JP2587687B2 - Stabilized polyethylene composition - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to stabilized polyethylene compositions. More specifically, the present invention relates to a polyethylene composition which is excellent in preventing polyethylene from being oxidatively degraded during melt-kneading.

[Prior Art] In general, polyethylene is relatively inexpensive and has excellent mechanical properties, and is therefore used in the production of various molded products such as injection molded products, hollow molded products, films, sheets, and fibers. However, when polyethylene is molded at a temperature equal to or higher than the melting point of the polyethylene, it undergoes oxidative deterioration due to heat during melt-kneading, and the processability due to crosslinking of the polyethylene, that is, the melt stability is reduced, and the appearance of the molded product is reduced. In addition, coloring and odor problems due to oxidative deterioration occur. In particular, in an extrusion molding method such as melt spinning, a continuous operation for a long time causes the crosslinking of polyethylene to proceed to generate a gelled product, which causes clogging of the screen pack due to the gelled product, resulting in a decrease in discharge amount and Problems such as a remarkable decrease in productivity due to frequent replacement of the screen pack and the like occur. Further, when formed into a film or sheet, there is a problem that fish eyes are generated due to a high molecular weight component due to a gelation reaction.

For this reason, conventionally, various phenolic and phosphorus-based antioxidants are used alone or in combination with each other for the purpose of preventing the thermal oxidation deterioration during melt-kneading of polyethylene and improving the melt stability and the anti-gelling property. Used.

[Problems to be Solved by the Invention] However, conventional phenolic antioxidants, especially low-molecular-weight phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol, are blended in polyethylene. Is excellent in heat-resistant oxidative deterioration during melt-kneading (hereinafter referred to as processing stability, and processing stability means melt stability and anti-gelling properties), but when a molded article is obtained. However, there is a disadvantage that the molded article is colored due to the antioxidant used. Further, a composition obtained by mixing only a high molecular weight phenolic antioxidant with polyethylene has disadvantages in processing stability and coloring property caused by the high molecular weight phenolic antioxidant. Further, a composition comprising the polyethylene in combination with the low-molecular-weight phenolic antioxidant and the high-molecular-weight phenolic antioxidant described above, although the processing stability of the composition is excellent, almost no synergistic effect due to the combination is observed. On the contrary, there is a problem that the coloring of the obtained molded article becomes conspicuous by increasing the amount of the phenolic antioxidant.

On the other hand, in the case of a composition obtained by mixing only a phosphorus-based antioxidant with polyethylene, the problem of the coloring property observed in a molded article obtained from the composition obtained by mixing the above-mentioned phenol-based antioxidant is remarkably improved. However, there is a disadvantage that the melt stability, which is the processing stability when subjected to severe heat history due to several times of melt-kneading, is significantly reduced. For this reason, it is conceivable to use a high-molecular-weight phenolic antioxidant having a synergistic action with the phosphorus-based antioxidant in combination. However, such a combined system can improve the processing stability, particularly the melt stability, and the coloring property caused by the used antioxidant, which are problems of the prior art, to some extent, but they are still insufficient. Particularly, in the case of a conventionally used combination system of a high-molecular-weight phenolic antioxidant and a phosphorus-based antioxidant, the effect of preventing gelation of the combined system is recognized to some extent, but is not yet sufficient. At present, in extrusion molding such as melt-spinning which performs continuous operation for a longer time than ever, improvement of gelation prevention among processing stability is strongly desired at present.

In order to solve the above-mentioned problems relating to the above-mentioned polyethylene composition, namely, the drawbacks of processing stability and colorability, the present inventors have previously disclosed in JP-A-62-223248 a specific acrylate group-containing phenolic antioxidant. In addition, a polyethylene composition using a phosphorus-based antioxidant comprising a specific phosphite compound or a specific phosphite compound has been proposed, but further studies have been made without satisfaction.

