Hot-melt adhesive composition

Abstract: A hot-melt adhesive composition containing, (A) 10 to 80 parts by weight of a base polymer, (B) 10 to 80 parts by weight of a stickiness-imparting agent which is a copolymer of a particular styrene-type monomer and a particular indene-type monomer, the molar ratio of the indene-type monomer to the styrene-type monomer being from 99/1 to 30/70, and the weight average molecular weight of said copolymer being from 300 to 5000. The hot-melt adhesive composition exhibits excellent heat-resistant adhesiveness and heat-resistant creeping property, and has a low-molecular weight and exhibits good hue.

Description: The present invention relates to a hot-melt adhesive composition and, particularly, to a hot-melt adhesive composition having excellent heat-resistant adhesiveness and heat-resistant creeping property. Attempts have been made to use low-molecular polymers and petroleum resins such as styrene, vinyltoluene, and α-methylstyrene as stickiness-imparting resins that are to be blended into rubber-type pressure-sensitive adhesive agents and into ethylene/vinyl acetate copolymer-type and styrene block copolymer-type hot-melt adhesive agents. For example, US Patent No. 3535153 describes a pressure-sensitive adhesive composition comprising a styrene-butadiene-copolymer as an elastomer and a styrenated liquid polymeric tackifier. However, when the above resins are used for the rubber-type pressure-sensitive adhesive agents, a sufficiently large adhesive force or sticking force is not obtained. When the above resins are used for the hot-melt adhesives, furthermore, compatibility becomes poor with respect to the ethylene/vinyl acetate copolymer which is a chief component of the adhesive agent. On the other hand, petroleum resins produced from the ordinary fractions of distillates containing unsaturated hydrocarbons involve problems in regard to hue and thermal stability. In order to solve these problems, the present inventors have previously proposed the use of a polymer which is obtained by polymerizing at a particular ratio the isopropenyltoluene and any fraction of distillate selected from those fractions of distillate having 4 to 5 carbon atoms that are by-produced at the time of refining petroleum or cracking petroleum, as well as the use of a homopolymer of the isopropenyltoluene (Japanese Laid-Open Patent Publications Nos. 118729/1974 and 128945/1974 and Japanese Patent Publication No. 34033/1979). Though the above-mentioned problems were improved by these proposals, however, lack of heat-resistant adhesiveness and lack of heat-resistant creeping property in the hot-melt adhesive agent have not still been solved. It has further been known that the above-mentioned homopolymer of isopropenyltoluene helps improve the heat resistance when it is used for the hot-melt adhesive agent of the styrene block copolymer type, but makes it difficult to obtain high softening-point products having softening points of higher than 120 °C maintaining good yields. Furthermore, a resin that has been placed in the market as a resin to impart heat resistance, has a high molecular weight and helps improve heat-resistant creeping property. This resin, however, exhibits poor compatibility with respect to the base resin that is a chief component of the adhesive agent, and gives such defects as decreased tacking property of the adhesive agent and increased melt viscosity of the hot-melt adhesive agent making the operation of application difficult. As a stickiness-imparting agent for improving the hue and the heat resistance, furthermore, there has been proposed a nuclear-hydrogenated copolymer resin of a cyclopentadiene, a dicyclopentadiene or an alkylsubstituted product thereof and an indene or an alkylsubstituted product thereof (Japanese Patent Publication No. 8849/1986). After the polymerization, however, a step is necessary for effecting the hydrogenation, causing the process to become complex and the cost to become high. The object of the present invention therefore is to provide a hot-melt adhesive composition having excellent heat-resistant