JPH0873697A - Rubber composition - Google Patents

Abstract

PURPOSE: To obtain a low-elastic composition uniformly containing a low- molecular material with good shape retaining properties by mixing a gelatinous composition prepared by mixing a thermoplastic block copolymer with the low-molecular material with a rubber material. CONSTITUTION: This composition is obtained by blending (A) a gelatinous composition prepared by mixing (i) 5-30wt.% thermoplastic block copolymer containing 15-70wt.% amorphous styrene blocks having >=60 deg.C glass transition temperature at both terminals with (ii) a low-molecular material having preferably <=10000 number-average molecular weight such as a softener, a plasticizer, a tackifier, an oligomer and a lubricant with (B) a rubber material such as an ethylene- propylene-based rubber composition, pre ferably at 0.4-4 weight ratio of the components (A)/(B).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low elasticity rubber composition containing a low molecular weight material uniformly and with good retention.

[0002]

2. Description of the Related Art Conventionally, ethylene-propylene rubber (EPR) and ethylene-propylene-diene rubber (EPDM) containing a third component in EPR have been used for vehicles, building materials, electric wires, Widely used for applications such as cables.

By the way, in the conventional EPR and EPDM, a large amount of low molecular weight materials may be mixed for the purpose of lowering the elastic modulus and improving impact absorption capacity. The ethylene-propylene rubber composition is difficult to uniformly disperse the low-molecular weight material, and the low-molecular weight material is weakly retained, so that the low-molecular weight material is likely to bleed, and thus the low elastic modulus of interest is obtained. I couldn't get anything.

The present invention has been made in view of the above circumstances and has a low elastic modulus in which a low molecular weight material is uniformly dispersed, and the low molecular weight material is satisfactorily held so that bleeding of the low molecular weight material is minimized. An object is to provide a rubber composition.

[0005]

Means and Actions for Solving the Problems The present inventors have
As a result of intensive studies to achieve the above objective, first,
Thermoplastic block copolymer having an amorphous styrene block at both ends, preferably, the content of the amorphous styrene block is 15 to 70 as the thermoplastic block copolymer.
A resin having a glass transition temperature Tg of 60% or more in weight% is used, and the thermoplastic block copolymer and the low molecular weight material are added so that the content of the thermoplastic block copolymer is 5 to 30% by weight. The rubber composition obtained by mixing to obtain a gel composition and then mixing the gel composition with a rubber material contains, for example, a low molecular weight material in a high proportion of about 50% by weight of the entire composition. However, the inventors have found that the low molecular weight material is uniformly dispersed in the composition and hardly bleeds. Therefore, the elastic modulus is extremely low, and the present invention has been completed.

Therefore, the present invention provides (A) a thermoplastic block copolymer having an amorphous styrene block at both ends and a low molecular weight material in a proportion of 5 to 30% by weight of the content of the copolymer. And a gel-like composition obtained by mixing so that
(B) A rubber composition characterized by being mixed with a rubber material.

The present invention will be described in more detail below. The rubber composition of the present invention is a mixture of the gel composition (A) and the rubber material (B) as described above.

This gel composition is obtained by mixing a thermoplastic block copolymer and a low molecular weight material.

Here, the thermoplastic block copolymer is required to have an amorphous styrene block at both ends, and when only one end or not at one end, a gel-like composition having desired properties is obtained. I can't get things.
The content of the amorphous styrene block in the thermoplastic block copolymer is 15 to 70% by weight, preferably 20 to 70% by weight.
The range of 60% by weight is desirable. Further, the glass transition temperature (Tg) of the amorphous styrene block portion is 60 ° C. or higher, preferably 80 ° C. or higher. Further, the polymer of the portion connecting the amorphous styrene blocks at both ends is also preferably an amorphous one, and examples thereof include an ethylene-butylene copolymer, a butadiene polymer, and an isoprene polymer. It may be a block or random copolymer of these. The number average molecular weight of the thermoplastic block copolymer is 5.0 × 10 5.
4 or more, preferably 8.0 × 10 4 or more is desirable.

