The present invention relates to adhesive compositions, in particular to hot melt adhesive compositions comprising cross-linkable silane-modified copolymers of ethylene and at least one polar comonomer,

Silane grafted ethylene homo- and co-polymers are widely used for the preparation of cable jacketing, wire insulation and piping and have been suggested for use as spacers in laminate materials. The preparation of such materials is described in for example US-A-3646155, GB-A-1286460, GB-A-1347426, GB-A-1406680, GB-A-1450934 and GB-A-1542543. US- A-3646155, for example, describes the production of such material by reaction of polyethylene with an unsaturated silane, e.g. vinyl triethoxysilane, in the presence of a peroxide initiator to produce the silane grafted polymer. A catalyst, for example dibutyl tin dilaurate, is incorporated into the grafted polymer which is then formed into the desired shape. Catalysed hydrolysis and cross-linking of the silane groups occurs to give the hardened end product. The reaction procedure may thus be represented as follows:-

(A) Grafting

-(CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ ) - + CH ₂ =CH.Si(OC ₂ H ₅ ) ₃

peroxide (CH _o 2CH2-jC ^■ HCH-2CH- 2,)' a-

C CHH ₂₂ CCHH ₂₂ SSii((0O(C ₂ H ₅ ) ₃ silane graft polymer

(B) Hydrolysis

-(CH ₂ CH ₂ CHCH ₂ CH ₂ ) - + 3 H ₂ 0

CH ₂ CH ₂ Si(OC ₂ H ₅ ) ₃

> -(CH ₂ CH ₂ CHCH ₂ CH ₂ ) - + 3 C^OH

CH ₂ CH ₂ Si{OH) ₃ (C) Cross-linking

-(CH ₂ CH ₂ CHCH ₂ CH ₂

CH ₂ CH ₂ Si

C IH„ ΔCH ΔSi -

- CH ₂ CH ₂ CHCH ₂ CH ₂ ) - - CH ₂ CH ₂ CHCH ₂ CH ₂ )

The product of stage (A) above may also be produced by copolymerisation of ethylene with a suitable trialkoxysilyl monomer, for example 4- (triethoxysilyl)-but-l-ene. References hereinafter to silane-grafted or silane-modified copolymers include such silane side-chain materials produced by copolymerisation, which are indistinguishable from the materials produced by grafting.

While teaching that for storage stability the -silanol condensation catalyst should be incorporated into the silane-grafted polymer only when initiation of the cross-linking reaction is desired, Dow Corning Limited have suggested in GB-A-1406680 that silane grafted polymers may find utility in adhesives.

In GB-A-2197326 Swift Adhesives Limited have however suggested the use of a silane-grafted medium range molecular weight ethylene-vinyl acetate copolymer as the base for cross-linkable hot melt adhesive systems (which can either be formulated as single compositions containing the grafted copolymer together with the condensation catalyst or as dual compositions, one containing the grafted copolymer and the other the catalyst) which are particularly suitable for use in product assembly, for example in the furniture and automobile industries.

The present invention is based on the recognition that cross-linkable hot melt adhesive systems, especially single composition systems, having advantageous properties in terms of adhesion (especially to polar substrates such as glass, cellulose and metal) and thermal stability, may be produced by the use of silane-modified copolymers of ethylene and at least one polar comonomer or of blends of such modified copolymers.

According to one aspect of the present invention therefore we provide an adhesive composition appliable in melt form to surfaces to be bonded, said composition comprising

(a) at least one silane modified, including silane- grafted, copolymer (hereinafter collectively SGC) of ethylene and at least one polar comonomer, with the proviso that where said composition contains a silane-modified ethylene vinyl acetate copolymer said silane-modified ethylene vinyl acetate copolymer is a silane modified segmented ethylene vinyl acetate copolymer or said composition also contains at least one silane modified copolymer of ethylene with at least one polar comonomer other than vinyl acetate or said composition also contains at least one further silane modified ethylene vinyl acetate copolymer wherein the modified silane moieties in the first mentioned and said further silane

modified ethylene vinyl acetate copolymers are the same and are grafted moieties and the melt flow indices of said first and further ethylene vinyl acetate copolymers before silane grafting are respectively in the ranges 1 to 30 (preferably 1 to 20) and 150 to 2500,

(b) a catalyst for the condensation of said silane- grafted copolymer, and, optionally but preferably,

(c) a plasticizer, preferably a polybutene, polyterpene or hydrocarbon plasticizer.

