RESINOUS COPOLYMER COMPOSITION BASED ON HYDROCARBONS AND USE THEREOF IN ADHESIVES AND COATINGS

Abstract: The invention relates to a resinous copolymer composition based on a vinylaromatic hydrocarbon monomer and at least one other hydrocarbon monomer having a copolymerizable unsaturation. The copo­ lymer composition comprises at least 5 % by weight of para­ methylstyrene, in an amount that is at least equal to any amount of metamethylstyrene units present in said copolymer composition. The resins according this invention can be used in adhesives and coatings.

Description: The invention relates to resinous copolymer compositions based on polymerized units of a vinylaromatic hydrocarbon monomer and at least one other hydrocarbon monomer having a copolymerizable unsa­ turation. Optionally, the copolymer composition may also contain one or more other copolymerizable compounds, chosen from the group formed by substituted benzene compounds, unsaturated carboxylic acid com­ pounds and conjugated diene compounds. The copolymers according to this invention are based in par­ ticular on polymerized units of a vinylaromatic hydrocarbon monomer and at least one other hydrocarbon monomer selected from the group comprising vinylaromatic compounds, dicyclopentadiene compounds, indene compounds and terpene compounds. Such resinous copolymers are known from US-A-3956250, which discloses resinous compositions containing copolymers of α-methyl­ styrene and vinyltoluene. Similar copolymers are known from US-A-3932332, which disclo­ ses copolymers containing of α-methylstyrene and styrene, from EP-A-23061, which discloses hydrocarbon resins based on dicyclopen­ tadiene, a vinylaromatic hydrocarbon and a mono-, di-, or tri-­ substituted benzene, and from EP-A-25241, which discloses resins based on α-methylstyrene, styrene and phenol. Resinous copolymer compositions of this type are known to have a relatively high softening point and good compatibility with natural or synthetic elastomers, and to have good peel strength, shear adhesion and tack, which makes them suitable for use in pressure-­ sensitive and hot-melt adhesives. However, the requirements posed with respect to these properties are becoming ever higher. It has now been found that these properties, in particular the softening point and the compatibility, are considerably improved if paramethylstyrene is used as vinylaromatic comonomer. The resinous copolymer composition according to the invention is made up of polymerized units of a vinylaromatic hydrocarbon monomer and at least one other hydrocarbon monomer with a copolymerizable unsaturation and is characterized in that said copolymer composition comprises at least 5 % by weight of paramethylstyrene units, in an amount that is at least equal to any amount of metamethyl-styrene units present in said copolymer composition. The resinous copolymer composition according to the invention in particular comprises preferably at least 25 % by weight, and most preferably at least 40 % by weight, of paramethylstyrene units. The use of paramethylstyrene as (co)polymerizing monomer is discussed in Mobil Chemical Technical Bulletin, January 1982, which refers in particular to the replacement of vinyltoluene mixtures by paramethylstyrene in polyester based resin mixtures. This publication does not pertain to hydrocarbon resins and does not give any indica­ tion about the advantages of the present invention. In view of the results obtained with polyester resins, it is quite surprising that application of paramethylstyrene in tackifying hydrocarbon resins yields such considerable improvements with respect to the highly specific properties, as compatibility with rubbers, elastomers and ethylene-vinylacetate copolymers. The other hydrocarbon monomer to be applied in combination with paramethylstyrene according to the invention, which contains a copolymerizable unsaturation, is selected in particular from the group comprising vinylaromatic compounds, dicyclopentadiene compounds, indene compounds and terpene compounds. Vinylaromatic compounds that according to the invention may be used in combination with paramethylstyrene are, for instance, styrene, α-methylstyrene, metamethylstyrene, orthomethylstyrene, vinyltoluene (a mixture consisting of about 1/3 parts by weight para­ methylstyrene and 2/3 parts by weight metamethylstyrene), or mixtures thereof. Use can be made of the pure compounds, but there is advantage in using the technical grades or concentrates with at least 60 % by weight, or preferably 80 % by weight, of one or more vinylaromatic compounds. Dicyclopentadiene compounds that may be used according to the invention are, for instance, unsubstituted dicyclopentadiene and substituted dicyclopentadiene. The substituents may be chosen from, for instance, C₁-C₁₂ alkyl, hydroxyl and halogen. The dicylopentadiene compounds may be applied in the form of the pure chemical compound, but there often is advantage in using a concentrate or a technical grade with 60 % by weight, or preferably 80 % more by weight, of the compound. Indene compounds that may be used