As a result, a phenolic compound represented by the following general formula [I] (hereinafter, referred to as compound A) and a phosphite-based compound represented by the following general formula [II] (hereinafter, referred to as compound B) are respectively specified in polyethylene. The inventors have found that a composition obtained by blending in a large amount can solve the above-mentioned disadvantages of the polyethylene composition, and based on this finding, completed the present invention.

(Wherein, R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms, R _{2 to} R ₅ are an alkyl group having 1 to 9 carbon atoms, a cyclohexyl group or 1-methylcyclohexyl group, and R ₆ is hydrogen or A methyl group, R ₇ and R ₉ each represent a branched alkyl group having 3 to ₉ carbon atoms, and R ₈ represents hydrogen or an alkyl group having 1 to 9 carbon atoms.) As apparent from the above description, An object of the present invention is to provide a polyethylene composition which is excellent in processing stability and can obtain a molded article free from coloring caused by an antioxidant used.

[Means for Solving the Problems] The present invention has the following configurations.

For 100 parts by weight of polyethylene, the following general formula [I]
(Hereinafter referred to as compound A) and a phosphite compound (hereinafter referred to as compound B) represented by the following general formula [II] are each 0.01.
A stabilized polyethylene composition, which is blended with 1 to 1 part by weight.

(Wherein, R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms, R _{2 to} R ₅ are an alkyl group having 1 to 9 carbon atoms, a cyclohexyl group or 1-methylcyclohexyl group, and R ₆ is hydrogen or A methyl group, R ₇ and R ₉ each represent a branched alkyl group having 3 to ₉ carbon atoms, and R ₈ represents hydrogen or an alkyl group having 1 to 9 carbon atoms.) The polyethylene used in the present invention is a crystal of ethylene. A homopolymer, an ethylene copolymer containing 50% by weight or more of an ethylene component, wherein ethylene and propylene, butene-
1, pentene-1, 4-methyl-pentene-1, hexene-1, octene-1, etc., with one or more α-olefins, such as a crystalline, low-crystalline or amorphous copolymer, Polyethylene such as a crystalline ethylene-propylene-nonconjugated diene copolymer, a copolymer of ethylene and vinyl acetate or acrylate, a saponified product of the copolymer, a copolymer of ethylene and an unsaturated silane compound, Copolymer of ethylene and unsaturated carboxylic acid or anhydride, reaction product of the copolymer and metal ion compound, modified polyethylene obtained by modifying the above polyethylene with unsaturated carboxylic acid or derivative thereof, polyethylene described above Examples thereof include silane-modified polyethylene modified with an unsaturated silane compound. , It can also be used in combination of two or more polyethylene. In addition, various synthetic rubbers (for example, polybutadiene, polyisoprene,
Polychloroprene, chlorinated polyethylene, chlorinated polypropylene, fluoro rubber, styrene-butadiene rubber,
Acrylonitrile-butadiene rubber, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-propylene-butylene-styrene block copolymer, etc. )
Or thermoplastic synthetic resins (for example, polyolefins other than polyethylene such as polypropylene, polybutene-1 and poly-4-methylpentene-1; polystyrene;
Styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyvinyl chloride, fluororesin, etc.) may be used as a mixture. A crystalline ethylene homopolymer, a crystalline ethylene copolymer containing 50% by weight of an ethylene component, comprising a crystalline ethylene-propylene copolymer, a crystalline ethylene-butene-1 copolymer, and a crystalline ethylene-propylene -Butene-1 terpolymer, crystalline ethylene-pentene-1 copolymer, crystalline ethylene-
Hexene-1 copolymer and a mixture of two or more thereof are particularly preferably used.

