JPH09118831A - Curing of thermosetting resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the curing of a coating film of a thermosetting resin, etc., and solve the problems of stable coating film quality and various troubles of the coated film by reacting a specific thermosetting resin with a specific curing agent, thereby imparting the resin with a function to generate water in the resin. SOLUTION: The thermosetting resin to be cured by this process is produced by the copolymerization of (i) a monomer containing polymerizable double bond and acetoacetyl group in the same molecule, e.g. an acetoacetoxyethyl methacrylate of formula I (R1 is an organic residue having polymerizable double bond; R2 is a 1-8C bivalent aliphatic hydrocarbon group), (ii) a monomer having polymerizable double bond and hydrolyzable alkoxysilyl group in the same molecule, e.g. a vinyltrimethoxysilane of formula II (R1' is same as R1; R2' is same as R2; R3 is a 1-6C hydrocarbon group; X is an alkoxy; (n) is >=3) and (iii) other monomers. The resin is cured by reacting with a compound having one primary amine group, e.g. dibutylaminopropylamine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for curing a thermosetting resin, which has excellent low-temperature curability and good weather resistance and can be used as a paint, adhesive or sealing agent. is there.

[0002]

2. Description of the Related Art Conventionally, a thermosetting resin containing a hydrolyzable alkoxy group has been widely used as a resin for paint because it has good weather resistance due to its molecular structure.
When using a hydrolyzable alkoxy group as a curing reaction group, especially when curing at a relatively low temperature such as a temperature around room temperature, the first step is hydrolysis of the alkoxy group with water in the air. Need to wake up. Subsequent to this, it is considered to cure by a reaction that forms a siloxane bond. Various resins utilizing these reactions are widely known and are often used particularly in the field of paints. However, these curing reactions are
It has the deficiency of using moisture to initiate the curing reaction. Many studies have been conducted to solve these defects and various patents have been issued, but it is not sufficient at present.

[0003]

When an alkoxy group-containing resin is used as a main binder for paints in applications such as paints, these curing reactions cause the surface layer to undergo alkoxysilyl groups and moisture in the air. -It is hydrolyzed by moisture to generate silanol groups, and is cured by dehydration condensation reaction of these. Therefore, the above-mentioned curing reaction occurs preferentially in the surface layer of the coating film, a strong cross-linked layer is formed, and moisture / moisture is blocked, so that the curing reaction rate of the inside / bottom is extremely reduced. Therefore, it is considered that various problems due to the above curing reaction process are occurring. That is, even in thin films such as paint films, the degree of curing often differs between the surface layer and the inner / bottom layers, and when such paints are applied repeatedly, "chijimi" occurs. Therefore, the progress of the curing reaction is different and the initial coating film performance is inferior, and the insufficient curing of the bottom causes problems such as poor adhesion to various coated objects.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, have found that a monomer having a polymerizable double bond and an acetoacetyl group and a polymerizable double bond. By using a resin in which a monomer containing a bond and a hydrolyzable alkoxy group is copolymerized and a specific curing agent together, the rate of hydrolysis of the alkoxysilyl group is controlled and the surface layer and bottom of the coating film are similarly cured. We have found a curing method for thermosetting resins that can achieve the above-mentioned degree. That is, the present invention relates to a monomer (A) containing a polymerizable double bond and an acetoacetyl group in the same molecule, and a monomer containing a polymerizable double bond and a hydrolyzable alkoxysilyl group in the same molecule. A method for curing a thermosetting resin, which comprises reacting a thermosetting resin obtained by copolymerizing (B) with another monomer (C) with a compound (D) containing one primary amine group. . The present invention has found that the thermosetting resin spontaneously generates water in the presence of a specific curing agent to cure the film of the composition from the inside. These curing reaction mechanisms are
Curing progresses simultaneously at the bottom, and there is little difference in the degree of curing between the surface and the inside of the cured coating film, and "chiji" does not occur, and the solvent of the top coat paint permeates into the bottom coat paint during overcoating. It prevents swelling of the coating film that is insufficiently cured.

The monomer (A) containing the polymerizable double bond and the acetoacetyl group in the same molecule of the thermosetting resin of the present invention is
It is exemplified by the following general formula (a). General formula (a)

[0006]

Embedded image

(R1 represents an organic residue having a polymerizable double bond, and R2 represents a divalent aliphatic hydrocarbon group having 1 to 18 carbon atoms.)

For example, there are acetoacetoxyethyl methacrylate, acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxypropyl acrylate, allyl acetoacetate and the like, and these monomers can also be obtained by the reaction of unsaturated alcohol with diketene. Examples of unsaturated alcohols include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol mono (meth) acrylate, and allyl alcohol. The copolymerization amount of the monomer (A) is to be determined in relation to the copolymerization amount of the monomer (B) described later, but 0.1 to 10 mol% is preferable. More preferably, it is 0.5 to 5 mol%. When the copolymerization amount is small, the amount of water generated in the curing reaction is small and the activity of the hydrolyzable alkoxysilyl group cannot be fully utilized. Also,
Even if the amount of copolymerization is large, the effect is small.

