JP2003113284A - Low elastic modulus polymer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low elastic modulus polymer composition, capable of being processed by an injection molding and recycled, easy for molding and processing, excellent in flexibility, having good mechanical characteristics such as tearing strength, tensile strength, elongation, etc., and also exhibiting an extremely small compressed permanent distortion in a wide range from a low temperature region to a high temperature region. SOLUTION: This low elastic modulus polymer composition contains (A) one or more thermoplastic elastomers selected from a group consisting of a SEPS, SEBS and SEEPS, (B) a rubber component containing >=50 wt.% rubber obtained by brominating a copolymer of p-methylstyrene with isobutylene and (C) a softening agent. At least a part of the (B) rubber component is cross-linked by a dynamic cross-linking, and also the blended amount of the (C) softening agent is >=200 pts.wt. based on 100 pts.wt. total amount of the (A) and (B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer composition having a low elastic modulus, and more particularly to a polymer composition having excellent flexibility and having a very small compression set in a wide temperature range from a high temperature region to a low temperature region. It relates to a molecular composition.

[0002]

2. Description of the Related Art Conventionally, a sealing material used for a closure of a communication cable and a vibration damping / vibrating member used for a motor of various electronic / electrical devices have excellent flexibility and followability, and a compression set. Is required to be small.
Therefore, conventional sealing materials and vibration damping / vibration damping materials include hydrogenated styrene-isoprene block copolymers, hydrogenated styrene-butadiene block copolymers, and styrene-isoprene-styrene block copolymers ( SIS)
Hydrogenated product of [styrene-ethylene-propylene-styrene block copolymer (SEPS)], hydrogenated product of styrene-butadiene-styrene block copolymer (SBS) [styrene-ethylene-butylene-styrene block copolymer ( SEBS)] and other hydrogenated thermoplastic elastomers, or ethylene-propylene-diene rubber (EPDM) and other rubbers having no double bond in the main chain.

Further, a softening agent is added to the thermoplastic elastomer and rubber for the purpose of improving flexibility, and the softening agent has a pour point of -20 ° C or higher, especially about -15 ° C. Paraffin oil is often used.

[0004]

However, when the rubber such as the EPDM is used for the sealing material and the vibration damping / vibration preventing member, a long vulcanization step is required, resulting in a decrease in production efficiency. is there. Furthermore, although recycling of resources has been demanded from the viewpoint of environmental protection in recent years, it is practically impossible to recycle a member made of rubber alone.
Moreover, the sealing material and the vibration damping / vibration-proofing member mentioned above are -30
While it is required that the compression set is small and the flexibility is excellent even in a low temperature region of up to 0 ° C., it is difficult for a conventionally known rubber such as EPDM to satisfy the above characteristics. Note that, for example, in EPDM, the compression set at −20 ° C. exceeds 90% and the hardness change at room temperature and −20 ° C. is extremely large. Therefore, when this is used as a sealing material, the sealing property deteriorates in the low temperature region. As a result, there is a problem that leakage occurs, or sufficient compression cannot be performed due to an increase in hardness.

On the other hand, the diblock copolymer, SEPS
Since both SEBS and SEBS have thermoplasticity,
There is a problem of high deformability at high temperatures. Further, since oils having a high pour point are usually blended with these thermoplastic elastomers, there arises a problem that the compression set abruptly increases in the low temperature region and the sealing performance and the like deteriorate. Therefore, the object of the present invention is to solve the above-mentioned problems and enable processing and recycling by injection molding.
It is easy to process, has excellent flexibility (low elastic modulus), good mechanical properties such as tear strength, tensile strength, and elongation.
Moreover, it is to provide a low elastic modulus polymer composition showing an extremely small compression set in a wide range from a low temperature region to a high temperature region.

[0006]

MEANS FOR SOLVING THE PROBLEMS AND EFFECTS OF THE INVENTION The inventors of the present invention previously found that at least a part of a dynamically vulcanized EPDM was added to a thermoplastic elastomer such as SEPS or SEBS.
It has been proposed a low elastic modulus polymer composition in which a rubber component such as the above is present in a fine state and a softening agent is contained in an amount of 200 parts by weight or more based on 100 parts by weight of the total of the thermoplastic elastomer and the rubber component. (Japanese Patent Application No. 2000-398703
issue). This material is injection-moldable and recyclable, and has a characteristic that the compression set is small and the elastic modulus is extremely small in a wide temperature range from a low temperature range of about -30 ° to a high temperature range of about 70 ° C. is doing.

