KR100246037B1 - Abrasion resistant coating composition - Google Patents

Abstract

The present invention provides a partial condensation product of (a) 5 to 85% by weight (based on solids) of colloidal silica and silanol represented by the general formula RSi (OH) ₃ , wherein R is an alkyl group or a hydroxyl group of C _1-5 At least one aqueous-alcoholic base resin dispersion comprising 25 to 95% by weight (based on solids), (b) a thermosetting catalyst, and (c) an alkoxysilane functionalized aromatic ultraviolet absorber. Provided is a wear resistant coating composition having excellent weather resistance including 1 to 20 parts by weight, based on parts by weight.

Description

Silicone-based wear resistant coating composition with excellent substrate adhesion and insensitive to moisture

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicone coating composition mainly used for coating a solid substrate, and more particularly, to a silicone coating composition which forms a wear-resistant coating on the surface layer of a subject when thermally cured by applying on a solid substrate such as plastic. It relates to a manufacturing method.

Many transparent plastic materials have been used as a substitute for glass in many fields because of their light and rupturable properties. In particular, applications in optical lenses, industrial safety goggles, or leisure goggles are prominent, and in recent years, they have been applied to large structures such as windows of transportation systems such as trains and airplanes, windows of large buildings, greenhouse walls or transparent soundproof walls. It is done. Such transparent plastics are mainly used such as polycarbonate, acrylic or polyethylene terephthalate. However, these transparent plastic materials have a soft surface and are easily scratched by dust, vacuum cleaners, and normal weathering. Therefore, there are many restrictions on the application to structures such as transparent soundproof walls.

In order to overcome these disadvantages, a protective film is usually formed on the surface of the plastic material with an organic material or a silicone coating. Silicone coating agents commonly used for this purpose are known scratch resistant coatings formed by mixing silica such as colloidal silica or silica gel with silane capable of hydrolysis in hydrolysis media such as alcohol and water.

Prior examples of such compositions include US Pat. Nos. 3,708,225, 3,986,997, 3,976,497, 4,159,206, 4,177,315, and the like.

However, the coating composition according to the patent has a long curing time of 2 to 4 hours and is sensitive to humidity, so that the coating conditions are very demanding, and especially during the rainy season, a whitening phenomenon often occurs to form a non-uniform or opaque coating film. . In addition, since the adhesiveness is expressed only on a specific substrate, application to other substrates is restricted. Therefore, there is a hassle to go through a separate pretreatment process to overcome this.

The present inventors have made a lot of research in order to compensate for the above drawbacks, and as a result, the curing time is reduced to 10 to 30 minutes, excellent wear resistance, solvent resistance, hot water resistance, salt water resistance, etc. The silicone-based coating composition having excellent physical properties has been developed. In addition, the coating composition has an advantage of forming a coating film having excellent adhesion to most transparent plastic substrates such as polycarbonate, acrylic, polydiethylene glycol bisaryl carbonate (CR-39), and polyethylene terephthalate without additional pretreatment.

The present invention relates to (a) 5 to 75% by weight of colloidal silica having a pH in the range of 2 to 11, and (b) 25 to 96% by weight of R ¹ _a Si (OR ² ) _4-a , wherein R ¹ and R ² can be independently selected from an alkyl group, an alkenyl group, a halogenated alkyl group, and an allyl group of C _1-6 ), or an organic silane compound or a partial condensate thereof as the base resin, wherein (c) thermosetting A composition comprising a catalyst, (d) 10 to 50% by weight of C _1-10 alcohol ethers or C _1-12 ketones or diketones, and (e) C _1-4 alcohols. Such a composition of the present invention is excellent in storage stability, abrasion resistance, solvent resistance, hot water resistance and salt water resistance, and is not sensitive to moisture and has a short curing time of 10 minutes to 30 minutes without any special pretreatment process. Provided is a silicone-based coating composition having excellent adhesion, which can be commonly applied to glycol bisaryl carbonate (CR-39) and polyethylene terephthalate. Hereinafter, the present invention will be described in more detail.

The first component, colloidal silica, which is the basic resin in the composition of the present invention, is typically a sol or stable dispersion of amorphous silica particles having a particle diameter of 5 to 100 nm.

