JP2002332360A - Multilayer pellet having rubber core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber pellet with an improved handleability which inhibits the mutual adhesion of pellets, even under conditions such as long term storage, and is therefore stable and may be used for preparing thermoplastic elastomers, or the like, via a continuous process. SOLUTION: The multilayer pellet has a core-sheath structure, wherein the core comprises a rubber and the sheath comprises a material having a lower adhesion compared to the rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rubber-based multilayer pellet which can be used for polymer blends and the like. More specifically, the present invention relates to a multilayer pellet having a core-sheath structure, in which the core is mainly composed of rubber, and the sheath is made of a material having lower adhesiveness than rubber.

[0002]

2. Description of the Related Art In recent years, a flexible synthetic resin or a thermoplastic elastomer which behaves as a rubber elastic body at room temperature and undergoes plastic deformation due to a rise in temperature has attracted attention.
They have the same moldability as thermoplastic resins without the need for a vulcanization step, and exhibit the same or better strength properties as vulcanized rubber reinforced without the addition of a reinforcing material. It has the advantage that an elastic body with a wide range of physical properties, from plastics to plastics, can be obtained by changing the chemical structure of the material (Practical Plastics Encyclopedia, Industrial Research Council), so it can be used for automobile parts, home appliance parts, medical equipment・
It is used in the fields of food machine parts, electric wires and miscellaneous goods. Such a soft synthetic resin or a thermoplastic elastomer can be obtained by, for example, a method of blending various resins (hard phase) with an elastic component (soft phase, soft segment) such as rubber. Based on the type of hard phase, it is classified into polyolefin-based, polystyrene-based, polyurethane-based, polyester-based, vinyl chloride-based, and the like, and each is commercially available.

[0003] Polyolefin-based soft synthetic resins and thermoplastic elastomers include polyolefin resins such as polyisobutylene rubber (PIB) and ethylene propylene rubber (E).
PR or EPDM), isobutylene rubber (IIR),
Styrene-butadiene rubber (SBR), natural rubber (N
R), butadiene rubber (BR) and the like are blended to improve their impact strength and low-temperature brittleness. Even for soft synthetic resins and thermoplastic elastomers other than polyolefins, rubber is used as a soft phase, and can be obtained by blending with a hard phase resin or the like.

[0004] As described above, a soft synthetic resin such as a polyolefin resin or a thermoplastic elastomer can be obtained by blending (kneading) a rubber with a resin of a hard phase and the like. Products can be. The synthetic resin used for kneading and molding is generally produced and supplied in a granular form called “pellet”, and is supplied to a kneading machine or a molding machine in the form of pellet. This is due to the pellet being in the form of a solid material suitable for a continuous processing step. However, when kneading, molding, and the like are performed using rubber, since the rubber as a raw material has a strong adhesiveness, very few are produced and supplied in the form of pellets or granules. 15-35 kg of a semi-molten (so-called rubber-like) mass referred to as "". The bale is 15-35kg
If the batch size is small, cut it into a block shape with a cutter or the like before use. But,
Even in this case, a batch-type production method using a Banbury mixer or the like must be used, and it is difficult to employ a continuous process.

[0005] As a method of producing a soft synthetic resin or a thermoplastic elastomer by employing a continuous process, a rubber is wound in advance on two rolls or the like, then cut out into a ribbon shape, and is forced into an extruder or the like. A way is being considered. However, this method has a problem that the supply amount is not stable.
In addition, a method of pulverizing rubber into an irregular shape for use has been considered. However, as described above, rubber has high fluidity and extremely strong tackiness in a temperature range higher than ordinary room temperature. For this reason, even if pelletization or pulverization is performed once, they are packaged in flexible containers or paper bags and then reattached within a short period of time, changing to a large lump state or a large number of connected grains or pellets, and extruder or injection It cannot be used on processing machines such as molding machines. Therefore, supply in the form of granules or pellets was practically impossible except for cases where storage and transportation were performed at extremely low temperatures.

