JP2665373B2 - Partially crosslinked thermoplastic elastomer foam and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a partially crosslinked thermoplastic elastomer foam and a method for producing the same, and more particularly, it is excellent in heat resistance, chemical resistance, tensile properties, flexibility, and rubber elasticity. The present invention relates to a partially crosslinked thermoplastic elastomer foam having a low expansion ratio or a high expansion ratio and excellent thermoformability, and a method for producing the same.

Technical Background of the Invention Conventionally, as a method for producing an elastomer foam, a vulcanizing agent and a foaming agent are added to natural rubber or synthetic rubber and kneaded, and then the kneaded product is molded into a predetermined shape and heated. A method is known in which vulcanization and foaming are performed to obtain an elastomer foam.

However, in the method as described above, when the rubber is formed into a predetermined shape by continuous extrusion, since the raw material is rubber, a compound such as a foaming agent is kneaded in batch with the rubber in advance to obtain a kneaded material. It must be performed before the step and continuous extrusion, and in order to easily supply the kneaded material to the extruder, it is necessary to perform a step of forming the kneaded material in a ribbon shape before the continuous extrusion. In addition, in the above-described method, there is a problem that a molded article having a wide sheet-like shape and a complicated irregular shape cannot be obtained. There is a problem that it cannot be obtained, and there is a problem that it is difficult to thermoform the obtained foam.

As a method for solving such a problem, a method using a thermoplastic resin such as a soft olefin-based plastic, for example, an ethylene-vinyl acetate copolymer or a low-density polyethylene, instead of natural rubber or synthetic rubber is already known. However, according to this method, not only the above-described steps can be omitted, but also the degree of freedom of the shape of the molded product of the continuously extruded kneaded material is high. Further, if the kneaded material is once crosslinked by irradiation or treatment with a chemical crosslinking agent and then foamed, the shape retention of the molded product during foaming is improved.

However, soft olefin-based plastics basically have drawbacks such as inferior heat resistance and tensile properties as compared with rubber, and there is a problem that the use of the obtained foam is greatly restricted.

JP-A-49-129957 discloses that a mixture of a foamed base material composed of an ethylene-propylene-based elastomer and a polyethylene resin and a pyrolytic foaming agent is molded into a desired shape and then crosslinked with ionizing radiation. And a method for producing a synthetic resin foam which is heated and foamed. According to this method, an elastomer foam having a high expansion ratio can be obtained.

However, in this case, using only the constituents used here, including extrusion of complicated irregular shapes, is not only slightly inferior in that it allows for a higher degree of freedom in moldability, but also in a foamed base material. , And other components,
Since only components having cross-linking properties by irradiation with ionizing radiation are used, the resulting foam is a cross-linked foam, and although having excellent flexibility, has poor thermoforming processability and is limited in application. There is a problem.

On the other hand, the fact that a partially crosslinked composition composed of an olefin copolymer rubber and an olefin plastic can be used as a thermoplastic elastomer as a material exhibiting an intermediate performance between a soft olefin plastic and a vulcanized rubber is, for example, a special feature. It is known from JP-A-48-26838.

A method for producing a foam using such a polyolefin-based thermoplastic elastomer as a foam base material is disclosed in
No. 60-11937, specifically,
A method for producing a thermoplastic elastomer foam comprising a peroxide-decomposed olefin-based plastic and a lightly cross-linked peroxide-crosslinked olefin-based copolymer rubber has been proposed.

However, in the above-described method, the foaming ratio is not more than about 3 times at most, because the foaming agent is simply mixed with the foaming agent into the thermoplastic elastomer which is already partially crosslinked and foamed, instead of being partially crosslinked at the time of foaming. Only a foam of the magnification can be obtained. Therefore, there is a problem that the foam obtained by this method is limited to the use of a large-sized thick product such as a vehicle exterior material.

In addition, the method of producing a thermoplastic elastomer foam is also referred to in The Japan Rubber Association, Vol. 61, No. 2, page 70.
Even in this case, since the base material is a thermoplastic elastomer after cross-linking, even if devised by a foaming method such as using a chemical foaming agent and a gas together, the specific gravity is at most about 0.2, practically the specific gravity is extremely high at 0.7. Only low foamed foams are obtained. Therefore, there is a problem that the foam obtained by this method is also limited to applications for large-sized thick products such as vehicle exterior materials.

Object of the Invention The present invention is intended to solve the problems associated with the prior art as described above, and is excellent in heat resistance, chemical resistance, tensile properties, flexibility, rubber elasticity and thermoforming processability. It is an object of the present invention to provide a partially crosslinked thermoplastic elastomer foam having a low expansion ratio or a high expansion ratio, and a method for producing the same.

SUMMARY OF THE INVENTION The partially crosslinked thermoplastic elastomer foam according to the present invention comprises (a) 100 to 10 parts by weight of a peroxide crosslinked olefin copolymer rubber, (b) 0 to 90 parts by weight of a peroxide crosslinked olefin plastic and ( c) a melt index composed of 0 to 90 parts by weight of a peroxide-decomposable olefin-based plastic [the total weight of the components (a), (b) and (c) is 100 parts by weight]
An uncrosslinked unfoamed foam comprising a foamable composition comprising a peroxide partially crosslinkable thermoplastic elastomer (A), a pyrolytic foaming agent (B), and a peroxide (C) for 0.1 to 100 g / 10 minutes. The thermoplastic elastomer molded article is characterized by being crosslinked and foamed.

