JPS61143441A - Production of rubber-fiber composite material - Google Patents

Abstract

PURPOSE:To obtain the titled composite material by coating fibrous reinforcer with a coating rubber partially crosslinked by electron been irradiation to significantly improve the green strength of the rubber without deterioration of said reinforcer due to irradiating only on the rubber. CONSTITUTION:A coating rubber is irradiated with electron beams to partially crosslink said rubber. A fibrous reinforcer is then coated with the resulting rubber, thus obtaining the objective composite material. The original rubber is e.g., natural rubber, SBR, BR, NBR. The does to be absorbed for the electron beam is 1-15 Mrad, (pref. 2-10 Mrad).

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a rubber/fiber composite material, and more specifically, the present invention relates to a method for manufacturing a rubber/fiber composite material, and more specifically, a method for manufacturing a rubber/fiber composite material, in which only the rubber phase is irradiated with an electron beam to prevent strength deterioration of the fiber reinforcing material. , relates to a method for improving the green strength of composite rubber.

[Prior art]

Composite materials of rubber and fiber reinforcement have traditionally been used as frame materials for tires, belt hoses, and the like.

Fiber reinforcement materials include nylon 6, nylon 66, polyester, rayon, vinylon, aromatic polyamide (
For example, in addition to organic synthetic fibers such as Kevlar (trademark), natural fibers such as cotton, and steel cords, many other types can be used.

Then, a composite material is manufactured by coating (also referred to as topping) rubber on these fiber reinforcing materials. 1. However, bonding the fiber reinforcement material and rubber requires advanced technology, and this technology directly affects the durability of products such as tires and belts.

Therefore, in order to ensure adhesive strength, the surface of the fiber reinforcement material is usually treated with a primer, steel cords, etc. are plated, and the coating rubber that covers the fiber reinforcement material is also compounded. Various efforts have been made.

However, since rubber/fiber composite materials are basically a combination of soft, i.e., rubber, and rigid, i.e., reinforcing fiber materials, they often lose their shape by the time they are formed into tires, belts, etc. Inconveniences such as the reinforcing fibers arranged in a straight line becoming irregular and the coating rubber phase elongating resulting in a thinner gauge have occurred, which has caused deterioration in product performance in terms of adhesion and uniformity.

In addition, especially when the fiber reinforcement material is steel cord, cobalt-based metal salts are often blended into the coating rubber.
As the amount of rubber compounded increases, the green strength of the rubber decreases, and the above-mentioned disadvantages as a composite material are further exacerbated, so the balance between processability and adhesive performance is currently severely restricted. be.

Therefore, as a countermeasure to this problem, it is possible to improve the green strength of rubber by adding green strength-imparting agents such as nitrosamines, partially causing a reaction of the sulfur already in the mixture by heating, or adding dicumyl peroxide, etc. Attempts have been made to partially crosslink the material.

However, nitrosamines and the like are not preferred from the standpoint of environmental hygiene (the heating method is difficult to suppress the reaction of sulfur midway through, and is not industrially suitable.

Further, the method using peroxide is not preferable if sulfur is used in combination because this will inhibit crosslinking reactions between the two.

On the other hand, there is a method that uses electron beam irradiation as a technique that has recently become popular.

That is, when a composite of rubber and fibers is irradiated with an electron beam, the rubber phase of the composite material is partially crosslinked, so that the green strength is improved, and this method is suitable as a method for solving the above-mentioned conventional drawbacks.

It also has the advantage of being able to freely adjust the green intensity depending on the degree of absorption of the electron beam, making it the most effective method industrially.

However, on the other hand, when a rubber/fiber composite is irradiated with an electron beam, not only the rubber phase but also the fiber reinforcement material is irradiated.
The fiber reinforcing material is degraded by the electron beam, and a phenomenon in which the strength of the fiber reinforcing material decreases occurs.

Such a decrease in strength occurs naturally in cellulosic fibers, such as collapsible polymers such as viscose rayon, but even in crosslinked polymers such as aliphatic polyamides such as nylon 6 and nylon 66, molecular cleavage occurs when irradiated with an electron beam in air. Deterioration such as this is seen.

Furthermore, the degree of deterioration depends on the chemical structure of the fiber reinforcing material and the absorbed dose of the electron beam, and in many cases there is a critical point in the absorbed dose dependence. Of course, since rubber is more amorphous than fiber reinforced materials, it is less affected by electron beams.

[Purpose of the invention]

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks, to prevent deterioration of fiber reinforcing materials due to electron beam irradiation to rubber/fiber composite materials, and to improve the green strength of reinforcing rubber.

[Structure of the invention]

The method for manufacturing a rubber/fiber reinforcing material of the present invention that achieves the above object is characterized by irradiating coated rubber with an electron beam to partially crosslink the rubber, and coating the fiber reinforcing material with the electron beam irradiated rubber. That is.

In the present invention, the coated rubber is first irradiated with an electron beam.

The coated rubber used here includes rubber that can be crosslinked by electron beam irradiation, such as natural rubber, SBR,
Examples include synthetic rubbers such as BR, NBR, and EPDM, and blend rubbers thereof.

The absorbed dose of electron beam is usually 1 to 15 Mrad, preferably 2 to 10 Mrad.

When the absorbed dose exceeds 15 Mrad, collapse due to main chain scission becomes dominant, and when the absorbed dose is less than 1 Mrad,
This is not preferable because sufficient green strength cannot be obtained.

