JP2005220229A - Olefinic thermoplastic elastomer composition and foam thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an olefinic thermoplastic elastomer composition capable of providing a foamed and molded product usable for a component of an interior material for an automobile, having ≥2 times expansion ratio, light weight, flexible cushioning properties and heat insulation, produced in excellent foamability in a mold, capable of being formed into a complicated molded shape, and having recyclability. <P>SOLUTION: The resin composition for the foam is constituted of (D) a branched gummy olefinic flexible resin composition of an olefinic thermoplastic elastomer obtained by a kneading reaction of (A) an organic peroxide-crosslinking type olefinic copolymer rubber and (B) an organic peroxide-decomposing type crystalline olefin resin, and (C) a wax compatible with the organic peroxide-crosslinking type olefinic copolymer rubber (A) compounded therewith. The organic peroxide-crosslinking type olefinic copolymer rubber (A) is present as a continuous phase, and the organic peroxide-decomposing type crystalline olefinic resin (B) is present as a discontinuous phase in the microcoagulation structure of the gummy olefinic flexible resin composition (D). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a highly fluid and highly foamable resin composition suitable for injection foam molding in a mold or the like, and a foamed product thereof. More specifically, it has a high degree of freedom in the foaming ratio from low foaming to high foaming that can be used for automobile interior parts, etc., and it is flexible and can provide a foamed molded product with excellent cushioning, heat insulation, and recyclability. The present invention relates to an olefin-based thermoplastic elastomer composition that can be produced, and a foam obtained using the composition.

  Conventional foam molding has high foaming ratio, excellent moldability in the mold, flexible foam and cushioning foam has been Uretafoam, but because it is a thermosetting resin, Although it is used as a chip foam in terms of recycling, it is difficult to recycle it as a foaming material, and it is a material with low recycling potential.

Thermoplastic olefin-based elastomers are widely used as highly recyclable materials, and efforts have been made on foams thereof (Patent Document 1). This prior art includes "(a) 90 to 50 parts by weight of peroxide-crosslinked olefin copolymer rubber and (b) 10 to 50 parts by weight of peroxide-decomposable olefin plastic (where (a) + (b ) Is 100 parts by weight) and (c) 5 to 50 parts by weight of a peroxide non-crosslinked rubbery material and / or (d) a mineral oil-based softener, and this mixture is obtained in the presence of an organic peroxide. A foamed composition comprising a rubber composition (A) and a decomposable foaming agent (B), which are lightly cross-linked by dynamic heat treatment, is obtained, and the foamed composition is heated and melted and then foamed and molded. A process for producing a thermoplastic elastomer foam characterized in that is obtained.
However, with the technique disclosed in Patent Document 1, as disclosed in the Examples, the foaming ratio of the obtained foam is extremely low and cannot be put to practical use. This was confirmed by a follow-up experiment by the present inventors.

As an effort to improve the problems in the technology disclosed in Patent Document 1, a cushion layer of an interior skin material excellent in recyclability by blending a small amount of a specific olefin resin with a partially crosslinked olefin-based thermoplastic elastomer. A method of forming (foamed molded article) has been proposed (Patent Document 2). In addition, an interior skin with excellent recyclability by blending a partially cross-linked olefinic thermoplastic elastomer with a plasticizer, lubricant, etc. as a softening agent and a small amount of a specific styrene thermoplastic elastomer. A method of forming a cushion layer (foamed molded body) of a material has also been proposed (Patent Document 3).
However, in the former technique, the foaming ratio is a maximum of 2.9 times by extrusion foaming, and in the latter technique, the foaming ratio is a maximum of 2.5 times by injection foaming. However, there is not enough.

  In the technique disclosed in Patent Document 3, a plasticizer such as paraffinic process oil is often blended as a softening agent in order to improve moldability of the olefinic thermoplastic elastomer, that is, fluidity. In general, in order to improve the foamability of a thermoplastic elastomer, it is important to keep the gas generated in the molding temperature region as foam in the elastomer. For this purpose, the fluidity of the elastomer must be moderately lowered and made viscous. Thus, since the foamability and fluidity of the foam-forming elastomer are in a trade-off relationship, a high foaming ratio exceeding 3 times has not been achieved so far. Further, when a large amount of softening agent is blended, the molded product has problems such as bleed out and fogging due to the oil component of the plasticizer leaching from the inside to the outside under high temperature conditions. In addition, in a laminated product with a skin material, there is a concern about durability such as peeling of the skin material due to leaching of the oil component to the interface.

  Conventionally, as a means to improve soft cushioning properties, a method of cross-linking olefin-based thermoplastic elastomer-based materials with a crosslinking agent or the like (increasing the gel fraction) and increasing flow viscosity to increase foaming (Patent Documents) 1, 2) is known.

  Although the techniques disclosed in these Patent Documents 1 and 2 contribute to the improvement of rubber elasticity of the resin itself, it has been clarified by the present inventors that there are various problems with foaming. . That is, in the techniques disclosed in Patent Documents 1 and 2, (i) since the foaming agent needs to be dispersed, dissolved, and dissolved in the base material before foam molding, the base material has a high crosslinking density (gel fraction). As a result, the foaming agent cannot be uniformly dispersed, dissolved, or dissolved in the base material, and (ii) the blended foaming agent cannot effectively contribute to foaming, and (iii) the foaming ratio as a result. The present inventors have found that such a problem arises. Furthermore, in the techniques disclosed in these documents, (iv) since the viscosity becomes high, shearing to the base resin becomes significant, and when the foaming agent is dispersed, the base resin is changed by a change in the micro-aggregation structure of the base material, or at the same time by decoction. (V) As a result, the present invention also leads to an extreme decrease in fluid viscosity, and the high foaming in the mold and the die and the control of the molded shape are unstable. From research, I came to know.

