CA1038992A - Hot melt adhesive - Google Patents

Abstract

ABSTRACT
A hot melt adhesive composition comprising a compatible mixture of: a) an aridic ethylene co- ol terpolymer having an acid number ranging from about 3 to about 80, b) a polyamide having an amine number ranging from about 70 to about 400, and c) a minor effective amount of a tackifying agent; components a) and b) being present in a relative proportion by weight ranging from about 30:70 to 60:40. An encapsulation method utilizing said adhesive is also described.

Description

~038g9Z
This inYentio~ relates to hot melt adhe~i~es.
The use of hot melt adhesive~ for bonding plaatic compo~ition~ to other plastic co~po~itions of the ~zme or a ~ -dif~ere~t type or to metals i~ o~ cours~ well known. In particular, hot melt adhesives are widely u~ed in bonding plastic sleeve~ and end caps to power cables or conduits or to variou~ type~ o~ metal or plastic pipe or tubing. Un~or-tunately, none of the currently a~ailable hot melt adhe~ive~
possesses all the properties which are de~irable ii the adhesive is to be truly e~fecti~e in a wide ~ariety o~ environ-ments. ~peci~icall~ de~irahle ~eatures all o~ which are not pos~essed by any currently available hot melt adhesi~e inclu~e good low temperature impact resi tance, i.e., the adhesive should not be bri~tle and ~rangible at temperatures at least as low as -40C, and good peel strength over the temperature ; range o~ -40C to at lea~t ~70C to ~hich such material~
ma~ be exposed in service. In particular, good peel strength is especially desirable ~or cable 8plicing and capping appli-; cat~ons using di~icultly bondable substrates such as lead and polye~hylene, bu~ is not obtainable with available adhe~ive~
; o~er the ab~ve indicated temperature range. ~uch ~de temperature ra~ge applicability i~ important because winter temperatures in many areas can easily drop to -40 & and conver~elg in direct sunlight a b1ac~ cable or pipe can reach ~- 2~ sur~ace akin temperatures o~ a~ lea~t +70C.
A pQrticular use ~or hot melt adhes~es ls with re~pect to heat recoYerable ~i.e., ela~t~c memory) end cap~
and 3ackets. In rece~t years ~ncreasing attention has been paid to the uae o~ artictes e~h;bit~ng the property o~ ela~tic ~L

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' ~ ' ' : ~038992 memory in providing environmental insulation to electrically conductive wire and cable pipelines and the like. An article having this property is one which has been deformed from an original heat-stable dimensional folm into a different, heat-unstable formO While this article is maintained below a certain temperature, it will retain its unstable form but when it is heated to above this temperature, termed the recovery temperature, it will recover towards its original form. One method of imparting the property of elastic memory, and materials to which that memory may be imparted, are disclosed in United States Patent No. 3,086,242 to Cook, et al. Generally, ~, provision is made for adhesive bonding between the elastic me ry article and the substrate about which it is recovered, and in particular cases the nature of the substrate has prevented obtainment of suitable bonds with adhesives heretofore available.
' For example, it has become common to employ heat shrinkable poly-ethylene end caps in sealing polyethylene jacketed telecommunica-tions lines, and much would be gained by extension of that . ~ - ,, :,. . . .
technology to the lead-jacketed lines in widespread current i 20 use. Lead, howe~er, is a notoriously poor adhesive substrate '. ant the adhesives heretofore available have generally proved : unsuitable, frequently affording peel strengths not signifi~
cantly greater than about 3 pounds per linear inch ~pli) at room temperature and even less at temperatures significantly ; above or below room temperature. As already indicated, while ; in service, telecommunication lines frequently encounter temperatures substantially greater and lower than room temperature. Currently extant specifications for cable end -~
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caps test peel strength at +70C. ~uture specifications will undoubtedly require good peel strength at -40C as well as at -l70C. In addition to -affording suitable peel strength over this temperature range, end cap ad-hesives must soften at a temperature below that at which the end cap itself is degraded yet sufficiently above the maximum service temperature so as to prevent the end cap "milking off" the cable end when in use. A need has therefore existed for an end cap adhesive of sufficient peel strength at both high and low temperatures to permit applications involving lead-jacketed cables, which adhesive nonetheless displays a low embrittlement temperature and a softening temperature suiting it to use in such applications.
- The present invention providPs a hot melt adhesive composition comprising a compatible mixture of: (a~ an acidic polymer of ethylene having - an acid number ranging from about 3 to about 80 selected from the group con-- sisting of a terpolymer of ethylene, an ethylenically unsaturated mono- or dicarboxylic acid and a vinyl ester of Cl to C6 aliphatic carboxylic acid and a copolymer of ethylene and a C2 to C20 aliphatic ester of a mono - ethylenically unsaturated mono- or dicarboxylic acid wherein a portion of the carboxylic acid moieties of said mono- or dicarboxylic acid component are not esterified, and ~b) a polyamide having an amine number ranging from about 70 to about 400 with a tackifying agent wherein said tackifying agent is present in an amount ranging from about 3 to about 20 parts by weight per 100 parts of (a) and (b~ together. ~- -The adhesive compositions of the present invention may be prepared by mixing the three components thereof at a temperature of at least about 100C and preferably about 150C. Any conventional mixing apparatus used for plastic compounding such, for example, as a steam-jacketed differential roller mill, a high shear mixer or a compounding extruder is suitable.
Components a~ and b~ will advantageously be present in ~_ 4 -- - ' ' , ~, .
'- , ' ' , ~ ' ' ' ,':

amounts by weigh~ within the range of from 40:60 to 60:400 - They are preferably present in approximately equal amounts by weight. The amount of c) which i~ desirably present i3 irom about 3 to 20 parts of c), preferably about 5 to 15 parts of c), per 100 parts of a) and b) together. As will be described ~n greater detail hereinafter, ratios of these components which deviate signi~icantly from those indicated may result in reduced adhesive effectivene~.
The three components of the adhesive mixture must be compatible. ~he term compatible a~ used by polymer physicists denotes that the mixture o~ polymers has a ~ingle ~lass transi- ~ ~
tion temperature, as oppo~ed to multiple gla3~ transition ~-temperature# characteri~tic o~ the constituent polymer~. All oi the amideQ an~ ethylene polymers disclosed and claimed ~ ;
1S herein are compatible with each other and with mo!~t conventional tackifiers when admi~ed as described in the ratios indicated.
- ~he compatibility of the three components may, o~ course, be determined simply by ascertaini~g that the mi~ture has only ~, a ~lngle glass transition temperature. We have found that in the required amounts most conventional tackifier~ are compatible and, of course, any which are incompatible can readily ~e ascertained by conventional technique~ which determine ii the blend has a single ~las~ transition temperature. It should be ~oted that compati~ ty of this type between polymers of different chemical types, i.e., amide and ethylene polymers, ~a comparati~ely rare (~ee~ e.g., J. ~acromol. Sci., C7 252 ~1972) and U.S0 Patent ~,484,40~)~
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Tackifying agents are well known in the adhesive art as useful adjuncts in adhesive formulations. The tackifying agents known to the art include a wide variety of natural and synethetic monomeric and polymeric substances, most of which, in general, have been found effective in the present adhesive formulations. Suitable tackifiers include:

Source Commercial Name Chemical Nature ;- (Trade Marks) Hercules Abalyn Methyl ester of rosin Hercules Abitol Hydroabietyl alcohol Diamond Alkali Chlorowax 70 Chlorinated paraffin - 10 Rohm q Haas Dibenzyl Ester sebacate - Argus Chemical Drapex 3.2 Epoxy plasticizer Baker Castor Oil 15 Oil Polymerized (oxidized) castor oil Hercules Flexalyn Glycol ester of rosin Hercules Hercoflex 150 n-Octyl n-decyl phthalate (mixture) Hercules Hercolyn Hyd. methyl ester rosin Hercules Hydrolyn A Hydroabietyl alcohol ester Pacific Vegetable Isano Oil Glyceride Oil ` Eimer ~ Amend Lead Stearate Lead Stearate ~~ Neville Nevillac 10~ Alkyl hydroxy resin 20 Hercules Petrex SS Alkyd of resinous terpene acid : Hercules Polypale Ester #l Fthylene glycol ester of poly-- merized rosin Hercules Polypale Ester #10 Glycerol ester of polymerized rosin Hercules Staybelite Ester #10 Glycerol ester of hydrogenated rosin - Pennsylvania Industrial Chemical Piccotex 75 Vinyl-toluene copolymer Corporation Union Carbide ZKMA 0251 Polyketone resin Union Carbide ZKMA 0252 Polyketone resin Union Carbide ZKMA 0250 Polyketone resin Mohawk Ind. MR 97 Aliphatic ketone resin Mohawk Ind. MR 82 Aliphatic ketone resin 30 Hercules Resin 7310 ~ehydrogenated rosin ~ercules ~-Piccolyte 100 Modified rosin :

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~038992 Rre~erred tacki~ier3 are low molecular weig~t, generally liquid tacXi~iers, especially of the polyketone type, e.g~ poly~etone resins ~old by Union Carbide a~d Mohawk Industr~es, Inc.
~he ab~ence of a tacki~ier or alternatively use o~ -a tac~i~ier in amounts outside o~ the above indicated propor- ~
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t$0n3 produces an inferior adhesive. ~he use of le~s than about 3 part~ tackifier in the adhesi~e formul~tion may result in poor wetting of the sub3trate with concomitant erratic adhesion with di-fficult-to-bond substrates and if greater than about 20 parts tackifier is added, the adhesi~e usually e~h~bits inadequate peel strength at any temperature with ~irtually all ~ubstr&te~.
~ As indicated, component a) is an acidic ethylene 5` 15 copolymer, the term copolymer as herein u~ed including ter-and higher copolymers, e.g. with two or more comonomers, but e~cluding graft copolymers o~ the type ba~ed on a polyethylene backbone.
Oomponent a) i8 pre~erably either a terpolymer o~
ethylene, an ethylenicall~ unsaturated mono- or dicarboxylic acid and a ~inyl ester o~ a C1 to C6 straight or branched chain aliphatic carboxylic acid or, alternatively, a copolymer Or ethylene and a C2 to C20 a1iphatic e~ter o~ a mono ethy-len~cally unsaturated mono-or dicarboxylic acid. If desired, a mi~ture of such a terpolymer and such a copolymer can be usedO ~ -In the case o~ the terpolgmer~ the weight percentage o~ units pre~ent ~ any terpolymer molecule which are der~ed i~rom each o~ thc three mol~omerl~ comp~nentu c:an ilultabl~ be .

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as follows:
Ethylene 60 to 95, pre~erably 70 to 85 Unsaturated mono or diba~ic acid 1 to 10, preferably 2 to 5 Vinyl ester5 to 40, pre~erably 10 to 30 ~he pre~ence of the indicated percentage o~ mono-or dibasic acid derived units will afford a terpolymer having the desired acid number. Terpolymers having acid numbers outside the indicated range afford ;~erior adhe~ive~ as hereinaiter indicated.
The vinyl esters of the ~1 to C6 aliphatic carboxylic - acid~ are known compounds mo~t of which, such as ~inyl acetate, vinyl propionate and vinyl butyrate, are commercially availablev - ~ny one of the~e vinyl esters or any mixture thereof can suitably be used.
In the case o~ the copolymer, the weight percentage o~ units in any copolymer molecule ~Ihich are derived ~rom each of the monomeric components may suitably be a~ follows:
ethylene 60 to 95, pre~erably 70 to 90, ~nd, correspond~ngly, C2 to C20 aliphatic ester o~ mono ethylenically unsaturated mono- or dicarbo2ylic acia 40 to ~, preferably ~0 to 1~. ~he desired acid number is achieved by including in the polymer~za-tion ch~rge the appropriate quantity o~ unsaturated ester monomer wherein the carbo~ylic acid moieties are not iully ecteri~ied~
2~ Co- or terpolymers having actd numbers outside the in~lcated range a~ord adhesives that are inferior in that they do not pro~ias the outstandiDg advantages of the a~hesi~e formulation~ of the present invention. Unlike conYentional . .

~ 8 -polyamide adhesives, the adhesive o~ the present in~ention do not become brittle until temperatures below -40C and in many instance~ even below -70C. ~onventional polya~ide~
generally embrittle at temperatures well above -40C.
Conversely, conventional ethylene co- and terpolymer adhesives do not ha~e use~ul peel strengths at room temperature much less at ~70C wherea~ our adhesives have good peel strength at this temperature.
It should be noted, moreover, that the mere combina-,. ~ .
tion o~ conventio~al polyamide and ~thylene co- or terpolymer adhesives does not in itself result in a ~igni~icantly superior adhesive forml~lation. It is only when amides and ethylene co- ~ -and terpolymers having the ~peci~ic above-enumerated character- ~ ~
i~tics plus tackifier are combined in the indicated ratios ~ -that the superior properties ensue. Whilst we do not wish to be bound by any particular m~chani~tic interpretation, it is believed that the e~traordinarily low brittle temperature and the high adhe~ive strength of the compositions o~ the pre~ent i- ~-- . .
invention are due to the fact that the formulations are compa-tible mi~tures. The combining of polyamides or ethylene co--or terpolymers not having the above-enumerated characteristlcs apparently doe~ not aiford a compatible mixture and hence such mixture~ do ~ot ehow a~y outstanding advantage~.
Suitable ethyle~ically unsaturated mono- or dibasic acids include acids having irom 3 to about 50 carbon~. Such . . .
acide ca~ ha~e one or more ethyle~i¢ dou~le ~onds and can be alicy¢lic or aliphatic. ~mongst ~uitable acid~ there may be mentioned, ~or e~amp~e, acrylic acid, methacrylic acid, ~ale~c `~ acid, fumaric ac~d c~taco~c acid, aco~itic acid, itacon~o ; acid, br~gidic acid, a(1-cYc~Ohe~enyl~-butyr~c acid, 2-r .