In the gel composition according to the present invention,
A polymer other than the thermoplastic block copolymer may be used as a mixture with the thermoplastic block copolymer, and such a polymer may be, for example, a block of polybutadiene and butadiene-styrene random copolymer. Polyethylene and ethylene-styrene random copolymer obtained by hydrogenating a copolymer, block copolymer of polybutadiene and polystyrene, or polyethylene and polystyrene obtained by hydrogenating a block copolymer of polybutadiene and polystyrene And a block copolymer, etc., with respect to the thermoplastic block copolymer described above.
It can be used in an amount of 90% by weight, preferably 20 to 80% by weight.

On the other hand, the low molecular weight material may be solid or liquid, and various materials can be used depending on the application.
If the low molecular weight material is an organic material, the number average molecular weight is 2
It is less than 0000, preferably 10,000 or less, and more preferably 5,000 or less. The low molecular weight material is not particularly limited, but the following can be exemplified. Softening agent: A softening agent for various rubbers such as mineral oil type, vegetable oil type, synthetic type, or resin. As mineral oils, process oils such as aromatics, naphthenes and paraffins. Vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, wood wax,
Pine oil, olive oil, etc. Plasticizer: phthalic acid ester, phthalic acid mixed base ester,
Various ester-based plasticizers such as aliphatic dibasic acid esters, glycol esters, fatty acid esters, phosphoric acid esters, and stearic acid esters, epoxy plasticizers, other plasticizers for plastics, or phthalate-based and adipate-based plasticizers,
Sebacate-based, phosphate-based, polyether-based, polyester-based plasticizers for NBR. Tackifier: various tackifiers such as coumarone resin, coumarone-indene resin, phenol terpine resin, petroleum hydrocarbon, rosin derivative, etc. Oligomer: Crown ether, fluorinated oligomer, polybutene, xylene resin, chlorinated rubber, polyethylene wax, petroleum resin, rosin ester rubber, polyalkylene glycol diacrylate, liquid rubber (polybutadiene, styrene-butadiene rubber, butadiene-acrylonitrile rubber, polychloroprene Etc.), silicone-based oligomers, various oligomers such as poly-α-olefins. Lubricants: Hydrocarbon lubricants such as paraffin and wax, fatty acid lubricants such as higher fatty acids and oxyfatty acids, fatty acid amide lubricants such as fatty acid amides and alkylenebis fatty acid amides, fatty acid lower alcohol esters, fatty acid polyhydric alcohol esters, fatty alcohols , Alcoholic lubricants such as polyhydric alcohol, polyglycol, polyglycerol,
Various lubricants such as metal soaps and mixed lubricants.

In addition, latex, emulsion, liquid crystal, bituminous composition, clay, natural starch, sugar, inorganic silicone oil, phosphazene and the like can be used. In addition, animal oil such as cow oil, pig oil, horse oil, bird oil,
Dairy products such as fish oil, honey, fruit juice, chocolate, yogurt, hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, acetals, ketone fatty acids, esters, nitrogen compounds, sulfur compounds Organic solvents such as type, or various medicinal components, soil conditioners,
Fertilizers, petroleum, water, aqueous solutions and the like can also be used.

Further, in the present invention, in addition to the above-mentioned materials, the following fillers may be blended, if necessary. That is, clay, diatomaceous earth, carbon black, silica, talc, barium sulfate, calcium carbonate, magnesium carbonate, metal oxides, mica, graphite, scale-like inorganic fillers such as aluminum hydroxide, various metal powders,
Wood chips, glass powder, ceramic powder, granular or powdered solid filler such as granular or powdered polymer, and other various natural or artificial short fibers, long fibers (for example, straw, wool, glass fiber, metal fiber, various other Polymer fibers and the like) can be blended.

The gel composition according to the present invention is formed by mixing the thermoplastic block copolymer and the low molecular weight material as described above. In this case,
It is desirable to use as little a thermoplastic block copolymer as possible to obtain the desired physical properties.

Here, where A is the amount of the thermoplastic block copolymer and B is the amount of the low molecular weight material and the like, the weight fraction of the thermoplastic block copolymer [{A / (A + B) × 10
0}] is 5 to 30%, preferably 7 to 25%.