The method for producing a partially crosslinked thermoplastic elastomer foam according to the present invention comprises: (a) 100 to 10 parts by weight of a peroxide crosslinked olefin copolymer rubber; (b) 0 to 90 parts by weight of a peroxide crosslinked olefin plastic; (C) Peroxide-decomposable olefin plastic 0
To 90 parts by weight [provided that the total weight of the components (a), (b) and (c) is 100 parts by weight]
The pyrolytic foaming agent (B) and the peroxide (C) are simultaneously or individually added to the peroxide partially crosslinkable thermoplastic elastomer (A) with a melt index of 0.1 to 100 g / 10 minutes. Molding a foamable composition obtained by melt-kneading at a temperature equal to or lower than the decomposition temperature of peroxide and a temperature equal to or lower than the decomposition temperature of peroxide (C) into a predetermined shape to obtain an uncrosslinked unfoamed thermoplastic elastomer molded article; A step of heating at a temperature not lower than the decomposition temperature of the pyrolytic foaming agent (B) and the decomposition temperature of the peroxide (C) to cause cross-linking and foaming. I have.

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the partially crosslinked thermoplastic elastomer foam according to the present invention and a method for producing the same will be specifically described.

First, the partially crosslinked thermoplastic elastomer foam according to the present invention will be described.

The partially crosslinked thermoplastic elastomer foam of the present invention is a foam obtained by crosslinking and foaming an uncrosslinked unfoamed thermoplastic elastomer molded article, and the uncrosslinked unfoamed thermoplastic elastomer molded article is basically composed of a peroxide. Partially crosslinkable thermoplastic elastomer (A) and pyrolytic foaming agent (B)
And peroxide (C). The above-mentioned peroxide partially crosslinkable thermoplastic elastomer (A) comprises (a) a peroxide-crosslinkable olefin-based copolymer rubber, (b) a peroxide-crosslinkable olefin-based plastic, and (c) a peroxide-decomposed olefin-based plastic. It is comprised, and (d) Mineral oil-based softener can be included as needed.

Peroxide Partially Crosslinkable Thermoplastic Elastomer (A) In the present invention, the term "peroxide partially crosslinkable thermoplastic elastomer (A)" refers to a competitive reaction between a decomposition reaction and a crosslinking reaction that occur when an olefinic thermoplastic elastomer is thermally reacted with peroxide. In the results of many cross-linking reactions,
A thermoplastic elastomer in which a portion where the molecular weight of the polymer in the composition increases and a portion where the molecular weight of the polymer in the composition decreases as a result of a large decomposition reaction coexist.

(A) Peroxide-crosslinked olefin copolymer rubber (a) The peroxide-crosslinked olefin copolymer rubber used in the present invention includes, for example, ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene rubber, ethylene -Like butadiene copolymer rubber, is an amorphous random elastic copolymer containing an olefin as a main component, and is mixed with a peroxide and crosslinked by kneading under heating to reduce fluidity, or An olefin copolymer rubber that does not flow. Among these, ethylene-propylene copolymer rubber, ethylene-
Propylene-non-conjugated diene rubber (here, non-conjugated diene refers to dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, ethylidene norbornene, and the like) is preferable.
Propylene-non-conjugated diene copolymer rubber, especially ethylene-propylene-ethylidene norbornene copolymer rubber, is particularly preferred in that a thermoplastic elastomer foam having an appropriate crosslinked structure can be obtained.

Mooney viscosity of this copolymer rubber (a) ML _{1 + 4} (100
C) is preferably in the range of 10 to 180, especially 40 to 140, and when the Mooney viscosity is less than 40, the melt tension of the foamable composition to be obtained is low, and the diameter of cells of the foam to be obtained is small. May be larger. On the other hand, Mooney viscosity is 140
When it exceeds, the moldability (flowability) of the foamable composition is inferior,
The appearance of the obtained foam may deteriorate.

Further, the iodination (degree of unsaturation) of the copolymer rubber is preferably 16 or less. When a copolymer rubber having an iodine value in the above range is used, a partially crosslinked thermoplastic elastomer foam having a good balance between foaming and crosslinking can be obtained.

In the present invention, (a) the peroxide-crosslinked olefin-based copolymer rubber is (a) a peroxide-crosslinked olefin-based copolymer rubber, (b) a peroxide-crosslinked olefin-based plastic, and (c) a peroxide-decomposed olefin-based plastic. 10 to 1 for 100 parts by weight of
00 parts by weight, preferably 40 to 90 parts by weight, more preferably
It is used in an amount of 50 to 80 parts by weight.

(B) Peroxide-crosslinked olefin-based plastic The (b) peroxide-crosslinked olefin-based plastic used in the present invention is mixed with a peroxide and kneaded under heating to be crosslinked to lower the fluidity, or to reduce the flowability. Olefin-based plastics that are no longer used, specifically, high-pressure low-density polyethylene, medium-low pressure low-density polyethylene, high-density polyethylene, other ethylene-α-olefin copolymers, or α-
Copolymers of olefins with 15% by mole or less of other polymerizable monomers such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-acrylic acid Resin-like polymer substances such as an ethyl copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylate copolymer are exemplified. Among these, low-density polyethylene is particularly preferred in that a thermoplastic elastomer foam having an appropriate crosslinked structure can be obtained.

The melt index of this (b) peroxide-crosslinked olefin plastic (ASTM D 1238-65T, 190
C) ranges from 0.1 to 50 g / 10 min, preferably from 2 to 20 g / 10 min.

In the present invention, (b) peroxide-crosslinked olefin-based plastic is the total weight of (a) peroxide-crosslinked olefin-based copolymer rubber, (b) peroxide-crosslinked olefin-based plastic and (c) peroxide-decomposed olefin-based plastic. 0-9 for 100 parts by weight
0 parts by weight, preferably 5 to 50 parts by weight, more preferably 1 part by weight
It is used in an amount of 0 to 30 parts by weight.

