JP4096450B2 - Surface treatment method for vulcanized rubber molded products - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface treatment method for a vulcanized rubber molded article. More specifically, the present invention relates to a surface treatment method for a vulcanized rubber molded product by radiation irradiation.
[0002]
[Prior art]
The present applicant firstly performs a surface treatment method for a vulcanized rubber molded product, in which a vulcanized rubber molded product having a polyfunctional unsaturated compound attached to the surface is irradiated with radiation such as electron beam, γ-ray, and X-ray. (Japanese Patent Laid-Open No. 1-240536).
[0003]
Although this proposed method achieves the purpose of reducing the friction and detackifying the vulcanized rubber molded article, it does not only require the steps of adhesion and drying of the polyfunctional unsaturated compound, but also uncured There was a problem that it was necessary to cope with the remaining of the functional unsaturated compound on the surface of the molded article.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a vulcanized rubber molding that achieves low friction and non-adhesion on the surface of a molded product by a simple radiation irradiation method without attaching a polyfunctional unsaturated compound to a vulcanized rubber molded product. The object is to provide a surface treatment method for an article.
[0005]
[Means for Solving the Problems]
An object of the present invention is to provide a surface treatment method for a vulcanized rubber molded product in which an electron beam having an acceleration voltage of about 300 kV or less is irradiated in an atmosphere having an oxygen concentration of about 10 to 500 ppm (volume) when irradiated. Achieved by:
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The vulcanized rubber molded products to be surface-treated include primary vulcanization or secondary vulcanization of synthetic rubber or natural rubber such as fluoro rubber, acrylic rubber, silicone rubber, NBR, hydrogenated NBR, ethylene / propylene copolymer rubber (EPDM). Subsequent vulcanized molded products may be mentioned.
[0007]
These vulcanized rubber molded articles are subjected to electron beam irradiation treatment. The electron beam irradiation treatment can treat only the surface of the vulcanized rubber molded article in a very short time of seconds, and can be said to be a treatment method with high productivity. On the other hand, when radiation other than electron beams is irradiated, the radiation penetrates to the inside of the vulcanized rubber molded product and hardens the entire rubber.
[0008]
When electron beam irradiation is performed in the air, ozone is generated, which not only deteriorates the rubber material, but also causes corrosion of metal parts such as electron guns. It is necessary to carry out in an atmosphere having a concentration of about 10 to 500 ppm (volume), preferably about 50 to 100 ppm (volume).
[0009]
Such adjustment of the oxygen concentration is performed by flowing an inert gas such as nitrogen or argon simultaneously with oxygen. An oxygen concentration of about 10 ppm (volume) or less is not only practical because it actually takes a great deal of time and amount of inert gas to achieve such a concentration, but the intended purpose of the present invention. Make it difficult to achieve. On the other hand, when the oxygen concentration is about 500 ppm (volume) or more, problems such as deterioration of rubber material and corrosion of metal parts occur.
[0010]
Since the electron beam irradiation only reduces the tackiness of the rubber surface, in an oxygen concentration atmosphere as described above, an acceleration voltage of about 300 kV or less, preferably about 80 to 250 kV and about 1 to 500 Mrad, preferably about It is carried out under irradiation conditions of an irradiation dose of 5 to 300 Mrad. If the acceleration voltage is higher than this, the electron beam will penetrate deeply and the hardness of the entire vulcanized rubber will become too high, and it will crosslink to the inside of the vulcanized rubber in the same way as when irradiating other radiation such as γ rays. To come. If the irradiation dose is less than this, the intended effect of the present invention cannot be obtained, while if it is more than this, not only the hardness of the surface portion of the vulcanized rubber molded product will be very high but also the elongation at break. Is extremely lowered to cause cracks and the like.
[0011]
【The invention's effect】
In the method of the present invention, it is easy to reduce the friction and non-adhesion on the surface of the molded article by simply irradiating the vulcanized rubber molded article with an electron beam at an acceleration voltage of about 300 kV or less in a specific irradiation oxygen concentration atmosphere. Can be achieved.
[0012]
【Example】
Next, the present invention will be described with reference to examples.
[0013]
Example 1
Fluororubber (Nippon Mektron RE230) 100 parts by weight
MT carbon black 20 〃
Magnesium oxide 15 〃
Vulcanizing agent (DuPont product Diak # 3) 3 〃
Each of the above blended components is kneaded using an open roll, and the kneaded product is subjected to press vulcanization at 150 ° C. for 30 minutes and oven vulcanization (secondary vulcanization) at 250 ° C. for 24 hours to obtain a sheet ( 100 × 100 × 2 mm) was vulcanized.
