JP2008069276A - Rubber composition, fiber/rubber composite and hose - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition obtaining a hose excellent in storage stability at non-vulcanization and extruding processability while sufficiently maintaining an adhesion property with a fiber material, a fiber/rubber composite using the rubber composition and a hose using the rubber composition for a rubber layer. <P>SOLUTION: The rubber composition contains a rubber component containing 50-100 mass% of an ethylene-propylene-diene copolymer rubber and magnesium oxide having a specific surface area measured by the BET method of 30-130 m<SP>2</SP>/g. The content of the magnesium oxide is 1-20 pts.mass relative to 100 pts.mass of the rubber component. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition, and a fiber rubber composite and a hose using the rubber composition.

An ethylene-propylene-diene copolymer rubber (hereinafter also referred to as “EPDM”), which is known as a rubber having excellent weather resistance, is widely used, for example, in an outer tube (outer rubber layer) of a hose.
However, since EPDM has low reactivity, there is a problem of low adhesion to the fiber material, and when used in the outer tube of the hose, there is a reinforcing layer made of a fiber material such as polyester fiber or polyamide fiber. There was a problem in that the adhesiveness of the hose was poor, thereby deteriorating the durability of the hose.

  In order to solve this problem, the present applicant has stated that "magnesium oxide is added to 100 parts by weight of rubber containing 50 to 100% by weight of ethylene-propylene-diene copolymer rubber containing 9 to 13% by weight of ethylidene norbornene. A hose having a rubber layer composed of a rubber composition containing 1 to 20 parts by weight and an organic fiber reinforcing layer adjacent to the rubber layer is provided (Patent Document 1).

JP 2002-273727 A

As a result of further study to improve the invention described in Patent Document 1, the present inventor has found that the storage stability of the rubber composition at the time of unvulcanization and the appearance of the hose at the time of hose manufacture, that is, at the time of extrusion (hereinafter referred to as the extrusion). , Also referred to as “extrusion processability”).
Therefore, the present invention uses a rubber composition capable of obtaining a hose excellent in storage stability during unvulcanization and extrudability while maintaining good adhesion to the fiber material, and the rubber composition. An object is to provide a fiber rubber composite and a hose using the rubber composition in a rubber layer.

  As a result of intensive studies to solve the above problems, the present inventor has obtained a rubber component containing ethylene-propylene-diene copolymer rubber at a predetermined ratio and magnesium oxide having a specific specific surface area at a specific ratio. The present inventors have found that the rubber composition to be contained can provide a hose excellent in storage stability and extrusion processability when unvulcanized.

That is, the present invention provides the following (1) to (5).
(1) A rubber component containing 50 to 100% by mass of EPDM and magnesium oxide having a specific surface area measured by the BET method of 30 to 130 m ² / g,
The rubber composition whose content of the said magnesium oxide is 1-20 mass parts with respect to 100 mass parts of said rubber components.
(2) A fiber rubber composite obtained by adhering the rubber composition according to the above (1) and a fiber material.
(3) A hose having a rubber layer formed using the rubber composition described in (1) above and a reinforcing layer adjacent to the rubber layer.
(4) The hose according to (3), wherein the reinforcing layer is formed using a fiber material.
(5) The hose according to (4), wherein the fiber material is a polyester fiber or a polyamide fiber.

  As will be described below, according to the present invention, a rubber composition capable of obtaining a hose excellent in storage stability during unvulcanized and extrudability while maintaining good adhesion with a fiber material, A fiber rubber composite using the rubber composition and a hose using the rubber composition for a rubber layer can be provided.

The present invention is described in detail below.
The rubber composition of the present invention contains a rubber component containing 50 to 100% by mass of EPDM and magnesium oxide having a specific surface area measured by the BET method of 30 to 130 m ² / g,
It is a rubber composition whose content of the said magnesium oxide is 1-20 mass parts with respect to 100 mass parts of said rubber components.
Next, the rubber component and magnesium oxide used in the rubber composition of the present invention will be described in detail.

<Rubber component>
The rubber component is a rubber component containing 50 to 100% by mass of EPDM.
Here, EPDM is not particularly limited as long as it is a synthetic rubber obtained by copolymerizing ethylene, propylene and a diene monomer.
Specific examples of such EPDM include, for example, synthetic rubbers obtained using ethylidene norbornene, dicyclopentadiene, and the like as the diene monomer.

