Note: Descriptions are shown in the official language in which they were submitted.
The invention concerns glass fiber laminates utilizing
unsaturated polyester resin syrup. Unsaturated polyester
resin syrup and chopped glass Eibers have been combined to
produce glass fiber reinforced plastic laminates. See
"Polyesters and Their Applications", Bjorksten et al, Reinhold
Publishing Corporation, 1956. The resulting laminates have
a high strength-to-weight ratio, good resiliency, electrical
properties, resistance to corrosion, moldability. Such
materials have been employed in aircraft components, boats,
automobile components, light transmissive building sheeting,
snowmobiles, golf carts, chairs, piping, tanks, window
surrounds, bathroom vanities, bathtubs and shower stalls,
building panels.
One type of product, known as a lay-up or spray-up
laminate, is obtained by spraying the unsaturated polyester
resin syrup along with appropriate free radical initiators,
accelerators, surfactants, inhibitors, pigments, dyes or
fillers against a stream of chopped glass fibers whereby the
fibers are wetted and collected on a substrate. Customarily
the wetted glass fibers are thereupon rolled or tamped to
embed the loose ends of the glass fibers and eliminate gas
pockets. The wetted fibers are retained in engagement with s ~-;
the substrate until the resinous components cure. Customarily
the free radical initiator and the promoter are selected so
that the curing will commence at room temperatures. The
curing is exothermic and causes a general increase in the
temperature of the laminate. Complete cures in spray-up or
lay-up operations normally require about one to four hours
before the glass fiber reinforced laminate can be separated
from the substrate and withdrawn as a product.
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The use of alpha hydroxy azo blowing agents to producefoamed polyester castings is known. See copending Canada
patent application serial number 237,381 filed October 6,
1975, and assigned to the assignee of this invention.
Other prior art attempts to develop foamed polyesters
include the use of (a) a mixture of alkali metal carbonate
and an organic acid, British 652,770 and U.S. 3,479,303; (b)
dissolved vaporizable organic blowiny agents such as trichloro
fluoro methane, U.S~ 3,232,893. No successful foamed polyester
product has been produced with saturated alkanes or halogenated
alkanes because the vaporization oE the blowing agent (a)
occurs before the resin has gelled sufficiently to form a
foam or (b) occurs after a strong gel has already been
formed.
According to the present inVention~ glass fiber rein-
forced unsaturated polyester resin articles are obtained
i:~ without significant sacrifice in the strength of the product
yet with a substantially lowered density which permits
production of useful articles with less materials. In
~ 20 general, the density of the glass fiber reinforced laminates
of this invention is less than 75 percent of the density of
a similar glass fiber rein~orced article formed from the
~; identical unsaturated polyester resin by the methods of the
prior art.
According to one embodiment of the present invention an
unsaturated polyester resin syrup is formed into a first :-
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~ stream and delivered to a mixing zone. The syrup contains a
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i; suitable initiator of free radicals, a promoter, inhibitors
~ and surfaFtants. A second stream containing an alpha hydroxy
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azo blowing agent is delivered to the mi~in~ ~one. The two
streams are combined in such proportions that their combined
total includes from 0.5 to 5.0 parts by weiyht of the alpha
hydroxy a~o blowing agent for each 100 parts by weight of
unsaturated polyester resin. The two streams are mixed to
form a combined stream which is immediately sprayed through
a nozzle onto chopped glass fibers which are wetted by the
combined stream and are collected as a coating on a substrate.
The collected wetted fibers are rolled or tamped and the
resin is allowed to cure. After the resin has cured, the
resulting laminate can be separated from the substrate or
can be recovered in combination with the substrate as a
product. The resin possesses useful adhesive properties
which may be exploited if the coating is intended to remain
on the substrate. Where the substrate is merely a form for
shaping the laminate, a release-coating or barrier membrane
may be applied to the substrate to thwart the adhesive
property.
AGcording to an alternative embodiment the unsaturated
~0 polyester resin syrup, along wi-th free radical initiator,
promoter, inhibitor and surfactant, is formed into a first
spray. An alpha hydroxy azo blowing agent is formed into a
second spray. The two sprays are impinged in a ratio such
that the combined sprays contain from 0.5 to 5.0 parts by
weight o~ the alpha hydroxy azo blowing agent for each 100
parts by weight of unsaturated polyester resin. The combined
sprays impinge upon chopped glass fibers which are collected
; as a coating~ rolled or tamped. Thereupon the resin is
allowed to cure as in the first method.
