KR20040073670A - Copolymeric polyester resin and coating composition containing it - Google Patents

Abstract

PURPOSE: A copolymerized polyester resin which is suitably applied as a paint for a coated steel plate is provided to improve weather resistance, chemical resistance and film hardness, thereby helping to prevent the film from being damaged, by using controlled amount of aromatic, aliphatic and alicyclic acid components. CONSTITUTION: The copolymerized polyester resin comprises: as acid components, 0-30mol% of one or more alicyclic acid component selected from 1,4-cyclohexane dicarboxylic acid, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride and ester derivatives thereof, 60-95mol% of one or more aromatic acid component selected from phthalic anhydride, terephthalic acid, isophthalic acid, trimaleic anhydride and ester derivatives thereof, and 5-40mol% of an aliphatic acid component selected from adipic acid, succinic acid, succinic anhydride and sebacic acid represented by the general formula 2: HOOC-(CH2)nCOOH, wherein n is an integer of 2-10; as a polyhydric alcohol component, 60-95mol% of a compound represented by the general formula 1, wherein R1 and R2 is hydrogen or alkyl group having C1-4, provided that at least one of R1 and R2 may be an alkyl group; 0-30mol% of a secondary alcohol other than the compound represented by the formula 1; and 1-10mol% of tertiary or more orders of an alcohol.

Description

Copolymer polyester resin and coating composition containing the same

The present invention relates to a copolyester resin and a coating composition containing the same useful as a binder resin of a paint for coating steel sheet, and more particularly, by adjusting the acid component and the polyhydric alcohol component to a new composition, damage to the coating film due to ultraviolet rays during external exposure. The present invention relates to a copolymerized polyester resin for weathering paint having excellent press formability (hereinafter processability), corrosion resistance and chemical resistance while suppressing

In general, the paint for coating steel sheet is an important factor such as press workability, adhesion to the steel sheet, corrosion resistance, chemical resistance and the like.

Alkyd resins, acrylic resins, fluororesins, silicones and silicone modified resins are used for this purpose, but alkyd resins have poor corrosion resistance and weather resistance, acrylic resins have poor workability, and silicone and silicone modified resins have weather resistance. Although it is excellent, its use is very limited due to the difficulty of line work due to silicon dust and the like, and is currently being replaced by many polyester resins.

However, polyester resins exhibit excellent physical properties in processability, appearance, chemical resistance, corrosion resistance, etc., but have a disadvantage in that they are inferior to acrylic or silicone type resins in terms of weather resistance.

Generally, the polyester resin was applied by applying the polyester copolymer which mixed aromatic carboxylic acid, such as isophthalic acid, and aliphatic carboxylic acid practically. However, while the aromatic acid of the polyester resin has good coating properties, the aliphatic acid has excellent processability but also provides a cause of relatively poor corrosion resistance, chemical resistance and weather resistance.

However, in order to solve the workability problem of the coating steel coating resin, the fact that aliphatic acid is a very useful raw material also causes many difficulties in development.

Therefore, the present invention provides an excellent coating film glass transition temperature and a dense coating structure in the manufacture of paint through the combination of a predetermined amount of aliphatic acid, cycloaliphatic acid, and selected alcohol raw materials, while having an aromatic acid as a main component that provides excellent mechanical properties. An object of the present invention is to provide a copolyester resin having excellent durability against overheating and environmental impact and mechanical strength of a coating film.

In other words, when only aromatic raw materials were applied in the past, excellent mechanical properties (hardness, gloss, chemical resistance, etc.) were confirmed, but a certain amount can be compensated for to solve problems such as processability, solvent power, and painting workability. The aliphatic acid was introduced and the weathering part concerned by this was supplemented as much as possible from the glycol side, and the aliphatic acid was selectively used to solve the durability and weatherability of the coating film at the same time.

In other words, it is an object of the present invention to provide a copolymer having excellent processability and excellent coating strength and weather resistance, particularly chemical resistance, by combining aliphatic acid with short chain length and aromatic acid in an appropriate ratio.

In addition, the present invention is to provide a polyester resin excellent in the chemical properties of the coating film and excellent weather resistance through a change in the raw material composition while satisfying the general physical properties of the paint for the coated steel sheet mentioned above.

