KR0177322B1 - Abrasion resistant coating composition with excellent weather resistance - Google Patents

Abstract

The present invention relates to a wear-resistant coating composition that has excellent adhesion to a solid substrate and does not require a pretreatment process. (A) 5 to 75% by weight of colloidal silica (based on a solid component) and a general formula RSi (OH) ₃ [ Wherein R is an alkyl or hydroxy group of C _1-6 ] an aqueous-alcoholic mood-bearing dispersion comprising from 25 to 95% by weight (based on solid components) of partial condensates of silanol, (b) a thermosetting catalyst, ( C) At least one alkoxysilane functionalized aromatic ultraviolet absorber represented by the following general formula (I) contains 1-20 parts by weight based on 100 parts of the basic resin dispersion of (A):

Description

Abrasion resistant coating composition with excellent weather resistance

The present invention relates to a wear resistant coating composition having excellent weather resistance that does not require a pretreatment step when applied to a resin.

Recently, transparent materials that do not break or have stronger tear resistance than glass have been widely used as substitutes for transparent glass. For example, synthetic resin transparent plates made of synthetic organic polymers are used in public transportation such as trains, buses, taxis, and airplanes, and are applied to transparent plates used in large buildings as well as lenses used in glasses and other optical instruments. These resin plates, which are lighter in weight than glass, are of particular interest in the transportation industry, where the weight of the vehicle is an important factor for fuel saving. The transparent synthetic resin board is lighter than glass and has strengths that are more resistant to tearing, but has a disadvantage in that grooves are easily formed or scratched because of daily contact with dust, abrasives such as vacuum cleaners, and normal weathering.

Attempts have been made to improve the wear resistance of such transparent plastics. For example, a scratch-resistant coating composition formed by mixing silica such as colloidal silica or silica gel with hydrolyzable silane in a hydrolysis medium such as alcohol and water is known. As prior arts for such compositions, U.S. Patent Nos. 3,708,225, 3,986,997, 3,976,497, 4,027,073, 4,159,206, 4,177,315 and the like are known. In addition, coating compositions that improve storage stability and provide excellent coatings on solid substrates are described in US Pat. Nos. 964,910 and 964,911.

However, the coating compositions mentioned in US Pat. Nos. 964,910 and 964,911 have good adhesion to the subject at first, but after exposure the coating layer does not peel off or block UV rays, resulting in yellowing and decomposition of the subject. Cause. In order to compensate for these disadvantages, U.S. Patent No. 91,716 proposes to add a sunscreen agent such as 2,4-dihydroxy-benzophenone, but these sunscreen agents exhibit a plasticizing step, which lowers abrasion resistance and prolongs exposure to ultraviolet light. Causes problems with poor adhesion. In addition, the alkoxysilane functionalized sunscreen mentioned in Korean Patent No. 84-1743 requires about 48 hours in three steps during preparation, and requires about seven days of aging for addition to the silicone coding material. There is a disadvantage.

In the present invention, the wear resistance coating composition having excellent weather resistance, prepared by a one-step reaction of about 2 hours to compensate for the various disadvantages described above, and containing sufficient alkoxysilane-functional UV absorber even when only about 1 hour is added to the silicone coating material. The purpose is to provide.

In order to achieve the above object, in the present invention, a silane represented by (a) colloidal silica 5 to 75% by weight (based on solid components) and general formula RSi (OH) ₃ , wherein R is an alkyl group or a hydroxyl group of C _1-5 Aqueous-alcoholic base resin dispersion containing 25 to 95% by weight of partial condensate of a solid (based on solid components), (B) thermosetting catalyst, and (C) alkoxysilane functional aromatic ultraviolet rays represented by the following general formula (I) Provided is a wear resistant coating composition having excellent weather resistance, comprising 1-20 parts by weight of at least one absorbent based on 100 parts by weight of the basic resin dispersion (a):

In the formula, -OR ¹ is ego,

R ² is a C ₁ -C ₆ alkyl group, R ³ is a C ₁ -C ₆ alkyl group or an aryl group, OR ⁴ is methoxy, ethoxy, propoxy, isopropoxy, butoxy or acetoxy, R ⁵ Is a C ₁ -C ₁₂ alkyl group or an aryl group, X is H or Cl, n is 0, 1 or 2, and m is an integer from 5 to 9.

Hereinafter, the present invention will be described in detail.