However, the above low elastic modulus polymer composition is fragile, and there is a problem that it breaks up when the surface is rubbed with a nail, and the mechanical strength such as tear strength and tensile strength of the material is low. Furthermore, the present inventors have found that rubbers such as EPDM at least partially dynamically vulcanized in thermoplastic elastomers SEPS, SEBS or styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS). A low elastic modulus polymer composition has been proposed in which the components are present in a fine state, and a polyolefin-based polymer is allowed to coexist, and a predetermined amount of a softening agent is added (Japanese Patent Application No. 2000-92026).

According to the latter low elastic modulus polymer composition, not only injection molding and recycling are possible, but the compression set in the low temperature region and the high temperature region can be further suppressed. However, in recent years, it has been required for the sealing material and the vibration damping / vibration preventing member to exhibit higher flexibility and followability and excellent flexibility over a long period of time. Therefore, the compression set should be further reduced, specifically, about 25% or less in the high temperature region (70 ° C), about 15% or less in the room temperature (23 ° C), and even in the low temperature region (-30 ° C). About 60%, preferably 50%
It is required to suppress it to below a certain level.

Therefore, as a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the rubber component in the above-mentioned low elastic modulus polymer composition is a copolymer of p-methylstyrene and isobutylene from EPDM or the like. Instead of using brominated rubber (abbreviated as "BIMS") for the coalescence, a thermoplastic elastomer SEPS, SEBS or SE is used.
The BI, at least part of which has been dynamically vulcanized during EPS.
When MS is present in a fine state and further mixed with a prescribed amount of softening agent, it can be processed and recycled by injection molding, is easy to mold and process, has excellent flexibility (low elastic modulus), and tears. Mechanical properties such as strength, tensile strength, and elongation are good, and it is possible to further reduce the compression set in a wide range from the high temperature region to the low temperature region. The facts have been found and the present invention has been completed.

That is, the low elastic modulus polymer composition according to the present invention comprises (A) a hydrogenated product of styrene-isoprene-styrene block copolymer, a hydrogenated product of styrene-butadiene-styrene block copolymer and styrene. A rubber obtained by brominated a copolymer of (B) p-methylstyrene and isobutylene, and one or more thermoplastic elastomers selected from the group consisting of ethylene-ethylene-propylene-styrene block copolymers. A rubber component contained in a proportion of 50% by weight or more and (C) a softening agent, wherein at least a part of the rubber component (B) is crosslinked by dynamic crosslinking, and The blending amount of the softening agent (C) is 200 parts by weight or more based on 100 parts by weight of the total amount of the thermoplastic elastomer (A) and the rubber component (B).

The low elastic modulus polymer composition of the present invention is the above-mentioned Japanese Patent Application No. 2000-398703 and Japanese Patent Application No. 2000-9.
Similar to the polymer composition disclosed in No. 2026, since at least a part of a dynamically vulcanized rubber component is present in a fine state in a thermoplastic elastomer, it can be processed or recycled by injection molding. Possible and easy to mold and process. When the degree of flexibility (low elastic modulus) of the low elastic modulus polymer composition is expressed by the hardness of the composition, the Shore A hardness is usually 10 or less.

In the low elastic modulus polymer composition of the present invention, a rubber component (B) containing 50% by weight or more of BIMS is dynamically crosslinked with the thermoplastic elastomer (A) in the presence of a softening agent. It is a thing. By this "dynamic cross-linking", the above (A)
The thermoplastic elastomer of (B) and the rubber component of (B) are uniformly mixed, and the rubber component (B) is present as an island phase in the sea phase of the thermoplastic elastomer (A) (so-called sea phase). -Island structure).

In the present invention, the term "dynamic crosslinking" means that the thermoplastic elastomer is present in the presence of an agent for crosslinking (at least a part of) the rubber component (B).
(A), the rubber component (B) and (and optionally an olefin polymer) are melted and blended, whereby the rubber component (B) is crosslinked during kneading, and the thermoplastic elastomer This is a method in which the rubber component (B) is finely dispersed in (A). In practical use, a vulcanizing agent may be kneaded in advance in rubber and vulcanized by increasing the temperature, or a crosslinking agent may be added and vulcanized after melting.

By this dynamic crosslinking, alloying of the polymer composition can be achieved uniformly and efficiently. Further, the state where at least a part of the rubber component (B) is dynamically crosslinked, the amount of the insoluble component is changed when the polymer composition obtained by dynamic crosslinking is dissolved in an appropriate solvent. It can be determined by whether or not the number is higher than before the physical crosslinking. The insoluble matter (%) before dynamic crosslinking is compared with the insoluble matter (%) after dynamic crosslinking, and if the latter is large, it can be said that the dynamic crosslinking has been performed. Generally, it is preferable that 50 parts by weight or more of 100 parts by weight of the rubber component be crosslinked.