The compound A used in the present invention includes 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2-t
-Butyl-6- (3-t-butyl-2-hydroxy-5
-Ethylbenzyl) -4-ethylphenyl acrylate, 2-nonyl-6- (3-nonyl-2-hydroxy-
5-methylbenzyl) -4-methylphenyl acrylate, 2,4-di-nonyl-6- (3,5-di-nonyl-2-hydroxybenzyl) phenyl acrylate, 2-cyclohexyl-6- (3-cyclohexyl- 2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- (1'-methylcyclohexyl) -6- [3
-(1'-methylcyclohexyl) -2-hydroxy-
5-methylbenzyl] -4-methylphenyl acrylate, 2,4-di-methyl-6- [3,5-di-methyl-2-hydroxy (α-propylbenzyl)] phenyl acrylate, 2,4-di- t-butyl-6- (3,5-di-t-butyl-2-hydroxybenzyl) phenyl acrylate,
2-tert-butyl-6- [3-tert-butyl-2-hydroxy-5-methyl (α-methylbenzyl)]-4-methylphenyl acrylate, 2-tert-butyl-6- [3-t
-Butyl-2-hydroxy-5-s-butyl (α-methylbenzyl)]-4-s-butylphenyl acrylate, 2,4-di-t-butyl-6- [3,5-di-t-butyl -2-hydroxy (α-methylbenzyl)] phenyl acrylate, 2-t-octyl-6- (3-t-octyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2- (1 ′ -Methylcyclohexyl) -6- [3- (1'-methylcyclohexyl)
-2-hydroxy-5-methyl (α-propylbenzyl)]-4-methylphenyl acrylate, 2,4-di-
Methyl-6- (3,5-di-methyl-2-hydroxybenzyl) phenyl acrylate, 2-tert-butyl-6
(3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl methacrylate, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-ethylbenzyl) -4- Ethylphenyl methacrylate,
2-nonyl-6- (3-nonyl-2-hydroxy-5-
Methylbenzyl) -4-methylphenyl methacrylate, 2,4-di-nonyl-6- (3,5-di-nonyl-2-hydroxybenzyl) phenyl methacrylate, 2-cyclohexyl-6- (3-cyclohexyl-2- (Hydroxy-5-methylbenzyl) -4-methylphenyl methacrylate, 2- (1′-methylcyclohexyl) -6-
[3- (1'-methylcyclohexyl) -2-hydroxy-5-methylbenzyl] -4-methylphenyl methacrylate, 2,4-di-methyl-6- [3,5-di-methyl-
2-hydroxy (α-propylbenzyl)] phenyl methacrylate, 2,4-di-t-butyl-6- (3,5-di-
(tert-butyl-2-hydroxybenzyl) phenyl methacrylate, 2-tert-butyl-6- [3-tert-butyl-2
-Hydroxy-5-methyl (α-methylbenzyl)]-
4-methylphenyl methacrylate, 2-t-butyl-
6- [3-tert-butyl-2-hydroxy-5-s-butyl (α-methylbenzyl)]-4-s-butylphenyl methacrylate, 2,4-di-tert-butyl-6- [3,5 -Di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl methacrylate, 2-t-octyl-6
-(3-t-octyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl methacrylate, 2-
(1′-methylcyclohexyl) -6- [3- (1′-
Methylcyclohexyl) -2-hydroxy-5-methyl (α-propylbenzyl)]-4-methylphenylmethacrylate and 2,4-di-methyl-6- (3,5-di-methyl-2-hydroxybenzyl) phenyl Examples thereof include methacrylate and the like, in particular, 2-t-butyl-6- (3-t
-Butyl-2-hydroxy-5-methylbenzyl) -4
-Methylphenyl acrylate, 2-t-butyl-6-
[3-tert-butyl-2-hydroxy-5-methyl (α-
Methylbenzyl)]-4-methylphenyl acrylate and 2,4-di-t-butyl-6- [3,5-di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl acrylate are preferred. These compounds A may be used alone, or two or more compounds A may be used in combination. The compounding ratio of the compound A is 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weight, based on 100 parts by weight of polyethylene. If the amount is less than 0.01 part by weight, the effect of improving the processing stability and the anti-coloring property of the polyethylene composition is not sufficiently exhibited, and the content may exceed 1 part by weight. It is not practical because the improvement effect cannot be expected, and it is uneconomical.