adhesiveness and heat-resistant creeping property by blending a stickiness-imparting resin that has a low molecular weight, excellent hue and excellent heat resistance. In order to solve the above-mentioned problems, the present invention provides a hot-melt adhesive composition which contains, (A) 10 to 80 parts by weight of a base polymer, (B) 10 to 80 parts by weight of a stickiness-imparting agent which is a copolymer of a styrene-type monomer represented by the general formula (I): wherein R 1 , R 2 , R 3 and R 4 are hydrogen atoms or alkyl groups with 4 or less carbon atoms, which may be the same or different, and an indene-type monomer represented by the general formula (II) wherein R 5 , R 6 and R 7 are hydrogen atoms or alkyl groups with 6 or less carbon atoms, which may be the same or different, the molar ratio of the monomers (I)/(II) being from 99/1 to 30/70, and the weight average molecular weight of the copolymer being from 500 to 5000 and optionally a petroleum refining or cracking C 4 to C 5 distillate fraction. The hot-melt adhesive composition of the present invention (hereinafter referred to as "composition of the present invention") will be described below in detail. Detailed Description of the Preferred Embodiments The base polymer (A) used for the composition of the present invention may be a polymer that is usually used for the hot-melt adhesive agent without any limitation. In the following are mentioned the examples. 1) Polyolefin polymer; e.g., a polyolefin homopolymer or a polyolefin copolymer such as a polyethylene, an atactic polypropylene, an isotactic or a syndiotactic polypropylene, an ethylene/propylene copolymer or an ethylene/propylene/diene copolymer. 2) Olefin/vinyl acetate type copolymer or saponified olefin/vinyl acetate copolymer; e.g., a copolymer of olefin and vinyl acetate or a saponified copolymer thereof such as an ethylene/vinyl acetate copolymer (EVA), an ethylene/vinyl acetate saponified copolymer (saponified EVA), or a graft-modified ethylene/vinyl acetate copolymer. 3) Olefin/(meth)acrylic acid copolymer or olefin/(meth)acrylic acid derivative copolymer; e.g., an ethylene/(meth)acrylate copolymer such as an ethylene/(meth)ethyl acrylate (EEA), or an ethylene/(meth)acrylic acid copolymer, an ionomer resin obtained by partly neutralizing the ethylene/(meth)acrylic acid copolymer (concrete example: "Himilan", tradename manufactured by Mitsui-Dupont Chemical Co.), or an ethylene/propylene/(meth)acrylate terpolymer. 4) Vinyl acetate type copolymer other than the above; e.g., a vinyl acetate/chronic acid copolymer, a vinyl acetate/phthalic anhydride copolymer, or a vinyl acetate/vinyl pyrrolidone copolymer. 5) Polyamide; a reaction product of dibasic acid and diamine, a reaction product of dimeric acid which is a dimer of fatty acid such as soybean oil, tung oil or tall oil and alkyldiamine such as ethylenediamine or diethylenetriamine, and nylons such as nylon 12. Concrete examples include Diamide (Dycel Kagaku Kogyo Co.), Platilon (Toa Gosei Kagaku Kogyo Co.), and Amilan (Toray Co.) which are the tradenames placed in the market. 6) Polyesters; e.g., Ester-Resins 200 and 300 (Toyobo Co.), or Vital 200 and 300 (Goodyear Co.) which are the tradenames placed in the market. 7) Copolymer comprising a vinyl aromatic compound and a conjugated diene compound, and hydrogenated product thereof; e.g., a styrene/butadiene random copolymer, a styrene/isoprene random copolymer, a butadiene/polystyrene block copolymer, a polystyrene/polyisoprene block copolymer, a polystyrene/polyisoprene/polystyrene triblock copolymer, a polystyrene/polybutadiene/polystyrene triblock copolymer, a poly(α-methylstyrene) /polybutadiene/poly(α-methylstyrene) triblock copolymer and hydrogenated products thereof. These polymers are available in the market and the hydrogenated products thereof are also available in the market. Examples include Kaliflex TR-1101, TR-1107, TR-4113 (Shell Kagaku Co.), Crayton G-6500, G-6521, G-1650, G-1652, G-1657 (Shell Kagaku Co.), Solbrene, and hydrogenated Solbrene (Phillips Co.) which are tradenames placed in the market. 