JPH0130854B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing plastic products used in various material fields such as building materials, industrial materials, and optical applications.

[Conventional technology]

In recent years, plastic products have become lightweight, easy to process,
Taking advantage of its characteristics such as impact resistance, glass is rapidly making inroads into materials fields where glass products have traditionally been mainly used, such as building materials, industrial materials, and optical applications. In particular, molded products made of polyester film, polycarbonate resin, or polymethacrylic resin have excellent mechanical and optical properties, so they can be used as protective covers for instruments and window glass, lenses, outdoor ceiling sheets, etc. It is widely used.

However, plastic products generally have low surface hardness, and have serious drawbacks such as surface damage due to friction or collision with other objects, resulting in loss of optical properties.

In order to overcome these drawbacks, various methods have been proposed for coating the surface of plastic molded articles with hard paints.

However, with conventional coating methods of this type, the hardness is insufficient, the adhesion to the substrate is insufficient, or the coating is extremely brittle and is susceptible to mechanical or thermal stimulation. However, it had the disadvantage that the coating film was prone to cracking. Generally, a coating film with better hardness tends to be more brittle and has poorer adhesion, and there is a strong desire for a coating film that has both surface hardness, toughness, and adhesion.

[Problem that the invention seeks to solve]

From the above viewpoint, the present invention solves the problem that it is difficult to combine the three characteristics of surface hardness, toughness, and adhesion to base materials in the conventional resin coating of plastic molded products. The object of the present invention is to obtain a plastic product with high surface hardness that is useful for optical applications and has excellent all of the above three properties.

[Means for solving problems]

As a result of intensive studies to achieve the above object, the inventors found that when the surface of a plastic molded product is subjected to a specific undercoat treatment, then a specific resin paint is applied and heat treated, the surface hardness and toughness are improved. They found that it was possible to achieve a resin coating with excellent adhesion to a substrate, and thus completed the present invention.

That is, this invention applies an organic titanium compound represented by the general formula Ti(OR) ₄ (R is an alkyl group having 1 to 8 carbon atoms) to the surface of a plastic molded product, and then hydrates the organotrialkoxysilane. The present invention relates to a method for producing a plastic product with a high surface hardness, which is characterized by applying a paint containing a decomposition product as an essential component and heat-treating the coating.

[Structure and operation of the invention]

Examples of plastic molded products used in this invention include polyester, polycarbonate, polyvinyl chloride, polystyrene, cellulose acetate, polymethyl methacrylate, polyamide, etc., and their shapes include film, sheet, and lump. , a variety of shapes such as a rod shape. Plastic moldings particularly suitable for the application of the invention are polyester film or polycarbonate moldings.

In this invention, the undercoat agent to be undercoated as the first layer on the surface of the molded article has the general formula Ti
Organic titanium compounds represented by (OR) ₄ (R is an alkyl group having 1 to 8 carbon atoms), such as tetraisopropyl titanate, tetrabutyl titanate, and tetraoctyl titanate.

This organic titanium compound is usually used after being dissolved in a suitable solvent, and examples of the solvent include alcoholic solvents such as isopropyl alcohol, aromatic hydrocarbon solvents such as toluene, and the like. The concentration of the organic titanium compound contained in the solvent cannot be determined simply because it affects the coating thickness and the operability of coating, but it is generally desirable to be 1 to 50% by weight.

This solution containing an organic titanium compound is applied to the surface of a plastic molded article by a constant velocity pulling method, a spray method, a spinner method, a roll coater method, a bar coater method, a printing method, or the like. After application, a transparent film is formed by drying at room temperature to 150°C for 5 minutes to 3 hours. The thickness of the coating film is
The thickness after drying is preferably 0.05 to 1 μm.

Next, the top coat applied as the second layer on the coating surface is a paint containing as an essential component a hydrolyzate of organotrialkoxysilane represented by the general formula R'Si(OR'') ₃ . In the formula, R'' represents an alkyl group, preferably having 6 or less carbon atoms. R′ represents an alkyl group, an aryl group, an alkenyl group,
R' may further have a substituent. Specific examples of R′ include methyl group, ethyl group, propyl group,
Examples include isopropyl group, pentyl group, hexyl group, phenyl group, vinyl group, γ-glycidyloxypropyl group, γ-(N-β-aminoethyl)aminopropyl group, and γ-aminopropyl group.

