阅读说明：本技术 共聚的饱和聚酯树脂和包含其的涂覆组合物 (Copolymerized saturated polyester resin and coating composition comprising the same ) 是由 金炯坤 沈宗基 金舜琪 于 2019-01-31 设计创作，主要内容包括：本发明涉及共聚的饱和聚酯树脂和包含其的涂覆组合物。提供了共聚的饱和聚酯树脂和涂覆组合物,其在形成为涂覆膜时具有优异的耐腐蚀性和耐化学品性,表现出优异的可加工性和树脂溶解性,因此特别可用于对罐和预涂覆金属(PCM)进行涂覆。(The present invention relates to a copolymerized saturated polyester resin and a coating composition comprising the same. Provided are a copolymerized saturated polyester resin and a coating composition, which have excellent corrosion resistance and chemical resistance when formed into a coating film, exhibit excellent workability and resin solubility, and thus are particularly useful for coating cans and pre-coated metals (PCMs).)

1. A copolymerized saturated polyester resin formed by polycondensation of an acid component and an alcohol component, an

A glass transition temperature of 60 ℃ to 120 ℃, an intrinsic viscosity of 0.4dl/g to 0.7dl/g, and a number average molecular weight of 12000g/mol to 20000g/mol,

wherein the acid component comprises (a-1)90 to 99 mol% of an aromatic dicarboxylic acid or C thereof_1-2An alkyl ester, and (a-2)0.5 to 2 mol% of a trifunctional or higher-functional carboxylic acid or anhydride thereof,

and the alcohol component comprises (b-1)45 to 80 mol% of a cycloaliphatic polyol, and (b-2)20 to 55 mol% of a polyol having C_1-3Aliphatic polyols with alkyl side chains.

2. The copolymerized saturated polyester resin of claim 1, wherein the acid component (a-1) is selected from the group consisting of isophthalic acid, terephthalic acid, 2, 6-naphthalenedicarboxylic acid, and C thereof_1-2At least one of an alkyl ester; and

the acid component (a-2) is at least one selected from trimellitic acid and an anhydride thereof.

3. The copolymerized saturated polyester resin according to claim 1, wherein the alcohol component (b-1) is tricyclodecanedimethanol, or a mixture of tricyclodecanedimethanol and at least one of cyclohexanedimethanol and isosorbide; and

the alcohol component (b-2) is at least one selected from the group consisting of 2-methyl-1, 3-propanediol, 1, 3-butanediol, and 1, 2-propanediol.

4. The copolymerized saturated polyester resin of claim 1, wherein the acid component (a-1) is selected from the group consisting of isophthalic acid, terephthalic acid, 2, 6-naphthalenedicarboxylic acid, and C thereof_1-2At least one of an alkyl ester;

the acid component (a-2) is at least one selected from trimellitic acid and an anhydride thereof;

the alcohol component (b-1) is tricyclodecanedimethanol or a mixture of tricyclodecanedimethanol and at least one of cyclohexanedimethanol and isosorbide; and

the alcohol component (b-2) is at least one selected from the group consisting of 2-methyl-1, 3-propanediol, 1, 3-butanediol, and 1, 2-propanediol.

5. The copolymerized saturated polyester resin of claim 1, having a polydispersity index of 2.0 to 4.0.

6. A coating composition comprising the copolymerized saturated polyester resin of any one of claims 1-5.

7. The coating composition of claim 6, further comprising a curing agent, wherein the curing agent is at least one selected from the group consisting of a phenolic resin, a polyfunctional polyisocyanate compound, a melamine-formaldehyde resin, a benzoguanamine resin, and combinations thereof.

Technical Field

The present invention relates to a copolymerized saturated polyester resin and a coating composition comprising the same. In more detail, the present invention relates to a copolymerized saturated polyester resin, which can be used to protect a metal substrate because it is excellent in corrosion resistance and chemical resistance when formed into a coating film, and has good resin solubility and workability, and a coating composition comprising the same.

