METHOD FOR PRODUCING CROSS-LINKED BODY

Abstract

A method for producing a cross-linked body is disclosed which includes providing a thermoplastic fluororesin composition and cross-linking the thermoplastic fluororesin composition by an ionizing radiation. The thermoplastic fluororesin composition includes a thermoplastic fluororesin (A) having a Shore D hardness of less than or equal to 50 measured at 23 C. in accordance with ASTM D2240, and a cross-linked structure forming agent (B) that is selected from a polyfunctional unsaturated compound (b-1), a polyamine compound (b-2), and a polyhydroxy compound (b-3) and that is capable of forming a cross-linked structure through a reaction with the thermoplastic fluororesin (A), the thermoplastic fluororesin composition not substantially containing a peroxide compound when containing the polyfunctional unsaturated compound (b-1), not substantially containing an acid acceptor when containing the polyamine compound (b-2), and not substantially containing at least one of the acid acceptor and an onium compound when containing the polyhydroxy compound (b-3).

Claims

1. A method for producing a cross-linked body comprising the steps of: providing a thermoplastic fluororesin composition; and cross-linking the thermoplastic fluororesin composition by an ionizing radiation, wherein the thermoplastic fluororesin composition comprises: a thermoplastic fluororesin (A) having a Shore D hardness of less than or equal to 50, the Shore D hardness being measured at 23 C. in accordance with ASTM D2240; and a cross-linked structure forming agent (B) that is selected from the group consisting of a polyfunctional unsaturated compound (b-1), a polyamine compound (b-2), and a polyhydroxy compound (b-3) and that is capable of forming a cross-linked structure through a reaction with the thermoplastic fluororesin (A), the thermoplastic fluororesin composition not substantially containing a peroxide compound when containing the polyfunctional unsaturated compound (b-1), not substantially containing an acid acceptor when containing the polyamine compound (b-2), and not substantially containing at least one of the acid acceptor and an onium compound when containing the polyhydroxy compound (b-3).

2. The method according to claim 1, further comprising a step of molding the thermoplastic fluororesin composition between the step of providing the thermoplastic fluororesin composition and the step of cross-linking the thermoplastic fluororesin composition.

3. The method according to claim 1, wherein the thermoplastic fluororesin composition further comprises a cross-linkable rubber component (C).

4. The method according to claim 3, wherein the cross-linkable rubber component (C) is a fluorine rubber.

5. The method according to claim 3, wherein a content of the cross-linkable rubber component (C) is less than or equal to 100 parts by weight per 100 parts by weight of the thermoplastic fluororesin (A).

Description

EXAMPLES

[0085] Hereinafter, the present invention is described in further detail with reference to examples and comparative examples. The present invention, however, is not limited to these examples. In the examples and comparative examples below, the compression set was measured according to the following method.

[0086] (Measurement of Compression Set)

[0087] In accordance with JIS K 6262, a sample (A568-214 0 ring) was sandwiched between iron plates at a compression rate of 25%, warmed by an electric furnace under the conditions of 200 C. for 72 hours, and then released from compression. The sample was allowed to cool for 30 minutes, and then the compression set of the sample was calculated by the following equation:

Compression set (%)={(T0T1)/(T0T2)}100%.

[0088] T0 denotes the height of the sample before the test, T1 denotes the height of the sample 30 minutes after the cooling, and T2 denotes the thickness (height) of a spacer. Table 1 shows the results.

Example 1

[0089] According to the compounding formulation shown in Table 1 (the unit of the compounding amounts in Table 1 is part by weight), the predetermined amounts of the compounding components were kneaded with an open roll. The kneading temperature was set to 140 C. Next, the resultant thermoplastic fluororesin composition was subjected to extrusion molding at 230 C. to give a molded body having a shape of a sealing member (O ring). The extrusion molding was easy that was melt molding of the thermoplastic fluororesin composition into the shape of the sealing member. Then, the molded body was irradiated with a radiation (-ray) at a radiation dose of 80 kGy to give a cross-linked molded body, or the sealing member (O-ring). The molded body before the irradiation with the radiation exhibited heat meltability, and it was also easy to perform the molding again by heat-melting the molded body.

