JP2005146136A - Weather strip for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a weather strip for automobiles which has a very small permanent compression set, exhibits oil resistance and scratch resistance and gives good external appearances. <P>SOLUTION: The weather strip for automobiles is obtained by electron beam irradiation of a foam mainly composed of a thermoplastic elastomer composition which comprises an ethylene-α-olefin copolymer (1) forming a matrix, and a crystalline polyethylene resin (2) and a conjugated diene block copolymer (3) forming a three-dimensional network structure in the matrix. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an automotive weather strip obtained by irradiating a foam of a thermoplastic elastomer composition with an electron beam.

  In recent years, as weather strips for automobiles, those made of a foam as a material having a buffer material against vibration and noise have been required. In particular, there is a demand for an automotive weather strip made of a foamed thermoplastic elastomer composition that can be easily foamed and molded.

Examples of the thermoplastic elastomer that can be foamed and molded include a dynamically crosslinked thermoplastic elastomer. A foam obtained from a dynamically cross-linked elastomer (for example, Patent Document 1) has better flexibility than a foam previously known. However, the crosslinked rubber component contained in the elastomer cannot be foamed uniformly.
That is, only the crystalline polyolefin portion is foamed, resulting in a nonuniform and rough cell structure.
Furthermore, since gas escape occurs on the foam surface, the outer surface cannot be kept smooth and the appearance is poor.
In addition, this elastomer cannot sufficiently prevent odor and discoloration.
For this reason, the obtained foam is not suitable as a weather strip for automobiles.
In addition, there are many problems to be solved, such as a complicated manufacturing process and contamination due to the crosslinking agent used.
For this reason, the foam obtained from the dynamically crosslinked elastomer cannot be suitably used as a weather strip for automobiles.
On the other hand, olefin-based non-crosslinked thermoplastic elastomer can be uniformly foamed by melting, but the resulting foam has a problem of large permanent set due to compression because it does not have a crosslinked structure. It cannot be suitably used as a weather strip.

Therefore, an olefin-based non-crosslinked thermoplastic elastomer in which a crystalline polyethylene resin and a conjugated diene block copolymer have a three-dimensional network structure in a matrix made of an ethylene / α-olefin copolymer has been developed. (Patent Document 2). This elastomer has a marked improvement in permanent set due to compression as compared with a normal non-crosslinked thermoplastic elastomer. However, even such an olefin-based non-crosslinked thermoplastic elastomer does not have a crosslinked structure, so that the permanent set by compression is not sufficiently satisfactory.
JP-A-6-73222 JP 2001-341589 A

  The problem to be solved by the present invention is to obtain a weather strip for an automobile having a small compression set and an excellent surface appearance as compared with conventional weather strips made of foam.

In the present invention, a crystalline polyethylene resin (2) and a conjugated diene block copolymer (3) form a three-dimensional network structure in a matrix composed of an ethylene / α-olefin copolymer (1). The present invention relates to a weather strip for automobiles, which is obtained by irradiating a foamed body mainly composed of a thermoplastic elastomer composition.
Secondly, (3) the conjugated diene block copolymer is (a) a crystalline ethylene polymer block, and (b) a crystalline polyethylene resin that is compatible with the ethylene / α-olefin copolymer. A weather strip for an automobile as described above, having a block that is higher in compatibility with
Third, the automobile weather strip according to claim 1 or 2, wherein the conjugated diene block copolymer (3) comprises the crystalline ethylene polymer block at both ends.
Fourthly, the conjugated diene block copolymer (3) is obtained by hydrogenating a conjugated diene block copolymer whose both terminal blocks are the following A blocks and whose intermediate block is the following B block. When the total of the A block and the B block is 100% by mass, the A block is 5 to 90% by mass, the B block is 10 to 95% by mass, and the conjugated diene block The automobile according to any one of claims 1 to 3, wherein the copolymer (3) has at least 80% of all double bonds contained before hydrogenation and has a number average molecular weight of 50,000 to 700,000. Weather strip.
A: butadiene polymer block having a 1,2-vinyl bond content of less than 25 mol% B; conjugated diene polymer block and / or vinyl aromatic-conjugated diene having a 1,2-vinyl bond content of 25 mol or more Random copolymer block,
Fifth, when the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100% by mass, The ethylene / α-olefin copolymer (1) is 10 to 94% by mass, the crystalline polyethylene resin (2) is 5 to 80% by mass, and the conjugated diene block copolymer (3 ) 1 to 80% by weight of the above automotive weather strip,
Sixth, when the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass The above-mentioned automotive weather strip containing 200 parts by mass or less of a softener,
Seventh, when the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass In addition, the weather strip for automobiles, wherein 0.1 to 10 parts by mass of a crosslinking aid is further added to the thermoplastic elastomer composition,
Eighth, the above-mentioned automobile weather strip having a cyclohexane insoluble content after electron beam irradiation of 50 to 100% by mass,
Ninth, the above-described automobile weather strip, in which the electron beam irradiation dose is 1,000 to 2,000,000 (kV · kGy) as a product of the electron beam acceleration voltage (kV) and the irradiation dose (kGy),
Tenth, the above-mentioned automobile weather strip obtained by electron beam irradiation while rotating,
It is about.

  INDUSTRIAL APPLICABILITY The present invention can provide a weather strip for automobiles that is obtained from a thermoplastic elastomer composition and has a very small compression set, oil resistance, scratch resistance, and excellent surface appearance.

Hereinafter, embodiments of the present invention will be described in detail.
In the automotive weather strip of the present invention, the thermoplastic elastomer composition constituting the foam before electron beam irradiation (hereinafter also referred to as pre-irradiation foam) is an ethylene / α-olefin copolymer (1), crystal The crystalline polyethylene resin is contained in a matrix comprising the conductive polyethylene resin (2) and the conjugated diene block copolymer (3) as main components and comprising the ethylene / α-olefin copolymer (1). The resin (2) and the conjugated diene block copolymer (3) form a three-dimensional network structure.

The ethylene / α-olefin copolymer (1)
The ethylene / α-olefin copolymer (1) (hereinafter also simply referred to as “EAO copolymer (1)”) is mainly composed of ethylene and an α-olefin having 3 to 10 carbon atoms excluding ethylene. It is a copolymer as a component. When the total of ethylene and α-olefin contained in the EAO copolymer is 100 mol%, the ethylene content is preferably 50 to 90 mol%. When the ethylene content exceeds 90 mol%, the flexibility tends to be insufficient, whereas when it is less than 50 mol%, the mechanical strength tends to be insufficient, which is not preferable.

  Here, examples of the α-olefin having 3 to 10 carbon atoms include propylene, 1-butene, 1-pentene, 4-methyl-pentene-1, 1-hexene, 1-heptene, 1-octene and 1-decene. Can be mentioned. Among these, propylene, 1-butene, 1-hexene and 1-octene are preferable, and propylene and 1-butene are more preferable. These compounds can be used alone or in combination of two or more. When an α-olefin having 10 or less carbon atoms is used, the copolymerizability between the α-olefin and the other monomer is improved.

Furthermore, 0-10 mol% of non-conjugated dienes may be contained in the EAO copolymer (1) as necessary.
Specific examples of non-conjugated dienes include linear acyclic dienes such as 1,4-hexadiene, 1,6-hexadiene, 1,5-hexadiene, 5-methyl-1,4-hexadiene, and 3,7-dimethyl. -1,6-octadiene, 5,7-dimethylocta-1,6-diene, 3,7-dimethyl-1,7-octadiene, 7-methylocta-1,6-diene, dihydromyrcene, etc. Acyclic diene, tetrahydroindene, methyltetrahydroindene, dicyclopentadiene, bicyclo [2.2.1] -hepta-2,5-diene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5- Propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl And alicyclic dienes such as 2-norbornene and the like.
These compounds can be used alone or in combination of two or more.
Moreover, as a preferable thing among said non-conjugated dienes, 1, 4-hexadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, etc. can be mentioned.

