JPS6139963B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to crosslinkable polyolefin compositions. More specifically, the present invention relates to a polyolefin composition containing a polyolefin, a Ziels-Alder adduct, and an organic peroxide and exhibiting excellent crosslinking speed and crosslinking effect. Cross-linked polyolefin maintains the original excellent properties of polyolefin, such as electrical properties and mechanical strength, while improving heat resistance, chemical resistance, environmental stress cracking resistance, and elastic modulus, making it suitable for heat-resistant pipes for insulating electric wires and cables. It is widely used in the fields of tubes, films, packing, and gaskets. In general, crosslinking methods for polyolefins include a crosslinking method using an organic peroxide, as seen in polyethylene, an irradiation crosslinking method using radioactivity, and a crosslinking method using water after grafting, as seen in silane compounds. It is being
Furthermore, as a method for crosslinking ethylene-propylene donor polymers, chlorinated polyethylene, ethylene-vinyl acetate copolymers, etc., methods are also known in which a polyfunctional compound is used in combination with an organic peroxide. Polyolefins are inherently difficult to crosslink, and it is difficult to quickly obtain a crosslinked product with a high crosslink density depending on the organic peroxide. In order to obtain a high crosslink density, a long reaction time is required, and if the reaction is attempted to proceed quickly, the result is a crosslinked product containing a non-uniform gel. In addition, molecular chain scission occurs, resulting in an increase in by-products. The irradiation crosslinking method using radiation requires very expensive crosslinking equipment. In the method of grafting a silane compound, the crosslinking rate is slow, and in order to particularly increase the internal crosslinking density, it is necessary to immerse in water for a long time or to increase the water temperature for a long time. The present inventors completed the present invention as a result of research to solve the above-mentioned drawbacks. That is, the gist of the present invention is a crosslinkable polyolefin composition comprising a polyolefin, a Ziels-Alder adduct of triallyl isocyanurate and cyclopentadiene, and an organic peroxide. Examples of the polyolefin of the present invention include the following polymers. That is, it is a thermoplastic polymer generally called polyolefin, which includes both crystalline and non-crystalline polymers. Also included are polyolefin derivatives obtained by chemically or physically treating polyolefin. Specific examples include high-pressure polyethylene, low-pressure polyethylene, medium-low-pressure polyethylene, isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, polybutene, 4-methylpentene-1, and other α-olefin polymers. Further examples include chlorinated polyethylene, chlorosulfonated polyethylene, halogenophosphorous polyethylene, and grafted modified polyethylene obtained by grafting maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, etc. onto polyethylene. Also included are olefin copolymers described below. Namely, random copolymers of ethylene and α-olefin, block copolymers of ethylene and α-olefin, copolymers of ethylene or α-olefin and other vinyl monomers, ethylene or α-olefin and conjugated dienes. Examples include alternating copolymers with Specifically, ethylene-propylene rubber, ethylene-propylene-
diene rubber, ethylene-propylene stereoblock copolymer, ethylene-vinyl acetate copolymer,
Examples include ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-methyl methacrylate copolymer, propylene-butadiene alternating copolymer, ethylene-diallyl ester copolymer, and the like. As an organic peroxide, the 1-minute half-life temperature is approximately 160°C.
-240°C is particularly preferred, such as t-butyl peroxyisopropyl carbonate, di-t-butyl diperoxy phthalate,
t-butylperoxyacetate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxylaurate, t-butylperoxymale acid, t-butylperoxybenzoate, Examples include methyl ethyl ketone peroxide, dicumyl peroxide, cyclohexanone peroxide, and t-butylcumyl peroxide. Two or more of these organic peroxides may be used in combination. The amount of these added is 0.001 to 0.02 mol, preferably 0.005 to 0.02 mol per 100 parts by weight of polyolefin.
It is 0.01 mole. A Ziels-Alder adduct generally refers to a product obtained by a thermal addition reaction between an unsaturated compound and a conjugated diene compound, but the Ziels-Alder adduct used in the present invention is obtained by, for example, reacting triallyl isocyanurate and cyclopentadiene under heating. 150~250℃
(Japanese Patent Publication No. 48-26025). The amount of the Ziels-Alder adduct added is 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, per 100 parts by weight of polyolefin. The composition of the present invention is produced by kneading at room temperature or under heating using a commonly used mixer such as a mixing roll, calendar roll, kneader, or extruder. There is no problem in using additives such as pigments, fillers, lubricants, process oils, heat stabilizers, antioxidants, and ultraviolet absorbers during kneading. Further, other polyfunctional compounds may be added. The composition of the present invention can be rapidly crosslinked by heating to 150 to 180°C, and can provide a crosslinked polyolefin with a high crosslink density. It is generally known that polyfunctional compounds such as trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, and 1,2-polybutadiene are used as crosslinking aids when polyolefins are crosslinked with organic peroxides. However, the fact that a polyolefin containing a Ziels-Alder adduct of triallyl isocyanurate and cyclopentadiene has a specifically fast crosslinking rate and a large crosslinking effect was revealed for the first time by the present inventors. . The reason why the polyolefin composition of the present invention has a fast crosslinking rate and excellent crosslinking effect is not clear, but the Ziels-Alder adduct of triallyl isocyanurate and cyclopentadiene has a higher compatibility with polyolefin than conventional polyfunctional It is presumed that this is because homogeneous kneading and crosslinking are possible due to the improved performance compared to other compounds. It is also presumed that the present Ziels-Alder adduct is activated and becomes a radical by the radicals generated by thermal decomposition of the organic peroxide. This radical is relatively stable and has a long life, and is considered to effectively participate in the crosslinking reaction of polyolefin. Next, the present invention will be explained with reference to examples. In the examples, "part" means part by weight, and "%" means weight %. Example 1 and Reference Examples 1 and 2 Polyethylene (MI = 2.0) was kneaded at 135°C for 5 minutes after adding organic peroxide using a Brabender Plalasticorder with the formulation shown in Table 1, and then kneaded at 180°C for 5 minutes. A cross-linked polyethylene sheet (2 mm thick) was produced by heating to .degree. Take 0.1 g of the obtained cross-linked polyethylene into a 100 ml Erlenmeyer flask,
Add 100ml of toluene (special grade reagent) and boil on a hot plate with a backflow condenser for 8 hours, then remove.
After air drying, it was vacuum dried at 50°C and the toluene insoluble area was measured as a gel fraction. Table 2 shows the relationship between crosslinking time and gel fraction.

