JPS6019774B2 - Method for producing epoxy resin dispersion - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing an eboxy resin dispersion.

More specifically, when applying multiple coats of paint for the purpose of mounting, corrosion protection, etc., it is possible to apply oil-based paints, phthalate resin paints, chlorinated rubber paints, etc. to the coated surface, and it is easy to work. This invention relates to a method for producing an epoxy resin dispersion for obtaining an excellent epoxy resin paint. Paints are applied to prevent corrosion of metal materials and metal products, and to make wooden products beautiful, but in this case, it is rarely applied in one coat, but is usually applied multiple times to create a multi-layered coating. This is the method. For example, if we explain the painting process using steel as an example, the steps are surface treatment → undercoat → intermediate coat → topcoat. Such surface treatment is performed by physical methods such as blasting and sanding. In addition, paints that are commonly used as undercoats include boiling oil (vegetable polymerized oil), long-oil phthalic acid resin varnish, epoxy resin varnish, etc., mixed with rust-preventing pigments and other pigments. be. The combination of the intermediate and top coats applied after the undercoat is naturally determined by the type of the undercoat.

In other words, when a so-called oxidative polymerization type paint using boiling oil, long-oil phthalic acid resin varnish, chloride rubber varnish, etc. as a brightening agent is used as an undercoat, the intermediate coat and top coat will be treated as the undercoat. Paints of the same type, i.e., boil oil, long-oil phthalate resin varnish, etc., are used as a color vehicle, and paints that use polymeric synthetic resin varnishes as a color vehicle, such as the above-mentioned epoxy resin varnishes, are intermediate coats. It cannot be applied as a paint or topcoat over an oxidative polymerization paint film. Because such epoxy resin has a high molecular weight, it has the ability to dissolve mineral spirits, solvent kerosene, etc., and is hardly soluble in aliphatic hydrocarbon solvents, such as xylene,
Aromatic hydrocarbon solvents such as toluene, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and acetone, ester solvents such as butyl acetate and ethyl acetate,
Alternatively, it is necessary to dissolve them using glycol-based solvents, etc., and these solvents have a strong ability to dissolve organic substances. This is because, if the paint is overlapped, the coating film of the oxidative polymerization type paint will be easily redissolved in the solvent, resulting in defects such as wrinkles and peeling from the steel surface. In recent years, many cases have been adopted in which epoxy resin paints, which have excellent paint film durability or chemical resistance, are applied over and over again as base coats, intermediate coats, and top coats, but epoxy resin paints Coatings that are applied under completely controlled conditions, such as when the steel is extremely clean by blasting before painting, exhibit extremely good coating performance, but even if there is some rust or other deposits, The durability of the paint film painted in the remaining state will be significantly inferior.

On the other hand, the above-mentioned oxidative polymerization type paints have been widely used for a long time because they do not require very strict surface treatment, have a high degree of corrosion resistance, and are easy to apply. It is an anti-rust paint, but as mentioned above, there are restrictions on the types of intermediate and top coats.
It is limited to oil-based or phthalic acid resin-based paints. The film resistance, chemical resistance, etc. of this type of paint are not very good, and in paint systems using these as intermediate and top coats, the durability of the paint film is limited due to recent air pollution. I'm in a short-lived mood. Therefore, the recent trend is to use epoxy resin paints, which have particularly excellent durability and chemical resistance, as intermediate and top coats, but the type of undercoat is determined for the reasons mentioned above. Therefore, by taking advantage of the advantages of oxidative polymerization type paints, we have adopted a method of recoating epoxy resin paints with good durability and chemical resistance as intermediate and top coats.
Phenol-modified phthalic acid resin varnish and M. 1.0 pigment (
Phenol in combination with Micaceous Iron Oxide (scaly iron oxide) ~M. 1.0. A paint is applied onto a coating film such as an oil-based anti-corrosion paint, and M. 1.0. Even if pigments are arranged in striped and flat multilayers and a strong solvent-containing paint is applied over and over again, M. 1.0. Currently, a conventional method is used to prevent the diffusion of solvents onto the coating surface of oil-based anti-corrosion paints through the shielding effect of a pigment layer.

