JP2616271B2 - Method for producing polyester resin for paint and paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention has excellent pigment dispersibility,
The present invention relates to a method for producing a polyester resin for paint capable of forming a coating film having good hardness and workability on the surface of iron, non-ferrous metal or the like, and a paint.

[0002]

2. Description of the Related Art Conventionally, painting of home electric appliances involves processing a steel plate,
After forming, it was performed in a box shape, but in order to solve various problems such as streamlining the coating line, improving productivity, preventing pollution, improving the work environment, etc., processing and forming after painting flat steel sheet It has shifted to the pre-coat coating method. The pre-coated steel sheet used in this method is processed into a complicated shape after painting, so that high workability is required. On the other hand, refrigerators, washing machines, and the like among home electric appliances are required to have excellent coating film hardness, stain resistance, and chemical resistance.

Hitherto, thermosetting acrylic resins have been mainly used for coating these home appliances, because acrylic resin coatings have excellent coating film hardness and stain resistance. However, acrylic resin paints have insufficient workability to be used for precoating, and in order to satisfy workability, it is necessary to soften the composition of the acrylic resin. It is difficult to show hardness and stain resistance.

[0004] Further, thermosetting polyester resins have been used for coil coating such as color tin, but still have the disadvantage that workability, coating film hardness and stain resistance cannot be balanced. However, the high molecular weight polyester resin obtained by condensation polymerization of the polyester resin under reduced pressure is excellent in balance between workability, coating film hardness and stain resistance as compared with a normal polyester resin, and a refrigerator,
It is also used for painting home appliances such as washing machines.

[0005]

However, these high molecular weight polyester resins have a narrower molecular weight distribution and a lower molecular weight portion than ordinary polyester resins. Further, since there are few functional groups in the molecular chain, there is a problem that the resin molecules are hardly adsorbed on the pigment, and the pigment is easily aggregated and the dispersibility is poor.

[0006] Although the pigment dispersibility can be improved by increasing the degree of branching of the polyester resin, the processability is remarkably reduced, and the balance between the coating film hardness, processability and stain resistance cannot be balanced. Accordingly, an object of the present invention is to provide a polyester resin for a thermosetting paint, which has excellent pigment dispersibility and a good balance of processability, coating film hardness and stain resistance.

[0007]

According to the present invention, 100 to 40 mol% of an aromatic dicarboxylic acid component and 0 to 60 mol% of an aliphatic dicarboxylic acid component are used as an acid component based on the total acid component, and the total alcohol component is used as an acid component. Dialcohol component 100-95
Mol% and 0-5 mol% of trihydric or higher polyhydric alcohol component
99.5 to 95% by weight of a polyester resin (a) synthesized using as an alcohol component

Embedded image (Wherein, n is an integer of 5 or more) 0.5 to 5% by weight of a long-chain α-olefin glycol (b)
And polycondensation under reduced pressure so that the number average molecular weight is 5,000 or more.

The polyester resin (a) used in the present invention
Examples of the aromatic dicarboxylic acid used include terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, and lower alkyl esters and acid anhydrides thereof, and one or more of these can be used.

The aliphatic dicarboxylic acids include adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, hymic acid, 1,6-cyclohexanedicarboxylic acid and the like. An anhydride or the like may be used, and one or more of these may be used.

The aromatic dicarboxylic acid and the aliphatic dicarboxylic acid are used in a proportion of 100 to 40 mol%, and the latter in a proportion of 0 to 60 mol%, based on all the acid components. When the amount of the aliphatic dicarboxylic acid component exceeds 60 mol%, the hardness and stain resistance are reduced.

The dialcohol component of the polyester resin (a) used in the present invention includes ethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4 -Butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol, 3-methylpentanediol, diethylene glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, 2 -Methyl-1,3-
Propanediol, 2,2-diethyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol xylylene glycol, hydrogenated bisphenol A, ethylene oxide adduct of bisphenol A or propylene oxide adduct And one or more of these can be used.

The above-mentioned dialcohol component is used in a proportion of 100 to 95 mol% based on the total alcohol component. Examples of the trihydric or higher polyhydric alcohol component include trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol, and one or more of these can be used. These polyhydric alcohols are used in a proportion of 0 to 5 mol% in all alcohol components. If it exceeds 5 mol%, the processability will decrease.

The long-chain α-olefin glycol (b) represented by the general formula (I) used in the present invention includes:
The long-chain α-olefin glycol having n of 5 or more, preferably 10 to 40 can be used in combination of one or more, preferably two or more kinds having different molecular weights. If n is less than 5, good pigment dispersibility cannot be obtained.

