JPS643228B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an ethylene film with excellent hot tack properties.
The present invention relates to an α-olefin copolymer composition. Low-melting point polyethylene resins such as ethylene/vinyl acetate copolymer and high-pressure low-density polyethylene are used in large quantities as film sealants because of their excellent low-temperature sealability and transparency. However, such resins have poor hot tack properties (resistance or temperature range when peeling force is applied to the sealed portion immediately after heat sealing), so when used for automatic filling packaging, it is necessary to control packaging speed and appropriate temperature. It was necessary to pay sufficient attention to. On the other hand, ionomers are known as one of the resins with excellent hot tack properties, but although such films have excellent hot tack properties, they have drawbacks such as poor tear strength and moisture absorption, which may cause foaming during molding. It was hot. In view of the current situation, the present inventors investigated the development of a resin with excellent hot tack properties to replace ionomers, and found that a specific ethylene α-
A composition made by adding an ethylene/vinyl acetate copolymer with a high vinyl acetate content to an olefin copolymer has excellent hot tack properties, as well as tear strength, transparency, impact strength, mechanical strength, and moldability. It was found that the present invention was excellent. That is, the present invention provides a copolymer (A) of ethylene and an α-olefin having 4 to 20 carbon atoms with a melt index of 0.1 to 20 g/10 min, a density of 0.910 to 0.940 g/cm ³ and a melting point of 115 to 130°C: 95 to 20
65 parts by weight and melt index 0.1 to 50g/
10min, density 0.920~0.980g/cm ³ , melting point 100~40℃ and vinyl acetate content 10~50% by weight.
Ethylene/vinyl acetate copolymer (B): 5 to 35
parts by weight (provided that (A) + (B) = 100 parts by weight). The ethylene/α-olefin copolymer used in the composition of the present invention has a melt index (ASTMD1238:E) of 0.1 to 20 g/10 min,
Preferably 0.5 to 5g/10min, density 0.910
from 0.940 g/cm ³ , preferably from 0.915 to 0.935
g/cm ³ and a melting point of 115 to 130°C, preferably
It is a copolymer of ethylene in the range of 118 to 125°C and an α-olefin having 4 to 20 carbon atoms, preferably an α-olefin having 6 to 18 carbon atoms. If the melt index is less than 0.1 g/10 min, the melt viscosity is high and the moldability is poor, and if it exceeds 20 g/10 min, the melt viscosity is low, the moldability is poor, and the mechanical strength is also low. If the density is less than 0.910 g/cm ³ , the surface will be sticky when made into a film, and the oil resistance and heat resistance will be poor. If the density exceeds 0.940 g/cm ³ , please use the ethylene/vinyl acetate copolymer (B) described below. Even if added, the hot tack property will not be improved. Those with a melting point of less than 115°C have poor heat resistance, and those with a melting point of over 130°C do not improve hot tack properties even when ethylene/vinyl acetate copolymer (B) is added. The melting point in the present invention refers to the highest temperature at a point showing an endothermic peak determined from an endothermic curve measured by a differential scanning calorimeter (DSC) at a heating rate of 10° C./min. The ethylene/α-olefin copolymer (A) used in the present invention has one or more endothermic peaks, often two or three. Specifically, the α-olefin having 4 to 20 carbon atoms copolymerized with ethylene is 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, copolymers with α-olefins having 6 or more carbon atoms are preferred because they have excellent impact resistance. In addition, ethylene α- within the above range used in the present invention
It is preferable to use an olefin copolymer (A) having a molecular weight distribution (value of weight average molecular weight/number average molecular weight) of 6 or less because a film with even better transparency can be obtained. The molecular weight distribution value is a value obtained by obtaining a molecular weight distribution curve using gel permeation chromatography (GPC) and calculating the weight average molecular weight and number average molecular weight. Ethylene/vinyl acetate copolymer added to the ethylene/α-olefin copolymer (A) used in the present invention
(B) means melt index (ASTM D1238:
E) is 0.1 to 50g/10min, preferably 0.5 to 30g/10min, and density is 0.920 to 0.980g/10min.
cm ³ , preferably 0.930 to 0.960 g/cm ³ , melting point
100 to 40°C, preferably 95 to 55°C and a vinyl acetate content of 10 to 50% by weight, preferably
In the range of 10 to 35% by weight. If the melt index is less than 0.1 g/10 min, the moldability will be poor, and if it exceeds 50 g/10 min, the mechanical strength will be low and the hot tack property will not be improved.
