JPH028242A - Polyester resin composition - Google Patents

Abstract

PURPOSE:To obtain a composition excellent in the balance between hardness and workability and suitable for a coating material for metal by blending a specified polyester resin with a curing agent. CONSTITUTION:(A) A polyester resin containing aromatic dicarboxylic acids in an amount of >=80mol% of the total acid components and 1,9-nonanediol and/or 1 or 2-methyl 1,8-octanediol in an amount of >=10-80mol% of polyol components is blended with (B) a curing agent in the ratio of (90-70):(10-30) (weight ratio). As the curing agent, an alkyletherified aminoformaldehyde resin is used. The component (A) contains >=trivalent acid and/or >=trivalent polyol in an amount of 0.5-10mol% in total based on the amount of the acid components and/or the polyol ones.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a polyester resin composition for metal coatings.

More specifically, the present invention relates to a copolymerized polyester resin composition used in a paint for metal coating, which has an excellent balance between hardness and workability.

<Prior Art> In recent years, the use of pre-painted steel sheets, which are processed after coating the steel sheets, has been expanding, mainly for use in home appliances and automobile parts. Paints used for pre-coated steel sheets are required to have contradictory properties such as workability, hardness, and stain resistance, in addition to the properties such as adhesion, gloss, and weather resistance that are required of other general paints. The combination of copolymerized polyester resin and 7-mino resin is currently widely used as a material that has these two contradictory properties.
I haven't found anything satisfying yet. For example, in JP-A-59-11370, a soft polyester resin with a low glass transition point (Tg) and a hard polyester resin with a high Tg are used in combination, and a methoxymethylolated melamine compound is used to give a relatively hard coating film. It has been proposed to improve the balance between the two by incorporating a butoxymethylolated melamine compound, which gives a flexible membrane. Also, JP-A No. 62-2) 830, JP-A No. 59-87
70 etc. are polyester resins with branches introduced by copolymerization of trimethylol 10 pan, trimellitic acid, etc.
．． 5-bentanediol, 1,6-hexanediol,
It has been proposed to increase processability and hardness by copolymerizing monomers with soft segments such as cepatic acid. Although this improves the balance between the two, it is still not sufficient. Furthermore, as the machining performance of pre-coated metals has improved, the scope of their use has expanded, and the requirements for the quality of pre-coated paints have become more demanding.) Expectations for paints with a good balance between processability and hardness are increasing.

<Problems to be Solved by the Invention> Generally, the processability, hardness, and stain resistance of a coating film are contradictory properties, and it is difficult to satisfy both.

In other words, by increasing the rigidity of the siborimer chain and increasing the Tg by introducing neopentyl glycol sane dimetatool, etc., and by increasing the content of the crosslinking agent, hardness and stain resistance improve, but the coating film becomes hard. Otherwise, the paint film will be damaged during the bending process. Further, if the concentration of the crosslinking agent containing soft segments and plasticizers is reduced, the coating film becomes flexible and the processability is improved, but the hardness and stain resistance are reduced.

The purpose of the present invention is to improve the balance of workability, hardness, and stain resistance while maintaining other basic performances as a paint such as weather resistance, water resistance, gloss, and adhesion, thereby satisfying both of them. An object of the present invention is to provide a polyester resin composition for metal coatings.

A study of various polyester compositions from this point of view revealed that 10 to 80 mol% of the polyol component was 1,9-nonanediol or 2-methyl-1,8-octanediol. The present invention was achieved by recognizing that a copolymerized polyester characterized in that 80 to 100 mol % of the acid component is an aromatic dicarboxylic acid achieves the above object. That is, 1
．． By copolymerizing 9-nonanediol or 2-methyl-1,8-octanediol with polyester,
The coating becomes more flexible and has increased workability, but the rate of decrease in hardness is small, and the overall balance between the two is improved. Furthermore, since the present invention uses a glycol having a long methylene chain in the polyol component, it does not reduce the aromatic ring concentration of the acid component, and provides favorable results in other properties such as weather resistance and water resistance.