(C) Peroxide-decomposition-type olefin-based plastic The (c) peroxide-decomposition-type olefin-based plastic used in the present invention is mixed with peroxide and kneaded under heating. An olefin-based plastic which decomposes to reduce its molecular weight and increase its fluidity, specifically, isotactic polypropylene or a copolymer of propylene and a small amount of other α-olefin, for example, propylene-ethylene copolymer Copolymer, propylene-1-butene copolymer, propylene / 1-hexene copolymer, propylene / 1-octene copolymer, propylene / 4-methyl-1-pentene copolymer, propylene / 1-decene copolymer Are used.

The melt index (ASTM D 1238: 230 ° C., 21 ° C.)
60 g) ranges from 1 to 80 g / 10 min, preferably from 5 to 50 g / 10 min.

The peroxide decomposable olefin-based plastic (c) used in the present invention has a role of improving fluidity and heat resistance of the foamable composition.

In the present invention, (c) peroxide-decomposable olefin-based plastic is the total weight of (a) peroxide-crosslinked olefin-based copolymer rubber, (b) peroxide-crosslinked olefin-based plastic, and (c) peroxide-decomposed olefin-based plastic. 0-90 for 100 parts by weight
Parts by weight, preferably 10 to 80 parts by weight, more preferably 20 parts by weight
Used in amounts of up to 50 parts by weight. (C) If the amount of the peroxide-decomposable olefin-based plastic exceeds 50 parts by weight, the flexibility and rubber elasticity of the obtained thermoplastic elastomer foam may decrease. On the other hand, when the amount of the (c) peroxide-decomposable olefin-based plastic is less than 20 parts by weight, the heat resistance and fluidity of the foamable composition are impaired, and the heat resistance and thermoforming processability of the obtained thermoplastic elastomer foam are reduced. May worsen.

(D) Mineral oil-based softening agent (d) As a mineral oil-based softening agent, usually, when a rubber is roll-processed, the intermolecular force of the rubber is weakened to facilitate the process, and at the same time, carbon black, white carbon, etc. A high-boiling petroleum fraction that is used for the purpose of increasing the flexibility or elasticity by assisting dispersion or lowering the hardness of the vulcanized rubber is used.Specifically, paraffinic, naphthenic, Alternatively, a mineral oil such as an aromatic oil is used.

The mineral oil-based softener (d) is used in an amount of 0 to 50 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the total of the components (a), (b) and (c). Used in (D) If the amount of the mineral oil-based softening agent is less than 10 parts by weight, a sufficient fluidity improving effect may not be obtained, while if it exceeds 20 parts by weight, the heat resistance of the obtained thermoplastic elastomer foam may be reduced. In some cases, the mineral oil-based softening agent exudes to the surface of the foam and impairs the appearance of the foam, which may cause undesirable effects.

The melt index (ASTM-D-) of the peroxide partially crosslinkable thermoplastic elastomer (A) used in the present invention.
1238-65T, 230 ° C) is 0.1-100 g / 10 min, preferably 5
8080 g / 10 min, more preferably 10-40 g / 10 min. When the melt index of the peroxide partially cross-linkable thermoplastic elastomer (A) is within the above range, the peroxide partially cross-linkable thermoplastic elastomer (A) at the time of mixing and kneading or at the time of molding into a desired shape before cross-linking and foaming. Excellent thermal flow characteristics.

The peroxide partially crosslinkable thermoplastic elastomer (A) as described above can be mixed with a conventionally known kneading apparatus, for example, an open mixing roll, a non-open Banbury mixer,
Using an extruder, a kneader, a continuous mixer, preferably a non-open kneader, each component of the above (a), (b) and (c) or each of the above components (a), (b) and (d) Can be obtained by melt mixing.

The above-described melt-kneading is preferably performed in an atmosphere of an inert gas such as nitrogen or carbon dioxide. The conditions for the above-mentioned melt-kneading are usually a kneading temperature of 150 to 280 ° C, preferably 170 to 240 ° C, and a kneading time of 1 to 20 minutes, preferably 3 to 10 minutes.

Pyrolytic foaming agent (B) The pyrolytic foaming agent (B) used in the present invention includes:
Conventionally known thermal decomposition type foaming agents can be used, and specifically, diethyl azodicarboxylate, azodicarbonamide, barium azodicarboxylate, 4,4 ′ oxybis (benzenesulfonyl hydrazide), 3,3′- Disulfone hydrazide phenylsulfonic acid, N, N'-dinitrosopentamethylenetetramine and the like can be mentioned.
Above all, it is most preferable to use azodicarbonamide in consideration of the resin temperature suitable for molding the resin composition used in the present invention. The amount of the thermal decomposition type foaming agent depends on the expansion ratio of the intended foam, but is usually (a) a peroxide crosslinked olefin copolymer rubber, (b) a peroxide crosslinked olefin plastic and ( c) It is used in an amount of 1 to 50 parts by weight, preferably 1 to 30 parts by weight based on 100 parts by weight of the total weight of the peroxide-decomposable olefin-based plastic. If the amount of the foaming agent is too small, foam molding becomes difficult. On the other hand, if the amount is too large, defoaming is apt to occur, and irregularities occur on the foam surface.

Peroxide (C) As the peroxide (C) used in the present invention, specifically, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di- (tert-butylperoxy) Hexane, 2,5-dimethyl-2,5-di (tert.
-Butylperoxy) hexyne-3,1,3-bis (tert
-Butylperoxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, p
Organic peroxides such as -chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperbenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butylcumyl peroxide; No.

Among them, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5
-Dimethyl-2,5-di (tert-butylperoxy) hexyne-3, 1,3-bis (tert-butylperoxyisopropyl) benzene, 1,1-bis (tert-butylperoxy) -3,3,5- Trimethylcyclohexane and n-butyl-4,4-bis (tert-butylperoxy) valerate are preferred, especially 2,5-dimethyl-2,5-di (tert-butyl).
Butylperoxy) hexyne-3 is preferred.