As compound B used in the present invention, bis (2,6-di-i-propyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2-i-propyl-
6-t-butylphenyl) pentaerythritol-diphosphite, bis (2-i-propyl-4-methyl-
6-t-butylphenyl) pentaerythritol-diphosphite, bis (2-i-propyl-4-ethyl-
6-t-butylphenyl) pentaerythritol-diphosphite, bis (2-i-propyl-4,6-di-t
-Butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-i-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2,6-di-i-butyl-4-ethyl) Phenyl) pentaerythritol-diphosphite, bis (2,4,6-tri-i-butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-i-butyl-4-t-)
Butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-s-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2,6-di-s-butyl-4-ethylphenyl) ) Pentaerythritol-diphosphite, bis (2,4,6-tri-s-butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-s-butyl-4-t-)
Butylphenyl) pentaerythritol-diphosphite, bis (2-s-butyl-4-methyl-6-t-butylphenyl) pentaerythritol-diphosphite, bis (2-s-butyl-4-ethyl-6- t-butylphenyl) pentaerythritol-diphosphite, bis (2-s-butyl-4-i-butyl-6-t-
Butylphenyl) pentaerythritol-diphosphite, bis (2,4-di-s-butyl-6-t-butylphenyl) pentaerythritol-diphosphite, bis (2-s-butyl-4,6-di- t-butylphenyl)
Pentaerythritol diphosphite, bis (2,6
-Di-t-butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl) -4-ethylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-n-propylphenyl)
Pentaerythritol diphosphite, bis (2,6
-Di-t-butyl-4-i-propylphenyl) pentaerythritol-diphosphite, bis (2,6-di-
t-butyl-4-n-butylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-i-butylphenyl) pentaerythritol-
Diphosphite, bis (2,6-di-t-butyl-4-
(s-butylphenyl) pentaerythritol-diphosphite, bis (2,4,6-tri-t-butylphenyl)
Pentaerythritol diphosphite, bis (2,6
-Di-t-butyl-4-n-amylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t
-Butyl-4-i-amylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-s-amylphenyl) pentaerythritol-diphosphite, bis (2,6-diphenyl) -T-butyl-4-t
-Amylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-n-hexylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4) -N-heptyl)
Pentaerythritol diphosphite, bis (2,6
-Di-t-butyl-4-n-octylphenyl) pentaerythritol-diphosphite, bis (2,6-di-
t-butyl-4-t-octylphenyl) pentaerythritol-diphosphite, bis (2-t-butyl-
4-methyl-6-i-amylphenyl) pentaerythritol-diphosphite, bis (2-t-butyl-4)
-Methyl-6-s-amylphenyl) pentaerythritol-diphosphite, bis (2-tert-butyl-4-)
Methyl-6-t-amylphenyl) pentaerythritol-diphosphite, bis (2-t-butyl-4-methyl-6-t-octylphenyl) pentaerythritol-diphosphite, bis (2-t-butyl- 4-ethyl-6-i-amylphenyl) pentaerythritol diphosphite, bis (2-t-butyl-4-ethyl-6-s-amylphenyl) pentaerythritol-
Diphosphite, bis (2-tert-butyl-4-ethyl-6-tert-amylphenyl) pentaerythritol-diphosphite, bis (2-tert-butyl-4-ethyl-)
6-t-octylphenyl) pentaerythritol-diphosphite, bis (2,4-di-t-butyl-6-t
-Amylphenyl) pentaerythritol-diphosphite and bis (2,4-di-t-butyl-6-t-octylphenyl) pentaerythritol-diphosphite, and especially bis (2,6-di- t-butyl-4-methylphenyl) pentaerythritol-diphosphite and bis (2,6-di-t-butyl-4-s)
-Butylphenyl) pentaerythritol-diphosphite is preferred. These compounds B may be used alone, or two or more compounds B may be used in combination.
The compounding ratio of the compound B is 0.01 to 1 part by weight, preferably 0.05 to 0.5 part by weight, based on 100 parts by weight of polyethylene. If the amount is less than 0.01 part by weight, the effect of improving the processing stability and the anti-coloring property of the polyethylene composition is not sufficiently exhibited, and the content may be more than 1 part by weight, but the processing stability and the anti-coloring property are further increased. It is not practical because the improvement effect cannot be expected, and it is uneconomical.

