JP2008255197A - Curing agent composition and its preparation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curing agent for coating excluding toxic substances, allergy incentive materials, exogenous endocrine-disrupting chemicals, etc., safety to human body and having a new structure. <P>SOLUTION: The curing agent composition is obtained by amidating a diester (A) from a 5-8C linear dicarboxylic acid and an alcohol having a 1-5C aliphatic hydrocarbon group, and a di(2-hydroyalkyl) amine (B) having a 1-5C aliphatic hydrocarbon group, in a molar ratio of 0.60-0.95 of the total molar numbers of the amino groups of the (B) to the total molar numbers of the ester group in the (A), wherein the average functional groups per mole is 4-8 in the curing agent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a curing agent for paint having a novel structure that is safe for the human body and does not contain a toxic substance, an allergenic substance, an exogenous endocrine disrupting chemical substance, and the like, and a method for producing the same.

The most important task for the paint industry is the development of paint that can avoid pollution of the global environment due to the volatilization of organic solvents. A powder paint is first mentioned as a paint with little environmental pollution. However, TGIC (triglycidyl isocyanurate), which has been widely used as a curing agent for powder coatings, has problems of skin irritation and toxicities such as rashes. There is a suspicion that it is a substance (generic name: environmental hormone), and block isocyanate has a problem that the blocking agent that is released during curing becomes VOC and contaminates the baking furnace and the environment. For this reason, 2-hydroxyalkylamide type curing agents, which have few problems of toxicity and have a volatilization product at the time of curing as water, have been widely used.
Thermosetting coatings using 2-hydroxyalkylamide as a curing agent for carboxy group-containing polyesters are known (Patent Document 1). Also, many inventions have been made mainly as polyester powder coatings using this combination. (Patent Documents 2 to 6)
: JP-A-51-17970 : Japanese Patent No. 2594346 : Japanese National Patent Publication No. 8-512077 : JP-A-63-090580 : Japanese Patent Laid-Open No. 04-247058 : JP 2000-038372 A

  Patent Document 1 is a patent relating to a solution-type paint. In the examples, a reaction product (triamide) of trimellitic acid and 2-methylaminoethanol is described, but it was a viscous liquid. An example of a powder coating material using a self-curing acrylic resin obtained by copolymerizing a monomer having 2-hydroxyalkylamide in the side chain is disclosed, but a 2-hydroxyalkylamide type curing agent is used as a carboxylic acid group-containing resin. There is no powder coating example in combination with. In addition, according to Examples of Patent Documents 2 to 6, a 2-hydroxyalkylamide type curing agent has a Bis-di (2-hydroxyalkyl) amide structure. This is because, among 2-hydroxyalkylamide compounds, Bis-di (2-hydroxyalkyl) amide having a symmetric structure is highly crystalline and solid at room temperature, so TGIC has been widely used as a curing agent for powder coatings. This is because it can be used as a curing agent that is non-toxic and safe for the human body instead of (triglycidyl isocyanurate).

  Bis-dihydroxyalkylamides mainly used at present are tetrafunctional types having a structure in which dialkanolamine is condensed at both ends of adipic acid. Examples include N, N, N ′, N′-tetrakis (2-hydroxyethyl) adipamide (trade name: PrimidXL552; CAS 6334-25-4) and N, N, N ′, N′-tetrakis (2-hydroxy). Propyl) adipamide (trade name: PrimidQM1260; CAS 57843-53-5) (all manufactured by EMS). A curing agent having a Bis-di (2-hydroxyalkyl) amide structure in which dihydroxyalkylamine is condensed at both ends of these alkyl chains (hereinafter, sometimes referred to as “primide” curing agent from its trade name) is crystalline. It is highly suitable for powder coating applications and has low-temperature curability (cured by baking at 160 ° C. for 30 minutes), showing good coating film performance. However, these conventionally used Bis-di (2-hydroxyalkyl) amide type “primide” curing agents have a very high hygroscopic property, which is why the cured coating film is exposed to a high humidity environment for a long time. There has been a problem that the adhesion to the substrate after moisture resistance load is insufficient, such as peeling. Therefore, a 2-hydroxyalkylamide type curing agent having higher curability and higher hydrophobicity has been demanded.

  The present invention is safe for the human body, has a high curability when used as a curing agent for powder coatings, and a cured agent composition in which the cured coating film has excellent base adhesion after a moisture resistance load and its production Provide a method.

  As a result of diligent research, the inventors have a highly hydrophobic raw material, and the functional ratio per molecule obtained by synthesizing the mixture ratio of the linear dicarboxylic acid diester and di (2-hydroxyalkyl) amine as insufficient of the amine. It has been found that a 2-hydroxyalkylamide type curing agent composition having a number of radicals greater than 4 has high curability and that the cured coating film has excellent undercoat adhesion after moisture resistance loading, and the curing agent composition It was found that the product can be produced by performing an amidation reaction of a linear dicarboxylic acid diester and di (2-hydroxyalkyl) amine under certain conditions, and the present invention has been completed.