In the present invention, the rubber component contains 50 to 100% by mass, preferably 70 to 100% by mass, more preferably 100% by mass of EPDM. In addition, 100 mass% containing means that a rubber component consists only of EPDM.
When the content of EPDM is within this range, the adhesion of the resulting rubber composition to the fiber material can be maintained well.

In the present invention, if the rubber component contains 50% by mass or more of EPDM, other rubber can be used in combination according to desired required characteristics.
Specific examples of other rubber include natural rubber (NR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), polyisoprene rubber (IR), butyl rubber (IIR), and chlorobutyl rubber. (Cl-IIR), bromobutyl rubber (Br-IIR), acrylonitrile butadiene rubber (NBR), chloroprene rubber, ethylene-propylene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, Isoprene-butadiene copolymer rubber, chlorosulfonated polyethylene and the like may be mentioned, and these may be used alone or in combination of two or more.
Of these, acrylonitrile-butadiene rubber (NBR) is preferably used in combination from the viewpoint of imparting oil resistance, and styrene-butadiene rubber (SBR) is preferably used in combination from the viewpoint of imparting wear resistance.

<Magnesium oxide>
The said magnesium oxide is magnesium oxide whose specific surface area measured by BET method is 30-130 m < ² > / g.
When the specific surface area measured by the BET method is within this range, the rubber composition was used for the rubber layer of the hose, particularly the outer rubber layer, while maintaining good adhesion of the resulting rubber composition to the fiber material. In this case, it is possible to obtain a hose excellent in storage stability and extrusion processability when not vulcanized. The reason why such an effect is obtained is not clear, but can be estimated as follows.
That is, since magnesium oxide is an alkali catalyst, if the specific surface area is large, the activity becomes high, and the adhesion reactivity between the rubber component and the fiber material can be enhanced. However, if the activity of magnesium oxide is too high, it becomes difficult to disperse in EPDM, and it tends to cause initial vulcanization, so that the storage stability and extrudability of unvulcanized rubber deteriorate. Therefore, when the specific surface area of magnesium oxide is 30 to 130 m ² / g, the balance between adhesiveness, storage stability, and extrusion processability is most excellent, and it is considered that the above-described effects can be obtained.
Here, the BET method is a method for adsorbing molecules (usually N ₂ gas) whose occupied area is known on the surface of powder particles and obtaining the specific surface area of the sample powder from the amount of adsorption. The specific surface area determined by this method is also called “specific surface area of BET”. In the case of magnesium oxide, the higher the BET specific surface area, the higher the activity.

  In the present invention, the magnesium oxide is surface-treated with a fatty acid (eg, stearic acid, hydroxystearic acid, higher fatty acid, alkali metal salts thereof), resin acid (eg, abietic acid), fatty acid amide, fatty acid ester, etc. What was processed can be used.

In the present invention, as the magnesium oxide, Kyowa Mag series manufactured by Kyowa Chemical Industry Co., Ltd. can be used as a commercial product. Specifically, Kyowa mug 100 (specific surface area 100 m ² / g), Kyowa mug 30 (ratio) Suitable examples include a surface area of 50 m ² / g) and Magsarat 30 (surface treated product, specific surface area of 50 m ² / g).

In this invention, content of the said magnesium oxide is 1-20 mass parts with respect to 100 mass parts of said rubber components, It is preferable that it is 2-10 mass parts, and it is about 5 mass parts more. preferable.
When the content of the magnesium oxide is within this range, the rubber properties such as adhesion to the fiber material of the resulting rubber composition, tensile strength, elongation at break, and hardness can be favorably maintained.

  The rubber composition of the present invention comprises, as necessary, a filler, a reinforcing agent, a process oil, an anti-aging agent, a vulcanizing agent, a vulcanization accelerator, a vulcanization activator, a plasticizer, a tackifier, a lubricant, Various additives such as a dispersant and a processing aid can be blended.

