JPH02229819A - Self-crosslinkable polyester resin - Google Patents

Abstract

PURPOSE:To obtain the title composition having excellent surface scratch resistance and useful for thermosetting coating, etc., by grafting a vinylalkoxysilane to a specific hydroxyl group-containing saturated polyester in the presence of a radical generating agent. CONSTITUTION:The aimed composition obtained by grafting a vinylalkoxysilane (e.g. vinyltriethoxysilane) expressed by the formula (R and R' are lower alkyl; n is 1-3) to a hydroxyl group-containing saturated polyester (preferably having 10000-25000 molecular weight) containing a 5-sulfoisophthalic acid metal salt residue, preferably at an amount of 0.5-2.5wt.% in the presence of a radical generating agent (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 surface scratch resistance. In particular, it relates to self-crosslinking polyester resin compositions used in thermosetting paints and the like.

(Prior art) The curing form of saturated polyester resin paint is amino resin. Generally, a cured coating film is obtained by blending an epoxy resin, a crosslinking agent such as a block of polyisocyanate brevolimer, a reaction catalyst, etc., and curing the mixture by heating.

However, the coating film obtained from such a combination of paints has the problem that it is difficult to achieve a balance between coating hardness and coating processability just by adjusting the compounding ratio of the crosslinking agent. In other words. If workability is emphasized, the hardness will be insufficient and the surface scratch resistance will be poor. Conversely, increasing the hardness and improving the surface scratch resistance tends to result in poor workability.

(Problem to be solved by the invention) The present inventors have conducted repeated research to solve the above problems. A self-crosslinking polyester resin composition is produced by grafting vinyl alkoxysilane onto a saturated polyester resin containing a 5-sulfoisophthalate residue. It was discovered that a coating film having excellent surface scratch resistance can be formed, and the present invention was developed.

[Structure of the invention]

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

General formula (I) CHz = CH S 1 (OR), IR'
z- (In the formula, R and R'' represent a lower alkyl group, and n represents an integer of 1 to 3.) In the present invention, raw materials for incorporating 5-sulfoisophthalic acid metal salt residues into saturated polyester include .5-Sodium sulfoisophthalic acid dimethyl 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, adipic acid, azelaic acid, sebacic acid, and glutaric acid. These include hexahydrophthalic anhydride, and these can be used alone or in combination of two or more. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, and trimethylolpropane. Propylene glycol. Dipropylene glycol. 1.6 hexanediol, neopentyl glycol, hydrogenated bisphenol A, 1. 4-
Phthanediol, l,4-cyclohexanediol, 2
, 2.4-1-limethylbentane 1,3-diol. It's polyethylene glycol. These can be used alone or in combination of two or more.

The molecular weight of the saturated polyester resin obtained from the raw materials is preferably in the range of 10,000 to 25,000. to
．． If it is less than ooo, the processability of the coating film will be poor, and if it is more than 25,000, it will thicken and become difficult to handle. Moreover, the content of 5-sulfoisophthalic acid metal salt residue is 0. A range of 1 to 5.0% by weight, preferably 0.5 to 2.5% by weight is preferred. If the amount is less than 0.1% by weight, the self-crosslinking properties of the paint will be insufficient, and if it is more than 5.0% by weight, the resin will thicken and become difficult to handle. Furthermore, hydroxyl groups can be introduced into the saturated polyester resin by synthesizing the resin to have hydroxyl groups at the ends.

The hydroxyl groups introduced in this way undergo a crosslinking reaction with the vinylalkoxysilane groups introduced by the graft reaction, resulting in self-crosslinking. Therefore, water MI& in saturated polyester can also be introduced by using trihydric or higher alcohol as a raw material for polyester. The preferred hydroxyl value of saturated polyester is. 3～3
0 mgKO}1/g, preferably 5 to 25 mg
κOH/g.

In the present invention, the self-crosslinking polyester resin is obtained by grafting vinyl alkoxysilane onto a polyester resin having a 5-sulfoisophthalic acid metal salt residue in the presence of a radical generator. The vinyl alkoxysilane is represented by the following general formula (I).

General formula (1) CHz = CH Si (OR)
- R's-R,R" is a lower alkyl group,
Preferably CH3, CH3CHt, CHs
CHt CHt -C H y C H t C H
z C H z-, etc.

