JPH0912818A - Fluororesin composition and heat-shrinking tube - Google Patents

Abstract

PURPOSE: To obtain a fluororesin composition being capable of a light color formulation and giving a molding having excellent heat resistance and mechanical strengths, a low hardness and easy bendability and to provide a heat- shrinking tube made therefrom. CONSTITUTION: This fluororesin composition is obtained by mixing 100 pts.wt. tetrafluoroethylene/propylene copolymer with above 50 to 400 pts.wt. thermoplastic fluorocopolymer having a compositional ratio among vinylidene fluoride, hexafluoro-propylene and tetrafluoroethylene within the region of a quadrangle defined by four points (10:35:55), (10:15:75), (55:5:40) and (55:15:30) in the triangular diagrame. In order to realize a light color formulation, it is desirable that the number-average molecular weight of the tetrafluoroethylene/propylene copolymer is 100,000 or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine-containing resin composition, and in particular, it has low hardness and heat resistance to withstand use at a high temperature of about 180 ° C., has excellent mechanical strength and insulation properties, and has a bright color compounding. The present invention relates to a fluorine-containing resin composition that can be used for a coating material for electric wires, an electrically insulating tube, a heat-shrinkable tube, and the like, and is particularly useful as a heat-shrinkable tube composition.

[0002]

2. Description of the Prior Art Tetrafluoroethylene-propylene copolymers have come to be used as electric insulating materials because they are excellent in heat resistance, oil resistance, chemical resistance, electric insulation and the like.

[0003] For example, JP-A-61-211114 discloses a block copolymer of vinylidene fluoride and hexafluoropropene or these and other ethylenically unsaturated monomers, and an elastomeric polymer chain segment and a non-elastomer. Described is a fluororubber compounding composition obtained by adding a polyfunctional monomer having two or more unsaturated bond functional groups in the molecule and a zinc compound or a lead compound to a fluorine-containing thermoplastic elastomer composed of a polymerizable polymer chain segment. JP-A-6-9844 discloses a composition containing a tetrafluoroethylene-propylene copolymer having a number average molecular weight of 100,000 or more and an ethylene-based polymer in a weight composition ratio of 98: 2 to 80:20. 50 parts by weight or less of a fluororubber copolymer containing vinylidene fluoride should be added to 100 parts by weight of the product. Electrically insulating composition, characterized is described.

However, in the composition disclosed in JP-A-61-211114, the mechanical strength of the fluorine-containing thermoplastic elastomer itself is low, and JP-A-6-984.
In the composition described in Japanese Patent Publication No. 4, since the fluororubber composition is mainly the main component, the mechanical strength is low, and conversely, if the ratio of the ethylene-based polymer is increased to increase the mechanical strength,
There is a problem that the heat resistance decreases.

Further, JP-A-2-258324 discloses a tetrafluoroethylene-propylene copolymer, a vinylidene fluoride-hexafluoropropylene copolymer,
A mixture of at least one selected from a fluorine-containing copolymer composed of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer and a fluorine-based graft copolymer, which is chemically crosslinked. Although a heat-shrinkable tube to be described is described, this mixture is a graft copolymer in which the fluorine-based graft copolymer is a vinylidene fluoride hexafluoropropylene-based copolymer and an ethylene-chlorotrifluoroethylene copolymer. In addition to having a chemical structure different from that of the copolymer of the present invention, it has excellent mechanical strength, but has a high hardness and is extremely difficult to bend when a tube or the like is molded. There's a problem.

Further, in Japanese Patent Laid-Open No. 284712/1988, a composition obtained by adding a crosslinking aid to tetrafluoroethylene-propylene copolymer, ethylene / vinyl acetate copolymer and polyvinylidene fluoride is crosslinked to form an electric wire. It is described to be used for the coating of the above-mentioned materials, and is disclosed in JP-A-63-3134.
No. 11, JP-A-63-284713 and JP-B No. 2-17341 disclose a tetrafluoroethylene-propylene copolymer and a fluorine-based polymer such as ethylene-tetrafluoroethylene which causes a small decrease in the molecular weight of the polymer upon irradiation with radiation. It is disclosed that the composition with the resin is crosslinked using ionizing radiation.