The monomer (B) containing the polymerizable double bond and the hydrolyzable alkoxysilyl group in the thermosetting resin of the present invention in the same molecule is exemplified by the following general formula (b). General formula (b)

[0010]

Embedded image

(R1 'is an organic residue having a polymerizable double bond, R2' is a divalent aromatic or aliphatic hydrocarbon group,
R3 'represents a hydrocarbon group having 1 to 6 carbon atoms, X represents an alkoxy group, and n represents an integer smaller than 3. )

For example, vinyltrimethoxysilane, vinylbutyltrimethoxysilane, γ-methacryloxypropyltrimethoxylane, γ-methacryloxypropylmethyldimethoxylane, γ-methacryloxypropyltriethoxylane, γ-methacryloxypropylmethyldimethane. Examples thereof include ethoxylane and γ-acryloxypropyltrimethoxylane. Monomers (B) containing these polymerizable double bonds and hydrolyzable alkoxy groups in the same molecule can be synthesized by various methods. Examples include acetylene, allyl acrylate, allyl methacrylate, diallyl phthalate and methyldimethoxy. It can be synthesized by reacting with silane, methyldichlorosilane, etc. in the presence of a transition metal catalyst. The monomer (B) is a major factor that determines the durability of the thermosetting resin of the present invention, and it is desirable to increase the amount as much as economically possible. However, in applications such as paints, an excessively crosslinked structure has a practical upper limit because it is necessary to maintain the flexibility of the coating film. From such a viewpoint, the copolymerization amount of the monomer (B) is preferably 3 to 40 mol%. More preferably, it is 3 to 20 mol%. If the copolymerization amount is too small, sufficient durability and weather resistance cannot be obtained. If the amount of copolymerization is too large, the crosslink density of the thermosetting resin is too high, and the thermosetting resin cannot be a general-purpose thermosetting resin.

In the present invention, the thermosetting resin of the present invention has other reactive double bonds in addition to the above-mentioned monomers (A) and (B) so that it can be used for various purposes. It is synthesized by copolymerizing the monomer (C). The types of these monomers (C) are not particularly limited, and generally, methacrylic acid esters, acrylic acid esters,
Vinyl esters, various vinyl compounds and the like can be used, and examples thereof include acrylic acid such as methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate; methacrylic acid esters; amides such as acrylamide, methacrylamide, and N-methylol acrylamide. Group-containing monomers, amino group-containing monomers such as diethylaminoethyl acrylate and aminoethyl vinyl ether, amino group-containing monomers such as diethylaminoethyl acrylate and aminoethyl vinyl ether, acrylic acids such as acrylic acid and methacrylic acid Other examples include acrylonitrile, styrene, α-methylstyrene, vinyl acetate, methyl propionate, and the like. The copolymerization amount of such a monomer (C) is preferably 96.5 to 50 mol%. When the copolymerization amount is small, the crosslinked structure of the thermosetting resin becomes too dense,
It is not preferable because it does not become a general-purpose thermosetting resin, and when it is too large, it is not preferable because sufficient durability and weather resistance cannot be obtained.

The thermosetting resin of the present invention can be synthesized by an ordinary solution polymerization method. That is, the monomer (A), the monomer (B), the monomer (C), the polymerization initiator and the solvent are added and the reaction is carried out at about 50 to 160 ° C. A chain transfer agent such as dodecyl mercaptan may be added for the purpose of adjusting the molecular weight. The solvent is not particularly limited, but aliphatic or aromatic hydrocarbons, alcohols, ethers, esters, alcohol ethers and the like are used.

The greatest feature of the present invention is a method of curing a thermosetting resin. That is, the thermosetting resin of the present invention and a compound (D) containing one primary amine group as a curing agent
By coexisting with the above, the reaction between the acetoacetyl group containing the monomer (A) and the primary amine group proceeds, and a small amount of water is generated. This small amount of water rapidly decomposes the hydrolyzable alkoxysilyl group at a temperature near room temperature to form a siloxane bond, which makes the thermosetting resin of the present invention insoluble and infusible. That is, a feature of the present invention is that the hydrolyzable alkoxysilyl group is rapidly decomposed at a temperature near room temperature to form a siloxane bond, and the content of the acetoacetyl group required to generate water is very small. It has been found that even in an amount, it cures.

As the compound (D) containing one primary amine group of the present invention, a compound containing one primary amine group in the molecule and having a property of reacting with an active ester can be generally used. Examples of the compound (D) having a primary amine group useful in the present invention include methylamine, ethylamine, propylamine, butylamine, hexylamine, dimethylaminopropylamine, diethylaminopropylamine, dibutylaminopropylamine, N-
(2-aminoethyl) piperazine, aminopropyltriethoxysilane, aminopropyltrimethoxysilane,
Examples include aminoethylaminopropyltriethoxysilane and aminoethylaminopropyltrimethoxysilane.
The compound (D) containing one of these primary amine groups can be used in the range of the molar ratio of acetoacetyl group to amine group of 0.1 / 1 to 4/1.

