JP2821688B2 - Fluorine-containing elastomer composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fluoroelastomer composition, and more particularly to a fluoroelastomer composition for extrusion molding which can be vulcanized with an organic peroxide.

<Prior art> Conventionally, fluoroelastomer has been used as a flexible and elastic polymer having excellent heat resistance, oil resistance, and chemical resistance in various applications such as gaskets, packings, diaphragms, and hoses. Are known. Among fluoroelastomer, tetrafluoroethylene-α-olefin copolymer has excellent balance of heat resistance and electrical properties, and various studies have been conducted in recent years to apply it to applications such as electric wires and tubes by extrusion molding while maintaining the characteristics. It has been done.

For example, Japanese Patent Application Publication No. 62-2407 discloses a tetrafluoroethylene-α-olefin copolymer having a specific molecular weight adjusted by heat treatment in the presence of oxygen and a specific amount of a polyallyl compound and an organic compound. It is described that an extrusion-molded fluoroelastomer composition in combination with a peroxide is heated and vulcanized to produce an electric wire having a good balance of heat resistance, electrical properties, and mechanical properties.

<Problems to be Solved by the Present Invention> However, among the tetrafluoroethylene-α-olefin copolymers, those having a low viscosity have good extrudability but a large decrease in initial physical properties due to high filling. The quantity and type were limited. On the other hand, a material having a relatively high viscosity has a good balance of physical properties, but the composition generates a large amount of self-heating during extrusion molding, and the temperature condition of the extruder also needs to be high as an elastomer.

Therefore, scorch is easily caused during extrusion molding, and it is necessary to work carefully, as well as the composition itself is greatly restricted. For example, organic peroxides with relatively high decomposition temperatures must be used,
Therefore, the heating vulcanization temperature was increased, the distance between shafts was increased, and productivity was restricted. In addition, when a large amount of filler is used, the viscosity of the composition increases and extrusion molding cannot be performed. Therefore, as in the case of low viscosity, the amount and type of filler used are limited.

As described above, a general problem in the case of the above-mentioned known literature is that even if a low-viscosity tetrafluoroethylene-α-olefin copolymer is used, or if a high-viscosity one is used, each has a different reason. The type and amount of fillers are limited, which limits the use of reinforcing fillers that are effective in improving strength at elevated temperatures. Therefore, the strength at a high temperature near the operating temperature is low, which may cause a problem in practical use.

<Means for Solving the Problems> The present invention solves various problems caused by the high viscosity of the copolymer by blending a small amount of another polymer with the tetrafluoroethylene-α-olefin copolymer. As a result of various investigations to solve the problem while maintaining the characteristics, it was completed.

That is, the present invention relates to an ethylene-ethylenically unsaturated ester copolymer containing 12% by weight or more of an ethylenically unsaturated ester, based on 100 parts by weight of a tetrafluoroethylene-α-olefin copolymer. , Vinylidene fluoride-6-fluoropropylene copolymer elastomer 20
A fluorine-containing elastomer composition comprising at least 100 parts by weight or less, and the ethylene-ethylenically unsaturated ester copolymer further comprises 12% by weight
A fluorine-containing elastomer composition which can be vulcanized with an organic peroxide, comprising at least 38% by weight or less of an ethylenically unsaturated ester.

Tetrafluoroethylene used in the present invention
As the α-olefin copolymer, one obtained by copolymerizing tetrafluoroethylene and propylene as the α-olefin is preferably used. Further, as other components,
Acrylic esters, hexafluoropropylene, vinylidene fluoride, perfluoroalkyl vinyl ether,
Chlorotrifluoroethylene, ethylene, butene-1,
Those obtained by copolymerizing glycidyl (meth) acrylate or the like may be used. Tetrafluoroethylene-propylene copolymers having various copolymerization ratios and molecular weights are commercially available and may be used.

The ethylene-ethylenically unsaturated ester copolymer used in the present invention is obtained by copolymerizing ethylene and an ethylenically unsaturated ester by a known method, and is mainly used for lowering the viscosity of the composition.

As ethylenically unsaturated esters, vinyl acetate,
Examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate. Preferred are methyl (meth) acrylate and ethyl (meth) acrylate, and more preferred is methyl methacrylate.