8) Other polymers: e.g., a cellulose derivative-type polymer, a polymethyl methacrylate-type polymer, a polyvinyl ether-type polymer, a polyurethane-type polymer, or a thermosetting resin-type polymer. In the composition of the present invention, the base polymers (A) may be used in one kind alone or in a combination of two or more kinds. Among these base polymers (A), it is desired to use a copolymer comprising a vinyl aromatic compound and a conjugated diene compound or a hydrogenated product alone or together with other base polymers, since it makes it possible to obtain a large cohesive force and to markedly improve heat-resistant adhesiveness and heat-resistant creeping property owing to the mutual action between the styrene blocks possessed by the base polymer (A) and the styrene blocks possessed by the stickiness-imparting resin (B). The stickiness-imparting resin (B) used for the composition of the present invention is obtained by the copolymerization of a styrene-type monomer represented by the aforementioned general formula (I) and an indene-type monomer represented by the general formula (II). The stickiness-imparting resin (B) may be any one of the bicopolymer, tercopolymer or tetracopolymer based upon the combination of the styrene-type monomer represented by the above general formula (I) and the indene-type monomer represented by the general formula (II). In the general formula (I) representing the styrene-type monomer, R 1 , R 2 , R 3 and R 4 are hydrogen atoms or alkyl groups with 4 or less carbon atoms, which may be the same or different. Examples of the alkyl group with 4 or less carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group. Concrete examples of the styrene-type monomer represented by the general formula (I) include a styrene, a vinyltoluene, an α-methylstyrene, an isopropenylbenzene, an isopropenyltoluene, an ethylvinylbenzene, a propylvinylbenzene, and a vinylcumene. In the present invention, the styrene-type monomers represented by the general formula (I) may be used in a single kind alone or in a combination of two or more kinds. Among these styrene-type monomers, it is desired to use a styrene, a vinyltoluene, an α-methylstyrene and an isopropenyltoluene from the standpoint of availability and cost. In the above-mentioned general formula (II) representing the indene-type monomer, R5, R6 and R7 are hydrogen atoms or alkyl groups with 6 or less carbon atoms, which may be the same or different. Examples of the alkyl group with 6 or less carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Concrete examples of the indene-type monomer include an indene,a methylindene, and an ethylindene. In the present invention, the indene-type monomers represented by the above-mentioned formula (II) may be used in one kind alone or in a combination of two or more kinds. Among the indene-type monomers, an indene is preferred from the standpoint of availability and cost. The molar ratio of styrene-type monomer represented by the general formula (I)/monomer represented by the general formula (II) is from 99/1 to 30/70 and, preferably, from 95/5 to 45/55 from the standpoint of good compatibility to the base polymer (A) and of obtaining adhesive composition having softness. The ratio of monomers in the stickiness-imparting resin (B) can be found by measuring the monomers remaining in the solution after the reaction based upon the gas chromatography. In order to further improve compatibility to the base polymer (A), the stickiness-imparting resin may contain, as a copolymer component, any fraction of distillate selected from those fractions of distillate having 4 to 5 carbon atoms by-produced during the refining of petroleum or cracking of petroleum. Among the fractions of distillate having 4 to 5 carbon atoms, the C4-fraction contains butane, butene-1, butene-2, isobutene, and butadiene, and the C5-fraction contains pentane, pentene, methylbutene, piperylene, isoprene, cyclopentene, and cyclopentadiene. When the stickiness-imparting resin contains the fractions having 4 to 5 carbon atoms as copolymerizable components, it is desired that the ratio