JPH02228345A - Stabilized polyethylene composition - Google Patents

Abstract

PURPOSE:To retard the decrease in flowability and gel formation during a high-temp. processing of a polyethylene compsn. and improve the resistance to thermal discoloration of an extrudate by compounding a specific phenolic antioxidant and a phosphorus antioxidant into polyethylene. CONSTITUTION:0.01-1 pt.wt. 2-t-amyl-6-[1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl)]-4-t- amylphenyl acrylate of the formula (wherein R1 is CH3; R2 and R3 are each t-amyl) and 0.01-1 pt.wt. phosphorus antioxidant are compounded into 100 pts.wt. polyethylene (a homopolymer of ethylene, or a copolymer of ethylene with an alpha-olefin such as propylene, butene-1, pentene-1, hexene-1, or octene-1) to give a thermally stabilized polyethylene compsn. Pref. phosphorus antioxidant is bis(2,4-di-t-butylphenyl)pentaerithritol diphosphite.

Description

[Detailed description of the invention] <Industrial application field> FIELD OF THE INVENTION This invention relates to stabilized polyethylene compositions.

More specifically, the present invention relates to a polyethylene composition that has excellent heat-resistant processing stability and heat-resistant discoloration during high-temperature molding.

<Prior art> Generally, polyethylene is molded by various methods such as extrusion molding, blow molding, and injection molding, but due to thermal deterioration and crosslinking during the molding process, fluidity (MI value) decreases and gelation occurs. In addition, there is a problem in that the polyethylene becomes discolored during repeated molding. In particular, in extrusion molding methods such as melt spinning, polyethylene gels are produced due to long-term continuous operation, and the screen packs of the extruder are clogged due to the gels.
As a result, there is a problem in that the discharge amount decreases and the screen pack needs to be replaced frequently, causing a significant decrease in productivity. Furthermore, when formed into a film or sheet, fish eye gel is generated, resulting in a problem that printing suitability is significantly reduced.

As a method for improving processing stability and discoloration during such molding processing, JP-A No. 62-223248 discloses that a phenolic compound (hereinafter referred to as "compound") represented by the following general formula C1) is added to polyethylene; ■ A phenolic compound represented by the general formula Cm below (hereinafter referred to as compound B), a phosphite compound represented by the following - formation CI [I] (hereinafter referred to as compound C), and a phosphonite represented by the following - formation CrV) It has been proposed to incorporate one or more compounds selected from the group of compounds (hereinafter referred to as "compounds").

(In the formula, R1 is defined as hydrogen or a methyl group, and R2-R9 are defined as hydrogen or the same or different alkyl groups having 1 to 8 carbon atoms, respectively.) Although the invention disclosed in this publication is a considerable improvement over previous stabilization techniques, it is still not fully satisfactory. That is, 2-t-butyl-6-(3-t-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenylacrylate (compound A), which is considered the most preferred in the publication, and 1.3. 5-) Listil-
2,4,6-)lis(3,5-di-t-butyl-4-hydroxybenzyl)benzene (compound B), bis(2,
4-di-t-butylphenyl)hentaerythritol diphosphite (compound C) or tetrakis(2,4-
(di-t-butylphenyl) 4,4'-biphenylene Diphosphonite (compound D) has insufficient heat-resistant processing stability during high-temperature molding aimed at improving productivity, and is difficult to repeatedly extrude. There still remains the problem that the heat history caused by molding causes discoloration. Therefore, further improvements in these areas have been required.

Means for Solving the Problems> The present inventors have conducted intensive research to further improve these insufficient characteristics, and as a result, have arrived at the present invention.

That is, the present invention provides polyethylene with (A) 2-t-amyl-6-(1-(3,5-di-t-
amyl-2-hydroxyphenyl)ethyl)-4-t-
The present invention provides a stabilized polyethylene composition containing amyl phenyl acrylate and (B) a phosphorus antioxidant. With such a composition, a high effect of suppressing a decrease in fluidity and an effect of preventing the formation of a gelled product can be obtained, and the heat resistance to discoloration during repeated extrusion molding is also improved.

