Note: Descriptions are shown in the official language in which they were submitted.
~146340
W O 94/07674 PC~r/EP93/02710
PROCESS FOR MOLDING ARTICLES HAYING A DURABLE HIGH STRENGTH HIGH GLOSS GEL
COAT.
This invention relates to coated, molded articles. In one
5 aspect, this invention relates to coated, molded articles comprising
a plastic l~min~ted to a gel coat which, upon cure, exhibits a high
quality gloss, while in another aspect, this invention relates to a
process for m~kin~ such articles.
Coated, molded articles. often fiber-reinforced, are typically
10 made by spreading over the surface of a mold having a surface
corresponding to the article in negative relief, a gel coat
composition which upon cure, becomes the first barrier ~in~t the
envilollment. The gel coat is spread across the surface of the mold
by any one of a number of conventional techniques, e.g. brushing,
15 hand lay-up, s~layillg, etc., and it is usually applied relatively thick,
e.g. 0.5 to 0.8 mm, to m~imi~e its weather and wear resistance and
if the molded article is fiber-reinforced, to help in hiding the fiber
reinforcement pattern which could otherwise show through the gel
coat due to the inherent resin shrinkage that occurs around the
2 0 fibers during cure. This effect is commonly termed "fiber print
through" in the fiber-reinforced plastic industry.
After the gel coat is applied to the surface of the mold, it is at
least partially cured. The plastic is then applied to the partially or
fully cured gel coat, again by any one of a number of conventional
25 techniques, and the resulting 1~min~te structure cured. The cure can
be promoted through the use of elevated temperature and pressure.
In addition to affording weather and wear resistance to the
molded article, the gel coat also imparts cosmetic properties to the
article. In many applications, particularly consumer applications
3 0 such as automobile parts, appliance facie, etc., a high initial gloss and
extended gloss retention are very desirable properties for the
molded article. Present gel coats often exhibit a high gloss upon
cure, but lose this gloss over time due to a variety of environmental
factors, e.g. s11n1i~ht, heat, cold, water, corrosive chemicals, etc.,
35 long before the end of the useful life of the article. Moreover, loss of
gloss is often accompanied by the appearance of surface defects such
WO 94/07674 ~ 1 ~ 6 3 ~ ~ PCr~EP93/02710
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as cracks, coarseness, blisters, etc., and these are often indicative of
structural dete~ioration of the molded article itself.
The high quality gel coats presently in use are isophtalic
acid/neopentyl glycol (IPE/NPG) based unsaturated polyesters
diluted in ~Lylelle monomer, but these compositions are rather soft
materials of overall low chemical resistance and limited outdoor
durability. The marine industry in particular is in need of an
imploved gel coat for boat hulls because IPA/NPG gel coats can fade
and challc before the boat is sold from the marine yard and actually
placed in the water.
Other gel coats presently in use include epoxy, urethane and
vinyl ester gel coats, particularly when greater flexibility and water
resistance are desired. How~vel, these materials also tend to fade
and lose their gloss quickly, and they usually require higher curing
temperatures or are much more difficult to use than the more
commonly available unsaturated polyester products. In addition,
these compositions are difficult to formulate into gel coats having
desirable physical properties, in-mold curing times and handling
properties without the use of more than a nominal amount of sty-rene
or simil~r volatile monomer as a reactive diluent. Moreover, these
diluents are the subject of numerous federal, state and local
regulations and as such, manufacturers of molded plastic articles
prefer to use gel coat compositions that contain minim~l styrene or
like volatile monomers.
Gel coats can, of coursel be applied to the plastic after it has
been at least partially cured and while these post-cure applied gel
coats improve the water resistance, initial gloss and gloss retention
of the plastic, they themselves often have a low initial gloss and poor
gloss retention relative to pre-cure applied gel coats.
Of course, various coatings can be applied to the demolded
article to improve the wear resistance, initial gloss and gloss
retention of the structure, but not only do these coatings require
another costly application step, but they also suffer from poor
adhesion to the gel coat, particularly if traces of mold release remain
3 5 on the surface of the gel coat. Moreover, 1lnlike the gel coat
compositions themselves, these coatings are normally low solids
WO94/07674 2146340 PCI/EP93/02710
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compositions that are prone to comestically undesirable rheological
surface defects such as brush marks, orange peel, craters, ripples,
fish eyes, and the like.
