JPH0832806B2 - Method for producing crosslinked ethylene-based polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a crosslinked ethylene-based polymer.
More specifically, a specific phosphite-based compound (hereinafter referred to as compound A), a thioether-based antioxidant and a radical generator for an ethylene polymer containing 5 ppm or more of titanium content or 0.5 ppm or more of vanadium content of a catalyst residue is used. The present invention relates to a method for producing a crosslinked ethylene-based polymer, which comprises blending in a specific amount and melt-kneading at a temperature of 150 ° C to 300 ° C.

[Conventional technology]

In general, ethylene-based polymers are relatively inexpensive and have excellent mechanical properties, and are therefore used for the production of various molded products such as injection molded products, hollow molded products, films, sheets and fibers. However, the ethylene-based polymer is molded and processed at a temperature equal to or higher than the melting point of the ethylene-based polymer, but it is oxidatively deteriorated by heat at the time of melt-kneading, causing problems of coloring and odor. There is also a problem with thermal stability. Therefore, for the purpose of preventing thermal oxidative deterioration during melt-kneading, 2,6-di-t-butyl-p-cresol (B
Low molecular weight phenolic antioxidants such as HT) and high molecular weight phenolic antioxidants are widely used to impart thermal stability during practical use.

However, when the ethylene-based polymer containing the above-mentioned phenol-based antioxidant is melt-kneaded, the phenol-based antioxidant used is melt-kneaded with a complex compound of titanium or vanadium which is a catalyst residue in the ethylene-based polymer. A problem occurs when the ethylene-based polymer obtained by being oxidized and forming a quinone compound is colored. In the process of studying the colorability of an ethylene-based polymer containing a large amount of titanium or vanadium as a catalyst residue, the present inventors have found that the ethylene-based polymer containing a large amount of titanium or vanadium contained in the catalyst residue Even if the above-mentioned phenol-based antioxidant is blended and melt-kneaded, coloring such that there is no problem in practical use does not occur, but an ethylene-based polymer blended with such a phenol-based antioxidant is used in the presence of a radical generator. It was found that when the melt-kneading treatment below was performed and crosslinking was performed, the resulting crosslinked ethylene-based polymer was significantly colored,
First, a method for producing a crosslinked ethylene polymer in which a polyol or a partial ester of a polyol and a fatty acid and a phenolic antioxidant are blended with an ethylene polymer and melt-kneaded in the presence of a radical generator (Japanese Patent Application No. 61-155599). issue)
Suggested.

Further, in order to improve the mechanical strength and heat resistance of the ethylene polymer, a method of crosslinking the ethylene polymer by subjecting the ethylene polymer to melt kneading treatment or electron beam irradiation treatment in the presence of a radical generator. Is well known.

[Problems to be solved by the invention]

The present inventors were not satisfied with the method for producing a crosslinked ethylene-based polymer previously proposed in Japanese Patent Application No. 61-155599, and radically modified an ethylene-based polymer containing a large amount of titanium or vanadium as a catalyst residue. Further studies have been made on a method for obtaining a crosslinked ethylene polymer which is not colored even when melt-kneaded in the presence of a generator. As a result, the titanium content of the catalyst residue was 5 ppm or more or the vanadium content was 0.5 p
When a specific amount of a phosphite compound (hereinafter referred to as compound A), a thioether antioxidant and a radical generator is added to an ethylene polymer containing pm or more in a specific amount and melt kneading is performed, no heat is generated during melt kneading without coloring. It was found that a crosslinked ethylene polymer having practically satisfactory oxidative deterioration resistance and thermal stability during practical use was obtained, and the present invention was completed based on this finding.

As is clear from the above description, the object of the present invention is that the titanium content of the catalyst residue is 5 ppm or more or the vanadium content is 0.5 ppm.
A compound A, a thioether antioxidant and a radical generator are added to the ethylene polymer contained above, and the mixture is melt-kneaded to provide a method for producing a crosslinked ethylene polymer without coloring.

[Means for solving problems]

 The present invention has the following configurations.

Titanium content of catalyst residue is 5ppm or more or vanadium content
With respect to 100 parts by weight of an ethylene polymer containing 0.5 ppm or more, 0.01 to 1 parts by weight of a phosphite compound represented by the following general formula [I] (hereinafter referred to as compound A) and a thioether antioxidant, respectively, Radical generator
A method for producing a crosslinked ethylene-based polymer, which comprises blending 0.001 to 0.5 part by weight and melt-kneading at 150 ° C to 300 ° C.

