMEE DE FIBRE DE VERRE
(52) Canadian Patent Classification (CPC):
  • 18/1016
  • 154/76
  • 154/89
(51) International Patent Classification (IPC):
  • B29C 70/50 (2006.01)
  • B29B 15/12 (2006.01)
  • B29C 43/22 (2006.01)
(72) Inventors :
  • BAUMANN, JOHN A. (United States of America)
(73) Owners :
  • PPG INDUSTRIES, INC. (United States of America)
(71) Applicants :
(74) Agent: BORDEN LADNER GERVAIS LLP
(74) Associate agent: BORDEN LADNER GERVAIS LLP
(45) Issued: 1982-11-23
(22) Filed Date: 1979-06-07
(30) Availability of licence: N/A
(30) Language of filing: English

(30) Application Priority Data:
Application No. Country/Territory Date
965,956 United States of America 1978-12-04

English Abstract




Abstract of Disclosure

A continuous process for producing a fiber glass reinforced
thermoplastic sheet is described in which fiber glass mat and thermo-
plastic resin are combined into an integral sheet by passing the resin
and glass mat through a heating phase under uniform temperature and
pressure conditions to produce a softened sheet product having glass
dispersed throughout and rapidly cooling the softened sheet product
continuously while maintaining the temperature and pressure in the cooling
zone constant. A hardened reinforced thermoplastic sheet is removed from
the cooling zone which is capable of being scamped under heat and pressure
into a thermoplastic part.


Note: Claims are shown in the official language in which they were submitted.


THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preparing a fiber glass reinforced resin
sheet comprising feeding a fiber glass mat to a heating zone, introduc-
ing resin in said zone with said mat, applying pressure to the mat and
resin at temperature sufficient to maintain the resin molten and thoroughly
wet the mat with resin, and subjecting the mat to cooling at temperature
sufficient to solidify the resin into a resin-mat sheet while maintaining
pressure on the resin and mat during cooling at least equal to the pressure
applied to the resin and mat in the heating zone and removing from the
cooling zone a solid sheet of glass mat reinforced resin.



2. A method of preparing a fiber glass reinforced thermoplastic
resin sheet comprising continuously feeding to a pressurized heating zone
fiber glass mat and thermoplastic resin maintaining sufficient pressure
and temperature in said heating zone to thoroughly impregnate said fiber
glass mat with molten resin, cooling the resin saturated mat and molten
resin to a temperature sufficient to solidify said resin, maintaining
pressure on said resin and resin saturated mat during cooling at least
equal to the pressure applied in said heating zone and removing from the
cooling zone a solid sheet of fiber glass reinforced thermoplastic resin.



3. The process of Claim 1 wherein the pressure on the resin
and mat in the said cooling zone is maintained at a value higher than the
pressure on the resin and mat in said heating zone.




4. The process of Claim 2 wherein the pressure applied to
the resin and mat in said cooling zone is greater than the pressure applied
to the resin and mat in the heating zone.




- 13 -




5. A method of preparing a fiber glass reinforced thermoplastic
resin sheet comprising feeding to a heated laminating zone glass mat and
molten thermoplastic resin, applying pressure to the mat and resin in the
laminating zone of at between 20 to 30 psig while maintaining temperature
sufficient to maintain said resin in a molten state, feeding the resin and
mat continuously from said laminating zone into a cooling zone, applying
pressure of 20 to 30 psig to said resin and mat in said cooling zone but at
least as great as the pressure used in said heating zone and cooling
the resin and mat in said zone to a temperature sufficient to solidify
said resin and removing a solid sheet of fiber glass reinforced resin
from said cooling zone.



6. A method of preparing a fiber glass reinforced thermoplastic
resin sheet comprising feeding to a heated laminating zone two glass mats,
molten thermoplastic resin and two sheets of thermoplastic film, said molten
thermoplastic resin being fed in between the said glass mats and the sheets
of thermoplastic film being fed on the outside of each of said mats, applying
pressure to the mats, said molten thermoplastic resin and said thermoplastic
film and heat in sufficient amount to cause said film to become molten,
passing the resulting resin-mat composite to a cooling zone maintained at a
pressure at least equal to the heated laminating zone and cooling the said
composite therein to a temperature sufficient to solidify said composite into
a solid sheet of fiber glass reinforced thermoplastic resin.



