KR100226979B1 - Siloxane-based coating composition having excellent storage stability, abrasion resistance and dyeability property - Google Patents

Abstract

(A) 5 to 75% by weight of aqueous colloidal silica or alcoholic colloidal silica having a pH in the range of 2.5 to 4, (b) 0.1 to 50% by weight of (C) 10 to 60% by weight of a hydrolyzate of an organosilane represented by the following general formula (II) or a partial condensate thereof; 1 to 100 parts by weight of a titanium-based organic compound represented by the following general formula (III) or an intermediate derivative thereof, (e) 0.1 to 10 parts by weight of a compound represented by the following general formula (IV) And a hydrolyzate or a partial condensate thereof, and (C) 10 to 50 parts by weight of a C _1-12 ketone or a diketone, which is excellent in storage stability, abrasion resistance and coloring property :

R ¹ aSi (OR ² ) _4-a (I)

R ³ _b Si (OR ⁴ ) _4-b (II)

R ⁸ cTi (OR ⁹ ) _4-c (III)

Al (OR < ¹⁰ >) ₃ (IV)

Wherein R ¹ and R ² are each independently selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group, an allyl group, and an aromatic group; R ³ is (i) R ⁵ OCH ₂ (R ⁶ ) (Wherein R ⁵ is a C _1-4 alkylene radical and R ⁶ is a hydrogen atom or a C _1-4 alkyl radical) and (ii) (Wherein R ⁷ is a hydrogen atom, a C _1-4 alkylene radical or a C _1-4 alkyl radical); R ⁴ is a C _1-6 alkyl group; R ⁸ is selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group and an allyl group; R ⁹ and R ¹⁰ are each independently a C _1-6 alkyl group; a is an integer from 0 to 3; b is an integer from 1 to 3; and c is an integer of 0 to 3.

Description

Siloxane coating composition excellent in storage stability, abrasion resistance and coloring property

The present invention relates to a siloxane-based coating composition, and more particularly to a siloxane-based coating composition which is coated on a solid substrate such as a plastic to form a coating having excellent abrasion resistance, storage stability and colorability.

Many transparent plastic materials are used as a substitute for glass in many fields because of their lightness and good resistance to breakage. In particular, it is mainly used in optical lenses, industrial safety glasses, and leisure goggles.

However, most plastic materials have a soft surface, which is easily scratched. In order to overcome these disadvantages, a protective film is generally formed on the surface of the plastic material with an organic material or a silicone coating agent. Examples of the coating agent commonly used for this purpose include polyurethane or acrylic organic materials and stearate silicone coating agents.

In general, it is preferable that the coating composition has all properties such as abrasion resistance, colorability, solvent resistance, adhesion and storage stability. However, existing coating compositions have a limitation in use because they have insufficient or at least one of these properties. Therefore, a great deal of research has been conducted to prepare coating compositions having all of these desirable properties.

For example, Korean Patent Application No. 89-2892 (published Aug. 8, 1989) and British Patent Application No. 2044787A disclose colorable abrasion-resistant siloxane-based coating compositions. However, this coating composition is disadvantageous in that discoloration occurs during curing and storage stability is poor, which makes it impossible to use for a long period of time, resulting in deterioration of abrasion resistance and peeling of the coating layer with time.

Japanese Patent Application Nos. 57-2735, 62-9266 and 53-30361 also disclose coating compositions similar to those described above. However, discoloration during curing, discoloration of the coating liquid itself due to changes over time, Problems such as abrasion resistance and weather resistance are exposed.

As a result, the inventors of the present invention have conducted extensive studies in order to overcome such drawbacks. As a result, it has been found that a coating composition comprising an inorganic-organic compound and an organic additive for controlling physical properties is added to a base resin containing an aqueous- Has excellent abrasion resistance, coloring property, solvent resistance, adhesion property, weather resistance and storage stability, and in particular, does not cause interference phenomenon in an optical lens.

