JPH04314770A - Production of polyester resin for coating material and coating material - Google Patents

Abstract

PURPOSE:To obtain a polyester for a thermosetting coating material excellent in pigment dispersion and the balance among processability, film hardness and staining resistance by mixing a specified polyester resin with a specified long- chain alpha-olefin glycol in a specified mixing ratio and polycondensing the mixture in a vacuum. CONSTITUTION:99.5wt.% polyester resin synthesized from an acid component comprising 100-40mol% aromatic dicarboxylic acid component and 0-60mol% aliphatic dicarboxylic acid component and an alcohol component comprising 100-95mol% dihydric alcohol component and 0-5mol% at least trihydric alcohol component is mixed with 0.5-5wt.% long-chain alpha-olefin glycol of the formula (wherein n is an integer of 5 or greater), and the obtained mixture is polycondensed in a vacuum.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester resin for paints that has excellent pigment dispersibility and can form coatings with good hardness and workability on the surfaces of iron, non-ferrous metals, etc., and paints.

0002

[Prior Art] Conventionally, painting of home appliances was done by processing steel plates.
Previously, flat steel plates were formed into a box shape after being painted, but in order to solve various problems such as streamlining the painting line, improving productivity, preventing pollution, and improving the working environment, flat steel sheets are now processed and formed after being painted. The company has moved to a pre-coat painting method. The prepainted steel sheet used in this method is processed into a complex shape after painting, so a high degree of workability is required. On the other hand, among home appliances, refrigerators, washing machines, etc. are required to have excellent coating film hardness, stain resistance, and chemical resistance.

[0003] Conventionally, thermosetting acrylic resins have been mainly used for coating these home appliances, and this is because acrylic resin paints have excellent coating hardness and stain resistance. However, acrylic resin paints do not have enough workability to be used for pre-coating, and in order to satisfy the processability, it is necessary to soften the composition of the acrylic resin, and it is necessary to soften the composition of the acrylic resin to create a coating film that can withstand practical use. It is difficult to demonstrate hardness and stain resistance.

[0004]Although thermosetting polyester resins have been used for coil coatings such as colored galvanized iron, they still have the drawback of not achieving a balance between processability, coating hardness, and stain resistance. However, high molecular weight polyester resin obtained by condensation polymerization of polyester resin under reduced pressure has a better balance of processability, coating hardness, and stain resistance than ordinary polyester resin, and is used in home appliances such as refrigerators and washing machines. It has also been put into practical use for painting.

[0005]

However, these high molecular weight polyester resins have a narrower molecular weight distribution and less low molecular weight portions than normal polyester resins. Furthermore, since there are few functional groups in the molecular chain, there is a problem that the resin molecules are difficult to adsorb to the pigment, and the pigment tends to aggregate, resulting in poor dispersibility.

[0006] Pigment dispersibility can be improved by increasing the degree of branching of the polyester resin, but processability is significantly reduced, making it impossible to balance coating film hardness, processability, and stain resistance. Therefore, an object of the present invention is to provide a polyester resin for thermosetting paints that has excellent pigment dispersibility and also has an excellent balance of processability, coating hardness, and stain resistance.

[0007]

[Means for Solving the Problems] The present invention has an aromatic dicarboxylic acid component of 100 to 40 mol% and an aliphatic dicarboxylic acid component of 0 to 60 mol% based on the total acid component as acid components, and based on the total alcohol component. Dialcohol component 100-95
Mol% and trihydric or higher polyhydric alcohol component 0-5 mol%
Polyester resin synthesized using alcohol as an alcohol component (
a) 99.5 to 95% by weight and general formula (I)

0.5 to 5% by weight of long-chain α-olefin glycol (b) represented by [Formula 2] (where n is an integer of 5 or more)
It relates to a method for producing a polyester resin for paints, which comprises blending the following and polycondensing it under reduced pressure so that the number average molecular weight becomes 5,000 or more.

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

Examples of aliphatic dicarboxylic acids include adipic acid, sebacic acid, azelaic acid, succinic acid, fumaric acid, maleic acid, hymic acid, and 1,6-cyclohexanedicarboxylic acid. Anhydrides and 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 % of the former and 0 to 60 mol % of the latter based on the total acid components. If the aliphatic dicarboxylic acid component exceeds 60 mol %, hardness and stain resistance decrease.

