Polyester laminating compositions with improved interlaminar adhesion

Polyester laminating compositions useful in the production of polyester laminates with improved interlaminar adhesion and a method of preparing same are described. The polyester laminating compositions include as adhesion promoters a polyvinyl acetate component or a polyvinyl acetate component in combination with at least one salt of a long chain polyaminoamide and a high molecular weight ester.

BACKGROUND OF THE INVENTION 
The invention relates to polyester laminating compositions useful in the 
production of polyester resin laminates with improved interlaminar 
adhesion and a method of preparing same. More particularly, the invention 
relates to wax-containing polyester laminating compositions which include 
as adhesion promoters a polyvinyl acetate component or a polyvinyl acetate 
component in combination with at least one salt of a long chain 
polyaminoamide and a high molecular weight ester. 
Polyester resins have been used for various purposes including the 
production of laminated articles. In the manufacture of such laminated 
articles a plurality of layers of polyester resin compositions are 
successively superimposed. Usually the article is reinforced by 
incorporating a reinforcing filler such as glass fiber or the like. 
Typically, the filler may be applied seprately as a mat or fabric which is 
impregnated with the liquid polyester resin composition or it may be 
dispersed as short strands in the composition. 
In the manufacture of fiber-reinforced polyester resin laminates it is 
important that the adhesion between superimposed layers is adequate. Good 
interlaminar adhesion is often difficult to obtain with wax-containing 
polyester laminating systems, i.e. polyester laminating compositions which 
include a waxy substance for the purpose of decreasing the evaporation of 
volatile cross-linking compounds in the compositions, since such waxy 
substances tend to interfere with the interlaminar properties of these 
systems. 
The unsaturated, polymerizable polyesters which are generally used in the 
production of such laminates are substantially condensation products of 
dicarboxylic acids and diols. Generally the dicarboxylic acid component 
consists primarily of an unsaturated acid and/or anhydride like maleic 
acid or fumaric acid. A portion of the unsaturated acid or anhydride may 
be substituted with a saturated acid and/or anhydride such as 
orthophthalic acid, isophthalic acid, adipic acid or the like. The diol 
component is normally selected from diols such as ethylene glycol, 
propylene glycol, diethylene glycol, dipropylene glycol, neopentyl glycol 
and mixtures thereof. 
In addition to the polyester component, polyester resin compositions 
contain volatile reactive monomeric material which is copolymerizable with 
the unsaturated polyester and which also acts as a solvent for the 
unsaturated polyester improving the workability of the composition, in 
particular, the viscosity. Examples of suitable volatile monomeric 
materials include styrene, vinyl toluene, alpha-methyl styrene, 
methacrylic acid and methyl methacrylate. 
The cure of unsaturated polyester resin laminating compositions is commonly 
catalysed by free radical catalysts such as suitable peroxides. The cure 
can be accelerated by further inclusion of cure promoters. 
During application of the polyester resin composition and before completion 
of the polymerization a portion of the volatile monomer, which in most 
cases is styrene monomer, evaporates. This may lead to insufficient 
cross-linking at the surface of the resin resulting in an undercured tacky 
surface. Moreover, evaporation of substances such as styrene is 
environmentally undesirable. To decrease the evaporation waxy substances 
such as paraffin wax, montan wax, carnauba wax and the like are usually 
added to the polyester resin composition. However, even though generally 
only small amounts of wax are required to reduce the evaporation of 
volatile monomer materials, the incorporation of wax tends to interfere 
with the interlaminar adhesion between layers in the cured laminated 
articles formed from such wax-containing compositions. 
Several ways of overcoming this drawback have been proposed but have not 
always been completely satisfactory. Thus it has been suggested to improve 
interlaminar adhesion by incorporating into the polyester resin 
composition compounds such as maleic acid derivatives (U.S. Pat. No. 
4,336,169 issued June 22, 1982), unsaturated vinyl compounds (U.S Pat. No. 
4,285,845 issued Aug. 25, 1981), an alkylaromatic compound or mono-alcohol 
(U.S. Pat. No. 4,347,170 issued Aug. 31, 1982), tertiary monoamine (U.S. 