[Wherein R ₁ is hydrogen, an alkyl group having 1 to 3 carbon atoms or —CH ₂ —CH (CH ₃ ) —R ₄ {R ₄ is —OP (OR ₅ ).
₂ (R ₅ is an alkyl group having 8 to 18 carbon atoms)}. R ₂ and R ₃ represent the same or different alkyl groups having 1 to 8 carbon atoms. The ethylene polymer used in the production method of the present invention includes high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc., and the titanium residue of the catalyst residue is 5 ppm or more or the vanadium content is 0.5 ppm or more. An ethylene polymer containing at least ppm, for example, obtained by a solution polymerization method using a saturated hydrocarbon solvent, a bulk polymerization method, a gas phase polymerization method, or a polymerization method by a combination of the bulk polymerization method and the gas phase polymerization method. Is. In the production method of the present invention, an ethylene polymer having a titanium content of less than 5 ppm or a vanadium content of less than 0.5 ppm in the catalyst residue may be used. The ethylene-based polymer used in the present invention is an ethylene-based polymer containing 5 ppm or more of titanium content of a catalyst residue or 0.5 ppm or more of vanadium content, a homopolymer of ethylene, ethylene and propylene, butene-1, A crystalline or amorphous copolymer with one or more α-olefins such as pentene-1,4-methyl-pentene-1, hexene-1, and octene-1, amorphous ethylene-propylene- Non-conjugated diene copolymer, copolymer of ethylene and vinyl acetate, acrylic acid ester or the like, or saponified product of the copolymer, copolymer of ethylene and unsaturated carboxylic acid or anhydride thereof, the copolymer Examples thereof include reaction products of a metal ion compound with a metal ion compound. Not only these ethylene polymers are used alone, but also two or more ethylene polymers are mixed. It is also possible to use Te. The above-mentioned ethylene polymer and various synthetic rubbers (for example, polybutadiene, polyisoprene, chlorinated polyethylene, chlorinated polypropylene, styrene-butadiene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer). , Styrene-ethylene-butylene-
Styrene block copolymers, styrene-propylene-butylene-styrene block copolymers) or thermoplastic synthetic resins (e.g. polypropylene, polybutene, polyolefins other than ethylene-based polymers such as poly-4-methylpentene-1, polystyrene, A mixture of styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, etc.) can also be used. Ethylene homopolymer, crystalline or amorphous ethylene-propylene copolymer, crystalline ethylene-butene-1 copolymer, crystalline ethylene-propylene-butene-1 terpolymer, crystalline ethylene-pentene- Particularly preferred is an ethylene-based polymer or a crystalline etalene-hexene-1 copolymer or a mixture of two or more thereof, wherein the catalyst residue has a titanium content of 5 ppm or more or a vanadium content of 0.5 ppm or more. To be

