JPH0138137B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing films and other molded products with excellent hydrophilicity. It is known that hydrophilicity can be imparted to a hydrophobic thermoplastic resin by mixing and melt-molding a hydrophilic resin with a hydrophobic thermoplastic resin. However, with this method, (1) hydrophilicity as expected from the amount added is not achieved. This is probably because the surface of the molded product is richer in hydrophobic thermoplastic resin than expected based on the mixing ratio. (2) Therefore, in order to impart the desired hydrophilicity, it is necessary to blend a considerably large amount of hydrophilic resin, which is disadvantageous in terms of cost, melt moldability, and strength of the molded product. (3) No effect beyond the hydrophilic properties originally possessed by hydrophilic resins could be expected, and there was a limit to the imparting of hydrophilic properties. Generally, the surface resistivity of hydrophobic thermoplastic resin is
For example, 50 parts by weight of polypropylene with a surface resistivity of 5 x ^{10 15 Ω} , an ethylene content of 32 mol% ^, and a saponification degree of the vinyl acetate component of 98 Ω.
Even if 50 parts by weight of saponified ethylene-vinyl acetate copolymer of mol % is added, the resistance decreases only to the order of 10 ¹³ Ω. However, as a result of extensive research, the present inventor found that the hydrophobic thermoplastic resin (A) contained 99 to 60 parts by weight and the ethylene content
15-55 mol%, saponification degree of vinyl acetate component 30-99
Mol%, and sodium salt as sodium 10
1 to 40 parts by weight of saponified ethylene-vinyl acetate copolymer (B) containing ~500 ppm is mixed and melt-molded, and then the resulting molded product is brought into contact with an aqueous solution of a surfactant to form a molded product. The inventors discovered that an excellent hydrophilic molded product can be obtained when a portion of (B) is removed from the material, leading to the completion of the present invention. By improving hydrophilicity, hydrophobic thermoplastic resin has antistatic properties, dust adhesion prevention properties, antifogging properties, wettability,
Printability, vacuum deposition properties, etc. are improved, and the appearance of the molded product becomes elegant with a faded appearance, and the texture is also favorable. The reason for such remarkable hydrophilicity is not necessarily clear, but it may be due to an increase in the exposed area of the saponified ethylene-vinyl acetate copolymer or adsorption of surfactants to the surface of the molded product. It is thought that it may contribute to imparting hydrophilicity. The hydrophobic thermoplastic resin (A) in the present invention includes low, medium, and high density polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer,
Ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, ethylene-unsaturated alboxylic acid copolymer, ionomer, polypropylene, propylene-ethylene copolymer, polybutene, polypentene, ethylene-vinyl acetate with high ethylene content Polyolefins such as saponified copolymers, modified polyolefins obtained by graft-modifying these polyolefins with derivatives such as unsaturated carboxylic acids or their anhydrides, polyamides, polyesters, polycarbonates, styrene polymers, acrylonitrile polymers, vinylidene chloride Examples include polymers. These can also be used in combination of two or more types. As the saponified ethylene-vinyl acetate copolymer (B), one having an ethylene content of 15 to 55 mol% and a degree of saponification of the vinyl acetate component of 30 to 99 mol% is used.
There is no problem in using a mixture of two or more types with different compositions. When the ethylene content is less than 15 mol%, the heat resistance during melt molding is poor, resulting in a lack of long-term moldability, and when it exceeds 55 mol%, hydrophilicity is insufficient and it is difficult to obtain the desired hydrophilic molded product. I can't. Furthermore, if the degree of saponification of the vinyl acetate component is less than 30 mol% or exceeds 99 mol%, the effect of imparting hydrophilicity is insufficient. A particularly preferred range of the degree of saponification of the vinyl acetate component is 50 to 98 mol%. In addition to the components of ethylene and vinyl acetate (or saponified vinyl alcohol), α-olefins having 3 or more carbon atoms, unsaturated carboxylic acids or esters thereof,
It may also contain small amounts of other components such as derivatives such as nitriles, amide anhydrides, salts, unsaturated sulfonic acids or salts thereof. In the present invention, it is essential that the saponified ethylene-vinyl acetate copolymer (B) contains a small amount of sodium salt, which further improves the hydrophilicity of the molded product after contacting with the surfactant aqueous solution. do. Sodium salts for such purposes include sodium acetate, sodium propionate, sodium tartrate, sodium malate, sodium citrate, sodium oxalate, sodium lactate, sodium dihydrogen phosphate, sodium hydrogen sulfate,
Examples include sodium chloride. The content of such sodium salt is 10 to 500 ppm as sodium based on the saponified ethylene-vinyl acetate copolymer.
In particular, it is desirable that the content be between 30 and 500 ppm.
