JPS6383143A - Production of molding of crosslinked thermoplastic urethane composition - Google Patents

Abstract

PURPOSE:To obtain the title molding having excellent water resistance, by mixing a thermoplastic polyurethane resin with a specified antioxidant, carbon black and a polyfunctional monomer, molding the resulting compsn. and irradiating the molded product with an ionizing radiation to crosslink it. CONSTITUTION:A molding of a thermoplastic polyurethane compsn. obtd. by mixing 100pts.wt. thermoplastic polyurethane resin with 0.5-10pts.wt. antioxidant having 3,5-di-tert-butyl-4-hydroxyphenyl groups [e.g., N,N'-hexamethylene bis(3,5-di-t-butyl-4-hydroxy-hydrocinnamide)], 0.1-10pts.wt. carbon black and 1-20pts.wt. polyfunctional monomer {e.g., a compd. of the formula [wherein m is 3-4, n is 1-0 and m+n=4; and R is a (hydroxy)alkyl] is irradiated with an ionizing radiation at a dose of 1-30 Mrad to crosslink it. The title compsn. having excellent water resistance can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a crosslinked thermoplastic urethane composition molded article having excellent water resistance.

(Prior art) In general, thermoplastic urethane resin softens at 150 to 200 cc and becomes a liquid with relatively low viscosity, so when it is used as an insulation coating material for electric wires, etc., the ambient temperature may change for some reason. When the temperature rises significantly or when exposed to high temperatures due to overcurrent, ordinary insulation coating materials, such as polyvinyl chloride, do not undergo any change, but polyurethane undergoes flow and is unable to retain its original shape. It had the disadvantage that it was not. In order to improve this drawback, it is being considered to irradiate thermoplastic polyurethane with ionizing radiation to crosslink it and improve its instantaneous heat resistance, but it is said that irradiation of thermoplastic polyurethane with radiation significantly reduces its water resistance. There were problems and it could not be put into practical use.

Note that thermoplastic polyurethane has poor crosslinking efficiency, so 50M
Although crosslinking does not occur unless a high dose of radiation is applied, such as with a land, even if a very small dose of radiation, such as about 2M rad, is applied, water resistance may deteriorate. It is also possible to crosslink by adding a crosslinking accelerator to thermoplastic polyurethane to reduce the irradiation dose, but even if a crosslinking accelerator is added, water resistance will decrease due to irradiation with a small amount of ionizing radiation. Therefore, this problem could not be solved.

(Problems to be Solved by the Invention) As a result of extensive research in view of the current situation, the present invention has found that it is possible to obtain a crosslinked thermoplastic polyurethane composition molded article with excellent water resistance by crosslinking by irradiation with ionizing radiation. We have developed a method that can do this.

(Means for Solving the Problems) The present invention provides 100 parts by weight of thermoplastic polyurethane resin, 3 parts by weight,
5 C 0.5 to 10 parts by weight of antioxidant having tert-butyl-4-hydroxyphenyl group, average particle size 1
A thermoplastic polyurethane composition containing 0 to 200 mμ car 2712720.1 to 10 parts by weight and 1 to 20 parts by weight of a polyfunctional monomer is molded into a desired shape, and then irradiated with 1 to 30 Mrad of E female radiation. It is characterized by crosslinking.

In the present invention, in particular, by adding a polyfunctional additive, it is possible to suppress the deterioration of performance such as water resistance and heat aging resistance as much as possible even when the thermoplastic polyurethane is crosslinked by irradiation with radiation. Among the polyfunctional monomers, trifunctional or higher functional monomers exhibit a remarkable effect of promoting crosslinking.

That is, the general formula CH3 (CH2-C-Co-0CH2÷1c-Rn (where m is 3 to 4, n is 1 to 0, and represents a positive integer in the relationship of m+n-4, and R is an alkyl group) (represents an organic group mainly composed of carbon or hydrogen such as a hydroxyalkyl group), and methacrylic acid ester is particularly preferred.

The reason why the amount is limited to 1 to 20 parts by weight is that if it is less than 1 part by weight, the effect of improving water resistance is weak, and if it exceeds 20 parts by weight, the effect of improving water resistance is not particularly improved. It's for a reason.