Polyester resin (a) used in the present invention
) as dialcohol components include 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 There are ethylene oxide adducts and propylene oxide adducts of bisphenol A and bisphenol A, and one or more of these can be used.

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

The long-chain α-olefin glycol (b) represented by the general formula (I) used in the present invention is as follows:
One or more types of long chain α-olefin glycols having n of 5 or more, preferably 10 to 40, preferably a combination of two or more types having different molecular weights can be used. Note that if n is less than 5, good pigment dispersibility cannot be obtained.

[0014] The production of the polyester resin according to the present invention includes:
First, using the above acid component and alcohol component, dibutyltin oxide, lead acetate, calcium acetate, N
-200-300 in the presence of a catalyst such as butyl titanate
After obtaining the polyester resin of component (a) by performing esterification or transesterification reaction at ℃, 95 to 99.5% by weight of the polyester resin of component (a) and the above component (b) are added.
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. The polycondensation reaction is carried out under the following reduced pressure, preferably at 200 to 300°C, particularly preferably at 230 to 280°C, and the number average molecular weight is 5,000 or more, preferably 10,000 to 2,500.
Adjust so that it is 0.

Alternatively, component (a) alone or a part of component (b) may be blended together and subjected to reduced pressure polycondensation.
After obtaining a polyester resin with a number average molecular weight of 10,000 or more, all or the remainder of the α-olefin glycol of component (b) is blended, and the number average molecular weight of 200 to 300
The desired polyester resin can also be obtained by depolymerizing at °C.

[0016] If the number average molecular weight of the polyester resin finally obtained is less than 5,000, the coating film hardness and stain resistance will be poor. Furthermore, if the amount of long-chain α-olefin glycol used as component (b) exceeds 5% by weight, stain resistance will be insufficient, and if it is less than 0.5% by weight, it will not be effective in improving pigment dispersibility. .

[0017] In the present invention, the "number average molecular weight" is calculated using gel permeation chromatography using a standard polystyrene calibration curve.

The polyester resin obtained by the present invention can be diluted with a solvent such as an aromatic hydrocarbon, an aliphatic hydrocarbon, an ester, or a ketone, if necessary. The polyester resin of the present invention is an amino resin obtained by reacting an amino compound such as melamine, urea, or benzoguanamine with formaldehyde, or an ether obtained by etherifying the amino resin with 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 a chemical amino resin. In this case, the solid content of the polyester resin and the amino resin is 90/10 to 90/10 by weight.
It is appropriate to mix them in a ratio of 60/40, preferably 85/15 to 70/30. Moreover, pigments, plasticizers, colorants, and acid catalysts such as p-toluenesulfonic acid can also be added as necessary.

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

[0020]

[Operation] One of the causes of poor pigment dispersibility is thought to be aggregation between pigment particles. Adsorption of resin around pigment particles makes it difficult for pigments to aggregate, but conventional high molecular weight polyester resins have fewer adsorption points for pigments such as hydroxyl groups, and from the viewpoint of coating film performance, the molecular structure Since the resin is linear or slightly branched, it is difficult for the resin to adsorb onto the pigment, resulting in poor pigment dispersibility. The polyester resin obtained according to the present invention is modified with α-olefin glycol and a long-chain alkyl group is introduced into the molecular chain of the polyester resin, so that the resin easily adsorbs to the pigment and has excellent pigment dispersibility. In addition, the introduced alkyl group does not have a functional group at the end, so it does not have a large effect on the crosslinked structure.
It does not reduce the processability of the coating film.

[0021]

EXAMPLES Next, the present invention will be explained in detail with reference to Examples, but the present invention is not limited to these in any way. Hereinafter, the number average molecular weight is expressed as Hitachi Model 635 HLC (manufactured by Hitachi, Ltd.) and Gel Pack R4 as a column.
40, R450, and R400M (all manufactured by Hitachi Chemical Co., Ltd., trade names) were used in series and tetrahydrofuran was used as the eluent to obtain a chromatogram, and then calculated 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 (0.75 mol) of azelaic acid, 1 part by weight of ethylene glycol
24 parts by weight (2.0 mol), neopentyl glycol 1
25 parts by weight (1.2 moles) and 0 dibutyltin dioxide
．． 1 part by weight was subjected to an esterification reaction at 250° C. in the presence of an inert gas, and the produced water was removed to obtain a polyester resin (a) with an acid value of 1.0. (B): Polyester resin obtained in (A) (a) 48
5 parts by weight, α-olefin glycol (n=12) 1
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 carried out at 280°C under a reduced pressure of 0.8 mmHg to obtain a modified polyester resin with a number average molecular weight of 20,000. Obtained.