The method for producing the rubber composition of the present invention is not particularly limited, and the rubber component, the magnesium oxide, and various additives that may optionally be contained are an open roll, a kneader, an extruder, a universal agitator, and a batch type. A method of mixing (kneading) with a kneader or the like can be mentioned.
Moreover, since mixing temperature changes with apparatuses to be used, it is not specifically limited, When a batch kneader is used, it is preferable that it is 50-160 degreeC, and it is more preferable that it is 50-120 degreeC.
Similarly, the mixing time is not particularly limited because it varies depending on the apparatus to be used. However, when a batch kneader is used, it is preferably about 1 to 15 minutes.

The fiber rubber composite of the present invention is a composite obtained by bonding the rubber composition of the present invention and a fiber material.
The method for adhering the rubber composition and the fiber material is not particularly limited, and examples thereof include a method of bonding the rubber composition of the present invention on the fiber material and then vulcanizing and adhering.

  Specific examples of the fiber rubber composite obtained by bonding by such a method include a conveyor belt, a fender, a marine hose, a tire, and the like, in addition to the hose described later.

In the present invention, the fiber material includes polyester fiber, polyamide fiber, aramid fiber, vinylon fiber, rayon fiber, PBO (polyparaphenylene benzobisoxazole) fiber, polyketone fiber, polyarylate fiber, polyketone fiber, and the like. Examples include fiber materials. Among these, polyester fibers and polyamide fibers excellent in dimensional stability, heat resistance and fatigue resistance are preferable.
The various fiber materials exemplified above may be subjected to an adhesion treatment with a treatment liquid such as resorcin / formalin / rubber latex (RFL).

  The hose of the present invention is a hose having a rubber layer formed using the rubber composition of the present invention and a reinforcing layer adjacent to the rubber layer.

Here, 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 of each hose layer cut away.
As shown in FIG. 1, the hose 1 has a rubber inner layer 2 as an inner tube, and has a reinforcing layer 3 and a rubber outer layer 4 as an outer tube on the upper layer.

  Next, the rubber layer (rubber inner layer and rubber outer layer) and the reinforcing layer constituting the hose of the present invention will be described in detail.

<Rubber layer>
The rubber layer is a layer adjacent to the reinforcing layer, and the hose of the present invention comprises the above-described rubber inner layer and rubber outer layer.
In the present invention, at least one of the rubber layers is formed using the rubber composition of the present invention, and from the viewpoint of weather resistance of the hose, at least the rubber outer layer is formed of the rubber composition of the present invention. Is preferably formed.
Thus, by forming a rubber layer using the rubber composition of the present invention, even when a fiber material is used as the reinforcing layer, the adhesiveness with the reinforcing layer is maintained well and unvulcanized A hose excellent in storage stability and extrudability can be obtained.

  Moreover, in this invention, it is preferable that the thickness of the said rubber inner layer is 0.2-4.0 mm, and it is more preferable that it is 0.5-2.0 mm. Similarly, the thickness of the rubber outer layer is preferably 0.2 to 4.0 mm, and more preferably 0.5 to 2.0 mm.

<Reinforcing layer>
The reinforcing layer is a layer provided on the outside of the rubber inner layer as desired from the viewpoint of maintaining strength.
In the present invention, the reinforcing layer may be formed in a blade shape or a spiral shape. Moreover, although the material which forms the said reinforcement layer is not specifically limited, The various fiber material mentioned above etc. are illustrated suitably.
Of these, it is preferable to use polyester fibers or polyamide fibers because of their excellent dimensional stability, heat resistance and fatigue resistance.

The method for producing the hose of the present invention having the rubber layer and the reinforcing layer is not particularly limited, and a conventionally known method can be used.
Specifically, after laminating the rubber inner layer, the reinforcing layer, and the rubber outer layer in this order on a mandrel, the layers are pressed vulcanized under conditions of 140 to 190 ° C. and 30 to 180 minutes, Preferred examples include a method of vulcanization adhesion by steam vulcanization, oven vulcanization (hot air vulcanization) or hot water vulcanization.

  Hereinafter, the hose of the present invention will be described in more detail using examples. However, the present invention is not limited to these examples.

