JP6922172B2 - Method for manufacturing rubber composition - Google Patents

Description

The present invention relates to a method for producing a rubber composition.

Conventionally, a rubber composition containing a halogen-based rubber such as chloroprene rubber that generates an inert gas during combustion has been used in the production of hoses (for example, hydraulic hoses) used in construction machinery and the like. Here, since the hose used for construction machinery and the like may drag on the ground, it is required to have excellent slipperiness.

Under such circumstances, as a rubber composition used for producing the hose, for example, Patent Document 1 discloses a rubber composition containing chloroprene rubber and ultra-high molecular weight polyethylene powder (claims and the like).

Japanese Unexamined Patent Publication No. 2014-09333

Recently, from the viewpoint of mass production and the like, rubber compositions are required to be further improved in processability. The present inventor mixed a diene rubber containing chloroprene rubber and Miperon XM-200 (melting point: 136 ° C.), which is an ultra-high molecular weight polyethylene, with reference to the examples of Patent Document 1, and released the mixture at 150 ° C. (Mixed release temperature: 150 ° C.), a rubber composition was produced by mixing a vulcanizing agent. Although the obtained rubber composition has excellent slipperiness, processability is recently required. It became clear that it did not necessarily meet the level.

Therefore, in view of the above circumstances, an object of the present invention is to provide a method for producing a rubber composition, which can obtain a rubber composition having excellent processability and slipperiness.

As a result of diligent studies on the above problems, the present inventor has found that the above problems can be solved by mixing a diene rubber containing chloroprene rubber and an ultra high molecular weight polyethylene rubber at a temperature equal to or lower than the melting point of the ultra high molecular weight polyethylene. , The present invention has been reached.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) A rubber composition precursor is obtained by mixing 100 parts by mass of a diene rubber containing chloroprene rubber and 12 to 50 parts by mass of an ultrahigh molecular weight polyethylene at a temperature equal to or lower than the melting point of the ultrahigh molecular weight polyethylene. , 1st mixing step and
A method for producing a rubber composition, comprising a second mixing step of obtaining a rubber composition by mixing the rubber composition precursor and a vulcanizing agent.
(2) The method for producing a rubber composition according to (1) above, wherein the diene-based rubber further contains styrene-butadiene rubber.
(3) The rubber composition according to (1) or (2) above, wherein the ultra-high molecular weight polyethylene is an ultra high molecular weight polyethylene having an average particle size of 5 to 180 μm and an average molecular weight of 1,000,000 or more. How to make things.
(4) The above (1) to (3), wherein the mixing in the first mixing step and / or the mixing in the second mixing step is a mixing using a closed mixer equipped with two rotors. The method for producing a rubber composition according to any one.
(5) The method for producing a rubber composition according to any one of (1) to (4) above, wherein the rubber composition is a rubber composition for a hose.

As shown below, according to the present invention, it is possible to provide a method for producing a rubber composition, which can obtain a rubber composition having excellent processability and slipperiness.

FIG. 1 is a perspective view showing an example of a preferred embodiment of the hose of the present invention by cutting out each layer of the hose. FIG. 2 is a perspective view showing each layer of the hose cut out for another example of a preferred embodiment of the hose of the present invention.

The method for producing the rubber composition of the present invention and the hose of the present invention will be described below.
The numerical range represented by using "~" in the present specification means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[Manufacturing method of rubber composition]
The method for producing a rubber composition of the present invention (hereinafter, also referred to as “the production method of the present invention”) includes the following first mixing step and second mixing step.
(1) First Mixing Step A rubber composition is obtained by mixing 100 parts by mass of a diene rubber containing chloroprene rubber and 12 to 50 parts by mass of an ultrahigh molecular weight polyethylene at a temperature equal to or lower than the melting point of the ultrahigh molecular weight polyethylene. Step to obtain precursor (2) Second mixing step A step to obtain a rubber composition by mixing the rubber composition precursor obtained in the first mixing step with a vulcanizing agent.