of the fractions having 4 to 5 carbon atoms in the stickiness-imparting resin is smaller than 20 mol % from the standpoint of maintaining good hue of the stickiness-imparting resin. The stickiness-imparting resin can be prepared by subjecting the styrene-type monomer, indene-type monomer and, as required, fractions with 4 to 5 carbon atoms to the copolymerization reaction in the presence of a catalyst. The catalyst used for the polymerization is the one that is generally known as Friedel-Crafts catalyst. Examples include various complexes such as an aluminum chloride, an aluminum bromide, a dichloromonoethyl aluminum, a titanium tetrachloride, a tin tetrachloride, and a boron trifluoride. It is desired that the catalyst is used in an amount of from 0.01 to 5.0% by weight and, preferably, from 0.05 to 3.0% by weight with respect to the total weight of the styrene-type monomer and the indene-type monomer. In order to remove the heat of reaction and to suppress the reaction mixture from becoming highly sticky, furthermore, it is desired to carry out the polymerization reaction in at least one kind of hydrocarbon solvent selected from aromatic hydrocarbons, aliphatic hydrocarbons and alicyclic hydrocarbons. Preferred examples of the hydrocarbon solvent include aromatic hydrocarbons such as a toluene, a xylene, an ethylbenzene, a mesitylene, a cumene, a cymene or a mixture thereof, or a mixture thereof with aliphatic hydrocarbons such as a pentane, a hexane, a heptane or an octane and/or alicyclic hydrocarbons such as a cyclopentane, a cyclohexane or a methylcyclohexane. During the polymerization, it is desired to adjust the amount of the hydrocarbon solvent so that the initial concentration of monomers in the reaction mixture ranges from 10 to 70% by weight. The polymerization temperature varies depending upon the kinds and amounts of the monomers and the catalyst that are used but should usually range from - 30 to 50°C. The polymerization time is usually from about 0.5 to about 5 hours. Generally, the polymerization is almost all finished in one to two hours. The mode of polymerization may be either the batchwise type or the continuous type. It is further allowable to carry out the multi-stage polymerization. The stickiness-imparting agent (B) of the present invention should have a weight average molecular weight of from 500 to 5000 and, preferably, from 500 to 3000 from the standpoint of obtaining stickiness-retaining property and stickiness, as well as good compatibility to the base polymer (A), good adhesiveness, adhesion-retaining property and tacking property which are well balanced. According to the present invention, furthermore, the stickiness-imparting resin (B) should have a softening point of from 60 to 180°C from the standpoint of markedly improving the heat resistance of the adhesive agent and facilitating the production. The ratio of blending the base polymer (A) and the stickiness-imparting resin (B) in the composition of the present invention is such thai the amount of the stickiness-imparting resin (B) is from 10 to 80 parts by weight while the amount of the base polymer (A) is from 10 to 80 parts by weight and, preferably, that the amount of the stickiness-imparting resin (B) is from 20 to 70 parts by weight while the amount of the base polymer (A) is from 20 to 70 parts weight. The weight ratio of A to B is, for example, from 5/2 to 2/5 and particularly 1/2, 1/1 or 2.5/1. As required, furthermore, the composition of the present invention can be blended with a variety of additives in addition to the base polymer (A) and the stickiness-imparting resin (B). In order to decrease the melt viscosity of the composition of the present invention to improve operability, for instance, the composition of the present invention may be blended with waxes. Examples of the wax that can be used include natural products such as a paraffin wax or a microcrystalline wax; synthetic products such as a petroleum-type wax or SASOL wax; synthetic products such as a coal-type wax, a polyethylene wax or a polypropylene wax; and a petroleum-type polyolefin wax. As