As it is found that the incorporation of a plasticizer into the adhesive system improves substrate wetting by the hot melt as well as providing improved flexibility in the cured adhesive it is particularly preferred that the adhesive system should comprise at least one plasticizer, such as for example an ester based plasticizer (e.g. benzoate plasticizers such as glycol dibenzoate and dipropylene glycol dibenzoate (available as Benzoflex 9-88) ) or a liquid hydrocarbon or liquid polyterepene plasticizer (such as those available respectively as Escorez 5000 and Wingtack 10 from Exxon and Goodyear) . Polybutene plasticizers however are especially preferred. The plasticizer conveniently constitutes 5 to 40%, preferably 10-35%, of the adhesive composition.

The SGCs used according to the present invention are, as mentioned above, silane-grafted copolymers of ethylene with at least one polar comonomer or are copolymers of a silane monomer with ethylene and a polar comonomer. Examples of polar comonomers include for example vinyl esters (e.g. vinyl acetate) , maleic acid and aleic anhydride, acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters (e.g. (C _1-4 alkyl)-(meth)acrylates such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate and butyl acrylate) . It should be noted however that where the copolymer

contains acid groupings these should preferably be protected by displaceable (e.g. thermally displaceable) blocking groups or be at least partially neutralized while silane-grafting is effected.

Copolymers which may be silane grafted to produce the SGCs are conveniently polymers of ethylene and one polar comonomer - however polymers of ethylene and two or more comonomers may if desired be used. The copolymers may also if desired be segmented copolymers, i.e. copolymers having alternate high and low densities of polar comonomer residues along the polymer's carbon skeleton (see for example the definition in WO85/04669) ; an example of a commercially available segmented copolymer of ethylene and a polar comonomer is the ethylene-vinyl acetate copolymer (EVA) available from E.I. Du Pont de Nemours & Company under the trade names ELVAX 170 and EP 170.

Silane-modified segmented copolymers are particularly interesting for use in book binding adhesives and in pressure sensitive adhesives, especially plasticizer resistant pressure sensitive adhesives and as they are novel they form another aspect of the invention. Thus in this further aspect of the invention we provide a silane-modified segmented copolymer of ethylene and at least one polar comonomer, e.g. the product of (a) grafting segmented ethylene-vinyl acetate with a silane selected from vinyl trimethoxy silane, vinyl triethoxy silane and gammamethacryloxypropyl-trimethoxy silane or (b) copolymerising one of the above silane monomers with ethylene and a polar comonomer to produce a segmented copolymer structure.

The novel silane modified segmented copolymers may be formulated as one- or multi-part systems and thus in further aspects of the invention we provide a pressure-sensitive adhesive composition comprising a silane modified segmented copolymer

according to the invention, a catalyst for the condensation thereof and, optionally, a plasticizer, and a pressure-sensitive adhesive system comprising a first composition comprising a silane modified segmented copolymer according to the invention and a second composition comprising a catalyst for the condensation of said silane modifiedeegmented copolymer, said first and second compositions being packed in separate containers, said first and second compositions optionally also containing a liquid plasticizer and/or a solid tackifying resin.

The silane modified segmented copolymer containing compositions or systems may be formulated in liquid form, e.g. for application at ambient temperature, by incorporation of an acceptable organic solvent, such as for example toluene, hexane or an ester or ketone solvent.

The silane modified segmented copolymer containing pressure-sensitive compositions and systems preferably comprise a plasticizer, especially a mixture of liquid plasticizers and a solid tackifying resin.

By liquid and solid it is meant that the midblock compatible plasticizer and tackifying resin components should be materials which are respectively liquid or solid at ambient conditions, for example at 21°C.

The tackifying component of the pressure sensitive adhesive composition of the invention is important in order that the pressure sensitive adhesive produced on the cross-linking of the SGC should have sufficient surface tack to perform as a pressure sensitive adhesive. Surface tack levels of pressure sensitive adhesives can readily be measured in many ways, for example using the rolling ball or loop tack tests. However, it may be noted that, unlike sealants, which on curing should retain substantially no surface tack even though they may contain tackifying resins, pressure

sensitive adhesives, on curing for example for 5 to 17 days, must retain some level of surface tack even if only a relatively low level such as that exhibited by the repositionable notes recently put onto the market by 3M under the trade name POST-IT. Generally, a pressure sensitive adhesive would be expected to have a score of less than 10 cm, more usually less than 5 cm, e.g. 2 cm, in the rolling ball test. In the loop tack (FTM No 9) test method, pressure sensitive adhesives would generally score greater than 1 Newtons/25 mm, e.g. about 10 N/25 mm. Thus in another aspect of the invention we provide a pressure sensitive adhesive composition scoring greater than 1 N/25mm in the loop tack (FTM No 9) test and comprising a pressure sensitive adhesive composition according to the invention cured to effect cross linking of said silane modified copolymer.

