JPS61266439A - Production of molding based on thermoplastic fluororubber elastomer - Google Patents

Abstract

PURPOSE:To obtain the titled molding which is non-tacky and has excellent solvent resistance, hardness, etc., by irradiating a preform of a thermoplastic fluororubber elastomer with ionizing radiation in an atmosphere contg. a specified amount of oxygen or ozone. CONSTITUTION:A thermoplastic fluororubber elastomer (e.g. elastomer composed of an elastomeric polymer chain segment and non-elastomeric polymer chain segment consisting of vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene) is performed. The perform is irradiated with ionizing radiation at a dose of 1-50Mrad in an atmosphere having an oxygen or ozone content of 1.5vol% or below to obtain the titled molding. The molding has excellent resistance to solvents and the ratio of volume reduction thereof is 0.35cm-% or below per unit area after it is immersed in acetone at room temp. for 98hr and dried.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing a molded article based on a fluororubber thermoplastic elastomer. The present invention relates to a method for producing a molded article based on a fluororubber thermoplastic elastomer that exhibits properties.

Technical background of the invention and its problems Fluororubber has excellent heat resistance, chemical resistance, and oil resistance, so it is widely used as a special rubber in industrial products such as packing, gaskets, diaphragms, and housing. There is. Demand for fluororubber as a rubber product used under particularly harsh conditions has been increasing in recent years.

Moreover, in the semiconductor industry, which has been experiencing high growth in recent years, strong acids and alkaline solutions are sometimes used at high temperatures as IC etching and cleaning solutions, so only fluororubber can be used as the rubber material. is the current situation.

Attempts have been made to impart thermoplasticity to this fluororubber, and the development has been successful in recent years. Such a fluororubber-based thermoplastic elastomer is composed of an elastomeric polymer chain segment and a non-elastomeric polymer chain segment, and has the following characteristics in addition to having the characteristics of a general fluororubber. It has the following characteristics.

('a) Unlike other fluororubbers, it can be molded without using vulcanizing agents, stabilizers, or fillers, so the resulting rubber molded products are chemically pure and can be used in the semiconductor industry, food industry, etc. It is excellent as a medical material.

(b) It does not require a complicated vulcanization process and can be molded in the same way as ordinary plastics.

(C) Waste generated during molding can be reused.

In order to form a sealing material, for example, from the above fluororubber thermoplastic elastomer, it is sufficient to fill the above elastomer into a mold and heat it. The strength is low and the compression set is large, so it is necessary to overcome the above-mentioned drawbacks by causing a crosslinking reaction by irradiation after molding, as proposed in JP-A No. 59-62,635. No.

By the way, in general, urethane rubber having thermoplasticity or fluororubber which is heat-compressed using a vulcanizing agent has been irradiated with radiation in order to improve its rubber properties. has been carried out in air or in polyethylene bags filled with nitrogen gas.

Furthermore, in the above-mentioned Japanese Patent Application Laid-open No. 59-62,635, it is stated that the irradiation of fluororubber-based thermoplastic elastomers may be carried out in any atmosphere, including in vacuum, in air, and in nitrogen. Furthermore, it is described that the process can be carried out in the presence of sucrose.

However, when a preformed product made from a fluororubber thermoplastic elastomer is subjected to a crosslinking reaction by irradiating it with radiation using the usual method described above, the surface of the resulting molded product becomes sticky and sticky. However, there were problems in that the hardness and tensile strength were low. Moreover, it has been found that the resulting molded product has a fatal problem in that the surface of the molded product dissolves in carbonyl compounds such as ketones. For example, a molded product is obtained by manufacturing a preformed product from a fluororubber thermoplastic elastomer using a mold, and irradiating it with radiation in air or in a polyethylene bag filled with nitrogen gas to cause a crosslinking reaction. When immersed in acetone for 98 hours at room temperature, the molded article dissolves in the acetone at a rate of 1.
A volume reduction rate of 5 cm-% or more was observed.

If you use a rubber molded product that has a sticky surface, poor hardness and tensile strength, and is soluble in carbonyl compounds such as acetone, the molded products will stick to each other and become difficult to handle. This becomes difficult and leaves traces of adhesion on the surface of the molded product, significantly reducing its commercial value. Further, when the molded product is a hose, the inner surfaces of the hoses adhere to each other, making it impossible to function as a hose. Furthermore, when the molded product is a sealing material, the sealing material not only dissolves in solvents such as acetone and esters and contaminates the fluid, but also becomes unable to maintain sealing properties. Furthermore, due to its low hardness and low tensile strength, it cannot be used as a sealing material where high pressure is applied.