required, furthermore, the synthetic petroleum-type polyolefin wax can be used being modified. The composition of the present invention may further be blended with components such as an aliphatic hydrogenated tackifier, a rosin, a modified rosin or an esterified product thereof, an aliphatic petroleum resin, an alicyclic petroleum resin, an aromatic petroleum resin, a copolymerized petroleum resin of an aliphatic component and an aromatic component, a low-molecular styrene-type resin, an isoprene-type resin, an alkylphenol resin, a terpene resin, a cumarone, or an indene resin. As required, furthermore, the composition of the present invention can be blended with a variety of blending agents such as a softening agent, a stabilizer, a filler, an antioxidizing agent and the like within a range that does not impair the object of the present invention. The composition of the present invention is prepared by feeding the base polymer (A), the stickiness-imparting resin (B) and, as required, the aforementioned components at a predetermined blending ratio to a mixing machine such as the Brabender, melting and mixing them together while being heated, and molding the mixture into a desired shape such as granules, flakes or rods. The composition of the present invention is melted by heating and is applied onto a material such as cloth, craft paper, aluminum foil or polyester film to form the layer of an adhesive agent which is then put into use. The composition of the present invention can further be used for instance as a hot-melt adhesive agent a printing ink or a resin for paint. [Examples] Examples of the invention are described below to more concretely illustrate the invention. Synthesis of stickiness-imparting resin. (Reference Examples 1 to 6) In all of these Examples, an autoclave equipped with stirrer vanes and having a real content of 1270 ml was continuously served with an isopropenyltoluene, an indene, a dehydrated and refined toluene and a boron trifluoride phenolate complex (phenol, 1.6 times equivalent) diluted into 10 times with the dehydrated and refined toluene at ratios as shown in Table 1, so that the total amount of the isopropenyltoluene and the indene was 1.0 1/hr, and the polymerization reaction was carried out at a reaction temperature of 5°C. The reaction mixture was then shifted to an autoclave of the second stage to continue the polymerization reaction at 5°C. When the total residence time in the autoclaves of the first and second stages has reached two hours, the reaction mixture was continuously discharged, and the polymerization reaction was finished when three times the residence time has passed. After the polymerization, a 1N NaOH aqueous solution was added to the reaction mixture to stop the polymerization reaction. The obtained reaction mixture was washed 5 times with large amounts of water. Then, the solvent and the unreacted monomer were distilled off in an evaporator under a reduced pressure to obtain an isopropenyltoluene/indene copolymer. The polymerization conditions (monomer feeding ratio, amount of catalyst, resin composition, yield) were as shown in Table 1. Properties (hue, softening point, molecular weight Mw, Tg, melt viscosity) of the obtained isopropenyltoluene/indene copolymer resin were measured in compliance with the methods described below. The results were as shown in Table 2. Hue: The Gardner number was measured in compliance with JIS K 5400. Softening point: Measured based on the ring and ball method in compliance with JIS K 2207. Weight average molecular weight: Measured by using a gel permeation chromatography under the following conditions. Solvent: THF Temperature: 40°C Column: manufactured by Toso Co., TSK gel G7000HXL, TSK gel G4000HXL, two columns, TSK gel G2000HXL, TSK guard column HXL. Tg: Measured by using DSC in compliance with ASTM D3418-75. Melt viscosity: Measured by using an EMILA viscometer. (Reference Example 7) An autoclave equipped with stirrer vanes and having a real content of 1270 ml was continuously served with an isopropenyltoluene, a dehydrated and refined toluene and a boron trifluoride phenolate complex (phenol, 1.6 times equivalent) diluted into 10 times with the dehydrated and refined toluene at ratios as shown in Table 1, so that the amount of the isopropenyltoluene that was fed was 1.0 l/hr, and the polymerization reaction was carried out at a reaction temperature of 5°C. The reaction mixture was then shifted to an autoclave of the second stage to continue the polymerization reaction at 5°C. When the total residence time in the autoclaves of the first and second stages has reached two hours, the reaction mixture was continuously discharged, and the polymerization reaction was finished when three times the residence time has passed. After the polymerization, a 1N NaOH aqueous solution was added to the reaction mixture to stop the polymerization reaction. The obtained reaction mixture was washed 5 times with large amounts of water. Then, the solvent and the unreacted monomer were distilled off in an evaporator under a reduced pressure to obtain an isopropenyltoluene homopolymer. The polymerization conditions (monomer feeding ratio, amount of catalyst, resin composition, yield) were as shown in Table 1. Properties (hue, softening point, molecular weight Mw, Tg) of the obtained isopropenyltoluene homopolymer resin were measured. The results were as shown in Table 2. (Reference Example 8) An autoclave equipped with stirrer vanes and having a real content of 1270 ml was continuously served with an isopropenyltoluene, an indene, a dehydrated and refined toluene and a boron trifluoride phenolate complex (phenol, 1.6 times equivalent) diluted into 10 times with the dehydrated and refined toluene at ratios as shown in Table 1, so that the total amount of the isopropenyltoluene and the indene was 1.0 l/hr, and the polymerization reaction was carried out at a reaction temperature of 0°C. The reaction mixture was then shifted to an autoclave of the second stage to continue the polymerization reaction at 0°C. When the total residence time in the autoclaves of the first and second stages has reached two hours, the reaction mixture was continuously discharged, and the polymerization reaction was finished when three times the residence time has passed. After the polymerization, a 1N NaOH aqueous solution was added to the reaction mixture to stop the polymerization reaction. The obtained reaction mixture was washed 5 times with large amounts of water. Then, the solvent and the unreacted monomer were distilled off in an evaporator under a reduced pressure to obtain an isopropenyltoluene/indene copolymer. The polymerization conditions (monomer feeding ratio, amount of catalyst, resin composition, yield) were as shown in Table 1. Properties (hue, softening point, molecular weight Mw, Tg) of the obtained isopropenyltoluene/indene copolymer resin were measured. The results were as shown in Table 2. Softening point (° C) Hue ( ) Tg (° C) Molecular weight Mn Mw Mw/Mn Reference Example 1 91.7 < 1 684 980 1.43 Reference Example 2 99.7 < 1 710 1135 1.59 Reference Example 3 118.3 < 1 995 1610 1.62 Reference Example 4 131.3 < 1 64.3 974 1574 1.62 Reference Example 5 134.4 < 1 865 1542 1.78 Reference Example 6 151.6 < 1 78.3 1300 2105 1.63 Reference Example 7 119.8 < 1 55.8 967 1491 1.54 Reference Example 8 155.0 < 1 93.0 2610 6470 2.47 (Examples 1 to 7) In these Examples, a hydrogenated product of a styrene-butadiene-styrene triblock copolymer (Crayton G-1657, produced by Shell Co.) as a base polymer and the isopropenyltoluene/indene copolymers obtained in Reference Examples 1 to 6 as stickiness-imparting resins were blended at ratios shown in Table 3, and were kneaded in a LABO PLASTOMILL at 180°C for 15 minutes to obtain a hot-melt adhesive composition. The obtained hot-melt adhesive composition was applied onto an aluminum foil (50 µm) into a thickness of 25 µm. The thus applied surfaces were then stuck to each other and were heat-sealed under the heating conditions of an upper bar at 120°C, a lower bar at 120°C, 3 kg/cm 2 for 10 seconds. The aluminum foil was then cut into 25 mm in width to prepare adhesion samples. The adhesion samples were put to the T-type peeling test at a