Since the production method of the present invention has such a configuration, it is considered that the above-mentioned effects can be obtained. The reason is not clear, but by mixing diene rubber and ultra-high molecular weight polyethylene at a temperature below the melting point of ultra-high molecular weight polyethylene, the entanglement of the two is suppressed, and as a result, the viscosity of the composition increases. It is thought that it is suppressed.
Hereinafter, each step will be described in detail.

[First mixing step]
In the first mixing step, 100 parts by mass of a diene-based rubber containing chloroprene rubber and 12 to 50 parts by mass of an ultra-high molecular weight polyethylene are mixed at a temperature equal to or lower than the melting point of the ultra high molecular weight polyethylene to prepare a rubber composition precursor. This is the process of getting a body.
First, each component used in the first mixing step will be described in detail.

<Diene rubber>
The diene rubber used in the first mixing step contains chloroprene rubber (CR). The diene-based rubber may further contain a rubber other than the chloroprene rubber.

(Chloroprene rubber)
The chloroprene rubber is not particularly limited, and conventionally known rubbers can be used.
The weight average molecular weight of the chloroprene rubber is not particularly limited, but is preferably 100,000 to 3,000,000, and more preferably 100,000 to 1,000,000. In the present specification, the weight average molecular weight (Mw) shall be measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent in terms of standard polystyrene.

The content of the chloroprene rubber in the diene rubber is preferably 10% by mass or more, more preferably 30% by mass or more, based on the entire diene rubber, for the reason that the effect of the present invention is more excellent. .. The upper limit is not particularly limited, but is preferably 90% by mass or less, and more preferably 70% by mass or less.

(Other rubber components)
The diene-based rubber may further contain other rubber components.
Examples of such rubber components include styrene-butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), and butyl rubber (IIR). Examples thereof include butyl halide rubber (Br-IIR, Cl-IIR) and ethylene propylene diene rubber (EPDM). Of these, one type may be used, or two or more types may be used in combination.

The diene-based rubber preferably further contains styrene-butadiene rubber (SBR) for the reason that the effect of the present invention is more excellent.
The content of the styrene unit (styrene content) in the styrene-butadiene rubber is not particularly limited, but is preferably 10 to 50% by mass, preferably 15 to 40% by mass, for the reason that the effect of the present invention is more excellent. Is more preferable.
The weight average molecular weight of the styrene-butadiene rubber is not particularly limited, but the preferred range is the same as that of the chloroprene rubber described above.

The content of other rubber components (particularly styrene-butadiene rubber) in the diene-based rubber is not particularly limited, but is 10 to 60% by mass with respect to the entire diene-based rubber for the reason that the effect of the present invention is more excellent. Is preferable.

<Ultra high molecular weight polyethylene>
As described above, in the first mixing step, 100 parts by mass of diene-based rubber containing chloroprene rubber and 12 to 50 parts by mass of ultra-high molecular weight polyethylene are mixed at a temperature equal to or lower than the melting point of the ultra high molecular weight polyethylene.

The average molecular weight of the ultra-high molecular weight polyethylene is preferably 1,000,000 or more, and more preferably 1,500,000 or more because the effect of the present invention is more excellent. The upper limit is not particularly limited, but is preferably 4,000,000 or less. The average molecular weight of the ultra-high molecular weight polyethylene means the viscosity average molecular weight, and is a value measured by the intrinsic viscosity method (ASTM D4020).

The average particle size of the ultra-high molecular weight polyethylene is preferably 1 to 200 μm, more preferably 5 to 170 μm, and even more preferably 10 to 50 μm because the effect of the present invention is more excellent. The average particle size of ultra-high molecular weight polyethylene is a value measured by the Coulter counter method.

The melting point of the ultra-high molecular weight polyethylene is preferably 100 to 150 ° C., more preferably 120 to 140 ° C., for the reason that the effect of the present invention is more excellent. The melting point of ultra-high molecular weight polyethylene is a value measured by differential scanning calorimetry (DSC) (ASTM D3418).