In the present invention, the effect of the copolymerization ratio between ethylene and the ethylenically unsaturated ester on the properties of the composition, particularly on the heat resistance, is very important. Therefore, when ethylene and an ethylenically unsaturated ester are copolymerized, the content of the ethylenically unsaturated ester in the copolymer is at least 12% by weight, preferably at least 12% by weight and at most 38% by weight. It is desirable to copolymerize so that the value of If the amount is less than 12% by weight or exceeds 38% by weight, the adverse effect on the heat resistance increases.

Further, the amount of the ethylene-ethylenically unsaturated ester copolymer relative to the tetrafluoroethylene-propylene copolymer also decreases the viscosity of the composition, and adversely affects the heat resistance of the ethylene-ethylenically unsaturated ester copolymer. It is important to keep it negligible. The amount is from 5 to 25 parts by weight of the ethylene-ethylenically unsaturated ester copolymer per 100 parts by weight of the tetrafluoroethylene-propylene copolymer. If it is less than 5 parts by weight, the effect of lowering the viscosity is not so much seen, and if it exceeds 25 parts by weight, the adverse effect on heat resistance cannot be ignored.

As the vinylidene fluoride-6-fluoride propylene copolymer elastomer, a terpolymer obtained by copolymerizing vinylidene fluoride-6-propylene copolymer with tetrafluoroethylene is further known. . These are produced by a known method such as an emulsion polymerization method, and many commercially available products are also known.

These are used for the purpose of complementing the slight decrease in the flame retardancy inherent in the tetrafluoroethylene-propylene copolymer by the ethylene-ethylenically unsaturated ester copolymer and for improving the oil resistance. It depends on the amount of the saturated ester copolymer used. At least 20 parts by weight of vinylidene fluoride-6-propylene copolymer elastomer based on 100 parts by weight of tetrafluoroethylene-propylene copolymer, without sacrificing other properties, for example
Flame retardancy such as UL VW-1 can be maintained. However, if it exceeds 100 parts by weight, a decrease in mechanical strength will be observed.

In the composition of the present invention, calcium carbonate, magnesium silicate-based mineral, aluminum silicate-based mineral, calcium silicate-based mineral, silica, carbon, aluminum hydroxide, if necessary to increase mechanical strength at high temperatures, A filler such as magnesium hydroxide is used, and these may be appropriately surface-treated. In addition, various additives such as pigments, lubricants, extrusion aids, antioxidants, acid acceptors, and stabilizers can be used.

The composition of the present invention further comprises a polyallyl compound, a known crosslinking aid such as a polyfunctional (meth) acrylate, a diacyl peroxide compound, a peroxyester compound,
After mixing a known crosslinking agent such as a monoperoxyether compound or a diperoxyether compound, the mixture is extruded as usual, and further heated to obtain a product such as an electric wire or a tube.

<Example> Hereinafter, the present invention will be described in more detail with reference to examples.

The properties of the materials used are shown in Table 1. Here, the ethylene-ethynylene unsaturated ester copolymer is simply referred to as an ethylene copolymer, and the vinylidene fluoride-6-propylene copolymer copolymer elastomer is simply referred to as a fluoroelastomer.

As a working method, the materials shown in Table 2 were kneaded with a 12-inch oven roll, and
At mmφ rubber extruder head 70 ° C., on a line from the tin plating annealed copper set of 0.5 mm ² at a temperature condition of the cylinder 60 ° C. 0.
It was extruded with a thickness of 35 mm and immediately contacted with high-pressure steam of 15 atm for 1 minute and 30 seconds to obtain a crosslinked electric wire.

The tensile strength was measured according to JISC3005. The viscosity of the composition was indicated by a direct reading of a two-disc viscometer at 80 ° C. The high temperature mechanical strength of the crosslinked composition is 90
The sharp metal edge of ゜ was slowly lowered onto the cross-linked electric wire, and evaluated by the stress at which the metal edge and the conductor of the electric wire were conducted, that is, the cut-through strength. The heat resistance was evaluated by aging the wire at 250 ° C. for 20 days, winding it around its own diameter, and checking for cracks. Soft flammability was evaluated according to UL Subject 758VW-1. Oil resistance was indicated by residual tensile strength after immersion in ASTM No. 2 oil at 150 ° C. for 72 hours.