[0006] To solve this problem, In the case of a synthetic rubber, the composition ratio of the monomers constituting the synthetic rubber is biased to reduce the adhesiveness. 2. kneading synthetic resin and various inorganic fillers to reduce the adhesiveness; 3. The surface of the material once pulverized or pelletized is covered with a powdery substance such as metal soap or resin powder to reduce tackiness and prevent mutual adhesion. Measures such as applying a release material to the surface of the material once pulverized or pelletized to reduce tackiness and prevent mutual adhesion have been considered. However, if the composition ratio of the monomers constituting the synthetic rubber is biased, its physical properties also change. In a method using a powdery substance or a release material, the amount of the powdery substance or the like must be increased in order to more completely prevent mutual adhesion, which is not preferable in terms of physical properties and economy. In addition, even in such a method, the substance is unstable under conditions such as long-term storage, and particles and pellets tend to adhere to each other and cannot be used.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have proposed a process for producing a thermoplastic elastomer which is a rubber pellet, which is stable without causing sticking between the pellets even under conditions such as long-term storage, and which is a continuous process. As a result of intensive studies to develop products that can be used for such purposes, the use of multilayer pellets made of rubber with a core that is less sticky than rubber can prevent co-sticking between pellets and handle rubber. The present invention was found to be improved in performance and capable of coping with continuous production and small lot production.

[0008]

That is, the present invention provides a multilayer pellet having a core-sheath structure, wherein the core is made of rubber and the sheath is made of a material having lower adhesiveness than rubber. By using this multilayer pellet, mutual adhesion of the pellets can be prevented, and the handling of rubber is improved, so continuous production or batch production in small lots for the production of flexible synthetic resins, thermoplastic elastomers, etc. Production can be easily adopted. Accordingly, the present invention provides a method for producing a soft synthetic resin or a thermoplastic elastomer, wherein a multilayered pellet having a core-sheath structure, the core is made of rubber, and the sheath is made of a material having lower adhesiveness than rubber is used. A method is also provided.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The multilayer pellet of the present invention has at least two layers, a core layer and a sheath layer. Other layers may be provided as needed as long as the object of the present invention is not impaired. The core layer contains rubber as a main component. The rubber used for the core layer is not particularly limited as long as it has rubber elasticity at room temperature, but the Mooney viscosity (ML _{1 + 4} 100 ° C.) of the core layer is 5 to 5.
The present invention particularly exerts its effect on rubber having a range of 200. Here, the Mooney viscosity is an index of the fluidity of the rubber, and a small Mooney viscosity value indicates that the fluidity is large. Also, (ML _{1 + 4} 100 ° C)
It represents the measurement condition of Mooney viscosity, the size of the rotor specified at the time of measurement is a large "L" size, the sample is set and preheated for 1 minute after setting, and the measurement temperature (retention temperature of the test sample) is 100C. , 4 minutes after the start of measurement (rotor rotation).

[0010] Types of rubber used for the core layer include styrene-butadiene rubber (SBR) and butadiene.
Rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), isobutylene / isoprene rubber (IIR, butyl rubber), ethylene / propylene rubber (EPM, EPDM), ethylene / butene rubber ( EBM, EBDM), copolymer rubber of two or more α-olefins, silicone rubber (Q), fluorine rubber (FKM), chlorosulfonated polyethylene (CS
M), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), ethylene / vinyl acetate rubber (EVA), natural rubber (NR), blends of two or more of the above synthetic and natural rubbers, and Examples of the composition include the above materials and various fillers and additives. Further, halobutyl rubber, a copolymer of p-alkylstyrene and an isomonoolefin having 4 to 7 carbon atoms such as isobutylene, which is halogenated (for example, brominated), and butyl rubber containing a repeating unit derived from divinylbenzene , Homo- or copolymers derived from at least one conjugated diene, and combinations thereof. In addition, amine-functionalized, carboxy-functionalized, or epoxy-functionalized rubbers can also be used, including maleated EPDM and epoxy-functionalized natural rubber. . These materials are available. In the present invention, the term “polymer” is used to mean a polymer having a repeating unit derived from one or more different monomers, that is, a homopolymer or a copolymer.

Basically, a core material (a material constituting a core layer)
When the polyolefin synthetic rubber is used as the core material, it is preferable that the sheath material has the same chemical structure as the sheath material (material constituting the sheath layer) or has a chemical affinity. Synthetic resins are often preferred.

EPDM-type rubbers usually comprise at least two different monoolefin monomers having 2 to 10 carbon atoms, preferably 2 to 4 carbon atoms, and at least one polyolefin having 5 to 20 carbon atoms. It is a terpolymer derived from a saturated olefin. The monoolefin monomer is (wherein, R is an alkyl having a carbon atom of H or 1-12.) Normal formula CH ₂ = CH-R expressed in, preferably ethylene and propylene. The repeating unit derived from at least two kinds of monoolefins is preferably a repeating unit derived from ethylene and propylene, and the weight ratio of the two kinds of repeating units is 1
The range of 0:90 to 90:10 is preferable, and the repeating unit derived from at least two kinds of monoolefins is
Preferably, it comprises about 80 to about 99.6% by weight of the polymer. The polyunsaturated olefin can be a linear, branched, cyclic, bridged, bicyclic, fused ring bicyclic compound, and the like, and is preferably a non-conjugated diene. Repeat units derived from non-conjugated polyunsaturated olefins are preferably from about 0.4 to about 20% by weight of the polymer.

