JP2005178084A - Rubber composition for tire vulcanizing bladder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire vulcanizing bladder having long product life. <P>SOLUTION: In the rubber composition for the tire vulcanizing bladder containing a composite material composed of a rubber, a polyolefin and a nylon, 0.3-10 pts.wt. of the nylon is contained with respect to 100 pts.wt. of the total rubber component in the rubber composition. The nylon preferably has a fibrous or granular shape. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition for bladders, and more particularly to a rubber composition for bladders having a long product life.

  In the tire manufacturing process, the green tire obtained in the molding process is changed to a vulcanized rubber structure having elasticity in the vulcanization process. In the vulcanization step, the green tire is usually heated from the outer surface by a method such as attaching a mold to a jacket type hot platen. Further, from the inner surface of the green tire, a bladder having a bag shape is inserted into the tire, and steam pressure is injected to heat the bladder.

  Since the bladder is repeatedly used under pressure and heating conditions, vulcanized butyl rubber, which is a resin with excellent heat resistance, is generally used. However, if the hardness is too high, cracks will develop due to bending due to use. The number of usable times is reduced and the product life is short. On the other hand, if it is too soft, the permanent elongation due to use will be great, the shape will collapse, and the life will be short. For this reason, the bladder is used after being adjusted to a suitable hardness.

  Therefore, a method of adding a specific substance such as methylolated phenol resin, alkylphenoxypoly (alkyleneoxy) alkanol or lecithin (for example, see Patent Documents 1 to 3), a method using a specific fluorine-based rubber (for example, Patent Document) 4)) and the like have been attempted to improve durability.

  However, when the bladder is used repeatedly for vulcanization molding of tires, there is a problem that hardness increases due to aging such as oil decrease and sulfur migration from the tire, cracks grow and become easy to break. there were.

  Therefore, when a plasticizer-containing porous inorganic filler is blended, the plasticizer is gradually released from the pores of the inorganic filler into the rubber, and the rubber is softened by the released plasticizer and used as a bladder. In addition, there is a method of reducing the increase in hardness due to repeated use (see, for example, Patent Document 5). However, since the inorganic filler itself has poor reinforcing properties, there is a problem that the physical properties are lowered.

Japanese Patent Laid-Open No. 10-130441 JP 2000-84938 A JP 2001-89619 A JP 2002-192528 A JP 2002-179847 A

  An object of this invention is to provide the rubber composition for bladders with a long product life.

  A rubber composition for a bladder, comprising a composite material comprising rubber, polyolefin and nylon, and 0.3 to 10 parts by weight of the nylon with respect to 100 parts by weight of the total rubber component in the rubber composition The present invention relates to a rubber composition for bladder.

  The nylon is preferably fibrous or particulate.

  According to the rubber composition for bladders of the present invention, by including a composite material composed of rubber, polyolefin and nylon, curing by heat is suppressed, and the product life of the bladder can be extended.

  The rubber composition for bladders of the present invention includes a composite material composed of rubber, polyolefin and nylon.

  Examples of the rubber include butyl rubber (IIR), halogenated butyl rubber, chloroprene rubber, and isobutylene-P-methylstyrene copolymer bromide. Of these, IIR is preferred because of its excellent cost performance.

  The lower limit of the rubber content in the composite material is preferably 25% by weight, more preferably 30% by weight, and particularly preferably 40% by weight. If the rubber content is less than 25% by weight, the familiarity between polyolefin and nylon tends to deteriorate. Further, the upper limit of the content is preferably 50% by weight, more preferably 45% by weight, and particularly preferably 40% by weight. If it exceeds 50% by weight, the resulting composite material pellets tend to stick to each other and become difficult to handle.

  Examples of the polyolefin include polymers of alkenes having 2 to 3 carbon atoms such as high density polyethylene (HDPE) and polypropylene. Of these, HDPE is preferred from the viewpoint of processability during production of the composite material.

  The lower limit of the polyolefin content in the composite material is preferably 15% by weight, more preferably 20% by weight, and particularly preferably 21% by weight. If the polyolefin content is less than 15% by weight, the processability during the production of the composite material tends to deteriorate. Further, the upper limit of the content is preferably 35% by weight, more preferably 30% by weight, and particularly preferably 27% by weight. If it exceeds 35% by weight, the heat resistance tends to decrease and the performance improvement effect tends to be small.

