Polyethylene resin composition and molded article composed of the same

Abstract

To provide a polyethylene resin composition which has good water vapor barrier property and transparency.SOLUTION: A polyethylene resin composition contains 200 to 2,500 ppm of the total of 1,2-cyclohexane dicarboxylate and stearate as nucleus agents B in a polyethylene resin A satisfying the following characteristics (a) to (c). (a) A density is 940 to 970 kg / m3. (b) A melt mass flow rate (hereinafter referred to MFR) which is measured according to JIS K 6922-1 at 190°C and under a load of 21.18 N is 0.1 to 50 g / 10 min. (c) A ratio (Mw / Mn) of a weight average molecular weight (Mw) to a number average molecular weight (Mn) is 5.0 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyethylene resin composition, and more particularly to a resin composition of a specific polyethylene and a nucleating agent, and a molded article made therefrom. [Background technology]

[0002] In recent years, there has been growing global interest in reducing waste from plastic packaging and plastic containers, leading to a demand for materials and technologies that can increase sustainability, and an increasing number of efforts are being made to reduce packaging thickness and promote recycling.

[0003] Many film packaging uses a multi-layer structure combining multiple materials such as polyethylene, polypropylene, ethylene vinyl alcohol copolymer, polyethylene terephthalate, and cyclic polyolefin, and is designed to take advantage of the characteristics of each material. However, when these different materials are combined, there is a problem that recycling is difficult. Therefore, a single packaging material is required, but the characteristics obtained with other resins are lost, making it difficult to maintain the performance and processing characteristics as a packaging container. For example, when polyethylene is used alone as a material, it has excellent moldability and post-processability, and is excellent in manufacturing cost, but the gas barrier properties against water vapor and oxygen are insufficient, and there is a risk that the performance as a container that maintains the properties of the contents will be reduced. By selecting polyethylene with a high crystallinity, i.e., a high density, a relatively high gas barrier property can be obtained, but the gas barrier property may not always be sufficient, and there is a problem that the transparency is reduced and the visibility of the contents is reduced. In addition, even when the packaging is made thin as a method of environmental response, there is a problem that the gas barrier property is reduced as the thickness is reduced. Therefore, a polyethylene resin that has sufficient gas barrier property and transparency even when used alone is desired.

[0004] Patent Document 1 proposes a method for achieving both recyclability and gas barrier properties by performing metal vapor deposition on a laminate consisting of a polyethylene main layer and a surface layer made of another resin.

[0005] In recent years, Patent Documents 2 and 3 have proposed nucleating agents that are effective for polyethylene resins. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-160255 [Patent Document 2] Patent No. 7019862 [Patent Document 3] Patent No. 7143508 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a polyethylene resin composition having excellent gas barrier properties and transparency. [Means for solving the problem]

[0008] Means for Solving the Problems The present inventors conducted intensive research to solve the above-mentioned problems and discovered that by adding a specific nucleating agent to polyethylene that satisfies specific requirements, it is possible to obtain a level of water vapor barrier property that is not available in conventional polyethylene resins, thereby solving the above-mentioned problems, and have thus completed the present invention.

[0009] That is, the respective aspects of the present invention are as follows [1] to [3]. [1] A polyethylene resin composition comprising a polyethylene resin A satisfying the following characteristics (a) to (c), and a nucleating agent B comprising a 1,2-cyclohexanedicarboxylate and a stearate in a total amount of 200 to 2,500 ppm: (a) Density is 940 kg / m 3 More than 970kg / m 3 The following is the result. (b) A melt mass flow rate (hereinafter referred to as MFR) of 0.1 to 50 g / 10 min or less, measured at 190°C and a load of 21.18 N in accordance with JIS K 6922-1. (c) The ratio (Mw / Mn) of number average molecular weight (Mn) to weight average molecular weight (Mw) is 5.0 or less. [2] The polyethylene resin composition according to [1], wherein nucleating agent B is 60 to 70% by weight of calcium 1,2-cyclohexanedicarboxylate and 30 to 40% by weight of zinc stearate. [3] A molded article made of the resin composition according to [1] or [2]. Effect of the Invention

