JPS62223248A - Stabilized polyethylene composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which has excellent processing stability, anti-gelling property and discoloration resistance during melt kneading and is suitable for use in the production of fibers, films, etc., by blending polyethylene with two specified compds. including a phenol compd. CONSTITUTION:A phenol compd. (A) of formula I (wherein R1 is H or methyl; R2 and R3 are each H or a 1-8C alkyl) and at least one compd. (B) selected from the group consisting of phenol compds. of formula II, phosphite compds. of formula III and phosphonite of formula IV (wherein R4, R5, R6, R7, R8 and R9 are each H or a 1-8C alkyl) is prepd. 100pts.wt. polyethylene is blended with 0.01-5pts.wt. component A and 0.01-5pts.wt. component B in combination. By the synergistic effect of the components A and B, an excellent stability can be imparted to polyethylene.

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 is excellent in preventing oxidative deterioration of polyethylene during melt intermixing.

[Conventional technology]

Generally, polyethylene is molded at a temperature higher than the melting point of the polyethylene, but it is subject to oxidative deterioration due to the heat during melt-kneading, resulting in decreased processability due to crosslinking or gelation of the polyethylene, and the appearance of molded products. Problems such as coloration and odor caused by deterioration of color and oxidative deterioration occur. In particular, in extrusion molding methods such as melt spinning, gelled polyethylene is produced due to long-term continuous operation, and this gelled product causes clogging of the screen pack of the extruder. There is a problem in that the quantity decreases and the screen pack needs to be replaced frequently, causing a significant decrease in productivity. Further, when formed into a film or sheet, there is a problem that fish eyes occur due to high molecular weight components caused by gelation reaction.

For this reason, various phenol-based and phosphorus-based antioxidants have conventionally been used individually or in combination for the purpose of preventing thermal oxidative deterioration during melt-kneading of shiborithelene.

[Problem that the invention seeks to solve]

However, conventional 7-enol antioxidants, especially low-molecular weight phenolic acids such as 2,6-di-t-butyl-p-L/sol (t4J inhibitors), cannot be mixed with polyethylene. Although it has excellent thermal oxidative deterioration resistance (hereinafter referred to as processing stability) during melt mixing, it suffers from discoloration due to the antioxidant used in the molded product. In addition, compositions made by blending only a high molecular weight phenolic antioxidant with polyethylene have problems with processing stability and coloring caused by the high molecular weight phenolic antioxidant. Although the processing stability of the composition formed by using a low molecular weight phenolic antioxidant and a high molecular weight phenolic antioxidant in combination is excellent as described above, there is almost no synergistic effect due to the combination. On the contrary, there is a problem in that as the amount of the phenolic antioxidant increases, the resulting molded product becomes more markedly colored.

On the other hand, a composition made by blending only a phosphorus antioxidant with polyethylene significantly improves the coloring problem seen in molded products using compositions containing the aforementioned phenolic antioxidant. There is a problem that processing stability is significantly reduced when subjected to severe thermal history due to several times of melt-kneading. For this reason, it is conceivable to use a high molecular weight phenolic antioxidant that has a synergistic effect with the phosphorus antioxidant in combination.

However, although it is possible to some extent to improve the processing stability and coloring caused by the antioxidant used, which are problems of the conventional technology, in such combination systems, it is still not sufficient, especially when using conventionally known high molecular weight In combination systems of phenolic antioxidants and phosphorus antioxidants, the anti-gelation effect of the combination system is limited to some extent, but is still sufficient (although it is still insufficient for extrusion molding such as melt spinning that requires continuous operation for a long time). In this field, there has been a strong desire to improve gelation prevention.

In order to solve the problems related to the above-mentioned polyethylene using the above-mentioned phenolic antioxidant and phosphorus-based antioxidant alone or in combination, the present inventor previously filed a patent application filed in Japanese Patent Application No. 59-2
No. 49184 proposed a composition in which a specific phenolic antioxidant and a phosphorous antioxidant made of a specific 7-osphonite compound were used in combination, but the authors were not satisfied with this and conducted further research. As a result, a phenolic compound represented by the following general formula (1) was added to polyethylene (
Hereinafter, it will be referred to as compound A. ), a phenolic compound represented by the following general formula (1) (hereinafter referred to as compound B),
Phosphite-based compounds represented by the following general formula [old] (
Hereinafter, it will be referred to as compound C. ), a composition comprising one or more compounds selected from the 7-osphonite compounds (hereinafter referred to as compounds) represented by the following general formula [IV] solves the above-mentioned problems of polyethylene. The present invention was completed based on this knowledge.