Examples of such colloidal silica include products sold under the trade names Ludox (manufactured by DuPont, USA) or Snowtex (manufactured by Nissan Chemical, Japan). In view of pH control and storage stability of the dispersion, the size of the silica particles is preferably 10 to 40 nm. The content of the colloidal silica is 5 to 75% by weight, preferably 10 to 30% by weight based on the total solids weight of the basic resin component (a) + (b).

Another component as the base resin is _a hydrolyzate of organosilane represented by the general formula R ¹ _a Si (OR ² ) _4-a or a partial condensate thereof. In the above formula, when a is 1 or more, R ¹ is most preferably a methyl group because the flexibility of the coating film is improved when the alkyl group is long, but the coating film obtained is soft and the wear resistance is worsened. If necessary, one having a methyl group and another radical may be used in combination, but the number of moles of the silane compound including the methyl group should be at least equal to or greater than the number of moles of the other silane compounds. And when a is 0, R ² is an alkyl group of C _1-6 . Examples of the silane compound used in the present invention include methyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, Phenyltrimethoxysilane, Tetraethoxysilane, Tetramethoxysilane, Ethoxymethylvinylsilane, Dibutoxymethylsilane, Butyltrimethoxysilane, Methyltriisopropoxysilane, Methyltriacetoxysilane, Tetraphenoxysilane , Tetrapropoxy silane, vinyl isopropoxy silane, and the like. The content of such organosilane compound is 25 to 95% by weight and preferably 30 to 75% by weight based on the total solids content of the basic resin component (a) + (b).

As mentioned above, the colloidal silica used in the present invention is an aqueous sol and the composition of the present invention is an aqueous-alcoholic dispersion.

The preparation of the basic resin dispersion is therefore carried out in an aqueous medium, and because of the nature of the starting material, alcohol is an essential component of the solvent system.

The great feature of the present invention is that the basic resin dispersion is obtained through a two-step reaction. In general, a small amount of acid is added to the aqueous colloidal silica, and an alkoxysilane is added thereto, followed by reaction for 24 to 48 hours, and then the solid content is adjusted to suit the purpose. However, the coating composition thus prepared has a limit of expressing adhesion only to a specific substrate. For example, when the adhesiveness is expressed in an acrylic resin, there is a problem in that a pretreatment with a urethane or acrylic primer is required to be applied to a substrate made of polycarbonate. This is because the molecular structure and molecular weight of the composition vary depending on the pH during the reaction of the composition, and thus the pH of the composition and the surface state of the silicon particles vary.

The present inventors adjusted the pH to 3-5 by adding an appropriate amount of acid or base as a hydrolysis catalyst to colloidal silica, and then mixed the alkoxysilane to hydrolyze and condensate for 2 to 5 hours in a temperature range of 20 to 60 ° C. After the addition, alcohol, such as methanol, ethanol, isopropanol or butanol, was added to prepare an intermediate composition having a solid content of 25 to 50% by weight. The intermediate composition thus made has a pH of 4.5-6. Hydrolysis catalysts used here include acetic acid, phosphoric acid, sulfuric acid, hydrochloric acid, nitric acid, fluoric acid, oxalic acid, chlorosulphonic acid, para-toluenesulphonic acid, trichloroacetic acid, polyphosphoric acid, and iodine Dibasic, iodic anhydride, perchloric acid and the like, base caustic soda, potassium hydroxide, normal butyl amine, di-normal butyl amine, imidazole, ammonium perchlorate, and the like, alone or two or more thereof. You can use together.

The alkoxysilane is added again to the intermediate composition prepared as above and refluxed for 1 to 5 hours. Alcohol ethers, such as ethylene glycol monoethyl ether, and ketones or diketones, such as acetylacetone or acetone, are added alone or in combination to prepare a coating liquid of a solid content suitable for the end use.

Add other ingredients, such as surfactants, as needed here. In the preparation of the composition, the thermosetting catalyst is added after the one-step reaction, which is generally intended to use the basic properties of the thermosetting catalyst. In other words, in the two-step reaction, the hydrolysis conditions are made weakly basic in the state of lack of water to undergo a particle growth process different from the one-step reaction. Therefore, partial condensates having two different types of structures may be mixed, which enables the development of adhesion regardless of the type of substrate.

