JPS6412300B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a surface-modified resin molded article. More specifically, the present invention relates to a method for producing a molded article whose purpose is to impart antifogging properties to the surface of a thermoplastic resin molded article and maintain this antifogging property over a long period of time. Conventionally, various thermoplastic resins have been industrially manufactured and used in a wide range of fields. Many of the molded products made from these thermoplastic resins have hydrophobic surfaces, so the temperature at which the molded product is used,
Depending on conditions such as humidity, the surface may become cloudy.
This has caused various inconveniences. For example, goggles, safety masks, etc. that use synthetic resin lenses may become cloudy, making it difficult to see, and food packaging films may become cloudy, making it difficult to see the contents. In addition, agricultural films used in greenhouses are cloudy, which impairs the penetration of sunlight, slowing down plant growth, and causing water droplets to fall on cultivated plants, damaging young shoots. It may cause the outbreak of diseases. In order to eliminate such inconveniences, it is known that antifogging properties may be imparted to the surface of thermoplastic resin molded articles. In order to impart antifogging properties to the surface of a thermoplastic resin molded product, a hydrophilic substance such as a surfactant may be kneaded into the thermoplastic resin to form a molded product, or the surface of the molded product may be coated with A method of applying a hydrophilic substance or a water-soluble polymer has been adopted. However, in the former method, the hydrophilic substance kneaded into the thermoplastic resin exudes onto the surface of the molded product and coordinates, giving the molded product antifogging properties, but it is washed away by water. The drawback is that the antifogging properties deteriorate over time. On the other hand, in the latter method, the applied hydrophilic substance or water-soluble polymer is easily soluble in water, so it exhibits excellent antifogging properties immediately after application, but it is easily washed away by water and deteriorates over time. Along with this, the antifogging property decreases. In order to solve this problem, attempts have been made to reduce the solubility of hydrophilic substances or water-soluble polymers in water, but this also reduces the antifogging properties themselves. This cannot be said to be a satisfactory improvement method. In addition, a method has been proposed in which a water-soluble polymer applied to the surface of a molded article is crosslinked to reduce its solubility in water. However, this method is only applicable to water-soluble polymers with specific structures.
After coating the surface of the molded article, a crosslinking reaction must occur on the coated surface, which makes the process complicated and is not a preferred method. Under such circumstances, the present inventors have provided an industrially advantageous method for imparting antifogging properties to the surface of a thermoplastic resin molded product and maintaining this antifogging property over a long period of time. It was completed as a result of intensive study. However, the gist of the present invention is to form a film of an anionic polymer electrolyte that is insoluble in water and soluble in organic solvents on the surface of the molded product when producing a surface-modified resin molded product. , a method for producing a surface-modified resin molded article, which comprises adsorbing a positively charged inorganic colloidal sol onto the film. Hereinafter, the present invention will be explained in detail. In the present invention, resins include polyethylene, polypropylene,
It refers to thermoplastic resins such as polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polycarbonate, polyamides, polyacetal, and polyesters, but is not limited to these examples. In the present invention, the molded product may be any molded product made of the above thermoplastic resin, and there are no restrictions on the shape, dimensions, etc. of the molded product. Among molded products, films, sheets, plates, etc. are preferred because the present invention can be easily applied thereto. In the present invention, first, a film of an anionic polymer electrolyte that is insoluble in water and soluble in organic solvents is formed on at least one surface of a thermoplastic resin molded article. This anionic polymer electrolyte film functions to adsorb a cationic polymer electrolyte, which will be described later. It is necessary to select an anionic polymer electrolyte that is insoluble in water but soluble in organic solvents. If it is soluble in water, it will dissolve in water and be washed away, making it impossible to maintain the antifogging properties of the molded product, which is undesirable.If it is not soluble in organic solvents, it will form a film on the surface of the molded product. This is because it is difficult. Generally, what is called a polymer electrolyte is