Background

The main purpose of the coating for protecting metallic materials is to prevent corrosion by water or acidic or basic aqueous solutions. Therefore, the coating film is required to have excellent corrosion resistance and chemical resistance.

The coating composition comprising the saturated polyester resin having a high molecular weight has excellent processability. However, since physical properties thereof are easily deteriorated by water or an acidic or basic aqueous solution, it is difficult to apply them to applications requiring corrosion resistance.

In particular, the deterioration of physical properties of the polyester resin is further accelerated under high temperature conditions. Therefore, it is inevitable to improve corrosion resistance to water or an acidic or basic aqueous solution at high temperature in order to coat the metal with the polyester resin.

In addition, in order to apply the resin to the coating composition, it must be stably dissolved or dispersed in a solvent or water. Generally, however, resins modified for the purpose of enhancing their corrosion and chemical resistance tend to have low solubility in solvents.

In order to achieve such improvement in solubility and corrosion resistance of the resin, high molecular weight polyester resins have been conventionally developed through a combination of various monomers. However, the polyester resins developed so far cannot satisfy both solubility and corrosion resistance. But may impair processability, which is an inherent advantage of high molecular weight saturated polyesters.

Disclosure of Invention

Technical problem

It is known that a phenomenon in which the characteristics of a coating film formed of a polyester resin are deteriorated by water or an acidic or basic aqueous solution is mainly caused by hydrolysis of the polyester resin caused by moisture permeating and diffusing into the coating film. In order to suppress such deterioration of physical properties due to moisture, it is necessary to chemically bond the binder resin and the curing agent component to have a high curing density so that moisture hardly penetrates and diffuses into the coating film.

As a result of the studies conducted by the present inventors, it was found that hydrolytic stability can be secured by designing the structure of the resin so that moisture is hardly accessible to ester bonds, and corrosion resistance and chemical resistance are significantly improved by controlling the glass transition temperature of the resin to thereby suppress the fluidity of the coating film at high temperatures. Further, it was confirmed that the solubility of the polyester resin in a solvent and the processability of a coating film can be improved by controlling the constituent components of the resin even at a high glass transition temperature.

Accordingly, it is an object of the present invention to provide a copolymerized saturated polyester resin which is excellent in solubility and processability and capable of producing a coating film having excellent corrosion resistance and chemical resistance.

Further, it is another object of the present invention to provide a coating composition comprising the copolymerized saturated polyester resin.

Technical scheme

According to the object of the present invention, there is provided a copolymerized saturated polyester resin formed by polycondensation of an acid component and an alcohol component, and having a glass transition temperature of 60 ℃ to 120 ℃, an intrinsic viscosity of 0.4dl/g to 0.7dl/g, and a number average molecular weight of 12000g/mol to 20000g/mol, wherein the acid component comprises (a-1)90 mol% to 99 mol% of an aromatic dicarboxylic acid or C thereof_1-2An alkyl ester, and (a-2)0.5 to 2 mol% of a trifunctional or higher-functional carboxylic acid or an anhydride thereof, and an alcohol component containing (b-1)45 to 80 mol% of a cycloaliphatic polyolAnd (b-2)20 to 55 mol% of a compound having C_1-3Aliphatic polyols with alkyl side chains.

According to another object of the present invention, there is provided a coating composition comprising the copolymerized saturated polyester resin.

Advantageous effects

The copolymerized saturated polyester resin is excellent in corrosion resistance and chemical resistance when formed into a coating film and has good workability and solubility in a solvent. Thus, it can be used as a coating for protecting a metal substrate.

Thus, coating compositions comprising copolymerized saturated polyester resins are particularly useful for pre-coated metal (PCM) and coating of the interior and exterior surfaces of cans.

Drawings

Fig. 1 shows the results of evaluating the corrosion resistance of coating films formed of the copolymerized polyester resins of examples 1 to 4 and comparative examples 2 and 3.

Detailed Description

Hereinafter, the present invention will be described in more detail.