When the thermosetting catalyst is added to the intermediate composition in an acidic state, it may be added in small amounts in a diluted state of about 10% by weight with respect to the soluble solvent under appropriate agitation to prevent local gelation.

In addition, if the thermosetting catalyst and other components are not uniformly dissolved in each other in the intermediate composition, a non-uniform coating film including mistones and opaque spots will be formed.

The thermosetting catalyst (d) includes alkali metal salts of carboxylic acid such as sodium acetate, potassium formate and the like, and also amine carboxylates such as dimethylamine acetate, ethanolamine acetate, dimethylaniline formate, tetramethylammonium acetate, benzyltrimethyl Quaternary ammonium carboxylates such as ammonium acetate, ethanoltrimethyl acetate (choline acetate), metal carboxylates such as tinoctoate, amines such as triethylamine, triethanolamine, pyridine and the like are also used as curing catalysts.

Alkali hydrates such as sodium hydroxide and ammonium hydroxide can also be used as curing catalysts.

Meanwhile, the intermediate composition after the one-step reaction is aged for 2 hours to 7 days in the temperature range of -10 ° C to 25 ° C as necessary or depending on the type of alkoxysilane used.

In addition, a mixture of alcohol ether and dikentone or ketone is added to the finished composition, followed by stirring sufficiently. In this process, the hydroxyl group of the partial condensates of the composition is partially substituted with the above additives, which makes the composition of the present invention insensitive to moisture. In addition, the mixed solvent also has a function of strengthening the adhesion between the solid substrate and the coating in the long-term wear test by increasing the mechanical bond between the silicon coating film and the substrate by slightly etching the substrate when applied to the substrate. However, in the mixed solvent, if the mixing ratio is out of an appropriate range, the spreadability may worsen or a defect such as pinholes may be left in the coated coating film or cracks may be formed in the substrate. In the mixed solvent, the ratio of alcohol ethers to diketones or ketones is about 0.3 to 3, and alcohol ethers may be used singly or in combination of two or more depending on the coating method. Diketones or ketones may be used either singly or in combination of two or more depending on the application.

Examples of the alcohol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, and the like. As diketones or ketones, there are acetyl acetone, acetone, and methyl ethyl. Ketones, 2,4-hexanedione, and the like.

The coating composition prepared as described above has a suitable total solids content of 10 to 45% by weight, preferably 15 to 35% by weight, with a pH range of 5.8 to 7.0, preferably 6.3 to 6.6. The final pH should not be adjusted after the preparation of the composition, but should be controlled by the amount of acid added during the one-step reaction or by adding a weak base such as acetic acid or a dilute base such as ammonium hydroxide to the intermediate composition after the one-step reaction.

In the case of coating the substrate, the substrate may be washed and coated by a conventional coating method such as dip coating, spray coating, spin coating, roller coating, oil coating or brushing. The physical properties of the coatings according to the invention are best when they have a thickness of 1.5 to 10 μm. Therefore, the coating film which has said optimal thickness by various coating methods can be obtained by adjusting the compounding ratio of solid content and the mixed solvent of the composition of this invention according to the coating method.

Curing of the applied coating film depends on the heat deformation temperature of the plastic substrate to be applied, but a temperature of 60 to 150 ° C. may be used. It should not overheat during curing and the plastic substrate should not deteriorate and deform. Therefore, it is appropriate to cure for 10 to 30 minutes at 80 to 130 ℃.

The coating composition of this invention can use various additives in the range in which the effect of this invention does not fall for the purpose of further improving workability, flexibility, UV blocking property, antireflection property, etc. Examples thereof include polyolefin epoxy resins, cyclohexane oxides, polyglycidyl esters, bisphenol A type epoxy resins, epoxy acrylate resins or ultraviolet absorbers such as benzophenones, benzotriazoles, and phenols. Moreover, in order to improve applicability | paintability, various surfactant can also be mix | blended. In particular, a block copolymer, a graft copolymer or a fluorine-based surfactant of dimethylsiloxane and polyether may be blended. In particular, block copolymers, graft copolymers or fluorine-based surfactants of dimethylsiloxane and polyether are typical.

The present invention is illustrated by the following examples.

