JP2015218279A - Rubber composition for coating of textile cord - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for coating of a textile cord which is improved in crack growth resistance at a higher level while improving adhesiveness to a textile cord.SOLUTION: A rubber composition for coating of a textile cord comprises 0.5-2 pts. wt. of a farnesene polymer, 0.3-3 pts. wt. of a thermosetting resin and 0.5-2 pts. wt. of a hardening agent acting on the thermosetting resin to 100 pts. wt. of a diene rubber.

Description

  The present invention relates to a rubber composition for covering a textile cord, which improves the crack growth resistance to a conventional level or more while improving the adhesion to the textile cord.

  Conventionally, cord reinforcing layers made of steel cords or textile cords are used for pneumatic tires. Among these, examples of the cord reinforcing layer made of textile cord include an organic fiber reinforcing layer that covers an end portion of a carcass layer of a pneumatic tire for passenger cars and a carcass layer of a heavy duty pneumatic tire such as a truck or a bus. These cord reinforcing layers are required to have excellent adhesion between the textile cord and the covering rubber covering it, in addition to high rubber strength and rubber hardness, in order to ensure basic tire performance, particularly tire durability. .

  In order to increase the adhesiveness with the textile cord, it is necessary to enhance the adhesion between the textile cord and the unvulcanized coating rubber composition in the rolling process for producing the cord reinforcing layer. For this reason, modified natural rubber may be used (for example, see Patent Document 1), butadiene rubber or styrene butadiene rubber may be blended with natural rubber, or a phenolic resin may be blended (for example, see Patent Document 2). Has been done.

  However, although these coating rubber compositions have an effect of improving the adhesion to the textile cord, the crack growth resistance is lowered, and as a result, the tire durability is sometimes lowered. Accordingly, there has been a demand for the development of a rubber composition for coating that improves the adhesion to the textile cord, maintains and improves the crack growth resistance, and improves the tire durability to a level higher than the conventional level.

JP 2010-255494 A JP 2010-13544 A

  An object of the present invention is to provide a rubber composition for covering a textile cord in which the crack growth resistance is improved to a conventional level or more while improving the adhesion to the textile cord.

  The rubber composition for covering a textile cord of the present invention that achieves the above-mentioned object is 0.5 to 2 parts by weight of a farnesene polymer and 0.3 to 3 parts by weight of a thermosetting resin with respect to 100 parts by weight of a diene rubber. Further, 0.5 to 2 parts by weight of a curing agent that acts on the thermosetting resin is blended.

  The rubber composition for covering a textile cord according to the present invention is prepared by blending a farnesene polymer, a thermosetting resin and a curing agent with a diene rubber, so that the adhesion to the textile cord is improved and the crack growth resistance is increased. The durability of the tire can be improved by maintaining and improving the performance.

  Further, the total amount of the farnesene polymer and the thermosetting resin is preferably 1 to 4 parts by weight, and the crack growth resistance can be further improved.

  The pneumatic tire using the rubber composition for covering a textile cord of the present invention as at least one selected from a carcass layer and an organic fiber reinforcing layer can improve the tire durability to a level higher than the conventional level.

It is sectional drawing of the tire meridian direction which shows an example of embodiment of the pneumatic tire using the rubber composition for textile cord covering of this invention.

  FIG. 1 is a meridian cross-sectional view illustrating an embodiment of a heavy duty tire such as a truck or a bus.

  In FIG. 1, the heavy duty pneumatic tire has a tread portion 1, a sidewall portion 2 and a bead portion 3, a carcass layer 4 is mounted between the left and right bead portions 3, 3, and both end portions thereof are bead cores 5. Is folded back from the inside of the tire so as to wrap the bead filler 8 around the tire. A belt layer 6 having a four-layer structure is disposed on the outer side in the tire radial direction of the carcass layer 4 in the tread portion 1. An inner liner 7 is disposed on the innermost side of the tire.

