JPH07247445A - Destaticizing aqueous coating composition - Google Patents

Abstract

PURPOSE:To obtain an aqueous coating composition useful for destaticizing films, etc., comprising a water dispersion sol of a specific electrically-conductive metal oxide, an aqueous silica sol, etc., having low resistance and stable destaticizing ability in an aqueous system without depending upon substitution, capable of forming a firm film on the surface of a synthetic resin. CONSTITUTION:This coating composition comprises (A) a water dispersion sol of an electrically-conductive metal oxide of one of tin, Sb and In, (B) an aqueous silica sol obtained by dispersing or hydrolyzing (i) lithium silicate and/or (ii) a hydrolyzable silicon compound in a water system, (C) an aqueous functional group-containing organic polymer for forming a chemical complex by reaction with the component B and (D) a surfactant. The component A is preferably a compound oxide of one of the metals and has <=1mum particle diameter. SiO2/Li2, for example, is used as the component (i) and a compound of the formula [X is a halogen, a 1-5C alkoxy (alkyl), an alkyl or an aryl; (n) is 0 or a positive number[, for example, is preferably used as the component (ii).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition having excellent ability to form an antistatic coating film.

[0002]

2. Description of the Related Art An antistatic agent utilizing a siloxane bond is called a permanent antistatic agent and exhibits excellent antistatic ability for a long period of time. Various types of antistatic agents have been proposed as described below. (1) Japanese Patent No. 231959 is a basic patent of an antistatic agent utilizing this type of siloxane bond. (2) JP-A-60-84366 proposes an antistatic coating agent comprising a silyl group-containing polymer and polysiloxane (alcoholic silica sol). (3) JP-A-62-280286 and JP-A-2-
In Japanese Patent No. 47166, a polysiloxane (alcoholic silica sol) is added with a metal compound, and a Si-OM bond (M represents a metal atom) is formed by a cohydrolysis process between these components. Disclosed is a coating composition capable of forming a conductive film, which is characterized by compounding components.

However, the conventionally proposed antistatic agents utilizing these siloxane bonds have the following problems. In terms of performance, it is not particularly satisfactory in terms of adhesion and antistatic ability to the surface of the synthetic resin substrate,
There is still room for improvement. This point can be easily understood from the fact that the coating composed of siloxane bonds is inorganic, and there is a strong demand for the formation of a strong coating on the synthetic resin surface. In both cases, the coating solution uses an organic solvent such as alcohol, so there is a problem with environmental resistance (environmental pollution due to disposal, effects on the human body during work, etc.), flammability, and the need for explosion-proof equipment. Have a point. Also, the use of organic solvents,
There is concern about the effect on the applied substrate.

[0004]

SUMMARY OF THE INVENTION The present invention does not utilize the conventional antistatic ability of a siloxane bond, but by using a conductive oxide, has a low resistance independent of humidity and a stable antistatic ability. The present invention aims to provide an antistatic aqueous coating composition capable of forming a strong coating film on a synthetic resin surface in combination with a conventional organic solvent system to an aqueous system. .

[0005]

The present invention provides (A) an aqueous dispersion sol of at least one conductive metal oxide selected from tin, antimony and indium, (B) lithium silicate and / or hydrolyzable silicon. An aqueous silica sol obtained by dispersing or hydrolyzing a compound in an aqueous system, (C) an aqueous functional group-containing organic polymer that reacts with the aqueous silica sol to form a chemical complex, and (D) a surfactant. A characteristic antistatic aqueous coating composition.

The present applicant invented and patented a conventional antistatic coating composition consisting of an aqueous silica sol, an aqueous functional group-containing polymer and a surfactant, which was changed from a conventional organic solvent system to an aqueous system (special feature Japanese Patent Application No. 4-350036). The present invention is a water-based antistatic coating composition that forms a strong coating film having a lower resistance in an aqueous system by further disposing an aqueous dispersion sol of a conductive metal oxide therein.

The present invention will be described in detail below. As the water-dispersed sol component of the conductive metal oxide (A) constituting the antistatic aqueous coating composition of the present invention, tin, antimony, indium oxide or a composite oxide of these metals is used. Specifically, antimony - compound oxide of tin _{(Sb 2 O 3 / SnO 2} , ATO), indium - composite oxide of tin _{(In 2 O 3 / SnO 2} , ITO) is preferably used. The content of Sb ₂ O ₃ in ATO is preferably 1 to 10% by weight, particularly preferably 8 to 9% by weight. IT
The content of SnO ₂ in O is 1 to 10% by weight, especially 4
~ 6 wt% is preferred.