The vinyl alkoxysilane can be used in an amount of 0.1 to 50 parts by weight per 10 parts by weight of the polyester resin having a 5-sulfoisophthalic acid metal salt residue. Preferably 5.0
~20 parts by weight. If it is 0.1 part by weight or less. Self-crosslinking properties do not appear, and when the amount exceeds 50 parts by weight, no effect is observed.

Furthermore, an ethylenically unsaturated monomer can be used in combination with the vinyl alkoxysilane. As an ethylenically unsaturated monomer. Acrylic acid. Methacrylic acid. Methyl methacrylate, ethyl methacrylate. Butyl methacrylate, styrene, itaconic acid, maleic anhydride, etc. can be used.

As a radical generator. There are peroxides such as benzoyl peroxide and azobis-based compounds such as azobisisobutylnitrile. A Redosox system which is a combination of these compounds and a reducing agent can also be used in the same way. The amount of the radical generator used is 0.1 to 25 parts by weight per 100 parts by weight of the polyester resin. Preferably it is 3 to 15 parts by weight. If it is less than 0.1 part by weight, the vinyl alkoxysilane will not 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. A polyester resin having a 5-sulfoisophthalic acid metal salt residue was dissolved in an organic solvent. It can be obtained by sequentially adding a radical generator and vinyl alkoxysilane. It is also possible to use a method in which the vinyl alkoxysilane is dissolved in an organic solvent together with the raw material polyester resin from the beginning, and only the radical generator is added sequentially. The reaction temperature is above the temperature required to generate radicals. The temperature is preferably 150°C or lower in order to suppress the reaction between the hydroxyl groups in the polyester resin and the alkoxy in the vinylalkoxysilane. Toluene is an organic solvent. Examples include aromatic hydrocarbons such as xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate-9-butyl acetate, and alcohol solvents such as ethanol and butanol, and mixed solvents of these may also be used. ．． The self-crosslinking polyester resin obtained in the present invention is. Generally known pigment. Fillers, additives. Contains crosslinking resin, catalyst, etc. It can be made into a thermosetting paint. (Example) The present invention will be explained below using examples. In the example. Parts represent parts by weight, and % represents weight %.

Example 1 Synthesis of self-crosslinking polyester (b) 426 parts of dimethyl terephthalate, 15 parts of 5-sodium sulfoisophthalate dimethyl ester, 5 ethylene glycol, 1 aes. 260 parts of neobentyl glycol. 0.07 parts of zinc acetate and 0.13 parts of antimony trioxide were charged into a reaction vessel, and the mixture was 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, 373 parts of isophthalic acid,
94 parts of azelaic acid was charged and an esterification reaction was carried out at 180 to 240°C. When the acid value became 20 or less, the pressure in the reactor was gradually reduced. Polymerization was carried out under reduced pressure of 10 Hg or less at 240°C for 3 hours to obtain a hydroxyl group-containing saturated polyester (a) containing 5-sulfoisophthalic acid metal salt residues. Polyester (a) is. Hydroxyl value 9. Acid value l. 2. The molecular weight is 12
,000.

Next, 100 parts of the polyester (a) obtained in the above procedure was dissolved in 150 parts of cellosolve acetate at 100°C, followed by peroxide solution previously dissolved in 100 parts of cellosolve acetate and 30 parts of butyl alcohol. 5 parts of benzoyl and 10 parts of vinyltriethoxysilane are added dropwise over 2 hours. After completion of the dropping, the mixture was kept at 100°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 100°C, and then the temperature was lowered to 80°C. 5 parts of benzoyl peroxide, 10 parts of vinyltrimethoxysilane, and 5 parts of styrene dissolved in a mixed solvent of 30 parts of butyl alcohol are added dropwise over 2 hours. 80℃ after completion of dripping
A self-crosslinking polyester (c) was obtained.
Example 3 Synthesis of self-crosslinking polyester (e) 388 parts of dimethyl terephthalate, ls part of 5-sodium sulfoisophthalic acid dimethyl ester. 124 parts of ethylene glycol. Neopentyl glycol 156 parts, l,6-
218 parts of hexanediol. trimethylolpropane 1
3 parts, zinc acetate 0.07 parts. Antimony trioxide value 0.14
1 part was placed in a reaction vessel and heated for 16 minutes while stirring under a nitrogen stream.
The transesterification reaction was carried out by heating to 0 to 220°C. After distilling off the theoretical methanol, 448 parts of isophthalic acid and 50 parts of sebacic acid were charged to this reaction vessel, and the reaction volume was 180 to 2.
The transesterification reaction was carried out at 40°C. When the acid value becomes 20 or less, gradually reduce the pressure in the reactor to 1 mHg or less. 2
Polymerization was carried out under reduced pressure at 40°C for 3 hours to obtain a hydroxyl group-containing saturated polyester (d) containing 5-sulfoisophthalic acid metal salt residues. Polyethylene (d) has a hydroxyl value of 20 and an acid value of 0.5.
, the molecular weight was 18,000.