The pressure sensitive adhesive compositions of the present invention preferably contain 10- 40%, more preferably 13-30% and especially preferably about 15-25%, of the SGC and 90-60%, more preferably 87-70%, especially preferably about 85-75% of a mixture of the liquid plasticizer and the solid tackifying resin, the percentages being by weight relative to the total weight of SGC,liquid plasticizer and solid tackifying resin within the composition. The mixture of liquid plasticizer and solid tackifying resin is preferably in a weight ratio of 15:85 to 90:10, more preferably 20:80 to 70:30, especially preferably 40:60 to 60:40 and particularly preferably 50:50 to 55:45.

Where is it desired that the pressure sensitive adhesive according to. the invention be stable at particularly low temperatures as well as at high temperatures, as might for example be the case for adhesives used in the automotive industry, a liquid plasticizer having a particularly low

glass transition temperature (T ) might be used, y for example a material for which T is less than about -30°C, or more preferably less than about

—40°C, and a value for the ratio of liquid plasticizer to solid tackifying resin towards the upper ends of the ranges specified about might be selected.

Liquid idblock compatible plasticizers suitable for use in the compositions of the invention are widely available commercially, In this regard, mention may be made particularly of ester-based plasticizers, paraffinic oil plasticizers, liquid polyterpene and liquid hydrocarbon plasticizers and polybutene plasticizers. Polybuten plasticizers, for example those available from BP Chemicals under the trade name H is, deserve particular mention. Liquid polyterpene and hydrocarbon plasticizers such as those available from Goodyear and Exxon under the trade names Wingtack 10 and Escorez 5000 respectively are particularly preferred. The liquid plasticizer component will generally constitute from 10-60% by weight of the total adhesive composition, excluding any solvent.

The solid midblock compatible tackifying resin used in pressure sensitive compositions of the present invention will preferably be a material having a softening point of at least 70°C, for example a material having a softening point in the range 90-115°C. Solid midblock compatible tackifying resins suitable for use in the compositions of the present invention are also widely available commercially. In this regard, particular mention may be made, for example, of aliphatic petroleum hydrocarbon resins and alicyclic hydrocarbon resins, for example Escorez 5300 and Escorez 5380 (available from Exxon) . The solid tackifying resin will preferably constitute from 10-60% by weight of the total adhesive composition, excluding any solvent.

The pressure sensitive adhesive compositions preferably contain at least one antioxidant and in this respect conventional adhesives antioxidants, such as butylated hydroxytoluene (BHT) may be used. A preferred antioxidant is pentaerythritol-tetrakis- 3-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionate, which is available under the trade name Irganox 1010 from Ciba-Geigy. The antioxidant will generally be present in the pressure sensitive adhesive compositions at about 0.1 to 2.5%, preferably 0.5 to 1%, by weight relative to the total composition weight, excluding any solvent.

The pressure sensitive compositions may if desired contain further polymers or polymer mixtures selected to achieve a balance between compatibility with the various components of the composition and the desired viscosity and tack characteristics. The further polymer will conveniently constitute up to 20% by weight, preferably up to 15% by weight, e.g. 1 to 10% by weight and especially preferably about 5% by weight, of the total adhesive composition, excluding any solvent.

The pressure sensitive adhesive may be presented in web form and thus in a further aspect of the invention we provide a pressure sensitive adhesive web, optionally coated on at least one surface thereof with a web substrate, said web comprising a cross-linked silane modified segmented copolymer of ethylene and at least one polar comonomer, a liquid plasticizer and a solid tackifying resin.

If the pressure sensitive adhesive is to be used in conjunction with a transparent substrate, it would be particularly advantageous to include within the adhesive composition a minor quantity, for example up to 1% by weight, of a UV stabilizer, for example one of the Tinuvin stabilizers available from Ciba-Geigy.