Pat. No. 4,296,009 issued Oct. 20, 1981), etc. 
SUMMARY OF THE INVENTION 
It has now been found that incorporation of small amounts of polyvinyl 
acetate into wax-containing polyester resin compositions can greatly 
improve the interlaminar adhesion properties of the cured resin while 
substantially retaining the desirable suppression of evaporation of 
volatile monomer material. Polyvinyl acetate surprisingly acts as an 
adhesion promoter. Particularly in highly reactive resins, i.e. resins 
having a relatively high content of maleic or an equivalent acid, addition 
of small amount of polyvinyl acetate improves the interlaminar adhesion of 
the cured resin considerably. 
For less reactive polyester resin compositions it is often advantageous to 
incorporate not only small amounts of polyvinyl acetate but also small 
amounts of at least one salt of a long chain polyaminoamide and a high 
molecular weight ester as adhesion promoters. The addition of such a salt 
by itself to a wax-containing polyester laminating composition does not 
generally influence either the interlaminar adhesion or the rate of 
evaporation of the volatile monomeric material. Unexpectedly, however, 
addition of such salts to a wax-containing polyester laminating 
composition which also contains small amounts of polyvinyl acetate further 
improves the interlaminar adhesion of the resulting resins without having 
any substantial effect on the evaporation of the volatile monomeric 
material. This effect is especially noticable in less reactive polyester 
laminating compositions commonly used for laminating purposes. 
In one aspect of the invention there are provided polyester laminating 
compositions comprising an unsaturated polyester, including a volatile 
reactive monomer as crosslinking agent and a wax for reducing evaporation 
of the volatile reactive monomer, 0.1 to 4% by weight of polyvinyl 
acetate, based on the total weight of the composition, and 0 to 2% by 
weight of at least one salt of a long chain polyaminoamide and a high 
molecular weight ester. 
In another aspect of the invention there is provided a method of producing 
laminating compositions exhibiting improved interlaminar adhesion 
properties. 
DETAILED DESCRIPTION 
According to the invention the failure of unsaturated polyester laminating 
compositions, containing wax for suppressing the evaporation of volatile 
material, to develop interlaminar adhesion as great as that of similar 
compositions without wax can be at least partially overcome by 
incorporating at least about 0.1% by weight of polyvinyl acetate based on 
the total weight of the polyester resin composition. As previously 
indicated, the incorporation of polyvinyl acetate into less reactive 
wax-containing polyester laminating compositions is not always as 
effective in increasing the resins' interlaminar adhesion as is the 
incorporation of polyvinyl acetate into highly reactive polyester 
laminating compositions. However, interlaminar adhesion properties of most 
commonly used polyester laminating compositions can be considerably 
enhanced by the addition of at least 0.1% by weight of polyvinyl acetate 
based on the total weight of the polyester resin composition in 
combination with at least 0.1% by weight of salts of a long chain 
polyaminoamide and a high molecular weight ester. 
Polyesters particularly useful for preparing polyester laminating 
compositions according to the invention include condensation products of a 
mixture in which the unsaturated acids are present in an amount of 25 to 
100 mole % of the total amount of dicarboxylic acid component and in which 
the diol component is made up of propylene glycol or a mixture of 
propylene glycol and ethylene glycol and/or diethylene glycol. 
After condensation the polyester is dissolved in a copolymerizable volatile 
reactive monomeric material. Preferably, 80 to 100% of the volatile 
reactive monomer consists of styrene. Alpha-methyl styrene may be added in 
an amount of up to 5%. Methacrylic acid may also be included. 
To enhance storage stability compounds such as hydroquinone, benzoquinone, 
para-tertiary butyl catechol and the like may be added to the polyester. 
Thixotropic agents such as fumed silica may be added in an amount of 
generally less than 2%, preferably 0.5 to 1.5%, along with promoters such 
as soluble salts of cobalt or copper, dimethyl and/or diethyl aniline and 
the like. 
