KR20010060093A - Highly hardness and highly processible film forming coating composition for P.C.M. - Google Patents

Abstract

PURPOSE: A paint composition for pre-coated metal, that is P.C.M. is provided to increase hardness and continue high workability compared with existing composition by containing polystyrene aryl alcohol resin together with a mixture of high molecular linear polyester and low molecular polyester resins. CONSTITUTION: The paint composition comprises 10-15 wt.% of linear polyester resin having the number mean molecular weight of 20,000-45,000, 5-10mgKOH/g of hydroxyl value, 3-7mgKOH/g of acid value and less than 60 deg.C of the glass transition temperature; 3-10 wt.% of low molecular weight polyester resin having the number mean molecular weight of 1,000-3,000, 150-250mgKOH/g of hydroxyl value, 1-30mgKOH/g of acid value and -15 to 10 deg.C of the glass transition temperature; and 3-5 wt.% of polystyrene aryl alcohol resin having the number mean molecular weight of 1,500-3,000 and more than 60 deg.C of the glass transition temperature.

Description

High hardness and highly processible film forming coating composition for P.C.M.}

The present invention relates to a coating composition for high hardness and high processability PCM, and more particularly, to use a mixed resin composed of a linear molecular resin having a large molecular weight and a low molecular weight polyester resin. And, by containing a polystyrene aryl alcohol resin, the present invention relates to a PCM coating composition that maintains high processability while increasing the hardness compared to the conventional PCM coating composition.

PCM steel sheet for home appliances requires excellent workability and hardness compared to steel plates for building materials. However, since these two physical properties are difficult to obtain at the same time, paint companies have continued to pay attention to the development of paint to maintain the hardness of the coating while giving the processability required for low temperature processing.

Conventional PCM steel sheet products have been widely used as a coating composition containing a polyester resin as a base resin and a melamine resin or isocyanate compound as a crosslinking agent, and a small amount of additives such as a curing catalyst and an antifoaming agent and a leveling agent. In the paint composition, a polyester resin having a linear structure having a low glass transition temperature (Tg) was used to provide workability so that cracks do not occur during processing of the steel sheet. However, when the linear polyester resin is used, the workability of the coated steel sheet coating film is good, but since the hardness of the coating film is low, the surface of the coating film is damaged due to the contact between the steel sheets during the processing or transportation of the steel sheet or by manual labor. There has been a problem.

In order to solve this problem, a method of attaching a protective film to the coating film is used after the manufacture of the PC steel sheet, but the protective film is not only expensive, but the coating film is damaged by the user's contact when using the home appliance after removing the protective film. The problem still remains.

Therefore, a method of using a branched polyester resin having a high glass transition temperature has been introduced to improve the hardness of the coating film, which is the above problem.

At the beginning of the method, a linear polyester resin having a hydroxyl value of 40 to 90 mgKOH / g and a branch polyester resin were used as a main component polyester resin, and a butylated melamine resin or an isocyanate resin was used as a crosslinking agent. .

Then, in order to impart hardness, processability and non-pollution property, a methyl etherified melamine resin or a butyl etherated melamine resin having an amino group or a methoxy group was mixed and a sulfonic acid compound and an amine compound were used as a curing catalyst.

When the branched polyester resin is used, the hardness is improved, but since the ductility of the coating film itself is reduced, cracks occur in the coating film during forming / processing of the steel sheet, and the steel sheet is exposed, and the steel sheet corrodes when it comes into contact with moisture. Problems occur.

For this reason, paints mainly made of linear polyester resins are used for PMM steel plates that require severe bending and processing.However, high hardness of coating films made mainly of branch polyester such as refrigerators are used for parts with small processing / molding degree such as refrigerators. Since the coating composition is selectively used, it was still difficult to overcome the opposing physical properties such as hardness and workability of the coating film.

In order to solve this problem, the present invention uses a mixture of a linear polyester resin having a higher molecular weight and a lower molecular weight polyester resin than a linear polyester resin currently used in a coating composition, and using styrene aryl alcohol. It aims at providing the coating composition for PCM excellent in the surface slip property and hardness of a coating film, maintaining the processability equivalent to the existing coating material by raising the hardness of a coating film using a small quantity.

