JPS59109543A - Ethylene copolymer resin composition for use in production of improved film - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which has excellent processability and gives a film having excellent optical properties, impact resistance and MD/TD balance in tear strength, consisting of an ethylene/alpha-olefin copolymer and an ethylene/vinyl acetate copolymer. CONSTITUTION:A resin compsn. consists of 85-95wt% ethylene/alpha-olefin copolymer having a density of 0.895-0.96g/cm<3> and a melt index of 0.1-5g/10min (pref. a density of 0.91-0.94g/cm<3> and a melt index of 0.5-2g/10min) and 5- 15wt% ethylene/vinyl acetate copolymer having a vinyl acetate content of 12- 36wt% and a melt index of 10-50g/10min.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improved ethylene copolymer resin compositions for films. °More specifically, the optical properties of a film made of a copolymer of ethylene and a σ-olefin having 3 to 18 carbon atoms (hereinafter referred to as ethylene-α-olefin copolymer) and ethylene-vinyl acetate copolymer The present invention relates to an ethylene copolymer resin composition for use in films having excellent properties, MD/TD balance of tear strength and impact resistance, and excellent processability. Here, MD represents the machine direction during molding, and TD represents the direction perpendicular thereto.

Ethylene-a-olefin copolymer resins are industrially produced in various processes using so-called Ziegler type catalysts and Phillips type catalysts. One of these is the linear low-density polyethylene commercially available these days. Ethylene-α-olefin copolymers are often compared to polyethylene produced by high-pressure radical polymerization. Ethylene-α-olefin copolymers have very good mechanical properties such as impact resistance when used in heated press sheets, but the processing stability is poor due to the high torque during processing and the low strength of the melt. It has the disadvantage of poor workability, such as poor performance. In addition, ethylene-α-olefin copolymers have a good mechanical quality MD/TD balance in thick molded products such as sheets, pipes, and molded products, and can provide good impact resistance inherent to resins. , T-die fill r≧For thin molded products such as blown film, due to the unique molecular orientation during the molding process, the tear strength MD/
The TD balance is poor and the good impact resistance inherent to the resin cannot be obtained.

Generally, in order to improve the impact resistance of polyethylene resin, ethylene-propylene rubber, butyl rubber,
The method of blending amorphous polymers such as styrene-butadiene rubber and polyisoprene rubber is well known, and when formed into a film, although the MD/TD balance of tear strength is improved, there are many fish eyes. Since the appearance of the film is poor, such as poor transparency, its value as a film is significantly impaired.

As a result of extensive research, the present inventors have discovered that the drawbacks of the ethylene-α-olefin copolymer can be solved by using an ethylene-vinyl acetate copolymer in combination, leading to the present invention. That is, the present invention comprises: (5) a copolymer of ethylene with a Vl of 0 minutes or less and an α-olefin having 8 or more and 18 or less carbon atoms in an amount of 85 to 95N; and (to) a vinyl acetate content of 12% by weight. The ethylene copolymer resin composition for ilms has a melt index of 101 with a content of 36% by weight or less. The present invention will be explained in more detail below.

The ethylene-α-oletetrafin copolymer resin used in the present invention is an a-olefin having 8 to 18 carbon atoms. Specific examples of a-olefins include propylene,
butene-1, pentene-11hexene-11butene-
11 octene-1, nonene-1, decene-1,4-methyl-hentene-1,4-methyl-hexene-114,4
-dimethyl-pentene-1 and the like.

Further, the ethylene-α-olefin copolymer of the present invention has a density of 0.895 to 0.96 P, y et al. and a melt index of 0.1 to 5V10 min.

In particular, those having a density of 0.915 to 0.94 Vcm3 and a melt index of 0.5 to 27710 minutes are preferably used. If the density is less than 0.895 Va13, the MD/TD balance of film tear strength and impact resistance are excellent, but the film lacks stiffness and has large blocking.
If it exceeds 3, the properties as an ethylene-α-olefin copolymer will be lost, and therefore it cannot be used in the composition of the present invention.