7. The method of Claim 6 wherein said laminating zone is at
pressure of 20 to 30 psig and said cooling zone is at pressure of 20 to 30 psig.

14

Note: Descriptions are shown in the official language in which they were submitted.

3~92~



PROCESS FOR LAMINATING TIIERMOPLASTIC RESIN
REINFORCED WITH FXBER GLASS




Bac~ground of the Inventlon
Fiber glass reinforced thermoplastic sheets capable of being
stamped under heat and pressure into a variety of shapes for automotive use
have been described in the literature. Typical of methods heretofore
employed to produce such products are those described in U. S. Patents
3,66~,909; 3,684,645; 3,713,96~ and 3,850,723. The glass strands which are
used to prepare the mats which are placed in the product are usuaLly
treated before mat formation with an appropriate sizing system. One such
system is described in U. S. Patent 3,849,148. The mat used in the thermo-
plastic sheet products produced i9 typically needled and this is described
in U. S. Patents 3,883,333 and 3,664,909.
The laminates produced by the prior are processes and the
instant invention may be processed in a stamping operation using the
procedures described in U. S. Patents 3,621,092 and 3,626,053.
In the prior art processes above described, layers of needled
mat and t~ermoplastic resin, polypropylene being typical, are laminated in
a platen press to produce the shee~ product. In~another process
20~ subsequently deecribed, the lamination of resins and mat takes
place in a cont1nuous laminator.
; - In the process employing the platen press acceptable product
is produced, but the manufacturing process itselE i9 slow and costly
since the maca and thermoplastic sheets used eO make the ~aminates are
laid up by hand and ~tbe process is~by its nature a batch operation.




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.,: ' ~ . .
..

~3,~ 3



In the continuous process depicted in FIG. 2, inadequate control of the
pressure exerted on the laminate in tbe cooling section frequently results
in the production of laminates having nonuniform void content.



The Present Invention
In accordance with the instant invention a process for producing
a laminated fiber glass reinforced thermoplastic resin continuously is
provided which overcomes many of the shortcomings of the prior art. The
process of the invention involves passing a fiber glass mat and the thermo-
plastic resin into a laminating zone which has two distinct temperature
regimes. In the first section of the lamination zone, heat and pressure
are applied to the thermoplastic resin and glass mat to insure that the
resin is maintained in the molten state during its passage through the
zone. The mat and molten resin during their passage through this zone are
given sufficient residence time ~o permit the molten resin to flow through
the glass mat and thoroughly impregnate it. The mat and molten resin sheet
are then passed into a cooling ~one which is maintained under pressure to
solidify the res;n throughout the mat and provide~at the exit end of the
cooling section of the laminating process a continuous sheet of fiber glass
reinforced thermoplastic having a controlled void content and which is
capable of being stamped into a finished part utilizing the stamping
procedures of the prior art hereinabove described.
Various thermoplastic resins may be employed to produce laminates
in accordance with the instant invention and typical resins suieed for this
use are homopolymers and copolymers of resrns such as~ vinyl resins
formed by the polymerization of vinyl halldes or by the copolymeri~ation of
vinyl haIides with unsaturated polymeriæable compounds, e.g., vinyl esters,




- 2 -


; .

23


alpha, beta-unsaturated acids, alpha, beta-unsaturated esters, alpha,beta-
unsaturated ketones, alpha,beta-unsaturated aldehydes and unsaturated
hydrocarbons such as butadienes and styrenes; ~2) poly-alpha-olefins such
as polyethylene, polypropylene, polybutylene, polyisoprene and the like,
including copolymers of poly-alpha-olefins; (3) phenoxy resins; (4) polyam:ides
such as polyhexamethylene adipamide; (5) polysulfones; (6) polycarbonates;
(7) polyacetals; (8) polyethylene oxide; (9) polystyrene, includlng copolymelo,
of styrene with monomeric compounds such as acrylonitrile and butadiene;

