JPS62256815A - Curing agent - Google Patents

Abstract

PURPOSE:To obtain a curing agent soluble in an aliphatic solvent, useful for paints, etc., and capable of giving a coating film excellent in water resistance and flexibility, by performing an addition reaction of a specified half-ester compound with a diisocyanate. CONSTITUTION:An addition reaction is performed between a half-ester compound (C) obtained by reacting at least one carboxylic acid (A) selected from a polycarboxylic acid such as terephthalic acid or trimellitic acid and a hydroxymonocarboxylic acid such a dimethylolpropionic acid with a monoepoxide (B) having a 6-30C linear or branched (un)saturated alkyl group, such as glycidyl caproate at a b to a molar ratio of 0.95-1/1 (wherein a is the number of moles of the COOH groups of component A and b is the number of moles of the epoxide of component B reacted) and a diisocyanate (D) such as 2,4-tolylene diisocyanate or hexamethylene diisocyanate at a d to (a+c) molar ratio of 0.95-1/1 (wherein c is the number of the OH groups of component A and d is the number of moles of component D reacted) to obtain a curing agent containing a polyisocyanate compound containing 20-60wt% alkyl groups of component B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a curing agent for resins, particularly a curing agent useful for coatings.

[Conventional technology]

In recent years, plastics have come to be widely used as a substitute for metal materials in various fields of industry, and their usage has rapidly increased. Along with this, the demand for coating plastic surfaces is also increasing.

Generally, due to the thermal properties of plastic materials, two-component urethane paints that cure at low temperatures are used as paints. These curing agents include trimethylolpropane adducts of tolylene diisocyanate, which are polyisocyanate compounds, 1 to 1-rimethylolpropane adducts of diphenylmethane diisocyanate, trimethylolpropane adducts 1 to 1 of hydrogenated diphenylmethane diisocyanate,
A trimethylolpropane adduct of hexamethylene diisocyanate or an insya slate thereof, or a biuret-reacted trimer thereof, a trimethylolpropane adduct of inphorone diisocyanate or an insya slate thereof, and the like are used.

[Problem that the invention seeks to solve]

By the way, among plastic materials, polycarbonate, polystyrene, etc. have poor solvent resistance and will crack when exposed to ketone solvents, ester solvents, aromatic solvents, etc., so paints must be made from aliphatic solvents. There are some items that cannot be used. On the other hand, among the polyisocyanate compounds as a curing agent, 1 to trimethylolpropane adduct of lylene diisocyanate, trimethylolpropane adduct of diphenylmethane diisocyanate,
Trimethylolpropane adducts of hydrogenated diphenylmethane diisocyanate, trimethylolpropane adducts of hexamethylene diisocyanate, their isocyaslates and their biuret-reacted 3 phosphors, trimethylolpropane adducts of isophorone diisocyanate, etc. are difficult to dissolve in aliphatic solvents. . In addition, the incyanurate of isophorone diisocyanate is soluble in aliphatic agents, but its reactivity is low, resulting in a problem that the coating film is poor in water resistance and flexibility.

Furthermore, some plastics are soft and highly flexible, and therefore the coatings applied to these plastics are also required to be flexible. However, the above-mentioned polyisocyanate compounds have a problem in that they are not flexible.

The present invention is intended to solve the above problems.

The object of the present invention is to provide a curing agent that is soluble in aliphatic solvents and can impart flexibility to resins such as coatings.

[Means for solving problems]

The present invention comprises (A) a carboxylic acid selected from polycarboxylic acids and hydroxymonocarboxylic acids, and (8) a carbon number of 6.
An addition reaction product obtained by adding diisocyanate (D) to a half-ester compound (C), which is a reaction product with a monoepoxide having ~30 alkyl groups, wherein the alkyl group of the monoepoxide is an addition reaction product. 20 to 60% by weight of the carboxylic acid, and the carboxyl group of the carboxylic acid is a
When the reacted monoepoxide is b moles, the hydroxyl group of the carboxylic acid is C moles, and the reacted diisocyanate is d moles, b/a = 0.95/1 to 1/1. d
/(a+c)=0.95/l to 1/1.