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cyclopentene-l-acetic acid, 5-norbornen-2-carbo~.ylic acid, ~-cyclohexene-1-carboxylic acid, endo-5-norbornene-2,3-dicarboxylic acid, ~,4,5,6-tetra-hydro phthalic acid, 1,2,3,6-tetra-hydro phthalic acid, and also citric acid and other acids which can be decomposed at the polymerization temperature to iorm unsaturated dicarboxylic acid~ in situ , or any mi~ture o~ two or more of said acids.
The co- or terpolymers used in the present in~ention can be readily prepared by copolymerizing a mixture of the appropriate comonomers in the presence o~ a free radical polymerization initiator such as a peroxygen compound, e.g., lauroyl peroxide or t-butyl peracetate, or an azobis compound, e.g., azobisisobutyronitrile, at a somewhat elevated temp0rature, e.g. irom 90 to 2~0C, and a pre~sure oi 1000 to 1750 atmospheres, the~ separating the resulting polymer from the unpoly~eri~ed materials, e.g., by vaporization of the latter.
By varying the monomer~ employed, the concentrations o~ the monomers and initiator~ in the reaction mixture, and conditions such as reaction time, pressure and temperature, polymers oi the de~ired ki~d and degree oi polymeri~ation and acid number ca~ ~e readily obtained. ~he terpolymers can also be made by ~atch polymerization methods, but non-homogeneous polymers generally result. Continuous method~ in which a suitable m~t~re oi the comonomers and initiator is continuou~ly passed t~rough a react~on zone maintained at the de3ired temperature and pressure aonditions are di~tinctly pre~erred since they yisld ~ubstantially homogeneous copolymer product~. The react~on zone and rate o~ ~low o~ reaction m~xture therethrough - should be ~uch as to pro~ide an appropria~e residence time.
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, .. ~, Ethylene terpolymers of the type useful in the practice of the present invention and the preparation thereof are de-scribed in United States Patents 3,215,657 and 3,215,678 and in duPont Elvax Product Information Bulletin P116_1070. It should be noted that although the Patents and the Bulletin describe the use of such terpolymers either alone or in com-bination with petroleum wax as hot melt adhesives, these prior art adhesives are significantly inferior to the a & esives of the present invention with respect to peel strengths~ especially at temperatures above room temperature, and with respect to -a &esion to difficultly-bondable substrates such as lead.
; The ethylene-unsaturated acid ester copolymers useful in the practice of the instant invention and the preparation thereof are described in: Bonotto~ S.~ Krevsky~ B H.~ SP~ -Journal, May, 1962, and Pecha, R J., Samuels, H., Kay~ D.C., United States Patent No. 2,953~541 assigned to Union Carbide -; Corporation.
Component b) will generally be a polyamide condensation interpolymer of at least one diamine with at least one dibasic acid~ with di~er acid being the preferred maior dibasic acid -component. These condensation polymers are ordinarily prepared by reacting a molar excess of the amine group containing ; molecules with the carboxylic acid group containing molecules.
The amount of excess amine utilized should be sufficient to `:
proYide a polyamide ha~ing an amine number ranging from about 70 to about 400. We have found this amine number is reguired to pro~ide an adhesive haYing the af~rementioned -, . I
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outstanding propertie~.
~ uitable diamines include prim2ry diamine~ which may be ideally repre~ented by the ~ormula ~herein R is an aliphatic, cycloaliphatic or aromatic radical, preferably having ~rom 2 to about 40 carbon atom3. While is pre~erably a hydrocarbon radical, R may optionally alæo contain ether linkagés such a~ in the diamines prepared from diphenyl ether. I~ R is aliphatic, it can be a saturated ~ 10 ~traight or branched chain radical. Representati~e o~ such - diamines are the al~ylene diamines ha~ing ~rom 2 to 20 ca~bon -~ - atom3 (pre~erably 2 to 6) such as ethylene diamine, 1,2-diamino propane, 1,3-diamino propane, 1,~-diamino butane, tetramethylene diami~e, pentamethylene diamine, he~amethylene diamine, decameth~lene diamine, and octadecamethylene diamine. In addition, aliphatic diamines carrying 1 to 3 lower alkyl sub~tituents or a higher alkyl substituent are use~ul, ~or egample, 2,5-dimethyl-hexamethylenediamine, 2-methyl-4-ethyl-hexamethylenediamine, 2-ethyl-4-methylhexamethylen~diamine, a mixture o~ 2,4,4-trimethylhexamethylenediamine and 2,2,4-trimethyIhexamethylenediamine or a mi~ture o~ 9-aminomethyl-~tearylamine and 10-aminoethylstearylamine. In addi~ion, aromat~c d~mines such a~ me~axylene diamine, paraxylylenc d~amine and a icyclic diamine~ such as cyclohexylene dlamine, 1,~-di-4-piperidyl propane, bis(~-aminoethyl)_benzene, -~ cyclohe~ane~ (methyl amine), diaminodicyclohexylmet~ane, meth~lylene diani~ine, bis(aminoethyl~ diphenyl oxide aDd ;, .

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~038992 dimeric fat diamin~ can be utilized.
Dimeric ~at diamine, ~ometimes reierred to a~ "dimer diamine," "dimeric iat amine," or "polymeric ~atty acid diamine" denotes the diamlnes prepared by amination o~ dimeric fatty acid~ as hereinafter de~cribed; reference is made thereto in U.S. Patent 3,010,782. As indicated therein, the6e amine~ are prepared by reacting polymeric iatty acids - -with ammonia to produoe the corresponding nitriles an~
~ub~e~uently hydrogenating the nitriles to the correspondin~ -amineB. Upon distillation, the dimeric iat diamine i~ provided which ha~ esQentially the same structure a~ a dimeric ~at acid except that the carboxyl groups are replaced by -C~2NE2 groups.
- ~urthsr, this diamine is also described in Research and Development Produots Bulletin, CDS 2-63 by General Mill~, Ino., June 1, 1g63, as "Dimer Diamine" illustrated by the iormula H2~-D-NE2 where D i8 an approximately 36-carbon hydrocarbon ; radical oi a dimeric fatty acid.
:- Diamines which are interrupted by oxygen atoms in the chain (also called ether diamine~) and which are also ~uitable can be repreeented by the general iormula:
~2~~(o~2)n~~~R ~ 0)X-(CH2)n-~H2 where n can be a number irom ~ to 5, where ~ can have a ~alue o~ 0, 1, 2, or 3, and where R is an alkyl group with a cha~n length oi 1 to 12 carbon atom~, which may al~o carry alkyl ~ubst~u~nts oi 1 to 4 carbon atom~. Example~ o~ ether diamine~
; oi thi~ ~eneral formula are: 1,7-diamino-4-o~oheptane, 1,11-diamino-6-oxoundecane, 1,7-diamino-3,~-dioxoheptane, 1,10-diamino-4,7-dioxoundecane, 1,10-diamino-4,7-dioxo-5-,';