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The resulting article has a density of 15 to 60 pounds
per cubic foot and contains from 15 to 50 weight percent of
randomly oriente~ glass fibers conf:;ned in a continuous mass
of cellular polymerized unsaturated polyester resin syrup.
The cells of the article are filled with a gas having a
greater nitrogen concentration than the atmospheric nitrogen
concentration.
Cellular plastic materials have been defined as "a
plastic, the apparent density o~ which is decreased sub-
stantially by the presence of numerous cells disposed through-
out its mass." The Eoaming of the present process arises
from the nitrogen gas which is developed from the alpha
hydroxy azo blowing agent. The expanding nitrogen gas
creates the cells and is confined therein in concentrations
which exceed the atmospheric nitrogen concentration.
! The polymerized unsaturated polyester resin is essen-
tially free of urethane linkages and allophanate linkages
which are an identifying feature of polyurethane foams.
FIGURE 1 is a schematic illustration of apparatus
useful in practicing a preferred embodiment of the present
invention.
FIGURE 2 is a fragmentary schematic illustration of
, equipment for practicing an alternative embodiment of the
~; present inventionO
;~ The three essential ingredients of tAe present invention
! ~ are chopped glass fibers, unsaturated polyester resin syrups
and alpha hydroxy azo blowing agents.
Unsaturated Polyester Resin Syrup -~
The unsaturated polyester resin syrup is a solution of
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an unsaturated polyestex resin in a copolymerizable monomer
which is usually styrene but may be other ethylenically
unsaturated monomers such as vinyl toluene, divinyl benzene,
acrylic acid, methacrylic acid, alkyl acrylates and meth-
acrylates, ortho-chlorostyrene, alpha-methylstyrene, ethylene
glycol dimethacrylate. The unsaturated polyester resin is
formed by polyesterification of polyol and polycarboxylic
acid or polycarboxylic acid anhydride at least a portion of
which contains ethylenic unsaturation. Typical polyols
include glycols such as ethylene glycol~ propylene glycol,
butylene glycol, neopentyl glycol, diethylene glycol, di-
propylene glycol, polyethylene glycol, polypropylene glycol
and the like. The polycarboxylic acid or anhydride may
include materials which do not possess ethylenic unsaturation
such as phthalic acid, phthalic anhydride, isophthalic acid,
terephthalic acid, adipic acid, succinic acid, glutaric
acid, malonic acid, pimelic acid, sorbic acid, halogenated
dibasic acids. Typical unsaturated dicarboxylic acids
include maleic acid, maleic anhydride, fumaric acid, endo-
methylene-tetrahydrophthalic acid or anhydride, itaconic
acid and the like. Typically the unsaturated polyester
resin is prepared by polyesterification of an excess of
polyol with polycarboxylic acid. Typically at least 40 mol
percent of the polycarboxylic acid is ethylenically unsatu-
rated polycarboxylic acid. The acid and polyol are cooked
in the presence of a polyesterification catalyst until the
polyesterification is essentially completed as indicated by
the acid number of the resulting product being reduced to 30
or less. The unsaturated polyester resin syrup contains
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about 1 part by weight of copolymerizab:Le monomer for every
1 to 10 parts by weight of -the unsaturated polyester resin.
Normally the unsaturated polyester resin syrup contains
25 to 45 weight percent monomer and 75 to 55 weight percent
unsaturated polyester. In connection with the present
invention, when the monomer content is below about 25 percent,
the resulting syrup is difficult to spray. When the monomer
content exceeds 45 weight percent the monomer tends to
separate out as a distinct phase from the foaming, ungelled
resin.
Initiator
A high temperature initiator is preferably employed in
the present process. The initiator is provided from 0.2 to
2 percent by weight of the unsaturated polyester resin
syrup. Useful initiators include tertiary butyl perbenzoate,
ditertiary butyl perben~oate, cumene hydroperoxide, methyl-
ethylketone peroxide and tertiary butyl hydroperoxide.
These initiators are ineffective at room temperature but
become effective when the temperature is increased, particu-
larly in the presence of metal salt promoters.