[0013] Butyl rubber is a polymer consisting of repeating units mainly derived from isobutylene, including repeating units derived from monomers providing crosslinking sites. The monomer providing the crosslinking site may be a polyunsaturated monomer such as a conjugated diene or divinylbenzene. Preferably, about 90 to about 99.5% by weight of the butyl rubber is a repeating unit derived from the polymerization of isobutylene, and about 0.5 to about 10% by weight of the repeating unit is one having from 4 to 12 carbon atoms. Derived from one or more polyunsaturated monomers. The polyunsaturated monomer is preferably isoprene or divinylbenzene.

In the present invention, the rubber which can be the core material may be a halogenated rubber. For example, the above-mentioned halogenated (eg, brominated) copolymers with halobutyl rubber, p-alkylstyrene, and isomonoolefins having 4 to 7 carbon atoms such as isobutylene can be used.

[0015] Other rubbers, such as natural rubber and synthetic polymers derived from one or more conjugated dienes, are more unsaturated than EPDM and butyl rubber. Synthetic polymers derived from natural rubber and one or more conjugated dienes can optionally be partially hydrogenated to increase thermal and oxidative stability. Synthetic polymers derived from one or more conjugated dienes can be non-polar or polar depending on the type of monomer copolymerized with the conjugated diene. Preferably, the synthetic polymer derived from one or more conjugated dienes has at least 50% by weight of repeating units derived from at least one conjugated diene monomer having from 4 to 8 carbon atoms.
Preferred examples of the monomer copolymerized with the conjugated diene monomer include unsaturated carboxylic acids, unsaturated dicarboxylic acids, and unsaturated dicarboxylic anhydrides.
Also included are vinyl aromatic monomer (s) having 2 carbon atoms and acrylonitrile or alkyl-substituted acrylonitrile (s) having 3 to 8 carbon atoms. Also included are divinylbenzene, alkyl acrylates, and other monomers having 3 to 20 carbon atoms.

When a thermoplastic elastomer is produced by the method of the present invention, a mineral oil-based softener can be used as a fluidity improver if necessary. For example, ML _{1 + 4}
When EPDM at 100 ° C of 30 to 350 is used and a large amount of a mineral oil-based softening agent is blended, it is possible to simultaneously ensure the flexibility, improve the processability by improving the fluidity, and improve the mechanical properties. An olefin-based thermoplastic elastomer can be obtained. In this case, the mineral oil softener
In the process of mixing with a polyolefin resin performed by using an extruder or the like, it can be supplied from an arbitrary location such as an extruder.

As described above, when a mineral oil-based softening agent is used as a fluidity improver, the mineral oil-based softening agent can be supplied in the process of mixing with the resin, or can be mixed with the rubber in advance and oil-extended. A thermoplastic elastomer can be obtained by forming a rubber and mixing the oil-extended rubber with a resin. However, when the rubber has an ML _{1 + 4 of} 100 to 30 ° C., the former method is preferred, and the ML _{1+ 4 When} 100 ° C. is 120 to 350, the latter method is preferred. From the viewpoint of the physical properties of the olefin-based thermoplastic elastomer, in order to obtain a thermoplastic elastomer having large mechanical properties, significantly improved tensile strength at break and elongation at break, and improved compression set, oil extension is required. ML _{1 + 4} 100 ℃ is 80 ~ 3
Preferably, 50 olefin copolymer rubbers are used. More preferably, ML _{1 + 4} 100 ° C. is 120-35.
0, more preferably 140-300. Therefore,
ML _{1 + 4} An olefin copolymer rubber having a temperature of 100 to 80 to 350 is used, and a mineral oil-based softener is added thereto to form an oil-extended olefin copolymer rubber, which is mixed with an olefin resin or the like. A method of making an olefinic thermoplastic elastomer is preferred.