according to the invention are, for instance, unsubstituted indene and substituted indene. The substituents may be chosen from, for instance, C₁-C₁₂ alkyl, hydroxyl and halogen. Here, too, concentrates or technical grades with 60 % by weight, or preferably 80 % or more by weight, of the compound may be used. Terpene compounds according to the invention that may be used are, for instance, β-pinene, α-pinene, limonene, carene and compounds such as dipentenes. Mostly a concentrate or a technical grade with 60 % by weight, or preferably 80 % or more by weight, of a terpene compound may be used. According to another embodiment of the invention, resins having an excellent compatibility with ethylene-vinylacetate copoly­ mers are obtained if the hydrocarbon resin is 'alkylated', i.e. by incorporation of substituted benzene into the hydrocarbon resin. The substituted benzene compounds that may optionally be used in the copo­ lymers according to the invention are preferably chosen from mono-, di-, and tri-substituted benzene, the substituents being chosen from C₁-C₁₂ alkyl, hydroxyl and halogen. Examples of suitable substituted benzenes that are preferred are, for instance, phenols, which may have the following structural formula: where R represents hydrogen or a C₁-₁₂ alkyl group, preferably a C₆-C₁₀ alkyl group. They can be used in the form of technical-grade compounds (purity higher than 95 %). Depending on the nature and reac­ tivity, some of the impurities may be incorporated in the resin. For use in adhesives those resins are preferred which comprise a combination of a phenol and a C₆-C₁₀ monoalkyl phenol such as e.g. octylphenol. Other examples of suitable substituted benzene compounds that are preferred include toluene, ethylbenzene, xylenes, mesitylene, tri­ methylbenzenes, and other C₁-C₁₂ alkylbenzenes. The amount of substi­ tuted benzene in the copolymers according to this optional embodiment of the invention preferably ranges from 2 to 15 % by weight and most preferably from 3 to 10 % by weight, of substituted benzene. Depending on the average molecular weight of the copolymers this corresponds to about 0.5 to 1.5, preferably 0.8 to 1.2 molecules of substituted ben­ zene per average molecule of copolymer, so that the majority of the resin molecules are believed to contain a substituted benzene (i.e. an 'alkylated') group. The 'alkylating' agent may be present in the reac­ tion mixture also in higher molar ratios than indicated above and partly act as a solvent, which is distilled off after termination of the reaction. The copolymers according to the invention may optionally comprise units derived from an unsaturated carboxylic acid with pre­ ferably 2-6 C-atoms per molecule, such as those derived from, for instance, unsaturated monocarboxylic acids and C₁-C₁₂ alkylesters thereof, unsaturated dicarboxylic acids and acid anhydrides. Suitable examples are acrylic and methacrylic acids and their esters, such as in particular 2-ethylhexylacrylate, and maleic anhydride. The amount of unsaturated acid compound in the copolymers according to this optional embodiment of the invention preferably range from 2 to 20 by weight, and most preferably from 3 to 10 % by weight. The copolymers according to the invention, and notably the copolymers based on paramethylstyrene and dicyclopentadiene compounds, may optionally comprise units deriving from conjugated diene com­ pounds. Preferred diene compounds are, for instance, pentadiene, and most preferably piperylene, i.e. 1.3-pentadiene (cis and trans). Copo­ lymers containing pentadiene, in particular piperylene, are preferred when a higher tack with respect to polyester and polyolefin substrates is desired. Pure piperylene can be used, but usually technical grade pentadiene or piperylene concentrates containing more than 45 % of pure pentadiene can be used, provided they contain less than 5 % of isoprene, the remainder being monoenes, dicyclopentadiene, methyl cyclopentadiene and non-polymerizable products. The optional amount of diene compound in the copolymers according to the invention preferably ranges from 2 to 20 % by weight, and most preferably from 3 to 10 %. According to a preferred embodiment of the invention, the resinous copolymer composition consists of paramethylstyrene together with at least one monomer chosen from the group formed by styrene, α-methylstyrene, vinyltoluene, dicyclopentadiene, indene and terpene. Optionally, the copolymer composition may also contain one or more monomers chosen from the group consisting of pentadienes, unsa­ turated carboxylic acids and their C₁-C₁₂ alkyl esters, unsaturated dicarboxylic acids and acid anhydrides and mono-, di- or tri-­ substituted benzene, the substituents being chosen from C₁-C₁₂ alkyl, hydroxyl and halogen. According to another preferred embodiment of the invention, the resinous copolymer composition consists of paramethylstyrene together with one or more comonomers from the group formed by styrene, α-methylstyrene and vinyltoluene. Optionally, the copolymer com­ position may also contain phenol and/or a C₆-C₁₀ alkyl-substituted