JPH0830115B2 - Method for producing polyalkylene glycol-modified polyester resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a polyalkylene glycol-modified polyester resin useful for a thermosetting paint having a good pigment dispersibility.

<Conventional technology> Conventionally, the coating of home electric appliances and the like was performed in a box shape after processing and forming a steel sheet, but the rationalization of the coating line, the improvement of productivity, the prevention of pollution, the improvement of the working environment, etc. In order to solve various problems, we are moving to a precoat coating method in which flat steel sheets are painted and then processed and formed. The pre-coated steel sheet used in this method is required to have high workability since it is processed into a complicated shape after painting. On the other hand, among home electric appliances, refrigerators, washing machines and the like are required to have high performance in coating film hardness, stain resistance and chemical resistance.

Conventionally, thermosetting acrylic resins have been mainly used for coating these home appliances. This is because the acrylic resin paint has excellent coating film hardness and stain resistance. However, the acrylic resin paint is insufficient in processability for use in precoat painting, and it is necessary to soften the composition of the acrylic resin in order to satisfy the processability.
It is difficult to show coating hardness and stain resistance that can be practically used.

Further, the thermosetting polyester resin has been used for the coil coating of color galvanized iron or the like, but it still has a drawback that the workability and the coating film hardness and stain resistance cannot be balanced. However, the high molecular weight polyester resin obtained by polycondensation of the polyester resin under reduced pressure has excellent processability as compared with ordinary polyester resins,
It has also been put to practical use in the painting of home appliances such as refrigerators and washing machines.

<< Problems to be Solved by the Invention >> However, these high-molecular-weight polyester resins have a narrow molecular weight distribution and a small number of low-molecular-weight portions as compared with ordinary polyester resins, and thus have a problem of poor pigment dispersibility. .

Increasing the degree of branching of the polyester resin in order to broaden the molecular weight distribution makes it impossible to balance the processability of the coated product with the coating film hardness and stain resistance.

Therefore, the present invention provides a method for producing a polyester resin useful for a thermosetting paint, which has a good pigment dispersibility and can produce a coated article having a good balance of processability, coating film hardness and stain resistance. The purpose is to

<< Means for Solving the Problems >> That is, the present invention is a polyalkylene glycol-modified polyester characterized by polycondensing the following components (a) and (b) so that the number average molecular weight becomes 10,000 or more. The present invention relates to a method for producing a resin.

Component (a): 100 to 40 mol% of aromatic dicarboxylic acid component, 0 to 60 mol% of aliphatic dicarboxylic acid component, 0 to 5 mol% of monocarboxylic acid component and polyvalent of trivalent or more based on all acid components Carboxylic acid component 0 to 5 mol% as an acid component, dialcohol component 100 to 95 relative to all alcohol
Polyester resin synthesized with mol% and trihydric or higher polyhydric alcohol component 0 to 5 mol% as alcohol component
95-99.5% by weight.

Component (b): 0.5 to 5% by weight of polyalkylene glycol having a molecular weight of 200 to 10,000.

Examples of the aromatic dicarboxylic acid component used in the polyester resin of component (a) used in the present invention include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, etc., or their lower alkyl esters, acid anhydrides, etc. One or more of these can be used.

Examples of the aliphatic dicarboxylic acid component include adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, and hymic acid, and lower alkyl esters, acid anhydrides and the like of these may be used. One or more types can be used.

Examples of the monocarboxylic acid component include benzoic acid, methylbenzoic acid, p-tert-butylbenzoic acid, indecanoic acid, cyclohexanoic acid, isooctanoic acid and the like, and lower alkyl esters thereof may be used. The above can be used.

Examples of the trivalent or higher polycarboxylic acid component include polycarboxylic acids such as trimellitic acid, trimesic acid and pyromellitic acid, and lower alkyl esters and acid anhydrides thereof may be used. One or more kinds can be used within a range that does not cause gelation reaction.