Mooney viscosity [ML _{1 + 4} (100 ° C.)] of these EAO-based copolymers (1) (hereinafter, Mooney viscosity is L-shaped rotor, preheating time 1 minute, rotor operating time 4 minutes, test temperature 100 ° C. The measured value) is preferably 10 to 500, and more preferably 30 to 400. If the Mooney viscosity is less than 10, the mechanical strength and elastic recovery are likely to be low, whereas if it exceeds 500, the dispersibility of the crystalline polyethylene resin (2) tends to be low, which is not preferable.

The EAO copolymer (1) used in the present invention may be an oil-extended polymer to which a softener is added during polymerization. Such an EAO copolymer (1) can be produced by the method described in Japanese Patent Application No. 2000-383320.

Crystalline polyethylene resin (2)
The crystalline polyethylene resin (2) contains ethylene as a main constituent, and the ethylene content is 90 to 100 mol%. The crystallinity of the crystalline polyethylene resin (2) is preferably 10% or more. When the crystallinity is less than 10%, the mechanical strength of the obtained automotive weather strip tends to be inferior. Furthermore, it is preferable that the melting peak of the crystal by a differential scanning calorimeter (DSC) is 100 ° C. or higher. When the melting peak is less than 100 ° C., the heat resistance and compression set of the resulting automotive weather strip tend to be inferior.

  As this crystalline polyethylene resin (2), polyethylene, ethylene content is 90 mol% or more, and carbon number of propylene, butene-1, 4-methyl-pentene-1, hexene-1, octene-1, etc. And a copolymer with an α-olefin in which is 3-6. Of these, polyethylene may be a resin obtained by either a high pressure method or a low pressure method. Two or more of these may be mixed.

Conjugated diene block copolymer (3)
As the conjugated diene block copolymer (3), compatibility with (a) crystalline ethylene polymer block and (b) ethylene / α-olefin copolymer is compatible with crystalline polyethylene resin. Those having higher blocks are preferred.
(A) The crystalline ethylene polymer block provided in the copolymer of the conjugated diene block copolymer (3) includes a copolymer having an ethylene content of 50% or more and an ethylene homopolymer. Can do.
The conjugated diene block copolymer (3) preferably includes a crystalline ethylene polymer block at both ends. In particular, by providing both ends, a uniform three-dimensional network structure can be obtained. The three-dimensional network structure formed in the EAO copolymer is usually mainly composed of a crystalline polyethylene resin (2) and a conjugated diene block copolymer (3).

Further, this conjugated diene block copolymer (3) was obtained by hydrogenating a conjugated diene block copolymer whose both terminal blocks are the following A blocks and whose intermediate block is the following B block. When the total of the A block and the B block is 100% by mass, the A block is 5 to 90% by mass, the B block is 10 to 95% by mass, and the conjugated diene block It is preferable that at least 80% of all double bonds contained in the union (3) before hydrogenation is saturated and the number average molecular weight is 50,000 to 700,000.
A: butadiene polymer block having a 1,2-vinyl bond content of less than 25 mol% B; conjugated diene polymer block and / or vinyl aromatic-conjugate having a 1,2-vinyl bond content of 25 mol% or more Diene random copolymer block

The preferred conjugated diene block copolymer (3) is a copolymer having an A block at both ends and a B block between two A blocks (ABA type block copolymer). It is a block copolymer obtained by hydrogenation. That is, each block of the A block and the B block is a block before hydrogenation.
When the total of the A block and B block in the conjugated diene block copolymer (3) is 100% by mass, the content of each block is 5 to 90% by mass (more preferably 10 to 80% by mass). %). When the A block is less than 5% by mass (the B block exceeds 95% by mass), it is difficult to exhibit relatively sufficient crystallinity with respect to the EAO copolymer (1) serving as a matrix, and a three-dimensional network structure It becomes difficult to form. On the other hand, when it exceeds 90 mass% (B block is less than 10 mass%), the hardness is excessively increased, which is not preferable.

  The A block is a 1,3-butadiene polymer block containing butadiene as a main component (90 mass% or more, preferably 95 mass% or more of the entire A block). Further, the 1,2-vinyl group content of the A block is preferably less than 25 mol% (more preferably 20 mol% or less, still more preferably 15 mol% or less). When the 1,2-vinyl group content of the A block is 25 mol% or more, the melting point of the crystal after hydrogenation is remarkably lowered, and the mechanical strength tends to be lowered. The number average molecular weight of the A block is preferably 25,000 to 630,000 (more preferably 100,000 to 480,000). In the conjugated diene block copolymer (3), the A block is hydrogenated to exhibit a structure similar to low density polyethylene.

The B block is a conjugated diene polymer block containing a conjugated diene compound as a main component (50% by mass or more, preferably 60% by mass or more of the entire B block).
Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4 , 5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene and the like. Among these, 1,3-butadiene, isoprene, and 1,3-pentadiene are preferably used, and 1,3-butadiene is particularly preferably used. B block may be comprised from 2 or more types of these.

  Further, the 1,2-vinyl group content of the B block is preferably 25 mol% or more (more preferably 25 to 95 mol%, still more preferably 30 to 90 mol%). If it is less than 25 mol%, it becomes a resinous property and the flexibility tends to be lowered. Further, the 1,2-vinyl group content contained in the B block exceeds the 1,2-vinyl group content of the A block. When the 1,2-vinyl group content is less than the A block, the flexibility of the thermoplastic elastomer composition used in the present invention tends to be lowered. The number average molecular weight of the B block is preferably 5,000 to 665,000 (more preferably 20,000 to 540,000).

  Further, when the vinyl aromatic polymer block is contained in the B block, the content of the vinyl aromatic polymer block is 35% by mass or less (more preferably 30% by mass) when the entire B block is 100% by mass. % Or less, more preferably 25% by mass or less). By including the vinyl aromatic polymer block, the glass transition temperature rises, and the low-temperature characteristics and flexibility tend to be lowered. The B block becomes a polymer block having a structure similar to that of a rubbery ethylene / butene-1 copolymer block or a vinyl aromatic compound / ethylene / butene-1 copolymer by hydrogenation.

Examples of vinyl aromatic compounds include styrene, tert-butylstyrene, α-methylstyrene, p-methylstyrene, p-ethylstyrene, divinylbenzene, 1,1-diphenylstyrene, vinylnaphthalene, vinylanthracene, and N, N-diethyl. -P-aminoethylstyrene, vinylpyridine, etc. are mentioned. Of these, styrene is preferred.

Further, the double bond contained in the conjugated diene block copolymer (3) obtained after hydrogenation is at least 80% (more preferably 90%, still more preferably 95 to 95%) of all double bonds before hydrogenation. 100%) is preferably saturated. If it is less than 80%, thermal stability and durability tend to be lowered.
The number average molecular weight of the conjugated diene block copolymer (3) is preferably 50,000 to 700,000 (more preferably 100,000 to 600,000). If it is less than 50,000, the heat resistance, strength, fluidity and workability tend to decrease, while if it exceeds 700,000, the fluidity, workability and flexibility tend to decrease.