.

methyldecane, 1S11-diamino-4,8-dioxoundecane, 1,11-diamino-4, 8~dio~o-5-ethylundecane, 1,12-di2mino-4,9-dioxododecane, 1,13-diamino-4,10-dioxotridecane, 1,14-diamino-4,11-dioxotetradecane, - 1,11-diamino-4,8-dioxo-5,6-dimethyl-7-propionylundecane, 1,14-diamino-4,7,10-trioxo-tetradecane, 1,13-diamino-4,7,10-trio~o-5,8-dimethyltridecane, 1,20-diamino-4,17-dio~oeicosane and 1,16-diamino-4,7,10,13-tetraoxohexadecane.
Monoalkanolamines may also be employed as starting material~ in place of or in conjunction with diamines.
- tO Suitable monoalkanol amines preferably have the general ~ormula . ~H2-R-OX
where R is a divalent aliphatic hydrocarbon radical from 2 to 8 carbon atoms. ~thanolamine is preferred but further suitable compounds include propanolamine, butanolamine, 2-amino-3-he~anol, 2-amino-i-pentanol, ~-amino-4-octanol, 3-amino-3-methyl-2-butanol and similar compounds. ~uch alkanol amines, . . .
o~ course, afford polyester amides.
~he diamine may be employed alone or mixturè~ of two or more may be employed. ~he most pre~erred diamines are the alkylene diamines in which the alkylene group has from 2 to 6 carbon atoms and mixtures thereo~ with dimeric fat diamine.
As heretofore indicated, the dibasic acid u~ed to ~orm the polyamide component b) preferably conqistq predomi~ant b o~ dimer acid. ~y predomin3ntly iR meant tbat at least about 60% of the carboxylic acid group~ present are present in the dimer acid component of a dibasic acid ."
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. mi~ture. It should be noted, however, that acceptable .
polyamides can be prepared using minor amounts or, indeed, no dimer acid. Other s1litable dicarbo~ylic acids are enumerated hereinafter.
Dimer acid connotes a co~mercially available material obtainable by the coupling o~ unsaturated long chain monocarboxyli.c ~atty acids, ~or eY.ample, oleic or linoleic acids. The resulting "dimer" i~ a mi~ture of ma~v isomers, with variou~ degrees of unsaturation and ring ~ormationt depending on the unsaturation of the starting m~terials. :~
The preci~e structure of the isomers and the proportion~ of each i~omer in the mixture ~ary with the method o~ combina--~ tion (which Yaries according to the manu~acturer), and, o~
- courseJ the starting material or materials. Trimers and higher degrees of polymerization are also present to ~ ~
minor extent. ~ ~ -The structure o~ these dimer acids has been the subject o~ considerable investigation. To indicate the background - o~ this aspect o~ the invention, the following re~erences .- 20 are listed, but it is to be understood that the scope of the present application is not limited by or to the structure~
disclosed in the references.

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-Based on the work of R. F. Paschkc, L. E. Peterson, and D. H.
Wheeler, Journal of the American Oil Chemists' Society, 41 723 ~1964), it is - conjectured that four possible structures or thermal dimers of 10-trans, 12-trans-linoleic acid are:
O O
C-OH C-OH
H ~CH2~8 0 ~CH2)8 11 ~ ~ ~CH2)8-c-cH ~ ~ CH=cH-~cH2)8-c-oH

~ H=CH-(CH2)4-CH3 ~ ~ tCH2)4-CH3 O O
C-OH C-OH
~CH2)8 H ~ H2)8 H ~ CH=CH-(CH2)4-CH3 ~ ~ (CH2)4-CH3 11 H ~ ~CH2)8-cooHH ~ CH=cH-~cH2)8-c-oH

(CH2)4 ~CiH2)4 : ', ~, ' ' It will be noted that the number of carbon atom between the carbonyl carbons ~laries between 18 and 21, that i3 , that - the chain length i~ bet~een 20 and 23 inclu~ive o~ the carbonyl carbons. ~urther, it will be noted that there are branches of up to 9 carbon atoms exclusive o~ the ring carbons.
J. a. Cowan, Journal of the ~merican O 1 Chemists' ~ociety, ~, 723 (1962) di~cus~es generally the pos~ible struc-tures of similar dimers. ~mery Indu~tries, Inc. ~echnical - Bulletin 412~, "Abstracts of Di er Acid Use-Patents and Journal Re~erencesn, January, 1967, at page~ 2 and 3, gives abstracts o~ a number of references, and R.F. Paschke, ~
Peterson, S.A. Harrison, and D. E. Wheeler, ~ourn~l of the American Oil Chemist~' Society, 41, 56 (1966) discusses the ;
i-. . .
~tructures of the dehydrodimer ~rom methyl oleate with di-t-butyl pero~ide. The~e re~erences all in turn refer to ~ her relevant literature.
- These dimer acids, whate~er their precise structure, which ~aries from producer to producer, all contain a mixture of isomers. At least some o~ the isomers, and in most ca4es all, contain ~ome unsaturated carbon-to-carbon bonds, and to -enh~nce oxidative stability of the amide prepared there~rom, - these are preferably removed by hydrogenation to give a saturated, or predom~nantly saturated, product. It haæ been ~- found that while all di~er acid_ may be converted into suita~le starting materials ~or the manu~acture o~ po~ amide~ u~eful in the pre~ent invention, the variou~ method_ of manufacture and ; d~f~erent ætarting ma~eria~s used by the di~ferent man~¢aeture~s ;; res~t in a range of pol~Yamides haYing ælightly vary~g ,,,, ;~' .

