JPH09176393A - Hollow molding of polyethylene-based resin excellent in transparency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hollow molding excellent in transparency, surface smoothness and appearance by using a polyethylene-based resin treated by ionizing irradiation as a part of a polyethylene-based resin and blending the polyethylene- based resin with a specific component. SOLUTION: A resin composition obtained by blending (A) 100 pts.wt. of a resin component comprising (i) 50-99wt.% of a polyethylene-based resin and (ii) 1-50wt.% of a resin prepared by treating the polyethylene-based resin by ionizing irradiation with (B) at least one selected from among (iii) 0.05-0.7 pt.wt. of a nucleating agent [preferably sodium-2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate, etc.], (iv) 0.01-0.5 pt.wt. of lithium carbonate and (v) 0.1-50 pts.wt. of an ethylene-acrylamide resin is blow molded. The component (ii) is preferably obtained by irradiating a polyethylene powder in an inert gas with ionizing radiation in a dose of 2-74kGy exposure rate γ-Rays and electron rays are preferable as the ionizing radiation. The temperature in irradiation is preferably <=40 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene resin hollow molded article, which is particularly useful as a container for foods, pharmaceuticals, chemicals, etc., and has excellent transparency, surface smoothness and appearance. The present invention relates to a hollow molded body.

[0002]

Polyethylene resins are generally inexpensive and
Mechanical strength, heat resistance, surface gloss, chemical resistance, oil resistance,
Since it has appropriate rigidity and bending fatigue resistance, and is excellent in moldability, products molded by the blow molding method by utilizing these features are containers for industrial materials, general daily necessities, foods, pharmaceuticals, etc. Is widely used as. However, the polyethylene-based resin has a drawback that it is inferior in transparency as compared with other resins such as polypropylene, and thus applications for which transparency is required are often limited. As a method for improving this, for example, a method of adding a dibenzylidene sorbitol derivative (JP-A-53-11).
7044, JP-A-58-85632, etc.) or a method of using the sorbitol derivative in combination with an aliphatic amine (JP-A-58-180542, US Pat. No. 4,410,649, etc.). is there.

It is also known that when a molded product is manufactured by the hollow molding method, the surface of the molded product is generally inferior in smoothness to other molding methods. As a way to improve this,
A method of heating and raising the temperature from the side of the metal cavity (for example, JP-A-3-219939) has been proposed. Further, when the hollow molded body is continuously manufactured, a resin deposit commonly referred to as "meyer" is formed at the tip of the die during the continuous production. After the generation of the porcelain porcelain, the ash is ashed with the passage of time to become hard and scorched, which comes into contact with the inner and outer surfaces of the extruded parison, and a die line is formed on the parison surface along the extrusion direction. The hollow molded body formed from the parison having this die line has a non-uniform surface roughened surface and a significantly roughened appearance, which is off-spec. As a method for preventing this, a method of maintaining the outside of the parison near the extrusion outlet in an inert gas atmosphere (for example, Japanese Patent Laid-Open No. 3-2).
No. 74138).

However, among the above-mentioned methods for improving transparency, in many cases, the additives are decomposed during molding to cause problems such as an offensive odor and inclusion of bubbles.
In addition, the method of improving the smoothness of the product surface by the heating method requires a special device, which lengthens the molding cycle and is insufficient in the improvement effect. Furthermore, the method for preventing the formation of die lines by an inert gas requires a special device and its effect is still insufficient.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a polyethylene resin hollow molded article which is excellent in transparency and has good surface smoothness and appearance even when manufactured by a hollow molding method without taking measures to prevent die lines. The purpose is to provide.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that A. (A) Polyethylene resin: 50 to 99% by weight and (b) Polyethylene resin treated by ionizing radiation irradiation: 1 to 50% by weight, based on 100 parts by weight of the resin content, B ． A polyethylene resin hollow molded article having excellent transparency, which is obtained by hollow molding a resin composition containing at least one selected from the following (c), (d) and (e):
Nucleating agent: 0.05 to 0.7 part by weight, (d) Lithium carbonate: 0.01 to 0.5 part by weight, (e) Ethylene-
Acrylamide resin: 0.1 to 50 parts by weight. A hollow molded article according to claim 1, wherein the polyethylene resin is high density polyethylene, and a hollow molded article according to claim 1, wherein the polyethylene resin is medium density polyethylene or low density polyethylene resin. The polyethylene resin hollow-molded article and the ethylene-acrylamide resin described in which the nucleating agent is an alkali metal salt of phosphoric acid are ethylene-acrylamide resins composed of at least 0.01 to 50% by weight of acrylamide compound units and ethylene units. The above object was achieved by developing the described hollow molded body.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene resin (a) in the present invention is mainly composed of high-density polyethylene, medium / low-density polyethylene, linear low-density polyethylene, and ethylene, which has 3 to 20 carbon atoms. And a copolymer with α-olefin. As the α-olefin, propylene, 1-butene, 1-pentene,
1-hexene, 4-methylpentene-1, vinylcyclopentane, vinylcyclohexane and the like can be mentioned. The copolymerization ratio of these α-olefins when copolymerized with ethylene is at most 10% by weight, preferably 6%.
% By weight or less. These α-olefins may be used alone or as a mixture of two or more.
(A) Polyethylene resin melt flow rate (JI
Values measured according to SK-7210, Table 1, Condition 4;
Hereinafter referred to as "MFR") is usually 0.05 to 100 g / 1
It is 0 minutes, and preferably 0.1 to 70 g / 10 minutes.