The present invention provides a coating composition for PCM containing a resin component, a crosslinking agent, a solvent, a curing catalyst, and an additive,

As the resin component, a linear polyester resin having a number average molecular weight of 20,000 to 45,000, a hydroxyl value of 5 to 10 mgKOH / g, an acid value of 3 to 7 mgKOH / g, and a glass transition temperature of 60 ° C. or less is 10 to 15% by weight in the total composition,

3-10 wt% of the low molecular weight polyester resin having a number average molecular weight of 1,000 to 3,000, a hydroxyl value of 150 to 250 mgKOH / g, an acid value of 1 to 30 mgKOH / g, and a glass transition temperature of -15 to 10 ° C; And,

It is characterized by the high hardness and high processability PMC coating composition which contains 3 to 5 weight% of polystyrene aryl alcohol resins with a number average molecular weights 1500-3000 and a glass transition temperature of 60 degreeC or more.

The present invention will be described in more detail as follows.

The polyester resin (A) used in the present invention is a linear polyester resin prepared using polyol and polybasic acid as monomers. It is preferable that the said resin has a number average molecular weight of 20,000-45,000, a hydroxyl value of 5-10 mgKOH / g, an acid value of 3-7 mgKOH / g, and a glass transition temperature (Tg) of 60 ° C in molecular weight. . Examples of the resin (A) may include LS415 of Hums Corporation, GK290 of Toyobo Corporation, and the like. If the molecular weight of the linear polyester resin is out of the above range, or if the acid value and acid value of the linear polyester resin is out of the above range, there is a problem that the hardness of the surface of the coating film is lowered or cracks are generated during processing have. Moreover, when the glass transition temperature of the said linear polyester resin is out of said range, the problem of the workability of a coating film falls.

In the present invention, the linear polyester resin (A) is used in an amount of 10 to 20% by weight, preferably 10 to 15% by weight in the total coating composition. This is because the hardness of the surface of the coating film is lowered when used in excess of 20% by weight.

In addition, the low molecular weight polyester resin (B) used in the present invention is a high gloss, high gloss when forming a coating film, and is used as a raw material having excellent stain resistance. In the present invention, the polyester resin has a number average molecular weight of 1,500 to It is 3,000, a hydroxyl value is 150-200 mgKOH / g, and when it considers hardening reactivity, it is preferable to use that whose acid value is 1-30 mgKOH / g. If the molecular weight of the polyester resin is lower than the above range, there is a problem that the processability of the coating film is lowered, and if the hydroxyl value and the acid value of the polyester resin is higher than the above range, appearance defects and paping due to rapid hardening at high temperature and small portions Popping may occur. In addition, although the glass transition temperature of the said resin is -15-10 degreeC, when it exceeds 10 degreeC, the processability of a coating film will fall, and below -15 degreeC, a coating film hardness will fall, and the said range is preferable. In this invention, it is preferable to use the said polyester resin (B) at 3 to 10 weight% in all the coating compositions. At this time, if the content is less than 3% by weight, the hardness of the coating film is lowered. If the content is more than 10% by weight, the crosslinking degree of the coating film is high, resulting in poor processability of the coating film, poor smoothness, poor anti-foaming property, and popping. It is not preferable for such a problem. Examples of the resin (B) include HS 706, H7 13, and SN 843 of DSM resin.

In particular, the present invention is characterized by using a polystyrene aryl alcohol resin (C) in addition to the polyester mixed resin to increase the coating film hardness while maintaining the workability of the coating film, and to increase the gloss of the coating film. The polystyrene aryl alcohol (C) has a molecular weight of 1,000 to 4,000, preferably 1,500 to 3,000, a glass transition temperature of 60 ° C. or more, preferably a hydroxyl value of 200 to 220 mgKOH / g and an acid value of 0 to 6 mgKOH / g. . Here, when the molecular weight of the said resin is less than 1,000, the workability of a coating film will fall, and when molecular weight exceeds 4,000, compatibility with polyester mixed resins (A, B) will fall, poor appearance, and glossiness of a coating film will fall. In the present invention, the polystyrene alcohol resin is preferably such that 3 to 5% by weight in the total coating composition. The limit of this range is not expected to increase the hardness of the coating film when using the resin (C) less than 3% by weight, it is preferable to use in the above range because the workability of the coating film is lowered when used in excess of 5% by weight. . Examples of the resin (C) include SAA 100, SAA 101 from Arco Chemical, RJ-100, RJ-101 from Monsanto, and the like.