However, this method is not perfect; for example, phenol to M. 1.0. If the dissolving power of the solvent contained in the top coat applied to the paint film is too strong, the phenol-modified phthalic acid resin may be redissolved or M. 1.0. Pigment layers are not necessarily arranged in a uniform, flat, multi-layered manner during coating, and there are many pinholes in the coating film, so there are disadvantages such as the inability to completely prevent penetration and diffusion of solvents, and the number of coating steps required. There is also the disadvantage that it adds one step. Therefore, if you try to recoat epoxy resin paint over a paint film with poor solvent resistance, such as an oxidative polymerization paint film, the main component is aliphatic hydrocarbon solvents such as mineral spirits and solvent kerosene, which have weak dissolving power. However, epoxy resins, which are solid at room temperature, are hardly soluble in aliphatic hydrocarbon solvents by normal methods.
On the other hand, compositions using water as a solvent have many problems. That is, as a known composition using water as a solvent, a method is well known in which a composition consisting of an epoxy resin, water, and an emulsifier is dispersed to emulsify it to form an aqueous dispersion.

However, when using a paint obtained using this composition, the biggest drawback is that the water scattering speed is extremely slow compared to that of a solvent, which delays the curing of the paint film. When used in a location, a high-temperature atmosphere is created, and the uncured coating film is washed away with water, causing a phenomenon of shearing. These above-mentioned phenomena hardly occur in coating films containing solvents. However, as described above, since epoxy resins that are solid at room temperature lack solubility in aliphatic hydrocarbon solvents, it has been difficult to obtain solutions of epoxy resins using such solvents. On the other hand, a method of obtaining a dispersion by dispersing it in a mixed solvent system of aromatic hydrocarbon solvents such as xylene or toluene and water is also known, but for the reasons mentioned above, it is difficult to apply multiple coats on the oxidative polymerization type paint film. It was impossible. The present invention provides a method for producing an epoxy resin dispersion containing an epoxy resin and an aliphatic hydrocarbon solvent as main components, which solves these drawbacks.

That is, the present invention uses epoxy resin 85-3 having a melting point of 50 qo or more.
and 10 to 35 parts by weight of an aliphatic hydrocarbon solvent to form a homogeneous mixture.
5 parts by weight of water (provided that the total amount of epoxy resin, solvent and water is 10 parts by weight, and the amount of water in the total amount of solvent and water does not exceed 5% by weight), and epoxy resin solids. minutes 10
An epoxy resin dispersion characterized by adding 1 to 1 part by weight of polyoxyethylene nonylphenyl ether or polyoxyethylene benzylated phenyl ether having an HLB value of 12 or more per part by weight of the epoxy resin dispersion, which is emulsified and dispersed. It pertains to the manufacturing method.

The epoxy resin used in the present invention is an epoxide containing at least two or more epoxy groups at the terminal or a derivative thereof with a melting point of 50 qo or higher, and is bisphenol A-epichlorohydrin type, side chain type, and alicyclic type. ,
These include polymerized fatty acid ester type, novolac type, butyl glycidyl ether type, polyalkylene ether type, glyceryl triepoxide, alkylphenol type epoxy resin, and the like.

For example, Epicoat 1001, Epicoat 1004, Epicoat 1007, Epicoat 1009 manufactured by Shell Chemical
; Ciba Araldite 6071, Araldite 6099
: Chissonox CP-1200 manufactured by Chisso ■; or commercially available resins such as DER611 and DER667 manufactured by Dow Chemical. In the present invention, the epoxy resin can be used alone or in combination of two or more to bring out the characteristics of each epoxy resin, or it is possible to use a low molecular weight epoxy resin that is liquid at room temperature and is compatible with the solid epoxy resin. Alternatively, other resins such as thermoplastic polyester resin and thermoplastic acrylic resin may be used by melt-mixing up to 25 parts by weight based on the weight part of the solid epoxy resin 10. Examples of aliphatic hydrocarbon solvents used in the present invention include (iso)pentane, (iso)hebutane, (iso)hexane, and (iso)octane, but the purity of the aliphatic hydrocarbon solvent It does not have to be 100%, and those that are broadly treated as aliphatic hydrocarbon solvents by those skilled in the art include those that contain aromatic hydrocarbon solvents as by-products of about 3% by weight or less. For example, rubber volatile oil, VM. &P. Examples include naphtha, mineral spirits, and solvent kerosene.