(lO) acrylic resins as exemplified by the polymers of methyl acrylate,
acrylamide, methylol acrylamide, acrylonitrils and copolymers of these with

styrene, vinyl pyridines, etc.; (ll) neoprene; (12) polyphenylene oxide resins;
(13~ polymers such as polybutylene terephthlate and polyethylene terephthlate;
and (14) cellulose esters including the nitrate, acetate, propionate, etc.
This list is not meant to be limit~ng or exhaustice, but merely ~o illustrate
the wide range of polymeric materials which may be employed in the present
invention.
The fiber glass mat used in the preparation of the laminates
may be made conveniently by the methods described in U. S. Patent 3~883~333
assigned to the assignee of this invention.
In the method described in this patent the mat is
Eormed by laying down continuous strand on a conveyor surface, typically an
intermeshing chain, to the desired depth. The strands are usually placed
on the chain by traversing the attenuators that project the strand to the
conveyor surface across the ~idth of the surface in a direction transverse
of the movement of the conveyor. The mat formed in this manner is then
passed through a needling device which is normally a conventional felting loom
containing a multiplicity of barbed needles which penetrate the mat causing




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1. ~"; 3 !~ ~3 ;~ rl 3


the continuous strands to become tangled in each other thereby providing
dimensional stability to the mat wh;le at the same time breaking them into
- random lengths. The needling operation provides a significant amount of
short glass fibers in the finished mat due to the action oE the barbed
needles penetrating the depth of the mat and, in doing so breaking a
significant number of the continuous strand6 into short lengths of stapLe
fibers. "Short fibers" as used herein means strands or fibers of 1 inch or
less in length. The amount of short fibers produced by the needling
operation will vary depending upon the speed of the needling, the number
and types of needles used. In general, the short fihers presen~ in _
the mat range between 10 to 25 percent, preEerably between 15 and 20
percent by weight of the mat. The remainder of the mat is composed of
strands and fibers in lengths in excess of l inch, generally 1-1/2 to 5
inches or longer. As also shown in the above patent, the speed of the
needler and the mat forming surface is coordinated to provide a uniform mat
density being recovered from the exit of the needler. The needles employed
may contain ~w~ r barb~in either a do~m or an up posi~ion so that upon ~ 3;~;~
penetrating the upper mat surface they push fibers from chat surface to the
interior of the mat or they pu11 fibers from the under surface of the mat
up to the interior, respectively. In soMe instances needles barbed in both
a down and up direction are used to provide for the penetration of strands
to the interior from both the upper and the lower surface in a single down
and up stroke of the mounting carrying the needles. If desired, the
process of the instant invention can also be practiced with chopped strand
mats used as the glass source. A typicaI' mat of this type is described in
U.S. Paten~ 2,790,741.
In the prac~ice o~ the invention the thermoplastic resin may
be fed to the laminating process in any of several forms. In some instances

rS~'3


the resin i8 fed to the laminating 7one in preformed sheet ~orm of desired
thickness and the number of sheets used will depend on the desired thick-
ness of the final product and the mat or mats used. It is also within the
purview of the invention to feed the thermoplastic resin to the laminating
process as a premelted extrudate Erom a hiigh temperature, high pressure
extrusion line. In this type of system the extrudate is fed between the
laminating surface in a sheet fonn, typically Erom an extrusion die which
is maintained at temperaC~re and pressure sufficient to maintain the resin
in a flowable state as it is fed to the laminating zone. In a typical
operation both molten extrudate is fed to the laminating zone as well as
sheet forms of the thermoplastic resin being employed as will be more fully
explained hereinafter.
It is also within the purview of this invention to add to th~
laminates produced by this invention compatible materials which do not
affect the basic and novel chacteristics of the product. Among such
materials are coloring agents, including dyes and pigments, fillers and
similar additives. Additives such as antioxidants, bacteriacides, anti-
static agents, stabilizers and antimarine fouling agents, may also be
added. Generally the quantity of additives if used, are below about
30 percent by weight of the product, typically 10 to 20 percent.
In the practice of the instant- invencion the laminating process
is conducted under various pressure and temperature conditions. Thus, the
initial stage of the oparation involves contacting the reinforcing fiber
glass mat with molten resin to insure adequate penetration of the mat
structure by the resin system being employed to produce the final sheet
product. Pressures are exerted in the hot stage portion of the laminating
.
system and may vary from 5 to 120 pounds per square inch, preferably in the