2-t-amyl-6-C1-(3,5-di-t-amyl-2-hydroxyphenyl)ethyl2 of the above (A)
-t-amyl phenyl acrylate is polyethylene 1
It is preferable to use the amount in the range of 0.01 to 1 part by weight per 0.00 parts by weight. If the amount is less than 0.01 parts by weight, the desired heat-resistant processing stability and heat-resistant discoloration property will not be sufficient;
Exceeding the weight part may cause bleeding.

The above (B) phosphorus antioxidant is polyethylene 100
It is preferable to use the amount in the range of 0.01 to 1 part by weight. If the amount is less than 0.01 part by weight, the desired heat-resistant processing stability and heat-resistant discoloration property are insufficient, and 1 part by weight is used. Exceeding this will cause bleeding.

The phosphorus-based antioxidant used in the present invention is not particularly limited, but includes, for example, distearyl pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, bis( 2,6-di-t-butyl-4-methylphenyl) pentaerythritol
Examples include diphosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(nonylphenyl) phosphite, and tetrakis(2,4-di-t-butylphenyl>4.4'-biphenylene diphosphonite). Among these, bis(2,4-
di-t-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-t-butylphenyl) phosphite, tetrakis(2,4-di-t-butylphenyl) 4.4
'-biphenylene diphosphonite is preferred.

The polyethylene used in the present invention includes high density polyethylene,
It includes medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, etc. Specific examples include ethylene homopolymers, ethylene and propylene, butene-1, pentene-1, hexene-1, etc. 1, octene-1, or a copolymer with two or more of these α-olefins.

The composition of the present invention contains various additives normally added to polyethylene, such as phenol-based and sulfur-based antioxidants, ultraviolet absorbers, hindered amine light stabilizers, and metal deactivators (copper). (harm preventive agent), nucleating agent, lubricant,
Antistatic agent, antifogging agent, antiblocking agent, non-drop agent,
Pigments, radical generators such as peroxides, dispersants or neutralizing agents such as metal soaps, and inorganic fillers (for example, talc, mica, clay, glass fiber), etc. may be blended.

Specific examples of these additives that can be used in the present invention include the following.

Examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, 4,4'-thiobis(3-methyl-6-t-butylphenol), n-octadecyl 3-(3, 5-di-butyl-4-hydroxyphenyl) propionate, triethylene glycol bis[3-(3t-butyl-4
-Hydroxy-5-methylphenyl)propionate]
, 3.9-bis[1,1-dimethyl-2 (β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy)ethyl)-2,4,8
, 10-tetraoxaspiro[5.5]undecane, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate comethane, tris(3,5-di-t- butyl-4-hydroquinebenzyl) isonenurate, tris(2-(3-(3,
5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl] incyanurate, 1.3.
5-) riftyl-2,4,6-tris(3,5-di-t)
-butyl-4-hydroxybenzyl)benzene and the like. In particular, when gas discoloration resistance (resistance to discoloration caused by NOX gas, propane gas combustion gas, automobile exhaust gas, etc.) is required, 3.9-bis(1,1-dimethyl-2-(β-(3 -t
-Butyl-4-hydroxy-5-methylphenyl)propionyloxy)ethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane is preferably used in combination.

Examples of sulfur-based antioxidants include dilauryl 3,3'-thiodipropionate, cimilistyl 3,3'-thiodipropionate, distearyl 3,3'-thiodipropionate, pentaerythrityltetrakis (β- lauryl thiopropionate), etc.

Examples of ultraviolet absorbers include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, and bis(5-benzoyl-4-hydroxy-2- methoxyphenyl)methane, 2.2',4.4'-tetrahydroxybenzophenone, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-[2-hydroxy-3-(3,4,5゜6-titrahydrobutarymidomethyl)-5-methylphenyl]benzotriazole, 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenztriazole, 2-(3,5- di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(2-hydroxy-5-
t-octylphenyl)benzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-[2-hydroxy-3
,5-bis(α.