What is illustrated in the following examples is intended to detail the present invention but is not intended to limit the invention to the following examples.

<Example 1>

While maintaining the temperature inside the reactor, 22 g of Dupont's colloidal silica AS-40 (22 nm in diameter) was added thereto, and 2 g of acetic acid was added thereto, followed by dropping 22.5 g of methyltrimethoxysilane with stirring and stirring for 5 hours. The hydrolysis and partial condensation reaction proceed. To this was added 7 g of isopropyl alcohol and 6.4 g of ethanol. To the solution prepared above was added 1.135 g of a 10 wt% isopropanol solution of colacetate and stirred well to obtain an intermediate composition. 30 g of the intermediate composition obtained above is aged at room temperature for 3 days. 10 g of methyltriethoxysilane is added dropwise thereto and reacted under reflux for 2 hours. 20 g of acetylacetone and ethylene glycol monobutyl ether were added to the reaction mixture, and the mixture was stirred well to obtain a final composition.

The composition was spray-coated on the surface of the polycarbonate and acrylic substrate with an injection pressure of 2 kg / cm ² with a 0.8 mm nozzle, dried at room temperature for 5 minutes, and cured at 125 ° C. and 85 ° C. for 30 minutes, respectively.

<Example 2>

In the one-step reaction of Example 1, methyl triethoxysilane is used instead of methyltrimethoxysilane and methyltrimethoxysilane is used instead of methyltriethoxysilane in the two-step reaction.

<Example 3>

Tetraethoxysilane is used instead of methyltrimethoxysilane in the one-step reaction of Example 1.

<Example 4>

As the alkoxysilanes of Example 1, methyltrimethoxysilane is selected and used.

<Example 5>

As the alkoxysilanes of Example 1, methyltriethoxysilane is selected and used.

<Example 6>

Diacetone alcohol is used in Example 1 except for acetylacetone.

<Example 7>

In Example 1, acetylacetone was changed to diacetone alcohol, and ethylene glycol monobutyl ether and ethylene glycol monoethyl ether were mixed in half.

<Example 8>

In Example 1, acetylacetone and acetone are mixed in half, and ethylene glycol monobutyl ether and ethylene glycol monoethyl ether are mixed in half.

<Example 9>

In Example 1, instead of DuPont's AS-40 product, Nissan Chemical's ST-40 product is used.

<Comparative Examples 1-3>

Prepared in the same manner as in Example 1, but instead of methyltrimethoxysilane in a one-step reaction using vinyl trimethoxysilane and methyl triethoxy silane and vinyl trimethoxysilane in half the two-step reaction is used .

<Comparative Example 4>

Prepared in the same manner as in Example 1, but using vinyl trimethoxy silane instead of methyl trimethoxy silane in a one-step reaction and methyl triethoxy silane in half the two-step reaction to use the vinyl trimethoxy silane.

<Comparative Example 5>

Prepared in the same manner as in Example 1, but instead of methyltrimethoxysilane in a one-step reaction using vinyl trimethoxysilane and methyl triethoxy silane and vinyl trimethoxysilane in half the two-step reaction is used .

<Comparative Example 6>

Prepared in the same manner as in Example 1, but using tetraethoxysilane instead of methyltrimethoxysilane in a one-step reaction and tetramethoxysilane instead of methyltriethoxysilane in a two-step reaction.

<Comparative Example 7>

In Example 1, acetylacetone was removed and only ethylene glycol monobutyl ether was used.

<Comparative Example 8>

In Example 1, acetylacetone and ethylene glycol monobutyl ether were removed, and methanol, ethanol, isopropyl alcohol and butanol were mixed and used in the same ratio.

The characteristics of the coating film prepared by the above method is shown in Table 1 below, the method of evaluating the properties of the coating film prepared by each method is as follows.

<Moisture sensitivity>

The coating composition is left in the freezer for 2 hours and then applied to the substrate, and then exposed to water vapor at 40 ° C. to determine whether bleaching occurs.

<Appearance>

Observe the film after hardening to check for pinholes or cracks.

<Adhesiveness>

According to ASTM D3359, 100 squares are made by drawing cells at intervals of 1 mm on the film, followed by three peel tests using a vertical tape of 24 mm in width from Nichiban, Japan.

