JPH04103646A - Rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition capable of effectively preventing ozone deterioration in high-temperature area and having excellent appearance by blending a diene based rubber with a specific petroleum paraffin at a prescribed ratio. CONSTITUTION:The objective rubber composition obtained by blending (A) 100 pts.wt. diene-based rubber with (B) 1-10 pts.wt. paraffin wax containing 3-5wt.% 34-44C straight-chain saturated hydrocarbon, >=2wt.% 22-33C straight- chain saturated hydrocarbon and 34-44C straight-chain saturated hydrocarbon of arithmetic mean weight content 0.5% higher than that of 22-33C straight-chain saturated hydrocarbon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rubber composition that can suitably prevent ozone deterioration in a relatively high temperature range, for example from 20°C to 70°C, and also has excellent appearance. be.

(Prior Art) Conventionally, it has been known to use wax-based anti-aging agents to prevent rubber from cracking due to the atmosphere or sunlight.

When a wax-based anti-aging agent is blended into rubber, it oozes out to the surface to form a thin film, and this thin film prevents rubber from coming into contact with ozone, thereby preventing aging.

Various wax-based rubber anti-aging agents have been commercially available for a long time, but the effect of oozing out and forming a thin film depending on the temperature and the phenomenon of the thin film once formed peeling off and falling off differ, so in order to improve this, we Anti-aging agent with carbon number distributed over a wide range from 16 to 41 (U.S. Patent No. 3.423.3)
48 specification), or anti-aging agents containing 25-70% of linear hydrocarbons having 26 to 29 carbon atoms and 30-75% of linear hydrocarbons having 34 to 40 carbon atoms (Japanese Patent Publication No. 34 -25062) etc. have been proposed.

Also, JP-A-48-91141 and JP-A-63-1453
In each publication of No. 46, carbon numbers 26 to 29 and carbon numbers 34 to
40 content and low carbon number content of 30 to 33,
A carbon number distribution having so-called two peaks has been disclosed.

Furthermore, in JP-A-1-230648, carbon number 36
Anti-aging agents have been disclosed that can increase the content of normally saturated hydrocarbons of ~51 and improve ozone resistance.

(Problems to be Solved by the Invention) However, all of the previously known wax-based anti-aging agents described above impair the appearance, have poor ozone resistance at relatively high temperatures, and Even if the amount of ozone is high (this was not necessarily sufficient for rubber compositions that require improvement without impairing ozone resistance and appearance).

Furthermore, in the above-mentioned Japanese Patent Application No. 1-230648, C51-
Although the content of normal saturated hydrocarbons in No. 51 is specified as 20 to 45%, for example, since there is no specification for each carbon number component, excessive bloom may occur. For example, at 40 to 50 degrees Celsius, where wax tends to bloom, Excessive content may cause the appearance to become white or brown, resulting in defects.

Therefore, the purpose of the present invention is to achieve a relatively high temperature range, for example, from 20°C to
The object of the present invention is to provide a rubber composition that can suitably prevent static ozone deterioration at 70°C, is free from excessive wax bloom, and has an excellent rubber surface appearance.

(Means for Solving the Problems) In order to solve the above problems, the rubber composition of the present invention contains linear saturated hydrocarbons having 34 to 44 carbon atoms of 3 to 5 weight by weight. %, any type of linear saturated hydrocarbons having 22 to 33 carbon atoms is 2% by weight or more, and the arithmetic average of linear saturated hydrocarbons having 34 to 44 carbon atoms A petroleum paraffin wax whose weight content C34-44 (wt%) is 0.5 wt% or more greater than the arithmetic average weight content C22-33 (wt%) of linear saturated hydrocarbons having 22 to 33 carbon atoms, Diene rubber 10
It is characterized by blending 1 to 10 parts by weight with respect to 0 parts by weight.

When the component ratio of C34-44 is less than 3%, the high temperature is 50 to 70%.
The ozone resistance of 8C is poor, and when it exceeds 5%, the appearance is poor. Therefore, the present invention requires a range of 3 to 5%.

If cwt-ss is less than 2%, ozone resistance will be poor when the operating temperature is low (10 to 30°C), and if it is 2% or more, desirable ozone resistance will be obtained. That is, ozone activity decreases below 0°C, but ozone cracks occur even below 0°C because wax bloom becomes smaller. Therefore, in order to prevent ozone cracks due to low temperatures, the content of Cwt-ss is required to be 2% or more.

If the arithmetic average weight content of C34-44 is not greater than that of Cm-33 by 0.5% by weight or more, ozone resistance in the target temperature range will be insufficient; ozone resistance is obtained.

The blending amount of the above petroleum paraffin wax is 10% of the diene rubber.
If it is less than 1 part by weight relative to 0 parts by weight, the amount of bloom on the rubber surface will be small and the function of the bloom film will be insufficient.If it is more than 1 part by weight of IO, the amount of bloom will be large, impairing the appearance and damaging the rubber. It is unsuitable because it also reduces strength.

In the petroleum paraffin wax according to the present invention, the total content of linear saturated hydrocarbons is preferably in the range of 85 to 65%. When it is more than 85%, the blooming rate is high and the appearance may be impaired, and when it is less than 65%, the blooming rate is slow and the ozone resistance performance cannot be sufficiently exhibited at the initial stage of use.

