JPH03217440A - Rubber composition for tire sidewall - Google Patents

Abstract

PURPOSE:To obtain the subject composition resistant to surface discoloration and having excellent performance to prevent degradation with ozone by compounding phenylenediamine and a petroleum wax to a diene rubber containing a specific carbon black. CONSTITUTION:The objective rubber composition is produced by compounding a diene rubber composition containing carbon black having an iodine adsorption of <=100g/kg with 0.5-4 pts.wt. (based on 100 pts.wt. of rubber in the composition) of N,N'-di-1-methylheptyl-p-phenylenediamine and 1-4 pts.wt. of a 19-54C petroleum wax. The obtained composition is formed in the form of a sidewall and used in a tire. The carbon number of the petroleum wax is preferably 22-50.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a rubber composition for tire sidewalls, and its object is to provide a rubber composition that exhibits little discoloration in appearance when used as a tire sidewall. An object of the present invention is to provide a composition.

Conventional technology> The diene rubber used for tire sidewalls is
It is well known that materials can eventually become unusable due to deterioration due to ozone, light, or heat.

Various methods have been proposed to prevent such deterioration, and most of them involve the use of various deterioration inhibitors.

In particular, to prevent deterioration due to ozone, N-phenyl-N'isobroby-p-phenylenediamine, N-
Phenyl-N'-1,3-dimethylbutyl-p-7 N-phenyl-N'alwy-p- such as 22-diamine
It is common practice to use phenylene diamine.

<Problem to be solved by the invention> However, these N-phenyl-N'-alkyl-p-phenylenediamines that are currently widely used are
Although ozone resistance performance is satisfactory over a relatively short period of time,
It has a tendency to discolor the tire surface brown, significantly contaminating the appearance of the tire while it is in stock or running, reducing the product value, and furthermore, after long-term use, it has almost lost its resistance to ozone. The problem was that the driver had no choice but to run on the road.

Against this background, the present inventors conducted intensive research to develop a rubber composition that has extremely little discoloration in appearance and has excellent ozone deterioration prevention performance over a long period of time.As a result, the present invention was achieved.

Means for Solving the Problems> That is, the present invention provides a diene rubber composition containing carbon black, the carbon black containing 100 g/k
It has an iodine adsorption amount of 1 g or less, and the rubber 1
00 parts by weight, 0.5 to 4 parts by weight of N,N'-di-1-methylheptyl-p-phenylenediamine and 1 to 4 parts by weight of petroleum wax having 19 to 54 carbon atoms. An object of the present invention is to provide an improved rubber composition for tire sidewalls.

The present invention also provides a tire using the above rubber composition for the sidewall, and a method for improving the hue of the tire sidewall.

In particular, the present invention uses a diene rubber containing a specific carbon black together with a specific N,N'-dialkyl p-phenylenediamine and a specific petroleum wax, thereby achieving extremely low discoloration in appearance and excellent It was discovered that the ozone deterioration prevention performance can be obtained.

In addition to natural rubber, the diene rubber used in the present invention includes diene synthetic rubbers such as synthetic polyisobrene rubber, styrene-butadiene rubber, polybutadiene rubber, butyl rubber, and ethylene-propylene-diene rubber. The rubber can be used in any form, such as alone or as a blend of two or more types.

N,N'-di-1-methylbutyl-p-phenylenediamine used in the present invention is known as a rubber deterioration inhibitor (for example, JP-A-464364). However, there have been no examples of its application to tire sidewalls, and the present invention is the first to reveal that the use of specific carbon blacks and specific petroleum waxes in combination has the effect of suppressing discoloration of sidewalls. It is.

The blending amount of butyl-p-phenylenediamine to N,N'-di-1-methyl is 0.5 to 4 parts by weight per 100 parts by weight of rubber.
Parts by weight. If it is less than 0.5 parts by weight, the ozone deterioration prevention performance will not be sufficient, and if it exceeds 4 parts by weight, mechanical properties will deteriorate and there will be a tendency for discoloration, which is not preferable.

In addition, the petroleum wax used in combination with this anti-deterioration agent,
The carbon number is in the range of 19 to 54, preferably the carbon number is in the range of 22 to 50. The carbon number here refers to the carbon number distribution of hydrocarbons that are components of the wax. It is not preferable to use a petroleum wax containing a significant amount of hydrocarbons having 18 or less carbon atoms or 55 or more carbon atoms because the appearance quality of the tire sidewall deteriorates. The amount of petroleum wax blended is 1 to 4 parts by weight per 100 parts by weight of rubber.

