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热水性、耐化学品性和可加工性,并且表现出优异的对金属基底的粘附性,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 hot water resistance, chemical resistance and workability when formed into a coating film, and exhibit excellent adhesion to a metal substrate, 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

An intrinsic viscosity of 0.4 to 0.65dl/g, a number average molecular weight of 12000 to 20000g/mol, and a polydispersity index (PDI) of 3.0 to 5.0,

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,

the alcohol component comprises (b-1)20 to 55 mol% of a cycloaliphatic polyol, and (b-2)45 to 80 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 at least one selected from the group consisting of cyclohexanedimethanol, tricyclodecanedimethanol, and isosorbide; and

the alcohol component (b-2) is at least one selected from the group consisting of 2, 2-dimethyl-1, 3-propanediol, 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 further comprises an aliphatic dicarboxylic acid in an amount of 0.1 to 9 mole%.

5. The copolymerized saturated polyester resin of claim 1, having a glass transition temperature in the range of 40 ℃ to 80 ℃.

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 copolymerized saturated polyester resins and coating compositions, which are particularly useful for coating of cans and precoated metals (PCMs) due to their excellent hot water resistance, chemical resistance, processability, and adhesion to metal substrates.

Background

The coating composition comprising the saturated polyester resin having a high molecular weight has excellent processability. However, since it is easily turbid during sterilization at high temperature, it is difficult to apply it to applications requiring hot water resistance.

In particular, since packaged foods in cans essentially require sterilization of foods under high heat and pressure, there is a constant demand for improvement of the turbidity of polyester resins in high-temperature environments. Furthermore, the coating, when applied to the interior of the can, should have good chemical resistance to various food products. In order to obtain chemical resistance and hot water resistance to various foods under such high temperature conditions, various polyester resins have been developed with various combinations of monomers.

For example, conventionally, a method of suppressing the fluidity of a coating film at high temperature by increasing the glass transition temperature of a polyester resin, in which the penetration of moisture and a solvent is prevented, has been mainly used. However, according to the above conventional methods, not only the workability of the coating film is greatly deteriorated due to the high glass transition temperature, but also the resin is not easily dissolved in typical organic solvents, which limits the production of the coating composition. In addition, if the glass transition temperature of the polyester resin is not significantly increased to reduce such side effects, it is difficult to obtain desired levels of hot water resistance and chemical resistance.

Disclosure of Invention

Technical problem

It is known that the phenomenon that a coating film formed of a polyester resin becomes cloudy by water or a compound under high temperature conditions is mainly caused by hydrolysis of the polyester resin caused by moisture permeating and diffusing into the coating film. In particular, this hydrolysis is accelerated in aqueous solutions containing acidic or basic compounds with increasing temperature. Therefore, in order to suppress such turbidity and hydrolysis, it is necessary to suppress penetration and diffusion of moisture 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 such that moisture is hardly accessible to ester bonds, and that an appropriate branched structure of the polyester resin can maintain its excellent workability and the hot water resistance and chemical resistance are significantly improved by suppressing the fluidity of the coating film.

Accordingly, it is an object of the present invention to provide a copolymerized saturated polyester resin which is excellent in workability and capable of producing a coating film having excellent hot water 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

In accordance with the purpose 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 an intrinsic viscosity of 0.4dl/g to 0.65dl/g, a number average molecular weight of 12000g/mol to 20000g/mol, and a polydispersity index (PDI) of 3.0 to 5.0, 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)20 to 55 mol% of a cycloaliphatic polyol, and (b-2)45 to 80 mol% of a polyol 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 chemical resistance and hot water resistance in various media when formed into a coating film. Therefore, it can be used for high temperature resistant coatings.

In addition, since the copolymerized saturated polyester resin is excellent in processability and flowability and has good adhesion to a metal substrate, it can be used for a coating on a metal.