The petroleum paraffin wax according to the present invention is called petroleum microcrystalline wax, and contains so-called normal paraffins, which are linear saturated hydrocarbons, isoparaffins (branched saturated hydrocarbons) as non-normal paraffins, and naphthenes (alicyclic It contains a small amount of aromatic hydrocarbons.

The diene rubber used in the present invention includes natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, isoprene-butadiene copolymer rubber, styrene-isoprene copolymer rubber, or styrene-butadiene-based rubber. A rubber polymer made by polymerizing a conjugated diene such as isoprene terpolymer rubber as one of the main monomer components. These rubbers may be used alone or
They may be used in a blended manner.

The method for producing the petroleum paraffin wax according to the present invention is not particularly limited, and may include directly obtaining the desired product by distillation from conventionally known petroleum-based or synthetic waxes;
Alternatively, a method can be used in which a wax containing evenly linear hydrocarbons having 22 to 33 carbon atoms is blended with a wax rich in linear hydrocarbons having 34 to 44 carbon atoms.

Generally, specific methods for obtaining such petroleum paraffin wax include the following methods. Crude oil is distilled under normal pressure, the bottom oil is further distilled under reduced pressure, the distillate is extracted with a solvent such as phenol or furfural to remove aromatic components, and preferably subjected to hydroxylation purification, and then ketones and aromatic components are removed. Solvent film waxing is performed using a mixed solution, etc., and crude wax is obtained in the dewaxing process as a by-product when dewaxing oil is obtained as a lubricating oil base oil. This crude wax is further deoiled with a solvent to remove low boiling point waxes to obtain an oil-free wax. It is also possible to obtain deoiled wax by sweating and deoiling crude wax. All deoiled waxes can be further refined by treatment with sulfuric acid, clay, etc.

As a method for separating normal paraffins, methods disclosed in, for example, JP-A-56-14583, JP-A-56-15218, and JP-A-56-15219 can be adopted.

In order to obtain the petroleum paraffin according to the present invention, the desired product can be obtained by distilling the deoiled wax obtained by the usual method as described above, or preferably by selecting crude oil as a raw material, and by distilling it at atmospheric pressure. When distilling residual oil under reduced pressure to obtain distillate oil, distillation is performed in a narrow boiling point range so that hydrocarbons having the composition according to the present invention are substantially distilled out, for example, hydrocarbons having 22 to 33 carbon atoms are distilled. The method is to obtain a fraction substantially containing hydrocarbons and a fraction substantially containing hydrocarbons having 34 to 44 carbon atoms, and to mix these.

Furthermore, the petroleum paraffin wax according to the present invention may include polyolefins obtained by polymerizing olefins such as ethylene, waxes obtained by thermally decomposing polyolefins, waxes synthesized by the Hirascher Trogis method, and furthermore, petroleum paraffin waxes that may be subjected to operations such as distillation and extraction. A composition having a predetermined number of carbon atoms can be used.

The composition of the petroleum paraffin wax was determined using a capillary CC (product name HP-5890) as an apparatus and an aluminum-coated capillary column (CBM) as a column.
-1, using Shimadzu Corporation (manufactured by Kiki, 25 m), carrier gas helium, flow rate 4 i/min, column temperature 1
Measurement was carried out under conditions of 80°C to 390°C and a temperature increase rate of 15°C/min.

(Example) Next, the present invention will be specifically explained using examples.

Using the 6 types of petroleum paraffin wax shown in Table 1, 12 types of rubber compositions were kneaded according to the formulations (parts by weight) shown in Tables 2 and 3, and then vulcanized at 155°C for 30 minutes. A rubber sheet piece was obtained.

These 12 types of test pieces were held in an elongated holder and placed in an ozone weather meter device at an ozone concentration of 1100p.
The amount of cracks generated after statically standing for 72 hours was visually evaluated under the conditions of p, temperature of 10° C., and elongation rate of 30% (Table 2) and 50% (Table 3).

In addition, the appearance of the rubber surface was determined by placing it in a constant temperature oven at a temperature of 40°C.
After leaving each test piece for a week, visually evaluate the appearance of the rubber surface. Those with no whitening on the surface are good, those with slightly whitening on the surface are acceptable, and those with significant whitening on the surface and poor appearance. It was evaluated on a three-level scale, with "poor" being considered poor.

In Table 2, the rubber composition of Comparative Example 3 was evaluated relative to the index of 100, and the index of no cracks was 0.

Further, in Table 3, the rubber composition of Comparative Example 6 was similarly evaluated with an index of 100.

(Effects of the Invention) As explained above, in the rubber composition of the present invention, by blending a predetermined amount of a specific petroleum rough-in wax into the diene rubber, ozone can be effectively removed in a relatively high temperature range. The effect is that deterioration can be prevented and the appearance is excellent.

Procedural amendment

Claims (1)

[Claims] 1. Linear saturated hydrocarbons having 34 to 44 carbon atoms account for 3 to 5% by weight of any carbon number;
The arithmetic average weight content of linear saturated hydrocarbons having up to 33 carbon atoms of any carbon number is 2% by weight or more, and the arithmetic average weight content of linear saturated hydrocarbons having up to 34 carbon atoms @C@_3_4_-
_4_4 (wt%) is the arithmetic average weight content of linear saturated hydrocarbons having 22 to 33 carbon atoms @C@_2_2_-_3
A rubber composition characterized in that 1 to 10 parts by weight of petroleum paraffin wax, which is 0.5% by weight or more larger than _3 (by weight), is blended with respect to 100 parts by weight of diene rubber.