Example 2 In (B) of Example 1, a mixture of n=13 to 15 as α-olefin glycol (manufactured by Daicel Chemical Industries, Ltd.,
A modified polyester resin having a number average molecular weight of 21,000 was obtained by operating in the same manner as in Example 1 except that AOG-X68) was used.

Example 3 In (B) of Example 1, 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 76 parts by weight and 24 parts by weight of a mixture of α-olefin glycol with n=13 to 15 were used.

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

Comparative Example 2 In (B) of Example 1, 450 parts by weight of 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 the mixture (3 to 15) was used.

[0027] The resins obtained in each example and comparative example were prepared into a resin liquid with a heating residue of 40% by weight using a solution of Solvesso 150 (Esso Oil, trade name)/cyclohexanone = 50/50 (weight ratio). did.

The resin liquid thus obtained was made into a paint according to the following formulation and tested. (1) White enamel paint formulation Polyester resin of Example or Comparative Example
300 parts by weight
Melan 523 (trade name of methyl etherified melamine resin manufactured by Hitachi Chemical Co., Ltd.)

30 parts by weight Taipei CR95 (Titanium white manufactured by Ishihara Sangyo)
100 parts by weight p-
toluenesulfonic acid
1
Parts by weight Thinner (Solvesso 150/Cyclohexanone = 50/50) 69 parts by weight

(2)
Test plate creation conditions Base material: Bonderite #144 treated steel plate (manufactured by Nippon Test Panel Co., Ltd., thickness 0.5 mm) Painting: Applicator (dry film thickness 20 μm) Baking: 280
°C x 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 ink (using an oil-based felt tip pen) on the test piece,
After being left for 4 hours, it was wiped with ethanol and the degree of contamination was expressed as a relative evaluation. <Evaluation> 5 points...No ink marks. 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: A test piece was bent 180°, and cracks at the bent portion were evaluated using a 20x magnifying glass according to the following criteria. <Evaluation> 5 points...No cracks. 4 points...between 5 points and 3 points. 3 points...There are some cracks. 2 points...between 3 points and 1 point. 1 point...There is a crack on the entire surface. Paint stability: 200g of paint is sealed in a metal can and heated to 50°C.
The appearance of the paint after being left in the atmosphere for 30 days was evaluated according to the following criteria. <Evaluation> 〇…No abnormality. △…Flocculation occurred. ×...Large sedimentation. Amount of resin adsorbed to the 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 to the pigment.
The amount of resin adsorbed per gram of pigment was determined. The test results according to the above are shown in Table 1.

[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 coating film hardness, processability, and stain resistance in a well-balanced manner. , excellent paint stability due to good pigment dispersibility. On the other hand, although Comparative Example 1 was not modified with long-chain α-olefin glycol, the pigment dispersibility was poor and the paint stability was also poor. Comparative Example 2 is a case in which the amount of α-olefin glycol is large, but the stain resistance and coating film hardness are decreased.

[0033]

Effects of the Invention According to the present invention, it is possible to obtain polyester resins for paints and paints which not only have excellent processability, coating film and stain resistance, but also have excellent pigment dispersibility.

Claims (3)

[Claims] Claim 1: 100 to 40 mol% of aromatic dicarboxylic acid components and 0 aliphatic dicarboxylic acid components based on the total acid components.
Polyester resin (a) 99 synthesized 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 as an alcohol component .5 to 95% by weight and 0.5 to 5% by weight of long chain α-olefin glycol (b) represented by the general formula (I) (where n is an integer of 5 or more) %
1. A method for producing a polyester resin for paints, which comprises blending and polycondensing under reduced pressure so that the number average molecular weight becomes 5,000 or more. 2. A paint comprising a polyester resin obtained by the production method according to claim 1. 3. A paint comprising a polyester resin obtained by the production method according to claim 1 and an amino resin.