JPH0588858B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a crosslinked ethylene polymer. For more details, check the titanium content of the catalyst residue.
A specific amount of a phenolic antioxidant, a polyol, or a partial ester of the polyol and a fatty acid (hereinafter referred to as compound A) to an ethylene polymer containing 5 ppm or more or 0.5 ppm or more of panadium.
and a radical generator, and the temperature is 150℃~300℃.
The present invention relates to a method for producing a crosslinked ethylene polymer, which is characterized by carrying out a melt-kneading treatment at °C. [Prior Art] Generally, ethylene polymers are relatively inexpensive and have excellent mechanical properties, so they are used to manufacture various molded products such as injection molded products, blow molded products, films, sheets, and fibers. . However, ethylene polymers are molded at temperatures above the melting point of the ethylene polymer, but they undergo oxidative deterioration due to the heat during melt-kneading, causing problems with coloration and odor. There are also problems with thermal stability.
For this reason, low molecular weight phenolic antioxidants such as 2,6-di-t-butyl-p-cresol (BHT) have traditionally been used to prevent thermal oxidative deterioration during melt-kneading. High molecular weight phenolic antioxidants are widely used to impart thermal stability. However, when the ethylene polymer containing the above-mentioned phenolic antioxidant is melt-kneaded, the phenolic antioxidant used is mixed with a complex compound of titanium or vanadium, which is a catalyst residue in the ethylene polymer. It is said that problems such as oxidizing quinone compounds are produced and the resulting ethylene polymer becomes colored. For this reason, an ethylene polymer composition (JP-A-58-213036) has been proposed in which an ethylene polymer is blended with pentaerythritol or a polyol which is a reaction product of pentaerythritol and propylene oxide. In addition, in order to improve the mechanical strength and heat resistance rigidity of ethylene polymers, there is a method of crosslinking ethylene polymers by melt-kneading or electron beam irradiation treatment in the presence of a radical generator. is well known. In addition, for the purpose of further improving the dielectric strength of an electrically insulating polyolefin composition with excellent dielectric strength, which is made by blending a voltage stabilizer consisting of a phosphorane derivative, a halogenated paranitroaniline, or a specific phosphosphate, A polyolefin composition for electrical insulation is crosslinked by adding an organic peroxide using a nonionic surfactant such as a polyhydric alcohol or sorbitan monostearate together with the voltage stabilizer (Japanese Patent Application Laid-Open No. 1989-1999).
40553, JP-A-52-40554, and JP-A-52-45647). [Problems to be Solved by the Invention] In the process of researching the coloring properties of ethylene polymers containing titanium or panadium as catalyst residue, the present inventors discovered that the titanium or panadium content of the catalyst residue Even if the above-mentioned phenolic antioxidant is blended into an ethylene-based polymer containing a large amount of It has been found that when a polymer is melt-kneaded and crosslinked in the presence of a radical generator, the resulting crosslinked ethylene polymer is significantly colored. This phenomenon was described in the above-mentioned Japanese Patent Application Publication No.
No. 58-213036, JP-A-52-40553, JP-A-52-40554, and JP-A-52-45647 do not contain any description. The present inventors aimed to improve the mechanical strength, heat-resistant rigidity, etc. of an ethylene polymer obtained by blending a phenolic antioxidant with an ethylene polymer containing a large amount of titanium or panadium in the catalyst residue described above. Therefore, we conducted intensive research on a method for obtaining crosslinked ethylene polymers that do not become colored even when melt-kneaded in the presence of a radical generator. As a result, the titanium content in the catalyst residue was reduced to 5ppm or more, or the panadium content was reduced to 5ppm or more.