[0010] According to the present invention, it is possible to provide a resin composition that suppresses water evaporation from the contents, which is a problem with polyethylene containers, improves the storage stability of the contents, and provides transparency that ensures the visibility of the contents. By using the resin composition, it is possible to obtain a molded product that is thinner than before while maintaining water vapor barrier properties. In addition, by using a single raw material for a multi-layer molded product that was previously manufactured using multiple raw material resins, it is possible to apply the composition to applications such as facilitating recycling after use. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention will be described in detail below. (1) Polyethylene resin A The polyethylene resin A used in the present invention is an ethylene homopolymer or a copolymer of ethylene and an α-olefin. The polyethylene resin A has a melt flow rate (hereinafter referred to as MFR) of 0.1 to 50 g / 10 min, preferably 0.5 to 30 g / 10 min, and more preferably 1.0 to 10 g / 10 min, measured at 190°C under a load of 2.16 kg according to JIS K 6922-1. If the MFR is 0.1 g / 10 min or more, the load on the extruder during molding is unlikely to increase, and surface roughness is unlikely to occur during molding. If the MFR is 50 g / 10 min or less, melt tension is ensured, and molding stability is obtained, which is preferable.

[0012] The polyethylene resin A has a density of 940 to 970 kg / m according to JIS K6760. 3 , preferably 940 to 960 kg / m 3 The density of the high density polyethylene is 940 kg / m 3 Above this level, high water vapor barrier properties are obtained, at 970kg / m 3 Transparency is ensured if:

[0013] The polyethylene resin A has a ratio (Mw / Mn) of weight average molecular weight (Mw) to Mn, as measured by gel permeation chromatography (hereinafter referred to as GPC), of 5.0 or less, preferably 2.0 to 4.0, and more preferably 2.0 to 3.5. When Mw / Mn is 5.0 or less, a molded article having high water vapor barrier properties and good transparency can be obtained, which is preferable. When Mw / Mn is 2.0 or more, the extrusion load during molding is small, and the appearance (surface skin) of the molded article is good, which is preferable.

[0014] The polyethylene resin A can be produced by, for example, a slurry method, a solution method, a gas phase method, etc. When producing the polyethylene resin A, a Ziegler catalyst consisting of a solid catalyst component containing magnesium and titanium and an organoaluminum compound, a metallocene catalyst consisting of an organic transition metal compound containing a cyclopentadienyl derivative and a compound and / or an organic metal compound that reacts with the organic transition metal compound to form an ionic complex, a vanadium-based catalyst, etc. can be used, and the polyethylene resin A can be produced by homopolymerizing ethylene or copolymerizing ethylene and an α-olefin using the catalyst, but production using a metallocene catalyst is particularly preferred because it gives a high-density polyethylene with narrow molecular weight distribution and composition distribution and high water vapor barrier property.

[0015] The polyethylene resin A may be a commercially available product, and examples thereof include Nipotec 06S84A (product name) manufactured by Tosoh Corporation, Nipotec 06S81H (product name) manufactured by Tosoh Corporation, Nipotec 06S81K (product name) manufactured by Tosoh Corporation, and Nipolon Hard 1200 (product name) manufactured by Tosoh Corporation. (2) Nucleating agent B The nucleating agent B used in the present invention is a 1,2-cyclohexanedicarboxylate. Examples of the 1,2-cyclohexanedicarboxylate include calcium 1,2-cyclohexanedicarboxylate and aluminum 1,2-cyclohexanedicarboxylate. In particular, calcium 1,2-cyclohexanedicarboxylate is preferred because it can be added to the polyethylene resin A to obtain a resin composition with high water vapor barrier properties. In order to disperse the nucleating agent well in the polyethylene resin, it is preferred to use a stearate in combination as a dispersion aid. Examples of the stearate include zinc stearate, calcium stearate, and magnesium stearate. In particular, when 1,2-cyclohexanedicarboxylate and zinc stearate are used in combination, the dispersibility of the 1,2-cyclohexanedicarboxylate is improved, and a high nucleating effect is obtained, which is preferred. The ratio of the 1,2-cyclohexanedicarboxylate and the stearate is preferably 60 to 70% by weight of the 1,2-cyclohexanedicarboxylate and 30 to 40% by weight of the stearate, which can obtain a high nucleating effect.

