JPS58204002A - Production of modified rubber - Google Patents

Abstract

PURPOSE:To obtain a modified rubber of an improved green strength, by reacting, under application of a sheraing force by a kneader, a hydrous rubber mixture prepared by adding maleic anhydride to a hydrocarbon solution of a rubber and evaporating the solvent by contacting with hot water under agitation. CONSTITUTION:0.5-1.5pts.wt. pref., 1-10pts.wt., per 100pts.wt. rubber, maleic anhydride is added to a solution of a rubber (e.g., diene rubber such as polyisoprene rubber) in an hydrocarbon (e.g., a hydrocarbon with b.p. of 50-100 deg.C, such as hexane). Then, a hydrous mixture, water content of 5-50wt%, is prepared by evaporating the solvent from the above solution by contacting it with hot water under agitation. A modified rubber having a low gel content, an increased green strength and excellent processability and breading strength is obtained by reacting the hydrous mixture by mechanically applying thereto a shearing force at 140-210 deg.C in a kneader.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing modified rubber. More specifically, it provides an industrially advantageous method for producing modified rubber with increased green strength by reacting rubber with maleic anhydride.Conventional synthetic rubber has a lower strength when unvulcanized than natural rubber. (Green strength) is low, and unvulcanized rubber may sag or deform during the molding process during the production of rubber products, which is a problem.

A number of methods are known as attempts to improve the green strength of synthetic rubber. Among these methods, there is a method of introducing maleic anhydride into synthetic rubber. Methods for introducing maleic anhydride into rubber include a method in which maleic anhydride is reacted in the presence of a radical generator in a rubber solution, and a method in which the reaction is performed in a solid phase. There are problems such as formation of polymers or decomposition of polymers, and strict control of reaction conditions is required. Although the production of gel can increase the green strength of rubber, it is difficult to manufacture, and it does not adversely affect the processability or vulcanization properties of the produced rubber. Reactions in a solution increase the viscosity of the system and complicate the control of reaction conditions, whereas reactions in a solid phase are industrially advantageous; however, they are prone to gel formation and polymer decomposition. Easy to get excited. For example, when maleic anhydride is mixed with polyisoperene rubber in a mixing machine, if the temperature is low, the rubber will not be modified, and if the temperature is high, the rubber will decompose. After adding maleic anhydride to the rubber solution and steam stripping, the rubber solution was heated at 180°C for 60 minutes under pressure.
A separation drying method is known, but this method requires a long heating process. As a result of extensive research into an industrially advantageous manufacturing method in which rubber, particularly diene rubber, and maleic anhydride are reacted in a solid phase, the inventors of the present invention have found that a water-containing rubber mixture is subjected to shearing force using a mixer in a water-containing state. The present inventors have discovered an industrially advantageous method for producing modified rubber, which has a low gel content, increased green strength, and excellent processability and breaking strength through reaction, and have arrived at the present invention. .

In the present invention, maleic anhydride is added to a rubber hydrocarbon solution, and the mixture is brought into contact with hot water while stirring to evaporate and separate the solvent.
Provided is a method for shaping modified rubber by applying shearing force at 0 to 210°C.

The rubber used in the present invention is polyisoprene rubber,
Examples include diene rubbers such as polybutadiene rubber and styrene-butadiene rubber, and olefin rubbers such as ethylene-tetrapyrene rubber and butyl rubber.

Among these, diene rubber is preferred, and polyisoprene rubber is particularly preferred. It has excellent properties and is desirable. Hydrocarbons that dissolve rubber include hexane, heptane, cyclohexane, methylcyclohexane, benzene, toluene, etc. with a boiling point of 50
Hydrocarbons at ~130°C are preferred because the solvent can be easily removed.

As the rubber solution, a polymer solution after polymerization during the production of synthetic rubber can be used.

The concentration of the solution is usually 1 to 50% by weight, preferably 3 to 30% by weight.
Weight -. Leic anhydride can be added as such or as a suspension or solution of the above hydrocarbon. The amount of maleic anhydride added is 0.5 to 15 parts by weight (PHR), preferably 1 to 15 parts by weight, per 100 parts by weight of rubber.
It is 10 parts by weight.