As mentioned above, the various adhesive compositions of the invention may contain one or more than one SGC. Where a blend of SGCs is used, it is particularly preferred that for each the silane side chain should be the same.

Where the silane side chains are introduced by grafting this may of course be effected either before or after the copolymers are blended.

Copolymers having a wide range of molecular weights may be silane grafted to produce the SGCs used for the preparation of the adhesive compositions of the present invention; in general copolymers having melt flow indices (MFIs) of from 1 to 2500 may conveniently be used and MFIs of 2-1000, especially 5-400 and particularly 10-150, are preferred. By blending copolymers having different pre silane grafting MFIs and indeed by blending grafted copolymers having different comonomer residues (e.g. by blending silane modified ethylene-ethyl acrylate with silane- modified ethylene-methyl acrylate) the performance profile of the final adhesive system, for example in terms of wetting, strength, adhesion, flexibility, and ease of application, may be adjusted to suit the intended end use of the adhesive system.

Thus in one embodiment the adhesive composition of the invention contains a blend of silane grafted copolymers for at least one of which the copolymer has an MFI before silane grafting in the range 1 to 20, preferably 2-15, and for at least one other of which the copolymer has an MFI before silane grafting in the range 150-2500, preferably 200-800.

While silane-grafted ethylene-vinyl ester copolymers, such as silane-grafted EVA (SGEVA) , are of interest for use in the preparation of the compositions of the invention, the use of silane grafted (meth)acrylate esters is of special interest in view of the increased thermal stability and

- li ¬ the reduced likelihood of production of corrosive thermal degradation products. Thus thermal degradation of SGEVA can lead to chain scission and the release of acetic acid while thermal degradation of the silane grafted ethylene-(meth)acrylate esters may have a lower tendency towards chain scission and will result in release of less corrosive alcohols. In the SGCs used according to the invention, the silane side chain is conveniently of general formula (I)

-A-Si(R)j,— _m (X) _m m (I)

wherein A represents an optionally substituted divalent organic radical, preferably an optionally substituted alkylene, alkyleneoxy, alkylene-phenylene, or alkylene-oxy-alkylene chain; X represents a leaving group displaceable by hydrolysis, conveniently a halogen atom (e.g. chlorine) or a group R 0-or

R COO- where R is a C,_ ₁₀ , preferably C, ., alkyl or alkoxyalkyl group; m is 1, 2 or 3, preferably

2 or 3; and R represents a blocking group not displaceable by hydrolysis, for example a C^_ ₄ alkyl group.

As mentioned above, the silane side chains may be present in a monomer which is copolymerised to produce the SGC.

The SGC component for inclusion in the adhesive compositions of the invention may also be prepared by reacting the ethylene copolymer (or blend thereof) with an unsaturated silane of formula II

(where A represents an ethylenically unsaturated organic group corresponding to the divalent group A in formula I and R, m and X are as defined above) in the presence of a catalyst, conveniently a peroxide catalyst, for example using the reagents and conditions specified in the literature.

In formula II, A conveniently represents a group of formula

2 where p is 0 or 1; R represents hydrogen or C, . alkyl; and R 3 represents a C _1-10 straight, branched or cyclic alkylene group, a phenylene group, a carbonyloxy group, a carbonyloxy C ₁ _ ₁₀ alkylene) group, a (C-,_- _jn alkylene)carbonyloxy group or a alkylene)carbonyloxy(C ₁ _ ₁₀ alkylene) group, optionally carrying pendant glycidoxy groups.

Such compounds are described by Dart Industries in GB-A-1347426.

Particularly preferably however A represents a C ₂ _ _g monoalkenyl group, such as vinyl or allyl, or a (C ₂ _3 alkenyl)carbonyloxy (C ₂ _ ₃ alkylene) group, such as a gamma-methacryloxy-propyl group, and particularly preferred unsaturated silanes of formula II include vinyl trimethoxy silane, vinyl triethoxy silane and gamma-methacryloxypropyl trimethoxy silane.

Unsaturated silanes of formula II are known or may be prepared by conventional methods.

The silane side chain need only constitute a minor part by weight of the SGC, e.g. up to 20%, conveniently 0.1 to 10%, generally 0.1-5%, preferably 0.5 to 3% and especially preferably about 2%, and the ratio of unsaturated silane to ethylene copolymer used in the grafting reaction should be chosen accordingly, or alternatively the weight ratio of monomers where copolymerisation is used.