The polyethylene-based resin (b) in the present invention is obtained by subjecting the polyethylene-based resin as the component (a) to irradiation treatment with ionizing radiation. However, in this case, the MFR of the polyethylene resin of (b) is usually 1 to 300.
g / 10 minutes, preferably 2 to 200 g / 10 minutes,
Especially, 3 to 100 g / 10 is preferable. MFR is 1
When it is less than 10 minutes, the MFR may be lowered and a part of the gel may be generated when the composition is irradiated with ionizing radiation, and the composition has poor moldability and further deteriorates the appearance of the molded article. On the other hand, if it is 300 g / 10 minutes or more, there is no particular problem, but the transparency may not be improved so much even when it is made into a composition. The ionizing radiation treatment can be performed on the polyethylene powder or pellets under vacuum in an inert gas atmosphere or an air atmosphere, but is preferably performed under an inert gas. The temperature at which the ionizing radiation is applied is usually room temperature, and is 50 ° C. or lower, preferably 40 ° C. or lower.

Examples of the ionizing radiation include X-rays, α-rays, γ-rays and electron rays, and γ-rays and electron rays are particularly preferable radiation sources. The irradiation dose is generally 0.5 to 150 kGy, preferably 1 to 100 K
Gy, especially 2-74 kGy. Irradiation dose is 15
When it exceeds 0 kGy, the MF of the polyethylene resin of (b)
Depending on the R and the density, gelation may occur, which causes inconvenience in terms of compatibility between resins, and also causes unevenness on the surface of the molded product, reducing the product value. Therefore, it is necessary to irradiate with ionizing radiation under the condition that it does not gel.

The composition ratio of the component (b) in the resin component of the present invention is 1 to 50% by weight, preferably 2 to 45% by weight, and more preferably 3 to 40% by weight. If the blending ratio is less than 1% by weight, the synergistic effect of improving the transparency is slight and poor even if the B component is blended. On the other hand, if it exceeds 50% by weight, it is effective, but if it is added more than 50% by weight, not only the saturated state but also the mechanical properties are deteriorated, which is not preferable.

As the component (c) nucleating agent, there may be mentioned a carboxylic acid metal salt, a dibenzylidene sorbitol derivative and an alkali metal salt, but it is particularly preferable to add an alkali metal salt of phosphoric acid. Specifically, sodium-2,2'-methylene-bis (4,6-di-t-butylphenyl) phosphate, sodium-2,2'-
Ethylidene-bis (4,6-di-t-butylphenyl)
Phosphate, sodium-2,2'-butylidene-
Bis (4,6'-di-methylphenyl) phosphate, sodium-2,2'-butylidene-bis (4,6)
-Di-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis (4-methyl-6-t-)
Butylphenyl) phosphate, sodium-2,
2'-methylene-bis (4-ethyl-6-t-butylphenyl) phosphate, sodium (4,4'-dimethyl-5,6'-di-t-butyl-2,2'-biphenyl) phosphate , Sodium-2,2'-ethylidene-bis- (4-m-butyl-6-t-butylphenyl) phosphate, sodium-2,2'-methylene-bis (4,6-di-methylphenyl) phosphate Fate, sodium-2,2'-methylene-bis- (4,6
-Di-ethylphenyl) phosphate, potassium-
2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate, potassium-bis (4,6-
Examples thereof include di-t-butylphenyl) phosphate. These nucleating agents may be used alone or in combination of two or more. Especially sodium-2,2 '
-Methylene-bis (4,6-di-t-butylphenyl)
Phosphate, sodium-2,2'-ethylidene-
Bis (4,6-di-t-butylphenyl) phosphate and the like are preferable.