It is not a good idea to obtain a high purity aliphatic hydrocarbon solvent as an industrial product because it is expensive, and as mentioned above, it is not advisable to obtain a high purity aliphatic hydrocarbon solvent as a by-product. It is rather preferable to use an aliphatic hydrocarbon solvent containing as epoxy resin from the viewpoint of imparting solubility to the epoxy resin. The nonionic emulsifier used in the present invention has an HLB value of 12 or more, most preferably an HLB value of 18.
The above polyoxyethylesononylphenyl ether or polyoxyethylesobenzylated phenyl ether.

For example, Nippon Emulsifier ■ product names Nucol 707, Nucol 710, 2 Ucol 714, Nucol 723 Nucol 504 Nucol 509 Nucol 510 Nucol 520; Kao Atlas ■ product names Emulgen A-500, Emulgen 93. Commercially available products such as Emulgen 985 and Emulgen 95 Beats can be used. These can be used singly or in a mixture of two or more. The nonionic emulsifier may be added in an amount of 1 to 1 part by weight, preferably 3 to 8 parts by weight, based on 10 parts by weight of the solid content of the epoxy resin, but most preferably, the stability of the dispersion is Considering the ease of obtaining a dispersion, etc., at least 3 parts by weight of polyoxyethylene nonylphenyl ether or polyoxyethylene benzylated phenyl ether having an HLB value of 1 or more as described above is added, and as necessary. The emulsifier having an HLB value of 12 or more is preferably added within the scope of the present invention. The method for producing the epoxy resin dispersion according to the present invention includes, for example, heating a mixture consisting of the epoxy resin and the entire amount of the aliphatic hydrocarbon solvent to a temperature higher than the thermal melting point of the epoxy resin used, and then using a high-speed mixer, homogenizer, etc. Mix well to make a homogeneous solution.

Then, while keeping the temperature at about 50d to 100°C, preferably around 80°C, add 1 to 1 part by weight of the emulsifier per 10 parts by weight of the solid content of the epoxy resin while stirring at high speed, and after thoroughly dispersing it, add water. to obtain a dispersion. The method described above is a standard example, and the aliphatic hydrocarbon solvent and water can be added separately, or the emulsifier can be dissolved in water in advance and then added together with the water. Possible methods include: In other words, any method may be used as long as distribution is possible. In the epoxy resin dispersion of the present invention, the amounts of the aliphatic hydrocarbon solvent and water relative to the epoxy resin are at least 1 part by weight of the aliphatic hydrocarbon solvent and 5 parts by weight of water per 85 parts by weight of the epoxy resin solid content. This is the required amount.

If the amount of aliphatic hydrocarbon solvent and water is less than the above range, the stability of the dispersion will be poor and it cannot be put to practical use. Furthermore, if the amount of epoxy resin in the dispersion is less than 3 parts by weight, the dispersion will fail. Problems with body stability arise. On the other hand, regarding the amounts of aliphatic hydrocarbon solvent and water, the above-mentioned respective amounts are the minimum required amounts, but if a total amount of 15 parts by weight or more of the solvent is required, the amount of aliphatic hydrocarbon solvent and water The amount of water in the total amount of water must be 5% by weight or less. If the amount of water in the total solvent exceeds the above 50% by weight, the storage stability of the dispersion will decrease, and furthermore, when using a paint using the dispersion obtained in the present invention, it may be difficult to use the dispersion in an environment with insufficient ventilation. This is not preferable because the paint film tends to fall off. Preferably, the total amount of water in the dispersion is 10 to 15% by weight, which is best from the viewpoint of stability. The dispersion obtained by the method of the present invention can be used mainly as a room-temperature-curing clear paint if one or more suitable curing agents such as polyvalent amines, amine adducts, polyamide resins, etc. are added thereto. You can.

