CN112390916A - Acrylic acid modified polyester resin and preparation method thereof - Google Patents

Abstract

The present invention relates to an acrylic modified polyester resin. Specifically, the modified polyester resin is prepared by grafting a polyester prepolymer which is formed by pentaerythritol, a polyol monomer, a polybasic organic acid monomer and a naphthenic dibasic acid monomer and contains double bonds on a main chain with an acrylic monomer. The invention also relates to a preparation method of the acrylic modified polyester resin.

Description

Acrylic acid modified polyester resin and preparation method thereof

Technical Field

The invention relates to an acrylic modified polyester resin and a preparation method thereof, in particular to a water-dilutable acrylic modified polyester resin.

Background

The coating can be coated on the surface of an article to provide a protective or decorative effect, and has wide application and various required functions. Therefore, how to obtain a coating with desired properties is a very important issue.

One common way is to prepare a multi-layer coating on the surface of the article to be coated using the same or different coating materials. For example, a primer coating (layer) may be applied first, followed by further application of one or more additional coating layers, such as an ink layer, a varnish layer, a topcoat layer, and a protective layer. The primary characteristic of the base coat is that the base coat has good adherence with the surface of the coated substrate and the ink layer; the ink layer can provide a desired pattern; the main properties of the gloss oil layer are high hardness (abrasion resistance), high flexibility (prevention of cracking of the coating upon impact), and high gloss. When applied to food packaging, the coating must be resistant to high temperatures, boiling water, high hardness, high flexibility, and have a degree of chemical resistance, etc., such that the integrity of the coating can still be maintained during the manufacturing process. When applied to the automotive industry or building materials, the coatings are also preferably resistant to high temperatures, boiling water, high hardness, high flexibility, and a certain degree of chemical resistance due to the constant exposure to the external environment. High gloss may also be required for the coating for aesthetic reasons.

Common coating compositions include acrylic system coatings, polyester system coatings, alkyd system coatings, and the like. It is believed that polyester-based coatings provide coatings superior to alkyd-based coatings in adhesion to the surface of the substrate to be coated, hardness, thermal plasticity, and yellowing resistance, and are superior to acrylic-based coatings in leveling, fullness, and impact (flexibility).

However, one of the problems encountered with the coating of the polyester system is boiling resistance and insufficient boiling resistance, and ester bonds in the main chain of the polymer are easily broken by hydrolysis reaction at high temperature, so that the coating is degraded by the collapse of chemical structure. Further, in response to environmental protection policies, many countries desire to reduce the amount of Volatile Organic Compounds (VOC), so the coating field is gradually shifted from a resin system containing a large amount of VOC to a water-dilutable resin system, and the amount of VOC used is reduced by diluting with water. Most water-dilutable resins are designed to incorporate functional groups with better hydrophilicity, such as carboxylic acid groups or sulfonic acid groups, to increase the solubility or compatibility of the resin with water. However, polyester resins modified by the introduction of hydrophilic functional groups are prone to excessive hydrophilicity, resulting in poorer water resistance and retort resistance than unmodified polyester coatings. Thus, there is still room for continued improvement in polyester system coatings.

In order to solve the above problems, various methods have been disclosed in the prior art. CN103554381A synthesizes acrylic acid modified polyester by introducing tertiary carbonic acid glycidyl ester to enhance the water resistance, alkali resistance and acid resistance of the coating; however, it is not disclosed whether the coating film formed from the resin has good water resistance at high temperature and passes the severe boiling or steaming resistance test.

In addition, the prior art (CN102875945A) attempted to use tertiary (tertiary) glycidyl carbonate, utilizing steric hindrance to protect the ester bond on the main chain; however, the present inventors have found that even when the improvement is carried out by using a tertiary glycidyl (t) carbonate, the obtained polyester can maintain stability for only 3 to 7 days in an environment of 60 ℃ after being diluted with water, and white precipitates are generated in the coating after 7 days, and the properties such as gloss and transparency of the coating film are impaired. If the treatment with boiling water is used, the coating is further caused to foam and fall off, and the adherence is remarkably reduced.