The present invention relates to the following curing agent composition and method for producing the same.
1. The total number of moles of the ester group of (A) from the linear dicarboxylic acid diester (A) represented by the general formula (I) and the di (2-hydroxyalkyl) amine (B) represented by the general formula (II) The average number of functional groups per molecule formed by amidation reaction at a ratio of the total number of moles of amino group (B) to 0.60 to 0.95 is less than 8 and less than 8 Hardener composition.

（式中Ｒ^１はそれぞれ同一又は異なって、炭素数１〜５の脂肪族炭化水素基を表し、ｎは５〜８の整数である。）

(In the formula, each R ¹ is the same or different and represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 5 to 8).

（式中Ｒ^２及びＲ^３は同一であっても異なっていてもよい水素原子または炭素数１〜５の脂肪族炭化水素基を表す。）
２．ジ（２−ヒドロキシアルキル）アミン（Ｂ）が一般式（II）においてＲ^２及びＲ^３が同一である対称構造のジアルカノールアミンである項１に記載の硬化剤組成物。
３．２０℃における水溶解度が０〜５０ｇ／１００ｇＨ_２Ｏである項１または２に記載の硬化剤組成物。
４．一般式（I）で表される直鎖ジカルボン酸ジエステル（Ａ）と、一般式（II）で表されるジ（２−ヒドロキシアルキル）アミン（Ｂ）を（Ａ）のエステル基の総モル数に対する（Ｂ）のアミノ基の総モル数の割合を０．６０〜０．９５にてアミド化反応させ、１分子あたりの平均官能基数が４よりも大かつ８よりも小とすることを特徴とする硬化剤組成物の製造方法。

(In the formula, R ² and R ³ represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms which may be the same or different.)
2. Item 2. The curing agent composition according to Item 1, wherein the di (2-hydroxyalkyl) amine (B) is a dialkanolamine having a symmetrical structure in which R ² and R ³ are the same in the general formula (II).
Water solubility at 3.20 ° C. curing agent composition according to claim 1 or 2 which is 0~50g / 100gH ₂ O.
4). The total number of moles of the ester group of (A) from the linear dicarboxylic acid diester (A) represented by the general formula (I) and the di (2-hydroxyalkyl) amine (B) represented by the general formula (II) The ratio of the total number of moles of the amino group of (B) to 0.60 to 0.95 is amidated, and the average number of functional groups per molecule is larger than 4 and smaller than 8. A method for producing a curing agent composition.

（式中Ｒ^１はそれぞれ同一又は異なって炭素数１〜５の脂肪族炭化水素基を表し、ｎは５〜８の整数である。）

(In the formula, each R ¹ is the same or different and represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 5 to 8).

（式中Ｒ^２及びＲ^３は同一であっても異なっていてもよい水素原子または炭素数１〜５の脂肪族炭化水素基を表す。）
５．アミド化反応温度が６０〜１２０℃である項４に記載の硬化剤組成物の製造方法。
６．項１〜３のいずれか１項に記載の硬化剤組成物とポリカルボン酸樹脂を含む粉体塗料組成物。

(In the formula, R ² and R ³ represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms which may be the same or different.)
5. Item 5. The method for producing a curing agent composition according to Item 4, wherein the amidation reaction temperature is 60 to 120 ° C.
6). Item 4. A powder coating composition comprising the curing agent composition according to any one of Items 1 to 3 and a polycarboxylic acid resin.

  The curing agent composition of the present invention uses a highly hydrophobic substance as a raw material, and di (2-hydroxyalkyl) amine is converted into di (2) with respect to the total number of ester groups of the linear dicarboxylic acid diester. 2-Hydroxyalkyl) A curing agent composition having a functional group number per molecule larger than 4 obtained by amidation reaction at a ratio of the total number of moles of amino groups in the amine of 0.60 to 0.95. By increasing the number of functional groups per molecule to more than 4, there is a problem that the adhesion of the base after the moisture resistance load of the coating film after curing that the 2-hydroxyalkylamide type curing agent that has been commercially available has been insufficient. can be solved. In addition, the method for producing a curing agent composition of the present invention is excellent in terms of energy saving because a target composition can be obtained by employing a aging step that consumes little energy.

  The present inventors consider increasing the hydrophobicity of the curing agent itself as a countermeasure. First, dicarboxylic acid diester used as a raw material is changed from an adipic acid diester having a methylene chain length of 4 to a dicarboxylic acid having a longer methylene chain length. Although an attempt was made to replace it with an acid diester, in order to obtain sufficient hydrophobicity, the methylene chain length must be 9 to 10 (nonanedicarboxylic acid to dodecanedioic acid) or more. It became liquid and could not be used for powder coatings.

  The above-mentioned “primid” curing agent is a tetrafunctional curing agent, but the present inventors have considered that moisture resistance can be improved by increasing the number of functional groups and increasing the crosslinking density, and have attempted polyfunctionalization. First, we tried to synthesize Tris-dihydroxyalkylamides in which diethanolamine was condensed to the terminal carboxylic acid ester of triamide in which diethanolamine and diethylenetriamine were used in combination, and 3 molecules of dicarboxylic acid diester were condensed to diethylenetriamine. The target substance could not be produced.