A polymerization initiator is not required in the
polyester resin syrup. Instead the resin can be cured by
means of the alpha hydro~y azo blowing agent alone although
the resulting product tends to be soft, friable and somewhat
crumbly. The additional initiator is preferred in the
unsaturated polyester resin syrup. Peroxy type initiators,
if employed, are used in the unsaturated polyester resin
syrup. Other types of initiators may be combined with the
alpha hydroxy azo blowing agent or with the unsaturated
polyester resin syrup.
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Metal Salt Promoters
The present compositions preferably contain metal salt
promoters in amounts from 1 to 100 parts by weight per
million (p.p.m.) of the weight of the unsaturated polyester
resin syrup. A preferred promoter is copper naphthenate
solution although cobalt salts, vanadium salts, manganese
salts, calcium salts, magnesium salts can also be employed~
Surfactants
In order to produce a foamed product having relatively
uniform foam cell sizes, a small quantity of a silicone
surfactant is employed in the amount of 0.1 to 2.5 weight
percent of the unsaturated polyester resin syrup.
Inhibitors
Customarily unsaturated polyester resin syrups are
provided with polymerization inhibitors to forestall unin- -
tended premature gelation.
Fillers
The unsaturated polyester resin syrup may be filled
with inert materials such as pigments, dyes, aluminum oxide
trihydrate, silica, limestone, ground glass, clays, mica and
thixotropic additives such as silica aerogel.
Where thixotropic additives are employed they are used
in quantities ranging from about 1/2 to about 3 percent by
weight of the unsaturated polyester resin syrup. The other
inert fillers may be employed up to about an equal weight of
the unsaturated polyester resin syrup.
A particularly preferred inorganic filler is powdered
aluminum oxide trihydrate from about 70 to 110 percent of
- the weight of the unsaturated polyester resin syrup. At
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concentrations above about 110 percent by weight aluminum
oxide trihydrate, the resulting mixture cannot be sprayed.
At concentrations below about 70 percent by weight aluminum
oxide trihydrate, no substantial benefit is observed.
However when the aluminum oxide trihydrate is employed from
about 70 to 110 percent by weight of the unsaturated poly-
ester resin syrup, the resulting larninate exhibits outstandiny
flame spread ratings and smoke inde~ ratings.
he ~lpha__H~d oxy Azo Blowing Agent
Alpha hydroxy azo blowing agents have the following
general formula:
1 1
HO-C-N=N-R3
R2
wherein Rl and R2 are lower alkyl groups having from 1 to 4
carbon atoms and R3 is a tertiary alkyl group having ~ to 8
carbon atoms or an aromatic substituted tertiary alkyl group
having 9 to 12 carbon atoms. Examples of the R3 substituent
are the tertiary-butyl radical and the alpha-cumyl radical.
A preferred alpha hydroxy azo blowing agent is identi-
fied as blowing agent I having the following formula:
HO-C-N=N-C(CH3)3
2H5 . '.
The azo blow:ing agent may be employed full strength or
it may be diluted with inert solvents which will not impede
the polymerization of the polyester resin syrup. Such
solvents include mineral oil and styrene for exampleO
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Glass Fibers
The glass fibers employed in the present reinforced
articles are normally the type which are conventionally used
in glass fiber reinforced articles, that is, chopped glass
roving with an average length of about 3/~ inch to about 4
inches although lengths ranging from 1/2 inch to 1 inch are
normally preferred. Commercial glass roving i8 usually
coated with a silane sizing to improve bond with khe resins.
The glass fibers normally constitute from about 5 to 30
weight percent of the product.
The Present Process
As shown in FIGURE 1, a tank 10 is supplied with an
unsaturated polyester resin syrup containing suitable quanti-
ties of free radical initiator, promoter, surfactant, and,
if desired, inert fillers. A tank 11 contains the alpha
hydroxy azo blowing agent in liquid form. A spool 12 contains
glass fiber rovings of the type customarily employed in
producing glass fiber reinforced plastic laminates.
Unsaturated polyester resin syrup from the tank 10 is
delivered through a tube 13 to a spray gun 1~. The alpha
hydroxy azo blowing agent is delivered from the tank 11
through a tube 15 to the spray gun 14. A supply of pressur-
ized air is delivered through the tube 16 to the spray gun
j 14. Within the spray gun 14 there is a mixing chamber where
the unsaturated polyester resin syrup and the alpha hydroxy
a~o blowing agent are mixed and formed into a spray 17 by
the atomization from the compressed air in the spray gun 14.