A specific amount of a phenolic antioxidant, a polyol or a partial ester of the polyol and a fatty acid (hereinafter referred to as compound A), and a radical generator are blended into an ethylene polymer containing 0.5 ppm or more,
It was discovered that a crosslinked ethylene polymer without coloring can be obtained by melt-kneading, and the present invention was completed based on this knowledge. As is clear from the above description, the purpose of the present invention is to add Compound A, a phenolic antioxidant, and a radical generator to an ethylene polymer containing 5 ppm or more of titanium or 0.5 ppm or more of panadium in the catalyst residue. It is an object of the present invention to provide a method for producing a colorless crosslinked ethylene polymer by blending and melt-kneading. [Means for solving the problems] The present invention has the following configuration. Ethylene polymer containing 5 ppm or more of titanium or 0.5 ppm or more of panadium in catalyst residue
100 parts by weight of a polyol or a partial ester of the polyol and fatty acid (hereinafter referred to as compound A) and a phenolic antioxidant, respectively.
1. A method for producing a crosslinked ethylene polymer, comprising blending 0.01 to 1 part by weight and 0.001 to 0.5 part by weight of a radical generator, and melt-kneading the mixture at 150°C to 300°C. The ethylene polymer used in the production method of the present invention contains 5 ppm or more of titanium or 0.5 ppm or more of panadium in the catalyst residue, and
For example, it is an ethylene polymer obtained by a solution polymerization method using a saturated hydrocarbon solvent, a bulk polymerization method, a gas phase polymerization method, or a polymerization method using a combination of a bulk polymerization method and a gas phase polymerization method. In the production method of the present invention, the titanium content of the catalyst residue is 5 ppm.
There is no problem in using an ethylene polymer with a panadium content of less than 0.5 ppm, but in this case, even if the above-mentioned compound A is not added, the resulting crosslinked ethylene polymer will Does not cause coloring to the extent that it becomes a problem. The ethylene polymer used in the present invention is an ethylene polymer containing 5 ppm or more of titanium or 0.5 ppm or more of panadium in the catalyst residue, an ethylene homopolymer, ethylene as the main component, i.e. An ethylene copolymer containing 50% by weight or more of ethylene, propylene, and butene.
1, pentene-1, 4-methyl-pentene-1,
Crystalline or amorphous copolymers with one or more α-olefins such as hexene-1 and octene-1, amorphous ethylene-propylene-nonconjugated diene copolymers, ethylene and vinyl acetate, Examples include copolymers with acrylic acid esters or saponified products of the copolymers, copolymers of ethylene and unsaturated carboxylic acids or their anhydrides, and reaction products of the copolymers with metal ion compounds. Not only can these ethylene polymers be used alone, but also two or more ethylene polymers can be used as a mixture. In addition, the above-mentioned ethylene polymers and various synthetic rubbers (e.g. polybutadiene, polyisoprene, chlorinated polyethylene, chlorinated polypropylene, styrene-butadiene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer) polymers, styrene-ethylene-butylene-styrene block copolymers, styrene-propylene-butylene-styrene block copolymers, etc.) or thermoplastic synthetic resins (e.g. polypropylene,