According to this invention, plastic articles having a high
initial gloss and extended retention are made by a process
comprising the steps of:
A~ Providing a mold having a surface corresponding to the article in
negative relief;
~ Spre~-ling over at least a portion of the surface of the said mold a
peroxide-curable gel coat composition comprising:
1. An a, ,~-ethylenically unsaturated oligomer selected from the
group consisting of 1m~tllrated polyesters, and acrylated and
methacrylated urethanes, epoxies, polyesters and polyethers;
2. A curing amount of a polyallylic cross1ink-?r-inifi~tQr; and
3. A cure-rate promoting amount of a metallic salt drier;
C At least partially curing the gel coat composition;
D. Spre~-ling at least a partially uncured, plastic composition over
the at least partially cured gel coat composition to form a
1~min~te;
E. Curing the l~min~te to form the plastic article; and
F. Removing the plastic article from the mold.
In one embodiment of this invention, the oligomer is diluted
with an a, ,~-ethylenically unsaturated monomer while in another
emborliment, the cros.s1ink~r-initi~tor is used in combin~tion with a
co-initiator. Other additives, e.g. reinforcing flber, leveling agents,
pi~ments, cure promoters other than metallic salt driers, etc., can
also be present.
The molded, plasffc articles made by the process of this
invention exhibit gel coats that not only have very desirable gloss and
3 0 gloss retention properties, but gel coats that exhibit excellent
outdoor durability, hardness, toughness and good handling
properties during the molding process. Moreover, the gel coat
compositions can be formulated with little, if any, s~yl~lle or other
volatile reactive diluents with emission properties .simi1~r to styrene.
Illustrative a, ~-ethylenically unsaturated oligomers which cure
by thermally induced free radical polymeri~,ation include unsaturated
W O 94/07674 2 ~ ~ ~ 3 ~ ~ PC~r/EP93/02710
polyesters, urethane acrylates, urethane methacrylates, epoxy
acrylates, epox~ methacrylates, polyester acrylates, polyester
methacrylates, polyether acrylates and polyether methacrylates.
Epoxy acryla~es and methacrylates include the reaction
products of diepoxid~s with acrylic or methacrylic acid, for example
the reaction product of methacrylic or acrylic acid with the
diglycidyl ether of bisphenol A. Urethane acrylates and methacrylates
include the reaction products of hydroxy alkyl acrylates and
methacrylates with organic isocyanates, for ~mple, the reaction
product of isophorone diisocyanate with hydlo~y ethyl methacrylate.
Other urethane acrylates include the reaction products prepared by
combining an organic diisocyanate, hydroxy alkyl acrylate or
methacrylate with a polyol such as ~.opylene glycol, a glycol diester,
or a polycaprolactone diol or triol. Unsaturated polyesters include
the reaction products of oc, ~ unsaturated dicarboxylic acids or
anhydrides and a polyhydric alcohol, for example the reaction
product of maleic anhydride with propylene glycol. Polyester
acrylates and methacrylates include the reaction products of
saturated polyester polyols with acrylic or methacrylic acid, for
ç~r~mple the reaction product of esters of adipic acid and neopentyl
glycol with acrylic acid. Polyether acrylates and methacrylates
include the reaction products of glycol ethers and acrylic or
methacrylic acid, for example the reaction product of
dipentaerythritol and acrylic acid.
2 5 The unsaturated oligomers used in the practice of this
invention are selected for opffml1m properties in the final product.
For outdoor weather resistant or abrasion resistant characteristics,
urethane acrylate and methacrylate based on ~liph~tic isocyanates
resins are optimum. For chemical resistance, epoxy acrylates and
methacrylates are optimllm.