(B) 0.1 to 50% by weight of a water-soluble colloidal silica or alcoholic colloidal silica having a pH of 2.5 to 4, (C) 10 to 60% by weight of a hydrolyzate of an organosilane represented by the following general formula (II) or a partial condensate thereof; 1 to 100 parts by weight of a titanium-based organic compound represented by the following general formula (III) or an intermediate derivative thereof, (e) 0.1 to 10 parts by weight of a compound represented by the following general formula (IV) And a hydrolyzate or a partial condensate thereof and 10 to 50 parts by weight of a C _1-12 ketone or a diketone, which is excellent in storage stability, abrasion resistance and coloring property ;

R ¹ aSi (OR ² ) _4-a (I)

R ³ _b Si (OR ⁴ ) _4-b (II)

R ⁸ _c Ti (OR ⁹ ) _4-c (III)

Al (OR < ¹⁰ >) ₃ (IV)

Wherein R ¹ and R ² are each independently selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group, an allyl group, and an aromatic group; R ³ is (i) R ⁵ OCH ₂ (R ⁶ ) (Wherein R ⁵ is a C _1-4 alkylene radical and R ⁶ is a hydrogen atom or a C _1-4 alkyl radical) and (ii) (Wherein R ⁷ is a hydrogen atom, a C _1-4 alkylene radical or a C _1-4 alkyl radical); R ⁴ is a C _1-6 alkyl group; R ⁸ is selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group and an allyl group; R ⁹ and R ¹⁰ are each independently a C _1-6 alkyl group; a is an integer from 0 to 3; b is an integer from 1 to 3; and c is an integer of 0 to 3.

Hereinafter, the present invention will be described in more detail.

Aqueous colloidal silica or alcoholic colloidal silica as a base resin in the composition of the present invention is usually a sol or stable dispersion of amorphous silica particles having a particle diameter of 5 to 100 nm. Examples of such a dispersion include products such as Ludox (manufactured by EI du Pont de Nemours and Company) or Oscal (manufactured by Hosung Industrial Co., Ltd.), which are widely marketed. The size of the silica particles is preferably 7 to 30 nm from the viewpoint of pH adjustment and storage stability of the dispersion. The content of the colloidal silica particles is 5 to 75% by weight, preferably 10 to 30% by weight, based on the total solids weight of (a) + (b) + (c)

Another component as the base resin is _a hydrolyzate of an organosilane represented by the general formula R ¹ _a Si (OR ² ) _4-a (I) or a partial condensate thereof. In this general formula (I), when a is 1 or more, R ¹ is most preferably a methyl group because a long alkyl group results in a soft composition. The number of moles of the methyl group-containing silane compound should be at least equal to or greater than the number of moles of the other silane compounds, if necessary, in combination with those having a methyl group and those having a different radical. When a is 0, R ² is a C _1-6 alkyl group. Examples of the silane compound used in the present invention include methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, dimethyldimetaxelsilane, dimethyldiethoxysilane, vinylmethyldimethoxysilane , Vinyl methyldiethoxysilane, phenyltrimethoxysilane, tetraethoxysilane, ethoxymethylvinylsilane, butoxytrimethylsilane, butyltrimethoxysilane, diphenylethoxyvinylsilane, methyltriisopropoxysilane, Methyltriacetoxysilane, tetraphenoxysilane, tetrapropoxysilane, vinyltriisopropoxysilane, and the like. The content of the organosilane compound is 0.1 to 50% by weight, preferably 1 to 10% by weight, based on the total solids content of (a) + (b) + (c)

The organosilane compound ( _c ) represented by the general formula R ³ _b Si (OR ⁴ ) _4-b (II) as a residual component constituting the base resin of the present invention is characterized by the fact that it has an epoxy functional group . The epoxy functionalities play a role in pigmentation or dyeing when the composition is cured on a substrate. Examples of the component (c) include 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropylmethylmethoxysilane, 3-glycidyloxypropyl Methyl ethoxysilane, and beta (3, 4-epoxycyclohexyl) ethyltrimethoxysilane. The content of the organosilane compound (c) is 10 to 60% by weight, preferably 15 to 30% by weight, based on the total solids weight of the basic components (a) + (b) + (c).

The titanium organic compound (d) represented by R ⁸ cTi (OR ⁹ ) _4-c (III) used in the siloxane coating composition of the present invention has an effect of controlling the refractive index and improving the film formability of the composition. By mixing such a titanium compound into the base resin, the refractive index of the cured coating on the substrate can be controlled within the range of about 1.50 to 1.70, contributing to improvement of weatherability and adhesion and relaxation of curing conditions (low temperature curing and rapid curing) . Examples of the titanium organic compound (D) include titanium tetraepoxide, titanium tetraisopropoxide, titanium 2-ethylhexoxide, and titanium butoxide.