1,9-nonanediol or 2- used in the present invention
The total amount of methyl-1,8-octanediol is 10 to 80 mol%, preferably 30 to 50 mol% of the polyol component. 1.9-nonanediol and 2-methyl-
1. If the amount of 8-octanediol used is small, the coating film will become hard, and even with a small amount of crosslinking agent, it will not be possible to obtain a product with good processability.On the contrary, 1,
When the amount of 9-nonanediol and 2-methyl-1,8-octanediol used exceeds 80 mol%, hardness cannot be achieved even if the amount of crosslinking agent is increased. 1 in polyester,
The ratio of 9-nonanediol and 2-methyl-1,8-octanediol can be any value between 100:0 and 0:100, but from the viewpoint of crystallinity, it is 9515-5.
It is preferable to use the mixture at a ratio of /95 from the viewpoint of balance for metal coating.

], 9-nonanediol and 2-mef Ru 1,8
- The polyol constituting the remaining component of octanediol is preferably divalent or trivalent or higher, and examples of divalent alcohols include ethylene glycol, 10
Pyrene glycol, trimethylene glycol, 1.4-
Examples include butanediol, 1,3-butanediol, neopentyl glycol 2,2,4-trimethyl-1,3-bentanediol, and cyclohexane dimetatool.

Examples of trivalent or higher polyols include trimethylolethane, trimethylolpropane, and pentaerythritol.

As the aromatic dicarboxylic acid, in addition to terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, or 4,4'-diphenylcarboxylic acid 8 can be used, but cyterephthalic acid or isophthalic acid is preferred from the viewpoint of weather resistance. A high content of these aromatic dicarboxylic acids is preferable in terms of weather resistance, water resistance, and solvent resistance, such as #1, but 20
Aliphatic dicarboxylic acids such as adipic acid, sepathic acid, and succinic acid may be contained as long as the amount is less than mol%. Further, trivalent aromatic acids such as trimellitic acid may also be included.

The total amount of trivalent or higher acid and polyol is α5 to 10 mol%
is preferred. If it is added in excess of 10%, the coating film will be brittle; on the other hand, if it is too small, the coating film will not be hard enough.

From the viewpoint of solubility, it is preferable to use a mixture of isophthalic acid and terephthalic acid instead of using one type of aromatic dicarboxylic acid alone. In this case, the amount of isophthalic acid is preferably 30 to 60 mol% of the total carboxylic acids, and the amount of terephthalic acid is preferably 30 to 60 mol% of the total carboxylic acids.

The copolyester of the present invention is conventionally PET-? P.I.
It can be produced by a known polymerization method, ie, transesterification or direct esterification followed by melt polycondensation reaction, and the catalyst used in this case is also the same. The molecular weight of the polymer is usually 0.2 to 1.5 (dl/
l ) +7) [circumference is 0.5 to 1.2 (ttV
I) is preferred. If the molecular weight is too low, the coating film will peel and processability will decrease. Furthermore, if the molecular weight is too high, the solubility in solvents will be reduced, and the viscosity of the solution will be high, resulting in poor coating properties.

The copolyester of the present invention is used in combination with a curing agent. Examples of the curing agent include polyfunctional 7-mino resins, isocyanates, epoxy compounds, etc., but alkyl etherified amino formaldehyde resins are preferred. Alkyl etherified amino formaldehyde resins include, for example, formaldehyde that has been alkyl etherified with an alkyl alcohol having 1 to 4 carbon atoms such as methanol, ethanol, n-10 panol, isopropanol, and n-butanol, or Hirobuff formaldehyde. It is a combination product with urea, N,N'-ethylene urea, dicyandiamide, aminotriazine, etc., specifically, methoxylated methylol urea, methoxylated methylol-N,
N'-ethylene urea, methoxylated methylol dicyandiamide, methoxylated methylol melamine, methoxylated methylol benzoguanamine, butoxylated methylol melamine, butoxylated methylol benzoguanamine, and the like.

From the viewpoint of processing performance, methoxylated methylolmelamine or butoxylated methylolmelamine is particularly desirable.

Ratio with monocopolymerized polyester curing agent is 90 to 70:10
~30 (weight ratio). If the proportion of the copolymerized polyester exceeds 90% by weight, the desired stain resistance and hardness will be insufficient, which is undesirable.