In the present invention, the peroxide (C) is used in an amount of 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 1.5 parts by weight, based on 100 parts by weight of the peroxide partially crosslinkable thermoplastic elastomer (A). Used in When the amount of the peroxide (C) is less than 0.1 part by weight, the degree of crosslinking between (a) the peroxide-crosslinked olefin-based copolymer rubber and (b) the peroxide-crosslinked olefin-based plastic becomes too low, and the heat resistance of the foam is reduced. In some cases, the elastic force may decrease, and the melt tension required for bubble formation may decrease. On the other hand, if the amount of the peroxide (C) exceeds 1.5 parts by weight, the degree of crosslinking between the components (a) and (b) becomes too high, and the fluidity of the foamable composition as a whole decreases,
The foam of the present invention may not be suitable for molding.

In the present invention, sulfur, p-quinonedioxime, p, p'-dibenzoylquinonedioxime, N- is added to the foamable composition constituting the uncrosslinked unfoamed thermoplastic elastomer molded article.
Methyl-N, 4-dinitrosoaniline, nitrobenzene,
Diphenylguanidine, trimethylolpropane-N,
Peroxide crosslinking aids such as N'-m-phenylenedimaleimide; or polyfunctional vinyl monomers such as divinylbenzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate Can be blended. With such a compound, an efficient crosslinking reaction can be expected.

In the present invention, the crosslinking aid or the polyfunctional vinyl monomer as described above is preferably used in an amount of 100 parts by weight of the peroxide partially crosslinkable thermoplastic elastomer (A).
It is used in an amount of 0.05 to 5 parts by weight, more preferably 0.1 to 1.5 parts by weight. When the amount of the crosslinking aid or the polyfunctional vinyl monomer exceeds 5 parts by weight, when the amount of the peroxide (C) is large, the crosslinking reaction proceeds excessively and the thermoforming processability of the foam is deteriorated. When the amount of the peroxide (C) is small, a crosslinking aid or a polyfunctional vinyl monomer is present as an unreacted monomer in the uncrosslinked unfoamed thermoplastic elastomer molded article. , The physical properties of the obtained foam change. Therefore, in the present invention, it is desirable to avoid excessive blending of the crosslinking aid or the polyfunctional vinyl monomer as described above.

Further, in the present invention, the foamable composition constituting the uncrosslinked unfoamed thermoplastic elastomer molded article contains the above-mentioned peroxide partially crosslinkable thermoplastic elastomer (A), the pyrolytic foaming agent (B) and the peroxide (C). In addition, if necessary, additives such as a foaming aid, a wetting agent, a tackifier, and a flame retardant can be further compounded within a range that does not impair the object of the present invention.

As the foaming auxiliary, specifically, stearic acid, lauric acid, organic acid-based auxiliary such as salicylic acid, fatty acid zinc,
Conventionally known foaming auxiliaries such as metal salt auxiliaries such as calcium, lead and barium, and urea auxiliaries are used.

As the wetting agent, specifically, conventionally known wetting agents such as DOP, DBP, DIDP, chlorinated paraffin, polybutene, liquid paraffin, and glycerin are used.

As the tackifier, a compound which is substantially a hydrocarbon compound such as chlorinated paraffin, polybutene, liquid paraffin, or oil, or a conventionally known tackifier such as rosin, terpene resin, or petroleum resin is used.

As flame retardants, trichloroethyl phosphite,
Liquid or semi-solid compounds such as tetrakis (2-chloroethyl) ethylene diphosphonate are used.

Chlorinated paraffins, compounds that are substantially hydrocarbon compounds such as polybutene, rosin, terpene resins, petroleum resins, and further, by using phosphorus-based flame retardants such as phosphite and phosphonate, waterproofness, flexibility and Adhesion to other material surfaces can be improved,
The partially crosslinked thermoplastic elastomer foam of the present invention can be used as a waterproof foam sealing material.

Further, in the present invention, the foamable composition constituting the uncrosslinked unfoamed thermoplastic elastomer molded article, a conventionally known heat stabilizer, weather stabilizer, antistatic agent, pigment, dye, filler,
Additives such as a nucleating agent, a lubricant, a slip agent and an anti-blocking agent can be blended within a range that does not impair the object of the present invention.

As the heat stabilizer, a conventionally known heat stabilizer such as a phenol-based, sulfite-based, phenylalkane-based, phosphite-based, or amine-based stabilizer is used.

As the pigment, specifically, conventionally known pigments such as carbon black, titanium oxide, zinc white, red iron oxide, ultramarine blue, navy blue, azo pigment, nitroso pigment, lake pigment and phthalocyanine pigment are used.

As the filler, specifically, calcium carbonate, calcium silicate, clay, kaolin, talc, silica, diatomaceous earth, mica powder, asbestos, alumina, barium sulfate, aluminum sulfate, calcium sulfate, molybdenum disulfide, graphite, Glass fibers, glass spheres, shirasu balloons, carbon fibers, and the like are used as long as the fluidity and rubber properties of the foamable composition are not impaired.

In the present invention, the foamable composition comprising the peroxide partially crosslinkable thermoplastic elastomer (A), the pyrolyzable foaming agent (B) and the peroxide (C) has a torque value of from 0.1 to 0.1 as measured by the following method. 15kgfcm, preferably
It is in the range of 0.5 to 8 kgf · cm.

The above torque values were measured using a Curastometer III S (P-300 type dies, amplitude angle = ± 1) manufactured by Nippon Synthetic Rubber Co., Ltd.
振動, frequency = 100 cpm), and measured by heating the above foamable composition at 199.9 ° C. for 15 minutes.

Foamable composition having a torque value in the above range,
It is possible to obtain a foam having fine cells having good fluidity, excellent foam moldability, and excellent heat resistance and rubber elasticity.