Polyolefins, polystyrene, styrene-acrylonitrile copolymers, acrylonitrile-butadiene-styrene copolymers, polyamides, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, excluding ethylene polymers such as prbutene and poly-4-methylpentene-1. ) can also be used. In particular, ethylene homopolymers, ethylene copolymers containing 50% by weight or more of ethylene component, including crystalline or amorphous ethylene-propylene copolymers, crystalline ethylene-butene-1 copolymers, crystalline ethylene-butene-1 copolymers, Ethylene-propylene-butene-1 ternary copolymer, crystalline ethylene-pentene-1 copolymer or crystalline ethylene-hexene-1 copolymer with a titanium content of 5 ppm or more or a panadium content of 0.5 in the catalyst residue. The effect is great when an ethylene polymer containing ppm or more is used. Compound A used in the present invention includes glycerin,
Polyols such as trimethylolethane, trimethylolpropane, erythritol, pentaerythritol, dipentaerythritol, tripentaerythritol, xylitol, sorbitol, mannitol, monoesters of glycerin and fatty acids, monoesters of diglycerin and fatty acids,
Monoesters of sorbitan and fatty acids, monoesters of sucrose and fatty acids, mono- or diesters of bentaerythritol and fatty acids, monoesters of trimethylolethane and fatty acids, monoesters of trimethylolpropane and fatty acids, monoesters of polyoxyethylene glycerin and fatty acids. Examples include partial esters of polyols and fatty acids such as esters, monoesters of polyoxyethylene sorbitan and fatty acids (the fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, pehenic acid, and oleic acid). Particularly preferred are trimethylolethane, monoesters of glycerin and fatty acids, and mono- or diesters of pentaerythritol and fatty acids. In addition, as a phenolic antioxidant, 2,6-di-t-butyl-p-
Cresol, 2-t-butyl-4,6-dimethylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-n
-butylphenol, 2,6-di-i-butyl-
4-n-butylphenol, 2,6-di-cyclopentyl-4-methylphenol, 2-(α-methylcyclohexyl)-4,6-dimethylphenol, 2,6-di-octadecyl-4-methylphenol, 2 , 4,6-tri-cyclohexylphenol, 2,6-di-t-butyl-4-methoxymethylphenol, n-octadecyl-β-
(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2,6-diphenyl-4-
Octadesiloxyphenol, 2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzylthio)-1,3,5-triazine, 2,6
-di-t-butyl-4-methoxyphenol,
2,5-di-t-butylhydroquinone, 2,5
-di-t-amylhydroquinone, 2,2'-thio-bis-(6-t-butyl-4-methylphenol), 2,2'-thio-bis-(4-octylphenol), 2,2' -thio-bis-(6-t-butyl-
3-methylphenol), 4,4'-thio-bis-
(6-t-butyl-2-methylphenol), 2,
2'-methylene-bis-(6-t-butyl-4-methylphenol), 2,2'-methylene-bis-(6
-t-butyl-4-ethylphenol), 2,
2'-methylene-bis-[4-methyl-6-(α-methylcyclohexyl)-phenol], 2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol), 2,2'-methylene -Bis-(6-
nonyl-4-methylphenol), 2,2'-methylene-bis[6-(α-methylbenzyl)-4-nonylphenol], 2,2'-methylene-bis-[6
-(α,α-dimethylbenzyl)-4-nonylphenol], 2,2′-methylene-bis-(4,6-di-t-butylphenol), 2,2′-ethylidene-bis-(4, 6-di-t-butylphenol),
2,2'-ethylidene-bis-(6-t-butyl-
4-i-butylphenol), 4,4'-methylene-bis-(2,6-di-t-butylphenol),
4,4'-methylene-bis-(6-t-butyl-2
-methylphenol), 4,4'-butylidene-bis-(6-t-butyl-2-methylphenol),
4,4'-Butylidene-bis-(6-t-butyl-
3-methylphenol), 4,4'-butylidene-
bis-(2,6-di-t-butylphenol),
4,4'-butylidene-bis-(3,6-di-t-
butylphenol), 1,1-bis-(5-t-butyl-4-hydroxy-2-methylphenyl)-
Butane, 2,6-di-(3-t-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol, 1,1,3-tris-(5-t-butyl-4-hydroxy-2 -methylphenyl)-butane, bis[3,3-bis(4'-hydroxy-
3'-t-butylphenyl)butylphenyl)
Ethylene glycol ester, di-(3-t-butyl-4-hydroxy-5-methylphenyl)-
Dicyclopentadiene, di-[2-(3'-t-butyl-2'-hydroxy-5'-methylbenzyl)-6
-t-butyl-4-methylphenyl]terephthalate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5- Tris-(3,
5-di-t-butyl-4-hydroxybenzyl)
Isocyanurate, 1,3,5-tris-(4-
t-Butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate, 1,3,5-tris-[(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxyethyl]isocyanurate Or tetrakis [methylene-3-
(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane can be exemplified. The compounding ratio of the compound A and the phenolic antioxidant is 0.01 to 1 part by weight, preferably 0.05 to 1 part by weight, per 100 parts by weight of the ethylene polymer.