The present inventors have discovered that when a preform obtained from the above-mentioned fluororubber thermoplastic elastomer is irradiated with radiation to produce a molded product, the surface becomes sticky or becomes contaminated with carbonyl compounds such as acetone. As a result of intensive research into the causes of solubility, the following facts were discovered.

(i> When irradiating a molded product made from a fluororubber thermoplastic elastomer with radiation, a specific phenomenon occurs, unlike when irradiating a fluororubber molded using urethane rubber or a vulcanizing agent. In other words, in the case of fluororubber thermoplastic elastomer,
If a small amount of oxygen or ozone is present during radiation irradiation, the surface of the molded product obtained after radiation irradiation will become sticky, but this phenomenon is unique to fluororubber-based thermoplastic elastomers; In the case of rubber, even if it is irradiated with radiation in the air, no phenomenon such as the surface becoming sticky is observed. Furthermore, although this molded article has sufficient solvent resistance against alcohols and the like, it is severely attacked by carbonyl compounds such as acetone and methyl ethyl ketone.

(ii> Even if a rubber molded product obtained from a fluororubber thermoplastic elastomer is irradiated with radiation in a polyethylene bag filled with nitrogen gas, the surface of the obtained rubber molded product will become sticky or resistant to acetone. The reason why it shows solubility is because a small amount of oxygen in the air permeates into a polyethylene bag filled with nitrogen gas.

The present invention is an attempt to solve the above-mentioned problems, and even if a molded product made of a fluororubber thermoplastic elastomer is irradiated with radiation, the surface of the molded product does not become sticky. It is an object of the present invention to provide a method for producing a molded article based on a fluororubber thermoplastic elastomer that does not exhibit solubility even in carbonyl compounds such as ketones.

Summary of the Invention The method for producing a molded article based on a fluororubber thermoplastic elastomer according to the present invention includes adding oxygen, ozone, or a mixture thereof to a preformed article obtained from a fluororubber thermoplastic elastomer. Ionizing radiation of 1 to 5 Qlvlrad is irradiated in an atmosphere where the concentration is 5% by volume or less, and the resulting molded body is immersed in an acetone compound solvent at 98%
It is characterized in that the volume reduction rate per unit area after soaking for a period of time and drying is suppressed to within 0.35 cm-%.

0 Dan Fu Sake Aoiho The present invention will be explained in more detail below.

The molded article produced according to the present invention is based on a fluororubber thermoplastic elastomer. This fluororubber thermoplastic elastomer has rubber elasticity when vulcanized at a temperature around room temperature, exhibits plastic flow when heated, and contains elastomeric polymer chain segments and non-elastomeric polymer chain segments. At least one of them is a fluorine-containing polymer chain segment. The ratio of elastomeric polymer chain segments to non-elastomeric polymer chain segments is from 40 to 95:60 by weight.
5 desirably 70-90:30-10.

The specific structure of this fluororubber-based thermoplastic elastomer consists of a chain consisting of the above-mentioned elastomeric polymer chain segment and non-elastomeric polymer chain segment, an iodine atom present at one end of this chain, and an iodine atom at the other end of the chain. It consists of a residue obtained by removing at least one iodine atom from an existing iodide compound. The elastomeric polymer chain segment consists of (1) vinylidene fluoride/hexafluoropropylene or pentafluoropropylene/tetrafluoroethylene (mole ratio 40-90:5-
50:O to 35), or (2) perfluoroalkyl vinyl ether/tetrafluoroethylene/vinylidene fluoride (molar ratio 15 to 75:O to 85:O
~85) copolymer with a molecular weight of 30,000~
1, 2oo, ooo. In addition, the non-elastomeric polymer chain segment is (3>vinylidene fluoride/tetrafluoroethylene (molar ratio O~100:0~100
) or (4) ethylene/tetrafluoroethylene/hexafluoropropylene, 3,3.3-trifluoropropylene-1,2-trifluoromethyl-
3,3,3-trifluoropropylene-1 or perfluoroalkyl vinyl ether (molar ratio 40-60:
60-40:0-30), and has a molecular weight of 3,000-400.000.

Details regarding this fluororubber thermoplastic elastomer are described in JP-A-53-3,495, and this elastomer is sold by Daikin Industries, Ltd. under the trade name Daiel.