The degree of crosslinking of the thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam of the present invention is from 2 to 90 as a gel fraction (hot xylene, 130 ° C.) measured by the following method.
%, Preferably 10-70%, more preferably 15-60%.

The measurement of the hot xylene-extracted gel component is performed as follows. That is, sample pellets (size of each pellet: 3
mm x 3 mm x 3 mm) is precisely weighed to about 0.3 g, and this weight is used as the initial weight (X).

Next, the sample pellet was immersed in 80 ml of boiling xylene in a closed container for 5 hours, filtered through a 325 mesh screen, and then air-dried of the residue on the screen.
After vacuum drying at 80 ° C. for 5 hours, the amount of the dried residue is taken as the final weight (Y).

If the thermoplastic elastomer contains hot xylene-insoluble fillers, pigments, etc., subtract the amount of these hot xylene-insoluble fillers, pigments, etc. from the weight of the sample pellet and the weight of the dry residue. The obtained weight is defined as an initial weight (X) and a final weight (Y), respectively.

From these initial weight (X) and final weight (Y),
The hot xylene-extracted gel fraction is determined by the following equation.

A partially crosslinked thermoplastic elastomer foam in which the gel fraction of the thermoplastic elastomer is in the above range has excellent rubber elasticity and heat resistance.

The partially crosslinked thermoplastic elastomer foam as described above is obtained according to the following production method according to the present invention.

As the first step of the production method according to the present invention, (a) 100 to 10 parts by weight of a peroxide-crosslinked olefin-based copolymer rubber, (b) 0 to 90 parts by weight of a peroxide-crosslinked olefin-based plastic, and (c) peroxide decomposition 0 to 90 parts by weight of olefin type plastic [However, component (a)
The total weight of the component (b) and the component (c) is 100 parts by weight], and a peroxide partially crosslinkable thermoplastic elastomer (A) having a melt index of 0.1 to 100 g / 10 minutes.
Then, the thermal decomposition type foaming agent (B) and the peroxide (C) are melt-kneaded simultaneously or separately at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent (B) and lower than the decomposition temperature of the peroxide (C). The foamable composition obtained in this manner is molded into a predetermined shape to obtain an uncrosslinked and unfoamed thermoplastic elastomer molded article.

The method for producing the above-mentioned peroxide partially crosslinkable thermoplastic elastomer (A) is as described above.

As a method of the above-mentioned melt kneading, there is a method in which a thermally decomposable foaming agent (B) and a peroxide (C) are individually melt kneaded with a peroxide partially crosslinkable thermoplastic elastomer (A).

As such a method, for example, a pellet of a peroxide partially crosslinkable thermoplastic elastomer (A) and a pyrolytic foaming agent (B) are once mixed with a V-type Brabender, a tumbler Brabender, a ribbon Brabender, a Henschel Brabender or the like. After mixing using a known kneading machine, kneading is performed with an extruder, a mixing roll, a kneader, a Banbury mixer or the like, if necessary. The kneading is preferably performed at a temperature not higher than the decomposition temperature of the thermal decomposition type foaming agent (B). Also,
Additives such as a foaming aid, a wetting agent, a weather resistance stabilizer, a heat resistance stabilizer, an antioxidant, and a coloring agent can be added at any stage of the melt kneading.

Next, to the kneaded product obtained as described above, a peroxide and, if necessary, a crosslinking aid, a vulcanization accelerator, etc. are added, and a tumbler Brabender, a V-type Brabender,
A known kneader such as a Henschel mixer, preferably
After uniformly kneading at a temperature of 50 ° C. or less, the kneaded material is kneaded and dispersed by a known kneading machine such as an open-type mixing roll or a non-open-type Banbury mixer, an extruder, a kneader, or a continuous mixer. Kneading is performed at a temperature below the decomposition temperature of the thermal decomposition type foaming agent and below the decomposition temperature of peroxide,
Preferably the peroxide has a half-life temperature of 20 to
It is desirable to perform at a temperature lower by 50 ° C.

Further, a thermally decomposable foaming agent (B) and a peroxide (C) are added to a peroxide partially crosslinkable thermoplastic elastomer (A).
And melt kneading at the same time.

As such a method, for example, a method of quantitatively charging and injecting the pyrolytic foaming agent (B) and the peroxide (C) from the middle of the kneading section using a twin-screw extruder or the like, and simultaneously melt-kneading the same. .

Next, the foamable composition obtained by melt-kneading as described above is heated at a temperature at which the pyrolytic foaming agent (B) and the peroxide are not decomposed into a predetermined shape, for example, a sheet shape, a film shape, an irregular shape, and a pipe shape. Then, it is molded into a tube to obtain an uncrosslinked and unfoamed thermoplastic elastomer molded article. The molding can be performed using a conventionally known molding machine such as a hot press, an injection molding machine, an extruder, and a calender roll.

In the present invention, each of the components (a), (b) and (c) of the peroxide partially crosslinkable thermoplastic elastomer (A) or the components (a), (b), (c) and (d) Melt kneading of each component, melt kneading of peroxide partially crosslinkable thermoplastic elastomer (A) with additives such as pyrolytic foaming agent (B), peroxide (C),
The process leading to the molding of the foamable composition obtained by the melt-kneading can be performed in one step using an injection molding machine, a single screw extruder, a multi-screw extruder, or the like.

Next, as a second step of the production method according to the present invention, the uncrosslinked unfoamed thermoplastic elastomer molded article obtained in the above step is subjected to the decomposition temperature of the pyrolytic foaming agent (B) and the decomposition of the peroxide (C). It is cross-linked and foamed by heating at a temperature higher than the temperature.

