WO2018225686A1

WO2018225686A1 - Hydrated silicic acid for rubber reinforcement filling and method for producing same

Info

Publication number: WO2018225686A1
Application number: PCT/JP2018/021369
Authority: WO
Inventors: 大祐古城; 英伸米井; 勇太今別府
Original assignee: 東ソー・シリカ株式会社
Priority date: 2017-06-09
Filing date: 2018-06-04
Publication date: 2018-12-13
Also published as: KR102278120B1; CN110719892B; KR20200018571A; JP6781106B2; JP2018203596A; CN110719892A

Abstract

The present invention relates to a hydrated silicic acid for rubber reinforcement filling, which has a surface solid acid density within the range of from 1.8 m-mol/m² to 2.4 m-mol/m², while containing a cationic or nonionic surfactant. The present invention also relates to a method for producing the above-described hydrated silicic acid for rubber reinforcement filling, which comprises addition of an aluminate salt and subsequent addition of a cationic or nonionic surfactant in a step during the production process of the hydrated silicic acid. The present invention is able to provide a hydrated silicic acid for rubber reinforcement filling, which enables the achievement of a rubber composition that is more improved than ever before in terms of wear resistance.

Description

Hydrous silicic acid for filling and reinforcing rubber and method for producing the same

The present invention relates to hydrous silicic acid for rubber reinforcement filling. Specifically, it is a hydrous silicic acid for filling a rubber that is effective for improving the reinforcing property of a diene rubber using a silane coupling agent. The hydrous silicic acid of the present invention is useful for reinforcing industrial rubber products such as tire treads and belts that require rubber reinforcement (particularly wear resistance).

Generally, hydrous silicic acid is known as white carbon and has been used as a rubber reinforcing filler for a long time along with carbon black. Hydrous silicic acid is excellent in the heat aging resistance, tear resistance, flex crack resistance, adhesion and the like of the vulcanized rubber. On the other hand, the dispersibility is poor compared to carbon black, the viscosity of the compound is high and the processability is inferior at the time of high filling compounding, and the reinforcing property (especially abrasion resistance) is inferior among the general rubber properties. In order to eliminate these drawbacks, a silane coupling agent and other organic compounds are used in combination. However, hydrous silicic acid that can provide satisfactory rubber properties has not yet been obtained. Therefore, further improvement of hydrous silicic acid is strongly desired along with research on rubber compounding recipes. For example, Patent Documents 1 and 2 disclose hydrous silicic acid that can improve the wear resistance of rubber.

From the viewpoint of controlling the pore structure of hydrous silicic acid and facilitating the penetration of rubber molecules into the pores of hydrous silicic acid, the present inventors have improved chemical bonding between the surface of hydrous silicic acid and rubber molecules. We have intensively studied from the viewpoint of strengthening, and found that hydrous silicic acid having a predetermined pore structure of hydrous silicic acid can provide a rubber composition having unprecedented wear resistance. Applied (Patent Document 3).

Patent Document 1: Japanese Patent Laid-Open No. 2000-302912 Patent Document 2: Japanese Laid-Open Patent Publication No. 11-236208 Patent Document 3: Japanese Patent Laid-Open No. 2017-002210 Patent Document 4: WO 2013/168424

However, in the market related to the rubber composition, for example, the tire market, there is a demand for a rubber composition having improved wear resistance as compared with the related art in relation to environmental problems and energy problems. Therefore, there is a need for a hydrous silicic acid for rubber reinforcement filling that can provide such a rubber composition. For example, it is desired to provide a hydrous silicic acid for rubber reinforcement filling that can provide a rubber composition with improved wear resistance, compared to the hydrous silicic acid for rubber reinforcement filling described in Patent Document 3.

An object of the present invention is to provide a water-containing silicic acid for reinforcing and filling a rubber capable of providing a rubber composition having improved wear resistance as compared with the prior art.

The present inventors pay attention to the reactivity of the silane coupling agent and the hydrous silicic acid, and efficiently perform the bonding between the hydrous silicic acid and the rubber molecule, and further improve the dispersibility, thereby improving the reinforcement. We have studied earnestly from the viewpoint. As a result, the solid acid density on the surface of the hydrous silicic acid is important for the bonding between the hydrous silicic acid surface and the rubber molecules via the silane coupling agent. In addition to adjusting the surface solid acid density within a predetermined range, the wear resistance cannot be remarkably improved, and by adding a predetermined surfactant, the diene rubber combined with the silane coupling agent is used. It has been found that a hydrous silicic acid that can be significantly improved can be provided.

That is, the present inventors have given a predetermined surfactant to hydrous silicic acid having a surface solid acid density within a predetermined range for imparting abrasion resistance to a rubber composition in combination with a hydrous silicic acid silane coupling agent. By containing, by improving the dispersibility of the hydrous silicic acid having excellent reinforcing properties to the rubber with a predetermined surfactant, this hydrous silicic acid can impart to the rubber composition. As a result, the present invention was completed.

The present invention is a hydrous silicic acid characterized in that the surface solid acid density is in the range of 1.8 to 2.4 m-mol / m ² and contains a predetermined surfactant. In addition, by blending with a rubber composition using a silane coupling agent in combination, the present inventors have succeeded in obtaining a rubber composition with significantly improved wear resistance compared to the conventional one.

The hydrous silicic acid for rubber reinforcement filling of the present invention has a surface solid acid density in an effective range for promoting chemical bonding with rubber molecules via a silane coupling agent in order to improve wear resistance. In addition, the greatest feature is that the wear resistance of the rubber composition is remarkably improved by containing a predetermined surfactant.

