JPH01207335A - Rubber composition having improved properties for preventing rubber flow - Google Patents

Abstract

PURPOSE:To obtain a rubber composition having improved properties for preventing rubber flow in improved tensile strength and modulus in uncuring without impairing workability, by each blending natural rubber and diene based synthetic rubber with specific two kind of nitroso compounds at specific amounts. CONSTITUTION:The aimed composition obtained by blending (A) 100 pts.wt. natural rubber and/or diene based synthetic rubber with (B) 0.1-5 pts.wt. nitroso compound (e.g., p-nitrosophenol or 1-nitroso-2-naphthol) expressed by formula I and/or formula II (R1-R5 are H, halogen, 1-5C alkyl or alkoxy) and (C) 0.1-5.0 pts.wt. nitroso compound (e.g., N, N-dimethyl-p-nitrosoaniline) expressed by formula III (R1 and R2 are H, 1-6C alkyl, hydroxyalkyl, cycloalkyl or aryl).

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition, and more specifically, the present invention relates to a rubber composition, and more particularly, to the tensile strength and elastic modulus (hereinafter referred to as green strength and green modulus) of a rubber composition when unvulcanized without impairing workability. The present invention relates to a rubber composition that has improved rubber flow prevention properties by improving the properties of rubber.

(Conventional technology) Improving the green strength and green modulus of rubber is
In the rubber processing industry, this is an extremely important issue in order to produce products as designed or to improve workability. In addition, especially for products that are used under harsh conditions, such as tires, each component has different performance requirements, and it is not uncommon for different rubber materials to be used for each component in order to satisfy these requirements.

However, in the step of vulcanizing a rubber article made of a plurality of rubber members, it has often been impossible to arrange the rubber members in a desired designed structure due to the flow of rubber between adjacent rubber members. In particular, during vulcanization of tires, as the tire inner pressure increases due to the bladder, the inner liner rubber is subjected to tension and at the same time is strongly pressed against the carcass compound, causing the inner liner rubber to be pushed between the carcass ply cords. As a result, the ply coating rubber may separate from the cord, causing ply separation, and in severe cases, the ply cord may be exposed from the inner liner rubber, causing failures such as tube punctures and ply separation. In addition, the effective thickness of the inner liner rubber was reduced, its properties as an air barrier were degraded, and the appearance was also unfavorable.

In order to prevent such problems, it is possible to increase the green strength of the rubber, for example, by increasing the green strength through ionic bonding, by creating a relatively small network during unvulcanization, or by adding high molecular weight components. Methods that utilize the entanglement of polymers, methods that improve green strength by increasing the crystallinity of polymers, and methods that involve the addition of block polymers or additives are known.

Among these, the method of increasing green strength by blending nitrosophenol described in Japanese Patent Publication No. 48-3900 can be said to be a relatively useful method from the viewpoint of effectiveness and economy.

(Problem to be Solved by the Invention) However, this nitrosophenol reacts with the polymer during rubber kneading and improves green strength through hydrogen bonding of 10H groups. It had the disadvantage that workability and extrusion workability were significantly reduced due to the high green strength. This is a common problem not only when using nitrosophenols, but also with most green strength improvement methods.

That is, in the prior art, there is currently no rubber composition that has improved green strength and green modulus without impairing rolling workability or extrusion workability, and that sufficiently prevents rubber flow.

Therefore, the object of the present invention is to achieve rolling, which could not be achieved in the past.
The object of the present invention is to provide a rubber composition that has improved green strength and green modulus without impairing extrusion workability and has improved flow prevention properties.

(Means for Solving the Problems) As a result of intensive research to solve the above problems, the present inventors found that rolling workability and extrusion workability depend on viscosity at high shear rates, and rubber flow at low shear rates. Based on this knowledge, when at least two specific nitroso compounds were blended in predetermined amounts into a rubber composition, workability was reduced as shown in Figure 1. The present invention was completed by confirming that it is possible to increase the strength of greens. In addition, FIG. 1 shows, in addition to the rubber compounding of Example 1, which will be described later, excluding the nitroso compound, (1) no nitroso compound is compounded, (2) 0.5 parts by weight of 2-methyl-4-nitrosophenol is compounded, and (2) 2- 1.0 parts by weight of methyl-4-nitrosophenol, ■ 1.0 parts by weight of p-nitrosodiphenylamine, ■ 1.0 parts by weight of 2-methyl-4-nitrosophenol.
3 shows the results of measuring the high shear rate viscosity and low shear rate viscosity of each rubber composition in the case where 1.0 parts by weight of p-nitrosodiphenylamine and 1.0 parts by weight of p-nitrosodiphenylamine were mixed in the same manner as in Example 1.

Therefore, the present invention provides the following general formula: % formula % () (in the formula R+, Rz, Ri, Rs and R5 may be the same or different and each represents a hydrogen atom, a halogen atom, or an alkyl group or alkoxy group having 1 to 5 carbon atoms); / or (I
I) 0.1 to 5 parts by weight and the following general formula ([) (In the formula, Ro and Rt are each a hydrogen atom and a carbon number of 1 to
6 represents an alkyl group, a hydroxyalkyl group, a cycloalkyl group, or an aryl group. The present invention relates to a rubber composition with improved rubber flow prevention properties, which contains 0.1 to 5.0 parts by weight of at least one nitroso compound represented by the following formula.