[0007] These compositions also have the drawback that when they are attempted to improve their mechanical properties, their hardness increases and, like the above-mentioned mixture, they become very difficult to bend when the tube is molded. There is.

When the number average molecular weight of the tetrafluoroethylene-propylene copolymer is 100,000 or more, the Mooney viscosity becomes too high and extrusion molding becomes difficult. Therefore, the molecular weight is lowered to 80,000 or less by firing. Those capable of extrusion molding are generally commercially available. The tetrafluoroethylene-propylene copolymer having such a adjusted molecular weight has a drawback that it is extremely difficult to blend a bright color such as white because it is black.

For example, even if 20 parts by weight of titanium oxide which is a pigment having a large hiding power is added to 100 parts by weight of the black tetrafluoroethylene-propylene copolymer, a satisfactory white color cannot be obtained. Satisfactory whiteness can be obtained for the first time by adding about 100 parts by weight of titanium oxide. However, addition of such a large amount of titanium oxide causes a problem that mechanical properties are deteriorated.

On the other hand, the composition ratio of vinylidene fluoride, propylene hexafluoride and ethylene tetrafluoride is 10:35:55,
10:15:75, 55: 5: 40, 55:15:30
The fluorine-containing copolymer within the range surrounded by 4 points is a conventional fluorine-containing elastomer (vinylidene fluoride, propylene hexafluoride, tetrafluoroethylene having a composition ratio of 25: 4).
0:35, 50:15:35, 75: 25: 0, 40:
(Within the range surrounded by 4 points of 60: 0), the properties are essentially different, and the conventional elastomer has a melting point which is not recognized, and its mechanical strength is 2% of that of the elastomer. It is as high as 3 to 3 times, and has recently attracted attention as a material that can be sufficiently used without mixing a filler that serves as a reinforcing material such as an elastomer and without cross-linking.

However, this fluorine-containing copolymer is
Although it has excellent mechanical properties, it has high hardness and tubes made of these materials are difficult to bend and have a melting point of 1
Since it is relatively low at about 10 to 160 ° C., there is a problem in heat resistance and the like.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems of the prior art and to enable bright color compounding.
It is an object of the present invention to provide a fluorine-containing resin composition having excellent heat resistance and mechanical strength, which has low hardness and is easily bent when formed into a tubular shape, and a heat-shrinkable tube using the composition.

[0013]

Means for Solving the Problems As a result of various studies to achieve the above object, the present inventor has found that tetrafluoroethylene-
The present invention has been completed based on the idea of mixing a propylene-based copolymer and a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer having a specific composition ratio.

That is, in the present invention, the composition ratio of vinylidene fluoride, propylene hexafluoride, and tetrafluoroethylene is 10:35:55, 10 with respect to 100 parts by weight of the tetrafluoroethylene-propylene copolymer. : 15:75, 55: 5: 4
A fluorine-containing resin composition containing more than 50 parts by weight and 400 parts by weight or less of a fluorine-containing thermoplastic copolymer within a range surrounded by four points of 0, 55:15:30, and further the above composition. A fluororesin composition in which 30 parts by weight or less of an ethylene-based polymer is further blended into the product, and a heat-shrinkable tube using the composition.

The tetrafluoroethylene-propylene-based copolymer used in the present invention is not particularly limited in the number average molecular weight when light-colored compounding is not required, but when light-colored compounding is required. It is preferable to use a high molecular weight copolymer having a number average molecular weight of 100,000 or more.

The composition of the fluorine-containing thermoplastic copolymer of vinylidene fluoride, propylene hexafluoride and tetrafluoroethylene used in the present invention is 10:35:55 as shown in FIG. 10:15:75, 55:
It is within the range surrounded by 4 points of 5:40 and 55:15:30, and is a conventional vinylidene fluoride-propylene hexafluoride-
The ethylene tetrafluoride-containing elastomer is a polymer having a different composition ratio and having completely different melting points.