If the density is less than 0.920 g/cm ³ , the effect of improving hot tack properties is poor, and if it exceeds 0.980 g/cm ³ , there is a problem in moldability. If the melting point is less than 40°C, the heat resistance and oil resistance will be poor, and if it exceeds 100°C, the hot tack property will not be improved. When the vinyl acetate content is less than 10% by weight, the effect of improving hot tack properties is small, and when it exceeds 50% by weight, the mechanical strength is low. The composition of the present invention comprises the ethylene/α-olefin copolymer (A) and the ethylene/vinyl acetate copolymer (B).
and 95/5 to (65/35) (parts by weight), preferably 90/10 to 70/30 (parts by weight). Ethylene/vinyl acetate copolymer (B)
If the amount is less than 5 parts by weight, the hot tack properties will not be improved, and if it exceeds 40 parts by weight, the mechanical strength will be significantly reduced. In order to obtain the ethylene/α-olefin copolymer composition of the present invention, the ethylene/α-olefin copolymer (A) and the ethylene/vinyl acetate copolymer (B) can be prepared by various known methods within the above range. For example, mixing with a V-blender, ribbon blender, Henschel mixer, tumbler blender, etc., granulating with an extruder after mixing, or kneading and granulating with an extruder, kneader, Banbury mixer, etc. sell. The ethylene/α-olefin copolymer composition of the present invention itself as a film has excellent hot-tack properties, as well as tear strength, transparency, low-temperature heat sealability, impact strength, and appropriate film stiffness. Because of this, it can be used alone as a packaging film, agricultural film, or protective film, but by taking advantage of its hot-tack properties and laminating it with various base materials, packaging films suitable for various uses can be obtained. As these base materials, any polymer having film-forming ability, paper, aluminum foil, cellophane, etc. can be used. Examples of polymers include high-density polyethylene, medium- and low-density polyethylene, ethylene-vinyl acetate copolymers,
Olefin polymers such as ethylene/acrylic acid ester copolymer, ionomer, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, polyvinyl chloride, polyvinylidene chloride,
Vinyl polymers such as polystyrene, polyacrylate, polyacrylonitrile, nylon 6, nylon 66, nylon 7, nylon 10, nylon 11,
Examples include polyamides such as nylon 12, nylon 610, and polymethaxylylene adipamide, polyesters such as polyethylene terephthalate, polyethylene terephthalate/isophthalate, and polybutylene terephthalate, polyvinyl alcohol, ethylene/vinyl alcohol copolymers, and polycarbonates. . These base materials can be appropriately selected depending on the purpose and the item to be packaged. for example,
If the packaged item is a food item that is prone to corrosion, select resins with excellent transparency, steel properties, and gas permeation resistance, such as polyamide, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and polyester. be done. For confectionery, textile packaging, etc., polypropylene or the like having good transparency, rigidity, and moisture permeation resistance can be selected as the outer layer. Further, if the base material is a polymer, it may be uniaxially or biaxially stretched. Methods for producing a composite film in which a film made of the ethylene/α-olefin copolymer composition of the present invention and the base material are laminated include a dry lamination method, an extrusion lamination method, a Sand-Deutsche lamination method, and a coextrusion method. Various known methods can be employed. The ethylene/α-olefin copolymer composition of the present invention also includes weathering stabilizers, heat stabilizers, antistatic agents, antifogging agents, antiblocking agents, slip agents, lubricants, pigments, dyes, droplets, etc. Various additives that are usually added to polyolefins, such as additives, may be added within the range that does not impair the purpose of the present invention. The ethylene/α-olefin copolymer composition of the present invention can be used as a packaging film for packaging various items, but it has excellent hot tack properties, low temperature heat seal properties, tear resistance, and transparency. For example, it is suitable for frozen food packaging, packaging for pickled foods such as pickles, tofu, konnyaku, etc., packaging for oily foods such as curry, yakiniku sauce, soup, butter, cheese, etc., and paste-like items such as miso and yam. It can be suitably used for packaging bags, etc. 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. Example 1 Melt index: 2.5g/10min, density:
0.915, melting point: 124°C (with peaks at 119°C and 101°C) and molecular weight distribution: 3.6 ethylene/4-methyl-1-pentene copolymer (hereinafter abbreviated as EMP-I): 70 parts by weight and melt index. Tsukusu: 2.0g/