Electron beam irradiation is normally performed in air, and the temperature during irradiation is room temperature.

Next, the fiber reinforcing material is coated with the coated rubber that has been irradiated with electron beams to produce the composite material of the present invention.

As for the coating method, the conventional rubber coating method used in the production of rubber/fiber composite materials can be used as is. For example, the original cord is passed through a calender roll equipped with four rolls, and the rubber is coated on both sides of the cord. There is a method of rubbing at the same time.

In addition, fiber reinforcing materials include natural fibers such as cotton, artificial fibers such as viscose rayon, and nylon 6 and nylon 6.
6 grade polyamide, polyester, aromatic polyamide,
Includes steel cord, etc.

〔Effect of the invention〕

As described above, according to the present invention, a rubber/fiber composite material is manufactured by irradiating a coated rubber with an electron beam to partially crosslink the rubber, and coating a fiber reinforcing material with the electron beam irradiated rubber. Ru.

That is, since only the coated rubber is irradiated with electron beam in advance,
Deterioration of the fiber reinforcing material itself in the composite material due to electron beams can be completely prevented.

Further, since the coated rubber itself is partially crosslinked by the electron beam, there is an advantage that the green strength of the coated rubber is improved.

Furthermore, since the deterioration of the coated rubber is prevented and the green strength is improved, when the rubber/fiber reinforcing material obtained by the present invention is used as a reinforcing layer for tires, conveyor belts, etc., the fiber reinforcing material will not be uneven during the molding process. It is possible to eliminate inconveniences such as smearing and maintain a uniform state.

Examples of the present invention will be described below.

〔Example〕

Examples 1 and 2 A coated rubber sheet with a thickness of 21 mm made of a blend of natural rubber, SBR and BR was irradiated with an electron beam at an acceleration voltage of 750 kV so that the absorbed dose was 4 Mrad and 10 Mrad. The rubber was kneaded with a roll for 1 to 2 minutes, and then fed to a calender roll and simultaneously passed through an original rayon cord (1650 d/2) to produce a composite material in which the surface of the rayon cord was coated with rubber.

Table 1 below shows the results of measuring the strength and elongation characteristics of the rayon cord taken out from the composite material and the green strength of the composite material.

Comparative Examples 1.2 and 3 Comparative Example 1 is a rayon cord taken out of a composite material that was not irradiated with an electron beam for comparison.

Comparative Example 2.3 is a composite material made of the same rayon cord coated with a coated rubber of the same composition as in the above example, with a total gauge of 1.5 mm, which was irradiated with an electron beam under the same conditions as in the above example, and was similarly treated. The strength and elongation characteristics of the rayon cord and the green strength of the composite material were measured.

The results are also listed in Table 1.

As is clear from Table 1, in Examples 1 and 2, there was no change in the strength and elongation of the rayon cords, and the green strength was almost the same as in Comparative Examples 2 and 3.

On the other hand, in Comparative Examples 2 and 3, the rayon strength was reduced by 15 to 40% compared to Comparative Example 1, and the elongation was also significantly reduced. That is, it is clear that the rayon cord has deteriorated.

In addition, when irradiation is performed so that the absorbed dose of the coated rubber is 10 Mrad as in Example 2, the sheet surface does not become smooth for about 2 minutes when the coated rubber is kneaded with a roll. You need to be careful because there are some problems, but you can solve the problem by spending about an extra minute of kneading.

The green strength of the composite material is an index of the value obtained by pulling a rectangular sample as shown in Figure 1 in the direction of arrow F using an autograph, and the index is 100%.
The stress at the time of elongation was taken and expressed as 100 in Comparative Example 1 in Table 1 and Comparative Example 4 in Table 2 to be described later, respectively.

In addition, in FIG. 1, 1 indicates a fiber reinforced cord, and 2 indicates a coated rubber.

Examples 3 and 4 Nylon 66 cord was used and treated in the same manner as in Examples 1 and 2.

The measurement results are shown in Table 2 below.

Comparative Examples 4.5.6 and 7 Comparative Example 4 is a case of a composite material without electronic irradiation and a nylon 66 cord extracted from this composite material, and Comparative Examples 5 and 6 are the case of the above comparison using a nylon 66 cord. This is a case where processing is performed in the same manner as in Examples 2 and 3.

Moreover, Comparative Example 7 is the green strength value of a composite material made of rayon cord, which was manufactured by blending a nitrosamine-based green strength imparting agent into coat rubber as a method other than electron beam irradiation.

The measurement results are also listed in Table 2.

From Table 2, it can be seen that in Example 3.4, the cord did not deteriorate and the green strength was higher than that of Comparative Example 4, which was not irradiated with an electron beam. It can be seen that the level is almost the same as in Example 5.6.

Moreover, it can be seen from Comparative Example 7 that even when a green strength imparting agent is used, the effect is much smaller than that of electron beam irradiation.

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[Brief explanation of drawings]

FIG. 1 is a plan view of a sample for green strength measurement of a composite material manufactured according to the present invention. 1.-Fiber reinforcement, 2-Coat rubber.

Claims (1)

[Claims] A method for producing a rubber/fiber composite material, which comprises irradiating a coated rubber with an electron beam to partially crosslink the rubber, and coating a fiber reinforcing material with the electron beam irradiated rubber.