Rs R3 (However, in the formula, R1 is hydrogen or a methyl group, R2 to
R0 each represents hydrogen or the same or different alkyl group having 1 to 8 carbon atoms. ) As is clear from the above description, an object of the present invention is to provide a polyethylene composition that is extremely effective in improving processing stability and coloring properties caused by the antioxidant used.

[Means for solving problems]

The present invention has the following configuration.

The following [1] and [2] are added to 100 parts by weight of polyethylene.
A stabilized polyethylene composition comprising 0.01 to 5 parts by weight of each compound.

■A phenolic compound represented by the following general formula (1) (hereinafter referred to as compound A) ■A phenolic compound represented by the following general formula (hereinafter referred to as compound B), represented by the following general formula (I) The phosphite-based compound shown (hereinafter referred to as compound C),
One or more compounds Rs Rs selected from the phosphite compounds represented by the following general formula [IV] (hereinafter referred to as compounds) Rs (wherein R0 represents hydrogen or a methyl group, R2 to
R0 each represents hydrogen or the same or different alkyl group having 1 to 8 carbon atoms. ) Polyethylene used in the present invention includes high density polyethylene, medium density polyethylene,
Including low-density polyethylene, linear low-density polyethylene, etc., ethylene homopolymer, ethylene and propylene, butene-1, pentene-1, hene and vinyl acetate,
Copolymers with acrylic acid esters or saponified products thereof, copolymers of ethylene and unsaturated carboxylic acids or their anhydrides, or reaction products of such copolymers with metal ion compounds, and mixtures of two or more of these. For example, Furthermore, modified polyethylene obtained by graft polymerizing an unsaturated carboxylic acid or a derivative thereof to polyethylene, or a mixture of the modified polyethylene and unmodified polyethylene can also be used. In addition, the above polyethylene and synthetic rubber (e.g. ethylene-propylene copolymer rubber, ethylene-propylene-nonconjugated diene copolymer rubber, polybutadiene, polyisoprene, chlorinated polyethylene, chlorinated polypropylene, styrene-butadiene rubber, styrene-butadiene rubber) - styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-ethylene-propylene-styrene block copolymer, etc.) or thermoplastic synthetic resin (e.g. polypropylene , polystyrene, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, etc.) can also be used. Particularly preferred are homopolymers of ethylene, copolymers of ethylene with propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or two or more of these α-olefins, and mixtures of two or more of these.

Compound A used in the present invention is 2-t-butyl-
6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2-t-
Butyl-6-(3-t-7'thyl-2-hydroxy-5
-ethylbenzyl)-4-ethyl phenyl acrylate, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-s-7'' thylbenzyl)-4-8-butylphenyl acrylate), 2-t-7'chill-6-(3,5
-di-t-butyl-2-hydroxybenzyl)-4-t
-butylphenyl acrylate, 2-t-octyl-6
-(3-t-octyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2-t-
Butyl-6-(3-t-butyl-2-hydroxy-5-
s-Butyl (α-methylbenzyl)-4-s-7'tylphenyl acrylate or 2-t-butyl-6-
Examples include 2-t-butyl-6-(3-
t-butyl-2-hydroxy-5-methylbenzyl)-
4-methylphenylacrylate is preferred. Compound B
An example of this is 1,3°5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene. Compound C is bis(2-
t-butylphenyl)-pentaerythritol-sifuosphite, bis(2-t-p-4-mef-ruphenyl)-pentaerythritol-sifuosphite or bis(2゜4-di-t-7'' tylphenyl)- Examples include pentaerythritol-shiphosphite.

Particularly preferred is nibis(2,4-di-t-butylphenyl)-pentaerythritol-siphosphite. The compound is tetrakis(2-t-7”tylphenyl)-
4,4'-biphenylene diphosphonite, tetrakis(2-butyl-4-methylphenyl)-4,
4'-biphenylene-di-phosphonite, tetrakis(2,4-di-t-butylphenyl)-4゜4'-biphenylene-di-phosphonite, tetrakis(2,
4-di-nonylphenyl)-4゜4'-biphenylene-
Examples include G-7 osphonite. Particularly preferred is tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite. The compounding ratio of each of these compounds, Compound A, Compound B, Compound C, and Compound R, is 0.01 to 5 parts by weight, preferably 0.05 to 0.5 parts by weight, based on 100 parts by weight of polyethylene. If the amount is less than 0.01 parts by weight, the desired processing stability and discoloration prevention effects will not be fully exhibited, and
Although it is possible to exceed 1 part by weight, no further improvement in the effect can be expected, which is not only impractical but also uneconomical.