~ 5 -

~l3~ 3


range of 20 to 60 pounds per square inch. The hot stage of the laminating
process is typically regulated in a temperature range of 350F. to 550F
(117C. to 288C.); this temperature being somewhat dependent upon the
melt cemperatures of the resins employed. For example, with a polypropylene
resin system, the temperatures in the hot stage of the laminating typically
range between 400F. to 450F. (204C. to 232C.). In the cold stage of
the process, pressures are applied generally at the same magnitude or
greater than those used in the hot stage and in general are within the
ranges set forth abo~e for the hot stage.
Attention is now directed to the drawing for a further explanation
of the invention and its advantages over the prior art.
In the drawings:
FIG. 1 is a diagrammatic illustration of a laminating machine
suitable for use in producing fiber glass reinforced thermoplastic sheets
in accordance with the instant invention.
FIG. 2 is a diagrammatic illustration of a continuous laminating
process currently in use for producing fiber glass reinforced thermoplastic
resin sheets suitable for stamping, and
As shown in FIG. 2, a double belt laminating machine is employed
to produce a continuous sheet 2 which is composed of a resin and fiber
glass mat. In the process depicted fiber glass mats 1 and 1' are fed
between two laminating belts 3 and 4. Molten resin 5 is fed between the
mats 1 and 1' from an adjustable slot 6 located along the length of an
extrusion die 7. Two sheets of resin 8 and 9 are fed to the laminating
belts 3 and 4 above and below the mats l~ and 1, respectively.
Belt 4 as it passes around rol]er 11 is preheated by a heater 13
prior to its engagement with the heating, press roll 15. Similarly, belt 3




~ 6 -

~3.S;~Z~


is preheated by heater 16 prior to its engagement with press roll 15. The
heating, press roll i6 equipped with heaters 18. Pressure is applied to
the laminate 2 by applying tension to the belts 3 and 4. Tension applied
to belts 3 and 4 results in the application of radial forces on the resin
mat composite. The radial forces and the resulting pressures assist in
saturating the mats 1 and l' with resin and render sheets 8 and 9 molten
when coupled with the heat applied as the tension is applied Roll 24
applies tension to belt 3 and roll Z5 applies tension to belt 4. The
material as a compact sheet of resin and fiber glass resulting from the
passage of the materials through the press roll 15 is then passed to a ..
cooling roll 20 between the belts 3 and 4 and during its passage over this
roll is partially cooled, but not completely solidified. The roll 20 is
equipped with a cooler 21 to reduce the temperature of the belts and the
resin. The sheet after leaving roLl 20 inbetween the belts 3 and 4 is then
passed through another elongated cooling zone 22 to further reduce the
te~perature of the belts 3 and 4 to further cool and solidify the mats and
resin into sheet 2. Belt 3 is then reflexed over roll 23 for return to the
tension roll 24 and belt 4 is returned over roller 25 to the roll 11 with
the product 2 being removed at the point where belts 3 and 4 separate.
~hile the laminating process depicted has been used to produce
useful, commercial products, it has certain shortcomings that the instant
invention overcomes. The impregnation pressures are applied to mat and
resin by the tension exerted on the belts 3 and 4 by the tension rolls 24
and 25, respectively. Experience has shown that, for example, when
a pressure of 30 pounds per square inch has been applied in the heating
press roll 15, only about l/2 to 1 pound per square inch can be maintained
in the cooling area of zone 22. This produces in many instances a larger