The production of the polyester resin according to the present invention comprises:
First, using the above-mentioned acid component and alcohol component, if necessary, dibutyltin oxide, lead acetate, calcium acetate, N
200-300 in the presence of a catalyst such as butyl titanate
The polyester resin of component (a) is obtained by carrying out an esterification or transesterification reaction at a temperature of 95 ° C., and then 95 to 99.5% by weight of the polyester resin of component (a) and the above component (b)
0.5 to 5% by weight of α-olefin glycol, and if necessary, in the presence of a catalyst such as antimony trioxide, germanium oxide or N-butyl titanate, preferably 10 mmHg or less, particularly preferably 1 mmHg or less.
The polycondensation reaction is carried out under the following reduced pressure, preferably at 200 to 300 ° C, particularly preferably 230 to 280 ° C, and the number average molecular weight is 5,000 or more, preferably 10,000 to 250.
Prepare to be 00.

As an alternative, only the component (a) or a part of the component (b) is blended and subjected to polycondensation under reduced pressure.
After obtaining a polyester resin having a number average molecular weight of 10,000 or more, all or the rest of the α-olefin glycol of the component (b) is blended, and the mixture is treated under an inert gas atmosphere at 200 to 300.
The desired polyester resin can also be obtained by depolymerizing at a temperature of ° C.

When the polyester resin finally obtained has a number average molecular weight of less than 5000, the hardness of the coating film and the stain resistance are poor. When the amount of the long-chain α-olefin glycol used in the component (b) exceeds 5% by weight, the stain resistance becomes insufficient, and when the amount is less than 0.5% by weight, there is no effect in improving the pigment dispersibility. .

In the present invention, the "number average molecular weight" is calculated by using gel permeation chromatography and using a standard polystyrene calibration curve.

The polyester resin obtained according to the present invention may contain, if necessary, an aromatic hydrocarbon, an aliphatic hydrocarbon,
It can be diluted with a solvent such as esters and ketones. The polyester resin of the present invention is an amino resin obtained by reacting an amino compound such as melamine, urea and benzoguanamine with formaldehyde, and an ether obtained by etherifying the amino resin with a lower alcohol such as methanol, ethanol, propanol and butanol. It can be used as a thermosetting paint in combination with an amino resin such as a fluorinated amino resin. In this case, the weight ratio of the solid content of the polyester resin and the amino resin is 90/1.
It is suitable to be blended at a ratio of 0/60/40, preferably 85 / 15-70 / 30. Further, if necessary, a pigment, a plasticizer, a colorant, and an acid catalyst such as p-toluenesulfonic acid can be added.

The paint thus obtained can be applied to the surface of iron, non-ferrous metal or the like by a known method such as spray coating or roll coating.

[0020]

One of the causes of poor pigment dispersibility is considered to be aggregation between pigment particles. Aggregation between pigments is less likely to occur due to the resin adsorbing around the pigment particles.However, with conventional high molecular weight polyester resins, there are few points of adsorption to pigments such as hydroxyl groups, and from the viewpoint of coating film performance, the molecular structure is low. Is linear or slightly branched, so that the resin is hardly adsorbed on the pigment, so that the pigment dispersibility is poor. The polyester resin obtained by the present invention is modified with α-olefin glycol, and by introducing a long-chain alkyl group into the molecular chain of the polyester resin, the resin is easily adsorbed on the pigment and has excellent pigment dispersibility. In addition, since the introduced alkyl group has no functional group at the terminal, it does not significantly affect the crosslinked structure,
Does not lower the processability of the coating film.

[0021]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Hereinafter, the number average molecular weight is determined by using a Hitachi 635 type HLC (manufactured by Hitachi, Ltd.) and a gel pack (GELPACK) R as a column.
440, R450, R400M (all manufactured by Hitachi Chemical Co., Ltd., trade names) were used in series, and tetrahydrofuran was used as an eluent. After obtaining a chromatogram, calculation was performed based on standard polystyrene. .

Example 1 (A): 299 parts by weight (1.8 mol) of terephthalic acid, 75 parts by weight (0.45 mol) of isophthalic acid, 141 parts by weight of azelaic acid (0.75 mol), ethylene glycol 1
24 parts by weight (2.0 mol), neopentyl glycol 1
25 parts by weight (1.2 mol) and 0.1 parts by weight of dibutyltin dioxide are subjected to an esterification reaction at 250 ° C. in the presence of an inert gas to remove generated water. (A) was obtained. (B): polyester resin (a) 48 obtained in (A)
Α-olefin glycol (n = 12) 1 in 5 parts by weight
5 parts by weight, 0.1 parts by weight of antimony trioxide and 0.2 parts by weight of triethyl phosphate were added, and a polycondensation reaction was performed at 280 ° C. under a reduced pressure of 0.8 mmHg to obtain a modified polyester resin having a number average molecular weight of 20,000. Obtained.

Example 2 In Example 1 (B), a mixture of n = 13 to 15 as α-olefin glycol (manufactured by Daicel Chemical Industries, Ltd.)
Except for using AOG-X68), the same operation as in Example 1 was carried out to obtain a modified polyester resin having a number average molecular weight of 21,000.