Colloidal silica, which is the first component of the basic resin dispersion (a) in the composition of the present invention, refers to a sol or stable dispersion of discrete amorphous silica particles, which either acidifies the sodium silicate solution, or It can be prepared by hydrolysis. Examples of such silica dispersions include those sold under the trademarks Ludox and Nalcoag by DuPont. As the colloidal silica, both acidic hydrosol and basic hydrosol can be used. In the present invention, basic colloidal silica sol is preferable. In addition, the use of colloidal silica with a low alkali (eg Na ₂ O) content can produce more stable coating compositions.

Colloidal silica is mainly used having an average particle diameter of 1 to 150㎛, in order to obtain excellent stability it is preferable to use a particle diameter of 5 to 30㎛, in order to obtain a high wear resistance is used by mixing two or more different particle diameters. It is desirable to.

This colloidal silica component is used at 5 to 75% by weight based on the total solid components of the base resin dispersion.

The second component of the basic resin dispersion (A) of the composition of the present invention is a partial condensate of silanol. Silanol contains the general formula RSi (OH)₃[Where R is C_1-6Alkyl group, C_6-20May be selected from an aryl radical or a hydroxyl group of Formula R₂Si (OH)₂[Where R is C_1-6Alkyl group, C_6-20May be selected from an aryl group of the general formula R,₂Si (OH)₂Phosphorus may be used to improve the flexibility of the coating, but since the wear resistance of the resulting film is not good, in the present invention, RSi (OH)₃Phosphorus silanol is used. The content of silanol is 25 to 95% by weight based on the total solid components of the base resin dispersion.

As described above, since the colloidal silica used in the present invention is an aqueous sol and the component (a) of the composition of the present invention is an aqueous-alcoholic dispersion, the basic resin dispersion is prepared in an aqueous medium and because of the nature of the starting material, alcohols are solvent-based. It is an essential ingredient.

The partial condensates of silanols described above may be prepared by obtaining RSi (OH) ₃ from a trialkoxysilane, a precursor having a structure of RSi (OR ′) ₃ , and condensing it. That is, RSi (OH) ₃ can be prepared in situ by adding the corresponding trialkoxysilane to an aqueous dispersion of colloidal silica. Suitable trialkoxysilanes RSi (OR ′) ₃ liberate the compatible alcohols when hydrolyzed in an aqueous medium so that at least a portion of the alcohols are present in the base resin dispersion. The alkoxy groups include methoxy, ethoxy, propoxy, Preference is given to butoxy or acetoxy. The alcohol can be added to the hydrolysis medium before the addition of the trialcohol silane, and mixtures of alcohols can also be used. When producing silanol from trialkoxysilane in an aqueous medium, hydroxyl groups condense to form siloxane bonds. At this time, a small amount of acid may be added to promote the hydrolysis and condensation reaction, with hydrofluoric acid, hydrochloric acid, nitric acid, volcano or acetic acid being preferred. This does not complete the condensation reaction, but instead yields a composition in which a hydroxy group is present in the siloxane. It is preferable to contain 70% or more that R of silanol RSi (OH) ₃ is a methyl group.

Basic resin dispersion (A) may contain 20 to 50 weight% of solid content. Preferably the base resin dispersion may contain 15 to 40 weight percent solids, depending on the end use of the coating composition.

In order to obtain the desirable properties of the basic resin dispersion and the excellent properties of the curable coating made from the resin, an appropriate amount of acetic acid is added to the basic colloidal silica as a hydrolysis catalyst (when using an aqueous acidic colloidal silica solution, acetic acid is generally added first), and trialkoxy After the silane is mixed and hydrolyzed at a temperature range of 20-30 ° C. for 1-2 hours, a solvent such as isopropanol or butanol can be added to the desired solid content to optimize the properties of the cured film.

After preparing a basic resin dispersion consisting of a partial condensate of colloidal silica and silanol, a thermosetting catalyst and other components are mixed thereto. It is important here that the thermosetting catalyst is uniformly mixed with the base resin dispersion and other components. Since the thermosetting catalyst is generally basic, when added to an acidic base resin dispersion, a small amount of the thermosetting catalyst is diluted with about 10% by weight of the soluble solvent under appropriate agitation to prevent local gelation in the resin. In addition, if the thermosetting catalyst and the other components are not mixed heterogeneously or uniformly dissolved in each other in the basic resin dispersion, an uneven cured film including ohbans and opaque spots may be formed.