In addition, in the present invention, it is preferable to use a melamine resin as a crosslinking agent for forming the coating film with the resins (A, B, C), and the conventional isocyanate resin is preferable because yellowing phenomenon occurs in a high temperature baking type. Not. Melamine resins include melamine resins containing amino or butoxy groups and melamine resins containing methoxy groups. Melamine containing an amino group or butoxy group is advantageous in hardness of the coating film, but when acid catalyst is used, the reaction rate is slightly slower than that of methoxy melamine resin, and the processability is lowered, whereas methoxy melamine resin is disadvantageous. When used with an acid catalyst, the curing reaction rate is fast, and the processability of the coating film is excellent, but the hardness of the coating film is poor compared to melamine containing an amino group or butoxy group. Therefore, in the present invention, in order to maintain a balance between the hardness and workability of the coating film, it is preferable to use a mixture of the amino type or butoxy type melamine resin and the methoxy type melamine resin at 0.3: 1 to 0.5: 1. In this case, when the mixing ratio of the two melamine resins is less than 0.3: 1, the workability of the coating film is good, but there is a problem that the surface hardness of the coating film is lowered. When the mixing ratio of the two melamine resins is more than 0.5: 1, the workability of the coating film is poor. There is a big problem. In this invention, it is preferable to use melamine resin in 3 to 13 weight% of all the coating compositions, and when it is less than this range, hardening will be inadequate and coating film properties will fall, and when this range is exceeded, the processability of a coating film will fall. have.

Examples of the amino type or butoxy type melamine resin include Cymel 325, Cymel 327, BIP's BE 3748, BE 3040, Monsanto's RESIMENE 717, and the methoxy type melamine resin is Sytec 303's Melel 303. , Cymel 301, BIP's BE 3747, BE 3745, and Monsanto's RESIMENE 745.

In addition, the solvent used in the present invention is used in consideration of the characteristics, such as when handling, coating work for the coating composition of the present invention, such solvents are aromatic hydrocarbons, glycol esters, glycol ethers, alcohol solvents and Mixtures of these can be used. The solvent is preferably to be contained 44 to 64% by weight in the total coating composition, the reason for limiting this range is that if the content of the solvent is less than 44% by weight, the viscosity of the paint is high, the air bubbles in the roll coating This is because there is a problem in that the appearance is poor, if the content exceeds 64% by weight, the viscosity of the paint is too low there is a problem that the roll coating operation is impossible.

The aromatic hydrocarbon solvents include Cocosol # 100, Cocosol # 150, and glycol ester solvents include ethyl acetate, n-butyl acetate, cellosolve acetate, propylene glycol monomethyl acetate, 3-methoxy butyl acetate, and the like. For example. Glycol ether solvents include methyl cellosolve, ethyl cellosolve, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, and alcohol solvents such as ethanol, isopropanol, n-butanol Amyl alcohol, cyclohexanol, etc. are mentioned.

The curing catalyst used in the present invention includes at least one neutralization product neutralized with amine or epoxy by selecting from p-toluene sulfonic acid, dinonyl naphthalene sulfonic acid (DNNSA), dinonylnaphthalene disulfonic acid (DNNDSA), and fluoro sulfonic acid. You can choose to use it. In this case, when the catalyst which is not neutralized by amine or epoxy is used as the curing catalyst, since the viscosity increases after storage of the paint or the physical properties of the coating are poor, it is preferable to use a catalyst neutralized with the amine or epoxy as described above. . Examples of the p-toluene sulfonic acid include King's NACURE 2500, NACURE 2510, and NACURE 2530. DNNSA includes King's NACURE 1323, NACURE 1419, and NACURE 1557. DNNDSA includes NACURE 3525, NACURE 3525 and NACURE 3327. Examples of fluoro sulfonic acid include FC 520 of 3M.

In the present invention, the slip additive used for the surface of the coating film is added to prevent scratches caused by the worker during the forming of the steel sheet, or by the nail of the user of the home appliance, and the like, and is based on polyethylene wax or polytetrafluoroethylene (PTFE). ) Wax can be used. The polyethylene wax should be used in an amount of 3 to 5% by weight in order to provide sufficient slip property to the coating film. In this case, as the content of the polyethylene wax increases, the gloss of the coating film is lowered. In addition, when PTFE wax is used, sufficient slipperiness can be obtained without lowering the coating film hardness. However, when the PTFE wax particles are too large, the appearance of the coating film is poor, and therefore it is preferable to have a particle size of 10 mu m or less. Therefore, in the present invention, since the gloss of the coating film is lowered when the amount of the PTFE wax is 3% by weight or more, 0.3 to 1.0% by weight is used in the overall coating composition. When the conventional silicone oils are used as slip additives, the surface tension of the silicone oils is so low that the continuous roll coating workability becomes poor, so it is not preferable to use the silicone oils.

In addition, the paint additive used in the present invention is added to improve the workability, it can be used in the 0.1 to 1% by weight of clay, amide wax, fume silica. In addition, it is preferable to use an acrylic, vinyl, silicone-based leveling agent and an antifoaming agent in an amount of 0.5 to 1.0 wt%, respectively, in order to maintain coating film smoothness and improve antifoaming during painting. Examples of the leveling agent and the antifoaming agent include L 1980, L 1984, AP 30, BYK 356, BYK 410, etc. of Disparon Corporation.