The carboxylic acid (A) is one or more selected from polycarboxylic acids and hydroxymonocarboxylic acids. Polycarboxylic acids may or may not contain hydroxyl groups,
Examples include oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, adipic acid, phthalic acid, isophthalic acid,
Terephthalic acid, tetrahydrophthalic acid, dodecanoic acid, pyromellitic acid, 1-limellitic acid, etc., as well as polyols such as ethylene glycol, neopentyl glycol, diethylene glycol, trimethylolpropane, pentaerythritol, etc., and acid anhydrides, such as succinic anhydride. Examples include partial ester compounds of polycarboxylic acids obtained by reacting acids, maleic anhydride, phthalic anhydride, pyromellitic anhydride, and the like.

Further, as the hydroxymonocarboxylic acid, for example, 12-
Hydroxystearic acid, dimethylolpropion W1
．． Examples include p-hydroxyphenylacetic acid and salicylic acid.

The monoepoxide (8) is a monoepoxide having a linear or branched saturated or unsaturated axial alkyl group having 6 to 30 carbon atoms, such as caproic acid glycidyl ester, caprylic acid glycidyl ester, capric acid glycidyl ester , saturated or unsaturated fatty acid glycidyl esters such as decanoic acid glycidyl ester, lauric acid glycidyl ester, myristate glycidyl ester, palmitic acid glycidyl ester, stearic acid glycidyl ester, soybean oil fatty acid glycidyl ester, coconut oil fatty acid glycidyl ester, and α- Examples include α-olefin epoxy compounds obtained by oxidation of olefins, and one or more of these can be used.

The half ester compound (C) is a mixture of the carboxylic acid (A) and (
It is a reaction product of 8) with a monoepoxide, and is a compound having a hydroxyl group produced by the reaction of active hydrogen and an epoxy group and a plurality of hydroxyl groups of the hydroxyl group originally included.

As the diisocyanate (D), since the polyisocyanate compound to be produced is soluble in aliphatic solvents and unreacted diisocyanate cannot be removed by solvent fractionation, one molecule of diisocyanate is quantitatively added to the hydroxyl group of the half ester compound. diisocyanates which can be reacted with, for example diisocyanates having inocyanate groups of different reactivity.

Alternatively, diisocyanates that can be distilled off under reduced pressure are preferred. Examples of diisocyanates having isocyanate groups with different reactivities include 2,4-tolylene diisocyanate, and examples of diisocyanates that can be distilled off under reduced pressure include hexamethylene diisocyanate.

The polyisocyanate compound, which is a component of the curing agent of the present invention, is produced by reacting the carboxylic acid (A) with the monoepoxide (8) to produce the half-ester compound (C), and this half-ester compound and (D). ) with diisocyanate. In the first reaction between carboxylic acid and monoepoxide, the same number of hydroxyl groups as the reacted carboxyl groups are generated, and in the next reaction with diisocyanate 1, diisocyanate 1 is added to this hydroxyl group and the hydroxyl group originally contained in the carboxylic acid. The molecules react quantitatively, thereby producing a polyisocyanate compound having multiple isocyanate groups.

Since the carboxyl group and the epoxy group react quantitatively, the conditions for synthesizing the half-ester compound (C) may be appropriately selected as necessary, such as the reaction temperature and reaction time. In addition, the reaction between the half ester compound (C) and the diisocyanate (D) is carried out by adding the half ester compound (C) little by little into the diisocyanate at a temperature below 80°C because it is necessary to react only one isocyanate group of the diisocyanate. The preferred method is to 2. When using 4-tolylene diisocyanate, 2 to 1 mole of water M, J & 1 mole of half ester compound.
, 4-tolylene diisocyanate is used in an amount of 0.95 to 1 mol.

When hexamethylene diisocyanate 1 to 1 is used, 3 to 10 times the mole of hexamethylene diisocyanate is used per mole of hydroxyl group of the half ester compound (C).

A method in which unreacted hexamethylene diisocyanate is distilled off under reduced pressure is preferred.