The conjugated diene block copolymer (3) includes, for example, an aliphatic hydrocarbon solvent such as pentane, hexane, heptane, and octane, an alicyclic hydrocarbon solvent such as cyclopentane, methylcyclopentane, cyclohexane, and methylcyclohexane, or In an inert organic solvent such as an aromatic hydrocarbon solvent such as benzene, xylene, toluene, ethylbenzene, etc., a vinyl aromatic compound and a conjugated diene compound, or a vinyl aromatic compound and a conjugated diene compound and other single monomers copolymerizable therewith. The monomer can be obtained by living anion polymerization using an organic alkali metal compound as a polymerization initiator, and the block copolymer (hereinafter also referred to as “pre-hydrogenation polymer”) is hydrogenated to produce the present invention. It is possible to easily obtain a hydrogenated diene copolymer of

Examples of the organic alkali metal compound that is a polymerization initiator include organic lithium compounds and organic sodium compounds, and organic lithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium are particularly preferable.
There is no particular limitation on the amount of the organic alkali metal compound used, and various amounts can be used as necessary. Usually, the amount is 0.02 to 15% by mass, preferably 0.03 to 100% by mass of the monomer. Used in an amount of 5% by weight.

  The polymerization temperature is generally −10 to 150 ° C., preferably 0 to 120 ° C. Furthermore, it is desirable to replace the polymerization atmosphere with an inert gas such as nitrogen gas. The polymerization pressure is not particularly limited as long as it is carried out within a range of pressure sufficient to maintain the monomer and solvent in the liquid phase within the above polymerization range.

  Further, in the process of polymerizing a copolymer block containing a vinyl aromatic compound and a conjugated diene compound, the method of introducing monomers of these compounds into the polymerization system is not particularly limited, and is batch, continuous, intermittent, Or the method which combined these is mentioned. Furthermore, when polymerizing a copolymer block containing a vinyl aromatic compound and a conjugated diene compound, the amount of other copolymer components added, the amount of polar substances added, the number and type of polymerization vessels, etc. The method of charging the body may be selected so that the physical properties of the obtained hydrogenated diene copolymer, its composition, and a molded body of the composition are preferable.

  The pre-hydrogenation polymer of the present invention is a copolymer obtained by obtaining a block copolymer by the above-described method, and then using a coupling agent in the copolymer molecular chain via a coupling residue. Good.

  Examples of coupling agents used include divinylbenzene, 1,2,4-trivinylbenzene, epoxidized 1,2-polybutadiene, epoxidized soybean oil, epoxidized linseed oil, and benzene-1,2,4-triisocyanate. Narate, diethyl oxalate, diethyl malonate, diethyl adipate, dioctyl adipate, dimethyl phthalate, diethyl phthalate, diethyl terephthalate, diethyl carbonate, 1,1,2,2-tetrachloroethane, 1,4-bis ( Trichloromethyl) benzene, trichlorosilane, methyltrichlorosilane, butyltrichlorosilane, tetrachlorosilane, (dichloromethyl) trichlorosilane, hexachlorodisilane, tetraethoxysilane, tetrachlorotin, 1,3-dichloro-2-propanone, etc. . Among these, divinylbenzene, epoxidized 1,2-polybutadiene, trichlorosilane, methyltrichlorosilane, and tetrachlorosilane are preferable.

  The hydrogenated diene copolymer of the present invention is obtained by partially or selectively hydrogenating the block copolymer obtained as described above. The hydrogenation method and reaction conditions are not particularly limited. Usually, the hydrogenation is performed at 20 to 150 ° C. under hydrogen pressure of 0.1 to 10 MPa in the presence of a hydrogenation catalyst.

  In this case, the hydrogenation rate can be arbitrarily selected by changing the amount of the hydrogenation catalyst, the hydrogen pressure during the hydrogenation reaction, or the reaction time. Usually, the hydrogenation catalyst is a compound containing any one of Group Ib, IVb, Vb, VIb, VIIb, and Group VIII metals, such as Ti, V, Co, Ni, Zr, Ru, Rh, Pd, Hf, A compound containing Re and Pt atoms can be used. Specifically, for example, metallocene compounds such as Ti, Zr, Hf, Co, Ni, Pd, Pt, Ru, Rh, and Re, and metals such as Pd, Ni, Pt, Rh, and Ru are carbon, silica, and alumina. , Supported heterogeneous catalyst supported on a carrier such as diatomaceous earth, homogeneous Ziegler catalyst combining organic salt of metal element such as Ni, Co or acetylacetone salt and reducing agent such as organic aluminum, Ru, Rh And the like, and fullerenes and carbon nanotubes which occlude hydrogen, and the like. Among these, a metallocene compound containing any of Ti, Zr, Hf, Co, and Ni is preferable in that it can be hydrogenated in a homogeneous system in an inert organic solvent. Furthermore, a metallocene compound containing any of Ti, Zr, and Hf is preferable. In particular, a hydrogenation catalyst obtained by reacting a titanocene compound with an alkyl lithium is preferable because it is an inexpensive and industrially useful catalyst. In addition, the said hydrogenation catalyst may use only 1 type, or can also use 2 or more types together. After the hydrogenation, if necessary, the catalyst residue is removed, or a phenol-based or amine-based antioxidant is added, and then the hydrogenated diene copolymer of the present invention is added from the hydrogenated diene copolymer solution. The coalescence is isolated. Isolation of the hydrogenated diene copolymer can be carried out, for example, by adding acetone or alcohol to the hydrogenated diene copolymer solution and precipitating, or by adding the hydrogenated diene copolymer solution to hot water with stirring. The solvent can be removed by distillation.

  In addition, the conjugated diene block copolymer before hydrogenation of the conjugated diene block copolymer (3) has a plurality of ABA type block copolymers linked via a coupling agent residue. May be contained. That is, [A-B-A-X] n- (A-B-A) [where n is an integer of 2 to 4, and X represents a coupling agent residue] may be used. Further, in the block copolymer before hydrogenation, the coupling agent residue has a sufficiently small molecular weight with respect to the A block and the B block, and does not affect the crystallinity of the conjugated diene block copolymer (3). In this case, [A-B-X] n- (B-A) [where n is an integer of 2 to 4, and X represents a coupling agent residue] may be used. That is, when a relatively small coupling agent residue is abbreviated, it may be [AB] n-A.

Further, the conjugated diene block copolymer (3) may be a modified block polymer modified with a functional group. As this functional group, at least one selected from the group consisting of a carboxyl group, an acid anhydride group, a hydroxyl group, an epoxy group, a halogen atom, an amino group, an isocyanate group, a sulfonyl group, and a sulfonate group can be used.
A known method can be used as the modification method.
The content of the functional group in the modified block polymer is 0.01 to 10 mol% (more preferably 0.1 to 8 mol%) when the entire constitutional unit constituting the block polymer is 100 mol%. And more preferably 0.15 to 5 mol%).
Preferred monomers that can be used to introduce functional groups include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, hydroxyethyl methacrylate, hydroxypropyl Examples include methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, and dimethylaminoethyl methacrylate.

In the present invention, a thermoplastic elastomer composition from which a foam constituting a weather strip for an automobile is obtained includes the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2), and a conjugated diene. In the matrix comprising the block copolymer (3) as a main component and comprising the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer The polymer (3) forms a three-dimensional network structure.
Since the conjugated diene block copolymer (3) can connect the EAO copolymer (1) and the crystalline polyolefin resin (2), the crystalline polyethylene resin (2) and the conjugated diene block It is considered that the copolymer (3) can form a three-dimensional network structure in the EAO copolymer (1).