In one embodiment of this invention, the unsaturated
oligomers are diluted with one or more oc, ~-ethylenically
llns:~tllrated monomers which crosslink with the oligomers through
thermally induced free radical polymerization. Illustrative monomers
3 5 include the mono-, di- and trifunctional acrylic and methacrylic
esters, N-vinyl-2-pyrrolidone, N-methylol acrylamide, the hydroxy
21~340
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allyl esters of acrylic and methacrylic acid, and aromatic vinyl and
divinyl compounds. Unsaturated monomers with relatively low
volatility under process conditions, such as the polyfunctional acrylic
and methacrylic esters, are preferred.
Representative of the polyallylic cros.slinker-initi~tors that can
be used in the practice of this invention are polyester resins based
on trimethylolpropane mono- or diallyl ethers and polyallylglycidyl
ether alcohol resins. Those crosslinker-initi~tQrs that function both
as latent initiators for low temperature free radical polymerization of
the oligomers and, if present, monomers, and as a multifunctional
crosslinker are the preferred crosslinker-initiators. Polyallylic
ethers having the general formula
HO ~o ~CH2CH2~ O~H
wherein n is an integer from 2 to 10 are representative of these
preferred crosslinker-initiators.
2 0 Any metallic salt drier that will promote or accelerate the rate
of cure of the a, ,B-ethylenically unsaturated oligomer, crosslinker-
initiator and, if present, monomer, can be used in the practice of
this invention. Typical of these driers are salts of metals with a
valence of two or more and unsaturated organic acids.
2 5 Representative metals include cobalt, magnesium, cerium, lead,
chromium, iron, nickel, uranium and zinc. Representative acids
include linoleates, n~phtht?n~tes, octoates, and resin~tes. Preferred
metallic salt driers include the octoates, naphtenates and
neodecanoates of cobalt, m~ng~ne~se~ vanadium, pot~.~sillm, zinc and
copper. Especially preferred metallic salt driers are the cobalt-based
~` driers such as cobalt octoate, cobalt naphtenate and the organo-
complexes of cobalt and potassium.
The rate of cure, especially at relatively low temperatures, e.g.
21 to 38C, can be further accelerated through the use of one or
more co-initiators. These co-initiators are typically non-polyallylic
peroxides, and inc~ e any of the common peroxides such as benzoyl
~t .
W O 94/07674 ~14 ~ ~ ~ O PC~r/EP93/02710
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peroxide; dialkyl or aralkyl peroxides such as di-t-butyl peroxide,
dicumyl peroxide, cumylbutyl peroxide, l,l-di-t-butylperoxy-3,5,5-
trimethylcycloh~x~ne, 2,5-dimethyl-2,5-di-t-butylperoxy hexane and
bis (~-t-butylperoxy isopropylbenzene); peroxyesters such as t-
butylperoxy pivalate, t-butyl peroctoate, t-butyl perbenzoate, 2,5-
dimethylhexyl-2, 5-di (perbenzoate), dialkylpel 02~ymonocarbonates
and peroxydicarbonates; hydroperoxides such as t-butyl
hydroperoxide, p-methane hydroperoxide, pentane hydroperoxide
and cumene hydroperoxide; and ketone peroxides such as
cycloh~x~none peroxide and methyl ethyl ketone peroxide.
The amount of l1n~t11rated oligomer and, if present, monomer
present in the gel coat composition can vary to convenience with the
exact amounts in any given forml1l~tio~ a function of the physical and
chemical properties desired in the cured coating. Typically, the
oligomer or if monomer is present, then the oligomer and monomer
mixture, comprises at least about weight 65 %, based on the
precured weight of the gel coat composition, of the composition,
preferably at least about weight 75 %.The m~ximum amount of these
materials in the composition usually does not exceed about 95 wt %,
preferably about 90 wt %. If an oligomer-monomer mixtllre is used
in the practice of this invention, then the amount of monomer
present in the mixtllre can vary to convenience but typically it does
not exceed about 30 wt %, preferably about 20 wt %, of the mixtllre.
At least a curing amount (i.e. an amount sufficient to cure or
crosslink the oligomer and, if present, monomer into a durable, high
quality gel coat) of polyallylic crosslink~r-initi~tQr is present in the
precured gel coat composition of this invention and although this
amount can vary, it usually does not exceed about 35 wt %,
preferably about 25 wt %, of the composition. Typically, the
minimllm amount of this crosslinker-initi~tor present is in excess of
about 5 wt %, preferably in excess of about l 0 wt %, of the
composition. If a co-initi~tor is present, then it is typically present
in an amount between about l and lO wt %, based on the precured
weight of the gel coat composition.
