JP5318378B2 - Manufacturing method of rubber products - Google Patents

Description

  The present invention relates to a silica-containing rubber composition having excellent wet grip properties and wear resistance.

  Silica is used as a reinforcing material in rubber compositions that make up tires due to market demands for low fuel consumption and grip performance of tires. However, the dispersibility of silica is inferior, viscosity increases, and vulcanization speed increases. In order to eliminate the processing problem of slowing down and the performance problem of poor wet grip properties, a silane coupling agent is blended together.

  However, in this case, in order to react the silane coupling agent and silica during processing, it is necessary to strictly control the kneading method, and there is a problem that the productivity is poor.

  Therefore, conventionally, diethylene glycol, fatty acid, carboxylic acid metal salt and the like have been added to a rubber composition containing silica. Further, for example, Patent Document 1 includes addition of dithiopropionic acid, Patent Document 2 adds calcium carbonate, Patent Document 2 adds modified silicone oil, Patent Documents 3 and 4 Describes adding an inorganic filler such as clay and aluminum hydroxide, and Patent Document 5 describes adding sodium thiosulfate.

  However, according to such a conventional method, there are performance problems such as a large change in physical properties due to the use of an auxiliary agent, and it cannot be said that the method is practically sufficient.

  Patent Document 6, Patent Document 7 and Patent Document 8 describe a technique for improving the wear resistance, low heat build-up and wettability of a rubber composition obtained by preheating silica. However, the heat treatment of silica performed in advance is complicated, and when such silica is used, the viscosity is remarkably increased and the processability is poor.

JP-A-9-176381 JP-A-9-150606 WO95-31888 pamphlet JP-A-8-59894 JP-A-9-118784 JP 9-157441 A JP-A-9-156307 JP-A-9-87433

  In view of the facts described above, the object of the present invention is to promote the reaction between silica and a silane coupling agent without adding an auxiliary agent, as a result, with respect to a rubber composition containing silica and a silane coupling agent. An object of the present invention is to provide a method for producing a rubber composition that is low in cost and excellent in wet grip and wear resistance.

（式中、Ｘは温度：４０〜１００℃、Ｙは時間であり、３００未満である。）を満たす条件で加熱処理したのちに加硫させるゴム製品の製造方法に関する。 In the present invention, a rubber composition is obtained by kneading a diene rubber, a filler containing silica and a silane coupling agent, and the rubber composition is represented by the formula (1):

(Wherein, X is a temperature: 40 to 100 ° C., Y is a time , and is less than 300 ). The present invention relates to a method for producing a rubber product that is vulcanized after heat treatment under the conditions.

  In this case, 20 to 100% by weight of the filler is preferably silica.

The silane coupling agent is represented by the formula (2): Z—R—S _n —R—Z or the formula (3): Z—R—SH (wherein R is a divalent hydrocarbon having 1 to 18 carbon atoms). radical, n is an integer of 2 to 8, Z is ^{_{-Si (R1) 2 R 2,}} -SiR 1 (R 2) 2 or -Si (R ²⁾ ₃ (provided that, R ¹ an alkyl group having 1 to 4 carbon atoms , A cyclohexyl group or a phenyl group, and R ² is an alkoxy group having 1 to 8 carbon atoms or a cycloalkoxy group having 5 to 8 carbon atoms).

  According to the production method of the present invention, with respect to a rubber composition containing silica and a silane coupling agent, wet grip properties can be added without adding an auxiliary agent to promote the reaction between silica and the silane coupling agent. A rubber composition having excellent wear resistance can be obtained.

  In the present invention, first, a rubber composition is obtained by kneading a diene rubber, a filler containing silica and a silane coupling agent.

  The diene rubber used in the present invention may be any of those conventionally used in the field of tires, for example, natural rubber (NR), styrene butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber ( BR) and the like, and any combination thereof can be used.

The filler used in the present invention contains silica as an essential component. Any silica may be used as long as it is conventionally used in the tire field, for example. When the nitrogen adsorption specific surface area is less than 50 m ² / g, the reinforcing effect is small, and when it exceeds 300 m ² / g, silica is used. poor dispersibility, terms exotherm increases is preferably nitrogen adsorption specific surface area of 50 to 300 m ² / g, further, from the viewpoint of the reinforcing property, and even a 100 to 250 m ² / g Particularly preferred.

