JP2002327040A - Method for producing phosphoric acid-modified epoxy resin, and one-part thermosetting coating composition and coating film using the phosphoric acid-modified epoxy resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a phosphoric acid-modified epoxy resin which can substantially control the introduced amount of a phosphate group into an epoxy resin raw material, and to provide a one pack type heat- curable coating composition excellent in the storage stability which contains the resin obtained by the method. SOLUTION: In the method, a reaction is performed in the formulation condition so that a solution containing an epoxy resin raw material, a phosphoric acid source, water and a water-miscible organic solvent without an active hydrogen can be homogeneous. The resin obtained by the method gives the one pack type heat-curable coating composition excellent in the storage stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a phosphoric acid-modified epoxy resin, and a one-part thermosetting coating composition and a coating film using the phosphoric acid-modified epoxy resin. Method for producing phosphoric acid-modified epoxy resin capable of substantially controlling the amount of group introduced, one-part thermosetting coating composition containing phosphoric acid-modified epoxy resin obtained by such method, and one-part thermosetting coating composition It relates to a coating film obtained by curing the composition.

[0002]

2. Description of the Related Art Epoxy resins have properties of cured products such as solvent resistance, mechanical strength, and the like.
Since it has excellent electrical insulation properties and dimensional stability and is easy to process, it is widely used in applications such as paints, electrical insulation encapsulating materials, printed circuit board materials, civil engineering and building materials, adhesives, and aircraft materials.

As epoxy resins, glycidyl ether type epoxy resins, glycidyl ester type epoxy resins,
Alicyclic epoxy resins, and modified epoxy resins based on these epoxy resins, phenol novolak type epoxy resin, cresol novolak type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin,
Aromatic amine type epoxy resins and the like are known. In order to cure these epoxy resins, a curing agent is generally required (a curing accelerator is also used as necessary). As the curing agent, industrially, aliphatic polyamines, alicyclic polyamines, aromatic polyamines, condensates of the above polyamines and aliphatic dicarboxylic acids, dicyandiamide and its derivatives, various imidazole and imidazoline compounds, polycarboxylic acids and It is known that acid anhydrides and the like are mainly used, and inorganic acids such as hydrochloric acid and phosphoric acid are also room temperature curing agents.

However, if the above-mentioned known curing agent is mixed with an epoxy resin in advance, curing starts even at room temperature and storage stability is poor. Therefore, usually, each time the epoxy resin and the curing agent are mixed immediately before use. Required (two-pack type), work efficiency is poor. Therefore, various kinds of latent curing agents that initiate a curing reaction when the temperature is raised to a certain temperature have been proposed.For example, a capsule-like latent curing agent having an amine-based curing agent as a core material and having an outer wall film that dissolves at a certain temperature, and the like have been proposed. No.
However, since amine curing agents are harmful to the human body,
Its use is preferably avoided.

[0005] Therefore, a one-part thermosetting epoxy resin composition having good storage stability and no pollution is desired. Therefore, for phosphoric acid-modified epoxy resin obtained by introducing phosphoric acid, which is a non-polluting curing agent, into epoxy resin, if a phosphoric acid group and a hydroxyl group coexist in one molecule, self-condensing type that does not require curing agent Resin may be obtained. For this purpose, it is necessary to control the amount of introduced phosphate groups. However, since phosphoric acid is trivalent, it often induces crosslinking of the epoxy resin and gels the reaction system, so that the epoxy groups of the epoxy resin cannot be removed. The technology of opening a ring and introducing a phosphate group into it has not been industrially successful. Therefore, the present inventors have filed Japanese Patent Application No. 11-356.
In 694, a technique for introducing a phosphate group into an epoxy resin was proposed. However, this method is effective for introducing as many phosphate groups as possible into the epoxy resin, but cannot control the amount of the phosphate groups.

Accordingly, an object of the present invention is to provide a method for producing a phosphoric acid-modified epoxy resin in which the amount of phosphoric acid groups introduced into a raw material epoxy resin can be substantially controlled, and a phosphoric acid-modified epoxy resin obtained by the method, An object of the present invention is to provide a one-part thermosetting coating composition having excellent storage stability.

[0007]

Means for Solving the Problems In view of the above-mentioned problems, as a result of intensive studies, the present inventors have made it possible to react phosphoric acid groups to a raw material epoxy resin by reacting under a specific raw material composition and under specific mixing conditions. The present inventors have found that a method for producing a phosphoric acid-modified epoxy resin in which the introduction amount can be substantially controlled can be obtained, and have reached the present invention.

That is, the method for producing a phosphoric acid-modified epoxy resin according to the present invention comprises reacting a solution containing a raw material epoxy resin, a phosphoric acid source, water and a water-miscible organic solvent having no active hydrogen under a blending condition under which the solution becomes uniform. It is characterized by the following.

It is preferable to use phosphoric anhydride as a phosphoric acid source. The mixing ratio of the phosphoric acid source to 1 mol of the epoxy group of the raw material epoxy resin (based on the phosphoric acid group) is as follows. (Ii) When producing a curing agent type phosphoric acid-modified epoxy resin used as a curing agent for an epoxy resin, the amount is preferably 0.6 to 2.0 mol. Epoxy group of raw material epoxy resin 1
The mixing ratio of water to mole is preferably 1.5 to 15.0 mole. The raw material epoxy resin preferably has an epoxy equivalent of 170 to 5,000 g / equivalent, and more preferably a bisphenol type or a novolak type. The reaction temperature is preferably from 15 to 80 ° C.