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, ~038992 properties.
Other dicarboxylic acids are appropriately used in lieu of, or jointly with, dimer acid to increase the softening point of the polyamides obtained therefrom. Suitable dicarboxylic acids include aliphatic, cycloaliphatic, or aromatic dicarboxylic acids or esters which may be defined by the formulae:
~ OOC-COO ~ and ~OOC-R-COO ~
wherein ~ is hydrogen or an alkyl group (preferably having from 1 to 8 carbon atoms) and R is an aliphatic, cycloaliphatic, or aromatic hydrocarbon radical preferably having from 1 to 20 carbon atoms (the most preferred being where R is an aIkylene radical having from 6 to 12 carbon atoms). Illustrative of such acids are oxalic acid, malonic acid, adipic acid, sebacic acic, subcric acid, pimelic acid, azelaic acid, succinic acid, - glutaric acid, isophthalic acid, terephthalic acid, the phthalic acids, benzenediacetic acid, p-phenylene dipropionic acid, the naphthalene dicarboxylic acids and 1,4- or 1,3- cyclohexane dicarboxylic acid.
The polyamides used in the practice of the present invention will preferably have a number average lecular weight ranging from about 2000 to about 10~000. Illustrati~e of commercially available polyamides suitable for incorporation into the adhesive compositions of the present invention are those described ~n United States Patents 3~249~629 and 3,449,273. The polyamides used in the present invention are prepared by conventional amidification techniques which form no part of the ' ' .--- ' ;~ ;; ~ ' , -, ~

~38992 in~ention. I~ gen~ral, this am1 di~ication i~ preferably conducted at a temperature ranging ~rom about 180 to about ~ 280C a~ter simple admixture of the de~ired quantities of -- amine and carboxylic acid moieties. Reactio~ with the diamines re~ult~ in formation of the desired po]yamide plus evolution of R10X (i.e., water or alcohol). ~ -Additional components which may optionally be advan-tageously added to the adhesive compositions of the p~esent invention include hardeners, ~illers, extenders, ~ort~fier~, carriers, and preser~atiYes ~f the type kno~n to the art.
It ~hould be noted that although all the individual components o~ the present adhe~ive compositio~ are ssparately - known to the prior art, the combination has never hereto~ore : been proposed. Furthermore, as already indicated, the combination of thc presen~ in~ention is uniquely superior in adhesi~e effecti~eness in comparison with the indi~idual component~ thereo~ either alone or in any of the combinations thereoi kno~n to the prior a~t. Such unegpected superiority will be shown in somewhat greater detail by the following ~ample~ which illu~trate the present in~ention.
~ , ' PrePa~ation o~ an ~~Proximately ~toichiometric ~att.Y PolYamide A one lltre resin ~ettle 1~as e~uipped ~ith a glass-25A~ ~hafted, ~e~lo.l-bladed stirrer, a therometer, a nitr~gen inlet ~; tube, and a Claisen distilling head9 ~he kettle was heated by a silicone oil bath on a magnetic-stir hot plate. The ta~e-of~ ~y~tem consi~ted oi the di~tilling head, a condenser~
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~03899~ ~
a receiver, and a gas bubbler. Dimer acid (Empol 1010, neu-tralization equivalent 289.2, 348.2 g, 0.60 mole) and hydrogenated di~tilled dimer diamine (neutrali~ation equiva-lent 289, 92.9 g, 0.17 mole) were added to the kettle.
Eth~lene diamine (Matheson, Coleman and ~ell, 99~o, 30~5 ml, 27.1 g, 0.45 mele) was added by pipette, the stirring was immediately started and heat wa~ applied to the oil bath.
There was an immediate temperature rise and thickening oi the kettle contents a~ salt formation took place (no precipi-tate ~ormed). Heating to 200 to 215C was accomplished in a~out 1.5 hours while a very ~low ætream oi nitrogen passed through the ~essel. As the temperature increased, the mass ; became les~ viæcous and water o~ reaction was giYen of~ at140 to 155Co The temperæture was maintained at 205 to 215C
~or about ~ hours while stirring continued. A~ter 3 hours at - temperature, the nitrogen inlet was plugged, the ~tirring- was stopped, and vacuum was carefully applied using a water aspirator. Heating at 210 to 215C with vacuum applied was - continued ~or about one hour. ~he ~iscous, clear yellow melt ~as poured out under a stream o~ nitrogen into a ~e~lon-lined ; pan and rapidly cooled on dry ice. ~he ma~erial was then ,. ohopped for analysis and compounding.
Analysis: Inherent viscosity (0.5~0 in CHCl~, 30C) ~ ;
o~ 0.27, softening point (ring and ball) o~ a, and amlne number ~milli-equivalents/kg o~ sample by titration of a chlorobenzene solution o~ the polyamide u~ing EC104 in glacial -~ `
acetic acid) of 25.

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Z~
~ , -EX~hP~E 2 ~E~5loL~c~ L~ h Fatty Polyam,i,de ~he apparatus o~ the previous example was u~ed. ~-'Al Dimer acid (~mpol 1010~ 348.2 g, 0060 mole) and hydrogenated, distilled dimer diamine (65.7 g, 0.11 mole) were added to the kettle iollowed by ethylene diamine (36.3 ml, 0.54 mole).
The heating and stirring were begun a~ be~ore and 200 to 210C
was maintained for about 4 hours. Heat and aspirator ~acuum were applied without stirring for an additional one hour .
~he batch was finished and cooled as be~ore.
Analy~is: Inherent ~i~cosity oY 0.24, softening -` point oi 101C, and amine number of 147.
, ~a~
. .
A peel test was carried out as ~ollows: -1~ Polyethylene or lead jacketed telephone cable -; approximately 1.5 inch in diameter by 5 inches long was wiped with a sol~ent such as methyl ethyl ketone or methylene ~-chloride to remo~e surface d~rt ~nd greage.
~, 2. ~ solut~on or melt cast ~heet of adhesi~e approximately 2.~ inches by 5 ~nches long by 0.025 inch thic~ was wrapped , around the clean cable ~uriace.
pre-expanded, heat recoverable, cros~linked, ~ polyethylene tube was slipped over the adhesive and ~hrunk : onto the adhe~ive-coated ca~le with a ga~ f~ame. ~hi~ he~ting al~o cau~ed the adhesive to melt and flow. ~ormal heating time ,; , to accompli~h the operation -was about 2 minutes.
~ 4. A~ter coolingt the 3acketed ca~le sample wa~ cut '-~ transver~ely to a~ford ~ive 1_inch wide ~egments and the d' rn~
` - 2~ -;-- , , , - . ~ .