If it is less than 0.5 parts by weight, the green strength will not increase;
If the amount is more than 15 parts by weight, green strength will increase, but processability and vulcanization properties will deteriorate. The water content i' in the water-containing rubber fed to the kneader is 5 to 50% by weight, preferably 10 to 30% by weight. If the water content is less than 5%, the rubber will decompose or gel during kneading. On the other hand, if the amount is more than 5 degrees, the kneading operation will not be carried out sufficiently.

As the mixer for applying shearing force to the water-containing rubber, a roll, a pravender, a screw type extruder, a screw type extruder with twists, etc. are used. The temperature during kneading is 140
-2xoc, preferably 150-200°C.

1401: If the temperature is too low, the green strength will not increase, and if the temperature is too high (210'C), the rubber will decompose and gel.

The kneading operation is carried out under normal pressure or increased pressure. When carrying out under pressure, the pressure is usually 10 to 100:9/-.

Mixing time varies depending on moisture content and temperature, but is usually 1.
The time is 5 seconds to 20 minutes, preferably 20 seconds to 5 minutes. It is preferable that the water in the hydrous rubber is gradually removed during kneading or divided by -4 after kneading. For the latter operation, it is preferable to use an extractor dryer.

In the present invention, the modified rubber (%) is produced by adding and kneading compounding agents such as inorganic fillers, softeners, plasticizers, colorants, anti-aging agents, vulcanizing agents, and vulcanization accelerators that are normally used in rubber. Then vulcanize and mold.

The rubber of the present invention can be used alone or mixed with other rubbers.
Can be widely used in rubber field.

Hereinafter, the present invention will be specifically explained with reference to Examples.

1R2200) was dissolved in a solvent in the proportions shown in Table 1, maleic anhydride powder of the weight shown in Table 1 was added, and the mixture was stirred for 3 minutes. Approximately 1/1 of the rubber solution! Steam is blown into the aqueous layer to which a volume of water has been added for about 20 minutes, and the mixture is heated to about 95°C.
The solvent was evaporated and a rubber was precipitated. 120% of precipitate
It was rolled to a moisture content of 181°C. Next, Table 1
The water-containing rubber was mechanically sheared using a mixer (roll) at the temperature and time indicated in .

After roll kneading at 980C according to the formulation shown in Table 2,
Vulcanization molding was performed at 145° C. for 25 minutes, and a tensile test was conducted according to JIS K6301. The results are shown in Table 3.

Example 6 Using polybutadiene (J8RBR01 manufactured by Japan Synthetic Rubber Co., Ltd.), an experiment was carried out according to the procedures in Table 1 and Example 1.

Table 1 Example 7 Polyisoprene rubber (Japan Synthetic Rubber Co., Ltd. II lR22
00) On-hexane solution (polymer concentration 10%”)
After adding 1.5-maleic anhydride to 383 kg and stirring at room temperature for 30 minutes, a small amount of dispersant was added using a stripper and high temperature steam was blown to remove the solvent. The water content in the obtained hydrous rubber is 41
The weight was -. This water-containing rubber was dehydrated to a water content of 20% by weight using a screw dehydrator, and then a die having a round hole with a diameter of 4.8 cm and a length of 8 cm was used at the outlet, and a die with a diameter of 10 cm with a broken bolt was used. Place in an expansion dryer with a length of 1.5 m under a pressure of 43 to 481 +/ai, 19
Extrusion was carried out at 2-200°C and the rubber was dried. The produced polymer was 39~.

Compounding, vulcanization, and tension J) IE tests were conducted in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Examples 1 and 2 The amount of maleic anhydride and the kneading temperature were set to the values shown in Table 3, and experiments were conducted in the same manner as in Example 1, and the results are shown in Table 3.

Comparative Example 3.4 Using the same rubber as in Examples 1 and 6: polyisoprene rubber and polybutadiene rubber, the formulations shown in Table 2 were made without adding maleic anhydride, and 80
Table 3 shows the results of kneading and vulcanization at °C.

According to the results in Table 3, the modified rubber of the present invention has good processability.
It can be seen that the green strength is high and the vulcanizate has excellent fracture properties.

Table 2 Volima −
100 parts by weight carbon black l8AF
50 h aromatic extender oil (JARAROMA) 10
= Zinc Turtle
5 ・Stearic acid 1 θ

Claims (1)

[Claims] (1) Add 0.5 to 15 parts by weight of maleic anhydride per 100 parts by weight of rubber to a rubber hydrocarbon solution,
Contact with hot water under stirring to evaporate and separate the solvent to form water-containing f5
~50% by weight water-containing rubber mixture,