Copolymerized saturated polyester resin

The present invention provides a copolymerized saturated polyester resin formed by polycondensation of an acid component and an alcohol component, and having a glass transition temperature of 60 ℃ to 120 ℃, an intrinsic viscosity of 0.4dl/g to 0.7dl/g, and a number average molecular weight of 12000g/mol to 20000g/mol, wherein the acid component comprises (a-1)90 mol% to 99 mol% of an aromatic dicarboxylic acid or C thereof_1-2An alkyl ester, and (a-2)0.5 to 2 mol% of a trifunctional or higher-functional carboxylic acid or an anhydride thereof, and an alcohol component containing (b-1)45 to 80 mol% of a cycloaliphatic polyol, and (b-2)20 to 55 mol% of a polyol having C_1-3Aliphatic polyols with alkyl side chains.

(a) Acid component

The copolymerized saturated polyester resin comprises (a-1) an aromatic dicarboxylic acid or C thereof_1-2Alkyl ester, and (a-2) trifunctional or higher-functional carboxylic acid or anhydride thereof as an acid component.

The copolymerized saturated polyester composition is poor in structural fluidity due to the acid component (a-1), whereby diffusion of moisture can be suppressed. Further, a branched structure is formed due to the acid component (a-2), whereby a coating film having a dense structure can be obtained. Therefore, corrosion resistance and chemical resistance can be enhanced by effectively suppressing the movement and diffusion of moisture.

The acid component (a-1) may be selected from isophthalic acid, terephthalic acid, 2, 6-naphthalenedicarboxylic acid, and C thereof_1-2At least one of an alkyl ester.

The content of the acid component (a-1) (based on the total acid component) is 90 to 99 mol%. If the content of the acid component (a-1) is less than 90 mol%, the glass transition temperature of the resin is too low, thereby making it difficult to ensure sufficient corrosion resistance and hardness. More specifically, the content of the acid component (a-1) (based on the total acid component) may be 90 to 95 mol%, 93 to 99 mol%, 95 to 99 mol%, or 93 to 97 mol%.

Further, the acid component (a-2) may be at least one selected from trimellitic acid and its anhydride.

The content of the acid component (a-2) (based on the total acid component) is 0.5 to 2 mol%. If the content of the acid component (a-2) is less than 0.5 mol%, it is difficult to obtain a sufficient level of corrosion resistance. If the content is more than 2 mol%, gelation occurs during synthesis of the resin or the viscosity of the resin becomes excessively high, thereby deteriorating the workability of the coating layer. More specifically, the content of the acid component (a-2) (based on the total acid component) may be 0.5 to 1.5 mol%, 1 to 2 mol%, 1.5 to 2 mol%, or 0.5 to 1 mol%.

(b) Alcohol component

The copolymerized saturated polyester resin comprises (b-1) a cycloaliphatic polyol, and (b-2) a polyester resin having C_1-3Alkyl side chain aliphatic polyols are used as the alcohol component.

Since the copolymerized saturated polyester resin contains the alicyclic polyol and the aliphatic polyol component, it becomes difficult for moisture to approach an ester bond, whereby hydrolysis resistance can be ensured.

Meanwhile, the branched structure of the resin is very useful for enhancing corrosion resistance and chemical resistance, but the processability of the resin may be deteriorated thereby. Therefore, a polyol having an alicyclic structure may be used in the resin to impart flexibility and enhance processability.

Preferably, the copolymerized saturated polyester resin contains tricyclodecane dimethanol as the alcohol component (b-1), so that the solubility of the saturated polyester resin and the processability of the resin can be ensured. In addition, it may further comprise at least one selected from the group consisting of cyclohexanedimethanol and isosorbide.

That is, the alcohol component (b-1) may be tricyclodecanedimethanol or a mixture of tricyclodecanedimethanol and at least one of cyclohexanedimethanol and isosorbide.