Thermoplastic Elastomer Composition In the thermoplastic elastomer composition used for producing the automotive weather strip of the present invention, an EAO copolymer (1), a crystalline polyethylene resin (2), and a conjugated diene block copolymer Each content ratio of the union (3) is 10 to 94% by mass (preferably 20 to 94% by mass, more preferably 20% by mass) when the total of these three components is 100% by mass. 25 to 94% by mass, more preferably 40 to 90% by mass, particularly preferably 50 to 94% by mass), and the crystalline polyethylene resin (2) is 5 to 80% by mass (preferably 5 to 50% by mass, More preferably, it is 5 to 30% by mass, and the conjugated diene block copolymer (3) is 1 to 80% by mass (preferably 2 to 50% by mass, more preferably 3 to 3% by mass). 30% by mass).

If the content of the EAO copolymer (1) is less than 10% by mass, it is difficult to obtain a thermoplastic elastomer composition having sufficient elastic recovery, whereas if it exceeds 94% by mass, sufficient moldability is obtained. It is difficult to obtain a thermoplastic elastomer composition having
If the content of the crystalline polyethylene resin (2) is less than 5% by mass, it is difficult to obtain a thermoplastic elastomer composition having sufficient elastic recovery, while if it exceeds 80% by mass, sufficient elasticity is obtained. It is difficult to obtain a thermoplastic elastomer composition.
In addition, when the content of the conjugated diene block copolymer (3) is less than 1% by mass, it is difficult to obtain a thermoplastic elastomer composition having sufficient elastic recovery, while when it exceeds 80% by mass, it is sufficient. It is difficult to obtain a thermoplastic elastomer composition having excellent moldability.

  Further, when the total of these three components is 100% by mass, the EAO copolymer (1) is 40 to 94% by mass (more preferably 50 to 94% by mass), and the crystalline polyethylene resin (2 ) And the conjugated diene block copolymer (3) is 6 to 60% by mass (more preferably 6 to 50% by mass), and the total of the crystalline polyethylene resin (2) and the conjugate (3) is When the content is 100% by mass, a three-dimensional network structure can be obtained particularly stably when the crystalline polyethylene resin (2) is 20 to 80% by mass (more preferably 30 to 70% by mass).

The thermoplastic elastomer composition used for producing the automotive weather strip of the present invention can be used in combination with a crystalline and / or amorphous α-olefin polymer. As a result, the surface of the automotive weather strip obtained can be made smoother. As this α-olefin copolymer, those mainly containing an α-olefin having 3 or more carbon atoms are preferable. For example, polypropylene, polybutene-1, poly-4-methyl-pentene-1, polyhexene-1, propylene- Examples thereof include an ethylene copolymer and a propylene-butene-1 copolymer.
These can be used in combination of two or more.

  However, the mixing ratio of this α-olefin copolymer is the sum of EAO copolymer (1), crystalline polyethylene resin (2), conjugated diene block copolymer (3) and α-olefin copolymer. When the amount is 100% by mass, it is preferably 10% by mass or less, more preferably less than 5% by mass (particularly preferably 4% by mass or less). By setting the content to 10% by mass or less, a particularly stable three-dimensional network structure can be obtained, and the compression set of a weather strip for automobiles obtained by forming this as a foam and irradiating it with an electron beam can be reduced. .

The thermoplastic elastomer used in the present invention can contain a softening agent. For example, paraffinic, naphthenic, and aromatic mineral oil hydrocarbons, and low molecular weight hydrocarbons such as polybutene and polybutadiene, among which mineral oil hydrocarbons are preferred, Those having a weight average molecular weight of 300 to 2,000, particularly 500 to 1,500 are preferred. A rubber softener comprising a mineral oil-based hydrocarbon is generally a mixture of an aromatic ring, a naphthene ring, and a paraffin chain, and the carbon number of the paraffin chain accounts for 50% or more of the total carbon number. Paraffinic oils, naphthenic oils with 30-45% of the total number of carbons in the naphthenic ring, and aromatic oils with 30% or more of the total number of carbons in the aromatic ring In the present invention, paraffinic ones are preferable, and hydrogenated paraffinic ones are particularly preferable. The mineral oil-based hydrocarbons preferably have a kinematic viscosity at 40 ° C. of 20 to 800 cSt, particularly 50 to 600 cSt, and a pour point of −40 to 0 ° C., particularly −30 to 0 ° C.
The content is preferably 200 parts by mass or less when the total of the EAO copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass. (More preferably 100 parts by mass or less, and still more preferably 50 parts by mass or less).
By containing a softening agent, processability and flexibility can be improved. This addition method and the process to add are not limited.

Preparation method of thermoplastic elastomer composition The preparation method of the thermoplastic elastomer composition includes an EAO copolymer (1), a crystalline polyethylene resin (2), a conjugated diene block copolymer (3), and If it can disperse | distribute suitably with the other component used according to it, it will not specifically limit, It is obtained by heat-processing dynamically.

The term “dynamically heat-treating” refers to both applying a shearing force and heating. This dynamic heat treatment can be performed using, for example, a melt-kneading apparatus.
Among these, examples of the apparatus that can perform kneading include apparatuses such as an open type mixing roll, a non-open type Banbury mixer, a single screw extruder, a twin screw extruder, and a kneader. Among these, it is preferable to use a single screw extruder and / or a twin screw extruder from the viewpoints of economy, processing efficiency, and the like. The treatment performed in this kneading apparatus may be a batch type or a continuous type.

The continuous extruder is not particularly limited as long as the thermoplastic elastomer composition can be melt-kneaded, and examples thereof include a single screw extruder, a twin screw extruder, a twin screw rotor type extruder, and the like. Of these, a twin screw extruder is preferably used. Of these, a twin screw extruder having L / D (ratio of effective screw length L to outer diameter D) of 30 or more, more preferably 36 to 60 is preferably used. As the twin-screw extruder, for example, an arbitrary twin-screw extruder such as one in which two screws mesh with each other or one that does not mesh with each other can be used. Those are more preferred.
Such twin screw extruders include GT / PCM manufactured by Ikegai, KTX / LCM / NCM manufactured by Kobe Steel, TEX / CIM / CMP manufactured by Nippon Steel, TEM manufactured by Toshiba Machine Co., and ZSK manufactured by Warner. Are also trademarks).

  The treatment temperature in the dynamic heat treatment is 120 to 350 ° C., preferably 150 to 290 ° C., and the treatment time is 20 seconds to 320 minutes, preferably 30 seconds to 25 minutes. The shearing force applied to the mixture is 10 to 20,000 / sec, preferably 100 to 10,000 / sec in terms of shear rate.

