JPH0653822B2 - Method for producing molded article based on fluororubber thermoplastic elastomer - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing a molded product based on a fluororubber thermoplastic elastomer, and more specifically, it has extremely excellent solvent resistance against an organic solvent such as acetone. And a method for producing a molded product based on a fluororubber thermoplastic elastomer.

Technical background of the invention and its problems Since fluororubber has excellent heat resistance, chemical resistance and oil resistance, it is widely used as a special rubber in industrial products such as packing, gaskets, diaphragms and hoses. There is. In recent years, the demand for fluororubber as a rubber product used under particularly severe conditions has been increasing more and more.
Moreover, in the semiconductor industry, which has achieved high growth in recent years, strong acids and alkaline solutions are sometimes used at high temperatures as IC etching solutions or cleaning solutions, so only fluororubber can be used as the rubber material. The current situation.

Attempts have been made to impart thermoplasticity to this fluororubber, which has been successfully developed in recent years. Such a fluororubber thermoplastic elastomer is constituted by including an elastomeric polymer chain segment and a non-elastomeric polymer chain segment, and in addition to having characteristics as a general fluororubber, It has various characteristics.

(A) Unlike other fluororubbers, a vulcanizing agent, a stabilizer,
Since it can be molded without using a filler, the obtained rubber molded product is chemically pure and is excellent as a material for the semiconductor industry, food industry, and medical use.

(B) A complicated vulcanization step is not required and molding can be performed in the same manner as ordinary plastic.

(C) It is possible to reuse the waste generated during the molding process.

To form, for example, a sealing material from the above-mentioned fluororubber thermoplastic elastomer, it is sufficient to fill the mold with the elastomer and heat it. However, as it is as it is, three-dimensional crosslinking is not carried out, so that mechanical The strength is weak and the compression set is large, and as described in JP-A-59-62,635, a crosslinking reaction is caused by irradiation with radiation after molding to overcome the above-mentioned drawbacks. I won't.

By the way, in general, it has been hitherto performed to irradiate a fluororubber obtained by heating and compression with a urethane rubber or a vulcanizing agent having thermoplasticity in order to improve its rubber properties. Have been performed in air or in polyethylene bags filled with nitrogen gas.

Also, in the above-mentioned JP-A-59-62,635, it is described that the radiation irradiation of the fluororubber thermoplastic elastomer may be performed in any atmosphere.
It is described that it can be carried out in vacuum, in air, in nitrogen and in the presence of monomers.

However, when the preform obtained from the fluororubber thermoplastic elastomer was irradiated with radiation in the usual manner as described above to cause the crosslinking reaction, the surface of the obtained molded product was tacky and sticky. However, there was a problem in that the hardness and tensile strength were low. Moreover, it was found that the obtained molded product had a fatal problem that the surface of the molded product was dissolved in carbonyl compounds such as ketones. For example, a molded product obtained by manufacturing a preformed product from a fluororubber thermoplastic elastomer by a mold and irradiating it with radiation in a polyethylene bag filled with nitrogen gas to cause a crosslinking reaction, When immersed in acetone at room temperature for 98 hours, the molded product dissolves in acetone to give 1.
A volume reduction rate of 5 cm-% or more is recognized.

If such a rubber molded product is used, which has a sticky surface, is inferior in hardness and tensile strength, and is soluble in a carbonyl compound represented by acetone, the molded products adhere to each other and are easy to handle. It becomes difficult, and traces of adhesion remain on the surface of the molded product, resulting in a marked decrease in commercial value. Further, when the molded product is a hose, the inner surfaces of the hose adhere to each other and cannot serve as a hose. Further, when the molded product is a sealing material, not only the sealing material is dissolved in a solvent such as acetone or ester to contaminate the fluid, but also the sealing property cannot be maintained. In addition, since it has low hardness and low tensile strength, it cannot be used as a sealing material in places where high pressure is applied.

