JP5054910B2 - Rubber composition and method for producing the same - Google Patents

Description

  The present invention relates to a rubber composition and a method for producing the rubber composition, and more particularly to a highly elastic rubber composition suitable for a bead filler of a tire and a method for producing the same.

  Conventionally, an ultra-hard rubber is disposed in a bead portion of a radial tire in order to improve the steering stability and durability of the tire (see Patent Documents 1 to 3). As the ultra-hard rubber, a rubber composition in which carbon black and sulfur are blended in a larger amount than usual with respect to a rubber component is used.

  In order to further increase the hardness of the super hard rubber, Japanese Patent Publication No. 57-30856 (Patent Document 4) discloses a novolac type phenol modified with a novolac type phenol resin, oil or the like with respect to a diene rubber. A rubber composition in which a system resin, a curing agent for a resin, and carbon black are blended is disclosed.

  Further, JP-A-5-51487 (Patent Document 5) discloses a technique for reducing deterioration of mechanical properties of rubber and amine deterioration of carcass cords by reducing the amount of hexamethylenetetramine which is a curing agent for resin. For example, a technique is disclosed in which hexamethylenetetramine, which is a curing agent, is internally added to a novolac-type phenol resin modified with oil or the like.

  Furthermore, JP-A-2004-43664 (Patent Document 6) discloses aggregation of a novolac phenolic resin due to a hydroxyl group by blending a polar additive with a rubber composition containing the novolac phenolic resin. Techniques for suppressing and improving the dispersibility of the resin are disclosed.

  Furthermore, JP-A-2004-43654 (Patent Document 7) discloses aggregation of a novolac phenolic resin due to a hydroxyl group by blending a novolac phenolic resin with a rubber component containing a polymer modified with a polar group. A technique for improving the dispersibility of the resin by suppressing the above is disclosed.

Japanese Utility Model Publication No. 47-16084 French Patent No. 1260138 specification US Pat. No. 4,067,373 Japanese Patent Publication No.57-30856 Japanese Patent Laid-Open No. 5-51487 JP 2004-43664 A JP 2004-43654 A

  However, when the rubber composition is made highly elastic by increasing the blending amount of carbon black and sulfur with respect to the rubber component, there is a limit in balancing the workability, heat build-up and aging resistance of the rubber composition.

  In general, novolac phenolic resins have poor dispersibility in rubber components, and the rubber component of the resin can be obtained simply by substituting a novolac phenolic resin modified with oil or the like for an unmodified novolac phenolic resin. It is not possible to sufficiently improve the dispersibility in the water. Furthermore, a rubber composition containing a novolac type phenolic resin modified with oil or the like has a problem that heat generation at a high temperature range is worse than a rubber composition containing an unmodified novolak type phenolic resin. .

  Furthermore, if a polar additive or a polymer modified with a polar group is used, the reactivity of the hydroxyl group of the novolak-type phenolic resin is lowered, the curing reaction of the resin is delayed, or the reaction is incomplete. There is a fear. In this case, there is also a problem that the blending cost increases.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, including a novolac-type phenolic resin, having sufficient workability, heat generation and aging resistance, and capable of sufficiently curing the used resin. It is to provide an elastic rubber composition. Another object of the present invention is to provide a method for producing such a rubber composition.

  As a result of intensive studies to achieve the above object, the present inventor carried out kneading of a rubber composition containing carbon black, a curing agent for resin and a novolac type phenolic resin in a plurality of kneading stages, (1 ) The best rubber composition in the kneading stage after the kneading stage in which the novolac type phenolic resin is added, and the kneading stage in which the novolac type phenolic resin is added in the stage after the kneading stage in which the carbon black is introduced By making the ultimate temperature less than the softening point of the novolac phenolic resin + 20 ° C or less, while suppressing aggregation of the novolac phenolic resin, the reinforcing effect of the carbon black is sufficiently exerted, and the rubber composition is sufficiently It can be highly elastic, and (2) Novola at a stage after the kneading stage where carbon black is introduced. A kneading stage for feeding a phenolic phenol resin is performed, and the maximum temperature of the rubber composition in the kneading after the kneading stage for feeding a novolak type phenolic resin is set to be equal to or lower than the temperature at which the curing agent for the resin begins to change. As a result, the novolac-type phenolic resin reacts efficiently, the reinforcing effect by the resin is efficiently exhibited, and the balance between the storage elastic modulus (E ′) and the loss tangent (tan δ) of the rubber composition is significantly improved. As a result, the present invention has been completed.