【table】

[Table] Example 2 and Reference Examples 3 and 4 Ethylene-propylene-diene rubber (EPDM)
With the formulation shown in Table 3, the roll size is 20.3
The mixture was kneaded using a 45.7 cm roll mixer at a rotation ratio of 1:1.18 and a rotation speed of 18 rpm at a temperature of 50±5°C. Table 4 shows the relationship between vulcanization time and physical properties when vulcanization was then carried out at 150°C. Measurement of physical properties of vulcanized products is based on JIS
Compliant with K6301.

[Table] The amounts in the above table are in parts.

[Table] Example 3 and Reference Examples 5 and 6 Chlorinated polyethylene was kneaded at 60±5°C using the same rolls as in Example 2 with the formulations shown in Table 5. Vulcanization time and JIS when vulcanized at 160℃
The physical properties of the vulcanizate obtained in accordance with K6301 are shown in Table 6.

[Table] The amounts in the above table are in parts.

[Table] × Not tested because it is unvulcanized.
Example 4 and Reference Examples 7 and 8 Regarding the ethylene-vinyl acetate copolymer, the seventh
A roll similar to Example 2 was used with the formulation shown in the table.
Kneading was carried out at 30-40°C. Vulcanization time and JIS K6301 when vulcanized at 160℃
The physical properties of the vulcanizate determined according to Table 8 are as follows.

[Table] The amounts in the above table are in parts.

【table】

Claims (1)

[Claims] 1. A crosslinkable polyolefin composition comprising a polyolefin, a Ziels-Alder adduct, and an organic peroxide. However, the above-mentioned Ziels-Alder adduct refers to a Ziels-Alder adduct of triallyl isocyanurate and cyclopentadiene.