The self-condensing one-part thermosetting coating composition of the present invention contains only a self-condensing phosphoric acid-modified epoxy resin as a resin component, and is characterized by being self-condensed and cured by heating. This is a self-condensation type phosphoric acid-modified epoxy resin, for example, the following formula (1):

Embedded image (In the general formula (1), R ₁ represents an epoxy resin skeleton.) Since one molecule has a phosphoric acid group and a hydroxyl group generated by ring-opening of the epoxy group of the raw epoxy resin in one molecule, It is. The self-condensation type phosphoric acid-modified epoxy resin is an epoch-making phosphoric acid-modified epoxy resin having sufficient storage stability at room temperature and self-condensation curing when heated. In particular, the mixing ratio (based on the phosphoric acid group) of the phosphoric acid source to 1 mol of the epoxy group of the raw epoxy resin is set to 0.8 to
The product prepared at 1.2 mol has substantially no change in viscosity for at least one month at room temperature, and does not cause precipitation.

It is known that a general-purpose epoxy resin is protected with an epoxy group by adding an excessive amount of ketone (hereinafter, the epoxy resin in this state is referred to as a blocked epoxy resin). This is a characteristic action of the ketone, and the epoxy group and the ketone form a cyclic acetal bond by association. This is an equilibrium reaction. The composition containing the curing agent type phosphoric acid-modified epoxy resin and the blocked epoxy resin obtained by the production method of the present invention is substantially stable in that the curing reaction does not proceed at room temperature, but the ketone is dissociated and volatilized by heating. Then, a crosslinking reaction of the epoxy group is induced by the catalytic action of the phosphoric acid group. That is, the curing agent-containing one-part thermosetting coating composition of the present invention comprises a blocked epoxy resin having an epoxy group protected by a ketone and a curing agent-type phosphoric acid-modified epoxy resin. . Acetone is preferred as the ketone. Further, the molar ratio of (epoxy group of blocked epoxy resin (in terms of unprotected)) / (phosphate group in phosphoric acid-modified epoxy resin) is preferably 4.0 / 1.0 to 1.0 / 5.0.

Further, a coating film obtained by curing the curing agent type and self-condensing type one-component thermosetting coating composition of the present invention has high surface hardness, gloss, excellent adhesion to a substrate, and the like.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a phosphoric acid-modified epoxy resin of the present invention and a one-part thermosetting coating composition and a coating film using the phosphoric acid-modified epoxy resin obtained by the production method will be described in detail. I do.

[1] Method for Producing Phosphoric Acid-Modified Epoxy Resin The method for producing the phosphoric acid-modified epoxy resin of the present invention comprises a solution containing a raw material epoxy resin, a phosphoric acid source, water and a water-miscible organic solvent having no active hydrogen. Is characterized by reacting under a blending condition under which the composition becomes uniform.

(1) Raw material epoxy resin The raw material epoxy resin preferably has an epoxy equivalent in the range of 170 to 5000 g / equivalent. If the amount is less than 170 g / equivalent, the product after phosphoric acid modification has a high water solubility, which makes separation and purification difficult. If it is more than 5000 g / equivalent, the addition amount of phosphoric acid becomes small because the epoxy group concentration is low, so that a phosphoric acid-modified epoxy resin having excellent thermosetting properties cannot be obtained.

The raw material epoxy resin is not particularly limited. For example, bisphenol type epoxy resins such as bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol S type, propylene oxide bisphenol A type, hydrogenated bisphenol A type, glycidyl ester Epoxy resins, alicyclic epoxy resins, and modified epoxy resins based on these epoxy resins, novolak epoxy resins such as phenol novolak type and cresol novolak type, biphenyl type epoxy resins, naphthalene type epoxy resins, and aromatic amines A type epoxy resin or the like can be used.

The starting epoxy resin has the following general formula:
(2):

Embedded image (In the general formula (2), R ₂ represents a residue derived from a bisphenol or a substituted or unsubstituted alkylene group having 1 to 4 carbon atoms, and n represents a degree of polymerization. A bisphenol-type epoxy resin represented by a co-condensate containing two or more types of structural units or a mixture of two or more types of structural units (for example, YD manufactured by Toto Kasei Co., Ltd.)
-128 and its series), or the following general formula (3):

Embedded image (In the general formula (3), R ₃ and R ₅ each represent a substituted or unsubstituted alkylene group, R ₄ represents a hydrogen atom, a halogen atom or a substituted or unsubstituted alkyl group, and n represents a degree of polymerization. The novolak type epoxy resin represented by the general formula (3) may be a copolymer containing two or more kinds of structural units or a mixture of two or more kinds of structural units.)

[0018] (2) a source of phosphate and the blending ratio phosphoric acid source as the anhydrous phosphoric acid (phosphorus pentoxide = P ₂ O _5), can be used pyrophosphate and polyphosphate. Phosphoric anhydride may have undergone pyrophosphoric acid or polyphosphoric acid in the course of the reaction, but the use of phosphoric anhydride is preferred because of its high reactivity and smooth introduction of phosphate groups into epoxy groups. When a compound such as orthophosphoric acid, phosphorous acid, or phosphonic acid is used, the reaction does not proceed, and the phosphoric acid-modified epoxy resin of the present invention cannot be obtained. As an example, FIG. 1 shows a reaction scheme when phosphoric anhydride is used as a phosphoric acid source.

When the phosphoric acid-modified epoxy resin of the present invention is used as a self-condensing epoxy resin (self-condensing type)
And a case where it is used as a curing agent for epoxy resin (curing agent type), and two kinds of uses are possible, and the charging ratio of the phosphoric acid source at the time of production differs depending on each use.

(2)-(a) Self-condensation type In the case of the self-condensation type, the mixing ratio of the phosphoric acid source is 0.6 mol based on the phosphoric acid group with respect to 1 mol of the epoxy group of the starting epoxy resin.
Must be ~ 1.5 mol. By setting the mixing ratio of the phosphoric acid source to 0.6 to 1.5 mol based on the phosphoric acid group with respect to 1 mol of the epoxy group of the raw material epoxy resin, a hydroxyl group generated by ring opening of the phosphoric acid group and the raw material epoxy group in one molecule. Can coexist. As a result, it has sufficient storage stability at room temperature and self-condensation during heating. If the amount exceeds 1.5 moles, the self-condensability of the obtained resin decreases. Preferably it is 0.8 to 1.2 mol. By setting the amount to 0.8 to 1.2 mol, the storage stability is further improved, and a substance which has substantially no change in viscosity at room temperature for at least one month and does not cause precipitation is obtained. The self-condensation type can also be used as a curing agent type.