The intermediate derivative of the titanium compound is prepared by adding a small amount of catalyst and water in an organic solvent such as methanol, ethanol, isopropyl alcohol, butanol or the like and reacting under reflux conditions for several hours to several hours depending on the desired properties. The content of the titanium-based organic compound (d) is 1 to 100 parts by weight, preferably 5 to 50 parts by weight, based on the total solid content of the base resin. When the content is less than 1 part by weight, it is difficult to obtain a film having a high refractive index. When the content is more than 100 parts by weight, the film has a disadvantage that the hardness of the film is decreased.

The aluminum alkoxide as component (e) in the composition of the present invention acts as a curing catalyst and a crosslinking agent and is represented by the general formula Al (OR ¹⁰ ) ₃ (IV). The aluminum alkoxide reacts with the above components (a), (b), (c) and (d) to form a stable molecular mass of a three-dimensional structure on the desk to improve storage stability, Thereby significantly accelerating the curing rate. Therefore, it is possible to obtain a film having a high hardness excellent in abrasion resistance within a short time at a low temperature. The aluminum alkoxide can be hydrolyzed and partially condensed by itself in consideration of storage stability and curing characteristics and can be selectively reacted with the organosilane of component (b) or (c) to form a stable molecular mass, It can be used by hydrolysis and condensation. Examples of such aluminum alkoxide (E) include aluminum tributoxide, aluminum triethoxide, aluminum isopropoxide and the like. The content of the aluminum alkoxide (E) is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on the total solid content of the base resin. When the content is less than 0.1, the hardness is relatively decreased. When the content is more than 10 parts by weight, the surface hardening is accelerated and the workability is poor.

When preparing the siloxane-based coating composition of the present invention, the base resin and the components (D) and (E) are required to be homogeneously mixed and therefore compatible with each other. At this time, if the mixing becomes uneven, the final product will show mislabeled and opaque spots, resulting in poor uniformity of the cured film.

The complex of the component (V) used in the composition of the present invention suppresses the condensation reaction of the above components (A), (B), (C), (D) and (E) as a C _1-12 ketone or a diketone compound And significantly improves storage stability. Examples of such a component (b) include acetyl acetone, acetone, methyl ethyl ketone, 2,4-hexanedione and the like, and the content thereof is 10 to 50 parts by weight, preferably 20 to 30 parts by weight.

The siloxane-based coating composition of the present invention needs to adjust its pH and reaction rate in consideration of various physical properties such as storage stability and abrasion resistance. For this purpose, catalysts are used, for example, acetic acid, impurities, boric acid, sulfuric acid, hydrochloric acid, nitric acid, chlorosulfonic acid, para-toluenesulfonic acid, trichloroacetic acid, polyphosphoric acid, iodic acid, iodic acid anhydride and perchloric acid Acid catalyst; And base catalysts such as caustic soda, ammonia water, potassium hydroxide, n-butylamine, di-n-butylamine, imidazole and ammonium perchlorate. These catalysts can be added to the final pH of the coating composition, And may be used alone or in combination of two or more in consideration of the reaction rate and adhesion to the applied substrate.

The silanol-based coating composition of the present invention is usually diluted with an organic solvent such as alcohols or cellosolve oil. Examples of such an organic solvent include methanol, ethanol, isopropanol, butanol, diacetone alcohol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, and cellosolve acetate. 10 to 50%.

The coating composition of the present invention may contain various additives in such an amount as not to deteriorate the physical properties of the composition of the present invention for the purpose of further improving adhesion, workability, antireflection property and the like to the base material in addition to the above components. Examples of additives that can be used in the composition of the present invention include ultraviolet absorbers such as polyolefin-based epoxy resin, cyclohexane oxide, polyglycidyl ester, bisphenol A type epoxy resin, epoxy acrylate, benzophenone, benzotriazole and phenols; Various surfactants such as block copolymers or graft copolymers of dimethylsiloxane and polyether or fluorine surfactants for improving the coating properties can be mentioned.

The coating composition of the present invention can be applied on various substrates by methods such as silk screen coating, roll coating, spray coating, dip coating or spin coating, which are customary in the art. The curing conditions are somewhat different depending on the components used and their mixing ratios, but are generally cured at a temperature below the softening point of the substrate, for example, a temperature range of 60 to 150 DEG C for about 20 minutes to several hours. The cured coating thus can be dyed as a disperse dye. The dyeing conditions are arbitrarily determined according to the concentration, temperature and time of the disperse dye, and they are generally dyed by immersing in a dye aqueous solution having a concentration of 0.1 to 1 wt% at a temperature of about 80 to 100 DEG C for 5 to 30 minutes.