3~P~


volume of voids in the product due to the tendency of the glass mat to
expand as pressure on it is relaxed thus causing expansion of trapped gases
while the resin is not fully solidified. The roll system used and the belt
curvatures that are required in this unit also resu~t in uneven belt speeds
since, for example, on the press roll 15 the belt 4 is on the outside and
in the cooling zone it i5 on the inside. Thus, belts 3 and 4, which travel
at equaL linear speeds, move relative to each other on the rolls due to the
fact that they pass the rolls at differing radii depending upon which roll
they are travelling around.
In the process diagrammatically illustrated in FIG. 1, resin
sheets 100 and 101, fiber glass mats 102 and 103 and molten resin 104
are fed between belts 105 and 106 of a continuous Laminating machine.
The belts 105 and 106 are continuous belts which are driven around rolls
107 and 108 and rolle 109 and llOj respectively.
The laminating machine is as shown divided into two dis,tinct --
sections indicated as 120 and 130. Two sections are shown for convenience
only since as will be readily apparent to the skilled artisan, each of
these sections may be one or more distinct units. In the illustrated
figure, section 120 is the hot lamination zone of the process and it is
equipped with an upper pla~en 121 and lower platen 122 which arP movable in
a direction perpendicular to the path of travel of belts 105 and 106.
These platens 121 and 122 are operated under hydraulic pressure and are
capable of exerting forces of 0 to 30 psig to the material being passed
through this zone for lamination between belts 105 and 106. With modifi-
cation the platens can be operated at even higher pressure. Movement
of the laminated material through this zone ;s maintained by a plurality of
rollers 123 and 124 located in the upper and lower sections of laminating


_ ~ _


, ~ .




zone 120, respectively. The rollers 123 and 12~ are rods which extend
across the width of the belts 105 and 106. They are coupled at their ends
by a link chain which in currl rides on the sprockets 125 for rods 123 and
sprockets 126 for rods 124. ~le sprockets 125 and 126 are driven by
a suitable motor, not shown. As will be appreciated from the drawing,
the laminating pressure applied to the belts 105 and 106 is transmitted to
the belts by the rollers 123 and 124 as the piatens 121 and 122 contact
them. The rollers L23 and 124 move the belts 105 and 106 through the zone
120 while the pressures from the platens 121 and 122 are being applied to
the belts 105 and 106 during their passage through this zone.
Zone 120 is also supplied with heat that is transmitted to
the sheet material as it passes through zone 120 to maintain it in a
molten state and thereby insure penetration of resin throughout the
glass matrix of the laminate being formed.
The laminate passes from zone 120 into zone 130 which is pro- -
vided with a platen 131 and 132 and rollers 133 and 13~ in the upper and
lower sections thereof, respectively. Similar to zone 120, the rollers
133 and 134 are moved by sprockets 135 and 136 riding on a chain 137
attached to rollers 133 and 134, the sprockets 135 and 136 being driven
by a suitable motor assembly (not shown). Platens 132 and 131 ap~ly
pressure to the laminate during its passage through zone 130 and zone
130 is supplied with heat transfer fluid in an indirect heat exchange
supply systen (not shown) that removes heat from the laminate through
rolls 133 and 134 to chill the laminate and solidify the resin through-
out. The solid finished product 140 is removed from zone 130 and may
then be subjected to slitting, cutting and paGkaging procedures which
form no part of the instant invention.


_ g _


.
,. . I .

~L~3~


As will be appreciated by the skilled artisan9 the instant
process provides considerable flexib;lity in the physical preparation
of laminates of thermoplastic resins reinEorced with glass fibers.
Thus, pressure may be applied in the hot zone 120 through the use of
platens 121 and 122 to any desired degree within the limits of the machine.
In general, pressures can be varied from t) to 30 psig and typicalLy they
range from 20 to 3a psig. Similarly in the hot æone l20 heat may be
applied in a range of values to insure adequate flow of resin throughout
the glass fiber matrix as the pressure is applied for a given line speed of
conveyors or belts 105 and 106. Thus, temperature of 300UF. to 600F. ~-
(149~C. to 316~C.~ are typically used in zone 120 to insure resin temper-
ature in the range of 250-F. to 550F. (121C. to 288C.). It has been
found that for a polyolefin a resin temperature range of 400F. to 450F.
(204C. to 232C.) is preferred. -
In the operation of zone 130 the application of pressures
through platens 131 and 132 as the laminate from zone 120 enters zone
130 can be used to precisely control the void volume of the Einished
laminate 140; a condiCion that was not heretofore possible with con-
tinuous Laminating processes such as shown in FIG. 2. Thus, if pressure in
zone 130 is maintained at a value greater than that in zone 120 it wiLl
result in a low void or almost zero void product. In a typical operation
of the system of FIG. 2, for example, it has been found that in laminating
a polypropylene with glass fiber mats at 30 psig in the hot zone that a
pressure of less ~han 1 psig is realized in the cooling zone 22 and
the resulting product has a void content of 8 to 10 percent by volume. -
Using the process of FIG. 1 and applying 30 psig in both the hot zone 120
and the cooling 130 a product having 3 to 4 percent voids by volume is
.