Examples of the compound A used in the present invention include 1,1'-bis (4-di-nonylphosphite-3,5-di-t-butylphenyl) methane, 1,1'-bis (4-di-tridede). Sylphosphite-3,5-di-t-butylphenyl) methane, 1,1'-bis (4-di-stearylphosphite-3,5-di-t-butylphenyl) methane, 1,1'-bis ( 3-Methyl-4-di-nonylphosphite-5-
t-butylphenyl) methane, 1,1'-bis (3-methyl-4-di-tridecylphosphite-5-t-butylphenyl) methane, 1,1'-bis (3-methyl-4-)
Di-stearyl phosphite-5-t-butylphenyl) methane, 4,4'-butylidene-bis (3-methyl-
6-t-butylphenyl) di-nonylphosphite,
4,4'-butylidene-bis (3-methyl-6-t-butylphenyl) di-tridecylphosphite, 4,4'-
Butylidene-bis (3-methyl-6-t-butylphenyl) di-stearyl phosphite, 1,1'-bis (2
-Di-nonylphosphite-3-t-butyl-5-methylphenyl) methane, 1,1'-bis (2-di-tridecylphosphite-3-t-butyl-5-methylphenyl) methane, 1,1 ′ -Bis (2-di-stearyl phosphite-3-t-butyl-5-methylphenyl) methane, 1,1′-bis (2-di-nonyl phosphite-
3-t-butyl-5-ethylphenyl) methane, 1,1 ′
-Bis (2-di-tridecylphosphite-3-t-
Butyl-5-ethylphenyl) methane, 1,1'-bis (2-di-stearylphosphite-3-t-butyl-5-ethylphenyl) methane, 1,1'-bis (2-di-nonylphosphite- 3,5-di-t-butylphenyl) methane, 1,1'-bis (2-di-tridecylphosphite-3,5-di-t-butylphenyl) methane, 1,
1'-bis (2-di-stearyl phosphite-3,5-
Di-t-butylphenyl) methane, 2,2'-bis (1-
Di-nonylphosphite-4,6-di-t-butylphenyl) ethane, 2,2'-bis (1-di-tridecylphosphite-4,6-di-t-butylphenyl) ethane,
2,2'-bis (1-di-stearyl phosphite-4,6
-Di-t-butylphenyl) ethane, 1,1'-bis (2
-Di-nonylphosphite-3-t-octyl-5-
Methylphenyl) methane, 1,1'-bis (2-di-tridecylphosphite-3-t-octyl-5-methylphenyl) methane, 1,1'-bis (2-di-stearylphosphite-3-t -Octyl-5-methylphenyl) methane, 1,1,3-tris (2-methyl-4-di-nonylphosphite-5-t-butylphenyl) butane, 1,1,3-tris (2-methyl-4) -Di-tridecyl phosphite-5-t-butylphenyl) butane, 1,
Examples thereof include 1,3-tris (2-methyl-4-di-stearylphosphaite-5-t-butylphenyl) butane and a mixture of two or more thereof. In particular 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl) di-tridecylphosphite, 1,1,3-tris (2-methyl-4-di-tridecylphosphite-5
-T-Butylphenyl) butane or mixtures thereof are preferred. As the thioether antioxidant, dilauryl thiodipropionate, ditridecyl thiodipropionate, dimyristyl thiodipropionate, dicetyl thiodipropionate, distearyl thiodipropionate, dilauryl thiodipropionate, Ditridecyl thiodibutyrate, dimyristyl thiodibutyrate,
Dicetyl thiodibutyrate, distearyl thiodibutyrate, pentaerythritol-β-lauryl-thiodipropionate, lauryl stearyl thiodipropionate, pentaerythritol-tetrakis- (3-lauryl thiodipropionate), pentaerythritol-tetrakis -(3-myristyl thiodipropionate),
Pentaerythritol-tetrakis- (3-stearylthiopropionate), bis (4-t-amylphenyl) sulfide, distearyldisulfide, thioethylene glycol-bis (β-aminocrotonate) and poly ((1,4 -Bis (hydroxymethyl) cyclohexane-thio-dipropionate)). Particularly preferred is dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol-tetrakis- (3-lauryl thiopropionate) or a mixture of two or more thereof. The compounding ratio of the compound A and the thioether antioxidant is 100% by weight of the ethylene polymer.
0.01 to 1 part by weight, preferably 0.
It is 0.5 to 0.5 parts by weight. If the amount is less than 0.01 part by weight, the effect of preventing the thermal oxidative deterioration during melt-kneading of the crosslinked ethylene polymer and the thermal stability during practical use are insufficient, and the amount may exceed 1 part by weight. The effect of preventing thermal oxidative deterioration during melt-kneading and the improvement of thermal stability during practical use cannot be expected, which is impractical and uneconomical.