The coating composition of the present invention is contacted with a solid substrate, particularly an optical lens (CR-39 or a medium refractive and high refractive index lens), and exposed to air to rapidly cure the coating film at room temperature or below 50 deg. It is possible to carry out the coating at a relatively low temperature at a relatively low temperature, and it is possible to prevent the lens from being deformed during curing.

The coating film formed by the siloxane coating composition of the present invention has properties such as excellent abrasion resistance, solvent resistance, adhesion and the like, has no discoloration upon curing, can arbitrarily adjust the refractive index within a range of 1.50 to 1.70, It is possible to exclude an interference effect caused by the above-mentioned impact resistance and exhibit excellent weather resistance.

The physical properties of the coating film formed on the lower side of the coating composition of the present invention were evaluated as follows.

Storage stability: It was evaluated by viscosity change when stored at 25 ℃ for 1 month. Each viscosity change was expressed as follows.

Less than 1: ◎

1 to 4: O

4 to 10:?

10 or more: x

Appearance: The state of the film after curing was visually observed to judge the presence or absence of the interference effect.

Abrasion resistance: The # 000 steel balls were tied to a hammer weighing 1.5 kg, the lens was rubbed with the hammer thirty times, and evaluated according to the degree of scratching, and was marked as follows.

No scratches: ◎

There are a few scratches: ○

Scratches are severe: x

Adhesion: In accordance with ASTM D 3359, a cell was drawn at intervals of 1 mm to form 100 cells, and then peel test was performed five times using a 24-mm-wide vertical tape of a Japanese Nichia reflector. The adhesion was evaluated by counting the number of chambers attached after the peeling test.

Resistance to solvent: Isopropyl alcohol, acetone, methanol or toluene, respectively, were rinsed with a cotton pad soaked 100 times, and then subjected to a visual inspection.

Each hot-water property: The coated lens was immersed in boiling water at 100 ° C for 30 minutes, and then subjected to visual inspection and adhesion test.

Color change during curing: After curing, the lens was visually observed.

Weatherability: The coated CR-39 lens was left in a weatherometer for 3 days using UVA 340 and then evaluated for yellowness index.

Dyeability: A CR-39 lens coated with 0.2 wt% aqueous solution of BPI sunray brown dye (manufactured by Brain Powe Inc.) was immersed at 90 ° C for 5 minutes, and then the transmittance of the lens was measured.

Abrasion resistance - Taber test: The abrasion resistance of the coatings was tested on a CR-39 disk specimen of 9 cm in diameter using a CS-14 abrasion wheel, with 500 g in each of the lower 500 g layers, 250 g on each side. The abrasion resistance was evaluated by the% change (% H) of the fogging change before and after the abrasion.

Hereinafter, the present invention will be described more specifically by way of examples, but the present invention is not limited to these examples.

[Example 1]

250 g of 3-glycidyloxypropyltrimethoxysilane, 100 g of tetraethoxysilane and 146 g of methanol were placed in a flask and stirred. 7.3 g of aluminum isopropoxide was added to the obtained mixture, and then stirred again until a clear solution was obtained. The stirred mixture was cooled to 25 DEG C and 80 g of acetic acid aqueous solution having a pH of 2.5 was added dropwise, followed by reaction for several hours. Further, 60 g of an intermediate derivative of titanium isopropoxide prepared by reacting an excess amount of isopropyl alcohol and titanium isopropoxide and a slight amount of acetic acid aqueous solution under refluxing conditions was added, reacted for about 3 hours, and acetylacetone 145 g was added and sufficiently stirred. Then 200 g of colloidal silica dispersed in methanol was added and aged for several hours. The aged mixture was immersed in an alkali-treated NK-55 (1.55 for Japanese refractory) lens, and cured at 110 DEG C for 60 minutes.

[Example 2]

The procedure of Example 1 was repeated except that an aqueous hydrochloric acid solution was used in place of acetic acid aqueous solution.

[Example 3]

Except that 175 g of 3-glycidyloxypropyltrimethoxysilane and 175 g of tetraethoxysilane were used as the initiator.

[Example 4]

The procedure was as described in Example 1, except that acidic, aqueous colloidal silica of pH 2.5 was used instead of alcoholic colloidal silica.