In the composition of the present invention, various additives which are usually added to polyethylene, such as phenol-based, thioether-based, phosphorus-based antioxidants, light stabilizers, heavy metal deactivators (copper harm inhibitors). , Clarifiers, nucleating agents, lubricants, antistatic agents, antifogging agents, antiblocking agents, drip-free agents, flame retardants, flame retardant aids, pigments, radical generators such as peroxides,
Dispersants or neutralizers such as metal soaps, inorganic fillers (for example, 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, aluminum silicate, glass fiber, potassium titanate, carbon fiber, carbon black, graphite, metal fiber, etc. or coupling agent (for example, silane, titanate, boron, aluminate, zircon) The inorganic filler or the organic filler (for example, wood flour, pulp, waste paper, synthetic fiber, natural fiber, etc.) surface-treated with a surface treating agent such as an aluminate-based agent within a range not to impair the object of the present invention. Can be used together.

The composition of the present invention is prepared by adding a predetermined amount of Compound A and Compound B to polyethylene and the above-mentioned various additives usually added to polyethylene by using a conventional mixing device such as a Hensel mixer (trade name), a super mixer, a ribbon blender,
Mixing using a Banbury mixer or the like, and melt-kneading pelletizing at a melt-kneading temperature of 120 ° C to 300 ° C, preferably 180 ° C to 270 ° C using a normal single-screw extruder, a twin-screw extruder, a Brabender or a roll or the like. Can be obtained by The obtained composition is used for production of a target molded article by various molding methods such as an injection molding method, an extrusion molding method, and a blow molding method.

[Action] In the present invention, the action mechanism itself of the combined use of compound A and compound B during melt-kneading of the polyethylene composition is not clear. However, the phenolic antioxidant represented by the compound A is used, for example, in a cylinder of an extruder (a system near an oxygen-free state).
Reported that a radical is added to a double bond of an acrylate group of compound A, and a proton of a hydroxyl group of phenol is transferred to a generated active carbon radical to stabilize as a phenoxy radical. It is generally known that a phosphorus-based antioxidant comprising a phosphite-based compound represented by Compound B acts as a peroxide decomposer. In the present invention, by using the compound A and the compound B together, a surprising synergistic effect which can hardly be predicted from a combination with various conventionally known antioxidants is exhibited.

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

The evaluation method used in the examples and comparative examples was based on the following method.

1) Processing stability (A) Melt stability The melt index (MI) of the obtained pellet is measured (based on JIS K 6760), and this is defined as the first MI. The obtained pellets were again melt-kneaded at a melt-kneading temperature of 270 ° C. and pelletized, and this was repeated four times. Each time the melt-kneaded MI of the obtained pellets was measured again by the above-described method, and these were respectively measured in the second MI, the third MI, and the fourth MI.
I, 5th MI.

Melt stability was evaluated based on the magnitude of MI retention as defined by the following equation.

(The 5th MI indicates the MI after five passes through the extruder.) The closer the numerical value of the MI retention rate is to 1.0, the more excellent the melt stability which is the processing stability at the time of repeated extrusion, in other words, the molding process. To indicate that

(B) Anti-gelling property The anti-gelling property was evaluated by any of the following methods using the obtained pellets.

(A) Fish eye Using a T-die extruder with a diameter of 30 mm, the cylinder temperature was 19
0 ° C. to 250 DEG ° C., die temperature 250 ° C., into a sheet having a thickness of 0.4mm in resin pressure 250kg / cm ² G, the diameter in the sheet 1000 cm ²
Fish eyes of 0.3 mm or more were detected and counted. The smaller the fisheye value is, the less the high molecular weight component (gelled product) is formed, indicating that the gelling prevention property is excellent.