[0016] The nucleating agent B may be a commercially available product, such as Hyperform HPN-20E (trade name) manufactured by Milliken Chemical. Hyperform HPN-20E contains 60-70% by weight of calcium 1,2-cyclohexanedicarboxylate and 30-40% by weight of zinc stearate. (3) Polyethylene resin composition The polyethylene resin composition according to one embodiment of the present invention is produced by adding nucleating agent B to polyethylene resin A. The concentration of nucleating agent B is 200 to 2500 ppm, preferably 300 to 2500 ppm, and more preferably 400 to 2200 ppm. When nucleating agent B is 200 ppm or more, it is preferable because high water vapor barrier properties and transparency can be obtained. When nucleating agent B is 2500 ppm or less, it is preferable because the production cost is suppressed and contamination of the contents due to bleed-out of the nucleating agent component does not occur. The method of adding nucleating agent B to polyethylene resin A is not particularly limited, and various known addition methods can be adopted. For example, a method of dry blending polyethylene resin A and nucleating agent B with a Henschel mixer, V-blender, ribbon blender, tumbler blender, etc., a method of melt kneading with an extruder, etc., etc. may be mentioned. In addition, a method of preparing a master batch containing a high concentration of nucleating agent B and mixing it with polyethylene resin A may be used.

[0017] The polyethylene resin composition may be blended with commonly used known additives, such as antioxidants, antistatic agents, lubricants, antiblocking agents, antifogging agents, organic or inorganic pigments, ultraviolet absorbers, dispersants, etc., as necessary, within the scope of not significantly impairing the effects of the present invention. The method for blending the above additives with the resin composition of the present invention is not particularly limited, but examples include a method of adding the additives to polyethylene resin A together with nucleating agent B by dry blending or melt kneading, and a method of preparing a high-concentration master batch in advance and dry blending this with the polyethylene resin composition of the present invention at the time of molding.

[0018] Furthermore, the resin composition according to one embodiment of the present invention may also be blended with other thermoplastic resins, such as high-density polyethylene, high-pressure low-density polyethylene, linear low-density polyethylene, ethylene-propylene copolymer rubber, and poly-1-butene, within a range that does not impair the effects of the present invention. (4) Molded products The type of molded article obtained by molding the resin composition of the present invention is not particularly limited, and it can be molded into, for example, a film, a sheet, an injection molded article, a tube, a pipe, a bottle, etc. The molded article obtained may be a single layer, or may contain the resin composition as one layer of a multilayer molded article or a laminate. EXAMPLES

[0019] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0020] <density> The density was measured by the density gradient tube method in accordance with JIS K 6760 (1995).

[0021] <mfr> The MFR (melt flow rate) was measured in accordance with JIS K 6922-1 at 190° C. and a load of 2.16 kg.

[0022] <Molecular weight, molecular weight distribution> Weight average molecular weight (Mw), number average molecular weight (Mn), and ratio of weight average molecular weight to number average molecular weight (Mw / Mn) were measured by GPC. A GPC device (Tosoh Corporation (trade name) HLC-8121GPC / HT) and a column (Tosoh Corporation (trade name) TSKgel GMHhr-H(20)HT) were used, the column temperature was set to 140°C, and 1,2,4-trichlorobenzene was used as the eluent. The measurement sample was prepared at a concentration of 1.0 mg / ml, and 0.3 ml was injected and measured. The molecular weight calibration curve was calibrated using a polystyrene sample with a known molecular weight. Note that Mw and Mn were calculated as values ​​converted into linear polyethylene. ~Production and evaluation of resin compositions and molded products~ <Polyethylene resin> The following polyethylene resin was used. The physical properties of the polyethylene resin are shown in Table 1.