It is 0.5 part by weight. If the amount is less than 0.01 part by weight, the effect of preventing coloring of the crosslinked ethylene polymer will not be sufficiently exhibited, and although it is OK to exceed 1 part by weight, no further improvement in the coloring prevention effect can be expected and in practice Not only is it unsuitable, but it is also uneconomical. For the radical generator used in the present invention, in order to obtain a uniform composition, it is preferable that the decomposition temperature is not too low, and the temperature to obtain a half-life of 10 hours is 70°C.
Above, 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, diquinyl peroxide, 2,5-di-methyl-2,5-di-(t-butylperoxy)
Hexane, 2,5-di-methyl-2,5-di-
(t-butylperoxy)hexyne-3,1,3
-bis-(t-butylperoxyisopropyl)
Benzene, t-butyl quinyl 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, cymene hydroperoxide, t-butyl hydroperoxide, p-cymene hydroperoxide, 1,1,3,3-tetra-methylbutyl hydroperoxide or 2,5-di-
Examples include organic peroxides such as methyl-2,5-di-(hydroperoxy)hexane. Especially 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 blending ratio of the radical generator is usually ethylene polymer.
The amount is 0.001 to 0.5 parts by weight, preferably 0.01 to 0.2 parts by weight per 100 parts by weight. In addition, the melt-kneading process is performed at a temperature of 150°C using various melt-kneading equipment described below.
It is carried out at a temperature of ~300°C, preferably 180°C to 270°C.
If the melt-kneading treatment temperature is less than 150°C, sufficient crosslinking will not occur, and if it exceeds 300°C, the thermal oxidative deterioration of the ethylene polymer will be accelerated and the coloration of the ethylene polymer will become noticeable, which is not preferred. In the production method of the present invention, the titanium content of the catalyst residue used is 5 ppm or more or the vanadium content is
Ethylene polymers containing 0.5 ppm or more contain various additives that are normally added to ethylene polymers, such as thioether-based, phosphorus-based antioxidants, light stabilizers, clarifying agents, nucleating agents, lubricants, and electrostatic charges. Preventive agents, antifogging agents, antiblocking agents, dropless agents, pigments, heavy metal deactivators (copper inhibitors), dispersants or neutralizing agents such as metal soaps, inorganic fillers (e.g. talc, mica, clay, wollastonite, zeolite, asbestos, calcium carbonate, aluminum hydroxide, magnesium hydroxide, barium sulfate, calcium silicate, glass fiber, carbon fiber, etc.) or coupling agents (for example, silane-based,
The above-mentioned inorganic fillers or organic fillers (e.g., wood flour, pulp, waste paper, synthetic fibers, natural fibers, etc.) that have been surface-treated with a surface treatment agent such as titanate-based, boron-based, aluminate-based, zirco-aluminate-based, etc. ) may be used in combination within a range that does not impair the purpose of the present invention. In particular, when a phosphorus-based antioxidant is used in combination, a synergistic coloring prevention effect is exhibited, so it is preferable to use them together. Preferred phosphorus antioxidants include distearyl-pentaerythritol-diphosphite, tetrakis(2,4
-di-t-butylphenyl)-4,4'-biphenylene-di-phosphonite, bis(2,4-di-t-butylphenyl)-pentaerythritol-diphosphite, bis(2,6-di-t-butyl-4 -methylphenyl)-pentaerythritol-diphosphite and tris(2,4-
An example is di-t-butylphenyl) phosphorite. The production method of the present invention reduces the titanium content of the catalyst residue.
The above-mentioned Compound A, phenolic antioxidant, radical generator, and each of the above-mentioned various additives that are usually added to ethylene polymers are added to an ethylene polymer containing 5 ppm or more or 0.5 ppm or more of vanadium. Using a mixing device such as a Hensel mixer (trade name), a super mixer, a ribbon blender, a Banbury mixer, etc., mix at a temperature that does not decompose the blended radical generator. Melt kneading temperature 150℃~300℃ with machine, Brabender or roll etc.
