JPH0212261B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a transparent film of a low-density ethylene-α-olefin copolymer. More specifically, the present invention relates to a method for producing a film having excellent transparency, photoselectivity, and high strength by adding and mixing a modified polyolefin to an ethylene-α-olefin copolymer and performing air-cooled inflation molding. Films produced by air-cooled inflation molding of low-density ethylene-α-olefin copolymers have the following advantages: (1) Compared to conventional radical-based, high-pressure low-density polyethylene films, they have: (1) greater strength and elongation, and a tougher film can be obtained; , (2) High rigidity and strong film stiffness, (3) High heat sealing strength and excellent hot sealing properties, (4) Excellent heat and cold resistance, (5) Good printability. It has many advantages, such as: (6) good drawdown properties and is suitable for molding thin materials; (7) no bubble break occurs even in the presence of foreign matter. On the other hand, (1) processability is poor due to high melt viscosity, (2) bubble stability is poor due to low melt tension, (3) optical properties change easily depending on processing conditions, (4) It has disadvantages such as high power consumption. In particular, when a film is formed by the usual inflation method, the melt tension is low, resulting in poor bubble stability and difficulty in rapid cooling, which significantly impairs optical properties such as transparency and gloss. In addition, it has some problems in moldability and processability compared to conventional high-pressure low-density polyethylene using radicals. The present invention was made to overcome the above problems, and improves optical properties such as transparency and gloss, and moldability without impairing mechanical properties such as impact resistance, tear resistance, and rigidity. The object of the present invention is to provide a transparent film manufacturing method that allows for the production of transparent films. As a result of extensive research in line with this objective, the present inventors have found that the objective of the present invention can be achieved by the transparent film manufacturing method shown below. That is, in the present invention, 0.01 to 20 parts by weight of a modified polyolefin containing an unsaturated carboxylic acid or a derivative thereof is added to 100 parts by weight of an ethylene-α-olefin copolymer having a density of 0.890 to 0.945 g/cc, and the mixture is heated in an air-cooled incubator. The present invention provides a method for producing a transparent film of an ethylene-α-olefin copolymer, which is characterized in that the film is formed by a flaction method. The ethylene-α-olefin copolymer of the present invention is a copolymer of ethylene and an α-olefin having 3 to 12 carbon atoms, preferably ethylene and an α-olefin having 3 to 8 carbon atoms.
It is a copolymer with α-olefin of Examples include mixtures thereof. The method for producing the ethylene-α-olefin copolymer is not particularly limited, such as gas phase polymerization using high, medium, or low pressure methods, slurry polymerization, and solution polymerization.
It is important that the density is in the range of 0.890 to 0.945 g/cc. If the density is less than 0.890 g/cc, the mechanical properties will deteriorate, and if it exceeds 0.945 g/cc, the effect of improving transparency will be poor. The resin physical properties of the above ethylene-α-olefin copolymer include melt index (hereinafter simply referred to as
(referred to as MI) is 0.1 to 7 g/10 min, preferably 0.3
~5g/10min, density 0.890~0.945 as above
g/cc, melt tension 0.3 to 6 g, preferably 0.5 to 5 g, N value 1.2 to 3.0, preferably 1.3
~2.0, molecular weight 80,000-300,000, molecular weight distribution (M _w /M
_o ) is preferably in the range of 2.5 to 10. In the present invention, the polyolefin used as a modified polyolefin is a polypropylene homopolymer produced by a high-, medium-, or low-pressure method, propylene containing ethylene as a main component, butene-1, hexene-
Copolymers with α-olefins such as 1, octene-1, 4-methyl-pentene-1, ethylene-vinyl acetate copolymers, polypropylene homopolymers, ethylene-propylene copolymers, propylene-butene-1 copolymers Copolymers with other α-olefins mainly composed of propylene such as polymers, polybutene-
1, poly-4 methyl pentene-1, ethylene-
Polyolefin resins such as propylene-diene copolymers and liquid polybutadiene are used. The unsaturated carboxylic acids or derivatives thereof of the present invention are monobasic acids such as acrylic acid, methacrylic acid, and methyl methacrylic acid, dibasic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and hymic acid, or these acids. anhydride, ester, amide,