As the radical generator used in the present invention, the decomposition temperature is preferably not too low to obtain a uniform composition, and the temperature for obtaining a half-life of 10 hours is 70 ° C or higher, preferably 100 ° C or higher. Benzoyl peroxide, t-butyl perbenzoate, t-butyl peracetate, t-butyl peroxyisopropyl carbonate, 2,5-di-methyl-2,5-di- (benzoylperoxy) hexane, 2, 5-di-methyl-2,5-di (benzoylperoxy) hexyne-3, t-butyl-di-peradipate, t-butylperoxy-3,5,5-trimethylhexanoate, methyl-ethylketone Peroxide,
Cyclohexanone peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,5-di-methyl-2,5-di- (t-butylperoxy) hexane,
2,5-di-methyl-2,5-di- (t-butylperoxy)
Hexine-3,1,3-bis- (t-butylperoxyisopropyl (benzene), t-butylquinyl peroxide, 1,1-bis- (t-butylperoxy) -3,3,5-
Trimethylcyclohexane, 1,1-bis- (t-butylperoxy) cyclohexane, 2,2-bis- (t-butylperoxy) butane, p-menthane hydroperoxide, di-isopropylbenzene hydroperoxide, kyumen Hydroperoxide, t-butyl hydroperoxide, p-cymene hydroperoxide, 1,1,3,3-tetra-methylbutyl hydroperoxide or 2,5-di-methyl-2,5-di- (hydro Organic peroxides such as peroxy) hexane can be exemplified. Particularly, 2,5-di-methyl-2,5-di- (t-butylperoxy) hexane, 2,5-di-methyl-2,5-di- (t
-Butylperoxy) hexyne-3 or 1,3-bis-
(T-Butylperoxyisopropyl) benzene is preferred. The mixing ratio of the radical generator is usually 0.001 to 0.5 part by weight, preferably 0.01 to 0.2 part by weight, based on 100 parts by weight of the ethylene polymer. The melt-kneading treatment is carried out at a temperature of 150 ° C to 300 ° C, preferably 180 ° C to 270 ° C, using various melt-kneading devices described later. Melt kneading temperature
If the temperature is lower than 150 ° C, sufficient cross-linking is not carried out, and if the temperature exceeds 300 ° C, thermal oxidation deterioration of the ethylene polymer is promoted and coloring of the ethylene polymer becomes remarkable, which is not preferable.

In the production method of the present invention, various additives that are usually added to an ethylene-based polymer, such as phosphorus-based oxidation, are added to an ethylene-based polymer containing a titanium residue of a catalyst residue of 5 ppm or more or a vanadium content of 0.5 ppm or more. Inhibitors, light stabilizers, clarifiers, nucleating agents, lubricants, antistatic agents, antifogging agents, antiblocking agents, non-dripping agents, pigments, heavy metal deactivators (copper damage inhibitors), metals Dispersants or neutralizers for soaps, etc., inorganic fillers (eg talc, mica, clay, wollastonite, zeolite, asbestos, calcium carbonate, aluminum hydroxide, magnesium hydroxide, silicon dioxide,
Titanium dioxide, zinc oxide, magnesium oxide, zinc sulfide, barium sulfate, calcium silicate, glass fiber, carbon fiber, potassium titanate, metal fiber, etc. or coupling agent (for example, silane-based, titanate-based, boron-based, aluminate-based) , Zircoaluminate, etc.) is used within a range that does not impair the object of the present invention by treating the inorganic or organic filler (eg, wood powder, pulp, waste paper, synthetic fiber, natural fiber, etc.) surface-treated with a surface treatment agent such as Can be used by mixing.

In the production method of the present invention, the above-mentioned compound A, a thioether antioxidant, a radical generator and a normal ethylene polymer are added to an ethylene polymer containing 5 ppm or more of titanium content or 0.5 ppm or more of vanadium content of a catalyst residue. The above-mentioned various additives are mixed in a predetermined amount with a conventional mixing device such as a Henscel mixer (trade name), a super mixer, a ribbon blender, or a Banbury mixer at a temperature at which the radical generator is not decomposed. Then, using a normal single-screw extruder, a twin-screw extruder, a Brabender or a roll, the melt-kneading temperature is 150 ° C to 300 ° C, preferably 180 ° C to 270.
It is carried out by melt-kneading treatment at ℃.

[Action]

In the present invention, the compound A has the functions of both a phenol-based antioxidant and a phosphorus-based antioxidant, and acts as a radical scavenger and a peroxide decomposer to prevent thermal oxidative deterioration during melt kneading and to be used practically. It contributes to the improvement of thermal stability. Furthermore, the thioether-based antioxidant serves as a peroxide decomposer to improve thermal stability during practical use, and the radical-generating agent generates radicals by melt-kneading treatment, that is, heating, and abstracts hydrogen atoms of the ethylene-based polymer. It is well known that a radical of an ethylene-based polymer is generated by performing the above-mentioned process and the ethylene-based polymer is crosslinked to improve mechanical strength, heat resistance and the like.

In the production method of the present invention, the above-mentioned compound A does not cause coloration because the hydroxyl group of hindered phenol forms a phosphite unlike the usual phenol-based antioxidant of compound A. It is considered that this does not generate a chromophoric atomic group such as a quinone compound as seen in the antioxidant process.