The wax added to reduce evaporation of the volatile reactive monomer is 
advantageously a paraffin wax. Preferred are paraffin waxes with melting 
points of between about 57.degree. and 64.degree. C., in particular 
paraffin waxes with melting points of about 60.degree. C. 
Optionally, dyes or pigments and the like may also be added. 
Advantageously the polyvinyl acetate added to improve interlaminar adhesion 
of wax-containing polyester laminating compositions according to the 
invention has a relatively low molecular weight. Lower molecular weight 
polyvinyl acetate generally dissolves more readily and affects the 
viscosity of the finished product to a lesser extent than higher molecular 
weight polyvinyl acetate. Preferably, the polyvinyl acetate has a 
molecular weight of between about 35,000 and 260,000, more preferably of 
between about 80,000 and 160,000. In cases when the final resin 
composition has a comparatively high viscosity it is desirable to use 
polyvinyl acetate having a relatively low molecular weight. 
The salts of a long chain polyaminoamide and a high molecular weight ester 
which are useful according to the invention include materials such as BYK 
W-980 which is a trademark of Byk-Mallinckrodt. BYK W-980 is a mixture 
comprising 80% of a salt of a long chain polyaminoamide and an ester of 
linoleic acid, said salt having a molecular weight approximately three 
times that of the oleylamine salt of linoleic acid, and 20% ethylene 
glycol monobutyl ether (butyl CELLOSOLVE (trademark)). 
In a brochure from the manufacturer dated June 1979 the following physical 
data for BYK W-980 are listed: 
______________________________________ 
Specific gravity 20/4.degree. C. 
0.99 g/cm.sup.3 
Weight/U.S. Gal. 8.26 lbs/Gal. 
Flash Point (Pensky-Martens) 
77.degree. C. 
Effective Substance 80% 
ASTM D 1644 Method-B 
Appearance Clear, light 
yellow liquid 
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In highly reactive polyesters according to the invention the dicarboxylic 
acid component generally contains a higher proportion of unsaturated acids 
than in the general purpose polyesters, i.e. the unsaturated acids are 
present in an amount of 50 to 100 mole % of the total amount of 
dicarboxylic acid component. 
INTERLAMINAR ADHESION TEST METHOD 
To evaluate the adhesion or bonding properties of glass fiber reinforced 
polyester laminating compositions a test developed by British Industrial 
Plastics is applied. 
Required Materials 
Chopped strand glass fiber mat 450 g/m.sup.2 ; 
Methylethylketone peroxide catalyst; 
Satin weave cloth (a Bay Mills Style 137) 300 g/m.sup.w ; 
MYLAR (trademark of DuPont) or cellophane parting film. 
Procedure 
(1) Cut 4 pieces of mat and 2 pieces of satin weave cloth about 30 
cm.times.30 cm each. 
(2) Prepare a "primary" laminate of a flat, mold released surface by 
applying 2 plies of mat, and 1 ply of satin weave cloth in that order, 
impregnated with the appropriate test resin properly catalyzed. The 
resultant laminate should contain 25% to 30% glass fiber. Approximately 5% 
resin loss in the paint brush, roller, etc. can be anticipated. 
(3) Allow this "primary" laminate to cure for four days (96 hours) at 
normal shop temperature (this time span represents the potential situation 
where a long week-end may elapse before any additional laminate can be 
applied). 
(4) At the end of the four day (96 hours) curing period, place a 10 cm wide 
strip of Mylar or Cellophane film onto the satin weave cloth surface at 
one edge so that about 3/4 of the width of the strip is on the laminate 
and the balance overhangs onto the workbench. The film can be secured to 
the laminate with a small amount of catalyzed resin. 
(5) Now apply a "secondary" laminate to the satin weave cloth surface of 
the "primary" surface, including the area covered by the parting film. For 
this purpose lay down the remaining piece of satin weave cloth first, and 
then the two pieces of mat. 
(6) Allow the "secondary" laminate to cure overnight. 
(7) Allow the complete laminate, "primary" and "secondary", to post-cure at 
40.degree. C. for 18 hours. Then allow to cool. 