  The ratio of silica in the filler may be in a range that does not impair the effects of the present invention, but is preferably 20 to 100% by weight of the filler from the viewpoint of extracting the characteristics of silica blending.

  Any filler other than silica may be used as long as it is conventionally used in the tire field, and examples thereof include carbon black, clay, calcium carbonate, and aluminum hydroxide.

In particular, when carbon black is used, it is preferable that the nitrogen adsorption specific surface area is 30 to 200 m ² / g and the oil absorption of compressed dibutyl phthalate (24M4DBP) is 30 to 150 ml / 100 g. This is because when the nitrogen adsorption specific surface area and the compressed dibutyl phthalate oil absorption amount are smaller than the lower limit value, the silica dispersibility improvement effect and the reinforcing effect by silica are small, and when the nitrogen adsorption specific surface area is larger than the upper limit value, the dispersion It is because it is inferior to heat and heat build-up increases. Further, from the viewpoint of reinforcing properties, it is particularly preferable that the nitrogen adsorption specific surface area is 50 to 200 m ² / g and the compressed dibutyl phthalate oil absorption is 50 to 150 ml / 100 g.

  The blending amount of the filler in the present invention may be in a range that does not impair the effects of the present invention, but is 30 to 100 parts by weight with respect to 100 parts by weight of the diene rubber from the viewpoint of achieving both a reinforcing effect and heat generation. The amount is preferably 40 to 100 parts by weight from the viewpoint of the reinforcing effect.

Next, as a silane coupling agent used in the present invention, any silane coupling agent conventionally used with silica may be used. However, from the viewpoint of compatibility between reinforcement and workability, the formula (2): ZRS _n- R-Z or Formula (3): Z-R-SH (wherein R is a divalent hydrocarbon group having 1 to 18 carbon atoms, n is an integer of 2 to 8, Z is -Si (R ¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ or —Si (R ² ) ₃ (wherein R ^{1 is} an alkyl group having 1 to 4 carbon atoms, a cyclohexyl group or a phenyl group, R ² is having 1 to 8 carbon atoms) An alkoxy group or a cycloalkoxy group having 5 to 8 carbon atoms).

In the formulas (2) and (3), Z is represented by —Si (R ¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ , or —Si (R ² ) ₃ , where R ¹ is methyl, ethyl, propyl, an alkyl group, a cyclohexyl group or a phenyl group having 1 to 4 carbon atoms such as butyl, R ² is methoxy, ethoxy, 1 to 8 carbon atoms such as butoxy alkoxy group or phenoxy, carbon such benzyloxy It is a cycloalkoxy group of formula 5-8. R is a C1-C18 divalent hydrocarbon group such as ethylene or propylene.

  Examples of the silane coupling agent represented by the formula (2) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyltetrasulfide, bis (2-triethoxysilylpropyl) tetrasulfide, and the like. Can be given.

  Examples of the silane coupling agent represented by the formula (3) include 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane. can give.

  Of these, bis (3-triethoxysilylpropyl) tetrasulfide and 3-mercaptopropyltriethoxysilane are preferably used from the viewpoint of the reinforcing effect and processability of the coupling agent, and bis (3-triethoxysilane). Particular preference is given to using ethoxysilylpropyl) tetrasulfide.

  The blending amount of the silane coupling agent in the present invention may be in a range that does not impair the effects of the present invention, and is preferably 2 to 20% by weight of the blending amount of silica in terms of the coupling effect. The content is particularly preferably 2 to 10% by weight from the viewpoint of coupling effect and cost.

  In the present invention, the rubber composition is first obtained by kneading the above-described diene rubber, a filler containing silica and a silane coupling agent.

  When the temperature for kneading the above components is less than 145 ° C., the silica and the silane coupling agent do not sufficiently react, so that the characteristics of silica blending cannot be fully exhibited, and when the temperature exceeds 165 ° C., it is included in the silane coupling agent. The crosslinking reaction proceeds by virtue of sulfur atoms, causing a gelation phenomenon and not only deteriorating the rubber skin, but also being inferior in rubber physical properties after vulcanization, it is preferably 145 to 165 ° C.

  In this case, the kneading time is preferably 2 to 30 minutes from the viewpoint of reaction and workability, and more preferably 2 to 15 minutes from the viewpoint of reaction, workability and cost. .