(2)-(b) Curing agent type In the case of the curing agent type, the mixing ratio of the phosphoric acid source is 0.6 to 0.6% based on the phosphoric acid group with respect to 1 mol of the epoxy group of the raw material epoxy resin.
2.0 mol is preferable, and 0.8 to 1.9 mol is more preferable. 0.6
If less than the mole, the phosphoric acid modification reaction itself can be easily performed,
The degree of phosphoric acid modification must be low. If it exceeds 2.0 mol, gelation is apt to occur during the reaction, so the amount of the reaction solvent must be increased (therefore, the solid content concentration is reduced), and the unreacted phosphoric acid source tends to remain,
A coating composition containing unreacted phosphoric acid is not preferable because it reacts with the metal contained in the substrate to generate black rust.

(3) Mixing ratio of water Water is necessary to open the epoxy group of the raw material epoxy resin and to introduce a hydroxyl group into the epoxy resin. Water is preferably used in an amount of 1.5 to 15.0 mol per 1 mol of the epoxy group of the raw material epoxy resin. If the amount is less than 1.5 moles, even if the epoxy resin is reacted with an appropriate ratio of phosphoric anhydride, water is insufficient, and the reaction product gels. On the other hand, if it exceeds 15.0 mol, part of the epoxy resin dissolved in the reaction solvent precipitates and the entire liquid phase becomes cloudy, and side reactions such as orthophosphoric acid generated by reacting only phosphoric anhydride and water are generated The product is not preferable because it contaminates the target phosphoric acid-modified epoxy resin.

(4) Solvent As the solvent, a water-miscible organic solvent having no active hydrogen and dissolving a raw material epoxy resin and a phosphoric acid-modified epoxy resin as a product is used. Examples of such a solvent include ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone, cyclic ethers such as tetrahydrofuran and dioxane, ethyl acetate, esters such as methyl propionate, and the following general formula:
(Four):

Embedded image (In the general formula (4), R ₆ represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 1 to 9.) Alkyl esters of cellosolve represented by the formula: dimethyl sulfoxide, and the like. it can. An aliphatic hydrocarbon such as hexane or heptane, an alicyclic hydrocarbon such as cyclohexane, or an aromatic hydrocarbon such as benzene, toluene, or xylene may be mixed with the above solvent. The solvent is used in an amount sufficient to dissolve the raw material epoxy resin and to form a uniform solution of the entire reaction product including the water and the phosphoric acid source. The preferred amount of the solvent used is such that the concentration of the epoxy resin becomes 50% by weight or less, more preferably about 10 to 40% by weight.

However, alcohol represented by the general formula ROH, RCO
Carboxylic acid represented by OH, a primary amine represented by RNH _2, a secondary amine represented by R ₂ NH, primary amide represented by RCONH _2, second represented by RCONHR ^' Class amides and the like are unsuitable because they have active hydrogen in the molecule. Ethylene carbonate is also not preferred as a solvent because it decomposes itself to form ethylene oxide and reacts with a hydroxyl group or a phosphoric acid group generated by ring opening of an epoxy group.

(5) Reaction method A preferred example of a method of reacting a solution comprising a raw material epoxy resin and a solvent by adding water and a phosphoric acid source is a predetermined amount of a solution comprising a raw material epoxy resin and a solvent. Is placed in a reaction vessel equipped with a thermometer, a jacket or a coiled condenser, a reflux condenser and a stirrer, the contents are stirred to cool the temperature to 15 ° C., and a predetermined amount of water is added thereto. Next, a predetermined amount of phosphoric anhydride is initially charged all at once, or divided into several times during the reaction process. Significant exotherms occur when the reaction of the epoxy group, water and the phosphoric acid source begins, but each time it is cooled and does not exceed 80 ° C. The reaction system is preferably maintained at 50-60 ° C. 45 at 50-60 ° C
After performing the reaction for 90 minutes, the mixture is cooled, the stirring is stopped, and the reaction product is taken out.

When the reaction is carried out at a temperature lower than 15 ° C., the added phosphoric anhydride does not act on the intended modification of the epoxy resin,
The polyphosphoric acid remains in the reaction mixture. On the other hand, when the temperature exceeds 80 ° C., the reaction mixture is gelled by inducing a cross-linking reaction between epoxy resin molecules at the same time as the reaction of introducing a phosphate group into the raw material epoxy resin. In either case, the desired phosphoric acid-modified epoxy resin cannot be obtained.

(6) Phosphoric Acid-Modified Epoxy Resin The degree of phosphoric acid modification can be controlled by the above production method, and a self-condensation type and curing agent type phosphoric acid-modified epoxy resin can be obtained. The reaction product (including the solvent) obtained by the above-described production method is a viscous and clear solution in which the phosphate-modified epoxy resin is a self-condensation type or a curing agent type. A phosphoric acid-modified epoxy resin having a phosphoric acid equivalent of 300 g / equivalent or less from a bisphenol A type epoxy resin is water-soluble. A phosphoric acid-modified epoxy resin having a phosphoric acid equivalent of 500 to 800 g / equivalent from a bisphenol A-type epoxy resin is insoluble in water, but emulsifies in a monoethanolamine salt aqueous solution. In the production method of the present invention, since the unreacted raw epoxy resin insoluble in water does not remain, it is considered that the reaction is completed.