Thermosetting catalysts which are one component of the coating composition of the present invention include alkali metal salts of carboxylic acids such as sodium acetate, potassium formate, and the like, and include amine carboxylates such as dimethylamine acetate, ethanolamine acetate, dimethylaniline formate, and the like; Quaternary ammonium carboxylates such as tetramethylammonium acetate, benzyltrimethylammonium acetate, ethanoltrimethyl acetate (choline acetate); Metal carboxylates such as tinoctoate; Amines such as triethylamine, triethanolamine, paraffin and the like can also be used. Alkali hydroxides such as sodium hydroxide and ammonium hydroxide can also be used as thermosetting catalysts. Moreover, typical colloidal silicas (particularly those having a basic pH) which are industrially useful contain free alkali metal bases, and alkali metal carboxylate catalysts are produced during hydrolysis reactions.

In general, colloidal silica has a coin point at about pH 2, the slowest condensation rate at this isoelectric point, and the trialkoxy silane represented by RSi (OR ') ₃ is the slowest at pH 4.5. However, when RSi (OR ') ₃ causes some hydrolysis and condensation reactions, the acidity is increased, and the condensation rate tends to be the fastest between pH 6-7 with an isoelectric point near pH 2, similar to colloidal silica. To date, the acid content used in the hydrolysis step of most coating compositions is about 0.005-0.1 parts by weight, based on 100 parts by weight of the total composition, with acidic colloidal silica being about 2.5-3.0, basic colloidal silica If used, it has a pH range of 4.5-6.

As mentioned above, when RSi (OR ') ₃ has a degree of condensation reaction, the condensation speed increases as the isoelectric point goes from pH 2 to 6-7. Therefore, the condensation rate between Si-OH of silanol is increased in the conventional pH range. It quickly counteracts the hydrolysis of the alkoxy groups remaining in the partial condensate. For this reason, the compositions up to now require a long reaction time of about 16-48 hours to obtain the desired degree of hydrolysis, and the particle size of the condensate increases due to condensation reactions occurring simultaneously for the same time, which is the final curing step after coating. It has caused a problem of abrasion resistance deterioration due to the reduction of the reaction surface area at. In the present invention, by using the acid content in the hydrolysis step of RSi (OR ') ₃ in an amount of 0.4-3% by weight based on the total composition, 1.8-2.2 when using the colloidal silica, basic colloidal silica is used. In this case, it is possible to prepare a coating composition having the desired hydrolysis resistance and excellent wear resistance even if the reaction is carried out for only 1-9 hours at a temperature range of 20-30 ° C. while maintaining a pH range of 1.8-4.5.

In order to uniformly mix the thermosetting catalyst in the basic resin dispersion, for example, a 10 wt% solution may be prepared by dissolving the catalyst in isopropanol (to this solvent), and 0.05 to 0.2 wt% based on the total composition, preferably 0.08-0.1 wt% is used. The pH of the final composition obtained therefrom is in the range of 5.7-7.0.

One of the other components of the present invention, an organic solvent, is a C ₁ -C ₄ alcohol, C ₄ -C ₆ cellosolve, or C ₁ -C ₅ ketone to maintain the adhesion between the solid substrate and the coating in the long-term wear test And acetates. These solvents are selected according to the solid substrate to be coated. For example, when the substrate is polymethyl methacrylate (PMMA), acetone, 1,4-dioxane, methyl ethyl ketone, and the like are useful, and the content is based on the total composition. 20 weight% or less is used. Of these, acetone shows the best properties. This organic solvent-added composition shows high abrasion resistance in the long-term wear test because colloidal silica diffuses from the PMMA surface while the PMMA substrate surface is micro swelled.

After preparing the base resin dispersion, the thermosetting catalyst component and other components are added, the composition is mixed to make the composition homogeneous, and isopropanol is added to adjust the total solid component to 10-50% by weight, preferably 18-25% by weight. do. The pH range of the coating composition produced at this time is 5.7-7.0, preferably 5.9-6.1. To adjust the final pH to the above range, a weak acid such as acetic acid or a dilute base such as ammonium hydroxide can be added to the composition.

The (poly) component which imparts weather resistance to the composition of the present invention is represented by the following general formula (I), which can be produced by the method described in the organosilane-based compound filed by the present applicant and the method for producing the same. That is, it is prepared by reacting a hydroxy phenyl benzotriazole-based compound of formula (III) with an alkoxysilane having an isocyanate functional group of formula (IV):

Wherein R ² , R ³ , R ⁴ , R ⁵ , X, m and n are as defined above.