Ultra-high molecular weight polyethylene is Mitsui Chemicals' Hi-Zex Million C30S, 145M, 240S, 240M, 320M, 340M, 530M (all trade names), and Miperon (trade name) XM-220 with a smaller average particle size. , XM-221U (both are trade names), etc., and can be obtained as commercial products.
As the ultra-high molecular weight polyethylene, one type may be used alone, or two or more types may be used in combination.

In the first mixing step, the amount of ultra-high molecular weight polyethylene mixed is 12 to 50 parts by mass with respect to 100 parts by mass of the above-mentioned diene rubber. Among them, 17 to 25 parts by mass is preferable for the reason that the effect of the present invention is more excellent.

<Other ingredients>
In the first mixing step, other components may be further mixed.
Other ingredients include, for example, carbon black, resins, fillers (eg, talc, mica), naphthen oils, aroma oils, stearic acid, zinc oxide, magnesium oxide, antioxidants, antioxidants, antioxidants, difficult Examples include fuel agents.

(Carbon black)
The carbon black is not particularly limited, and for example, various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, FEF, GPF, and SRF. Can be used.
One type of carbon black may be used alone, or two or more types may be used in combination.
In the first mixing step, the amount of carbon black to be mixed is not particularly limited, but for the reason that the effect of the present invention is more excellent, it is preferably 30 to 100 parts by mass with respect to 100 parts by mass of the above-mentioned diene rubber. ..

<Mixing method>
The mixing method in the first mixing step is not particularly limited, and examples thereof include a method of mixing the above-mentioned components using a known method or apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). Of these, a method using a closed mixer equipped with two rotors is preferable.

In the first mixing step, each of the above-mentioned components is mixed at a temperature equal to or lower than the melting point of the above-mentioned ultra-high molecular weight polyethylene. Examples of the method of mixing at a temperature equal to or lower than the melting point of the ultra-high molecular weight polyethylene include a method of setting the temperature at the time of discharging from the closed mixer to be equal to or lower than the melting point of the above-mentioned ultra high molecular weight polyethylene.
The mixing temperature in the first mixing step is not particularly limited as long as it is a temperature equal to or lower than the melting point of the above-mentioned ultra-high molecular weight polyethylene, but is preferably 120 to 130 ° C. for the reason that the effect of the present invention is more excellent.

[Second mixing step]
The second mixing step is a step of obtaining a rubber composition by mixing the rubber composition precursor obtained in the first mixing step described above with a vulcanizing agent.

<Vulcanizing agent>
The vulcanizing agent is not particularly limited, and examples thereof include sulfur and resin vulcanizing agents. Of these, sulfur is preferable.
The mixing amount of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 4.0 parts by mass with respect to 100 parts by mass of the diene rubber in the first mixing step described above.

In the second mixing step, it is preferable to further mix the vulcanization accelerator.

<Mixing method>
The mixing method in the second mixing step is not particularly limited, and specific examples and preferred embodiments thereof are the same as those in the first mixing step described above.
The mixing temperature in the second mixing step is preferably 70 to 130 ° C. for the reason that the effect of the present invention is more excellent.

[Use]
The rubber composition obtained by the production method of the present invention is suitably used for hoses (particularly, rubber outer layer (cover rubber)), tires, conveyor belts, anti-vibration materials, rubber rolls, outer hoods of railway vehicles, and the like. Among them, it is preferably used for hoses (particularly, rubber outer layer (cover rubber)).

[hose]
The hose of the present invention is a hose manufactured by using the rubber composition obtained by the above-mentioned production method of the present invention (hereinafter, also referred to as "composition of the present invention").
Hereinafter, an example of a preferred embodiment of the hose of the present invention will be described with reference to FIG.
FIG. 1 is a perspective view showing an example of a preferred embodiment of the hose of the present invention by cutting out each layer of the hose. As shown in FIG. 1, the hose 10 of the present embodiment has a rubber inner layer 11, a reinforcing layer 12, and a rubber outer layer 13 laminated in this order.