The rubber components used in the present invention include natural rubber and synthetic polyisoprene rubber as a diene-based synthetic rubber.
Examples include polybutadiene rubber and styrene-butadiene rubber, which may be used alone or as a blend.

Further, examples of the nitroso compound (1) or (II) used in the present invention include p-nitrosophenol,
2-Methyl-4-nitrosophenol, 2-chloro-4
-Nitrosophenol, 3-chloro-4-nitrosophenol, 3-methyl-4-nitrosophenol, 3.5
-dimethyl-4-nitrosophenol, 3.5-dimethyl-4-nitrosophenol, 2-t-butyl-4
-Nitroso-5-methylphenol, 2-octyl-4
-Nitroso-5-methylphenol, 2,3.6 -1
-dimethyl-4-nitrosophenol, 1-nitrone-
2-naphthol, 2-nitroso-1-naphthol, 5.
Examples include 6-simethoxy-1-nitroso-2-naphthol, and these may be used alone or in combination of two or more. The nitroso compounds used in the examples can be purchased as reagents or purchased from H.E. Albert (H.
, E., AIbert) [Journal of American Chemical Society, 764985]
(1954)), can be obtained by reacting an aqueous sodium nitrite solution to an ethanol aqueous solution of phenols or naphthols and hydrochloric acid at 0°C.

In the present invention, specific examples of the nitroso compound '# (III) include N,N-dimethyl-P-nitrosoaniline (
DMNA), N,N-diethyl-p-nitrosoaniline (DENA), N-phenyl-p-nitrosoaniline (
to PN), N,N-di-2-hydroxyethyl-p-nitrosoaniline (DBNA), N-methyl-N-hexyl-p-nitrosoaniline, N,N-di-2-hydroxyethyl-p
-Nitrosoaniline, N-ethyl-N-2-hydroxyethyl-p-nitrosoaniline (EIIN8), N-methyl-p-nitrosoaniline (MNA), N-hexyl-P-nitrosoaniline (IINA) and N-cyclohexyl-p-nitrosoaniline (CHNA), which may be used alone or in combination. In addition, when conducting the tests shown in the Examples, the nitroso compound may be a commercially available product or a known synthesis method (J. Willenz) Journal of the Chemical Society (J. Chem. Soc. ,,
1955, p. 1677) was used.

By the way, in the rubber composition of the present invention, in addition to the above-mentioned nitroso compounds, compounding agents commonly used in the rubber industry, such as softeners, anti-aging agents, vulcanization accelerators,
It goes without saying that a vulcanization accelerator, a vulcanizing agent, a reinforcing filler, etc. can be appropriately blended within the range of usual blending amounts as necessary.

(Function) In the present invention, the nitroso compound (1) or (I
The blending amount of [) is 0.1 to 5 parts by weight, preferably 0.3 to 5 parts by weight.
The amount is set within the range of 2 parts by weight, because if it is less than 0.1 part by weight, the effect of addition will not be exhibited, while if it exceeds 5 parts by weight, rolling or extrusion workability will deteriorate, which is not preferable.

In addition, the blending amount of nitroso compound (III) was 0.1 to 5.
Part by weight, preferably within the range of 0.3 to 2 parts by weight.The reason for this is that if it is less than 0.1 part by weight, the added effect will not be exhibited, while if it exceeds 5 parts by weight, polymer chain cleavage will occur. This is because if the amount is too large, the mechanical properties after vulcanization will deteriorate, which is undesirable.

(Example) Next, the present invention will be explained in detail with reference to Examples and Comparative Examples.

1-4, 6 1-3 A rubber composition was prepared according to the formulation shown in Table 1 below, and the green modulus and green strength at room temperature were determined by J.
Measured according to IS K 6301. Also, Monsanto Processability Tester (manufactured by Monsanto)
was used to evaluate the shear rate dependence of viscosity at 100°C. The results are also listed in Table 1. Furthermore, rolling workability was also evaluated at the factory.

*l Unit: Kpas, sec As is clear from Table 1, the viscosity of the rubber composition of the present invention is highly dependent on the shear rate, and the green modulus and green strength, which are indicators of workability and prevention of rubber flow, are improved. It can be seen that it is possible to achieve both workability and workability.

(Effects of the Invention) As explained above, in the rubber composition of the present invention, by using at least two specific nitroso compounds in combination, the rubber composition during vulcanization has improved rolling and extrusion workability that could not be achieved conventionally. It becomes possible to achieve both flow prevention properties and is extremely useful for rubber articles made of multiple members such as tires.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between high shear rate viscosity and low shear rate viscosity.

Claims (1)

[Claims] 1. For 100 parts by weight of at least one rubber selected from the group consisting of natural rubber and diene-based synthetic rubber, the following general formula: ▲ Numerical formula, chemical formula, table, etc. Yes (I) There are mathematical formulas, chemical formulas, tables, etc. 0.1 to 5 parts by weight of a nitroso compound (I) and/or (II) represented by ~5 alkyl or alkoxy groups) and the following general formula ▲ Numerical formula, chemical formula, table, etc. ▼ (III) At least one nitroso compound represented by (in the formula, R_1 and R_2 each represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a hydroxyalkyl group, a cycloalkyl group, or an aryl group) 0.1 A rubber composition with improved rubber flow prevention properties, characterized in that it contains ~5.0 parts by weight.