  In the heavy duty pneumatic tire, the carcass layer 4 is made of a steel cord. An organic fiber reinforcing layer 9 is disposed at the folded end of the carcass layer 4 outside the bead portion 3. By disposing the organic fiber reinforcing layer 9, it is possible to suppress a failure caused by the end portion of the carcass layer 4 made of a steel cord and improve tire durability. The organic fiber reinforcing layer 9 is composed of a textile cord and a rubber composition for coating the textile cord, and the rubber composition for covering a textile cord of the present invention can be suitably applied.

  As described above, the carcass layer of the heavy duty pneumatic tire is made of a steel cord, but the carcass layer of a passenger car pneumatic tire (not shown) is made of a textile cord and a covering rubber composition. Therefore, the carcass layer of the pneumatic tire for passenger cars is also preferably configured with the rubber composition for covering a textile cord of the present invention.

  In this specification, the textile cord refers to a cord other than a metal cord represented by a steel cord, and examples thereof include an organic fiber cord, a carbon fiber cord, and a polyester fiber cord. Of these, organic fiber cords are preferable. Examples of organic fiber cords include polyester fiber cord, nylon fiber cord, aramid fiber, polyimide fiber, polyacrylate fiber, vinylon fiber, acrylic fiber, polyolefin fiber, polyurethane fiber, rayon fiber cord, and lyocell. A fiber cord etc. can be illustrated.

  In the rubber composition for covering a textile cord of the present invention, the rubber component is a diene rubber. Examples of the diene rubber include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, and nitrile rubber, which can be used alone or as any blend. The diene rubber preferably includes natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber, and particularly natural rubber is a main component.

  The content of the natural rubber is preferably 50 to 100% by weight, more preferably 70 to 100% by weight in 100% by weight of the diene rubber. If the content of natural rubber is less than 50% by weight, adhesion to textile cords and / or crack growth resistance may be reduced.

  The content of diene rubber other than natural rubber such as butadiene rubber and styrene-butadiene rubber is preferably 0 to 50% by weight, preferably 0 to 30% by weight, in 100% by weight of diene rubber. If the content of the other diene rubber exceeds 50% by weight, adhesion to the textile cord and / or crack growth resistance may be deteriorated.

  The rubber composition for covering a textile cord of the present invention can improve adhesion to the textile cord and improve crack growth resistance by blending a farnesene polymer. The farnesene polymer has high affinity with natural rubber, and is liquid and excellent in permeability from room temperature to the processing temperature of the coating rubber composition. Therefore, the textile cord and the coating rubber composition in the rolling process of the cord reinforcing layer are used. It is possible to improve the adhesion. In addition, since the farnesene polymer has a relatively high molecular weight and a crosslinkable structure, the rubber hardness of the coating rubber composition can be increased after vulcanization.

  The farnesene polymer is a polymer of α-farnesene, a polymer of β-farnesene or a copolymer of α-farnesene and β-farnesene, and preferably a polymer of β-farnesene. Further, the polymer of farnesene has a constitutional unit derived from α-farnesene and / or β-farnesene, preferably 90% by weight or more, more preferably 95% by weight or more, more preferably 100% by weight, butadiene, A structural unit derived from another monomer such as isoprene may be included.

  The blending amount of the farnesene polymer is 0.5 to 2 parts by weight, preferably 0.6 to 1.8 parts by weight, more preferably 0.8 to 1.5 parts by weight with respect to 100 parts by weight of the diene rubber. is there. If the blending amount of the farnesene polymer is less than 0.5 parts by weight, the effect of improving the adhesion to the textile cord and the crack growth resistance cannot be sufficiently obtained. On the other hand, when the blending amount of the farnesene polymer exceeds 2 parts by weight, the rubber hardness is lowered.

  The weight average molecular weight of the farnesene polymer is not particularly limited, but is preferably 2000 to 25000, more preferably 2500 to 20000. When the weight average molecular weight of the farnesene polymer is less than 2000, the rubber strength and rubber hardness of the rubber composition are lowered, and further, bleeding out from the rubber composition is facilitated. On the other hand, when the weight average molecular weight of the farnesene polymer exceeds 25,000, the yarn adhesiveness is lowered.

