JP2009029840A - Rubber composition for organic case topping and tire having case using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for organic case topping, having improved processability and high mileage properties without damaging the durability of a tire. <P>SOLUTION: The rubber composition for the organic case topping contains a deproteinized natural rubber having ≤0.3 wt.% total nitrogen content as an index of proteins. The tire has a case using the rubber composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition for organic case topping and a tire having a case using the same.

  In general, since a large load is applied to an automobile tire, a steel cord is used as a reinforcing material. In particular, if the tires generate heat during running and the rubber and steel cord peel off, a fatal tire failure may occur.

  By the way, in order to reduce the rolling resistance of the tire, a technique using a low exothermic compound for the rubber for case topping has been used. In order to further reduce the heat generation of the rubber for a fuel-efficient steel case, it is conceivable to reduce the carbon black content or increase the carbon black particle size. However, when the amount of carbon black is reduced or carbon black having a large particle size is used, the strength of the rubber composition is lowered. This decrease in strength is undesirable because it causes a decrease in tire durability and a decrease in rigidity.

  In general, in rubber compositions used for rubber for case topping, natural rubber is used as the rubber component, and in this, there are about 5 to 10% by weight of non-rubber components such as proteins and lipids. Yes. These non-rubber components, especially proteins, are said to cause entanglement of molecular chains, causing gelation, which has the disadvantage of increasing the viscosity of rubber and degrading processability. . In general, in order to improve the processability of natural rubber, a method of kneading with a kneading roll machine or a closed mixer and lowering the molecular weight is used. Since it cuts at random, it causes deterioration of fuel consumption characteristics.

  Therefore, a method for removing a protein, which is one of the factors of gelation, is known, and it has been proposed to use the obtained deproteinized natural rubber as a rubber for a tire component (Patent Document). 1).

Japanese Patent No. 3294901

  An object of the present invention is to provide a rubber composition for organic case toppings that has improved processability and fuel efficiency without deteriorating tire durability.

  The present invention relates to a rubber composition for organic case topping containing a deproteinized natural rubber having a total nitrogen content of 0.3% by weight or less as a protein index.

  The total nitrogen content of the deproteinized natural rubber is preferably 0.1% by weight or less.

  The content of the deproteinized natural rubber in the rubber component is preferably 10 to 100% by weight.

  The content of the deproteinized natural rubber in the rubber component is preferably 50 to 100% by weight.

  The present invention also relates to a tire having a case using the rubber composition for organic case topping.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for organic case toppings by which processability and low-fuel-consumption property were improved can be provided, without deteriorating tire durability by including predetermined deproteinized natural rubber.

  The rubber composition for organic case topping of the present invention contains a rubber component containing a predetermined deproteinized natural rubber (hereinafter sometimes referred to as DPNR).

  In the present invention, a DPNR which is contained in natural rubber (NR) in an amount of about 5 to 10% by weight, removes a protein causing gelation, and has a total nitrogen content of 0.3% by weight or less as a protein index. By blending as part of the rubber component, processability, fuel efficiency and durability are improved. As the treatment for deproteinizing NR, conventionally known methods described in JP-A-6-329838, JP-A-2005-47993 and the like can be employed. In addition, as a NR to be deproteinized, a conventionally used grade such as RSS # 3 or TSR20 can be used.

  In the present invention, the total nitrogen content is used as an index of the protein content of the deproteinized natural rubber. The total nitrogen content of the deproteinized natural rubber is 0.3% by weight or less, preferably 0.25% by weight or less, more preferably 0.1% by weight or less, and further preferably 0.05% by weight or less. When the total nitrogen content exceeds 0.3% by weight, gelation is caused, and fuel efficiency and durability are deteriorated. The lower limit of the total nitrogen content of the deproteinized natural rubber is preferably low, and it is desirable not to contain nitrogen if possible. However, the lower limit is usually 0.01% by weight due to limitations such as the production method.

  The weight average molecular weight of DPNR is preferably 1,400,000 or more, and more preferably 1,500,000 or more from the viewpoint of high raw rubber strength and excellent fracture strength even after vulcanization. The upper limit of the weight average molecular weight of DPNR is not particularly limited, but is usually preferably 2 million or less from the viewpoint of excellent processability.

  Further, DPNR is NR with reduced gel content, and the gel content of DPNR measured as toluene insoluble is 10% by weight or less from the viewpoint of suppressing the increase in the viscosity of unvulcanized rubber and being excellent in processability. Is preferred. The gel content of DPNR is preferably low, and it is desirable that the gel content is not contained if possible. However, the lower limit is usually 1% by weight because of limitations such as the production method.

  The DPNR content in the rubber component is 10% by weight or more, preferably 50% by weight or more. If the DPNR content is less than 10% by weight, the effect of improving fuel economy and durability by blending DPNR is reduced, which is not preferable. The upper limit of the DPNR content in the rubber component is not particularly limited and may be 100% by weight, but is preferably 80% by weight or less from the viewpoint of cost reduction.