The present inventors produced a molded article by irradiating a pre-molded article obtained from the above-mentioned fluororubber thermoplastic elastomer with radiation, and the surface was sticky, or carbonyl compounds such as acetone were formed. As a result of diligent research on the cause of the solubility, the following facts were found.

(I) When a molded product obtained from a fluororubber-based thermoplastic elastomer is irradiated with radiation, a specific phenomenon occurs unlike irradiation of a fluororubber molded with a urethane rubber or a vulcanizing agent. Is recognized. That is, in the case of a fluororubber thermoplastic elastomer, when a large amount of oxygen or ozone is present during irradiation with radiation, the surface of the molded article obtained after irradiation with radiation becomes sticky. In the case of urethane rubber or ordinary fluororubber, which is peculiar to elastomers, the phenomenon that the surface thereof becomes sticky even when irradiated with radiation in the air is not recognized. Further, although this molded article has sufficient solvent resistance to alcohol and the like, it is severely attacked by carbonyl compounds such as acetone and methyl ethyl ketone.

(Ii) Even when the rubber molded body obtained from the fluororubber thermoplastic elastomer is irradiated with radiation in a polyethylene bag filled with nitrogen gas, the surface of the obtained rubber molded body is sticky, or it is against acetone. The reason for the solubility is that oxygen in the air penetrates into the polyethylene bag filled with nitrogen gas.

OBJECT OF THE INVENTION The present invention is intended to solve the problems as described above, and even when a molded product obtained from a fluororubber thermoplastic elastomer is irradiated with radiation, its surface is sticky, It is an object of the present invention to provide a method for producing a molded product based on a fluororubber thermoplastic elastomer, which does not exhibit solubility in carbonyl compounds such as ketones.

SUMMARY OF THE INVENTION In the method for producing a molded article based on a fluororubber thermoplastic elastomer according to the present invention, a premolded article obtained from the fluororubber thermoplastic elastomer has a partial pressure of oxygen or ozone or a mixture thereof of 11 or less. 1 to 50 Mr in an atmosphere of more than 4 mmHg and less than 76 mmHg
It is characterized in that the volume reduction rate per unit area after irradiating the ionizing radiation of ad and immersing the obtained molded product in an acetone compound solvent for 98 hours and drying it is kept within 0.9 cm-%. .

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in more detail below.

The molded product produced by the present invention is based on a fluororubber thermoplastic elastomer. This fluororubber thermoplastic elastomer is vulcanized at room temperature to have rubber elasticity, exhibits plastic flow by heating, and contains an elastomeric polymer chain segment and a non-elastomeric polymer chain segment. At least one is a fluoropolymer chain segment. The ratio of the elastomeric polymer chain segment to the non-elastomeric polymer chain segment is 40 to 95:60 by weight.
It is preferably 5 to 70:30 to 10:30.

The specific structure of this fluororubber thermoplastic elastomer is a chain composed of the above-mentioned elastomeric polymer chain segment and non-elastomeric polymer chain segment,
It consists of an iodine atom present at one end of the chain and a residue obtained by removing at least one iodine atom from the iodide compound present at the other end of the chain. The elastomeric polymer chain segment is (1) vinylidene fluoride /
Hexafluoropropylene or pentafluoropropylene / tetrafluoroethylene (molar ratio 40-90: 5
~ 5: 0 to 35) copolymer, or (2) perfluoroalkyl vinyl ether / tetrafluoroethylene / vinylidene fluoride (molar ratio 15 to 75: 0 to 85:
0-85) copolymer having a molecular weight of 30,000
˜1,200,000. The non-elastomeric polymer chain segment is (3) vinylidene fluoride / tetrafluoroethylene (molar ratio 0 to 100: 0 to 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 to 30) copolymer having a molecular weight of 3,000 to
It is 400,000.

Details of this fluororubber thermoplastic elastomer are described in JP-A-53-3,495,
This elastomer is sold by Daikin Industries, Ltd. under the product name DAIEL.