This is carried out by melt-kneading at 180°C to 270°C. [Function] In the present invention, the phenolic antioxidant acts as a radical chain inhibitor, and the radical generator generates radicals through melt-kneading treatment, that is, heating, and extracts hydrogen atoms from the ethylene polymer. It is well known that it generates radicals and crosslinks ethylene polymers to improve mechanical strength, heat-resistant rigidity, etc. In the production method of the present invention, the above-mentioned compound A is
When an ethylene polymer stabilized by a phenolic antioxidant is melt-kneaded in the presence of a radical generator, what kind of action does it have on titanium or vanadium complex compounds?The mechanism of its action itself is Although it is not clear, the effect of the present invention is not achieved when a complete ester of polyol and fatty acid is used, so the alcoholic hydroxyl group of compound A acts on the titanium or vanadium complex compound to produce a stable chelate compound. It is estimated that [Effects] The crosslinked ethylene polymer obtained by the production method of the present invention can be produced using a radical generator using a conventionally known phosphorus antioxidant or an ethylene polymer prepared by blending a polyol with a complete ester of fatty acid. Compared to cross-linked ethylene polymers obtained by cross-linking, injection molding, extrusion molding (especially wire coating, foaming), blow molding, etc. It can be suitably used to manufacture desired molded products by various molding methods such as. [Examples] Hereinafter, the present invention will be specifically explained using Examples, Comparative Examples, and Reference Examples, but the present invention is not limited thereto. The evaluation method used in Examples, Comparative Examples, and Reference Examples was as follows. Colorability: YI (Yellowness) of the obtained pellets
(based on JIS K7103), and this YI
The colorability was evaluated based on the magnitude of the numerical value. The smaller this number is, the less coloring there is. Examples 1 to 16, Comparative Examples 1 to 4, Reference Example 1 As an ethylene polymer, MI (discharge amount of molten resin in 10 minutes when a load of 2.16 kg at 190°C is applied) is 1.5 g/10 minutes in powder form Trimethylolethane, glycerin monostearate, pentaerythritol monostearate or pentaerythritol distearate as compound A, 2,6 as phenolic antioxidant to 100 parts by weight of Ziegura-Natsuta ethylene homopolymer (titanium content 8 ppm) -di-t-butyl-p-cresol, tetrakis [methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]
Methane, 1,3,5-trimethyl-2,4,6-
Tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris-
(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate or n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2 as a radical generator , 5-di-methyl-2,5-di-(t-butylperoxy)hexane or 1,3-bis-
(t-butylperoxyisopropyl)benzene and other additives were added to the
Add the blending ratio listed in the table to a Hensel mixer (trade name), stir and mix for 3 minutes, and then melt-knead at 200℃ using a 40mm diameter single screw extruder to crosslink.