  Although synthesis using tricarboxylic acid ester was also attempted, when tributyl citrate, which has a dense structure of acid, was reacted with diethanolamine, the condensation reaction of the two acid esters and amine proceeded, but the third acid ester The condensation reaction did not proceed due to steric hindrance, and Tris-dihydroxyalkylamide could not be synthesized. On the other hand, a reaction between a polycarboxylic acid ester in which the carboxylic acid esters are separated from each other and diethanolamine was attempted, but a transesterification reaction occurred between the hydroxy group of 2-hydroxyethylamide formed during the reaction and the unreacted acid ester group. The viscosity increased and this could not be synthesized.

  Based on the above process, the present inventors have conducted extensive research. As a result, aliphatic dicarboxylic acid esters having a higher methylene chain length of 5 to 8 and di- (2-hydroxyalkyl) having higher hydrophobicity than adipic acid. ) (2-Hydroxyalkyl) amide synthesized by using amine as a raw material and charging and reacting the ratio of the total number of moles of amino groups to the total number of moles of ester groups within a specific range has appropriate crystallinity. Therefore, it is solid at room temperature, is hydrophobic, has many functional groups, and is excellent in curability, so it is suitable as a curing agent for powder coatings, and has excellent base adhesion after moisture resistance loading of a cured coating film As a result, the present invention has been completed.

  The curing agent composition of the present invention, the production method thereof, and the powder coating composition using the same will be described below.

  The curing agent composition of the present invention has an average functional group number of more than 4 and 8 or less per molecule. The conventional commercially available curing agent ("primid") and the curing agent composition of the present invention are common in that linear dicarboxylic acid diester (A) and di (2-hydroxyalkyl) amine (B) are used as raw materials. . There was a method of synthesizing a carboxylic acid (ester) and an amine with a charge ratio which is not an equimolar amount even in a conventional method of synthesizing a curing agent, but these were intended to be Bis-di (2-hydroxyalkyl) amide (Note 1). In the curable composition of the present invention, the amount of amine is less than the chemical equivalent of the carboxylic acid at the time of manufacture, and the reaction is gently reacted to increase the average number of functional groups, that is, the curability is higher, and the backbone of the linear dicarboxylic acid diester is higher. Due to the synergistic effect of hydrophobicity due to the methylene chain length being 5 to 8, it was possible to obtain a curing agent composition having excellent adhesion to the substrate after the moisture resistance load of the coated film after curing.

  Note 1: For example, Patent Document 4 (Example G), Patent Document 5 (Examples 1 and 3), and Patent Document 6 (Claim 1) are charged with an excess of amine even after a conventional tetrafunctional curing agent is synthesized. In this method, unreacted excess amine is removed.

Regarding the average functional group number First, the calculation method of the average functional group number of the curing agent composition and the problems in production will be described.

  Assume that a mole of (A) linear dicarboxylic acid diester and b mole of (B) di (2-hydroxyalkyl) amine are charged as initial preparations in the production of the curing agent. At this time, the chemical equivalent of the carboxylic acid ester by (A) is 2a, the chemical equivalent of the amine by (B) is b, and the chemical equivalent of the hydroxyl group is 2b. At this time, since the chemical equivalent of the amine is equal to the chemical equivalent of the carboxylic acid ester (prior art) or less (the present invention), 2a ≧ b.

  The actual reaction is first preceded by a condensation reaction between the carboxylic acid ester of (A) and the active hydrogen (amino group and hydroxyl group) of the amine of (B). That is, an amidation reaction by a reaction between a carboxylic acid ester and an amino group, and a transesterification reaction between the carboxylic acid ester and a hydroxyl group. The condensate undergoes an intramolecular amide-ester transfer reaction. The amide-ester transfer reaction using diethanolamine as the amine is shown in Formula III.

（III）
（ここでＲは直鎖カルボン酸残基を示す。）
この平衡はアミド側が安定であるので通常は縮合物はアミド構造が優位となる。この段階を段階１とする。計算上の簡単のため仮に（Ａ）のカルボン酸エステルと（Ｂ）のアミンの縮合では生成物は全てアミドとなると仮定する。

(III)
(Here, R represents a linear carboxylic acid residue.)
Since this equilibrium is stable on the amide side, the condensate usually has an amide structure. This stage is referred to as stage 1. For the sake of simplicity of calculation, it is assumed that in the condensation of the carboxylic acid ester (A) and the amine (B), the product is all an amide.

  The state of the system when the amidation reaction is completed in Step 1 is described. At this time, all of the amine is consumed, so the remaining amount of amine is 0 mol, b mol of carboxylic acid ester is consumed by reaction with amine, so the remaining amount is (2a-b) mol, and the hydroxyl group reacts. 2 b mol remains as it is. The number of molecules in the system is a mole because the amine of (B) is bonded to the total amount (A).