To obtain a preform from a fluororubber-based thermoplastic elastomer, a conventional method may be used, for example, a die having a desired shape may be filled with this elastomer and heated. At this time, it is not necessary to add a vulcanizing agent and 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 it is, but since it does not have a three-dimensional crosslinked structure as it is, it is inferior in mechanical strength and compression set characteristics. ing. Therefore, in the present invention, the preform is irradiated with a specific amount of ionizing radiation under specific conditions. As the ionizing radiation for irradiating the preform in the present invention, X-ray, gamma ray, electron beam, proton ray, deuteron ray, alpha ray, beta ray and the like are used.

1 to 50 Mrad, preferably 5 to 1 is added to the above preform in an atmosphere in which the partial pressure of oxygen, ozone, or a mixed gas thereof is more than 11.4 mmHg and less than 76 mmHg.
Irradiate with 5 Mrad of ionizing radiation.

If the partial pressure of oxygen or ozone exceeds 76 mmHg in the atmosphere, the surface of the molded product obtained after irradiation with radiation will be sticky and will be dissolved in a carbonyl compound solvent such as ketone or acetone. It is not preferable because it will happen. The balance gas in the atmosphere is preferably an inert gas such as helium, argon, xenon or nitrogen, or a hydrocarbon such as acetylene, ethylene, methane or ethane.

The present invention can be carried out even under reduced pressure, and in this case as well, the partial pressure of oxygen or ozone is preferably 76 mmHg or less.

In order to suppress the partial pressure of oxygen or ozone in the atmosphere to 76 mmHg or less, it is not enough to fill a commonly used polyethylene bag with nitrogen and keep the preform sealed in this bag. It is considered that this is because oxygen in the air penetrates polyethylene and enters the bag. Therefore, it is preferable to irradiate the preform with radiation in a state where the preform is sealed in a bag made of a material through which oxygen hardly permeates, such as a bag made of a combination of nylon materials.

As described above, the irradiation amount of radiation to the preformed body is 1 to
50 Mrad is preferably 5 to 15 Mrad, but if this irradiation amount is less than 1 Mrad, the mechanical strength and compression set of the molded product due to radiation irradiation are not significantly improved, which is not preferable. It is not preferable because the disintegration reaction of the rubber-based thermoplastic elastomer proceeds, the intermolecular bonds are partially cut, and the mechanical strength of the obtained molded article decreases.

By irradiating the preformed body with 1 to 50 Mrad of ionizing radiation in an atmosphere in which the partial pressure of oxygen or ozone exceeds 11.4 mmHg and 76 mmHg or less, a carbonyl compound system represented by ascent is obtained. A molded article based on a fluororubber thermoplastic elastomer showing almost no dissolution in a solvent is obtained. The molded body was immersed in a carbonyl compound solvent represented by acetone for 98 hours, taken out, and sufficiently dried, and the volume reduction rate per unit area was measured.
A value within 9 cm-% is shown. The volume reduction rate per unit area is expressed by the following formula (I).

If the volume reduction rate per unit area exceeds 0.9 cm-%, the obtained molded article will be largely dissolved in a carbonyl solvent such as acetone and cannot be used as a sealing material or the like in practice.

Incidentally, the preformed body irradiated with ionizing radiation in the present invention,
As described above, it was found that the solubility in a carbonyl solvent represented by acetone is improved, but at the same time, the durability against hot water is also significantly improved.

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Reference Example 1 85% by weight of an elastomeric polymer chain segment composed of vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene (molar ratio 50:30:20) and ethylene / tetrafluoroethylene / hexafluoropropylene (molar ratio 43:49 : 8) A non-elastomeric polymer chain segment consisting of 15% by weight of a fluororubber thermoplastic elastomer (Daiel T-530 manufactured by Daikin Industries, Ltd.) is placed in a mold and heated to 220 ° C. to give O-
A ring-shaped preform was produced.