(8) To test the laminate for interlaminar adhesion remove the parting film 
insert and separate the "primary" and "secondary" laminates using a wedge. 
(9) Inspect the separated surfaces of the laminate for "whitening". The 
higher the percentage of the surface area which exhibits the "whitening 
phenomenon", the higher is the interlaminar adhesion. To "pass" the 
adhesion test, both of the separated surfaces must exhibit "whitening" 
over at least 85% of their surface areas. Approximately 100% whitening was 
rated "excellent", about 90 to 100% whitening was rated "very good", about 
80 to 90% whitening was rated "good" and about 60 to 80% whitening was 
rated "fair". 
"PAN-TEST" FOR STYRENE LOSS 
300 grams of the resin to be tested is mixed with methylethylketone 
peroxide as catalyst. Then 290 grams are transferred to a tared pan 
(20.times.30 cm) on a balance and the weight loss at ambient temperature 
is recorded as percent of the resin or in g/m.sup.2.

The following examples further illustrate the invention. 
EXAMPLE 1 
Laminating compositions were formulated using Fiberglas Canada Inc.'s 
polyester resin composition VIBRIN F-1072 (trademark) which is a highly 
reactive, high heat distortion resin suitable for laminating. The resin 
contains as dicarboxylic acid component 80 mole % maleic acid and 20 mole 
% phthalic acid and as diol component 61 mole % propylene glycol and 39 
mole % dipropylene glycol. 
To this resin 0.06% by weight paraffin wax having a melting point of about 
60.degree. C. was added. This wax-containing composition was used as 
standard. The standard composition was mixed with either 2% or 3% MOWILITH 
30 (trademark of Hoechst). MOWILITH 30 is a solid polyvinyl acetate having 
an average molecular weight of about 110,000. Methylethylketone peroxide 
was added just before use. The styrene loss of the composition and the 
interlaminar adhesion of the cured resin were measured. 
TABLE 1 
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Samples % Styrene Loss 
Interlaminar Adhesion 
______________________________________ 
Standard 1.62 poor 
Standard and 
2.00 very good 
2% MOWILITH 30 
Standard and 
2.20 good 
3% MOWILITH 30 
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The results of Table 1 show that the addition of polyvinyl acetate to the 
highly reactive wax-containing polyester resin composition improves the 
interlaminar adhesion of the resulting resin considerably while at the 
same time increasing the styrene loss to some extent. 
EXAMPLE 2 
Laminating compositions were formulated using Fiberglas Canada Inc.'s 
polyester resin composition VIBRIN F-1029 (trademark) which is a fast 
gelling, fast curing, low viscosity resin suitable for laminating. The 
resin contains as acid component 35 mole % maleic acid and 65 mole % 
phthalic acid and as diol component 73 mole % propylene glycol and 27 mole 
% diethylene glycol. 
This wax-free composition was used as standard in two separate tests. To 
this standard composition there was added (a) 0.1% paraffin wax, (b) 0.1% 
paraffin wax and 1% MOWILITH 30, (c) 0.1% paraffin wax and 0.5% BYK W-980 
(trademark of Byk-Mallinckrodt), or (d) 0.1% paraffin wax, 1% MOWILITH 30 
and 0.5% BYK W-980. BYK W-980 is a mixture comprising 80% of a salt of 
along chain polyaminoamide and an ester of linoleic acid, said salt having 
a molecular weight approximately three times that of the oleylamine salt 
of linoleic acid, and 20% ethylene glycol monobutyl ether (butyl 
CELLOSOLVE (trademark)). The paraffin wax used had a melting point of 
about 60.degree. C. 
Methylethylketone peroxide was added just before use and the styrene loss 
and interlaminar adhesion were measured. 