The water-dispersed sol of these conductive oxides can be obtained by adjusting and dispersing the pH of water, which is a dispersion medium, of fine particles having a particle size of 1 μm or less, preferably 0.2 μm or less. pH is 4 or more, preferably pH 5
Up to 6 is well dispersed.

Generally, the water-dispersed sol has the maximum scattering at a particle size of 1/2 of the wavelength of visible light of 0.4 to 0.8 μm, and when the particle size becomes smaller than that, the scattering sharply decreases and the particles are dispersed. Is known to gain transparency. Therefore, it is particularly preferable that the fine particles have an average particle diameter of 0.2 μm or less.
When the particle size is ½ or more of the wavelength of visible light, the particles are coagulated and precipitated, a uniform coating film is not formed, the antistatic effect is lost, and the coating film loses transparency.

In the present invention, the amount of the above-mentioned conductive oxide used is determined by the required surface resistance value, but as the solid content in the entire coating composition of the present invention (including water), it is calculated in terms of oxide. It is preferably used in an amount of 0.5 to 50% by weight, particularly 5 to 20% by weight.

Next, the aqueous silica sol as the constituent component (B) of the coating composition of the present invention will be described. The aqueous silica sol is a uniform and stable aqueous silica sol obtained by dispersing or hydrolyzing a lithium silicate and / or a hydrolyzable silicon compound in an aqueous system. here,
The meaning of being dispersed or hydrolyzed in an aqueous system means that 10% or less of the entire composition of the present invention may be present in an organic solvent.

As one means for preparing an aqueous, homogeneous and stable aqueous silica sol from lithium silicate and / or a hydrolyzable silicon compound, an amount of the organic solvent in the entire composition of the present invention is 10% or less. There is a method in which a lithium silicate and / or a hydrolyzable silicon compound is dissolved in an organic solvent, and hydrolysis is performed in the presence of a catalyst.

In the hydrolysis, by preliminarily dissolving lithium silicate and / or a hydrolyzable silicon compound in an organic solvent, a rapid reaction with water during hydrolysis is prevented, and silica (SiO ₂ ) is deposited or The reaction product is prevented from becoming cloudy, and a uniform and stable aqueous silica sol is obtained. In this reaction, even if the amount of the organic solvent increases, the hydrolysis reaction occurs similarly, so that the control of the amount of the organic solvent is important. Generally, 1 organic solvent is included in the final composition.
Manage so that it will be 0% or less. The organic solvent used is preferably alcohols such as methanol and ethanol.

As another means for preparing an aqueous silica sol which is homogeneous and stable in water, there is a method which does not use an organic solvent. In this case, it can be obtained by preparing a solution in which the catalyst is uniformly dissolved in water, and adding the lithium silicate and / or the hydrolyzable silicon compound therein.

The lithium silicate used in the present invention is represented by SiO ₂ / Li ₂ O and has a Si / Li molar ratio of 3 to 6. The amount of this lithium silicate used is determined in combination with the hydrolyzable silicon compound, but the solid content in the entire composition of the present invention (silica conversion value)
It is preferably used so as to be 0.1 to 5% by weight.

The hydrolyzable silicon compound used in the present invention is represented by the following general formula (1).

[0017]

[Chemical 1]

The hydrolyzable silicon compound represented by the general formula (1) is preferably one in which n is 1 to 10. Specifically, silicon tetrachloride (SiCl ₄ ), tetraethyl silicate (Si (OEt) ₄ ), tetramethyl silicate (Si (OMe) ₄ ), and condensates of these alkyl silicates, for example, tetraethyl silicate quintuple (trade name: ethyl silicate) 40, manufactured by Colcoat Co., Ltd., and the like.

In the present invention, the amount of the hydrolyzable silicon compound used is 1 to 1 as solid content in terms of silica in the entire composition.
Preference is given to using in the range 10% by weight.

The method of dispersing or hydrolyzing the lithium silicate and / or the hydrolyzable silicon compound is carried out as follows. That is, a lithium silicate and / or a hydrolyzable silicon compound is dissolved in a predetermined amount of an organic solvent in an amount to give a predetermined solid content concentration to form a uniform solution, which is dispersed or hydrolyzed in the presence of a catalyst.