In the present invention, the thermoplastic elastomer component
SEPS, SEBS, SEE used as (A)
PS alone has the property of being deformed at high temperatures (thermal deformability). However, like the low elastic modulus polymer composition of the present invention, deformation at high temperature is substantially prevented due to being dynamically crosslinked with the rubber component (B) such as BIMS. Such characteristics cannot be obtained by the thermoplastic elastomer (A) alone.

The rubber (BIMS) obtained by brominating the copolymer of p-methylstyrene and isobutylene used as the rubber component (B) in the present invention becomes sticky when a large amount of oil is contained. However, it is a material that is difficult to form an extremely flexible composition by itself. However, like the low elastic modulus polymer composition of the present invention, by combining this BIMS with a thermoplastic elastomer such as SEPS, it is extremely flexible (low elastic modulus) and has tear strength, tensile strength, and elongation. It is possible to produce a polymer composition having good mechanical properties such as. Moreover, the polymer composition of the present invention thus obtained surprisingly exhibits extremely small compression set in a wide range from a low temperature region to a high temperature region.

Incidentally, according to the conventional research results, EPDM
There was a concern that the amount of oil (softening agent) that could be added without bleeding (bleeding) would be extremely small by using BIMS instead of rubber such as.
However, as a result of the study by the present inventors, BIMS
It has been found that a large amount of oil (plasticizer) can be added without bleeding, as in the case where a rubber such as EPDM is used, by combining with and a thermoplastic elastomer such as SEPS.

Thus, the low elastic modulus polymer composition of the present invention can be processed and recycled by injection molding, is easy to mold and process, and has excellent flexibility (low elastic modulus).
Tear strength, tensile strength, as well as having good mechanical properties such as elongation, since it is possible to further reduce the compression set in a wide range from the high temperature region to the low temperature region, It is suitable for applications such as sealing materials used in communication cable closures and vibration damping / vibration damping members used in motors of various electronic / electrical devices.

In the low elastic modulus polymer composition of the present invention, the olefin polymer is added in an amount of 2 to 50 parts by weight based on 100 parts by weight of the total amount of the thermoplastic elastomer (A) and the rubber component (B). It is preferable to include the parts by weight from the viewpoint of strengthening the surface texture of the rubber, improving the flowability, and improving the moldability during injection molding. In the low modulus polymer composition of the present invention, the pour point of the softening agent (C) is preferably -35 ° C or lower. In this case, the excellent flexibility in the low temperature region can be further ensured, and the compression set can be further reduced.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the low elastic modulus polymer composition according to the present invention will be described in detail. [Component (A), thermoplastic elastomer] The thermoplastic elastomer of component (A) in the low elastic modulus polymer composition of the present invention is selected from the group consisting of the following (A-1) to (A-3) Or a block copolymer of two or more kinds.

(A-1): Hydrogenated product of styrene-isoprene-styrene block copolymer (SIS) [ie,
Styrene-ethylene-propylene-styrene block copolymer (SEPS)] (A-2): Hydrogenated product of styrene-butadiene-styrene block copolymer (SBS) [ie, styrene-ethylene-butylene-styrene block copolymer] Coalescence (SEB
S)] (A-3): Styrene-ethylene-ethylene-propylene-
Styrene Block Copolymer (SEEPS) The SEPS of (A-1) above is SIS with hydrogen added, but ethylene and propylene are always arranged alternately. On the other hand, SEEPS in (A-3) above is SEPS.
It has a structure in which ethylene units are contained in a block shape, that is, in addition to units in which ethylene and propylene are alternately arranged, units made of only ethylene are present in a block shape.

When a low elastic modulus polymer composition is used as a sealing material in a communication cable closure or the like, it is necessary to consider weather resistance, and therefore, a double bond is almost (or not) formed in the molecular chain. ) It is preferable to use a thermoplastic elastomer having no In this respect, none of the above-exemplified SEPS, SEBS, and SEEPS has a double bond, and therefore it is suitable for the above-mentioned applications. In the above-mentioned thermoplastic elastomer, when the amount of styrene (corresponding to the hard segment) in the block copolymer is small, the elasticity at room temperature decreases (that is,
The compression set becomes large) and too much makes it too hard.
Usually, the amount of styrene is preferably 10 to 35% by weight.