-- 10 --


~ " .
.-- . . . ..

23


typical. Lower void volume content using higher pressures in the cooling
zone 130 than used in the heating zone are readily obtained.
Void content may also be controlled to some e~tent by usin~
molten resin alone without having recourse to laminating systems using
sheet products. Thus, by using molten resin 104 alone with mats 102 and
103 and eliminating the overlay sheets lO0 and IOl, the laminate produced
is found to possess considerably less void volume than laminate produced
using overlay resin sheets. If surface appearances are not of paramount
importance, this provides a useful system for continuous production of low
void volume 1aminates. Coupling this with careful control of ~he pressure
in the cooling area of the laminating process to maintain it at or greater
than the pressure in the heating zone of the process produces laminates
having consistently low void volumes.
In general the fiber glass mats employed in the preparation
of laminates in accordance with the instant process are needled to provide
ma~ integrity and to supply broken filaments and strands to the mat so that
it possesses inherently after needling lO to 25 percent by weight of
the mat of short fibers (i.e. fibers in the range of to l inch or le s in
length) with the balance of the mat being composed of longer strands.
The continuous strand mats may be formed by the process of U. S. Patent
3,883,333 from fibers ranging in diameter from a "T" fiber to a l'G" or
less. I'he strands of fibers used to prepare the mat are typically in
bundles of 50 fibers or less although bundles of fibers with lOa or more
-filaments may be usecl.
The continuous strand mat may be- prepared directly from a
bushing as in U. S. Patent 3,883,333 or it` may be formed by drawing
strands from previously formed forming pac~ages with a suitable attenuator



1 1


~ ~ .
.
~ .'' ' , : ' '




and laying the strands on a conveyor in a manner sin~ilar to that described
in U. S. Patent 3,883,333.
In FIG. 2 preformed films of thermoplastic 100 and 101 are
used with a molten ex~rudate 104 being placed between the glass mats lOZ
and 103. It is not necessary that the process be conducted in this
manner although this method does represent a preferred method of opera-
tion. It is contemplated that the process oE the instant invention may
be conducted by using multiple layers of extrudate, either fronl separate
extruders or using a single, multiple head extruder. In the latter
instance the mats or mat is Eed in such a manner that extrudate is fed on
the outside of the glass mat as well as on the inside. The advantage o~
using extrudate in lieu of the film layers 100 and lOl is that the extru-
date heat of the molten thermoplastic will not require the heat load in the
hot zone 120 that is required to melt the iilms 100 and 101 and thus
the machinery is not subjected to the heating loads used when film is
employed. It is also contemplated that a single mat may be used itl
conjunction aith a preformed thermoplastic film or l~ith extrudate alone.
It is preferred with single mat structures to employ extrudate rather
thal~ film as the thermoplastic source. As stated above the use of extru-
date where possible is desirable since the total energy input to the system
is reduced if it is applied primarily to the resin employed by the extruder
rather than through the indirect heat exchange system of the hot zone of
the laminating machine. - -
While the in~ention has been described with reference to
: ~ .
certain specific embodiments, it is not intended to be limited thereby
except Insofar as appears in ~he accompaDylng claims.




~ 12 -

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Admin Status

Title Date
Forecasted Issue Date 1982-11-23
(22) Filed 1979-06-07
(45) Issued 1982-11-23
Expired 1999-11-23

Abandonment History

There is no abandonment history.

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Filing $0.00 1979-06-07
Current owners on record shown in alphabetical order.
Current Owners on Record
PPG INDUSTRIES, INC.
Past owners on record shown in alphabetical order.
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.

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Description 1994-03-01 12 507
Drawings 1994-03-01 2 55
Claims 1994-03-01 2 81
Abstract 1994-03-01 1 30
Cover Page 1994-03-01 1 32