In utilizing the method for curing the thermosetting resin of the present invention, various known additives such as antioxidants,
Ultraviolet absorbers, flow control agents, pigments, surfactants, catalysts and solvents can be added.

[0018]

【Example】

<Synthesis Examples 1 to 4> A solvent equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen condenser was charged with the solvent described in Table 1 and heated to 83 ° C under a nitrogen atmosphere, and described in Table 1. The mixture of was added dropwise over 3 hours under total reflux. During this time, the temperature is 8
It rose to 7 ° C. After completion of dropping, the temperature was maintained for 1 hour, 0.3 part by weight of tert-butylper-2-ethylhexanoate was added, and the temperature was further maintained for 2 hours. The resin properties of the resulting resin solution are shown in Table 1. The dropping mixture is part by weight.

[0019]

[Table 1]

Evaluation of Curing Reactivity In order to determine the curability of the above polymer resin solution, various curing agents were added to 100 g of the resin solution shown in Table 1 at a ratio shown in Table 2, and The curability of the above resin and the resin of Reference Example was evaluated. Table 2 shows the results.

[0021]

[Table 2]

Measuring Method 100 g of the resin solution is put into a 250 ml sample bottle, and after mixing the above-mentioned curing agent, the state of the resin is observed after 3 hours. From the results of Table 2, it was found that the thermosetting resin of the present invention had very good curability.

Evaluation as Thermosetting Paint As one application example of the thermosetting resin of the present invention, a white paint having a PWC of 50% was prepared with a composition as shown in Table 3 and as shown in Table 3. A curing agent was added, and the mixture was diluted with xylene to a viscosity such that it could be roller coated. 50 μm for some coated plates by brushing every day
Was repeatedly applied, and the recoatability was evaluated.
The accelerated weathering test of the samples coated with these materials was performed by S-WO.
The weather resistance was evaluated by performing the test for 5000 hours in M. Table 3 shows the results
Shown in

Preparation of Pigment Dispersion Sample Titanium oxide (Taipaque R-820 manufactured by Ishihara Sangyo Co., Ltd.) 100 parts by weight Pigment dispersant (Dispapic BYK-164 manufactured by BYK) 1 part by weight Dispersion stabilizing resin (DM-55 manufactured by Hoechst) 5 parts by weight 50 parts by weight of xylene was mixed and dispersed by a pearl mill so that the dispersion of titanium oxide was 10 μm or less. Preparation of coating plate for coating film evaluation To each coating material, a compound containing one primary amine group and a curing agent in which a tin compound is dissolved in xylene of the type and amount shown in Table 3 are added, and further suitable for brush coating with xylene. It was diluted to different viscosities and coated on a polished mild steel plate so that the dry coating film had a thickness of 20 μm. In order to evaluate the coatability, the same number of days as shown in Table 3 was allowed to elapse and then coating was performed in the same manner, and the coatability was evaluated.

[0025]

[Table 3]

(Note 1) DBAPA: dibutylaminopropylamine (Note 2) DBSnDA: dibutyltin diacetate (Note 3) DBSnDL: dibutyltin dilaurate (Note 4) AEP: N-aminoethylpiperazine (Note 5) AETES: amino Ethyltriethoxysilane

Evaluation Criteria for Coatability ⊚: No swelling of the coating film and no swelling in the coating part ○: Swelling of the coating film but normal coating after drying of the coating part x: Overcoating Swelling and blistering occur on the part, and blisters remain after drying. The results in Table 3 show that the coating film made of the thermosetting resin of the present invention is cured from the inside of the coating film, and thus has excellent weather resistance. It has shown that it has.

[0028]

EFFECTS OF THE INVENTION By hardening the thermosetting resin that absorbs moisture in the air to generate moisture inside, the curing of paint etc. is controlled and stable coating quality and after coating Various problems can be solved now.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Tsuka 6-1073 Minamitsukaguchi-cho, Amagasaki City, Hyogo Prefecture Shinto Paint Co., Ltd.

Claims (2)

[Claims] 1. A monomer (A) containing a polymerizable double bond and an acetoacetyl group in the same molecule and a monomer (A) containing a polymerizable double bond and a hydrolyzable alkoxysilyl group in the same molecule ( A method for curing a thermosetting resin, which comprises reacting a thermosetting resin obtained by copolymerizing B) with another monomer (C) with a compound (D) containing one primary amine group. 2. 0.1 to 10 mol% of a monomer (A) containing a polymerizable double bond and an acetoacetyl group in the same molecule, a polymerizable double bond and a hydrolyzable alkoxysilyl group in the same molecule. A compound (D) containing one primary amine group in a thermosetting resin obtained by copolymerizing 3 to 40 mol% of the monomer (B) and 96.5 to 50 mol% of the other monomer (C) contained in ) Is made to react, The hardening method of thermosetting resin characterized by the above-mentioned.