The catalyst used in the preparation of the SGCs is preferably a .free-radical generating compound such as for example benzoyl peroxide, dicumyl peroxide or other such catalysts referred to by US-A-3646155. The free radical generator may conveniently be used in a concentration of about 0.01 to 3% relative to the weight of polymer used.

The silane grafting reaction is conveniently effected at a temperature of at least 140°C, preferably between 150°C and 250°C and may be performed in conventional apparatus such as a Ko-Kneader.

The SGC component preferably forms up to 99%, conveniently 10-40%, and especially preferably about 30%, of the adhesive composition.

In the adhesive composition of the invention, SGCs having a 3-membered or longer chain linking the silicon atoms with the ethylene copolymer backbone will result in a cured adhesive having a generally more open structure than that achieved with only a 2-membered linking chain. The open structure may advantageously permit both a high degree of curing and the inclusion of relatively high concentrations of tackifying resin and other components in the uncured adhesive composition. In this way, the viscosity, tack and melting characteristics of the uncured adhesive may be tailored to particular desired levels, for example to permit the use with the new adhesive of conventional hot melt adhesive melting, mixing and application apparatus.

As the catalyst for the SGC hydrolysis and cross-linking, a silanol condensation catalyst may be used. Many such materials are known to the art. Thus suitable catalysts include, for example, metal carboxylates, e.g. dibutyl tin dilaurate, organometallics, e.g. tetrabutyl titanate, organic bases, e.g. ethylamine, and mineral and fatty acids. Several such compounds are identified for example in US-A-3646155. Among suitable condensation catalysts, organotin compounds, such as dibutyl tin dilaurate are preferred. The catalyst, conveniently makes up from 0.005-0.2%, preferably about 0.02%, of the adhesive composition as a whole.

The adhesive compositions of the invention conveniently also contain further components selected from: antioxidants; tackifying resins; further polymers; and diluents and modifiers.

The tackifying resin component of the hot melt adhesive composition of the present invention may comprise any suitable resin or resin mixture, for example those conventional for hot melt adhesives. The resin or resin mixture should however be selected to achieve the desired balance between compatibility with the SGC and the other components of the adhesive, the melt flow properties of the adhesive as a whole and the specific adhesion to the substrates intended to be bonded with the adhesive. In this respect, suitable tackifying resins may include: aromatic modified resins such as α-methyl styrene homopolymers or copolymers, e.g. Krystalex F100 (α-methyl styrene polymer) , Krystalex FR75 (a modified α-methyl styrene copolymer) or Piccotex (a vinyl toluene- α-methyl styrene copolymer) , all three available from Hercules Chemical Co.; aliphatic petroleum hydrocarbon resins; styrene-modified hydrocarbon resins; and, particularly preferably, alicyclic hydrocarbon resins, e.g. Escorez 5300 (available from Exxon) .

The tackifying resin will conveniently make up from.5 to 40%, preferably 10-40%, and especially preferably about 30%-35%, of the adhesive.

The hot melt adhesive of the invention preferably contains at least one antioxidant. In this respect, conventional adhesives antioxidants, such as butylated hydroxytoluene (BHT) may be used. A preferred antioxidant is pentaerythritol-tetrakis-3-(3,5- di-tert.butyl-4-hydroxyphenyl)-propionate, which is available under the trade name Irganox 1010 from Ciba-Geigy UK Ltd. of Manchester. The antioxidant will generally be present in the adhesive at about 0.1-2.5%, preferably .0.5-1%.

The adhesive compositions of the invention preferably also comprise a further polymer or polymer mixture. The further polymer or polymer mixture, which should not be cross-linkable under the action

of the catalyst, will be selected to achieve, inter alia, a balance between co patability with the catalyst and the other components of the adhesive and the viscosity and tack characteristics of the adhesive. Since the SGC is based on an ethylene copolymer backbone, the further polymers are preferably selected from ethylene copolymers, such as for example EVA, ethylene-methyl acrylate (EMA) , ethylene ethylaσrylate (EEA) and ethylene butyl acrylate

(EBA) , conveniently copolymers having polar comonomer residue contents of 12-40%, preferably 18-35% and especially preferably about 28% and MFIs of 1 to

2500, conveniently 5-800, preferably 20-500 and most preferably 150-400. The further polymer conveniently constitutes up to 15%, preferably 1 to 10%, and especially preferably about 5%, of the adhesive of the invention and generally will be present at about half the concentration of the SGC.