The mixing amount of the mineral oil-based softening agent is preferably such that the ML _{1 + 4} 100 ° C. of the oil-extended rubber after mixing is _{5 to} 200. Mineral oil-based softeners are high-boiling petroleum fractions incorporated for the purpose of improving processability and mechanical properties, and include paraffinic, naphthenic, and aromatic types. It is preferably used. When the amount of the aromatic component increases, the contamination becomes strong, and there may be a case where the use for a transparent product or a bright color product is limited.

As the oil extension method, a known method is used. For example, in the case of EPDM oil extension, a method of mechanically kneading EPDM and a mineral oil-based softener using a device such as a roll or a Banbury mixer, or adding a predetermined amount of a mineral oil-based softener to an EPDM solution Then, there is a method of removing the solvent by a method such as steam stripping.
Of these, a preferred oil-extending method is a method using an EPDM solution, and the EPDM solution is obtained by polymerization using
The operation is easier when a solution is used.

Such an oil-extended rubber can also be used as the core of the multilayer pellet of the present invention. The present invention particularly exerts its effect on a rubber having a Mooney viscosity (ML _{1 + 4} 100 ° C.) of 5 to 200. The Mooney viscosity of the oil-extended rubber is preferably ML _{1 + 4} 100 ° C. 5 to 200. .

The rubber constituting the core material of the multilayer pellet of the present invention may comprise other components such as antioxidants, processing aids, reinforcing and non-reinforcing fillers, pigments, waxes, as long as the formability and physical properties are not impaired. , Rubber process oil, extender oil,
It may contain anti-adhesives, UV stabilizers, antistatics, plasticizers, foaming agents, flame retardants and other known processing aids used in the rubber compounding field.

As the sheath material of the multilayer pellet of the present invention, one having lower adhesiveness than the rubber constituting the core material is used. By using a material having low tackiness, cohesion of pellets can be prevented, and handling of rubber can be facilitated. When the multilayer pellet of the present invention is used for the production of a soft synthetic resin or a thermoplastic elastomer, it is preferable to use a soft synthetic resin or a resin serving as a hard phase of the thermoplastic elastomer as the sheath material.

Examples of such resins include polyolefin resins such as polyethylene resin and polypropylene resin, polyamide resins such as polystyrene resin, AS resin, ABS resin and nylon resin, polyethylene terephthalate resin, and the like.
(Meth) acrylic resin such as polybutylene terephthalate resin, polycarbonate resin, polymethyl methacrylate resin, vinyl chloride resin, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal resin, acetyl cellulose, fluorine resin, polyester resin, allyl Resin, silicone resin, other various thermoplastic synthetic resins, various thermoplastic elastomers, blends of two or more of the above synthetic resins and thermoplastic elastomers, and compositions obtained by adding various fillers and additives to the above materials Objects are exemplified.

In the multilayer pellet of the present invention, the combination of the core material and the sheath material is not particularly limited. However, basically, the core material and the sheath material have the same chemical structure or those having a chemical affinity. preferable. For example, styrene-butadiene rubber (SBR) and polystyrene resin or ABS resin, butadiene rubber (BR) and polystyrene resin or ABS
Resin, acrylic nitrile / butadiene rubber (NB
R) and nylon resin, isobutylene isoprene rubber (IIR) and polyethylene resin or polypropylene resin, ethylene propylene rubber (EPM, EPD)
M) or ethylene butene rubber (EBM, EBDM)
Or, a combination of an α-olefin (two or more) copolymer rubber and a polyethylene resin or a polypropylene resin, an acrylic rubber (ACM, ANM) and a polymethyl methacrylate resin may be used. However, there is a case where a material having no or poor affinity is intentionally mixed with each other to exhibit a unique property, and therefore, the combination is not limited to a combination of a core material and a sheath material having good chemical affinity.

The ratio between the core layer and the sheath layer in the multilayer pellet of the present invention is not particularly limited. The sheath layer may be any thickness as long as it covers the core material made of rubber and can exhibit an anti-adhesion property capable of preventing mutual adhesion between rubbers. On the other hand, when the thermoplastic elastomer is produced by blending the rubber constituting the core material and the resin constituting the sheath material, the ratio of the core material and the sheath material is made equal to the blend ratio, thereby making the thermoplastic elastomer. Can be easily manufactured. Therefore,
The thickness of the sheath layer can also be changed according to the blending ratio, and the upper limit is not particularly limited. In a normal case, the weight ratio between the core layer and the sheath layer is preferably in the range of 10/90 to 99/1, and more preferably in the range of 50/50 to 95/5.

