JPH0155661B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to an electron beam irradiation crosslinked polyolefin composition. [Prior Art] Polyolefins are widely used due to their excellent electrical and mechanical properties. However, depending on the usage environment, their heat deformation resistance, mechanical properties, chemical resistance, etc. Further improvements may be required and crosslinking is usually carried out for this purpose.
One such crosslinking method is the electron beam irradiation method, which is much more efficient than steam crosslinking methods, especially for thin coating materials such as thin insulated wires used in equipment wiring. Because of its advantages, electron beam irradiation is mainly used, at least in this field. In general, in order to use polyolefins in high-temperature environments, it is important to improve their heat deformation resistance through crosslinking and at the same time improve their heat aging resistance. Crosslinking accelerators and heat aging inhibitors have been added to resins to increase crosslinking efficiency. The crosslinking accelerator is, for example, trimethylolpropane trimethacrylate (hereinafter abbreviated as TMPT), and the heat aging inhibitor is 4,4'-thio-bis(6-t-
Butyl-m-cresol) (hereinafter abbreviated as phenolic anti-aging agent) is used. [Problems to be Solved by the Invention] However, when conventional crosslinking accelerators and heat aging inhibitors are used together with polyolefins, the following problems occur. In other words, the crosslinking promoting effect of TMPT is not very large. Phenolic anti-aging agents further reduce the crosslinking promoting effect of TMPT. TMPT has poor affinity and tends to cause bleed phenomenon. It is. [Means for Solving the Problems] In order to solve the above problems, the present invention provides 100 parts by weight of polyolefin resin with 0.5 to 5 parts by weight of diallyl chlorendate and 2-mercaptobenzimidazole or 2-mercapto-methyl. −
This method employs a method of preparing a composition containing 2 to 30 parts by weight of benzimidazole. [Example] The polyolefin referred to in this invention is, for example,
Refers to one or more polymers of _C2 to _C8 olefin monomers, polymers of _C2 to _C8 diene monomers, ethylene vinyl acetate copolymers, ethylene ethyl acrylate copolymers, and mixtures thereof. . Furthermore, the diallyl chlorendate referred to in this invention has the effect of promoting dehydrogenation reaction from polymer chains and promoting crosslinking reaction when irradiated with electrons.
The following chemical structure It is expressed as Note that n may be approximately 1 to 4, but preferably 1 or 2. This diallylchlorendate is a liquid and has a very good affinity for polyolefins and is well dispersed. In the present invention, it is desirable that the amount of diallyl chlorendate added is 0.5 to 5 parts by weight per 100 parts by weight of polyolefin. This is because if the amount added is less than 0.5 parts by weight,
This is because no crosslinking promoting effect is observed, and conversely, if the amount exceeds 5 parts by weight, not only is there no improvement in the crosslinking promoting effect, but also a bleeding phenomenon occurs, which significantly reduces the commercial value. Next, as the heat aging inhibitor in this invention, 2-mercaptobenzimidazole is used in combination with the above-mentioned crosslinking accelerator.

[Formula] or 2-mercapto-methyl-benzimidazole These compounds prevent the aging of polyolefins due to oxygen during electron beam irradiation in the air, do not inhibit the crosslinking reaction, do not cause any bleeding phenomenon, and exhibit extremely remarkable effects on heat aging resistance. The amount of such heat aging inhibitor added is 2 to 100 parts by weight of polyolefin.
The amount is preferably 30 parts by weight. This is because if the heat aging inhibitor is used in a small amount, less than 2 parts by weight, it is insufficient to improve heat resistance.On the other hand, if the amount is more than 30 parts by weight, not only can no effect be expected from increasing the amount, but also a decrease in mechanical properties. This is because it becomes noticeable and undesirable. Now, the following standard composition, namely (parts by weight) (1) Linear low-density polyethylene (manufactured by Nihon Unitika Co., Ltd.: GS-650) ...80 parts (2) Ethylene-ethyl acrylate copolymer (manufactured by Nippon Unitika Co., Ltd.: DPDJ-6182) ) ...20 parts as a flame retardant and flame retardant aid, (3) decabromodiphenyl ether (manufactured by Mitsui Fine Chemicals: Planelon DB-102)
...50 parts (4) Antimony trioxide ...20 parts Also as a processing aid (5) Zinc white ...5 parts (6) Zinc stearate ...2 parts (7) Barium-zinc stabilizer ...3 parts plus Table 1 crosslinking accelerator and heat aging preventer in the proportions shown in

【table】

[Table] An inhibitor was added (Examples 1 to 10). The raw materials in each of these examples were heated and kneaded at 150 to 180°C using a mixing roll, then press-formed under the conditions of a gauge pressure of 150 kg/cm ² and 180°C for 10 minutes to produce a 0.5 mm thick sheet, and then accelerated. The obtained sheet was irradiated with an electron beam in air at a voltage of 750 keV and 44 mA. The amount of electron beam irradiation at this time was 20 Mrad in each case, and the tensile strength (Kg/mm ² ) and elongation (%) of the sheet after the electron beam irradiation were measured. For sheets after electron beam irradiation, the tensile strength and elongation after a heat aging test held in an air heat aging tester at 158°C for 7 days in accordance with the UL standard's 125°C rating evaluation method are calculated based on the heat aging test. It was determined in the form of residual percentage (%) with respect to the value before the aging test, and was obtained along with the gel fraction (%) after electron beam irradiation, presence or absence of bleeding phenomenon (present is indicated by × mark, absence is indicated by ○ mark), etc. The results are summarized in Table 1. In crosslinked polyolefins, as the degree of crosslinking increases, the gel fraction increases, and the heat deformation decreases. After immersion, it was dried at 120°C for 24 hours, and the gel fraction (%) was determined by the equation: weight after drying/weight before immersion x 100. In addition, "TMPR" in the same table is trimethylolpropane trimethacrylate as described above. Furthermore, in contrast to this, a crosslinking accelerator and a heat aging inhibitor were added to the standard formulations of Examples 1 to 10 in the proportions shown in Table 2 (Comparative Examples 1 to 15). here,
The crosslinking accelerator was the same as in Examples 1 to 10, but the heat aging inhibitor was 4,4'-thio-bis(6-t-butyl-m-cresol), manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.: Nokrac 300; 2,2,4-trimethyl-1,2-dihydroquinoline polymer Manufactured by the same company: Nokrac 224, 2,2'-methylene-bis(4-methyl-6-
t-Butylphenol) manufactured by the same company: Nokrac NS-6; N,N'-diphenyl-P-phenylenediamine manufactured by the same company: Nokrac DP was used. The sheet manufacturing conditions, electron beam irradiation conditions, and physical property measurement methods were all the same as in the previous example, and the obtained results were summarized and listed in Table 2. However, the physical property values shown in Table 2 were Comparing with those in the table, Comparative Example 1 has elongation after heat aging test, Comparative Example 2 has tensile strength after irradiation, Comparative Examples 3, 4, and 5 have bleed phenomenon, Comparative Example 4
After further heat aging test

【table】

〔effect〕

As described above, the present invention has enabled electronics to exhibit previously unseen good results in terms of excellent crosslinking promotion effects, mechanical properties such as tensile strength and elongation, heat aging resistance, and bleed resistance. A radiation-irradiated polyolefin composition was obtained.

Claims (1)

[Claims] 1. An electron beam irradiation crosslinked polyolefin composition comprising 0.5 to 5 parts by weight of diallylchlorendate and 2 to 30 parts by weight of 2-mercaptobenzimidazole or 2-mercapto-methyl-benzimidazole to 100 parts by weight of polyolefin.