Concurrently the glass fiber roving 18 is drawn from
the spool 12 and chopped in a chopper 19 to form a descending
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cloud 20 of chopped glass fibers which impinge the spray 17
and thereby become wetted with the spray mixture. The
wetted ~ibers 17 fall onto a substrate 21 and are collected
as a coating 22. The exposed surface 23 of the substrate 21
is coated with a suitable mold release agent to facilitate
subsequent separation of the coating 22 from the substrate
21. Alternatively the substrate 21 may be a ~inal product
which will contain the coating 22 in its completed form. An
example i5 where the substrate 21 is a premolded sheet of
10 acrylic resin shaped into the form of a bathtub. The coating
22, as depos~ted, contains randomly oriented glass fibers
and objectionable air pockets. Accordingly, it is preferred
that the coating 22 be rolled and/or tamped to embed any
projecting glass fibers and to minimize the unintended
porosity resulting from unwanted air pockets. The rolling
and tamping should be carried out promptly inasmuch as the
mixture of unsaturated polyester resin syrup and alpha
hydroxy azo blowing agent commences gelation almost immedi-
ately upon mixing. The coating 22, following rolling and/or
20 tamping, should be allowed to remain quiescent ~or a suitable
time to allow the coating to develop an e~otherm, to complete
cure and commence cooling.
Example 1 - A commercially available unsaturated poly-
ester resin is fabricated from 105 mol parts propylene
glycol, 50 mol parts isophthalic acid and 50 mol parts ~-
maleic anhydride. The three ingredients are cooked to a
final acid value between 17 and 25, measured at 60 percent
solids content in methyl cellosolve solvent. 73 parts by
weight of the described unsaturated polyester resin is
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combined with 27 parts by weight of styrene to produce an
unsaturated polyester resin syrup having an acid value of 27
to 33.
The unsaturated polyester resin was combined with 0.5
weight percent tertiary butyl perbenzoate as a free radical
initiator, 1 percent by weight silicone fluid as a surfactant,
4-1/2 parts per million by weight of copper naphthenate as a
promoter. No filler was employed in this example. The
chopped glass roving was a type known in the trade as 60-end
roving chopped into lengths of l-1/2 to 3 inches. The alpha
hydroxy azo blowing agent I was employed at a flow rate of 1
percent by weight of the unsaturated polyester resin flow
rate. Both the unsaturated polyester resin and the alpha
hydroxy azo blowing agent I were introduced into a spra~ gun ~-
combined with a glass roving chopper. The chopped glass
fibers, wetted with the combined spray, were applied against
a drum lid mold which was previously coated with a mold
release agent. ~he spray was applied in three passes over
the surface. The coated drum lid was rolled with a glass
compacter roller and allowed to rise freely at room tempera-
ture. The laminate was demolded from the drum lid after
about 15 minutes. The laminate had a flexural strength of
4100 psi, a flexural modulus of 0.26 x 106 psi, a tensile
strength of 2900 psi, a tensile modulus of 0.217 x 106 psi,
~ a density of 26 pounds per cubic foot and a closed cell
;~ content of about 92 percent. The laminate contained 26
percent by weight glass fibers. The starting thickness of
the laminate after compacter rolling was 0.125 inch. After
;~` curing the final :Laminate thickness was 0.432 inch.
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_ample 2 - A conventional lamlnate was prepared from
the unsaturated polyester resin described in Example 1
combined with an equal weight of powdered aluminum oxide
trihydrate. The 50-50 mixture of aluminum oxide trihydrate
and unsa-turated polyester resin syrup was sprayed with
chopped glass fibers to produce a laminate having a ~inal
density after cure of about 90 pounds per cubic foot.
Example 3 - The filled unsaturated polyester resin
syrup of Example 2 including an equal weight of aluminum
oxide trihydrate was combined in a spray gun as described in
Example 1 with 1 percent by weight of alpha hydroxy azo
blowing agent type I. Chopped glass fibers wetted with the
combined spray produced a laminate having a density of about
45 pounds per cubic foot. This laminate was subjected to
combustion tests in an Underwriters' Laboratories test and
yielded a smoke index of 182 and a flame spread of 44. The
glass content in the panel was 20 percent by weight. The
panel had a thickness from about 1/4 inch to about 1/2 inch.
The laminate of Example 3 had a density (45 p.c.f.)
about 50 percent of the density of the Example 2 laminate
(90 p.c.f.).