<Wear resistance>

It is determined by measuring the quantitative value (Δ% Haze) of the cloudiness of the coating composition according to ASTM D-1044 and ASTM D-1003.

<Scratch resistance>

Tie a # 000 steel wool to 1.5 kg of hammer and rub it 15 times on the surface of the object to make 1, 2 a little and 3 severe.

<Solvent resistance>

Rub 100 times with cotton soaked in isopropyl alcohol and acetone.

<Hot water resistance>

The coated object was immersed in hot water at 60 ° C. for 48 hours, and the appearance of cracks on the coating film was examined and the adhesion test was performed.

<Saline resistance>

The object is immersed in 10% brine for 10 days and then tested for adhesion.

Claims (11)

In the coating composition which consists of a silica and an organosilane compound as a base resin, a) the silica is an aqueous colloidal silica in the pH range of 2 to 11, 5 to 75% by weight relative to the total amount of the base resin, the organosilane compound is R _a ¹ Si (OR ² ) _4-a -where R ¹ and R ² is An organic silane compound represented by each independently C _1-6 alkyl group, alkenyl group, halogenated alkyl group and allyl group, or a partial condensate thereof, containing 25 to 95% by weight based on the total amount of the basic resin 100 parts by weight of resin; b) thermosetting catalyst; c) 10 to 50 parts by weight of C _1-10 alcohol ethers, or C _1-12 ketones or diketones; And d) C _1-4 alcohols Coating composition comprising a. The method of claim 1, The aqueous colloidal silica has a particle diameter of 10 to 40 nm. The method of claim 1, The composition of Formula ¹ R ¹ _a Si (OR ² ) _4-a wherein a is 0 and R ² is alkyl of C _1-6 . The method of claim 1, The composition of Formula ¹ R ¹ _a Si (OR ² ) _{4-a wherein} a is an integer of 1 or more and R ² is methyl. The method of claim 1, The organic silane compound is methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane , Methyl diethoxysilane, phenyltrimethoxysilane, tetraethoxysilane, tetramethoxysilane, ethoxymethylvinylsilane, dibutoxymethylsilane, butyltrimethoxysilane, methyltriisopropoxysilane, methyltriacetosilane , Tetraphenoxysilane, tetrapropoxysilane, vinyl isopropoxysilane. The method of claim 1, The thermosetting catalyst is an alkali metal salt of carboxylic acid such as sodium acetate, potassium formate or the like or an amine carboxylate such as dimethylamine acetate, ethanolamine acetate, dimethylaniline formate, tetramethylammonium acetate, benzyltrimethyl ammonium acetate, ethanoltrimethyl acetate From the group consisting of amines such as quaternary ammonium carboxylates (choline acetate), metal carboxylates such as tinoctoate, triethylamine, triethanolamine, pyridine and the like and alkali hydrates such as sodium oxide, ammonium hydroxide Composition selected. The method of claim 1, The alcohol ethers are ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, and the like. As diketones or ketones, acetylacetone, acetone, methyl ethyl ketone, 2,4 A composition selected from the group consisting of hexanedione and the like. In the method of manufacturing the coating composition which consists of a silica and an organosilane compound as a base resin, a) adding a hydrolysis catalyst to the aqueous clad silica to adjust the pH to 3-5; b) R _a ¹ Si (OR ² ) _4-a on the silica, wherein R ¹ and R ² are each independently selected from C _1-6 alkyl groups, alkenyl groups, halogenated alkyl groups and allyl groups Mixing the alkoxy silane to be hydrolyzed and condensed; c) adding a C _1-4 lower alcohol to the reaction product to prepare an intermediate composition; d) mixing and refluxing the alkoxy silane into the intermediate product; And e) adding C _1-10 alcohol ethers or C _1-12 ketones alone or in mixture to the refluxed composition Coating composition manufacturing method comprising a. The method of claim 8, The aqueous colloid has a particle diameter of 10 to 40 nm. The method of claim 8, Wherein a is 0 and R ² is alkyl of C _1-6 in formula R _a ¹ Si (OR ² ) _4-a . The method of claim 8, Wherein a is an integer of 1 or more and R ² is methyl in the formula R _a ¹ Si (OR ² ) _4-a .