JPS6281425A - Surface treatment of vulcanized rubber molding - Google Patents

Abstract

PURPOSE:To obtain a nonsticky, low-friction coefficient vulcanized rubber molding having a surface-treated layer excellent in adhesion and elasticity and suited for oil seals, diaphragms, O-rings, etc., by treating the surface of a specified vulcanized rubber molding with metallic Na in liquid NH3. CONSTITUTION:100pts.wt. rubber such as acrylonitrile/butadiene rubber is mixed with 1-100pts.wt. cellulose in the form of a powder or a fiber of a length of 10-200mu and a width of 0.1-1mu and a filler, a vulcanizer and other additives, and the mixture is molded by vulcanization under vulcanization conditions to obtain a vulcanized rubber molding. The obtained molding is surface-treated by immersion in a solution comprising 1l of liquid NH3 and 1-50g of metallic Na at -70--34 deg.C for 0.5-120min.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface treatment of vulcanized rubber molded articles. More specifically, the present invention relates to a surface treatment method for a vulcanized rubber molded product that improves the adhesiveness, frictional properties, etc. of the vulcanized rubber molded product.

[Conventional technology]

In general, rubber has a high frictional resistance, so molded products made of rubber may have a high sliding resistance, make noise, or wear out, so there are restrictions on the uses.

For this reason, various methods have been proposed to chemically or physically treat the surface of vulcanized rubber molded products. However, chemical treatment methods such as mineral acid treatment harden the surface of the molded product and cause it to become rubbery. In addition, physical treatment methods such as coating methods, high-energy etching methods, and deposition methods cannot fully achieve the objectives of non-sticking and low friction coefficients. However, the disadvantage is that the processing cost is high.

[Problem that the invention seeks to solve]

Applicant Taku first chemically treated the surface of a vulcanized fluororubber molded product among various vulcanized rubber molded products by treating it with metallic sodium in liquid ammonia, making it non-adhesive. It has been found that the purpose of reducing the coefficient of friction can be achieved (Japanese Patent Application No. 60-8898+), but on the other hand, when this method is applied to various vulcanized rubber molded products other than vulcanized fluororubber molded products, it is possible to achieve the non-adhesive The objectives of reducing friction and reducing the coefficient of friction were not achieved.

Therefore, the present inventors have conducted various studies in search of a method that can be broadly applied to various vulcanized rubber molded products in general, and as a result, the inventors have determined that a vulcanized rubber molded product containing cellulose mixed therein may be used. It has been found that this problem can be solved.

[Means for Solving the Problem] and [Operation] Therefore, the present invention relates to a method for surface treatment of a vulcanized rubber molded product, and the surface treatment of a vulcanized rubber molded product is performed using a vulcanized rubber molded product mixed with cellulose. This is done by treating the product with metallic sodium in liquid ammonia.

Vulcanized rubbers to which the method of the present invention is applied include natural rubber, styrene-butadiene rubber, butyl rubber, acrylonitrile-butadiene rubber, ethylene-propylene (-
Examples include various synthetic rubbers such as diene) rubber, chloroprene rubber, acrylic rubber, and fluororubber.

Examples of celluloses blended into these vulcanized rubbers include cellulose, cellulose esters represented by acetylcellulose, and cellulose ethers such as methylcellulose and carboxycellulose. 1 (1-200 μn
+, width approximately 0.1 to 1 μl11).

Cellulose is used in a proportion of about 1 to 100 parts by weight, preferably about 10 to 50 parts by weight, per 100 parts by weight of rubber. If the mixing ratio is lower than this, the desired treatment effect cannot be obtained except for the fluororubber, while if the mixing ratio is higher than this, the original properties of the rubber will be impaired. In addition to cellulose, fillers, vulcanizing agents, and other additives that are normally added to rubber may be optionally added to the rubber compound as needed, depending on the type of rubber used. Vulcanized under specific vulcanization conditions.

The surface treatment of the obtained cellulose-containing vulcanized rubber molded article is carried out using a solution containing about 1 to 50 g, preferably about 3 to 20 g of metallic sodium in liquid ammonia IQ.
This is carried out by immersion at a temperature of -70 to -34°C, preferably -45 to -35°C for about 0.5 to 120 minutes, preferably about 5 to 90 minutes.

As mentioned above, this treatment method is a chemical surface treatment method, and the reaction mechanism is that liquid ammonia first forms a complex with metallic sodium, and the hydroxyl groups of cellulose blended into the rubber form a complex with ammonium salt. It can be thought of as a substitution reaction.