Turned into pellets. In addition, as comparative examples 1 to 4, MI
100 parts by weight of a powdered Ziegler-Natsuta ethylene homopolymer (titanium content: 8 ppm) with a weight of 1.5 g/10 minutes was blended with a predetermined amount of each of the additives listed in Table 1 below, and Examples 1 to 16 were prepared. Crosslinked pellets were obtained by stirring, mixing, and melt-kneading according to the method. Furthermore, as Reference Example 1, 100 parts by weight of a powdered Ziegler-Natsuta ethylene homopolymer (titanium content 1 ppm) with an MI of 1.5 g/10 minutes was blended with predetermined amounts of each of the additives listed in Table 1 below. Then, crosslinked pellets were obtained by stirring, mixing and melt-kneading according to Examples 1 to 16. Using the obtained pellets, the coloring property was evaluated according to the test method described above. The results are shown in Table 1. Examples 17 to 32, Comparative Examples 5 to 8, Reference Example 2 As the ethylene polymer, powdered Ziegler-Natsuta ethylene-propylene copolymer (3.0 methyl branches/1000 carbon, titanium Content: 8 ppm) 100 parts by weight, as compound A, trimethylolethane, glycerin monostearate,
Pentaerythritol monostearate or pentaerythritol distearate, 2,6-di-t-butyl- as a phenolic antioxidant
p-cresol, tetrakis [methylene-3-
(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-
butyl-4-hydroxybenzyl)benzene,
1,3,5-tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate or n-octadecyl-β-(4'-hydroxy-
3',5'-di-t-butylphenyl)propionate, 2,5-di-methyl- as a radical generator
Predetermined amounts of 2,5-di-(t-butylperoxy)hexane or 1,3-bis-(t-butylperoxyisopropyl)benzene and other additives are blended in the proportions listed in Table 2 below. The mixture was placed in a Hensel mixer (trade name), stirred and mixed for 3 minutes, and then melt-kneaded at 200°C in a single-screw extruder with a diameter of 40 mm to crosslink and form pellets. Also,
Comparative Examples 5 to 8 are powdered Ziegler-Natsuta ethylene-propylene copolymers with an MI of 0.5 g/10 min (3.0 methyl branches/1000 carbons, titanium content
Predetermined amounts of each of the additives listed in Table 2 below were blended into 100 parts by weight (8ppm), and crosslinked pellets were obtained by stirring, mixing, and melt-kneading in accordance with Examples 17-32. Furthermore, as reference example 2, MI is 0.5g/
10 minute powder Ziegler-Natsuta ethylene-propylene copolymer (3.0 methyl branches/1000 carbons,
A predetermined amount of each of the additives listed in Table 2 below was blended with 100 parts by weight (titanium content 1 ppm), and
Crosslinked pellets were obtained by stirring, mixing and melt-kneading according to 17-32. The resulting pellets were evaluated for colorability using the test method described above. The results are shown in Table 2. Examples 33 to 48, Comparative Examples 9 to 12, Reference Example 3 As an ethylene polymer, a powdered Ziegler-Natsuta ethylene-butene-1 copolymer (0.014 ethyl branches/1000 carbons) with an MI of 1.0 g/10 min. , vanadium content 0.6 ppm) to 100 parts by weight of compound A, trimethylolethane, glycerin monostearate, pentaerythritol monostearate or pentaerythritol distearate,
2,6-di-t- as a phenolic antioxidant
Butyl-p-cresol, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,3,5
-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris-(3,5-di-t-butyl-4-hydroxy benzyl) isocyanurate or n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2,5-di-methyl-2,5-di-( Predetermined amounts of t-butylperoxy)hexane or 1,3-bis-(t-butylperoxyisopropyl)benzene and other additives were mixed in the Hensel mixer (trade name) at the mixing ratios listed in Table 3 below. ), stirred and mixed for 3 minutes, and then melt-kneaded at 200°C in a single-screw extruder with a diameter of 40 mm to crosslink and pelletize. In addition, as Comparative Examples 9 to 12, 100 parts by weight of a powdered Ziegler-Natsuta ethylene-butene-1 copolymer (0.014 ethyl branches/1000 carbon, vanadium content 0.06 ppm) with an MI of 1.0 g/10 minutes was added to 100 parts by weight as described below. By blending the prescribed amounts of each of the additives listed in Table 3, Example