  In this way, according to any of the previous proposals, it has excellent recyclability, in-mold molding processability, a high foaming ratio of the cushion layer, a flexible cushioning property with excellent texture, and a complicated molded shape In the present situation, a resin composition that can realize an in-mold foam-molded product that can cope with the above has not yet been provided.

JP-A-54-112967 JP-A-9-143297 JP 2002-206034 A

  The present invention has been made in view of the above circumstances, and the problem is that it can be used for automotive interior parts and the like, and can have a high expansion ratio, and can also be used for forming complicated shapes. An object of the present invention is to provide a resin composition that is flexible, excellent in fluidity and heat resistance, and suitable for injection foam molding in a mold, and a foam obtained using the resin composition.

  As a result of diligent research, the present inventors have obtained a desired foam by using an olefinic thermoplastic elastomer composition having a specific composition as a resin composition for foam molding. It came to confirm that it was possible.

(Olefin-based thermoplastic elastomer composition for foam molding)
The resin composition that has been specified by the present inventors is capable of a high expansion ratio, can be applied to molding of complicated shapes, has excellent fluidity and heat resistance, and is injection-foamed in-mold. It is an olefin-based thermoplastic elastomer that can obtain a foam having a light weight and excellent flexibility. This olefinic thermoplastic elastomer is an olefinic elastomer obtained by a kneading reaction between an organic peroxide crosslinked olefinic copolymer rubber (A) and an organic peroxide decomposable crystalline olefin resin (B). A wax (C) having a melting point of 100 ° C. or higher that is compatible with the organic peroxide cross-linked olefin copolymer rubber (A), and in the micro-aggregated structure, the organic peroxide The product-crosslinked olefin copolymer rubber (A) is present as a continuous phase, and the organic peroxide-decomposable crystalline olefin resin (B) is present as a discontinuous phase. This is a thermoplastic elastomer composition. It is considered that the organic peroxide cross-linked olefin copolymer rubber (A) is branched in the molecule by the kneading reaction of the present invention, and this branch is considered to increase the expansion ratio.

  The micro-aggregation structure as used in the present invention means that a resin composition for foam molding comprising a rubber component, a resin component and a wax component is treated with a staining agent such as osmium trioxide or ruthenium tetroxide, and a transmission electron microscope. (Acceleration voltage 200 kV: hereinafter referred to as TEM) means a “micro (structure of rubber phase and crystal phase)” obtained when observed. In the olefinic thermoplastic elastomer according to the present invention, as described below, the rubber component forms a continuous phase, and the structure is characterized in that the resin component is dispersed in islands in the continuous phase of the rubber component. There is.

  Judgment of the rubber phase and the crystal phase in such a micro-aggregated structure becomes possible as follows. That is, the organic peroxide cross-linked olefin copolymer rubber (A) alone treated with a dye and subjected to TEM observation is entirely dark black, while the organic peroxide decomposable crystalline olefin resin ( B) What was observed by the same treatment only with a simple substance was a clear color on the entire surface, so that it can be determined that the rubber component phase is dark black and the crystal component phase is clear color.

  As described above, the characteristic of the resin composition of the present invention is that “the organic peroxide cross-linked olefin copolymer rubber (A), which is a constituent component thereof, exists as a continuous phase and other constituent components. A certain organic peroxide decomposition type crystalline olefin resin (B) is contained in a dispersed state as a discontinuous phase ". This micro-agglomerated structure is not fixed in this narrow range and has a relatively wide range of variation. That is, the area occupied by the continuous phase and the discontinuous phase is not fixed and has a certain fluctuation range, and a wide magnification range from a low expansion ratio to a high expansion ratio can be arbitrarily set by the fluctuation range. Therefore, in the present invention, by controlling such a micro-aggregated structure, it is possible to cope with a complicated molded shape and obtain a foam having a desired expansion ratio from a low expansion ratio to an unprecedented high ratio. .

  There are various control factors for the expansion ratio as follows. That is, the “micro-aggregated structure composed of a continuous phase and a discontinuous phase” of the present invention can be controlled by the composition, molecular weight, and blending ratio of the rubber component and the crystalline resin component, and the degree of shear and temperature conditions during mixing, Wax dispersible in both continuous and discontinuous phases, as described below, degree of branching (gel fraction) of rubbery olefin-based soft resin, difference in melt viscosity of each component, interfacial tension such as compatibilizer The amount of dispersion can be controlled. The fact that there are various control factors means that the foaming ratio can be finely controlled by controlling various combinations of these various factors. This contributes to the “characteristics of the present invention that it is possible to provide a foam having an arbitrary expansion ratio that covers up to a magnification”. In the present invention, the fluidity of the elastomer composition can be further improved by the addition of the wax, and the improvement of the fluidity can not only maintain or improve the expansion ratio, but also can be applied to a molding die. Since the inflow of the elastomer is facilitated, the number of injection gates of the mold can be reduced, and it is possible to cope with a more complicated molded shape.