(B) Extrusion characteristics (clogging of screen pack) Spinning machine with 20 mm diameter (using a die having 50 nozzle holes with 0.5 mm diameter and three 300mesh screen packs)
Cylinder temperature 190 ℃ ~ 250 ℃, Die temperature 250
° C., to start the melt-spun at a resin pressure 30kg / cm ² G, a continuous operation until the resin pressure is 50kg / cm ² G. 50k resin pressure
The time (days) when g / cm ² G is reached is regarded as clogging of the screen pack. The larger the number of days, the less the gelled product is formed, and the more excellent the gelation preventing property.

2) Anti-coloring property YI (Yellowness Index) of the obtained pellet is measured (based on JIS K 7103), and the YI value at this time is defined as the first YI. Then, using the obtained pellets, melt-kneading temperature again
The mixture was melt-kneaded at 270 ° C. and pelletized, and this was repeated four times. Each time the YI of the obtained pellets is melt-kneaded,
Measured again by the method described above,
These are YI, fourth YI, and fifth YI.

The anti-coloring property was evaluated based on the magnitude of ΔYI defined by the following equation.

ΔYI = 5th YI−1st YI (5th YI indicates YI after passing through the extruder five times.) The smaller the value of ΔYI, the better the anti-coloring property.

Examples 1 to 6 and Comparative Examples 1 to 15 Unstabilized powdered Ziegler as polyethylene, MI (discharge rate of molten resin for 10 minutes when a load of 2.16 kg at 190 ° C. is applied) of 2.0 g / 10 minutes 100 parts by weight of Natta high-density ethylene homopolymer (density 0.963 g / cm ³ )
As compound A, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2-t-butyl-6- [3-t
-Butyl-2-hydroxy-5-methyl (α-methylbenzyl)]-4-methylphenyl acrylate or
2,4-di-t-butyl-6- [3,5-di-t-butyl-2
-Hydroxy (α-methylbenzyl)] phenyl acrylate, compound B as bis (2,6-di-t-butyl-
4-methylphenyl) pentaerythritol-diphosphite or bis (2,6-di-tert-butyl-4-s)
-Butylphenyl) pentaerythritol-diphosphite and other additives in predetermined amounts, respectively,
The mixture was placed in a Henssel mixer (trade name) at the compounding ratio shown in the table, and stirred and mixed for 3 minutes, and then melt-kneaded at 200 ° C. with a single screw extruder having a diameter of 40 mm to form pellets. As Comparative Examples 1 to 15, 100 parts by weight of an unstabilized powdery Ziegler-Natta type high-density ethylene homopolymer (density 0.963 g / cm ³ ) having an MI of 2.0 g / 10 min are shown in Table 1 below. A predetermined amount of each of the additives described was blended and melt-kneaded according to Examples 1 to 6 to obtain pellets.

The obtained pellets were evaluated for melt stability, gelling inhibitor (fish eye) and anti-coloring properties as processing stability by the test method described above. The results are shown in Table 1.

Examples 7 to 12, Comparative Examples 16 to 30 Unstabilized powdered Ziegler-Natta high-density ethylene-butene-1 copolymer (density 0.948 g / cm ³ , ethyl 0.014 branches / 10
Unstabilized powdery low-density ethylene homopolymer (density 0.918 g / cm ³ ) 10
% By weight and 10% by weight of an unstabilized powdery amorphous ethylene-propylene random copolymer (propylene content: 25% by weight) having a Mooney viscosity of ML1 + 4 (100 ° C.) of 65 A represents 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate;
t-butyl-6- [3-tert-butyl-2-hydroxy-
5-methyl (α-methylbenzyl)]-4-methylphenyl acrylate or 2,4-di-t-butyl-6
[3,5-Di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl acrylate, compound B as bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite Or screw (2,
A predetermined amount of each of 6-di-t-butyl-4-s-butylphenyl) pentaerythritol-diphosphite and other additives was added to a Hensel mixer (trade name) in a mixing ratio shown in Table 2 below. The mixture was stirred and mixed for 3 minutes, and then melt-kneaded at 200 ° C. with a single-screw extruder having a mouth diameter of 40 mm to form pellets. In addition, MI was 3.0 g as Comparative Examples 16 to 30.
Powdered Ziegler-Natta high-density ethylene-butene-1 copolymer (density 0.948 g / c)
m ³ , 0.014 ethyl branches / 1000 carbon) 80% by weight, MI 0.5 g
10% by weight of unstabilized powdered low-density ethylene homopolymer (density 0.918 g / cm ³ ) 10% by weight and Mooney viscosity
ML1 + 4 (100 ° C.) is 65 parts of unstabilized powdery amorphous ethylene-propylene random copolymer (propylene content 25% by weight) and 10% by weight. A prescribed amount of each of the additives described was blended and melt-kneaded according to Examples 7 to 12 to obtain pellets.