At this time, the reaction temperature is 40 to 60 ℃, by reacting for 1 to 4 hours to obtain the target compound.

When the composition of the invention is coated on a substrate, the substrate is washed and optionally coated after pretreatment. Coating can be performed by a conventional coating method, for example, immersion coating, spraying, brushing, spin coating, roller coating, oil coating or laminated coating. The composition of the present invention can be coated with various thicknesses by coating on a substrate and drying, followed by curing for 1-4 hours at 50 to 150 ℃, preferably 90-130 ℃. Usually the coating composition of the present invention is best when the thickness of the cured coating is 1-15 μm. It should not overheat during curing and the plastic substrate should not deteriorate and deform. Therefore, about 1-4 hours are preferable at 80-130 degreeC.

The coating composition of the present invention is particularly useful for plastic substrates such as polycarbonate, acrylic, CR-39 ie poly (diethyleneglycolbisaryl) carbonate, polyester, cellulose acetate, butyrate, acrylonitrile-butadiene-styrene .

The composition of the present invention exhibits excellent properties in terms of impact resistance and shortening of the application process, which are disadvantages of conventional wear resistant coatings. That is, when a wear resistant coating of several microns is applied to a plastic substrate such as polycarbonate having excellent impact resistance, a low temperature impact resistance may be rapidly decreased, but the composition of the present invention may be coated on polycarbonate. The low temperature impact resistance is then maintained as much as uncoated polycarbonate. This is because the molecular structure, molecular weight and molecular weight of silicon in the coating liquid, while maintaining the characteristic of silicon having high flexibility because of long atomic bond distance of siloxane bond (Si-O-Si), low electron density, and free rotation of bond. It is believed that this is because the distribution is optimized to balance the flexibility and the wear resistance after curing.

In terms of shortening of the coating process, various conventional silicone coating materials have poor adhesive strength when not applied to polycarbonate (primer coating), but weather resistant coating materials composed of the composition of the present invention have excellent adhesion to polycarbonate without such a pretreatment process. Indicates. This is expected to be due to acid-base interactions between the basic urethane linkages of the alkoxysilane functionalized ultraviolet absorbers and the carboxylic acid with the polycarbonate ends remaining.

Other additives may be added to the compositions of the present invention to increase the usefulness of the coating, for example surfactants, antioxidants, thickeners, leveling agents and the like may be added.

The present invention will be described in more detail with reference to the following examples.

However, the scope of the present invention is not limited only to the following Examples.

In the following Examples, physical properties were measured by the following method.

(1) wear resistance

a) Teva wearability: Quantitative value of cloudiness of the coating composition according to ASTM D-1044 and ASTM D-1003 (Δ% haze, 100 revolutions, 250 g)

(2) Scratch resistance: Scratch test by # 0000 steel wool

The steel wool is mounted horizontally on the tip of a 25 mm diameter cylinder, and then contacted with the sample surface and rotated five times under a load of 100 g.

○: no damage

△: slight damage

×: much surface damage

(3) Adhesion: Cross cut cellotape peeling test on the cross-linked cured film, that is, 11 films each having 11 mm horizontally and vertically reaching the substrate at intervals of 1 mm to make 100 eyes of 1 mm2 Stick the cello tape on top and sharply beat. This operation is repeated three times in one place.

(Circle): There is no peeling of a crosslinked cured film even if it repeats 3 times.

(Triangle | delta): When the number of peeling eyes is 1-50 by repeating 3 times

X: 3 times repeated peeling eyes 51-100

(4) Impact resistance: The plate-shaped specimens with the film formed on the polycarbonate substrate were stored for 24 hours at a temperature of 20 ° C, 0 ° C, -20 ° C, immediately taken out, and the flank specimens were damaged after shooting with an air gun at a distance of 1 m. Observe the degree.

○: Only traces of bullets remain

×: Track occurs or bullet is penetrated

(5) Light resistance: Adhesion and yellow index are measured after 300 hours using a QUV accelerated weathering tester (UVB 313 lamp, 60 ° C.).

Example 1

[Step 1] Synthesis of Organosilane-based UV Absorber

While maintaining the internal temperature of the reactor at 50 ° C while mixing 657 g of benzotriazole-based ultraviolet absorbent Tinuvin 1130 (Shiba-Geigi Co., Ltd.) with 904 g of 1-methyl-2-pyrrolidone, Stirred. 247 g of γ-isocyanato propyl triethoxysilane was added dropwise thereto for 30 minutes and then reacted at 50 ° C. for 90 minutes to obtain a reaction product having a solid content of 50%.