It is a polymer substance with many ionizable groups, and when dissolved in water, it dissociates into highly charged polymer ions and low molecular ions. Polyelectrolytes with many ionizable groups are soluble in water but insoluble in common organic solvents. When such a polymer electrolyte is applied to the surface of a molded article, it dissolves in water adhering to the surface of the molded article and is washed away. Even in the case of polymer electrolytes, reducing the number of ionizable groups causes a large change in the solubility of the material in solvents, and the solubility of certain organic solvents that are insoluble in water, such as polar solvents, or the compatibility between polar solvents and water. It exhibits the property of being soluble in mixtures, etc., and exhibits the characteristics of a polymer electrolyte in these solvents. Anionic polymer electrolytes that are insoluble in water and soluble in organic solvents can be produced by any of the following methods. (1) A method of copolymerizing a monomer with an anionic ionizable group and a vinyl monomer without an ionizable group. For example, a method of copolymerizing sodium styrene sulfonate and a vinyl monomer. Examples of copolymerizable vinyl monomers include acrylic acid alkyl esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, i-butyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate; acrylate, ethyl methacrylate,
Methacrylic acid alkyl esters such as n-propyl methacrylate, i-propyl methacrylate, i-butyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, diethylene glycol mono Hydroxyl group-containing acrylic acid alkyl esters such as acrylate, triethylene glycol monoacrylate, and tetraethylene glycol monoacrylate; examples include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, acrylonitrile, methacrylonitrile, styrene, vinyl chloride, etc. However, it is not limited to these examples. Conventionally known methods such as suspension polymerization, emulsion polymerization, solution polymerization, and bulk polymerization can be used to produce the copolymer. (2) A method in which a vinyl monomer that does not have an ionizable group is grafted onto an anionic polymer electrolyte. Examples of anionic polymer electrolytes include sodium alginate, carboxymethyl cellulose sodium salt, cellulose sulfate salt, polyacrylic acid and its sodium salt, polymethacrylic acid and its sodium salt, maleic acid copolymer sodium salt, and polystyrene sulfone. Examples include sodium salts of acids and sodium salts of polyacrylamide partial hydrolysates. These are dissolved and dispersed in an organic solvent or a mixture of an organic solvent and water to graft the vinyl monomers listed in (1). (3) A method of introducing carboxyl groups, sulfonic acid groups, and sulfate ester groups into polymers that do not have ionizable groups. (4) A method of neutralizing carboxyl groups and sulfonic acid groups in the molecular chains of polymers. In the method of the present invention, an anionic polymer electrolyte film produced by the above method that is insoluble in water and soluble in organic solvents is formed on the surface of a molded article. The film formed on the surface of the molded article may cover the entire surface, or may cover only a portion of the surface. To form a film on the surface of a molded article, the anionic polymer electrolyte that is insoluble in water and soluble in an organic solvent is dissolved in an organic solvent and applied to the molded article. Examples of organic solvents that can be used in this case include tetrahydrofuran, dioxane, methylene chloride, cyclohexane, isopropyl alcohol, dimethylformamide, and acetone. These can be used alone or mixed with water. As a method for forming a film on the surface of a molded product, a method can be employed in which coating is applied by a technique normally employed for forming this kind of film, and an organic solvent is scattered. The coating method can be appropriately selected from roll coating, spray coating, dip coating, knife coating, etc. depending on the shape and size of the molded product. To scatter the organic solvent, a hot air drying method, a drying method using infrared irradiation, or the like can be employed. The thickness of the film thus formed on the surface of the molded article is preferably in the range of several microns to several tens of microns. In the present invention, a positively charged inorganic colloidal sol is adsorbed onto the film formed on the surface of the molded article by the above method. This is because the anionic polymer electrolyte previously formed on the molded article is insoluble in water, and this alone cannot provide sufficient antifogging properties to the surface of the molded article. Generally, when particles having a particle diameter of 1 mμ to 100 mμ are dispersed in a dispersion medium to create a stable dispersion system, this dispersion system is called a colloid or colloid sol. The reason why such ultrafine particles can be stably dispersed in a dispersion system is thought to be because the surfaces of the ultrafine particles (referred to as colloidal particles) have an electric charge. Colloidal particles have either a positive or negative charge (charged), but
Which charge it has depends on the composition of the colloidal particle.
