Process for the preparation of thermoplastic elastomer compositions

Abstract: A partially crosslinked thermoplastic elastomer composition having an excellent heat-bondability is obtained by dynamically heat-treating a peroxide-­ crosslinking olefin copolymer rubber with an α,β-­ unsaturated carboxylic acid or a derivative thereof in the presence of an organic peroxide.

Description: The present invention relates to the production of thermoplastic elastomer compositions having excellent heat-bondability to various resins and metals and having a high rubbery elasticity, a good moldability and a high heat resistance. More particularly, the present invention relates to the production of partially crosslinked thermoplastic elastomers, which are formed by dynamically heat-treating a peroxide-crosslinking olefin copolymer rubber with an unsaturated carboxylic acid or a derivative thereof in the presence of an organic peroxide. Thermoplastic elastomers are known as energy-saving and resource-saving substitutes for cured rubbers. As the thermoplastic elastomer of this type, there is known, for example, an olefinic thermoplastic elastomer comprising as the main component an ethylene/propylene/non-conjugated diene copolymer rubber. This thermoplastic elastomer is excellent in thermoplastic elastomer performances, but since the bondability to various resins or metals is insufficient, the application range of this thermoplastic elastomer is considerably limited. Graft modification of the above-mentioned rubber component with maleic anhydride or the like has been tried for improving the bondability. In this case, the bondability is improved, but such a disadvantage as reduction of the rubbery elasticity, the moldability and the like cannot be avoided. Thus a thermoplastic elastomer which has excellent properties such as rubbery elasticity and moldability and has an excellent bondability to various resins and metals has not been known. We made research with a view to developing a thermoplastic elastomer being excellent in not only such properties as rubbery elasticity and moldability but also bondability to various resins and metals. As the result, we have now completed the present invention. More specifically, in accordance with one aspect of the present invention, there is provided a process for producing a thermoplastic elastomer composition comprising the steps of blending 10 to 95 parts by weight of an ethylene/propylene/non-conjugated diene copolymer rubber (a), 5 to 90 parts by weight of an olefinic plastic (b), the sum of the amounts of the components (a) and (b) being 100 parts by weight, and (c) 0.01 to 5 parts by weight of an unsaturated carboxylic acid or a derivative thereof and, using an extruder, dynamically heat-treating the blend at a temperature of 170 to 240°C in the presence of 0.1 to 1% by weight, based on the total weight of components (a), (b) and (c), of an organic peroxide to effect partial crosslinking. In accordance with another aspect of the present invention, said blend further comprises at least one additive selected from the group consisting of (d) 0 to 100 parts by weight of a peroxide-non-crosslinking rubbery substance, (e) 0 to 200 parts by weight of a mineral oil type softener and (f) 0 to 100 parts by weight of a fibrous filler, per 100 parts by weight of the sum of the amounts of the components (a) and (b). In accordance with still another aspect of the present invention, the fibrous filler (f) is incorporated after partial crosslinking. Furthermore, the present invention includes an embodiment in which a polyolefin plastic is blended in the above-mentioned thermoplastic elastomer composition. The thermoplastic elastomer composition produced in accordance with the present invention has excellent properties such as rubbery elasticity and moldability and also bondability to various resins and metals, and if additive substances as described above are incorporated before or after the dynamic heat treatment, these characteristics are further improved. In accordance with the present invention, the peroxide-crosslinking olefin copolymer rubber (a) is a component imparting a rubbery elasticity, and since the component (a) is partially crosslinked, it ensures a high heat resistance. The olefinic plastic (b) is a component imparting a flowability at an elevated temperature, and by dint of the presence of this component, a predetermined moldability is retained in the thermoplastic elastomer composition. The unsaturated carboxylic acid or derivative thereof such as maleic anhydride as the component (c) is a modifier which imparts a good bondability to various resins and metals to the thermoplastic elastomer composition. According to the present invention, by the actions of the respective components, the rubbery elasticity, heat resistance and moldability can be maintained at predetermined levels and the bondability to various resins and metals can be highly improved. In the preferred embodiment of the present invention, the peroxide-non-crosslinking rubbery substance (d) and the mineral oil softener (e) act as the flowability improver for the rubber component, and the moldability and processability of the composition of the present invention can be improved. Furthermore, the fibrous filler (f) imparts a good dimension stability (low linear expansion coefficient) and a good shape stability (appropriate rigidity) to the composition, and the olefinic plastic to be incorporated into the thermoplastic elastomer after partial crosslinking acts especially as the agent for improving the heat resistance and flowability. In this preferred embodiment, since the olefinic plastic is incorporated after the dynamic heat treatment of the rubber component, the plastic hardly undergoes degradation or crosslinking by the organic peroxide, and as compared with the case where the plastic is incorporated before the dynamic heat treatment, the characteristics of the polyolefin such as high heat resistance and high flowability are strongly reflected on the thermoplastic elastomer composition. The respective components of the thermoplastic elastomer composition of the present invention will now be described. (a) Peroxide-crosslinking olefin copolymer rubber The peroxide-crosslinking olefin copolymer rubber used in the present invention is an ethylene/propylene/non-conjugated diene rubber having such a property that if the rubber is mixed with an organic peroxide and kneaded under heating, the flowability is reduced