1038~9Z
copper conductor wires were removed from within the s~gments.
50 The 1-inch wide segment was slipped over a cylindrical metal mandrel which was fixed at the ends. The ~ndrel was ~ree to rotate about its longitudinal axis. ~he mandrel was attached to a jig which ~itted the gripping jaws of an Instron ~est ~chine.
6. A longitudinal slit was made across the 1 inch ' dimension in the outer polyethylene tube through to the adhesi~e layer to ~orm a tab which ~as in~erted in the top '' ~O jaw o~ the test machine.
7.- The adhesive bond holding the polyethylene tube to , the cable jacket was tested ~or strength in peel (This peel -,, test is æimilar to ~STM D8176-69 except that the speclmen is ' peeled ~rom a mandrel fixture rather than a T-peel con~i~ura- -tion). The cro~shead speed of the test machine was set at 8 jaw separation rate o~ 2 inches per minute. An enclosure ',' ,' f' was available to permit testing the adhesi~e bond strength --, at temperatures above or below room temperature.
'' Result~ are given in pounds per linear inch to iailure. ~ailure can be either adhesiYe~ iOe., failure ,~
'-,' occurs at the interface between the adhesive and either :, .
'' sub~trate; or cohesive, i~e., the adhe~ive bond to the sub~
''~ Btrates exceeds the cohesive strength of either the substrates ,~ or the a~hesive it~e~f and ~ailure doe~ not occur at any inter~ace ~ut in the buIk of the adhesive or sub~trat~
', A~hesi~e~,adherent enough to provide for cohe~ive ~ailure are, o~ ¢ourse, highly de~irable.
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The following test results were obtained using a~ a polyethylene jacketed and b~ a lead jacketed telephone cable.
SampleTest Peel Type Temperature Temperature Strength of of (~C~ (pli~ Failure Embrittlement a)* b)*
Elvax 4355 + -40 ~10 2Adhesive ~-50 10% ZKMA 0251~+25 15 3Cohesive +70-0 -0 Adhesive "
Polyamide of -40Brittle -- Adhesive -20 Example 1 l25Ca. 10 2 Cohesive "
1 10% ZKMA 0251 ~l70 _0 -- Adhesive "
Polyamide of -40Brittle -- Adhesive -20 Example 2 +25Ca. 10 2 Cohesive "
+ 10% ZKMA 0251~+70 -0 -- Adhesive "
A -40Brittle -- Adhesive -20 B +25Fell apart -- Adhesive "
C l70 -10 2 Cohesive "
D -40 20 6 Cohesive ~ -50 E ~70 5 7 Cohesive "
F +25 40 20 Cohesive "
G l25 12 2 A & esive -30 H +25 10 3 Adhesive -20 I ~25 46 16 Cohesive ~ -50 J l25 38 18 Cohesive ~ -50 K t25 25 14 Cohesive ~ -50 L +70 8 8 Cohesive ~ -50 M +70 ~10 9 Cohesive ~ -50 -N l70 3 1 Adhesive -30 - -0 +70 ,10 7 Cohesive ~ -50 p ~70 ~ 0 -- Adhesive -30 Q +70 ~ 0 -- Adhesive -20 R l70 3 3 Cohesive ~ -50 . .:
S +70 4 2 Cohesive -45 T ~70 ~ 1 ~1 Cohesive -45 U ~70 ~1 ~1 Cohesive ~-50 * a~ indicates peel stre~gth to polyethylene jacketed Cab~e; b~ indicated peel strength to lead jacketed cable.
Trade Mark ., ~
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10;~8992 -The ethylene terpolymer u;ed in Samples A through U of Example 3 was duPont Elvax 4355*. This material is a terpolymer of ethylene (74%), vinyl acetate (25%), and methacrylic acid (~1%~ (all parts by weight) and has an acid number of about 6. All Samples A through P contained equal amounts of Elvax* and polyamide. Samples A through U contained 10 parts of ZKMA 0251* tackifier per 100 parts of combined Elvax* and polyamide. All samples were prepared by mixing the constituents in a compounding extruder at - 150C. All Samples A through U had ring and ball softening points within the range of 90 to 160C. When samples were tested for glass transition 10 temperature, Samples D through P, I, J, K, L, M, 0, R, S, T and U showed a :single glass transition temperature while Samples A through C, G, H, N, P
and Q showed two distinct peaks.
The sample constituents were as follows:
- A through C: Polyamide of Example 1 D through F: Polyamide of Example 2 N through G: Versalon 1165* (General Mills polyamide), amine nur~er =
25 (amide of dimer acid and ethylene diamine) H: Coramide 230*~Cooper Polymer), amine number = 53 I: Versalone 1140* (General Mills~, amide of dimer acid, sebacic acid, ethylene diamine, and dipiperidyl propane, amine number ~-= 150 J: Versalon 1300* (General Mills), amide of dimer acid, ethylene diamine and dimer diamine, amine number - 180 K: Polyamide prepared according to Example 2, but containing suf- -ficient ethylene diamine to afford an amine n unber of 619 L: Polyamide prepared using the procedure of Example 1 from an 80:20 mole percent mixture of Empol lOlO* ~dimer acid) and phthalic acid and sufficient butanol amine to afford polyamide ;
of amine nu~er of llO.

M: Polyamide prepared using the procedure of Example 1 from Empol 1014~ (mixture of dimer and trimer acid) and excess de~amethy-lene diamine (amine number of l~0).
N: Same as M but limited excess diamine (amine number of 50~ -~Trademark : '' z4_ ~
`',' :. , 0 : Polyamide prepared according to procedure of Example 1 using 50:50 - mole percent mixture of Empol 1010* dimer acid and sebacic acid and 50:50 mole percent fumethylene dipiperidine and dimer diamine, amine number of 130.
P : Same as 0 but limited excess amine, amine number of 44.
Q : Elvax 4355* (60% by weight) plus polyamide of Example 1 (40% by weight) R : Elvax 4355* (60% by weight) plus polyamide of Example 2 ~40% by weight) S : Elvax 4355* (40% by weight) plus polyamide of Example 2 (60% by weight) T : Elvax 4355* (25% by weight) plus polyamide of Example 2 (75% by weight) ~ : Elvax 4355* (75% by weight) plus polyamide of Example 2 ~25% by weight) A variety of ethylene copolymers and terpolymers were evaluated for adhesive strength both alone and in conjunction with polyamide. All samples contained ZKMA 0251* (10 parts by weight per 100 parts of ethylene - polymer or combined ethylene polymer plus polyamide). The ethylene polymer/ ~-polyamide ratio was 50:50 by weight in all samples containing polyamide plus ethylene polymer. The polyamide used in all cases was essentially iden$ical - -:~ to that prepared in Example 2.
Samples were as follows: Samples A through E were duPont Elvax* terpolyme~s which are te~polymers of ethylene, methacrylic acid and - vinyl acetate of the following approximate composition.