The cross-linking and foaming is usually carried out by heating a non-cross-linked and non-foamed thermoplastic elastomer molded body by a conventionally known heating method such as hot air circulation heating, salt bath heating, infrared heating, or heating by a hot press. After heating to a partially molded thermoplastic elastomer foamable molded body,
The foamable molded body is further thermally decomposed by a conventionally known method such as hot air circulation heating, salt bath heating, infrared heating, and heating by a hot press to decompose the pyrolytic foaming agent (B) contained in the foamable molded body. And foaming.

Effect of the Invention The partially crosslinked thermoplastic elastomer foam according to the present invention is a foamable composition comprising a specific peroxide partially crosslinked thermoplastic elastomer (A), a pyrolytic foaming agent (B), and a peroxide (C). Since it is a foam obtained by crosslinking and foaming an uncrosslinked and unfoamed thermoplastic elastomer molded product made of a product, it has excellent heat resistance, chemical resistance, tensile properties, flexibility, rubber elasticity, and thermoforming processing There is an effect that it is excellent.

Further, according to the production method according to the present invention, a partially crosslinked thermoplastic elastomer foam having the above-mentioned effects can be obtained, and a partially crosslinked heat having a low expansion ratio of 3 times or less and a high expansion ratio of more than 3 times can be obtained. There is an effect that a plastic elastomer foam can be obtained.

The partially crosslinked thermoplastic elastomer foam of the present invention has 3
Foams with low expansion ratio of less than 2 times to high expansion ratio of more than 3 times are available. They are excellent not only in heat resistance, weather resistance, chemical resistance, tensile properties, flexibility and rubber elasticity but also in thermoforming processability. By utilizing this characteristic, it can be widely applied to the use of interior and exterior materials for vehicles and the like, sealing materials for vehicles, home electric appliances, civil engineering and construction, and sound absorbing and sound insulating materials. For example, in applications for vehicle interior and exterior materials, since a foam having a high expansion ratio has properties such as touch, cushioning, restoring, and sound absorbing properties in addition to the above-described properties of the foam, a door skin material is used. It is suitable for ceiling materials, seat leather, and the like, and a foam having a low expansion ratio can be used for dashboards, weather strips, and the like. In addition, when the foam of the present invention is used in these applications, the foam of the present invention is excellent in thermoforming processability, so that complicated shapes such as vacuum forming, pressure forming, hot press forming, and welder forming are used. Can be easily formed. In addition, in the application of sealing materials, from low foam to high foam, it can be applied to sealing materials used for waterproofing, windproofing, and soundproofing of vehicles, home appliances, civil engineering, etc. It is suitable for a heat-resistant sound-absorbing sound-insulating material such as a room sound-absorbing material.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. The molding of the foam and the evaluation of the basic physical properties in the examples were performed according to the following conditions and evaluation methods.

[Forming of foam] (1) Extrusion molding An uncrosslinked and unfoamed thermoplastic elastomer sheet was extruded under the following apparatus and conditions.

Molding machine: Single screw extrusion molding machine [Nippon Steel Works Co., Ltd., model number P4
0-25AB, 40mmφ], twin-screw extruder [Ikekai Iron Works Co., Ltd., Model No. PCM-30, 30m
mφ] Molding temperature: 160 ° C. Molding speed: 0.1 to 1.0 m / min (2) Foam molding A non-crosslinked, unfoamed thermoplastic elastomer sheet was foam-molded under the following apparatus and conditions.

Foaming furnace: Hot air circulation furnace [Micro Electronics Co., Ltd., model number MHV-0
8L] Foaming heating temperature: 200 to 230 ° C Heating time: 2 minutes 30 seconds [Evaluation method of basic physical properties] (1) Foaming ratio Value obtained by dividing the density 0.89 g / cm ³ of the unfoamed product by the apparent density of the foam molded product. Is the expansion ratio.

(2) Tensile properties The tensile strength at break and elongation at break of the foam were measured according to JIS-K-630.
Measure according to the measurement method specified in 1.

(3) Flexibility The flexibility of the foam is evaluated by a flexibility index (N).

N = (25% compressive strength) × (expansion ratio) Here, the 25% compressive strength is measured according to the measuring method specified in JIS-K-667-1976, and the expansion ratio is foam. Is represented by the reciprocal of the apparent density.

(4) When the number of cells per 3.3 mm square is n using a microscope with an average bubble cross section diameter of 50 times, Expressed by

(5) Thermoforming processability The thermoforming processability of the foam is evaluated by performing vacuum forming according to the following forming conditions, and the formability.

(Vacuum forming conditions) Surface temperature: 260 ° C Vacuum forming time: 100 seconds (Evaluation method) The presence or absence of sheet cutting by deep drawing and changes in appearance such as wrinkles are examined.

も の indicates that the thermoforming processability is excellent, 良好 indicates that it is good, 優 れ indicates that it is slightly good, and x indicates that it is not good.

(6) Heating Dimensional Change Heating dimensional change of the foam is evaluated based on the heat shrinkage in the vertical, horizontal, and thickness directions by heat treatment in accordance with the measurement method specified in JIS-K-6767.

A measurement sample (foam) is marked with a square of 10 cm square and 10 cm square, the thickness is measured, and the sample is heat-treated in a hot air oven at 80 ° C. for 22 hours. Then, after cooling the sample to room temperature,
The dimensions of the width and thickness are measured, and the dimensional change (thermal shrinkage) due to this process is determined.

(7) Appearance of the molded article Observation of the presence or absence of irregularities on the surface due to defoaming, 5 for a smooth surface, 3 for irregularities on the surface in some places, and marked roughness due to defoaming on the surface Is 1 and 4
Indicates that the surface state is between 5 and 3, and 2 indicates that the surface state is between 3 and 1.