or lost. As the non-conjugated diene, there can be mentioned dicyclopentadiene, 1,4-hexadiene, dicyclooctadiene, methylene-norbornene and 5-ethylidene-2-norbornene. Of these copolymer rubbers, an ethylene/propylene/nonconjugated diene rubber is preferably used in which the molar ratio between ethylene units and propylene units (ethylene/propylene molar ratio) is from 50/50 to 90/10, especially from 55/45 to 85/15, is preferred. An ethylene/propylene/non-conjugated diene copolymer rubber, particularly an ethylene/propylene/5-ethylidene-2-norbornene copolymer rubber or an ethylene/propylene/5-ethylidene-2-norbornene/dicyclopentadiene quadripolymer, is especially preferred because an thermoplastic elastomer excellent in heat resistance, tensile characteristics and repulsion elasticity can be obtained. In order to obtain a composition excellent in the tensile characteristics and flowability, it is preferred that the Mooney viscosity ML₁+₄ (100°C) of the copolymer rubber be 10 to 120, especially 40 to 80. It also is preferred that the iodine value (unsaturation degree) of the copolymer rubber be smaller than 16. If this requirement is satisfied, a thermoplastic elastomer which is well-balanced between the flowability and the rubbery properties can be obtained. (b) Olefinic plastic The olefinic plastic as the component (b) is a crystal line high-molecular-weight solid product obtained by polymerizing at least one mono-olefin according to the high-pressure method or low-pressure method. For example, there can be mentioned isotactic and syndiotactic mono-olefin homopolymer and copolymer resins, and typical mono-olefin polymer resins are commercially available. As preferred examples of mono-olefin, there can be mentioned ethylene, 1-butene, 1-pentene, 1-hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene and 5-methyl-1-hexene. In the present invention, a peroxide-decomposing olefinic plastic and polyethylene are especially preferred as the olefinic plastic. By the peroxide-decomposing olefinic plastic is meant an olefinic plastic having such a property that if the olefinic plastic is mixed with a peroxide and kneaded under heating, the molecular weight is decrease by thermal decomposition and the flowability of the resin is increased. For example, there can be mentioned isotactic polypropylene and copolymers of propylene with a minor amount of other α-olefin, such as a propylene/ethylene copolymer, a propylene/1-hexene copolymer and a propylene/4-methyl-1-pentene copolymer. It is preferred that the melt index (ASTM D-1238-65T, 230°C) of the incorporated olefinic plastic be 0.1 to 50, especially 5 to 20. In the present invention, the olefinic plastic exerts the effects of improving the flowability and heat resistance of the composition. (c) Unsaturated carboxylic acid or derivative thereof In the present invention, as the unsaturated carboxylic acid or derivative thereof as the component (c), there can be used α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid and tetrahydrophthalic acid, unsaturated carboxylic acids such as bicyclo 2,2,1 hept-2-ene-5,6-dicarboxylic acid, α,β-unsaturated carboxylic anhydrides such as maleic anhydride, itaconic anhydride, citraconic anhydride and tetrahydrophthalic anhydride, unsaturated carboxylic anhydrides such as bicyclo(2,2,1)hept-2-ene-5,6-dicarboxylic anhydride, and unsaturated carboxylic acid esters such as methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconate, dimethyl tetrahydrophthalate and dimethyl bicyclo(2,2,1)hept-2-ene-5,6-dicarboxylate. Of these compounds, maleic acid, bicyclo (2,2,1)hept-2-ene-5,6-dicarboxylic acid and anhydrides thereof are preferred. The component (c) acts as a grafting modifier and improves the bondability. Other additives The present invention includes an embodiment in which at least one additive selected from the group consisting of (d) a peroxide-non-crosslinking rubbery substance, (e) a mineral oil type softener and (f) a fibrous filler is used in addition to the above-mentioned components (a) through (c). A hydrocarbon type rubbery substance (d) having such a property that even if the rubbery substance is mixed with a peroxide and kneaded under heating, the rubbery substance is not crosslinked and the flowability is not reduced is used as the peroxide-non-crosslinking rubbery substance. For example, there can be mentioned polyisobutylene, butyl rubber (IIR), a propylene/ethylene copolymer rubber having a propylene content of at least 70 mole% and atactic polypropylene. In view of the performance and the handling easiness, polyisobutylene and butyl rubber (IIR) are especially preferred as the component (d). The component (d) exerts a function of improving the flowability and the permanent set of the elastomer composition. It is preferred that the Mooney viscosity of the component (d) be lower than 60. The mineral oil type softener as the component (e) is a high-boiling-point petroleum fraction ordinarily used for weakening the intermolecular force of a rubber in roll processing of the rubber to facilitate the processing, assisting the dispersion of carbon black or white carbon incorporated as the filler, or reducing the hardness of a cured rubber to increase the softness and elasticity, and this fraction includes a paraffin type, a naphthene type and an aromatic type. The fibrous filler (f) preferably has a diameter of 0.1 to 15 µm and a length of 5 to 10 µm. As specific examples, there can be mentioned glass fiber (chopped strand, roving milled glass fiber and glass flake), wollastonite, cut fiber, rock fiber, micro fiber, processed mineral fiber, carbon fiber, gypsum fiber, aromatic polyamide fiber and potassium titanate fiber. Of these fillers, milled glass fiber, glass flake and potassium titanate fiber are preferred. In order to further improve the wettability with the thermoplastic elastomer, it is preferred that the fibrous filler be treated with a silane type, chromium type or titanium type coupling agent. The fibrous filler can also be incorporated before the partial crosslinking but the fibrous filler can also be incorporated at the grafting step or the subsequent step. In the present invention, a polyolefin plastic can be incorporated into the thermoplastic elastomer composition after the partial crosslinking. It is preferred that the polyolefin plastic be incorporated in such an amount that the polyolefin plastic/thermoplastic elastomer composition weight ratio is from 0/100 to 75/25. Namely, it is