JPH02219808A - Self-crosslinking polyester resin composition - Google Patents

Abstract

PURPOSE:To obtain the title composition of improved pigment dispersion stability by grafting a specified N-alkoxy-methylacrylamide onto a saturated hydroxy polyester containing a metal 5-sulfoisophthalate residue. CONSTITUTION:0.1-50 pts.wt. N-alkoxymethylacrylamide (A) of the formula (wherein R is a lower alkyl) is grafted onto 100 pts.wt. saturated hydroxy polyester (B) of a metal 5-sulfoisophthalate residue content of 0.1-5.0wt.%, an MW of 10000-25000 and a hydroxyl value of 3-30mgKOH/g at 160 deg.C or below in an organic solvent (e.g. toluene) in the presence of 0.1-25 pts.wt., per 100 pts.wt. component B, radical generator (e.g. benzoyl peroxide).

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a self-crosslinking polyester resin composition with excellent pigment dispersion stability, and in particular to a self-crosslinking polyester resin composition used in thermosetting paints. The present invention relates to a resin composition.

(Prior art) Thermosetting paints containing saturated polyester resin have excellent adhesion,
It has excellent flexibility and is widely used as a baking paint for metals. These paints use blocks of amino resin, epoxy resin, or polyisocyanate prepolymer mixed with a reaction catalyst and the like as a curing agent.

However, when a pigment component is contained in a paint made from such a combination, the paint stability is poor, and the physical properties of the cured paint film are also deteriorated accordingly.

(Problems to be Solved by the Invention) As a result of repeated research in order to solve the above problems, the present inventors have grafted N-alkoxymethylacrylamide onto a saturated polyester resin containing 5-sulfoisophthalate residues. Paint containing self-crosslinking polyester resin
The present invention was based on the discovery that the coating material has excellent paint stability.

[Structure of the invention]

(Means for Solving the Problems) The present invention involves adding N-alkoxymethylacrylamide represented by the following general formula (I) to a hydroxyl group-containing saturated polyester containing a 5-sulfoisophthalic acid metal salt residue as a radical generator. The present invention relates to a self-crosslinkable polyester resin composition obtained by grafting in the presence of the present invention.

General formula (1) %Formula% (In the formula, R represents a lower alkyl group.) In the present invention, the raw material for incorporating the 5-sulfoisophthalic acid metal salt residue into the monosaturated polyester is dimethyl 15-sodium sulfoisophthalate. ester, 5-potassium sulfoisophthalic acid dimethyl ester, 5-lithium sulfoisophthalic acid dimethyl ester, etc. can be used.

As the dibasic acid, which is another component of the polyester into which these raw materials are incorporated, commonly known raw materials can be used. Specifically, isophthalic acid, terephthalic acid, phthalic anhydride, isophthalic acid dimethyl ester, terephthalic acid dimethyl ester, and adipic acid.

These include azelaic acid, sebacic acid, glutaric acid, and hexahydrophthalic anhydride, and these can be used alone or in combination of two or more. Specific examples of dihydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 126hexanediol, neopentyl glycol, hydrogenated bisphenol A, 1,4-butanediol, l,4-cyclohexane. Diol, 2,2.4
-trimethylpentane 1,3-diol, polyethylene glycol, etc., and these can be used alone or in combination of two or more.

The molecular weight of the saturated polyester resin obtained from the raw material is preferably in the range of 10.000 to 25.000, 10
,000 or less, the processability of the coating film is poor.

If it exceeds 25,000, the viscosity increases and handling becomes difficult.

Further, the content of 5-sulfoisophthalic acid metal salt residue is 0.
1 to 5.0% by weight 2 Preferably, the range is 0.5 to 2.5% by weight. If it is less than 0.1% by weight, the self-crosslinking property of the paint will be insufficient, and if it is more than 5.0% by weight, The resin will thicken and become difficult to pump out. Furthermore, hydroxyl groups can be introduced into the saturated polyester resin by synthesizing the resin to have hydroxyl groups at the ends.

The hydroxyl group thus introduced undergoes a crosslinking reaction with the N-alkoxymethyl group introduced by the graft reaction, thereby becoming self-crosslinked. Therefore, the hydroxyl group in the saturated polyester can also be introduced by using a trihydric or higher hydric alcohol as a raw material for the polyester. The preferred hydroxyl value of the saturated polyester is 3 to 30.
mgKOH/g, preferably OH to 5~L5+u
/ g.