The present invention is as follows.
[1]
A hydrous silicic acid for rubber reinforcement filling, characterized by having a surface solid acid density in a range of 1.8 to 2.4 m-mol / m ² and containing a cationic or nonionic surfactant.
[2]
The hydrous silicic acid for reinforcing and filling a rubber according to [1], which is used for reinforcing and filling a diene rubber composition in combination with a silane coupling agent.
[3]
The hydrous silicic acid for rubber reinforcement filling according to [1] or [2], wherein the CTAB specific surface area is 130 to 300 m ² / g.
[Four]
The content of the surfactant (parts by mass / 100SiO ₂ parts by weight (solids)) rubber reinforcing filler according to the ratio of the CTAB specific surface area (m ² / g) is in the range of 0.001-0.01 [3] Hydrous silicic acid.
[Five]
In any stage of the process for producing hydrous silicic acid,
The method for producing hydrous silicic acid for rubber reinforcement filling according to any one of [1] to [4], comprising adding an aluminate and then adding a cationic or nonionic surfactant.
[6]
The step of producing the hydrous silicic acid includes any one of a step of adding an acid after completion of the addition of the alkali silicate aqueous solution, a step of washing with filtered water, and a step of drying, and in any of these steps The production method according to [5], wherein aluminate is added, and then a surfactant is added.
[7]
The aluminate is sodium aluminate, the sodium aluminate has a Na ₂ O / Al ₂ O ₃ molar ratio of 1.8 to 20.0, and an Al ₂ O ₃ concentration of 1.0 to 16.0 wt% [5] or [ [6] The production method according to [6].
[8]
The production method according to any one of [5] to [7], wherein the surfactant is added as an aqueous solution in a range of 20 to 90 wt% based on solid content.
[9]
The step of forming hydrous silicic acid in the aqueous solution is performed by adding an alkali silicate aqueous solution and sulfuric acid to an alkali silicate aqueous solution heated to 70 to 90 ° C. having a SiO ₂ concentration of 5 to 50 g / L and a pH of 10 to 12, and 70 to 90%. The neutralization reaction is carried out while controlling the addition amount (ratio) of the alkali silicate aqueous solution and sulfuric acid so that the pH of the reaction solution is in the range of 10 to 11, and the SiO ₂ concentration is 50 to 50 ° C. The production method according to any one of [5] to [8], comprising performing the addition until the amount is in a range of 80 g / L.

The hydrous silicic acid for filling and reinforcing rubber according to the present invention can improve the rubber reinforcement (particularly the wear resistance) when blended with natural rubber and synthetic rubber, for example, diene rubber, and therefore is resistant to wear resistance. It can be usefully used as a reinforcing filler for rubber industrial products such as tires and belts that are highly demanded.

<Hydrosilicate for rubber reinforcement filling>
The hydrous silicic acid for rubber reinforcement filling of the present invention is
(A) The surface solid acid density is in the range of 1.8 to 2.4 m-mol / m ² , and
(B) It contains a surfactant.

The hydrous silicic acid of the present invention is highly reactive with a silane coupling agent, and is added to the rubber composition together with the silane coupling agent to provide a rubber composition having excellent reinforcing properties (particularly abrasion resistance). In view of this, the solid acid amount is not in the predetermined range, but the surface solid acid density is in the predetermined range (1.8 to 2.4 m-mol / m ² ).

Conventionally, in order to improve the dispersibility between hydrous silicic acid and rubber, silane coupling agents have been widely used when blending hydrous silicic acid. In the reaction between hydrous silicic acid and the silane coupling agent, first, the hydrolyzable group of the silane coupling agent undergoes a hydrolysis reaction to produce a silanol group (-SiOH). The silanol group of the silane coupling agent and the hydrous silicic acid Silanol groups present on the surface bind to the hydrous silicic acid surface through a dehydration condensation reaction. It is known that these reactions are generally promoted under acidic or alkaline conditions.

It is known that when a heteroatom such as aluminum is incorporated into hydrous silicic acid, it becomes a solid acid due to the localization of electric charges around the atom. When the solid acid is present on the surface of the hydrous silicic acid, it becomes a surface solid acid and exhibits an acid catalytic effect.

The surface solid acid is expected to exhibit a catalytic action on the surface of the hydrous silicic acid and promote the reaction between the hydrous silicic acid and the silane coupling agent. There have been examples of investigations on the amount of surface solid acid in the past. However, in the present invention, it was considered that it is important that the surface solid acid is distributed at a certain density with respect to the surface of the hydrous silicic acid because the surface solid acid acts as a catalyst. In other words, the catalytic action is expected to promote the binding of hydrous silicic acid and silane coupling agent when a solid acid is present at a constant density on the hydrous silicic acid surface, and to exert a reinforcing effect when rubber is compounded. did.

However, as a result of the study by the present inventors, as shown in Reference Example 1, the presence of a solid acid at a constant density with respect to the surface area of the hydrous silicic acid makes it possible to slightly improve the reinforcement (the water content of Comparative Example 1). Although a comparison with silicic acid) was obtained, it was not possible to obtain a remarkable reinforcing effect when rubber was blended as expected above. On the other hand, in the result of Reference Example 1, the dispersibility is lower than when the hydrous silicic acid of Comparative Example 1 is used, and if this is improved, a higher reinforcing effect can be obtained. The experiment of Reference Example 2 was conducted under the prediction that there was a possibility. That is, a surfactant was used in combination for the purpose of improving the dispersibility of hydrous silicic acid when blended with rubber. However, as shown in Reference Example 2, a sufficient dispersibility improvement effect was not obtained under the conditions of Reference Example 2, and a reinforcement improvement effect was not obtained.