That is, the first rubber composition of the present invention comprises 30 to 100 parts by mass of carbon black, a novolac phenolic resin, and a methylene donor with respect to 100 parts by mass of a rubber component mainly composed of a diene rubber. A rubber composition obtained by blending and kneading a certain curing agent for a resin,
The kneading stage in which the novolac type phenolic resin in the kneading is charged is a stage after the kneading stage in which the carbon black is charged,
The maximum attainable temperature of the rubber composition in the kneading after the kneading stage into which the novolac type phenol resin is added is characterized by being the softening point of the novolac type phenol resin + 20 ° C or lower. In the present invention, the novolac phenolic resin includes an unmodified novolac phenolic resin and a modified product thereof.

The second rubber composition of the present invention comprises 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, and a methylene donor with respect to 100 parts by mass of a rubber component mainly composed of a diene rubber. A rubber composition obtained by blending and kneading a certain curing agent for a resin,
The kneading stage in which the novolac type phenolic resin in the kneading is charged is a stage after the kneading stage in which the carbon black is charged,
The maximum attainable temperature of the rubber composition in the kneading after the kneading stage into which the novolak-type phenolic resin is charged is not more than the change start temperature of the curing agent for resin. Here, in the present invention, the alteration start temperature of the resin curing agent is determined by measuring the DSC (mW) under a temperature rising condition of 20 ° C./min using DSC / TA with respect to the resin curing agent, and measuring the temperature (° C. ) And DSC (mW), the temperature at the displacement point of the graph when graphed.

  In a preferred example of the rubber composition of the present invention, the novolac phenolic resin is a novolac phenol-formaldehyde condensate or a modified product thereof. In the rubber composition of the present invention, the amount of the novolac phenolic resin is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component.

  In another preferred embodiment of the rubber composition of the present invention, the curing agent for resin as the methylene donor is hexamethylenetetramine and / or hexamethoxymethylmelamine.

In addition, the first rubber composition production method of the present invention comprises 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, methylene based on 100 parts by mass of a rubber component mainly composed of a diene rubber. A method of kneading and producing a rubber composition comprising a resin curing agent as a donor,
In a stage after the kneading stage for charging the carbon black in the kneading, a kneading stage for charging the novolac type phenolic resin is performed,
The maximum attainable temperature of the rubber composition in the kneading after the kneading stage into which the novolak type phenolic resin is charged is characterized by the softening point of the novolac type phenolic resin + 20 ° C. or lower.

Furthermore, the second rubber composition production method of the present invention comprises 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, methylene, based on 100 parts by mass of a rubber component mainly composed of a diene rubber. A method for producing a rubber composition obtained by blending and kneading a resin curing agent as a donor,
In a stage after the kneading stage for charging the carbon black in the kneading, a kneading stage for charging the novolac type phenolic resin is performed,
The maximum attainable temperature of the rubber composition in the kneading after the kneading stage into which the novolak-type phenolic resin is added is set to be equal to or lower than the change start temperature of the resin curing agent.

  According to the present invention, kneading of a rubber composition containing carbon black, a curing agent for resin and a novolac-type phenolic resin is performed in a plurality of kneading stages, and (1) after the kneading stage into which carbon black is charged. In this stage, a kneading stage for adding a novolac type phenolic resin was performed, and the maximum temperature of the rubber composition in the kneading stage after the kneading stage for adding the novolak type phenolic resin was determined to soften the novolak type phenolic resin. And / or (2) performing a kneading stage in which a novolac phenolic resin is introduced at a stage after the kneading stage in which the carbon black is introduced, and then a novolac phenolic Maximum reached temperature of rubber composition in kneading after the kneading stage where resin is added By following deterioration starting temperature of the resin curing agent, it is possible to provide a high-elasticity rubber composition.