  The kneading may be performed by a conventional method using a kneader such as a Banbury mixer, a kneader, or an extruder.

  Next, in the present invention, the rubber composition is heat-treated. The inventors of the present invention can effectively and completely react silica and a silane coupling agent by performing such heat treatment without using the auxiliary agent described in the above prior art, and a rubber obtained by compounding silica. It has been found that the characteristics of the composition, such as wet grip characteristics and fuel efficiency, can be maximized.

  The heat treatment conditions must be such that the vulcanization reaction does not proceed. The treatment temperature of the heat treatment in the present invention is 40 to 100 ° C. If the temperature is lower than 40 ° C, the reaction between the silane and the silane coupling agent is very slow, so that the effect of the heat treatment cannot be sufficiently exhibited. If the temperature exceeds 100 ° C, the vulcanization reaction proceeds and the problem of rubber burning It can occur. Furthermore, it is preferable that it is 50-80 degreeC from the point of the efficiency of heat processing, and rubber | gum burning.

（式中、Ｘは４０〜１００℃）を満たす時間Ｙであるのが好ましいことを実験的に発見した。 Furthermore, the present inventors have said that the processing time is represented by the formula (1) when the temperature of the heat treatment is X ° C. and the time of the heat treatment is Y time in terms of reaction and processing cost:

It has been experimentally discovered that it is preferable that the time Y satisfies (where X is 40 to 100 ° C.).

  According to the formula (1), when the processing temperature is 40 ° C., it is 43 to 300 hours, when it is 50 ° C., it is 24 to 166 hours, when it is 60 ° C., it is 13 to 156 hours, when it is 70 ° C. It is preferably 7 to 86 hours, 4 to 28 hours at 80 ° C, and 2 to 16 hours at 90 ° C.

  Examples of the method for performing the heat treatment include a method in which the heat treatment is continued in the kneader in which the kneading has been performed, a method in which the rubber composition is transferred from the kneader to an oven, and the like.

  Next, in the present invention, the heat-treated rubber composition is vulcanized. The method and conditions for vulcanization may be the same as those conventionally used. The vulcanization temperature is usually 130 to 180 ° C., and the vulcanization time is usually 10 minutes to 1 hour.

  In addition to the above components, the rubber composition of the present invention includes, for example, fillers such as talc, clay and carbon black, softeners such as paraffinic, aromatic and naphthenic process oils, coumarone indene resins, The present invention includes tackifiers such as rosin resins and cyclopentadiene resins, vulcanizing agents such as sulfur and peroxides, vulcanization accelerators, vulcanization aids such as stearic acid and zinc oxide, and antiaging agents. In the range which does not impair the effect, it can mix | blend suitably as needed.

  The rubber composition obtained by such a method can be applied to rubber products that require mechanical properties of various industrial products such as tire treads, sidewalls, cases, hoses, belts, shoes, and balls. Such a rubber product of the present invention can be produced by a conventional method.

  As described above, the rubber product obtained by the method of the present invention has an effect of improving wet skid performance and wear resistance.

  The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

  First, Table 1 summarizes each component used in the examples.

Examples 1-7
According to the blending ratio shown in Table 1, first, a 250 cc BR type Banbury mixer (manufactured by Toyo Seiki Co., Ltd.) was used, and components other than sulfur and vulcanization accelerator were set at a set temperature of 100 ° C., a rotation speed of 75 rpm, and a kneading time Mix for 5 minutes, then transfer the resulting mixture to an open roll and knead with 1.5 parts by weight of sulfur, 1 part by weight of vulcanization accelerator A and 0.5 parts by weight of vulcanization accelerator B I gave

  Next, using a hot air circulation oven, the rubber composition obtained under the conditions shown in Table 2 was heat-treated, and then vulcanized at 150 ° C. for 30 minutes to obtain rubber products 1 to 7.

  The obtained rubber products were evaluated by the following test methods.

[Test method]
(1) Mooney test and tensile test: Mooney viscosity in compliance with JIS K6301, was measured M100, M300, T _B and E _B.