A : Elvax 4260~, vinyl acetate 28%, methacrylic acid ~ 10%, - ethylene 71%, acid number = 6 B : Elvax 3689.3~, vinyl acetate 12%, methacrylic acid 4%, ethylene 84%, acid number = 30 ~ -C : Elvax 3633.6*, vinyl acetate 24%, methacrylic acid 4%, ethylene 72%, acid number = 30 . . I .
D : Elvax 4355~, vinyl acetate 2S%, methacrylic acid 1%, ethylene 74%, acid number = 6 ';~
*Trademar~

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E : Elvax 3633.3*, vinyl acetate 28%, methacrylic acid 4%, ethylene 68%, acid number = 20 Samples F through H are copolymers of ethylene and acrylic acid containing, respectively, 6%, 15%, and 20% acrylic acid. Sample I is a modi- -fied copolymer of ethylene and ethyl acrylate (18%) wherein part of the ethyl : acrylate has been saponified and then acidified to provide the necessary acid groups.
The polymers of Samples F through H when combined with poly-amide were effective, thus indicating that copolymcrs of ethylene with un-saturated acid without any ester moieties being present are also effective.
.. :: .
Sample I demonstrates another method of achieving the desired acid number.
That is, an ethylene unsaturated ester copolymer can be modified by partial saponification and then acidified to a hieve the desired acid number. The - ~
commercial name and acid number of these samples is as follows: ~ -F : Union Carbide E M 9060*, acid number = 45 G : Union Carbide E M 9320*, acid number = 115 H : Union Carbide EAA 9300*, acid number = 150 I : Union Carbide DPD 9169*, acid number = 35 -J through I, : Elvax 4260* plus polyamidc M through 0 : Elvax 3689.3* plus polyamide P : Elvax 3633.6* plus polyamide ;
Q : Elvax 3633.3* plus polyamide -; R : DPD 9169* (modified) plus polyamide S : DPD 9169* (modified to scid number = 2) plus polyamide T : DPD 9169* ~modified to acid number = 7) plus polyamide U : DPD 9169* (modified to acid number = 35) plus polyamide V : Experimental terpolymer of ethylene (65%), vinyl acetate `-~
(20%~, methacrylic acid (15%), acid number = 100, plus polyamide W : ~xperimental terpolymer of ethylene (75~%), vinyl acctate (24%) and methacrylic acid (0.25~ acid number = Z
- , . . ..
~Trademark , :

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.
1~38992 X: ~xperimental terpolymer containing 75% wt. ethylene, 20% wt. vinyl pro-pionate and 5% wt. tetrahydrophthalic acid, acid number = 15, plus polyamide.
Y: Experimental copolymer containing 80% wt. ethylene and 20% wt. mixed mono- and diethyl maleate with sufficient monoethyl maleate being present to provide an acid number of 10 ~ .
- Z: Union Carbide EAA 9060 plus polyamide M : Union Carbide ~AA 9320 plus polyamide BB: Union Carbide EAA 9300 plus polyamide Test Peel Type Temperature Temperature Strength of of Sample ~C) (pli) FailureEmbrittlement ; a)*b)~ (C~
A +2510 3 Adhesive ~-50 B +2512 2 Adhesive ~-50 C ~2515 3 Adhesive ~-50 D +2511 2 Adhesive ~-50 E ~2511 2 Adhesive ~-50 F +25 7 2 Adhesive ~-50 G +25 5 2 Adhesive ~-50 H +25 5 1 Adhesive ~-50 I +2520 4 Adhesive ~-50 J -40 35 lO Cohesive ~-50 K +25~ 5020 Cohesive (-50 ~ -- L +70>10~10 Cohesive <-50 M -40 30 8 Cohesive <-50 N +2545 18 Cohesive ~-50 0 l70~10 9 Cohesive ~-50 ' P -40 25 7 Cohesive ~-50 Q -40 27 9 Cohesive ~-50 R -40 5 2 Adhesive ~-50 S -40 7 3 Adhesive -30 T -40 15 6 Cohesive ~-50 ; . U -40 32 9 Cohesive ~-50 V +2519 4 Adhesive ~-50 W (2515 2 Adhesive -30 ~-` X ~2541 16 Cohesive ~-50 Y ~2537 14 CohesiYe ~-~0 Z t2535 13 Cohesive <-50 -` AA l70 2 1 Adhesive <-50 B5 -40 5 1 Adhesive <-50 * a) peel strength to polyethylene jacketed cable, b) peel strength to -~ lead ~acketed cable * Trade Mark ~ 899Z
The melt index (M.I.) of a polymer is well recognized as being related to its molecular weight, the lower the melt index the higher being the molecular weight. The melt index values of our polymers were de-termined by the tentative ASTM test method D1238-70, Condition E (ASTM
Standards, 1972, Part 27, pages 424 to 434). The value is the weight in grams that is extruded through an orifice 0.0825 inch in diameter and 0.315 ~ -inch long over a period of 10 minutes at 190C under a pressure of 2160 grams.
The melt index values of the polymers of the instant invention can range from 0.5 to 200 and are generally from about 5 to 25 to provide a readily flowable material. Pa~ticularly preferred adhesive compositions are obtained when the polyamide has an amine number ranging from about 100 to 300 and the ethylene co- or terpolymer has an acid number ranging from about 5 to 40 A variety of tackifiers were also evaluated. In all cases, the adhesive formulation showed a single glass transition temperat~re. All formulations contained 50 parts by weight Versalon 1300, 50 parts Elvax - 4260, and 10 parts tackifier. All tests were at +70C. In all, the embrittle-ment temperature was below -40C.
Peel Strength ~ype Tackifier (pli~ Fail=rc AZMA 0251** ~ 10 ~ 10 Cohesive Alpha Piccolyte 100** 9 8 Cohesive Polypale #1 10 8 Cohesive None 7 5 Cohesive ;
- Arochlor 1260** 8 6 Cohesive Chlorowax 70** 10 6 Cohesive Flexol 3GO** 9 6 Cohesive Santicizer 8** 8 6 Cohesive Pentalyn C** 9 7 Cohesive - ~evillac ~0** 9 8 Cohesive Drapex 3.2** 8 6 Cohesive a~ peal strength to polyethylene jacketed cable, b) peel strength to lead jackete~ cable r~
~ ** Trademar~ - 28 --: , : - ~

Most of the above-indicated tackifier~ have been heretofore described in the body of the application. Th~
- iollowing, however, although not described herein, are like-:~ wise ~uitable as the im~ediately-above recorded re~ults - 5 indicate.
Co~nercial Source ~me ~ gE~
Monsanto Arochlor 1260 Chlorinated biphenyl Union Carbide ~lexol 3G0 ~ ~riethylene glycol di(2-ethyl he~oate) Monsanto Sar.ticizer 8~ ~-ethyl mi~ed ortho and para toluene-sulfonamide~ . -Argu~ ~emical Drape~ 3.2 Epoxy plasticizer In su~mary it will be seen in addition to their superior high and low temperature peel strength, which is of great advantage in cable insulation employment especially in polyethylene/lead type situations, and their low embrittle-~ ment charac'er~stics at low temperature the adhesive composi-.-. tion~ oi the present inYention exhibit a ring and ball soitening point within the range of about 90 to 160C and thus pos~ess particularly suitable flowability characteri~tic~ :
~ ior uss with heat reco~erable polyethylene end cap~ and x sleeve~.