  In general, the micro-aggregation structure of the continuous phase and the discontinuous phase is determined by the ratio of each component in the mixed system and the shear during mixing in the case of a three-component mixed system composed of a rubber component, a crystalline resin component and a wax component. It is considered that it is determined from the relationship between the melt viscosity of each component and the interfacial tension depending on the conditions such as the degree of temperature and temperature.

  According to the study by the present inventors, the olefin-based thermoplastic elastomer composition (D) has a micro-aggregated structure, the organic peroxide-crosslinked olefin copolymer rubber (A) exists as a continuous phase, and the organic When the peroxide-decomposable crystalline olefin resin (B) has a systematic structure in which it exists as a discontinuous phase, it is excellent in fluidity and foamability, and a foaming ratio of 3 times or more is possible. In contrast, the micro-aggregated structure of the olefin-based thermoplastic elastomer composition (D) has an organic peroxide-decomposable crystalline olefin resin (B) as a continuous phase, and the organic peroxide-crosslinked olefin-based copolymer. When the polymer rubber (A) has a systematic structure in which it exists as a discontinuous phase, the foamability is poor and it is difficult to stably obtain a foaming ratio of 3 times or more, and the continuous phase is a crystalline olefin resin (B Therefore, it has been found that the flexibility and cushioning properties are further deteriorated.

(Organic peroxide cross-linked olefin copolymer rubber (A))
The organic peroxide cross-linked olefin copolymer rubber (A) used in the present invention is an amorphous random elastic copolymer or crystal having an α-olefin content of 2 to 20 carbon atoms of 50 mol% or more. It is an elastic copolymer having a degree of conversion of 50% or less, and is an amorphous α-olefin composed of two or more kinds of α-olefins, or two or more kinds of α-olefins and a non-conjugated diene copolymer.

Specific examples of such olefin copolymer rubbers include the following rubbers.
(A) Ethylene / α-olefin copolymer rubber
[Ethylene / α-olefin (molar ratio) = about 90/10 to 50/50]
(B) Ethylene / α-olefin / non-conjugated diene copolymer rubber
[Ethylene / α-olefin (molar ratio) = about 90/10 to 50/50]
(C) Propylene / α-olefin copolymer rubber
[Propylene / α-olefin (molar ratio) = about 90/10 to 50/50]
(D) Butene / α-olefin copolymer rubber
[Butene / α-olefin (molar ratio) = about 90/10 to 50/50]

  Specific examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1 -Undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl -1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl -1-hexene, 9-methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene, and combinations thereof. .

  Specific examples of the non-conjugated diene include dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylene norbornene, and ethylidene norbornene.

  The Mooney viscosity [ML1 · 4 (100 ° C.)] of these copolymer rubbers is preferably 10 to 250, particularly preferably 40 to 150.

  The ethylene / α-olefin / non-conjugated diene copolymer rubber (b) preferably has an iodine value of 25 or less.

  In the mixture of the organic peroxide crosslinked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B) used in the present invention, the organic peroxide crosslinked olefin copolymer is used. The blending amount of the combined rubber (A) is preferably based on 100 parts by weight of the total of the organic peroxide crosslinked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B). Is 30 parts by weight or more and less than 100 parts by weight, more preferably 60 parts by weight or more and less than 100 parts by weight, and particularly preferably 65 to 95 parts by weight.

  When the mixing ratio of the organic peroxide cross-linked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B) deviates from a preferable ratio to an unfavorable ratio, it is obtained by mixing and kneading. In the micro-aggregated structure of the branched rubbery olefin-based soft resin composition (D), the components of the continuous phase and the discontinuous phase shift in the reverse direction, and the expansion ratio tends to decrease.

(Organic peroxide decomposition type crystalline olefin resin (B))
Examples of the organic peroxide-decomposable crystalline olefin resin (B) used in the present invention include homopolymers or copolymers of α-olefins having 2 to 20 carbon atoms.

Specific examples of the organic peroxide-decomposable crystalline olefin resin (B) include the following (co) polymers.
(A) Propylene homopolymer (b) Random copolymer of propylene and other α-olefins up to 10 mol% (c) Block copolymer of propylene and other α-olefins up to 30 mol% ( D) 1-butene homopolymer (e) 1-butene homopolymer Random copolymer (f) 4-til-1-pentene homopolymer (g) 4 with 10 mol% or less of other α-olefin -Random copolymer of methyl-1-pentene and 20 mol% or less α-olefin

  Specific examples of the α-olefin include α-olefins similar to the specific examples of the α-olefin constituting the olefin copolymer rubber described above.

  In the “mixture of organic peroxide-crosslinked olefin copolymer rubber (A) and organic peroxide-decomposable crystalline olefin resin (B)” used in the present invention, organic peroxide-decomposable crystallinity The blending amount of the olefin resin (B) is 100 parts by weight based on the total amount of the organic peroxide crosslinked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B). The amount is preferably less than 70 parts by weight, more preferably less than 40 parts by weight, particularly preferably 5 to 35 parts by weight.

(Wax (C))
The wax (C) in the present invention has a melting point of 100 ° C. or more and is mainly composed of hydrocarbons. Such a wax causes a sudden viscosity drop when the melting point is exceeded, and is an olefin-based one. It must be compatible with the copolymer rubber (A) and the crystalline olefin resin (B).