(2) Viscoelasticity test: Using a viscoelasticity spectrometer VES manufactured by Iwamoto Seisakusho Co., Ltd. under conditions of temperatures 70 ° C. and 0 ° C., initial strain 10%, dynamic strain 2% and 0.5%. ^{* Was} measured. The tan δ (0 ° C., 0.5%) is preferably 0.18 or less.

(3) Swelling degree of toluene: The obtained rubber composition was immersed in toluene at 20 ° C. for 48 hours,
Toluene swelling degree (%) = (volume after swelling / volume before swelling) × 100
According to the above, the degree of toluene swelling was measured. The smaller the value of toluene swelling degree, the better.

(4) Abrasion test: Using a Lambourn abrasion tester, the volume loss of the rubber composition was measured under the conditions of a temperature of 23 ° C., a load load of 2 kg, a slip rate of 20%, a falling sand amount of 20 g / min, and a test time of 5 minutes. In the case of Comparative Example 1 described later, the loss amount is set to 100,
Abrasion index = ((loss amount in Comparative Example 1) / (loss amount of each rubber composition)) × 100
The wear resistance was evaluated according to The higher the index, the better the wear resistance.

(5) Wet skid performance: Using a portable skid tester manufactured by Stanley, measured according to the method of ASTM E303-83,
Wet skid index =
((Measured value of each rubber composition) / (Measured value in Comparative Example 1)) × 100
The wet skid performance was evaluated according to The larger the index, the better the wet skid performance.

  The results of the test are summarized in Table 2.

Comparative Examples 1-5
Comparative rubber products 1 to 5 were obtained in the same manner as in Example 1 except that the conditions shown in Table 2 were changed, and evaluated by the same test method as in Example 1. The results are shown in Table 2.

  From Table 2, the influence of time in Comparative Examples 1 to 3 and Examples 1 to 4 was examined. Rolling resistance index of 70 ° C., 2% tan δ, wet performance index of 0 ° C., 0.5% tan δ, wear resistance and wet skid test, heat treatment time does not satisfy equation (1) It turns out that it is inferior to the case (especially when time is short). Moreover, when time is too long, intensity | strength will fall and it will be inferior to the said performance. It can also be seen that the effect is small when the temperature is too low, and the performance decreases when the temperature is too high.

Comparative Examples 6-9
In Comparative Examples 6 and 7, polyethylene glycol was blended in place of the silane coupling agent, and in Comparative Examples 8 and 9, carbon black (N220, nitrogen adsorption specific surface area of 115 m ² / g, DBP oil absorption of 114 ml / in place of silica) A rubber product was obtained in the same manner as in Example 2 except that 100 g) was added, and evaluated by the same test method as in Example 2. In Comparative Examples 6 and 8, no heat treatment was performed. The results are shown in Table 3.

Comparative Example 10
A rubber composition was obtained in the same manner as in Example 2, and subsequently kneaded at 120 ° C. for 10 minutes in a BR type Banbury mixer to obtain a rubber product, which was evaluated by the same test method as in Example 2. The results are shown in Table 3.

  From Table 3, it can be seen that, even when silica is blended, the effect of heat treatment is small when no silane coupling agent is used and when carbon black is blended.

Claims (5)

A rubber composition is obtained by kneading a diene rubber, a filler containing silica and a silane coupling agent, and the rubber composition is represented by the formula (1):

(Wherein, X is temperature: 40 to 100 ° C., Y is time , and is less than 300 ). The method for producing a rubber product according to claim 1, wherein the formula (5):

(Wherein, X is temperature: 40 to 100 ° C., Y is time , and is less than 300 ). The method for producing a rubber product according to claim 1 or 2, wherein Y in formula (1) or formula (5) is 5 to 170. The method for producing a rubber product according to any one of claims 1 to 3, wherein 20 to 100% by weight of the filler is silica. The silane coupling agent is represented by formula (2): Z—R—S _n —R—Z or formula (3): Z—R—SH (wherein R is a divalent hydrocarbon group having 1 to 18 carbon atoms, n is an integer of 2 to 8, Z is —Si (R ¹ ) ₂ R ² , —SiR ¹ (R ² ) ₂ or —Si (R ² ) ₃ (where R ¹ is an alkyl group having 1 to 4 carbon atoms) , A cyclohexyl group or a phenyl group, and R ² is an alkoxy group having 1 to 8 carbon atoms or a cycloalkoxy group having 5 to 8 carbon atoms). Method.