The composition of the present invention contains various additives normally added to polyethylene, such as phenol-based, thioether-based, phosphorus-based antioxidants, light stabilizers, clarifying agents, nucleating agents, lubricants, and charging agents. Inhibitors, antifogging agents, anti-blocking agents, dropless agents, pigments, heavy metal deactivators (copper inhibitors), radical generators such as peroxides, dispersants or neutralizers for metal soaps, etc. and 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 ( The inorganic filler or organic filler (for example, wood flour,
Pulp, waste paper, synthetic fibers, natural fibers, etc.) can be used in combination without impairing the purpose of the present invention.

The composition of the present invention is prepared by adding predetermined amounts of one or more compounds selected from the group consisting of Compound A, Compound B, Compound C1, and the above-mentioned various additives that are usually added to polyethylene using a conventional mixing device, for example. Mix using a Hensel mixer (trade name), super mixer, ribbon blender, Banbury mixer, etc., and melt and knead at 150° with a normal single screw extruder, twin screw extruder, plastic bender, roll, etc. C to 300°C, preferably by melt-kneading and pelletizing at 180°C to 250°C. The obtained composition is processed by injection molding method,
It is used to manufacture desired molded products by various molding methods such as extrusion molding and blow molding.

[Effect]

In the present invention, the mechanism of action of the combined use of Compound A, Compound B1, Compound C, or Compound RI is not clear as to what effect the combination of Compound A, Compound B1, Compound C, or Compound RI will have upon melt mixing of a polyethylene composition.

However, when the phenolic antioxidant represented by Compound A is used in a cylinder such as an extruder (a system that is close to an oxygen-free system), radicals are added to the double bond of the acrylate group of Compound A, and the generated active carbon A presumed mechanism has been reported in which the proton of the hydroxyl group of phenol moves toward the radical and stabilizes it as a phenoxy radical. In addition, the phenolic antioxidant represented by Compound B is a radical chain inhibitor, and the phosphite-based antioxidant represented by Compound C and the phosphorus-based antioxidant consisting of a phosphite-based compound represented by Compound R are peroxides. It is generally known that it acts as a substance decomposer.

In the present invention, it has been found that by using the compound A in combination with compound B, compound C, or compound R, a surprising synergistic effect that could not be expected from combinations with various conventionally known antioxidants is exhibited. Ta.

〔effect〕

The composition of the present invention has (1) processing stability and coloration prevention properties during molding compared to polyethylene compositions that use conventionally known phenolic antioxidants and phosphorus antioxidants alone or in combination. significantly superior to (2
) In extrusion molding such as melt spinning, which is operated continuously for a long period of time, problems such as decreased productivity due to gelation of polyethylene are significantly alleviated. Therefore, the composition of the present invention can be advantageously used for products in various molding fields, especially for textile applications that require a high degree of processing stability. Furthermore, the composition of the present invention is particularly suitable for applications where it is used as recycled products (films, sheets, etc.) because it has extremely excellent processing stability during melt-kneading when subjected to thermal history due to several melt-mixing wires. It's advantageous.

〔Example〕

EXAMPLES The present invention will be specifically explained below 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 is as follows.

■) Processing stability (melt stability): Measure the melt index (Ml) of the obtained pellet (JIS K 67
60), and this is the first YI. Then, the obtained pellets were again melt-kneaded and pelletized at a melt-kneading temperature of 270°C, and the pellets were turned over four times. The MI of the obtained pellet was measured again by the above method each time the melt crosstalk was performed.

(The 5th YI shows the MI after passing through the extruder 5 times.)
The closer the MI retention value is to 1.0, the better the processing stability (melt stability) during repeated extrusion, in other words, during molding.

■) Preventing gelation (crosslinking) The anti-gelation property was evaluated using one of the following methods using the obtained pellet.

(a) Fisheye: Using a T-die extruder with a diameter of 30ff, the cylinder temperature is 190°C to 250°C, the die temperature is 250°C, and the resin pressure is 250kli/dG, and the thickness is 0.
A sheet of 4 mackerel was prepared, and fish eyes with a diameter of 0.3 mackerel or more were detected and counted in 1000 d of this sheet.

The smaller the fisheye value, the less high molecular weight components are produced and the better the gelation prevention properties are.