(Examples 1-6, Comparative Examples 1-7)
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below to prepare rubber compositions.
Specifically, first, among the components shown in Table 1 below, the components other than the vulcanization accelerator and sulfur are kneaded for 4 minutes with a Banbury mixer (3.4 liters), and released when the temperature reaches 160 ° C. Got a batch.
Next, the obtained master batch was kneaded with a vulcanization accelerator and sulfur with an open roll to obtain a rubber composition.
Each rubber composition obtained was measured for storage stability in an unvulcanized state and physical properties after vulcanization (tensile strength, elongation at break, hardness) by the following methods. The results are shown in Table 1.

<Storage stability>
Storage stability is determined by the minimum Mooney viscosity (Vm) and scorch time t ₅ before storage (blank), and _V m and scorch time t ₅ after storage at 40 ° C. for a certain period (14 days, 21 days, 28 days). Were evaluated by the Mooney scorch test.
Vm uses a Mooney viscometer (L-shaped rotor) according to “Mooney Viscosity Test” described in JIS K6300-1: 2001 for each rubber composition obtained, preheating time 1 minute, test temperature 125 It is the minimum value of the Mooney viscosity in the Mooney viscosity-time curve when the rotor is rotated under the condition of ° C.
Further, the scorch time t ₅ represents a time 5 M higher than Vm, and M represents a Mooney unit.
Furthermore, in Table 1 below, “burn” refers to a phenomenon in which the compounded rubber undergoes initial vulcanization during storage or during processing prior to the vulcanization process, making it impossible to process the product.
As a result of comparison, even when stored at 40 ° C. for 28 days, the rubber composition Vm slightly increased and the scorch time t ₅ slightly decreased was evaluated as “◯ (good)”. A case where the Vm is greatly increased and the scorch time t ₅ is significantly shortened is evaluated as “△ (not good)”, and burned and the Mooney scorch test cannot be measured as “× ( Bad) ”.

<Physical properties (tensile strength, elongation at break, hardness)>
(1) Tensile strength, elongation at break Each rubber composition obtained was vulcanized for 45 minutes under a surface pressure of 3.0 MPa using a press molding machine at 148 ° C. to obtain a vulcanized sheet having a thickness of 2 mm. Produced. From this sheet, a JIS No. 3 dumbbell-shaped test piece was punched out, and a tensile test at a tensile speed of 500 mm / min was conducted in accordance with JIS K6251-2004. Tensile strength (T _B ) [MPa] and elongation at break ( E _B ) [%] was measured at room temperature.

(2) JIS A hardness About each dumbbell-shaped No. 3 type test piece similar to the above, JIS A hardness was measured according to "Type A durometer hardness test" of JIS K6253-1997.

The following were used for each component in Table 1 above.
EPDM1: esprene 505, Mooney viscosity 75ML _{(1 + 4)} (100 ° C), ethylidene norbornene type, manufactured by Sumitomo Chemical Co., Ltd. EPDM2: esprene 505A, Mooney viscosity 45ML _{(1 + 4)} (100 ° C), ethylidene norbornene Type, manufactured by Sumitomo Chemical Co., Ltd. ・ EPDM3: Esprene 305, Mooney viscosity 57ML _{(1 + 4)} (100 ° C), dicyclopentadiene type, manufactured by Sumitomo Chemical Co., Ltd. ・ Carbon black: SRF grade carbon black, manufactured by Asahi Carbon Co., Ltd. ・ Magnesium oxide 1: Kyowa Mag 150 (specific surface area 150 m ² / g), manufactured by Kyowa Chemical Industry Co., Ltd. • Magnesium oxide 2: Kyowa Mag 100 (specific surface area 100 m ² / g), manufactured by Kyowa Chemical Industry Co., Ltd. • Magnesium oxide 3: Kyowa Mag 30 (specific surface area 50 m) ² / g), manufactured by Kyowa Chemical Industry Co., Ltd. ・ Magnesium oxide M4: Magsarat 30 (surface-treated product, specific surface area 50 m ² / g), manufactured by Kyowa Chemical Industry Co., Ltd. Magnesium oxide 5: Kyowa Mag 20 (specific surface area 22 m ² / g), manufactured by Kyowa Chemical Industry Co., Ltd. Sulfur: powder sulfur, Karuizawa Refinery ・ Vulcanization accelerator 1: Dibenzothiazyl disulfide (Sunceller DM, manufactured by Sanshin Chemical Industry Co., Ltd.)
・ Vulcanization accelerator 2: N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) (Sunseller CM, manufactured by Sanshin Chemical Industry Co., Ltd.)