The obtained pellets were evaluated for melt stability, anti-gelling property (fish eye) and anti-coloring property as processing stability by the test method described above. Table 2 shows the results.

Examples 13-18, Comparative Examples 31-45 Unstabilized powdered Ziegler-Natta high-density ethylene-propylene copolymer having a MI of 25.0 g / 10 min as polyethylene (density 0.950 g / cm ³ , methyl branch 3.0 Pieces / 1000
Carbon) in 100 parts by weight of compound A as 2-t-butyl-
6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2-t-
Butyl-6- [3-tert-butyl-2-hydroxy-5-
Methyl (α-methylbenzyl)]-4-methylphenyl acrylate or 2,4-di-t-butyl-6- [3,5
-Di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl acrylate, compound B as bis (2,
6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite or bis (2,6-di-t-butyl-4-s-butylphenyl) pentaerythritol-diphosphite and other additives Are placed in a Hensel mixer (trade name) at the mixing ratios shown in Table 3 below, and stirred and mixed for 3 minutes.
The mixture was melt-kneaded at 200 ° C. with a single-screw extruder having a diameter of 40 mm to form pellets. Further, as Comparative Examples 31 to 45, an unstabilized powdery Ziegler-Natta high-density ethylene-propylene copolymer having an MI of 25.0 g / 10 min (density 0.950 g / cm ³ , 3.0 methyl branches / 1000 carbons) A predetermined amount of each of the additives described in Table 3 described below was blended with 100 parts by weight, and Examples 13 to 18 were added.
Pellets were obtained by a melt-kneading treatment according to.

The obtained pellets were evaluated for melt stability, anti-gelling properties (extrusion properties (clogging of screen pack)) and anti-coloring properties as processing stability by the test method described above. The results are shown in Table 3.

The compounds and additives according to the present invention shown in Tables 1 to 3 are as follows.

Compound A [I]: 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenylacrylate Compound A [II]: 2-tert-butyl-6 [3-t-butyl-2-hydroxy-5-methyl (α-methylbenzyl)]-4-methylphenylacrylate Compound A [III]: 2,4-di-t-butyl-6- [3,5- Di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl acrylate compound B [I]: bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite compound B [ II]: bis (2,6-di-t-butyl-4-s
-Butylphenyl) pentaerythritol-diphosphite 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 phosphorus antioxidant 1: tris (2,4-di-t-butylphenyl) phosphite phosphorus antioxidant 2 : Tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene-di-phosphonite phosphorus antioxidant 3: bis (2,4-di-t-butylphenyl) -pentaerythritol -Diphosphite Ca-St: Calcium stearate The examples and comparative examples described in Table 1 are cases where a Ziegler-Natta high density ethylene homopolymer is used as polyethylene. As can be seen from Table 1, Examples 1 to 6 contain the compounds A and B according to the present invention, and Examples 1 to 6 and Comparative Examples 1 to 7 (Compound A and compound according to the present invention) B or other phenolic antioxidants or phosphorus-based antioxidants, each of which was independently compounded.
6 shows that both the processing stability and the coloring prevention property are excellent. In particular, Examples 1 to 6 show almost no decrease in the melt stability even after five heat histories, as is clear from the MI retention rate which indicates the melt stability which is the processing stability in repeated extrusion at high temperatures. Also, it can be seen that the value of fish eye caused by the gelation reaction is small. Comparative Examples 8 to 12 and Examples 1 to 6 which are a combination system of a conventionally known phenolic antioxidant 2 and a phenolic antioxidant 1 or various phosphorus-based antioxidants including compound B.
Compared to Comparative Examples 8 to 12, although the processing stability was improved to some extent by the combined use, the effects were still insufficient, and the effect on the anti-coloring property was not yet sufficient. Furthermore, Comparative Examples 13 to 15 and Examples 1 to 6 in which the compound A according to the present invention was used in combination with various phenolic antioxidants or various phosphorus antioxidants other than the compound B were compared with Comparative Examples 13 to 15.
Although the processing stability and the anti-coloring property are improved as compared with Comparative Example 1 in which Compound A alone is blended, it is still insufficient. Therefore, it can be seen that a remarkable synergistic effect is observed when the compound B is used in combination with the compound A.

