JPH0360304B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a film or sheet using a gas containing fluorine gas as an inert gas in an inflation molding method. More specifically, the present invention relates to a method of modifying a film or sheet at the same time as production by using a gas containing fluorine gas as an blown gas in an inflation molding method. [Prior Art] As is well known, the inflation molding method for a film or sheet involves extruding a material from an annular die of an extruder, pinching the tip of the extruded material with pinch rolls, and blowing air into the inside. This method involves continuously cooling the material while inflating it into an annular tube shape to form a rolled product. Many thermoplastic films or sheets, such as polyethylene and polypropylene, obtained in this manner are often subjected to surface modification such as imparting printability or adhesion, depending on the purpose of use. These surface modification methods include corona treatment, flame treatment, steam treatment, acid treatment, and solvent treatment, but these treatment methods inevitably require the installation of special treatment equipment, and they also require the installation of special treatment equipment. Setting conditions for this process may be complicated, and the surface of the film or sheet may be significantly damaged. In particular, the majority of olefin resins such as polyethylene and polypropylene are manufactured using the inflation molding method, and many of these products are composited with other materials for the purpose of adding cosmetic properties and functionality. surface modification has been carried out. As this surface modification method, corona treatment, which is the simplest of the treatment methods mentioned above (corona, steam, flame, acid, solvent, etc.), is often used.
The degree of surface modification of the film or sheet obtained by this corona treatment method (generally expressed as surface wetting tension) often changes over time and varies, resulting in problems due to insufficient surface modification in some areas. do. [Problems to be Solved by the Invention] The present inventors have arrived at the present invention as a result of intensive study on how to easily and efficiently surface-treat a film or sheet obtained by an inflation molding method. . [Means for Solving the Problems] That is, the present invention facilitates surface modification by using a mixed gas containing an inert gas and a fluorine gas as the blown gas during the inflation molding method. The present invention is directed to a method for obtaining films and sheets. It is known to modify the properties of resin surfaces with fluorine gas. The present invention is characterized in that the resulting film or sheet is modified at the same time as inflation molding, without requiring the installation of special processing equipment for modifying the film or sheet as described above. There is. In inflation molding, the annular tube immediately after being extruded from the extrusion die is in a softened state due to heat, and the present invention also shows that when brought into contact with fluorine gas in this state, the surface of the resin is modified extremely smoothly. This is one of the characteristics of Thermoplastic resins manufactured using the inflation molding method include olefin resins such as polyethylene and polypropylene, vinyl chloride resins, polyamide resins, ionomer resins,
Examples include 1,2 polybutadiene and polystyrene resins, as well as modified resins of these thermoplastic resins and polymers with other monomers. Of course, these resins are also used in the present invention. The mixed gas used in the present invention can be an inert gas containing 0.1 to 20% by volume of fluorine (valve inlet concentration...the same applies hereinafter), and more preferably 0.1 to 10% by volume of fluorine. It is a gas that If the fluorine concentration is less than 0.1% by volume, the effect of surface modification of the film or sheet in this production method will be small and the degree of modification will be non-uniform. Films or sheets obtained by increasing the fluorine concentration can maintain high surface wetting tension for a long period of time, but if the concentration becomes higher than necessary, the resin may be burnt out by the fluorine gas. The tendency to increase significantly. In the present invention, during resin inflation processing, the fluorine gas in the gas blown into the bubble is gradually consumed over time, but the amount of gas at the bubble inlet,
By adjusting the amount of exhaust gas, it can be kept almost constant. In the present invention, the contact time between the gas containing fluorine gas and the sheet or film is determined depending on the desired degree of surface modification, but usually the above-mentioned gas concentration and tension speed of the annular tube (valve) are determined. This is done by adjusting. Further, the inflation method used in the present invention is not particularly limited, and may be a commonly used method as described above. That is, the resin that has been heated to a temperature above the softening point of the resin constituting the sheet or film (usually at a temperature of about 10 to 30 degrees Celsius above the softening point) is heated to a molten state, and then passed upward or downward through an annular die. This is a method of extruding, blowing gas into the inside to form a valve, and then cooling it with air or water cooling to form a film or sheet. The thickness of the film or sheet obtained is
It is 10μ to 150μ. [Effects of the Invention] The present invention can be carried out simply by using a fluorine-containing gas as the blowing gas.
Furthermore, since the surface wetting tension of the film or sheet obtained by the surface modification method of the present invention maintains the same surface wetting tension immediately after production for a long period of time, problems due to insufficient surface modification will not occur. [Example] Next, the present invention will be explained in more detail with reference to Examples. EXAMPLE The inflation method was carried out using the apparatus shown in the flow sheet of FIG. Table 1 shows the resins used in this test and the inflation processing conditions. Table 2 shows the gases used. The operation was performed as follows. The resin melted by the extruder 4 was extruded from the annular die 5, and the resulting tube-shaped film was held between nip rolls 10 and wound up by the winder 7. As the blowing gas, gas from the gas storage tank 2 was introduced from the center of the die 5 through an automatic valve 17 using a pump 13. When the gas was introduced, the molten resin expanded and became bubbles 6. After the bubble 6 had a certain width and a certain thickness, it was cut with a cutter 11 and wound up with a winder 7. When a fluorine mixed gas was used as the blowing gas (Examples 1 to 5, Comparative Example 1), the gas pump 13, exhaust gas pump 14, and bubble diameter detector 8 were linked to adjust the bubble diameter to be constant. The gas discharged from the exhaust gas pump 14 was sent to the exhaust gas treatment device 3 through an automatic valve 18 for treatment. Also, when using air as the blowing gas (Comparative Example 2)
-4) Adjusted the bubble diameter detector 8 and pump 13 to keep the bubble diameter constant. Materials for Examples 1 to 5 and Comparative Examples 1 to 4 were created under the above conditions. For comparison, a film was prepared by the above-mentioned processing method using air e) using resin A, and a corona treatment machine 9 was used to perform surface treatment (Comparative Example 5). Table 3 shows the results of measuring the surface wetting tension of Examples 1 to 5 and Comparative Examples 1 to 4 based on JIS K6768, and the results regarding surface discoloration. Table 4 shows changes over time in surface wetting tension of Example 4 and Comparative Example 5.

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【table】 [Brief explanation of drawings]

FIG. 1 is a flow diagram showing one embodiment of an apparatus implementing the present invention. In the figure, 1 is an air storage tank, 2 is a fluorine mixed gas storage tank,
3 is an exhaust gas treatment device, 4 is an extruder, 5 is a die,
6 is a bubble, 7 is a winder, 8 is a bubble diameter detector,
9 is the corona treatment machine used in the comparative example, 10 is Nipprol, 11 is the cutter, 12 is the air pump, 1
3 is a mixed gas pump, 14 is an exhaust gas pump, 15
16 is an air exhaust gas pump, 16 is an air automatic valve, 17 is a mixed gas automatic valve, and 18 is an exhaust gas automatic valve.

Claims (1)

[Claims] 1. A method for producing a modified film or sheet using an inflation molding method, characterized in that a mixed gas containing an inert gas and a fluorine gas is used as the blown gas. .