The polyisocyanate compound thus obtained is (8)
Depending on the alkyl group content of the monoepoxide, the solubility in aliphatic solvents and the flexibility of the coating film when the curing agent is used as a coating material vary. As a result of investigating the solvent resistance of plastics with poor solvent resistance, such as polycarbonate and polystyrene, we found that it is possible to use up to 80% aliphatic solvents and 20% aromatic solvents in the solvent composition of the paint; It was found that when the solvent content exceeds 20%, cracks appear in the plastic.

In the polyisocyanate compound, which is a component of the curing agent of the present invention, if the content of alkyl groups in the monoepoxide decreases, the solubility in aliphatic solvents and the flexibility imparted to the coating film will deteriorate. The content of alkyl groups in monoepoxide is 20% by weight based on the compound
If it is less than this, it will become insoluble in a mixed solvent of aliphatic solvent/aromatic solvent = 80/20, and the effect of imparting flexibility to the cured coating will not be significant. Also, the content of alkyl groups is 2
If it is 0 to 60% by weight, the solubility and flexibility in aliphatic solvents are sufficient, and there is no need to use more than 60% by weight.

If the monoepoxide (n) has less than 6 carbon atoms, the alkyl group content will be less than 20% by weight, resulting in poor solubility in aliphatic solvents. Further, it takes 1 minute to impart solubility in an aliphatic solvent when the number of carbon atoms is 6 to 30, and there is no need to use a material having more than 30 carbon atoms.

Next, 21 mol of the carboxyl group of the carboxylic acid (A),
Assuming that the monoepoxide of (Il) reacted with this carboxyl group is b mol, the hydroxyl group of (A) is C mol, and the diisocyanate reacted with all the hydroxyl groups is d mol, the molar ratio to b is 0.95/]. :1!1, a curing agent insoluble in aliphatic solvents is obtained. Since this molar ratio is based on 11, the b/a molar ratio never exceeds 1/1. Moreover, when the molar ratio of d/(a+c) is less than 0.9571, the resulting curing agent gels during storage. This molar ratio is based on (a+c).

The molar ratio of reacted d/(a+c) never exceeds 1/1.

The curing agent of the present invention contains the above-mentioned polyisocyanate compound as an active ingredient, and may contain other ingredients. The curing agent of the present invention is used as a curing agent for resins used in paints, adhesives, kneeling agents, etc., and is particularly suitable as a curing agent for paints.

Examples of the resin to be cured include resins that can be cured with polyisocyanate 1-, such as acrylic resins, polyester resins, alkyd resins, polyurethane resins, and epoxy resins.

When the curing agent of the present invention is used for paints, various binder varnishes, various pigments,
Paints can be obtained by combining additives and the like. As the binder varnish, varnishes commonly used for paints, such as acrylic varnish, polyester varnish, alkyd varnish, and polyurethane varnish, can be used.

Since the curing agent of the present invention has good solubility in aliphatic solvents, it can be used as a curing agent for coatings 11 made of aliphatic solvents6.Therefore, paints using the curing agent of the present invention are heat resistant, Suitable for coating plastic materials with poor solvent resistance. Furthermore, when the curing agent of the present invention is used as a coating material, the resulting coating film has excellent flexibility, so it can also be used as a curing agent for coatings such as automobile bumpers.

〔Effect of the invention〕

According to the present invention, since a specific polyisocyanate compound is used as a component, a curing agent that is soluble in aliphatic solvents and has flexibility can be obtained.

〔Example〕

Next, the present invention will be explained in further detail by giving examples. In each example, parts are parts by weight, and percentages are percentages by weight.

Production Example 1 Production of half-ester compound C As shown in Table 1, xylene, an alkyl group-containing monoepoxide, and a polycarboxylic acid or a hydroxycarboxylic acid were added to a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser. The mixture was charged and reacted at 160 to 170°C for 4 hours to obtain a solution of compound C. Table 1 shows the solid content, Gardner-Holdt viscosity, acid value, hydroxyl value, etc. of the obtained Compound C solution. The obtained solutions of compound C are designated as C-1 to C-11, respectively.