Furthermore, depending on the purpose, it is also possible to form an epoxy resin coating material with good coating film properties by adding pigments and the like. Furthermore, by adding one or more of melamine resin, phenol resin, urea resin, acrylic resin, etc., or a mixture or derivative thereof, it can also be used as a thermosetting paint. The pigment used here may be any pigment used in general paints, but it may be unstable under baking conditions, or may partially dissolve upon contact with a solvent and lose the dispersing effect of the emulsifier. Use of such items should be discouraged. Furthermore, if necessary, in addition to pigments, antifungal agents, antifoaming agents, and other additives may be added. The coating material obtained from the dispersion according to the present invention does not require special equipment and can be easily applied by known methods such as brush coating, airless spraying, and air spraying. Conventional solvent-based epoxy resin paints are strong solvent-based and cannot be coated over coatings with poor solvent resistance, such as oil-based undercoat coatings, but the dispersion obtained by the method of the present invention The epoxy resin paint used has solved the above-mentioned problems, and has also solved the phenomenon of paint film shedding under poor exhaust conditions, which is a drawback of epoxy resin aqueous dispersions obtained by known methods. be. The present invention will be further explained below with reference to Examples. In addition, "parts" or "%" in Examples and Comparative Examples are "parts by weight" or "% by weight".
” is shown. Example 1 Pulverized bisphenol A - epichlorohydrin type, molecular weight approximately 900, epoxy equivalent 450-500, melting point 64
85 parts of solid epoxy resin of ~74 oz and 1 part of mineral spirit were mixed and heated to 90 qo while stirring to melt.

After complete dissolution, the mixture was kept warm at 80 qo and while continuing high-speed fly swarming, a mixture of 5 parts of polyoxyethylene benzylated phenyl ether with an HLB value of 18 and 5 parts of water was gradually added and mixed and dispersed well. An epoxy resin dispersion of No. 1 was obtained. Example 2 Parts of solid epoxy resin 7 similar to those used in Example 1 and 2 parts of mineral spirit were mixed and heated to 90° C. under lighting to melt.

After completely dissolving, keep the temperature at 80 oo and gradually add a mixture of 2.1 parts of polyoxyethylene nonyl phenyl ether with an HLB value of 19.5 and 10 parts of water while continuing high-speed heating. The epoxy resin dispersion of Example 2 was obtained by mixing and dispersing. Example 3 65 parts of a solid epoxy resin similar to that used in Example 1 and 2 parts of rubber volatile oil were mixed and heated to 90° C. under lighting to melt.

After completely melting, keep the temperature at 80°C, and while continuing high-speed dissolution, gradually add a mixture of 1.95 parts of polyoxyethylene benzylated phenylenal with an HLB value of 18.2 and 15 parts of water, and mix and disperse well. An eboxy resin dispersion of Example 3 was obtained. Example 4 55 parts of solid epoxy resin similar to that used in Example 1 and 3 parts of solvent kerosene were mixed and heated at 90oC while stirring.
It was heated to melt.

After completely dissolving, the temperature was kept at 80 qo, and while continuing the high-speed feeding, 1.65 parts of polyoxyethylene nonylphenyl ether with an HLB value of 18.5 and polyoxyethylene benzylated phenyl ether with an HLB value of 12 were added. A mixture of 0.5 parts of water and 15 parts of water was gradually added and thoroughly mixed and dispersed to obtain the epoxy resin dispersion of Example 4. Example 5 Four solid epoxy resins similar to those used in Example 1 and three mineral spirits were mixed, and 80
It was melted by heating to ℃.

After completely dissolving, keep warm at 90 oo and continue to cross at high speed to dissolve polyoxyethylene benzylated phenyl ether with HLB value of 18.2.2. A mixture of 3 parts of water and 3 parts of water was gradually added and thoroughly mixed and dispersed to obtain the epoxy resin dispersion of Example 5. Comparative Example 1 9 parts of a solid epoxy resin similar to that used in Example 1 and 5 parts of mineral spirit were mixed and heated to 90:00 while stirring to melt.

