JPH0116651B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a crosslinked fluorine-containing elastomer molded article. [Prior art] Tetrafluoroethylene-propylene copolymer is
It is an elastomer that can be extruded and crosslinked in a wide temperature range from room temperature to 300℃, and its excellent electrical insulation, heat resistance, oil resistance, and chemical resistance can be used to make gaskets, packing, diaphragms,
It has been used for applications such as hoses. However, conventional tetrafluoroethylene-propylene copolymer elastomers do not have sufficient mechanical strength at high temperatures, and as a result, when subjected to mechanical stresses such as tension, rotation, and twisting at high temperatures, There was a problem of breakage, and there were various limitations in practical use. To increase mechanical strength at high temperatures, ethylene-
One possible method is to blend fluorine resins such as tetrafluoroethylene copolymer or polyvinylidene fluoride, but compositions made by blending these cannot be extruded unless the temperature is higher than the crystalline melting point of the fluorocarbon resin. Therefore, when trying to carry out crosslinking with peroxide, which is usually carried out with tetrafluoroethylene-propylene copolymers, the peroxide reacts in the extruder and causes discoloration, making it difficult to carry out. [Problems to be Solved by the Invention] The present invention has been made based on the above, and provides that the mechanical strength of a tetrafluorinated ethylene-propylene copolymer can be improved by peroxide crosslinking at high temperatures. The object of the present invention is to provide a method for producing a crosslinked molded body. [Means for Solving the Problems] The present invention provides ethylene-tetrafluoride ethylene copolymer or polyvinylidene fluoride having a particle size of 100μ or less per 100 parts by weight of tetrafluoroethylene-propylene copolymer. A resin composition containing 10 to 100 parts by weight of at least one fluororesin selected from the following and further adding an organic peroxide having a half-life of 10 hours or more at 100°C is prepared at a temperature of 150°C or less. It is characterized in that it is extruded and then crosslinked under pressure at a temperature higher than the melting point of the fluororesin. [Function] In the present invention, the tetrafluoroethylene-propylene copolymer includes, in addition to the main components tetrafluoroethylene and propylene, components copolymerizable with these, such as ethylene, butene-1, isobutene, Acrylic acid and its alkyl esters, methacrylic acid and its alkyl esters, vinyl fluoride, vinylidene fluoride, hexafluoropropene, chloroethyl vinyl ether, glycidyl vinyl ether, chlorotrifluoroethylene,
It may also contain a suitable amount of perfluoroalkyl vinyl ether or the like. In such a copolymer, tetrafluoroethylene/
The molar ratio of propylene is 95/5 to 30/
70, particularly from the range of 90/10 to 45/55, is preferable from the viewpoint of heat resistance, moldability, etc. Also, the content of components other than the main component, which may be added as appropriate, is usually 50 mol% or less, especially It is preferable to select from a range of 30 mol% or less. The fluororesin to be blended with the tetrafluoroethylene-propylene copolymer is at least one of ethylene-tetrafluoroethylene copolymer and polyvinylidene fluoride. It is necessary to select such a fluororesin having a particle size of 100 μm or less; if a particle size larger than this is used, the surface of the molded product will be severely roughened and sufficient crosslinked physical properties will not be obtained. In addition, the amount of fluororesin mixed is 10 to 100 parts by weight per 100 parts by weight of tetrafluoroethylene-propylene copolymer.
It is necessary to keep the amount in the range of 100 parts by weight; if it is less than 10 parts by weight, there is almost no effect of improving mechanical strength at high temperatures, and if it exceeds 100 parts by weight, extrusion molding becomes impossible. The crosslinking agent used in the present invention includes:
It is a peroxide with a half-life of 10 hours or more at 100°C. This is because if the half-life is less than 10 hours, early crosslinking occurs during extrusion molding. Such peroxides include dicumyl peroxide, 2,5-dimethyl-2,5-di(t
-butylperoxy)benzene, 1,3-bis(t-butylperoxyisopropyl)benzene,
t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-
Di(t-butylperoxy)hexyne-3, 2,
Examples include 2-di(t-butylperoxy)butane. These can be used alone or in combination of two or more, and the amount added is usually 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, per 100 parts by weight of the resin component. In the present invention, a crosslinking aid can be used in addition to the crosslinking agent, and such crosslinking aids include sialyl phthalate, triallyl phosphate, triallyl cyanurate, triallyl isocyanurate, and the like. The amount of the crosslinking aid added is 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, per 100 parts by weight of the resin component. In addition to the above ingredients, the composition that can be used in the present invention includes fillers, reinforcing agents, pigments, lubricants, extrusion aids,
It can contain antioxidants, stabilizers, etc.
Such a composition has a Mooney viscosity of ML1+4 (100
℃) is 20-150, especially 30-90 for moldability,
This is preferable from the viewpoint of the surface condition of the molded product. In addition, it is desirable that each compounded component is uniformly dispersed in the composition.
Uniform dispersion can be achieved by kneading for about 10 to 30 minutes. The composition thus obtained must be extruded at a temperature below 150° C.; higher temperatures will result in premature crosslinking in the extruder. Further, crosslinking after extrusion molding must be carried out at a temperature equal to or higher than the melting point of the fluororesin, and if the temperature is lower than this, the mechanical strength at high temperatures cannot be sufficiently improved. [Example] Various ingredients were mixed in the proportions shown in each example in Table 1 and kneaded for 15 minutes using an 8-inch roll maintained at 50 to 60°C. Next, head: 100℃, cylinder 1: 100
℃, Cylinder 2: Extruder (L/
D=22), the outer periphery of a tin-plated copper stranded wire having an outer diameter of 1.6 mm was coated with a thickness of 1 mm, and heat crosslinking was carried out under the conditions shown in each example in Table 1. The evaluation results regarding the surface smoothness and tensile strength of the obtained covered wire are shown in the lower column of Table 1.

[Table] As is clear from Table 1, all of Examples 1 to 4 within the scope of the present invention had good extrusion appearance and excellent tensile strength at 100°C. Comparative Example 1 does not contain any fluororesin, and has an excellent extruded appearance but poor tensile strength.
Comparative Example 2 has a particle size larger than that specified in the present invention.
It uses 500μ fluororesin, which has poor extruded appearance and poor dispersion, making it impossible to obtain sufficient tensile strength. In Comparative Example 3, crosslinking was carried out at a temperature below the melting point of the ethylene-tetrafluoroethylene copolymer, and the tensile strength was insufficient. [Effects of the Invention] As explained above, the present invention has excellent mechanical strength at high temperatures due to peroxide crosslinking,
Moreover, it becomes possible to obtain a crosslinked fluorine-containing elastomer molded article having a good extrusion appearance.

Claims (1)

[Claims] 1 Tetrafluoroethylene-propylene copolymer
Ethylene with a particle size of 100μ or less per 100 parts by weight
Contains 10 to 100 parts by weight of at least one fluororesin selected from tetrafluoroethylene copolymer or polyvinylidene fluoride, and further contains an organic peroxide having a half-life of 10 hours or more at 100°C. Extrusion molding the resin composition at a temperature of 150°C or less,
A method for producing a crosslinked fluorine-containing elastomer molded article, which comprises then crosslinking under pressure at a temperature higher than the melting point of the fluororesin.