(Note) 1) Cardura E-10: Yuka Shell Epoxy Co., Ltd.
manufactured by Nippon Oil & Fats Co., Ltd., trademark, synthetic fatty acid glycidyl ester with 10 carbon atoms 2) Bremmer S [l: manufactured by NOF Corporation, trademark,
Soybean oil fatty acid glycidyl ester 3) AOE-YO8: manufactured by Daicel Chemical Industries, Ltd.
Trademark, α-olefin epoxy compound having 20 to 28 carbon atoms 4) AO[E-X24: manufactured by Daicel Chemical Industries, Ltd., trademark, α-olefin epoxy compound having carbon fA 12 to 14 Production Example 2 For binder varnish Production A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser tube, and a dropping funnel was charged with 1210 parts of oxidizer and 20 parts of Isopar E (Exxon Chemical Co., Ltd. j!A-trademark, aliphatic solvent), and the reflux Ω degree ( Heat to approx. 140°C. While maintaining the reflux state, the following vinyl monomer mixture was added dropwise at a constant speed from the dropping funnel over a period of 3 hours.

Styrene 15.0 parts Methyl methacrylate 5.9 parts Butyl methacrylate 3.1 parts Lauryl methacrylate 17.2 parts 2-hydroxyethyl methacrylate 7.8 parts Acrylic acid
After the completion of the dropping of 0.5 part of t-butyl peroxybenzoate, the mixture was kept at reflux temperature for 1 hour. Next, 0.05 parts of t-dipyl peroxybenzoate and 1 part of xylene were mixed and added dropwise from the dropping funnel. After continuing the reaction by keeping the temperature at reflux for another 2 hours, 95 parts of Isopar EIL was added and the non-volatile content was 49.8.
% glue varnish was obtained. Note that this varnish had a Gardner-Holdt viscosity of Z.

Examples 1 to 9 As shown in Table 2, 2,4-tolylene diisocyanate and ethylcyclohexane were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a dropping funnel.
The mixture was heated and stirred at 0 to 70°C, and a solution of compound C was added dropwise from the dropping funnel over 3 hours. The reaction was further continued at 60 to 70°C for 3 hours, and the transparent curing agent solutions of Examples 1 to 9 were added. Obtained. Table 2 shows the solid content, Gardnerholt viscosity, and solubility of the obtained curing agent solution when mixed in a mixed solvent of 5 times the amount of hebutane/xylene = 80/20.

Next, the curing agent solution prepared in '41) and the binder varnish were weighed and mixed according to the paint formulation shown in Table 2, the diluting thinner shown in Table 2 was added, and the mixture was heated using a Ford cup N0.4 for 20 seconds (20°C). ) diluted paint was obtained. .

1:) The diluted paint was spray coated on a 3 m thick polycarbonate resin plate and a polystyrene resin plate, and baked at 80°C for 30 minutes to obtain a dry coating film. Table 2 shows the dry film thickness, film appearance, acetone solubility, flexibility, and other film performances of the obtained dried paint film.

Examples 10 to 12 As shown in Table 2, hexamethylene diisocyanate and ethylcyclohexane were charged into a reaction vessel similar to Examples 1 to 9, heated to 60 to 70°C with stirring, and a solution of compound C was added to the reaction vessel through a dropping funnel. was added continuously over 3 hours, and the reaction was further continued at 60 to 70°C for 3 hours. After applying the obtained reaction product solution to a rotary evaporator and distilling off unreacted hexamethylene diisocyanate and the solvent under reduced pressure, 30 parts of Isopar E/xylene = 80/20 mixed solvent was added and the mixture of Examples 10 to 12 was prepared. A clear hardener solution was obtained.

Table 2 shows the solid content, Gardnerholt viscosity, and solubility of the obtained curing agent solution when mixed in a mixed solvent of 5 times the amount of hebutane/xylene: 80/20.

Next, the obtained curing agent solution and the binder varnish were weighed and mixed according to the paint formulation shown in Table 2, and the diluent thinner shown in Table 2 was added, and the diluted paint was diluted with Ford Cup N004 for 20 seconds (20°C). I got it.