Melt intex is 0. If the I Vl is less than 0 minutes, the processing torque is so large that it cannot be processed by normal processing methods, and if it exceeds 5V10 minutes, the bubble stability is poor and only blown film processing is possible, so the composition of the present invention cannot be used. is not used.

Such an ethylene-α-olefin copolymer is obtained by copolymerizing ethylene and α-olefin using a transition metal catalyst. The density is controlled by the type and amount of copolymerization of the α-olefin, and the melt index is controlled by the type and amount of the chain transfer agent.

There are no particular restrictions on the catalyst or polymerization method, and examples of the catalyst include so-called Ziegler type catalysts and Phillips type catalysts, and examples of the polymerization method include so-called slurry polymerization, gas phase polymerization, solution polymerization, etc.5.

The ethylene-vinyl acetate copolymer of the present invention has a vinyl acetate content of 12 to 36% by weight and a melt index of 10 to 50 Vl 0 min.

In particular, those with a vinyl acetate content of 16 to 22% by weight and a melt index of 15 to 4054/1 (1 are preferred. Those with a vinyl acetate content of more than 36% by weight are
Although it has the effect of improving the MD/TD balance of tear strength and impact resistance of the film, blocking of the film is not used to a large extent. When the vinyl acetate content was 12% by weight, the tear strength of the film was MD/TDt<lance, and no impact resistance improvement effect was observed. In addition, if the melt index is less than 10 Vl 0 min, there is no effect of improving the MD/TD balance of the tear strength of the film, and if the melt index is less than 10 Vl 0 min,
If the time exceeds 0 minutes, the blocking of the film is large and the film is not used.

Such an ethylene-vinyl acetate copolymer can be produced, for example, by combining ethylene and vinyl acetate under conditions of a pressure of 1000 to 8500 Kt/2 and a temperature of 160 to 350°C in the presence of a radical polymerization initiator and, if necessary, a chain transfer agent. It can be obtained by polymerization in the presence of. Melt index is controlled by the type and amount of chain transfer agent.

The composition of the present invention comprises 85 to 95% by weight of ethylene-α-olefin copolymer and 15% by weight of ethylene-vinyl acetate copolymer.
・-5% by weight. If the amount of ethylene-vinyl acetate copolymer is less than 5% by weight, the effect of modification is slight;
If it exceeds 5% by weight, the optical properties of the film will deteriorate;
Moreover, it is not preferable because the film loses its stiffness.

There are no particular restrictions on the mixing method for producing the composition of the present invention, and any known method can be used. For example, ethylene-α
- After producing the olefin copolymer and ethylene-vinyl acetate copolymer individually, batch melt mixing method using two rolls or Banbury mixer, OIM (Nippon Steel New Co., Ltd.), FOM (Kobe Steel Fracture Copolymer), etc. Continuous melt-mixing methods using a twin-screw kneader or single-screw kneader are also common, as well as solution mixing methods in which each of the components is dissolved separately or together in a solvent and the solvent is removed after mixing to obtain a mixture. be.

As a method for forming a film from the composition of the present invention, a inflation film molding method or a T-die film molding method is used. Moreover, a blown film molding method is preferably used.

By using the composition of the present invention, processing torque can be reduced during film processing, compared to the case where the ethylene-α-olefin copolymer resin is used alone.
Moreover, the resulting film does not significantly impair its stiffness, does not cause blocking, has markedly improved transparency and gloss, and has improved MD/TD tear strength.
The balance is improved and the falling weight impact strength is also significantly improved. Further, the composition of the present invention is of extremely high practical value in that a superior film can be easily obtained using the processing machines for high-pressure radically polymerized polyethylene that are currently in widespread use.

Next, definitions of physical property values used in the present invention are shown below.

(]) Melt index JIS K6760
The measurement temperature of the wax according to the method specified in 1981 is 190°C.

(2) Density JIS K67
60-1981.

(3) Brabender torque is a value that serves as a guideline for motor power consumption during kneading when molding resin. If it is 8,000%m or less, it can be processed with a normal processing machine. The lower the torque, the better the workability.