[Rubber layer (rubber inner layer 11, rubber outer layer 13)]
The rubber layer is a layer adjacent to the reinforcing layer, and the hose 10 of the present embodiment has a rubber inner layer 11 and a rubber outer layer 13. In the present embodiment, one or both of the rubber inner layer 11 and the rubber outer layer 13 of the rubber layers are formed by using the composition of the present invention, and the oil resistance of the hose 10 is determined. At least the rubber outer layer 13 is formed by using the composition of the present invention from the viewpoint of having a good balance of weather resistance, excellent adhesiveness to brass, and excellent durability against the external environment. Is preferable.

As the rubber composition used for the rubber inner layer 11 other than the composition of the present invention, a suitable rubber composition is appropriately selected and configured from the viewpoint of oil resistance, chemical resistance, processability and the like. The raw material rubber is selected from the group of synthetic rubbers such as NBR, SBR, acrylic rubber, hydrin rubber, ethylene-acrylic acid ester copolymer rubber (particularly ethylene acrylate rubber (AEM)), and hydride acrylonitrile-butadiene copolymer rubber. Examples thereof include rubber compositions containing at least one type of rubber as a main component. Further, if necessary, it may be a mixture with a thermoplastic resin or a thermoplastic elastomer. The rubber composition used for the rubber inner layer 11 preferably has a 100% modulus (M100) after vulcanization of 4 MPa or more, and more preferably 5 MPa or more and 20 MPa or less, from the viewpoint of excellent hose durability. In addition, in this specification, 100% modulus shows the value measured according to JIS K6251-2004.

As the rubber composition used for the rubber outer layer 13, the composition of the present invention is preferably used, but it has excellent durability against the external environment such as oil resistance, weather resistance, and adhesiveness between the rubber layer and the reinforcing layer. It is also possible to appropriately select and compose a suitable rubber composition from the viewpoint of having the rubber composition.

Raw material rubbers used in rubber compositions other than the composition of the present invention include butyl-based copolymer rubber, ethylene-propylene-based copolymer rubber, EPDM, NBR, SBR, acrylic rubber, NR, BR, and ethylene-acrylic acid ester. Examples thereof include a rubber composition containing at least one rubber as a main component selected from the group of synthetic rubbers such as system copolymer rubber (particularly AEM), hydride NBR, and hydrin rubber. Further, if necessary, it may be a mixture with a thermoplastic resin or a thermoplastic elastomer.

The rubber outer layer 13 is a layer provided adjacent to the outer peripheral side of the reinforcing layer 12.

Further, in the hose 10 of the present embodiment, the thickness of the rubber inner layer 11 is preferably 1.0 mm or more and 4.0 mm or less, and more preferably 1.5 mm or more and 1.8 mm or less. Similarly, the thickness of the rubber outer layer 13 is preferably 0.5 mm or more and 2.5 mm or less, and more preferably 0.8 mm or more and 1.5 mm or less.

Further, the rubber inner layer 11 is limited to one layer in the present embodiment, but is not limited to this, and may be, for example, a two-layer structure of the innermost layer (inner surface resin layer) and the rubber layer.

[Reinforcing layer]
The reinforcing layer 12 is a layer whose surface is brass-plated, which is arranged adjacent to the outer peripheral side of the rubber inner layer 11. The reinforcing layer 12 is provided on the outside of the rubber inner layer 11 from the viewpoint of maintaining strength. In the present embodiment, the reinforcing layer 12 may be formed in a blade shape or a spiral shape. Two or more reinforcing layers 12 may be provided. When two or more reinforcing layers 12 are provided, examples of the rubber composition used for the rubber intermediate layer between the reinforcing layers include NBR, NR, SBR, BR, EPDM, and ethylene-acrylic acid ester-based copolymer rubber (particularly AEM). Examples thereof include a rubber composition containing at least one rubber as a main component selected from the group of synthetic rubbers such as. Further, if necessary, it may be a mixture with a thermoplastic resin or a thermoplastic elastomer.