The larger the molecular weight of the above-exemplified thermoplastic elastomer, the higher the strength and the larger the amount of the softening agent absorbed. Therefore, it is advantageous to use a thermoplastic elastomer having a large molecular weight in the polymer composition of the present invention. Specifically, the molecular weight of the thermoplastic elastomer generally needs to be 100,000 or more, preferably 150,000 or more, and more preferably 200,000 or more. Among the above thermoplastic elastomers, a specific example of SEPS is, for example, a product name “Septon 206 manufactured by Kuraray Co., Ltd.
3 "(styrene content 13% by weight), company-made" Septon 2023 ", company-made" Septon 2002 ", company-made" Septon 2005 ", company-made" Septon 201 ".
4 ”and the like.

Specific examples of SEBS include, for example, the product name "Tuftec H1075" (styrene content 20% by weight) manufactured by Asahi Kasei Kogyo Co., Ltd., and the product name "KRATON G1650" (styrene content contained by Shell Japan Co., Ltd.). Two
9% by weight), trade name “Elastomer AR730” manufactured by Aron Kasei Co., Ltd., and the like. As a specific example of SEEPS, for example, the product name “Septon 40 manufactured by Kuraray Co., Ltd.
77 "(styrene content 30% by weight)," Septon 4055 "manufactured by the same company (styrene content 30% by weight)," Septon 4033 "manufactured by the same company (styrene content 30% by weight)
Etc.

[Component (B), rubber component] Since the rubber of the component (B) in the low elastic modulus polymer composition of the present invention is to be mixed with the thermoplastic elastomer of the above (A),
It is preferable that the thermoplastic elastomer has an affinity with the above-exemplified thermoplastic elastomer. Further, considering that the polymer composition of the present invention is applied to a sealing material or the like in a closure or the like of a communication cable, it is more preferable that it has excellent weather resistance.

In the present invention, a rubber (BIMS) obtained by brominated a copolymer of p-methylstyrene and isobutylene is mainly used as the rubber component. BIM
S is a hydrogen atom in the methyl group in the p-methylstyrene unit of the copolymer in which bromine is substituted. Due to the action of the isobutylene unit having the same structure as butyl rubber (IIR), its loss coefficient tan δ is large, and therefore BIMS has a small resonance magnification and excellent vibration damping capability.

Further, since BIMS does not have a double bond in the main chain which causes ozone deterioration and aging, BIMS is extremely excellent in weather resistance, ozone resistance and aging resistance. In particular,
Regarding ozone resistance, it is superior to butyl rubber, brominated butyl rubber, chlorinated butyl rubber, etc., which have the same main skeleton of isobutylene. Although the weight ratio of p-methylstyrene in BIMS is not particularly limited,
It is preferably 5 to 20% by weight of the whole IMS,
It is more preferably 10% by weight. When the weight ratio of p-methylstyrene is high, the glass transition point is high and the hardness is high, and the vibration damping ability is low. On the contrary, when the weight ratio is low, the crosslinking point is low and the crosslinkability is low. . When the weight ratio of p-methylstyrene is within the above range, the flexibility, vibration damping ability, crosslinkability and the like of BIMS are maintained in an appropriate range.

The content ratio of bromine in BIMS (hereinafter,
It is called "bromine content". ) Is not particularly limited, but is preferably 0.6 to 2% by weight, and more preferably 1.2 to 2% by weight based on the whole BIMS. The higher the bromine content (the higher the content of brominated p-methylstyrene), the higher the reactivity of BIMS, but the higher the crosslink density and the higher the hardness. On the contrary, the smaller the bromine content (the smaller the content ratio of brominated p-methylstyrene), the less the progress of crosslinking and the larger the tendency of creep. If the bromine content is within the above range, BI
The flexibility and crosslinkability of MS are maintained in an appropriate range.

A specific example of BIMS is, for example, "EXXPR" manufactured by Exxon Chemical Co., Ltd.
O 90-10 "[weight ratio of p-methylstyrene 7.
5% by weight, bromine content 2.0% by weight, Mooney viscosity 45
ML (1 + 8) 125 ° C.] and the same “EXXXPRO 89-
1 "[p-methylstyrene weight ratio 5% by weight, bromine content 1.2% by weight, Mooney viscosity 35 ML (1 + 8) 1
25 ° C.], the same “EXXPRO 89-4” [weight ratio of p-methylstyrene 7.5% by weight, bromine content 1.2% by weight, Mooney viscosity 45 ML (1 + 8) 125 ° C.], the same “EXXPRO93-5”. [Weight ratio of p-methylstyrene 7.5% by weight, bromine content 0.7% by weight, Mooney viscosity 45 ML (1 + 8) 125 ° C.], “EXXPRO”.
93-4 "[p-methylstyrene weight ratio 5.0% by weight, bromine content 2.0% by weight, Mooney viscosity 35 ML
(1 + 8) 125 ° C.] and the like.

