JPS6351096B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a sheet of ethylene-propylene block copolymer that is transparent and has excellent impact resistance, heat resistance, etc.
This invention relates to a method for forming films and the like. Ethylene-propylene block copolymer sheets and films not only have excellent heat resistance and impact resistance at low temperatures, but also excellent mechanical strength, making them suitable as packaging materials for products that require particularly strong strength. It has been adopted. Ethylene-propylene block copolymers are generally considered to be a heterogeneous mixture consisting of a relatively low-viscosity polypropylene portion and a high-viscosity ethylene-propylene copolymer rubber.
In particular, except for special block copolymers with low ethylene concentration and weak low-temperature impact strength, transparency is difficult, and conventional molding methods have not been able to produce transparent sheets or films. This opacity of sheets, films, etc. is a phenomenon that already occurs when they are extruded at a higher temperature than the commonly used T-type die or other dies. It was difficult to obtain a transparent sheet or film even if the material was heated and cooled rapidly. This opacity is caused by the fact that when a heterogeneous mixture with a large viscosity is extruded from a die into a film, the flow becomes non-uniform, and as a result, the thin film becomes opaque due to its excellent low-temperature impact strength. This is unavoidable since it is an ethylene-propylene block copolymer. For this reason, even if a material has excellent heat resistance and strength, its use as a packaging material is limited to packaging products that do not require transparency. It is said that transparency must be improved through measures. This invention has been made in view of the above points, and its purpose is to
The purpose of this invention is to produce transparent sheets, films, etc. of ethylene-propylene block copolymers. The transparency obtained by the present invention means that the film or sheet has little diffused reflection on the surface, is glossy, and has good transparency. Furthermore, this invention can be applied to not only ordinary sheets and films but also other transparent sheets and films based on similar means.
It is also an attempt to manufacture sheets, films, etc. with excellent transparency by combining them with films. The present inventors have been conducting research for many years on a method of making a heterogeneous mixture of opaque copolymers transparent. As a result, even if a mixture of substances with widely different viscosities, such as ethylene-propylene block copolymer, is melted without being affected by viscosity, that is, with little deformation strain, and then rapidly cooled, a transparent sheet can be formed. , it was discovered that a film could be obtained. Therefore, based on the above facts, we conducted extensive research and discovered a method for stably producing transparent ethylene-propylene block copolymer sheets and films. That is, the main idea is to sequentially fix an opaque sheet or film onto the flat surface of a support with a smooth surface and good heat resistance, heat it together with the support to a temperature above the melting point, and then cool it. . The ethylene-propylene block copolymer that can be made transparent in the present invention is produced by the method described in Japanese Patent Publication No. 44-16668, Japanese Patent Publication No. 55-8011, etc. Ethylene content concentration is 3-40%, preferably 5-30%
%, melt flow index (hereinafter referred to as MFI) is 0.1 to 40g/10min (ASTM-D
- value according to 1238) is preferably 2° or less, and 720
Absorbance ratio of cm- ¹ and 731cm- ¹ , A720/A731 is 0.5
It refers to the above ethylene-propylene block copolymer or a blend with another polyolefin resin containing 50% or more of the above ethylene-propylene block copolymer. In this case, as the polyolefin resin, homopolymers of olefins having 2 to 20 carbon atoms, such as propylene polyethylene, ethylene-propylene random copolymers, polybutene, and ethylene-butene copolymers, and copolymers thereof are used. , These can improve moldability, impact resistance, and the like. In the present invention, it is not necessary to use a specific die to form a sheet or film of ethylene-propylene block copolymer, which is the first step of the process, but a commonly used T-shaped die or circular die can be used. This can be done by using extrusion molding methods, molding methods using calender rolls, etc.
If necessary, it can also be extruded and laminated onto a transparent heat-resistant film such as nylon or polyester. No matter which of the above molding methods is used, as long as the molten material is an ethylene-propylene block copolymer, the resulting sheet or film will be opaque, as described above. Polypropylene/ethylene
In the case of propylene random copolymers, etc., they are transparent when extruded, but ethylene-
When a propylene block copolymer is used, the opaque sheet or film will not become transparent unless some means is applied to it. In the present invention, the opaque sheet or film is made transparent by melting and rapid cooling. We refer to this transparency as the second step of the method. This second step involves placing the extruded sheet or film on a support with a smooth surface;
The method includes a step of heating them above their melting point to melt them, and further includes a continuous cooling step. In order to continuously obtain transparent sheets and films, a support with good heat resistance that can maintain the ethylene-propylene block copolymer in a sheet or film state even in the molten state is needed. is necessary. Supports used in the present invention include sheets with excellent surface smoothness that do not deform at temperatures higher than the melting point of the ethylene-propylene block copolymer;
Film or plate-like substances, such as thin plates and foils made of metal materials such as aluminum or its alloys and stainless steel, as well as plastic films made of acrylonitrile, nylon, polyester, etc., either singly or in composite form. can be used. In addition, in order to fix a sheet or film to the above-mentioned support, it is sufficient to simply press it with a nip roll or the like during heating, or to fix the sheet or film of ethylene-propylene block copolymer to other heat-resistant sheets or films and their composites. When used, the heat-resistant sheet or film is used as a support, and it is completely laminated by a commonly used dry lamination method, extrusion lamination method, or the like. As a method for heating the sheet or film to a temperature above the melting point, it is preferable to use a hot roll, and a thermal oven, an infrared heater, etc. can also be used. Although there are no particular restrictions on the cooling method, the best results can be obtained by cooling with a metal roll. In order to take out the transparent ethylene-propylene block copolymer sheet, film, etc. of the present invention, it is sufficient to separate the molded sheet, film, etc. from the support after cooling, and it is particularly inexpensive to produce commercially. In order to do this, the above-mentioned support is made of a thin stainless steel plate whose surface has been further smoothed by chrome plating, and this is processed into a belt shape and connected endlessly, creating a circulation structure from the hot roll to the cooling roll and back to the hot roll again. It is preferable to use it as Also, other plastic sheets with good heat resistance,