To obtain a preform from a fluororubber thermoplastic elastomer, a conventional method may be followed, for example, the elastomer may be filled into a mold of a desired shape and heated. At this time, it is not necessary to add a vulcanizing agent or a filler to the elastomer, but a vulcanizing agent such as polyol or peroxide may be used depending on the case.

The preform obtained from the fluororubber thermoplastic elastomer as described above can be used as is, but since it does not have a three-dimensional crosslinked structure, it has poor mechanical strength and compression set properties. Inferior. Therefore, in the present invention, the preform is irradiated with a specific amount of ionizing radiation under specific conditions. The ionizing radiation irradiated to the preform in the present invention includes X-rays, gamma rays, electron beams,
Proton beams, deuteron beams, alpha rays, beta rays, etc. are used.

The above preform is heated with 1 to 10% of oxygen, ozone, or a mixed gas thereof in an atmosphere containing 1.5% by volume or less.
Ionizing radiation of 50 Mrad, preferably 5 to 15 Mrad is applied.

If oxygen or ozone is present in the atmosphere in excess of 1.5% by volume, the molded product obtained after irradiation with radiation will have a sticky surface and will not dissolve in carbonyl compound solvents such as ketones and acetone. This is not desirable because it causes The remaining gas in the atmosphere is helium,
Inert gas such as argon, senone, nitrogen or
Hydrocarbons such as acetylene, ethylene, methane, and ethane are preferred.

Note that the present invention can be carried out even under reduced pressure, and in this case as well, it is preferable that the amount of oxygen or ozone is 1.5% by weight or less.

In order to keep the amount of oxygen or ozone in the atmosphere below 1.5% by volume, it is not enough to simply fill a commonly used polyethylene bag with nitrogen and keep the preform sealed inside the bag. It is.

This is thought to be because oxygen in the air permeates the polyethylene and enters the bag.

Therefore, it is preferable to irradiate the preform with radiation while the preform is sealed in a bag made of a material that is difficult to pass through oxygen, such as a bag made of nylon material.

As mentioned above, the amount of radiation applied to the preform is 1~
50 Mrad is preferably 5 to 15 Mrad, but if the irradiation amount is less than 1 Mrad, it is not preferable because the mechanical strength and compression set of the molded product will not improve much due to radiation irradiation, whereas if it exceeds 5Q Mrad, fluorine This is not preferable because the disintegration reaction of the rubber thermoplastic elastomer progresses, some intermolecular bonds are severed, and the mechanical strength of the resulting molded product is reduced.

In this way, the preform is irradiated with 1 to 50 Mrad of ionizing radiation in an atmosphere with an oxygen or ozone content of 1.5% by volume or less, and then dissolved in a carbonyl compound solvent such as acetic acid. A molded article based on a fluororubber thermoplastic elastomer that exhibits almost no oxidation can be obtained. This molded body is prepared by soaking the molded body in a carbonyl compound solvent such as acetone for 90 minutes.
After being immersed for 8 hours, it was taken out and thoroughly dried, and the volume reduction rate per unit area was measured to be 0°35cm-%.
It shows a value within 0.20 cm-%, preferably within 0.20 cm-%. This volume reduction rate per unit area is expressed by the following equation (1,).

Volume reduction rate per unit area (cm-%) = Surface area of the molded body If the volume reduction rate per unit area exceeds 0.35 cm-%, the resulting molded body will be highly soluble in carbonyl solvents such as acetone. Therefore, it cannot actually be used as a sealing material.

In addition, the preformed body irradiated with ionizing radiation in the present invention is
As mentioned above, it was found that the solubility in carbonyl solvents typified by acetone is improved, but at the same time, the durability against hot water is also significantly improved.

EXAMPLES The present invention will be explained below using Examples, but the present invention is not limited to these Examples.

衷凰■ - 85% by weight of elastomeric polymer chain segmentate consisting of vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene (molar ratio 50:30:20)
and 15% by weight of non-elastomeric polymer chain segments consisting of ethylene/tetrafluoroethylene/hexafluoropropylene (molar ratio 43:49:8);
A fluororubber thermoplastic elastomer (Daiel T-530 manufactured by Daikin Industries, Ltd.) was placed in a mold and heated to 220'C to produce an O-ring-shaped preform.

The obtained preform was placed in a nylon bag with a thickness of 15 μm, and after the bag was evacuated, the bag was filled with argon, and then almost all of the argon in the bag was mechanically extruded. Next, this bag was filled with argon again, and about 80% of the argon in the bag was mechanically extruded again. This bag was then filled with argon, and the bag body was sealed using a heat sealing method.