The material for forming the reinforcing layer 12 is not particularly limited, and for example, a metal material such as a hard steel wire (for example, brass-plated (Cu—Zn alloy) wire, galvanized wire, etc.) is preferably used. As the reinforcing layer 12, a brass-plated one is preferable because it has excellent adhesiveness to the composition of the present invention.

The method for manufacturing the hose 10 of the present embodiment having the rubber layer and the reinforcing layer 12 is not particularly limited, and a conventionally known method can be used. An example of the method for manufacturing the hose 10 of the present embodiment will be described. First, the rubber composition for the rubber inner layer 11 is extruded on the outside of the core body (mandrel) having a diameter similar to the inner diameter of the hose to cover the mandrel, and the rubber inner layer (inner tube rubber) 11 is formed (inside). Tube extrusion process). Next, a predetermined number of brass-plated wires are knitted on the outside of the rubber inner layer 11 formed in the inner tube extrusion step to form the reinforcing layer 12 (knitting step), and the composition of the present invention is extruded on the outside of the reinforcing layer 12. It is molded to form a rubber outer layer (coat rubber) 13 (coat extrusion step). Further, the outside of the rubber outer layer 13 formed in the outer cover extrusion step is coated with a resin (resin mold coating step), and this is subjected to predetermined conditions (for example, the temperature is 140 ° C. or higher and 190 ° C. or lower, and the heating time is 30 minutes or longer and 180 minutes or more. Vulcanization and adhesion by press vulcanization, steam vulcanization, oven vulcanization (hot air vulcanization) or hot water vulcanization (vulcanization step). After vulcanization, the coating resin is peeled off (resin mold peeling step) and the mandrel is removed (mandrel extraction step) to manufacture a hose 10 having a reinforcing layer 12 between the rubber inner layer 11 and the rubber outer layer 13. Can be done.

The hose 10 of the present embodiment has a three-layer structure in which the rubber inner layer 11, the reinforcing layer 12, and the rubber outer layer 13 are sequentially laminated from the inside as described above, but when further strength or the like is required, the present embodiment has a three-layer structure. The hose 10 may be provided with a plurality of the reinforcing layers 12 and a rubber intermediate layer (intermediate rubber) may be provided between the reinforcing layers 12. The hose 10 of the present embodiment has, for example, as shown in FIG. 2, a rubber inner layer 11, a first reinforcing layer 12-1, a rubber intermediate layer 15, a second reinforcing layer 12-2, and a rubber outer layer. It is also possible to have a five-layer structure having 13 and 13 in this order from the inside. The number of reinforcing layers 12 can be appropriately adjusted according to the required characteristics of the hose and the like.

At this time, the composition of the present invention is preferable as the rubber composition used for the rubber intermediate layer 15. The rubber composition used for the rubber intermediate layer 15 preferably has, for example, a 100% modulus (M100) after vulcanization of 2 MPa or more.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[Manufacturing of rubber composition]
Using a closed mixer (equipped with two rotors), components other than sulfur and vulcanization accelerator among the components shown in Table 1 below were mixed at the ratio (parts by mass) shown in the same table. .. The temperature at the time of release is as shown in the mixed release temperature in Table 1. The temperature at the time of discharge is the highest temperature in the first mixing step. That is, the mixing temperature in the first mixing step is equal to or lower than the temperature shown in the mixing / discharging temperature in Table 1. In this way, a rubber composition precursor was obtained (first mixing step).
Then, the sulfur and the vulcanization accelerator shown in Table 1 are mixed (100 ° C.) with the obtained rubber composition precursor at the ratio (parts by mass) shown in the same table to obtain a rubber composition. (Second mixing step).