preferred that the polyolefin plastic be incorporated in an amount of up to 300 parts by weight, especially up to 200 parts by weight, per 100 parts by weight of the thermoplastic elastomer composition. As the polyolefin plastic to be incorporated into the thermoplastic elastomer composition, there can be mentioned, for example, known high-density, medium-density and low-density polyethylenes, isotactic polypropylene and copolymers of propylene with other α-olefin, such as a propylene/ethylene copolymer, a propylene/1-butene copolymer, a propylene/1-hexene copolymer and a propylene/4-methyl-1-pentene copolymer. It is preferred that the melt index (ASTM D-1238-65T, 230°C) of the incorporated olefinic plastic be 0.1 to 50, preferably 5 to 20. In the present invention, the olefinic plastic exerts the effects of improving the flowability and heat resistance of the composition. Preparation of elastomer composition According to the present invention, the thermoplastic elastomer composition is prepared by blending (a) 10 to 95 parts by weight, preferably 40 to 95 parts by weight, of the peroxide-crosslinking olefin copolymer rubber, (b) 5 to 90 parts by weight, preferably 5 to 60 parts by weight, of the olefinic plastic the sum of the amounts of the components (a) and (b) is 100 parts by weight and (c) 0.01 to 5 parts by weight of the α,β-unsaturated carboxylic acid or derivative thereof and dynamically heat-treating the blend in the presence of an organic peroxide to effect partial crosslinking. According to another preferred embodiment of the present invention, the thermoplastic elastomer composition is prepared by blending the above-mentioned components (a), (b) and (c) and at least one additive selected from the group consisting of (d) 0 to 100 parts by weight, preferably 5 to 100 parts by weight, especially preferably 5 to 50 parts by weight, of the peroxide-non-crosslinking rubbery substance, (e) 0 to 200 parts by weight, preferably 3 to 100 parts by weight, especially preferably 3 to 80 parts by weight, of the mineral oil type softener and (f) 0 to 100 parts by weight, preferably 0.1 to 100 parts by weight, especially preferably 4 to 35 parts by weight, of the fibrous filler and dynamically heat-treating the blend in the presence of an organic peroxide to effect partial crosslinking. If the copolymer rubber component (a) is used in an amount within the above-mentioned range, a composition excellent in rubbery characteristics such as rubbery elasticity and moldability can be obtained. If the olefinic plastic (b) is incorporated in an amount within the above-mentioned range, a composition excellent in rubbery characteristics such as rubbery elasticity, and flowability and moldability can be obtained. The moldability and heat bondability can be improved if the unsaturated carboxylic acid or derivative thereof (c) is used in an amount within the above-mentioned range. If the components (d) and (e) are used in amounts within the above-mentioned ranges, the rubbery characteristics and moldability can be improved. If the fibrous filler (f) is used in an amount within the above-mentioned range, the flowability, dimension stability and size stability can be improved. A filler or colorant can be incorporated in the elastomer composition, so far as the flowability (moldability), rubbery characteristics and heat bondability of the final composition are not degraded. As the filler, there can be mentioned calcium carbonate, clay kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, molybdenum disulfide, graphite, glass fiber, glass bead, shirasu balloon and carbon fiber, and as the colorant, there can be mentioned carbon black, titanium oxide, zinc flower, red iron oxide, ultramarine, prussian blue, an azo pigment, a nitroso pigment, a lake pigment and a phthalocyanine pigment. Furthermore, in the present invention, known heat stabilizers such as phenol type, sulfite type, phenylalkane type phosphite type and amine type stabilizers, aging-preventing agents, weathering agents, antistatic agents, and lubricants such as metal soaps and waxes can be incorporated in amounts customarily used for olefinic plastics or olefin copolymer rubbers. In the present invention, the blend comprising the above-mentioned components is dynamically heat-treated in the presence of an organic peroxide to effect partial crosslinking. By the dynamic heat treatment is meant kneading in the molten state. As the organic peroxide used in the present invention, there can be mentioned dicumyl peroxide, ditert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexine-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valelate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl perbenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide and tert-butylcumyl peroxide. Of these peroxides, in view of the smell and scorch stability, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexine-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane and n-butyl-4,4-bis(tert-butylperoxy)valelate are preferred, and 1,3-bis(tert-butylperoxyisopropyl)benzene is most preferred. The organic peroxide is incorporated in an amount of 0.1 to 1% by weight, based on the total amount of the components (a), (b) and (c). If the organic peroxide is incorporated in an amount within the above-mentioned range, the heat resistance, the tensile characteristics, the rubbery characteristics such as elastic recovery and repulsion elasticity, and the strength are highly improved. In the present invention, at the partial crosslinking treatment with the organic peroxide, there can be used peroxy-crosslinking assistants such as p-quinone dioxime, p,p'-dibenzoylquinone dioxime, N-methyl-N,N-dinitrosoaniline, nitrobenzene, diphenylguanidine, trimethylolpropane-N,N'-m-phenylene maleimide and N-methyl-N,N'-m-phenylene dimaleimide, divinylbenzene, triallyl isocyanurate, polyfunctional methacrylate monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate and allyl methacrylate, and polyfunctional vinyl monomers such as vinyl butyrate and vinyl stearate. It is expected that if such a compound as described above is used, the crosslinking reaction will be advanced uniformly and mildly. In the present invention, especially, if divinylbenzene is used, since divinylbenzene is easy to handle, has a good compartibility with the olefinic plastic as the main component to be treated and acts as a dispersing agent for the organic peroxide by its organic peroxide-solubilizing action, a uniform