Equipment Brabender Plasticorder PLV15 manufactured by Nibrabender Co., Ltd. L-type roller mixer type 50 Mixer filling amount = 38? Mixer temperature: 160°C Mixer rotation speed: 6 Q rpm Kneading was performed under the above conditions, and the torque value after 30 minutes was (?
・Express with m).

(4) Cloudiness According to the method specified in A'STM DlooB. The larger the value, the poorer the transparency of the film.

(5) Gloss According to the Saleta method specified in JIS Z-8741. The larger the value, the better the film gloss.

(6) Tear strength Elmendorf tear strength test according to the method specified in JIS Z-1702. The larger the size, the better the tearability.

(7) Tear strength balance Tear strength is expressed as the ratio of MD value to TD value. The closer it is to 1, the better the balance is.

(8) Falling weight impact strength: A3 for dirt impact
According to the method specified in Th/1D1709. The larger the value, the better the impact resistance of the film.

(9) Stiffness Strength is expressed by the secant modulus at 1% elongation when a strip of film is pulled at a speed of 5 minutes. If it is 1.200 Kglon 2 or more, there is no practical problem.

01 Blocking The stress required to separate the inner surfaces of the infrastructure false chillum is expressed in terms of weight per 100 C2.

EXAMPLES Next, the present invention will be specifically explained using Examples, but the present invention is not limited to the Examples unless it departs from the gist thereof.

Example 1 and Comparative Examples 1 to 5 Ethylene-α-olefin copolymer, melt index 0.89 P/10 min, density 0.928
OIM ( The compositions shown in Table 1 were obtained by kneading them at 240°C. Each of the obtained compositions was evaluated for processability and the following film properties. The film was obtained by inflate processing under the following conditions.

The results are shown in Table 1.

(1) Equipment IFA-600-50 manufactured by Nidomy Kikai Kogyo ■
(2) Diameter 5φ, gap 2. flB, B-row spiral die (3) Processing temperature = 190°C (4) Blow ratio = 2.8 (5) Frost line height = 300 cm (6) Cooling:
Air-cooled two-stage cooling (7) Extrusion amount: 15 Kf/Hr (8) Take-up speed: 16.7 WV min (9) Film thickness 280μ 300 Examples 2 to 8 and Comparative Examples 6 to 7 Melt index is 0. 96P/10 minutes, density 0.
927P/cII317)-r-thiL/:/-phthene-1 copolymer and melt index is 20P/10
Example 1 Comparative Example 1
A composition was obtained by kneading under the same conditions as in 5. Processability and film properties of each composition were evaluated in the same manner as in Example 11 and Comparative Examples 1 to 5. The results are shown in Table 2.

Examples 4 to 6 and Comparative Examples 8 to 10 Various ethylene-butene-1 copolymers shown in Table 8,
An ethylene-vinyl acetate copolymer with a melt index of 20V for 10 minutes and a vinyl acetate content of 20% by weight was
A composition was obtained by kneading in the proportions shown in the table and under the same conditions as in Example 1 and Comparative Examples 1 to 5. For each composition, Example 1. Processing properties and film properties were evaluated in the same manner as in Comparative Examples 1 to 5. The results are shown in Table 8.

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Claims (3)

[Claims] (1) (^ Ethylene with a density of 0.895 gauze 3 or more and 0.96 oki 3 or less, a melt index of 0.1 fl-710 min or more and 5P/10 min or less, and a carbon number of 8 or more and 18
85 to 95% by weight of a copolymer with the following α-olefins; and 2) a vinyl acetate content of 12% to 36% by weight, and a melt index of 105'/10min to 50p/10min. An ethylene copolymer resin composition for film, comprising 5 to 15% by weight of an ethylene-vinyl acetate copolymer. (2) The vinyl acetate content of the ethylene-vinyl acetate copolymer is 16% by weight or more and 22% by weight or less, and the melt index is I1M'710 minutes or more and 405'/10 minutes or less, Claim 1 Compositions as described. (3) Copolymerization of ethylene and α-olefin having 3 to 7 18 carbon atoms, the density of the polymerization is 0.915y-/3 to 0.94111-/am3 or less, and the tear index is 0. The composition according to claim 1 or 2, wherein 5 is 10 minutes or more and 2p710 minutes or less.