As the dialcohol, ethylene glycol, 1,2-
Pulpandiol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5 ... pentanediol, 1,6-hexanediol, diethylene glycol, neopentyl alcohol, 1,4-cyclohexane Dimethanol, 3-methylpentane-1,5-diol, 1,4
One or more kinds of aliphatic or aromatic dialcohols such as dicyclohexanedimethanol, xylylene glycol and hydrogenated bisphenol A can be used.

Examples of the trihydric or higher polyhydric alcohol component include trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol, and one or more of them can be used.

In the component (a), as the carboxylic acid component, an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component, a monocarboxylic acid component, and a trivalent or higher polyvalent carboxylic acid component are used in the above-mentioned formulation. Too little dicarboxylic acid component,
If the amount of the aliphatic dicarboxylic acid component is too large, the obtained resin will be softened and the hardness of the coating film will be likely to decrease. If the amount of the monocarboxylic acid component is too large, the resulting resin tends to have a low molecular weight, resulting in deterioration of coating film performance. Further, if the amount of the trivalent or higher polyvalent carboxylic acid is too large, gelation is likely to occur during the polycondensation reaction.

Further, in the component (a), as the alcohol component, a dialcohol component and a trihydric or higher polyhydric alcohol component are used in the above-mentioned formulation, but if the trihydric or higher polyhydric alcohol component is too much, a gel is generated during the polycondensation reaction. It is easy to convert.

The acid component and the alcohol component are used in an appropriate equivalent ratio, but it is preferable to use 1 to 1.3 equivalents of the alcohol component to 1 equivalent of the acid component.

As the polyalkylene glycol as the component (b), polyethylene glycol or polypropylene glycol having a molecular weight of 200 to 10,000 can be used. Polyalkylene glycol is not only one kind, but also has a molecular weight and / or
Alternatively, two or more different types can be used in combination.

The component (a) polyester resin used in the present invention is
If necessary, a catalyst such as dibutyltin oxide, zinc acetate, calcium acetate, N-butyl titanate, etc. is used to reduce the acid component and alcohol component to atmospheric pressure or pressure, and
It is obtained by performing a transesterification reaction and / or an esterification reaction at 0 to 260 ° C., and it is preferable that the oxidation of the resin is 3 or less.

To obtain the polyalkylene glycol-modified polyester resin of the present invention, the polyester resin 95 to 9 as the component (a) is used.
9.5% by weight and (b) component polyalkylene glycol
0.5 to 5% by weight, if necessary, in the presence of a catalyst such as antimony trioxide, germanium oxide, N-butyl titanate, at a reduced pressure of 10 mmHg or less, preferably 1 mmHg or less, 200 to 300 ° C., preferably Conducts a polycondensation reaction at 230 to 280 ° C to prepare a polyester resin having a number average molecular weight of 10,000 or more. Whether or not the number average molecular weight is 10,000 or more can be determined by using, for example, stirring power or stirring torque as an index. It can also be confirmed by gel permeation chromatography measurement.

When the average molecular weight of the finally obtained polyalkylene glycol-modified polyester resin is less than 10,000, the coating film hardness and stain resistance are poor. When the amount of the polyalkylene glycol used as the component (b) exceeds 5% by weight,
The stain resistance and coating film hardness are insufficient, and if it is less than 0.5% by weight, there is no curing for improving the pigment dispersibility.

Alternatively, as the component (a), the number average molecular weight is 15,000.
Using the polyester resin prepared as described above or a resin obtained by reacting this with a part of polyalkylene glycol, the whole or the rest of the polyalkylene glycol of the component (b) is mixed and heated at 200 to 280 ° C., It is also possible to obtain a target polyalkylene glycol-modified polyester resin by subjecting it to a depolymerization reaction. In this case, the amount of polyalkylene glycol used in the depolymerization reaction needs to be selected so that the number average molecular weight of the resin obtained after depolymerization is 10,000 or more.

In the present invention, the “number average molecular weight” is measured by using gel permeation chromatography and using a calibration curve of standard polyethylene.