On the other hand, as a result of controlling the surface solid acid density, an attempt was made to add a predetermined surfactant to the hydrous silicic acid having reduced dispersibility before the rubber compounding. As a result, as shown in Examples 1 to 6, it was found that although the dispersibility was not significantly improved (equivalent to Comparative Example 2), the wear resistance could be remarkably improved. In the hydrous silicic acid of the present invention, it is speculated that the predetermined surfactant is adsorbed on the surface of the hydrous silicic acid, thereby preventing aggregation of the hydrous silicic acid and improving dispersibility. The resulting improvement in wear resistance is far more than expected.

The addition of surfactants is widely known as a method for inhibiting and preventing the aggregation of hydrous silicic acid, and the surfactant is added during rubber kneading, or added in advance to hydrous silicic acid. (Patent Document 4). However, until now, in the production of hydrous silicic acid, an aluminum compound that strengthens aggregation and a surfactant that is used for the purpose of improving dispersibility have not been used at the same time. The present inventors use these in a suitable method for the production of hydrous silicic acid, thereby controlling the surface solid acid density within a predetermined range and using a predetermined surfactant to obtain a silane of hydrous silicic acid. It has been found that the reactivity with the coupling agent and the dispersibility with respect to the rubber composition are improved, and a greater effect of improving the rubber reinforcement and wear resistance can be obtained.

In the hydrous silicic acid of the present invention, since the surfactant is adsorbed on the surface in advance, when dispersed in the rubber, the maximum aggregation suppression effect or the dispersion effect can be exhibited with the minimum necessary addition amount. I can do it. As a result, the characteristics of the surfactant (the dispersion effect of the hydrous silicic acid) can be used more efficiently compared to the conventional method of adding a surfactant during rubber compounding.

The surface solid acid density of the hydrous silicic acid in the present invention can be determined from the surface solid acid amount and the CTAB specific surface area as follows.

Surface solid acid measurement:
To about 0.1 g of hydrous silicic acid dried at 105 ° C. for 2 hours, 10 drops of a methyl red indicator benzene solution prepared at 0.5 m-mol / L was added dropwise, and 5 mL of benzene was further added. Titration is performed using a benzene solution of n-butylamine prepared to 50 m-mol / L, and the amount of surface solid acid per gram of hydrous silicic acid is determined from the amount of n-butylamine dropped when the color changes to yellow.

Although the hydrous silicic acid of the present invention has a predetermined surface solid acid density, depending on the CTAB specific surface area, the amount of solid acid is suitably in the range of 300 to 500 m-mol / g, for example. is there.

CTAB specific surface area measurement:
Performed according to JIS K6430 (rubber compounding agent-silica-test method). The CTAB specific surface area is a value (m ² / g) calculated from the amount adsorbed on hydrous silicic acid with the cross-section area of CTAB molecules as 35 ² .

Precipitated silica of the present invention, in order to have a predetermined surface solid acid density, depending on the amount of solid acid, CTAB specific surface area is preferably 130 ~ 300m ² / g, more preferably 0.99 ~ 290 m ² / g, more preferably in the range of 170 to 280 m ² / g.

Generally, it is known that when atoms having different valences and electronegativity are present on the surface of hydrous silicic acid, surface solid acid spots are formed. It is considered that the solid acid present on the surface of the hydrous silicic acid can improve the reinforcement by chemically bonding the rubber molecule and the surface of the hydrous silicic acid via a silane coupling agent.

There are Al, Ti, Mg, and the like as metal ions that create a solid acid point by being incorporated into hydrous silicic acid, but aluminum is preferable in consideration of availability and stability. Moreover, as an aluminum source used for hydrous silicic acid production, it is preferable that it is alkaline, because it erodes the hydrous silicic acid surface and is taken in efficiently, aluminate is preferred, and sodium aluminate is most preferably used. Has been.

In the present invention, when the surface solid acid density is less than 1.8 m-mol / m ^2, the effect of accelerating the reaction with the silane coupling agent is insufficient, so that the effect of improving the wear resistance over the prior art cannot be obtained. On the other hand, if it exceeds 2.4 m-mol / m ² , the reactivity becomes too high and the silane coupling agent may react locally, which is not preferable. The surface solid acid density is preferably in the range of 1.8 m-mol / m ² or more and 2.35 m-mol / m ² or less.

Hereinafter, the types of surfactants to be added will be described, but the surfactants are limited to cationic and / or nonionic surfactants added to the hydrous silicic acid of the present invention. Cationic surfactants and nonionic surfactants can be used alone or in combination.

The cationic surfactant is a surfactant having a positive charge when dissolved in water, such as a quaternary ammonium salt, a tertiary ammonium salt, a secondary ammonium salt, a primary ammonium salt, Examples include pyridinium salts and amine salts. Examples of commercially available cationic surfactants include coatamine (manufactured by Kao Corporation) and cationogen (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). However, it is not the intention limited to this.

The nonionic surfactant is a surfactant having a hydrophilic group that does not ionize when dissolved in water, for example, polyethylene glycol alkyl ether, polyethylene glycol fatty acid ester, alkyl glycoside, fatty acid alkanolamide, glycerin fatty acid ester, alkyl glyceryl. Ether, sorbitan fatty acid ester, polyethylene glycol sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene tridecyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyvinyl pyrrolidone, polyoxyalkylene lauryl ether, polyoxyethylene phenyl ether Etc. Examples of commercially available nonionic surfactants include Emulgen (manufactured by Kao Corporation) and Neugen (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). However, it is not the intention limited to this.