(b) Extrusion characteristics (screen pack clogging) A spinning machine with a diameter of 20 ff (a nozzle hole with a diameter of 0.511 M)
Honfuchurugui and 300〆throat screen pack 3
cylinder temperature R190℃~250''
c2 die temperature 250℃, resin pressure 30kq/cd
Start melt spinning at G, resin pressure is 50kQ/aAG
Continue to operate until . Resin pressure increased to 509/dQ
The time (number of days) when the screen pack becomes clogged is determined. The larger the number of days, the less gelled products are formed and the better the gelling prevention properties are.

■) Coloration prevention property: YI (Yello
wness Index) k measurement (JIS K71
03), and the YI value at this time is defined as the first YI.

Then, the obtained pellets were melted and kneaded again at a temperature of 27
The mixture was melt-kneaded and pelletized at 0°C, and this process was repeated a total of 4 times. The obtained pellet OYI was subjected to melt mixing.

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

Examples 1 to 5, Comparative Examples 1 to 15 As polyethylene, MI (load 2 at 190°C
．． Discharge amount of molten resin in 10 minutes when adding 16 kg) 15.0 g/l 2-t-butyl-6- as compound A was added to 100 parts by weight of powdered Ziegler-Natsuta ethylene homopolymer for 0 minutes. (3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 1,3.5-)listyl as compound B2.
4.6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(2,4
-di-t-butyl7enyl)-pentaerythritol-
Di-phosphite, tetrakis (2,
4-di-t-butylphenyl)-4,4'-biphenylene-di-phosphonite and other additives in Hensel mixer (trade name) at the mixing ratios listed in Table 1 below. After mixing, the mixture was melt-kneaded at 200°C in a single-screw extruder with a diameter of 40 fl and pelletized. Further, as Comparative Examples 1 to 15, predetermined amounts of the additives listed in Table 1 were blended with 100 parts by weight of a powdered Ziegler-Natsuta ethylene homopolymer having an MI of 15.0 y/10 minutes. Pellets were obtained according to.

Using the obtained pellets, processing stability and anti-coloring properties were evaluated by the test method described above. Moreover, the anti-gelling property was evaluated by the above-mentioned fish-eye test.

These results are shown in Table 1.

Examples 6 to 10, Comparative Examples 16 to 30 As polyethylene, MI25. (2-butyl-6-(3-t- Butyl-
2-hydroxy-5-methylbenzyl)-4-methyl 7
enyl acrylate, 1,3.5-trimethyl-2,4,6-)lis(3,5-di-t-7'-4-hydroxybenzyl)benzene as compound B, bis( 2,4-di-t-butylphenyl)-pentaerythritol-di-phosphite, as a compound tetrakis(2,4-di-t-butylphenyl)-4,
Predetermined amounts of 4'-biphenylene di-phosphonite and other additives were placed in a Hensel mixer (trade name) at the mixing ratios listed in Table 2 below, mixed, and then extruded using a single screw having a diameter of 40 m. The mixture was melted and mixed in a machine at 200°C and pelletized. In addition, MI is 25.0 as Comparative Examples 16 to 30.
A predetermined amount of each of the additives listed in Table 2 was blended with 100 parts by weight of a powdered Ziegler-Natsuta ethylene-propylene copolymer (8.0 methyl branches/1000 carbons) of jF/10 min. Pellets were obtained according to 10.

Processing stability and discoloration prevention properties were evaluated using the obtained Beretsu) 1 according to the test method described above. In addition, the gelation prevention property is determined by the extrusion characteristics (screen pack clogging #).
) The evaluation was conducted through a test. The results are shown in Table 2.

The compounds and additives according to the present invention shown in Tables 1 and 2 are as follows.