Polyester resin of the present invention for achieving the above object is 1,4-cyclohexane dicarboxylic acid, hexahydro phthalic anhydride, methylhexa hydrophthalic anhydride, methyltetrahydrophthal as the acid component 0-30 mol% of one or two or more selected from alicyclic acid components such as talic anhydride, tetrahydrophthalic anhydride and ester derivatives thereof, phthalic anhydride, terephthalic acid, isophthalic acid, anhydrous 60 to 95 mol% of one or two or more selected from trimaleic acid and ester derivatives thereof and 5 to 40 mol% of aliphatic acid components selected from adipic acid, succinic acid, succinic anhydride, and sebacic acid represented by the following formula (2): 60 to 95 mol% of a compound represented by the following Chemical Formula 1 as a polyhydric alcohol component, except a compound represented by the following Chemical Formula 1 It is characterized by containing 0-30 mol% of dihydric alcohol, and 1-10 mol% of alcohol which has a trivalent or more reactor.

Formula 1

Wherein R ₁ and R ₂ represent H (hydrogen) or an alkyl group having 1 to 4 carbon atoms, provided that one of R ₁ and R ₂ must be an alkyl group.

Formula 2

HOOC-(-CH _2- ) _n -COOH

Where n is an integer from 2 to 10

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

The present invention uses 60 to 95 mol% of aromatic acids such as isophthalic acid, phthalic anhydride or ester derivatives thereof as the acid component, and 5 to 40 mol% of aliphatic acids such as adipic acid, sebacic acid and succinic acid. 1,4-cyclohexane dicarboxylic acid, hexahydro phthalic anhydride, methylhexa hydrophthalic anhydride, methyltetra hydrophthalic anhydride, tetra hydrophthalic anhydride and esters thereof 0-30 mol% of alicyclic acids like derivatives are used.

At the same time, 60 to 95 mol% of a compound represented by the following Chemical Formula 1 as a polyhydric alcohol component, 0 to 30 mol% of a dihydric alcohol except the compound represented by the above Chemical Formula 1, and 1 to 10 mol% of an alcohol having a trivalent or higher reactor It is characterized by including.

Specifically, in the preparation of the copolyester of the present invention, as the polyhydric alcohol component, the compound represented by the formula (1) contains 60 to 95 mol% of the total alcohol raw material composition.

When using a raw material having an H (hydrogen) group of R ₁ , R ₂ in the general formula (1) compared to the raw material composed of both alkyl groups R ₁ , R ₂ has no difference in weather resistance, but is advantageous for high solidification of the resin and with a curing agent In curing, the reactivity is improved, and there is an advantage that the coating film hardness and scratchability can be improved.

Examples of the alcohol represented by Formula 1 include neopentyl glycol, methyl propanediol, butyl ethyl propanediol, and the like.

If the content of such an alcohol compound is less than 60 mol% of the total alcohol raw material composition may have a problem that the weather resistance is reduced.

Others such as 1,6-hexanediol, propylene glycol, diethylene glycol, triethylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,4-cyclohexanedimethanol, butylethylpropanediol Since the dihydric alcohol can be added, the content thereof is preferably 0 to 30 mol% in the total alcohol raw material composition. If the content is more than 30 mol% There may be problems in physical properties such as chemical resistance, solubility, weather resistance, and the like.

In addition, a bar having an alcohol having a trivalent or higher reactor is included, and specific examples thereof include trimethylolpropane, trimethylolethane, ditrimethylolpropane, and the like.

The reason for using an alcohol having a trivalent or higher reactor among the alcohol components is that the coating film hardness and chemical resistance may be lower than that of using an aromatic raw material due to the characteristics of the aliphatic raw material by adjusting the gel density when thermosetting with the melamine resin during high temperature drying to form the final coating film. This is because a certain gel density may be a factor to improve weather resistance.

However, when 10 mol% or more of the raw material having a trivalent or higher reactor among alcohol components is used, the processability, which is a main characteristic of the coated steel sheet, is poor, and thus it is not possible to add a product value.

Therefore, the content is preferably 1 to 10 mol% in the total alcohol raw material composition.

On the other hand, 1,4-cyclohexane dicarboxylic acid, hexahydro phthalic anhydride, methylhexa hydrophthalic anhydride, methyl tetrahydro phthalic anhydride, And one or two or more alicyclic acid components such as tetrahydrophthalic anhydride and ester derivatives thereof.

It is preferable that such an alicyclic acid component is added in 0-30 mol% among all the acid components.

And phthalic anhydride, terephthalic acid, isophthalic acid and trimaleic anhydride and ester derivatives thereof, which are classified as aromatic acids, are contained in 60 to 95 mol% of the total acid components, and if the content is less than 60 mol%, workability and coating film There may be problems with hardness deterioration.

