KR100889220B1 - High density polyethylene resin composition for chemical bottle - Google Patents

Abstract

A high density polyethylene resin composition is provided to prevent the bending of the surface due to oxidation and to ensure excellent impact resistance and stack property, by comprising a phenol-based antioxidant, or a mixture of phenol-based and phosphate-based antioxidants. A high density polyethylene resin composition comprises high density polyethylene 100.0 parts by weight and antioxidant 0.07~0.2 parts by weight. The high density polyethylene has the high load melt index of 5.0 g/10 minute, the weight average molecular weight of 12~25, MI21.6/MI2.16 of 50~200 and the density of 0.95 g / cm or more. The high density polyethylene is a copolymer consisting of an ethylene homopolymer or ethylene and at least one kind of a monomer.

Description

High Density Polyethylene Resin Composition For Chemical Bottle

The present invention relates to a high density polyethylene resin composition suitable as a material of a container for chemicals, and more particularly to a high rigidity high density polyethylene resin composition having excellent impact resistance and appearance.

The contents of the chemical container include, for example, hydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, hydrogen peroxide, ammonia water, phenol, etc. And non-hazardous drugs such as dyes, and chemicals used in daily life, such as fruit juice, soy sauce, vinegar and neutral detergents.

Containers containing such chemicals require chemical resistance to be stored for a long period of time without a change in ingredients, and also require excellent drop impact resistance, which is a basic physical property, which is damaged during handling of containers containing high purity chemicals. This is because the risk to the human body and the pollution or removal of the surrounding environment is not so easy. Accordingly, efforts have been made to increase the melt tension and the weight average molecular weight in order to increase the drop impact resistance.

Japanese Patent Application Laid-Open No. 11-80259 discloses a polyethylene resin for large blow molding of 50L or more, and has a density (JIS K6760) of 0.94-0.97g / cm3 and a high load (21.6kg, 190 ° C) melt flow index ( JIS K7210, HLMI) is 1 to 15 g / 10 minutes, the ratio of weight average molecular weight and number average molecular weight required from gel permeation chromatography is 8 to 15 and 15 to 65 g of melt tension (MT, unit g) at 190 ° C. It relates to a resin and a container satisfying the relationship of high load (21.6kg, 190 ° C) melt flow index (JIS K7210) and LogMT≥-0.455 × LogHLMI + 1.64,

Korean Patent Publication No. 2002-0049130 discloses a polyethylene-based resin composition used as a material for hollow moldings containing high purity chemicals, and has a high load (21.6kg, 190 ° C) melt flow index (based on ASTM D1238) of less than 2.0 g / 10 minutes. Polyethylene-based resin prepared by Ziegler catalyst or chromium catalyst [A] 65-95% by weight and polyethylene-based resin prepared by metalocene catalyst having high load melt flow index in the range of 2-50 g / 10 min [B] 35 It relates to a polyethylene-based resin composition by a heterogeneous catalyst composed of ~ 5% by weight,

Korean Patent Laid-Open Publication No. 2003-0066409 relates to a technique for increasing impact strength by manufacturing HDPE having a density of 0.957 to 0.967 g / cm 3 and a Z-average molecular weight greater than -4x10 ⁵ logMFR + 1.2x10 ^6. The ratio of MFR measured at 21.6kg load and MFR measured at 2.16kg load (MFR21.6kg / MFR 2.16kg) is less than 200.

However, the above techniques have the advantage that the impact strength is improved, but it does not improve the glossiness of the surface of the container and does not improve the dynamic stiffness (stiffness) in addition to the drop impact strength, resulting in the bulging of the container.

An object of the present invention, in order to solve the above problems, by using a phenolic antioxidant alone in high-density polyethylene, or by using a combination of phenolic and phosphite-based antioxidants to suppress the surface curvature by oxidation An object of the present invention is to provide a high-density polyethylene resin composition having excellent container impact resistance and loadability.

The polyethylene resin composition according to the present invention has a high load melt flow index of 5.0 g / 10 minutes or less, a weight average molecular weight of 250,000 to 450,000, a molecular weight distribution of 12 to 25, MI _21.6 / MI _2.16 of 50 to 200, and a density of 0.950 It is characterized by including 0.07-0.2 weight part of antioxidant with respect to 100 weight part of high density polyethylene which is g / cm <3> or more.