Specific examples of organotrialkoxysilane include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, isopropyltriisopropoxysilane, and vinyltriethoxysilane. Silane, phenyltrimethoxysilane, γ-glycidyloxypropyltrimethoxysilane, γ
- methacryloxypropyltrimethoxysilane,
Commercially available silane coupling agents such as γ-(N-β-aminoethyl)aminopropyltrimethoxysilane and γ-aminopropyltrimethoxysilane can be mentioned. One type of these compounds may be used, or a mixture of two or more types may be used if necessary.

Hydrolysis of the organotrialkoxysilane is carried out, for example, by adding water to a lower alcohol solution of the organotrialkoxysilane in the presence of an acid catalyst. Examples of lower alcohols include methanol, ethanol, isopropanol, butanol, and the like.

Further, in the above hydrolysis, an aqueous dispersion of colloidal silica may be added together with an acid catalyst. This colloidal silica gives good results in increasing the surface hardness of the cured film of the top coat. The amount of colloidal silica added is 100 parts by weight of organotrialkoxysilane (calculated on solid content,
Less than 200 parts by weight (calculated as R′SiO _1.5 ) are preferred. If it is used in excess of this range, the resulting silicone coating will be brittle and have poor adhesion, which is not good. Colloidal silica dispersion liquid has dispersed silica of 5 to 150 millimicrons (mμ).
It generally has a particle size in the range of . These silica dispersions are already commercially available.

The organotrialkoxysilane hydrolyzate thus obtained contains, as a curing catalyst,
carboxylic acid salts, e.g. dimethylaniline acetate,
Ethanolamine acetate, dimethylaniline formate,
Tetraethylammonium benzoate, sodium acetate, sodium propionate, etc. are added. The amount of these catalysts can be varied depending on the desired curing conditions, but is preferably 0.05 to 2% by weight based on the solid content of the coating material. If it is less than 0.05% by weight, its function as a catalyst is insufficient and a coating film with sufficiently high surface hardness cannot be obtained. If it exceeds 2% by weight, the lifetime of the solution will be shortened, accompanied by the formation of gels, and the optical properties of the coating will often be impaired.

In addition to the above-mentioned components, the above-mentioned top coat according to the present invention may contain various additives such as a surfactant to improve wettability with the undercoat layer and other antistatic agents for the purpose of improving the properties of the paint film. can contain agents. It is generally desirable for the solid content concentration of this paint to be 5 to 30% by weight in terms of stability of the paint and ease of application operation.

The above paint is applied to the undercoated surface using the same method as the undercoat, and then heated at 80 to 150℃ for 5 minutes to
Hardened by heat treatment for 15 hours. The thickness after curing is usually 0.2 to 5 μm. If the thickness is too thin, the abrasion resistance will be insufficient, and if it is too thick, distortion and cracks will easily occur due to the volumetric shrinkage phenomenon during curing, so neither is preferable.

〔Effect of the invention〕

As described above, in this invention, an organic titanium compound is applied as an undercoat to the surface of a plastic molded product and dried, and then a topcoat containing a hydrolyzate of organotrialkoxysilane as an essential component is applied to the coated surface and hardened. As a result, the cured coating film has high hardness and excellent toughness, making it difficult to crack due to mechanical or thermal shock. As a result, the coating film has excellent adhesion to the base plastic.

Therefore, it is possible to provide plastic products with stable optical properties such as high surface hardness and resistance to surface scratches due to friction and collisions, and this product can be used as an alternative to glass products for building materials, industrial materials, and optical applications. It can be very advantageously applied to various fields such as

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples. In addition, in the following, parts shall mean parts by weight.

Example 1 A 15% by weight isopropyl alcohol solution of tetrabutyl titanate was prepared as an undercoat for the first layer. This was applied to the surface of a 100 μm thick polyester film using a bar coater and dried at 80° C. for 10 minutes. The film thickness of the undercoat at this time was 0.2 μm.