phenol. According to yet another preferred embodiment according to the invention, the resinous copolymer composition consists of para­ methylstyrene together with dicyclopentadiene and with one or more comonomers from the group formed by phenol, C₆-C₁₀ alkyl phenols and C₁-C₆ alkyl benzenes. Optionally, the copolymer composition may also contain one or more comonomers from the group formed by vinylaromatic compounds (excluding paramethylstyrene), pentadienes, in particular piperylene and C₁-C₁₂ alkylesters of acrylic and methacrylic acid. The resins according to the invention usually show softening points (Ring & Ball according to ASTM E28) of about 100◊ to 120◊C, which is extremely high compared with the softening points of the state of the art resins, which are on the order of 70-90◊C. The com­ patibility with elastomers, such as natural and synthetic rubbers, is excellent, giving typical cloud points below 30◊C and even yielding clear mixtures at room temperature. The average molecular weight of these resins preferably ranges from about 400 to 2.000. The resins according to the invention can be prepared by reacting, optionally in the presence of a hydrocarbon solvent, for instance methylcyclohexane or toluene, the desired amounts of starting materials and a small amount of a Friedel-Crafts type catalyst, for instance BF₃, AlCl₃, TiCl₄ or a complex thereof, with, for instance, ether or phenol, and keeping the reaction temperature between -10◊ and 80◊C, preferably between 20◊ and 50◊C. The resinous copolymer composition according to the invention preferably is prepared at a temperature between -10 and 80◊C, with a. 5 to 90 parts by weight of paramethylstyrene; b. 10 to 95 parts by weight of at least one other hydrocarbon having a copolymerizable unsaturation; c. 0 to 15 parts by weight of (a) substituted benzene compound(s); d. 0 to 20 parts by weight of conjugated diene compound; and e. 0 to 20 parts by weight of unsaturated carboxylic acid compound being reacted in the presence of a Friedel-Crafts type catalyst. This preparation may take place in the presence of a solvent. According to a preferred embodiment according to the inven­ tion, paramethylstyrene is used in an amount between 40 and 90 parts by weight and the other hydrocarbon with a copolymerizable unsatura­ tion in an amount between 10 and 60 parts by weight. The substituted benzene compound(s), the conjugated diene compound and the unsaturated carboxylic acid compound may be used in a total amount between 0 and 10 parts by weight. Slow additon of the catalyst -which is preferably BF₃ or a complex thereof- may be recommendable in view of the exothermic nature of the reaction. Special measures to control the temperature during the reaction may be required to secure good and reproducible technical results. The reaction mixture is normally kept for several hours at the desired reaction temperature (-10◊C - 80◊C), after which the cata­ lyst is destroyed, preferably by addition of a base and washing, whereafter the volatiles, e.g. solvent and any unreacted starting material, are removed. The resins according to the present invention can advan­ tageously be used in adhesives, more particularly in hot-melt adhes­ vies which do not require the presence of organic solvents. The com­ patibility of the resin with rubber is excellent (50 : 50 mixtures). In some instances elastomers like rubber and certain ethylene-vinylacetate copolymers (EVA), ethylacrylate copolymers (EEA) and amorphous polypropylene (APP) can be used, either in combination or separately, together with these resins in hot-melt pressure-­ sensitive adhesives. The present invention also provides pressure-sensitive adhe­ sives which are mixtures of a resin in accordance with the invention and an elastomer such as natural or synthetic rubber. As natural rubber crude gum can be used and as synthetic rubbers any thermo­ elastomer, such as styrene butadiene styrene (SBS) and e.g. styrene isoprene styreen (SIS) block copolymers. The resins and elastomers can be combined in weight ratios of between 0.3 to 3 parts of resin per part of rubber, preferably between 0.5 and 2. Optional further ingredients such as waxes, tackifying oils (usually a naphthenic oil) and stabilizers against oxidation and ultraviolet light can be incorporated in minor amounts. The resin and rubber are melted at a temperature ranging from about 80◊ to 200◊C and kept at this temperature for 10-30 minutes. Sometimes, better results are obtained by combining more than one type of rubber or more than one type of resin. The use of solvents (aliphatic or aromatic hydro­ carbons, chlorinated derivatives thereof or e.g. ketones) is often superfluous, though the usual additives, such as anti-oxidants, fillers and the like, may be incorporated in minor amounts. In another preferred embodiment of the present invention hot-­ melt adhesives are provided, which comprise substantially a mixture of an ethylene-vinylacetate copolymer (EVA) containing at least 20 and at most 55 % by weight of vinylacetate, and copolymeric hydrocarbon resin as described above, optionally