  The molecular weight distribution of the farnesene polymer (Mw / Mn; Mw is the weight average molecular weight, Mn is the number average molecular weight) is preferably 1.0 to 2.0, more preferably 1.0 to 1.5, and even more preferably 1. It is good that it is .0 to 1.3. When the molecular weight distribution of the farnesene polymer is within such a range, variation in viscosity is reduced. In the present specification, the weight average molecular weight Mw and the number average molecular weight Mn of the farnesene polymer are measured by GPC (gel permeation chromatography) and determined by standard polystyrene conversion.

  The melt viscosity of the farnesene polymer is preferably 0.1 to 3.5 Pa · s, more preferably 0.1 to 2 Pa · s, and still more preferably 0.1 to 1.5 Pa · s. When the melt viscosity of the farnesene polymer is within such a range, kneading of the rubber composition becomes easy and processability is improved. In this specification, the melt viscosity of the farnesene polymer is a melt viscosity at 38 ° C. measured by a Brookfield viscometer.

  The farnesene polymer can be synthesized by an ordinary method, and examples thereof include an emulsion polymerization method and a solution polymerization method, and preferably a synthesis by a solution polymerization method.

  The rubber composition for covering a textile cord of the present invention improves the adhesion when rolled into a textile cord by blending a thermosetting resin and its curing agent with a diene rubber, thereby improving the adhesion after vulcanization. Improve. In addition, although there is a concern that the crack growth resistance is reduced by blending the thermosetting resin and the curing agent, the blending amount of the thermosetting resin and the curing agent is blended together with the above-described farnesene polymer. And crack growth resistance can be improved.

  In the present invention, the total amount of the farnesene polymer and the thermosetting resin is preferably 1 to 4 parts by weight, more preferably 1 to 2 parts by weight, based on 100 parts by weight of the diene rubber. If the sum of the farnesene polymer and the thermosetting resin is less than 1 part by weight, the rubber hardness may be insufficient and tire durability may not be sufficiently improved. On the other hand, if the total of the farnesene polymer and the thermosetting resin exceeds 4 parts by weight, the crack growth resistance may be lowered, and the tire durability may be lowered.

  The compounding quantity of a thermosetting resin is 0.3-3 weight part with respect to 100 weight part of diene rubbers, Preferably it is 0.5-2.0 weight part. When the blending amount of the thermosetting resin is less than 0.3 parts by weight, the effect of improving the adhesion with the textile cord cannot be sufficiently obtained. Moreover, when the compounding quantity of a thermosetting resin exceeds 3 weight part, crack growth resistance will fall.

  As a thermosetting resin mix | blended by this invention, what is normally mix | blended with the rubber composition for a coating | cover can be used. For example, a phenol resin, an epoxy resin, a polyester resin, a urethane resin, a urea resin, a melamine resin, etc. can be illustrated. Among these, phenol resin and melamine resin are good in properties and durability as a coating rubber composition. A phenol resin is particularly preferable, and a cresol resin, a resorcin resin, an alkylphenol resin, or a modified phenol resin may be used. Examples of the modified phenol resin include cashew modified phenol resin, oil modified phenol resin, epoxy modified phenol resin, aniline modified phenol resin, melamine modified phenol resin and the like.

  The cresol resin is a compound obtained by reacting cresol and formaldehyde, and a compound using m-cresol is particularly preferable. Examples of the cresol resin include Sumicanol 610 manufactured by Sumitomo Chemical Co., Ltd. and SP7000 manufactured by Nippon Shokubai Co., Ltd. Resorcin resin is a compound obtained by reacting resorcin and formaldehyde. For example, Penacolite B-18-S, B-19-S, B-20-S, B-20-S, etc. manufactured by INDSPEC Chemical Corporation, etc. Can be illustrated. Further, as the resorcin resin, a modified resorcin resin may be used, and examples thereof include a resorcin resin modified with alkylphenol and the like, and a resorcin / alkylphenol / formalin copolymer can be exemplified. The cashew-modified phenol resin is a phenol resin modified with cashew oil, such as Sumitomo Bakelite's Sumilite Resin PR-YR-170, PR-150, Dainippon Ink & Chemicals Phenolite A4-1419, etc. Can be illustrated. The phenol resin is an unmodified resin obtained by a reaction between phenol and formaldehyde, and examples thereof include Sumikanol 620 manufactured by Sumitomo Chemical Co., Ltd.