As can be seen from Table 2, Example 1 is an example using a fluoroelastomer 1 of a binary copolymer, and Examples 2 and 3 vary the amount of an ethylene-ethylenically unsaturated ester copolymer. The case shows the effect on the characteristics of the wire. In any of the examples, the viscosity value is as low as about 15 or less, and the extrudable material can be extruded, and the mechanical properties, heat resistance, flame retardancy, and oil resistance are well balanced. On the other hand, in Comparative Example 2, when the amount of the ethylene-ethylenically unsaturated ester copolymer is too small, and in Comparative Example 4, the amount is too large. Extrusion is impossible when the amount is too small, and heat resistance is poor when the amount is too large. turn into. In Comparative Example 3, with the formulation of Comparative Example 2,
The filler is reduced. In this case, extrusion is possible, but the reinforcing effect of the filler is reduced, so that the high-temperature cut-through strength exceeds 1 kg, which may cause problems in practical use.

Examples 4, 5, and 6 and Comparative Example 1 differ in the type and content of the ethylenically unsaturated ester of the ethylene-ethylenically unsaturated ester copolymer. In Example 4, the content of the ethylenically unsaturated ester in the copolymer was 38% by weight.
In many cases, Example 5 shows the case where the content of the ethylenically unsaturated ester in the copolymer is as small as 15% by weight, but all of them maintain the balance of properties. Example 6 is an example using vinyl acetate as the ethylenically unsaturated ester. As compared with Example 4, although the tensile strength and the cut-through strength are slightly reduced, the balance of the characteristics is maintained. Comparison between Example 4 and Example 6 shows that methyl methacrylate is particularly preferred as the ethylenically unsaturated ester.

On the other hand, Comparative Example 1 was a case where the content of methyl methacrylate in the copolymer was as small as 10% by weight, and probably because the compatibility with the tetrafluoroethylene-propylene copolymer deteriorated, or the tensile strength decreased. , Heat resistance is rejected.

Comparative Examples 5 and 6 are cases where the amount of vinylidene fluoride-6-propylene fluoride copolymer-based elastomer in the composition exceeds the limit of the present invention. Compared with Examples 2 and 3, in Comparative Example 5 in which too much vinylidene fluoride-6-fluoropropylene copolymer-based elastomer was used, the decrease in tensile strength was large, and in Comparative Example 6, in which no vinylidene fluoride-6-propylene copolymer elastomer was used, it was difficult. It turns out that it becomes a flammability rejection.

<Effects of the Invention> According to the present invention, a small amount of an ethylene-ethylenically unsaturated ester copolymer is blended with a tetrafluoroethylene-α-olefin copolymer, and vinylidene fluoride-6 is further blended.
By adding fluorinated propylene copolymer-based elastomers, problems caused by the high viscosity of the tetrafluoroethylene-α-olefin copolymer can be maintained while maintaining properties such as mechanical strength, heat resistance, and flame retardancy. However, the oil resistance can be improved rather than solved.

For example, this makes it possible to stably produce extruded products such as tubes and electric wires with good productivity even if they are thin products. Further, since the restriction on the amount of the filler used is reduced, a large amount of the reinforcing filler can be used, so that the high-temperature physical properties as shown by the high-temperature cut-through strength can be improved. In addition, the use of a large amount of the filler leads to a reduction in the unit price of the composition, and thus the molded product, and is extremely useful in industry such that it can be used in applications where conventional expensive fluoroelastomer could not be used. .

Claims (2)

(57) [Claims] 1. An ethylene-ethylenically unsaturated ester copolymer containing at least 12% by weight of an ethylenically unsaturated ester with respect to 100 parts by weight of a tetrafluoroethylene-α-olefin copolymer. , Vinylidene fluoride-6-fluoropropylene copolymer elastomer 20 or more
A fluorine-containing elastomer composition comprising at least 100 parts by weight or less. 2. The method according to claim 1, wherein the ethylene-ethylenically unsaturated ester copolymer contains from 12% by weight to 38% by weight of the ethylenically unsaturated ester. Fluorine-containing elastomer composition.