  A transesterification condensation reaction between the remaining carboxylic acid ester in Step 2 and the hydroxyl group of the 2-hydroxyalkylamide produced in Step 1 occurs. Describe the state in which the remaining amount of the carboxylic acid ester is consumed by this step 2 and the desired curing agent is obtained. At this time, since the hydroxyl group (2a-b) mol is consumed by the reaction with the carboxylic acid ester, the remaining amount is 2b- (2a-b), that is, (3b-2a) mol. The number of molecules in the system is 2 x (2a-b) moles of molecules bonded by reaction to form (2a-b) moles of molecules, so subtracting a- (2a-b) or (ba) moles is there.

That is, the average number of functional groups is represented by Formula IV because it is the number of moles of hydroxyl groups remaining divided by the number of molecules.

Average number of functional groups (mol / molecule) = (3b-2a) / (ba) (IV)

In the actual production process, the amidation reaction and transesterification reaction, which are condensation reactions between the molecules (A) and (B), proceed with an intramolecular amide / ester transfer reaction (amide superiority), and at the same time, the produced diesters. A condensation reaction between the hydroxyl group of (2-hydroxyalkyl) amide and an unreacted dicarboxylic acid ester also occurs. In the latter reaction, an amidated compound having a functional group number greater than 2 (such as Bis-di (2-hydroxyalkyl) amide) and a dicarboxylic acid ester may react to form a three-dimensional network and the system may gel. . In the conventional technique, this inconvenient reaction is achieved by making the compounding amount of the amine equal to or more, and isolating the produced Bis-di (2-hydroxyalkyl) amide from the reaction system by utilizing the solubility and crystallinity. (Gelation) was avoided.

  The curable composition of the present invention is synthesized with an excess of carboxylic acid having a mole ratio of ester groups / moles of amino groups of from 0.60 to 0.95 in the feed formulation, but under mild reaction conditions such as a reaction temperature of 60. The reaction is allowed to proceed while avoiding gelation of the system at ~ 120 ° C. Therefore, a small amount of ester structure remains in the intramolecular amide-ester tautomer in the method of the present invention. As is apparent from Reaction Formula III, the ester structure has an amine value due to secondary amine, and the residual amine concentration (obtained from the amine value) decreased to 2-hydroxyalkylamide structure due to the ester structure. Equal to concentration.

  Therefore, the average number of functional groups of the actual curing agent composition is a value obtained by correcting the value calculated from Formula IV with the amine value. Calculation examples are described in the examples.

Table 1 shows a comparison of the average number of functional groups calculated from Formula IV of the curing agent composition obtained under the manufacturing conditions of the conventional (primid) curing agent and the manufacturing conditions of the present invention. (The actual curing agent composition of the present invention has a smaller value than the calculated value when there is a residual amine value.)
Table 1

About water solubility Water solubility is a measure of the affinity of a substance for water. The curing agent composition of the present invention is characterized by having a hydrophobic trunk and lower water solubility than the conventional “Primid” curing agent. In general, an amide compound has a high affinity with water due to hydrogen bonding. For example, N, N, N ′, N′-tetrakis (2-hydroxyethyl) adipamide (trade name: PrimidXL552), which is a typical “primid” curing agent, Dissolve 80 g or more in 100 g of water at 20 ° C. The influence of the water solubility of the curing agent is large as a cause of insufficient adhesion of the base after the moisture resistance load of the cured coating film. Water solubility of the curing agent composition in order to improve the underlying adhesion after humidity load of the cured film is preferably in the range of 0~50g / 100gH 2 _0.

About the raw material of a hardening | curing agent composition The hardening | curing agent composition of this invention uses a linear dicarboxylic acid diester (A) and di- (2-hydroxyalkyl) amine (B) as a starting material.

Linear dicarboxylic acid diester (A)
The component (A) of the present invention is a diester of a linear aliphatic dicarboxylic acid having a structure represented by the following chemical formula I.

（I）
（式中Ｒ１は炭素数１〜５の脂肪族炭化水素基を表し、ｎは５〜８の整数である。）
かかる化合物としては、ピメリン酸、スベリン酸、アゼライン酸及びセバシン酸のジメチル、ジエチル、ジプロピル、ジブチル、ジペンチルエステル化合物などが挙げられる。これらのうちで特にセバシン酸ジエステル化合物が製造された硬化剤の疎水性を高くする観点から好ましく、両末端の脂肪族炭化水素基Ｒ^１については製造時の容易性からメチル基またはエチル基であるのが好ましく特にメチル基が好ましい。また、化合物（Ａ）として１種のみを用いてもよいし、２種以上を併用してもよい。

(I)
(In the formula, R1 represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 5 to 8).
Such compounds include dimethyl, diethyl, dipropyl, dibutyl, dipentyl ester compounds of pimelic acid, suberic acid, azelaic acid and sebacic acid. Of these, sebacic acid diester compounds are particularly preferred from the viewpoint of increasing the hydrophobicity of the curing agent produced, and the aliphatic hydrocarbon groups R ^{1 at} both ends are methyl groups or ethyl groups for ease of production. Of these, a methyl group is particularly preferable. Moreover, only 1 type may be used as a compound (A) and it may use 2 or more types together.

Di- (2-hydroxyalkyl) amine (B)
The component (B) of the present invention is di- (2-hydroxyalkylamine), and its structure is shown in the following chemical formula II.