The content of the alcohol component (b-1) (based on the total alcohol component) is 45 mol% to 80 mol%. If the content of the alcohol component (b-1) is within the above range, the glass transition temperature and corrosion resistance of the resin can be improved, and good solubility thereof can be enhanced. If the content is less than 45 mol%, it is difficult to obtain sufficient corrosion resistance and chemical resistance. If the content is more than 80 mol%, polymerization of the resin is difficult or processability is significantly reduced.

More specifically, the content of the alcohol component (b-1) (based on the total alcohol component) may be 45 mol% to 75 mol%, 45 mol% to 70 mol%, 45 mol% to 65 mol%, or 50 mol% to 80 mol%.

Further, the alcohol component (b-2) may be at least one selected from the group consisting of 2-methyl-1, 3-propanediol, 1, 3-butanediol, and 1, 2-propanediol.

In particular, the sum of carbon atoms constituting the side chain in the alcohol component (b-2) is preferably 3 or less.

If the carbon chain as the side chain is long, there is a possibility that chemical resistance and hot water resistance may be impaired when the coating composition is applied.

The content of the alcohol component (b-2) (based on the total alcohol component) is 20 to 55 mol%. If the content of the alcohol component (b-2) is within the above range, polymerization reactivity, solubility, flowability, and processability can be ensured. If the content is less than 20 mol%, the polymerization reactivity is significantly reduced. If the content is more than 55 mol%, the corrosion resistance and chemical resistance are lowered.

More specifically, the content of the alcohol component (b-2) (based on the total alcohol component) may be 25 to 55 mol%, 30 to 55 mol%, 35 to 55 mol%, or 20 to 50 mol%.

Meanwhile, the alcohol component preferably does not contain 2, 2-dimethyl-1, 3-propanediol.

If the coating film is formed using a polyester resin containing 2, 2-dimethyl-1, 3-propanediol, the corrosion resistance of the coating film may be significantly impaired when the film comes into contact with food containing alcohol.

Characteristics of copolymerized saturated polyester resin

In the present invention, since the copolymerized saturated polyester resin has a specific level of high molecular weight, flexibility can be imparted when treating a coated substrate.

The copolymerized saturated polyester resin may have an intrinsic viscosity of 0.4dl/g to 0.7dl/g, more specifically 0.45dl/g to 0.60dl/g, 0.4dl/g to 0.65dl/g, or 0.4dl/g to 0.6 dl/g.

The number average molecular weight of the copolymerized saturated polyester resin is 12000g/mol to 20000 g/mol. If the number average molecular weight of the copolymerized saturated polyester resin is less than 12000g/mol, the processability is deteriorated. If it is more than 20000g/mol, the viscosity increases, which impairs coating workability when used in paints.

More specifically, the number average molecular weight of the copolymerized saturated polyester resin may be 14000g/mol to 19000g/mol, 16000g/mol to 19000g/mol, 14000g/mol to 17000g/mol, 12000g/mol to 17000g/mol, or 16000g/mol to 20000 g/mol.

Preferably, the polydispersity index (PDI) of the copolymerized saturated polyester resin may be in the range of 2.0 to 4.0. The polydispersity index is calculated as the ratio of weight average molecular weight to number average molecular weight (Mw/Mn), which is an index for determining whether the branched structure can improve the hot water resistance of the resin. If the polydispersity index of the copolymerized saturated polyester resin is in the range of 2.0 to 4.0, it may be advantageous to obtain good corrosion resistance and melt viscosity.

More specifically, the PDI of the copolymerized saturated polyester resin may be in the range of 2.0 to 3.0, 3.0 to 4.0, 2.5 to 4.5, 2.5 to 4.0, or 2.0 to 3.5.

The glass transition temperature (Tg) of the copolymerized saturated polyester resin may be 60 to 120 ℃. If the Tg of the copolymerized saturated polyester resin is 60 ℃ to 120 ℃, the fluidity of the resin coating film at high temperature can be suppressed, thereby enhancing the corrosion resistance and chemical resistance.

