JP2020023644A - Method for producing rubber composition - Google Patents

Abstract

To provide a method for producing a rubber composition to be a raw material for vulcanized rubber with excellent low heat build-up properties.SOLUTION: A method for producing a rubber composition has a first mixture step of mixing at least a rubber component, carbon black and a compound described in the formula (I) (where Rand Reach denote a hydrogen atom, or a C1-20 alkyl group, alkenyl group or alkynyl group, Rand Rmay be the same or different. Mdenotes a sodium ion, potassium ion or lithium ion) and, after the first mixture step, a second mixture step of mixing further at least wax. As the total amount of the rubber component is 100 pts.mass, the content of the compound described in the formula (I) is 0.1 pts.mass or more and 0.75 pts.mass or less.SELECTED DRAWING: None

Description

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

  In general, carbon black is added to rubber products such as pneumatic tires in order to enhance reinforcing properties, but in order to improve rubber strength and low heat build-up of rubber products, the dispersibility of carbon black in the rubber component is important. Need to be improved. For the purpose of improving the low heat build-up of the finally obtained vulcanized rubber, for example, sodium rubber (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoate is used as a rubber composition. The technique of blending into them has been reported (Patent Documents 1 to 3 below).

JP 2016-210834 A JP 2014-95013 A JP 2014-95014 A

  The present inventors have conducted intensive studies on the techniques described in Patent Documents 1 to 3, and found that there is still room for improvement in order to improve the low heat build-up of the finally obtained vulcanized rubber.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a rubber composition as a raw material of a vulcanized rubber having excellent low heat buildup.

（式（Ｉ）中、Ｒ^１およびＲ^２は、水素原子、ならびに炭素数１〜２０のアルキル基、アルケニル基またはアルキニル基を示し、Ｒ^１およびＲ^２は同一であっても異なっていてもよい。Ｍ^＋はナトリウムイオン、カリウムイオンまたはリチウムイオンを示す。）を混合する第１混合行程と、前記第１混合行程の後、さらに少なくともワックスを混合する第２混合行程とを有し、ゴム成分の全量を１００質量部としたとき、前記式（Ｉ）に記載の化合物の配合量が０．１質量部以上０．７５質量部以下であることを特徴とするゴム組成物の製造方法に関する。 The above object can be achieved by the present invention as described below. That is, the present invention provides at least a rubber component, carbon black and a compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, alkenyl group or alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents a sodium ion, a potassium ion or a lithium ion.), And after the first mixing step, a second mixing step of mixing at least a wax. When the total amount of the components is 100 parts by mass, the compounding amount of the compound represented by the formula (I) is 0.1 to 0.75 parts by mass. .

  The compound represented by the formula (I) can react with radicals generated by molecular chain scission in the polymer constituting the rubber component and various functional groups present on the carbon black surface. Therefore, when the polymer constituting the rubber component reacts with the carbon black via the compound described in the formula (I), the dispersibility of the carbon black in the rubber component is improved. Here, the present inventors examined these reactions in detail, and found that when wax was present, radicals generated by molecular chain cleavage in the polymer constituting the rubber component, and various functional groups present on the carbon black surface It has been found that the reactivity of at least one of the compounds tends to decrease. Therefore, in the present invention, in the first mixing step, at least the rubber component, carbon black and the compound represented by the formula (I) are sufficiently reacted in the absence of wax, and then the wax is mixed (second mixing step). . As a result, in the method for producing a rubber composition according to the present invention, since a rubber composition having excellent dispersibility of carbon black in a rubber component can be produced, the low heat build-up of the finally obtained vulcanized rubber is improved. . In addition, in the present invention, when the total amount of the rubber component is 100 parts by mass, the compounding amount of the compound represented by the formula (I) is suppressed to a low compounding amount (0.1 to 0.75 parts by mass). Therefore, an increase in viscosity at the rubber composition manufacturing stage can be suppressed. Therefore, in the first mixing step, the dispersibility of carbon black in the rubber composition can be further improved while maintaining the processability of the rubber composition.

  In the above production method, it is preferable that stearic acid is further mixed in the second step. The present inventor has studied and found that, when the compound represented by the formula (I) and carbon black were reacted in the state where wax and stearic acid were coexisted, the reaction was caused by molecular chain cleavage in the polymer constituting the rubber component. It has been found that the reactivity of at least one of the radicals and various functional groups present on the carbon black surface tends to be further reduced. Therefore, in the first mixing step, at least the rubber component, carbon black and the compound represented by the formula (I) are sufficiently reacted in the absence of the wax and the stearic acid, and thereafter, the wax and the stearic acid are mixed. The dispersibility of carbon black in the rubber composition can be further improved.