（II）
（式中Ｒ^２及びＲ^３は同じであっても異なっていてもよい水素原子または炭素数１〜５の脂肪族炭化水素基を表す。）
かかる物質としてはジ−２−ヒドロキシエチルアミン（ジエタノールアミン）、Ｎ−２−ヒドロキシエチル−Ｎ−２−ヒドロキシプロピルアミン、ジ−２−ヒドロキシプロピルアミン（ジイソプロパノールアミン）、Ｎ−２−ヒドロキシエチル−Ｎ−２−ヒドロキシブチルアミン、ジ−２−ヒドロキシブチルアミン（ジ−２―ブタノールアミン）などのジアルカノール型の２級アミンが挙げられる。中でも２つの２−ヒドロキシアルキル基が互いに同じものである、対称構造を持つジアルカノールアミンが好ましい。特にジエタノールアミンもしくはジイソプロパノールアミンである事が好ましい。また、ジ−２−ヒドロキシアルキルアミン（Ｂ）として１種のみを用いてもよいし、２種以上のものを併用してもよい。

(II)
(In the formula, R ² and R ³ represent the same or different hydrogen atom or C 1-5 aliphatic hydrocarbon group.)
Such materials include di-2-hydroxyethylamine (diethanolamine), N-2-hydroxyethyl-N-2-hydroxypropylamine, di-2-hydroxypropylamine (diisopropanolamine), N-2-hydroxyethyl-N. Examples include dialkanol-type secondary amines such as 2-hydroxybutylamine and di-2-hydroxybutylamine (di-2-butanolamine). Among them, dialkanolamine having a symmetrical structure in which two 2-hydroxyalkyl groups are the same is preferable. Particularly preferred is diethanolamine or diisopropanolamine. Moreover, only 1 type may be used as di-2-hydroxyalkylamine (B), and 2 or more types may be used together.

Production of curing agent composition (amidation reaction)
A linear dicarboxylic acid diester (A) is reacted with di- (2-hydroxyalkyl) amine (B) to produce a desired curing agent composition. At this time, when the charge ratio of the total number of moles of the amino group of (B) to the total number of moles of the ester group of (A) is 1.0 or more (stoichiometric excess of amino groups), Can be used to obtain a tetrafunctional curing agent having a Bis-di- (2-hydroxyalkyl) amide structure ("primid" curing agent). However, in the present invention, the ratio of the total number of moles of the amino group (B) to the total number of moles of the ester group (A) is 0.60 to 0.95, preferably 0.75 to 0.92, more preferably 0. By making the amino group deficient stoichiometrically in the range of 80 to 0.90, the transesterification reaction of some β-hydroxyl groups and ester groups proceeds simultaneously with the amidation reaction. A polyfunctional curing agent having a higher functional number than that of the functional curing agent is produced.
At this time, the length (hardness) of the alkyl group in the trunk part of the compound (A) represented by the general formula (I), the structure of di- (2-hydroxyalkyl) amine (B), and the amount charged The melting point of the functional curing agent fluctuates to obtain a liquid to solid state at normal temperature. Among them, as a combination for obtaining a solid at room temperature as a curing agent for powder coating, (A) has a short alkylene group (for example, n = 5: pimelic acid derivative in general formula (I)), and (B) has a symmetrical structure. In the case of dialkanolamine, particularly diethanolamine, a solid product can be produced even if the charge amount of (B) to (A) is about 0.60. On the other hand, the alkyl group of (A) is long (for example, n = 8 in the general formula (I): sebacic acid derivative) and (B) is an asymmetrical di-alkanolamine (for example, N-2-hydroxyethyl-N-2). In the case of -hydroxybutylamine), a solid product cannot be produced at room temperature even if the charge amount of (B) to (A) is 1.0. In general, in order to produce a desired curing agent for powder coating, when the trunk part of the linear dicarboxylic acid diester (A) is combined with one having n = 7 or 8, di- (2-hydroxyalkyl) The amine (B) is preferably a dialkanolamine having a symmetric structure, particularly preferably diethanolamine.
The ratio of the total number of moles of the amino group (B) to the total number of moles of the ester group (A) is 0.60 to 0.95, preferably 0.75 to 0.92, more preferably 0.80 to 0. It is possible to produce a powder coating curing agent that is solid at room temperature.

  The hardening | curing agent composition of this invention is manufactured by carrying out ester-amide exchange of the ester group of (A), and the amino group of (B) by mixing and heating raw material (A) and (B). This is a known process described in, for example, Japanese Patent Laid-Open No. 51-017970. This reaction may be performed in the absence of a solvent, or may be performed in a solvent that dissolves both raw materials well. However, in order to obtain a solvent-free curing agent composition for use in a powder coating, it is preferable to perform the reaction without a solvent. At this time, a catalyst for the amidation reaction may be added. The catalyst used is not particularly limited as long as it promotes amidation, but is preferably a basic substance, and examples thereof include metal alcoholates such as sodium methylate.