After completely dissolving, the polyoxyethylene benzylated phenyl ether having an HLB value of 18 was dissolved while keeping the temperature at 80oC and continuing high-speed lighting.3. A mixture of the anchor part and 5 parts of water was gradually added and mixed and dispersed well to obtain an epoxy resin dispersion of Comparative Example 1. Comparative Example 2 65 parts of a solid epoxy resin similar to that used in Example 1 and 15 parts of rubber volatile oil were mixed and heated to 9,000 ml while stirring to melt.

After completely dissolving, keep the temperature at 8020℃ and gradually add a mixture of 2.6 parts of polyoxyethylene nonyl phenyl ether with an HLB value of 18.5 and 2 parts of water while continuing high-speed punching. The mixture was well mixed and dispersed to obtain an epoxy resin dispersion of Comparative Example 2. Comparative Example 3 Four solid epoxy resins similar to those used in Example 1 and two mineral spirits were mixed and melted by heating at 900°C while stirring.

After completely dissolving, keep warm at 80q0, and while continuing to heat at high speed, add 0.5 part of polyoxyethylene benzylated phenyl ether with HLB value of 12 and 1 part of polyoxyethylene nonyl phenyl ether with HLB value of 18.5. A mixture of .65 parts and 4 parts of water was gradually added to the mixture and thoroughly mixed and dispersed to obtain an epoxy resin dispersion of Comparative Example 3. Comparative Example 4 An epoxy resin dispersion of Comparative Example 4 was obtained in the same manner as in Comparative Example 1 except that 80 parts of solid epoxy resin, 8 parts of mineral spirit, and 12 parts of water were used.

Comparative Example 5 Solid epoxy resin 6, similar to that used in Example 1, was heated to 9,000 ℃ while stirring to melt it, and then polyoxyethylene benzylene having an HLB value of 18 was converted while continuing high-speed heating. A mixture of 2.0 parts phenyl ether and 4 parts water was slowly added.

However, it was not possible to obtain a dispersion.

Comparative Example 6 8 pieces of solid eboxy resin similar to those used in Example 1 and 2 pieces of mineral spirit were mixed and heated to 9,000°C to melt while shaking the mixture. After completely dissolving the mixture, the temperature of the mixture was returned to room temperature to obtain a composition of Comparative Example 6. Comparative Example 7 A dispersion of Comparative Example 7 was obtained in the same manner as in Comparative Example 1 except that the epoxy resin was changed to 40 parts, the mineral spirit meter was changed to 38 parts, the dispersant was changed to 2 parts, and the water was changed to 22 parts. .

Comparative Example 8 85 parts of the same solid epoxy resin as used in Example 1 was melted by heating to 9000°C while stirring, and then 3 parts of polyoxyethylene benzylated phenyl ether having an HLB value of 18 was added while heating at high speed. and 5 parts of water were gradually added.

Next, 1 part of mineral spirit was added and mixed, but a dispersion could not be obtained. Comparative Example 9 A comparative example was made in the same manner as in Comparative Example 1 except that the epoxy resin was replaced with 6 parts, the mineral spirit was replaced with 3 parts of xylene, the dispersant was replaced with 2 parts, and the water was replaced with 1 part. A dispersion of No. 9 was obtained.

In order to test the storage stability of the epoxy resin dispersions of Examples 1 to 5 and Comparative Examples 1 to 9 thus obtained, each specimen was placed in a glass container with a diameter of 30 m/m and a length of 300 m/m, and the height The test results are shown in Table 1.

--- 1 [W] [Creation of epoxy resin dispersion] {11 Dispersion A Pulverized bisphenol A ~ epichlorohydrin type, molecular weight approximately 900, epoxy equivalent 450-50, melting point 64-
60 parts of a solid epoxy resin at 74°C and 3 g of mineral spirit were mixed and heated to 90 qo while stirring to melt.

After completely dissolving, keep the temperature at 80 qo, and while continuing high-speed hawking, gradually add a mixture of 2.4 parts of polyoxyethylene benzylated phenyl ether with an HLB value of 18.2 and 10 parts of water, and mix well. Dispersion A was obtained.
■ Dispersion B Pulverized bisphenol A - epichlorohydrin type, molecular weight approximately 1400, epoxy equivalent 900-100, melting point 9
6 to 104 oO of solid epoxy resin and 3 parts of mineral spirit were mixed and heated to 120 QO to melt while stirring.