The amount of the surfactant in the hydrous silicic acid of the present invention is not a problem as long as the dispersibility can be ensured without interfering with the reaction with the silane coupling agent by the surface solid acid, and the surface activity with respect to 100 parts by mass of the hydrous silicic acid. The ratio of the amount of the agent based on the solid content (parts by mass / 100 SiO ₂ parts by mass) and the CTAB specific surface area (m ² / g) can be in the range of 0.001 to 0.010, for example, in the range of 0.002 to 0.009. Is preferred.

For example, in the case of hydrous silicic acid having a CTAB specific surface area of 250 m ² / g, the amount of surfactant added (solid basis) is 100% hydrous silicic acid. It can be calculated as 250 × 0.001 to 250 × 0.01 = 0.25 to 2.5 (parts by mass) per part by mass.

As the type of surfactant, it must be a cationic or nonionic surfactant in order to adsorb efficiently on the surface of the hydrous silicate, and an anionic surfactant has not found a sufficient dispersion effect.

In order to uniformly treat the surface of the hydrous silicate, the surfactant is preferably wet-treated by a method described later. In the case of a dry treatment in which a surfactant is directly mixed with a hydrous silicate dry powder, not only does not have an effect of preventing aggregation due to drying, but also a non-uniform treatment tends to occur and a dispersibility improvement effect cannot be sufficiently obtained.

The hydrous silicic acid of the present invention exhibits a particularly excellent effect for reinforcing and filling a diene rubber composition using a silane coupling agent in combination. Examples of the silane coupling agent and the diene rubber composition will be described later.

<Method for producing hydrous silicic acid>
The hydrous silicic acid of the present invention is produced by a method comprising adding an aluminate and then adding a cationic or nonionic surfactant at any stage of the process of producing the hydrous silicic acid. The The aluminate is preferably sodium aluminate from the viewpoint of easy availability.

The step of producing the hydrous silicic acid includes, for example, any one of a step of adding an acid after the addition of the alkali silicate aqueous solution, a step of washing with filtered water, and a step of drying, and any of these steps. In this case, the aluminate, preferably sodium aluminate, can be added, and then the surfactant can be added. The sodium aluminate preferably has a Na ₂ O / Al ₂ O ₃ molar ratio of 1.8 to 20.0 and an Al ₂ O ₃ concentration of 1.0 to 16.0 wt%. The surfactant is preferably added as an aqueous solution in the range of 20 to 90 wt% based on the solid content.

The step of forming hydrous silicic acid in the aqueous solution in the production process includes, for example, an alkali silicate aqueous solution and an alkali silicate aqueous solution heated to 70 to 90 ° C. having a SiO ₂ concentration of 5 to 50 g / L and a pH of 10 to 12. Sulfuric acid is added at a temperature of 70 to 90 ° C, and the neutralization reaction is performed while controlling the addition amount (ratio) of the alkali silicate aqueous solution and sulfuric acid so that the pH of the reaction solution is in the range of 10 to 11. The addition may be performed until the SiO ₂ concentration is in the range of 50 to 80 g / L.

It is known that the wet manufacturing method of hydrous silicic acid of the present invention is generally performed by reacting an aqueous alkali silicate solution with a mineral acid (generally sulfuric acid). The method for producing hydrous silicic acid according to the present invention is also basically based on this method. As a particularly preferred embodiment, the sulfuric acid excess method in which the pH is gradually lowered from the start to the end of the reaction is easy to obtain hydrous silicic acid having excellent dispersibility and a high CTAB surface area, but is not limited to this method. In order to achieve the object of the present invention, a method for adding aluminum and a method for adding a surfactant are also important.
Specific examples of each process are as follows.

(A) An alkali silicate aqueous solution and sulfuric acid are added to an alkali silicate aqueous solution heated to 70 to 90 ° C. having a SiO ₂ concentration of 5 to 50 g / L and pH 10 to 12 at a temperature of 70 to 90 ° C. to react. Perform neutralization reaction while controlling the addition amount (ratio) of alkali silicate aqueous solution and sulfuric acid so that the pH of the solution is in the range of 10 to 11, until the SiO ₂ concentration is in the range of 50 to 80 g / L. Performing the addition to form silicic acid in the aqueous solution.

(A) A step of stopping the addition of the alkali silicate aqueous solution and continuing the addition of sulfuric acid until the pH of the reaction solution becomes 5 or less to obtain a precipitate.

(C) A step of filtering and washing the resulting precipitate to obtain a cake.

(D) If necessary, a step of emulsifying the cake obtained in (C) can be added.

(E) A step of drying and pulverizing the obtained cake or emulsified slurry to obtain a hydrous silicate powder.

Aluminum and surfactant are added during any of steps (i) to (d). When added in the reaction stage (a), the agglomerated structure of the hydrous silicic acid may change and the dispersibility of the hydrous silicic acid may deteriorate. It is preferable.

It should be noted that the addition of the surfactant is more preferably performed at least before the drying of (e), since aggregation during drying can also be prevented.

Aluminates are preferred as the aluminum source, with sodium aluminate being most suitable. Hydrous silicic acid dissolves in a slight amount in weakly alkaline solutions. By adding an alkaline Al ₂ O ₃ solution such as sodium aluminate, only the surface of hydrous silicic acid dissolves and aluminum is easily taken up. Become.