The thermoplastic elastomer composition was selected from the following thermoplastic resins and rubbers in such an amount that does not impair the mechanical strength, flexibility and moldability of the automotive weather strip of the present invention finally obtained. A high molecular compound and various additives can be contained.
Such a polymer compound is not particularly limited as long as it is other than a specific functional group-containing copolymer, and various compounds can be used. Specific examples thereof include ionomers, aminoacrylamide polymers, polyethylene and Its maleic anhydride graft polymer, polyisobutylene, ethylene-vinyl chloride polymer, ethylene-vinyl alcohol polymer, ethylene-vinyl acetate copolymer, polyethylene oxide, ethylene-acrylic acid copolymer, polypropylene and its maleic anhydride Graft polymer, atactic poly-1-butene homopolymer, α-olefin copolymer resin (propylene (containing 50 mol% or more)) and other α-olefins (ethylene, 1-butene, 1-pentene, 1- Hexene, 4-methyl-1-pentene, 1-octene, 1-dece 1-butene (containing 50 mol% or more) and other α-olefins (ethylene, propylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-decene, etc.), polyisobutylene and its maleic anhydride graft polymer, chlorinated polypropylene, 4-methylpentene-1 resin, polystyrene, ABS resin, ACS resin, AS resin, AES resin, ASA Resin, MBS resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinylidene chloride resin, polyamide resin, polycarbonate, acrylic resin, methacrylic resin, vinyl chloride resin, vinylidene chloride resin, vinyl alcohol resin, vinyl acetal resin, methyl methacrylate resin , Fluorine resin, polyether resin, polyethylene Terephthalate, polyacrylate, polyamide resin, ethylene / α-olefin copolymer rubber and its maleic anhydride graft polymer, ethylene / α-olefin / non-conjugated diene copolymer rubber, styrene / butadiene rubber and its hydrogenation , Maleic anhydride graft polymer of hydrogenated styrene / butadiene rubber, butadiene rubber and hydrogenated product thereof, maleic anhydride graft polymer of hydrogenated butadiene rubber, polyisobutylene-isopreneprene copolymer, isoprene Rubber and hydrogenated products thereof, maleic anhydride graft polymer of hydrogenated products of isoprene rubber, styrene / isoprene rubber and hydrogenated products thereof, maleic anhydride graft polymer of hydrogenated products of styrene / isoprene rubber, nitrile rubber and Its hydrogenated products, acrylic rubber, silicone Rubber, fluoro rubber, butyl rubber, natural rubber, chlorinated polyethylene thermoplastic elastomer, syndiotactic-1,2 polybutadiene, hydrogenated styrene / butadiene block copolymer, hydrogenated styrene / isoprene block copolymer , Simple blend type olefin thermoplastic elastomer, implant type olefin thermoplastic elastomer, dynamically crosslinked olefin thermoplastic elastomer, polyvinyl chloride thermoplastic elastomer, polyurethane thermoplastic elastomer, polyester thermoplastic elastomer, polyamide Examples thereof include thermoplastic elastomers and fluorine-based thermoplastic elastomers, and crystalline / amorphous α-olefin polymers such as polypropylene and propylene / butene-1 copolymer resins are particularly preferable.
These polymer compounds can be used singly or in combination of two or more.
The use ratio of the polymer compound is 300 parts by mass or less, preferably 1 to 200 parts by mass with respect to 100 parts by mass of the specific functional group-containing copolymer.

  Further, various additives include, for example, antioxidants, antistatic agents, blocking agents, sealability improvers, lubricants, anti-aging agents, heat stabilizers, weathering agents, metal deactivators, ultraviolet absorbers, and light stabilizers. Stabilizers, antibacterial and antifungal agents, dispersants, plasticizers, crystal nucleating agents, flame retardants, tackifiers, foaming aids, titanium oxide, carbon black and other colorants, pigments , Metal powders such as ferrite, inorganic fibers such as glass fibers and metal fibers, organic fibers such as carbon fibers and aramid fibers, composite fibers, inorganic whiskers such as potassium titanate whiskers, glass beads, glass balloons, glass flakes, asbestos, Mica, calcium carbonate, talc, wet silica, dry silica, alumina, alumina silica, calcium silicate, hydrotalcite, kaolin, diatomaceous earth, Fillers such as lafite, pumice, evo powder, cotton flock, cork powder, barium sulfate, fluororesin, polymer beads or mixtures thereof, polyolefin wax, cellulose powder, rubber powder, filler such as wood powder, low molecular weight polymer, etc. Can be contained.

Foaming of thermoplastic elastomer composition The foam as a material of the weather strip for automobiles of the present invention has a foaming ratio of 1.2 to 20, preferably 1.4 to 10 in the thermoplastic elastomer composition. It can be obtained by blending with a foaming agent and then foaming. In this case, a pre-irradiation automobile weather strip made of foam can be obtained simultaneously with foaming and molding.

Examples of the foaming agent include a pyrolytic foaming agent, a volatile foaming agent, a hollow particle foaming agent, and a supercritical fluid. This foaming agent can be selected according to the production method.
These foaming agents may be used alone or in combination of two or more.

Pyrolytic foaming agents include N, N′-dinitrosopentamethylenetetramine, N, N′-dimethyl-N, N′-dinitrosotephthalamide and the like; azodicarbonamide, barium azodicarboxylate Azo foaming agents of barium azodicarboxylate; sulfohydrazide foaming agents such as p, p-oxybisbenzenesulfonyl hydrazide, 4,4′-oxybis (benzenesulfonyl hydrazide), p-toluenesulfonylyl semicarbazide; Examples include triazine foaming agents such as trihydrazinotriazine; tetrazole foaming agents such as 5-phenyltetrazole, azobistetrazole diguanidine, and azobistetrazoleaminoguanidine; and inorganic foaming agents such as sodium hydrogen carbonate.
These foaming agents may be used in combination of two or more.
The amount of these thermally decomposable foaming agents may be selected so that the expansion ratio falls within the above range depending on the type of foaming agent, but it is 0.1 to 100 masses per 100 parts by mass of the thermoplastic elastomer composition. Part.

Furthermore, examples of the volatile foaming agent include aliphatic hydrocarbons such as propane, butane and pentane; alicyclic hydrocarbons such as cyclobutane, cyclopentane and cyclohexane; chlorodifluoromethane, difluoromethane, trifluoromethane, and trichloro. Fluoromethane, dichloromethane, dichlorofluoromethane, dichlorodifluoromethane, trichlorofluoromethane, chloromethane, chloroethane, dichlorotrifluoroethane, dichlorofluoroethane, chlorodifluoroethane, dichloropentafluoroethane, pentafluoroethane, trifluoroethane, dichlorotetrafluoro Oroethane, trichlorotrifluoroethane, tetrachlorodifluoroethane, chloropentafluoroethane, perfluorocyclobutane, etc. Gen hydrocarbons; carbon dioxide, nitrogen, inorganic gas such as air; and water can be mentioned.
Two or more kinds of these foaming agents may be mixed and used.
The addition amount of these volatile foaming agents may be selected so that the expansion ratio is in the above range depending on the type, but is 0.1 to 100 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer composition. It is preferable.

  Moreover, a foam can also be shape | molded using a supercritical fluid. Examples of the supercritical fluid include nitrogen and carbon dioxide. These supercritical fluids may be used as a mixture of two or more. The amount of gas injected when foaming using these supercritical fluids varies depending on the type of the supercritical fluid, and may be selected so that the expansion ratio is in the above range.

The hollow particle type foaming agent is a thermoplastic resin thermally expandable microsphere that contains an expansion agent and uses a thermoplastic resin as an outer shell component. Examples of the expanding agent constituting the hollow particle type blowing agent include the same as the above volatile type blowing agent. The ratio of the expanding agent to the thermally expandable microspheres is preferably 5 to 30% by mass.
On the other hand, thermoplastic resins such as (meth) acrylonitrile, (meth) acrylate, vinyl halide, vinylidene halide, styrene monomer, vinyl acetate, butadiene, chloroprene, vinyl pyridine, etc. Resins can be mentioned.
This thermoplastic resin is divinylbenzene, ethylene glycol (meth) acrylate, triethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, allyl (meth). It may be made crosslinkable or crosslinkable with a crosslinking agent such as acrylate, triacryl formal, triallyl isocyanurate or the like.
The mass average particle diameter of this hollow particle type foaming agent (unexpanded microsphere state) is usually preferably 1 to 100 μm. The addition amount of these hollow particle type foaming agents may be selected so that the expansion ratio is in the above range according to the type, but is 0.1 to 100 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer composition. It is preferable to do.