Step 2) Synthesis of weather resistant silicone based wear resistant coating material

While maintaining the temperature inside the reactor at 20-30 ° C, 13.86 g of Ludox SM-30 (7 nm), 0.726 g of HS-30 (12 nm) and 7.414 g of AS-40 (22 nm) were added After adding 2 g of acetic acid thereto, 22.5 g of methyltrimethoxysilane was added dropwise while stirring with a magnetic stirrer, and hydrolysis and partial condensation reaction were performed for 7 hours under stirring. 61.05 g of isopropanol and 15.85 g of n-butanol were added to the solution. To 100 g of the base resin prepared above, 10 wt% of synthetic choline acetate, 1.135 g of isopropanol solution, and 7.5 g of the reaction product of 50% solids obtained in step 1) were added thereto, followed by stirring for 10 minutes to obtain a final composition. The composition was immersed in a polycarbonate substrate, dried at room temperature for 5 minutes, and heated at 120 ° C. for 1 hour to obtain a coating, which was tested for physical properties and the results are shown in Table 1.

Example 2

A coating was obtained in the same manner as in Example 1 except that methyltrimethoxysilane was mixed with 7.5 g of the alkoxysilane functionalized ultraviolet absorber and then added together, and the properties thereof were tested and the results are shown in Table 1. .

Example 3

A coating was obtained in the same manner as in Example 1, except that 15 g of the alkoxysilane-functionalized UV absorber was added, and the results are shown in Table 1 below.

Comparative Example 1

A coating was obtained in the same manner as in Example 1 except that no alkoxy silane functionalized ultraviolet absorber was added, and the results were shown in Table 1 by the physical property test.

Comparative Example 2

The coating was obtained in the same manner as in Example 1 except for adding the same molar number of organic ultraviolet absorbent Tinuvin-1130 instead of the alkoxysilane functionalized ultraviolet absorber, and the properties were tested for the results and are shown in Table 1. .

As shown in Table 1, the coating material obtained from the coating composition of the present invention is excellent in scratch resistance, adhesion, abrasion resistance and impact resistance, and excellent in adhesive strength even after exposure to ultraviolet rays, and did not have a high degree of yellowing.

Claims (8)

(A) from 5 to 75% by weight of colloidal silica (based on solid components) and 25 to 95 parts by weight of partial condensates of silanol represented by the general formula RSi (OH) _3, wherein R is an alkyl or hydroxy group of C _1-6 An aqueous-alcohol basic aqueous dispersion containing% (based on solid components), (b) a thermosetting catalyst, and (c) at least one alkoxysilane functionalized aromatic ultraviolet absorber represented by the following general formula (I): Abrasion resistant coating composition having excellent weather resistance including 1-20 parts by weight based on 100 parts of resin dispersion: -OR ¹ in the above formula R ² is a C ₁ -C ₆ alkyl group, R ³ is a C ₁ -C ₆ alkyl group or an aryl group, OR ⁴ is methoxy, ethoxy, propoxy, isopropoxy, butoxy or acetoxy, R ⁵ is a C ₁ -C ₁₂ alkyl group or an aryl group, X is H or Cl, n is 0, 1 or 2, and m is an integer from 5 to 9. 2. The silanol according to claim 1, wherein the silanol is prepared by hydrolysis of RSi (OR ' ₃ ), wherein OR' is methoxy, ethoxy, butoxy or acetoxy, using 0.5-3% by weight of acid. Composition. The composition of claim 2, wherein the colloidal silica is a single particle diameter or a mixture of two or more particles having different particle diameters. The composition according to claim 1, wherein the silanol RSi (OH) ₃ contains at least 70% of R being a methyl group. The composition of claim 1 wherein the acid is hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid or acetic acid. The composition of claim 1 wherein the solvent is selected from C ₁ -C ₄ alcohols, C ₄ -C ₆ cellosolves, or C ₁ -C ₅ ketones and acetates. A method of coating a thermosetting composition on a solid substrate, the method comprising coating the coating composition according to claim 1 on a solid substrate, drying and curing at 90-130 ° C. for 1-4 hours. 8. The method of claim 7, wherein a surfactant, antioxidant, thickener or leveling agent is added to the coating composition to coat it on a solid substrate.