As a method for producing a multilayer pellet according to the present invention, rubber and a material constituting a sheath layer, for example, a synthetic resin is supplied in a molten state to a two-layer or multilayer strand die apparatus, and the rubber is used as an outer layer to form a synthetic resin or the like. A method of extruding, cooling, and cutting a two-layer or multilayer strand as an inner layer is exemplified. There is no particular limitation on the method for supplying the rubber and the material constituting the sheath layer. The rubber constituting the core layer and the material constituting the sheath layer may be supplied by separate extruders, respectively, or a line after the synthetic rubber polymerization apparatus may be used. Examples of the rubber supply device include a feeder ruder, a cold feed extruder, and a twin-screw extruder. The extruder may be a single-screw extruder or a twin-screw extruder.

Although the thickness of the strand to be melt-extruded is not particularly limited, the diameter is preferably 0.5 to 20 mm, more preferably 2 to 8 mm. The multilayer pellet of the present invention can be obtained by cutting the cooled core-sheath type strand to a length of preferably 1 to 5 mm, more preferably 2.5 to 3.5 mm. The multilayer pellet of the present invention has a structure in which a core layer containing rubber is covered with a sheath layer containing a thermoplastic resin having low adhesiveness similarly to the strand. Examples of the method for cooling and cutting the strand include a method in which the strand is cut after melt extrusion and then dropped into water and cooled, and a method in which the strand is introduced into a cooling water tank, cooled, and then cut into pellets. Usually, a method of introducing a strand into a cooling water tank is general. The shape of the pellet is usually cylindrical, but the cross-sectional shape is arbitrary. By selecting an appropriate die, the pellet can be formed into an arbitrary shape such as a prismatic or elliptical cross-section. In order to improve the productivity of pellets, a method of simultaneously manufacturing a plurality of strands using a strand forming apparatus having a plurality of concentrically arranged extrusion ports can be adopted.

The multilayer pellet of the present invention thus obtained can be used for producing a soft synthetic resin or a thermoplastic elastomer. These can be obtained by blending and kneading the multilayer pellets of the present invention with a synthetic resin or the like, if necessary, to obtain a soft synthetic resin or a thermoplastic elastomer. As a production method at that time, a method of melt-blending a rubber component such as EPDM which retains thermoplasticity with a thermoplastic resin of a hard phase, and a method of simultaneously crosslinking a rubber component with a rubber component such as EPDM when melt-blending the thermoplastic resin. There is a method in which an agent is added and partial crosslinking is performed simultaneously with the melt blending, but any of the methods can be employed in the present invention. That is, EPDM as a core material of the pellet of the present invention
And the like may be crosslinked to some extent, or a crosslinking agent may be added when kneading the pellets of the present invention.

When a thermoplastic elastomer is produced by blending a rubber constituting a core material and a resin constituting a sheath material,
When the ratio of rubber and resin in the pellet is different from the ratio of rubber and resin in the target thermoplastic elastomer, a step of adding rubber or resin to the pellet to adjust the ratio of rubber and resin is required. On the other hand, when the ratio of rubber and resin in the pellet is the same as the ratio of rubber and resin in the target thermoplastic elastomer, it is not necessary to add rubber or resin to the pellet to adjust the ratio of rubber and resin. Instead, the desired thermoplastic elastomer can be obtained by directly kneading the pellets, so that the production process is short, rational, and the cost can be reduced. The thermoplastic elastomer produced in this way has the same advantages as the thermoplastic elastomer produced by the conventional method, and is used in the fields of automobile parts, home appliance parts, medical / food machine parts, electric wires and miscellaneous goods. Can be used.

[0030]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 EPDM rubber (Esprene E-201 manufactured by Sumitomo Chemical Co., Ltd., ML _{1 + 4} 100 ° C .: 43,
(49% ethylene, 51% propylene, 25 kg bale shape) was cut by a cutter and then pulverized by a pulverizer to obtain an irregularly shaped EPDM rubber. This irregular shaped EPD
M rubber was melt-extruded at 180 ° C. by a twin-screw extruder and supplied to a two-layer strand die device. Simultaneously, polypropylene was melt-extruded at 200 ° C. from a single-screw extruder for a sheath and supplied to a two-layer strand die apparatus. The supply ratio between the EPDM rubber and the polypropylene was 85 parts by weight: 15 parts by weight. The strand coming out of the two-layer strand die apparatus was cooled in a water tank and cut with a pelletizer to obtain a pellet. Even if 25 kg of the obtained pellet is put in a paper bag and stored in a warehouse for one month, no blocking or mutual adhesion occurs.

