JPH0413368B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hydrophilic film obtained by graft polymerizing a hydrophilic unsaturated monomer to a hydrophobic polymer such as polyethylene, polypropylene or polyethylene terephthalate in the presence of ionized gas plasma, and a method for producing the same. Hydrophobic polymers such as polyethylene, polypropylene and polyethylene terephthalate are used in a wide range of fields as extremely important substrates.
However, when these base materials are used as films, because they are hydrophobic, they tend to generate static electricity, are prone to static electricity problems such as dust adhesion, tend to fog up in humid areas, and have poor printing performance. It is well known to those skilled in the art that they also have drawbacks such as lack of adhesion. As a method to improve these drawbacks, for example, organic polymers are irradiated with ionizing radiation in the air to generate peroxide groups, and then the peroxide groups are cleaved when brought into contact with a vinyl compound. A method for obtaining a graft copolymer has been proposed. In addition, in Japanese Patent Publication No. 50-6490, organic polymers are exposed to 2000 ml of water in an air or oxygen atmosphere.
A method is disclosed in which a graft copolymer is obtained by irradiating ultraviolet rays mainly having a wavelength shorter than Å to generate peroxide groups, and then contacting with a polymerizable vinyl monomer. Furthermore, in Japanese Patent Application Laid-Open No. 19384-1984, organic polymers are
We have proposed a method in which the material is treated with high-voltage discharge under gas pressure, exposed to oxygen gas, and then immersed in a vinyl monomer solution for graft polymerization. However, the method using ionizing radiation mentioned above still has some problems from an industrial standpoint in terms of safety of irradiation operation and cost of irradiation, and the second and third methods still have some problems. Also, active species are created in organic polymers by ultraviolet rays or high voltage discharge, but instead of directly reacting with vinyl monomers, they are first reacted with oxygen to form peroxides, and then reacted with vinyl monomers. If oxygen is present during the reaction, the progress of the reaction is slow and the process is complicated, such as replacing the reaction with a vacuum or nitrogen atmosphere, making it industrially difficult. Moreover, in either method, the degree of polymerization of the grafted polymer is within the range of radical polymerization, and when the peroxide is cleaved, some homopolymers do not graft onto organic polymers unrelated to graft polymerization. Problems remain in terms of effectiveness and efficiency, such as generation. The present inventors have completed the present invention as a result of intensive study and research in order to eliminate the conventional defects. An object of the present invention is to provide a method for producing a film with excellent hydrophilicity, and another object of the present invention is to provide a hydrophilic film with excellent water absorption, adhesiveness, reactivity, ion exchange property, aggregation property, or metal collection property. To provide a manufacturing method. Still another object is to provide a method for manufacturing such a hydrophilic film industrially easily and at low cost. In the method of the present invention, a film made of a hydrophobic polymer and a gas of a hydrophilic unsaturated monomer and/or a gas of an aqueous solution of the monomer are treated with ionized gas plasma under deoxidized conditions, and then the film is is immersed in an aqueous solution of the monomer and polymerized in the absence of the plasma. The hydrophobic film applied to the present invention may be any film made of a hydrophobic polymer, but from the viewpoint of quality and cost, a hydrophobic film made of polyethylene, polypropylene or polyethylene terephthalate is preferred. The hydrophilic unsaturated monomer is not particularly limited as long as it has a vinyl group or an allyl group and is hydrophilic and can be subjected to normal radical polymerization. Generally acrylamide, methacrylamide,
N-vinylpyrrolidone, acrylic acid, methacrylic acid, P-styrenesulfonic acid, vinylsulfonic acid, 2-methacryloyloxyethylsulfonic acid, 3-methacryloyloxy-2-hydroxypropylsulfonic acid, allylsulfonic acid, methacrylsulfonic acid , and the ammonium salts and alkali metal salts of these acids, dimethylaminoethyl acrylate, dimethylaminomethacrylate, diethylaminoethyl acrylate and diethylaminoethyl methacrylate, 2-vinylpyridine and 4-vinylpyridine of hydrochloric acid, nitric acid, dimethyl sulfate, diethyl sulfate or It is a quaternized product of ethyl chloride. Preferred hydrophilic unsaturated monomers include acrylic acid, methacrylic acid, 2hydroxyethyl methacrylate, 2hydroxyethyl acrylate, acrylamide, methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N,N dimethylaminoethyl methacrylate, or N , N dimethylaminoethyl acrylate. Further, the graft polymerization rate in the graft polymerization in the present invention can be freely varied depending on the purpose and use, but is preferably at least 0.1% by weight, preferably 0.5% by weight or more, based on the hydrophobic polymer forming the film. The graft polymerization rate of the hydrophilic film of the present invention can be varied over a wide range depending on the purpose. For example, when improving wettability, adhesion, printability, or coating properties, the graft polymerization rate is 0.1 to 5% by weight, ion exchange ability, and hygroscopicity. Or, when imparting reactivity or when used as a battery diaphragm, the graft polymerization rate is several percent by weight to 100 percent by weight, and when imparting water absorption, ion exchange, aggregation, or metal trapping ability, the graft polymerization rate is several tens of percent. 1000% by weight is used. Of course, it is also possible to use several thousand percent by weight exceeding this range. The polymerization in the present invention is so-called plasma initiated polymerization. That is, plasma-initiated polymerization is one in which a non-equilibrium ionized gas plasma is used to initiate polymerization or create active species, and most of the polymerization is completed in the absence of plasma. Generation of an ionized gas plasma can be accomplished by any of the known methods for generating plasma. For example, J. R. Hollahan and A. T. Bell, “Applied Techniques of Plasma Chemistry”, Wiley, New York 1974 and M. Shen.