〔evaluation〕
<Workability>
The obtained rubber composition (unvulcanized) was extruded to prepare an unvulcanized rubber sheet. Then, the surface of the obtained unvulcanized rubber sheet was visually observed, and the workability was evaluated according to the following criteria. The results are shown in Table 1. It is preferably ◯ or Δ, and more preferably ◯.
-○: The surface of the unvulcanized rubber sheet is uniform.
-△: Unevenness is seen on the surface of the unvulcanized rubber sheet.
-X: The rubber composition (unvulcanized) does not come together and does not form a sheet.

<Slipperiness>
An unvulcanized rubber sheet was produced in the same manner as in the evaluation of processability described above. The obtained unvulcanized rubber sheet was vulcanized at 148 ° C. for 45 minutes using a press vulcanizer to prepare a vulcanized rubber sheet having a thickness of 2 mm. Then, the slipperiness of the obtained vulcanized rubber sheet was evaluated by a HEIDON friction tester. The friction tester was measured using a general tester. Specifically, the friction tester was measured using HEIDON TYPE-14 manufactured by Shinto Kagaku Co., Ltd. The results are shown in Table 1. The evaluation criteria are as follows. It is preferably ◯ or Δ, and more preferably ◯.
・ ○: Very good ・ △: Good ・ ×: Insufficient

<Elongation when cutting>
A vulcanized rubber sheet was produced in the same manner as in the evaluation of slipperiness described above. The obtained vulture rubber sheet was subjected to a tensile test under the conditions of a tensile speed of 500 mm / min and 23 ° C. according to JIS K 6251, and the elongation at cutting (EB) [%] was measured. The results are shown in Table 1. The evaluation criteria are as follows. ⊚, ◯ or Δ is preferable, ⊚ or 〇 is more preferable, and ⊚ is even more preferable.
・ ◎: 190% or more ・ ○: 170% or more and less than 190% ・ △: 120% or more and less than 170% ・ ×: less than 120%

Details of each component in Table 1 are as follows.
-SBR: Nipol 1502 (emulsion polymerization SBR, manufactured by Nippon Zeon Corporation, styrene content: 23.5% by mass)
-CR: Denka chloroprene S-41 (non-sulfur modified chloroprene rubber, manufactured by Denki Kagaku Kogyo Co., Ltd.)
・ FEF: Niteron # 10N (FEF grade carbon black, manufactured by Shin Nikka Carbon Co., Ltd.)
-GPF: Niteron #GN (GPF grade carbon black, manufactured by Japanophile Carbon Co., Ltd.)
-Ultra high molecular weight polyethylene 1: Miperon XM220 (ultra high molecular weight polyethylene, melting point: 136 ° C., average particle size: 30 μm, average molecular weight: 2,000,000, manufactured by Mitsui Chemicals, Inc.)
-Ultra high molecular weight polyethylene 2: Hi-Zex Million 145M (ultra high molecular weight polyethylene, melting point: 136 ° C., average particle size: 150 μm, average molecular weight: 1,150,000)
・ Naphthenic oil: Cosmo Rex No. 2 (manufactured by Nippon Oil Co., Ltd.)
・ Aroma oil: A / O MIX 2010 (manufactured by Sankyo Yuka Kogyo Co., Ltd.)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
-Magnesium oxide: Kyowa Mag 150 (manufactured by Kyowa Chemical Industry Co., Ltd.)
・ Stearic acid: Stearic acid (manufactured by NOF CORPORATION)
・ Anti-aging agent: Ozonon 6C (manufactured by Seiko Kagaku Co., Ltd.)
・ Sulfur: Oil-treated sulfur (oil-treated 5%) (manufactured by Hosoi Chemical Industry Co., Ltd.)
・ TS: Sunseller TS-G (thiuram-based vulcanization accelerator, manufactured by Sanshin Chemical Co., Ltd.)
-DT: Soxinol DT-O (guanidine-based vulcanization accelerator, manufactured by Sumitomo Chemical Co., Ltd.)

