JP5021203B2 - Method for producing rubber composition - Google Patents

Description

  The present invention relates to a method for producing a rubber composition.

  In recent years, there has been a strong demand for reduction in rolling resistance of tires and improvement in braking performance, and in order to satisfy these demands, silica is added to tire rubber compositions.

  In general, silica is difficult to disperse in a rubber composition, and sufficient reinforcement to the rubber composition cannot be obtained. Therefore, a silane coupling agent is used in combination with silica. The reaction of the agent tends not to be sufficiently completed in the rubber kneading step. Therefore, the silane coupling agent that could not be reacted during kneading causes a reaction in the extrusion process of the rubber kneaded product to generate alcohol (ethanol, etc.) and generate bubbles in the extruded rubber kneaded product. There was a problem.

  As a method for solving such a problem, it is disclosed to blend a sodium salt into a rubber composition (see Patent Document 1). However, the sodium salt is not sufficient in suppressing the generation of bubbles in the extruded tread, and further, there is a problem that the sodium salt is not sufficiently dispersed in the rubber composition.

JP 2001-247718 A

  An object of this invention is to provide the manufacturing method of the rubber composition which suppressed generation | occurrence | production of the bubble in a rubber kneaded material and improved workability and abrasion resistance.

  The present invention relates to a method for producing a rubber composition containing potassium salt, water and 20 parts by weight or more of silica with respect to 100 parts by weight of a rubber component, the potassium salt, a part of the silica, and the The present invention relates to a method for producing a rubber composition, comprising a step of mixing water to produce a master batch, and a step of kneading the master batch together with a rubber component.

  The potassium salt is preferably at least one selected from the group consisting of potassium carbonate, potassium hydrogen carbonate and potassium borate.

  A master batch prepared by mixing a potassium salt, a part of silica, and water in advance was kneaded with the rubber component to sufficiently disperse the potassium salt and further improve workability and wear resistance. A rubber composition can be produced.

  The method for producing a rubber composition of the present invention comprises (1) a step of preparing a master batch by previously mixing a potassium salt, a part of silica, and water, (step 1), and (2) the master batch. It consists of the process (process 2) knead | mixed with a rubber component.

  The potassium salt mixed in step 1 may be either an inorganic potassium salt or an organic potassium salt.

  Examples of the inorganic potassium salt include potassium carbonate, potassium hydrogen carbonate, potassium sulfate, potassium hydrogen phosphate, potassium dihydrogen phosphate, and potassium oxalate.

  Examples of the organic potassium salt include potassium acetate, potassium gluconate, potassium citrate, potassium fumarate, potassium laurate, potassium palmitate, potassium stearate, potassium oleate, and potassium linoleate.

  Among these, as the potassium salt, an inorganic potassium salt is preferable because the reaction efficiency of the silane coupling agent is further improved, and potassium selected from the group consisting of potassium carbonate, potassium hydrogen carbonate, and potassium borate is particularly preferable. More preferably, it is a salt. The inorganic potassium salt and the organic potassium salt may be an anhydrous potassium salt or a hydrated potassium salt.

  The content of the potassium salt in the master batch is preferably 1% by weight or more, and more preferably 5% by weight or more. When the content of the potassium salt in the master batch is less than 1% by weight, the effect of suppressing the generation of bubbles is small when the rubber compound is formed, and the degree of adhesion to the roll is large, which is not preferable. Moreover, it is preferable that the content rate of the potassium salt in a masterbatch is 50 weight% or less, and it is more preferable that it is 40 weight% or less. When the content of potassium salt in the masterbatch exceeds 50 weight, poor dispersion of potassium borate tends to occur, and there is a tendency that performance such as wear is not sufficiently obtained.

  Examples of the silica mixed in step 1 include silica produced by a wet method or a dry method, but there is no particular limitation.

  The content of silica in the master batch is preferably 10% by weight or more, and more preferably 20% by weight or more. When the silica content in the master batch is less than 10% by weight, the master batch is not well-organized and tends not to be sufficiently dispersed when mixed into the rubber.