〔effect〕

The crosslinked ethylene-based polymer obtained by the production method of the present invention has no further coloration as compared with the crosslinked ethylene-based polymer according to the above-mentioned Japanese Patent Application No. 61-155599 filed by the present inventors, and has high mechanical strength and heat resistance. Since the rigidity and the like are improved, it can be preferably used for the production of a target molded article by various molding methods such as an injection molding method, an extrusion molding method (especially electric wire coating, foaming) and a blow molding method.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

The evaluation methods used in Examples and Comparative Examples were as follows.

Colorability: The obtained pellet YI (Yellowness Index) was measured (in accordance with JIS K 7103), and the colorability was evaluated based on the value of this YI.

 The smaller this value is, the less the coloring is.

Examples 1 to 12 and Comparative Examples 1 to 3 As an ethylene-based polymer, MI (load at 190 ° C. 2.1.
Discharge amount of molten resin for 10 minutes when 6kg is added) 1.5g / 10
100 parts by weight of unstabilized powdered Ziegler-Natsuta high-density ethylene homopolymer (titanium content 8 ppm) was added to compound A as 4,4'-butylidene-bis (3-methyl-6-t-). Butylphenyl) di-tridecylphosphite or 1,1,3-tris (2-methyl-4-di-tridecylphosphite-5-t-butylphenyl) butane, dimyristylthiodipropionate as a thioether antioxidant , Distearyl thiodipropionate or pentaerythritol-tetrakis-
(3-laurylthiopropionate), 2,5-di-methyl-2,5-di- (t-butylperoxy) hexane or 1,3-bis- (t-butylperoxyisopropyl) as a radical generator ) Predetermined amounts of benzene and other additives were added to the Henschel mixer (trade name) at the compounding ratios shown in Table 1 below, and the mixture was stirred and mixed for 3 minutes, and then heated to 200 ° C with a single screw extruder having a diameter of 40 mm. It was melt-kneaded, crosslinked, and pelletized. Also, as Comparative Examples 1 to 3, MI was 15
In accordance with Examples 1 to 12, 100 parts by weight of powdery Ziegler-Natsuta ethylene homopolymer (titanium content of 8 ppm) was added to each of predetermined amounts of the additives shown in Table 1 below, and the amount was 10 g. Then, the mixture was melt-kneaded to obtain a crosslinked pellet.

Using the pellets thus obtained, the colorability was evaluated by the test method described above. The results are shown in Table 1.

Examples 13 to 24, Comparative Examples 4 to 6 As an ethylene-based polymer, an unstabilized powdered Ziegler-Natsuta-based high-density ethylene-propylene copolymer having an MI of 0.5 g / 10 min (3.0 methyl branches / 1000) Carbon, titanium content 8 ppm) 100 parts by weight, compound A as 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl)
Di-tridecyl phosphite or 1,1,3-tris (2-methyl-4-di-tridecyl phosphite-5
-T-butylphenyl) butane, dimyristylthiodipropionate, distearyl thiodipropionate or pentaerythritol-tetrakis- (3-laurylthiopropionate) as a thioether antioxidant, and 2,5- Predetermined amounts of di-methyl-2,5-di- (t-butylperoxy) hexane or 1,3-bis- (t-butylperoxyisopropyl) benzene and other additives are shown in Table 2 below. Put it in the Henschel mixer (trade name) in the stated mixing ratio, and 3
After stirring and mixing for a minute, the mixture was melt-kneaded at 200 ° C. with a single-screw extruder having a diameter of 40 mm to crosslink and pelletize. As Comparative Examples 4 to 6, unstabilized powdered Ziegler-Natsuta high-density ethylene-propylene copolymer having an MI of 0.5 g / 10 min (methyl branch 3.0 / 1000 carbon, titanium content 8 pp
m) 100 parts by weight of each of the additives shown in Table 2 described below were added in a predetermined amount, and melt kneading was carried out in accordance with Examples 13 to 24 to obtain crosslinked pellets.

Using the pellets thus obtained, the colorability was evaluated by the test method described above. The results are shown in Table 2.