Addition of sodium aluminate prepared to a Na ₂ O / Al ₂ O ₃ molar ratio of 1.8 to 20.0 and an Al ₂ O ₃ concentration of 1.0 to 16.0 wt% is most preferable for the reason described later, and is uniformly applied to the surface of the hydrous silicate. In order to perform the treatment, it is desirable that the addition is performed in a wet manner, and the mixture is stirred for 5 minutes or more and added to the surface of the hydrous silicic acid.

If the Al ₂ O ₃ concentration of sodium aluminate is 1.0 wt% or more, aluminum will be sufficiently taken into the surface of the hydrous silicate, and if it is 16.0 wt% or less, aggregation of the hydrated silicic acid may be caused at the time of addition. Absent. Furthermore, sodium aluminate, depending on the concentration of Al ₂ O ₃ and Na ₂ O / Al ₂ O ₃ molar ratio in an aqueous solution, it and causing hydrolysis, it is known to crystallize, Al ₂ O _{3 If the} Na ₂ O / Al ₂ O ₃ molar ratio is 1.8 or more at a concentration of 1.0 wt% to 16.0 wt%, a stable sodium aluminate aqueous solution can be obtained. The higher the molar ratio, the easier it is to obtain a stable solution, but the higher the molar ratio, the stronger the alkali. If the Na ₂ O / Al ₂ O ₃ molar ratio is 20.0 or less, there is no worry of causing aggregation of hydrous silicic acid. The molar ratio is preferably low as long as stable sodium aluminate can be obtained.

The surfactant is added after the aluminate is added. It is preferable to add a surfactant having a solid content reference concentration adjusted to a range of 20 to 90 wt%. In order to uniformly treat the surface of the hydrous silicic acid, it is desirable that the surfactant is always added to the slurry (wet treatment) and stirred for 5 minutes or more after the addition to uniformly treat the surface of the hydrous silicic acid.

If the solid content standard concentration of the surfactant is 20 wt% or more, the surfactant is satisfactorily adsorbed on the hydrous silicate surface, and if it is 90 wt% or less, it is uniformly treated on the hydrous silicate surface and agglomerates. The inhibitory effect can be sufficiently exerted. Further, when added to the emulsified slurry in the step (d), the concentration can be added without causing a phenomenon such as gelation. After the addition, it is desirable that the surfactant be placed almost evenly on the surface of the hydrous silicic acid and stirred for 5 minutes or more so as to suppress aggregation of the hydrous silicic acid.

In the present invention, the order and method of adding aluminate (for example, soda) and surfactant are important. In the method for producing hydrous silicic acid of the present invention, when the order of addition of the aluminate and the addition of the surfactant is reversed, the surfactant causes the aluminum to be taken into the hydrous silicic acid surface to form a solid acid. Since it is inhibited, a hydrous silicic acid having a desired effect of improving wear resistance cannot be obtained.

The hydrous silicic acid of the present invention can be applied for reinforcing and filling various rubber compositions, but is preferably used for reinforcing and filling diene rubbers. The use of the rubber composition can be widely used in the industrial rubber field where wear resistance is required, such as tires and belts.

The rubber composition in which the hydrous silicic acid of the present invention can be used is not particularly limited, but the rubber is a rubber composition containing natural rubber (NR) or diene synthetic rubber alone or blended with them. Can do. Examples of the synthetic rubber include synthetic polyisoprene rubber (IR), polybutadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), and the like. The hydrous silicic acid of the present invention has a remarkable effect of improving wear resistance, particularly in a rubber composition containing a diene synthetic rubber used in combination with a silane coupling agent. The hydrous silicic acid of the present invention can be blended, for example, 5 to 100 parts by mass with respect to 100 parts by mass of natural rubber and / or diene synthetic rubber. However, it is not intended to limit to this range.

The rubber composition may be one to which a silane coupling agent is added. Examples of the silane coupling agent include those used in rubber compositions, and examples include at least one of the following formulas (I) to (III).

(In the formula, X represents an alkyl group having 1 to 3 carbon atoms or a chlorine atom, n represents an integer of 1 to 3, m represents an integer of 1 to 3, p represents an integer of 1 to 9, and q represents an integer of 1 or more. May have a distribution)

(Wherein X is an alkyl group having 1 to 3 carbon atoms or chlorine atom, Y is a mercapto group, vinyl group, amino group, imide group, glycidoxy group, methacryloxy group or epoxy group, n is an integer of 1 to 3, m Is an integer from 1 to 3, and p is an integer from 1 to 9.)

(Wherein X is an alkyl group having 1 to 3 carbon atoms or chlorine atom, Z is a benzothiazolyl group, N, N-dimethylthiocarbamoyl group or methacrylate group, n is an integer of 1 to 3, and m is an integer of 1 to 3 , P represents an integer of 1 to 9, and q may be an integer of 1 or more and have a distribution.)

Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) polysulfide, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, and γ-aminopropyl. Triethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylcarbamoyl tetrasulfide 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, and the like. The compounding amount of the silane coupling agent is, for example, 1 to 20% by mass, preferably 2 to 15% by mass, with respect to the mass of the hydrous silicic acid. However, it is not intended to limit to this range.

When the hydrous silicic acid of the present invention is used in a rubber composition, in addition to the above rubber and silane coupling agent, carbon black, softening agent (wax, oil), anti-aging agent, vulcanizing agent may be used as necessary. Compounding agents usually used in the rubber industry, such as vulcanization accelerators and vulcanization accelerators, can be appropriately blended. The rubber composition can be prepared by using a kneader such as a Banbury mixer with the rubber component, the hydrous silicic acid of the present invention, a silane coupling agent, the carbon black blended as necessary, the rubber compounding agent, and the like.