crosslinking effect is attained by the heat treatment and a composition which is well-balanced between the flowability and the physical properties can be obtained. Therefore, use of divinylbenzene is most preferred in the present invention. In the present invention, it is preferred that the above-mentioned crosslinking agent or polyfunctional vinyl monomer be incorporated in an amount of 0.1 to 2% by weight, especially 0.3 to 1% by weight, based on the total amount of the components to be treated. If the crosslinking assistant or polyfunctional vinyl monomer is incorporated in an amount within the above-mentioned range, the flowability of the composition is improved, and even if the composition undergoes heat history, the physical properties are not changed. A decomposition promotor may be incorporated so as to promote decomposition of the organic peroxide. As the decomposition promotor, there can be mentioned tertiary amines such as triethylamine, tributylamine and 2,4,6-tris(di-methylamino)phenol, and naphthenic acid salts of metals such as aluminum, cobalt, vanadium, manganese, magnesium, lead and mercury. It is preferred that kneading be carried out in a closed apparatus in an atmosphere of an inert gas such as nitrogen or carbon dioxide gas. The kneading temperature is such that the half-value period of the used organic peroxide is shorter than 1 minute. More specifically, the kneading temperature is 170 to 240°C. The kneading time is ordinarily 1 to 20 minutes and preferably 1 to 10 minutes. The shearing force is selected so that the shearing speed is ordinarily 10 to 10⁴ sec⁻¹ and preferably 10² to 10³ sec⁻¹. As extruder, there can be mentioned a monoaxial and biaxial extruders. According to the present invention, by the dynamic heat treatment in the presence of the organic peroxide, partial crosslinking is effected and a thermoplastic elastomer composition graft-modified with maleic anhydride or the like is obtained. For example, as is shown in the examples given hereinafter, it is understood that the M value indicating the maleic anhydride content is increased in the composition of the present invention. Incidentally, In the present invention, by the term "partial crosslinking", it is meant that the gel content is at least 20%, preferably 20 to 99.5%, especially preferably 45 to 98%, as determined according to the following method. Method for determination of gel content About 100 mg of a sample of a thermoplastic elastomer is weighed and cut into small pieces having a size of 0.5mm x 0.5mm x 0.5mm, and the cut pieces are immersed in 30 mℓ of cyclohexane at 23°C for 48 hours in a sealed vessel. Then, the sample is recovered on a filler paper and dried at room temperature for more than 72 hours until the weight is not changed any more. The weight of the cyclohexane-insoluble components except the polymer component (for example, fibrous filler, filler, pigment and the like) and the weight of the olefinic plastic in the sample before immersion in cyclohexane are subtracted from the weight of the drying residue. The obtained value is designated as "collected final weight (Y)". The weight of the peroxide-crosslinking olefin copolymer in the sample (namely, the value obtained by subtracting 1 ○ the weight of olefinic plastic and 2 ○ the weight of the cyclohexane-soluble components other than the peroxide-crosslinking olefin copolymer rubber (for example, mineral oil and plasticizer) and 3 ○ the weight of the cyclohexane-insoluble components other than the polymer component (for example, fibrous filler, filler, pigment and the like) from the weight of the sample) is designated as "corrected initial weight (X)". The gel content is calculated according to the following formula: In the present invention, by dynamically heat-treating a blend comprising at specific ratios (a) a peroxide-crosslinking olefin copolymer rubber, (b) an olefinic plastic and (c) an unsaturated carboxylic acid or a derivative thereof, optionally together with (d) a peroxide-non-crosslinking rubbery substance, (e) a mineral oil type softner and (f) a fibrous filler, in the presence of an organic peroxide to effect partial crosslinking, (that is, the gel content is within the above-mentioned range), there can be obtained a composition which is excellent in rubbery characteristics, moldability, bondability to resins and metals, strength, heat resistance and softness. The composition of the present invention is particularly excellent in heat resistance over the mere blend (uncrosslinked blend) of the components (a), (b) and (c) or the mere blend (uncrosslinked blend) of the peroxide-crosslinked olefin copolymer rubber component (a) graft-modified with and unsaturated carboxylic acid component and the olefinic plastic component (b). The effect of improving the flowability by incorporation of the components (d) and (e) is especially conspicuous when the gel content is in the above-mentioned range. The so-obtained thermoplastic elastomer composition of the present invention is excellent in the moldability and can be molded by a molding apparatus customarily used for molding ordinary thermoplastic plastics, and the composition of the present invention is suitable for extrusion molding, calender molding, injection molding and the like. Furthermore, by incorporation of an unsaturated carboxylic acid or derivative thereof such as maleic anhydride, the polymer component is graft-modified, and therefore, as is apparent from the examples given hereinafter, the heat-bondability to various resin and metals is prominently improved and the composition of the present invention is suitably used for formation of laminates or covering of metals. The present invention will now be described in detail with reference to the following examples that by no means limit the scope of the invention. Molding conditions for preparing test samples from elastomer compositions prepared in the examples and test methods are described below. (1) Injection molding Molding machine: Dynamelter (supplied by Meiki Seisakusho) Molding temperature: 220°C Injection pressure: primary pressure of 1000 kg/cm² and secondary pressure of 700 kg/cm² Injection speed adopted: maximum Molding speed: 90 sec/cycle Gate: direct gate (land length of 10 mm, width of 10 mm and thickness of 3 mm) Molded product: length of 150 mm, width of 120 mm and thickness of 3 mm (2) Extrusion molding T-die sheets were prepared by extrusion molding under the following conditions. Molding machine: extruder