As the mixing conditions of the thermoplastic block copolymer and the low molecular weight material, specifically, a high speed mixer such as a high shear mixer is used, and the stirring speed is 300 rpm or more, preferably 500 rpm or more. , And more preferably 10
It is recommended to mix at 00 rpm or more. When the mixture is not stirred at a high speed, it is difficult to obtain a gel composition having the desired physical properties by mixing at a low speed using, for example, a roll or rotor type mixer or a cylinder type mixer. Furthermore, the mixing temperature is preferably 90 to 200 ° C., preferably 100 to 180 ° C., and the mixing time is 5 to 1
20 minutes, preferably about 10 to 90 minutes.

The gel composition thus obtained is
It has a physical feel such as natural konjac or agar, follows the load with good deformability, and quickly returns to its original shape after the load is removed. As an index of the recoverability after deformation, at a deformation recovery rate v (% / 0.5 sec) after 50% compression deformation release described later, the gel composition according to the present invention is preferably 20 or more, more preferably It has a value of 30 or more, and most preferably 40 or more, and is soft and excellent in recoverability after deformation.

The deformation recovery rate after 50% compression deformation release is a value measured by the following method.

The thickness of the sample before compression is L ₀ , which is compressed to 1/2 L ₀ (50%) and fixed for 1 minute.

When the sample is decompressed (released) after 1 minute and the sample is recovered to the thickness of x 0.5 seconds after the compression is removed, the deformation recovery speed v is calculated by the following equation. v (% / 0.5 sec) = (x−1 / 2L ₀ ) × 1/2
L ₀ = (2x−L ₀ ) / L ₀ Therefore, the deformation recovery speed v is
It takes a value from 0 to 100, and v = 0 corresponds to a state in which the sample has not returned from the compressed state after 0.5 seconds, and v = 1.
00 corresponds to the state where the sample has completely returned to the original state after 0.5 seconds.

The rubber material which is one component of the rubber composition of the present invention includes natural rubber, SBR, BR, IR and C.
Typical rubbers such as R, IIR and NBR can be mentioned, but among them, ethylene-propylene rubbers such as EPR and EPDM can be preferably used. The EPR has an ethylene content of 60% by weight or more, preferably 65% by weight or more, more preferably 70% by weight or more, and the upper limit thereof is 95% by weight, particularly 90% by weight, and Crystallinity is 3% or more, preferably 5%
Or more, more preferably 8% or more, the upper limit is 60%,
In particular, it is 50%, and the melting point (Tm) of the polyethylene part showing the block property of ethylene is the differential scanning calorimetry (D
SC) is 25 ° C or higher, preferably 30 ° C or higher, more preferably 35 ° C or higher, and the EPR has a number average molecular weight of 20.
000 or more, preferably 30,000 or more, and more preferably 40,000 or more. Further, as the copolymerization component of the third component of EPDM, for example, 1,5-hexadiene, 1,4-hexadiene, dicyclopentadiene,
Examples include ethylidene and norbornene. in this case,
The content of the third component is 1 to 15% by weight, preferably 2 to 10% by weight based on the whole EPDM.

The mixing ratio of the gel composition of the component (A) and the rubber of the component (B) is such that the weight ratio of (A) / (B) is 0.3 to 8, preferably 0.35 to 6. And more preferably in the range of 0.4 to 4, whereby the elastic modulus can be controlled in a wide range. (A)
If the ratio of the polymer network structure of the component is too high, the function of the resulting rubber composition as a rubber may be impaired, while if it is too low, the desired rubber composition having a low elastic modulus cannot be obtained. There are cases.

The method of mixing the components (A) and (B) is not particularly limited, and for example, they can be easily blended with a general roll, kneader, mixer, Banbury mixer or the like. In this case, the mixing temperature is 30 to 120 ° C., preferably 40 to 100 ° C., and the mixing time is 1 to 40.
Minutes, preferably 2 to 30 minutes.