  Examples of the nylon include nylon 6 and nylon 66. Of these, nylon 66 is preferred because of its excellent heat resistance.

  The lower limit of the content of the nylon composite material is preferably 25% by weight, more preferably 30% by weight, and particularly preferably 33% by weight. If the nylon content is less than 25% by weight, the performance improvement effect tends to be small. Further, the upper limit of the content is preferably 40% by weight, more preferably 35% by weight, and particularly preferably 33% by weight. If it exceeds 40% by weight, the workability during production of the composite material tends to deteriorate.

  The composite material preferably has a structure in which three components of the rubber, polyolefin and nylon are chemically bonded to each other, and fine nylon fibers or particles are uniformly dispersed in a matrix made of rubber and polyolefin. Nylon fiber is anisotropic and has a high modulus in the extrusion direction. On the other hand, particles are not anisotropic. Both have the effect of suppressing changes in physical properties of the bladder after aging.

  When the nylon is fibrous, the lower limit of the average fiber diameter of the fiber is preferably 0.1 μm, more preferably 0.2 μm. When the average fiber diameter is less than 0.1 μm, when a tire is produced using the obtained rubber composition for a bladder, the fiber tends to be broken due to the expansion and contraction of the rubber. Further, the upper limit of the average fiber diameter is preferably 0.3 μm, more preferably 0.2 μm. When the average fiber diameter exceeds 0.3 μm, the anisotropy tends to decrease.

  Further, the lower limit of the average fiber length is preferably 80 μm, and more preferably 100 μm. When the average fiber length is less than 80 μm, the anisotropy tends to be small. Further, the upper limit of the average fiber length is preferably 200 μm, and more preferably 100 μm. When the average fiber length exceeds 200 μm, when a tire is produced using the obtained rubber composition for a bladder, the fiber tends to break due to the expansion and contraction of the rubber.

  The lower limit of the average aspect ratio of the fibers is preferably 250, more preferably 500. If the average aspect ratio is less than 250, the anisotropy tends to be small. The upper limit of the average aspect ratio is preferably 2000, more preferably 500. When the average aspect ratio exceeds 2000, when a tire is produced using the obtained rubber composition for a bladder, the fibers tend to be broken due to elastic expansion and contraction of the rubber.

  When the nylon is in the form of particles, the lower limit of the average particle diameter of the particles is preferably 0.5 μm, and more preferably 2 μm. If the average particle diameter is less than 0.5 μm, the sea-island structure of nylon and rubber is not formed, and there is a tendency that the improvement effect by blending nylon is small. Further, the upper limit of the average particle diameter is preferably 5 μm, and more preferably 3 μm. When the average particle diameter exceeds 5 μm, the particles become the starting point of destruction, and the physical properties tend to decrease.

  The composite material can be produced, for example, by three steps: (1) a rubber / polyolefin kneading / reaction step, (2) a rubber / polyolefin / nylon reaction step, and (3) a spinning step. Specifically, first, in step (1), rubber, polyolefin and a reactive agent (for example, a vinyl silane coupling agent) are charged into a Banbury mixer to obtain a kneaded / reacted material. At this point, the polyolefin phase forms a sea-island structure with the sea and the rubber phase is an island, and is in a pellet form. Next, in step (2), the kneaded / reacted product and nylon together with the reactant are supplied to a biaxial extruder to obtain a rubber / polyolefin / nylon ternary graft copolymer. By controlling the graft ratio, nylon is dispersed in the rubber / polyolefin matrix as 2 to 3 μm particles. Subsequently, in step (3), extrusion is performed from a nozzle installed at the tip of the twin-screw extruder, and spinning is performed. Here, the nylon particles in the extrudate strand are deformed to form a fiber. In addition, if a reactive resin (for example, glycidyl methacrylate) is filled and spun, nylon can be kept in a particulate form. Through the above steps, a pellet-shaped composite material is obtained.