Example 1 Molecular weight 32000 (n), molecular weight distribution 9.3 (w / n),
Mooney viscosity ML _{1 + 4} (100 ° C) 65, ethylene-propylene norbornene copolymer rubber having an iodine value of 12 (hereinafter abbreviated as EPDM) 60 parts by weight, melt index (ASTM-D-1238-
65T, 230 ℃) 3.0g / 10 min, referred to as polypropylene (hereinafter PP density 0.910g / cm ³⁾ 10 parts by weight, a melt index (ASTM-D-1238-65T, 190 ℃) 1.6g / 10 min, density 0.921
After mixing 20 parts by weight of low-density polyethylene (hereinafter abbreviated as LDPE) of g / cm ³ and 10 parts by weight of a naphthene (paraffin) -based process oil (hereinafter abbreviated as oil) with a Henschel mixer, The mixture is melt-kneaded in a first kneading section by a twin-screw extruder at 160 ° C., and then 10 parts by weight of azodicarbonamide (hereinafter abbreviated as ADCA) as a foaming agent is passed between the first kneading section and the second kneading section. 1.0 parts by weight of a crosslinking agent 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3 (hereinafter abbreviated as TBPH-3) and a crosslinking aid 0.5 parts by weight of allyl cyanurate (hereinafter abbreviated as TAC) was quantitatively supplied and kneaded. The kneaded material thus obtained was extruded into a sheet from a flat die having a lip width of 1 m and a lip thickness of 3 mm to obtain a continuous sheet of an uncrosslinked and unfoamed thermoplastic elastomer.

Next, the continuous sheet was heated for 200 to 2 hours using a hot air circulating furnace.
The sheet was heated and foamed at 30 ° C. to obtain a sheet-like foam.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (ASTM-D-1238-65T, 230 ° C.) of the kneaded product (partially crosslinkable thermoplastic elastomer) composed of EPDM, LDPE, PP and oil is 0.4 g / 10
Minutes.

Example 2 A foam having a round bar was obtained in the same manner as in Example 1, except that a round die (nozzle diameter: 5 mmφ) was used instead of the flat die.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 3 After the raw material to be the foam base material in Example 1 was kneaded by a Banbury mixer, the kneaded product was passed through a roll, and pellets were produced by a sheet cutter. The melt index (ASTM-D-1238-65T, 230 ° C.) of this kneaded product (partially crosslinkable thermoplastic elastomer) was 0.4 g / 10.
Minutes. Then, 100 parts by weight of the pellet and ADCA 1
After mixing 0 part by weight, 1.0 part by weight of TBPH-3 and 0.5 part by weight of TAC with a high-speed mixer, the mixture is continuously extruded into a sheet at a molding temperature of 160 ° C. using a single-screw extruder to have a width of 1 m. Thus, a continuous sheet of an uncrosslinked unfoamed thermoplastic elastomer having a thickness of 3 mm was obtained.

Next, the continuous sheet was heated for 200 to 2 hours using a hot air circulating furnace.
The sheet was heated and foamed at 30 ° C. to obtain a sheet-like foam.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 4 After the raw material to be the foam base material in Example 1 was kneaded by a Banbury mixer, the kneaded material was passed through a roll, and pellets were produced by a sheet cutter. The melt index (ASTM-D-1238-65T, 230 ° C.) of this kneaded product (partially crosslinkable thermoplastic elastomer) was 0.4 g / 10.
Minutes. Then, 100 parts by weight of the pellet and ADCA 1
After mixing 0 parts by weight, 1.0 part by weight of TBPH-3 and 0.5 parts by weight of TAC with a high-speed mixer, this mixture is continuously extruded into a round bar in an irregular shape at a molding temperature of 160 ° C. using a single screw extruder. Thus, a molded article of an uncrosslinked unfoamed thermoplastic elastomer was obtained.

Next, the molded body is heated to 200 to 230 ° C. using a hot air circulating furnace.
To obtain a foam having an irregular shape of a round bar.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 5 In Example 1, the compounding amounts of PP, LDPE and ADCA were
Except that they were 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively.
In the same manner as in Example 1, a sheet-like foam was obtained.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (AS) of the kneaded product (partially crosslinked thermoplastic elastomer) consisting of EPDM, PP and oil
TM-D-1238-65T, 230 ° C) was 0.5 g / 10 minutes.

Example 6 In Example 2, the compounding amounts of PP, LDPE and ADCA were
Except that they were 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively.
In the same manner as in Example 2, a round-shaped foam having a different shape was obtained.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (AS) of the kneaded product (partially crosslinked thermoplastic elastomer) consisting of EPDM, PP and oil
TM-D-1238-65T, 230 ° C) was 0.5 g / 10 minutes.

Example 7 In Example 3, the amounts of PP, LDPE and ADCA were
Except that they were 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively.
In the same manner as in Example 3, a sheet-like foam was obtained.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (AS) of the kneaded product (partially crosslinked thermoplastic elastomer) consisting of EPDM, PP and oil
TM-D-1238-65T, 230 ° C) was 0.5 g / 10 minutes.

Example 8 In Example 4, the compounding amounts of PP, LDPE and ADCA were
Except that they were 30 parts by weight, 0 parts by weight, and 5 parts by weight, respectively.
In the same manner as in Example 4, a foam having a round bar with a different shape was obtained.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (AS) of the kneaded product (partially crosslinked thermoplastic elastomer) consisting of EPDM, PP and oil
TM-D-1238-65T, 230 ° C) was 0.5 g / 10 minutes.

Example 9 A sheet-like foam was obtained in the same manner as in Example 1 except that the amount of ADCA was changed to 2 parts by weight.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 10 In the same manner as in Example 2 except that the amount of ADCA was changed to 2 parts by weight, a foam having a round bar with a different shape was obtained.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 11 60 parts by weight of EPDM, melt index (ASTM-D-65
T, 230 ° C) 2.0 g / 10 min, density of 0.910 g / cm ³ PP10 parts by weight, L
Pellets were produced with a Banbury mixer using a raw material to be a foam base material containing 20 parts by weight of DPE and 10 parts by weight of oil. The melt index (ASTM-D-1238-65T, 2) of this pellet (partially crosslinked thermoplastic elastomer)
30 ° C.) was 0.4 g / 10 minutes.