Example 3 In Example 1 (B), the polyester resin (a) 4
A modified polyester resin having a number average molecular weight of 20,000 was obtained in the same manner as in Example 1 except that the mixture of α-olefin glycol having n = 13 to 15 and 24 parts by weight were used in 76 parts by weight.

Comparative Example 1 The procedure of Example 1 (B) was repeated except that the polyester resin (a) was used in an amount of 500 parts by weight and the α-olefin glycol was omitted.
0 polyester resin was obtained.

Comparative Example 2 In Example 1 (B), 450 parts by weight of the polyester resin (a) and α-olefin glycol (n = 1)
A modified polyester resin having a number average molecular weight of 22,000 was obtained in the same manner as in Example 2, except that 50 parts by weight of a mixture of 3 to 15) 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 weight using a solution of Solvesso 150 (Esso Petroleum, trade name) / cyclohexanone = 50/50 (weight ratio). did.

The resin solution thus obtained was made into a paint with the following composition and tested. (1) Formulation of white enamel paint 300 parts by weight of polyester resin of Example or Comparative Example 30 parts by weight of melan 523 (trade name of methyl etherified melamine resin manufactured by Hitachi Chemical Co., Ltd.) 100 parts by weight of Taipaque CR95 (titanium white manufactured by Ishihara Sangyo) Parts p-toluenesulfonic acid 1 part by weight Thinner (Solvesso 150 / cyclohexanone = 50/50) 69 parts by weight

(2) Test plate preparation conditions Base material: Bondelite # 144 treated steel plate (manufactured by Nippon Test Panel Co., Ltd., thickness 0.5 mm) Coating: applicator (dry film thickness 20 μm) Baking: 280 ° C. × 90 seconds

(3) Test method Gloss: According to JIS K5400. Pencil hardness: according to JIS K5400. Stain resistance: After applying blue, black and red magic inks (using an oil-based ink felt-tip pen) on the test piece, apply 2
After leaving it for 4 hours, it was wiped off with ethanol, and the degree of contamination was shown by relative evaluation. <Evaluation> 5 points: No ink trace. 4 points ... between 5 points and 3 points. 3 points: Slight ink marks remain. 2 points ... between 3 points and 1 point. 1 point: Ink marks clearly remain. Workability: The test piece was bent at 180 °, and the crack at the bent portion was evaluated with a 20-fold loupe according to the following criteria. <Evaluation> 5 points: No crack. 4 points ... between 5 points and 3 points. 3 points ... Some cracks. 2 points ... between 3 points and 1 point. 1 point: There are cracks on the entire surface. Paint stability: Seal 200g of paint in a metal can, 50 ℃
The appearance of the paint after standing for 30 days under the following atmosphere was evaluated according to the following criteria. <Evaluation> 〇: No abnormality. Δ: flocculation occurred. ×: Large sedimentation. Resin adsorption amount to pigment: The amount of polyester resin before and after pigment dispersion was determined by gel permeation chromatography, and the difference was taken as the amount of polyester resin adsorbed on pigment,
The resin adsorption amount per 1 g of the pigment was determined. Table 1 shows the test results.

[0031]

[Table 1]

As is clear from Table 1, the modified polyester resin obtained by the present invention is excellent as a resin for thermosetting paints, and has excellent balance of coating film hardness, processability and stain resistance. Because of good pigment dispersibility, paint stability is excellent. On the other hand, Comparative Example 1
Is not modified with long-chain α-olefin glycol, but has poor pigment dispersibility and poor paint stability. Comparative Example 2 is a case where the amount of α-olefin glycol is large, but the stain resistance and the coating film hardness are reduced.

[0033]

According to the present invention, it is possible to obtain a polyester resin for a coating material and a coating material having not only excellent workability, coating film and stain resistance but also excellent pigment dispersibility.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08G 63/91 NLL C08G 63/91 NLL // (C09D 167/02 161: 20)

Claims (3)

(57) [Claims] 1. An aromatic dicarboxylic acid component of 100 to 40 mol% and an aliphatic dicarboxylic acid component of 0 to 0% based on the total acid component.
Polyester resin (a) synthesized by using 60 mol% as an acid component, 100 to 95 mol% of a dialcohol component and 0 to 5 mol% of a trihydric or higher polyhydric alcohol component with respect to all alcohol components as an alcohol component 5 to 95% by weight
And the general formula (I) (Wherein, n is an integer of 5 or more) 0.5 to 5% by weight of a long-chain α-olefin glycol (b)
And a polycondensation under reduced pressure so that the number average molecular weight is 5,000 or more. 2. A paint containing the polyester resin obtained by the production method according to claim 1. 3. A paint containing a polyester resin obtained by the production method according to claim 1 and an amino resin.