with a microcrystalline and/or paraffin wax and/or a tackifying oil. The amounts by weight of hydrocarbon resin and EVA copolymer can range between 35 : 65 and 60 : 40, pre­ ferably between 40 : 60 and 50 : 50. The ethylene-vinylacetate copo­ lymer to be applied contains 25 to 55 %, preferably 28 to 50 %, by weight of vinylacetate. Mixing of resin and copolymer is effected in the melt at a temperature of 150-200◊C, preferably 160-180◊C for 15-60 minutes. Minor quantities of antioxidants may also be present. By this process hot-melt adhesives can be provided which are particularly suitable for packaging, bookbinding or the manufacture of disposables, such as diapers, sanitary towels, disposable dressings, packaging tapes, masking tapes for automobile windows, carpet-laying tapes, labels, floor tiles, wall coverings, automobile upholstery, etc. The non-pressure-sensitive hot melts as formulated herein are characterized by superior adhesion, hot and cold resistance and stabi­ lity and as such are suitable for packaging, bookbinding and non-­ pressure-sensitive disposables applications. The resins according to the present invention can also advan­ tageously be used in coatings. A preferred embodiment of the invention provides in coatings that consist of 3-15 % by weight, preferably 5-10 % by weight, resinous copo­ lymer composition according to the invention, 2-10 % by weight, preferably 4-6 % by weight, ethylene-­ vinylacetate copolymer and 75-95 % by weight wax, for instance paraffine wax. The usual additives can be added. The ethylene-vinylacetate copolymer can be replaced by other polymers, as long as they result in coatings with the same performance. The invention is illustrated by the following examples. Example I 60 parts by weight of paramethylstyrene and 31 parts by weight of alpha-methylsiyrene were mixed with 9 parts by weight of phenol and dissolved in 120 parts by weight of toluene. Subsequently 0,25 wt.% of gaseous borontrifluoride (BF₃) was added to the reaction mixture, which was kept for 5 hours at 20◊C. After this the catalyst was neutralized with NaOH and washed and the volatiles were distilled off. A resin I having a Ring and Ball softening point of 100◊C (according to ASTM E28/67) and a Gardner colour below 1 was obtained. The copolymeric hydrocarbon resin was compatible with ethylene-vinyl­ acetate copolymers containing 15-40 wt.% of vinylacetate, with micro­ crystalline waxes, paraffins, polyethylene waxes and natural and synthetic rubbers. Example II Using the procedure of Example I, a copolymer resin was pre­ pared based on the following reaction mixtures: 45 parts by weight of paramethylstyrene 45 parts by weight of alpha-methylstyrene parts by weight of phenol 120 parts by weight of toluene. A resin II having a Ring and Ball softening point of 100◊C ± 2◊ was obtained. Comparative example 1 Copolymeric hydrocarbon resin based on vinyltoluene, alpha­ methylstyrene and phenol. Using the procedure of Example I a resin was prepared based on the following reaction mixture: 60 parts by weight of vinyltoluene (i.e. 33 % paramethylstyrene 66% metamethylstyrene 0,3 % orthomethylstyrene) 31 parts by weight of alpha-methylstyrene 9 parts by weight of phenol 120 parts by weight of toluene. A resin III having a Ring and Ball softening point of 83◊C was obtained. The compatibility of resins I, II and III with various ethy­ lene vinylacetate copolymers (comprising about 15-30 wt.% vinylaceta­ te) and with an acid EVA-terpolymer was tested. The results are given in Table I. Table I Comparison of the compatibility of copolymers according to the invention and of state of the art copolymers with ethylene-­ vinylacetate copolymers (50 % by weight copolymer and 50 % by weight EVA). Elvax is the trade mark of ethylene-vinylacetate copolymer products marketed by Dupont de Nemours. Example III Using the procedure of Example I a resin was prepared by polymerizing the following reaction mixture at a temperature between 40 and 45◊C: A resin was obtained having a Ring and Ball softening point above 100◊C and showing an excellent compatibility with an ethylene vinyl­ acetate copolymers. Example IV Using the same procedure as in Example I, a resin was pre­ pared by polymerizing the following reaction mixture at a temperature between 25 and 35◊C: The resin obtained showed a Ring and Ball softening point of 95◊C and had the following properties: tack : 2 cm (according to PSTC-6 test method) peel strength : at 180◊, 600 grams per cm of ribbon (according to PSTC-1 test method) shear adhesion: more than 24 hours (according to PSTC-7 test method). (PSTC standing for: Pressure Sensitive Tape Council). Example V Using the same procedure as in Example I, a resin was pre­ pared by polymerizing the following reaction mixture at a temperature of 25◊C. The resin, obtained in a yield of 90 %, had a Ring and Ball softening point of 140◊C. Comparative example 2 Using the same procedure as in Example V, a resin was pre­ pared by polymerizing the following reaction mixture: The resin, obtained in a yield of 90 %, had a Ring and Ball softening point of 120◊C.