  The present invention is described in detail below. The rubber composition of the present invention comprises 30 to 100 parts by mass of carbon black, a novolac phenolic resin, and a resin curing agent that is a methylene donor with respect to 100 parts by mass of a rubber component mainly composed of a diene rubber. And blended. In the rubber composition of the present invention, carbon rubber and novolac type phenolic resin are dispersed in the rubber component, and the rubber composition has a high elastic modulus due to a synergistic effect expressed by reinforcing each other.

  The rubber component used in the rubber composition of the present invention contains a diene rubber as a main component. As the diene rubber, in addition to natural rubber (NR), polybutadiene rubber (BR), polyisoprene rubber (IR), styrene- Synthetic diene rubbers such as butadiene copolymer rubber (SBR) can be used. These rubber components may be used alone or in a blend of two or more.

  In the rubber composition of the present invention, carbon rubber and novolac type phenolic resin are dispersed in the rubber component, and the rubber composition has a high elastic modulus due to a synergistic effect obtained by reinforcing each other. The compounding amount of carbon black needs to be in the range of 30 to 100 parts by mass with respect to 100 parts by mass of the rubber component. If the blending amount of carbon black is less than 30 parts by mass with respect to 100 parts by mass of the rubber component, the rubber composition cannot be increased in elasticity, and even if it exceeds 100 parts by mass, the rubber composition is further increased in elasticity. However, the exothermic property of the rubber composition is deteriorated. Here, the carbon black is not particularly limited, and various grades of carbon black can be used.

  Examples of the novolak type phenolic resin used in the rubber composition of the present invention include novolac type phenol-formaldehyde condensate, novolac type cresol-formaldehyde condensate, novolac type resorcin-formaldehyde condensate, and modified products thereof. Among these, novolac type phenol-formaldehyde condensates and modified products thereof are preferable. Here, as the modified product, the condensate is modified with an oil such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid or linolenic acid, or modified with an aromatic hydrocarbon such as xylene or mesitylene. And those modified with rubber such as nitrile rubber. These novolac type phenol resins may be used alone or in a combination of two or more. Moreover, the compounding amount of the novolac-type phenol resin is not particularly limited, but is preferably in the range of 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. If the compounding amount of the novolac-type phenolic resin is 5 parts by mass or more with respect to 100 parts by mass of the rubber component, the rubber composition can have a sufficiently high elasticity, and if it is 30 parts by mass or less, the rubber composition The exothermic deterioration of can be sufficiently suppressed.

  Examples of the curing agent for resin that is a methylene donor used in the rubber composition of the present invention include hexamethylenetetramine, hexamethoxymethylmelamine, and paraformaldehyde. Among these, hexamethylenetetramine and hexamethoxymethylmelamine are preferable. . These curing agents for resins may be used alone or in combination of two or more. In addition, the compounding amount of the curing agent for resin is not particularly limited, but is preferably in the range of 5 to 50% by mass with respect to the compounding amount of the novolac type phenol resin.

  The rubber composition of the present invention includes the above-described rubber component, carbon black, novolac-type phenolic resin, and a curing agent for resin that is a methylene donor, a vulcanizing agent, a vulcanization accelerator, zinc oxide, stearic acid, A compounding agent usually used in the rubber industry such as an anti-aging agent can be appropriately selected and blended within a range not impairing the object of the present invention. In addition, as these compounding agents, a commercial item can be used conveniently.

  The rubber composition of the present invention is produced by blending the above rubber component with carbon black, a novolac-type phenolic resin, a resin curing agent as a methylene donor, and various appropriately selected compounding agents, and kneading them. However, the kneading stage in the kneading step is divided into a plurality of times, and (1) the kneading stage in which the novolac-type phenolic resin is introduced in a stage after the kneading stage in which the carbon black is introduced, and further The maximum reached temperature of the rubber composition in the kneading after the kneading stage into which the novolac phenolic resin is added is controlled to be the softening point of the novolac phenolic resin + 20 ° C. or below, or (2) At the stage after the kneading stage where carbon black is introduced, the kneading stay where the novolac type phenol resin is introduced. It was carried out, further, required to control the maximum temperature, the following alteration initiation temperature of the resin curing agent in the rubber composition in the mixing-kneading after kneading stage to inject the novolak phenolic resin.