Next, a solution in which 1.0 part by weight of TBPH-3 was melt-dispersed in 0.5 part by weight of TAC was uniformly attached to the surface of the pellet, and then the pellet was extruded at 200 ° C. under a nitrogen atmosphere using an extruder. Thermoplastic elastomer 100 obtained by the above method
Part by weight and 5 parts by weight of an azodicarbonamide foaming agent were mixed by a blender mixer, and the resulting pellets were continuously extruded into a sheet at a molding temperature of 160 ° C. using a single-screw extruder to have a width of 1 m and a thickness of 3 mm. A continuous sheet of uncrosslinked unfoamed thermoplastic elastomer was obtained.

Next, the continuous sheet was heated for 200 to 2 hours using a hot air circulating furnace.
The sheet was heated and foamed at 30 ° C. to obtain a sheet-like foam.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 12 A sheet-like foam was obtained in the same manner as in Example 11, except that the amount of ADCA was changed to 5 parts by weight.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

Example 13 A sheet-like foam was obtained in the same manner as in Example 1, except that the blending amounts of PP and LDPE were changed to 30 parts by weight and 0 part by weight, respectively.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

The melt index (AS) of the kneaded product (partially crosslinked thermoplastic elastomer) consisting of EPDM, PP and oil
TM-D-1238-65T, 230 ° C) was 0.5 g / 10 minutes.

Example 14 A sheet-like foam was obtained in the same manner as in Example 13, except that the amount of ADCA was changed to 5 parts by weight.

 Table 1 shows the evaluation of the basic physical properties of the obtained foam.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigeki Ichimura 1170 Ako, Komagane, Nagano Prefecture (72) Inventor Noboru Murata 1170 Ako, Komagane City, Nagano Prefecture

Claims (10)

(57) [Claims] (1) 100 to 100 parts by weight of a peroxide-crosslinked olefin copolymer rubber, (b) 0 to 90 parts by weight of a peroxide-crosslinked olefin plastic, and (c) 0 to 90 parts of a peroxide-decomposed olefin plastic. Parts by weight (provided that the total weight of component (a), component (b) and component (c) is 100 parts by weight), and a partially crosslinked thermoplastic elastomer (A) having a melt index of 0.1 to 100 g / 10 minutes. ), A pyrolytic foaming agent (B), and a peroxide (C). A non-crosslinked, non-foamed thermoplastic elastomer molded article composed of a foamable composition is cross-linked and foamed. Partially crosslinked thermoplastic elastomer foam. 2. The partially crosslinked thermoplastic elastomer foam according to claim 1, wherein the peroxide partially crosslinkable thermoplastic elastomer (A) contains (d) a mineral oil-based softener. 3. The torque of the foamable composition constituting the uncrosslinked unfoamed thermoplastic elastomer molded article is 0.1 to 15 kgf.
3. The partially crosslinked thermoplastic elastomer foam according to claim 1, wherein the foam is a cm. 3. 4. The crosslinked thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam has a gel fraction (hot xylene, 130 ° C.) of 2 to 90%. A partially crosslinked thermoplastic elastomer foam according to any one of claims 3 to 7. 5. The method according to claim 1, wherein the expansion ratio of the partially crosslinked thermoplastic elastomer foam exceeds 3 times.
Item 5. The partially crosslinked thermoplastic elastomer foam according to any one of Items 1 to 4. 6. A peroxide-crosslinked olefin copolymer rubber (a) 100 to 100 parts by weight, (b) a peroxide-crosslinked olefin-based plastic 0 to 90 parts by weight, and (c) a peroxide-decomposed olefin-based plastic 0 to 90 parts by weight. Parts by weight (provided that the total weight of the component (a), the component (b) and the component (c) is 100 parts by weight), and a peroxide partially crosslinkable thermoplastic elastomer (A) having a melt index of 0.1 to 100 g / 10 minutes. ), The thermal decomposition type foaming agent (B) and the peroxide (C) are melt-kneaded simultaneously or separately at a temperature lower than the decomposition temperature of the thermal decomposition type foaming agent (B) and lower than the decomposition temperature of the peroxide (C). Molding the foamable composition obtained by the above into a predetermined shape to obtain an uncrosslinked unfoamed thermoplastic elastomer molded article; and Decomposition temperature and peroxide thermal decomposition type foaming agent (B) (C)
A step of heating at a temperature equal to or higher than the decomposition temperature to cause cross-linking and foaming. 7. The method for producing a partially crosslinked thermoplastic elastomer foam according to claim 6, wherein the peroxide partially crosslinkable thermoplastic elastomer (A) contains (d) a mineral oil-based softening agent. . 8. The foamable composition constituting the uncrosslinked unfoamed thermoplastic elastomer molded article has a torque value of 0.1 to 15 kgf.
The method for producing a partially crosslinked thermoplastic elastomer foam according to claim 6 or 7, wherein the diameter is cm. 9. The thermoplastic elastomer foam according to claim 6, wherein the degree of crosslinking of the thermoplastic elastomer in the partially crosslinked thermoplastic elastomer foam is 2 to 90% in terms of gel fraction (hot xylene, 130 ° C.). A method for producing a partially crosslinked thermoplastic elastomer foam according to any one of claims 8 to 13. 10. The partially crosslinked thermoplastic elastomer foam according to claim 6, wherein the expansion ratio of the partially crosslinked thermoplastic elastomer foam is more than 3 times. Production method.