  At this time, since the reaction is an equilibrium reaction, in order to proceed with the amidation, the reaction is advanced by removing the alcohol produced during the amidation out of the system. At this time, the hydrocarbon group at the end of the linear dicarboxylic acid diester represented by the chemical formula (I) is removed as the corresponding alcohol, but if the reaction temperature is high, amide-ester exchange without the leaving product represented by the following formula III The reaction is closer to the ester side, the hydroxyl function of the product 2-hydroxyalkylamide structure is consumed, and the curability is impaired. (The hydroxyl functional group of 2-hydroxyalkylamine structure does not react with carboxylic acid under low temperature conditions below 200 ° C.) Therefore, it is important to proceed the reaction gently, and the reaction temperature is preferably 60 to 120 ° C., 70-100 degreeC is more preferable.

（III）
この平衡はアミド側が優勢であるので反応物を溶融状態または固体単離してから固層で熟成する事によりアミド構造体を選択的に得る事が出来る。

(III)
Since this equilibrium is dominant on the amide side, an amide structure can be selectively obtained by aging in a solid layer after the reaction product is melted or solid-isolated.

  The amide formation reaction between the linear dicarboxylic acid diester (A) and the di- (2-hydroxyalkyl) amine (B) and the amide-ester exchange reaction shown in Formula III can be followed by the amine value.

  The catalyst added to the system during the reaction also acts as a catalyst for the equilibrium reaction of formula III. When the obtained curing agent composition is used in a powder coating, the catalyst remains when baking and curing is performed. The equilibrium of formula III may be returned to the ester side, resulting in an effect of reducing curability. For this reason, in this production method, it is preferable to first include a step of removing or deactivating the catalyst when it is confirmed by amine value measurement that the amide-ester exchange reaction by (A) and (B) has reached the desired reaction rate. . Although the reaction rate can be arbitrarily set here, it is generally preferably 85% or more, and more preferably 90% or more. The method for removing the catalyst is not particularly limited, and examples thereof include a method for washing the reaction mixture with a solvent or water and a method for ultrafiltration. Similarly, the method of deactivating the catalyst can be selected according to the catalyst to be used. For example, when a metal alcoholate is used, a method of neutralizing with Brensted acid is simple. In this case, the amine value of the system is corrected by the amount of catalyst added / the amount of acid used for neutralization. One advantage of the system of the present invention is that the carboxylic acid ester is excessively added to the amine as a starting material, so that the amine value tends to decrease (reaction is fast).

  After confirming that the desired reaction rate has been reached by measuring the amine value, the system is cooled to a viscous molten or solid state. At this time, since the equilibrium reaction shown in Formula III is dominant on the amide side, the concentration of the curing agent having the target amide structure gradually increases in the system. Since this equilibrium shift is an aging reaction that proceeds very slowly, it is preferable to proceed with aging in the reaction vessel as an aging step in order to prevent contamination of the curing agent composition, adsorption of water, and the like. The ratio of amide / ester here can be traced by nuclear magnetic resonance spectroscopy or infrared spectroscopy. However, since the amide structure is symmetrical in practice, it becomes a hard solid due to crystallinity, so that the system is hard enough to enable subsequent processing, that is, atomization / powdering for use as a powder coating. You may move on to the next process at that time.

  Atomization and pulverization can be performed by a known method such as pulverization by an impact pulverizer such as a hammer mill or an airflow pulverizer such as a jet mill.

  In the curing agent composition produced by the production method of the present invention, the ratio of the amide structure is the same or gradually increased after aging even after being powdered. Therefore, it is a feature that the curability does not decrease by storage.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Hereinafter, both “parts” and “%” are based on weight.

Example 1
A 1000 mL four-necked flask was charged with 359.6 g (3.42 mol) of diethanolamine, 414.5 g (1.80 mol) of dimethyl sebacate and 7.0 g (0.036 mol) of 28% sodium methoxide methanol solution as a catalyst. And heated to 90 ° C. under a nitrogen atmosphere. After the white suspension changed to a colorless transparent liquid, the temperature was lowered to 70 ° C. and stirred for 1.5 hours, and then the pressure was reduced to 50 mmHg and the mixture was stirred at 70 ° C. for 4 hours while removing methanol. Next, 2.2 g (0.036 mol) of acetic acid was added to deactivate the catalyst, followed by stirring for 15 minutes. By cooling the contents of the flask, a white solid curing agent composition having a residual amine concentration of 0.16 mmol / g (amine number = 9.0) was obtained. The residual amine concentration after this white solid curing agent composition was sealed in a sealed container and stored for 3 weeks at room temperature was 0.09 mmol / g (amine number = 5.0). There was no change in the appearance properties of the curing agent composition after storage. Its water solubility was 12 g / 100 g H ₂ O immediately after production and 10 g / 100 g H ₂ O after storage. The average number of functional groups calculated according to Formula IV of this curing agent composition is 4.11, but a portion of the 2-hydroxyalkylamide structure becomes an ester structure due to the amide-ester exchange reaction of Formula III, and the hydroxyl functionality corresponding to that portion. The group cannot contribute to the curing reaction. The amount of decrease in 2-hydroxyalkylamide structure, that is, the amount of decrease in the average number of functional groups can be calculated from the amount of remaining amine.