Therefore, the amount of change in the reacted surface treatment layer increases as the amount of cellulose increases, the concentration of sodium increases, and the reaction time increases. For this reason, the sodium concentration as mentioned above is used, that is, at least 1 g of metallic sodium in liquid ammonia IQ is used, but even if it is used at a concentration of more than about 50 g, the treatment effect does not increase significantly.

〔Effect of the invention〕

As a result of this treatment, a treated layer is formed on the surface of various vulcanized rubber molded products, and this treated layer has the properties of good adhesion to various rubbers, non-stick properties, and an extremely low coefficient of friction. ing. Furthermore, the formed treated layer has elasticity and does not generate any cracks when stretched. Therefore, the method of the present invention can be applied to oil seals, valves, diaphragms, O-rings, etc., which are vulcanized products of various rubbers, which have problems such as stickiness and friction, and can effectively solve these problems. let

〔Example〕

Next, the present invention will be explained with reference to examples.

Example 1 Cellulose powder θ~40 sulfur
0.8 Tetramethylthiuram disulfide 2.5 A blend of the above composition,
Knead with a 12-inch open roll, press this with a 180°C heat press for 4 minutes, and mix 240 x 120 x
A 2 mm test piece was prepared.

This test piece was placed in a treatment solution containing 15 g of sodium metal in liquid ammonia JQ at -40°C for 1 hour.
After immersion treatment for 0 minutes, and then thoroughly rinsing with water and drying, the treated product was measured using a Hayton surface property measuring machine.
The friction coefficient was measured under the conditions of a load of 10 g and a test speed of 50 mm/min, and the results are shown in Table 1 below along with the values of the untreated sample.

Table 1 Cellulose - 1 cliff, 1 reed, 111 plates L ij! ! jL filling 1 stroke 1 0
2.1 2.12 10 1.
7 0.83 20 1.3 0.
74 40 1.2 0.3 Furthermore, the surface-treated test pieces were stretched 100%, but no cracks were observed on the surface of any of them.

Example 2 Ft? F Carbon black 40 Methyl cellulose powder 0-30 Dibasic lead phosphite 5 Stearic acid
1 Hexamethylene diamine carbamate 0.7 The above blended composition was kneaded using a 12-inch open roll, pressed for 10 minutes in a 180°C hot press, and then crosslinked in an oven at 150°C for 15 hours. A test piece of 240 x 120 x 2nv+ was prepared.

This test piece was placed in a treatment solution containing tog of metallic sodium in liquid ammonia LA for 2 hours at -40°C.
Immerse for 0 minutes, then wash with water until the pH becomes neutral,
It was dried at 100°C for 1 hour.

The tackiness of this treated product was measured as follows. That is, a surface treated test piece with a surface area of 1 d is placed on an aluminum plate, a metal body is placed on top of it and adhered with instant adhesive, and a load of 500 g is applied to the adhered metal body.
Place a weight on it and leave it in an oven at 150°C for 24 hours. Thereafter, the weight was removed, a spring scale was hooked to the metal part, and the balance was lifted to measure the adhesive force between the vulcanized rubber and the aluminum plate. The results obtained are
The values are shown in Table 2 below along with the values for the untreated product.

Table 2: Methylcellulose 1F μC Mey-K Furthermore, when the surface-treated test pieces were stretched 100%, no cracks were observed on the surface of any of them.

Example 3 Cellulose powder θ
~20 Magnesium Oxide
Calcium trihydroxide
5 The above blend was kneaded using a 12-inch open roll.

This was pressed with a heat press at 180°C for 10 minutes, and then heated to 240°C.
A test piece of ×120X2+i■ was prepared and heated to 200°C.
Crosslinking was carried out in an oven for 24 hours.

This test piece was immersed for 15 minutes at -40°C in a treatment solution containing 5 g of metallic sodium in liquid ammonia IQ, thoroughly washed with water, and dried. p after rotation for 10 minutes using
The v value (P: pressure kg/aJ, V: speed m/sec) was measured. The obtained results are shown in Table 3 below, and it can be seen that the treated product showed a high pv value, that is, it had good wear resistance.

(Margin below) Table 3 Cellulose hourly value Dan -11 Iku) -Last W' thing Okitei dog- 100,050,1 2100,070,3 3200,10,5

Claims (1)

[Claims] 1. A method for surface treatment of a vulcanized rubber molded product, which comprises treating a vulcanized rubber molded product mixed with cellulose with metallic sodium in liquid ammonia. 2. A method for surface treatment of a vulcanized rubber molded article according to claim 1, which is applied to a vulcanized rubber molded article containing about 1 to 100 parts by weight of cellulose per 100 parts by weight of rubber. 3. The method for surface treating a vulcanized rubber molded article according to claim 1 or 2, wherein the treatment is carried out in the presence of about 1 to 50 g of metallic sodium in 3.1 liter of liquid ammonia.