JPH0331737B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for continuously producing a perforated synthetic resin film having excellent moisture permeability and appropriate water permeability. [Prior Art] Conventionally, methods for producing perforated synthetic resin films include stretching a film to which a filler has been added (Japanese Patent Application Laid-open No. 57-203520), and immersing a film to which a filler has been added in a solvent to remove the filler. Method of elution (Special Publication 1978
-30899), and a method in which a film in which through holes are previously formed with a needle or the like is subjected to electrical discharge treatment (Japanese Patent Application Laid-Open No. 54-58775). [Problems to be solved by the invention] A synthetic resin film that has been stretched with a filler added has fracture holes in multiple layers in the thickness direction.
Since they are continuous and communicate from one side of the film to the other, the synthetic resin film has moisture permeability, but it is not sufficient and has almost no water permeability. Furthermore, when the moisture permeability was improved by increasing the stretching ratio, the sizes of the fractured holes became non-uniform, making it impossible to stably produce a perforated film. Continuous production is difficult in the method of immersing a filler-added film in a solvent. In addition, the method of applying electrical discharge treatment to a film in which through-holes have been previously formed with a needle or the like can only produce large through-holes with diameters of several m/m or more. [Means for solving the problems] The present invention provides a synthetic resin film (hereinafter referred to as a film) to which an inorganic and/or organic filler is added.
By stretching the film by at least 1.05 times in one direction and subjecting the film to a post-discharge treatment that produces break holes, uniform through-holes with a diameter of several tens of microns to several hundred microns are continuously formed. . DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an apparatus for continuous production of a perforated film according to the present invention, and FIG. 2 is a perspective view of an electric discharge treatment apparatus for subjecting the stretched film to electric discharge treatment. In FIG. 1, a film 3 extruded from a forming die 2 provided at the tip of an extruder 1 is preheated to an appropriate temperature with preheating rolls 4 and 5 as necessary, and then vertically with pinch rolls 6 and 7. The film 3 is stretched by a factor of 1.0 or more in the direction of the film 3 to form minute holes. Thereafter, the film 3 is guided between a pair of electrodes 8 and 9 to which a high voltage is applied, which is transmitted from the high voltage generator 10, and subjected to a discharge treatment to form through holes of uniform size. The synthetic resins used in the present invention include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyester, and the like. Fillers added to the film include inorganic fillers such as calcium carbonate, talcum clay, silica, diatomaceous earth, barium sulfate, and titanium oxide, organic fillers such as rice husk powder, starch, wood flour, and pulp powder, or the above-mentioned inorganic and organic fillers. A mixture of fillers is used. The amount of filler added is 20 to 200% by weight of the synthetic resin.
Preferably, if it is less than 20%, the number of breakage holes generated in the film is small and a good perforated film cannot be obtained.
Moreover, if it exceeds 200% by weight, the strength of the film decreases, which is not preferable. The size of the filler is 0.5~
200μ is preferred. The film may be stretched in either one direction or two directions, but unidirectional stretching is preferred because it is easier to operate. The stretching ratio is appropriately determined depending on the size of the filler, the addition rate, and the stretching temperature, but it is preferably in the range of 1.05 to 10 times, and if it is less than 1.05 times, break holes will not occur.
If it exceeds 10 times, the fracture holes will become non-uniform, some will become abnormally large, and the film will be cut, which will reduce workability, which is not preferable. If the film is preheated to an appropriate temperature during stretching, the occurrence of break holes can be suppressed or uneven stretching can be reduced. Furthermore, the density of the through holes in the film can be adjusted by adjusting the density of the terminals 11 of the electrodes 8. Furthermore, when stretching the film to which the filler has been added, the film is partially heated by heating only a portion of the preheating rolls 4 and 5. The heated portion of the film has fewer fracture holes than other portions, and the density of fracture holes within the same film can be varied. [Example] Example 1 A high-pressure polyethylene film with a thickness of 0.06 m/m to which 50% by weight of calcium carbonate with an average particle size of 2 μ was added was preheated to 80°C, stretched twice in one direction, and subjected to electric discharge treatment at a voltage of 14 KV. An effective film with a thickness of 0.03m/m was obtained. Example 2 Thickness with addition of 50% by weight of talc with an average particle size of 5μ
1 after preheating 0.1m/m vinyl chloride film to 80℃
The film was stretched 4 times in the direction and subjected to discharge treatment at a voltage of 14 KV to obtain a perforated film with a thickness of 0.03 m/m. Example 3 A polypropylene film with a thickness of 0.3 m/m to which 25% by weight of rice husk powder with an average particle size of 100 μm was added was made into 135
After preheating to ℃, it was stretched 3 times in one direction and subjected to discharge treatment at a voltage of 14 KV to obtain a perforated film with a thickness of 0.15 m/m. Comparative Examples 1 to 3 The perforated films of Examples 1 to 3 were not subjected to discharge treatment in the manufacturing method as comparative examples corresponding to the respective examples. Table 1 summarizes the manufacturing conditions, moisture permeability, water permeability, etc. of the obtained films for each Example and Comparative Example.

〔Effect of the invention〕

The method for producing a perforated film of the present invention includes stretching a film to which a filler has been added to create break holes;
Since the through-holes are formed by performing a discharge treatment after that, it is possible to continuously form uniform and minute through-holes. Further, due to the synergistic effect of the fracture holes caused by stretching and the through holes caused by discharge treatment, a film can be obtained which has excellent moisture permeability and also has appropriate water permeability.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus for continuous production of a perforated film according to the present invention, and FIG. 2 is a perspective view of an apparatus for subjecting the stretched film to electrical discharge treatment. 3...Synthetic resin film, 4,5...Preheating roll,
6, 7...pinch roll, 8, 9...electrode, 11...terminal.

Claims (1)

[Claims] 1. A synthetic resin film containing 20 to 200% by weight of the synthetic resin of an inorganic and/or organic filler is stretched at least 1.05 times in one direction, and the film is guided between a pair of electrodes to which a high voltage is applied. 1. A continuous manufacturing method for a perforated synthetic resin film, characterized in that through-holes are formed by subjecting it to electrical discharge treatment.