The rubber composition containing the hydrous silicic acid of the present invention can be suitably applied to rubber products such as tires and conveyor belts, and rubber products such as tires and conveyor belts are excellent in reinforcing properties, wear resistance, etc. It will be.

Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but of course not limited thereto. In addition, the measurement of each physical-property value of a hydrous silicic acid was implemented by the method shown next.

● Surface solid acid amount / density To approximately 0.1 g of hydrous silicic acid dried at 105 ° C for 2 hours, add 10 drops of methyl red indicator benzene solution prepared at 0.5m-mol / L, and add 5mL of benzene. It was. Titration was performed using a benzene solution of n-butylamine prepared to 50 m-mol / L, and the amount of surface solid acid was calculated from the amount of n-butylamine dropped when the color changed to yellow. Further, the surface solid acid density was calculated by dividing the surface solid acid amount by the CTAB specific surface area.

● CTAB specific surface area JIS K6430 (rubber compounding agent-silica-test method) was used. However, the adsorption cross section of CTAB molecules was calculated as 35 ² .

Formulation Preparation Method According to the formulation shown in Table 1, a rubber test sample was prepared by the following kneading procedure.
(i) Knead 700g of polymer (30 seconds) with a 1.7L Banbury mixer (manufactured by Kobe Steel), add the compound A shown in Table 1, and adjust the ram pressure so that the compound temperature at the time of removal is 140-150 ° C. Adjustment was performed at the number of rotations, and the mixture was taken out after kneading for about 5 minutes.
(ii) After cooling the compound at room temperature, add the compound B shown in Table 1 and knead for about 1 minute, then take it out (the temperature at the time of taking out is 100 ° C. or less), perform sheeting with an 8-inch open roll, and unvulcanize The product and vulcanizate properties were measured.

Unvulcanized properties (Scorch time t5)
Using a Mooney viscometer VR-1132 (manufactured by Ueshima Seisakusho), measured with an L-shaped rotor at 125 ° C.
Vulcanizate properties (tensile strength)
Measurements were performed according to the JIS test method.

● Dispersibility test Measured with Optigrade Dispers Grader. Magnification 100 times E scale It was calculated | required by the dispersibility index | exponent when the X value of the comparative example 1 was set to 100. A higher index indicates better dispersibility.

● Abrasion test Measured with an Akron-type abrasion tester. Tilt angle: 15 °, load; 6 pound test number; wear reduction at 1000 revolutions was measured. The measurement result was obtained as an abrasion resistance index when Comparative Example 1 was set to 100. A higher index indicates better wear resistance.

In the evaluation of the present invention, paying attention to dispersibility and wear resistance, when the dispersibility index is 100 or more and the wear index is 150 or more, it is set as A, the dispersibility index is 100 or more, and the wear index is 180. The above case was designated as S. In addition, those with a dispersibility index of 100 or more and an abrasion resistance index of 100 or more and less than 140 are those where either B, dispersibility index, or wear resistance index is less than 100 because the improvement effect is insufficient. It was set as C because the improvement effect was not seen.

(Example 1)
In a 240 L jacketed stainless steel vessel equipped with a stirrer, 80 L of water and 14 L of sodium silicate aqueous solution (SiO ₂ 150 g / L, SiO ₂ / Na ₂ O mass ratio 3.3) were charged and heated to a temperature of 82 ° C. . At this time, the SiO ₂ concentration was 22 g / L and the pH was 11.5.

To this aqueous solution, the same sodium silicate aqueous solution and sulfuric acid (18.4 mol / L) as above are maintained so that the SiO ₂ concentration becomes 65 g / L and the pH becomes 10.9 in 100 minutes while maintaining the temperature at 82 ° C. ± 1 ° C. Only 100% of sodium silicate was stopped after 100 minutes.

After completion of the predetermined neutralization reaction, the same sulfuric acid was added until the pH reached 3.0 to obtain a precipitate. Thereafter, the obtained reaction product was filtered and washed with water to obtain a cake. The resulting cake was emulsified. For this emulsified slurry, an aqueous solution of sodium aluminate prepared with a Na ₂ O / Al ₂ O ₃ molar ratio of 5.9 and an Al ₂ O ₃ concentration of 5.0 wt% was uniformly treated with Al ₂ O ₃ / It was added over a sufficient period of time so that the SiO ₂ mass ratio was 0.8%. By adding sodium aluminate having a sufficiently thin Al ₂ O ₃ concentration in this manner, the surface of the hydrous silicic acid can be uniformly treated, and the amount of aluminum taken into the hydrous silicic acid surface increases. After stirring for 10 minutes to incorporate aluminum into the surface of the hydrous silicate, cation A (cationic surfactant: polydiallyldimethylammonium chloride) prepared to a solid content concentration of 20 wt% was added to the surfactant / SiO ₂ mass ratio ( (Solid content basis) was added to 1.4% and stirred for 10 minutes. Then, it dried and manufactured hydrous silicic acid, and evaluated.

(Example 2)
In a 240 L jacketed stainless steel vessel equipped with a stirrer, 80 L of water and 3.5 L of sodium silicate aqueous solution (SiO ₂ 150 g / L, SiO ₂ / Na ₂ O mass ratio 3.3) are charged and heated to a temperature of 72 ° C. did. At this time, the SiO ₂ concentration was 6.0 g / L, and the pH was 10.9.