If the content is too large, the thermal stability will be poor when melt-molding the resin mixture. Methods for incorporating the above sodium salt into the saponified ethylene-vinyl acetate copolymer (B) include adding the sodium salt to (B) in powder or solution form, and adding the sodium salt to the slurry of (B). (B) A method of adding sodium salt at a certain stage of the polymerization-saponification-post-treatment-drying process for production; A method in which an alkaline compound containing sodium is used as a saponification catalyst, sodium acetate is produced as a by-product during the saponification reaction, and then the content of sodium acetate is adjusted in a washing step, or saponified particles are produced after producing sodium acetate as a by-product. A method of converting it into the sodium salt of the acid through acid treatment with phosphoric acid, sulfuric acid, etc. is adopted. The mixing ratio of the hydrophobic thermoplastic resin (A) and saponified ethylene-vinyl acetate copolymer (B) should be selected from the range of (A) 99 to 60 parts by weight and (B) 1 to 40 parts by weight. ,
If the mixing ratio of (B) is too low, the desired effect of imparting hydrophilicity will not be achieved, while if the mixing ratio of (B) is too high, the inherent properties of the hydrophobic thermoplastic resin (A) will be impaired. . The mixture of hydrophobic thermoplastic resin (A) and saponified ethylene-vinyl acetate copolymer (B) further contains fillers, colorants, glass fibers, plasticizers, stabilizers, lubricants, blowing agents, and antistatic agents. Known additives such as these may also be blended. The mixture of (A) and (B) above is subjected to melt molding. The melt molding temperature is selected from a range of about 150 to 300°C. Molded products having shapes such as films, sheets, filaments, containers, etc. are obtained by melt molding. Next, in the present invention, by bringing the molded article obtained above into contact with an aqueous solution of a surfactant,
Remove part of (B) from the molding process. As the surfactant, nonionic, cationic or anionic surfactants are used, and it is particularly preferable to use anionic surfactants. Examples of anionic surfactants include alkyl sulfates, alkyl sulfonates, alkylbenzenesulfonates, dialkyl sulfonates, alkali fatty acid salts, alkylnaphthanesulfonates, alkylphenolsulfonates, rosin soaps, and the like. The concentration of the surfactant in the surfactant aqueous solution is not particularly limited, but it is usually set in the range of 0.1 to 20% by weight. Incidentally, the surfactant aqueous solution may contain a substance effective in dissolving (B), such as phenol, alcohol, formaldehyde, and N-methylpyrrolidone. Contact between the molded product and the surfactant aqueous solution is carried out by immersion,
This can be done by any means such as coating or showering. Although the temperature of the aqueous solution at the time of contact is arbitrary, it is efficient to heat the aqueous solution to 45 to 95°C and contact the molded article. The contact is continued until a part of the saponified ethylene-vinyl acetate copolymer (B) in the molded product is removed. Usually 0.01 to 50% by weight of (B) in the molded article, especially 0.1
~20% by weight may be removed. The molded article after contact with the surfactant aqueous solution is washed as necessary. In the present invention, a part of the saponified ethylene-vinyl acetate copolymer (B), which is a hydrophilic component, is removed from the molded product, and even though the proportion of (B) in the molded product is reduced, The unexpected effect is that the hydrophilicity of the molded product after contact is significantly improved. Next, the method of the present invention will be further explained with reference to Examples. In the following, "parts" and "%" are expressed on a weight basis unless otherwise specified. Note that measurements in the following experimental examples were performed in the following manner. Transparency was determined by measuring haze using a reflection transmittance meter RM-15A manufactured by Murakami Color Research Institute. Surface resistivity is measured at 20℃ according to JISK6911.
Measurements were made in an atmosphere with relative humidity of 65%. The contact angle was measured using a goniometer type contact angle measuring device manufactured by Elma Optical Co., Ltd., and water was used as the droplet. Example 1 A: Low density polyethylene with a melt index of 2 and a density of 0.922 B: A saponified ethylene-vinyl acetate copolymer with an ethylene content of 25 mol% and a degree of saponification of the vinyl acetate component of 92 mol%, containing 180 ppm of sodium acetate and
Contains 250 ppm sodium dihydrogen phosphate (total 118 ppm as sodium) Mix 92 parts of the above resin A and 8 parts of resin B.
Supplied to a 40m/m diameter extruder (L/D=28, with full-flight screw), melted and kneaded at a cylinder metering temperature of 220℃ and extruded from a T-die at a temperature of 210℃ to a width of 300m/m. , a film with a thickness of 60μ was obtained. This film will be referred to as a non-contact film. Next, this uncontacted film was placed in a 10% aqueous solution of sodium n-dodecylbenzenesulfonate at a temperature of 65°C.
It was immersed at ℃ for 1 minute to elute and remove an amount equivalent to 3% of the resin B, and then dried. The film thus obtained will be referred to as a contact film. The results of examining the properties of both films are shown in Table 1, and it can be seen that the surface resistivity is surprisingly reduced despite the small amount of resin B blended.