In the present invention, the self-crosslinking polyester resin is produced by grafting N-alkoxymethylacrylamide onto a polyester resin having a 5-sulfoisophthalic acid metal salt residue in the presence of a radical generator, thereby producing N-alkoxymethylacrylamide in the polyester molecule. This is the introduction of

N-alkoxymethylacrylamide and ζ are represented by the following general formula (I).

General formula (1) CH2=CHC0NHCH2ORR is a lower alkyl group, preferably CH3CHs CHz
+, CHs CHz CH2, CH3CHzcHtc
Hg - etc.

N-alkoxymethyl acrylamide is a polynystyl resin 100 having a 5-sulfoisophthalic acid metal salt residue.
0.1 to 50 parts by weight can be used. Preferably it is 5.0 to 20 parts by weight. If the amount is less than 0.1 part by weight, no self-crosslinking property will be exhibited, and if it is more than 50 parts by weight, no effect will be observed.

Moreover, an ethylenically unsaturated monomer can be used in combination with N-alkoxymethylacrylamide. Ethylenically unsaturated monomers include acrylic acid, methacrylic acid, methyl methacrylate, and ethyl methacrylate.

Butyl methacrylate, styrene, itaconic acid, maleic anhydride, etc. can be used.

Examples of radical generators include peroxides such as benzoyl peroxide and azobis-based compounds such as azobisisobutylnitrile. A redox system in which these compounds are combined with a reducing agent can also be used. The amount of the radical generator used is 0.1 to 25 parts by weight, preferably 3 to 15 parts by weight, based on 100 parts by weight of the polyester resin. If it is less than 0.1 part by weight, the N-alkoxymethylacrylamide may react sufficiently, and if it is more than 25 parts by weight, no effect will be observed.

The self-crosslinking polyester resin in the present invention is:

It can be obtained by dissolving a polyester resin having a 5-sulfoisophthalic acid metal salt residue in an organic solvent and sequentially adding a radical generator and N-alkoxymethylacrylamide. It is also possible to use a method in which N-alkoxymethylacrylamide is dissolved in an organic solvent at the same time as the polyester resin, and only the radical generator is added sequentially. The temperature is preferably 150° C. or lower in order to suppress the reaction between the hydroxyl group in the polyester resin and the alkoxy in N-alkoxymethylacrylamide.

Examples of organic solvents include aromatic hydrocarbons such as toluene and xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, and 2-ethoxyethanol and 2-ethoxyethyl acetate. .

A mixed solvent of these may be used.

The self-crosslinking polyester resin obtained in the present invention is as follows.

Generally known pigments, fillers, additives, crosslinkable resins, catalysts, etc. can be blended to form a thermosetting paint.

(Example) The present invention will be explained below with reference to Examples. In the examples, 0 part means part by weight, and 9% means % by weight.

Example 1 Synthesis of self-crosslinking polyester (b) 492 parts of dimethyl terephthalate, 18 parts of 5-sodium sulfoisophthalate dimethyl ester, 252 parts of ethylene glycol, 281 parts of neopentyl glycol, 0.07 part of zinc acetate, antimony trioxide 0.15 part was charged into a reaction vessel and heated to 160 to 220° C. with stirring under a nitrogen stream to perform a transesterification reaction. After distilling off the theoretical amount of methanol, 411 parts of isophthalic acid,
209 parts of azelaic acid was charged and an esterification reaction was carried out at 180 to 240°C. 8 when the acid value is below 20
The reaction vessel was gradually reduced in pressure and polymerization was carried out under reduced pressure at 240° C. for 3 hours at less than 1 μg to obtain a hydroxyl group-containing saturated polyester (a) containing 5-sulfoisophthalic acid metal salt residues. Hydroxyl value of polyester (a)9. acid value 1.21 molecular weight 12
．． It was 000.

Next, 100 parts of the polyester (a) obtained in the above procedure was dissolved in 150 parts of cellosolve acetate at 100°C, and then 5 parts of benzoyl peroxide, which had been previously dissolved in 130 parts of cellosolve acetate, and N-( 10 parts of n-butoxymethyl)acrylamide was added dropwise over a period of 2 hours. After completion of the dropwise addition, the mixture was kept at 110° C. for 60 minutes to obtain a self-crosslinking polyester (b).