In these foaming agents (thermal decomposition foaming agent, volatile foaming agent, hollow particle foaming agent, and supercritical fluid), sodium bicarbonate, citric acid or citric acid or A foam nucleating agent such as talc may be used in combination.
Usually, the foam nucleating agent is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the thermoplastic elastomer composition.

  The foam obtained from the above-mentioned thermoplastic elastomer composition has a three-dimensional network structure that does not depend on chemical crosslinking, is excellent in elastic recovery and flexibility, is uniformly foamed, has high closed cell properties, and is foamed. The shape and size of the bubbles are uniform and the surface appearance is excellent, and it is suitable as a material for the weather strip for automobiles of the present invention obtained by electron beam irradiation.

Forming Foam Before Irradiation Further, the method for adding the foaming agent and the foam molding method (that is, the method for producing the foam before irradiation) are not particularly limited. For example, the following methods can be mentioned.
(1) A method in which a thermoplastic elastomer composition and a foaming agent are melt-kneaded in a melt extruder and then extruded.
(2) A method of adding a foaming agent to the thermoplastic elastomer composition by dry blending and extruding with a melt extruder.
(3) A method in which a foaming agent is pressed into a molten thermoplastic elastomer composition and then extruded in a melt extruder.
(4) A method of injection molding after adding a foaming agent to the thermoplastic elastomer composition.
(5) A method of injection molding after melt-kneading a thermoplastic elastomer composition and a foaming agent in a melt extruder.
(6) A method in which a thermoplastic elastomer composition and a foaming agent are melt-kneaded with a melt extruder and then put into a press mold and subjected to hot press molding.
(7) A method in which a plastic elastomer composition and a foaming agent are melt-kneaded with a batch kneader, calendered, and then heated.
Especially, the extrusion method of (1)-(3) is preferable.

  When producing a pre-irradiation foam by extrusion molding, the optimum temperature and residence time are appropriately determined depending on the expansion ratio, the type and amount of the thermoplastic elastomer component, the type and amount of the foaming agent, etc. The residence time is 15 seconds to 5 minutes at a temperature of 140 to 280 ° C.

  As described above, an automotive weatherstrip-shaped foam is obtained. The automotive weatherstrip may have any conventionally known shape, for example, Japanese Patent Laid-Open Nos. 4-368223 and 11-48788. Examples thereof include those described in JP-A-11-70544.

Electron Beam Irradiation The automobile weather strip of the present invention is obtained by irradiating the above-mentioned automobile weather strip-shaped foam with an electron beam.
The thermoplastic elastomer composition used in the weather strip for automobiles of the present invention has a three-dimensional network structure that does not depend on chemical crosslinking and is excellent in elastic recovery and flexibility, but when irradiated with an electron beam, The radical reaction of the non-conjugated diene and ethylene component in the thermoplastic elastomer composition results in a three-dimensional cross-linked structure and further increases the elastic recovery.
Moreover, in this invention, since it bridge | crosslinks by electron beam irradiation, there is no contamination by a crosslinking agent.
The electron beam is permeable to the synthetic resin, and the degree of transmission depends on the thickness of the synthetic resin and the kinetic energy of the electron beam.
By adjusting the energy of the electron beam so that it can be transmitted uniformly in the thickness direction according to the irradiation thickness, a weather strip for an automobile having a uniform degree of crosslinking in the thickness direction can be obtained.

  The electron beam accelerating voltage is preferably 100 to 2,000 kV, more preferably 200 to 1,000 kV with respect to the above molded product, but if it is smaller than 100 kV, the proportion of electrons captured and absorbed by the surface layer portion is small. This is not preferable because the number of electron beams that pass through the molded product is relatively small, the number of electron beams that pass through the molded product is reduced, internal crosslinking is delayed as compared with the surface layer portion, and the degree of crosslinking is different. On the other hand, when it is larger than 2,000 kV, the mechanical strength is lowered by molecular cutting, which is not preferable.

  In this case, the irradiation amount of the electron beam is preferably 10 to 1,000 kGy (Gy: gray, J / kg), more preferably 100 to 800 kGy, and crosslinking and curing is performed. If it is less than 10 kGy, the degree of crosslinking is small, while if it exceeds 1,000 kGy, the mechanical strength is reduced by molecular cutting, which is not preferable.

  The crosslinking effect by electron beam irradiation can be expressed by the product of the electron beam acceleration voltage and the irradiation amount. In the present invention, the product of the electron beam acceleration voltage (kV) and the irradiation dose (kGy) is preferably 1,000. ˜2,000,000 (kV · kGy), more preferably 10,000 to 500,000 (kV · kGy). If it is smaller than 1,000 (kV · kGy), the proportion of electrons captured and absorbed by the surface layer portion becomes relatively large, and the number of electron beams that permeate the molded product is reduced. Is delayed, and a difference occurs in the degree of crosslinking. On the other hand, when it is larger than 2,000,000 (kV · kGy), the mechanical strength is lowered by molecular cutting, which is not preferable.

  Although the rubber elasticity can be improved only by electron beam cross-linking, a cross-linking aid may be added to the thermoplastic elastomer composition as a raw material of the automobile weather strip of the present invention in order to further increase the rubber elasticity. The amount added is when the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass. And 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass. If it is less than 0.01 parts by mass, no further effect of improving rubber elasticity is observed, while if it exceeds 10 parts by mass, the effect of improving rubber elasticity is saturated.

Examples of the crosslinking aid include sulfur or sulfur compounds such as powdered sulfur, colloidal sulfur, precipitated sulfur, insoluble sulfur, surface-treated sulfur, dipentamethylene thiuram tetrasulfide; p-quinone oxime, p, p′-dibenzoyl Oxime compounds such as quinone oxime; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) Acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, glycerin di (meth) acrylate, polyethylene glycol (PEG # 200) di (meth) acrylate, polyethylene Glycol (PEG # 400) di (meth) acrylate, polyethylene glycol (PEG # 600) di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate , Neopentyl glycol di (meth) acrylate, diallyl phthalate, tetraallyloxyethane, triallyl isocyanurate, N, N′-m-phenylene bismaleimide, N, N′-toluylene bismaleimide, maleic anhydride, divinylbenzene , 2,4,6-trimercapto-S-triazine, polyfunctional monomers such as isocyanuric acid, zinc methacrylate, magnesium methacrylate, zinc dimethacrylate, magnesium dimethacrylate, etc. Include the metal compounds. Of these crosslinking aids, p, p′-dibenzoylquinone oxime, N, N′-m-phenylenebismaleimide, trimethylolpropane tri (meth) acrylate, and divinylbenzene are preferred.
The crosslinking aids can be used alone or in admixture of two or more.

The crosslinking aid may be added at the time of producing the thermoplastic elastomer composition, or may be added after the production of the thermoplastic elastomer composition part.
As the addition method, the thermoplastic elastomer composition and the crosslinking aid may be mixed by dynamic heat treatment, or simply mixed with the thermoplastic elastomer composition.

When irradiating an electron beam, it is preferable to irradiate while rotating the foam of a weatherstrip shape for automobiles. By carrying out in this way, the entire surface of the weather strip for automobiles can be uniformly irradiated with an electron beam and can be uniformly crosslinked. Irradiation may be batch or continuous.
By subjecting an automobile weatherstrip-shaped foam before irradiation to electron beam irradiation as described above, the compression set of the automobile weatherstrip after electron beam irradiation can be made smaller than that before electron beam irradiation.