TABLE 2 
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Sample % Styrene Loss 
Interlaminar Adhesion 
______________________________________ 
Standard 2.14 good 
Standard and 
1.44 borderline - good 
1% MOWILITH 30 
0.1% paraffin wax 
Standard and 
1.35 excellent 
1% MOWILITH 30 
0.5% BYK W-980 
0.1% paraffin wax 
______________________________________ 
TABLE 3 
______________________________________ 
Sample % Styrene Loss 
Interlaminar Adhesion 
______________________________________ 
Standard 2.41 very good 
Standard and 1.21 fair 
0.1% paraffin wax 
Standard and 0.93 good 
0.1% paraffin wax 
1.0% MOWILITH 30 
0.93 good 
Standard and 1.17 fair 
0.1% paraffin wax 
0.5% BYK W-980 
Standard and 1.10 excellent 
0.1% paraffin wax 
1% MOWILITH 30 
0.5% BYK W-980 
______________________________________ 
The results of Tables 2 and 3 show the influence of the addition of wax, 
polyvinyl acetate and BYK W-980 separately and in combination on the 
interlaminar adhesion properties and on the styrene loss of the fast 
curing polyester resin. It follows that the addition of polyvinyl acetate 
to wax-containing resin improves the interlaminar adhesion while at the 
same time slightly reducing the styrene loss. The addition of BYK W-980 to 
the wax-containing resin does not substantially influence either the 
interlaminar adhesion or the styrene loss. The addition of polyvinyl 
acetate in combination with BYK W-980 to the wax-containing resin, on the 
other hand, greatly improves interlaminar adhesion without having any 
substantial effect on the styrene loss. 
EXAMPLE 3 
Laminating compositions were formulated using Fiberglas Canada Inc.'s 
polyester resin composition MIAPOL 2T1114 (trademark) which is a low 
viscosity, medium cure general purpose resin. The resin contains as acid 
component 35 mole % maleic acid and 65 mole % phthalic acid and as diol 
component 73 mole % propylene glycol and 27 mole % diethylene glycol. 
This composition was used as standard. To the standard composition there 
was added either (a) 0.1% paraffin wax having a melting point of about 
60.degree. C. or (b) 0.1% paraffin wax, 1.0% MOWILITH 30 and 0.5% BYK 
W-980. Methylethylketone peroxide was added just before use and the 
styrene loss and interlaminar adhesion were measured. 
TABLE 4 
______________________________________ 
Sample % Styrene Loss 
Interlaminar Adhesion 
______________________________________ 
Standard 3.27 good 
Standard and 0.896 very poor 
0.1% paraffin wax 
Standard and 0.896 good 
0.1% paraffin wax 
1.0% MOWILITH 30 
0.5% BYK W-980 
______________________________________ 
The results in Table 4 show that the addition of polyvinyl acetate in 
combination with BYK W-980 to the wax-containing all purpose resin 
increases the interlaminar adhesion without affecting the styrene loss. 
COMATIVE EXAMPLES 
Laminating compositions were formulated using the environmental resin from 
Ashland, which is available under the trademark Ashland C520 which is 
based on U.S. Pat. No. 4,285,845 to Scott Bader Company Ltd., and 
Fiberglas Canada Inc.'s polyester resin composition MIAPOL J-446 which is 
a general purpose resin based on MIAPOL 2T1114 and which contains 0.1% 
paraffin wax, 1.0% MOWILITH 30 and 0.5% BYK W-980. 
TABLE 5 
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Interlaminar 
Styrene Loss 
Styrene Loss 
Adhesion 
Sample % g/m.sup.2 % 
______________________________________ 
Ashland C520 
1.72 65.9 75 
(sample 1) 
Ashland C520 
2.28 -- -- 
(sample 2) 
MIAPOL J-446 
1.58 60.8 90-95 
______________________________________ 
The results of Table 5 show that the interlaminar adhesion of an all 
purpose polyester resin to which polyvinyl acetate and BYK W-980 were 
added is higher than the interlaminar adhesion exhibited by a commercial 
embodiment of the resins described in U.S. Pat. No. 4,285,845 which 
contains as adhesion promoter lauryl methacrylate, vinyl decanoate or 
related compounds. At the same time the loss of styrene was lower in the 
resin according to the invention than in the Ashland C520 resin.