In the method of (1), in the rubber composition kneading step, the highest temperature reached by the rubber composition in the kneading stage after the kneading stage in which the novolak type phenolic resin is added is determined by the novolac type phenolic resin added. By controlling the softening point to + 20 ° C. or less, the novolac type phenolic resin can be highly dispersed in the rubber component mainly composed of the diene rubber. Here, during the kneading, if the temperature of the rubber composition is higher than the softening point of the novolac phenolic resin charged by 20 ° C., the novolac phenolic resin can be kneaded with extremely high fluidity. The novolac type phenolic resin is inherently not compatible with the diene rubber, resulting in a large agglomerate. As a result, the dispersibility of the novolak type phenolic resin with respect to the rubber component decreases, and the novolac type resin The reinforcing effect by the phenolic resin is not sufficiently exhibited, and the reinforcing property of the rubber composition is rapidly lowered.

  On the other hand, in the method of (2), in the kneading step of the rubber composition, the highest reached temperature of the rubber composition in the kneading after the kneading stage in which the novolac type phenol resin is added is set as the curing agent for the resin. By controlling the temperature below the transformation start temperature, the novolac-type phenolic resin reacts efficiently, and the reinforcing effect of the resin is efficiently exhibited. The storage elastic modulus (E ′) and loss tangent (tanδ) of the rubber composition And the balance is significantly improved.

  In addition, when the carbon black and the novolac phenolic resin are added and kneaded on the same stage, the carbon black and the novolac phenolic resin are highly compatible. Is taken in, and the reinforcing effect of carbon black is lost. Further, generally, in the stage where carbon black is introduced, the kneading temperature tends to be high, and when novolac type phenolic resin is present in the system, the novolac type phenolic system in which the temperature of the rubber composition to be kneaded is introduced. The temperature becomes higher than the softening point of the resin + 20 ° C., and the novolak type phenol resin is aggregated for the above-mentioned reason. On the other hand, if the kneading temperature of the stage where carbon black is introduced is kept low, the formation of carbon gel will be insufficient, the reinforcing effect of carbon black will not be fully demonstrated, and the reinforcing property of the rubber composition will be reduced. End up. Therefore, it is necessary to perform a kneading stage in which a novolac-type phenolic resin is introduced in a stage after the kneading stage in which carbon black is introduced.

In addition, it is preferable to select suitably the timing of injection | throwing-in of the hardening agent for resins which is the said methylene donor according to the kind of hardening agent for resins to be used. For example, in the case of a highly reactive curing agent such as hexamethylenetetramine, in order to prevent curing of the novolak type phenolic resin in the kneading machine, the curing agent is introduced at the later stage of the kneading step, Furthermore, it is preferable to keep the kneading temperature as low as possible within a range that does not hinder the dispersion of the compounding agent. Further, in the case of a curing agent having a relatively low reactivity such as hexamethoxymethylmelamine, since there is a low risk of curing the novolak type phenolic resin in the kneader, it is preferably introduced at the earlier stage.

  Various kneaders can be used for kneading the rubber composition. For example, a Banbury mixer, a kneader, a roll, or the like can be used. Moreover, the rubber composition of the present invention obtained as described above has a very high elastic modulus, and can be particularly suitably used as an ultra-hard rubber such as a tire bead filler and a hard stiffener.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition having a formulation shown in Table 1 was prepared by kneading in a total of three kneading stages. For natural rubber (NR), carbon black and HMMM (curing agent for resin) were introduced at the first stage, and novolac type phenolic resin was introduced at the stage shown in Table 1. The storage elastic modulus (E ′) and loss tangent (tan δ) were measured for the obtained rubber composition by the following method, and the results shown in Table 1 were obtained. The alteration start temperature of the resin curing agent was measured by the following method.