The hot melt adhesive system may if desired be formulated as two compositions which are not mixed until the adhesive is melted for application so as to avoid earlier contact between the SGC and the condensation catalyst. Thus according to a further aspect of the invention we provide a hot melt adhesive system comprising a first composition comprising at least one SGC as defined above and a second composition comprising a catalyst for the condensation of said SGC, said first and second compositions being packed in separate containers.

The adhesive compositions or systems may also contain further components such as diluents or modifiers, conveniently as about 5-40%, preferably about 30%, of the total adhesive. These components may serve to regulate the viscosity and setting speed of the adhesive and may be included to enhance the wicking of the adhesive into the substrates to be bonded. In this respect, polyolefins (for example low crystallinity range molecular weight

homo-or copolymers, such as that available under the trade name Vestoplast 608 from Huls (UK) Limited of Manchester) and conventional diluents and modifiers for hot melt adhesives, such as waxes (e.g. petroleum waxes such as paraffin waxes or microcrystalline waxes such as Okerin 8981 from Astor Chemicals of West Drayton, Middlesex) , low molecular weight polyethylene, atactic polypropylene, hydrogenated animal or vegetable fats (e.g. hydrogenated castor oil or hydrogenated tallow) , and synthetic waxes, such as Fischer Tropsch waxes may be used, here waxes or low molecular weight polyethylenes are used as diluents, they should conveniently have softening temperatures in the range of 50-120°C.

Microcrystalline waxes, Fisher Tropsch waxes and paraffin waxes having softening temperatures in the ranges 65 to 94°C (e.g. 79°C) , 110 to 120°C and 54 to 72°C respectively are particularly suitable.

A mixture of low molecular weight polyethylene, such as polyethylene AC6 or AC8 available from

Allied Chemical Corporation International NV SA of Birmingham, and a microcrystalline wax having a softening temperature of about 90°C, such as

Micro 549 available from Holmes Chemical Company of Uxbridge, may also be particularly suitable, especially where the polyethylene and the wax constitute about 5 and about 15% by weight respectively of the adhesive.

Where the adhesive is formulated as a two part system, the SGC and the catalyst being separately packaged, the optional components can appear in one or both of the separate compositions; the SGC- containing composition will however preferably contain the antioxidant and the tackifier and the catalyst-containing composition will preferably contain a further polymer; the plasticizers, diluents and modifiers may be in either or both compositions In a two composition system, the catalyst containing

composition particularly conveniently comprises about 99% of an ethylene copolymer compatible with the SGC (e.g. EVA,EMA,EEA or EBA - for example a copolymer having an MFI of 400 and a polar comonomer residue content of 29%) and 1% of a catalyst (e.g. dibutyl tin dilaurate) .

Where the hot melt adhesives of the invention are formulated as a single composition they will advantageously be packaged in water-tight containers, for example aluminium cartridges, which containers advantageously will also include a desiccant, for example a sachet of silica gel at the end of a cartridge for a hot melt adhesive applicator. Thus, according to a further aspect of the invention we provide a hot-melt adhesive applicator cartridge comprising a water-tight container containing therein a desiccant and a hot-melt adhesive composition, said composition comprising an SGC as hereinbefore defined and a catalyst for the condensation thereof.

Besides the components discussed above, it may be desirable to incorporate into the adhesive a colouring agent, for example a whitener such as titanium dioxide. Such colouring agents are particularly readily dispersed within the adhesive if introduced as solid dispersions in an ethylene copolymer compatible with the SGC, e.g. in EVA. Thus for example small quantities, e.g. 0.1-4%, of a 1:1 dispersion of Ti0 ₂ in EVA (available under the trade name E/Va M/B from ICI Plastics Division of Welwyn Garden City) may be included in the hot melt adhesive.

In use, the hot melt adhesive of the present invention will be heated to melting, generally to 100-200°C preferably about 110-140°C, mixed (e.g. in a cartridge loaded applicator or by the mixing in a mixer head of the two compositions of a two composition system) and applied to the substrates to be bonded, generally in a film thickness

of up to about 3 mm, preferably up to about 1 mm, although this can be achieved by applying a larger amount and scraping off the excess. The adhesive characteristics of the system should be sufficient to maintain a bond between the substrates while the curing of the SGC component by hydrolysis and cross-linking occurs.