  In this invention, what is normally mix | blended with the rubber composition for coating | cover can be used as a hardening | curing agent of the resin component mentioned above. Examples of the curing agent include hexamethylenetetramine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, para-formaldehyde polymer, N-methylol derivative of melamine, and the like. These curing agents can be used alone or as any blend.

  Examples of hexamethylenetetramine include Sunseller HT-PO manufactured by Sanshin Chemical Industry Co., Ltd. Examples of hexamethoxymethylmelamine (HMMM) include CYREZ 964RPC manufactured by CYTEC INDUSTRIES. Examples of pentamethoxymethylmelamine (PMMM) include BARA CHEMICAL Co. , LTD. An example is Sumikanol 507A manufactured by the company.

  The compounding amount of these curing agents is 0.5 to 2 parts by weight, preferably 0.7 to 1.5 parts by weight with respect to 100 parts by weight of the diene rubber. If the blending amount of the curing agent is less than 0.5 parts by weight, the effect of increasing the rubber hardness and strength cannot be obtained sufficiently. Moreover, when the compounding quantity of a hardening | curing agent exceeds 2 weight part, crack growth resistance will fall.

  In the rubber composition for covering a textile cord of the present invention, crack growth resistance can be increased by blending carbon black. The compounding amount of carbon black is preferably 20 to 70 parts by weight, more preferably 30 to 60 parts by weight, based on 100 parts by weight of the diene rubber. When the blending amount of the carbon black is less than 20 parts by weight, the rubber composition cannot be sufficiently strengthened and crack growth resistance is lowered. On the other hand, if the blending amount of carbon black exceeds 70 parts by weight, the heat buildup deteriorates and the tire durability decreases.

The carbon black used in the present invention has a nitrogen adsorption specific surface area N ₂ SA of preferably 40 to 100 m ² / g, more preferably 70 to 90 m ² / g. When N ₂ SA is less than 40 m ² / g, mechanical properties such as rubber hardness and dynamic elastic modulus of the rubber composition are lowered, and crack growth resistance is deteriorated. If N ₂ SA exceeds 100 m ² / g, the heat buildup deteriorates and the tire durability deteriorates. N ₂ SA shall be measured according to JIS K6217-2. Such carbon black can be appropriately selected and used from FEF class to HAF class.

  It should be noted that a reinforcing filler other than carbon black can be blended in the textile cord covering rubber composition. Examples of other reinforcing fillers include silica, clay, mica, talc, calcium carbonate, aluminum oxide, titanium oxide, activated zinc white and the like. Of these, silica and clay are preferable.

  Textile cord coating rubber compositions contain various additives commonly used in textile cord coating rubber compositions such as vulcanization or crosslinking agents, vulcanization accelerators, various oils, anti-aging agents, and plasticizers. These additives can be compounded and kneaded by a general method to form a rubber composition, which can be vulcanized or crosslinked. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. The rubber composition for covering a textile cord of the present invention can be produced by mixing the above components using a normal rubber kneading machine such as a Banbury mixer, a kneader, or a roll.

  The rubber composition for covering a textile cord of the present invention can be suitably used for at least one selected from a carcass layer and an organic fiber reinforcing layer in a pneumatic tire. The pneumatic tire using the rubber composition of the present invention for the carcass layer and / or the organic fiber reinforcing layer improves the adhesion of the textile cord and maintains / improves the crack growth resistance so that it has a conventional durability level. This can be improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  In preparing 18 kinds of rubber compositions (Examples 1 to 9, Comparative Examples 1 to 9) having the compounding agents shown in Table 3 as the common compounding and the compositions shown in Tables 1 and 2, sulfur and vulcanization acceleration, respectively. The components excluding the agent were weighed and kneaded for 5 minutes with a 1.8 L closed mixer, and then the master batch was discharged and cooled at room temperature. This master batch was subjected to a 1.8 L closed mixer, and sulfur and a vulcanization accelerator were added and mixed to obtain a rubber composition for textile cord coating.