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Claims (33)

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

1. A hot melt adhesive composition comprising a compatible mixture of: (a) an acidic polymer of ethylene having an acid number ranging from about 3 to about 80 selected from the group consisting of a terpolymer of ethylene, an ethylenically unsaturated mono- or dicarboxylic acid and a vinyl ester of C1 to C6 aliphatic carboxylic acid and a copolymer of ethylene and a C2 to C20 aliphatic ester of a mono ethylenically unsaturated mono- or dicarboxylic acid wherein a portion of the carboxylic acid moieties of said mono- or dicarboxylic acid component are not esterified, and (b) a polyamide having an amine number ranging from about 70 to about 400 with a tackifying agent wherein said tackifying agent is present in an amount ranging from about 3 to about 20 parts by weight per 100 parts of (a) and (b) together.

2. A hot melt adhesive composition as claimed in claim 1, wherein components a) and b) are present in a relative proportion by weight of from 40 : 60 to 60 : 40.

3. A hot melt adhesive as claimed in claim 2, wherein components a) and b) are present in 5 equal amounts by weight.

4. A hot melt adhesive composition as claimed in claim 1, wherein the tackifying agent is present in an amount ranging from 5 to 15 parts by weight per 100 parts of a) and b) together.

5. A hot melt adhesive composition as claimed in claim 1, wherein said tackifying agent is a polyketone resin.

6. A hot melt adhesive composition as claimed in claim 1, wherein component a) is a terpolymer of ethylene, an ethylenically unsaturated mono-or dicarboxylic acid and a vinyl ester of a C1 to C6 aliphatic carboxylic acid.

7. A hot melt adhesive composition as claimed in claim 6, wherein the vinyl ester is vinyl acetate.

8. A hot melt adhesive composition as claimed in claim 6 or claim 7, wherein the unsaturated acid is acrylic acid, methacrylic acid or a mixture thereof.

9. A hot melt adhesive composition as claimed in claim 6, wherein the weight percentage of units present in the terpolymer derived from the three monomeric precursors of said terpolymer is ethylene, 60 to 95; ethylenically unsaturated mono- or dicarboxylic acid, 1 to 10; and vinyl ester of C1 to C6 carboxylic acid, 5 to 40.

10. A hot melt adhesive composition as claimed in claim 9, wherein said weight percentages are ethylene, 70 to 85; unsaturated acid, 2 to 5; and vinyl ester, 10 to 30.

11. A hot melt adhesive composition as claimed in claim 1, wherein compon-ent a) is a copolymer containing units derived from ethylene, a C2 to C20 mono ethylenically unsaturated mono- or dicarboxylic acid and an ester thereof.

12. A hot melt adhesive as claimed in claim 11, wherein the copolymer is a copolymer of ethylene and a C2 to C20 aliphatic ester of a mono ethylenically unsaturated mono- or dicarboxylic acid wherein the mono- or dicarboxylic acid component is not fully esterified.

13. A hot melt adhesive composition as claimed in claim 11, wherein the weight percentage of ethylene units present in the copolymer is from 60 to 95.

14. A hot melt adhesive composition as claimed in claim 13, wherein the weight percentage of ethylene units is from 70 to 90.

15. A hot melt adhesive composition as claimed in claim 11, wherein the un-saturated acid is acrylic acid, methacrylic acid, maleic acid or fumaric acid.

16. A hot melt adhesive composition as claimed in claim 1, wherein compon-ent b) is a condensation polymer of at least one diamine, monoalkanol amine or a mixture thereof with at least one dibasic acid, dibasic ester or a mix-ture thereof.

17. A hot melt adhesive composition as claimed in claim 16, wherein the dibasic acid component comprises at leat 60% wt.
dimer acid.

18. A hot melt adhesive composition as claimed in claim 16, wherein the dibasic acid component comprises a dicarboxylic acid or ester of the formula R1OOC-COOR1 or R1OOC-R-COOR1 wherein the R1 radicals, which may be the same or different, each represents hydrogen or an alkyl group and R represents an aliphatic, cycloaliphatic or aromatic hydrocarbon radical.

19. A hot melt adhesive composition as claimed in claim 18, wherein R1 is an alkyl group of from 1 to 8 carbon atoms and R has from 1 to 20 carbon atoms.

20. A hot melt adhesive composition as claimed in claim 16, wherein the diamine has the formula H2NRNH2 wherein R is an aliphatic, cycloaliphatic, or aromatic radical having from 2 to 40 carbon atoms.

21. A hot melt adhesive composition as claimed in claim 20, wherein R is an alkylene radical having from 2 to 20 carbon atoms.

22. A hot melt adhesive composition as claimed in claim 21, wherein R is an alkylene radical having from 2 to 6 carbon atoms.

23. A hot melt adhesive composition as claimed in claim 16, wherein the diamine comprises dimeric fat diamine.

24. A hot melt adhesive composition as claimed in claim 16, wherein the diamine has the general formula H2N-(CH2)n-O-(R - O)x-(CH2)n-NH2 wherein n is from 3 to 5, x is 0, 1, 2 or 3 and R represents an alkyl group having a chain length of from 1 to 12 carbon atoms.

25. A hot melt adhesive composition as claimed in claim 24, wherein the alkyl group R is substituted by an alkyl radical having from 1 to 4 carbon atoms.

26. A hot melt adhesive composition as claimed in claim 16, wherein the monoalkanol amine has the formula wherein R is a divalent aliphatic hydrocarbon radical having from 2 to 8 carbon atoms.

27. A heat-recoverable article provided with an internal or external lining or preform of a hot melt adhesive composition as claimed in claim 1.

28. A heat-recoverable article as claimed in claim 27, which is made from cross-linked polyethylene.

29. A heat-recoverable article as claimed in claim 28, wherein the polyethylene is irradiation cross-linked.

30. A method of bonding together two substrates which comprises applying a hot melt adhesive composition as claimed in claim 1 between said substrates and then heating to activate the hot melt adhesive composition and cause adhesion.

31. A method as claimed in claim 30, wherein at least one of said substrates is made from polyethylene.

32. A method as claimed in claim 30 or claim 31, wherein at least one of said substrates consists of lead.

33. In a process for encapsulating telephone cables com-prising a) forming a preform consisting essentially of a heat-recoverable outer member and a fusible inner member, said fusible inner member being in abutting relationship with said outer member; and b) positioning said preform in relation to a telephone cable such that the recovery of said recoverable member will urge said fusible inner member toward said telephone cable the improvement comprising forming said fusible member from a hot melt adhesive composition as claimed in claim 1.