  Specific examples of the composite material include, for example, “Butyl-based SHP (containing fibrous nylon)” (composition: IIR 40 wt%, polyolefin 27 wt%, nylon 33 wt%, shape: diameter 2 mm, manufactured by Daiwa Polymer Co., Ltd. , A butyl-based SHP (containing particulate nylon) (composition: IIR 31% by weight, polyolefin 21% by weight, nylon 33% by weight, reactive resin 15% by weight, shape: diameter) 2 mm and a pellet-like solid having a length of about 5 mm).

  Usually, since a bladder is repeatedly used for vulcanization molding of a tire, it is exposed to a high temperature of 180 ° C. to 200 ° C. every time it is used, and carbon black existing in IIR binds rubber more and hardens. However, “butyl-based SHP (containing fibrous nylon)” or “butyl-based SHP (containing particulate nylon)”, which is a blend of IIR with a fibrous or particulate thermoplastic resin (nylon, high-density polyethylene, etc.) and a reactive resin. Can be used to bond the interface between IIR and the thermoplastic resin with a reactive resin, and to reinforce the rubber with the thermoplastic resin through the reactive resin. These are relatively hard to cure by heat, and can be suppressed by being partially replaced with carbon black blended with a bladder. Further, by orienting “butyl-based SHP (containing fibrous nylon)” in the stretching direction of the bladder, the elongation (permanent strain) associated with the use of the stretching direction can be suppressed.

  Therefore, a bladder blended with “butyl-based SHP (containing fibrous nylon)” or “butyl-based SHP (containing particulate nylon)” can suppress cracking of the bladder due to curing because the rubber is hardened by use. The bladder blended with “butyl-based SHP (containing fibrous nylon)” can suppress the elongation (permanent strain) associated with the use in the stretching direction, and as a result, the product life of the bladder is prolonged.

  The rubber composition for bladders of the present invention can contain ordinary rubber in addition to the rubber in the composite material. By blending the composite material with rubber, an elastomer having excellent durability can be obtained. The rubber is not particularly limited, and examples thereof include IIR, chloroprene rubber, brominated isobutylene-p-methylstyrene copolymer, and silicone rubber. Of these, IIR is preferred because of its excellent cost performance. These can be used alone or in combination.

  In addition, the rubber composition for bladders of the present invention preferably contains 0.3 parts by weight of a nylon component at the lower limit and more preferably 3 parts by weight with respect to 100 parts by weight of the total rubber components in the rubber composition. Preferably, 5 parts by weight is included. If the nylon component is less than 0.3 parts by weight, the effect of improving the life of the bladder product tends to be small. Further, the upper limit is preferably 10 parts by weight, more preferably 8 parts by weight, and particularly preferably 6 parts by weight. If the nylon component exceeds 10 parts by weight, the elongation tends to decrease, and the effect of improving the life tends to be small.

  The rubber composition for bladders of the present invention comprises polyolefin based on 100 parts by weight of all rubber components in the rubber composition (the total of the rubber components in the composite material and the rubber components in the other rubber composition for bladders). The lower limit is preferably 0.2 parts by weight, and more preferably 0.4 parts by weight. If the polyolefin is less than 0.2 parts by weight, the processability during production of the composite material tends to deteriorate. Further, the upper limit is preferably 8 parts by weight, and more preferably 6 parts by weight. When the amount of polyolefin exceeds 8 parts by weight, the heat resistance tends to decrease and the performance improvement effect tends to be small.

  When a reactive resin is compounded in the composite material of the rubber composition for bladders of the present invention, all the rubber components in the rubber composition (the rubber components in the composite material and the rubber components in the other rubber composition for bladders) The total amount of the reactive resin is preferably 0.1 parts by weight, more preferably 0.2 parts by weight, based on 100 parts by weight. If the reactive resin is less than 0.1 part by weight, the shape of the nylon particles tends to be unstable. Further, the upper limit is preferably 4.5 parts by weight, and more preferably 4 parts by weight. If the reactive resin exceeds 4.5 parts by weight, the processability during the production of the composite material tends to deteriorate.

  In addition, the rubber composition for bladder of the present invention includes zinc oxide, stearic acid, plasticizer (such as aroma oil), inorganic filler (carbon black, white carbon, anhydrous silicic acid, hydrous silicic acid, synthetic silicic acid, Activated calcium carbonate, talc, alumina, etc.), organic reinforcing agents (high impact styrene resin, coumarone indene resin, phenol resin, lignin, modified melamine resin, petroleum resin, etc.), vulcanizing agent, vulcanization accelerator, anti-aging An agent, a heat resistance improver, a flame retardant, a heat conduction imparting agent and the like can be contained.