Crosslinked pellets were obtained by stirring, mixing, and melt-kneading in accordance with 33-48. Furthermore, as reference example 3
Powdered Ziegler-Natsuta ethylene-butene-1 copolymer (ethyl branched 0.014
pcs/1000 carbon, vanadium content 0.01ppm) 100
Predetermined amounts of the additives listed in Table 3 below were added to the parts by weight, and crosslinked pellets were obtained by stirring, mixing, and melt-kneading according to Examples 33 to 48. Using the obtained pellets, the coloring property was evaluated according to the test method described above. The results are shown in Table 4. Examples 49 to 64, Comparative Examples 13 to 16, Reference Example 4 As an ethylene polymer, Mooney viscosity ML1
To 100 parts by weight of a powdery amorphous ethylene-propylene copolymer (propylene content 25% by weight, vanadium content 0.6ppm) of Erythritol monostearate or pentaerythritol distearate, 2,6-di-
t-Butyl-p-cresol, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,
3,5-trimethyl-2,4,6-tris (3,
5-di-t-butyl-4-hydroxybenzyl)
Benzene, 1,3,5-tris-(3,5-di-
t-butyl-4-hydroxybenzyl)isocyanurate or n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 2,5-di-methyl- as a radical generator 2,5-di-(t-butylperoxy)
Predetermined amounts of hexane or 1,3-bis-(t-butylperoxyisopropyl)benzene and other additives were placed in a Hensel mixer (trade name) at the mixing ratios listed in Table 4 below, and
After stirring and mixing for a minute, use a single-screw extruder with a diameter of 40 mm to
The mixture was melt-kneaded at ℃ to crosslink and form pellets. In addition, as comparative examples 13 to 16, Mooney viscosity
To 100 parts by weight of a powdery amorphous ethylene-propylene copolymer (propylene content 25% by weight, vanadium content 0.6 ppm) with ML1+4 (100°C) of 25, each of the additives listed in Table 4 below was added. A fixed amount was blended, stirred, mixed and melt-kneaded according to Examples 49 to 64 to obtain crosslinked pellets. Furthermore, as reference example 4, Mooney viscosity ML1+4 (100℃) is 25
powdered amorphous ethylene-propylene copolymer (propylene content 25% by weight, vanadium content
Predetermined amounts of each of the additives listed in Table 4 below were blended into 100 parts by weight (0.01 ppm), and crosslinked pellets were obtained by stirring, mixing and melt-kneading according to Examples 49-64. Using the obtained pellets, the coloring property was evaluated according to the test method described above. The results are shown in Table 4. The various compounds and additives shown in Tables 1 to 4 are as follows. Compound A []; Trimethylolethane compound A []; Glycerin monostearate compound A []; Pentaerythritol monostearate compound A []; Pentaerythritol distearate phenolic antioxidant []; 2,6-di -t
-Butyl-p-cresol phenolic antioxidant []; Tetrakis [methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate] Methanephenolic antioxidant [] ;1,3,5-trimethyl-2,4,6-tris(3,5-di-
t-Butyl-4-hydroxybenzyl)benzenephenolic antioxidant []; 1,3,5-tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate phenolic antioxidant [] ];n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl)propionate radical generator [];2,5-di-methyl-2,
5-di-(t-butylperoxy)hexane radical generator []; 1,3-bis-(t-butylperoxyisopropyl)benzenephosphorus antioxidant 1; Tetrakis(2,4-di-
t-butylphenyl)-4,4'-biphenylene-di-phosphonitophosphorous antioxidant 2; bis(2,4-di-t-butylphenyl)-pentaerythritol-diphosphite polyol compound (polyol and fatty acid Pentaerythritol Tetrastearate Ca-St; Calcium Stearate

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[Table] The Examples and Comparative Examples listed in Table 1 are cases where an ethylene homopolymer was used as the ethylene polymer. As can be seen from Table 1, Examples 1-
16 has a titanium content of 8 ppm in the catalyst residue related to the present invention.
Compound A, a phenolic antioxidant, and a radical generator are blended with the ethylene homopolymer contained therein, and the mixture is melt-kneaded and crosslinked. Comparing Examples 1 to 16 and Comparative Examples 1 to 3, Examples 1 to 16
It can be seen that Comparative Examples 1 to 3, in which Compound A was not used or a phosphorous antioxidant was used in place of Compound A, had significant coloring.