having a diameter of 40 mm (supplied by Toshiba Kikai) Screw: full-flight type (L/D = 28, CR = 3.5) Screen pack: 80 mesh x 2 sheets Molding temperature: 160°C on hopper side and 210°C on die side Die lip: 1.5 mm Take-up speed: 5 m/min (3) Basic properties Test pieces were cut out from square plates having a thickness of 3 mm, which were obtained by injection molding according to the method described in (1) above, and the basic properties were determined according to the following methods. Tensile characteristics: method of JIS K-6301 M100: stress at 100% stretching T B : tensile strength E B : elongation at break Spring hardness (HS): method A of JIS K-6301 or Shore-D method of ASTM D-2240 Initial flexural modulus (FM): method of ASTM D-790 Izod impact strength (Izod): method of ASTM D-256 Permanent elongation (PS): measured by method of JIS K-6301 and expressed by residual elongation at 100% stretching Softening temperature (SP): temperature at which penetration of 0.1 mm was attained by needle having diameter of 0.8 mm under load of 49 g at temperature-elevating rate of 20°C/min in TMA-measuring apparatus supplied by du Pont (4) Bonding strength A. Preparation of test pieces The extrusion sheet (1.0 mm in thickness) of the elastomer composition molded under the conditions described in (2) above and an adhered having a thickness of 0.5 mm were press-molded (mold-clamping pressure of 50 tons) to form a test piece having a size of 150 mm x 150 mm. The following adherends were used. Nylon: nylon 6 supplied by Toray (Amilane CM1021) EVAL: EP-F101A supplied by Kuraray Steel sheet: SS-41 supplied by Nippon Test Panel (sandblasted at surface roughness of 30 microns) B. Peeling test Test piece: punched strip having width of 25 mm and length of 100 mm Test method: 180°, peeling Pulling speed: 25 mm/min Bonding strength: value (kg/cm) obtained by dividing peeling load by width of test piece Incidentally, in the case where the substrate was broken, the sample was indicated by "broken" in the following tables. (5) M value The M value indicating the maleic anhydride content was measured in the following procedures. Unreacted maleic anhydride in W O g of the sample was extracted with acetone for 12 hours by using Soxhlet's extractor. The extraction residue sample was dried and press-molded at 210°C to form a film for the infrared spectrophotometry, having a thickness of about 100 µm. With respect to the so-obtained film, the absorbance attributed to the characteristic absorption band (C=O region) of maleic anhydride was measured by an infrared spectrophotometer, and the content (% by weight) of graft-polymerized maleic anhydride in W O g of the sample was determined based on a calibration curve formed by using a reference sample standarized separately by the titration method. The so-determined maleic anhydride content was designated as the M value. In the present invention the content ratio between the components (a) and (b) in the elastomer composition can be determined by the D.S.C. method or the infrared absorbency analysis method. The contents of the components (d) and (e) in the composition can be determined by the solvent extraction method (Soxhlet extraction method using acetone as the solvent) or the infrared absorbance analysis method. The content ratio of the component (f) to the organic components can be determined by the thermal weight analysis method. The content of the grafted component (c) was measured by the infrared absorbane analysis method or the chemical analysis method. Example 1 A blend comprising 70 parts by weight of an ethylene/propylene/ethylidene-norbornene copolymer rubber having an ethylene content of 70 mole%, an iodine value of 15 and a Mooney viscosity M₁+₄ (100°C) of 120 (hereinafter referred to as "EPDM (1)") and 30 parts by weight of polypropylene having a melt index (ASTM D-1238-65T, 230°C) of 13 and a density of 0.91 g/cm³ (hereinafter referred to as "PP") was kneaded at 190°C for 5 minutes in a nitrogen atmosphere by a Banbury mixer, and the kneaded blend was passed through rolls and square pellets were prepared by a sheet cutter (first step). Then, 100 parts by weight of the so-prepared pellets, 0.5 part by weight of maleic anhydride (hereinafter referred to as "MAH") and 0.3 part by weight of 1,3-bis(t-butylperoxyisopropyl)benzene hereinafter referred to as "peroxide (A)" were stirred and mixed by a Henschel mixer and the blend was extruded at 200°C in a nitrogen atmosphere (second step). The basic properties and bonding strength of the obtained elastomer composition are shown together with those of elastomer compositions obtained in the subsequent examples and comparative examples in Table 1. Example 2 An elastomer composition was prepared in the same manner as described in Example 1 except that at the second step, the amount incorporated of MAH was changed to 1.0 part by weight and 0.5 part of divinylbenzene (hereinafter referred to as "DVB") was further added. Comparative Example 1 A elastomer composition was prepared in the same manner as described in Example 2 except that at the second step, MAH was not incorporated. Comparative Example 2 An elastomer composition was prepared in the same manner as described in Example 2 except that peroxide (A) and DVB were not added. Example 3 By using kneading a Banbury mixer, 50 parts of EPDM (1) and 50 parts of PP were kneaded at 190°C for 5 minutes in a nitrogen atmosphere, and the kneaded blend was passed through rolls and square pellets were formed by using a sheet cutter (first step). Then, 100 parts by weight of the so-prepared pellets, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (A) were stirred and mixed by a Henschel mixer. The blend was extruded at 220°C in a nitrogen atmosphere by an extruder to form an elastomer composition (second step). Example 4 An elastomer composition was prepared in the same manner as described in Example 3 except that at the second step, the amount incorporated of MAH was changed to 1.0 part by weight and DVB was not incorporated. Comparative Example 3 An elastomer composition was prepared in the same manner as described in Example 3 except that at the second step. MAH was not incorporated. Comparative Example 4 An elastomer composition was prepared in the same manner as described in Example 4 except that at the second step, peroxide (A) was not added. Example 5 In a Henschel mixer, 30 parts by weight of the pellets of EPDM (1), 70 parts by weight of PP, 1.0 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of 