JPS5952900B2 - rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rubber composition containing finely powdered silicic acid as a filler. The object of the present invention is to provide a method for accelerating vulcanization and to obtain a rubber composition exhibiting excellent physical properties.

In general, natural rubber and various synthetic rubbers cannot be used to make practical rubber products from raw rubber itself, but are made by mastication,
The necessary performance is initially imparted to the product through various processes such as mixing with various compounding agents, rolling, extrusion, molding, and vulcanization.

In particular, with synthetic rubber it is necessary to mix far more compounding agents than with natural rubber, and the compounding composition not only controls the performance of the product rubber, but also affects workability and efficiency during processing.・Because this has an important effect, countless formulation compositions have been proposed depending on the type of raw material rubber and filler used, and some of these have been put into practice.

On the other hand, fine powder silicic acid is a typical white filler essential for synthetic rubber compositions that require a high degree of reinforcing effect. However, in order to provide a high degree of reinforcing effect as a filler, the particles must be as fine as possible.

However, as the particles become finer, their adsorption to moisture, vulcanization accelerators, activators, etc. becomes more pronounced. Therefore, when fine powdered silicic acid consisting of ultrafine particles is blended as a filler, vulcanization accelerators, activators, etc. The reinforcing effect is reduced, and various troubles associated with the adsorption of moisture and various compounds are more likely to occur.

In particular, an extreme decrease in the vulcanization rate not only reduces the efficiency of the vulcanization process, but also extends the working time at high temperatures, which accelerates the thermal decomposition of the rubber and compounding ingredients, leading to physical problems in the product rubber. This may cause deterioration in performance and durability or increase in coloring.

In order to avoid such troubles, it may be possible to increase the amount of vulcanization accelerator or activator added, but using a large amount of vulcanization accelerator is not only expensive, but also This increases the risk of premature vulcanization (scorch), making the vulcanization process unstable, and impairs the physical performance and durability of the product rubber.

In addition, the use of multiple activators has drawbacks such as causing a vulcanization reversion phenomenon and reducing the reinforcing effect, and giving a product rubber with poor elasticity. As long as strong white carbon is used, the reinforcing effect and vulcanization rate have a mutually contradictory relationship, so it is possible to simultaneously increase both the filling reinforcing effect and the vulcanization acceleration effect, and to achieve an efficient vulcanization process. This means that it is extremely difficult to do so. By the way, several proposals have been made regarding rubber compositions containing zeolite as a means of promoting vulcanization (Japanese Patent Publication No. 36-5989).
No., Special Publication No. 36-12442, Special Publication No. 38-6631
No., Special Publication No. 47-18082). However, in all of these, the characteristics as a rubber composition can be improved by adsorbing and supporting a specific vulcanization accelerator on an activated zeolite with particularly high molecular sieving properties, and then blending it into a specific rubber or synthetic rubber. Further, in order to enhance the effect of this product, a release agent is used in combination so that the adsorbed and supported vulcanization accelerator is easily replaced.

On the other hand, in view of the above-mentioned problems in various rubber compositions containing finely powdered silicic acid as a filler, the present inventors have conducted intensive research and found that the mode of use of zeolite according to the invention of the above-mentioned document is In contrast, when A-type zeolite itself (that is, not as a support for other vulcanization accelerators) was blended into a conventional rubber composition containing finely powdered silicic acid, vulcanization was significantly accelerated. The present invention has been completed based on the findings that there is an improvement in reinforcement properties and reinforcement properties.

That is, the present invention uses finely powdered silicic acid as a filler, and uses one or more selected from styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, polybutaz diene rubber, ethylene propylene rubber, and natural rubber as a raw material rubber. The present invention relates to a rubber composition characterized in that 0.3 to 5 parts by weight of type A zeolite is blended as a vulcanization aid per 100 parts by weight of raw rubber.

The raw material rubber used in the present invention includes styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR), polybutadiene rubber (BR), and ethylene propylene rubber (EPDM).
) and natural rubber, and they may also be blended rubbers. In many cases, it can be preferably applied to rubbers with low polarity. The fine powder of silicic acid used in the present invention includes fine powder of amorphous hydrated silicic acid produced from sodium silicate by a wet method, fine powder of amorphous silicic anhydride produced by a dry method, etc. Yes, any of them can be used, even those with extremely strong adsorption properties can be used.

These finely powdered silicic acids easily absorb water and usually contain 0.5 to 20% water in some form.

Furthermore, many conventionally known techniques can be applied to the use of various additives and auxiliaries such as vulcanization accelerators, anti-aging agents, activators, mixing accelerators, sulfur, oils, and pigments as compounding agents. be able to.

On the other hand, the type A zeolite used in the present invention has the general formula (1
．． 0±0.2) M2O・Al2O3・ (1.9±0.
5) Hydrous aluminosilicate or , an anhydride obtained by its dehydration, which has a specific cubic crystal structure that can be distinguished from various other rubber compositions and silicates by the method of X-ray diffraction. .