Example 2 Synthesis of self-crosslinking polyester (C) 100 parts of the polyester (a) obtained in the above procedure was dissolved in 150 parts of cellosolve acetate at 110°C, and then dissolved in 130 parts of cellosolve acetate in advance. 5 parts of benzoyl peroxide, 10 parts of N-methoxymethylacrylamide, and 10 parts of styrene are added dropwise over 2 hours. After completion of the dropwise addition, the mixture was kept at 110° C. for 60 minutes to obtain polyester (C).

Comparative Example 1 Synthesis of self-crosslinking polyester (e) In polyester (a) obtained by the above procedure.

Polyester (
d) was obtained.

Next, 100 parts of the polyester (d) obtained in the above procedure was dissolved in 150 parts of cellosolve acetate at 110°C, followed by 5 parts of benzoyl peroxide previously dissolved in 130 parts of cellosolve acetate.

10 parts of N-(n-butoxymethyl)acrylamide was added dropwise over a period of 2 hours. After the completion of the addition, the mixture was kept at 110° C. for 60 minutes to synthesize polyester (e).

Example 3 Synthesis of self-crosslinking polyester (f) 388 parts of dimethyl terephthalate, 15 parts of 5-sodium sulfoisophthalate dimethyl ester, 318 parts of diethylene glycol, 295 parts of 1,6 hexanediyl, 0.08 part of zinc acetate, antimony dioxide Charge 0.15 parts into a reaction vessel and reduce the temperature to 160 to 220 while stirring under a nitrogen stream.
The mixture was heated to ℃ to carry out transesterification reaction. After distilling off the theoretical amount of methanol.

In this reaction vessel, 592 parts of phthalic anhydride and 191 parts of sebacic acid were added.
A transesterification reaction was carried out at 180 to 240°C. When the acid value became 20 or less, the pressure in the reaction vessel was gradually reduced, and polymerization was carried out under reduced pressure at 240°C for 6 hours at a temperature of 1 mmHg or less to remove 6.0 hydroxyl groups. A polyester (f) with an acid value of 1.09 and a molecular weight of 19,000 was obtained.

100 parts of the polyester (f) obtained in the above procedure was dissolved in 130 parts of cellosolve acetate, followed by 5 parts of benzoyl peroxide and 10 parts of N-(n-butoxymethyl)acrylamide previously dissolved in 130 parts of cellosolve acetate. drip over 2 hours.

After completion of the dropwise addition, the mixture was kept at 110° C. for 60 minutes to obtain polyester (f).

Example 4 Synthesis of self-crosslinking polyester (h) In the synthesis procedure for polyester (g) above, the same method was used except that benzoyl peroxide was changed to 8 parts and N-(n-butoxymethyl)acrylamide was changed to 20 parts. Polyester (h) was obtained.

Application Examples 1 to 5 and Reference Examples 1 to 3 Using the polyester resins obtained in Examples 1 and 2 and Comparative Example 1, paints were prepared with the paint compositions shown in Table 1, and the R-material dispersion stability and bake-curing coating were evaluated. Curability of the film.

Physical property tests were conducted.

The paint was baked at 200° C. for 10 minutes by applying the paint to a thickness of 20 μm on a bonded steel plate. The results are shown in Table 1.

The test results were judged as follows.

(1) Paint stability The paint was stored at 50°C for 1 month, and the sedimentation state of the pigment was examined with the naked eye.

(2) Paint film curability (MEK rubbing) Rub the coated surface with a cloth soaked in MEK.

It is expressed as the number of times the coating surface peeled off.

(3) Adhesion It was measured and evaluated according to JISK540Q.

(Effect of the invention) The self-crosslinking polyester resin composition of the present invention.

N-alkoxymethylacrylamide is grafted onto the main chain to give it a branched structure to improve pigment dispersibility, and at the same time, the 5-sulfoisophthalic acid metal salt residue in the main chain further promotes self-crosslinking.

Furthermore, since the self-crosslinking polyester resin composition of the present invention has excellent pigment dispersion stability, it has many advantages when used as a paint resin.

Claims (1)

[Claims] N-alkoxymethylacrylamide represented by the following general formula (I) is grafted onto a hydroxyl group-containing saturated polyester containing a 1,5-sulfoisophthalic acid metal salt residue in the presence of a radical generator. The resulting self-crosslinking polyester resin composition. General formula (I) CH_2=CHCONHCH_2OR (in the formula, R represents a lower alkyl group)