The preform sealed in the bag filled with argon was irradiated with a 10 Mrad copper wire to obtain a molded product based on a fluororubber thermoplastic elastomer.

This molded body was placed in acetone at room temperature for 5 minutes, 1 hour at 98°C.
The surface condition was observed after soaking for a period of time.

Next, the volume reduction rate per unit area of the molded body immersed in acetone for 98 hours was measured as follows. First, the volume and surface area of the molded body were measured before being immersed in acetone, and then the molded body was taken out after being immersed in acetone for 98 hours.
After drying at room temperature for 16 hours and further drying at 70'C for 2 hours, the volume was measured.

Based on the volume before immersion, the dry volume after immersion, and the surface area before immersion, the volume reduction rate per unit area of the molded body was measured based on the above formula (I). Also, the hardness of the molded object JI
SA), tensile strength (kaf/cm2), elongation (%), and tensile stress (k+jf/cm2) were measured. The results are shown in Tables 1 and 2.

In Example 1, in four bags made of nylon,
Oxygen 0.025%, 0.125%, 0.25% respectively
A molded article based on a fluororubber thermoplastic elastomer was formed in the same manner as in Example 1 except that the content was 1.25%, and an acetone immersion test was conducted. In addition, various physical properties of the molded product were measured. The results are shown in Tables 1 and 2.

Comparative Example] A molded article was formed in the same manner as in Example 1 except that 2.5% by volume of oxygen was contained in the bag made of nylon, and an acetone immersion test was conducted. Various physical properties of the molded product were also measured. The results are shown in Tables 1 and 2.

Comparative Example 2 A molded article was formed in the same manner as in Example 1 except that air was filled into the bag made of nylon, and an acetone immersion test was conducted.

Various physical properties of the molded product were also measured. The results are shown in Table 1 and Table 2.
Shown below.

Example 3 A molded body was formed in the same manner as in Example 1 except that helium was filled into the bag made of nylon, and an acetone immersion test was conducted. In addition, various physical properties of the molded product were measured. The results are shown in Tables 1 and 2.

In Example 1, a molded body was formed in the same manner as in Example 1 except that the bag made of nylon was filled with nitrogen.
An acetone immersion test was conducted. Various physical properties of the molded product were also measured. The results are shown in Tables 1 and 2.

Comparative Example 3 In Example 1, instead of the bag made of nylon,
A molded body was formed in the same manner as in Example 1 except that a bag made only of polyethylene having the same film thickness was used, and a immersion test was conducted in acetone. Tables 1 and 2 show the results of measuring various physical properties of the molded product.

Comparative Example 4 In Example 1, instead of the bag made of nylon,
A molded body was formed in the same manner as in Example 1, except that a bag made only of polyethylene with the same film thickness and pure acetylene gas was used as the introduced gas, and an acetone immersion test was conducted. Various physical properties of the molded product were also measured. The results are shown in Tables 1 and 2.

Le school trunk-1 In Example 1, instead of the bag made of nylon,
A molded body was formed in the same manner as in Example 1, except that a bag made only of polyethylene with the same film thickness and pure nitrogen was used as the introduced gas, and an acetone immersion test was conducted. In addition, Tables 1 and 2 show the results of measuring various physical properties of the molded bodies.

A molded body was formed in the same manner as in Example 1, except that the preformed body that had not been irradiated with radiation was used as it was in Example 1, and the acetone immersion test was conducted. I did it. The results are shown in Table 2.

From Tables 1 and 2, when irradiating a preform obtained from a fluororubber thermoplastic elastomer with radiation, if more than 1.5% by volume of oxygen or ozone is present in the atmosphere, the resulting molding It can be seen that the solvent resistance of the body to carbonyl compound solvents typified by acetone is significantly reduced.

Moreover, if only the compression set and mechanical strength of the obtained molded body are considered without considering the solvent resistance, JP-A No. 59
As described in Japanese Patent No. 62,635, it can be seen that there is no significant difference in the atmosphere of radiation irradiation.

21-112 Ma-2

Claims (1)

[Claims] A preform obtained from a fluororubber thermoplastic elastomer is irradiated with ionizing radiation of 1 to 50 Mrad in an atmosphere containing 1.5% by volume or less of oxygen or ozone,
The obtained molded body was immersed in an acetone solvent at room temperature for 98 hours and dried, and the volume reduction rate per unit area was 0.
1. A method for producing a molded article based on a fluororubber thermoplastic elastomer, characterized in that the molded article is kept within 35 cm-%.