The blending ratio of the (c) nucleating agent is 0.05 to 0.7 parts by weight, and particularly preferably 0.07 to 0.6 parts by weight, based on 100 parts by weight of the total amount of the component A. Is. If the blending ratio is less than 0.05 part by weight, the improvement in transparency is poor.
On the other hand, if the amount is more than 0.7 parts by weight, the effect of improving transparency cannot be expected and the compound is saturated, which is not preferable in terms of cost.

Lithium carbonate (d) as an additive in the present invention is a white powder used as a compounding agent for medicines, ceramics, enamel raw materials, heat-resistant glass and the like.
The average particle size of this lithium carbonate is usually 50 μm or less, preferably 20 μm or less. The purity of lithium carbonate is not particularly limited, but it is preferable to select a high purity one in consideration that impurities and the like may adversely affect. The blending amount of lithium carbonate is 0.01 to 0.5 parts by weight based on 100 parts by weight of the total amount of the component A,
It is preferably 0.03 to 0.45 parts by weight. If the blending amount of lithium carbonate is less than 0.01 part by weight, the effect of improving transparency becomes insufficient. On the other hand, if it is compounded in an amount of more than 0.5 part by weight, the molded product is colored milky white.

The ethylene-acrylamide resin (e) in the present invention can be produced by a method of polymerizing ethylene and an acrylamide compound under high pressure, or a method of graft-polymerizing acrylamide on a polyethylene resin. Means known to those skilled in the art (for example, JP-B-43-9063 and JP-B-44-1953)
These can be manufactured by adopting the publication No. 7). Examples of the acrylamide compound used here include N-alkylacrylamide, N, N-dialkylacrylamide, N-alkylmethacrylamide, and N, N-dialkylmethacrylamide. Specifically, N-ethylacrylamide, Nn
-Propyl acrylamide, N-isopropyl acrylamide, Nn-butyl acrylamide, N-isobutyl acrylamide, Nt-butyl acrylamide, N,
N-dimethyl acrylamide, N, N-diethyl acrylamide, N-ethyl methacrylamide, Nn-propyl methacrylamide, Nt-butyl methacrylamide, N, N-dimethyl methacrylamide, N, N-diethyl methacrylamide, N-methyl-N-ethyl acrylamide etc. can be mentioned. In the graft reaction, it is preferable to use high density polyethylene in order to improve the graft ratio. These compounds may be used as a mixture of two or more kinds. Among these compounds, preferred are N-ethylacrylamide and N-
Isopropyl acrylamide, Nt-butyl acrylamide, N, N-dimethyl acrylamide, N, N-diethyl acrylamide, N-methyl-N-ethyl-acrylamide, Nn-propyl methacrylamide, N-
t-butyl methacrylamide may be mentioned.

Depending on the method of further copolymerization, ethylene-
When producing an acrylamide resin, a third monomer may be contained in addition to ethylene and an acrylamide compound. As the third monomer, unsaturated acid esters such as vinyl acetate, methyl acrylate and methyl methacrylate, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid, unsaturated such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether. Examples include ether. The content of these third monomers is at most 50% by weight in total with the acrylamide compound.
And preferably 45% by weight. (E) The mixing amount of ethylene-acrylamide resin is 10 in total of the component A.
It is 0.1 to 50 parts by weight, preferably 0.15 to 45 parts by weight, and more preferably 0.2 to 40 parts by weight with respect to 0 parts by weight.
Parts by weight. If the blending ratio is less than 0.1 part by weight, the effect of improving transparency is poor. On the other hand, if the amount is more than 50 parts by weight, the effect is saturated, the transparency is not improved, and the physical properties are deteriorated depending on the composition, which is not preferable.