As shown in FIG. 1 described above, the reaction proceeds by the opening of the epoxy group of the raw material epoxy resin and the generation of a hydroxyl group and a phosphoric acid group. For example, a diglycidyl ether type epoxy resin is used as a raw material. When the mixing ratio of the phosphoric acid source is 1 mol based on the phosphoric acid group with respect to 1 mol of the epoxy group of the raw material epoxy resin, two phosphoric acid groups and two epoxy groups formed by ring-opening of the epoxy group in one molecule are obtained. And a phosphoric acid-modified epoxy resin containing a hydroxyl group.

The deduced structure of the self-condensation type phosphoric acid-modified epoxy resin obtained by partially introducing a phosphate group into the bisphenol type epoxy resin represented by the general formula (2) is represented by the following general formula (5):

Embedded image (However, in the general formula (5), V, W, X, Y and Z each independently represent an -OH group, -OP (O) (OH) ₂ group or -OP (O) (OH) -OP
(O) (OH) ₂ represents a group, R ₂ represents the same substituent as in the general formula (2), and n represents a degree of polymerization. However, (total number of -OP (O) (OH) ₂ groups) / (total number of substituents V, W, X, Y and Z) = 1.2 / (n
+4) to 3 / (n + 4) (provided that -OP (O) (OH) -OP (O) (OH) ₂
Group is converted into -OP (O) (OH) ₂ group two minutes). ).

The estimated structure of a curing agent type phosphoric acid-modified epoxy resin obtained by introducing a phosphate group into a bisphenol type epoxy resin represented by the general formula (2) is represented by the following general formula:
(6):

Embedded image (However, in the general formula (6), V, W, X, Y and Z each independently represent a substituent similar to the above general formula (5), and R ₂ represents a substituent similar to the above general formula (2) And n represents the degree of polymerization, provided that (total number of -OP (O) (OH) ₂ groups) / (total number of substituents V, W, X, Y and Z) = 1.2 / (n + 4) 4 / (n + 4) (where-
OP (O) (OH) -OP (O) (OH) ₂ group is converted into -OP (O) (OH) ₂ group two minutes). ).

The deduced structure of a self-condensation type phosphoric acid-modified epoxy resin obtained by partially introducing a phosphate group into the novolak type epoxy resin represented by the general formula (3) is represented by the following general formula (7):

Embedded image (However, in the general formula (7), X and Y are each independently -OH group, -OP (O) (OH) ₂ group or -OP (O) (O
H) -OP (O) (OH) ₂ represents a group, R ₃ , R ₄ and R ₅ are represented by the above general formula
Represents the same substituent as in (3), and n represents the degree of polymerization. However, (-
OP (O) (OH) total number of ₂ groups / (total number of substituents X and Y) =
Is 0.3 to 0.75 (where -OP (O) (OH) -OP (O) (OH) 2 group is -
OP (O) (OH) is converted into ₂ groups two minutes). ).

The estimated structure of a curing agent type phosphoric acid-modified epoxy resin obtained by introducing a phosphate group into the novolak type epoxy resin represented by the general formula (3) is represented by the following general formula:
(8):

Embedded image (However, in the general formula (8), X and Y each independently represent a substituent similar to the above general formula (7) for each structural unit;
₃ , R ₄ and R ₅ represent the same substituents as in the above general formula (3), n
Represents the degree of polymerization. Where (-OP (O) (OH) total number of ₂ units) /
(Total number of substituents X and Y) = 0.3 to 1.0 (provided that -OP
(O) (OH) -OP ( O) (OH) ₂ group is converted into -OP (O) (OH) ₂ group two minutes). ).

[2] One-part thermosetting coating composition The one-part thermosetting coating composition of the present invention includes a self-condensing type and a curing agent type phosphoric acid-modified containing a self-condensing type phosphoric acid-modified epoxy resin. There are two types of curing agent-containing types containing an epoxy resin as a curing agent. Both of the one-part thermosetting coating compositions are excellent in safety and health because no amine-based curing agent is required, and are also excellent in storage stability at room temperature.

(1) Self-condensing type One kind of the one-component thermosetting coating composition of the present invention is a composition containing a self-condensing type phosphoric acid-modified epoxy resin. Such a composition has sufficient storage stability at room temperature. In particular, those prepared by adjusting the mixing ratio of the phosphoric acid source to 1 mol of the epoxy group of the raw material epoxy resin (based on the phosphoric acid group) to 0.8 to 1.2 mol have substantially no change in viscosity at room temperature for at least one month, and Does not occur. When heated to 120 ° C. or higher, preferably 150 ° C. or higher, self-condensation curing occurs. Such self-condensation curing is due to the condensation reaction of the hydroxyl group between the molecules, and it is considered that the phosphoric acid group present in the molecule acts as a catalyst. Heating time for curing
Preferably 10 to 60 minutes. Further, before heat curing, it is preferable that the coated film is allowed to stand at room temperature to evaporate the solvent and apparently dried.

As such a self-condensing type one-component thermosetting coating composition, it is preferable that the self-condensing type phosphoric acid-modified epoxy resin is dissolved in an organic solvent having no active hydrogen. . Examples of the water-miscible organic solvent having no active hydrogen include ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone and cyclohexanone; cyclic ethers such as tetrahydrofuran and dioxane; ethyl acetate; methyl propionate; 4) alkyl esters of cellosolve represented by
Dimethyl sulfoxide and the like can be mentioned. Aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene may be mixed and used with the above-mentioned solvents. Therefore, the self-condensation type phosphoric acid-modified epoxy resin of the present invention can be used in the form containing the solvent used when the resin was used. The viscosity can be adjusted by adjusting the solid concentration, selecting a solvent, and adding an inorganic filler. However, it is not preferable to use a mixture of a high boiling point solvent because the firing temperature must be increased.