In the present invention, as the rubber component (B),
Although it does not prevent blending of other rubber with BIMS, the content of BIMS in the rubber component (B) is 50% by weight or more, preferably 55% by weight or more, more preferably 60% by weight or more. Is adjusted. BI
Examples of rubbers other than MS include ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR),
Butadiene rubber (BR), isoprene rubber (IR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), natural rubber (NR), 1,2-polybutadiene, acrylonitrile-butadiene rubber (NBR), ethylene-propylene rubber (EPM), acrylic rubber (A
CM), chlorosulphonated polyethylene (CSM) and the like.

[Softening agent (C)] The softening agent of the component (D) in the low elastic modulus polymer composition of the present invention is intended to adjust the hardness of the low elastic modulus polymer composition to a desired value. It is added in. Examples of such softening agents include BIMS, S
Those having a high affinity with EPS, SEBS, SEEPS, etc. are preferable, and paraffin oil is usually preferable. Above all, in consideration of allowing the polymer composition of the present invention to sufficiently exhibit the function as a sealing material even at a low temperature, paraffin oil having a reduced pour point by removing a wax component is more preferably used. To be

The pour point of paraffin oil is JIS K
It is generally -15 ° C according to the measurement standard of 2269, but those having a pour point of -35 ° C or lower are preferable in the field where low temperature characteristics are required as described above. Specific examples of such paraffin oil include "Diana Process Oil PX-9" manufactured by Idemitsu Kosan Co., Ltd.
0 "(pour point −45 ° C.) and the like. [Olefin Polymer] An olefin polymer can be further added to the low elastic modulus polymer composition of the present invention.

Examples of such an olefin polymer include polypropylene polymer (PP), polyethylene polymer (PE), etc., which can achieve a low hardness of the polymer composition and have an adverse effect on low temperature characteristics. A polypropylene-based polymer is also preferably used to reduce the amount. The polypropylene-based polymer is not limited to a propylene homopolymer (PP homopolymer), and may be, for example, a block copolymer having a polyethylene block or a random copolymer having an ethylene portion.

Specific examples of such polypropylene-based polymer include, for example, trade name "Novatech PP BC6" (P / E block copolymer) manufactured by Nippon Polychem Co., Ltd., trade name "Novatech PP MG05B" manufactured by the same company.
S ”(P / E random copolymer), trade name“ Novatech PP FY6H ”(PP homopolymer) manufactured by the same company, and the like. (Blending ratio of each component) In the low elastic modulus polymer composition of the present invention, the blending ratio of the thermoplastic elastomer (A) and the rubber component (B) can sufficiently exhibit the above-mentioned various properties. The range is appropriately selected. Such range is not particularly limited, but usually the thermoplastic elastomer (A)
And the rubber component (B) are mixed in a weight ratio of 75: 2.
5 to 25:75, preferably 70:30 to 30:
70. If the proportion of the rubber component (B) becomes too large, dynamic crosslinking becomes difficult, and even if an attempt is made to carry out extrusion molding, the molded product will be shattered and an appropriate molded product cannot be obtained. On the other hand, if the proportion of the rubber component (B) is too small, the compression set becomes large and the flexibility is impaired.

Thermoplastic elastomer (A) and rubber component (B)
In addition to the above, when blending an olefin-based polymer, the ratio of the amount of the rubber component (B) to the amount of the olefin-based polymer added to the thermoplastic elastomer (A) satisfies the above blending ratio range. Adjust it to The blending amount of the olefin polymer alone is usually 2 to 50 parts by weight, preferably 5 to 40 parts by weight, based on 100 parts by weight of the total amount of the thermoplastic elastomer (A) and the rubber component (B). It is preferably set to 7 to 35 parts by weight.
By blending the olefin polymer, the effects of improving the surface texture during molding and improving the mechanical strength such as tear strength and tensile strength can be obtained. However, if the blending amount of the olefin-based polymer exceeds the above range, the hardness increases and the flexibility is impaired, so that it is not suitable as a sealing material, for example.