Incidentally, the conventional fluorine-containing elastomer is
As shown in FIG. 1, the composition ratio is 25:40:35, 5
4 of 0:15:35, 75: 25: 0, 40: 60: 0
It is within the range surrounded by dots and basically has no melting point. As the fluorine-containing thermoplastic copolymer used in the present invention, THV polymer [manufactured by 3M] can be preferably used.

In the fluorine-containing resin composition of the present invention,
It is necessary to add more than 50 parts by weight and 400 parts by weight or less of the above fluorine-containing thermoplastic copolymer to 100 parts by weight of the tetrafluoroethylene-propylene-based copolymer. When the blending amount of the fluorinated thermoplastic copolymer is 50 parts by weight or less, when the heat-shrinkable tube is processed, the diameter retention becomes weak when expanded, and conversely, when it exceeds 400 parts by weight, the hardness is increased. Problems such as high temperature and low heat resistance occur.

A more preferable range of blending amount is 55 to 150.
Parts by weight. In order to reduce the hardness of the vulcanized product, it is generally preferable to add 30 parts by weight or less of binary or ternary fluororubber.

Further, when a tetrafluoroethylene-propylene copolymer having a number average molecular weight of 100,000 or more is used for light-colored compounding, the Mooney viscosity of the compound is generally high and the compound is powdery at the time of extrusion molding. Therefore, it is preferable to mix an ethylene polymer to reduce the compound viscosity.

Examples of the ethylene polymer used in the present invention include homopolymers or copolymers of olefins such as ethylene, propylene, butene, octene, dicyclopentadiene and ethylidene norbornene. Examples of polymers include copolymers of the above polyolefins with vinyl acetate, ethyl acrylate, methyl acrylate, ethyl methacrylate, and the like. In particular, an ethylene-vinyl acetate copolymer having a melting point of 100 ° C. or lower is used. This ethylene-based polymer is used for the purpose of lowering the viscosity of the compound while avoiding the scorch of the compound.
Those having no melting point or having a melting point of 100 ° C. or lower are preferable.

The amount of the ethylene polymer blended is 30 parts by weight or less based on 100 parts by weight of the tetrafluoroethylene-propylene copolymer. When the ethylene polymer has a number average molecular weight of 100,000 or less of a tetrafluoroethylene-propylene copolymer, there is no problem in molding even if it is not blended, but a copolymer having a number average molecular weight of more than 100,000 is used. By incorporating an ethylene polymer into the coalescence, the processability is improved regardless of the molecular weight. However, if the blending amount exceeds parts by weight, the heat deterioration of the ethylene-based polymer rapidly progresses, and heat resistance that can withstand use at 180 ° C. cannot be obtained practically.

The fluorine-containing resin composition of the present invention is generally crosslinked by using chemical crosslinking or ionizing radiation. Examples of the ionizing radiation include X rays, γ rays, proton rays, deuteron rays, neutron rays, α rays, and β rays, but γ rays or β rays are preferably used. Further, chemical crosslinking can generally be performed by lowering the molding temperature, but since vulcanization time becomes very long and moldability is poor, it is generally preferable to carry out crosslinking by ionizing radiation.

Further, it is preferable to use a crosslinking aid in order to achieve the improvement of the degree of crosslinking. Examples of the cross-linking aid include allyl-type compounds, sulfur, organic amines, maleimides, methacrylates, divinyl compounds, polybutadiene and the like, but allyl-type compounds represented by triallyl isocyanurate and triallyl cyanurate are the most preferable. Preferably, the blending amount thereof is usually 2 to 10 parts by weight, preferably 3 to 5 parts by weight, from the viewpoint of both improvement of crosslinking degree and saturation of effect.

Further, an inorganic filler is used in order to facilitate the kneading of the crosslinking aid and the components of the resin and rubber at the time of extrusion molding. As the inorganic filler, talc, clay,
Examples thereof include anhydrous silicic acid, calcium carbonate, calcium silicate, etc., but anhydrous silicic acid, calcium carbonate, calcium silicate,
Talc is preferred because it does not significantly deteriorate the tensile properties even if it is blended in a large amount.

Particularly, calcium carbonate or talc having a particle diameter in the range of 1 to 3 μm is effective in suppressing the occurrence of foaming during extrusion molding, preventing the settling of the tube during tube molding, and improving the inner surface tackiness. -50 parts by weight, preferably 20-30 parts by weight.