There is no particular limitation on the solid content concentration in the coating composition, but the viscosity may be adjusted by adjusting the amount of the solvent used in accordance with the coating method of the coating and the performance required for the coating film. The preferred viscosity is between 20 and 400 mPa · s / 25 ° C. However, if the solid content concentration is too low, the amount of the solvent to be volatilized / recovered increases, which is not preferable. The preferred concentration of the resin in the coating composition is 5 to 50% by weight.

(2) Curing Agent-Containing Type Another kind of the one-part thermosetting coating composition of the present invention is:
It is a composition containing a curing agent type phosphoric acid-modified epoxy resin and a blocked epoxy resin. In such a composition, the curing agent type phosphoric acid-modified epoxy resin functions as a curing agent for the epoxy resin.

The blocked epoxy resin is a resin in which an epoxy group is protected by a ketone as a result of reacting an epoxy group with a ketone to form a cyclic acetal bond by association. When the ketone is dissociated and volatilized by heating, a crosslinking reaction of the epoxy group becomes possible. There is no particular limitation on the unprotected epoxy resin used for the blocked epoxy resin, for example, bisphenol A type having an epoxy equivalent in the range of 170 to 5000 g / equivalent, bisphenol F type,
Glycidyl ether type epoxy resin such as bisphenol S type, glycidyl ester type epoxy resin, alicyclic epoxy resin, and modified epoxy resin based on these epoxy resins, phenol novolak type epoxy resin, cresol novolak type epoxy resin, biphenyl type Any of an epoxy resin, a naphthalene type epoxy resin and an aromatic amine type epoxy resin can be used. For use in paints, bisphenol-type epoxy resins having an epoxy equivalent of 220 g / equivalent or less (for example, YD-128 manufactured by Toto Kasei Co., Ltd.)
And their series) are preferred.

Specific examples of ketones include acetone, methyl ethyl ketone, isopropyl methyl ketone, cyclobutanone, methyl propyl ketone, diethyl ketone, and isobutyl methyl ketone. The use of acetone is preferred because dissociation from epoxy groups and volatilization from the composition occur at relatively low temperatures. Ketone is an epoxy group 1
It is preferably used in an amount of 4.0 mol or more, more preferably 6.0 mol or more, per mol. Blocked epoxy resins are obtained by reacting unprotected epoxy resins with ketones at room temperature. Taking acetone as an example, the following formula
(9):

Embedded image (In the general formula (7), R ₇ represents an epoxy resin skeleton.) An equilibrium state is formed as shown in FIG. Acetone protects the epoxy group at room temperature and lowers its reactivity, but the dissociation and volatilization with the rise in temperature restores the reactivity of the epoxy group. Then, the crosslinking reaction of the epoxy group induced by the phosphoric acid group of the curing agent proceeds. If the phosphoric acid-modified epoxy resin and the unprotected epoxy resin are mixed without protecting the epoxy group with a ketone, the polymerization proceeds even at room temperature and gels, resulting in poor storage stability.

Such a one-part thermosetting coating composition containing a curing agent has a composition in which a blocked epoxy resin and a curing agent-type phosphoric acid-modified epoxy resin are dissolved in an organic solvent having no active hydrogen. It is preferably an object. As the water-miscible organic solvent having no active hydrogen, any of the above-mentioned [2] (1) can be used.

The curing agent-containing one-part thermosetting coating composition can be obtained by mixing a blocked epoxy resin and a curing agent-type phosphoric acid-modified epoxy resin at room temperature. For example, a solution of a blocked epoxy resin and a solution of a curing agent type phosphoric acid-modified epoxy resin dissolved in a water-miscible organic solvent having no active hydrogen may be mixed. The mixing ratio of the blocked epoxy resin and the curing agent type phosphoric acid-modified epoxy resin is (epoxy group of blocked epoxy resin (unprotected)) / (phosphate group in phosphoric acid-modified epoxy resin) = 4.0 /1.0-1.0/5.0 (molar ratio) is preferable, and the range of 2.0 / 1.0-1.0 / 3.0 is more preferable.

There is no particular limitation on the solid content concentration in the curing agent-containing coating composition, and the viscosity can be adjusted by adjusting the amount of the solvent used in accordance with the coating method of the coating and the performance required for the coating. Good. The preferred viscosity is 20 to 400 mPa · s / 25 ° C. However, if the solid content concentration is too low, the amount of the solvent to be volatilized / recovered increases, which is not preferable. The preferred solid content concentration of the resin is 5 to 50% by weight. It is not preferable to use a mixture of a high-boiling solvent because it is necessary to increase the firing temperature.

The hardener-containing one-part thermosetting coating composition has no change in viscosity at room temperature for about one week and precipitates when dissolved in a water-miscible organic solvent having no active hydrogen. And has good storage stability. And
When heated to 120 ° C. or higher, preferably 150 ° C. or higher, the ketone is dissociated and volatilized, and a crosslinking reaction occurs. The heating time for curing is preferably 10 to 60 minutes. Further, before heat curing, it is preferable that the coated film is allowed to stand at room temperature to evaporate the solvent and apparently dried.

(3) Other Additives The following one-part one-part thermosetting paint compositions described above are added to the following additives used in ordinary baking paints, for example, for the purpose of adjusting viscosity. Thickeners, various color pigments for cosmetic purposes, fillers for increasing hiding power, leveling agents added for improving the smoothness of the coated surface, cups added for improving the adhesion to the substrate Ring agents, conventionally known antioxidants, lubricants, antiblocking agents, antioxidants, flame retardants, conductive agents, defoamers, and the like can be arbitrarily selected and added.

[3] Coating Film The one-component thermosetting coating composition of the present invention can be used for coating various substrates, and is particularly suitable for metal coating. It is. The metal used as the base material is preferably a metal mainly composed of iron, aluminum, magnesium or the like, and is suitably used for a cold-rolled steel plate, a stainless steel plate, an aluminum alloy plate, etc. having a thickness of 0.01 to 2.0 mm. The surface of these metals is generally treated with alumite, phosphoric acid, etc., but depending on the case, it may be plated with an inorganic metal such as chromium, tin, zinc, nickel or its oxide, or these may be deposited. Alternatively, a silicon compound typified by silicon may be deposited.