The content of the softening agent (C) in the low elastic modulus polymer composition of the present invention is such that the thermoplastic elastomer (A), the rubber component (B) and (when an olefin polymer is blended, The total amount (including the added amount) is 200 parts by weight or more, preferably 250 parts by weight or more, and more preferably 300 parts by weight or more. If the content of the softening agent (C) is less than the above range, it may not be possible to impart sufficient flexibility to the polymer composition, or it may be impossible to achieve low hardness.
On the other hand, the upper limit of the content of the softening agent (C) is within a range in which the above-mentioned various properties of the polymer composition of the present invention are not impaired, and is a range in which exudation of the softening agent does not occur. Although not limited, it is generally suitable that the amount of each component is 1000 parts by weight based on 100 parts by weight.

[Crosslinking Agent, Vulcanization Accelerator and Vulcanization Activator] In the present invention, as the crosslinking agent for crosslinking the rubber component such as BIMS, a conventionally known vulcanizing agent (for example, sulfur) or resin can be used. Vulcanizing agents, zinc white and stearic acid can be used. Among them, in the present invention, it is preferable to use a resin vulcanizing agent. Examples of the resin vulcanizing agent include alkylphenol-formaldehyde resin, halogenated phenol-formaldehyde resin, and the like, and specific examples thereof include the trade name "Tacky Roll" series (Tucky Roll "201", manufactured by Taoka Chemical Industry Co., Ltd.). Same as “25
0-I ", the same" 250-III ") and the like.

Resin vulcanizing agents generally vulcanize faster than sulfur. The amount of the cross-linking agent to be added is usually 2 to 20 parts by weight, preferably 5 to 17 parts by weight, based on 100 parts by weight of the rubber component such as BIMS. Vulcanization of rubber components such as BIMS is performed by using the above resin vulcanizing agent, and by using zinc white and stearic acid [if necessary, vulcanization accelerator for sulfur DM
(Using dibenzothiazyl disulfide) together, or using only zinc white and stearic acid.

In the present invention, in addition to the crosslinking agent,
A vulcanization accelerator and a vulcanization activator (vulcanization acceleration aid) may be added. The vulcanization accelerator is mainly added at the time of sulfur crosslinking, and is a conventionally known thiazole type, thiuram type,
Dithiocarbamate type, sulfenamide type and the like can be used. The vulcanization accelerator is usually used in an amount of about 0.1 to 10 parts by weight based on 100 parts by weight of the rubber component such as BIMS. As the vulcanization activator, zinc white, stearic acid and the like can be used. The vulcanization activator is usually added in an amount of 0.1 to 100 parts by weight of the rubber component such as BIMS.
~ 100 parts by weight is used.

[Other Additives] The low elastic modulus polymer composition of the present invention contains a processing aid, a reinforcing agent, a
A colorant, an antiaging agent, a light stabilizer, an ultraviolet absorber, a flame retardant, a tackifier, etc. can be added as appropriate. Examples of the reinforcing agent include silica and carbon black. The compounding amount of the reinforcing agent is set in the range of 0 to 300 parts by weight based on 100 parts by weight of the total amount of the thermoplastic elastomer (A), the rubber component (B), and the olefin-based polymer optionally further added. It Examples of the filler include calcium carbonate, clay and magnesium carbonate.
(A) and component (B) (or component (A), component (B) and olefin-based polymer) in total of 100 parts by weight,
It is added in the range of 0 to 300 parts by weight. Examples of the flame retardant include aluminum hydroxide, antimony trioxide and the like, and the component (A) and the component (B) (or the component (A),
It is added in the range of 0 to 300 parts by weight based on 100 parts by weight of the total amount of the component (B) and the olefin polymer). Examples of the tackifier include coumarone-indene resin, aliphatic hydrocarbon resin, alicyclic hydrocarbon resin and the like, liquid polybutene, low molecular components such as liquid polyisoprene, and the like,
Component (A) and component (B) (or component (A), component
It is added in the range of 0 to 300 parts by weight based on 100 parts by weight of the total amount of (B) and the olefin polymer).