  Specific examples of the wax (C) include paraffin wax and micro wax as natural wax. Moreover, as synthetic wax, synthetic waxes, such as alpha olefins, such as ethylene and a polypropylene, and mixtures thereof are mentioned. Alpha-olefins include ethylene, polypropylene, 1-butene, 1-octene, 1-nonene, and combinations thereof. Among these, olefin waxes are preferred, and polyethylene and polypropylene are particularly preferred from the viewpoints of resin compatibility and heat resistance. These blends have extremely low viscosity, but the foamability is maintained or improved. Highly preferred.

  The wax (C) in the elastomer composition of the present invention is blended in advance during the kneading reaction of the organic peroxide-crosslinked olefin copolymer rubber (A) and the organic peroxide-decomposable crystalline olefin resin (B). It may be added or may be blended after the kneading reaction is completed. The blending amount is from 1 part by weight to 50 parts by weight with respect to a total of 100 parts by weight of (A) + (B). The range of 1 to 30 parts by weight is particularly preferable from the viewpoint of kneading dispersibility. It is preferable to add the wax (C) in advance at the time of the kneading reaction because the kneading operation is effectively advanced and the foaming property is good. On the other hand, the blending after the kneading reaction of the wax (C) has an advantage that the viscosity can be lowered by simply blending at the time of injection molding. The wax (C) is considered to be contained in a dispersed state in the continuous phase of the organic peroxide-crosslinked olefin copolymer rubber (A). In molding, it is considered that fluidity is improved and foamability is maintained or improved.

  The melting point of the wax was measured by an ascending melting point, a softening point (JIS K2207, JIS K2531-1960), a Vicat softening point (ASTM D1525), a condensation point (IP76 / 70), a dropping point (ASTM D127-63), and the like. Shows melting point.

  As a modifier for the above-mentioned “mixture of organic peroxide-crosslinked olefin copolymer rubber (A), organic peroxide-decomposable crystalline olefin resin (B) and wax (C)”, styrene・ Butadiene (isoprene) -styrene block copolymer, polybutadiene rubber, polyisoprene rubber, and various hydrogenated rubbers, isobutylene rubber, chlorinated polyethylene, etc. When added in an amount of 50% by weight or less with respect to the total amount of 100% by weight, the microaggregated structure in the present invention can be stabilized.

  The organic peroxide cross-linked olefin copolymer rubber (A) is composed of the organic peroxide cross-linked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B). In the unfoamed olefin-based thermoplastic elastomer for foam molding composed of a mixture of styrene and wax (C), it exists mainly in a branched state, and since the ratio of crosslinking is small, there is a problem in the dispersion, kneading and dissolution of the foaming agent. There is no problem in fluidity and foaming during injection molding or extrusion molding.

(Branch)
In the present invention, the following gel fraction is preferable as an evaluable indicator of “chemical branching that contributes to enhancing foamability”. This gel fraction is measured as follows. That is, 0.5 g of an olefin-based thermoplastic elastomer for foam molding, which has been cut and adjusted to a size of 0.5 mm square, is precisely weighed and wrapped in a stainless steel mesh (# 600), which is wrapped in boiling xylene (138 ° C.). After extraction for 3 hours, thoroughly wash again with boiling xylene prepared separately, then replace with acetone, dry in an oven at 80 ° C. for 24 hours, weigh the residue after extraction in the mesh, The weight ratio of the residue after extraction to the weight is calculated, and this value is taken as the gel fraction (%).

  A conventionally used method for measuring the gel fraction uses cyclohexane as a solvent, and a compound to be measured is immersed in this solvent at room temperature for 48 hours, and a component insoluble in the solvent is handled as a gel fraction. Cyclohexane can substantially dissolve non-crosslinked EPDM rubber, but hardly dissolves non-crosslinked crystalline polypropylene. When evaluating the cross-linked part of EPDM rubber as the gel content, or when evaluating the non-cross-linked crystalline polypropylene as the pseudo-cross-linked gel content, the conventional gel fraction measurement method and measurement value using cyclohexane as a solvent are The term “crosslink” in a broad sense including the crosslink has a meaning as an index representing the mechanical properties of the base material. However, as a result of research by the present inventors, it has been found that the major factor for enhancing foamability taken up in the present invention is chemical crosslinking and branching, and pseudo-crosslinking hardly contributes. It was. Therefore, it has also been found that the gel fraction measured using cyclohexane as a solvent is an improper measurement method having no meaning as an index of crosslinking that governs foamability.

  In the olefinic thermoplastic elastomer for foam molding of the present invention, in order not to hinder the flowability and foamability during foam molding, the proportion of branching present in the olefinic thermoplastic elastomer is boiling xylene. The gel fraction in the (138 ° C.) 3 hour extraction is desirably less than 10 wt%, and more preferably less than 5%.

  It is particularly preferred that the gel fraction is less than 10 wt% because it is excellent in fluidity and has a high foaming ratio and facilitates foam molding in a mold or a die. In contrast, since the foaming agent must be dispersed, dissolved, and dissolved in the base material before foam molding, when the gel fraction is 10 wt% or more, that is, the crosslinking density (gel fraction) of the base material is high. If it becomes too hard, it becomes difficult to uniformly disperse, dissolve and dissolve the foaming agent in the base material, and the foaming ratio will not increase, and the fluidity will be poor, so it will tend to be extremely inferior to the foam molding shape in the mold or die. .