  In the present invention, when a rubber component other than DPNR is used as the rubber component, examples of the rubber component used in combination with DPNR include NR, isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), Styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR) and the like can be mentioned, and NR is preferred from the viewpoint of excellent low heat build-up.

  As NR, the grade used conventionally, such as RSS # 3 and TSR20, can be used similarly to NR used for DPNR.

  The organic case is obtained by forming a raw material such as polyester, nylon, rayon, or polyethylene terephthalate into a fibrous form. Among them, it is preferable to use polyester or rayon as an organic case among the raw materials because it is excellent in thermal stability and is inexpensive.

  The rubber composition for organic case topping of the present invention preferably further contains a filler.

  Carbon black is well known as a filler, and even if silica is used instead of carbon black, an equivalent effect can be obtained as a rubber composition for organic case topping. In addition to these, calcium carbonate, magnesium oxide, magnesium hydroxide, alumina, aluminum hydroxide, clay, talc and the like are also included. Of these, carbon black is preferred because of its excellent durability.

  The blending amount of the filler is preferably 20 parts by weight or more and more preferably 30 parts by weight or more with respect to 100 parts by weight of the rubber component from the viewpoint of excellent durability. In addition, the blending amount of the filler is preferably 90 parts by weight or less, more preferably 80 parts by weight or less with respect to 100 parts by weight of the rubber component, from the viewpoint of excellent processability and low fuel consumption. In addition, when using carbon black as a filler, the compounding quantity has preferable 20-90 weight part with respect to 100 weight part of rubber components.

  When carbon black is used as the filler, for example, commercially available products such as “N220”, “N330”, “N550” manufactured by Cabot Japan Co., Ltd. can be mentioned.

  In the present invention, when silica is used as the filler, it is preferable to contain a silane coupling agent. The silane coupling agent that can be suitably used in the present invention can be any silane coupling agent conventionally used in combination with silica. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) Tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide Bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3- Riethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide Bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxy Silylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolylte Sulfides such as rasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltrisulfide Mercapto series such as ethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyl series such as vinyltriethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltri Amino series such as methoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ Glycidoxy systems such as glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 3-nitropropyltrimethoxysilane, Nitro-based compounds such as 3-nitropropyltriethoxysilane, chloro-based compounds such as 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane and 2-chloroethyltriethoxysilane It is done. Bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-mercaptopropyltrimethoxysilane and the like are preferably used because of both the effect of adding a silane coupling agent and cost. These silane coupling agents may be used alone or in combination of two or more.

  The rubber composition for organic case topping according to the present invention includes a compounding agent conventionally used in the tire industry, for example, a vulcanizing agent such as a resin, an anti-aging agent, zinc oxide, and sulfur, in addition to the rubber component and the filler. Further, a vulcanization accelerator and the like can be appropriately blended.

  The rubber composition for organic case topping of the present invention is produced by a general method. That is, the rubber composition for organic case topping of the present invention can be produced by kneading the rubber component, if necessary, other compounding agents with a Banbury mixer, kneader, open roll, etc., and then vulcanizing. it can.

  The rubber composition for organic case toppings of the present invention is used as a case among tire members because it is specialized for the purpose of coating organic fibers as a case.

  Here, organic case topping refers to attaching rubber to organic fibers that are cases.

  The tire of the present invention is produced by an ordinary method using the organic case topping rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention blended with the above-mentioned compounding agent is extruded in accordance with the shape of the tire case at an unvulcanized stage, and molded by a usual method on a tire molding machine. Thus, an unvulcanized tire is formed. The unvulcanized tire is heated and pressed in a vulcanizer to produce a tire.

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

Hereinafter, various commercially available chemicals used in Examples and Comparative Examples will be described.
Natural rubber (NR): RSS # 3
Carbon black: N330 manufactured by Cabot Japan
Anti-aging agent: Nonflex RD (2,2,4-trimethyl-1,2-dihumanloquinoline) manufactured by Seiko Chemical Co., Ltd.
Zinc oxide: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. NS: Noxeller NS (N-tert-butyl manufactured by Ouchi Shinsei Chemical Co., Ltd.) -2-Benzothiazolylsulfenamide)

Preparation Example 1: Preparation of Deproteinized Natural Rubber (DPNR) 150 ml of high ammonia type natural rubber latex (solid content 60.2%) manufactured by Soctech (Malaysia) was distilled into 2 L so that the rubber solid content was 10%. Diluted with water, stabilized with 0.12% sodium naphthenate, and adjusted to pH 9.2 by adding sodium dihydrogen phosphate. Subsequently, a deproteinase alcalase (Novo Nordisk Bio Industry Co., Ltd.) was dispersed in 100 ml of distilled water and added to the diluted natural rubber latex. After adjusting the pH of the latex to 9.2 again, it was maintained at 37 ° C. for 24 hours for deproteinization treatment. The anionic surfactant polyoxyethylene lauryl ether sulfate sodium (KP4401 manufactured by Kao Corporation) was added at a rate of 1% by weight to the latex that had been subjected to deproteinization treatment, and centrifuged at 10,000 rpm for 30 minutes. Separation was performed. After centrifugation, the creamy rubber component separated into the upper layer was taken out and further diluted with water to obtain a deproteinized natural rubber latex having a rubber solid content of 60%. The obtained deproteinized natural rubber latex was cast on a glass plate, dried at room temperature, and then dried under reduced pressure to obtain a polymer.