[Preparation of Low Elastic Modulus Polymer Composition] The low elastic modulus polymer composition of the present invention comprises the thermoplastic elastomer (A), the rubber component (B) containing BIMS, and a softening agent.
It can be prepared by kneading (C) and, if necessary, an olefin-based polymer together with an appropriate additive and subjecting this to dynamic crosslinking. That is, the low elastic modulus polymer composition according to the present invention includes, for example, (i) a rubber component
(B) and a suitable vulcanizing agent, a step of kneading and shredding with a vulcanization activator, (ii) a step of adding a softening agent (C) to the thermoplastic elastomer (A), and then (iii) A step of mixing these admixtures, further adding a crosslinking agent and an appropriate additive if necessary, and dynamically crosslinking so that at least a part of the rubber component (B) is crosslinked, Can be obtained by

When the amount of the softening agent (C) is large, slipping may occur and uniform dispersion may not be achieved even if all the components are kneaded at once in a kneader or an extruder. In this case, the softening agent may be mixed separately in the steps (i) and (ii). That is, first, a softening agent is absorbed in the thermoplastic elastomer, and a rubber component such as BIMS that is shredded with the thermoplastic elastomer (here, it is advantageous to knead the vulcanizing agent into the rubber component in advance). A uniform dispersed state can be obtained by kneading and kneading.

Further, the low elastic modulus polymer composition according to the present invention is prepared by blending the thermoplastic elastomer (A) and the rubber component (B) and, if necessary, each component of the olefin polymer. It can also be obtained by absorbing the softening agent (C) into the above to perform dynamic crosslinking. The dynamic crosslinking can be carried out using a usual rubber kneader. For example, an extruder, a kneader, a Banbury mixer can be used, and an extruder, especially a twin-screw extruder is preferable.

The number of rotations at the time of crosslinking is preferably set to about 50 to 400 rpm. Further, the dynamic crosslinking is usually 16
It is carried out at 0 to 220 ° C.

[0045]

[Preparation of low elastic modulus polymer composition]

Example 1 Brominated rubber of a copolymer of p-methylstyrene and isobutylene [BIMS, manufactured by ExxonMobil Chemical Co., Ltd. under the trade name of "EXPRO" MDX90-1
0 ", bromine content 2%, Mooney viscosity 45ML (1 + 8)
125 ° C.] 50 parts by weight, 1 part by weight of vulcanization accelerator dibenzothiazyl disulfide (trade name “NOXCELLER DM” manufactured by Ouchi Shinko Chemical Co., Ltd.), and stearic acid 0.5.
Parts by weight and carbon black [HAF, Mitsubishi Chemical Corporation
Twenty-five parts by weight of the trade name “Diamond Black H” manufactured by K.K. were mixed sufficiently with a kneader, then made into a sheet with a roll, and further pelletized with a pelletizer. When pelletizing,
Minimal talc was added for the purpose of anti-sticking.

Separately from this, a styrene-ethylene-ethylene-propylene-styrene block copolymer [SEE
PS, Kuraray Co., Ltd. product name "Septon (SEPTO
N) 4077 "] 35 parts by weight and polypropylene which is an olefin polymer [trade name" NOVATEC PP BC6 "manufactured by Japan Polychem Co., Ltd.] 15"
Parts by weight and a crushed resin vulcanizing agent [trade name “TACKIROL 250-made by Taoka Chemical Industry Co., Ltd.
III "] 7.2 parts by weight (including 1.44 parts by weight of talc)
After thoroughly mixing and, 300 parts by weight of paraffin oil [trade name "Diana Process Oil PX-90" manufactured by Idemitsu Kosan Co., Ltd.] as a softening agent was soaked.
Then, add the above pellets to this and stir well,
Furthermore, twin-screw extruder [Product number “KTX-made by Kobe Steel, Ltd.
30 "] to carry out dynamic crosslinking. The conditions for dynamic crosslinking were 220 ° C. and 500 rpm.

The polymer composition thus obtained was extremely flexible. Further, the obtained polymer composition was injected into an injection molding machine [injection molding machine manufactured by Sumitomo Heavy Industries, Ltd., model number "SG25
-HIPRO MIIA "] and molded to evaluate the physical properties. Example 2 A polymer composition was prepared in the same manner as in Example 1 except that the amount of paraffin oil added was 400 parts by weight, and the physical properties were evaluated after injection molding.

Example 3 A polymer composition was prepared in the same manner as in Example 1 except that the amount of paraffin oil added was 500 parts by weight, and the physical properties were evaluated after injection molding. Example 4 A polymer composition was prepared in the same manner as in Example 1 except that the blending amount of SEEPS and BIMS was set to 50 parts by weight and no olefin polymer was blended, and physical properties were evaluated after injection molding. went.

Example 5 35 parts by weight of BIMS and E were used in place of 50 parts by weight of BIMS.
A polymer composition was prepared in the same manner as in Example 1 except that 15 parts by weight of PDM was used, and the physical properties were evaluated after injection molding. Comparative Example 1 Ethylene-propylene-diene rubber [EPDM, trade name "Esprene 532" manufactured by Sumitomo Chemical Co., Ltd., ethylene content 51% by weight, Mooney viscosity 81ML (125
° C), diene: ethylidene norbornene ratio 3.5%]
50 parts by weight, 2.5 parts by weight of zinc oxide, 0.5 parts by weight of stearic acid, and 25 parts by weight of carbon black HAF (the above-mentioned "Diablack H") were kneaded with a kneader,
A rubber composition pelletized by a pelletizer was obtained.