And, including the aliphatic acid represented by the formula (2), when the content of the aliphatic acid exceeds 40 mol% of the total acid component is the cause of poor coating film hardness, chemical resistance and weather resistance. However, it is possible to compensate pigment dispersibility and processability by using a certain amount, but it is necessary to adjust the amount of use very carefully according to the resin composition because it has a structure that affects the chemical and weather resistance of the resin much. Specific examples of the aliphatic acid represented by Formula 2 include adipic acid (AA), succinic acid and succinic anhydride, sebacic acid, and the like.

In order to esterify the acid component of the composition and the polyhydric alcohol as described above, it is preferable to use a catalyst. As the catalyst, acetate compounds of Ca, Ce, Pb, Mn, Mg, Sb and Sb ₂ O ₂ , GeO _2, etc. use.

The copolyester resin of the present invention thus obtained has a number average molecular weight of 2000 to 6500, preferably 2500 to 6000. If the number average molecular weight of the copolymerized polyester resin is less than 2000, the hardness, chemical resistance, water resistance, etc. are poor, and if the molecular weight is greater than 6000, the curing density decreases and the hardness begins to decrease. It causes problems with the appearance of the coating. Therefore, in order to exhibit excellent paint workability and weather resistance, it is preferable to have a number average molecular weight of 2500-6000 preferably.

Copolymerized polyester resin was prepared by a known method using such components, and the copolymerized resin obtained in the present invention has excellent processability and chemical resistance, particularly weather resistance, as mentioned above, and is useful as a binder for film coating of various coated steel sheets. In addition, it can be usefully used as a binder resin excellent in coating film hardness and weather resistance even when applied as an automotive upper paint.

The coating composition applicable to the upper part of the vehicle is prepared by blending the above polyester resin with a pigment, a curing agent, a curing catalyst, an antifoaming agent, a dispersing agent and other conventional additives, and the curing agent used in the coating composition is a polyisocyanate curing agent, amino Formaldehyde or urea resins can be used.

Hereinafter, the present invention will be described in detail with reference to Examples. However, the rights of the present invention are not limited to the following examples.

Examples 1-3

A four-necked flask, thermometer, mantle, stirrer, column, vacuum pump and the like were prepared, and the acid and alcohol components and catalyst were added to the composition shown in the following Table 1, and the mixture was stirred under nitrogen inlet, and gradually heated up to 240 ° C. at room temperature.

When the condensed water is removed as the reaction proceeds, the acid or alcohol component in the condensed water is managed up to the theoretical outflow, and the temperature is raised to 240 ° C. When the resin component reaches the target specification at the same temperature after checking the transparent state at room temperature. The reaction was completed by selecting a solvent that can be used in the vacuum reaction or coating of solvents such as xylene, solveso 100, solveso 150, etc. from a few minutes to several hours until a reflux reaction was performed.

After reaching the target specification, the reactant was cooled, and then a prepared diluent solvent was added to prepare a polyester resin composition having a solid content of 59 to 66%.

Comparative Examples 1 and 2

The charged ingredient ratio was used according to the following Table 1 and the reaction process was carried out in the same manner as in the above Example.

Raw material name Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Polyacid (mol%) Phthalic anhydride 45 50 50 50 30 Terephthalic acid - 5 8 10 10 Isophthalic acid 20 10 20 15 10 Adipic acid 25 25 22 25 25 Tetra Hydrophthalic Anhydride 10 10 0 - 25 Polyhydric alcohol (mol%) Neopentyl glycol 90 79 75 50 90 Trimethylolpropane 6 6 4 4 6 Methylpropanediol 4 5 6 4 4 1,4cyclohexanedimethanol - 10 15 10 - Ethylene glycol - - - 32 - DBTO (ester catalyst) 0.1 0.1 0.1 0.1 0.1 N.V. (Solvesso 100) 60 60 60 60 60 Number average molecular weight 3000 2700 3100 6700 1500

Experimental Example

In order to measure the physical properties of the polyester resins prepared in Examples 1 to 3 and Comparative Examples 1 and 2, a paint was prepared with the composition shown in Table 2 below.

Name content Polyester resin (65% solids) 129.2 parts by weight Solvesso # 100 48.0 parts by weight ESTASOL 32.0 parts by weight TiO ₂ 272.0 parts by weight Polyester resin (65% solids) 172.2 parts by weight Cymel 303 (Cytec) 34.0 parts by weight Solvesso # 100 32.0 parts by weight ESTASOL 20.0 parts by weight Acid catalyst (paratoluic sulfonic acid, 50% solution) 4.0 parts by weight

The paint was prepared by mixing the raw materials so that the dispersion particle size was 5 탆 or less.

The paint thus prepared was applied to a galvanized steel sheet coated with an epoxy undercoat with a cured coating film (15-20 μm) obtained by drying in a hot air dryer at 275˜290 ° C. for 25-30 seconds.