The polyalkylene glycol-modified polyester resin obtained by the present invention has a number average molecular weight in consideration of the characteristics.
It is preferably 100,000 or less.

The polyalkylene glycol-modified polyester resin obtained by the present invention, if necessary, contains an aromatic hydrocarbon,
It can be diluted with a solvent such as an aliphatic hydrocarbon, an ester or a ketone.

The polyalkylene glycol-modified polyester resin obtained by the present invention is an amino resin obtained by reacting an amino compound such as melamine, urea or benzoguanamine with formaldehyde. The amino resin is a lower alcohol such as methanol, ethanol, propanol or butanol. It can be used as a thermosetting paint in combination with an amino resin such as an etherified amino resin obtained by etherification. In this case, the polyalkylene glycol-modified polyester resin and the amino resin are 90 / 10-60 / 40, preferably 85 / 15-70 /, in the former / the latter in a solid content weight ratio.
It is suitable to be blended in a ratio of 30. Further, if necessary, a pigment, a plasticizer, a colorant and an acid catalyst such as P-toluenesulfonic acid can be added.

The coating material thus obtained can be coated on the surface of ferrous or non-ferrous metal by a known method such as spray coating or roll coating.

<Operation> It is considered that one of the causes of poor pigment dispersion is agglomeration between pigment particles. Agglomeration between pigments is less likely to occur due to the adsorption of high molecular weight polyester resin around the pigment particles, but with conventional high molecular weight polyesters, there are few adsorption points on the pigment such as hydroxyl groups, and resin adsorption on the pigment Compared to the small amount, the polyalkylene glycol-modified polyester resin obtained by the present invention has a large number of ether bond portions serving as adsorption points to the pigment, and a small amount of modification shows a large effect. Therefore, the pigment dispersibility is improved without breaking the balance of processability, coating film hardness, and stain resistance.

<< Examples >> Next, the present invention will be described in detail based on Examples, but the present invention is not limited thereto.

Below, for the number average molecular weight, Hitachi 635 type HLC and gel pack (GELPACK) R440, R450 and R400M (all are trade names of Hitachi Chemical Co., Ltd.) are used in series and tetrahydrofuran is used as the eluent. Then
After obtaining the chromatogram, it was calculated based on standard polythrene.

Example 1 (A), 299 parts by weight of terephthalic acid (1.8 mol), 75 parts by weight of isophthalic acid (0.45 mol), 141 parts by weight of azelaic acid (0.75 mol), 124 parts by weight of ethylene glycol (2.0 mol), neopentyl alcohol 125 parts by weight (1.2 moles) and 0.1 parts by weight of dibutyltin dioxide are subjected to an esterification reaction at 250 ° C. under an inert gas pressure to remove water produced to obtain a polyester resin (a) having an acid value of 1.0. It was

To 490 parts by weight of the polyester resin obtained in (B) and (A), 10 parts by weight of polyethylene glycol (molecular weight 400), 0.1 parts by weight of antimony trioxide, and 0.2 parts by weight of triethylphosphite were added, and the pressure was reduced to 0.8 mmHg. Then, polycondensation reaction was performed at 280 ° C. to obtain a polyethylene glycol-modified polyester resin having a number average molecular weight of 20,000.

Example 2 A polyethylene glycol-modified polyester resin having a number average molecular weight of 22,000 was obtained in the same manner as in Example 1 (B) except that polyethylene glycol having a molecular weight of 2,000 was used.

Example 3 A polypropylene glycol-modified polyester resin having a number average molecular weight of 20,000 was obtained in the same manner as in Example 1 except that polypropylene glycol (molecular weight 3,500) was used in (B) of Example 1.

Comparative Example 1 Polyester resin (a) in (B) of Example 1
Was used in the same manner as in Example 1 except that polyethylene glycol was omitted, and a polyester resin having a number average molecular weight of 21,000 was obtained.

Comparative Example 2 Polyester resin (a) in (B) of Example 1
450 parts by weight and polyethylene glycol (molecular weight 40
0) A polyester resin having a number average molecular weight of 20,000 was obtained in the same manner as in Example 1 except that 50 parts by weight was used.