After completely dissolving, keep the temperature at 90 qo, and while continuing high-speed mixing, gradually add a mixture of 3 parts of polyoxyethylene nonyl phenyl ether with an HLB value of 19.0 and 1 part of water. A dispersion B was obtained by mixing and dispersing. '3}
Dispersion C 60 parts of the solid epoxy resin used in Dispersion A and 3 parts of xylene were mixed and heated to 90°C to melt while shaking.

After completely dissolving, a mixture of 2.4 parts of polyoxyethylene benzylated phenyl ether with an HLB value of 18.2 and 1 part of water was gradually added while keeping the temperature of 80q and continuing high-speed lighting. The mixture was well mixed and dispersed to obtain a dispersion C.
Example 6 15 parts of a curing agent was added to 85 parts of a composition prepared by mixing 85 parts of Dispersion A having the above composition and 15 parts of pigment base, and the mixture was thoroughly mixed.

Next, rust preventive paint A was applied to a cold-rolled steel sheet that had been previously polished and degreased with #240 sandpaper to a dry film thickness of 35 microns, and dried for 2 hours under conditions of 200°C and 75% RH. A dispersion coating material mixed with the above curing agent was coated over and over to a dry film thickness of 40 microns, and the mixture was heated at 20°C for 70 minutes.
A feed body was obtained by drying for 7 days under 5% RH conditions.

Example 7 A specimen was obtained in exactly the same manner as in Example 6, except that rust preventive paint A in Example 6 was replaced with rust preventive paint B.

Example 8 A curing agent was added to a composition of 9 yen consisting of 8 parts of Dispersion B and 2 parts of Pigment Base having the above composition, and the mixture was thoroughly mixed.

Next, rust preventive paint C was applied to a cold-rolled steel sheet that had been previously polished and degreased with #240 sandpaper to a dry film thickness of 35 microns, and was heated at 2,000°C under 75% RH conditions.
A dispersion coating material mixed with the above-mentioned curing agent was overcoated on the dried coating film to a dry film thickness of 40 microns, and
, and dried under 75% RH conditions for 7 days to obtain a specimen.

Example 9 A dispersion coating material mixed with the hardening agent of Example 6 was applied to a cold-rolled steel sheet that had been polished and degreased with #240 sandpaper to a dry film thickness of 40 microns, and heated at 20°C for 70 minutes.
Dry for 2 hours under 5% RH condition, and further coat the same dispersion coating material over the coating to a dry film thickness of 40 microns,
2000 and dried for 7 days under 75% RH conditions to obtain a specimen.

Comparative Example 10 15 parts of the curing agent was added to 85 parts of a composition prepared by mixing 85 parts of Dispersion C having the above composition and 15 parts of the mineral base, and the mixture was thoroughly mixed.

Next, anti-corrosion paint A was applied to a cold rolled steel sheet that had been previously polished and degreased with #240 sandpaper to a dry film thickness of 35 microns, and then heated at 2000°C under 75%RH conditions for 24 hours.
A dispersion coating material mixed with the curing agent was applied over the dried coating film to a dry film thickness of 40 microns.
, and dried under 75% RH conditions for 7 days to obtain a specimen.

Comparative Example 11 A specimen was obtained in exactly the same manner as in Comparative Example 10, except that rust-preventing paint A in Comparative Example 10 was replaced with rust-preventing paint B.

Comparative Example 12 Comparative Example 13 A specimen was obtained in exactly the same manner as Comparative Example 10 by replacing the rust-preventing paint A in Comparative Example 10 with rust-preventing paint C. Comparative Example 13 The dispersion 8 anchor group obtained in Comparative Example 4 and the pigment A sparse portion of the hardening agent 2 was added to 8 parts of the composition obtained by mixing the base 2 parts and the mixture was thoroughly mixed with a pestle.

Then, a specimen was obtained using the same method as in Comparative Example 10.

Comparative Example 14 The dispersion obtained in Comparative Example 6 was mixed with a commercially available solvent-based pigment base and a commercially available solvent-based curing agent in the same proportions as in Comparative Example 13, and then a specimen was obtained in the same manner.