Comparing Comparative Example 4, in which a complete ester of polyol and fatty acid was used in place of Compound A, and Examples 1 to 16, Comparative Example 4 improved the colorability to some extent, but was still not fully satisfactory. Furthermore, Examples 9 to 10 in which Compound A according to the present invention, a phenolic antioxidant, a radical generator, and a phosphorus antioxidant were blended, melt-kneaded, and crosslinked were compared to Example 5. It can be seen that the excellent anti-coloration effect of Compound A is not inhibited, and a remarkable synergistic effect is observed when the phosphorus antioxidant is used in combination. In addition, the titanium content of the catalyst residue was
Reference Example 1 in which a phenolic antioxidant and a radical generator were blended into an ethylene homopolymer containing 1 ppm, that is, less than 5 ppm, and crosslinked by melt-kneading treatment.
As is clear from comparison with Comparative Example 1, no significant coloring occurred, and the above-mentioned significant coloring was caused by adding a phenolic antioxidant to the ethylene polymer containing 5 ppm or more of titanium in the catalyst residue of the present invention. This can be said to be a unique phenomenon that occurs when the mixture is melt-kneaded in the presence of a radical generator. Tables 2 to 4 show Ziegler-Natsuta ethylene-propylene copolymers and Ziegler-Natsuta ethylene-butene-1 as ethylene polymers, respectively.
A copolymer and an amorphous ethylene-propylene copolymer were used, and the same effects as described above were confirmed for these as well. It can be seen that the crosslinked ethylene polymer obtained by the production method of the present invention is free from coloration and has improved mechanical strength, heat-resistant rigidity, and the like. From this, the crosslinked ethylene polymer obtained by the production method of the present invention is more effective than the crosslinked ethylene polymer obtained by blending a conventionally known compound with an anti-coloration effect and melt-kneading it in the presence of a radical generator. As a result, it was found that the coloring prevention property was extremely excellent, and the remarkable effect of the present invention was confirmed.

Claims (1)

[Claims] 1. A polyol or a partial ester of the polyol and a fatty acid (hereinafter referred to as compound A) is added to 100 parts by weight of an ethylene polymer containing 5 ppm or more of titanium or 0.5 ppm or more of vanadium in the catalyst residue. and phenolic antioxidants, respectively.
1. A method for producing a crosslinked ethylene polymer, comprising blending 0.01 to 1 part by weight and 0.001 to 0.5 part by weight of a radical generator, and melt-kneading the mixture at 150°C to 300°C. 2. The method for producing a crosslinked ethylene polymer according to claim 1, wherein compound A is trimethylolethane, a monoester of glycerin and a fatty acid, or a mono- or diester of pentaerythritol and a fatty acid. 3 2,6-di- as a phenolic antioxidant
t-Butyl-p-cresol, tetrakis[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, 1,
3,5-trimethyl-2,4,6-tris (3,
5-di-t-butyl-4-hydroxybenzyl)
Benzene, 1,3,5-tris-(3,5-di-
Claim 1, which contains t-butyl-4-hydroxybenzyl) isocyanurate or n-octadecyl-β-(4'-hydroxy-3',5'-di-t-butylphenyl) propionate. A method for producing a crosslinked ethylene polymer. 4 2,5-di-methyl- as a radical generator
2,5-di-(t-butylperoxy)hexane,
2,5-di-methyl-2,5-di-(t-butylperoxy)hexyne-3 or 1,3-bis-
The method for producing a crosslinked ethylene polymer according to claim 1, which comprises blending (t-butylperoxyisopropyl)benzene. 5 Ethylene homopolymer as ethylene polymer, ethylene copolymer containing 50% by weight or more of ethylene component, including crystalline or amorphous ethylene-propylene copolymer, crystalline ethylene-butene-1 copolymer Coalescence, crystalline ethylene-propylene-butene-1 ternary copolymer, crystalline ethylene-
The method for producing a crosslinked ethylene polymer according to claim 1, using a pentene-1 copolymer or an ethylene-hexene-1 copolymer.