The resin composition of the present invention can be produced by mixing the above components using a ribbon blender, a Henschel mixer or the like, and further melt-kneading them using a kneader, an extruder, a mixing roll or a Banbury mixer. it can. Particularly, in the present invention, by further mixing the component (a) and the component (b), and then mixing the component B with the mixture, a further excellent transparency can be obtained. The MFR of the obtained resin composition is usually 0.1 to 100 g / 10 minutes.

The hollow molded article of the present invention is obtained by hollow molding the above resin composition, and it is used for toiletries such as shampoo and conditioner, food containers such as mayonnaise, ketchup and dressing, pharmaceutical containers and other liquids. It can be used as a container for pastes, granular solid products and the like. In the present invention, as the hollow molding method, a usual molding method can be adopted, but in particular, extrusion direct blow molding can obtain a molded article having good transparency under general molding conditions.

[0018]

The present invention will be specifically described below with reference to examples. Inspection method: Total light transmittance and haze (haze value): JIS K-71
In accordance with 05, it was measured with a haze meter manufactured by Suga Test Instruments Co., Ltd. Surface smoothness: According to DIN 4768/1, the centerline roughness was measured using a surface roughness meter (T1000 type, manufactured by HOMMELWERKE). Generation state of die line: The presence or absence of a die line on the surface of the parison after 8 hours from the start of molding was evaluated according to the following three grades. ○: No die line was generated. Δ: Some die line was generated. X: Die lines are significantly generated.

Component (a) polyethylene resin PE-1: MFR 12 g / 10 min, density 0.956
High density polyethylene with g / cm ³ . PE-2: MFR 0.58 g / 10 minutes, density 0.9
47 g / cm ³ high density polyethylene. PE-3: MFR 7.8 g / 10 minutes, density 0.93
Medium density polyethylene of 5 g / cm ³ . PE-4: MFR 0.9 g / 10 minutes, density 0.91
8 g / cm ³ linear low-density polyethylene PE-5: MFR 0.6 g / 10 min, density 0.92
1g / cm ³ low density polyethylene

Polyethylene resin used for component (b) PE-6: MFR 22 g / 10 min, density 0.958
g / cm ³ high density polyethylene PE-7: MFR 5.2 g / 10 min, density 0.95
6 g / cm ³ high density polyethylene PE-8: MFR 19 g / 10 min, density 0.917
g / cm ³ linear low-density polyethylene PE-9: MFR 16 g / 10 min, density 0.921
g / cm ³ low density polyethylene

Production Examples of Component (b) (XPE-1 to 5) Polyethylene resins shown in the following Table 1 as the component (b) are γ-ray irradiators (made by Koga Isotope Co.) or electron beam irradiators ( Irradiation doses shown in Table 1 were applied at room temperature under a nitrogen atmosphere using Nisshin High Voltage Co., Ltd.). After that, MFR was measured, and the results are shown in Table 1.

[0022]

[Table 1]

Component (c) nucleating agent as component B: c-1: sodium-2,2'-methylene-bis (4
6-di-t-butylphenyl) phosphate c-2: sodium-2,2'-ethylidene-bis (4,6-di-t-butylphenyl) phosphate B component (d) lithium carbonate: d -1: Average particle size of 16 μm and purity of 99.1% d-2: Average particle size of 7 μm and purity of 99.1%

Production Example of Component B (e): (Ethylene-acrylamide resin) Using an autoclave type reactor divided into 2 zones with an internal capacity of 4 L, the temperature is 190 to 210 ° C. and the pressure is 1100 to 1300 atm. Under the conditions described above, N, N-dimethylacrylamide was injected upstream of the second-stage compressor using t-butylperoxypivalate as a polymerization initiator, and fed together with ethylene to the first zone of the reactor. In the produced copolymer, unreacted monomers were separated by a high pressure separator and a low pressure separator, and pelletized by using an extruder. The obtained copolymer had an N, N dimethylacrylamide content of 17.2% by weight and an MFR of 2.5 g /
There was 10 minutes. (Hereinafter referred to as DMA-1).

Similarly, a copolymer having an N, N-diethylacrylamide content of 33% by weight, an MFR of 3.2 g / 10 minutes (hereinafter referred to as DMA-2) and an acrylamide content of 10.4% by weight. , MFR is 3.6g / 10
A copolymer (hereinafter, referred to as DMA-3), which is a component, was produced.