Examples 2 to 5, Comparative Examples 1 to 3

[0090] A cross-linked molded body, or a sealing member was manufactured in the same manner as in Example 1 except that the compounding components and the compounding amounts of the thermoplastic fluororesin composition were set as shown in Table 1. Also in any of Examples 2 to 5 and Comparative Examples 1 to 3, the extrusion molding was easy that was melt molding of the thermoplastic fluororesin composition into the shape of the sealing member. In addition, the molded body before the irradiation with the radiation exhibited heat meltability, and it was also easy to perform the molding again by heat-melting the molded body.

Comparative Example 4

[0091] A kneaded material was obtained by kneading, with an open roll, the cross-linked structure forming agent (B) and the cross-linkable rubber component (C) according to the compounding formulation shown in Table 1. This kneaded material, the thermoplastic fluororesin (A), and a peroxide were kneaded according to the compounding formulation shown in Table 1 with LABO PLASTOMILL [manufactured by Toyo Seiki Seisaku-sho, Ltd.). The kneading temperature during the kneading was set to 200 C., and the rotation speed was 50 rpm. Next, the resultant thermoplastic fluororesin composition was subjected to extrusion molding at 230 C. to give a molded body having the shape of the sealing member (O ring). The extrusion molding was easy that was melt molding of the thermoplastic fluororesin composition into the shape of the sealing member. Then, the molded body was irradiated with a radiation (-ray) at a radiation dose of 80 kGy to give a cross-linked molded body, or the sealing member (O-ring).

TABLE-US-00001 TABLE 1 Thermoplastic fluororesin composition Cross-linked Cross-linkable Thermoplastic structure rubber fluororesin forming component Dose of (A) agent (B) (C) Peroxide radiation Compression a-1 a-2 a-3 b-1 c-1 c-2 d-1 (kGy) set (%) Example 1 100 6 80 45 2 80 6 20 80 43 3 60 6 40 80 45 4 100 5 80 48 5 60 6 40 80 47 Comparative 1 100 80 97 Example 2 100 80 86 3 100 6 80 98 4 40 4 60 1 80 70

[0092] The details of the compounding components used in the examples and the comparative examples are as follows.

[0093] [1] Thermoplastic fluororesin a-1: thermoplastic resin formed of VDF-HFP copolymer (Kynar UltraFlex B manufactured by Arkema Inc., Shore D hardness at 23 C. measured in accordance with ASTM D2240: 40),

[0094] [2] Thermoplastic fluororesin a-2: fluorine-based thermoplastic elastomer being block polymer of vinylidene fluoride (VDF) polymer and tetrafluoroethylene-ethylene polymer (ETFE) (DAI-EL Thermoplastic T-530 manufactured by DAIKIN INDUSTRIES, LTD., Shore D hardness at 23 C. measured in accordance with ASTM D2240: 18),

[0095] [3] Thermoplastic fluororesin a-3: thermoplastic resin formed of VDF-HFP copolymer (Kynar 2850-00 manufactured by Arkema Inc., Shore D hardness at 23 C. measured in accordance with ASTM D2240: 73),

[0096] [4] Cross-linked structure forming agent b-1: triallyl isocyanurate (TAIC manufactured by Nippon Kasei Chemical Company Limited),

[0097] [5] Cross-linkable rubber component c-1: vinylidene fluoride (VDF)-hexafluoropropylene (HFP)-tetrafluoroethylene (TFE) polymer (DAI-EL G902 manufactured by DAIKIN INDUSTRIES, LTD.),

[0098] [6] Cross-linkable rubber component c-2: vinylidene fluoride (VDF)-hexafluoropropylene (HFP) polymer, and

[0099] [7] Peroxide d-1: 5-dimethyl-2,5-di(tert-butylperoxy)hexane (PERHEXA 25B manufactured by NOF corporation).