α-dimethylbenzyl)phenyl)-2H-benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenztriazole, 2,2'-methylenebis(6-(2H- benzotriazol-2-yl)-4-(1゜1.3.3-tetramethylbutyl〉phenol), poly(3-11)(ethylene glycol) and methyl
3- (3-(2H-benzotriazol-2-yl)
Condensation product with -5-t-butyl-4-hydroxyphenyl]propionate, 2-ethylhexyl 3-[3-t-butyl-5-(5
-chloro-2H-benzotriazol-2-yl)-4
-hydroxyphenyl]propionate, octyl 3-(3-t-butyl-5-(5-chloro-2H-benzotriazol-2-yl)-4-hydroxyphenyl]frobionate, methyl 3-(3-t-butyl- 5-(5-chloro-2
H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate, 3-(3-t-butyl-5-(5-chloro-28-benzotriazol-2-yl)-4-hydroxyphenyl]propionic acid , 2,2'-methylenebis[4-t-butyl-6-(2H-benzotriazol-2-yl)phenol], and the like.

Examples of hindered amine light stabilizers include bis(2
, 2,6,6-tetramethyl-4-piperidyl) sebacate.

Polycondensate of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2゜6.6-tetramethylbiperidine, poly[(6-morpholino-1,3,5-) Reazine
2,4-diyl)((2,2,6゜6-tetramethyl-
4-Piperidyl)imino)hexamethylene ((2,2,
6,6-tetramethyl-4-piperidyl)imino],
Bis(1,2,2,6,6-bentamethyl-4-piperidyl)2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-butylmalonate, 4-(3-(3, 5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-1-C2-(3-
(3,5-di-t-butyl-4-hydroxyphenyl)
propionyloxy)ethyl)-2,2,6,6-tetramethylbiperidine, bis(1,2,2,6,6-bentamethyl-4-piperidyl)decanedioate, tetrakis(2,2,6,
6-tetramethyl-4-piperidyl)1,2,3.4-
Butane tetracarboxylate, poly ((6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-)riazine-2,4-diyl)
((2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl)imino)], 1.2.3.4- Butanetetracarboxylic acid and 1,2,2
, 6.6-bentamethyl-4-piperiditul and 1
- Mixed esterified product with tridecanol, 1.2,3.4-butanetetracarboxylic acid and 2.2,6
．． 6-tetramethyl-4-piperiditul and 1-)
Mixed esterified product with ridecanol, 1.2,3.4-butanetetracarboxylic acid and 1.2,2
, 6.6-bentamethyl-4-piperiditul and 3
,9-bis(2-hydroxy-1,1-dimethylethyl)-2゜4.8.10-tetraoxaspiro[5.5]
Mixed esterified product with undecane, 1,2,3,4-butanetetracarboxylic acid and 2,2,6
．． 6-tetramethyl-4-piperiditul and 3.9
-bis(2-hydroxy-1,1-dimethylethyl)-
Mixed ester of 2,4゜8.10-tetraoxaspiro[5,5]undecane, N,N'-bis(2,2,6,6-tetramethyl-4
-piperidyl)hexamethylenediamine and 1,2-dibromoethane, 2-methyl-2-(2,2,6,6-natomethyl-4-
piperidylamino)-N-(2゜2.6.6-tetramethyl-4-piperidyl)propionamide, N,N',4,7-tetrakis(4,6-bis(N-butyl-N(2, 2,6,' 6-tetramethyl-
4-piperidyl)amino)-1,3,5-triazine-
2-yl]-4゜7-cyazadecane-1,10-diamine, N,N',4-tris[4,6-bis(N-butyl-N-(2,2,6,6-tetramethyl-4 -piperidyl)amine)-1,3°5~triazin-2-yl24. fudiadidecane-1,10-diamine, bis(l-acryloyl-2,2,6,6tetramethyl-4-piperidyl)2,2-bis(3,5-di-t-butyl-4-hydroxybenzyl) malonate, N,N'4,7-tetrakis[4,6 bis(N-butyl-N-(1,2,2,6°6-bentamethyl-4-piperidyl)amino)-1,3,5-)riazine -2-yl]-4゜7-thiazadecane-1. lO
-diamine, N, N', 4) Lis[4,6-bis(N-butyl-N-(1,2,2,6,6-bentamethyl-4-piperidyl)amino)-1°3.5-triazine -2-yl]-4,7-cyazadecane-1,10-diamine, bis(2,2,6,6-tetramethyl-4piperidyl)
Succinate, 2.2.6.6-Tetramethyl-4-piperidyl methacrylate, 1.2.2,6.6-bentamethyl-4-piperidyl methacrylate, Tetrakis(1,2,2,6,6-bentamethyl-4-
piperidyl) 1.2.3.4-butanetetracarboxylate and the like.