Separately, 35 parts by weight of SEEPS (“Septon 4077” described above), 15 parts by weight of polypropylene (“Novatech PP BC6” described above), and a crushed resin vulcanizing agent (“ Tucky Roll 250-III ")
7.2 parts by weight (including 1.44 parts by weight of talc) and paraffin oil (“Diana Process Oil PX-
90 ") 300 parts by weight were blended to sufficiently absorb the paraffin oil. Then, to this, the pelletized rubber composition described above was added and thoroughly blended,
It was supplied to a twin-screw extruder (“KTX-30” described above) to perform dynamic crosslinking. The conditions for dynamic crosslinking are the same as in Example 1, 2
It was set to 20 ° C. and 500 rpm.

The polymer composition thus obtained was extremely flexible. Further, the obtained polymer composition was put into an injection molding machine (“SG25-HIPROMIIA” described above) and molded, and the physical properties were evaluated. Comparative Example 2 A polymer composition was prepared in the same manner as in Comparative Example 1 except that the oil of Comparative Example was 400 phr, and the physical properties were evaluated after injection molding.

Example 3 Comparative Example 1 except that the oil comparative example was 500 phr
A polymer composition was prepared in the same manner as in Example 1 and injection-molded, and then the physical properties were evaluated. [Evaluation of Physical Properties] After injection molding of the polymer compositions obtained in the above Examples and Comparative Examples,
Tensile strength T _B according to the method described in IS K 6251
(MPa), tensile stresses at 100% and 300% elongation M ₁₀₀ and M ₃₀₀ (MPa), and elongation at break E _B (%)
Then, the tear strength (N / mm) was determined according to the method described in JIS K 6252.

The compression set of the above injection molded product was measured according to the method described in JIS K6262. The measurement is 70 ° C. × 72 hours, 70 ° C. × 24 hours, 23 ° C. × 24 hours, −20 ° C. × 24 hours, −30 ° C.
It was conducted under the five conditions of × 24 hours. In the case of measuring at -20 ° C and -30 ° C, after the jig was released, the temperature was kept for 30 minutes, and then the thickness was immediately measured to calculate the strain. The hardness of the injection-molded product was measured by a Shore A hardness meter and an Asker C2 hardness meter (manufactured by Kobunshi Keiki Co., Ltd.).

Table 1 shows a list of blending components in Examples 1 to 5 and Comparative Examples 1 to 3, and Table 2 shows a list of kneading conditions and measured physical property values.

[0055]

[Table 1]

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[Table 2]

As is clear from Table 2, SEEPS as the thermoplastic elastomer and BIMS as the rubber component.
In Examples 1 to 5 using, in comparison with Comparative Examples 1 to 3 using EPDM instead of BIMS as a rubber component, in the case of applying a load for a long time in a high temperature region (70 ° C. × 72 hours) Compression set and low temperature range (-20 ℃, -30 ℃)
It was found that the value of compression set was even better, that is, smaller.

From the above results, the polymer compositions obtained in the examples are used as sealing materials used in communication cable closures, vibration damping / vibration damping members used in motors of various electronic / electrical devices, and the like. It turned out to be suitable for.

Claims (3)

[Claims] 1. A hydrogenated product of (A) styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer and styrene-
One or two or more thermoplastic elastomers selected from the group consisting of ethylene-ethylene-propylene-styrene block copolymers, and (B) a rubber obtained by brominated a copolymer of p-methylstyrene and isobutylene. A rubber component contained in a proportion of not less than wt%, and (C) a softening agent, wherein at least a part of the rubber component of (B) is crosslinked by dynamic crosslinking, and, A low elastic modulus polymer composition in which the amount of the softening agent (C) is 200 parts by weight or more based on 100 parts by weight of the total amount of the thermoplastic elastomer (A) and the rubber component (B). 2. A thermoplastic elastomer of the above (A) and the above
The low elastic modulus polymer composition according to claim 1, which contains 3 to 100 parts by weight of an olefin polymer based on 100 parts by weight of the total of the rubber component (B). 3. The low elastic modulus polymer composition according to claim 1 or 2, wherein the softening agent (C) has a pour point of -35 ° C or lower.