The MFR is 8.1 g / 10 min and the density is 0.
High-density polyethylene (954 g / cm ³ ) was subjected to electron beam irradiation treatment (30 kGy) in a nitrogen atmosphere, 500 g of treated powder, 2 liters of toluene and 75 g of N, N-dimethylacrylamide were added to a 5 liter separable flask, and a nitrogen gas atmosphere was added. The reaction was carried out at a temperature of 60 ° C. for 5 hours. Then, the mixture was filtered, 2 liters of toluene was further added, the mixture was stirred at 50 ° C. for 1 hour, washed, and filtered. The filtered residue was washed twice with acetone and dried at 80 ° C for one day. The obtained graft polymer had 11.2% by weight of N, N-dimethylacrylamide and MFR of 1.2 g / 10 minutes (hereinafter referred to as g-DMA-1).

MFR is 7.6 g / 10 minutes and density is 0.
High-density polyethylene of 946 g / cm ³ was subjected to γ-ray irradiation treatment (30 kGy) in a nitrogen atmosphere, 75 g of N, N-diethylacrylamide was added, and the reaction and treatment were performed in the same manner as above. The grafted amount of N, N-diethylacrylamide was 10.6% by weight, and the MFR was 0.8 g / 10 minutes (hereinafter referred to as g-DMA-2). MFR is 19
Linear low-density polyethylene having a density of g / 10 min and a density of 0.917 g / cm ³ was subjected to electron beam irradiation treatment (15 kGy) under a nitrogen atmosphere, and 75 g of N, N-diethylacrylamide was added in the same manner as above. The reaction and treatment were carried out.
The graft amount was 4.3% by weight and the MFR was 0.8 g / 10 minutes (hereinafter referred to as g-DMA-3) and MF.
Electron beam irradiation treatment (20 kGy) on low density polyethylene with R of 18 g / 10 min and density of 0.921 g / cm ³ .
Then, similarly, 75 g of N, N-diethylacrylamide was added, and the reaction and treatment were performed in the same manner as above. A graft amount was 5.7% by weight and MFR was 0.7 g / 10 minutes (hereinafter, referred to as g-DMA-4). The acrylamide content was measured by an infrared spectrophotometer and ¹³ C-NMR.
It measured using.

(Examples 1 to 23, Comparative Examples 1 to 10) Table 2
And the types and blending amounts shown in Table 3, (a) component and (b)
After the components were mixed using a tumbler, the mixture was made into pellets by using an extruder (KTX-37 manufactured by Kobe Steel, Ltd.) with a coaxial biaxial vent, and the pellets were further mixed with the component (c), and then the coaxial 2 Pelletized using an axial vented extruder. A cylindrical container (thickness: 1 mm) having an outer diameter of 55 mm and an inner volume of 300 cc was produced from each of the obtained pellets using a blow molding machine (JB105, manufactured by Japan Steel Works). The optical characteristics (total light transmittance and haze) and center line surface roughness of each container were measured. Moreover, the generation state of the die line was visually observed. Tables 2 and 3 show these results.

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

The hollow molded article of the present invention has excellent transparency,
Good surface smoothness and appearance, for food, medical,
It is preferably used as another industrial container.

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Claims (5)

[Claims] 1. A. First Embodiment (A) Polyethylene resin ... 5
0 to 99% by weight and (b) a resin obtained by ionizing radiation treatment of a polyethylene-based resin ... 100 parts by weight of a resin content consisting of 1 to 50% by weight, B. A polyethylene resin hollow molded article having excellent transparency, which is obtained by hollow molding a resin composition obtained by blending at least one selected from the following (c), (d) and (e). (C)
Nucleating agent: 0.05 to 0.
7 parts by weight, (d) lithium carbonate ...
0.01 to 0.5 parts by weight, (e) ethylene-acrylamide resin ... 0.1 to 50 parts by weight 2. The hollow molded article according to claim 1, wherein the polyethylene resin is high-density polyethylene. 3. The hollow molded article according to claim 1, wherein the polyethylene resin is medium density polyethylene or low density polyethylene resin. 4. The polyethylene resin hollow molded article according to claim 1, wherein the nucleating agent is an alkali metal salt of phosphoric acid. 5. The hollow molded article according to claim 1, wherein the ethylene-acrylamide resin is an ethylene-acrylamide resin containing at least 0.01 to 50% by weight of an acrylamide compound unit and an ethylene unit.