<Examples> Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

Examples 1 to 3 and Comparative Examples 1 to 6 100 parts by weight of high-density polyethylene (MI=15.190t) was triblended with the phenolic compound and phosphorus compound described below in the amounts shown in Table 1. Thereafter, the mixture was melt-kneaded at 200° C. using a single-screw extruder with a diameter of 30 mm, and pelletized. The following physical properties were measured using the obtained pellet, and the results are shown in Table 1.

Processing stability (melting stability): Using a melt indexer (manufactured by Takara Kogyo@), JIS
According to K-7210, at 300℃ for 5 minutes and 60℃
The fluidity after residence for 5 minutes (MI value: g/10mln) was evaluated. The smaller the difference between the fluidity after residence for 5 minutes and the fluidity after residence for 60 minutes, the better the high temperature processing stability. do.

Gelation (crosslinking) prevention property: Using a T-die extruder with a diameter of 30 mm, cylinder temperature 2
40-280℃, Gui temperature 280℃, resin pressure 200K
A sheet with a diameter of 0.4 mm was prepared by grinding with g/am2, and fish eyes with a diameter of 0.3 mm or more present in 1000 cff12 of this sheet were detected and counted. The smaller the fisheye value, the fewer gelled substances and the better the anti-gelling property.

Preventing discoloration: Extrusion was repeated 5 times at 300°C using a single-screw extruder with a diameter of 30 mm, and the resulting pellet was further molded into a flat plate of IM thickness using a 5.5 oz injection molding machine (250°C). did. The discoloration prevention property was evaluated based on the difference in the Yr value of the 1 mm thick plate between the first and fifth repetitions, that is, ΔYl.

The smaller the value of ΔYl, the better the discoloration prevention property.

The symbols for phenolic compounds and phosphorus compounds listed in Table 1 mean the following, respectively.

An-12-t-amyl-6-(1-(3,5-di-t
-amyl-2-hydroxyphenyl)ethyl: ]-4-t-amyl phenyl acrylate An-22-t-butyl-6-(3-t-butyl-5-
Methyl-2-hydroxybenzyl)-4-methylphenylacrylate An-31,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene P-1 Bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite P-2tetrakis(2,4-di-t-butylphenyl)
4.4'-Piphenylene diphosphonite P-3 tris(2,4-di-t-butylphenyl) phosphite

Claims (3)

[Claims] (1) Polyethylene (A) 2-t-amyl-6-[1-(3,5-di-t-
amyl-2-hydroxyphenyl)ethyl]-4-t-
A stabilized polyethylene composition comprising amyl phenyl acrylate and (B) a phosphorus antioxidant. (2) The phosphorus antioxidant is bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-t-butylphenyl) phosphite, or tetrakis(2,4-di-t-butylphenyl) phosphite. 2. The polyethylene composition according to claim 1, which is 4,4'-biphenylene diphosphonite (-di-t-butylphenyl). (3) The polyethylene is a homopolymer of ethylene or a copolymer of ethylene and propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or two or more of these α-olefins. The polyethylene composition described.