Carbon black, which is another component of the present invention, contains 1
It has an iodine adsorption amount of 00g/kg or less,
For example, HΔF, SPF, FEF, GPF, SRF, etc. can be used. Carbon black with an iodine adsorption amount of more than 100 g/kg is unfavorable in terms of the appearance quality and mechanical properties of the tire sidewall. The amount of carbon black added is not particularly limited, but is generally preferably about 10 to 150 parts by weight per 100 parts by weight of rubber.

In the present invention, in addition to the above-mentioned compounding agents, compounding agents commonly used in the rubber industry, such as vulcanizing agents, vulcanization accelerators, vulcanization accelerators, vulcanization retarders, reinforcing agents, fillers, Plasticizers, softeners, anti-aging agents, tackifiers, and the like can be blended in the usual amounts as necessary.

The rubber composition of the present invention is mixed by a conventional processing method using a mixer such as an Ehalol, a Banbury mixer, or a kneader. Then, it can be formed into a sidewall by a method commonly used in the tire industry and combined with other members to form a tire.

<Examples> The present invention will be explained in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto. In addition, in the following examples, all parts mean parts by weight.

Examples 1, 2 and Comparative Examples 1 to 6 To 100 parts of the diene rubber listed in Table 1, 3 parts of zinc white, 2 parts of stearic acid, 5 parts of γ-romatic oil, and an anti-aging agent (2,2.4- }1 part of dimethyl-1,2-dihydroquinoline polymer), 2 parts of sulfur, 1 part of a vulcanization accelerator (N-t-butyl-2-penzothiazylsulfenamide), and the carbon black listed in Table 1. , an amine compound, and a petroleum wax were mixed and kneaded in a Banbury mixer to obtain a rubber composition. The obtained rubber composition was
After vulcanization at 0° C. for 30 minutes, the physical properties of the rubber were evaluated by the method shown below, and the results are summarized in Table 1.

1. After exposing the external hue change test piece for 20 days outdoors, the test piece was measured using a color difference meter CR-10 manufactured by Minolta Camera Co., Ltd.
L'' (lightness) was measured using 0 J. The smaller the value, the higher the degree of blackness and the better the appearance. At the same time, visual observation was performed, and the results were expressed according to the following criteria.

○ No discoloration △ Slight discoloration × Discoloration to brown 2. The ozone deterioration prevention performance test piece was held in an elongated holder and placed in an ozone weather meter device at an ozone concentration of 5 Qppbm and a temperature of 40°C.
The sample was left under the condition of an elongation rate of 20%, and the time until crack generation was measured by visual observation.

3. Tensile stress M3. .

Based on JIS K-6301, stress at 300% elongation was measured using a dumbbell-shaped test piece.

\ \ \ \ \ \ \ \ \ \ \ The carbon numbers of the petroleum waxes listed in Table 1 were analyzed by gas chromatography, and the analysis conditions were as follows.

Gas chromatography analysis conditions Model Detector Column VANACO G-80 FID Silicon DV-1 (3%) 0. 7 5m Glass Chromosolve WAW DMCS 60-80 mesh 150-320℃ (8℃/min) 320℃ N2 25 1nl/min H2 0. 7 kg/am2 air 1 2
ji! /min 1 Injection carrier gas chart speed 5 mm/+min Effects of the Invention> The rubber composition of the present invention has little discoloration in appearance and is also excellent in ozone deterioration prevention performance. Therefore, it is suitable as a rubber for tire sidewalls. In addition, a tire with this composition applied to the sidewall has excellent commercial value and performance.

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Claims (3)

[Claims] (1) A diene rubber composition containing carbon black, in which the carbon black has an iodine adsorption amount of 100 g/kg or less, and N,N'-di- 0.5-4 parts by weight of 1-methylheptyl-p-phenylenediamine and 19-5 carbon atoms
A rubber composition for tire sidewalls with improved hue, characterized in that it contains 1 to 4 parts by weight of the petroleum wax of No. 4. (2) A tire using the rubber composition according to claim 1 in a sidewall. (3) Iodine adsorption amount 100g/k for diene rubber
g of carbon black or less, and 0.5 to 4 parts by weight of N,N'-di-1-methylheptyl-p-phenylenediamine and 19 to 5 carbon atoms per 100 parts by weight of rubber.
A method for improving the hue of a tire sidewall, which comprises blending 1 to 4 parts by weight of the petroleum wax of No. 4 and molding the mixture into a sidewall.