M is Na, K, Ca, Mg, etc. or two of them.
Those containing more than one species can be used. Note that it is desirable that the powder be made of fine particles with a primary particle diameter of 10 μm or less. Any type A zeolite having the above-mentioned properties may be used, but as an example, Japanese Patent Application No. 53-67 related to the invention of the inventors of the present application, etc.
236 manufacturing method (i.e., a sodium silicate solution prepared by dissolving anhydrous sodium silicate glass in a caustic soda aqueous solution and a sodium aluminate solution prepared by dissolving aluminum hydroxide in a caustic soda aqueous solution are mixed and stirred to react, and the mother liquor caustic soda In a caustic soda aqueous solution with a concentration of 5% by weight or more, A
Generate type zeolite crystals.

After completion of the reaction, the mother liquor containing substantially no free unreacted substances is separated and recovered, divided into two parts, and recycled as a caustic soda aqueous solution for dissolving anhydrous sodium silicate glass and aluminum hydroxide. ) is suitable for the present invention. These A-type zeolites can be used alone when kneading raw rubber and various compounding agents on a 10-layer 1.
2) Add and mix in advance to one or more other raw materials and compounding agents such as raw material rubber, finely powdered silicic acid, and vulcanization accelerator, and add and mix this with other raw materials and compounding agents according to a conventional method. Various methods such as kneading are possible.

1. Furthermore, if necessary, it is also possible to reduce the amount of the vulcanization accelerator or activator by adding type A zeolite. The vulcanizable rubber composition obtained by such kneading is a rubber composition vulcanized through the same steps as in conventional methods such as rolling, extrusion, molding, and vulcanization. becomes.

In this case, the amount of A-type zeolite blended is 1 1 of the raw material synthetic rubber.
It is necessary to set it to 0.3 parts or more per 00 parts.

When the amount is less than 0.3 parts, the effect is insufficient, and in most cases, addition of 0.5 to 5 parts can significantly shorten the vulcanization time and significantly improve the physical properties of the rubber product.

Although it is possible to add the A-type zeolite in an amount of 5 parts or more, the effect tends to gradually become saturated. The effects of the A-type zeolite blend in the present invention are determined by vulcanization degree tests conducted on unvulcanized rubber compositions using a culastometer and various physical performance tests conducted on vulcanized rubber compositions. can be evaluated.

When comparing the effects of adding type A zeolite to the case without the addition, it is generally observed that there is a significant increase in the vulcanization rate and a significant improvement in the physical properties of the vulcanized rubber, such as tensile strength, tear strength, modulus, and hardness. .

In particular, improvements in the tensile strength and modulus of the vulcanized rubber are remarkable, and a high degree of build-up that could not be achieved by adjusting the amount of additives such as vulcanization accelerators and activators using conventional techniques has been achieved. It will be done. Therefore, in the rubber composition of the present invention, the efficiency of the vulcanization process can be improved by shortening the vulcanization time without reducing the physical performance of the rubber.

2 In particular, when shortening the vulcanization time is not required, the amount of conventional secondary vulcanization accelerators, activators, etc. added can be reduced.

3. It is also possible to use finely powdered silicic acid, which has conventionally been unusable due to its excessive adsorption properties.

It is clear that other advantages can also be achieved. moreover,
The rubber composition of the present invention generally has the advantage that there is little tendency for premature vulcanization (scorch) and that a vulcanized product with good reproducibility can be obtained even if there are slight fluctuations in roll temperature, etc. . The mechanism of action of type A zeolite in the present invention is not necessarily clear, but in general, type A zeolite has strong activity against water and various compounds due to its unique crystal structure, and is always an insoluble solid in rubber compositions. Since it exists as particles, it is a type of adsorbent for rubber molecules, vulcanization accelerators, activators, moisture, etc. in the composition, or a crosslinking reaction of rubber molecules during vulcanization performed at temperatures around 150°C. By acting as a type of solid catalyst, it is thought to play a role in bringing out the original reinforcing filling effect and vulcanization accelerator ability of fine powder silicic acid, which were not fully exhibited in conventional rubber compositions.
Type A zeolite itself has almost no toxicity to the human body, is tasteless and odorless, and does not color or contaminate rubber, so it can be used in rubber for food-related applications. Next, examples will be shown.

Example 1 100 parts of styrene butadiene rubber (SBR) was added with the following
Type A zeolite was added together with various compounding agents in the amounts shown in the table, and kneaded with a roll in a conventional manner to obtain a vulcanizable rubber composition.

Furthermore, for comparison, a case in which type A zeolite was not added was treated in the same manner to obtain a vulcanizable rubber composition. Table 1 shows the results of measuring the vulcanizability of these compositions using a culastometer. The vulcanization curve drawn at 150° C. is shown in FIG.