Next, 50 parts of 0.05N hydrochloric acid was added to 200 parts of methyltrimethoxysilane and 160 parts of isopropyl alcohol, and a hydrolysis reaction was carried out at room temperature for 3 hours.
To this were added 120 parts of isopropyl alcohol and 1.2 parts of sodium acetate, and the mixture was stirred to completely dissolve the mixture to obtain a top coat.

Apply this topcoat to the surface of the polyester film treated with the above primer using a bar coater.
It was applied to a thickness of 1 μm and heated at 150° C. for 30 minutes.

The surface hardened polyester film obtained in this way has a surface hardness (according to the pencil hardness method) of
was 3H, and there was almost no damage even when rubbed strongly with #0000 steel wool. In addition, 100 dots were made on the paint film with a knife at 1 mm intervals, and after pasting cellophane adhesive tape on top of the dots, the tape was suddenly peeled off to examine the adhesion. The result was 100/100, indicating good adhesion.

Example 2 As an undercoat for the first layer, a 10% by weight isopropyl alcohol solution of tetraisopropyl titanate was prepared, and a 100 μl solution was prepared in the same manner as in Example 1.
It was applied onto a polyester film having a thickness of m. The film thickness was 0.1 μm.

Next, 0.2 part of acetic acid was added to 150 parts of an aqueous dispersion of colloidal silica (trade name Snotex, manufactured by Nissan Chemical Co., Ltd.) containing 20% by weight of SiO ₂ with a particle size of 10 to 20 mμ. A solution of 200 parts of methyltrimethoxysilane and 150 parts of isopropyl alcohol was added thereto with stirring, and a hydrolysis reaction was carried out at room temperature for about 2 hours. To this, 50 parts of isopropyl alcohol,
1.5 parts of sodium acetate was added and stirred to completely dissolve it and use it as a top coat. This topcoat,
It was coated on the undercoated polyester film surface in the same manner as in Example 1, and heated at 150°C for 30 minutes to form a 2.0 μm thick topcoat film.

The obtained polyester film with high surface hardness had a surface hardness of 4H and good scratch resistance and adhesion as in Example 1.

Example 3 200 parts of methyltrimethoxysilane, 40 parts of γ-glycidyloxypropyltrimethoxysilane, 180 parts of isopropyl alcohol, and 80 parts of 0.05N hydrochloric acid.
1 part was added thereto, and the hydrolysis reaction was carried out at room temperature for 3 hours. Add to this 120 parts of isopropyl alcohol, 0.6 parts of sodium acetate, and 0.6 parts of benzyl ammonium acetate.
1 part was added and stirred to completely dissolve it and use it as a top coat.

This topcoat was applied to the uncoated polyester film surface in the same manner as in Example 1 using a bar coater to a coating thickness of 1 μm, and heated at 120°C.
It was heated for 2 hours.

The obtained polyester film with high surface hardness had a surface hardness of 3H, and the scratch resistance and adhesion were as good as in Example 1.

Comparative Example The topcoat used in Example 2 was applied directly to the surface of a 100 μm thick polyester film in the same manner as in Example 2 without performing an undercoat treatment, and heat treated. The thickness of the resulting coating film was 1 μm.

The surface hardness of the polyester film coated with this top coat was the same as in Example 2, but the coating was easily peeled off by bending or rubbing lightly with the tip of a nail.

As is clear from the above results, according to the present invention, after applying an organic titanium compound to a plastic molded product and drying it, a top coat agent containing a hydrolyzate of organotrialkoxysilane as an essential component is applied,
Furthermore, it can be seen that those subjected to heat treatment have high surface hardness, toughness, and excellent scratch resistance, as well as excellent adhesion to plastic substrates.

Claims (1)

[Claims] 1. On the surface of the plastic molded product, the general formula Ti
After applying and drying an organic titanium compound represented by (OR) ₄ (R is an alkyl group having 1 to 8 carbon atoms), a paint containing a hydrolyzate of organotrialkoxysilane as an essential component is applied to the coated surface, A method for producing a plastic product with a high surface hardness characterized by heat treatment.