2,5-dimethyl-2,5-di-(t-butylperoxy)hexine-3 (hereinafter referred to as "peroxide (B)") were stirred and mixed. The blend was extruded at 220°C in a nitrogen atmosphere by a Warner biaxial extruder (L/D = 43, mating type, same direction rotation, three-thread screws) to form an elastomer composition. Comparative Example 5 An elastomer composition was prepared in the same manner as described in Example 5 except that MAH was not incorporated Comparative Example 6 An elastomer composition was prepared in the same manner as described in Example 5 except that DVB and peroxide (B) were not incorporated. Example 6 In a Henschel mixer, 40 parts by weight of the pellets of EPDM (1), 30 parts by weight of PP, 30 parts by weight of linear low-density polyethylene melt index (ASTM D-1238-65T, 190°C) = 2.1, density = 0.92 g/cm³ (hereinafter referred to as "LLDPE"), 0.5 part by weight of MAH and 0.3 part by weight of peroxide (B) were stirred and mixed. The blend was extruded at 200°C in a nitrogen atmosphere by the above-mentioned Warner biaxial extruder to form an elastomer composition. Example 7 An elastomer composition was prepared in the same manner as described in Example 6 except that 0.5 part by weight of DVB was further incorporated. Comparative Example 7 An elastomer composition was prepared in the same manner as described in Example 7 except that MAH was not incorporated. Comparative Example 8 An elastomer composition was prepared in the same manner as described in Example 7 except that DVB and peroxide (B) were not incorporated. Example 8 Square pellets were prepared by kneading 70 parts by weight of EPDM (1), 30 parts by weight of PP, 10 parts by weight of butyl rubber (IIR-065 supplied by Esso, unsaturation degree = 0.8 mole%) (hereinafter referred to as "IIR") and 30 parts by weight of paraffinic process oil (hereinafter referred to "Oil") in the same manner as described in Example 1 (first step). Then, 100 parts by weight of the so-prepared pellets, 0.3 part by weight of MAH, 0.3 part by weight peroxide (A) and 0.3 part by weight of DVB were stirred and mixed by a Henschel mixer, and the blend was extruded at 220°C in a nitrogen atmosphere by using an extruder (second step). The basic properties and bonding strength of the obtained elastomer composition are shown together with those of elastomer compositions prepared in the subsequent examples and comparative examples in Table 2. Example 9 through 11 Elastomer compositions were prepared in the same manner as described in Example 8 except that at the second step the amounts incorporated of MAH and DVB were changed as shown in Table 2. Comparative Example 9 An elastomer composition was prepared in the same manner as described in Example 8 except that at the second step, MAH was not incorporated. Comparative Example 10 An elastomer composition was prepared in the same manner as described in Example 10 except that at the second step, peroxide (A) and DVB were not incorporated. Example 12 By using a Banbury mixer, 50 parts of EPDM (1), 50 parts by weight of PP, 10 parts by weight of IIR and 10 parts by weight of Oil were kneaded at 190°C for 5 minutes in a nitrogen atmosphere, and the blend was passed through rolls and square pellets were prepared by using a sheet cutter (first step). Then, 100 parts by weight of the so-prepared pellets, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (A) were stirred and mixed by a Henschel mixer. Then, the blend was extruded at 220°C in a nitrogen atmosphere by an extruder to prepare an elastomer composition (second step). Example 13 An elastomer composition was prepared in the same manner as described in Example 12 except that at the second step, the amount incorporated of MAH was changed to 1.0 part by weight and DVB was not incorporated. Comparative Example 11 An elastomer composition was prepared in the same manner as described in Example 12 except that at the second step, MAH was not incorporated. Comparative Example 12 An elastomer composition was prepared in the same manner as described in Example 12 except that at the second step, peroxide (A) and DVB were not incorporated. Example 14 In a Henschel mixer, 60 parts by weight of a pelletized ethylene/propylene/ethylidene-norbornene copolymer [ethylene content = 78 mole%, iodine value = 10, Mooney viscosity ML₁+₄ (100°C) = 160, extended oil content = 40% by weight (43 parts by weight of EPDM and 17 parts by weight of oil)) (hereinafter referred to as "EPDM (2)"), 40 parts by weight of PP, 0.5 part by weight of MAH, 0.3 part by weight of peroxide (B) and 0.5 part by weight of DVB were stirred and mixed. Then, the mixture was extruded at 220°C in a nitrogen atmosphere by using a Warner biaxial extruder (L/D = 43, mating type, same direction rotation, three-thread screws) to obtain a thermoplastic elastomer composition. Example 15 An elastomer composition was prepared in the same manner as described in Example 14 except that the amount incorporated of MAH was changed to 1.0 part by weight and DVB was not incorporated. Comparative Example 13 An elastomer composition was prepared in the same manner as described in Example 14 except that MAH was not incorporated. Example 16 In a Henschel mixer, 35 parts by weight of pelletized EPDM (2) (25 parts by weight of EPDM and 10 parts by weight of oil), 65 parts by weight of PP, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (B) were stirred and mixed. Then, the mixture was extruded at 220°C in a nitrogen atmosphere by the above-mentioned Warner biaxial extruder to obtain an elastomer composition. Example 17 An elastomer composition was prepared in the same manner as described in Example 16 except that the amount incorporated of MAH was changed to 1.0 part by weight. Comparative Example 14 An elastomer composition was prepared in the same manner as described in Example 16 except that MAH was not incorporated. Comparative Example 15 An elastomer composition was prepared in the same manner as described in Example 16 except that DVB and peroxide (B) were not incorporated. Example 18 A mixture comprising 20 parts by weight of EPDM (1), 60 parts by weight of PP, 10 parts by weight of IIR, 10 parts by weight of Oil and 5 parts by weight of a milled glass fiber ("Micro Glass Milled Fiber RX-EMFP" supplied by Nippon Sheet Glass, fiber diameter = 11 µm, average fiber length = 240 µm) (hereinafter referred to as "Milled Glass Fiber") was kneaded and square pellets were prepared in the same manner as described