Further, in addition to the above-mentioned components, addition of rare earth oxides for improving the crosslinking efficiency, stabilizers, pigments, antioxidants,
Various additives such as lubricants can be blended.

[0028]

EXAMPLES The present invention will be described in more detail with reference to Examples 1 to 9 and Comparative Examples 1 to 10. The total weight was determined according to the specific gravity so that the total volume of the kneaded composition would be 2.4 liters, and the materials shown in Tables 1 and 2 were preheated to 160 ° C. according to the compounding ratio, and the pressure was 3 liters. I put it in a kneader. The pressure lid was lowered, one rotation speed of the pair of rotary blades was set to 29 rpm, and the other rotation speed was set to 43 rpm to start kneading. First, the polymer alone was kneaded for 2 minutes, then all the compounding ingredients were added and kneaded for 5 minutes. Then, the kneaded product was discharged, and the sheet was shaped by a roll mill.

This kneaded product was a 40 mm extruder (L / D = 80 ° C., head temperature 180 ° C., cylinder 1 temperature 170 ° C., cylinder 2 temperature 130 ° C.
22) was used to extrude a tube having an inner diameter of 2.5 mm and a wall thickness of 0.5 mm.

Next, Co with a holding capacity of 1 million Curie
^{A 60-} ray source was used to irradiate 100 KGy of γ-rays for crosslinking.

Further, the crosslinked tube was inserted into a stainless pipe having an inner diameter of 6.0φ, both ends of the crosslinked tube were taken out from the stainless pipe, one end thereof was sealed, and the other end was introduced by an air compressor. Connect with a pipe. After leaving the stainless steel pipe in an oven at 140 ° C for 15 minutes, introduce an air pressure of 5 kgf / cm ² into the cross-linking tube to expand the cross-linking tube and then put it in water together with a stainless steel tube to fix the shape. A shrink tube was formed.

In Comparative Examples 1 and 2, kneading was performed at a kneader temperature of 80 ° C. and extrusion temperature was 80 ° C. In Comparative Example 3, kneader kneading was not performed, and pellets were used as they were.
It was extruded at 80 ° C. Further, in Comparative Examples 4 and 5, both the kneader temperature and the extrusion temperature were 250 ° C., and in Comparative Example 6, the kneader kneading was performed at 180 ° C., and the cross-linking agent was added at 110 ° C. by a roll mill, and then the extrusion temperature was 140 ° C.
The temperature was adjusted to 0 ° C., and after extrusion, it was left in a steam can of 6 kg / cm ² for 30 minutes to crosslink.

The processing temperature for processing the heat-shrinkable tube was about 20 ° C. higher than the melting point of the resin component with respect to the resin component blended in the composition. To be precise, Comparative Example 1: 60 ° C., Comparative Example 2: 105 ° C., Comparative Example 3: 140
C., Comparative Example 4: 240 ° C., Comparative Example 5: 250 ° C., Comparative Example 6: 185 ° C., Comparative Example 7: 180 ° C.

The cross-linked tube was measured for tensile strength, elongation, heat resistance, hardness and dimensional stability during storage after heat-shrink processing as described above. These measuring methods are as follows. However, with respect to tensile strength, elongation, heat resistance, and hardness, the heat-shrinkable tube was allowed to stand in an oven at the processing temperature for processing the heat-shrinkable tube for 10 minutes to shrink the tube, and then tested.

(1) The initial tensile strength and the initial elongation are JIS
According to C 3005 (Insulator tensile test), the tube shape was measured. Initial tensile strength 1.3kg
/ Mm ² or more and an initial elongation rate of 200% or more are generally required values.

(2) The tensile strength and residual elongation after aging were measured according to JIS after the crosslinked tube was heat aged at 220 ° C. for 96 hours.
Tensile strength and elongation were measured by C3005 (insulator tensile test) and expressed as a percentage of the initial tensile strength and elongation.

(3) Regarding the hardness, according to JIS K 6253, the crosslinked tube was torn in the longitudinal direction, three such test pieces were stacked to prepare a micro test piece, and IRHD was measured using a Wallace hardness tester. It was directly read and measured.
Below 85 is a general requirement value.