  As the carbon black, for example, carbon black such as SAF, ISAF, HAF, FEF, GPF, and acetylene black can be used. The content in the case of containing carbon black is not particularly limited, but the total rubber component in the rubber composition (the total of the rubber component in the composite material and the rubber component in the other rubber composition for the bladder) is 100. The lower limit is preferably 20 parts by weight and more preferably 30 parts by weight with respect to parts by weight. When the content of carbon black is less than 20 parts by weight, the wear resistance is greatly lowered and tends to be unsuitable for use with a bladder. Moreover, 80 weight part is preferable at an upper limit, and 60 weight part is more preferable. When the amount exceeds 80 parts by weight, the elongation of the obtained rubber composition tends to be low, and it tends to be unsuitable for the use of a bladder.

  The rubber composition for bladders of the present invention can be produced by a known method. For example, the components are kneaded at a kneading temperature of 110 to 150 ° C. and a kneading time of 5 to 150 using a kneader such as a Banbury mixer. It can be produced by kneading under conditions of minutes.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these.

Examples 1-6 and Comparative Examples 1-3
(Production method)
According to the blending contents shown in Table 1, the mixture was kneaded using a Banbury mixer under conditions of a kneading temperature of 130 ° C. and a kneading time of 10 minutes. Next, extrusion was performed using an extruder to produce a bladder. In Table 1, “Butyl-based SHP (containing fibrous nylon)” means IIR 40 wt%, HDPE 27 wt%, and nylon short fibers (type: nylon 66, average fiber diameter 0.2 μm, average fiber length 100 μm, average aspect) The butyl base SHP (particulate nylon containing) is composed of 31% by weight IIR, 21% by weight HDPE, 15% by weight reactive resin, nylon particles (type: nylon 66, average particle diameter 2 μm). 33% by weight.

(Test method)
(1) Tensile test A sample was punched out from the prepared rubber composition of a new bladder using a No. 3 dumbbell in accordance with JIS-K6251, and a tensile test was performed. Stress at 200% elongation (M200 (when new)) And elongation (when new) was measured. The measured value of elongation (when new) was expressed as an index with the value of Comparative Example 1 as 100. The larger the elongation (when new) index is, the larger the elongation is.

  In order to evaluate the hardness after aging, the sample was exposed for 24 hours in an atmosphere of 180 ° C., and then a tensile test was performed to measure a stress at 200% elongation (M200 (after aging)). The index was displayed with the value of M200 (when new) as 100. The larger the index, the more cured.

(2) Tensile permanent strain measurement A sample was prepared according to JIS K6262, and after applying 50% strain in the extrusion direction under an atmosphere of 180 ° C for 24 hours, tensile permanent strain was measured. The total strain (50%) was taken as 100 and expressed as an index. The larger the index, the greater the tensile set.

(3) Measurement of product life The obtained bladder was repeatedly used for tire molding, and the product life was measured by counting the number of times until puncture. The product life of each bladder was indexed with the value of Comparative Example 1 being 100. The larger the index, the better the product life.

(Test results)
The results are shown in Table 2. In Examples 1-6, it turns out that M200 after aging is close to the value at the time of a new article, and hardening by heat is controlled. In particular, in Examples 4 to 6 containing “butyl-based SHP (containing fibrous nylon)”, the tensile permanent strain is small. As a result, the product life of the bladder is also improved. In Comparative Examples 2 to 3 filled with 40 parts by weight of “butyl-based SHP (containing fibrous nylon)” or “butyl-based SHP (containing particulate nylon)”, the amount of nylon fiber or nylon particle component relative to the IIR component Too much, little elongation, and the product life of the bladder is decreasing.

Claims (2)

A rubber composition for a bladder, comprising a composite material comprising rubber, polyolefin and nylon, and 0.3 to 10 parts by weight of the nylon with respect to 100 parts by weight of the total rubber component in the rubber composition A rubber composition for bladder. The rubber composition for bladders according to claim 1, wherein the nylon is fibrous or particulate.