  In the case of this example, the curing agent composition yields 359.6 (diethanolamine) +414.5 (dimethyl sebacate) -115.3 (3.6 mol of methanol is released) = 658.8 g. When calculated from the amine concentration of 0.09 mmol / g after storage for 3 weeks, there is 658.8 × 0.09 / 1000 = 0.059 mol of ester structure. Then, the hydroxyl function of the curable 2-hydroxyalkylamide structure is reduced by two per ester structure. As described in the induction process of Formula IV, the number of molecules of the curing agent composition produced by this charge blending is 3.42-1.80 = 1.62 mol, so that it averages per molecule of the curing agent composition. There are 0.059 / 1.62 = 0.0364 ester structures, so that 0.0364 × 2 = 0.073 functional groups (hydroxyl functional groups of 2-hydroxyalkylamide structure) are reduced. Therefore, the average number of functional groups of the present curing agent is 4.11-0.07 = 4.04 (pieces / molecule).

Comparative Example 1
A 1000 mL four-necked flask was charged with 378.5 g (3.60 mol) of diethanolamine, 414.5 g (1.80 mol) of dimethyl sebacate and 7.0 g (0.036 mol) of 28% sodium methoxide methanol solution as a catalyst. And heated to 90 ° C. under a nitrogen atmosphere. After the white suspension changed to a colorless transparent liquid, the temperature was lowered to 70 ° C. and stirred for 1.5 hours. Next, 2.2 g (0.036 mol) of acetic acid was added to deactivate the catalyst, followed by stirring for 15 minutes. The contents of the flask were transferred to an aluminum pan and dried under reduced pressure at 50 mmHg using a vacuum oven to obtain a white solid curing agent composition having a residual amine concentration of 0.21 mmol / g (amine number = 11.8). . The residual amine concentration after this white solid curing agent composition was sealed in a sealed container and stored for 3 weeks at room temperature was 0.13 mmol / g (amine number = 7.3). There was no change in the appearance properties of the curing agent composition after storage. Its water solubility was 11 g / 100 g H ₂ O immediately after production and 10 g / 100 g H ₂ O after storage. The average number of functional groups calculated according to Formula IV of the hardener composition is 4.00. Further, the average number of functional groups after 3 weeks of storage, corrected from the amount of residual amine in the same manner as in Example 1, was 3.90.

Examples 2-8 and Comparative Examples 2-4
Substantial production conditions are as described above, and the raw material (A) is dimethyl adipate (n = 4 in the general formula (I)), dimethyl pimelate (n = 5), dimethyl suberate (n = 6). ), Dimethyl sebacate (carbon number n = 8), dimethyl undecanedioate (n = 9), the ratio of the total number of moles of amino groups in (B) to the total number of moles of ester groups in (A) Example 2-8 and Comparative Examples 2-4 were manufactured in the ratio shown in 2. In the table, the average number of functional groups calculated from the initial blending moles of raw materials (A) and (B) using Formula IV and the average number of functional groups corrected from the amount of residual amine after storage for 3 weeks were also entered.

Table 2

Residual amine concentration (mmol / g): determined by titration with hydrochloric acid.

Evaluation Results of Curing Agent Table 3 shows the evaluation results of water solubility and tackiness of the curing agent composition obtained above.
Table 3

Water solubility : 100 g of pure water at 20 ° C. was put into a glass beaker having a capacity of 200 ml, and the curing agent was added little by little while gently stirring. The table shows the weight (g) of the curing agent that could be added before the insoluble material appeared. Under the same conditions, even when 80 g of N, N, N ′, N′-tetrakis (2-hydroxyethyl) adipamide was added, the aqueous solution was transparent.

Hardener non-tackiness : A small amount of hardener powder after storage for 3 weeks after synthesis was placed on a watch glass, and the index finger was pressed to evaluate the degree of stickiness. I put it on a small amount of fingers and can take it right away.
X: It is sticky and sticks to a finger.

Powder coating production example 1
94.4 parts of carboxyl group-containing polyester resin (manufactured by Daicel-Cytec Co., Ltd., trade name CRYLCOAT4642-3, acid value 33 mgKOH / g, glass transition temperature 62 ° C.), curing agent composition 5 obtained in Example 1 above .6 parts, JR605 (manufactured by Teika Co., Ltd., titanium oxide) 45.0 parts, barium sulfate 100 (manufactured by Sakai Chemical Industry Co., Ltd., precipitated barium sulfate) 10.0 parts, Nicalite XK-81 (manufactured by Nippon Carbide Industries, Inc.) (Surface conditioner) 1.0 part and 0.5 part of benzoin were mixed, melt-kneaded by an extruder, cooled, finely pulverized by an atomizer, and filtered through a 150 mesh sieve to produce a polyester resin powder coating 1.

Production Examples 2-13 of Powder Coating
Powder coating materials 2 to 13 were manufactured in the same manner as in the above powder coating manufacturing example 1 except that the types and blending amounts of the polyester resin and the curing agent were in accordance with Table 3. The curing agent used in 13 was PrimidXL552 (trade name, manufactured by EMS, N, N, N ′, N′-tetrakis (2-hydroxyethyl) adipamide). In addition, in Production Examples 1 to 13 of the powder coating material, they were blended so that the carboxyl group of the polyester resin and the hydroxy group of the curing agent composition were equivalent.