Next, as shown below, a hose-like test piece having a rubber outer layer made of each rubber composition and a reinforcing layer made of polyester fiber A (three strands of 1000 dtex) dip-treated with an RFL treatment solution Produced.
First, the polyester fiber A was wound in a blade shape on a mandrel having an outer diameter of 34 mm to form a reinforcing layer.
Next, an unvulcanized sheet having a thickness of 2.5 mm prepared in Examples 1 to 6 and Comparative Examples 1 to 7 was bonded onto the reinforcing layer to produce a vulcanized test piece.
About each obtained hose-like test piece, the adhesiveness of a rubber outer layer and a reinforcement layer was evaluated by the method shown below. The results are shown in Table 2.

<Adhesiveness>
About each obtained hose-shaped test piece, the adhesive strength (unit = N per 25 mm width) when the rubber outer layer is peeled off at a peeling speed of 50 mm / min and with rubber (%, the ratio of the area where the rubber remains without peeling off) ) Was measured.
As a result, those having an adhesive strength of 50 N / 25 mm or more and having a rubber attachment of 50% or more are evaluated as “Good (good)”, and an adhesive strength of 50 N / 25 mm or more and a rubber attachment of 50% or more. Those satisfying only one of these were evaluated as “Δ (defect)”, and those having an adhesive strength of less than 50 N / 25 mm and less than 50% with rubber were evaluated as “x (bad)”.

  Moreover, the extrusion processability as a hose was evaluated by extruding each rubber composition obtained above by the method shown below and evaluating the external appearance of the extrudate. The results are shown in Table 2.

<Extrudability>
Extrusion processability is determined according to ASTM D2230-96 using a Rheomex (registered trademark) 104 type laboratory mixing extrusion tester (manufactured by HAAKE) using the ASTM A method, that is, a so-called Garvey die. Extrusion molding was carried out at a temperature of 80 ° C., a head temperature of 80 ° C., and a screw rotation speed of 60 rpm, and the appearance of the extract of each rubber composition obtained above was evaluated.
The appearance of the extrudate was evaluated by scoring method B. The scoring method B is a maximum of 10 points and a minimum of 1 point for the “30 ° edge sharpness and continuity” of the extrudate, and a maximum of A and a minimum E for the “smoothness of the surface skin” of the extrudate.
Here, the sharpness and continuity of the 30 ° edge is 8 to 10 points, and the surface skin is A is evaluated as “◯ (good)”, and the sharpness and continuity of the 30 ° edge is 6 to 7 points. Or, the surface skin of B is evaluated as “△ (slightly bad)”, and the 30 ° edge sharpness and continuity is 5 points or less, or the surface skin of C to E is “× ( Bad) ”.

  From the results shown in Table 1 and Table 2, the rubber compositions prepared in Examples 1 to 6 are excellent not only in storage stability when not vulcanized but also in physical properties after vulcanization, and Comparative Examples 3 to 5 It was found that the rubber composition has an adhesive property equivalent to that of the rubber composition and can provide a hose excellent in extrudability.

FIG. 1 is a perspective view showing an example of the hose of the present invention.

Explanation of symbols

1 Hose 2 Rubber inner layer 3 Reinforcement layer 4 Rubber outer layer

Claims (5)

A rubber component containing 50 to 100% by mass of an ethylene-propylene-diene copolymer rubber, and magnesium oxide having a specific surface area measured by the BET method of 30 to 130 m ² / g,
The rubber composition whose content of the said magnesium oxide is 1-20 mass parts with respect to 100 mass parts of said rubber components.   A fiber rubber composite obtained by bonding the rubber composition according to claim 1 and a fiber material.   A hose having a rubber layer formed using the rubber composition according to claim 1 and a reinforcing layer adjacent to the rubber layer.   The hose according to claim 3, wherein the reinforcing layer is formed using a fiber material.   The hose according to claim 4, wherein the fiber material is a polyester fiber or a polyamide fiber.

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