Exampla 4 - The present foamed resinous materials were
.
employed in the construction of a number of boats, one of
which will be described. A 21 foot long inboard motor boat
hull was prepared from a commercial hull mold which itself
was fabricated from reinforced polyester materials. Initially
a mold release agent was applied to the surface of the hull
mold by wipi~y with a rag~ Thereafter a pigmented gel coat
was sprayed over the entire surface and allowed to cure.
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Therea~ter a conventional unsaturated polyester resin and
glass fiber spray-up coating was applied over the cured gel
coat in an average thickness of abo~lt 80 mils. This spray-
up coating was allowed to cure. Thereafter a number of pre-
cut wooden reinforcing stringers and cross-pieces were
applied against the cured spray-up coating by press fitting.
Thereafter a polyester resin foam and ylass fiber
coating of this invention was applied to the original spray-
up coating to an initial thickness of about 15 mils prior to
foaming. After foaming the coating had a thickness of about
40 mils. The foam-glass fiber coating covered the si~e
surfaces of the wooden stringers and cross-pieces and served
as a binder for retaining them permanently in position.
After the foamed resin coating had been cured, a further
skin coating of unsaturated polyester resin and glass fibers
was applied as a spray-up coating in a thickness of about 80
mils. The total thickness of the boat hull was 0.4 to 0.5
inch. The total weight of the boat hull including wooden
stringers and cross-pieces was about 400 pounds.
Corresponding boats are made commercially from conven-
tional polyester resin and glass spray-up techniques in two
separate spray-up operations having a total thickness of
0.25 to 0.375 inch. A conventional boat hull, if overturned,
will sink in water. The boat hull manufactured in accordance
with this invention had the same total weight as the conven-
tional boat hull but floated when overturned.
The foamed polyester glass spray-up employed a polyester
fabricated from a 50/50 weight percent mixture of isophithalic
acid and maleic anhydride esterified with a slight excess of
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propylene glycol to an acid value of about :L8 at 60 percent
solids. The polyester is mixed into a syrup containing 40
percent by weight styrene, 0.5 ~eight percent of a silicone
surfactant, 0.7 weight percent tertiary butyl perbenzoate
and 6 parts per million of copper naphthenate. This material
is combined with 1.75 weight percent (based on the weight of
the polyester syrup) oE the azo blowing agent I. The chopped
glass fibers constitute 1~ percent of the weight of the foam
layer. Two samples of the foamed g:Lass layer taken at
different times showed densities of 23 pounds per cubic foot
and 34 pounds per cubic foot.
'rhe foamed polyester-glass fiber coating served to
adhere the wooden stringers and wooden cross-pieces firmly
to the boat hull surfaces.
General
__
Inhibitors which are customarily employed with unsatu-
rated polyester syrups are not efEective in the presence of
alpha hydroxy azo blowing agents. In a typical unsaturated
polyester resin syrup, the addition of 1,000 p.p.m~ hydro-
20 quinone will extend the gel time about three-fold. Where an
alpha hydroxy azo blowing agent is employed, 1,000 p.p.m.
hydroquinone extends the gel time by only about 10 percent.
Alternative Method
Referring to FIGURE 2, an alternative method for making
the present spray-up, lay-up laminates is illustrate~ which
employs two different spray nozzles identified by the numerals
24, 25. Compressed air from a tube 16A is delivered to both
of the nozzles 24, 25. The unsaturated polyester resin
syrup is delivered through a tube 13A to the nozzle 24. The
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alpha hydroxy azo blowing agent is delivered through a tube
15A to the spray nozzle 25 whence it emanates as a spray 26.
The unsaturated polyester resin syrup is delivered as a
spray 27 from the nozzle 24. The two sprays 26, 27 combine
to produce a composite spray 28 wherein the alpha hydroxy
azo blowing agent is intimately admixed with the unsaturated
polyester resin syrup. The combined spray 28 wets a descending
cloud 20A of glass fibers to form a coating 22A on the
substrate 2lA.
Some of the useful products which can be fabricated
from the present process include one-piece tub and shower
stall units, bathroom vanities, automobile fenders and
hoods, cold molded formed shapes such as building window
surrounds and cornices, backing for thermoformed acrylic
sheeting, snowmobile shrouds, barge covers, bui.lding infill
panels, mobile homes, liners for railroad boxcars, tote
boxes, silo roofs and panels, tanks and the like, boat
hulls, surfboards.
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