As the high density polyethylene used in the resin composition of the present invention, an ethylene homopolymer or a copolymer of ethylene and at least one monomer is used. As the monomer, linear or branched alpha olefins containing 4 to 6 carbon atoms, for example, butene-1, hexene-1, 4-methylpentene-1 and the like can be used. The high density polyethylene has a high load melt flow index of 5.0 g / 10 min or less, preferably 2.5 to 4.0 g / 10 min, and a weight average molecular weight of 250,000 to 450,000 by gel permeation chromatography. Preferably 300,000-400,000, molecular weight distribution (= weight average molecular weight / number average molecular weight) is _12-25 , MI _{21 .6} / MI _2.0 is 50-200, preferably _90-150 , and the density is It is 0.950 g / cm <3> or more, Preferably it is 0.950-0.970g / cm <3>.

When the high load melt flow index exceeds 5.0 g / 10 minutes, the melt tension is lowered, the thickness uniformity of the molded article is deteriorated, or the molding is poor, which is not preferable, and thus the weight average molecular weight If the molecular weight distribution is less than 250,000, it is not preferable because the impact resistance of the container is weakened. If the molecular weight distribution is less than 12, it is difficult to obtain the target molecular weight distribution of the final resin composition. It is not preferable because the appearance is not satisfactory due to the decrease, and if it exceeds 25, the low molecular weight component increases, causing parison droop and deterioration of container load. In addition, when MI _21.6 / MI _2.16 is less than 50, the fluidity of the resin during processing becomes poor, and the resin is exothermic, and it is not easy to cause melt fracture, and when it exceeds 200, the mechanical properties of the molded article are deteriorated, so that appropriate container properties are achieved. It is not preferable because it does not have a density, and if the density is less than 0.950 g / cm 3, the strength of the blow molding vessel is lowered, which is not preferable.

The said antioxidant used for the resin composition of this invention can be used individually by a phenol type, or can also be used in combination of a phenol type and a phosphite type antioxidant, As a specific example of the said antioxidant, octadecyl-3- ( 3,5-di-tert-butyl-4-hydroxyphenyl) propionate and tris (2,4-di-tert-butylphenyl) phosphite may be used, and oxidized with respect to 100 parts by weight of the high density polyethylene. It is preferable to use 0.07 to 0.2 parts by weight of an inhibitor, but if it is less than 0.07 parts by weight, the flowability of the molten resin is drastically reduced during processing, which causes undesirable appearance problems. It is lowered and is not preferable.

To the polyethylene resin composition of this invention, various additives added to normal polypropylene resin compositions, such as a heat stabilizer, a slip agent, and a neutralizing agent, can be added within the range which does not deviate from the characteristic of this invention.

The manufacturing method of the polyethylene resin composition of this invention is as follows. The resin and additives are first dry blended using a Henschel Mixer and then melt blended above the melting point of the resin using a single-screw extruder to produce pellets. do. The blended pellet-like kneaded material is introduced into a hopper attached to an Extrusio Blow Machine and melted using an extruder above the melting point of the resin to prepare a plastic container in an extrusion blow molding machine.

The blow molding container using the polyethylene resin of the present invention can be applied to a single layer or a multilayer container. The blow molding method includes an extrusion blow molding method, a two-stage blow molding method, an injection molding method, and the like, but the extrusion blow molding method is most suitable for the resin composition of the present invention.

Containers molded using the polyethylene resin composition prepared according to the method of the present invention exhibit excellent container impact resistance and a smooth appearance, so that they can be widely applied to chemical containers, food containers, detergent containers, etc. that require hazardous materials handling and multi-stage loading. Can be.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the examples.

The measuring method of the physical property in each Example and a comparative example is as follows.

Heavy load  Melt Flow Index Measurement

It measured at 190 degreeC and 21.6 kg according to ASTMD1238.

Weight average molecular weight measurement

Measured by gel permeation chromatography.

MI _{21 .6} Of MI _{2 . 16} value  Measure

According to ASTM D1238, the ratio of each high load melt flow index measured at 21.6 kg and 2.16 kg load is shown. Here, the MI _{21 .6} / MI _{2 .16,} and is independent of the molecular weight distribution of the polyethylene resin, it shows a general tendency that the molecular weight distribution broad The higher the number.