Examples 25 to 36, Comparative Examples 7 to 9 As an ethylene-based polymer, an unstabilized powdered Ziegler-Natsuta-based high-density ethylene-butene-1 copolymer having an MI of 1.0 g / 10 min (0.014 ethyl branches) / 1000 carbon, vanadium content 0.6 ppm) 100 parts by weight as compound A 4,
4'-butylidene-bis (3-methyl-6-t-butylphenyl) di-tridecylphosphite or 1,1,
3-tris (2-methyl-4-di-tridecylphosphaite-5-t-butylphenyl) butane, dimyristyl thiodipropionate, distearyl thiodipropionate or pentaerythritol-tetrakis- as a thioether antioxidant (3-laurylthiopropionate), 2,5-di-methyl-2,5-di- (t-butylperoxy) hexane or 1,3-bis- (t-butylperoxyisopropyl) as a radical generator )
Henschel mixer (trade name) with the respective prescribed amounts of benzene and other additives in the blending ratios shown in Table 3 below.
In a single screw extruder with a diameter of 40 mm after stirring and mixing for 3 minutes.
The mixture was melt-kneaded at 200 ° C., crosslinked, and pelletized.
Further, as Comparative Examples 7 to 9, unstabilized powdery Ziegler-Natsuta high-density ethylene-butene-1 copolymer (ethyl branch 0.014 / 1000 carbon, vanadium content 0.6) was used. ppm) and 100 parts by weight of each of the additives shown in Table 3 to be described later were mixed and melt-kneaded in accordance with Examples 25 to 36 to obtain crosslinked pellets.

Using the pellets thus obtained, the colorability was evaluated by the test method described above. The results are shown in Table 3.

Examples 37 to 48, Comparative Examples 10 to 12 As an ethylene-based polymer, Mooney viscosity ML1 + 4 (100
C) 25, and 100 parts by weight of non-stabilized powdery amorphous ethylene-propylene copolymer (propylene content 25%, vanadium content 0.6 ppm) are added to compound A as 4,4'-butylidene-bis ( 3-Methyl-6-t-butylphenyl) di-tridecylphosphite or 1,1,3-tris (2-methyl-4-di-tridecylphosphite-5-t-butylphenyl) butane, thioether antioxidant Dimyristyl thiodipropionate, distearyl thiodipropionate or pentaerythritol-tetrakis- (3-lauryl thiopropionate) as an agent, 2,5-di-methyl-2,5-
Di- (t-butylperoxy) hexane or 1,3-
A predetermined amount of each of bis- (t-butylperoxyisopropyl) benzene and other additives was put in a Henschel mixer (trade name) at a blending ratio described in Table 4 below.
After stirring and mixing for 3 minutes, the mixture was melt-kneaded at 200 ° C. in a single-screw extruder having a diameter of 40 mm, crosslinked and pelletized. Further, as Comparative Examples 10 to 12, unstabilized powdery amorphous ethylene-propylene copolymer having a Mooney viscosity ML1 + 4 (100 ° C.) of 25 (propylene content 25%, vanadium content 0.
6 ppm) and 100 parts by weight of each of the additives shown in Table 4 described below were mixed in a predetermined amount, and melt-kneaded in accordance with Examples 37 to 48 to obtain crosslinked pellets.

Using the pellets thus obtained, the colorability was evaluated by the test method described above. The results are shown in Table 4.

Various compounds and additives shown in Tables 1 to 4 are as follows.

Compound A [I]; 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl) di-tridecylphosphite Compound A [II]; 1,1,3-tris (2-methyl-4) -The-
Tridecyl phosphite-5-t-butylphenyl)
Butane thioether antioxidant [I]; dimyristyl thiodipropionate thioether antioxidant [II]; distearyl thiodipropionate thioether antioxidant [III]; pentaerythritol-tetrakis- (3-laurylthio Propionate) Radical generator [I]; 2,5-di-methyl-2,5-di-
(T-Butylperoxy) hexane radical generator [I
I]; 1,3-bis- (t-butylperoxyisopropyl) benzene phenolic antioxidant 1; 2,6-di-t-butyl-p-
Cresol phenolic antioxidant 2; tetrakis [methylene-3-
(3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate] methane polyol compound (partial ester of polyol and fatty acid); pentaerythritol monostearate phosphite compound (phenolic hydroxyl group remains Phosphite compounds); bis (p-octyl) phenyl-bis [2-t-butyl-5-methyl-4 [α-
(3-t-Butyl-6-methyl-4-hydroxyphenyl)] butylphenyl] -1,6-hexanediol-diphosphite Ca-St; calcium stearate The examples and comparative examples shown in Table 1 are the cases where a Ziegler-Natsuta high density ethylene homopolymer was used as the ethylene polymer. As can be seen from Table 1, in Examples 1 to 12, the ethylene homopolymer containing 8 ppm of titanium in the catalyst residue according to the present invention was compounded with Compound A, a thioether antioxidant and a radical generator, and melt-kneaded. Treated and crosslinked. Examples 1 to 12 and Comparative Example 1 (Method for producing a crosslinked ethylene-based polymer of Japanese Patent Application No. 61-155599 previously proposed by the present inventors, that is, a partial ester of a polyol and a fatty acid and a phenol-based polymer are added to the ethylene-based polymer. It is understood that Examples 1 to 12 are less colored than Comparative Example 1 and the anti-coloring property is improved when compared with those in which an antioxidant and a radical generator are blended, melt-kneaded and cross-linked. Comparing Comparative Example 2 and Examples 1 to 12 using a phosphite compound in which a phenolic hydroxyl group remains instead of the compound A, Comparative Example 2 is markedly colored, and this coloring is the phenolic property of the phosphite compound. It can be seen that the hydroxyl group is caused by forming a quinone compound. Further, comparing Comparative Examples 3 and 1 to 12 in which the partial ester of the polyol and the fatty acid used in Comparative Example 1 is further added to Comparative Example 2, Comparative Example 3 is similar to Comparative Example 1 in that the coloring property is improved. It turns out that it is less than Examples 1-12.