Table 4

Examples and Comparative Examples Blocking resistance and performance of cured coatings of powder coatings manufactured according to the above-described powder coating manufacturing examples were evaluated. The test coating plate used for the performance evaluation of the cured coating film was prepared by applying the above powder coating to a SPCC-SD PB-3118 zinc phosphate-treated steel plate (0.8 × 70 × 150 mm) with a cured film thickness of 60 to 80 μm. It was prepared by applying electrostatic powder and heating at 160 ° C. for 30 minutes. Various performance tests were performed on each of the obtained test coated plates. The results are shown in Table 5.
Table 5

Blocking resistance of paint : The powder paint placed in a polycup was allowed to stand at 40 ° C. for 10 days, and then taken out from the polycup, and the state of the paint was observed visually and by touch.
○: A powdery form that is smooth and unchanged before storage.
△: It does not feel smooth and seems to be solid at first glance, but it easily collapses when touched with a finger and immediately returns to the state before storage.
X: The mass does not loosen and cannot be used as a powder coating.

Appearance of coating film : The appearance of the coating film was visually evaluated.
A: A coating film with good smoothness and gloss.
X: Coating film appearance such as rattling, roughness, and glossiness is inferior.

Gloss : The 60-degree specular gloss of the cured coating film was measured according to JIS K-5600-4-7.

Pencil hardness : Based on the pencil hardness test described in JIS K-5600-5-4. (Broken law).

Initial adhesion : According to JIS K-5600-5-6, a cut was made in the coating film using a cutter, and 6 incisions reaching the substrate were made at 1 mm intervals both vertically and horizontally, and a cross-cut adhesion test using a 24 mm wide cellophane tape was performed. .
(Double-circle): It does not peel at all.
○: Peeling is observed, but the peeled area is smaller than 5%.
Δ: Peeling is observed, but the peeled area is 5 to 15%.
X: Peeling is observed, but the peeled area is larger than 15%.

Moisture resistance secondary adhesion : The test piece was taken out after being placed in a moisture resistance test box at 50 ° C. and 98 to 100% RH for 500 hours, and left at room temperature for 2 hours, and then the adhesion was evaluated. The evaluation method for adhesion is the same as that for initial adhesion.
(Double-circle): It does not peel at all.
○: Peeling is observed, but the peeled area is smaller than 5%.
Δ: Peeling is observed, but the peeled area is 5 to 15%.
X: Peeling is observed, but the peeled area is larger than 15%.
Since the curing agent composition of the present invention has low water solubility and no stickiness, it can be suitably used as a powder coating. The powder coating using the curing agent composition of the present invention has high curability and excellent base adhesion after moisture resistance loading of the cured coating film.

1 is a diagram illustrating a ¹ H-NMR chart of a curing agent composition obtained in Example 1. FIG. 3 is a diagram illustrating a ¹ H-NMR chart of a curing agent composition obtained in Example 2. FIG.

¹ H-NMR is measured with a heavy aqueous solution having a sample concentration of 0.5% by weight. The horizontal axis of the chart indicates the value of chemical shift (unit: PPM) and the vertical axis indicates the intensity (unit: anonymous number) of the resonance spectrum.

Claims (6)

The total number of moles of the ester group of (A) from the linear dicarboxylic acid diester (A) represented by the general formula (I) and the di (2-hydroxyalkyl) amine (B) represented by the general formula (II) The average number of functional groups per molecule formed by amidation reaction at a ratio of the total number of moles of amino group (B) to 0.60 to 0.95 is less than 8 and less than 8 Hardener composition.

(In the formula, each R ¹ is the same or different and represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 5 to 8).

(In the formula, R ² and R ³ represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms which may be the same or different.) The curing agent composition according to claim 1, wherein the di (2-hydroxyalkyl) amine (B) is a dialkanolamine having a symmetrical structure in which R ² and R ³ are the same in the general formula (II). Hardener composition of claim 1 or 2 water solubility is 0~50g / 100gH ₂ O at 20 ° C.. The total number of moles of the ester group of (A) from the linear dicarboxylic acid diester (A) represented by the general formula (I) and the di (2-hydroxyalkyl) amine (B) represented by the general formula (II) The ratio of the total number of moles of the amino group (B) to 0.60 to 0.95, and the average number of functional groups per molecule is larger than 4 and smaller than 8. A method for producing a hardener composition.

(In the formula, each R ¹ is the same or different and represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, and n is an integer of 5 to 8).

(In the formula, R ² and R ³ represent a hydrogen atom or an aliphatic hydrocarbon group having 1 to 5 carbon atoms which may be the same or different.) The manufacturing method of the hardening | curing agent composition of Claim 4 whose amidation reaction temperature is 60-120 degreeC. A powder coating composition comprising the curing agent composition according to any one of claims 1 to 3 and a polycarboxylic acid resin.

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