To this aqueous solution, the same sodium silicate aqueous solution and sulfuric acid (18.4 mol / L) as above are maintained so that the SiO ₂ concentration becomes 65 g / L in 100 minutes while maintaining the temperature at 72 ° C. ± 1 ° C. and pH 10.9. In 100 minutes, only the addition of sodium silicate was stopped.

After completion of the predetermined neutralization reaction, the same sulfuric acid was added until the pH reached 3.0 to obtain a precipitate. Thereafter, the obtained reaction product was filtered and washed with water to obtain a cake. The obtained cake was emulsified, and an aqueous sodium aluminate solution prepared at a Na ₂ O / Al ₂ O ₃ molar ratio of 3.0 and an Al ₂ O ₃ concentration of 10.0 wt% was added to this emulsified slurry with an Al ₂ O ₃ / SiO ₂ It was added over a sufficient amount of time so that the mass ratio was 1.5%. After stirring for 5 minutes to incorporate aluminum into the hydrous silicate surface, cation B (cationic surfactant: stearylamine acetate) prepared to a solid content of 40 wt% was added to the surfactant / SiO ₂ mass ratio (based on solid content) ) Was added to 1.5% and stirred for 5 minutes. Then, it dried and manufactured hydrous silicic acid, and evaluated.

Example 3
The reaction was carried out in the same manner as in Example 2, and only the addition of sodium silicate was stopped in 100 minutes. While adding the same sulfuric acid, the sodium aluminate aqueous solution prepared to a Na ₂ O / Al ₂ O ₃ molar ratio of 3.0 and an Al ₂ O ₃ concentration of 10.0 wt% becomes 0.8% by mass ratio of Al ₂ O ₃ / SiO _2. Was added as follows. After stirring for 5 minutes to incorporate aluminum into the surface of the hydrous silicate, cation A prepared to a solid content of 50 wt% was added to a surfactant / SiO ₂ mass ratio (solid content basis) of 0.5%, Stir for 5 minutes or more.

After the addition of the surfactant, the same sulfuric acid addition was continued until the pH reached 3.0 to obtain a precipitate. Thereafter, the obtained reaction product was filtered and washed with water to obtain a cake. The obtained cake was dried to produce hydrous silicic acid and evaluated.

Example 4
In a 240 L jacketed stainless steel container equipped with a stirrer, 85 L of water and 6.0 L of sodium silicate aqueous solution (SiO ₂ 150 g / L, SiO ₂ / Na ₂ O mass ratio 3.3) are charged and heated to a temperature of 90 ° C. did. At this time, the SiO ₂ concentration was 10.0 g / L, and the pH was 11.2.

To this aqueous solution, the same sodium silicate aqueous solution and sulfuric acid (18.4 mol / L) as above are maintained at a temperature of 90 ° C. ± 1 ° C. and pH 10.9 so that the SiO ₂ concentration becomes 60 g / L in 100 minutes. In 100 minutes, only the addition of sodium silicate was stopped.

While adding the same sulfuric acid, the sodium aluminate aqueous solution prepared to a Na ₂ O / Al ₂ O ₃ molar ratio of 19.7 and an Al ₂ O ₃ concentration of 1.0 wt% becomes 0.8% in an Al ₂ O ₃ / SiO ₂ mass ratio. Was added as follows. After stirring for 5 minutes to incorporate aluminum into the hydrous silicate surface, cation A adjusted to a solid content of 80 wt% was added to a surfactant / SiO ₂ mass ratio (solid content basis) of 1.3%, Stir for 5 minutes or more.

(Example 5)
The obtained cake was emulsified, and an aqueous sodium aluminate solution prepared to have a Na ₂ O / Al ₂ O ₃ molar ratio of 2.2 and an Al ₂ O ₃ concentration of 15.0 wt% was added to this emulsified slurry as Al ₂ O ₃ / SiO _2. It was added over a sufficient amount of time so that the mass ratio was 1.5%. After stirring for 5 minutes to incorporate aluminum into the hydrous silicate surface, cation C (cationic surfactant: distearyldimethylammonium chloride) prepared to a solid content of 75 wt% was added to the surfactant / SiO ₂ mass ratio (solid (Based on minute) to be 1.5%, and stirred for 5 minutes. Except for this operation, hydrous silicic acid was produced in the same manner as in Example 3 and evaluated.

Example 6
The obtained cake was emulsified, and an aqueous sodium aluminate solution prepared to have a Na ₂ O / Al ₂ O ₃ molar ratio of 2.2 and an Al ₂ O ₃ concentration of 15.0 wt% was added to this emulsified slurry as Al ₂ O ₃ / SiO _2. It was added over a sufficient amount of time so that the mass ratio was 1.5%. After stirring for 5 minutes to incorporate aluminum into the surface of the hydrous silicate, nonionic (nonionic surfactant: polyoxyethylene oleyl ether) prepared to a solid content of 80 wt% was added to the surfactant / SiO ₂ mass ratio (solid content (Standard) to be 1.5%, and stirred for 5 minutes. Except for this operation, hydrous silicic acid was produced in the same manner as in Example 3 and evaluated.

Comparative Example 1 is N ipsil AQ (manufactured by Tosoh Silica). Nipsil AQ is a hydrous silicic acid that is widely used as a rubber reinforcing filler. As shown in Table 2, the hydrous silicic acids of Examples 1 to 6 were equivalent to or higher in dispersibility than Comparative Example 1, and a remarkable improvement effect in wear resistance was observed.