[Table] Examples 2 to 4, Comparative Example 1 A: Low density polyethylene used in Example 1 B: A saponified ethylene-vinyl acetate copolymer having the same copolymer composition as Example 1, containing sodium acetate and diphosphoric acid. Hydrogen-sodium as sodium
20ppm (Example 2), 200ppm (Example 3),
Containing 450 ppm (Example 4) and 5 ppm (Comparative Example 1) An uncontacted film and a contacted film were produced in the same manner as in Example 1, except that a mixture of 92 parts of resin A and 8 parts of resin B was used. The results are shown in Table 2.

【table】

[Table] Comparative Example 2 When the same experiment as in Example 1 was conducted using a saponified ethylene-vinyl acetate copolymer containing 550 ppm of sodium acetate and dihydrogen-sodium phosphate as sodium, the following results were obtained. The film had a marked yellow coloration and was of poor practical use. Example 5 A: Polyethylene terephthalate B: Saponified ethylene-vinyl acetate copolymer used in Example 1 85 parts of the above resin A and 15 parts of resin B were mixed and supplied to an extruder, and melt-kneaded at a temperature of 270°C. temperature 270
℃ extrusion through a T-die, then the obtained film was sequentially biaxially stretched 3.5 times vertically and 3.5 times horizontally at a temperature of 180℃, and heat-set at a temperature of 190℃ to obtain a stretched film with a thickness of 20μ. Ta. This film was placed in a 6% aqueous solution of sodium monobutylphenol monosulfonate at a temperature of 77°C.
It was immersed for 1.5 minutes to elute an amount equivalent to 1.4% of resin B, and then dried. The results are shown in Table 3.

[Table] Example 6 A: Isotactic polypropylene with melt flow 3 B: Saponified ethylene-vinyl acetate copolymer with ethylene content of 38 mol% and degree of saponification of vinyl acetate component of 88 mol%, containing 75 ppm of acetic acid as sodium. Materials containing sodium Mix 75 parts of the above resin A and 25 parts of resin B, feed it to an extruder, melt and knead it at a temperature of 200°C, and heat it to a temperature of 190°C.
It is extruded into a filament from a die at 145°C, and the resulting filament is stretched at a temperature of 145°C to a certain thickness.
A drawn filament of 800 denier was obtained. This filament was placed in a 15% aqueous solution of sodium n-hexadecylbenzenesulfonate at a temperature of 60°C.
The resin was immersed in water for 5 minutes to elute an amount equivalent to 0.8% of the resin B, and then dried. When the frictional voltage between the filament and Tetron taffeta was measured using a rotary static tester manufactured by Koa Shokai Co., Ltd., the following results were obtained. A single filament 6500V Uncontacted filament 4000V Contacted filament 550V Example 7 A: Sodium type ionomer (Surlyn 1707 manufactured by Dupont) B: Ethylene-acetic acid with 20 mol% ethylene content and 75 mol% saponification degree of vinyl acetate component A saponified vinyl copolymer containing 280 ppm of sodium dihydrogen phosphate as sodium. 65 parts of the above resin A and 35 parts of resin B were mixed and fed to an extruder, melted and kneaded at a temperature of 190°C, and then heated to a temperature of 180°C.
Extruded into a film from a die at ℃, width 300m/m,
A film with a thickness of 30μ was obtained. This filament is then coated with 15 ml of naphthenic acid soap.
% aqueous solution at a temperature of 50°C for 0.5 minutes.
After eluting 6.5% of it, it was dried. The results are shown in Table 4.

[Table] Example 8 A: Isotactic polypropylene with melt flow 5 B: Saponified ethylene-vinyl acetate copolymer with an ethylene content of 38 mol% and a degree of saponification of the vinyl acetate component of 65 mol%, containing 175 ppm of citric acid as sodium. 95 parts of the above resin A and 5 parts of resin B are mixed and fed to an extruder, melted and kneaded at a temperature of 210°C, and then heated to a temperature of 200°C.
It was extruded into a tape shape through a die at ℃ to obtain a tape with a width of 80 m/m and a thickness of 75 μm. Next, this tape was placed in a 5% aqueous solution of sodium n-hexadecylbenzenesulfonate at a temperature of 50°C.
The resin was immersed in water for 1 minute to elute 15% of the resin B, and then dried. The results are shown in Table 5.

【table】

Claims (1)

[Claims] 1 Hydrophobic thermoplastic resin (A) 99 to 60 parts by weight, ethylene content 15 to 55 mol%, degree of saponification of vinyl acetate component
1 to 40 parts by weight of a saponified ethylene-vinyl acetate copolymer (B) containing 30 to 99 mol% and 10 to 500 ppm of sodium salt as sodium is mixed and melt-molded, and then the resulting molded product is melt-molded. A method for producing a hydrophilic molded article, which comprises removing a portion of (B) from the molded article by bringing it into contact with an aqueous solution of an activator.