measuring temperature of 0°C to 80°C to measure the adhesion strength (tension speed: 300 mm/min). A load of 500 g was applied to the adhesion samples, and a temperature at which the load fall was measured in an atmosphere in which the temperature was raised at a rate of 25°C/hr in order to measure the heat-resistant creeping property. The blending ratios of the base polymer and the stickiness-imparting resin, and the melt viscosities of the adhesive agents were as shown in Table 3, and the adhesion strengths and the heat-resistant creeping properties as measured were as shown in Table 4. (Comparative Example 1) Compositions were prepared in the same manner as in Examples 1 to 7 with the exception of using Alcon P-100 (produced by Arakawa Kagaku Kogyo Co.) which is a product placed in the market instead of using the stickiness-imparting resins prepared in Reference Examples 1 to 6, and the adhesion samples were prepared in order to carry out the adhesion tests and to measure the heat-resistant creeping properties. The blending ratios of the used base polymers and the stickiness-imparting resins, and the melt viscosities of the adhesive agents were as shown in Table 3, and the adhesion strengths and the heat-resistant creeping properties as measured were as shown in Table 4. (Comparative Examples 2, 3) In these examples, the compositions were prepared in the same manner as in Examples 1 to 7 with the exception of using the stickiness-imparting resins of Reference Example 7 or 8 instead of the stickiness-imparting resin prepared in Reference Examples 1 to 6, and the adhesion samples were prepared in order to carry out the adhesion tests and to measure the heat-resistant creeping properties. The blending ratios of the used base polymers and the stickiness-imparting resins, and the melt viscosities of the adhesive agents were as shown in Table 3, and the adhesion strengths and the heat-resistant creeping properties as measured were as shown in Table 4. Blending ratio (by weight) Compatibility Melt viscosity (cps) 180° C 200° C Example 1 G-1657/Ref.Exam.2 = 1/2 ○ 63000 45000 Example 2 G-1657/Ref.Exam.4 = 1/2 Δ 335000 160000 Example 3 G-1657/Ref.Exam.6 = 1/2 Δ > 10 6 410000 Example 4 G-1657/Ref.Exam.4/ Alcon P-100 = 1/1/1 ○ 183000 55000 Example 5 G-1657/Ref.Exam.6/ Alcon P-100 = 1/1/1 Δ 335000 84000 Example 6 G-1657/Ref.Exam.4/ Alcon P-100=1/0.4/1.6 ○ 57500 28300 Example 7 G-1657/Ref.Exam.6/ Alcon P-100=1/0.4/1.6 ○ 70500 33000 Comp. Exam. 1 G-1657/Alcon P-100 = 1/2 ○ 48000 25000 Comp. Exam. 2 G-1657/Ref.Exam.7 = 1/2 Δ 115000 45000 Comp. Exam. 3 G-1657/Ref.Exam.8 = 1/2 × > 10 6 800000 Ref.Exam. : the sample of Reference Example Comp.Exam.: the sample pf Comparative Example Note: Alcon P-100 is a hydrogenated petroleum resin which comprises a fraction with 9 carbon atoms of distillate as a chief component (produced by Arakawa Kagaku Kogyo Co., commercially available). ○ :good, Δ :fair, × :bad Adhesion strength (g/25mm) 0° C 20° C 40° C 60° C 80° C Heat-resistant creeping property (° C) Exam. 1 500 550 500 400 50 115.0 Exam. 2 480 530 680 470 60 122.1 Exam. 3 520 630 550 440 50 136.5 Exam. 4 730 1500 2120 1320 440 114.9 Exam. 5 1090 1660 1940 2300 880 127.4 Exam. 6 910 1660 2690 2390 1890 98.3 Exam. 7 720 1750 6000 6350 240 104.3 Comp.Ex.1 200 280 1380 1350 720 82.0 Comp.Ex.2 490 730 690 160 60 116.2 Comp.Ex.3 390 370 270 40 10 128.0

Claims: A hot-melt adhesive composition which comprises 10 to 80 parts by weight of a base polymer (A), 10 to 80 parts by weight of a stickiness-imparting agent (B) which is a copolymer of at least one styrene-type monomer of formula (I): wherein R 1 , R 2 , R 3 and R 4 are hydrogen atoms or alkyl groups with 4 or less carbon atoms, which may be the same or different; and at least one indene-type monomer of formula (II) wherein R 5 , R 6 and R 7 are hydrogen atoms or straight-chain, branched or cyclic alkyl groups with 6 or less carbon atoms, which may be the same or different, the molar ratio of the monomers (I)/(II) being from 99/1 to 30/70 and the weight average molecular weight of the copolymer being from 500 to 5000; and optionally a