(I) Storage elastic modulus (E ′) and loss tangent (tan δ)
A sample obtained by vulcanizing the obtained rubber composition at 145 ° C. for 24 minutes was measured using a spectrometer manufactured by Toyo Seiki Co., Ltd. at a strain of 2%, 52 Hz, at a measurement temperature of 80 ° C., and storage modulus (E ′) and loss tangent ( tan δ) was measured, and each index was displayed with Example 1 as 100. As for the storage elastic modulus (E ′), the larger the index value, the higher the elastic modulus, indicating that the rubber composition is highly elastic, and the loss tangent (tan δ), the higher the index value, The heat generation of the rubber composition is large, indicating that the heat generation is deteriorated.

(Ii) Deformation start temperature of resin curing agent For resin curing agent, DSC (mW) was measured under a temperature rising condition of 20 ° C / min using DSC / TA manufactured by Seiko Instruments Inc. The temperature at the displacement point of the graph when the relationship between (° C.) and DSC (mW) was graphed was defined as the alteration start temperature of the curing agent for resin. FIG. 1 shows a graph of calorimetric displacement (DSC results) of HMMM (hexamethoxymethylmelamine).

* 1 N330.
* 2 Sumitomo Bakelite, Sumilite Resin PR-50235, softening point: 121 ° C.
* 3 Hexamethoxymethylmelamine, manufactured by AMERICANYANAMID COMPANY, CYREZ964, transformation start temperature: 120 ° C.

  As is apparent from Table 1, when carbon black having a blending amount specified in the present invention is introduced in the first stage, novolac type phenolic resin is introduced in the second or third stage, and further, novolac type phenolic resin is added. It can be seen that a rubber composition having a high storage elastic modulus can be obtained by setting the maximum reached temperature of the rubber composition in the kneading after the addition of the above to be the softening point of the novolac phenolic resin + 20 ° C or less.

  In addition, from the results of Example 3, the novolac type phenolic resin was introduced in a stage after the stage in which the carbon black was introduced, and the highest rubber composition in the kneading after the addition of the novolac type phenolic resin. It can be seen that a rubber composition having a particularly excellent balance between the storage elastic modulus (E ′) and the loss tangent (tan δ) can be obtained by setting the ultimate temperature to be equal to or lower than the change start temperature of the curing agent for resin.

  On the other hand, since the rubber composition of Comparative Example 1 does not contain a curing agent for resin that is a methylene donor, the storage elastic modulus is low, and the rubber composition of Comparative Example 2 has too little compounding amount of carbon black. The storage elastic modulus is low, and the rubber composition of Comparative Example 3 has too much carbon black, so that the exothermic property is deteriorated. The rubber composition of Comparative Example 4 is a novolak type phenolic resin and a methylene donor. Since it does not contain a certain curing agent for resin, the storage elastic modulus was remarkably low.

  In addition, since the rubber composition of Comparative Example 5 was introduced with the novolac type phenolic resin in the first stage together with the carbon black, the carbon black was taken into the novolac type phenolic resin and the reinforcing effect of the carbon black was exhibited. In addition, since the temperature of the kneaded rubber exceeded the softening point of the novolac type phenolic resin + 20 ° C., the novolac type phenolic resin was aggregated, so that the storage elastic modulus was lowered.

  Further, in the rubber composition of Comparative Example 6, the maximum reached temperature of the rubber composition in the kneading after the addition of the novolak type phenolic resin became a temperature exceeding the softening point of the novolak type phenolic resin + 20 ° C. Since the novolak-type phenolic resin was agglomerated, the storage elastic modulus decreased.

  Furthermore, although the rubber composition of Comparative Example 7 sufficiently suppressed the maximum temperature of the rubber composition in the kneading after the addition of the novolak type phenolic resin, the carbon black and the novolak type phenolic resin in the first stage. Therefore, carbon black was taken into the novolac-type phenolic resin, the reinforcing effect of carbon black was not exhibited, and the storage elastic modulus was lowered.