  Further, when the gel fraction is 10 wt% or more, the fluid viscosity is high, so that the molecules are severely cut by shearing heat during dispersion kneading with the foaming agent before in-mold foam molding. For example, olefinic thermoplastic elastomer (D ) The organic peroxide cross-linked olefin copolymer rubber (A) has a component fraction of 65 to 95 parts by weight (the organic peroxide-decomposable crystalline olefin resin (B) is 35 to 5 parts by weight). Even if there is a micro-aggregate structure, the organic peroxide decomposition-type crystalline olefin resin (B) constitutes a continuous phase, and the organic peroxide cross-linked olefin copolymer rubber (A) constitutes a discontinuous phase. Therefore, the phase structure is reversed from the preferable continuous / discontinuous phase structure, and the foaming ratio is remarkably lowered.

  As a method of performing branching with a gel fraction of less than 10 wt%, the organic peroxide crosslinked olefin copolymer rubber and the organic peroxide decomposable crystalline olefin resin may be reacted by kneading at a high temperature. In addition, as a crosslinking agent, a crosslinking agent usually used for rubber vulcanization can be used. Preferably, known methods such as a method using a peroxide, electron beam irradiation, sulfur vulcanization, and silane crosslinking can be used. Furthermore, as the phenol resin, a bromide of an alkylphenol resin or a curing agent such as a mixed crosslinking system containing a halogen donor such as tin chloride or chloroprene and an alkylphenol resin can be used. Among these branching methods, the method using a peroxide and the electron beam irradiation are preferable because they are easily controlled.

  Specific examples preferably used as the peroxide include 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) -3,3,3-trimethylcyclohexane N-butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4 dichlorobenzoyl peroxide, tert-butylperoxybenzoate, tert-butylperbenzoate, tert- Butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroy Peroxides, such as tert- butyl cumyl peroxide.

  Among these peroxides, in terms of odor and scorch stability, 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-bryl-4,4 -Bis (tert-butylperoxy) valerate is preferred, and 1,3-bis (tert-butylperoxyisopropyl) benzene is most preferred.

  The peroxide is preferably blended in an amount of usually about 0.01 to 2.5 parts by weight with respect to 100 parts by weight of the whole unfoamed foamed resin base material. It is adjusted in consideration of a balance such as gel fraction and density.

  In the present invention, sulfur, p-quinonedioxime, p, p′-benzoylquinonedioxime, N-methyl-N-4-dinitrosoaniline, nitroso are used as auxiliary agents in the branching treatment with the peroxide. Peroxy crosslinking aids such as benzene, diphenylguanidine, N, N'-m-phenylenedimaleimide, or divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate And polyfunctional vinyl monomers such as acrylic methacrylate, vinyl butyrate and vinyl stearate can be blended.

The fluidity and foamability of the foam base resin can be adjusted as appropriate depending on the blending amount of these auxiliaries.
However, when the resin is branched by irradiation with ionizing radiation such as electron beam, neutron beam, α ray, β ray, γ ray, X ray, ultraviolet ray, etc., it is not necessary to add a crosslinking agent, When branching by irradiation with radiation, auxiliary agents such as divinylbenzene, triallyl cyanurate, ethylene glycol dimethacrylate, trimethylpropane trimethacrylate, polyfunctional methacrylate monomers such as acrylic methacrylate, vinyl butyrate, vinyl stearate Such a polyfunctional vinyl monomer can be blended.

(Other additives)
In addition, in the foamed base resin used in the present invention, various other weather resistance stabilizers, heat stabilizers, plasticizers, flame retardants, thickeners, lubricants, colorants, etc. Additives usually used for the plastic resin and the thermoplastic elastomer composition can be added as long as the object of the present invention is not impaired.

  In addition to these, as fillers that can be blended in the olefin-based thermoplastic elastomer for foam molding, specifically, carbon black, nitroso pigment, bengara, phthalocyanine pigment, pulp, fibrous chip, agar etc. Organic filling materials, clay, kaolin, silica, diatomaceous earth, aluminum hydroxide, zinc oxide, magnesium hydroxide, calcium oxide, magnesium oxide, titanium oxide, mica, bentonite, shirasu balloon, zeolite, silicate clay, cement, silica fu -Inorganic fillers such as

As a method for kneading the composition, kneading is performed using a known kneader such as a V-type Brabender, a tumbler mixer, a ribbon Brabender, a Henschel mixer, and the kneaded product is mixed with an open mixing roll or a non-open type. A kneading and dispersing method using a known kneader such as a Banbury mixer, an extruder, a kneader, or a continuous mixer can be preferably used.
The composition may be branched during such a kneading step, or kneaded so as not to branch, and the obtained mixture is heated again in an oven or a hot press device to be branched statically. May be.

  The unfoamed olefinic thermoplastic elastomer composition for foam molding prepared by these is preferably used in the form of pellets with a known pelletizer.

(Foaming resin and foam)
In the present invention, an unfoamed foamable masterbatch can be prepared by kneading a thermally decomposable foaming agent into the olefin-based thermoplastic elastomer composition for foam molding at or below the decomposition temperature of the foaming agent.

  For example, if it is necessary to knead the olefinic thermoplastic elastomer for foam molding and the foaming agent using a known kneader such as a V-shaped Brabender, tumbler mixer, ribbon Brabender, Henschel mixer, etc. Kneading and adjusting at a temperature at which the pyrolyzable foaming agent does not decompose, using an extruder, mixin roll, kneader, Banbury mixer or the like.

  A foaming agent is normally used in the ratio of 1-25 weight part with respect to 100 weight part of unfoamed foam base resin.