Edition “Plasma Chemistry of Polymers” Detzker. New York. Listed in 1976. That is, the monomer can be placed under vacuum between parallel plate electrodes connected to a high frequency generator, and the plasma can be generated using the parallel plates either outside or inside the vacuum chamber.
Alternatively, an electric field may be created by an external induction coil to generate a plasma of ionized gas, or a plasma may be generated by placing oppositely charged electrodes spaced apart directly into a vacuum chamber. In the present invention, polymerization of a film made of a hydrophobic polymer and a gas of a hydrophilic unsaturated monomer and/or a gas of an aqueous solution of the monomer is started in the presence of ionized gas plasma under deoxygenation, Thereafter, the film is immersed in an aqueous solution of the monomer to perform graft polymerization on the film in the absence of the plasma. Instead of polymerizing with an aqueous solution of a hydrophilic unsaturated monomer in the absence of an ionized gas plasma, an emulsion or an organic solvent solution in or of the monomer may be used. To explain the method of the present invention in more detail, degassing is performed at ¹⁰⁰
A film made of a hydrophobic polymer is irradiated with plasma using the above method at a pressure of ~10 ^-4 Torr. Glow discharge is preferably performed at 20 to 200 watts, more preferably 40 to 100 watts, to generate active species in the hydrophobic polymer. The irradiation time is usually 1 to 3600 seconds, preferably 1 to 1800 seconds. After plasma irradiation, when the film is polymerized in an aqueous solution of a hydrophilic unsaturated monomer in the absence of the plasma, the monomer begins to be consumed by the active species of the film. , so-called graft polymerization proceeds. Post-polymerization temperature and time vary depending on the type of monomer used and are not particularly limited, but usually the temperature is 1~
A temperature of 60°C for 1 to 25 hours is sufficient. Depending on the type of monomer, if the temperature exceeds 60°C, thermal polymerization may occur and low-molecular polymers may also be produced, so care must be taken. The thus obtained graft polymerization compound of the hydrophilic unsaturated monomer onto the hydrophobic film has a straight chain hydrophilic polymer having a high degree of polymerization grafted onto the surface of the film. Its properties are modified and used for various purposes. For example, when 24% by weight of acrylic acid is grafted onto polyethylene using the method of the present invention, the contact angle of water is higher than that of untreated polyethylene.
It can be seen that the angle is significantly improved from 101° to 56°. Furthermore, the film of the present invention graft-polymerized using acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc. contains Cu ²⁺ , Co ²⁺ , Cr ³⁺
Since it instantly adsorbs metal ions such as, it is also useful as a metal trapping film. The present invention will be explained in detail below with reference to Examples. In the Examples, the grafting rate and water contact angle were measured by the following methods. a Grafting rate Grafting rate is calculated by weight after drying by washing the grafted film with stirring in a good solvent for 2 days to completely remove unreacted monomers and homodipolymer Grafting rate (%) = After treatment Film weight - Initial film weight / Initial film weight x 100 b Water contact angle Measured using Kyowa Kagaku Co., Ltd. contact angle type CA-P. Examples Example 1 A monomer aqueous solution prepared by dissolving the hydrophilic monomers shown in Table 1 in distilled water to a monomer concentration of 50% by weight was placed in one of the test tubes with two forked legs, and the other leg was filled with a monomer aqueous solution prepared by dissolving the hydrophilic monomers shown in Table 1 in distilled water to a monomer concentration of 50% by weight. A polyethylene film having a square shape with a thickness of 50 μm and a side of 50 mm was put in, first the vacuum was applied to about 1 Torr, the aqueous solution was immersed in liquid nitrogen to cool it down sufficiently, and then the vacuum was removed to a high vacuum of 10 ^-4 Torr. Gradually return to room temperature while maintaining vacuum to push out oxygen in the aqueous solution. This operation is repeated three times to sufficiently remove oxygen from the aqueous solution. Next, while maintaining the vacuum, the aqueous solution was sufficiently cooled with liquid nitrogen, and the solution was drawn to a high vacuum of 10 ^-4 Torr.