It depends on how the particles are prepared. Which charge a colloidal particle has can be easily determined by electrophoresis. Among inorganic colloids, colloids of inorganic oxides and inorganic hydroxides are preferable as colloid particles that can be used in the present invention. This is because colloids of these materials are highly hydrophilic and help improve the wettability of the surface of the molded product. The above-mentioned inorganic colloidal sol may be prepared by any known method. Among positively charged inorganic colloidal sols, alumina sol is the most common. In order to adsorb the above-mentioned positively charged inorganic colloidal sol onto the film formed on the surface of the molded product, this colloidal sol is dispersed in a medium such as water or alcohol, and then the colloidal sol is dispersed in a medium such as water or alcohol, and then coated using a roll coating method, a spray coating method, or a dip coating method. The medium may be applied by a method such as a coating method or a knife coating method, and the medium may be scattered by drying. an ionizing group of positively charged inorganic colloid particles;
The ionizable groups of the anionic polymer electrolyte film already formed on the surface of the molded article do not need to correspond exactly, and the former may predominate. The present invention has the following effects and has extremely great industrial utility value. (1) The method of the present invention involves forming a film of an anionic polymer electrolyte that is insoluble in water and soluble in organic solvents on the surface of a thermoplastic resin molded article, and on this film,
Since we adopt a method of adsorbing positively charged inorganic colloidal sol, the manufacturing process is not complicated.
Industrially advantageous. (2) The surface of the molded product obtained by the method of the present invention has been modified by the combination of an anionic polymer electrolyte and a positively charged inorganic colloidal sol. Wetting is greatly improved and water droplets adhering to the surface of the molded product are formed into a thin film, resulting in excellent antifogging properties. (3) On the surface of the molded product obtained by the method of the present invention, the film formed as a base is made of an anionic polymer electrolyte that is insoluble in water, so this film will not be washed away by water. . Furthermore, since the positively charged inorganic colloidal sol adsorbed on this film is ionically adsorbed with the anionic polymer electrolyte, it is also difficult to be washed away by water. As a result, the antifogging property of the molded product surface is maintained for a long period of time. Hereinafter, the present invention will be explained in detail based on examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The anionic polymer electrolyte used in the following examples was synthesized according to the synthesis example shown below. Synthesis Example 1 (Synthesis of acrylic anionic polymer electrolyte) 250 g of isopropyl alcohol was added to a 500 ml three-neck flask equipped with a reflux device and a stirrer. To this were added 60 g of methyl methacrylate, 30 g of butyl methacrylate, and 10 g of methacrylic acid, and the mixture was reacted at 80° C. for 8 hours with stirring under a nitrogen blanket. After the reaction was completed, sodium hydroxide was added in an amount to neutralize half of the methacrylic acid component, and the resulting polymer was made into an electrolyte. The product was insoluble in water and soluble in acetone, alcohols, and ethyl acetate. The product was mixed with 2% by weight of isopropyl alcohol.
The solution was prepared as follows. Synthesis Example 2 (Synthesis of maleic anhydride-based anionic polymer electrolyte) A commercially available styrene-maleic anhydride copolymer (maleic anhydride content 25% by weight) was dissolved in acetone, and the maleic anhydride group was dissolved in acetone. Sodium hydroxide was added to electrolyte the copolymer so that 20% was neutralized. This product was insoluble in water and soluble in acetone, dimethylformamide, tetrahydrofuran, and dioxane. The weight ratio of the product to tetrahydrofuran to water is 8.
It was dissolved in a mixed solvent at a ratio of 1:1 to form a 2% by weight solution. Synthesis Example 3 (Synthesis of styrenic anionic polymer electrolyte) A monomer mixture of 95% by weight of styrene and 5% by weight of sodium styrene sulfonate was polymerized by emulsion polymerization to obtain a copolymer. This copolymer was insoluble in water and soluble in acetone, dimethylformamide, tetrahydrofuran, dioxane, etc. The weight ratio of the product to tetrahydrofuran to water is 8.
It was dissolved in a mixed solvent at a ratio of 1:1 to form a 2% by weight solution. Examples 1 to 3 The anionic polymer electrolyte shown in the synthesis example above (both 2% by weight) was coated on one side of a 0.1 mm thick soft polyvinyl chloride film (Mitsubishi Monsanto Chemical Co., Ltd., dripped vinyl). (solution) was applied by roll coating and dried at a temperature of 120°C. As shown above, a film of anionic polymer electrolyte is formed on one side of the film, and alumina sol (manufactured by Nissan Chemical Industries, Ltd., Alumina Sol-100) is applied on this film.