[0014]
The obtained vulcanized sheet was irradiated with an electron beam under the following conditions using an electron beam irradiation apparatus manufactured by Iwasaki Electric. The oxygen concentration was adjusted by flowing nitrogen gas simultaneously.
Accelerating voltage: 250kV
Irradiation dose: 300Mrad
Irradiation time: Approximately 10 seconds Oxygen concentration during irradiation: 100 ppm (volume)
[0015]
Non-adhesive by measuring the load when vulcanized sheets (area 20 x 20 mm) treated with electron beam irradiation under such conditions are pressurized with a load of 1 kg for 30 minutes and peeled again using an autograph As a guideline.
[0016]
Example 2
In Example 1, the oxygen concentration during irradiation was changed to 50 ppm (volume).
[0017]
Comparative Example 1
In Example 1, the electron beam irradiation was not performed.
[0018]
Comparative Example 2
The vulcanized sheet obtained by the same method as in Example 1 was immersed in a 50% acetone solution of triallyl isocyanurate (Nippon Kasei Kogyo Taik 100) for 10 minutes and then allowed to stand at room temperature for 2 hours. For this immersion-treated vulcanized sheet, the same electron beam irradiation as in Example 1 and load measurement at the time of peeling were performed.
[0019]
Comparative Example 3
In Example 1, the oxygen concentration during irradiation was changed to 1000 ppm (volume). Deterioration due to ozone generation occurred, and microcracks on the irradiated surface and oxidation of the titanium thin film of the electron gun were observed.
[0020]
Example 3
NBR (Nippon Synthetic Rubber Product N240S) 100 parts by weight Magnesium oxide 5 〃
SRF carbon black 50 〃
Calcium carbonate 10 〃
Dioctyl phthalate 20 〃
Anti-aging agent
(Ouchi Emerging Chemical Product Nocrack ODA) 1.5 〃
Vulcanization accelerator
(Ouchi Emerging Chemicals Noxeller D) 1.5 〃
Vulcanization accelerator
(Ouchi Emerging Chemicals Noxeller TT) 1.5 〃
Sulfur 0.3 〃
[0021]
Each of the above blended components is kneaded using an open roll, and the kneaded product is subjected to press vulcanization at 150 ° C. for 15 minutes and oven vulcanization (secondary vulcanization) at 160 ° C. for 2 hours to obtain a sheet ( 100 × 100 × 2 mm) was vulcanized.
[0022]
The obtained vulcanized sheet was subjected to electron beam irradiation and peeling load measurement under the following conditions (however, the pressing time was changed to 1 hour) in the same manner as in Example 1.
Accelerating voltage: 150kV
Irradiation dose: 20Mrad
Irradiation time: Approx. 1 second Oxygen concentration during irradiation: 200 ppm (volume)
[0023]
Comparative Example 4
In Example 3, no electron beam irradiation was performed.
[0024]
Example 4
Acrylic rubber (Nippon Mektron product Noxtite A1095) 100 parts by weight anti-aging agent (Ouchi Emerging Chemicals product NOCRACK CD) 1 〃
FEF carbon black 60 〃
Sodium stearate 1.75 〃
Potassium stearate 0.75 〃
Sulfur 0.25 〃
[0025]
Each of the above blended components is kneaded using an open roll, and the kneaded product is subjected to press vulcanization at 170 ° C. for 10 minutes and oven vulcanization (secondary vulcanization) at 180 ° C. for 8 hours. 100 × 100 × 2 mm) was vulcanized.
[0026]
The obtained vulcanized sheet was subjected to electron beam irradiation and peeling load measurement under the following conditions (however, the pressing time was changed to 1 hour) in the same manner as in Example 1.
Accelerating voltage: 180kV
Irradiation dose: 100Mrad
Irradiation time: Approximately 3 seconds Oxygen concentration during irradiation: 200 ppm (volume)
[0027]
Comparative Example 5
In Example 4, no electron beam irradiation was performed.
[0028]
The measurement results in the above examples and comparative examples are shown in the following table.

Claims (2)

A surface treatment method for a vulcanized rubber molded product, comprising irradiating an electron beam with an acceleration voltage of 300 kV or less in an atmosphere having an oxygen concentration of 10 to 500 ppm (volume) when irradiated with the vulcanized rubber molded product. 2. The surface treatment method for a vulcanized rubber molded article according to claim 1, wherein the oxygen concentration during irradiation is adjusted by flowing an inert gas simultaneously.