Example  And Comparative example

As shown in Table 1 below, the resin compositions of Examples and Comparative Examples of the present invention were dry blended in a Henschel mixer, and then melt blended in a single screw extruder to prepare pellet samples. This pellet-shaped sample was molded in an extrusion blow molding machine under the following processing conditions to prepare a 20-L container.

Pellet Compounding ( Pellet Compounding ) Condition

Extruder Temperature Profile: C1 / C2 / C3 / C4 / DIE = 200/220/240/240/230 ° C

Extrusion speed: 60 ~ 80rpm

N2 Gas Purge

Extrusion Blow ( Extrusion Blow Molding ) Processing condition

Facility: 80mmΦ Blow Molding Machine

Temperature condition: C1 / C2 / C3 / C4 / AD / HI / H2 / DIE = 170/180/190/190/195/200/200/190 ℃

TABLE 1

Example Comparative example One 2 3 One 2 3 Configuration High density polyethylene 100 100 100 100 100 100 Phenolic antioxidant ^{1 )} 0.2 0.02 0.02 0.02 0.02 0.01 Phosphite-based antioxidants ²⁾ 0 0.05 0.1 0.1 0.05 0 Properties Heavy Load Melt Flow Index (g / 10min) 4.0 2.5 3.2 4.9 31.0 3.1 Weight average molecular weight 290,000 400,000 310,000 280,000 190,000 310,000 Molecular weight distribution 20.6 12.8 18.5 27.2 11.4 19.5 Density (g / cm 3) 0.953 0.952 0.953 0.964 0.959 0.952

Note) 1) Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name: songnox1076, manufactured by Songwon Industrial Co., Ltd.)

2) Tris (2,4-di-tert-butylphenyl) phosphite (trade name: Irgafos 168, manufactured by Ciba Specialty Chemicals)

After performing the same physical property evaluation for the hollow molded container of the Example and the comparative example, the result is shown in Table 2.

TABLE 2

Example Comparative example One 2 3 One 2 3 Drop resistance (m) ^{1 )} 3.8 4.0 3.8 1.4 2.4 3.2 Loading strength ^{2 )} pass pass pass fail pass pass Appearance ^{3 )} Good Good Great Great Good Bad

Note 1) Drop impact resistance was carried out in accordance with UN standards. That is, the water at room temperature was filled up to a 20 L scale, and a stopper was dropped five times at a predetermined height to check for damage and leakage of the container. The maximum height at which no breakage or leakage occurred was evaluated as drop impact resistance.

2) The loading strength was determined by cracking of the container after being left for 28 days at 40 ℃ and 250kg load.

3) The appearance was visually observed and judged good or bad by the detection of melt fracture or die line.

As shown in Table 2, Comparative Example 2 having a high load melt flow index of more than 5 has poor drop resistance regardless of the antioxidant content, while Examples 1 to 3 having a high load melt flow index of 5 or less have excellent resistance. The impact resistance was shown, and the crosslinking was greatly prevented to show excellent container loading, impact resistance, and good appearance. In Comparative Example 3, even if the high load melt flow index is within the scope of the present invention, the antioxidant content is out of the range of the present invention. It is not suitable to apply due to the large amount of products. In Comparative Example 1, a phosphite-based antioxidant was used in combination, and the appearance was excellent, but due to the presence of a large amount of low molecular weight due to a wide molecular weight distribution, compared to Examples 1 to 3, the container loading and impact resistance were inferior. Comparative Example 2 was superior in Examples 1 to 3 and Comparative Example 3 with a narrower molecular weight distribution, but had excellent container loadability, but was relatively inferior in impact resistance.

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Claims (4)

High load melt flow index is 5.0g / 10min or less, weight average molecular weight is 250,000 ~ 450,000, molecular weight distribution is _12-25 , MI _21.6 / MI _2.16 is 50 ~ 200, density is 0.95g / cm3 or more Polyethylene resin composition comprising 0.07 to 0.2 part by weight of antioxidant in the portion. The polyethylene resin composition of claim 1, wherein the high density polyethylene is an ethylene homopolymer or a copolymer of ethylene and at least one monomer. 3. The polyethylene resin composition according to claim 2, wherein the monomer is a linear or branched alpha olefin containing 4 to 6 carbon atoms. The polyethylene resin composition according to claim 1, wherein the antioxidant is used alone or in combination with phenol and phosphite.