Tables 2 to 4 show Ziegura-Natsuta high-density ethylene-propylene copolymers as ethylene-based polymers,
A Ziegler-Natsuta high-density ethylene-butene-1 copolymer and an amorphous ethylene-propylene copolymer were used, and the same effects as those described above were confirmed.

Therefore, it can be seen that the crosslinked ethylene polymer obtained by the production method of the present invention is not colored and its mechanical strength, heat resistance and the like are improved.

From this, the cross-linked ethylene polymer obtained by the production method of the present invention is compared with a cross-linked ethylene polymer obtained by blending a compound having a conventionally known coloring preventing effect and melt-kneading the mixture in the presence of a radical generator. It was found that the anti-coloring property was remarkably excellent, and the remarkable effect of the present invention was confirmed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // (C08K 5/00 5:14 5:36 5: 524)

Claims (6)

[Claims] 1. A phosphite-based compound represented by the following general formula [I] (hereinafter referred to as compound A) based on 100 parts by weight of an ethylene-based polymer containing 5 ppm or more of titanium content or 0.5 ppm or more of vanadium content in a catalyst residue. 0.01 to 1 part by weight of a thioether antioxidant and 0.001 to 0.5 part by weight of a radical generator, and melt-kneading at 150 ° C to 300 ° C. Manufacturing method. [Wherein R ₁ is hydrogen, an alkyl group having 1 to 3 carbon atoms or —CH ₂ —CH (CH ₃ ) —R ₄ {R ₄ is —OP (OR ₅ ).
₂ (R ₅ is an alkyl group having 8 to 18 carbon atoms)}. R ₂ and R ₃ represent the same or different alkyl groups having 1 to 8 carbon atoms. ] 2. The crosslinked ethylene polymer according to claim 1, wherein the alkyl group represented by R ₂ and R ₃ in the general formula [I] is a methyl group or a t-butyl group. Manufacturing method. 3. As compound A, 4,4'-butylidene-bis (3-methyl-6-t-butylphenyl) di-tridecylphosphite, 1,1,3-tris (2-methyl-4)
A method for producing a crosslinked ethylene polymer according to claim (1), which comprises blending di-tridecylphosphaite-5-t-butylphenyl) butane or a mixture thereof. 4. As a thioether antioxidant, dimyristyl thiodipropionate, distearyl thiodipropionate, pentaerythritol-tetrakis- (3
-Lauryl thiopropionate) or a mixture of two or more thereof, the method for producing a crosslinked ethylene polymer according to claim (1). 5. As a radical generator, 2,5-di-methyl-2,5-di- (t-butylperoxy) hexane, 2,5-
The compound according to claim (1), which comprises di-methyl-2,5-di- (t-butylperoxy) hexyne-3 or 1,3-bis- (t-butylperoxyisopropyl) benzene. 1. A method for producing a crosslinked ethylene polymer. 6. The ethylene polymer, ethylene homopolymer, crystalline or amorphous ethylene-propylene copolymer, crystalline ethylene-butene-1 copolymer, crystalline ethylene-propylene-butene-13. Original copolymer, crystalline ethylene-pentene-1 copolymer, crystalline ethylene-
The method for producing a crosslinked ethylene-based polymer according to claim (1), which uses a hexene-1 copolymer or a mixture of two or more thereof.