The obtained diluted paint was spray-coated on a polycarbonate resin plate and a polystyrene resin plate with a thickness of 31 Tn, and baked at 80° C. for 30 minutes to obtain a dry coating film. Table 2 shows the dry film thickness, film appearance, acetone solubility, flexibility, and other film performances of the obtained dried paint film.

Comparative Examples 1-3 As shown in Table 2, in the same reaction vessels as Examples 1-12,
2. 4-Tolylene diisocyanate and ethylcyclohexane were charged, heated and stirred at 60 to 70°C, and a solution of compound C was added dropwise to this from a dropping funnel over 3 hours,
The reaction was further continued at 60 to 70°C for 3 hours to obtain a curing agent solution.

The obtained curing agent solution of Comparative Example 1 was cloudy, indicating that a curing agent insoluble in the aliphatic solvent was generated. The curing agent solution of Comparative Example 2 gelled after being left at 20° C. for one day. In the curing agent solution of Comparative Example 3, insoluble matter precipitated during synthesis.

Next, the curing agent solution of Comparative Example 1 and the binder varnish prepared in 1' were weighed and mixed according to the paint formulation shown in Table 2, and the diluting thinner shown in Table 2 was added to the Ford Cup N
A diluted paint of 0.4 for 20 seconds (20° C.) was obtained.

The obtained diluted paint was spray coated on a polycarbonate resin board and a polystyrene resin board with a thickness of 31 mm.

A dry coating film was obtained by baking at 80° C. for 30 minutes. Table 2 shows the properties of the dried coating film, such as dry coating thickness, coating appearance, acetone solubility, and flexibility.

(Note) 1) Alkyl group content Mv: Molecular group of polyisocyanate compound M: Alkyl group content in polyisocyanate compound 2) Add a mixed solvent of heptane/xylene = I'IO/20 in an amount 5 times the solubility. Good solubility: when completely transparent 3) Isopar E manufactured by Exxon Chemical Co., Ltd., trademark, aliphatic solvent 4) Torzol 19 manufactured by Shell Chemical Co., Ltd., commercial t':! , aliphatic solvent 80%
, a mixed solvent containing 20% aromatic solvent 5) Coating 1. Good appearance: smooth and glossy 6) Soak acetone-soluble gauze in acetone and move it back and forth on the coated surface 10 times.

Good: There is no abnormality such as melting of the painted surface or loss of gloss 7) Bend it along an iron bar with a diameter of 10+ m with the flexible paint film facing up 6 Good: No abnormality such as cracks or cracks in the paint film or material As is clear from the results in Table 2, the curing agent of the present invention has excellent solubility in aliphatic solvents, coating appearance, acetone solubility,
Excellent coating performance such as flexibility.

In contrast, the curing agent solution of Comparative Example 1 in which the alkyl group content in the curing agent was less than 20% was cloudy.

The coating properties such as coating appearance and flexibility are also poor.

The curing agent solution of Comparative Example 2, in which the molar ratio of d/(a + c) was less than 0.95/l, gelled after being left at 20° C. for one day.

In the curing agent solution of Comparative Example 3 using Compound C with a b/a molar ratio of less than 0.95/1, insoluble matter precipitated during one synthesis,
No material that could be used as a curing agent was obtained.

Claims (2)

[Claims] (1) (A) a carboxylic acid selected from polycarboxylic acids and hydroxymonocarboxylic acids; and (8) a carbon number of 6 to 3.
An addition reaction product obtained by adding diisocyanate (D) to a half-ester compound (C) which is a reaction product with a monoepoxide having 0 alkyl groups, wherein the alkyl group of the monoepoxide is the addition reaction product of the addition reaction product. 20-60% by weight
And when the carboxyl group of the carboxylic acid is a mol, the reacted monoepoxide is b mol, the hydroxyl group of the carboxylic acid is c mol, and the reacted diisocyanate is d mol, b/a=0.95/1 ~1/1, d/(a+
c) A curing agent characterized by containing a polyisocyanate compound having a ratio of 0.95/1 to 1/1. (2) The curing agent according to claim 1, wherein the diisocyanate is 2,4-tolylene diisocyanate or hexamethylene diisocyanate.