At least a cure-rate promoting amount (i.e. an amount that
promotes the rate of cure of the oligomer, polyallylic crosslinker-
o ~1~6~4D
WO 94/07674 . . PCI~/EP93/02710
initiator and if present, monomer) of the metallic salt drier is
present in the precured gel coat compositions of this invention. This
amount, like the amount of crosslink.or-initi~tQr, can vary, but this
amount, based on the wt % of metal in the drier (usually between
about 4 and 15 wt %), typically is in excess of 0.005 wt %, preferably
in excess of 0.01 wt %, and more preferably in excess of 0.03 wt %.
Typically, this amount is not in excess of about 0.08 wt %, preferably
not in excess of about 0.05 wt %, and more preferably not in excess
of about 0.04 wt %.
The precured gel coat compositions can contain one or more
additives to f~çilit~te processing or to impart some desirable feature
or property to the molded plastic article. For ç~mple, solvents may
be added to reduce the viscosity of the precured gel coat composite,
which in turn makes easier to apply the composition to the mold.
Preferably these solvents are reactive diluents, e.g. one or more of
the oc, ~-ethylenically unsaturated monomers, that are relatively
nonvolatile at curing conditions. If the solvent is a nonreactive
diluent, then it must be removed prior to or during the cure
process. Other additives, such as flourocarbons, silicones, pigments,
2 0 cellulose acetate butyrate, and the like, may also be present to
control flow, leveling, color, thixotropy, and the like. Cure
promoters in ~ lition to the metallic salt driers can also be present,
such as N,N-dimethyl-p-toluidine, N,N-dimethyl ~niline~ N,N-diethyl
aniline, 2,4-p~nt~nedione and N,N-dimethyl acet~niline.
In the process of this invenffo~ for molding a l~min~ted plastic
article, a mold surface corresponding to the article in negative relief
is at least partially, preferably completely, covered with the
peroxide-curable gel coat composition. Typically, this composition is
formulated from its constituent components just prior to its
application to the mold surface. The oligomer and metallic salt drier
are blended with one another prior to the addition of the polyallylic
crosslink~r-initi~tor. If an ~c, ,B-ethylenic~lly unsaturated monomer is
present, then it is blended with the oligomer and metallic salt drier
prior to the addition of the polyallylic crosslinker-initiator or, if
present, a co-initiator. If a co-initiator is present, then it is blended
W O 94/07674 ~ 1 ~ 6 3 ~ Q PC~r/EP93/02710
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with the polyallylic crosslinker-initiator prior to the crosslinker-
initiator being blended with the oligomer and metallic salt drier.
The gel coat composition is applied as a thick coat, relative to
the thickness of a coat of paint, but usually less than l mm,
5 preferably less than 0.5 mm. The composition is then at least
partially cured, either at ~mhiçnt conditions, e.g. 20 to 40C and
atmospheric pressure, or at an elevated temperature, e.g. at a
temperature in the range of about 40 to 9~C. "Partially cured" here
means that the gel coat composition is sufficiently cured to retain its
10 shape without signific~nt distorsion, while still on the mold surface,
during the application of at least a partially uncured plastic to its
exposed surface. The cure time will vary with the nature of the gel
coat composition, curing conditions, thickness of the gel coat, and a
host of other factors but typical cure times for many of the
15 commçrcially available unsaturated oligomers, in comhin~tion with a
polyallylglycidyl ether crosslinker-initiator are in the range of about
240 to 300 minlltes at about 20 to 27C, and about 20 to 45 minutes
at about 65 to 70C, for a coat of less than l mm in thickness. The
gel coat composition can be applied to the mold surface in any
20 convenient manner, e.g. hand lay-up, splayi~lg~ dipping, brushing,
rolling, etc. The mold contact surfaces may be made of any
conventional materials such as glass, reinforced polyesters, epoxies,
steel, ~ minillm, and the like.