petroleum refining or cracking C 4 to C 5 distillate fraction. A hot-melt adhesive composition according to claim 1, wherein base polymer (A) is a copolymer of a vinyl aromatic compound and a conjugated diene compound, or is a hydrogenated product thereof. A hot-melt adhesive composition according to claim 2, wherein the base polymer (A) comprises at least one polymer selected from butadiene/polystyrene block copolymers, polystyrene/polyisoprene block copolymers, polystyrene/polyisoprene/polystyrene triblock copolymers, polystyrene/polybutadiene/polystyrene triblock copolymers, poly(α-methylstyrene)/polybutadiene/poly(α-methylstyrene) triblock copolymers and hydrogenated products of these polymers. A hot-melt adhesive composition according to claim 3, wherein the base polymer (A) is a hydrogenated product of a polystyrene/polybutadiene/polystyrene triblock copolymer. A hot-melt adhesive composition according to any one of claims 1 to 4 wherein the or each monomer of formula (I) is a styrene, a vinyltoluene, an α-methylstyrene, or an isopropenyltoluene. A hot-melt adhesive composition according to claim 5, wherein the monomer of formula (I) is an isopropenyltoluene. A hot-melt adhesive composition according to any of claims 1 to 6 wherein the or each monomer of formula (II) is an indene, a methylindene and an ethylindene. A hot-melt adhesive composition according to claim 7, wherein the monomer of formula (II) is an indene. A hot-melt adhesive composition according to any one of claims 1 to 8 wherein the resin (B) is an isopropenyltoluene/indene copolymer. A hot-melt adhesive composition according to any one of claims 1 to 8 wherein the resin (B) is obtainable by copolymerizing at least one styrene-type monomer of formula (I): wherein R 1 , R 2 , R 3 and R 4 are hydrogen atoms or alkyl groups with 4 or less carbon atoms, which may be the same or different; at least one indene-type monomer of formula (II) wherein R 5 , R 6 and R 7 are hydrogen atoms or straight-chain, branched or cyclic alkyl groups with 6 or less carbon atoms, which may be the same or different, in a molar ratio of 99/1 to 30/70; the weight average molecular weight of the copolymer being from 500 to 5,000; and optionally a petroleum refining or cracking C 4 to C 5 distillate fraction. A hot-melt adhesive composition according to claim 10, wherein the distillate fraction represents less than 20 mol% of the total resin (B). A hot-melt adhesive composition according to any one of claims 1 to 11 wherein the weight of the ratio of A to B is from 5/2 to 2/5, particularly 1/2, 1/1 or 2.5/1. A process for the production of a hot-melt adhesive composition according to any one of the preceding claims, which process comprises: (a) copolymerising at least one styrene-type monomer of formula (I): wherein R 1 , R 2 , R 3 and R 4 are hydrogen atoms or alkyl groups with 4 or less carbon atoms, which may be the same or different; at least one indene-type monomer of formula (II) wherein R 5 , R 6 and R 7 are hydrogen atoms or straight-chain, branched or cyclic alkyl groups with 6 or less carbon atoms, which may be the same or different; in a molar ratic of 99/1 to 30/70; and optionally a petroleum refining or cracking C 4 to C 5 distillate fraction to obtain a copolymerised composition (B) having a weight average molecular weight of 500 to 5,000, which is a stickiness-imparting resin; (b) kneading the copolymerised composition (B) with a base polymer (A) to obtain a hot-melt adhesive composition. Use of a composition according to any one of claims 1 to 12 or obtainable by the process of claim 13 as a hot-melt adhesive.

Inventors: INAGAKI HAJIME, KUROIWA TOSHIAKI, MURO TUNEAKI, TOKITA SUGURU, INAGAKI, HAJIME, KUROIWA, TOSHIAKI, MURO, TUNEAKI, TOKITA, SUGURU, INAGAKI, HAJIME, C/O MITSUI PETROCHEMICAL, KUROIWA, TOSHIAKI, C/O MITSUI PETROCHEMICAL, MURO, TUNEAKI, C/O MITSUI PETROCHEMICAL, TOKITA, SUGURU, C/O MITSUI PETROCHEMICAL
Applicants: MITSUI CHEMICALS INC, MITSUI CHEMICALS, INC.
Application year: 1993
Main classification: C09J125
IPC codes: C08F212, C09J125, C09J137, C08F232, C08F32, C08L53, C08L101, C08F234, C09J145