Example 2 Cold-polymerized styrene / butadiene rubber (Sumitomo SBR1502, 35k, manufactured by Sumitomo Chemical Co., Ltd.)
g bale shape) was melted by masticating with a Banbury mixer, and then supplied to a two-layer strand die device using a feeder ruder. At the same time, from the single screw extruder for sheath
At 00 ° C., a polystyrene resin (Nippon Polystyrene G590 manufactured by Nippon Polystyrene, MFR = 3.5 g / 10 min, d =
1.04) was supplied to a two-layer strand die apparatus. The supply ratio of the styrene / butadiene rubber to the polystyrene resin was 80 parts by weight: 20 parts by weight. It was formed into 20 double-layer strands with a double-layer strand die device, cooled in a water bath, and then cut with a pelletizer to obtain rubber pellets having a core-in-sheath structure. 25 kg of obtained rubber pellets
Was placed in a paper bag and stored in a warehouse for one month to check the storage state. As a result, there was no occurrence of blocking or mutual adhesion, and the state was good.

Example 3 By the same method as in Example 1 or Example 2, the core material was synthetic rubber, the sheath material was synthetic resin, and the weight ratio of the core layer to the sheath layer was 80:20. Make a two-layer pellet. 50 kg (composition: synthetic rubber 40 kg and synthetic resin 10
(kg), 50 kg of the same synthetic resin as the sheath material is added and kneaded to obtain a thermoplastic elastomer. Its final composition is
40 kg of synthetic rubber and 60 kg of synthetic resin. On the other hand, by the same method as in Example 1 or Example 2, a double-layer pellet in which the core material is synthetic rubber, the sheath material is synthetic resin, and the weight ratio of the core layer to the sheath layer is 40:60 is prepared. I do. Kneading 100 kg of the two-layer pellet thus obtained,
A thermoplastic elastomer consisting of a final composition of 40 kg of synthetic rubber and 60 kg of synthetic resin can be obtained without additional synthetic resin. In this method, the steps are short, rational, and cost reduction is possible.

[0034]

The multilayer pellet of the present invention has a core-sheath structure in which the outside of a rubber core layer is coated with a layer having low adhesiveness, so that blocking and mutual adhesion of the rubber pellet are prevented, and the handling property is improved. It is an improvement. Since pellets having this rubber as a core material do not cause blocking or mutual adhesion, a continuous production process can be employed in the production of a soft synthetic resin or a thermoplastic elastomer by using the pellets,
It can also handle small lot production. In the method for producing a flexible synthetic resin or thermoplastic elastomer of the present invention using the multilayer pellet, a continuous production process can be adopted, so that the production cost can be reduced as compared with the conventional method.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 101: 12 B29K 101: 12 F term (Reference) 4F070 AA02 AA04 AA05 AA06 AA07 AA08 AA09 AA12 AA13 AA15 AA16 AA18 AA22 AA23 AA26 AA28 AA32 AA34 AA42 AA47 AA50 AA52 AA54 AA60 AA71 AB02 AB03 AB06 DA11 DC02 4F201 AA03 AA09 AA11 AA13 AA45 BA02 BC02 BC12 BC37 BD05 BL08 BL42 BL43 4J002 AA01W AB01W AC02X ACB BC06W BD03W BD05W BD10W BD12W BD12X BE02W BG06W BG13W BN15W CB00W CF06W CF07W CG00W CH02X CL00W CP03W CP03X FD020

Claims (6)

[Claims] (1) a core-sheath structure, wherein the core is made of rubber;
A multilayer pellet, wherein the sheath is made of a material having lower adhesiveness than rubber. 2. The Mooney viscosity of the core material (ML _{1 + 4} 100
C) is from 5 to 200. 3. The multilayer pellet according to claim 1, wherein the core is made of an olefin-based synthetic rubber. 4. The multilayer pellet according to claim 1, wherein the sheath is made of a resin which becomes a hard phase of a soft synthetic resin or a thermoplastic elastomer. 5. A core-sheath structure, wherein said core is made of rubber;
A method for producing a soft synthetic resin or a thermoplastic elastomer, wherein a multi-layered pellet having a sheath having a lower adhesiveness than rubber is used. 6. The method for producing a soft synthetic resin or a thermoplastic elastomer according to claim 5, further comprising a step of mixing the multilayered pellet and the synthetic resin.