In addition, the paint composition of the present invention may be used as a transparent paint composition containing no pigment, but is generally used as a paint composition containing a conventional pigmented pigment. As such pigments, organic pigments such as cyanine blue and cyanine green, which are conventional coloring pigments usable in the field of coating compositions, and inorganic pigments such as titanium oxide, iron oxide, carbon black, chrome yellow and various plastic pigments may be used. In addition, the paint composition of the present invention may include a sieving pigment, such as talc, clay, silica, mica, alumina, fillers.

Although this invention is demonstrated in detail based on an Example, this invention is not limited to the following Example.

Example 1

To prepare a coating composition according to the composition shown in Table 1, the manufacturing process is as follows.

Linear polyester resin LS-415 (13 g, Hew's) was put in a tin can, and cellosolve acetate (9 g) was added, followed by stirring sufficiently. Titanium oxide (27 g, CR-95, TIPAQUE Co., Ltd.) was slowly added to the solution, followed by stirring. When stirring was completed, glass beads having a diameter of 2-3 mm were added thereto and sufficiently dispersed in a shake-type disperser for 2-3 hours ( At this time, the dispersion was terminated when measured to grind (Grind Gage) when dispersed to less than 5 ㎛). LS 415 (20 g) and HS 706 (8 g) were added to the solution, and Cymel 303 (2.7 g) and Cymel 325 (1.3 g) were added thereto and stirred. Cocosol # 100 (9 g) was added to the vein and stirred, and cyclohexanol (1.25 g) was added thereto and stirred. As an additive, L-1984 (0.45 g) and AP-30 (0.45 g) were added and stirred. SAA 100 (3.5 g, Arco Chemical Co., Ltd.) was added to a separate container, cyclohexanol (3.5 g) was added thereto, and the mixture was stirred while gradually heating to dissolve sufficiently. After stirring until there was no resin solid content, the mixture was slowly cooled and added to the paint. As an acid catalyst, a parasulfonic acid neutralization product (0.15 g) and a neutralization product of dinonyl naphthalene sulfonic acid (0.35 g) were added and stirred.

As a result, 100 g of coating composition was obtained.

Examples 2-3 and Comparative Examples 1-7

Manufactured in the same manner as in Example 1, the raw material supplied in a solid state was mixed in a ratio of 1: 1 with an organic solvent in a separate container and then stirred while raising the temperature to prepare a liquid phase and then used for preparing the paint. .

(week)

1.LS-415: Product made by U.S. Hulls, 40 wt% solids, number average molecular weight 25000, glass transition temperature 15 ℃, acid value 3 mgKOH / g, hydroxyl value 5 mgKOH / g

2. HS-706: Product made by U.S. Herth, 80 wt% solids, number average molecular weight 1000, glass transition temperature -15 ° C, acid value 1-15 mgKOH / g hydroxyl value 200 mgKOH / g

3.KK-290: Japan Toyobo Co., Ltd., 100% by weight solids, number average molecular weight 30000, glass transition temperature 54 ℃, acid value 5 mgKOH / g, hydroxyl value 7 mgKOH / g

4. LH-828: manufactured by USA HULSE, 70 wt% solids, number average molecular weight 2000, glass transition temperature 10 ° C, acid value 1-10 mgKOH / g, hydroxyl value 50 mgKOH / g

5. SAA 100: The polystyrene aryl alcohol resin which is an Arco Chemical company, a number average molecular weight 1500, an acid value 210 mgKOH / g, and a hydroxyl value of 5-6 mgKOH / g.

6. Cymel 303: A low molecular weight melamine resin produced by Seatec, having a number average molecular weight of about 500 and a methoxy melamine content of 98% by weight.

7. Cymel 325, manufactured by Texa, having a number average molecular weight of about 500, methyl etherified and iminized melamine resin.

8. CR 95: Product made by TIPAQUE, titanium oxide.

9. Cocosol # 100: Perforated product, aromatic organic solvent.

10. Cellosolve Acetate: Eastman-Kodak Products.

11. Cyclohexanol: Eastman-Kodak product.

12. CERAFLOUR 996: Polytetrafluoroethylene / Polyethylene Wax Mixture Powder, manufactured by BEIKA.

13. CERAFLOUR 991: Products from Biwaike. Polyethylene Wax Powder.

14. Disparon L-1980: manufactured by Kusumoto Chemical Co., Ltd., acrylic polymer type leveling agent.

15. Disparon AP30: Kusumoto Chemical Co., Ltd., Acrylic Polymer Type Antifoaming Agent

16. P-toluene sulfonic acid neutralization product: Neutralizing product of p-toluene sulfonic acid and di-n-butyl amine with a neutralization equivalent of acid and amine of 1.0.

