JPS58219247A - Polyethylene composition - Google Patents

Abstract

PURPOSE:The titled composition that is obtained by adding dibenzylidene sorbitol, its derivative substituted on its nuclei and a specific higher fatty acid metal salt to a low-density polyethylene produced by the low- or medium-pressure process, thus giving films of improved transparency and luster as well as surface smoothness. CONSTITUTION:The objective composition comprises (A) 100pts.wt. of an ethylene-alpha-4-20C olefin copolymer with a melt flow rate of 0.1-20g/10min., a density of 0.910-0.940g/cm<2> and a melting point of 110-130 deg.C, (B) 0.1-1.0pt.wt. of dibenzylidene sorbitol and/or its nuclei-substituted derivative and (C) 0.1-2pts.wt. of at least one selected from the group consisting of lithium 12-hydroxystearate, sodium laurate, potassium, lithium and sodium stearates and calcium licionolate where the weight ratio of B/C is in the range from 5/95 to 60/40. The use of a component A of less than 6mol.wt. distribution gives films of higher clarity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medium-low pressure low density polyethylene composition for use in films that has excellent transparency, gloss, and surface smoothness.

Compared to high-pressure low-density polyethylene, medium- and low-pressure low-density polyethylene has superior mechanical strength such as tear strength, tensile strength, and impact strength, as well as heat resistance, cold resistance, oil resistance, heat sealability, stress cracking resistance, etc. It also has excellent chemical resistance and moisture permeability, which are the general properties of polyethylene, so it is widely used in fields such as food packaging. However, if optical properties such as transparency and gloss are further improved, the fields of use thereof can be expanded. Various methods have been proposed to improve optical properties such as transparency and gloss of polyolefins. For example, JP-A-54-149752
No. 1, No. 2002-11-1696 discloses a method for obtaining a polyolefin composition with excellent transparency and gloss by blending a condensate of sorbitol and an aldehyde compound with an aliphatic amide, an aliphatic ester, and a silicone compound. Also, JP-A-55-71732
The method of blending the Zibenjidensolbitol and / or its nuclear replacement is disclosed in the issue. However, by these methods, when blown film is made of low-density polyethylene using a medium-low pressure method,
It is true that the seismic intensity (Haze) improves numerically, but surface roughness occurs to the extent that these values are not affected, the smoothness is lost, and surface unevenness can be seen visually, so in the end it cannot be used as a product. The problem is that it is difficult. In addition to these methods, there are methods using various known nucleating agents, but these methods are insufficient to improve the transparency of medium-low pressure low density polyethylene.

In view of the current situation, the present inventors have developed a film that has excellent optical properties such as transparency and gloss even when formed into a film, and
As a result of research to provide medium-low pressure low density polyethylene that prevents film surface unevenness and has excellent smoothness, it was discovered that the problem could be solved by blending specific compounds in specific ratios, and the present invention was achieved.

That is, the present invention provides: (A) Melt 7 roller) 0.1 to 20 g/
10mln, density 0.910 to 0.940g, /
cnI3, 100 parts by weight of a copolymer of ethylene and α-olefin having 4 to 20 carbon atoms with a melting point of 110 to 130°C, (B) 0.1 to 1.0 parts by weight of dibenzylidene sorbitol and/or its nuclear substituted product ((J12-At least one selected from the group consisting of lithium hydroxystearate, sodium laurate, potassium stearate, lithium stearate, sodium stearate, and calcium ricinoleate is 0
．． 1 to 2.0 parts by weight, and (B): ((weight ratio of 5:φ
5 to 60:40.

The polyethylene used in the composition of the present invention has a melt flow rate (ASTMD123811j) of 0.1 to 20.
g710m1n, preferably 0.5 to 10 g/
10m1n.

Density is 0.910 to 0.940 g/cnr3, preferably 0.915 to 0.937 g/cnr3, melting point is 110 to 130° C1, preferably 110 to 12
It is a copolymer of ethylene in the range of 7°C and an a-olefin having 4 to 20 carbon atoms, preferably an a-olefin having 6 to 18 carbon atoms. Melt flow rate is 0.1g/10m
If it is less than 1n, it has a high melt viscosity and poor moldability, and if it exceeds 20 g/IQmin, it has a low melt viscosity, poor moldability, and has low mechanical strength. Density is 0.910g
If it is less than 10 ij', the surface will be sticky when made into a film, and it will have poor oil resistance and heat resistance, and if it exceeds 0.940 g 70 m3, it will have poor transparency. Also, those with a melting point of less than 1'10'C have poor heat resistance;
If the temperature exceeds 130'C, the hot tack properties will deteriorate.

Note that the melting point in the present invention refers to a differential scanning calorimeter (DSO
) is the highest temperature at the point showing the endothermic peak determined from the endothermic curve at a heating rate of 10°C/min.

The copolymer of ethylene and α-olefin used in the present invention has one to a plurality of endothermic peaks, and in many cases two to six endothermic peaks. Carbon number 4 to 2 copolymerized with ethylene
0 α-olefin specifically refers to 1-butene, 1-
Pentene, 1-hexene, 4-methyl-1-pentene,
1-octene, 1-decene, 1-tetradecene, 1-octadecene, or a mixture thereof. Those copolymerized with propylene are not preferred because they have poor mechanical strength and heat seal strength. In particular, a copolymer with an α-olefin having 6 or more carbon atoms is suitable because it has excellent impact resistance.