For the hydrolysis of the SGC, water is required. In general, the necessary water can be supplied by ambient moisture. However, if desired, the adhesive may contain further components, moisture releasing agents, which gradually release moisture into the system, for example fillers with surface- bound moisture or moisture filled polymer microspheres such as those sold as paint opacifiers by Rohm and Haas Company under the trade name ROPAQUE 0P- 62 (see EP-A-119054 of Rohm and Haas) .

The hot melt adhesive of the invention may be used in most applications where hot melt adhesives have been used and where full bonding strength is not required immediately after the application of the adhesive. The adhesive of the invention is thus particularly suited to use in product assembly (for example in the furniture and automobile industries) , packaging and labelling.

Thus according to a further aspect of the invention we provide the use of the adhesive compositions and systems of the invention in product assembly.

Because of the silane cross-linking reaction, the adhesive of the invention is capable of chemically bonding to the surfaces of certain substrates to produce an enhanced adhesive effect. Thus the adhesive of the present invention is particularly suitable for the bonding of cellulosic and silicaceous substrates, for example paper and glass.

The SGC and catalyst components in the adhesive of the present invention may be selected to achieve particular desired characteristics, for example

rate or controlability of curing, and by varying the polar comonomer content and the MFI of the ethylene copolymer precursor for the SGC, and by utilizing blends of SGCs, the formulation character¬ istics (such as viscosity, softening point, wetting ability, etc.) , for the adhesive may be controlled to give a readily processable material.

In a particularly preferred embodiment of the invention, further organic components, such as for example fillers, tack and viscosity modifiers, plasticizers and colorants can be bonded onto the cross-linked lattice produced by curing the silane grafted polymer by using for such components compounds containing, or chemically modified to contain, silanol, alcohol, amine or thiol groups. The use of such compounds is particularly advantageous since although they are unreactive towards the SGC in the adhesive composition before the application of the adhesive, on application they are able to bond to the silanols produced in the hydrolysis reaction and thereafter will be chemically bound into the cured adhesive.

In this way where such components are polyfunctional, i.e. contain two or more such groups on each molecule, the components may act as intermediaries in the cross-linking and by becoming part of the cross- linked lattice may modify the physical properties of the cured composition. However even when such components are monofunctional they may bond to the silane-modified polymer so reducing any tendency they may have to leach out of the cured composition even under adverse conditions. In this regard mention may be made in particular of glycerol esters of resins, polyamines, diols, polyethylene glycols, hydroxylated waxes and the like.

The use of such reactive components may be particularly advantageous in increasing the thermal stability of the cured composition or where the

optional component is capable of discoloring or otherwise damaging the substrate or where loss of the component would cause the adhesive bond to deteriorate.

The following Examples are provided to illustrate the present invention further without limiting the scope of protection sought therefor (all percentages and parts referred to herein are by weight unless otherwise specified) :

Example 1

One part adhesive composition

The composition is the admixture of the following components:

SGEBA* 31.3% Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7%

175°F Micro wax (microcrystalline wax) 20.0%

Sasol Wax (Fischer Tropsch wax) 10.0%

Irganox 1010 (antioxidant) 1.0% Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0% Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

+ The SGEBA is the reaction product of vinyltrimethoxysilan and 20-7 EBA, prepared with a silane content of 2-3% using the procedure of US-A-3646155.

The composition is homogenized prior to the addition of the catalyst. The catalyst is then mixed in and the composition is filled into aluminium cartridges for a hot melt adhesive applicator. A silica gel sachet is placed in the filled cartridge which is then sealed.

The compositions of Examples 2 to 8 are mixed and filled into containers as for Example 1.

Example 2

One part adhesive composition

The composition is the admixture of the following components:

SGEBA ⁺ 31.3%

Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SGEBA is the reaction product of vinyltrimethoxy- silane and 20-7 EBA, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 3

One part adhesive composition

The composition is the admixture of the following components:

SGEMA ⁺ 31.3%

Catalyst/EMA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SGEMA is the reaction product of vinyltrimethoxysilane and 20-20 EMA, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 4

One part adhesive composition

The composition is the admixture of the following components:

SGEEA ⁺ 31.3%

Catalyst/EEA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SGEEA is the reaction product of vinyltrimethoxy¬ silane and 18-3 EEA, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 5

One part adhesive composition

The composition is the admixture of the following components:

SGEBA ⁺ 31.3%

Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SGEBA is the reaction product of gamma-methacryloxy- propyltrimethoxy silane and 20-7 EBA, prepared with a silane content of about 5-6% using the procedure of US-A-3646155.