Therefore, the coating composition comprising the copolymerized saturated polyester resin is particularly useful for coating of pre-coated metal (PCM) and inner surfaces of cans which are sterilized at high temperature and come into contact with various foods.

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 an intrinsic viscosity of 0.4 to 0.65dl/g, a number average molecular weight of 12000 to 20000g/mol, and a polydispersity index (PDI) of 3.0 to 5.0, 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 an anhydride thereof, and an alcohol component containing (b-1)20 to 55 mol% of a cycloaliphatic polyol, and (b-2)45 to 80 mol% of a polyol having C_1-3Aliphatic polyols with alkyl side chains.

Hereinafter, each component will be specifically described.

(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, hot water 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 excessively low, thereby making it difficult to ensure sufficient hot water 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 hot water resistance level. 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%.

In addition, the copolymerized saturated polyester resin may further include an aliphatic dicarboxylic acid as an additional acid component. For example, the aliphatic dicarboxylic acid may be selected from sebacic acid, succinic acid, azelaic acid, and combinations thereof.

The aliphatic dicarboxylic acid may be contained in an amount of 0.1 to 10 mol%, 0.1 to 9 mol%, 0.1 to 7 mol%, or 0.1 to 5 mol% based on the total acid component.

(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.

Further, if the content of the alicyclic polyol component and the aliphatic polyol component is controlled within the above content range, solvent solubility for easily preparing the coating composition may be imparted.

The alcohol component (b-1) may be at least one selected from the group consisting of cyclohexanedimethanol, tricyclodecanedimethanol, and isosorbide.

The content of the alcohol component (b-1) (based on the total alcohol component) is 20 mol% to 55 mol%, more specifically 30 mol% to 40 mol%. If the content of the alcohol component (b-1) is less than 20 mol%, it is difficult to obtain sufficient chemical resistance and hot water resistance. If the content is more than 55 mol%, it is not dissolved in a solvent used for the coating composition, or workability is significantly deteriorated.

More specifically, the content of the alcohol component (b-1) (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%.

Further, the alcohol component (b-2) may be at least one selected from the group consisting of 2, 2-dimethyl-1, 3-propanediol, 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 45 mol% to 80 mol%, more specifically 60 mol% to 70 mol%. If the content of the alcohol component (b-2) is less than 45 mol%, the fluidity and solubility are significantly deteriorated. If the content is more than 80 mol%, hot water resistance is deteriorated.

More specifically, the content of the alcohol component (b-2) (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%.

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 0.65dl/g, more specifically 0.45dl/g to 0.60dl/g, 0.45dl/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, viscosity increases, which impairs coating workability when it is used for coating.

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.

The polydispersity index (PDI) of the copolymerized saturated polyester resin is in the range of 3.0 to 5.0. 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 3.0 to 5.0, good hot water resistance and melt viscosity can be obtained.

More specifically, the PDI of the copolymerized saturated polyester resin may be in the range of 3.0 to 4.0, 4.0 to 5.0, 3.5 to 4.5, 3.5 to 5.0, or 2.5 to 5.0.

The glass transition temperature (Tg) of the copolymerized saturated polyester resin may be in the range of 40 ℃ to 80 ℃. Within the above range, it may be more advantageous to improve the performance by suppressing the fluidity of the resin coating film caused by hot water.

More specifically, the Tg of the copolymerized saturated polyester resin may be in the range of 40 ℃ to 70 ℃, 40 ℃ to 60 ℃, 50 ℃ to 70 ℃, 60 ℃ to 70 ℃, or 45 ℃ to 65 ℃.

Process for preparing copolymerized saturated polyester resins

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 280 ℃ 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 titanium tetrabutoxide. 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 phenolic resin is used as the curing agent, it is advantageous to obtain excellent physical properties in hot water resistance and chemical resistance. Examples of commercially available phenolic resins include PR516, PR566, PR827, and VPR1785 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 hot water resistance and chemical resistance and is excellent in workability.

Embodiments for carrying out the invention