A 1% by weight aqueous solution of was applied by spray coating and dried at a temperature of 80°C. The film prepared in this manner was spread over a water tank kept at a water temperature of 50°C, with the coated side facing down, at an angle of 5 degrees with respect to the water surface, and water droplets were applied to the film coated surface. The condensation status was observed with the naked eye. Table 1 shows the observation results of antifogging properties over time. In Table 1, the indication of anti-fog durability has the following meanings. A: Those exhibiting the same anti-fogging properties as those showing the most excellent anti-fogging properties immediately after spreading. B: Showing anti-fogging properties of about 80% based on the one showing the most excellent anti-fogging properties immediately after spreading. C: Showing about 60% anti-fogging property, based on the one showing the best anti-fogging property immediately after spreading. D: Showing about 40% anti-fogging property based on the one showing the best anti-fogging property immediately after spreading. E: Those exhibiting anti-fogging properties of about 20% or less based on those exhibiting the most excellent anti-fogging properties immediately after spreading. Comparative Examples 1 to 3 The same flexible polyvinyl chloride film used in the above examples was coated with an anionic polymer electrolyte film that was insoluble in water and soluble in organic solvents (Comparative Example 1), and water A film was formed using a 2% by weight aqueous solution of sodium alginate, which is an anionic polymer electrolyte soluble in (Comparative Example 3), and a film was formed using the material shown in Synthesis Example 1 (Comparative Example 3) and were prepared. Of these three types of films, two types of films, Comparative Example 1 and Comparative Example 2, were further adsorbed with alumina sol in the same manner as described in the above example. These three types of films were also evaluated for antifogging durability using the same method as shown in the above examples.
The results are shown in Table 1.

[Table] From Table 1, the following is clear. (1) The molded article obtained by the method of the present invention has significantly superior surface wettability and exhibits excellent antifogging properties. (2) The antifogging properties of the molded articles obtained by the method of the present invention do not deteriorate significantly over time, and therefore the antifogging properties are excellent. (3) On the other hand, the one shown in the comparative example without a film does not adsorb alumina sol, so
It showed no antifogging property at all (Comparative Example 1), had poor surface wettability (Comparative Example 3), and had poor antifogging durability (Comparative Example 2). Examples 4 to 6 The anionic polymer electrolyte shown in the synthesis example above (both 2% solutions) was added to one side of a biaxially oriented polystyrene sheet (manufactured by Mitsubishi Monsanto Chemical Co., Ltd., Santo Clear) with a thickness of 0.18 mm. , applied by roll coating method and dried at a temperature of 80°C. On top of the anionic polymer electrolyte film formed on one side of the sheet, 1% by weight of alumina sol was applied.
The aqueous solution was applied by spraying and dried at a temperature of 70°C. The sheet prepared as above was spread on a water tank kept at 50°C with the coated side facing the water side and tilted at 5 degrees with respect to the water surface in the same manner as described in Examples 1 to 3. The state of condensation of water droplets on the sheet coating surface was observed with the naked eye. Observation results of anti-fog properties over time.
It is shown in Table 2. The indication of anti-fog durability in Table 2 has the same meaning as in Table 1. Comparative Examples 4 to 6 Biaxially oriented polystyrene sheets of the same type as those used in the above examples were not coated with an anionic polymer electrolyte film that was insoluble in water and soluble in organic solvents (Comparative Example 4), and those that were. (Comparative Example 5) and one in which a film of a 2% by weight aqueous solution of sodium alginate, which is a water-soluble anionic polymer electrolyte, was formed (Comparative Example 6) were prepared. A cationic polymer electrolyte was adsorbed on two types of sheets except for the sheet of Comparative Example 5 in the same manner as described in the above example. These three types of sheets were also evaluated for antifogging durability using the same method as shown in the above examples. The results are shown in Table 2.

[Table] Although the type of resin of the molded product was different from that shown in Table 1, the effects of the present invention that were made clear from Table 1 were also confirmed in Table 2.

Claims (1)

[Claims] 1. In producing a surface-modified resin molded product, a film of an anionic polymer electrolyte that is insoluble in water and soluble in organic solvents is formed on the surface of the molded product, and this film is A method for producing a surface-modified resin molded article, which comprises adsorbing a positively charged inorganic colloidal sol onto the surface of the resin molded article. 2. Claim 1, wherein the positively charged inorganic colloidal sol is an alumina sol.
A method for producing a surface-modified resin molded product as described in Section 1.