The coating film is coated or dipped on the surface of the inorganic substrate by brush coating, bar coater coating, spraying, dipping, roll coating, blade coating, flow coating or electrostatic coating, or the like, and then heat-cured. Obtained at least. The coating film obtained by curing the one-part thermosetting coating composition of the present invention has adhesion to a substrate, solvent resistance, water resistance,
Excellent hardness, gloss, weatherability, rust prevention, etc.

[0047]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example 1 (Production of a curing agent type phosphoric acid-modified epoxy resin; bisphenol A type) Epoxy resin YD-128 (manufactured by Toto Kasei Co., Ltd., epoxy equivalent = 190 g) containing bisphenol A diglycidyl ether as a main component (Equivalent) 95 g was dissolved in 700 g of dioxane, put in a thermometer, a cooler, a stirrer, a glass separable flask with an addition port (internal volume 2 liter), and 90 g of water was added to obtain a transparent homogeneous solution. . The contents of this flask were cooled externally with vigorous stirring, and when they reached 14 ° C,
71 g of phosphoric anhydride was added all at once through the addition port. The temperature of the reaction mixture increased from 30 ° C. at the time of adding phosphoric anhydride to 70 ° C. in about 10 minutes, and thereafter, stirring and temperature control were continued to 50 to 60.
The reaction was performed at 40 ° C. for 40 minutes. Thereafter, a reaction product containing dioxane was taken out without separation and purification.

Examples 2 to 5 (Production of a self-condensing type / curing agent type phosphoric acid-modified epoxy resin; bisphenol A type) YD-128 which is an epoxy resin containing bisphenol A diglycidyl ether as a main component
(Epoxy equivalent = 190 g / equivalent, manufactured by Toto Kasei Co., Ltd.), YD
-011 (made by the company, epoxy equivalent = 470 g / equivalent), YD-012
(Epoxy equivalent = 640 g / equivalent, manufactured by the company), and the same procedure as in Example 1 was carried out except that water and phosphoric anhydride were added at the respective ratios shown in Table 1.

Comparative Examples 1 and 2 Using YD-128, water and phosphoric anhydride were added at the respective ratios shown in Table 1, and the reaction was carried out in the same manner as in Example 1 except that the reaction was carried out under the conditions shown in Table 1. .

The physical properties of the self-condensation type and / or curing agent type phosphoric acid-modified epoxy resins obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were measured by the following methods. -Appearance: Observed visually. Water miscibility: A sample (phosphoric acid-modified epoxy resin containing a solvent) was mixed with water at a ratio of 1: 1 (weight ratio) and visually observed. -Miscibility with 10 wt% monoethanolamine aqueous solution: The sample was mixed with a 10 wt% monoethanolamine aqueous solution at a ratio of 1: 1 (weight ratio) and visually observed. -Non-volatile content concentration: About 0.5 g of a sample was collected in an aluminum dish, precisely weighed, extended by adding acetone, and the remaining dry amount after heating at 120 ° C for 60 minutes was measured. Phosphoric acid value: Titration was performed using a 1N-KOH solution, and the end point was a point at pH = 10.3. It was converted to 1 g of non-volatile content. -Phosphoric acid equivalent: Calculated from phosphoric acid value-Stable storage period: At room temperature (15 to 20 ° C), the number of days in which no gelation, precipitation, etc., occurred in the mixed system and no apparent increase in viscosity was observed . Table 1 shows the measurement results.

[0052]

[Table 1]

As shown in Table 1, in Example 1 in which the molar ratio of phosphoric anhydride / epoxy groups (based on phosphoric acid groups) was 2.0, and in Example 2 in which the molar ratio was 1.0, a remarkable increase in temperature due to the initial heat generation of the reaction was observed. As can be seen, in Example 3 where the ratio was 0.6, the temperature rise was small. In all of Examples 1 to 3, a reaction product (including dioxane) was obtained in the form of a homogeneous solution without gelation. From the comparison between the measured value and the calculated value in the phosphoric acid equivalent, the charged phosphoric anhydride was almost introduced into the raw material epoxy resin as a phosphate group, and the amount of the phosphate group introduced into the raw material epoxy resin by the production method of the present invention. Has been found to be substantially controllable. However, in Example 3, the measured value of the phosphoric acid equivalent deviated from the calculated value, which is due to the weak self-hydrolyzing property of the pyrophosphate ester group in the phosphoric acid-modified epoxy resin molecule. It is presumed that the amount of phosphate groups introduced is not small relative to the charge. The homogeneous solution composition (solvent dioxane, solids concentration 18.8%) containing a phosphoric acid-modified YD-128 obtained in Example 2 as a main component is stable at room temperature, and its viscosity increases even when left for one month or more. No precipitation occurred.

In each of Examples 4 and 5, a relatively mild reaction course was obtained to obtain a reaction product in the form of a homogeneous solution. These reaction products were not soluble in water, but were only emulsified and dispersed in an aqueous solution of 10% monoethanolamine. This seems to be due to the high molecular weight of the starting epoxy resin.

On the other hand, in Comparative Examples 1 and 2, the reaction was carried out under the compounding conditions under which the reactants were not uniform, so that the reaction system of Comparative Example 1 gelled in about 10 minutes even though the heat generation was small. In Comparative Example 2, gel was generated in about 5 minutes with rapid heat generation, and the desired liquid reaction product could not be obtained.