  Moreover, the weather strip for automobiles of the present invention after irradiation with an electron beam usually has a cyclohexane insoluble content of 50 to 100% by mass, preferably 60 to 100% by mass, and more preferably 70 to 100% by mass. The cyclohexane insoluble content is a barometer indicating how much the thermoplastic elastomer composition is crosslinked by irradiating the foam with an electron beam.

Here, the cyclohexane insoluble content was calculated as follows.
About 200 mg of the automotive weather strip of the present invention is weighed and cut into pieces. The resulting strip is then immersed in 100 ml cyclohexane at 23 ° C. for 48 hours in a sealed container. Next, this sample is taken out on a filter paper, and dried under reduced pressure at 105 ° C. for 1 hour in a vacuum dryer. From the mass of this dry residue, (a) cyclohexane insoluble components (packing) other than ethylene-α-olefin copolymer (1), crystalline polyethylene resin (2), and conjugated diene block copolymer (3) (B) the value obtained by subtracting the mass of the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) in the sample before immersion in cyclohexane. Final mass (p) ”.

On the other hand, from the mass of the sample before measurement, cyclohexane other than (c) ethylene-α-olefin copolymer (1), crystalline polyethylene resin (2), and conjugated diene block copolymer (3) can be used. Mass of soluble component (for example, mineral oil softener), (a) Other than ethylene-α-olefin copolymer (1), crystalline polyethylene resin (2), and conjugated diene block copolymer (3) The value obtained by subtracting the mass of the cyclohexane insoluble component (filler, pigment, etc.) and the mass of (d) the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) was corrected. Initial mass (q) ”. Here, the cyclohexane insoluble matter as the crosslinking density is determined by the following formula. In addition, when (alpha) -olefin type polymer resin (polypropylene etc.) is added as other components, it calculates similarly to crystalline polyethylene type resin (2).
Cyclohexane insoluble matter [mass%] = [{corrected final mass (p)} ÷ {corrected initial mass (q)}] × 100

  When the cyclohexane insoluble content of the automobile weather strip after crosslinking by electron beam irradiation is less than 50% by mass, crosslinking by electron beam irradiation is insufficient and the rubber elasticity is poor. The cyclohexane insoluble matter can be easily adjusted by setting the product of the electron beam acceleration voltage (kV) and the irradiation dose (kGy) to 1,000 to 2,000,000 (kV · kGy). .

  The automotive weather strip of the present invention thus obtained is excellent in elasticity and has a very small compression set and is suitably used as an automotive weather strip.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to these.

Example 1
[1] Preparation of thermoplastic elastomer composition As the ethylene / α-olefin copolymer (1), an oil-extended ethylene-propylene-5-ethylidenenorbornene copolymer rubber (manufactured by JSR, product name “EP98A”, ethylene content) 79 mol%, propylene content 21 mol%, iodinated 15, paraffinic oil 75 phr oil) 58 parts by mass, crystalline polyethylene resin (2), linear low density polyethylene (manufactured by Nippon Polychem, product name " Novatec LL UF423 ", crystallinity 40%, DSC melting point 124 ° C) 21 parts by mass, conjugated diene block copolymer (3) shown below 21 parts by mass, crystalline polypropylene as α-olefin polymer 5 parts by mass (made by Nippon Polychem Co., Ltd., product name “Novatech PP BC5CW”, crystallinity 70%), and aging 0.2 parts by mass of tetraester type polymer hindered phenolic antioxidant (product name “Irganox 1010”, manufactured by Ciba Specialty Chemicals Co., Ltd.) as an inhibitor is mixed with a 10-liter pressure kneader (manufactured by Moriyama Co., Ltd.). The mixture was melt-kneaded at a preset temperature of 150 ° C., a kneading time of 15 minutes, and 40 rpm (shear rate of 200 / sec). The obtained composition in the molten mass state was pelletized with a feeder ruder (manufactured by Moriyama Co., Ltd.) to obtain the intended thermoplastic elastomer composition.
Conjugated diene block copolymer (3);
It was obtained by the method shown below.
Cyclohexane (24 kg), tetrahydrofuran (1 g), 1,3-butadiene (1200 g), and n-butyllithium (3.3 g) were added to a reaction vessel having an internal volume of 50 liters purged with nitrogen, and heat insulation from 70 ° C. Polymerization was performed. After completion of the reaction, the temperature was set to 5 ° C., tetrahydrofuran (340 g) and 1,3-butadiene (2800 g) were added, and adiabatic polymerization was performed. After 30 minutes, methyldichlorosilane (2.3 g) was added and reacted for 15 minutes.
After the reaction was completed, hydrogen gas was supplied at a pressure of 0.4 MPa-G, stirred for 20 minutes, and reacted with living polymer anion lithium as a living anion to obtain lithium hydride.
The reaction solution was brought to 90 ° C., tetrachlorosilane (7.2 g) was added, and the mixture was stirred for about 20 minutes. Then, a hydrogenation catalyst mainly composed of a titanocene compound was added, and a hydrogenation reaction was performed at a hydrogen pressure of 0.8 MPa for 2 hours. It was.
When the absorption of hydrogen is completed, the reaction solution is returned to room temperature and normal pressure and extracted from the reaction vessel, and then the reaction solution is stirred into water and the solvent is removed by steam distillation to remove the hydrogenated diene polymer. A hydrogenated block polymer having an A-B-A structure (A is a polybutadiene having a low 1,2-vinyl bond content and B is a polybutadiene having a high 1,2-vinyl bond content) was obtained.
The resulting hydrogenated conjugated diene block copolymer has a hydrogenation rate of 99%, a weight average molecular weight of 300,000, and the vinyl bond content of the first polybutadiene A block of the pre-hydrogenation polymer is 15%. The vinyl bond content of the second stage polybutadiene B block of the polymer was 78%. Moreover, the melt flow rate measured at 230 degreeC and 21.2N of the polymer after hydrogenation was 2.5 g / 10min.

[2] Manufacture of automotive weather strips Each thermoplastic elastomer composition obtained in [1] is mixed with a chemical foaming agent, subjected to foam molding and electron beam crosslinking by the following method, and is shown in the schematic cross-sectional view of FIG. An automotive weather strip having a cross-sectional shape was obtained.

(Foam molding method)
To the thermoplastic elastomer composition obtained in [1], 2.5 parts by mass of a pyrolytic chemical foaming agent master batch (manufactured by Eiwa Kasei Kogyo Co., Ltd., product name “Polyslen EE206”) is added and stirred as a foaming agent. Mix to obtain a masterbatch. This master batch is put into a single screw extruder of 40 mm in diameter (FS-40 manufactured by Ikegai Co., Ltd., L / D = 28, foaming temperature 210 ° C., screw rotation speed 30 rpm, full flight screw) and extruded and foamed to form a weather strip for automobiles. Foam was obtained.

(Electron beam crosslinking)
The obtained foam was processed with an acceleration voltage of 800 kV and an irradiation dose of 500 kGy in a nitrogen atmosphere using an electron beam irradiation apparatus “manufactured by Nissin High Voltage, product name“ ESP800-35 ”).
The automobile weather strips thus obtained were evaluated as follows. The results are shown in Table 1.

Example 2
A foam was obtained in the same manner as in Example 1 except that 1 part by mass of trimethylolpropane trimethacrylate (product name “TMP”, manufactured by Kyoeisha Chemical Co., Ltd.) was added as a crosslinking aid.
Thereafter, the obtained foam was subjected to a treatment with an acceleration voltage of 800 kV and an irradiation dose of 100 kGy in a nitrogen atmosphere using an electron beam irradiation apparatus “manufactured by Nissin High Voltage, product name“ ESP800-35 ”).
The automobile weather strips thus obtained were evaluated as follows. The results are shown in Table 1.