After the gel coat composition has at least partially cured,
2 5 preferably completely cured, the at least partially uncured,
preferably essentially completely uncured, plastic is applied to the
exposed surface of the gel coat. "Partially uncured" here means that
the plastic is sufflciently fluid to permit its application to the
exposed surface of the at least partially cured gel coat composition
3 0 by one or more conventional means, e.g. spraying, brushing,
injection, etc. The nature of the plastic can vary to convenience, but
typical plastics include lm.~tllrated polyesters, phenolics, epoxies,
ureth~nes, etc.
The mold may be an open mold or a m~tched mold, i.e. a two
35 component mold compnsing a female mold surface and a male mold
surface that when joined, define a volume with the shape of the
-
214~63~O
W O 94/07674 PC~r/EP93/02710
desired molded product. If an open mold, then once the plastic has
been applied to the exposed surface of the at least partically cured
gel coat composition, then it is allowed to cure under ambient
conditions or more commonly, placed in an oven to promote cure. If
a matched mold, then once the gel coat is at least partially cured the
mold is closed and the plastic injected under pressure into the mold
to completely fill the volume formed by the two mated mold
surfaces. The mold is retained in this closed position for a sufficient
period of time to allow the molded article to complete cure, typically
at an elevated temperature and pressure, and to allow a strong bond
to form between the gel coat and the plastic. The mold is then
opened, and the molded article removed. Mold release agent can be
used with both open and m~tched molds as desired.
In one embodiment of this invention, the plastic is fiber-
reinforced. The reinforcing fiber can vary to convenience, and
typical reinforcing flbers include glass, polyethylene, metal, ceramic
and the like. While the fiber can be ~lmixed with the plastic prior to
the application of the plastic to the at least partially cured gel coat
composition, more commonly the fiber is applied to the at least
2 0 partially cured gel coat composition as a preform. Typically, a
m~tched mold is used. The preform is inserted over the at least
partially cured gel coat composition, the mold is closed, and the
plastic injected. Upon cure, a fiber-reinforced plastic article is
formed.
The gel coats of the l~min~ted~ flber-reinforced plastic molded
articles of this invention exhibit high physical strenghts, a very
desirable high initial gloss and an excellent gloss retention in
addition to such other desirable properties of providing protection
to the underlying flber-reinforced plastic against heat, cold, slmlight,
water, corrosive chemicals, and the like. Moreover, these desirable
, properties are obtained with coatings that are thinrelative to the
thickness of conventional coatings, e.g. those based on isopthalic
acid and neopentyl glycol.
The following ~mples are illustrative of certain embo-liments
of this invention. Unless indicated to the contrary, all parts and
percent~ges are by weight.
21~6340
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- 10 -
Example 1
Preparatior~ of Urethane Acrylate Oli~omer
Into a reaction flask equipped with an agitator, liquid
additional filnnel, thermometer and inlet tube for the introduction of
5 dry air for m~int~inin~ an anhydrous atmosphere were placed 1453
grams of isophoronediisocyanate, 4 grams of dibutyl tin dilaurate and
1 gram of toluene hydroquinone. To this solution was slowly added
760 grams of 2-hydroxyethylacrylate over a 1 hour period while
m~int~ining a reaction temperature of between 30 and 40C. After
10 ~git~tin~ the re~ction m~ lre in this temperature range for 1 hour,
the temperature was raised to about 70C and 600 grams of
ethyltriglycolmethacrylate and 1177 grams of 540 molecular weight
caprolactone triol were added. The resulting m~ lre was agitated
and held in a temperature range of 70 to 80C until infrared analysis
15 indicated disappearance of the -NCO absorption peak (3 hours).
Preparation and testin~ of a Gel Coat
A gel coat composition was prepared by combining a pigment
grind comprised of 31.5 grams of the urethane acrylate oligomer
prepared above, 8.6 grams of propylene glycol monomethyl ether
20 acetate, 12.9 grams of aromatic solvent, 43.1 grams of titanium
dioxide (rutile grade R902 from the E.I. Du Pont de Nemours, Co.),
2.2 grams of acetoacetoxyethyl methacrylate, 0.28 grams of cobalt
naphtenate, 0.004 grams of methyl ethyl ketoxime, pigment
grinding aides, flow additives with 8.6 grams of Santolink~ 100
25 (sold by MONSANTO Company) as a crosslinker-initi~tor, and 0.43
grams of cllmene hydroperoxide.