Examples 6 to 8 (Production of a self-condensation type / curing agent type phosphoric acid-modified epoxy resin; ortho-cresol novolak type) Using the same apparatus as in Example 1, an ortho-cresol novolak type epoxy resin YDCN was used as a raw material epoxy resin. -704 (Toto Kasei Co., Ltd.)
100 g of an epoxy equivalent = 206.5 g / equivalent), dissolved in 700 g of a solvent dioxane, water and phosphoric anhydride were added at the respective ratios shown in Table 2, and the mixture was cooled under vigorous stirring under cooling to 50-60 g. The reaction was carried out at a temperature of about 1 hour. Table 2 shows the raw material composition.

Comparative Examples 3 and 4 Using YDCN-704, water and phosphoric anhydride were added at the respective ratios shown in Table 2, and the reaction was carried out under the conditions shown in Table 1.
The same was done.

The self-condensation type and / or curing agent type phosphoric acid-modified epoxy resins obtained in Examples 6 to 8 and Comparative Examples 3 and 4 were measured for solubility in water, nonvolatile content, phosphoric acid value and phosphoric acid equivalent. Table 2 shows the results of the examination.

[0059]

[Table 2]

In each of Examples 6 to 8, a reaction product in the form of a transparent homogeneous solution was obtained. From the comparison between the measured value and the calculated value in the phosphoric acid equivalent, the charged phosphoric anhydride was almost introduced into the starting epoxy resin as a phosphoric acid group, and the amount of the phosphate group introduced into the starting epoxy resin by the production method of the present invention. Can be substantially controlled. On the other hand, in Comparative Examples 3 and 4, since the reaction was carried out under the compounding condition in which the reaction product was not uniform, gelation occurred in the reaction process, and no liquid reaction product was obtained.

Examples 9 and 10 (Self-condensation type one-part thermosetting coating composition; bisphenol A type) The homogeneous solution composition obtained in Example 2 was applied to a clean steel plate surface using a bar coater. 20 after drying
It was coated to a thickness of μm, dried at room temperature, placed in a hot air drying oven, and baked for 30 minutes after the steel sheet temperature rose to 120 ° C. or 150 ° C.

Comparative Example 5 The same procedure as in Example 9 was carried out using YD-128 into which no phosphate group had been introduced, followed by firing at 150 ° C. for 30 minutes.

The physical properties of the coating films obtained in Examples 9 and 10 and Comparative Example 5 were measured by the following methods. -Pencil hardness: Measured according to JIS D0202. -Adhesion (Goban test): The coating film is scratched parallel to each other with a cutter knife to reach the substrate at 1mm intervals, and then 11 similar scratches perpendicular to this are made, and 100 1mm squares are formed. create. A cellophane (registered trademark) is stuck on this, and the number of the remaining eyes that are not peeled off even when pulled apart in the 180-degree direction is counted. -Solvent resistance: The sample pieces were each immersed in water, methanol, and acetone at 20 ° C. each for one liquid, and then the coating film was observed for cloudiness, swelling, and peeling. Table 3 shows the measurement results.

[0064]

[Table 3]

As shown in Table 3, the phosphoric acid-modified epoxy resin of the present invention has a property of being self-condensed and cured by heating. In Example 9, which was heat-treated at 120 ° C. for 30 minutes, the appearance was hardened, but the hardness and solvent resistance of the coating film were not sufficient. As is evident from Example 10, when heat treatment was performed at 150 ° C. for 30 minutes, the composition was almost completely cured and exhibited sufficient physical properties. As shown in Comparative Example 5, even if the unmodified epoxy resin is heat-treated under such conditions, no condensation occurs to form a film.

[0066] Examples 11 and 12 (curing agent-containing type one-component thermosetting coating composition; bisphenol A type) as the base resin, the epoxy groups to 1 mole 4.0
A bisphenol A type blocked epoxy resin (YD-128) to which moles or more of acetone was added was used. As a curing agent, a dioxane solution (solid content concentration: 23.8% by weight) of the curing agent type phosphoric acid-modified bisphenol type epoxy resin obtained in Example 1 was used, and the main agent and the curing agent were mixed at the respective ratios shown in Table 4, After standing at room temperature (about 20 ° C.), the progress of gelation over time was observed. Table 4 shows the results.

Comparative Example 6 The procedure of Example 11 was repeated except that the ratio of acetone to 1 mol of epoxy group was changed as shown in Table 4. The results of observing the progress of gelation are shown in Table 4.

[0068]

[Table 4]

The curing agent-containing one-part thermosetting coating composition of the present invention had a pot life of about one week at room temperature. In Comparative Example 6 in which the mixing ratio of acetone was less than the lower limit of the range of the present invention, the pot life was 0.5 days or less.

Examples 13 to 18 (One-part thermosetting coating composition containing curing agent) Bisphenol A type epoxy resin YD-128: acetone: dioxane =
1: 2: 1 (weight ratio) = 1.00: 6.55: 2.16 (molar ratio of acetone and dioxane based on the number of moles of epoxy group of YD-128), homogeneous containing 25% by weight of nonvolatile components mixed Solution (solution A) and ortho-cresol novolak epoxy resin YDCN-704: acetone: dioxane = 1: 3:
1 (weight ratio) = 1.00: 10.69: 2.35 (molar ratio of acetone and dioxane based on the number of moles of epoxy group of YDCN-704) mixed with a homogeneous solution (solution B) containing 20% by weight of non-volatile components. It was prepared as the main ingredient. As a curing agent, a dioxane solution containing a phosphoric acid-modified bisphenol-type epoxy resin prepared in Example 2 (non-volatile content concentration 18.8% by weight, non-volatile content phosphoric acid value = 373.8) (K solution) was used. Solution A or Solution B was mixed with Solution K at the respective nonvolatile content conversion ratios shown in Table 5 and coated on a clean steel plate surface using a bar coater so that the film thickness after drying was 20 μm. 150 inside
Bake at ℃ for 30 minutes. Thereafter, the pencil hardness of the coating film and the adhesiveness of the rubbing eyes (separation of cellophane tape) were measured, and the sample pieces after the adhesiveness test were immersed in water, methanol, and acetone at 20 ° C. overnight, respectively. It was observed whether any abnormalities such as swelling and peeling occurred. Table 5 shows the results.