Furthermore, as the ethylene/α-olefin copolymer within the above range used in the present invention, the molecular weight distribution (weight average molecular weight (
It is preferable to use a film having a ratio of MW )/number average molecular weight (Tin) of 6 or less, since a film with better transparency can be obtained. The molecular weight distribution value is a value obtained by obtaining a molecular weight distribution curve by gel permeation chromatography (GPO) and calculating the weight average molecular weight and number average molecular weight.

The dibenzylidene sorbitol to be blended into the ethylene/α-olefin copolymer of the present invention may be any of the nine-form, L-form, and racemic form.

In addition, as a nuclear substitute of dibenzylidene sorbitol,
Alkyl group; for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, etc., or alkoxy group;
Examples include methoxy, ethoxy, propoxy, butoxy groups, and derivatives substituted with a halogen such as chlorine.

In the present invention, 0.1 to 1.0 parts by weight, particularly preferably 0.2 to 0.5 parts by weight of dibenzylidene sorbyl and/or its nuclear substituted product are blended. If the amount is less than 0.1 part by weight, the improvement effect on transparency, gloss, etc. will be small, and if it exceeds 1.0 part by weight, the improvement effect will reach a plateau, which is not only economically disadvantageous but also causes bleed-out. So I don't like it.

The third component blended into the present invention is a higher fatty acid metal salt, specifically lithium 12-hydroxystearate,
Sodium laurate, potassium stearate, lithium stearate, sodium stearate and calcium ricinoleate. These higher fatty acid metal salts are
They may be used alone or in combination of two or more in an amount of 0.1 to 2.0 parts by weight. If the amount is less than 0.1 part by weight, the surface smoothness will be poor, and if it exceeds 2.0 parts by weight, the slip property in the extruder screw will increase, resulting in poor moldability and bleed-out, so it is preferable. do not have.

Furthermore, in the polyethylene composition of the present invention, the dibenzylidene sorbitol and/or its nuclear substituted product (
The blending weight ratio of B) and higher fatty acid metal salt (0) is important, and (E):(0) is 5:95 to 60:4.
Must be within the range of 0. If the number of dibenzylidene sorbitol and/or its nuclear substituted product is less than 5, gloss and surface smoothness will be poor, and if it exceeds 60, transparency will be poor, which is not preferred.

To obtain the polyethylene composition of the present invention, (A) ethylene/α-olefin copolymer, (B) dibenzylidene sorbitol and/or its nuclear substituted product, and (0) 12
- lithium hydroxystearate, sodium laurate, potassium stearate, lithium stearate,
At least one member selected from the group consisting of sodium stearate and calcium ricinoleate may be mixed at the above-mentioned mixing ratio using various known methods such as a V-blender, a ribbon blender, a Henschel mixer 1 tumbler blender, etc., after mixing. How to granulate with an extruder,
Alternatively, a method of kneading and granulating with an extruder, kneader, Banbury mixer, etc. may be adopted.

The polyethylene composition of the present invention also contains various compounding agents that are usually added to polyolefins, such as weathering stabilizers, heat stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, pigments, and dyes. may be blended within a range that does not impair the purpose of the present invention.

The polyethylene composition of the present invention prevents unevenness on the film surface during film formation, maintains smoothness, and has excellent optical properties such as transparency and gloss, so it can be suitably used for various packaging materials.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist of the invention is exceeded.

Examples 1 to 7 Melt flow rate) 1.35 g/10 m1n,
Ethylene 4-methyl-1 with a density of 0.93g/cry3
- 0.3 parts by weight of dibenzylidene sorbitol and the higher fatty acid metal salts shown in Table 1 were blended with 100 parts by weight of the pentene random copolymer, and the mixture was granulated using a 3Q mmφ extruder at a resin temperature of 250°C. This pellet is 33mmφ
Inflation inflation film molding, Gui humidity 20
A film with a thickness of 30 μm was formed at 0°C and the following ? M-determination was performed.

Haze; ASTM D1003 52 (%
) Film Smoothness: Visual evaluation was made as × for films with visible skin irritation, ○ for films with no skin irritation, and Δ for films in the middle.

Average roughness: Surface roughness measuring device manufactured by Koita Institute (S
E-4A), the surface of the blown film is scanned and measured over a length of 1.0 mm or more to obtain a roughness curve. From this roughness curve, the relationship (amplitude histogram) between the amplitude between adjacent uneven peaks and its appearance frequency was determined, and the average amplitude was calculated (mμ).

Comparative Examples 1 to 6 The copolymer of Example 1 was mixed with dibenzylidene sorbitol and higher fatty acid metal salts in the amounts shown in Table 2, and the same procedure as in Example 1 was conducted. The results are shown in Table 2.

Examples 8 to 12 and Comparative Example 7 0.3 parts by weight of diethylbenzylidene sorbitol was blended with 100 parts by weight of the copolymer of Example 1, and higher fatty acid metal salts shown in Table 3 were further blended. I did the same. The results are shown in Table 3.

Examples 13 to 17 and Comparative Example 8

Claims (1)

[Claims] (1 ton (A) Melt flow rate 0.1 to 20 g
/10m1n. Density 0.910 to 0.940 g/ayt3, melting point 1
Ethylene at 10 to 150°C and a having 4 to 20 carbon atoms
- 100 parts by weight of copolymer with olefin, (B)
Dibenzylidene sorbitol and/or its nuclear substituted product 0.1 to 1.0 parts by weight, (0) lithium 12-hydroxystearate, sodium monolaurate, potassium stearate, lithium stearate, sodium stearate, and calcium ricinoleate. A polyethylene composition comprising 0.1 to 2.0 parts by weight of at least one selected from the group consisting of, and (B)
: A polyethylene composition characterized in that the weight ratio of (0) is within the range of 5:95 to 60:40.