  An unfoamed olefin-based thermoplastic elastomer masterbatch prepared by these is preferably used in the form of pellets with a known pelletizer.

  The foaming agent blended in the above-mentioned olefin-based foamed resin base material is a thermal decomposition type foaming agent that generates gas upon thermal decomposition. As such a foaming agent, specifically, azodicarbonamide ( ADCA), diethylazocarboxylate, barium azodicarboxylate, 4,4-oxybis (benzenesulfonyl hydrazide), 3,3-disulfone hydraside phenyl sulfonic acid, N, N'-dinitrosopentatetramine, p-toluenesulfonyl hydrazide Organic foaming agents such as trihydrazinotriazine, and inorganic foaming agents such as sodium hydrogen carbonate, ammonium hydrogen carbonate, and ammonium carbonate. In particular, azodicarbonamide (ADCA), N, N'-dinitrosopentatetramine, and trihydrazinotriazine are preferable as the organic foaming agent, and sodium hydrogen carbonate is preferable as the inorganic foaming agent. Further, sodium hydrogen carbonate, monosodium citrate and glycerin fatty acid ester may be mixed and used. These foaming agents can be used singly or in combination, or in combination with a so-called decomposition aid.

  In addition, additives such as foaming aids, wetting agents, weathering stabilizers, heat stabilizers, anti-aging agents, colorants, and fillers are blended at any stage of the kneading.

  In addition, when various raw materials are introduced from the hopper during injection or extrusion molding, in addition to the foamable masterbatch material made of foaming olefinic thermoplastic elastomer as a resin material, amorphous olefin rubber or crystalline olefin resin is added. You may mix and use.

  Specific examples of the amorphous olefin rubber include ethylene / α-olefin copolymer rubber [ethylene / α-olefin (molar ratio) = about 90/10 to 50/50], ethylene / α-olefin / Non-conjugated diene copolymer rubber ethylene / α-olefin (molar ratio) = about 90 / 10-50 / 50], propylene / α-olefin copolymer rubber [propylene / α-olefin (molar ratio) = about 90 / 10-50 / 50], butene / α-olefin copolymer rubber [butene / α-olefin (molar ratio) = about 90 / 10-50 / 50].

  Examples of the α-olefin include ethylene, propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene and 1-dodecene. 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 3 -Ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 9 -Methyl-1-decene, 11-methyl-1-dodecene, 12-ethyl-1-tetradecene, and combinations thereof.

  Examples of the crystalline olefin resin include random copolymers of propylene and other α-olefins of 10 mol% or less, block copolymers of propylene and other α-olefins of 30 mol% or less, 1- Butene homopolymer, 1-butene homopolymer 10 mol% or less of other α-olefin random copolymer, 4-methyl-1-pentene homopolymer, 4-methyl-1-pentene and 20 mol% There are random copolymers with the following α-olefins.

In the present invention, instead of foaming with a pyrolytic foaming agent, the resin can be foamed with a volatile solvent, water, or the like.
Further, the gas itself can be dispersed or impregnated into the foamed resin base material, and in this case, carbon dioxide gas or nitrogen gas can be used as the foaming agent.
Specifically, a method of injecting, kneading, and dispersing steam such as carbon dioxide, nitrogen, volatile solvent, or water before taking out the foam base resin from the molding machine at the time of injection, stamping molding or extrusion molding. Is used.
The conditions for injecting and kneading these foaming agents before injection or extrusion may be either a supercritical state or a non-supercritical state.
After the foaming agent is kneaded and dispersed before injection or extrusion, the foamable olefin-based thermoplastic elastomer is foam-molded through a nozzle or through a die.
In the case of injection molding, it is possible to mold the foamable olefin-based thermoplastic elastomer delivered through the nozzle by a known mold operation. That is, injection molding into a mold-clamped state, stamping molding, and core back molding are possible.

  The resin composition for foams of the present invention is an olefin-based product obtained by a kneading reaction between an organic peroxide-crosslinked olefin copolymer rubber (A) and an organic peroxide-decomposable crystalline olefin resin (B). A thermoplastic elastomer, which is further blended with a wax (C) having a melting point of 100 ° C. or higher that is compatible with the organic peroxide-crosslinked olefin copolymer rubber. The product-crosslinked olefin copolymer rubber (A) exists as a continuous phase, and the organic peroxide-decomposable crystalline olefin resin (B) exists as a discontinuous phase in the continuous phase. It is a thermoplastic elastomer and is suitable for in-mold molding such as injection molding. The composition of the present invention can exhibit a high foaming ratio by having the micro-aggregation structure, and can obtain a foam that is lightweight and flexible with excellent cushioning properties and heat insulation properties. Due to the dispersed content, the fluidity is high, the injection into the mold is easy, and it is possible to cope with complicated molded shapes. Therefore, according to the present invention, it is possible to use high or low foaming ratio that can be used for automobile interior parts, etc., lightweight and flexible fluidity, heat resistance, injection molding, press molding, transfer molding. In addition, it is possible to provide a recyclable foamed product having excellent in-mold foam moldability such as stamping molding.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are merely examples for suitably describing the present invention, and do not limit the present invention.

The injection molding machine used for molding the foam of the present invention is an apparatus of a type having a clamping force of 450 tons, a plasticizing capacity of 197 kg / h, a screw diameter of 58 mm, a maximum injection pressure of 216 MPa, and a maximum injection rate of 528 cm ³ / s. The core back molding method was applied.

