Adhesive compositions

This invention is directed to an adhesive composition comprising: PA0 (a) a copolymer of ethylene or a mixture of ethylene and another ethylenically unsaturated polymerizable monomer with a hydroxyalkyl ester or an epoxyalkyl ester, and PA0 (b) an organometallic compound of lead, tin, or titanium.

BACKGROUND OF THE INVENTION 
The present invention relates to adhesive compositions based on copolymers 
of ethylene and a hydroxyalkyl ester or epoxyalkyl ester containing an 
organometallic compound. 
The adhesive properties of compositions based on a copolymer of ethylene 
and of an ester of a carboxylic acid with an ethylenic unsaturation or of 
terpolymers of ethylene, an ester of a carboxylic acid with an ethylenic 
unsaturation and carboxylic acid or of an ester with an ethylenic 
unsaturation are known. While generally satisfactory, their resistance to 
heat is not entirely satisfactory. 
SUMMARY OF THE INVENTION 
According to the present invention, these properties are clearly improved, 
in particular in their resistance to heat, when slight quantities of 
organometallic compounds of lead, tin or titanium are added to them. 
Briefly, the present invention is directed to an adhesive composition 
comprising: 
(a) a copolymer of ethylene or a mixture of ethylene and another 
ethylenically unsaturated polymerizable monomer with a hydroxyalkyl ester 
or an epoxyalkyl ester, and 
(b) an organometallic compound of lead, tin, or titanium. 
DETAILED DESCRIPTION 
The copolymers of ethylene-hydroxyalkyl ester or epoxyalkyl ester entering 
into the adhesive compositions according to the invention result from the 
copolymerization of about 60 percent to about 99.5% by weight of ethylene 
or of a mixture of ethylene with another ethylenically unsaturated 
polymerizable monomer and of about 0.5 percent to about 40 percent by 
weight of a hydroxyalkyl ester or of an epoxyalkyl ester of an alpha, 
beta-ethylenically unsaturated acid of the formula: 
##STR1## 
in which: 
(a) R is hydrogen or a methyl group; 
(b) X is a --COO(CHR').sub.m --(CH.sub.2).sub.n --Z, in which 
(i) Z is OH or 
##STR2## 
(ii) m is a whole number from 0 to 5, (iii) n is a whole number from 1 to 
6; with m and n being a number from 1 to 6, preferably from 2 to 6 when Z 
is OH, and 
(iv) R' is a hydrocarbon radical, possibly halogenated; and 
(c) Y is hydrogen, X or --COO--CH.sub.2 --R'; X and R' being defined as 
above. 
In the usual case, R' comprises hydrogen and organic radicals containing up 
to 8 carbon atoms, without however excluding those containing a greater 
number, if desired. Among these radicals, one can cite methyl, ethyl, 
propyl, butyl, 2-ethyl hexyl, cyclohexyl, phenyl, tolyl, ethyl phenyl, as 
well as these same radicals possessing at least one substituted halogen; 
particularly chlorine. 
As used herein, the terms "hydroxyalkyl ester" and "epoxyalkyl ester" mean 
the esters possessing hydroxyalkyl or epoxyalkyl groups of the formula: 
EQU (CHR').sub.m (CH.sub.2).sub.n OH 
or 
##STR3## 
m and n being defined as previously. 
The hydroxyalkyl esters or the epoxyalkyl esters of the ethylenically 
unsaturated acids comprise hydroxyalkylated esters or epoxyalkylated 
esters of monocarboxylic and dicarboxylic acids such as acrylic acid, 
alpha substituted acrylic acids and particularly methacrylic acid, maleic 
acid and fumaric acid. 
As ethylenically unsaturated polymerizable monomers which can be associated 
with the ethylene up to a ratio by weight of 1/1, one can choose for 
instance from among: the alpha olefins; the aromatic compounds such as the 
styrene; the alkyl acrylates like ethyl acrylate, n-butyl acrylate and 
2-ethyl-hexyl acrylate; the alkyl methacrylates; the acrylic and 
methacrylic nitriles; the maleic esters like diethyl maleate; the fumaric 
esters; the esters of unsaturated alcohols like vinyl acetate. 
According to the object of the invention, these copolymers, prepared for 
instance according to the technique described in U.S. Pat. No. 3,300,452, 
are associated with an organometallic compound of lead, tin or titanium. 
These organometallic compounds are favorably selected from among the salts 
of organic acids and, more particularly, from among the salts of organic 
acids containing up to 25 carbon atoms in their molecule and better still 
up to 20 carbon atoms. The organometallic compounds of low molecular 
weight are easily migrating, such as for instance liquid compounds being 
the best adapted ones, one of their characteristics being an easier and 
more homogeneous distribution in the copolymer. 
Among the more particularly suitable organometallic compounds of lead and 
tin, one can cite the salts of acids from C.sub.2 to C.sub.13 such as 
dibutyltin diacetate and dilaurate, lead octoate, lead and tin stearates; 
the mercaptides like alkyltin thioglycolates and alkyltin 
mercaptoacetates; the sulfides like alkylated tin sulfides; and the 
carboxylates. 
Particularly recommended among the titanium compounds are the compounds of 
a general formula of Ti(OR).sub.4 in which the radicals R, which can be 
the same or different, represent hydrogen or a hydrocarbon radical 
containing from 1 to 18 and better still from 1 to 14 carbon atoms. These 
radicals R preferably are: alkyl, aryl, alkylaryl or cycloaliphatic 
radicals. 
Quantities from 0.05 to 5; and, preferably, from 0.5 to 2; percent by 
weight, of organometallic compound with respect to the copolymer of 
ethylene-hydroxyalkyl ester or epoxyalkyl ester are suitable in these 
adhesive compositions which are customarily used at temperatures generally 
between the ambient temperature, about 20.degree. C., and 300.degree. C. 
The particularly recommended adhesive compositions with improved adhesive 
properties are prepared from copolymers based on ethylene including those 
mixed with at least one other polymerizable monomer which is ethylenically 
unsaturated such as, for instance, vinyl acetate or ethyl acrylate, and 
hydroxyalkyl or epoxyalkyl acrylate or methacrylate. As in the general 
case these copolymers can contain from 0.5 to 40 percent by weight of 
polymerization product of hydroxylated or epoxidated acrylate or 
methacrylate. 
The adhesive composition is prepared and used in the usual manner by 
mixing, in homogeneous manner, the copolymer in the fluid state with the 
organometallic compound, and then deposited between the substrates to be 
made to adhere before placing the whole under pressure; from 0.05 to 0.5 
MPa is suitable, in the hot state, usually from 150.degree. to 250.degree. 
C. for about 1 to 60 minutes. 
However, the copolymer being in solid form such as a film, granulate, 
powder or the like can be placed in contact directly with the 
organometallic compound at the same time as with the substrates to be made 
to adhere or by prior paste-making at ambient temperature. 
These compositions possess good adhesive properties on supports such as 
metals, glass, and rubbers.