In order to take out a composite with a film or the like, the ethylene-propylene block copolymer may be wound up in a winder together with the plastic sheet or film support. In addition, when the cooled material is heat-treated at a temperature below the melting point for a required period of time, sheets, films, etc. with even higher impact resistance and strength can be obtained. Of course, this is true whether the sheet, film, etc. is a single unit or a composite. In the present invention, the melting point of the ethylene-propylene block copolymer is around 158 to 162 DEG C., so the temperature of the heated film must be higher than the melting point. Further, the cooling is preferably performed at a cooling rate of ΔT≧45°C/sec and at a cooling temperature of 90°C or less. By heat-treating the resulting composite with the vehicle body or support such as a sheet or film at a temperature of 70°C or higher and below the melting point for a required period of time, the single body or composite obtained in the second step can have excellent transparency, etc. It is possible to further improve impact resistance and increase rigidity without impairing the physical properties. The method of heat treatment is preferably a thermal oven. As a result, although it has good heat resistance and good impact resistance, it has a haze value of 50% or more, poor transparency, and whitening phenomenon (deformation of minute sections, that is, whitening due to bending, etc.) For this reason, the uses of ethylene-propylene block copolymer sheets and films, which had low value as packaging materials, are expanding. That is, according to the present invention, in addition to the excellent impact resistance, heat resistance, high rigidity, and easy heat-sealability of the ethylene-propylene block copolymer, transparency and whitening resistance can be imparted to the ethylene-propylene block copolymer, thereby providing a good packaging material. be able to. Next, examples of the present invention and their results will be shown. The samples used in each of the Examples and Comparative Examples were obtained by extruding an ethylene-propylene block copolymer at a die temperature of 250°C and molding the film into a 70μ thick film using a chill roll at a temperature of 30°C. Table 1 shows the physical properties of the film. Example 1 Sample A was fixed on aluminum foil as a support, passed through a hot roll at a temperature such that the surface of the aluminum foil was in contact with the hot roll, and the film temperature was 180°C, and then further heated for 2 seconds. The film and aluminum foil are rapidly cooled by passing through a cooling roll at a temperature such that the film temperature reaches 40°C within 50 minutes. After cooling, the film and aluminum foil are separated from the support and a portion is placed in an oven at 135°C for 5 minutes. Heat treated for minutes.
The results are shown in Table-2. Example 2 In the same process as in Example 1 above, only the temperature of the hot roll was set so that the film temperature was 165° C., and the film was melted. Example 3 In the same process as in Example 1, only the temperature of the cooling roll was set so that the film temperature was 70° C. for cooling. Example 4 In the same process as in Example 1 above, the temperature of the hot roll was set so that the film temperature was 165°C, and the temperature of the cooling roll was set so that the film temperature was 70°C. was melted and cooled. Examples 5 to 7 The procedure was carried out in the same manner as in Example 1, except that the samples shown in Table 2 were used instead of Sample A.
The results shown in 2 were obtained. Comparative Example 1 Example 1 except that the film temperature was 150°C.
The same procedure as above was carried out, and the results shown in Table 2 were obtained. Example 8 The same procedure as in Example 1 was conducted except that Sample A was integrated into a 15 μm thick polyethylene terephthalate film by dry lamination and no aluminum foil was used as a support. The haze value of the laminate after melting and quenching was 18%, and the haze value after heat treatment was 22%, resulting in a composite with good transparency.

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Claims (1)

[Claims] 1. Ethylene content is 3 to 40%, melt flow index is 0.1 to 40 g/10 min, and 720 cm- ^1.
Ethylene-propylene block copolymer with an absorbance ratio A720/A731 of 731cm- ¹ of 0.5 or more or 50% of the above ethylene-propylene block copolymer
An opaque sheet or film with a thickness of 1 mm or less made of a blend with a polyolefin resin containing the above is fixed on a support with a smooth surface and good heat resistance, and b. is heated and melted at a temperature above the melting point. , followed by rapid cooling and then separation from the support. 2 Ethylene content is 3-40%, melt flow index is 0.1-40g/10min, and 720cm- ¹
Ethylene-propylene block copolymer with an absorbance ratio A720/A731 of 731cm- ¹ of 0.5 or more or 50% of the above ethylene-propylene block copolymer
An opaque sheet or film with a thickness of 1 mm or less made of a blend of polyolefin resin containing the above is pasted and fixed on a support with a smooth surface and good heat resistance and transparency, and then heated at a temperature above the melting point. A method for forming a sheet or film of an ethylene-propylene block copolymer, which is characterized by heating and melting the copolymer, followed by rapid cooling to make it transparent and forming a composite with a support. 3 Ethylene content is 3~40%, melt flow index is 0.1~40g/10min, and 720cm- ¹
Ethylene-propylene block copolymer with an absorbance ratio A720/A731 of 731cm- ¹ of 0.5 or more or 50% of the above ethylene-propylene block copolymer
After fixing an opaque ethylene-propylene block copolymer sheet or film with a thickness of 1 mm or less made of a blend with the polyolefin resin containing the above onto a support with a smooth surface and good heat resistance,
The sheet or film obtained by heating and melting at a temperature above the melting point and then cooling is heat-treated at a temperature above 70°C and below the melting point for a required period of time to improve impact resistance. A method for forming a sheet or film of an ethylene-propylene block copolymer, which is characterized by forming a sheet or film with excellent properties and high rigidity.