[Comparative Example 1]

The procedure of Example 1 was repeated except that tetraethoxysilane was not used.

[Comparative Example 2]

The procedure of Example 1 was repeated except that ethylcellosolve was used instead of methanol for colloidal silica dispersion.

[Comparative Example 3]

The procedure of Example 1 was repeated except that 3-glycidyloxypropylmethyldiethoxysilane was used instead of tetraethoxysilane.

[Comparative Example 4]

The same procedure as described in Example 1 was carried out except that the titanium organic compound was not used.

[Comparative Example 5]

Except that the basic, aqueous colloidal silica was adjusted to pH 2.5 to 4 with acetic acid in place of the alcoholic colloidal silica.

[Comparative Example 6]

Except that 3-glycidoxypropyltrimethoxysilane was not used as a catalyst.

[Comparative Example 7]

The procedure was as described in Example 1, except that aluminum isopropoxide was not used.

[Comparative Example 8]

The procedure of Example 1 was repeated except that no colloidal silica was used.

The properties of the coatings formed from the respective coating compositions in the above Examples and Comparative Examples are shown in Table 1 below.

Claims (6)

(A) 5 to 75% by weight of an aqueous colloidal silica or alcoholic colloidal silica having a pH in the range of 2.5 to 4, (b) 0.1 to 50% by weight of an organosiloxane represented by the following general formula (I) Silane or a partial condensate thereof, and (c) 10 to 60% by weight of a hydrolyzate of an organosilane represented by the following general formula (II) or a partial condensate thereof; 1 to 100 parts by weight of a titanium-based organic compound represented by the following general formula (III) or an intermediate derivative thereof, (e) 0.1 to 10 parts by weight of a compound represented by the following general formula (IV) And a hydrolyzate or a partial condensate thereof, and (C) 10 to 50 parts by weight of a C _1-12 ketone or a diketone, wherein the siloxane-based coating composition is excellent in storage stability, abrasion resistance and coloring property; R ¹ aSi (OR ² ) _4-a (I) R ³ _b Si (OR ⁴ ) _4-b (II) R ⁸ _c Ti (OR ⁹ ) _4-c (III) Al (OR < ¹⁰ >) ₃ (IV) In this formula, R ¹ and R ² are each independently selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group, an allyl group and an aromatic group; R ³ is (i) R ⁵ OCH ₂ (R ⁶ ) (Wherein R ⁵ is a C _1-4 alkylene radical and R ⁶ is a hydrogen atom or a C _1-4 alkyl radical) and (ii) (Wherein R ⁷ is a hydrogen atom, a C _1-4 alkylene radical or a C _1-4 alkyl radical); R ⁴ is a C _1-6 alkyl group; R ⁸ is selected from a C _1-6 alkyl group, an alkenyl group, a halogenated alkyl group and an allyl group; R ⁹ and R ¹⁰ are each independently a C _1-6 alkyl group; a is an integer from 0 to 3; b is an integer from 1 to 3; and c is an integer of 0 to 3. The composition according to claim 1, wherein the particles of the aqueous or alcoholic colloidal silica (a) have a particle diameter of 7 to 30 nm. The method according to claim 1, wherein the hydrolyzate of the organosilane (b) or a partial condensate thereof is at least one selected from the group consisting of methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, dimethyldimethoxy Silane, dimethyldiethoxy silane, vinyl methyl dimethoxy silane, vinyl methyl diethoxy silane, phenyl trimethoxy silane, tetraethoxy silane, ethoxymethyl vinyl silane, dibutoxymethyl silane, Wherein the composition is selected from the group consisting of methoxy silane, diphenyl ethoxy vinyl silane, methyl triisopropoxy silane, methyl triacetoxy silane, tetraphenoxysilane, tetrapropoxy silane and vinyl triisopropoxy silane. The method according to claim 1, wherein the hydrolyzate of the organosilane (c) or a partial condensate thereof is 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3- 3-glycidyloxypropylmethylethoxysilane, and beta (3, 4-epoxycyclohexyl) ethyltrimethoxysilane. The composition of claim 1, The composition according to claim 1, wherein the content of the titanium-based organic compound (d) or an intermediate derivative thereof is 5 to 50 parts by weight. The composition according to claim 1, wherein the content of the aluminum alkoxide or hydrolyzate thereof in (e) is 1 to 5 parts by weight.