  Next, kneading conditions of the rubber composition having the same composition as in Example 1 (the introduction stage of the novolac type phenolic resin and the maximum temperature reached by the kneading after the addition of the novolac type phenolic resin) are as follows. The rubber elastic modulus (E ′) of each rubber composition was measured. As in Example 1, the total number of kneading stages was three, and carbon black was charged in the first stage. The results are shown in FIG.

  FIG. 2 shows that even with a rubber composition having the same composition, the rubber obtained by the difference in the charging stage of the novolak type phenolic resin and the difference in the maximum temperature of the rubber composition in the kneading after the charging of the novolak type phenolic resin. In order to produce a rubber composition in which the storage elastic modulus of the composition greatly changes and the storage elastic modulus is high, a kneading stage in which a novolac-type phenolic resin is introduced at a stage after the kneading stage in which carbon black is introduced In addition, it is understood that it is necessary to control the maximum reached temperature of the rubber composition in the kneading stage after the kneading stage where the novolac type phenol resin is added to the softening point of the novolac type phenol resin + 20 ° C or less. .

It is a graph which shows the calorimetric displacement (DSC result) of HMMM (hexamethoxymethyl melamine). Storage elastic modulus (E ′) of the rubber composition having the same composition as that of Example 1 prepared by changing the kneading conditions, and the highest reached temperature of the rubber composition after the introduction of the novolak-type phenol resin—the novolak-type phenol system It is a graph which shows the relationship with the softening point of resin.

Claims (7)

100 parts by mass of a rubber component mainly composed of a diene rubber, 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, and a curing agent for resin that is a methylene donor are blended and kneaded. A rubber composition comprising:
The kneading stage in which the novolac type phenolic resin in the kneading is charged is a stage after the kneading stage in which the carbon black is charged,
A rubber composition, wherein a maximum temperature of the rubber composition in kneading after the kneading stage into which the novolac phenolic resin is added is a softening point of the novolac phenolic resin + 20 ° C or less. 100 parts by mass of a rubber component mainly composed of a diene rubber, 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, and a curing agent for resin that is a methylene donor are blended and kneaded. A rubber composition comprising:
The kneading stage in which the novolac type phenolic resin in the kneading is charged is a stage after the kneading stage in which the carbon black is charged,
A rubber composition characterized in that the highest temperature of the rubber composition in the kneading after the kneading stage into which the novolak-type phenolic resin is introduced is equal to or lower than the temperature at which the curing agent for resin is altered.   The rubber composition according to claim 1 or 2, wherein the novolac type phenol resin is a novolac type phenol-formaldehyde condensate or a modified product thereof.   The rubber composition according to claim 1 or 2, wherein the curing agent for resin which is the methylene donor is hexamethylenetetramine and / or hexamethoxymethylmelamine.   4. The rubber composition according to claim 1, wherein the compounding amount of the novolac-type phenolic resin is 5 to 30 parts by mass with respect to 100 parts by mass of the rubber component. 100 parts by mass of a rubber component mainly composed of a diene rubber, 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, and a curing agent for resin that is a methylene donor are blended and kneaded. A method for producing a rubber composition comprising:
In a stage after the kneading stage for charging the carbon black in the kneading, a kneading stage for charging the novolac type phenolic resin is performed,
Production of a rubber composition characterized in that the maximum temperature of the rubber composition in the kneading after the kneading stage into which the novolak type phenolic resin is added is the softening point of the novolac type phenolic resin + 20 ° C or less. Method. 100 parts by mass of a rubber component mainly composed of a diene rubber, 30 to 100 parts by mass of carbon black, a novolac type phenolic resin, and a curing agent for resin that is a methylene donor are blended and kneaded. A method for producing a rubber composition comprising:
In a stage after the kneading stage for charging the carbon black in the kneading, a kneading stage for charging the novolac type phenolic resin is performed,
A method for producing a rubber composition, characterized in that the maximum temperature reached by the rubber composition in the kneading after the kneading stage into which the novolak-type phenolic resin is introduced is set to be equal to or lower than the start temperature of alteration of the curing agent for resin.

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