When no organic solvent is used, a lithium silicate and / or a hydrolyzable silicon compound is added to a uniform solution of water and a catalyst in an amount so as to give a predetermined solid content concentration, and dispersed or hydrolyzed. Dispersion or hydrolysis is
It is carried out by adding water in an amount required for a desired hydrolysis rate in the presence of an acid or alkali catalyst.

Examples of the catalyst for dispersion or hydrolysis include basic hydroxide catalysts such as LiOH, NaOH and KOH, and 0.01 to 10% by weight based on the silicon compound is used. As the catalyst to be used, in a system in which an aqueous silica sol and an aqueous functional group-containing polymer described later are reacted to form a complex, a basic catalyst is used to prevent decomposition of the complex or precipitation of silica. Catalysts are preferred.

The reaction temperature for dispersion or hydrolysis is sufficient from room temperature to 50 ° C., and the reaction time is generally 1 to 24 hours, varying depending on the reaction temperature and the amount of catalyst. By the above dispersion and hydrolysis reaction, an aqueous silica sol can be obtained from lithium silicate and / or a hydrolyzable silicon compound.

Further, in the present invention, since the aqueous silica sol is prepared by dispersion and hydrolysis, the terminal group of the aqueous silica sol contains an OH group and becomes unstable with time. Also in the sense of stabilizing this, the (C) aqueous functional group-containing polymer described below is used.

Next, the aqueous functional group-containing polymer that reacts with the aqueous silica sol (C), which is a constituent of the aqueous antistatic coating composition of the present invention, to form a chemical complex will be described. In the present invention, the aqueous functional group-containing polymer includes a water-soluble or water-dispersible polymer.

Since the aqueous functional group-containing polymer is, for example, a water-dispersible polymer, it has good compatibility with the aqueous silica sol (B), and when the coated surface is a synthetic resin, it has excellent adhesiveness and transparency. A composition capable of forming a coated film is provided. Further, as described above, the aqueous silica sol tends to change with time because it has a terminal OH group, but an aqueous functional group-containing polymer is used to prevent this destabilization with time. Thus, in the present invention, a water-dispersible functional group-containing polymer is reacted with an aqueous silica sol to form a chemical complex, and (C) the water-dispersible functional group-containing polymer is an important component. .

As the aqueous functional group-containing polymer, for example, a water-dispersible polyester having an ester bond is typical. That is, the polyester polymer having an ester bond is an unreacted hydrolysis group or silanol group (Si-) in the polysiloxane constituting the aqueous silica sol of (B).
(OH) and other chemical reactions, or ester bonds that form hydrogen bonds, other functional groups (such as hydroxyl groups and carboxyl groups)
Therefore, it reacts with the aqueous silica sol to form a chemical complex.

As a specific example of the water-dispersible polyester, commercially available Bayronal (manufactured by Toyobo Co., Ltd.) or the like is used, and the number average molecular weight of these is 1,000 to 50,000.
0, preferably 10,000 to 20,000.

The aqueous functional group-containing polymer is not limited to the above water-dispersible polyester, is a conventionally known water-soluble or water-dispersible emulsion type coating agent, and reacts with the above aqueous silica sol. It goes without saying that polymers that can be used can be used. Specific examples of this type of aqueous functional group-containing polymer include vinyl alcohol-based polymers, ethylene glycol-based polymers, polyester polyol-based polymers, polyether polyol-based polymers, and aqueous urethane resins.

In the present invention, it is sufficient to use the aqueous functional group-containing polymer in an amount of 0.1 to 5% by weight based on the total composition of the present invention.

The present invention further comprises (D) a surfactant in an aqueous coating composition containing a chemical composite of (B) aqueous silica sol and (C) aqueous functional group-containing polymer. In the composition of the present invention, the surface tension is lowered and the wettability is improved by blending a surfactant, so that a film having excellent adhesiveness to the surface to be coated is formed.

The surfactant is not particularly limited, but it is preferable to use a nonionic surfactant. This includes, for example, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkylphenyl ether, sorbitan fatty acid ester, polyglycerin fatty acid ester, polyethylene glycol fatty acid ester, silicone-based,
Nonionic surfactants such as fluorine-based compounds (perfluoroalkylethylene oxide adducts, perfluoroalkylpolyoxyethylene ethanol, fluorinated alkyl esters) and the like can be mentioned as preferable ones.