More specifically, the Tg of the copolymerized saturated polyester resin may be in the range of 60 ℃ to 110 ℃, 60 ℃ to 100 ℃, 70 ℃ to 110 ℃, 80 ℃ to 110 ℃, or 65 ℃ to 105 ℃.

Method for producing copolymerized saturated polyester film

The copolymerized saturated polyester resin of the present invention can be prepared by conventional esterification and polycondensation methods. For example, the acid component and the alcohol component are charged into a reactor, and the esterification catalyst is subsequently added thereto. Then, the temperature was gradually increased from room temperature to about 200 ℃ to 260 ℃. When by-products such as water or methanol are discharged, a polycondensation catalyst and a heat stabilizer are added. The reaction temperature was raised to 220 to 300 ℃ and copolymerization was performed for several hours to thereby obtain a polyester resin having an appropriate intrinsic viscosity.

In such a case, examples of the acid component and the alcohol component to be used are as described above.

Further, the polymer structure can be suitably controlled by distributing and adding a trifunctional or higher-functional carboxylic acid or an anhydride thereof to the esterification reaction step and the polycondensation step at the time of production.

Specifically, a trifunctional or higher-functional carboxylic acid or an anhydride thereof may be fed in the esterification step to have a branched structure. Alternatively, it may be added to the polycondensation step to adjust the acid value and a proper level of the branched structure, thereby improving the adhesion of the coating film.

During the production of the copolymerized saturated polyester resin, an esterification catalyst, a polycondensation catalyst, a heat stabilizer, and the like may also be added. Examples of the esterification catalyst include acetates of Ca, Ce, Pb, Mn, Zn, Mg, Sb, etc., and tetrabutoxyTitanium. Further, examples of the polycondensation catalyst include Sb₂O₃、GeO₂Titanium tetrabutoxide, and the like. Examples of thermal stabilizers include phosphate salts, phosphoric acid, and the like.

In particular, in the present invention, by carrying out esterification and polycondensation reactions using a saturated compound having no unsaturated bond (e.g., double bond) as an acid component and an alcohol component to be used as a comonomer of the polyester resin, a copolymerized saturated polyester resin having no unsaturated bond in its final resin structure can be provided.

Since the copolymerized saturated polyester resin of the present invention as described above has no unsaturated bond, it is possible to prevent the physical properties from being changed in response to heat, light, or the like. Further, the copolymerized saturated polyester resin as described above may be suitable as the thermoplastic resin for forming the coating film.

Coating composition

The present invention also provides a coating composition comprising the copolymerized saturated polyester resin.

For example, the coating composition may comprise a copolymerized saturated polyester resin, a curing agent, a solvent, an additive, and the like.

In such a case, the composition and characteristics of the copolymerized saturated polyester resin are as described above.

The curing agent may be at least one selected from the group consisting of a phenol resin, a polyfunctional polyisocyanate compound, a melamine-formaldehyde resin, a benzoguanamine resin, and a combination thereof. Preferably, if a phenol resin or a benzoguanamine resin is used as the curing agent, it is advantageous to obtain excellent physical properties in terms of corrosion resistance and chemical resistance. Examples of commercially available phenolic resins include PR516, PR566, PR827, VPR1785, and CYMEL 659 from Allnex.

The weight ratio of the copolymerized saturated polyester resin to the curing agent may be in the range of 95:5 to 40:60, more specifically, in the range of 90:10 to 50: 50.

The solvent may be an ester-based solvent, a glycol ether-based solvent, a ketone-based solvent, an aromatic hydrocarbon-based solvent, an aliphatic hydrocarbon-based solvent, or an alcohol-based solvent. More specifically, xylene, propylene glycol monoethyl acetate, and dibasic esters are suitable.

Further, examples of the additive may include pigments, waxes, lubricants, antifoaming agents, wetting agents, catalysts, and the like.

The coating composition is particularly useful for coating of PCM and inner and outer surfaces of cans because it is significantly improved in corrosion resistance and chemical resistance and is excellent in workability.

Embodiments for carrying out the invention