  The water content in the masterbatch is preferably 5% by weight or more, and more preferably 10% by weight or more. When the water content in the master batch is less than 5% by weight, the potassium salt tends not to be sufficiently dispersed. The water content in the master batch is preferably 90% by weight or less, and more preferably 80% by weight or less. When the water content in the masterbatch exceeds 90% by weight, the masterbatch tends to be poorly organized and difficult to handle.

  In step 2, the master batch is kneaded with the rubber component.

  Specifically, as rubber components, natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber (IR), chloroprene rubber (CR), etc. are generally used in the rubber industry. Things. Among these, the rubber component is preferably one or more selected from the group consisting of NR, BR and SBR, and particularly preferably one consisting of NR, BR and SBR.

  The compounding amount of the master batch in Step 2 is preferably 2 parts by weight or more, more preferably 10 parts by weight or more, and further preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. . When the blending amount of the master batch is less than 2 parts by weight, the effect of the potassium salt tends to be difficult to obtain. Moreover, it is preferable that the compounding quantity of the masterbatch in the process 2 is 150 weight part or less with respect to 100 weight part of rubber components, and it is more preferable that it is 120 weight part or less. When the blending amount of the masterbatch exceeds 150 parts by weight, the moisture in the masterbatch is not sufficiently evaporated during kneading, and as a result, the effect of suppressing the generation of bubbles tends to be small.

  In step 2, additives such as silica, carbon black and other reinforcing fillers, silane coupling agents, zinc oxide, stearic acid, softeners, anti-aging agents, waxes, vulcanizing agents, vulcanization accelerators and the like are further added. It is preferable to knead.

  As a silane coupling agent, it can be set as the silane coupling agent conventionally used together with a 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 Sulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, Screw (3 Triethoxysilylpropyl) 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-trimethoxysilylpropylbenzothiazolyl Sulfide systems such as trisulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide; 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl Mercapto series such as triethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane; Vinyl series such as vinyltriethoxysilane, vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyl Amino acids such as trimethoxysilane, 3- (2-aminoethyl) aminopropyltriethoxysilane, and 3- (2-aminoethyl) aminopropyltrimethoxysilane Glycidoxy systems such as γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane; 3- Nitro group such as nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane; 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane And chloro-based. Bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-mercaptopropyltrimethoxysilane and the like are preferably used from the viewpoint of both the effect of adding a coupling agent and cost. These silane coupling agents may be used alone or in combination of two or more.

  The content of the silane coupling agent is 3 to 15 parts by weight with respect to 100 parts by weight of silica. When the content is less than 3 parts by weight, the coupling effect is insufficient and the wet grip performance is not sufficiently obtained, and the wear resistance is lowered. On the other hand, when the content exceeds 15 parts by weight, the obtained rubber composition becomes hard and wet grip performance is deteriorated. In addition, let the compounding quantity of the silica used as the reference | standard of content of a silane coupling agent be the compounding quantity of all the silica in a rubber composition.

  The rubber composition obtained by the production method of the present invention can be used for tires and the like, but can be suitably used for tire treads among tire members.

  The content of silica in the rubber composition is 20 parts by weight or more, preferably 30 parts by weight or more, more preferably 40 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of silica is less than 20 parts by weight, the effect of wet performance, which is a merit of silica addition, becomes small. The content of silica in the rubber composition is preferably 150 parts by weight or less, more preferably 130 parts by weight or less, and 120 parts by weight or less with respect to 100 parts by weight of the rubber component. Is more preferable. When the content of silica exceeds 150 parts by weight, the adhesion to the roll in the process deteriorates, and there is a tendency to cause poor dispersion of silica in rubber. The silica content includes the silica content in the masterbatch.

  The present invention will be described in detail based on examples, but the present invention is not limited thereto.