in Example 1 (first step). Then, 100 parts by weight of the so-prepared pellets, 0.3 part by weight of peroxide (A), 0.5 part by weight of DVB and 0.5 part by weight of MAH were mixed and extruded at 220°C in a nitrogen atmosphere by an extruder (second step). Examples 19 through 24 The procedures of Example 18 were repeated in the same manner except that at the first step, the kind and amount of the filler were changed as shown in Table 3. The following fillers were used. (Glass Flake) A scaly filmy glass having a thickness of 3 µm and a 325 mesh-pass fraction content higher than 88% (Micro Glass Flake EF325 supplied by Nippon Sheet Glass; hereinafter referred to as "Glass Flake"). (Potassium Titanate Fiber) A potassium titanate fiber having a fiber diameter of 0.2 to 0.5 µm and an average fiber length of 10 to 20 µm (Tismo D supplied by Otsuka Kagaku Uakuhin; hereinafter referred to as "Potassium Titanate") Comparative Examples 16 and 17 The procedures of Example 19 were repeated in the same manner except that the filler was not incorporated at the first step or maleic anhydride was not incorporated at the second step. The physical properties of the compositions obtained in Example 18 through 24 and Comparative Examples 16 and 17 are shown in Table 3. Example 25 A mixture comprising 50 parts by weight of a pelletized ethylene/propylene/ethylidene-norbornene copolymer rubber [ethylene content = 78 mole%, iodine value = 10, Mooney viscosity ML₁+₄ (100°C) = 160, extended oil content = 30% by weight (15 parts by weight of oil)][hereinafter referred to as "EPDM (3)"], 50 parts by weight of PP, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (B) was stirred and blended by a Henschel mixer. Then, the blend was extruded at 230°C in a nitrogen atmosphere by a Warner biaxial extruder (L/D = 43, mating type, same direction rotation, three-thread screws) (first step). Then, 100 parts of the obtained pellets were kneaded with 5 parts by weight of Milled Glass Fiber at 200°C for 5 minutes in nitrogen atmosphere by a Banbury mixer, and the kneaded mixture was passed through rolls and square pellets were prepared by a sheet cutter (second step). Examples 26 through 31 The procedures of Example 25 were repeated in the same manner except that at the second step, the kind and amount of the filler were changed as shown in Table 4. Comparative Examples 18 and 19 The procedures of Example 27 were repeated in the same manner except that the filler was not incorporated at the second step or MAH was not incorporated at the first step. The physical properties of the compositions prepared in Examples 25 through 31 and Comparative Examples 18 and 19 are shown in Table 4. Example 32 A composition comprising 70 parts by weight of EPDM (3) (50 parts by weight of EPDM and 20 parts by weight of oil), 30 parts by weight of PP, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 5 parts by weight of Milled Glass Fiber was stirred by a Henschel mixer. The resulting mixture was extruded at 230°C in a nitrogen atmosphere by the above-mentioned Warner biaxial extruder (first step). In a Banbury mixer, 100 parts by weight of the so-obtained pellets were kneaded with 5 parts by weight of Milled Glass Fiber at 200°C for 5 minutes in a nitrogen atmosphere, and the kneaded mixture was passed through rolls and square pellets were prepared by a sheet cutter (second step). Examples 33 through 38 The procedures of Example 32 were repeated in the same manner except that at the second step, the kind and amount of the filler were changed as shown in Table 5. Comparative Examples 20 and 21 The procedures of Example 32 were repeated in the same manner except that the filler was not incorporated at the second step or MAH was not incorporated at the first step. The physical properties of the compositions obtained in Examples 32 through 38 and Comparative Examples 20 and 21 are shown in Table 5. Example 39 The procedures of Example 22 were repeated in the same manner except that two kinds of fillers were used in combination at the second step, as shown in Table 5. The obtained results are shown in Table 5. Example 40 Square pellets were prepared in the same manner as described in Example 1 from 100 parts by weight of EPDM (1), 3 parts by weight of MAH, 20 parts by weight of IIR, 30 parts by weight of Oil, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (A) (first step). Then, 70 parts by weight of the pellets were mixed with 30 parts by weight of PP by a blender, and the mixture was extruded at 220°C in a nitrogen atmosphere by an extruder to obtain a thermoplastic elastomer composition (second step). The basic properties and bonding strength of the obtained elastomer composition are shown together with those of elastomer compositions obtained in the subsequent examples and comparative examples in Table 6. Example 41 An elastomer composition was prepared in Example 40 except that at the second step, each of the amounts incorporated of the pellets and PD was changed to 50 parts by weight. Example 42 An elastomer composition was prepared in Example 40 except that high-density polyethylene [density = 0.97 g/cm³, melt index (ASTM D-1238-65T, 190°C) = 5.3 g/10 min] (hereinafter referred to as "HDPE") was used instead of PP at the second step. Example 43 An elastomer composition was prepared in the same manner as described in Example 40 except that linear low-density polyethylene (density = 0.92 g/cm³, melt index = 6.0 g/10 min) (hereinafter referred to as "LLDPE") was used instead of PP at the second step. Example 44 An elastomer composition was prepared in the same manner as described in Example 40 except that low-density polyethylene [density = 0.92 g/cm³, melt index = 3.0 g/10 min] (hereinafter referred to as "LDPE") was used instead of PP at the second step. Example 45 An elastomer composition was prepared in the same manner as described in Example 40 except that at the second step, the amount of the pellets obtained at the first step was changed to 50 parts by weight, and 25 parts by weight of PP used in Example 40 and 25 parts by weight of LLDPE used in Example 43 were incorporated. Comparative Examples 22 and 23 Elastomer compositions were prepared in the same manner as described in Example 40 or 43 except that maleic anhydride was not incorporated at the first step. Comparative Examples 24 and 25 Elastomer compositions were prepared in the same manner as described in Example 40 or 43 except that divinylbenzene and maleic anhydride were not