Table 2 shows the results obtained by using a mixture of a Ziegler-Natta high-density ethylene-butene-1 copolymer, a low-density ethylene homopolymer and an amorphous ethylene-propylene random copolymer as polyethylene. The same effect as above was confirmed.

Table 3 shows the results obtained by using a Ziegler-Natta high-density ethylene-propylene copolymer as polyethylene, and the same effect as described above was confirmed for this as well. In particular, as is clear from the result of clogging of the screen pack, the composition of the present invention has a remarkable anti-gelling effect.

[Effects of the Invention] The composition of the present invention has the following advantages: (1) Processing stability at the time of molding processing, compared to a polyethylene composition obtained by using a conventionally known phenolic antioxidant and a phosphorus-based antioxidant alone or in combination. Excellent in properties and anti-coloring properties.

(2) Since it is remarkably excellent in melt stability, which is processing stability when subjected to heat history due to several times of melt-kneading, it can be advantageously used for applications (films, sheets, etc.) used as recycled products.

(3) In extrusion molding, such as melt spinning, in which continuous operation is performed for a long time, problems such as a decrease in productivity due to gelation of polyethylene are significantly reduced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08K 5: 527)

Claims (4)

(57) [Claims] 1. A phenolic compound represented by the following general formula [I] (hereinafter referred to as compound A) and a phosphite compound represented by the following general formula [II] (hereinafter referred to as “compound A”) per 100 parts by weight of polyethylene. (Hereinafter referred to as Compound B) in an amount of 0.01 to 1 part by weight. (Wherein, R ₁ is hydrogen or an alkyl group having 1 to 3 carbon atoms, R _{2 to} R ₅ are an alkyl group having 1 to 9 carbon atoms, a cyclohexyl group or 1-methylcyclohexyl group, and R ₆ is hydrogen or A methyl group, R ₇ and R ₉ each represent a branched alkyl group having 3 to ₉ carbon atoms, and R ₈ represents hydrogen or an alkyl group having 1 to 9 carbon atoms. 2. R ₂ , R ₅ , R _{7 in the} general formulas [I] to [II]
The stabilized polyethylene composition according to claim 1, wherein R ₉ is a t-butyl group. (3) Compound A is 2-t-butyl-6- (3-
t-butyl-2-hydroxy-5-methylbenzyl)-
4-methylphenyl acrylate, 2-t-butyl-6
-[3-t-butyl-2-hydroxy-5-methyl (α
-Methylbenzyl)]-4-methylphenyl acrylate, 2,4-di-t-butyl-6- [3,5-di-t-butyl-2-hydroxy (α-methylbenzyl)] phenyl acrylate or a mixture thereof The stabilized polyethylene composition according to claim 1, which is a mixture of two or more kinds. 4. Compound (B) is bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol-diphosphite, bis (2,6-di-t-butyl-4-s-butyl) The stabilized polyethylene composition according to claim 1, which is (phenyl) pentaerythritol-diphosphite or a mixture of two or more thereof.