In the present invention, a silicone-based and perfluoroalkyl group containing a side chain modified copolymer having a Si--C bond as its structure or a terminal modified copolymer having a Si--O--C bond is used as a nonionic surfactant. Fluorine-based surfactants containing are preferred. In the present invention, the above-mentioned surfactant is 0.0
It is sufficient to use it in a proportion of 5 to 5% by weight.

The antistatic aqueous coating composition of the present invention can be used in any desired manner. That is, the use condition is not particularly limited, and for example, in-line,
It can be used in any form such as offline. Further, the application object of the antistatic aqueous coating composition of the present invention is not particularly limited and can be used for any thing, for example, a molded product of polyester-based or polyethylene-based resin, particularly It is suitable for antistatic charging of films and sheets.

[0035]

EXAMPLES The present invention will now be described in more detail by way of examples. In the description, “part” means part by weight. The performance evaluation tests in Examples and Comparative Examples were carried out as follows. [Appearance / transparency test] When the coating film coated on the test piece is compared with the test piece before coating, ○ indicates that the coating film has almost the same transparency as the test piece before coating, and x indicates that it does not. did. [Surface resistance value] Tokyo Denshi Co., Ltd., surface resistance meter TR-3
Shaped, measured at 23 ± 5 ° C and 55 ± 5% RH. [Adhesion test] Cellophane tape (24 mm cellophane tape: trade name, manufactured by Nichiban Co., Ltd.) was attached to the test piece, and when the film was peeled off instantly, the one in which the coating film was not peeled was marked with ◯ and the one in which it was peeled was marked with x.

Reference Example (Preparation of Aqueous Silica Sol) In a 500 ml separable flask equipped with a stirrer, a thermometer, and a reflux condenser, 365.7 parts of ion-exchanged water and lithium silicate (manufactured by Nissan Chemical Industries, Ltd., Product name LSS-4
5) 10.0 parts was charged and stirred to homogenize, then 0.3 parts lithium hydroxide monohydrate (LiOH.H ₂ O) was charged and stirred at 30 ° C. until constant. 24.0 parts of ethyl silicate (manufactured by Colcoat Co., Ltd., ethyl silicate 28, trade name) was added to the mixed solution, and a hydrolysis reaction was carried out at 30 ° C. for 4 hours. The solid content concentration of the obtained aqueous silica sol was 2% as SiO ₂ content.

Example 1 100 parts of the aqueous silica sol obtained in Reference Example was added with 30 parts of ion-exchanged water, and a water-dispersible polymer polyester MD-1100 as an aqueous functional group-containing polymer.
(Toyobo Co., Ltd. “Vylonal” (trade name) solid content 30%) 3.4 parts, antimony / tin composite oxide dispersion SN-38F (Ishihara Sangyo Co., Ltd., conductive oxidation) 66.6 parts of solid dispersion (solid content 17%) and added at 30 ° C.
Reacted for hours. Next, L-7607N (a silicone-based surfactant manufactured by Nippon Unicar Co., Ltd., trade name) was added to the reaction solution in a proportion of 0.4% by weight (hereinafter the same) with respect to the total composition containing water, followed by uniform mixing. Then, an antistatic aqueous coating composition (1) was prepared.

The coating liquid (1) thus obtained was applied on a polyethylene terephthalate resin film by Meyer bar # 4.
And was dried for 1 minute at 120 ° C. using a constant temperature thermostat (manufactured by Isuzu Seisakusho Co., Ltd., model CNS-115S), and various performance tests were conducted. The results are shown in Table 1.

(Example 2) 25.8 parts of ion-exchanged water, M
D-1220 (manufactured by Toyobo Co., Ltd., water-dispersible high-molecular polyester "Bylonal" solid content 25%) 40.0 parts,
Weigh out 133.4 parts of SN-38F and measure 1 at 30 ° C.
Reacted for hours. L-7607N (Nippon Unicar Co., Ltd. silicone surfactant) was added to the reaction solution at a ratio of 0.4% by weight and mixed uniformly to prepare an antistatic aqueous coating composition (2). The same test as in Example 1 was performed. The results are shown in Table 1.