10 min, density: 0.950 g/cm ³ , melting point: 78°C, vinyl acetate content: 25% by weight ethylene/vinyl acetate copolymer (Evaflex P-2505 manufactured by Mitsui Polychemical Co., Ltd.: hereinafter abbreviated as EVA-I): After mixing with 30 parts by weight in a tumbler blender, melt in a 50 mmφ extruder (set temperature: 180℃), extrude bubbles from a 100 mmφ circular die (die lip: 1.2 mm, set temperature: 170℃), cool in air, and then fold the width. An inflation film of 230mm and 30μ thickness was obtained. Next, physical properties were evaluated by the following method. Haze (%): ASTM D1003 Gloss (%): ASTM D2457 Incident angle: 20 degrees Impact strength (Kg-cm/cm): ASTM D3420 Tear strength (Kg/cm): JIS Z1702 Bending rigidity (Kg/cm ² ) : Prepare a 140 x 140 mm test piece and use a Handle-o-Meter (Thwing
Albert Inc. (USA) was used to apply bending stress to the test piece with a slit width of 5 mm, the maximum stress was determined, and the value divided by the thickness of the test piece was defined as the bending rigidity (Kg/cm ² ). The bending rigidity was determined at two points in the longitudinal and lateral directions of the sample. Peel strength of heat-sealed part (g/15mm): Overlapping film surfaces, 100℃, 105℃, 110℃,
Temperatures of 120℃, 130℃, 140℃, 150℃, width 5
1 at a pressure of 2Kg/cm ² with a seal bar of mm
After sealing for a second, it was allowed to cool. 15 from these
Cut out a test piece with a width of mm, peel off the heat-sealed part at a crosshead speed of 200 mm/min,
The strength at that time was defined as the peel strength. Hot-tack test (mm): 550 mm long x 20 mm wide test pieces were stacked at 105℃, 110℃, 120℃,
After sealing for 1 second at a pressure of 2 kg/cm ² using a sealing bar with a width of 5 mm and a length of 300 mm at temperatures of 130°C, 140°C, and 150°C, a load of 43 g was applied to each specimen at the same time as the pressure was removed. was forcibly peeled off, and the hot-tack property was evaluated based on the peeled distance (mm). That is, the shorter the peeling distance, the better the hot-tack properties. The results are shown in Table 1. Examples 2 and 3 The same procedure as in Example 1 was carried out except that the mixing ratio of EMP-I/EVA-I = 70/30 in Example 1 was changed to 77/23 and 90/10 (parts by weight). The results are shown in Table 1. Example 4 Instead of EVA-I used in Example 1, melt index: 2.5g/10min, density: 0.94g/
^cm3 , melting point: 85℃ and vinyl acetate content: 19% by weight
Ethylene-vinyl acetate copolymer (EVAFLEX P-1905 manufactured by Mitsui Polychemical Co., Ltd.: hereinafter referred to as EVA)
Example 1 was carried out in the same manner as in Example 1, except that ``-'' was used. The results are shown in Table 1. Comparative Example 1 Instead of EVA used in Example 1, melt index: 1.7g/10min, density: 0.93g/
cm ³ , melting point: 98°C, and vinyl acetate content of 8% by weight ethylene/vinyl acetate copolymer (EVAFLEX P-0803 manufactured by Mitsui Polychemical Co., Ltd.: hereinafter EVA)
The same procedure as in Example 1 was carried out except that the mixture ratio was 80/20. The results are shown in Table 1. Comparative Example 2 The same procedure as in Example 1 was carried out except that the mixing ratio of EMP-/EVA-=70/30 in Example 1 was changed to 50/50 (parts by weight). The results are shown in Table 1. Example 5 Instead of EMP used in Example 1, melt index: 2.5g/10min, density: 0.923
Other than using ethylene-4-methyl-1-pentene copolymer (hereinafter abbreviated as EMP-), g/cm ³ , melting point: 123°C (there are also peaks at 119°C and 104°C), and molecular weight distribution: 3.6. was carried out in the same manner as in Example 1.
The results are shown in Table 1. Comparative Examples 3 and 4 The same procedure as in Example 1 was conducted except that the EMP used in Example 1 and the EMP used in Example 5 were each used alone as a film. The results are shown in Table 1. Reference Example Instead of the composition used in Example 1, an ionomer (Himilan 1650, manufactured by Mitsui Polychemical Co., Ltd.) was used.
The same procedure as in Example 1 was carried out except for using IM (hereinafter abbreviated as IM). The results are shown in Table 1.

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Claims (1)

[Claims] 1. Melt index 0.1 to 20g/10min,
Copolymer (A) of ethylene and α-olefin having 4 to 20 carbon atoms with a density of 0.910 to 0.940 g/cm ³ and a melting point of 115°C to 130°C: 95 to 65 parts by weight, and a melt index of 0.1 to 50 g/ 10min,
Density 0.920~0.980g/ ^cm3 , melting point 100℃~
Ethylene/vinyl acetate copolymer (B) at 40°C and vinyl acetate content of 10% to 50% by weight: 5 to 50%
35 parts by weight of ethylene.
α-olefin copolymer composition.