17. Dinonyl naphthalene sulfonic acid neutralization product: Neutralizing product of dinonyl naphthalene sulfonic acid and dimethyl oxazolidine, the neutralization equivalent of acid and amine is 1.0.

Experimental Example

Preparation of Test Specimen

0.5 T of EGI steel sheet was degreased with methyl ethyl ketone, and coated with a bar coater so as to have a dry coating thickness of 6 µm, FP-1809 [Korea Chemical], followed by baking in Examples 1 to 3, The coatings of Comparative Examples 1 to 7 were bar-coated to have a dry coating thickness of 20 μm, followed by baking for 35 seconds at an ambient temperature of 280 ° C. to prepare a physical test specimen. Before coating, the paint was diluted with a coating viscosity (Pod Cup No. 4, 80 seconds at 25 ° C) and coated with a bar coater.

Coating property measurement

The coating film physical properties of Examples 1 to 3 and Comparative Examples 1 to 7 were measured by the following method, and the results are shown in Table 2 below.

[Test Methods]

1. Glossy

It measured using the 60 degree polisher [BYK-GARDNER company].

2. Pencil Hardness

It was evaluated according to the trace formed by carrying out pencil hardness test using a machine according to JIS K5400 8.4.1.

3. Processability

After the T-bending test, the specimen was observed for the state of the coating film, and the number of bendings where cracking did not occur was compared.

4. Adhesiveness

The coating film was cut into 100 squares at 1 mm intervals, and then lightly tapped to compare the number of coating films remaining without peeling.

5. Pollution resistance

After marking the coating film with red, blue, and black oily magic, rubbing with xylene and isopropanol, and evaluating the presence of marking marks (◎: excellent, ●: good, ×: poor).

6. Alkali resistance

5% aqueous NaOH solution was dropped on the coating film, and the lid was capped so that the aqueous solution did not evaporate. After 48 hours at 25 ° C., the coating film was evaluated (◎: no abnormality, ●: gloss reduction, ×: swelling). .

7. Acid Resistance

5% aqueous HCl solution was dropped on the coating surface, and the cover was capped so that the aqueous solution did not evaporate. After 48 hours at 25 ° C, the condition of the coating surface was evaluated (◎: no abnormality, ●: gloss reduction, ×: swelling). .

8.slipness

The surface of the coating film of the specimen was scraped with a fingernail for relative evaluation (?: No abnormality,?: Gloss reduction, x: swelling occurred).

As described above, when the coating composition of the present invention is used for PCM, it is possible to obtain a coating film having excellent surface slip properties and hardness while maintaining processability equivalent to existing paints.

Claims (4)

In the coating composition for PCM containing a resin component, a crosslinking agent, a solvent, a curing catalyst, and an additive, As the resin component, a linear polyester resin having a number average molecular weight of 20,000 to 45,000, a hydroxyl value of 5 to 10 mgKOH / g, an acid value of 3 to 7 mgKOH / g, and a glass transition temperature of 60 ° C. or less is 10 to 15% by weight in the total composition, 3-10 wt% of the low molecular weight polyester resin having a number average molecular weight of 1,000 to 3,000, a hydroxyl value of 150 to 250 mgKOH / g, an acid value of 1 to 30 mgKOH / g, and a glass transition temperature of -15 to 10 ° C; And, A polystyrene aryl alcohol resin having a number average molecular weight of 1500 to 3000 and a glass transition temperature of 60 ° C. or more is contained in the total composition at 3 to 5% by weight. The method of claim 1, wherein the crosslinking agent contains 2 to 8% by weight of a methyl etherified melamine resin having a methoxy group and 1 to 5% by weight of a methyl etherified melamine resin having an amino group or a methoxy group in the total composition. Paint composition for PC, characterized in that it is. The method of claim 1, wherein the curing catalyst is one or more obtained by neutralizing sulfonic acid selected from p-toluene sulfonic acid, dinonyl naphthalene sulfonic acid (DNNSA), dinonylnaphthalene disulfonic acid (DNNDSA), and fluoro sulfonic acid by amine or epoxy. Coating composition for PC, characterized in that the neutralization product. The coating composition of claim 1, wherein the additive contains polytetrafluoroethylene wax powder pulverized to 10 µm or less in an amount of 0.3 to 1.0 wt% in the total composition.