Moreover, if it is less than 7011fi%, post-processability will be poor, which is not preferable.

Any curing catalyst can be added to the composition of the present invention. When an alkyl etherified formaldehyde resin is selected as the curing agent, examples of the curing catalyst include p-toluenesulfonelkyl ester and amine salt of p-)toluenesulfonic acid. The amount of catalyst used is 0 to 5% by weight based on the formaldehyde resin.

Furthermore, the composition of the present invention generally includes ethyl acid, butyl acetate, methyl cellosolve, butyl cellosolve, dissolved in an organic solvent.
Methyl cellosolve acetate, methyl ethyl ketone, methyl isobutyl ketone, clohexanone, isophorone, ethylene glycol monoacetate, butanol, octatool, diacetone alcohol, carpitol acetate, methoxybutyl acetate, etc., arbitrarily selected depending on its solubility and evaporation rate. be able to.

In many cases, high-speed painting and high-temperature, short-time baking are performed in metal painting, which is the object of the present invention. s
boiling point of 100 to prevent paint film defects such as pinholes.
It is desirable to use a mixture of two or three or more kinds of solvents having a temperature of 0.degree. C. or higher. Generally, it is preferable to use 90 to 30% by weight of aliphatic hydrogen dihydride or aromatic hydrogen and 10 to 70% by weight of a polar solvent such as esters, ketones, and ethers.

The composition of the present invention exhibits sufficient performance when applied and baked by itself, but if further improvement in corrosion resistance is required, epoxy resin, such as commercially available Ebicor) can be used. 1001.1004.1009 (manufactured by Shell Chemical Co., Ltd.), Araldite 6097 (Chipa・
(manufactured by Geigy Co., Ltd.) etc. can be applied. Further, in order to improve the stain resistance of the sea layer of the composition of the present invention, an acrylic resin such as Lasdrazole A602-sos (manufactured by Dainippon Ink and Chemicals) may be used as a top coating agent. In this case 2
It is preferable to adopt a coat/two-bake method.

The temperature for baking the composition of the present invention may be arbitrarily selected depending on the size and thickness of the steel plate, the baking capacity of the furnace, the hardenability of the paint, etc.

Mixing machines such as roll kneading machines, ball mills, and grinders are used to produce coating compositions. When it comes to painting, roller painting, roll coater, spray painting, electrostatic painting, etc. are selected as appropriate.

Additives such as pigments such as titanium oxide, glass fiber silica, and wax may be added to the coating composition of the present invention depending on the purpose and use.

<Example> The present invention will be explained in more detail with reference to Examples below.

In the examples, the term ``part'' indicates a weight part, and the term % indicates weight %. Each measurement item was measured according to the following method.

(1) Reduced viscosity ηap/a (dl/I) 0.101 of the copolymerized polyester was dissolved in 200C of a mixed solvent of phenol/tetrachloroethane (volume ratio 6/4) and measured at 30°C.

(2) Hardness (Empty hardness) The painted surface of the steel plate was measured according to JIS K-5400 using a high-grade pencil specified in JIS S-6006.

(3) Bending degree The coated steel plate was bent by 180 degrees, and cracks occurring at the bent portion were determined. 2T indicates that no cracks will occur when two sheets of the same thickness are sandwiched in the bending section. IT indicates that no cracks will occur when one sheet of the same thickness is sandwiched between the bends. In addition, OT indicates that no cracks occur when the needle is bent directly without any pinching.

(4) Stain-resistant oil-based ink was applied to a coated surface of 0.5 cs x 23, and after being left at room temperature for 24 hours, the degree of staining was measured when wiped with gauze impregnated with toluene. O indicates good quality, Δ indicates slightly poor quality, and × indicates insufficient quality.