Comparative Example 15 To the composition 9 obtained by mixing the dispersion 9 obtained in Comparative Example 7 with 1 part of the pigment base, the curing agent 1 was added and thoroughly mixed.

A specimen was then obtained in the same manner as in Comparative Example 10.

Comparative Example 16 85 parts of a composition obtained by adding 15 parts of a commercially available solvent-based pigment base to 85 parts of the dispersion obtained in Comparative Example 9, and 15 parts of a commercially available solvent-based curing agent were mixed.

Then, a specimen was obtained in the same manner as in Comparative Example 10.

Comparative Example 17 Pulverized bisphenol A - epichlorohydrin type, molecular weight approximately 900, epoxy equivalent 450-500, melting point 64-
54 parts of 74oo solid epoxy resin, aliphatic gepoxide, molecular weight approximately 300, epoxy equivalent weight 130
~145, viscosity 0.012~0.025 poise (25o
The liquid epoxy resin 1 of o) was mixed and heated to melt by overflowing with 8,000 ml while stirring.

After completely melting and compatibility, 12 parts of a polyoxyethylene benzylated phenyl ether solution with an HLB value of 18.2 prepared with water to a non-volatile content of 50% was added while keeping the temperature at 8000°C, and the mixture was thoroughly mixed and emulsified to form an aqueous dispersion. After this, water was gradually added little by little while using a high-speed disperser to obtain an aqueous dispersion with a non-volatile content of 75%. 65 parts of the aqueous dispersion thus obtained, 15 parts of the pigment base, and 2 parts of the curing agent were mixed. Table 2 shows the results of a comparative test of the selectivity of the undercoat coating strength, the appearance of the coating film, and the shade performance of the thus obtained specimens of Examples 6 to 9 and Comparative Examples 10 to 16. Further, Table 3 shows the results of comparing the sagging condition after coating between the coating composition obtained in Example 6 of the present invention and the coating composition obtained in Comparative Example 17.

-2Note-1) Outdoor exposure test method Use a cutter knife to remove the coating surface. A cross cut that reaches the steel plate base on the surface. The test specimens containing the ingredients were exposed outdoors and After several months, check whether there are any abnormalities on the surface of the paint film. Bell.

-3 (Note-2) 70x polished with #240 sandpaper
Each of the paints was applied to a 150×0.8 skin/wall mild steel plate so that the dry film thickness was 150 μm.

Immediately after coating, the test piece was placed vertically in a cabinet box at a temperature of 26° C. and a humidity of 90% RH, and after being left for 2 hours, the state of the coating film was examined.

It is clear from the comparative test results in Tables 1 to 3 above that the epoxy resin dispersion obtained by the method of the present invention has excellent storage stability and is superior to coating films obtained from conventional aqueous epoxy resin dispersions. Epoxy resin dispersions using strong solvents such as aromatic hydrocarbon solvents (Comparative Examples 10, 11, No. 12 and 16), there was no selectivity of the uncoated film (the undercoat film was dissolved by the solvent, causing creases).

Furthermore, the epoxy resin dispersions obtained by methods other than the method of the present invention (Comparative Examples 1 to 8, 13 to 15) have extremely poor storage stability, and in some cases, no dispersion can be obtained, and the coating film performance is also poor. It was very inferior.

As mentioned above, the present invention provides coatings on undercoat films with poor solvent resistance.
It can be said that it has great industrial value in that it has made it possible to recoat epoxy resin paint, which was previously considered impossible.

Claims (1)

[Claims] 1. 85 to 30 parts by weight of an epoxy resin with a melting point of 50°C or higher and 10 to 35 parts by weight of an aliphatic hydrocarbon solvent are hot-melted and mixed to form a homogeneous mixture, and then 5 to 35 parts by weight of water (however, epoxy The total amount of resin, solvent and water is 100
parts by weight, and the amount of water in the total amount of solvent and water does not exceed 50%), and polyoxyethylene nonyl phenyl ether or polyoxyethylene with an HLB value of 12 or more based on 100 parts by weight of the epoxy resin solid content. A method for producing an epoxy resin dispersion, which comprises adding 1 to 10 parts by weight of benzylated phenyl ether and emulsifying and dispersing it.