Example 6

One part adhesive composition

The composition is the admixture of the following components:

SG(EVA/EBA) ⁺ 31.3%

Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7% Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SG(EVA/EBA) is the reaction product of vinyltri¬ methoxysilane and a 5 :50 blend of EVA and EBA which blend has an ethylene content of 71% and an MFI of 20, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 7

One part adhesive composition

The composition is the admixture of the following components:

SG(EMA/EBA) ⁺ 31.3%

Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0%

Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0%

Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 20.0%

Benzoflex 9-88 (dipropylene glycol dibenzoate - plasticizer) 10%

+ The SG(EMA/EBA) is the reaction product of vinyltri- methoxysilane and a 50:50 blend of EMA and EBA which blend has an ethylene content of 80% and an MFI of 14, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 8

One part adhesive composition

The composition is the admixture of the following components:

SGEBA ⁺ 31.3% Catalyst/EBA blend (1% dibutyl tin dilaurate) 1.7%

Irganox 1010 (antioxidant) 1.0% Escorez 5300 (hydrogenated alicyclic hydrocarbon - tackifying resin) 26.0% Piccotex 100 (α-methyl styrene-vinyl toluene copolymer - tackifying resin) 10.0%

Hyvis 30 (polybutene - plasticizer) 10.0%

PEG 400 (polyethyleneglycol plasticizer) 20.0%

+ The SGEBA is the reaction product of vinyltrimethoxysilane and 20-7 EBA, prepared with a silane content of about 2-3% using the procedure of US-A-3646155.

Example 9

Two composition adhesive system

The first composition comprises the following components:

SGEBA 34%

Wingtack 95 (polyterpene resin) 33%

Okerin 8981 (microcrystalline wax) 32.4%

Irganox 1010 (antioxidant) 0.6%

*

The SGEBA is the reaction product of 20-7 EBA with vinyltrimethoxy silane, prepared with a silane content of 2-3% using the procedure of US-A-3646155.

The second composition comprises the following components:

28-400 EVA 99%

Dibutyl tin dilaurate 1%

In use, the first and second compositions are melted, mixed in a weight ratio of 98:2 and the mixture is applied to the substrates to be bonded.

If desired, a plasticizer may be incorporated in the two-composition system of Example 9, for example in place of the microcrystalline wax in the first composition. In this regard a 2:1 mixture of plasticizers such as Hyvis, 30 and Benzoflex 9-88 or PEG400 may be used.

Examples 10-13

One part hot-melt adhesive compositions

The compositions are produced by admixing the following components:

SGC* 33 parts

Paraffin wax 150/155 33 parts

Escorez 5380 (tackifying resin) 33 parts

Catalyst/28-800 EVA blend 1.7 parts (1% dibutyl tin dilaurate)

(A liquid plasticizer, e.g. Wingtack 10 or Escorez 5000, may if desired be included, for example as 30% by weight of the composition) .

* The SGC is the reaction product of a copolymer or copolymer mix and a silane as set forth in the Table below. Grafting to a silane content of about 2-3% is effected using a procedure as described in US-A-3646155 or in a PR46 Buss Ko-Kneader, e.g. using a procedure analogous to that described in British Patent Application No. 8826479.1.

TABLE

Example No. Copolymer Silane

10 28-40 EBA Gamma-methacryloxypropy -trimethoxy silane

11 50:50 28-40 EVA/ Vinyl trimethoxy

32-40 EMA blend silane

12 50:50 28-40 EVA/ Vinyl trimethoxy

14-2500 EVA blend silane

13 28-40 EBA Vinyl trimethoxy silane

Example 14

One part pressure sensitive adhesive composition

The composition is produced by admixing the follwing components:

SG(EVA) * 15 parts

SG(Segmented EVA) ⁺ 20 parts

Catalyst/28-800 EVA blend 1.7 parts

(1% dibutyl tin dilaurate)

Irganox 1010 (antioxidant) 0.5 parts

Escorez 5320 (hydrocarbon resin) 20 parts

Edelex 45 (paraffinic oil 15 parts plasticizer)

Wingtack 10 (liquid polyterpene 29.5 parts plasticizer)

* + 28-800 EVA and segmented EVA (EP170) in a 3:4 blend are co-grafted with vinyl trimethoxy silane to a silane content of about 2-3% using the procedure of the preceding examples.