The resulting peroxide-curable gel coat composition was
drawn down on a waxed glass plate at a wet film thickness of 10 mils
(d~ film thickness of 0.18 mm). After curing for 60 minutes at 75C,
30 the gel coat surface in contact with the glass plate was tack free and
the surface exposed to air had a slight t~kiness. At this polnt a
peroxide catalyzed unsaturated polyester l~min~ting resin was
applied onto the gel coat and allowed to harden for 12 hours before
removing the composite from the glass plate. The resulting white gel
35 coated panel had an initial gloss of 89 on the 60 degree Gardner
scale and 76 on the 20 degree scale.
WO 94/07674 214 ~ 3 4 ~ PCr/EP93/02710
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The panel was then placed in an ultra-violet accelerated
weathering unit alongside a panel of white 0.5 mm thick high
performance conventional isophtalic acid /neopentyl glycol
unsaturated polyester gel coated l~min~te. Similar panels of each
5 were also placed on a 45 degree exposure rack in south Florida. The
gloss of the exposed panels was periodically measured. The results of
both the ultra-violet accelerated weathering unit and the south
Florida exposure tests are reported in Table I.
Table I
QW EXPOSURE (light hours) 0 305 507 811 1319
60 GLOSS
Urethane Acrylate Based
Gel Coat 89 75 69 47 46
Collv~lltion~l Gel Coat 94 15 7 0 0
20 GLOSS
Urethane Acrylate Based
Gel Coat 76 52 30 10 9
Convention~l Gel Coat 81 2 0 0 0
FLORIDA EXPOSURE (months) 0 3 6 9 12
60 GLOSS
Urethane Acrylate Based
GelCoat 91 91 93
Collv~.~t;on~l Gel Coat 82 89 75 55 49
20 GLOSS
Urethane Acrylate Based
Gel Coat 81 80 82
Convçnffon~l Gel Coat 75 56 36
Example 2
Preparation of the Urethane MethacIylate Oli~omer
f In the apparatus described in Example 1 were placed 1616
grams of isophoronediisocyanate, 5 grams of dibutylffnf1il~llrate, and
1 gram of toluhydroquinone. To this solution was slowly added 948
grams of 2-hydroxyethylmethacrylate over a period while
maint~inin~ a reaction temperature in the range of 30 to 40C. After
~it~ting the reaction mixtllre in this temperature range for 1 hour,
WO 94/07674 2 1 4 6 3 4 ~ PCI~/EP93/02710
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the temperature was raised to 70C and 500 grams of 2-
ethylhexylmethacrylate and 1921 grams of a 530 molecular weight
caprolactone diol were added. The resulting m1~ctl7re was ~git~ted
and heated in a temperature range of 70 to 80C until infrared
5 analysis ln~lic~ted the disappearance of the -NCO absorption peak (3
hours).
Preparation and Tes~1n~ of a Gel Coat
The urethane methacrylate prepared above was substituted for
the urethane acrylate in the formulation and procedure of Example
10 1.
The resulting white gel coat was subject to the same
accelerated weathering and outdoor Florida exposure tests as the
panels of ~ mple 1. Results are reported in table II below.
Table II
QW EXPOSURE (light hours) 0 115 478 669 1051 1437
60 GLOSS
Urethane Acrylate Based
Gel Coat 84 86 46 32 36 30
20 GLOSS
Urethane Acrylate Based
Gel Coat 65 44 16 7 20 12
FLORIDA EXPOSURE (month.~) o 3 6 9 12
60 GLOSS
Urethane Acrylate Based
Gel Coat 90 89 93
20 GLOSS
Urethane Acrylate Based
Gel Coat 57 58 54
F~r~mple 3
Preparation of an Unsaturated Polyester Oli~omer
Into a reaction flask equipped with an ~it~tor, nitrogen gas
inlet tube, packed column, and condensor were placed 1129 of
grams neopentyl glycol and 1564 grams of 1,4 cyclohexane
dimethanol. This mi~ lre was heated to 94C at which time 1082
grams isophtalic acid and 0.7 gram butyl stannoic acid were
214634~
W O 94/07674 PC~r/EP93/02710
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introduced. The reaction mixture was heated to 180C and then
gradually to 220C while removing the esterification water.