Various chemicals used in the examples will be described in detail.
SBR: Nipol 9520 manufactured by Nippon Zeon Co., Ltd. (Emulsion SBR, containing 37.5 parts by weight with respect to 100 parts by weight of rubber solid content)
BR: BR150B manufactured by Ube Industries, Ltd.
NR: RSS # 3
Silica: VN3 manufactured by Degussa Japan
Carbon black: N220 manufactured by Mitsubishi Chemical Corporation
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Zinc oxide: Silver candy R made by Toho Zinc Co., Ltd.
Stearic acid: Paulownia aroma oil manufactured by Nippon Oil & Fats Co., Ltd .: Diana Process AH24 manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent: Santoflex 6C manufactured by Flexis
Wax: Ozoace 0355 manufactured by Nippon Seiki Co., Ltd.
Potassium borate master batch (potassium borate MB):
Potassium tetraborate: Yoneyama Chemical Co., Ltd. Silica: Degussa Japan Co., Ltd. VN3

(Production method of potassium borate master batch (potassium borate MB))
Potassium tetraborate MB was prepared by mixing potassium tetraborate, pure water and silica with a stirrer at 40 ° C. for 30 minutes (potassium tetraborate 20 wt%, pure water 50 wt%, and silica 30 weight%).

Examples 1-2 and Comparative Examples 1-3
(Method for producing rubber sheets of Examples 1-2 and Comparative Examples 1-3)
First, various chemicals listed in Table 1 were kneaded at about 150 ° C. for 5 minutes in accordance with the blending amounts in Table 1, in addition to sulfur and a vulcanization accelerator, using 1.7 L Banbury.

  Furthermore, using a biaxial open roll, the compounded amounts of sulfur and vulcanization accelerator listed in Table 1 were added to the obtained kneaded product, kneaded at about 80 ° C. for 5 minutes, and pressed at 170 ° C. for 12 minutes. A rubber sheet (sheet thickness: 2 mm) was produced by vulcanization. The following tests were performed using the produced rubber sheets.

(Air-in test)
A rubber specimen (5 cm square, thickness 16 mm) cut out from the rubber sheet was left in an oven at 130 ° C. for 1 hour. Then, the rubber test piece was taken out from the oven, the state inside the rubber test piece was observed, and the evaluation was performed based on the score as follows.
5 points: No bubbles are observed 4 points: 1 mm or less of fine air can be confirmed 3 points: 1 mm or more of air can be confirmed 2 points: 1 mm or more of air is generated (you can see that it is swollen from the outside)
1 point: Air is connected to form a cavity (can be seen from outside)

(Adhesion test)
Of the two open rolls, the temperature of one machine is set to 70 ± 3 ° C. (Unit 1), and the temperature of the other machine is set to 25 ± 3 ° C. (Unit 2). The rubber sheet was heated in Unit 1 and after confirming that the rubber temperature reached 70 ° C. or higher, it was put in Unit 2 and the degree of adhesion to the roll was observed, and score evaluation was performed as follows.
3 points: Can be easily peeled off from the roll 2 points: Although it is close to the roll, it can be peeled off 1 point: Since continuous operation is not possible due to close contact, the roll must be stopped and the rubber must be peeled off Must

(Visual confirmation of dispersion)
The rubber sheet was cut with a cutter knife, the cross section was observed, and score evaluation was performed as follows.
3 points: no white particles are visible 2 points: white particles are slightly visible (less than 1 / cm ² )
1 point: Many white particles can be confirmed

(Lambourn abrasion test)
Using a Lambourn abrasion tester, the volume loss of each rubber sheet was measured under the conditions of a slip rate of 60% and a test time of 2 minutes. Each volume loss was indexed by the following formula. The higher the index, the better the wear resistance.
(Abrasion index) = (Volume loss amount of Comparative Example 1) / (Volume loss amount of each formulation) × 100

  Each evaluation result is shown in Table 1.

Claims (2)

A method for producing a rubber composition containing potassium salt, water, 20 parts by weight or more of silica, and 3 to 15 parts by weight of a silane coupling agent with respect to 100 parts by weight of silica based on 100 parts by weight of the rubber component. And
A step of preparing a masterbatch by previously mixing the potassium salt, a part of the silica, and the water, and kneading the masterbatch with a rubber component , silica other than silica mixed in the masterbatch, and a silane coupling agent A method for producing a rubber composition comprising a step. The method for producing a rubber composition according to claim 1, wherein the potassium salt is at least one selected from the group consisting of potassium carbonate, potassium hydrogen carbonate and potassium borate.