JPS5912833A - Modification of rubber surface - Google Patents

Abstract

PURPOSE:To improve adhesion property between a paint and a metal or the like, by a method wherein the surface of an unvulcanized or vulcanized rubber is coated with polyphosphoric acid and heated or irradiated with ultraviolet rays. CONSTITUTION:The surface of an unvulcanized or vulcanized rubber (e.g., isoprene rubber) is coated with polyphosphoric acid and heated to an ordinary temperature or a temperature above the softening point of the rubber, or irradiated with ultraviolet rays to introduce a polar group and is then rinsed and dried.

Description

[Detailed description of the invention] The present invention relates to a method for modifying a rubber surface.

When painting rubber products such as natural rubber, diene-based synthetic rubber, ethylene/propylene rubber, etc.

Prior to painting, the rubber surface is generally pretreated using chlorine or perchloric acid, but this is because these rubbers do not have polar groups in their molecular chains. Improves adhesion with paint,
This is to measure sexual improvement.

However, pretreatment agents such as chlorine and perchloric acid that have been conventionally used for this purpose are relatively expensive, are inconvenient to handle, and pose problems in terms of work hygiene.

The present inventors have completed the present invention by discovering that polyphosphoric acid, which has not been considered as such a pretreatment agent in the past and is easy to handle and is easy to handle, can be used as a substitute for the conventional pretreatment agent.

That is, the invention relates to a method for modifying the surface of rubber, which comprises treating unvulcanized rubber or vulcanized rubber with polyphosphoric acid.

The polyphosphoric acid used in the present invention includes birophosphoric acid, triphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid, or any mixture thereof.

Polyphosphoric acid can be used as it is, or if desired, diluted with a solvent such as an alcoholic organic solvent such as methanol, ethanol, or ethanol, or a mixed solvent of these and an aliphatic or aromatic organic solvent such as hexanoate or toluene in any proportion. and @cloth or rl to the object to be processed! 4. Alternatively, the rubber to be treated may be immersed in polyphosphoric acid.

The rubber to be treated to which polyphosphoric acid has been attached is usually left as is to modify the rubber surface.

The standing time depends on the temperature, the type of rubber to be treated, the type of polyphosphoric acid, etc., and is not particularly limited, but is generally 20 to 60 hours at room temperature.

When heated to a temperature above the softening point of the polyphosphoric acid middle end rubber, the time can be significantly shortened.
Excellent processing effects can be obtained.

Further, the treatment with polyphosphoric acid is preferable because excellent treatment effects can be obtained in a short time even if it is performed under ultraviolet irradiation.

The rubber treated with polyphosphoric acid as described above is thoroughly washed with water, dried, and subjected to subsequent processes such as painting.

The combs to be processed that are subject to the method of the present invention are not limited;
It doesn't matter whether it is vulcanized, 11-sulfur, or filler-containing, but particularly preferred are natural rubber, back, isoprene-based combs such as butylcomb, and synchropentadiene, ethylidene norbornene, or methylene norbornene as a tertiary compound. It is an unvulcanized product or a sulfurized product of ethylene propylene terpolymer as a component.

Therefore, the method of the present invention can be used not only as a pretreatment for painting products, but also as a pretreatment for adhesion between rubber products and metals, and as a pretreatment for shielding between rubber products and metal cords, etc. It is effective, and as a result, the peel strength of the coating film is greatly increased, and the adhesion between the comb and metal, etc., is also greatly improved.Hereinafter, non-explosion IUI will be explained with reference to examples.

Example 1 The thick phase rubber shown in Table 1 was masticated using a mill roll,
After sheeting, the slab T45WI with a smooth surface was sandwiched between cellophane paper and heated at 120°C.
mφ, thickness 2 yrr).

This slab was coated with reagent-grade polyphosphoric acid and kept at room temperature [approx.
℃) for 48 hours, thoroughly washed with water and dried. The obtained test piece and untreated test piece were subjected to fluorescent X-ray analysis (=t L
, P diffraction intensity was investigated and the results are shown in Table 1.

The analysis conditions are as follows.

Equipment: Cat manufactured by Rigaku Denki Co., Ltd. High 5122 words 1 several tubes 2 PCs Spectroscopic crystal: EDDT Spectrum: α88.66° (2θ) X-ray tube: Cr Recording conditions: 4QKV, 3QmA = Finegain
7. Corse gain 3 Example 2 A test piece prepared in the same manner as in Example 1 except that the sample piece coated with polyphosphoric acid was left at 70°C for 24 hours was subjected to fluorescent X-ray analysis, and the results are displayed. -1 Example 3 Sulfur-vulcanized natural rubber sheet with a thickness of 0.5M coated with polyphosphoric acid (crosslinking density 7.5X) 0'mole/cc
) was prepared in the same manner as in Example 1 except that it was left at 70°C for 2.5 hours, and the test pieces were subjected to fluorescent X-ray analysis, and the results are shown in Table 1.

Table 1 Example Example 4 After puffing the surface of a sulfur-cured natural balatus slab (crosslinking density 4.0XIOmole/cc) with sandpaper, polyphosphoric acid was applied, and after 70°C it was placed in an oven. It was left to stand for 24 hours, dried with water, and coated with urethane paint. After drying the paint film, use a goblin tester to make gongs at intervals of '; Hrm on the paint film, and then apply cellophane tape on top of it. When this was carried out, the survival rate of Gobanales was 100/100.

Further, in a similar peeling test in which the film was simply puffed with sandpaper and no polyphosphoric acid treatment was performed, the rate of remaining stitches was O/100.

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Claims (1)

[Claims] (1) A rubber surface modification method characterized by treating unvulcanized rubber or vulcanized rubber with polyphosphoric acid. 2. The method according to item 1, wherein the polyphosphoric acid treatment is carried out at a temperature higher than the temperature at which the rubber is soaked. 3. Perform polyphosphoric acid treatment under ultraviolet irradiation □1st
The method described in section. 4. The method according to item 1, wherein the rubber is an in-prene rubber or an ethylene propylene terpolymer.