Examples include imides and metal salts, and at least one of these is used, with maleic acid or maleic anhydride being particularly preferred. The modified polyolefin of the present invention can be obtained by reacting at least one of the polyolefins with 0.01 to 10% by weight of at least one of the unsaturated carboxylic acids or derivatives thereof in the presence of an organic peroxide. The reaction can be carried out by melt-mixing in an extruder or a kneader such as a Banbury mixer without a solvent, or with aromatic hydrocarbons such as benzene, xylene, and toluene, and aliphatic hydrocarbons such as hexane, heptane, and octane. Although there are no particular limitations on the method of reaction by heating and mixing in a solvent such as, it is preferable to carry out the reaction in an extruder because the operation is simple and inexpensive. In order to incorporate the modified polyolefin into the ethylene-α-olefin copolymer of the present invention, a concentrated masterbatch of the modified polyolefin is prepared in advance and blended with the unmodified ethylene-α-olefin copolymer. Alternatively, the ethylene-α-olefin copolymer may be modified by directly adding a predetermined unsaturated carboxylic acid. The above blend may be either a dry blend or a melt blend. Further, examples of the organic peroxide include benzoyl peroxide,
Lauryl peroxide, azobisisobutyronitrile, dicumyl peroxide, t-butylhydroperoxide, α,α'-bis(t-butylperoxydiisopropyl)benzene, di-t-
Organic peroxides such as butyl peroxide and 2,5-di(t-butylperoxy)hexane are preferably used. The present invention uses a resin composition obtained by adding and mixing 0.01 to 20 parts by weight of a modified polyolefin containing an unsaturated carboxylic acid or a derivative thereof to 100 parts by weight of the ethylene-α-olefin copolymer, and air-cooling inflation. Conventionally, ethylene films have poor transparency, low melt tension, and can only be formed in an unstable manner.
This can significantly improve the drawbacks of α-olefin copolymers. If the amount of the polyolefin modified product added is less than 0.01 part by weight, the effect of improving transparency is poor, and if it exceeds 20 parts by weight, the strength of the film is impaired and the transparency effect is also reduced. Furthermore, since it imparts adhesive properties, it may not be suitable for general film applications. The molding method using the air-cooled inflation method uses the resin composition as a raw material and molds die gaps 1 to 3.
mm, preferably 1.2 to 2.8 mm, and extruded in an upward or downward direction at a forming temperature of 150 to 260 °C, preferably 170 to 240 °C, and expand the tube to the desired size while cooling in air. , and flatten it into a product film. The thickness of the film is generally about 5 to 300 microns. Hereinafter, the present invention will be specifically explained based on Examples and Comparative Examples, but the present invention is not limited to these unless it departs from the gist thereof. Examples 1 to 10 and Comparative Examples 1 to 8 Ethylene-α-olefin copolymers having the properties shown in Table 1 obtained by various production methods were added with various polyolefin modified products obtained as follows and commercially available Admar-LF300 (manufactured by Mitsui Petrochemicals Co., Ltd.), a polyolefin modified product, was added to each, and an extruder with a screw diameter of 50 mmφ and L/D=26 and an inflation device equipped with a die with a diameter of 100 mmφ and a die lip width of 1.8 mm were used. A film with a blow ratio of 1.9, a fold diameter of 300 mm, and a thickness of 30 μm was molded. Properties of ethylene-α-olefin copolymer,
Table 1 shows the film forming conditions and film properties. In addition, for comparison, films were molded using only various ethylene-α-olefin copolymers without adding any modified polyolefin, using the same apparatus and under the same molding conditions as in Example 1. The properties of this film are also shown in Table 1. Furthermore, ethylene-
Table 1 also shows the results of molding a film in the same manner as in Example 1 by adding a large amount of modified polyolefin to the α-olefin copolymer (Comparative Example 8). <Preparation of modified polyolefin> (1) Ethylene-butene-1 copolymer (butene-1 content 4 mol%) with MI2.0 and density 0.922 g/cc 100
0.25 parts by weight of maleic anhydride and 2,
0.02 parts by weight of 5-dimethyl-2,5-di(t-butylperoxine)-hexine-3 (hereinafter referred to as perhexine 2,5B) was dry blended and mixed, and the mixture was heated at 230°C using a 50mmφ extruder. By extrusion, maleic anhydride-modified polyethylene (hereinafter referred to as MPE) was obtained. (2) 100 parts by weight of polypropylene (Nisseki Polypro GEB-G) with MI 0.5 and density 0.90 g/cc, 0.2 parts by weight of maleic anhydride and 2.5B perhexine.
Dry blend 0.05 parts by weight and mix to form 50mm
Maleic anhydride-modified polypropylene (hereinafter referred to as MPP) is produced by extruding it with a φ extruder at 230℃.
I got it. (3) Ethylene-vinyl acetate copolymer (Nisseki Rexron Eva V251) 100 with MI1.0 and density 0.928g/cc
0.2 parts by weight of maleic anhydride and 0.02 parts by weight of Perhexine 2,5B are dry-blended and mixed, and extruded at 230°C using a 50 mmφ extruder to obtain a maleic anhydride-modified ethylene-acetic acid copolymer (hereinafter referred to as MEVA) was obtained.

