KR19990065047A - Coextrusion Polyolefin Film - Google Patents

Abstract

The present invention relates to a coextruded polyolefin film, comprising a melt flow index of 1 to 15 (g / 10 minutes), a melt temperature of 160 to 170 ° C., a density of 0.9 to 0.91 and an isotactic index of 95% or more. Ethylene propylene butyl having a melt flow index of 1 to 15 (g / 10 min) and a melting temperature of 100 to 160 ° C. comprising a central layer of isotactic polypropylene resin having By including the surface layer of the rent polymer on one or both sides 1/40 to 1/3 of the total film thickness, it is possible to prepare a co-extruded polyolefin film having excellent slip properties and heat adhesion without a separate extrusion lamination process, The film of the present invention can be applied to an automated facility that operates at high speed, and can be widely used for various applications requiring heat adhesiveness.

Description

Coextrusion Polyolefin Film

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coextruded polyolefin film, and specifically to a coextruded polyolefin film having a polypropylene resin as a center layer and an ethylene propylene butylene terpolymer containing silica as a surface layer. It is about.

As society develops, it seeks to move away from a simple consciousness-oriented lifestyle and pursue a convenience- and efficiency-oriented lifestyle, and as a result, it is widely used throughout packaging and stationery, office supplies, electrical appliances, tools, and toys that can store contents for a long time. The market demand for plastic sheets is gradually increasing, especially in recent years, the demand for plastic products with excellent transparency to see the contents at any time is rapidly increasing.

Examples of plastics that can be used for this purpose include polystyrene, polyvinyl chloride, polypropylene and polyethylene terephthalate. Among them, polyvinyl chloride is inexpensive and has excellent processability and does not require any special technology or equipment. However, due to the generation of chlorine gas that pollutes the environment during combustion, its usage is decreasing due to the recent tightening of legal regulations. Although it has good transparency and mechanical properties, it causes environmental problems due to odor and black smoke, ash, dust, etc. generated during incineration, and has become a major obstacle to its widespread use in general because of its relatively expensive economic burden. In addition, polyester has excellent transparency, but it is expensive, stiff, and has a heavy turbidity, and thus has a very difficult processing condition.

Therefore, polyolefins having the advantage as an alternative resin capable of satisfying the requirements of the application without such a problem are now widely used as packaging materials. However, polyolefin films typically have poor thermal adhesion with homogeneous films, and have been provided with thermal adhesiveness by extrusion lamination of polyethylene or lamination of unstretched polypropylene. Thus, film makers in the Western market directly give the polyolefin film itself the thermal property of the film, which is the secondary property of the film. Since the heat-adhesive film has the heat adhesive force of the film itself, the weight of bread, straw, etc. It is used as a single layer in the packaging of lightweight materials that do not go out.

In the method for producing a thermally adhesive polyolefin film as described above, US Patent No. 4,297,411 coextruded a polylayer or a center layer composed of polyolefin and polypropylene, and a surface layer composed of ethylene, a higher olefin copolymer or a higher olefin copolymer. Heat adhesiveness. In addition, US Patent 433,968 extrudes and laminates an ethylene vinyl acetate copolymer on a polypropylene film to impart heat adhesiveness. US Pat. No. 4,564,558 provides a center layer composed of polyolefin and a surface layer composed of ethylene propylene butylene terpolymer. Coextrusion gives heat adhesiveness. As described above, when co-extrusion of the central layer composed of polypropylene and the surface layer composed of terpolymer or ethylene with a higher olefin copolymer or a higher olefin copolymer gives thermal adhesiveness, thermal adhesion characteristics can be obtained, but a coefficient of friction In the continuous packaging device that is operated at high speed due to high blocking and sticking of the film surfaces to each other, there are many problems in its operation. In addition, in the case where the polypropylene film is extruded and laminated with ethylene vinyl acetate copolymer to impart heat adhesiveness, a separate extrusion laminate process is required, which is not preferable in view of cost.

Accordingly, the present inventors have continued their intensive studies and found that the above problems can be solved by coextrusion of a central layer made of polypropylene resin and a surface layer made of ethylene propylene butylene terpolymer including silica. It became.

It is an object of the present invention to provide a coextruded polyolefin film having excellent slip properties and heat adhesion.

In order to achieve the above object, in the present invention, the melt flow index including the center layer made of isotactic polypropylene resin, and 0.05 to 0.5% by weight of silica, the melt flow index is 1 to 15 (g / 10 minutes) and the melting temperature is 100 It provides a coextruded polyolefin film comprising a surface layer consisting of ethylene propylene butylene terpolymer of from 160 to 160 ℃ in one or both of 1/40 to 1/3 of the total film thickness.

Hereinafter, the present invention will be described in more detail.

The center layer and the surface layer of the film of this invention make a polypropylene resin and ethylene propylene butylene terpolymer, respectively, as a base resin. In particular, the central layer of the film of the present invention has a melt flow index of 1 to 15 (g / 10 minutes), a melting temperature of 160 to 170 ℃ and a density of 0.9 to 0.91, the eye isotactic index is 95% or more Preference is given to using sootactic polypropylene resins.

In the present invention, the ethylene propylene butylene terpolymer forming the surface layer is a terpolymer having an ethylene content of 0.5 to 10% by weight and a butylene content of 0.5 to 15% by weight, more preferably 1 to 15 (g / 10 minutes), more preferably. It has a melt flow index of 1 to 15 (g / 10 minutes) and a melting temperature of 100 to 160 ° C. If the melt flow index is less than 1 (g / 10 min), the molecular weight of the resin is so large that it is difficult to obtain a surface layer of uniform thickness during film molding, and if it exceeds 15 (g / 10 min), the molecular weight of the resin is too small. Mechanical properties are inferior. In addition, when the melting temperature is less than 100 ℃, the mechanical strength is lowered, and when it exceeds 160 ℃, it is difficult to obtain a surface layer of uniform thickness during film molding.