Comparative Example Aqueous silica sol 1 obtained in Reference Example
00 parts, H ₂ O 96.6 parts, MD-1100 3.4
Each part was weighed and reacted at 30 ° C. for 1 hour. A silicon-based surfactant L-7607N was added to the reaction solution at a ratio of 0.4% by weight and mixed uniformly to prepare an antistatic aqueous coating solution (3), and the same test as in Example 1 was conducted. It was The results are also shown in Table 1.

Example 3 A 500 ml separable flask equipped with a stirrer, a thermometer, and a reflux condenser was charged with 372.0 parts of ion-exchanged water, and lithium hydroxide monohydrate (LiOH.H ₂ O) 0 0.4 parts was added and stirred at 30 ° C. until constant. Ethyl silicate (Ethyl silicate 28 manufactured by Colcoat Co., Ltd.) 27.6 was added to the mixed solution.
Parts were added and the hydrolysis reaction was carried out at 30 ° C. for 4 hours.
The solid content concentration of the aqueous silica sol obtained as described above was 2% in terms of SiO ₂ content.

100 parts of the above aqueous silica sol, 30 parts of ion-exchanged water, 3.4 parts of MD-1100 and 66.6 parts of SN-38F were weighed and reacted at 30 ° C. for 1 hour. L-7607N was added to the reaction solution at a ratio of 0.4% by weight and mixed homogeneously to prepare an antistatic aqueous coating composition (4), and the same test as in Example 1 was conducted. The results are shown in Table 1.

[0043]

[Table 1]

[0044]

According to the present invention, an aqueous antistatic coating composition of silica sol type is provided instead of the conventional organic solvent type coating composition. In particular, the antistatic aqueous coating composition of the present invention has a low resistance independent of humidity dependence by using a conductive oxide, and has a stable antistatic property, and the coated surface is a synthetic resin surface. When it is, since it uses an aqueous functional group polymer that reacts with the aqueous silica sol component to form a complex, the adhesion is improved, stable for a long time, and excellent coating performance. Demonstrate.

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[Procedure amendment]

[Submission date] April 22, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 4

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

The lithium silicate used in the present invention is represented by SiO ₂ / Li ₂ O, and SiO ₂ / L
The molar ratio of i ₂ O is 3 to 6. The amount of this lithium silicate used is determined in combination with the hydrolyzable silicon compound, but it is preferable to use it so that the solid content (silica conversion value) is 0.1 to 5% by weight in the entire composition of the present invention. preferable.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The hydrolyzable silicon compound represented by the general formula (1) is preferably one in which n is 1 to 10. Specifically, silicon tetrachloride (SiCl _4), tetraethyl silicate (Si _{(OEt) 4),} tetramethyl silicate (Si _{(OMe) 4)} and pentamer (trade name Ethyl condensates e.g. tetraethyl silicate of alkyl silicate Examples thereof include silicate 40 and Colcoat Co., Ltd.

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Claims (5)

[Claims] 1. An aqueous dispersion sol of (A) at least one conductive metal oxide selected from tin, antimony and indium, and (B) lithium silicate and / or a hydrolyzable silicon compound dispersed or hydrolyzed in an aqueous system. An antistatic aqueous solution comprising the aqueous silica sol obtained by the above, (C) an aqueous functional group-containing organic polymer that reacts with the aqueous silica sol to form a chemical complex, and (D) a surfactant. Coating composition. 2. The antistatic aqueous coating composition according to claim 1, wherein the conductive metal oxide is a composite oxide of any one of tin, antimony and indium. 3. The antistatic aqueous coating composition according to claim 1, wherein the particle size of the conductive metal oxide is 1 μm or less. 4. The antistatic aqueous coating composition according to claim 1, wherein the aqueous functional group-containing organic polymer is an ester group-containing polymer. 5. (A) 0.5 to 50% by weight (as solid content) of an aqueous dispersion sol of at least one conductive metal oxide selected from tin, antimony and indium, (B) lithium silicate and / or 0.1 to 10% by weight (as solid content) of an aqueous silica sol obtained by dispersing or hydrolyzing a hydrolyzable silicon compound in water, (C) an aqueous functional group that reacts with the aqueous silica sol to form a chemical complex An antistatic aqueous coating composition comprising 0.1 to 5% by weight of an organic polymer contained and 0.05 to 5% by weight of (D) a surfactant.