Here, RMT is the maximum torque value corresponding to the modulus of vulcanized rubber, TO. , is the time (minutes) required to obtain 90% of the maximum torque value. The vulcanization time (minutes) is the time T required for the torque value to rise by 1.5 units from the minimum torque value. (
minute) and T. ．． , that is, the calculation formula T. ．． ,-T.O.
Therefore, the smaller the value, the faster the vulcanization rate. A: Layered duck ↑? ♂Kor1zuke - Consists of fine particles of 0.5 to 1μ.

Table 1 Jff). As is clear from the results of Example 2 (Example), the unvulcanized rubber composition prepared by adding 5 parts of type A zeolite according to the present invention is different from the unvulcanized rubber composition prepared by adding 5 parts of type A zeolite.
The vulcanization rate is significantly higher than that of (comparative example).

Furthermore, these unvulcanized compositions were heated to 150°C by a purifying method.
Regarding the rubber composition obtained by vulcanization with JIS. K-6
Table 2 shows the results of measuring the physical performance according to 301.

From Table 2, SI. The rubber composition prepared by adding the A-type zeolite of the present invention in No. 2 has higher physical properties such as M3OO, M5OO, and tensile strength within a shorter vulcanization time than Black No. 1 in which no A-type zeolite is added. It is clear that it shows value.

The vulcanization degree test method was performed as follows.

Roll used for kneading: Dimensions: 8x18 inches Rotation speed: 18r
pm Rotation ratio 1.18 Surface temperature 50±5°C Vulcanization conditions: 150°C x 20, 30, 40 minutes Evaluation method Tensile test: Test piece JIS No. 3 Tampel testing machine: Schottspa complete set tensile testing machine (capacity 50kgf) Test method: In accordance with JIS K63Ol, the following examples were also carried out under the same conditions.

Example 2 100 parts of styrene butadiene rubber (SBR) was added with the following third
Vulcanizable rubber compositions were prepared in the same manner as in Example 1 by adding Type A zeolite together with various compounding agents in the amounts shown in the table, and the vulcanizability of each was measured. Table 3 shows the results.

Furthermore, Table 4 shows the results of measuring the physical properties of the rubber compositions obtained by vulcanizing these vulcanizable compositions at 150° C. in the same manner as in Example 1.

From the results of Table 3, Washing 4 and 5 (Example), it can be seen that in the case of the rubber composition in which almost anhydrous type A zeolite is added according to the present invention, boiling 3 without adding type A zeolite (comparative example) It is clear that the vulcanization rate is significantly higher than that of

In addition, from the results of Table 4, Sections 4 and 5 (Example), the rubber composition containing the A-type zeolite of the present invention was found to be black 3 (Example).
It is clear that the physical properties such as M3OO, M5OO, and tensile strength are significantly larger and superior than those of Comparative Example.

Example 3 100 parts of styrene butadiene rubber (SBR) was added with the following
Vulcanizable rubber compositions were prepared in the same manner as in Example 1 by adding type A zeolite together with various compounding agents in the amounts shown in the table, and the vulcanizability of each was measured. Table 5 shows the results.

Furthermore, Table 6 shows the results of measuring the physical properties of the rubber compositions obtained by vulcanizing these vulcanizable compositions at 150° C. in the same manner as in Example 1.

From the results in Tables 5 and 6, it can be seen that even when the amount of type A zeolite added is about 1 part per 100 parts of synthetic rubber, a clear vulcanization accelerating effect and an effect of improving physical performance are recognized.

Example 4 A type A zeolite was added to fine powder silicic acid in advance to prepare a fine powder silicic acid composition (premix) containing 8% by weight of A type zeolite.
A vulcanizable rubber composition was prepared in the same manner as in Example 1 by blending this finely powdered silicic acid composition with various compounding agents in 100 parts of BR) in the amounts shown in Table 7 below.

However, in this example, a finely powdered silicic acid having particularly remarkable adsorption properties was used as the finely powdered silicic acid, and a hydrated product and an anhydride were used as the A-type zeolite.

Further, Table 8 shows the results of measuring the physical properties of the rubber compositions obtained by vulcanizing these unvulcanized rubber compositions at 150° C. in the same manner as in Example 1.

From the results in Table 8, 11 and 12 [Example], it can be seen that the rubber composition prepared by adding type A zeolite according to the present invention is black 10 [
It is clear that vulcanization progresses in a shorter time than in Comparative Example, and the tensile strength shows a high value.

In addition, during the vulcanization test, 10 (comparative example) had poor releasability of the vulcanized rubber from the mold and required the use of a mold release agent.
Both Black 11 and 12 [Example] had good peelability and other workability.

Claims (1)

[Claims] 1. A rubber composition containing finely powdered silicic acid as a filler and one or more selected from styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, polybutadiene rubber, ethylene propylene rubber, and natural rubber as a raw material rubber, A rubber composition comprising 0.3 to 5 parts by weight of type zeolite as a vulcanization aid per 100 parts by weight of raw rubber.