incorporated at the first step. Example 46 An elastomer composition was prepared in the same manner as described in Example 40 except that Oil and IIR were not incorporated at the first step. Example 47 In the Henschel mixer, 140 parts by weight of EPDM (2), 3 parts by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (B) were stirred and mixed. The blend was extruded at 220°C in a nitrogen atmosphere by a Warner biaxial extruder (L/D = 43, mating type, same direction rotation, three-thread screws) to form a graft-modified composition (A) (first step). Then, 80 parts by weight of the graft-modified composition was mixed with 20 parts by weight of PP by a blender, and the blend was extruded at 220°C in a nitrogen atmosphere by an extruder to obtain an intended thermoplastic elastomer composition. Example 48 An elastomer composition was prepared in the same manner as described in Example 47 except that at the second step, the grafted composition/polypropylene mixing ratio was changed to 60/40. Example 49 An elastomer composition was prepared in the same manner as described in Example 48 except that at the second step, HDPE used in Example 42 was used instead of PP. Example 50 An elastomer composition was prepared in the same manner as described in Example 48 except that at the second step, LLDPE used in Example 43 was used instead of PP. Example 51 An elastomer composition was prepared in the same manner as described in Example 48 except that at the second step, LDPE used in Example 44 was used instead of PP. Example 52 An elastomer composition was prepared in the same manner as described in Example 47 except that at the second step, 40 parts by weight of the graft-modified composition, 30 parts by weight of PP and 30 parts by weight of LLDPE were incorporated. Comparative Examples 26 and 27 Elastomer compositions were prepared in the same manner as described in Example 47 or 49 except that at the first step, MAH was not incorporated. Comparative Examples 28 and 29 Elastomer compositions were prepared in the same manner as described in Example 47 or 49 except that at the first step, DVS and peroxide B were not incorporated. Example 53 Square pellets (hereinafter referred to as "thermoplastic elastomer A") were prepared in the same manner as described in Example 1 from 78 parts by weight of EPDM (1), 22 parts by weight pf PP, 0.5 part by weight of MAH, 0.5 part by weight of DVB and 0.3 part by weight of peroxide (A) (the first step). Then, 90 parts by weight of thermoplastic elastomer A was mixed with 10 parts by weight of PP by means of a blender and the mixture was extruded at 220°C in a nitrogen atmosphere by an extruder to obtain a thermoplastic elastomer composition (hereinafter referred to as "thermoplastic elastomer B") (the second step). The basic properties and bonding strength of the obtained elastomer composition and those of elastomer compositions obtained in the subsequent examples are shown in Table 7. Examples 54 through 61 Thermoplastic elastomers B were prepared in the same manner as described in Example 53 except that the kinds and amounts of the components were changed as shown in Table 7.

Claims: A process for producing a thermoplastic elastomer composition comprising the steps of blending 10 to 95 parts by weight of an ethylene/propylene/non-conjugated diene copolymer rubber (a), 5 to 90 parts by weight of an olefinic plastic (b), the sum of the amounts of the components (a) and (b) being 100 parts by weight, and (c) 0.01 to 5 parts by weight of an unsaturated carboxylic acid or a derivative thereof and, using an extruder, dynamically heat-treating the blend at a temperature of 170 to 240°C in the presence of 0.1 to 1% by weight, based on the total weight of components (a), (b) and (c), of an organic peroxide to effect partial crosslinking. A process for producing a thermoplastic elastomer according to claim 1, wherein at least one additive selected from (d) 0 to 100 parts by weight of peroxide-non-crosslinking rubbery substance, (e) 0 to 200 parts by weight of a mineral oil softener and (f) 0 to 100 parts by weight of a fibrous filler, per 100 parts by weight of the sum of the component (a) and (b), is incorporated into the blend. A process for producing a thermoplastic elastomer composition according to claim 1 or claim 2 wherein the ethylene/propylene non-conjugated diene copolymer rubber (a) is a copolymer in which the molar ratio of ethylene units to propylene units is from 50:50 to 90:10. A process for producing a thermoplastic elastomer composition according to any one of claims 1 to 3 wherein the ethylene/propylene/non-conjugated diene copolymer rubber is an ethylene/propylene/5-ethylidene-2-norbornene copolymer rubber or an ethylene/propylene/5-ethylidene-2-norbornene/dicyclopentadiene quadripolymer rubber. A process for producing a thermoplastic elastomer composition according to any one of claims 1 to 4 wherein the olefinic plastic (b) is selected from isotactic and syndiotactic homopolymer and copolymer resins of ethylene, 1-butene, 1-pentene, 1-hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene and 5-methyl-1-hexene. A process for producing a thermoplastic elastomer composition according to any one of claims 1 to 5 wherein the unsaturated carboxylic acid or derivative thereof is selected from acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic acid, maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo[2,2,1]hept-2-ene-5,6-dicarboxylic anhydride, methyl acrylate, methyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethylcitraconate, dimethyl tetrahydrophthalate and dimethyl bicyclo[2,2,1]-hept-2-ene-5,6-dicarboxylate. A process for producing a thermoplastic elastomer composition according to any one of claims 1 to 6 wherein a polyolefin plastic is further incorporated into the blend after partial cross-linking. A process for producing a thermoplastic elastomer composition according to claim 7 wherein the weight ratio of the polyolefin plastic to the thermoplastic elastomer composition is from 0/100 to 75/25. A polymer composition obtainable by a process according to any one of claims 1 to 8.

Inventors: HIRAOKA KUNIHIDE, OKAMOTO KATSUO, OTAWA YASUHIKO, SHIMIZU SHIZUO, UCHIYAMA AKIRA, HIRAOKA, KUNIHIDE, OKAMOTO, KATSUO, OTAWA, YASUHIKO, SHIMIZU, SHIZUO, UCHIYAMA, AKIRA
Applicants: MITSUI PETROCHEMICAL IND, MITSUI PETROCHEMICAL INDUSTRIES, LTD.
Application year: 1987
Main classification: C08L23
IPC codes: C08K7, C08F255, C08L23, C08K5, C08L91, C08L51