  Similarly, the mold used for the molding of the foam of the present invention was an A4 size office receiving box with a wall thickness of 4 mm.

(Example 1)
1. Ethylene / propylene / non-conjugated diene copolymer rubber [EPT: ethylene content 68 mol%, iodine value 12, Mooney viscosity (JIS K6300) 38] 70 parts by weight, polypropylene [PP; MFR (ASTM 1238, 230 ° C.), 2. 16 kg load) 5.0 / 10 minutes] 20 parts by weight of polypropylene synthetic wax (melting point 145 ° C.) 10 parts by weight of 2,5-dimethyl-2,5-di (tert-dibutylperoxy) hexyne- 3 [Peroxide] in the presence of 0.17 parts by weight, kneaded and foamed olefinic thermoplastic elastomer (1. Micro-aggregated structure, continuous phase is rubber phase, discontinuous phase is crystalline phase, 2. gel Fraction: 3.0 wt%) was obtained.
To 100 parts by weight of the resulting olefin thermoplastic elastomer for foaming, 2.3 parts by weight of a mixture of sodium bicarbonate and citric acid (foaming agent) is kneaded to obtain a master batch (foamable olefin thermoplastic elastomer ) Was prepared. This master batch was melt-dispersed again in a 230 ° C. cylinder and then injected into a closed mold formed from upper and lower molds (injection conditions were: injection speed: 200 mm / s, mold temperature) : 30 ° C.).
When the obtained olefinic thermoplastic elastomer foam molded product was taken out, the molded product had a foaming ratio of 3.9 times (foaming ratio: specific gravity after foaming / specific gravity before foaming), good molding shape and good feel ( Asker C hardness: 22).

(Example 2)
1. Ethylene / propylene / non-conjugated diene copolymer rubber [EPT: ethylene content 68 mol%, iodine value 12, Mooney viscosity (JIS K6300) 38] 70 parts by weight, polypropylene [PP; MFR (ASTM 1238, 230 ° C.), 2. 16 kg load) 5.0 / 10 min] 20 parts by weight and 10 parts by weight of a polyethylene synthetic wax (melting point 107 ° C.), 2,5-dimethyl-2,5-di (tert-dibutylperoxy) hexyne-3 [ Peroxide] In the presence of 0.11 part by weight, kneaded and foamed olefinic thermoplastic elastomer (1. Micro-aggregate structure, continuous phase is rubber phase, discontinuous phase is crystalline phase, 2. gel fraction : 1.3 wt%).
Master batch (expandable olefin-based thermoplastic elastomer) by kneading 2.3 parts by weight of a mixture (foaming agent) of sodium hydrogen carbonate and citric acid to 100 parts by weight of the resulting olefin-based thermoplastic elastomer for foaming Was prepared. This master batch was melt-dispersed again in a 230 ° C. cylinder and then injected into a closed mold formed from upper and lower molds (injection conditions were: injection speed: 200 mm / s, mold temperature) : 30 ° C.).
When the obtained olefinic thermoplastic elastomer foam molded product was taken out, the foaming ratio of the molded product was 4.5 times (foaming ratio: specific gravity after foaming / specific gravity before foaming), the molding shape was good, and the feel was good ( Asker C hardness: 21).

(Example 3)
1. Ethylene / propylene / non-conjugated diene copolymer rubber [EPT: ethylene content 68 mol%, iodine value 12, Mooney viscosity (JIS K6300) 38] 70 parts by weight, polypropylene [PP; MFR (ASTM 1238, 230 ° C.), 2. 16 kg load) 5.0 / 10 min] 20 parts by weight and 10 parts by weight of a polypropylene-based synthetic wax (melting point 153 ° C.), 2,5-dimethyl-2,5-di (tert-dibutylperoxy) hexyne- 3 [Peroxide] Kneaded in the presence of 0.17 part by weight of olefin-based thermoplastic elastomer for foaming (1. Micro-aggregated structure, continuous phase is rubber phase, discontinuous phase is crystalline phase, 2. (Gel fraction: 3.4 wt%)
To 100 parts by weight of the resulting olefin thermoplastic elastomer for foaming, 2.3 parts by weight of a mixture of sodium hydrogen carbonate and citric acid (foaming agent) is kneaded to obtain a master batch (foamable olefin thermoplastic elastomer ) Was prepared. This master batch was melt-dispersed again in a 230 ° C. cylinder and then injected into a closed mold formed from upper and lower molds (injection conditions were: injection speed: 200 mm / s, mold temperature) : 30 ° C.).
When the obtained olefinic thermoplastic elastomer foam molded product was taken out, the foaming ratio of the molded product was 4.1 times (foaming ratio: specific gravity after foaming / specific gravity before foaming), the molding shape was good, and the feel was also good. (Asker C hardness: 22).