COMPARATIVE EXAMPLE 7 The molar ratio of (epoxy groups of blocked epoxy resin (unprotected)) / (phosphate groups in phosphoric acid-modified epoxy resin) in the nonvolatile components of the base resin and the curing agent was changed to 6.3. A coating film was prepared and evaluated in the same manner as in Example 13. Table 5 shows the results.

Comparative Example 8 A coating film was prepared and evaluated in the same manner as in Example 16 except that orthophosphoric acid was used as a curing agent. Table 5 shows the results.

[0073]

[Table 5]

As is clear from Table 5, (epoxy group of blocked epoxy resin (unmodified)) / (phosphoric acid-modified) of unmodified epoxy resin (main component) and phosphoric acid-modified epoxy resin (curing agent) A coating composition in which the molar ratio of phosphoric acid groups in the epoxy resin) is within a range of 4/1 to 1/5 is 150%
The film is cured sufficiently by heat treatment at 30 ° C. for 30 minutes to give a coating film having excellent physical properties, but if the ratio is more than 4/1, curing is insufficient and a coating film having satisfactory physical properties cannot be obtained. When orthophosphoric acid is used instead of the phosphoric acid-modified epoxy resin as a curing agent, curing is insufficient and black rust is generated on a steel plate as a substrate.

[0075]

As described above in detail, by the production method of the present invention, a commercially available bisphenol-type or novolak-type epoxy resin is modified with phosphoric acid to obtain a self-condensation type and curing agent type phosphoric acid-modified epoxy resin. . A coating composition containing a self-condensation type phosphoric acid-modified epoxy resin is a one-part coating, has a storage stability of about one month or more at room temperature, hardens when heated, and has excellent hardness, adhesion, and solvent resistance. give. The coating composition containing a blocked epoxy resin whose epoxy group is protected by acetone and a curing agent type phosphoric acid-modified epoxy resin is one-part, has a storage stability of about one week at room temperature, and cures when heated. To give a coating film having excellent hardness, adhesion and solvent resistance. Therefore, it is not necessary to treat hardening agents harmful to the human body, and it can be treated as a one-part solution, so that it is free from the complicated task of compounding on site, and it is greatly superior in terms of improving safety and health and improving work efficiency. There is.

[Brief description of the drawings]

FIG. 1 is a reaction scheme when phosphoric anhydride is used as a phosphoric acid source in the method for producing a phosphoric acid-modified epoxy resin of the present invention.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Munehiro Kanzaki 18-3-316, Minamimiya-cho, Ashiya-shi, Hyogo (72) Inventor Ikko Ito 1-7-12-201 Tsukahara, Takatsuki-shi, Osaka F-term (reference) 4J036 AC01 AC08 AD07 AD08 AD15 AD21 AF05 AF06 AF07 CC02 HA12 JA01 KA01 4J038 DB061 DB062 DB071 DB072 DB091 DB092 DB261 DB262 DB271 DB272 DB281 DB282 DB321 DB322 DB401 DB402 GA14 JA33 NA26 PB05 PB07 PB09

Claims (15)

[Claims] 1. A method for producing a phosphoric acid-modified epoxy resin, which comprises reacting a solution containing a raw material epoxy resin, a phosphoric acid source, water, and a water-miscible organic solvent having no active hydrogen under uniform compounding conditions. A method for producing a phosphoric acid-modified epoxy resin. 2. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein phosphoric anhydride is used as the phosphoric acid source. 3. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein 1.5 to 15.0 mol of the water is added to 1 mol of the epoxy group of the raw material epoxy resin. A method for producing an acid-modified epoxy resin. 4. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein an epoxy equivalent having an epoxy equivalent of 170 to 5000 g / equivalent is used as the raw material epoxy resin. A method for producing a phosphoric acid-modified epoxy resin. 5. The method for producing a phosphate-modified epoxy resin according to claim 1, wherein a bisphenol-type epoxy resin is used as the raw material epoxy resin. . 6. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein a novolak type epoxy resin is used as the raw material epoxy resin. . 7. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein 0.6 to 2.0 mol of the phosphoric acid source (phosphoric acid) is added to 1 mol of the epoxy group of the raw material epoxy resin. A method for producing a phosphoric acid-modified epoxy resin, wherein 8. The method for producing a phosphoric acid-modified epoxy resin according to claim 1, wherein 0.6 to 1.5 mol of the phosphoric acid source (phosphoric acid) is added to 1 mol of the epoxy group of the raw material epoxy resin. A method for producing a phosphoric acid-modified epoxy resin, wherein 9. A one-part thermosetting coating composition comprising a phosphoric acid-modified epoxy resin obtained by the production method according to claim 8, wherein the phosphoric acid-modified epoxy resin is self-condensed and cured by heating. object. 10. The one-part thermosetting coating composition according to claim 9, wherein at room temperature there is substantially no change in viscosity for at least one month and no precipitation occurs. Curable coating composition. 11. A coating film obtained by curing the one-component thermosetting coating composition according to claim 10. 12. A method comprising a phosphoric acid-modified epoxy resin obtained by the production method according to claim 1 and a blocked epoxy resin in which an epoxy group is protected by a ketone. Liquid thermosetting coating composition. 13. The one-part thermosetting coating composition according to claim 12, wherein the ketone is acetone. 14. The one-part thermosetting coating composition according to claim 12, wherein (epoxy group of the blocked epoxy resin (unprotected)) / (in the phosphoric acid-modified epoxy resin). The one-part thermosetting coating composition, wherein the molar ratio of the (phosphate group) is 4.0 / 1.0 to 1.0 / 5.0. 15. A coating film obtained by curing the one-part thermosetting coating composition according to claim 12.