According to the present invention, the slip property is improved by adding silica to the surface layer of the film of the present invention made of ethylene propylene butylene terpolymer. At this time, the addition amount of silica is 0.05 to 0.5% by weight, when the addition amount is less than 0.05% by weight, it is difficult to obtain the effect of the present invention, and when it exceeds 0.5% by weight, there is a fear that the transparency of the film becomes. In addition, the average particle size of silica to be added is 0.5 to 5 mu, and when the particle size is less than 0.5 mu, the particle size is too small to form a sufficient roughness on the surface of the film, and thus the effect of the present invention is difficult to obtain. There is a risk of harming the transparency of the.

According to the present invention, in the coextruded film, the thickness of the surface layer located on one or both sides of the center layer is preferably in the range of 1/40 to 1/3 of the total film thickness, more preferably in the range of 1/40 to 1/7. Do. If the surface layer is thinner than 1/40, it is difficult to obtain the effect of the present invention, and if it is thicker than 1/3, the mechanical strength is significantly reduced.

According to the present invention it is possible to produce a polyolefin film excellent in slip properties and heat adhesion without the need for a separate extrusion lamination process, the film is applicable to an automated facility that operates at high speed, and requires heat adhesion It can be widely used in various applications.

Hereinafter, the present invention will be described in more detail based on the following examples. However, the following examples are not intended to limit the present invention, but are not limited thereto. Various performance evaluations of the films prepared in Examples and Comparative Examples of the present invention were performed by the following methods.

(1) coefficient of friction

The coefficient of friction was measured under the conditions of 100 g load and a speed of 150 mm / min using a surface tester (model name: Haydon-14) of Haydon Corporation (Japan).

(2) heat adhesion strength

After sealing the polyethylene film and the polyolefin film of the present invention by pressing for 2 seconds at a pressure of 3 kg / cm ² at 150 ° C. using a heat gradient tester (Model: HG-100) manufactured by Toyo Seiki Co., Ltd. The thermal bond strength was measured using a Peeling Tester while pulling a 25 mm wide suture film at a rate of 100 mm / min.

Example 1

The surface layer is an ethylene propylene butylene terpolymer having a melt flow index of 3 (g / 10 min) and a melting temperature of 120 ° C., in which a polypropylene resin is used as a center layer and 0.1 wt% of silica having an average particle size of 2 μ is added. After coextrusion through a die at a temperature of 250 ℃, and quenched in a cooling drum of 30 ℃ to prepare a sheet of 850μ thick. Subsequently, the film was sequentially stretched 5 times in the longitudinal direction and 8 times in the lateral direction while being reheated at a temperature of 140 ° C., and then heat-set at a temperature of 160 ° C. The performance evaluation results of the finally prepared 20μ thick film are shown in Table 1 below.

Examples 2 to 10 and Comparative Examples 1 to 5

A polyolefin film was prepared in the same manner as in Example 1 while changing the properties of the ethylene propylene butylene terpolymer, the surface layer thickness ratio, and the concentration of silica as shown in Table 1 below. The performance evaluation results of the films are shown in Table 1 below.

division Ethylene Propylene Butylene Terpolymer Silica Characterization item Melt flow index Melting temperature Surface layer thickness ratio density Coefficient of friction Thermal bonding strength g / 10 minutes ℃ Surface layer / center layer weight% - g / 25mm Example One 3 120 1/30 0.2 0.4 More than 1000 2 3 120 1/30 0.5 0.35 More than 1000 3 3 120 1/30 0.05 0.5 More than 1000 4 3 120 1/20 0.2 0.4 More than 1000 5 3 120 1/10 0.2 0.4 More than 1000 6 3 120 1/5 0.2 0.4 More than 1000 7 3 120 1/40 0.2 0.4 More than 1000 8 3 120 1/30 0.2 0.4 More than 1000 9 5 110 1/30 0.2 0.4 More than 1000 10 10 100 1/30 0.2 0.4 More than 1000 Comparative example One 3 120 1/50 - 1.0 200 2 3 120 - - 0.6 100 3 20 120 1/30 - 1.0 More than 1000 4 3 120 1/30 0.01 0.8 More than 1000 5 3 120 1/30 0.03 0.7 More than 1000

The coextruded polyolefin film according to the present invention, as can be seen in Table 1, can be applied to an automated facility that operates at high speed because of excellent slip properties and heat adhesion, and can be widely used in various applications requiring heat adhesion. have.

Claims (3)

Ethylene propylene having a melt flow index of 1 to 15 (g / 10 minutes) and a melting temperature of 100 to 160 ° C. comprising a central layer made of isotactic polypropylene resin and 0.05 to 0.5 wt% silica. A coextruded polyolefin film comprising a surface layer made of butylene terpolymer on one or both sides of 1/40 to 1/3 of the total film thickness. The method of claim 1, Coextrusion, characterized in that the isotactic polypropylene resin has a melt flow index of 1 to 15 (g / 10 minutes), a melting temperature of 160 to 170 ° C., a density of 0.9 to 0.91 and an isotactic index of 95% or more. Polyolefin film. The method of claim 1, Co-extruded polyolefin film, characterized in that the ethylene propylene butylene terpolymer consists of 0.5 to 10% by weight of ethylene and 0.5 to 15% by weight of butylene.