  In the method for producing a rubber composition according to the present invention, a first mixing step of mixing at least the rubber component, carbon black and the compound represented by the formula (I), and at least a wax after the first mixing step are further mixed. And a second mixing step.

As the rubber component, for example, a diene rubber can be suitably used. Examples of the diene rubber include natural rubber (NR), polyisoprene rubber (IR), polystyrene butadiene rubber (SBR), polybutadiene rubber (BR), chloroprene rubber (CR), and nitrile rubber (NBR). If necessary, a modified terminal (for example, modified terminal BR, modified SBR, etc.), or a modified material for imparting desired properties (for example, modified NR) can be suitably used. As for polybutadiene rubber (BR), WO2007 is used in addition to those synthesized using a cobalt (Co) catalyst, a neodymium (Nd) catalyst, a nickel (Ni) catalyst, a titanium (Ti) catalyst, and a lithium (Li) catalyst. Those synthesized using a polymerization catalyst composition containing a metallocene complex described in JP-129670 can also be used.

  As carbon black, for example, conductive carbon black such as acetylene black and Ketjen black can be used, in addition to carbon black used in the ordinary rubber industry, such as SAF, ISAF, HAF, FEF, and GPF. The carbon black may be a granulated carbon black or a non-granulated carbon black granulated in the ordinary rubber industry in consideration of its handling property. Considering the rubber properties of the finally obtained vulcanized rubber, the content of carbon black in the rubber composition is 10 to 100 parts by mass, when the total amount of the rubber component in the rubber composition is 100 parts by mass. And preferably 20 to 70 parts by mass. In the present invention, it is necessary to react the rubber component, carbon black and the compound represented by the formula (I) in the first mixing step, but a part of the carbon black is mixed in the second mixing step. You may.

（式（Ｉ）中、Ｒ^１およびＲ^２は、水素原子、ならびに炭素数１〜２０のアルキル基、アルケニル基またはアルキニル基を示し、Ｒ^１およびＲ^２は同一であっても異なっていてもよい。Ｍ^＋はナトリウムイオン、カリウムイオンまたはリチウムイオンを示す。）で表すことができる。 The compound according to formula (I) has the following structural formula:

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, alkenyl group or alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents a sodium ion, a potassium ion or a lithium ion.)

を使用することが特に好ましい。 In order to increase the affinity for carbon black, a compound represented by the following formula (I ′) wherein R ¹ and R ² in the formula (I) are a hydrogen atom and M ⁺ is a sodium ion:

It is particularly preferred to use

  In order to improve the low heat build-up property of the finally obtained vulcanized rubber, when the total amount of the rubber component in the rubber composition is 100 parts by mass, the compounding amount of the compound represented by the formula (I) is 0.1%. It is preferably from 1 part by mass to 0.75 part by mass, more preferably from 0.1 part by mass to 0.5 part by mass.

  As the wax, microcrystalline wax or paraffin wax usually used in the rubber industry can be used. As a compounding amount of the wax in the rubber composition, for example, 0.1 to 10 parts by mass can be exemplified. The amount of stearic acid is not particularly limited, and may be, for example, 0.1 to 10 parts by mass.

  In the method for producing a rubber composition according to the present invention, at least a rubber component, carbon black and a compound represented by the formula (I) are mixed in a first mixing step, and after the first mixing step, at least a wax, if necessary, To mix stearic acid in a second mixing step. Compounding agents other than the vulcanizing compounding agent can be compounded in either the first mixing step or the second mixing step. Compounding agents other than wax and stearic acid include, for example, additional rubber, carbon black, silica, silane coupling agents, antioxidants, zinc oxide, processing aids, and the like.

  Examples of the anti-aging agent include aromatic amine anti-aging agents, amine-ketone anti-aging agents, monophenol anti-aging agents, bisphenol anti-aging agents, polyphenol anti-aging agents, and dithiocarbamic acid which are usually used for rubber. Antioxidants such as salt antioxidants and thiourea antioxidants may be used alone or in a suitable mixture.

  After the first mixing step and the second mixing step, the vulcanizing compound is mixed and dispersed in a third step. Examples of the vulcanization-based compounding agent include vulcanizing agents such as sulfur and organic peroxides, vulcanization accelerators, vulcanization acceleration aids, and vulcanization retardants.

  The sulfur as the sulfur-based vulcanizing agent may be any ordinary sulfur for rubber, and examples thereof include powdered sulfur, precipitated sulfur, insoluble sulfur, and highly dispersible sulfur.

  Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators, thiuram-based vulcanization accelerators, thiazole-based vulcanization accelerators, thiourea-based vulcanization accelerators, and guanidine-based vulcanization accelerators commonly used for rubber vulcanization. A vulcanization accelerator such as an accelerator and a dithiocarbamate-based vulcanization accelerator may be used alone or in an appropriate mixture.

  Since the rubber composition produced by the production method according to the present invention can be a raw material for a vulcanized rubber having excellent low heat build-up, it is particularly useful as a raw material for a rubber member such as a tread portion and a sidewall portion of a pneumatic tire. is there.

  Hereinafter, embodiments of the present invention will be described in more detail.

(Raw materials used)
a) Natural rubber; RSS # 3
b) Butadiene rubber; "BR150B" (manufactured by Ube Industries)
c) Compound described in formula (I); sodium (2Z) -4-[(4-aminophenyl) amino] -4-oxo-2-butenoate (Sumitomo Chemical Co., Ltd.)
d) Carbon black (N234); "Seast 7HM" (manufactured by Tokai Carbon Co., Ltd.)
e) Zinc oxide; two types of zinc oxide (manufactured by Mitsui Mining & Smelting Co., Ltd.)
f) Stearic acid; "Lunac S-20" (manufactured by Kao Corporation)
g) Wax; "OZOACE0355" (manufactured by Nippon Seiro Co., Ltd.)
h) Antioxidant: "6PPD" (manufactured by Monsanto)
i) Sulfur: "5% oil-containing fine powder sulfur" (Tsurumi Chemical Co., Ltd.)
j) Vulcanization accelerator; "Sanseller NS-G" (manufactured by Sanshin Chemical Co., Ltd.)

Examples 1-4
The mixture was kneaded using an ordinary Banbury mixer, and at least the rubber component, carbon black and the compound represented by the formula (I) were mixed as shown in Table 1 (first mixing step). After the first mixing step, at least wax was further added and mixed (second mixing step). After the second mixing step, sulfur and a vulcanization accelerator were added and mixed as a vulcanizing compound (third mixing step) to prepare a rubber composition.

Comparative Examples 1 to 8
The rubber composition was prepared in the same manner as in Example except that the compound described in Formula (I) was not blended, or in the first mixing step, the compound described in Formula (I) and the wax were simultaneously mixed. It was adjusted.

  By vulcanizing the obtained rubber composition, a vulcanized rubber sample having a predetermined shape was produced. The low heat build-up of the vulcanized rubber was evaluated under the following conditions.

Low exothermicity of vulcanized rubber (tan δ)
According to JIS K-6394, the low heat build-up of the produced vulcanized rubber was evaluated by a loss coefficient tan δ. Specifically, tan δ was measured at a frequency of 10 Hz, a static strain of 10%, a strain of 1%, and a temperature of 60 ° C. using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd. The evaluation was performed with respect to Examples 1 and 2 and Comparative Examples 2 to 4 by index evaluation with tan δ of the vulcanized rubber obtained in Comparative Example 1 as 100. Index evaluation was performed with tan δ of the vulcanized rubber obtained in Comparative Example 5 as 100. A lower value means that the vulcanized rubber has more excellent low heat build-up.

  From the comparison between Comparative Example 2 and Example 1, and Comparative Example 6 and Example 3, Examples 1 and 6 in which the compound represented by the formula (I) and the wax are mixed in different processes, It can be seen that the vulcanized rubber is superior in low heat build-up as compared with Comparative Examples 2 and 6 in which the compound described in the formula (I) and the wax are simultaneously mixed. From the comparison between Example 1 and Example 2 and Example 3 and Example 4, not only the wax but also the stearic acid was separately mixed with the compound described in the formula (I) to further vulcanize. It can be seen that the low heat build-up of the rubber is improved.

Claims (2)

At least a rubber component, carbon black and a compound represented by the following formula (I):

(In the formula (I), R ¹ and R ² represent a hydrogen atom and an alkyl group, alkenyl group or alkynyl group having 1 to 20 carbon atoms, and R ¹ and R ² may be the same or different. M ⁺ represents a sodium ion, a potassium ion or a lithium ion.), And after the first mixing step, a second mixing step of mixing at least wax.
When the total amount of the rubber component is 100 parts by mass, the compounding amount of the compound represented by the formula (I) is 0.1 to 0.75 parts by mass. . The method for producing a rubber composition according to claim 1, wherein stearic acid is further mixed in the second step.