【table】

【table】

[Table] As shown in Table 1, various types of ethylene-α
- Examples 1 to 10 in which various modified polyolefins were added and mixed to the olefin copolymer are compared to Comparative Example 1 in which various modified polyolefins were not added and mixed.
- Compared to 7, haze degree without loss of impact strength,
Photoselectivity can be improved. Comparative Example 8 in which 30 parts by weight of polyolefin molded product was added and mixed.
was inferior to Example 1 not only in haze and gloss but also in impact strength. As explained above, according to the present invention, the optical properties such as transparency can be improved without impairing the mechanical properties of the film. This greatly eliminates the drawbacks of ethylene-α-olefin copolymers, which could only be molded into small shapes.

Claims (1)

[Scope of Claims] 1. Adding and mixing 0.01 to 20 parts by weight of a modified polyolefin containing an unsaturated carboxylic acid or a derivative thereof to 100 parts by weight of an ethylene-α-olefin copolymer having a density of 0.890 to 0.945 g/cc, A method for producing a transparent film of an ethylene-α-olefin copolymer, which comprises forming the film by an air-cooled inflation method. 2. The method for producing a transparent film of an ethylene-α-olefin copolymer according to claim 1, wherein the ethylene-α-olefin copolymer is an ethylene-butene-1 copolymer. 3. The method for producing a transparent film of an ethylene-α-olefin copolymer according to claim 1, wherein the ethylene-α-olefin copolymer is an ethylene-hexene-1 copolymer. 4. The ethylene-α-olefin copolymer according to claim 1, wherein the ethylene-α-olefin copolymer is an ethylene-4-methyl pentene-1 copolymer.
A method for producing a transparent film of α-olefin copolymer. 5. The method for producing a transparent film of an ethylene-α-olefin copolymer according to any one of claims 1 to 4, wherein the polyolefin of the modified polyolefin is an ethylene-α-olefin copolymer. 6. The method for producing a transparent film of an ethylene-α-olefin copolymer according to any one of claims 1 to 4, wherein the polyolefin of the modified polyolefin is an ethylene-vinyl acetate copolymer. 7. The method for producing a transparent film of an ethylene-α-olefin copolymer according to any one of claims 1 to 4, wherein the polyolefin of the modified polyolefin is a polyethylene homopolymer. 8. The method for producing a transparent film of an ethylene-α-olefin copolymer according to any one of claims 1 to 4, wherein the polyolefin of the modified polyolefin is a polypropylene homopolymer. 9. Transparent ethylene-α-olefin copolymer according to any one of claims 1 to 8, wherein the unsaturated carboxylic acid or its derivative of the polyolefin modified product is maleic acid or its anhydride. Film manufacturing method.