Claims: 1. Resinous copolymer composition based on polymerized units of a vinylaromatic hydrocarbon monomer and at least one other hydrocar­ bon monomer having a copolymerizable unsaturation, characterized in that said copolymer composition comprises at least 5 % by weight of paramethylstyrene, in an amount that is at least equal to any amount of metamethylstyrene units present in said copolymer composition. 2. Resinous copolymer composition according to claim 1, characterized in that said copolymer composition comprises at least 25 % by weight of paramethylstyrene. 3. Resinous copolymer composition according to claim 2, characterized in that said copolymer composition comprises at least 40 % by weight of paramethylstyrene. 4. Resinous copolymer composition according to any of claims 1-3, characterized in that it consists of paramethylstyrene together with at least one monomer chosen from the group formed by styrene, α-methylstyrene, vinyltoluene, dicyclopentadiene, indene and ter­ pene. 5. Resinous copolymer composition according to claim 4, characterized in that it contains paramethylstyrene together with one or more comonomers from the group formed by styrene, α-methylstyrene and vinyltoluene. 6. Resinous copolymer composition according to any of claims 1-4, characterized in that it contains paramethylstyrene together with dicyclopentadiene and with one or more comonomers from the group formed by phenol, C₆-C₁₀ alkylphenols and C₁-C₆ alkylbenzenes. 7. Process for the preparation of a resinous copolymer composition, characterized in that, at a temperature between -10 and 80◊C, a. 5 to 90 parts by weight of paramethylstyrene; b. 10 to 95 parts by weight of at least one other hydrocarbon having a copolymerizable unsaturation; c. 0 to 15 parts by weight of (a) substituted benzene compound(s); d. 0 to 20 parts by weight of conjugated diene compound; and e. 0 to 20 parts by weight of unsaturated carboxylic acid com­ pound are reacted in the presence of a Friedel-Crafts type catalyst. 8. Process according to claim 7, characterized in that paramethyl­ styrene is used in an amount between 40 and 90 parts by weight and the other hydrocarbon with a copolymerizable unsaturation in an amount between 10 and 60 parts by weight. 9. Use as hot-melts adhesives of a resinous composition according to any of claims 1-6 or obtained by the process according to either of claims 7-8, in combination with an elastomer, a natural or synthetic rubber or an ethylene-vinylacetate copolymer with 20-55 % by weight vinylacetate, optionally in combination with a wax and/or a tackifying oil. 10. Hol-melt adhesive, characterized in that it consists to 20-60 % by weight, calculated on the total composition, of a resinous copo­ lymer composition according to any of claims 1-6 or obtained by the process according to either of claims 7-8. 11. Coating, characterized in that it consists to 3-15 % by weight, calculated on the total composition, of a resinous copolymer com­ position according to any of claims 1-6, 2-10 % by weight ethylene-vinylacetate copolymer and 75-95 % by weight wax.

Inventors: RUNAVOT, YVES, SALVETAT, JACQUES, THIOT, ANDRE, Thiot, André
Applicants: DSM RESINS BV
Application year: 1986
Main classification: C08F212
IPC codes: C08F12, C08L21, C08F212, C09J125