In addition to the component (A) and the component (B), the rubber composition of the present invention may further contain, in addition to the above ethylene-propylene copolymer and the low molecular weight material, when mixed. The following fillers may be added. That is, clay, diatomaceous earth, carbon black, silica, talc, barium sulfate, calcium carbonate, magnesium carbonate, metal oxides, mica, graphite, scale-like inorganic fillers such as aluminum hydroxide, various metal powders, wood chips, glass powders , Ceramic powder, granular or powdered solid filler such as granular or powdered polymer, other various natural or artificial short fibers, long fibers (for example, straw, hair, glass fiber, metal fiber, other various polymer fibers, etc.) Etc. can be blended.

Since the rubber composition of the present invention can hold a large amount of low molecular weight material such as liquid, the elastic modulus can be controlled to an extremely low range. Therefore, the present composition can provide products in a wide range of industrial fields, particularly household appliances, sports equipment, industrial equipment, precision equipment, transportation equipment, construction, civil engineering, medical care, leisure, and the like. For example, as the vibration-proof / vibration-damping / cushioning material, a sealing member, a packing, a gasket, a fixing member such as a grommet, a support member such as a mount, a holder, and an insulator, and a cushioning member such as a stopper, a cushion, and a bumper can be cited. Furthermore, as shock absorbers, sports equipment such as grabs, mitts, golf clubs, and tennis rackets, insoles for shoes, various toys, audio equipment, electronic and electrical equipment, or beds and chairs, especially for medical applications that keep the same posture for a long time. It is preferably used as a bed, a barber / beauty bed, a theater chair, and a vehicle material that receives vibration.

It can also be used in medical devices such as artificial limbs, artificial hands, robots, electrode materials for measuring electrocardiogram, and electrode materials for low-frequency therapeutic devices. Furthermore, it can be used as an ultra-low hardness rubber for OA equipment, seismic isolation rubber, anti-vibration rubber, and even racing tires. In addition, it can be used as a low hardness plastic for various molding materials. Furthermore,
Since it is possible to control the release of the low molecular weight material to the outside, it is also used for various sustained release materials that utilize the release characteristics of fragrances, medical agents, functional materials and the like. In particular, paper (including thin-leaf materials other than paper) feed rubber rolls, for example, copiers, printers, and other OA equipment and automated teller machines (ATM),
It is suitable for various feeding rolls such as money changers, counters, vending machines, and cash dispensers (CDs).

[0027]

INDUSTRIAL APPLICABILITY Since the rubber composition of the present invention can be blended with a large amount of low molecular weight materials and has good retention of low molecular weight materials, the elastic modulus can be controlled to an extremely low range, It can be applied to various fields using the elastic modulus.

[0028]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 3 and Comparative Example] A gel composition having the composition and composition shown in Table 1 was prepared (comparative examples are low molecular weight materials only). A rubber composition was obtained by mixing at the mixing ratio shown.

[0030]

[Table 1] * Polymer of connecting part E / B: Ethylene / butylene B: Butadiene I: Isoprene * Low molecular weight material PI: Polyisobutylene P: Paraffin oil * Rubber EPDM (1): Nodell 1040 EPDM (2): EP33 made by JSR

The rubber compositions obtained in the examples were vulcanized rubbers having good processability and very little exudation.

On the other hand, the rubber compositions obtained in Comparative Examples had poor processability and had very large exudation.

Claims (4)

[Claims] 1. (A) A thermoplastic block copolymer having an amorphous styrene block at both ends and a low molecular weight material are mixed so that the content of the copolymer is 5 to 30% by weight. A rubber composition obtained by mixing the gel composition obtained by the above and (B) a rubber material. 2. The content of the amorphous styrene block in the thermoplastic block copolymer is 15 to 70% by weight, and the glass transition temperature of the amorphous styrene block part is 60 ° C.
The rubber composition according to claim 1, which is the above. 3. The rubber composition according to claim 1, wherein the rubber material is an ethylene-propylene rubber composition. 4. The rubber composition according to claim 1, wherein the weight ratio (A) / (B) of the component (A) and the component (B) is 0.4 to 4.