(Comparative Example 2)
The reaction was carried out in the same manner as in Example 2, and only the addition of sodium silicate was stopped in 100 minutes. While adding the same sulfuric acid, the cation A prepared to a solid content of 40 wt% was added to a surfactant / SiO ₂ mass ratio (solid content basis) of 1.5% and stirred for 5 minutes or more.

(Reference Example 1)
The reaction was carried out in the same manner as in Example 2, and only the addition of sodium silicate was stopped in 100 minutes. While adding the same sulfuric acid, the sodium aluminate aqueous solution adjusted to a Na ₂ O / Al ₂ O ₃ molar ratio of 3.0 and an Al ₂ O ₃ concentration of 10.0 wt% has an Al ₂ O ₃ / SiO ₂ mass ratio of 0.8%. And stirred for more than 5 minutes. Thereafter, the obtained reaction product was filtered and washed with water to obtain a cake. The obtained cake was dried to produce hydrous silicic acid and evaluated.

(Reference example 2)
To Reference Example 1, 1.69 phr (surfactant active ingredient / SiO ₂ mass ratio of 1.5%) of 40% active ingredient was further added during rubber kneading.

As shown in Table 2, Examples 1 to 6 are significantly more effective in improving the wear resistance than Comparative Example 1.
In Reference Example 1 in which the surface solid acid density is within the scope of the present invention, the wear resistance is improved compared to Comparative Example 1, but the dispersibility is lowered. The significant improvement in wear resistance obtained in Examples 1 to 6 cannot be obtained. Further, as shown in Reference Example 2, the same cation A as that used in Examples 1, 3, and 4 has the same surface solid acid density as in Reference Example 1 and is kneaded with rubber. Even when kneaded together, the wear resistance and dispersibility are almost the same as in Reference Example 1. The hydrous silicic acid of Comparative Example 2 is equivalent to Examples 10 and 16 of Patent Document 4, and contains the same cation A as used in Examples 1, 3, and 4. However, the surface solid acid density is outside the scope of the present invention, and no significant improvement in wear resistance like the hydrous silicic acid of Examples 1 to 6 is observed. The hydrous silicic acid of Examples 1 to 6 and the hydrous silicic acid of Comparative Example 2 are substantially the same in dispersibility, or the hydrous silicic acid of Examples 3 and 6 is the hydrous silicic acid of Comparative Example 2. Somewhat inferior. However, in spite of this, the effect of improving the abrasion resistance of the hydrous silicic acids of Examples 1 to 6 is significantly higher than that of the hydrous silicic acid of Comparative Example 2.

From these results, the effect of improving the wear resistance of the diene rubber composition used in combination with the silane coupling agent obtained by the hydrous silicic acid of the present invention is that the surface solid acid density is in a predetermined range, and the predetermined surface activity. This is a synergistic effect obtained by loading the agent on hydrous silicic acid, and simply adjusting the surface solid acid density to a predetermined range, or adjusting the surface solid acid density to a predetermined range and a predetermined surfactant. This is an unexpected effect that cannot be obtained only by kneading into a rubber composition together with hydrous silicic acid.

The water-containing silicic acid for reinforcing and filling rubber according to the present invention is capable of providing a useful rubber composition in the industrial rubber field that requires particularly abrasion resistance, such as tire treads and belts.

Claims

A hydrous silicic acid for rubber reinforcement filling, characterized by having a surface solid acid density in a range of 1.8 to 2.4 m-mol / m 2 and containing a cationic or nonionic surfactant.
2. The water-containing silicic acid for reinforcing and filling rubber according to claim 1, which is used for reinforcing and filling a diene rubber composition in combination with a silane coupling agent.
3. The hydrous silicic acid for rubber reinforcement filling according to claim 1, wherein the CTAB specific surface area is 130 to 300 m 2 / g.
4. The rubber reinforcement filling according to claim 3, wherein the ratio of the surfactant content (parts by mass / 100 parts by mass of SiO 2 (solid content basis)) and the CTAB specific surface area (m 2 / g) is in the range of 0.001 to 0.01. Hydrous silicic acid.
In any stage of the process for producing hydrous silicic acid,
5. The method for producing hydrous silicic acid for rubber reinforcement filling according to claim 1, comprising adding an aluminate and then adding a cationic or nonionic surfactant.
The step of producing the hydrous silicic acid includes any one of a step of adding an acid after completion of the addition of the alkali silicate aqueous solution, a step of washing with filtered water, and a step of drying, and in any of these steps 6. The production method according to claim 5, wherein the aluminate is added, and then the surfactant is added.
The aluminate is sodium aluminate, and the sodium aluminate has a Na 2 O / Al 2 O 3 molar ratio of 1.8 to 20.0 and an Al 2 O 3 concentration of 1.0 to 16.0 wt%. The manufacturing method as described in.
The production method according to any one of claims 5 to 7, wherein the surfactant is added as an aqueous solution in a range of 20 to 90 wt% based on solid content.
The step of forming hydrous silicic acid in the aqueous solution is performed by adding an alkali silicate aqueous solution and sulfuric acid to an alkali silicate aqueous solution heated to 70 to 90 ° C. having a SiO 2 concentration of 5 to 50 g / L and a pH of 10 to 12, and 70 to 90%. The neutralization reaction is carried out while controlling the addition amount (ratio) of the alkali silicate aqueous solution and sulfuric acid so that the pH of the reaction solution is in the range of 10 to 11, and the SiO 2 concentration is 50 to 50 ° C. The production method according to any one of claims 5 to 8, comprising the addition until the addition is in a range of 80 g / L.