  The obtained polymer and a commercially available high ammonia natural rubber latex (Hytex, manufactured by Nomura Trading Co., Ltd.) were cast on a glass plate, dried at room temperature, and then dried under reduced pressure. After drying, extraction with a mixed solvent of acetone and 2-butanone (3: 1) was performed to remove impurities such as homopolymer. The total nitrogen content as a protein index of the obtained natural rubber latex was 0.25% by weight.

(Total nitrogen content)
The total nitrogen content was measured by the Kjeldahl test method.

  The results of analysis for NR and DPNR are shown in Table 1.

Examples 1 to 3 and Comparative Example 1
Using a 1.7 L Banbury mixer manufactured by Kobe Steel, various materials excluding sulfur and a vulcanization accelerator were kneaded at 150 ° C. for 5 minutes to obtain a kneaded product. Thereafter, sulfur and a vulcanization accelerator were added to the obtained kneaded material on an open roll, and kneaded for 5 minutes at 90 ° C. to obtain an unvulcanized rubber composition. Furthermore, the rubber composition for organic case toppings of Examples 1 to 3 and Comparative Example 1 was obtained by press vulcanizing the obtained unvulcanized rubber composition for 30 minutes at 150 ° C. In the following characteristic evaluation, in Examples 1 to 3 and Comparative Example 1, Comparative Example 1 was used as a reference formulation.

(Mooney viscosity)
According to JIS K 6300 “Testing method for unvulcanized rubber”, a small rotor is rotated at a temperature of 130 ° C. heated by preheating for 1 minute using a Mooney viscosity tester manufactured by Shimadzu Corporation. The Mooney viscosity of the unvulcanized rubber composition after 4 minutes was measured. The Mooney viscosity index of the reference blend was set to 100, and the Mooney viscosity of each blend was displayed as an index according to the following calculation formula. In addition, it shows that it is easy to process and the workability is excellent, so that the value of Mooney viscosity index is large.
(Mooney viscosity index) = (Mooney viscosity of Comparative Example 1)
÷ (Mooney viscosity of each formulation) x 100

(Viscoelasticity test)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho, tan δ and E * at 70 ° C. were measured under conditions of an initial strain of 10%, a dynamic strain of 2%, and a vibration frequency of 10 Hz. Then, the rolling resistance index and the rubber strength index of the reference blend were set to 100, and tan δ and E * of each blend were displayed as indices according to the following calculation formulas. In addition, it shows that it is excellent in low-fuel-consumption property, so that a rolling resistance index is large, and it shows that it is excellent in rubber strength, so that a rubber strength index is large.
(Rolling resistance index) = (tan δ of Comparative Example 1) ÷ (tan δ of each formulation) × 100
(Rubber Strength Index) = (E * of each compound) ÷ (E * of Comparative Example 1) × 100

(Cord pull-out adhesion)
As shown in FIG. 1 and FIG. 2, polyester cord 2 (wire diameter: 0.66 mm) is embedded in 1 cm in unvulcanized sample rubber 1, and vulcanized at 150 ° C. for 30 minutes. The load when pulling out was measured. Then, the pulling adhesive strength index of the cords of the reference blend was set to 100, and the pulling adhesive strengths of the cords of the respective blends were displayed as indexes by the following calculation formulas. In addition, it shows that it is excellent in the adhesiveness of a code | cord | chord and a rubber composition, so that the pulling-out adhesive force index | exponent of a code | cord | chord is large.
(Cull pull-out adhesive strength index) = (Cull pull-out adhesive strength of each formulation) / (Cull pull-out adhesive strength index of Comparative Example 1) × 100

  The evaluation results are shown in Table 2.

It is explanatory drawing of the test piece for the measurement of the pulling-out adhesive force of a code | cord | chord. It is a side view of the test piece for the measurement of the pull-out adhesive force of a cord.

Explanation of symbols

1 Sample rubber 2 Polyester cord

Claims (5)

A rubber composition for organic case topping, comprising a deproteinized natural rubber having a total nitrogen content of 0.3% by weight or less as a protein indicator. 2. The rubber composition for organic case topping according to claim 1, wherein the total nitrogen content of the deproteinized natural rubber is 0.1% by weight or less. The rubber composition for organic case topping according to claim 1 or 2, wherein the content of the deproteinized natural rubber in the rubber component is 10 to 100% by weight. The rubber composition for organic case topping according to any one of claims 1 to 3, wherein the content of the deproteinized natural rubber in the rubber component is 50 to 100% by weight. The tire which has a case using the rubber composition for organic case toppings in any one of Claims 1-4.

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