next. Polyester (d) obtained in the above 1'''Y
100 parts in 150 parts of cellosolve acetate at 100°C.
Then, add Cellosolve Acetate 100 in advance.
5 parts of benzoyl peroxide and 20 parts of vinyltriethoxysilane, which had been dissolved in a mixed solvent of 1 part and 30 parts of butyl alcohol, were added dropwise over 2 hours.

After completion of the dropwise addition, the mixture was kept at 100°C for 60 minutes to obtain a self-crosslinking polyester (e). Example 4 Synthesis of self-crosslinking polyester (f) The loop part of polyester (d) obtained in the above procedure was dissolved in 150 parts of cellosolve acetate at 100'C, and then 100 parts of cellosolve acetate and 30 parts of butyl alcohol were dissolved in advance. 7 parts of benzoyl peroxide, 10 parts of vinyltrimethoxysilane, and 10 parts of styrene, which had been dissolved in 1 part, were added dropwise over 2 hours. After completion of the dropping, the mixture was kept at 100° C. for 60 minutes to obtain a self-crosslinking polyester (f).

Comparative Example l Synthesis of self-crosslinking polyester (h) In the synthesis of polyester (a). Polyester (g) was obtained in exactly the same manner except that the raw material 5-sodium sulfoisophthalic acid dimethyl ester was removed. Using this polyester (g), it was changed to polyester (a) in Example 1, and a self-crosslinking polyester (h) was obtained by the same procedure as in Example 1 except for that.

Comparative Example 2 Synthesis of self-crosslinking polyester (i) In Example 2, polyester (a) was replaced with polyester (g).
Self-crosslinking polyester (i) was obtained by the same procedure except for changing to .

Application Examples 1 to 4 and Reference Examples 1 to 3 Using the self-crosslinking polyester resin compositions obtained in each example, paints were made with the paint compositions shown in Table 1, and the surface scratch resistance of the baked paint films was tested. I did it. The firing of the paint.
The paint was applied to a thickness of 20 μm on a bonded steel plate with a thickness of 0.6 mm, and the coating was applied at 200° C. for 10 minutes. The results are shown in Table 1.

The test results were judged as follows.

(I) Paint film surface scratch resistance A loaded needle (sapphire with a radius of curvature of 200 μR) is moved perpendicularly onto the paint film surface. If the surface is not damaged, increase the load and repeat the process. It is expressed as the maximum load (unit: 2 g) that will not cause damage.

(2) Coating film curing property (MEK rubbing) The coating surface was repeatedly rubbed with a cloth soaked in MEK, and the number of times the coating surface peeled off was expressed.

(3) Bending processability test The plate was bent to 180'' and the state of crack occurrence at the bent portion was examined and marked in four stages: ◎, ○, △.

(Effects of the Invention) The self-crosslinking polyester resin composition of the present invention further promotes self-crosslinking properties by grafting vinylalkoxysilane onto the main chain and using 5-sulfoisophthalic acid metal salt residues in the main chain. . When the self-crosslinking polyester resin composition obtained by the present invention is used as a paint resin composition, the resulting paint film has a high crosslink density and high paint film hardness. Furthermore, the flexibility of the coating film is equivalent to that of conventional polyester resin paints.

Therefore, the self-crosslinking polyester composition of the present invention provides a baking paint with an excellent balance between surface scratch resistance and bending processability, which was not possible with conventional polyester resin paints. Taking advantage of these characteristics, the self-crosslinking polyester resin composition of the present invention is useful as a finishing paint or a precoating paint.

Claims (1)

[Claims] Obtained by grafting a vinyl alkoxysilane represented by the following general formula (I) onto a hydroxyl group-containing saturated polyester containing a 1,5-sulfoisophthalic acid metal salt residue in the presence of a radical generator. Self-crosslinking polyester resin composition. General formula (I) CH_2=CH-Si(OR)_nR'_3_-_n (wherein, R and R' represent a lower alkyl group, and n is 1 to
Represents an integer of 3. )