The test method is as follows, and the results are shown in Table 3.

[ Test Methods ]

* Gloss (GLOSS 60 °: measured using BYK or SHEEN polisher)

* Workability: Two sheets of material having the same thickness as the material were put at room temperature, and processed at 180 degrees, and the peeled state and the crack state were evaluated by winding the processed part with scotch tape.

(Score: no crack 5 ←, → 1 cracked and peeled off entirely)

* Acid resistance: 5% hydrochloric acid solution was applied to the coating film and the surface was covered and the surrounding was shielded with petroleum jelly, which was left at 25 ℃ for 24 hours, and the state of the coating film was evaluated.

(Score: no trace 5 ←, → 1 full peeling)

* Basic resistance: 5% sodium hydroxide solution was applied to the coating film, the surface was covered and the surrounding was shielded with petroleum jelly, which was allowed to stand at 25 ℃, 24 hours, and the state of the coating film was evaluated.

(Score: no trace 5 ←, → 1 peeling)

* Accelerated weathering: Using UV-UV QQ-se equipment manufactured by Q-PANEL, UV wavelength is adjusted to A-Type (340 nm), the cycle is irradiated at 60 ℃ for 8 hours, and condensed at 40 ℃ for 4 hours, 2,000 hours have elapsed. After the test against the initial gloss of the coating film after the gloss was compared to evaluate the retention.

* Pencil hardness: Mitsubishi's coating hardness measurement pencil (load: 500g)

* Curing degree of coating film: The number of reciprocating motions was measured by winding the crawfish on a rod loaded with 500 g and wetting methyl ethyl ketone (MEK) until the bottom was visible.

Example Comparative example One 2 3 One 2 Curing condition 270 ° C x 8 seconds Glossy (60 °) 90 94 93 76 90 Machinability 5 5 5 5 4 Acid resistance 5 5 5 4 4 Base resistance 4+ 4+ 4+ 4- 4- Promoting weather resistance gloss retention rate (%) 82 74 70 30 42 Pencil hardness H H H F HB Coating film hardening degree (time) More than 100 More than 100 More than 100 50 80

As described in detail above, in the present invention, the aromatic, aliphatic, and alicyclic acid raw materials are used at an appropriate ratio to improve weather resistance, chemical resistance, coating hardness, and the like. Introduced more than trihydric alcohol that can have the maximum network structure at the level to ensure the correct processability, and other polyhydric alcohol raw material to reflect the raw material that can have a rigid coating structure rather than a structurally flexible structure to maximize the external physical after paint production It was designed to delay the damage of the coating due to chemical factors as much as possible, and when the resin composition was applied to the paint to check the physical properties, excellent weather resistance results were obtained.

Claims (5)

1,4-cyclohexane dicarboxylic acid, hexahydro phthalic anhydride, methylhexa hydrophthalic anhydride, methyltetra hydrophthalic anhydride, tetra hydrophthalic anhydride and esters thereof as acid component One to two or more selected from alicyclic acid components such as derivatives 0 to 30 mol%, one or two or more selected from aromatic phthalic anhydride, terephthalic acid, isophthalic acid, trimaleic anhydride and ester derivatives thereof % And 5 to 40 mol% of an aliphatic acid component selected from adipic acid, succinic acid, succinic anhydride, and sebacic acid represented by the following Chemical Formula 2; 60 to 95 mol% of a compound represented by the following Chemical Formula 1 as a polyhydric alcohol component, 0 to 30 mol% of a dihydric alcohol excluding the compound represented by the following Chemical Formula 1, and 1 to 10 mol% of an alcohol having a trivalent or higher reactor Co-polyester resin. Formula 1 Wherein R ₁ and R ₂ represent H (hydrogen) or an alkyl group having 1 to 4 carbon atoms, provided that one of R ₁ and R ₂ must be an alkyl group. Formula 2 HOOC-(-CH _2- ) _n -COOH Where n is an integer from 2 to 10. The dihydric alcohol excluding the compound represented by Chemical Formula 1 is 1,6 hexanediol, propylene glycol, diethylene glycol, triethylene glycol, 1,3 butylene glycol, 1,4 butylene glycol, Copolymerized polyester resin, characterized in that one or two or more selected from 1,4 cyclohexane dimethanol and butyl ethyl propanediol. The copolyester resin according to claim 1, wherein the alcohol having a trivalent or higher reactor is one or two or more selected from trimethylolpropane, trimethylolethane and ditrimethylolpropane. The copolyester resin according to claim 1, wherein the number average molecular weight is 2500 to 6000. The coating material for coating steel sheets containing the copolyester resin of Claim 1.