(Comparative Example 1)
1. Ethylene / propylene / non-conjugated diene copolymer rubber [EPT: ethylene content 68 mol%, iodine value 12, Mooney viscosity (JIS K6300) 38] 70 parts by weight, polypropylene [PP; MFR (ASTM 1238, 230 ° C.), 2. 16 kg load) 5.0 / 10 min] 30 parts by weight in the presence of 0.19 parts by weight of 2,5-dimethyl-2,5-di (tert-dibutylperoxy) hexyne-3 [peroxide] And kneading to obtain an olefin-based thermoplastic elastomer for foaming (1. micro-aggregated structure, continuous phase is rubber phase, discontinuous phase is crystal phase, 2. gel fraction: 3.7 wt%).
To 100 parts by weight of the resulting olefin thermoplastic elastomer for foaming, 2.3 parts by weight of a mixture of sodium hydrogen carbonate and citric acid (foaming agent) is kneaded to obtain a master batch (foamable olefin thermoplastic elastomer ) Was prepared. This master batch was melt-dispersed again in a 230 ° C. cylinder and then injected into a closed mold formed from upper and lower molds (injection conditions were: injection speed: 200 mm / s, mold temperature) : 30 ° C.). As a result, since no wax was blended, the fluidity was poor, the pressure in the cylinder increased, and injection was not possible.

(Comparative Example 2)
Ethylene / propylene / non-conjugated diene copolymer rubber [EPT: ethylene content 68 mol%, iodine value 12, Mooney viscosity (JISK6300) 38] 65 parts by weight and polypropylene [PP; MFR (ASTM 1238, 230 ° C., 2.16 kg) Load) 5.0 / 10 minutes] 25 parts by weight and 10 parts by weight of polypropylene having high fluidity instead of wax [PP; MFR (ASTM 1238, 230 ° C., 2.16 kg load) 23.0 / 10 minutes] 2,5-Dimethyl-2,5-di (tert-dibutylperoxy) hexyne-3 [peroxide] is kneaded in the presence of 0.11 part by weight to produce an olefin-based thermoplastic elastomer for foaming (1 And a micro-aggregated structure, the continuous phase was a crystalline phase, the discontinuous phase was a rubber phase, and 2. a gel fraction: 1.6 wt%
Kneading 2.3 parts by weight of a mixture of sodium hydrogen carbonate and citric acid (foaming agent) with 100 parts by weight of the resulting olefin thermoplastic elastomer for foaming, a master batch (foamable olefin thermoplastic) Elastomer) was prepared. This master batch was melt-dispersed again in a 230 ° C. cylinder and then injected into a closed mold formed from upper and lower molds (injection conditions were: injection speed: 200 mm / s, mold temperature) : 30 ° C.).
When the obtained olefinic thermoplastic elastomer foam molded product was taken out, the molding shape was poor, the foaming ratio was 2.0 times (foaming ratio: specific gravity after foaming / specific gravity before foaming), and the feel was hard and not good (Asker C hardness: 51).

  The respective viscosities of the olefinic thermoplastic elastomer compositions of Examples 1, 2, 3 and Comparative Examples 1, 2 were measured. Furthermore, the viscosity index [viscosity at 180 ° C. (V1) divided by viscosity at 230 ° C. (V2) (V1 / V2)] was shown as an index of the viscosity gradient with respect to temperature. The results are shown in Table 1 below. The viscosity was measured using a capillary rheometer (Flow Tester CFT-500A manufactured by Shimadzu Corporation), and the viscosity was measured by a temperature rising method with a load of 20 kg.

As seen in Table 1 above, the viscosities of the elastomers of Examples 1, 2, and 3 are stable without significant fluctuations regardless of temperature changes, and this indicates that the viscosity index (V1 / V2) is It can be understood from a small value of 1.00 to 1.5. This effect appears in the height of the expansion ratio. On the other hand, the viscosity of the elastomer of Comparative Example 1 was relatively high as compared with the elastomer of the Examples as the temperature increased, and became so high that injection molding could not be performed. In Comparative Example 2, the viscosity index (V1 / V2) was as large as 3.52, and the viscosity was not significantly decreased as the temperature increased. Therefore, the expansion ratio is extremely low and the hardness is high.
As described above, in the present invention, since the wax is appropriately blended, the flowability is improved, but the foamability is not lowered, and a product having a good feel can be obtained.

  As described above, according to the olefinic thermoplastic elastomer composition and the foamed body thereof according to the present invention, it is possible to use for automobile interior parts and the like, and the lightweight and flexible cushioning property and heat insulation with a foaming ratio of 2 times or more. It is possible to provide a foamed molded product that is recyclable and has excellent moldability and in-mold foam moldability, and can have a complex molded shape.

Claims (4)

  An olefin-based thermoplastic elastomer obtained by a kneading reaction between an organic peroxide-crosslinked olefin copolymer rubber (A) and an organic peroxide-decomposable crystalline olefin resin (B), A wax (C) having a melting point of 100 ° C. or higher that is compatible with the oxide-crosslinked olefin copolymer rubber (A) is further blended, and in the microaggregated structure, the organic peroxide-crosslinked olefin copolymer is mixed. An olefinic system characterized in that the polymer rubber (A) exists as a continuous phase, and the organic peroxide-decomposable crystalline olefin resin (B) exists as a discontinuous phase in the continuous phase. Thermoplastic elastomer composition.   2. The olefin-based thermoplastic according to claim 1, wherein the wax (C) contains at least one selected from the group consisting of polyethylene, polypropylene, hydrocarbons, and mixtures thereof as synthetic waxes. Elastomer composition.   The compounding amount of the wax (C) is 100 parts by weight in total of the organic peroxide crosslinked olefin copolymer rubber (A) and the organic peroxide decomposable crystalline olefin resin (B). The olefinic thermoplastic elastomer composition according to claim 1 or 2, wherein the composition is 1 part by weight or more and 50 parts by weight or less.   A foam obtained by foaming the olefinic thermoplastic elastomer composition according to claim 1.