When an acid value of 0.8 was reached the reaction m~ re
was cooled to 177C and 958 grams of maleic anhydride and 0.4
5 grams of monotertiarybutyl hydroqllinone were added. This reaction
m~ re was heated to 204C and held at this temperature until the
acid value reached 29. Xylene (100 grams) was then added for
refluxing and the temperature was held at 204C until the acid value
was reduced to 5. The resulting resin was cooled, and additional
10 xylene was added to give a 80 % resin solution.
Preparation and Tesffn.~ of a Gel Coat
The polyester prepared above was substituted for the urethane
acrylate in the formlll~ffon and procedure of F,x~mple 1.
The resulting white gel coat was subj ected to the same
15 accelerated weathering and outdoor Florida exposure as the gel coats
of F,x~mples 1 and 2. Results are reported in Table III below.
Table III
~W EXPOSURE (light hours) 0 304 478 669 1051 1437
60 GLOSS
Urethane Acrylate Based
Gel Coat 90 84 86 73 51 4
20 GLOSS
Urethane Acrylate Based
GelCoat 71 55 50 10 6 5
FLORIDA EXPOSURE (months) 0 3 6 9 12
60 GLOSS
Urethane Acrylate Based
Gel Coat 84 86 88
20 GLOSS
Urethane Acrylate Based
Gel Coat 65 67 72
Example 4
- A gel coat composition was prepared by combining a pigment
grind comprised of 24.4 grams of the urethane acrylate of Example
1, 6.1 grams of the reaction product of one mole of
isophoronediisocyanate and 2 moles of hydlo2~,yethylmethacrylate,
2~463~0
WO 94/07674 PCI/EP93/02710
- 14 -
11.3 grams of rutile grade titanium dioxide, 0.3 grams of cobalt
naphtçn~te, 0.08 gr~lins of methyl ethyl ketoxime, 1.9 grams of
acetoacetoxyethylmethacrylate, pigment grinding aids, and flow
control additives with 0. 5 grams of the mono-adduct of
5 hydroxylethylmethacrylate and phtalic anhydride, 9.5 grams
S~ntolink8~ X~-100, and 0.7 grams of cllmene hydloperoxide.
A 0.13 mm thick fllm of the resulting peroxide-curable gel
coat composition was drawn down on a waxed glass plate. After
curing for 30 minutes at 75C, the gel coat surface which had been
10 in contact with the glass plate was tack free and the surface which
had been in contact with the atmosphere had a very slight tack.
Then an acid-catalyzed phenolic molding resin filled with 2 layers of
one and one half ounce continuous strand glass mat was 1~min~ted to
the gel coat and allowed to cure for one hour at 65C.
The resulting gel coated panel had a "F" pencil hardness on
the gel coated side and gloss readings of 87 on the 60 degree
Gardner scale and 77 on the 20 degree Gardner scale. There was no
gel coat adhesion loss when the panel was subj ected to
cros~sh~tchin~ and tape pulling with No. 600 Scotch Brand adhesive
2 0 tape.
When the gel coat composition was post applied to a cured
phenolic panel. the gel coat showed 50 % ~rlhe.sion failure and had
gloss readings of 78 and 42, respectively, on the 60 and 20 degree
Gardner scales.
~,~ample 5
The gel coat composition of Example 4 was modified by
substituting 14.8 grams of dipentaerythritol mono-
hydroxypentaacrylate (SR 399 from the Sartomer Co.) for the 6.0
grams of methylmethacrylate.
3 0 From this composition a gel coated reinforced polyester
l~min~te was prepared in a mZ~nn~r simil~r to F'~mple 4.
The resulting panel displayed a greater than 7H pencil
hardness, could not be scratched with No. 00 steel wool, did not
lose bond when subjected to the crossh~tch - tape pull test and had
gloss re~rlin~s of 90 and 75, respectively, on the 60 and 20 degree
Gardner scales.