In addition, in the present invention, the reason why the antioxidant is limited to 0.5 to 10 parts by weight and the carbon blank is limited to 0.1 to 10 parts by weight is that if the content is less than the respective ranges, the effect of improving water resistance is weak and the This is because if it exceeds this range, the effect of improving water resistance will not be noticeable.

Further, the reason why the irradiation dose of ionizing radiation is limited to 1 to 30 Mrad is that the thermoplastic urethane composition can hardly be crosslinked at less than IM rad;
This is because if it exceeds d, the water resistance of the composition will be reduced.

(Example) Examples (1) to (7), Comparative Examples (1) to (To) As shown in Table 1, thermoplastic polyurethane, antioxidant, carbon blank, and polyfunctional monomer were each mixed at 150-190%
The composition of the present invention and the composition of the comparative example were uniformly kneaded using a roll mill at ℃ and formed into a sheet shape, and then cooled and pelletized to form a pellet shape.

Using this pellet, a copper conductor with an outer diameter Q of 8 mm was extruded and coated using an extruder with a diameter of 30 mm and L/D = 22 at about 180°C to an outer diameter of 1.4 mm. then 500
A crosslinked I-urethane electric wire was obtained by irradiating an electron beam with a KeV electron beam accelerator under the conditions shown in Table 1.

The water resistance and glue fraction of the crosslinked polyurethane wire thus obtained were measured. The results are listed in Table 1 and shown in the drawings.

In addition, the water resistance was measured after winding the above electric wire to the same diameter.
The crosslinked polyurethane insulator was immersed in hot water at 95° C. to observe whether or not cracks were generated.

The glue fraction is measured by immersing the sample in dimethylformamide at 120° C. for 8 hours and then evaporating the solvent, and then calculating the weight as 100% of the weight before immersion.

Notes (1) Caprolactone-based thermoplastic polyurethane (manufactured by Nihon Elastolan Co., Ltd.) (2) Ether-based thermoplastic polyurethane (manufactured by Nippon Elastolan Co., Ltd.) (3) Tetrakis [methylene-3 (3,5-di-t-butyl- 4-Hydroxyphenyl)propionate comethane (manufactured by Cibageigi) (4) NN'-hexamethine/bis(3,5-di-t-
Butyl-4-hydroxy-hydrocinamide (manufactured by Ciba Geigi) (5) 44'-thiobis(6-t-butyl-3-methylphenol) (manufactured by Kawaguchi Chemical Co., Ltd.) (6) NN'-di-β-su7thirup -Finini diamine (manufactured by Daien Shinko Co., Ltd.) (7) Caden black average particle diameter 27 mμ (8) Trimethylol methane trimethacrylate (manufactured by Shin Nakamura Chemical Co., Ltd.) (9) Tetramethylol methane trimethacrylate (Shin Nakamura (manufactured by Kagaku Co., Ltd.) α0 triallyl isocyanate (manufactured by Nippon Kasei Co., Ltd.) As is clear from the above table, cross-linked urethane insulated wires produced by the method of the present invention have a high glue fraction and have cross-linked bonds, but have excellent water resistance. This is something that can be done.

(Effects) As detailed above, according to the method of the present invention, a crosslinked thermoplastic urethane composition formed body having excellent water resistance can be obtained, which is extremely useful industrially.

[Brief explanation of the drawing]

The drawing is a graph showing the relationship between the water resistance and the glue fraction as a function of the irradiation dose when a thermoplastic urethane composition is irradiated with radiation.

Claims (2)

[Claims] (1) 100 parts by weight of thermoplastic polyurethane resin, 3.5
-Antioxidant having di-tert-butyl-4-hydroxyphenyl group 0.5 to 10 parts by weight, average particle size 10 to 10 parts by weight
A molded body made of a thermoplastic polyurethane composition mixed with 0.1 to 10 parts by weight of 200 mμ carbon black and 1 to 20 parts by weight of a polyfunctional monomer was exposed to 1 ionizing radiation.
A method for producing a molded article of a crosslinked thermoplastic urethane composition, which comprises crosslinking it by irradiating it with ~30 Mrad. (2) The polyfunctional monomer has a general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (However, in the formula, m is 3 to 4, n is 1 to 0, and m + n =
Represents positive integers in the relationship 4. R represents an organic group mainly composed of carbon or hydrogen, such as an alkyl group or a hydroxyalkyl group. manufacturing method.