The preform thus obtained was placed in a nylon bag having a thickness of 15 μ, the bag was evacuated, and then 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 then about 80% of the argon in the bag was mechanically extruded again. Then, the bag was filled with argon and the bag was sealed by a heat sealing method.

The preform thus sealed in the bag filled with argon was irradiated with 10 Mrad of radiation to obtain a form based on the fluororubber thermoplastic elastomer.

This molded body was placed in acetone at room temperature for 5 minutes for 1 hour and then 98
It was immersed for a period of time and its surface condition was observed. 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, dried at room temperature for 16 hours, and further dried at 70 ° C. for 2 hours, and then the volume was measured. did. Based on the formula (I), the volume reduction rate per unit area of the molded body was measured from the volume before immersion, the dry volume after immersion, and the surface area before immersion. Also, the hardness (JISA), tensile strength (kgf / cm ² ), elongation (%) and tensile stress (kgf / cm ² ) of the molded body were measured. The results are shown in Tables 1 and 2.

Example 1 In Reference Example 1, in four bags made of nylon,
Partial pressure of oxygen is 30.4 mmHg, 45.6 mmHg, 6
Reference Example 1 except that 0.8 mmHg and 76.0 mmHg were included.
In the same manner as above, a molded article based on a fluororubber thermoplastic elastomer was formed and subjected to an acetone immersion test. Moreover, various physical properties of the molded body were measured. The results are shown in Tables 1 and 2.

Comparative Example 1 A molded article was formed in the same manner as in Reference Example 1 except that 91.2 mmHg of oxygen was contained at a partial pressure 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 Table 1 and Table 2.
Shown in.

Comparative Example 2 A molded article was formed in the same manner as in Reference Example 1 except that the bag made of nylon was filled with air, and an acetone immersion test was performed. Various physical properties of the molded product were also measured. The results are shown in Tables 1 and 2.

Reference Example 2 A molded article was formed in the same manner as in Reference Example 1 except that the bag made of nylon was filled with helium in Reference Example 1, and an acetone immersion test was performed. Moreover, various physical properties of the molded body were measured. The results are shown in Tables 1 and 2.

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

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

Comparative Example 5 In Reference Example 1, instead of the bag body made of nylon,
A molded body was formed in the same manner as in Reference Example 1 except that a bag made of polyethylene having the same film thickness was used and pure nitrogen was used as an introduction gas, and an acetone immersion test was performed. Tables 1 and 2 show the results of measuring the physical properties of the molded product.

Comparative Example 6 A molded article was formed in the same manner as in Reference Example 1 except that the pre-molded article that had not been irradiated with radiation was used as it was in the acetone immersion test, and the acetone immersion test was performed. It was The results are shown in Table 2.

From Tables 1 and 2 above, when a preform obtained from a fluororubber thermoplastic elastomer is irradiated with radiation, if oxygen or ozone exceeding 76 mmHg in partial pressure is present in the atmosphere, the obtained form will be obtained. It can be seen that the solvent resistance to the carbonyl compound solvent represented by Acetone is significantly reduced.

Further, if only the compression set and the mechanical strength are taken into consideration without considering the solvent resistance of the obtained molded article, it is disclosed in JP-A-59-59.
It can also be seen that there is no great difference in the atmosphere of radiation irradiation as described in JP-A-62,635.

Claims (1)

[Claims] 1. A preform obtained from a fluororubber thermoplastic elastomer having a partial pressure of oxygen or ozone of 11.
1 to 5 in an atmosphere of more than 4 mmHg and less than 76 mmHg
It is characterized by irradiating 0 Mrad of ionizing radiation, immersing the obtained molded product in an acetone solvent for 98 hours at room temperature, and drying it, and then suppressing the volume reduction rate per unit area within 0.9 cm-%. And a method for producing a molded article based on a fluororubber thermoplastic elastomer.