As can be seen from Table 1, the rubber compositions obtained by the production methods of Examples 1 to 9 in which a diene rubber containing chloroprene rubber and ultra-high molecular weight polyethylene were mixed in advance at a temperature equal to or lower than the melting point of the ultra high molecular weight polyethylene. Showed excellent workability and slipperiness. Among them, Examples 1 to 8 in which the average particle size of the ultra-high molecular weight polyethylene was 100 μm or less showed more excellent processability.
From the comparison of Examples 1 and 4 to 8 (contrast between modes in which ultra-high molecular weight polyethylene 1 is used and the mixed release temperature is 130 ° C.), the blending amount of ultra-high molecular weight polyethylene is 100 parts by mass of diene rubber. Examples 1 and 6 to 8 having 17 parts by mass or more showed better slipperiness.
Further, from the comparison of Examples 1 to 8, Examples 1 to 5 in which the blending amount of the ultra-high molecular weight polyethylene is 25 parts by mass or less with respect to 100 parts by mass of the diene rubber has more excellent mechanical properties (at the time of cutting). (Elongation) was shown.
Further, from the comparison of Examples 1 to 3 (contrast between modes in which 20 parts by mass of ultra-high molecular weight polyethylene 1 is blended), the difference between the melting point of the ultra-high molecular weight polyethylene and the mixed discharge temperature is 10 ° C. or less. And 3 showed better mechanical properties (elongation at the time of cutting).

On the other hand, the rubber composition obtained by the production method of Comparative Example 1 in which a diene rubber containing chloroprene rubber and an ultrahigh molecular weight polyethylene are mixed in advance at a temperature higher than the melting point of the ultrahigh molecular weight polyethylene has insufficient processability. Met.
Further, the rubber compositions obtained by the production methods of Comparative Examples 2 and 3 in which the blending amount of the ultra-high molecular weight polyethylene was less than 12 parts by mass with respect to 100 parts by mass of the diene rubber had insufficient slipperiness. ..
Further, the rubber composition obtained by the production method of Comparative Example 5 in which the blending amount of the ultra-high molecular weight polyethylene exceeded 50 parts by mass with respect to 100 parts by mass of the diene-based rubber was insufficient in processability.

10 Hose 11 Rubber inner layer 12 Reinforcing layer 12-1 First reinforcing layer 12-2 Second reinforcing layer 13 Rubber outer layer 15 Rubber intermediate layer

Claims (5)

A rubber composition precursor is obtained by mixing 100 parts by mass of a diene-based rubber containing chloroprene rubber and 12 to 50 parts by mass of an ultra-high molecular weight polyethylene at a temperature equal to or lower than the melting point of the ultra-high molecular weight polyethylene. Mixing process and
A second mixing step of mixing the rubber composition precursor and the vulcanizing agent to obtain a rubber composition is provided .
The mixing in the first mixing step is mixing using a closed mixer equipped with two rotors.
In the first mixing step, the difference between the melting point of the ultra-high molecular weight polyethylene and the mixing / discharging temperature, which is the temperature at which the rubber composition precursor is discharged from the closed mixer, is 10 ° C. or less . A method for producing a rubber composition. The method for producing a rubber composition according to claim 1, wherein the diene-based rubber further contains styrene-butadiene rubber. The method for producing a rubber composition according to claim 1 or 2, wherein the ultra-high molecular weight polyethylene is an ultra high molecular weight polyethylene having an average particle size of 5 to 180 μm and an average molecular weight of 1,000,000 or more. Method for producing a mixed prior Symbol second mixing step is a mixed using an internal mixer having two rotors, the rubber composition according to any one of claims 1 to 3. The method for producing a rubber composition according to any one of claims 1 to 4, wherein the rubber composition is a rubber composition for a hose.

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