The resin obtained in each of the Examples and Comparative Examples was prepared into a resin solution having a heating residue of 40% by Solvesso 100 (Zell Chemical Co., trade name) / cyclohexane / cellosolve acetate = 1/1/1 (weight ratio). did.

The resin solution thus obtained was made into a paint with the following composition and tested.

(1) White enamel paint formulation 300 parts by weight of polyester resin of Examples or Comparative Examples, melan 523 (trade name of methyl etherified melamine resin manufactured by Hitachi Chemical Co., Ltd.) 30 parts by weight titanium white (rutile type) 100 parts by weight P -Toluenesulfonic acid 1 part by weight Thinner (solveso / cyclohexane / cellosolve acetate = 1/1/1) 69 parts by weight (2) Test plate preparation conditions Base material: Bonderite # 144 treated steel plate (Nippon Test Panel Co., thickness 0.5) mm) Coating: Applicator (impression film thickness 20 μm) Baking: 280 ° C., 120 seconds (3) Test method Gloss: Pencil hardness measured at incident angle 60 ° Pencil hardness: Measured using Mitsubishi Uni.

Workability: A 70 × 40 mm test piece was bent 180 ° from the center in the longitudinal direction and pressed.

Evaluation: 5 points: No crack 3 points: 1/3 crack 1 point: Full-scale crack Contamination resistance: Wipe off the traces of the magic ink on the test piece for 24 hours, using xylol.

Evaluation 5 points: No ink trace 3 points: Ink trace slightly remains 1 point: Ink trace clearly remains Paint stability: Appearance of paint after sealing 200 g of paint in a metal can and leaving it in an atmosphere of 50 ° C for 30 days ○: No abnormality △: Flocculation occurs ×: Large sedimentation Resin adsorption amount on pigment: The amount of polyester resin before and after pigment dispersion is determined by gel permeation chromatography, and the difference is the amount of polyester resin adsorbed on the pigment. Then, the amount of resin adsorbed per 1 g of the pigment was determined.

The test results according to the above are shown in the table As is clear from the table, the polyalkylene glycol-modified polyester resin obtained by the present invention is excellent as a resin for thermosetting paints, and is excellent in coating film hardness, processability and stain resistance, and As is clear from Examples 1 to 3, since the pigment dispersibility is good, the coating stability is excellent.

On the other hand, in Comparative Example 1, which is not modified with polyalkylene glycol, the pigment dispersibility is poor, and thus the coating stability is also poor.

Comparative Example 2 has a large amount of polyalkylene glycol, but the stain resistance and coating film hardness are lowered.

<< Effects of the Invention >> According to the present invention, a polyalkylene glycol having a large number of ether bond portions serving as adsorption points for the pigment is introduced into the polyester, so that the amount of resin adsorbed on the pigment increases and the pigment dispersibility is excellent. It is possible to obtain a polyester resin which is excellent not only in workability but also in workability, coating film hardness and stain resistance.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-56-92919 (JP, A) JP-A-56-125424 (JP, A) JP-A-57-108178 (JP, A)

Claims (1)

[Claims] 1. A process for producing a polyalkylene glycol-modified polyester resin, which comprises subjecting the following components (a) and (b) to polycondensation so that the number average molecular weight becomes 10,000 or more. Component (a): 100 to 40 mol% of aromatic dicarboxylic acid component, 0 to 60 mol% of aliphatic dicarboxylic acid component, 0 to 5 mol% of monocarboxylic acid component and polyvalent of trivalent or more based on all acid components Carboxylic acid component 0 to 5 mol% as acid component, dialcohol component 100 to 95 mol% and trihydric or higher polyhydric alcohol component 0 to 5 mol% with respect to all alcohol components
Polyester resin 95 synthesized with alcohol as the alcohol component
~ 99.5% by weight. Component (b): 0.5 to 5% by weight of polyalkylene glycol having a molecular weight of 200 to 10,000.