[0023] HDPE1: Tosoh Corporation (product name) Nipotec 06S81K, MFR 5.0g / 10min, density 958kg / m 3 HDPE2: Tosoh Corporation (product name) Nipotec 06S81H, MFR 1.0g / 10min, density 952kg / m 3 HDPE3: Tosoh Corporation (product name) Nipotec 06S84A, MFR 3.0g / 10min, density 945kg / m 3 HDPE4: Tosoh Corporation (product name) Nipolon Hard 1200, MFR 21g / 10min, density 952kg / m 3 HDPE5: Tosoh Corporation (product name) Nipolon Hard 5110, MFR 0.9g / 10min, density 961kg / m 3 HDPE6: Tosoh Corporation (product name) Nipolon Hard 5700, MFR 1.0g / 10min, density 954kg / m 3 HDPE7: Tosoh Corporation (product name) Nipolon Hard 7300A, MFR 0.05g / 10min, density 952kg / m 3 LL1: Tosoh Corporation (product name) Nipolon-Z HF250K, MFR 2.0g / 10min, density 930kg / m 3

[0024] [Table 1]

[0025] <Resin composition> The resin composition according to the present invention was prepared by dry-blending the polyethylene resin pellets shown in Table 1 with calcium 1,2-cyclohexanedicarboxylate and zinc stearate so that the nucleating agent had a predetermined concentration. The mixture was melt-kneaded at a cylinder temperature of 180°C using a 20 mm single-screw extruder (manufactured by Toyo Seiki Seisakusho, Ltd.), and the strands were cut to prepare pellets of the resin composition.

[0026] <Press sheet> Next, the resin composition pellets were compressed using a press (manufactured by Shinto Metal Industry Co., Ltd.) at a temperature of 200°C and a pressure of 0.1 MPa for 240 seconds, further compressed at a temperature of 200°C and a pressure of 1.0 MPa for 240 seconds, and then compressed at a temperature of 25°C and a pressure of 1.0 MPa for 180 seconds to produce a sheet with a thickness of 100 μm.

[0027] <Amount of transpiration> The press sheet was cut into 80 mm x 160 mm, folded to 80 mm x 80 mm, and three-sided sealed bags with a liquid contact surface of 60 mm x 70 mm, in which 18 mL of ultrapure water was sealed using an impulse sealer (manufactured by Fuji Impulse), were prepared for each resin composition. The weight of the prepared three-sided sealed bag was measured, and the bag sample was immediately weighed after storing it for 14 days in a thermo-hygrostat (manufactured by Hitachi Global Life Solutions) set at a temperature of 40 ° C and a humidity of 70% RH. The difference in weight of the bag before and after storage in the thermo-hygrostat was taken as the amount of evaporation. When the average value of the amount of evaporation of the two bags was 40 mg or less, the water vapor barrier property was evaluated as good.

[0028] <Haze> The haze of the press sheet was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd.) When the average value of five tests was 55% or less, the transparency was evaluated as good.

[0029] <Examples 1 to 6> The evaluation results of the resin compositions shown in Table 2 are shown in Table 2.

[0030] [Table 2]

[0031] <Comparative Examples 1 to 13> The same procedure as in Example 1 was carried out except that the types and mixing ratios of the resin pellets were changed as shown in Tables 3 and 4. The results are shown in Tables 3 and 4.

[0032] [Table 3]

[0033] [Table 4] < / mfr>

Claims

1. A polyethylene resin composition comprising a polyethylene resin A satisfying the following characteristics (a) to (c), and a nucleating agent B, which contains a 1,2-cyclohexanedicarboxylate and a stearate in a total amount of 200 to 2500 ppm: (a) Density is 940 to 970 kg / m ３ It is. (b) A melt mass flow rate (hereinafter referred to as MFR) measured in accordance with JIS K 6922-1 at 190° C. and a load of 21.18 N is 0.1 to 50 g / 10 min. (c) The ratio (Mw / Mn) of number average molecular weight (Mn) to weight average molecular weight (Mw) is 5.0 or less.

2. 2. The polyethylene resin composition according to claim 1, wherein said nucleating agent B is 60 to 70% by weight of calcium 1,2-cyclohexanedicarboxylate and 30 to 40% by weight of zinc stearate.

3. A molded article comprising the polyethylene resin composition according to claim 1 or 2.

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