Example 3
The same procedure as in Example 2 was performed except that the irradiation dose was 300 kGy.
The automobile weather strips thus obtained were evaluated as follows. The results are shown in Table 1.

Example 4
80 parts by mass of ethylene / α-olefin copolymer (1), 20 parts by mass of crystalline polyethylene resin (2), 20 parts by mass of conjugated diene block copolymer (3), α-olefin polymer Was performed in the same manner as in Example 3, except that 18 parts by mass of paraffinic mineral oil (manufactured by Idemitsu Kosan Co., Ltd., product name “Diana Process Oil PW380”) was added as a softening agent.
The automobile weather strips thus obtained were evaluated as follows. The results are shown in Table 1.

Comparative Example 1
The procedure was the same as in Example 1 except that no electron beam irradiation was performed.
The automobile weather strips thus obtained were evaluated as follows. The results are shown in Table 1.

In addition, each raw material shown in Table 1 is as follows.
Ethylene / α-olefin copolymer (1);
Oil-extended ethylene-propylene-5-ethylidene norbornene copolymer rubber (manufactured by JSR, product name “EP98A”, ethylene content 79 mol%, propylene content 21 mol%, iodinated 15, paraffinic oil 75 phr oil)
Crystalline polyethylene resin (2);
Linear low-density polyethylene (manufactured by Nippon Polychem, product name “Novatech LL UF423”, crystallinity 40%, melting point 124 ° C. by DSC)
Conjugated diene block copolymer (3);
A hydrogenated conjugated diene block copolymer obtained by the method shown in Example 1. The hydrogenation rate is 99%, the weight average molecular weight is 300,000, the vinyl bond content of the first polybutadiene A block of the polymer before hydrogenation is 15%, the vinyl bond content of the second polybutadiene B block of the polymer before hydrogenation Was 78%. Moreover, the melt flow rate measured at 230 degreeC and 21.2N of the polymer after hydrogenation was 2.5 g / 10min.

Other components α-olefin polymer;
Crystalline polypropylene (Nippon Polychem Co., Ltd., product name “Novatech PP BC5CW”, crystallinity 70%)
Anti-aging agent;
Tetraester type polymer hindered phenolic antioxidant (Ciba Specialty Chemicals, product name "Irganox 1010")
Softener;
Paraffinic mineral oil (product name “Diana Process Oil PW380”, manufactured by Idemitsu Kosan Co., Ltd.)
Foaming agent Thermal decomposition type chemical foaming agent master batch (manufactured by Eiwa Kasei Kogyo Co., Ltd., product name “Polyslen EE206”)
Crosslinking aid trimethylolpropane trimethacrylate (Kyoeisha Chemical Co., Ltd., product name "Light Ester TMP")

Confirmation of 3D network structure
Using the thermoplastic elastomer composition obtained in [1], a sheet-like molded product having a thickness of 2 mm, a length of 120 mm, and a width of 120 mm was obtained by an injection molding machine (Toshiba Machine Co., Ltd., model “IS-90B”). Fabricate a thin film piece in the thickness direction using a microtome, and then dye it with RuO _4, etc., and then take a 2000 × photograph with a transmission electron microscope. From this photograph, whether or not a three-dimensional network structure is formed I confirmed. All the compositions obtained in Examples 1 to 4 had a three-dimensional network structure.

Evaluation of Weather Strip for Automobile The evaluation shown in Table 1 was based on the following method.
(1) Foaming ratio It was set as the conversion value from the specific gravity measurement value.
(2) cyclohexane insoluble matter;
The measurement method is shown in the text.
(3) compression set test;
Measurement was performed in accordance with JIS K6262 (70 ° C., 22 hrs, 50% compression) and used as an index of rubber elasticity.
(4) Long-term compression set test;
Measurement was performed in accordance with JIS K6262 (70 ° C., 200 hrs, 50% compression) and used as an index of rubber elasticity.
(5) Oil resistance;
A method according to JIS K6258 (IRM903 oil, immersed at room temperature for 24 hours).
(6) Scratch resistance test;
The surface of the sheet was rubbed with a thumb nail, and the degree of damage was visually determined according to the following criteria.
○;
×: Scratched (7) Appearance;
The surface state of the foam was visually evaluated.

From the results shown in Table 1, in the examples of the present invention, the weather for automobiles has a smaller compression set for a short time and longer time than the comparative example, and has excellent elastic recovery, oil resistance, and scratch resistance. A strip is obtained. Also, the appearance was good.

  The automotive weather strip of the present invention has a very small compression set, oil resistance, scratch resistance, good appearance, and can be suitably used as an automotive weather strip.

It is a schematic sectional drawing of the weather strip for motor vehicles of this invention.

Claims (10)

  Thermoplastic elastomer in which crystalline polyethylene resin (2) and conjugated diene block copolymer (3) form a three-dimensional network structure in a matrix comprising ethylene / α-olefin copolymer (1) A weatherstrip for automobiles, which is obtained by irradiating a foam containing the composition as a main component with an electron beam.   The (3) conjugated diene block copolymer is more compatible with (a) a crystalline ethylene polymer block and (b) an ethylene / α-olefin copolymer than with a crystalline polyethylene resin. The automobile weather strip according to claim 1, further comprising a higher block.   The weather strip for automobiles according to claim 1 or 2, wherein the conjugated diene block copolymer (3) has a crystalline ethylene polymer block at both ends. The conjugated diene block copolymer (3) is obtained by hydrogenating a conjugated diene block copolymer whose terminal blocks are the following A blocks and whose intermediate block is the following B block. When the total of the A block and the B block is 100% by mass, the A block is 5 to 90% by mass, the B block is 10 to 95% by mass, and the conjugated diene block copolymer ( The automotive weather strip according to any one of claims 1 to 3, wherein 3) is saturated at least 80% of all double bonds contained before hydrogenation and has a number average molecular weight of 50,000 to 700,000.
A: butadiene polymer block having a 1,2-vinyl bond content of less than 25 mol% B; conjugated diene polymer block and / or vinyl aromatic-conjugate having a 1,2-vinyl bond content of 25 mol% or more Diene random copolymer block   When the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100% by mass, the ethylene / α -The olefin copolymer (1) is 10 to 94 mass%, the crystalline polyethylene resin (2) is 5 to 80 mass%, and the conjugated diene block copolymer (3) is 1 to 1 mass%. It is 80 mass%, The weather strip for motor vehicles in any one of Claims 1-4.   200 masses when the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass. The automotive weather strip according to any one of claims 1 to 5, which contains up to 5 parts of a softener.   When the total of the ethylene / α-olefin copolymer (1), the crystalline polyethylene resin (2) and the conjugated diene block copolymer (3) is 100 parts by mass, thermoplasticity The weather strip for automobiles according to any one of claims 1 to 6, wherein 0.1 to 10 parts by mass of a crosslinking aid is further added to the elastomer composition.   The automobile weather strip according to any one of claims 1 to 7, wherein the cyclohexane insoluble matter after electron beam irradiation is 50 to 100 mass%.   The amount of electron beam irradiation is 1,000 to 2,000,000 (kV · kGy) as a product of electron beam acceleration voltage (kV) and irradiation dose (kGy). Weather Strip. The weather strip for automobiles according to any one of claims 1 to 9, which is obtained by electron beam irradiation while rotating.

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