(4) Regarding the dimensional stability of the heat-shrinkable tube during storage, the inner diameter of the heat-shrinkable tube immediately after processing was measured according to JIS C 2133 (Dimensional stability during storage). After leaving it in an oven at ℃ for 336 hours, the inner diameter of the tube was measured again, and the change rate of this inner diameter was expressed as a percentage of the following equation. 90% or more is a general requirement value.

(Equation 1)

The results are shown in Tables 1 and 2.

[Table 1]

[Table 2] As is clear from the results shown in Tables 1 and 2, Examples 1 to 9
Is excellent in initial strength, elongation, heat resistance, and has a hardness of 85 or less at the maximum in the Wallace hardness tester type A durometer hardness, which is much easier to bend than conventional ones and has a hardness similar to that of soft vinyl chloride. The dimensional stability during storage after heat shrink processing was also good. Further, in Examples 2 and 4 to 9 in which the tetrafluoroethylene-propylene copolymer having a number average molecular weight of 100,000 was used, white bright color blending could be performed.

On the other hand, when the fluorine-containing thermoplastic copolymer is not compounded (Comparative Example 1), initial tensile strength and dimensional stability during storage are low, and when the compounding amount is too small (Comparative Examples 8 and 9). The value of dimensional stability during storage was low. Furthermore, even when a usual vinylidene fluoride-based ternary fluorine-containing elastomer was blended in place of the fluorine-containing thermoplastic copolymer, the initial tensile strength was increased and the dimensional stability during storage was low (comparison). Example 2). Especially in Comparative Examples 1 and 2, since there is almost no crystalline polymer, heat shrinkage hardly occurs, and it cannot be used as a heat shrink tube.

In the case of only the fluorine-containing thermoplastic copolymer (Comparative Example 3), the ethylene-tetrafluoroethylene copolymer (Comparative Example 5), and the Cefralsoft type fluorine-containing thermoplastic elastomer (Comparative Example 6) were blended. In this case, and in the case where the fluorine-containing thermoplastic copolymer was blended in an amount more than necessary (Comparative Example 10), the hardness increased and it became very difficult to bend.

Furthermore, when polyvinylidene fluoride is blended (Comparative Example 7), the hardness is increased and the heat resistance is lowered. When a Daiel thermoplastic type fluorine-containing thermoplastic elastomer (Comparative Example 4) is blended, both initial tensile strength and dimensional stability during storage are low.

[0043]

EFFECTS OF THE INVENTION According to the fluorine-containing resin composition of the present invention, it is possible to obtain a bright color compound, and it is possible to obtain a molded product which is excellent in heat resistance and mechanical strength and has low hardness and is easy to bend. When used as a tube formulation, the dimensional stability during storage is good, and an excellent heat-shrinkable tube can be obtained.

[Brief description of the drawings]

FIG. 1 is a ternary composition diagram showing the composition ratio of a fluorine-containing thermoplastic elastomer used in the present invention and the composition ratio of a conventional fluorine-containing elastomer.

[Explanation of symbols] VDF Vinylidene fluoride HFP Hexafluoropropylene TFE Tetrafluoroethylene

Claims (4)

[Claims] 1. A composition ratio of vinylidene fluoride, propylene hexafluoride, and tetrafluoroethylene to 10 parts by weight of 100 parts by weight of a tetrafluoroethylene-propylene copolymer is 10:35:
55, 10:15:75, 55: 5: 40, 55: 1
A fluorine-containing resin composition, characterized by blending more than 50 parts by weight and 400 parts by weight or less of a fluorine-containing thermoplastic copolymer within a range surrounded by 4 points of 5:30. 2. The fluorine-containing resin composition according to claim 1, wherein the tetrafluoroethylene-propylene-based copolymer has a number average molecular weight of 100,000 or more. 3. The fluorine-containing resin composition according to claim 2, which further contains 30 parts by weight or less of an ethylene polymer. 4. A fluorine-containing heat-shrinkable tube comprising the fluorine-containing resin composition according to claim 1, 2 or 3.