Next, the aqueous solution is taken out from liquid nitrogen and the vacuum level is
Wait until the temperature reaches 10 ^-1 torr, insert the end with the film between two copper electrode plates connected to a 13.56MHz high frequency generator, and generate plasma at 100W output at 90MHz.
Generates and irradiates for seconds. Thereafter, the aqueous solution was dissolved and transferred to the film side through a branch pipe. Then, post-polymerization was carried out at 25° C. for 12 hours while the aqueous solution was in full contact with the film. The obtained graft film was washed with water for 2 days with stirring, the solvent was removed, and dried to prepare a sample, and the contact angle of water was measured. The results are shown in Table 1.

[Table] Sulfonic acid Example 2 When 10 grams of the acrylamide grafted polyethylene film obtained in Example 1, No. 3 was immersed in 200 ml of a suspension of 10 grams of benite in 1000 ml of water, it became suspended after 15 minutes. The liquid became clear and it was found that this polyethylene film had flocculating ability for bentonite. The ungrafted film showed no aggregation ability. Example 3 Dry acrylic acid obtained in Example 1, No. 8/
3 grams of AMPS-grafted polyethylene film was immersed in 1500 ml of water for 12 hours, then taken out of the water, lightly touched with a rolling paper to remove water droplets on the surface, and weighed.The film weighed 840 grams. This revealed that this film had the ability to absorb approximately 280 times more water. The ungrafted polyethylene had no water absorption capacity at all. Example 4 Using the same equipment as in Example 1, a polyethylene film in 10 ^-3 Torr was irradiated with plasma at an output of 100 W for 90 seconds, and then a 60% by weight aqueous acrylic acid solution was added and graft polymerized for 15 hours. The resulting graft polymerization rate was 275%. When 0.71 g of the graft film was immersed in 50 ml of a 6.2×10 ⁻³ molar aqueous solution of Cu ⁺² , about 57% of Cu ²⁺ was adsorbed.

Claims (1)

[Claims] 1. A film made of a hydrophobic polymer and a gas of a hydrophilic unsaturated monomer and/or a gas of an aqueous solution of the monomer are treated with ionized gas plasma under deoxidation, and then immersing the film in an aqueous solution of the monomer in the absence of the plasma;
1. A method for producing a hydrophilic film in which a hydrophilic unsaturated monomer is graft-polymerized onto the film. 2. The method according to claim 1, wherein the hydrophobic polymer is polyethylene, polypropylene or polyethylene terephthalate. 3 The hydrophilic unsaturated monomer is acrylic acid, methacrylic acid, 2hydroxyethyl methacrylate, 2hydroxyethyl acrylate, acrylamide,
2. The method according to claim 1, which is methacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N,N dimethylaminoethyl methacrylate or N,N dimethylaminoethyl acrylate. 4. The method according to claim 1, wherein the ionized gas plasma is obtained by irradiation at 20 to 200 Watts for 1 to 3,600 seconds under a vacuum of ¹⁰⁰ to 10 ^-4 Torr. 5. The method according to claim 1, wherein the ionized gas plasma is obtained by irradiation at 40 to 100 Watts for 10 to 1800 seconds under a vacuum of 10 ^-1 to ^{10 -4} Torr. 6. The method according to claim 1, wherein the polymerization rate in the polymerization in the presence of ionized gas plasma is 5% by weight or less. 7. The method according to claim 1, wherein the postpolymerization in the absence of ionized gas plasma is carried out at 60° C. or lower. 8. The method according to claim 1, wherein the polymerization rate of the graft polymerization is at least 0.1% by weight based on the hydrophobic polymer forming the film.