  The obtained 18 kinds of rubber compositions were press vulcanized at 170 ° C. for 10 minutes in a predetermined mold to prepare vulcanized rubber test pieces made of a rubber composition for covering a textile cord. The resulting vulcanized rubber specimens were evaluated for crack growth resistance and rubber hardness by the following methods. Further, the yarn adhesiveness was evaluated by the following method.

Crack growth resistance Using the obtained vulcanized rubber test piece, in accordance with JIS K6260 dematcher bending crack growth test, the crack growth [unit mm] after stroke 57mm, speed 300 ± 10rpm, bending number 100,000 times It was measured. The obtained results were indexed so that the reciprocal of Comparative Example 1 was 100, and are shown in the column of “Crack growth resistance” in Tables 1 and 2. Larger index means smaller crack growth and better crack resistance.

Rubber Hardness Using the obtained vulcanized rubber test piece, rubber hardness was measured at a temperature of 20 ° C. with a durometer type A in accordance with JIS K6253. The obtained results are shown in the “Rubber Hardness” column of Tables 1 and 2 as an index with the value of Comparative Example 1 as 100. The larger the index, the greater the rubber hardness, which means that the steering stability is excellent when the tire is made.

Yarn Adhesion A plurality of polyester fiber cords were arranged in parallel with each other at 15 mm intervals, embedded in an unvulcanized textile cord coating rubber composition, and vulcanized at 170 ° C. for 15 minutes to prepare test samples. Using the test sample, a peel test was performed in accordance with JIS L1017, and the rubber coverage (with rubber [%]) on the polyester fiber cord was measured visually. The obtained results are shown in the “Thread Adhesion” column of Tables 1 and 2 as an index with the value of Comparative Example 1 being 100. The larger this index, the greater the adhesive strength to the textile cord, and the better the durability when made into a tire.

  18 kinds of pneumatic tires for small trucks (tire size; 201 /) using the obtained 18 kinds of rubber compositions and polyester fiber cords for the carcass layer (or the organic fiber reinforcing layer disposed at the end of the steel carcass) 85/16) was vulcanized. The tire durability of the obtained pneumatic tire for light trucks was evaluated by the following method.

Tire durability The obtained pneumatic tire for small trucks is attached to a standard rim (5 1 / 2J), filled with JATMA prescribed air pressure, and applied to an indoor drum tester (drum diameter 1707 mm) in accordance with JIS D4230. The mileage until tire failure was measured under the condition of 150% of the JATMA prescribed load and speed of 81 km / h. The obtained results are shown in the “Tire durability” column of Tables 1 and 2 as an index with the value of Comparative Example 1 being 100. It means that tire durability is excellent, so that this index | exponent is large.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, RSS # 3
BR: butadiene rubber, Nipol BR1220 manufactured by Nippon Zeon
SBR: styrene butadiene rubber, Nipol 1502 manufactured by Nippon Zeon Co., Ltd., non-oil exhibition carbon black 1: Show Black N330 manufactured by Cabot Japan, HAF grade, nitrogen adsorption specific surface area of 75 m ² / g
Carbon black 2: Shown black N220 manufactured by Cabot Japan, ISAF grade, nitrogen adsorption specific surface area is 111 m ² / g
Thermosetting resin: Resorcin resin, Penacolite Resin B-18-S manufactured by INDSPEC Chemical Corporation
Hardener: Hexamethoxymethylmelamine, CYTEC INDUSTRIES INC
. CYREZ 964RPC
Farnesene polymer: β-farnesene polymer polymerized according to the following synthesis example, weight average molecular weight 140000, molecular weight distribution 1.2, melt viscosity 69 Pa · s