Compound A i 2-, t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate Compound Ba1e a,5-) Listyl-2,4°6-tris (3,5-di-t-butyl-4-hydroxybenzyl)benzene compound C; bis(2,4-di-t-butylphenyl)-
Pentaerythritol-di-phosphite compound D; Tetrakis(2,4-di-t-butylphenyl)-4,4'-piphenylene-diphos 7-onite low molecular weight phenolic antioxidant 92.6-di-t -Butyl-p-cresol High molecular weight phenolic antioxidant Tetrakis [methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)gropionate] Methanephosphorus antioxidant 1; Tris( 2,4-di-t-butylphenyl) phosphite Ca -St icalcium stearate The Examples and Comparative Examples listed in Table 1 are cases where a Ziegler-Natsuta ethylene homopolymer was used as the polyethylene. As can be seen from Table 1, Examples 1 to 5 are those in which Compound A according to the present invention and one or more compounds of Compound B, Compound C, or Compound R are used in combination. Comparing with Comparative Examples 1 to 7, Examples 1 to 5
It can be seen that both processing stability and coloring prevention properties are excellent. In particular, the MI retention rate, which indicates processing stability during repeated extrusion at high temperatures, was 0.91 to 0 in Examples 1 to 5.
．． 96, it can be seen that there is almost no decrease in processing stability even after five thermal cycles, and the value of fish eyes caused by the gelation reaction is also small. Furthermore, when comparing Comparative Examples 8 to 11, which are combination systems of conventionally known high molecular weight phenolic antioxidants and low molecular weight phenolic antioxidants or phosphorus antioxidants, and Examples 1 to 5, Comparative Example 8
Although processing stability is improved by the combined use of compounds 1 to 11, it is still not sufficient, and the effect on color prevention is still not sufficient. Further, a compound A according to the present invention and a compound B according to the present invention.

Comparing Examples 1 to 5 with Comparative Examples 12 to 15 in which Compound Ct or various antioxidants other than Compound R were used in combination, it was found that Comparative Examples 12 to 15 had better processing stability than Comparative Example 1 in which Compound At was used alone. Although the anti-coloring property has been improved, it is still not sufficient.

Compared with Examples 1 to 5, Comparative Examples 12 to 15 are inferior in all respects, and it can be seen that a remarkable synergistic effect is observed in the composition of the present invention. In addition, in the composition of the present invention, Examples 1 to 3 (two-part combination system) in which Compound A and Compound B, Compound Ct, or Compound Ri were combined, Compound A, Compound B, Compound C, or Compound Ri Comparing Examples 4 and 5 (three-way combined use), it was found that Examples 4 and 5 had all the results.

Table 2 shows the Ziegler-Sututa ethylene-propylene copolymer (3.0 methyl branches/10
00 carbon), and the same effect as described above was confirmed for this as well. Screen pack clogging on bamboo! As is clear from the results of Example 2, it can be seen that the composition of the present invention exhibits a remarkable anti-gelling effect.

This shows that the composition of the present invention is superior in all respects to compositions that use conventionally known phenolic antioxidants and phosphorus antioxidants alone or in combination. The remarkable effects of the composition of the invention were confirmed.

that's all

Claims (6)

[Claims] (1) A stabilized polyethylene composition comprising 100 parts by weight of polyethylene and 0.01 to 5 parts by weight of each of the following compounds [1] and [2]. [1] A phenolic compound represented by the following general formula [I] (hereinafter referred to as compound A) [2] A phenolic compound represented by the following general formula [II] (hereinafter referred to as compound B), the following general formula One or more phosphite compounds represented by [III] (hereinafter referred to as compound C) and phosphonite compounds represented by the following general formula [IV] (hereinafter referred to as compound D). Compounds ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [I] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [II] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [III] ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [IV] (However, in the formula, R_1 is hydrogen or a methyl group, R_
2 to R_9 each represent hydrogen or the same or different alkyl group having 1 to 8 carbon atoms. ) (2) Compound A, Compound B, and Compound C or Compound D are each added at 0.0 parts by weight per 100 parts by weight of polyethylene.
The polyethylene composition according to claim (1), which contains 1 to 5 parts by weight. (3) In the general formulas [I] [II] [III] and [IV], R_1 is hydrogen, R_2 is a t-butyl group, R_3 is a methyl group, and R_4 to R_9 are t-butyl groups. The polyethylene composition according to any one of item (1) and item (2). (4) As compound A, 2-t-butyl-6-(3-
Butyl-2-hydroxy-5-methylbenzyl)-4-
The polyethylene composition according to claim 1 or 2, which contains methyl phenyl acrylate. (5) 1,3,5-trimethyl-2,4 as compound B
, 6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis(2,4-
di-t-butylphenyl)-pentaerythritol-diphosphite, compound D as tetrakis(2,4-
di-t-butylphenyl)-4,4'-biphenylene-
The polyethylene composition according to claim 1 or 2, which contains one or more compounds selected from diphosphonites. (6) Claims in which the polyethylene is a homopolymer of ethylene, or a copolymer of ethylene and propylene, butyne-1, pentene-1, hexene-1, octene-1, or two or more of these α-olefins. The polyethylene composition according to any one of item (1) and item (2).