(5) Pheasant Roll Resistance (Solvent Resistance) Degreased Mllζ Pheasant Roll was rubbed on the coated surface and expressed as the number of times until the bare surface was exposed. ○ is 5oo "Example 1 324 parts of dimethyl terephthalate, 3245 parts of dimethyl isophthalate, 207 parts of ethylene glycol, 1.9
-240 parts of nonanediol, 1 part of neopentyl glycol
04fHr and titanium iso-10 booxide 0.2
A portion of the mixture was charged into a reaction vessel, and transesterification reaction was carried out at 200°C for 2 hours. Next, 9 parts of trimethylolpropane was added, the temperature was raised to 250°C, and after reaction for 30 minutes, the pressure was reduced to 20 rmHf for 30 minutes, and the pressure was further reduced to 0.3 wsH9 for 60 minutes.
A partial polycondensation reaction was performed. The obtained copolymerized polyester (
As a result of compositional analysis using NMR, 4) has a molar ratio of terephthalic acid/isophthalic acid = 50,750.

Ethylene glycol/neopentyl glycol 1,9-
Nonanediol/trimethylolpropane = 3 8/
It was 267'34/2, pale yellow and transparent with a reduced viscosity of 0.50 dt/f/.

Thereafter, a copolymerized polyester CB) whose polymer composition is shown in Table 1 was synthesized in the same manner.

*The abbreviations are as follows: TA: terephthalic acid, IPA: isophthalic acid, TMA nitrimellitic acid, SbA: cepatic acid, EG: ethylene glycol, NPG: neopentyl glycol, HD: ], ]6-hexanediol ND: 1. 9-nonanediol, MOD: 2-methyl-1,8-octanediol, TM
P:) Limethylolpropane, BP: Bisphenol A 2,2M ethylene oxide adduct copolymerized polyester (4) ~ (Foundation), respectively, in a mixed solvent of cyclohexanone/Turupetz-150 (volume ratio 5075G)
), and the nonvolatile content was adjusted to 40%.

100 parts of the above copolyester solution, 4 parts of titanium oxide
0 parts, methyl etherified methylolmelamine (trade name:
Sumimaru M-408. In a ball mill, 10 parts of non-volatile content 8096 (manufactured by Sumima Kagaku Kogyo), 0.5 parts of p-)luenesulfonic acid solution (benzyl alcohol 20 wt% solution) and 0.20 parts of Polyflow S (manufactured by Kyoeisha Yushi Kagaku Kogyo) were mixed in a ball mill. ! The mixture was kneaded at night to obtain a composition for metal coating.

Copolymerized polyester (4) of copolymerized polyester) ~
Alternatively, as an alkyl etherified amino formaldehyde resin, methyl etherified methylol melamine can be used as butyl ether melamine (trade name: Varnish-Perbeckamine J-820).
.

The coating compositions shown in Table 2 were similarly obtained in place of the coating compositions (manufactured by Dainippon Ink & Chemicals).

The obtained coating composition was applied to a 0.3-thick galvanized iron plate (JI
After coating S a-3302) on a test piece treated with zinc phosphate solution to a film thickness of 15 to 20μ, 2)
9. Bake at 0℃ for 2 minutes. The test results of the obtained coated steel plate are shown in Table 2. As is clear from Table 2, the coating composition of the present invention is excellent in flexibility and other physical properties as a coating material.

Margins below <Effects of the Invention> As explained above, according to the present invention, the resin composition has an excellent balance between hardness and processability, and is excellent as a paint for metal coating with excellent stain resistance and solvent resistance. You can get things. When this composition is used particularly for pre-coated metal, it is not only possible to obtain a steel plate with high hardness and easy processing, but also a coating film with excellent weather resistance and water resistance can be obtained.

Patent applicant RiRashi Co., Ltd.

Claims (1)

[Scope of Claims] 1) At least 80 mol% of the acid component consists of an aromatic dicarboxylic acid, and 10 to 80 mol% of the polyol component consists of 1,9-nonanediol and/or 2-methyl-1,8
- A polyester resin composition comprising a polyester resin made of octanediol and a curing agent mixed in a ratio of 90 to 70:10 to 30 (weight ratio). 2) The polyester resin composition according to claim 1, wherein the curing agent is an alkyl etherified aminoformaldehyde resin. 3) The total amount of trivalent or higher acid and/or trivalent or higher polyol is 0.5 with respect to the acid component and/or polyol component.
The polyester resin composition according to claim 1 or 2, wherein the polyester resin is used in an amount of ~10 mol%. 4) The polyester resin composition according to claim 1, 2 or 3, wherein the polyester resin composition is used for metal coatings.