Synthesis example (farnesene polymer polymerization)
In a pressure vessel that was purged with nitrogen and dried, 274 g of hexane and 1.2 g of n-butyllithium (17 wt% hexane solution) were charged, and the temperature was raised to 50 ° C., followed by addition of 272 g of β-farnesene and polymerization for 1 hour. . After adding methanol to the obtained polymerization reaction solution, the polymerization reaction solution was washed with water. The farnesene polymer was obtained by separating water and drying the polymerization reaction solution at 70 ° C. for 12 hours.

In addition, the kind of raw material used in Table 3 is shown below.
Oil: Extract 4 S, Showa Shell Sekiyu
Anti-aging agent 1: SANTOFLEX 6PPD manufactured by FLEXSYS
Anti-aging agent 2: Nocrack 224RD made by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: NOF beads manufactured by NOF Co., Ltd .: Zinc oxide stearate: Zinc Oxide Chemical Co., Ltd.
Sulfur: Fine powder sulfur with Jinhua seal oil manufactured by Tsurumi Chemical Industry Co., Ltd. (sulfur content is 95.24% by weight)

  As is clear from Table 1, it was confirmed that the rubber compositions of Examples 1 to 9 were improved in crack growth resistance, rubber hardness (20 ° C.), yarn adhesion and tire durability over conventional levels. Also, the total amount of the farnesene polymer and the thermosetting resin (described in the column of “total of farnesene and resin” in the table) should be 1 to 4 parts by weight per 100 parts by weight of the diene rubber. Thereby, the balance of crack growth resistance, yarn adhesion, and rubber hardness can be further improved.

  As is clear from Table 1, the rubber composition of Comparative Example 2 improved the yarn adhesion because part of the natural rubber was replaced with butadiene rubber compared to the rubber composition of Comparative Example 1, but the crack growth resistance was improved. The tire durability deteriorated.

  In the rubber composition of Comparative Example 3, the rubber hardness was improved because part of the natural rubber was replaced with styrene butadiene rubber in comparison with the rubber composition of Comparative Example 1, but the crack growth resistance and yarn adhesion were sufficiently improved. Tire durability was deteriorated.

  Since the rubber composition of Comparative Example 4 did not contain a thermosetting resin, a curing agent, and a farnesene polymer, the thread adhesion, rubber hardness, and tire durability were deteriorated.

  In the rubber compositions of Comparative Examples 5 and 6, although the blending amounts of the thermosetting resin and the curing agent were changed with respect to the rubber composition of Comparative Example 1, no farnesene polymer was blended, so crack growth resistance and tire durability Worsened.

  In the rubber composition of Comparative Example 7, since the carbon black was changed from the HAF grade to the ISAF grade with respect to the rubber composition of Comparative Example 1, the rubber hardness and crack growth resistance were improved, but the yarn adhesion was improved. Tire durability deteriorated.

  In the rubber composition of Comparative Example 8, since the blended amount of the farnesene polymer is less than 0.5 parts by weight, improvement in yarn adhesion cannot be confirmed.

  In the rubber composition of Comparative Example 9, since the blending amount of the farnesene polymer exceeds 2 parts by weight, the hardness decreases.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5 Bead core 6 Belt layer 7 Inner liner 8 Bead filler 9 Organic fiber reinforcement layer

Claims (3)

  0.5 to 2 parts by weight of farnesene polymer, 0.3 to 3 parts by weight of thermosetting resin, and 0.5 to 2 of a curing agent that acts on the thermosetting resin with respect to 100 parts by weight of diene rubber. A rubber composition for covering a textile cord, characterized by blending parts by weight.   The rubber composition for covering a textile cord according to claim 1, wherein the total amount of the farnesene polymer and the thermosetting resin is 1 to 4 parts by weight.   A pneumatic tire comprising the rubber composition for covering a textile cord according to claim 1 or 2 as at least one selected from a carcass layer and an organic fiber reinforcing layer.

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