In view of the above, there is a need in the art for an acrylic modified polyester resin that can resist high temperature cooking in addition to maintaining good flexibility and solvent resistance, and thus has an increased application field, which is still the goal of the industry.

Disclosure of Invention

In order to solve the above problems, the inventors have repeatedly studied and found that an acrylic modified polyester resin having excellent flexibility, high solvent resistance, high water resistance and high-temperature retort resistance can be prepared by selecting a polyester prepolymer and a naphthenic dibasic acid monomer and controlling the introduction manner of a (meth) acrylic monomer. Accordingly, it is an object of the present invention to provide a novel acrylic modified polyester resin comprising:

(i) a polyester comprising units derived from a polyester prepolymer and a naphthenic dibasic acid monomer, wherein the polyester prepolymer is prepared from the following monomers by polycondensation:

(A-1) a step of adding pentaerythritol,

(A-2) a trihydric alcohol,

(A-3) a diol, and

(a-4) a polybasic organic acid monomer, an ester thereof, or an anhydride thereof, wherein the polybasic organic acid comprises an aromatic polybasic acid, an alkane polybasic acid, an alkene polybasic acid, or a combination thereof; and

(ii) a (meth) acrylic monomer grafted to the polyester;

wherein at least one of the monomers (A-2), (A-3) and (A-4) has a double bond, and the (meth) acrylic monomer is grafted onto the polyester by reacting with the double bond.

In a spectrum obtained by analysis of a thermal cracking gas chromatography-mass spectrometry method (PY-GC-MS), the ratio of signal integral values of pentaerythritol and trihydric alcohol is 0.05 to 0.35, and a coating formed by the acrylic modified polyester resin has 60 DEG glossiness of at least 76 in a GB/T9754-2007 standard test, and the 60 DEG glossiness of the coating in a boiling resistance test is at least 67.

The invention also relates to a method for preparing the acrylic modified polyester resin, which comprises the following steps:

(1) subjecting monomers (A-1), (A-2), (A-3), (A-4) and a naphthenic dibasic acid to a polycondensation reaction to form a polyester, wherein at least one of the monomers (A-2), (A-3) and (A-4) comprises a double bond; and

(2) (meth) acrylic monomers are added and grafted onto the polyester by reaction with the double bonds to form an acrylic modified polyester resin.

The invention also relates to a coating composition which comprises the acrylic modified polyester resin.

Drawings

FIG. 1 is a photograph of the appearance of coatings prepared using (a) comparative example 9, (b) comparative example 1, and (c) the polyester of example 1, after retort testing.

FIG. 2 is the thermal cracking mass spectrum of pentaerythritol and triol (1,1, 1-trimethylolpropane) standard.

Figure 3 is run data of the acrylic modified polyester resin of example 1 from fruit body run data according to thermal cracking mass spectrometry.

Fig. 4 is run data of the acrylic modified polyester resin of comparative example 1 from fruit body run data according to thermal cracking mass spectrometry.

Detailed Description

Each aspect and each embodiment of the invention disclosed herein is intended to be combined individually and in all possible combinations with all other disclosed aspects and embodiments of the invention.

In this specification and the claims, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

It should be understood that any numerical range recited in this specification is intended to include all sub-ranges subsumed therein. For example, a range from "50 ℃ to 70 ℃ includes all subranges between and including a minimum value of 50 ℃ and a maximum value of 70 ℃ (e.g., from 58 ℃ to 67 ℃, 53 ℃ to 62 ℃, 60 ℃, or 68 ℃), i.e., a range including a minimum value equal to or greater than 50 ℃ and a maximum value equal to or less than 70 ℃. Because the disclosed numerical ranges are continuous, they include every value between the minimum and maximum values. Unless otherwise indicated, all numerical ranges specified in this specification are approximate values.

Noun definitions

The term "hydrocarbyl" as used herein refers to organic radicals containing only carbon and hydrogen atoms in the main structure, such as alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, carboaryl, and the like. The hydrocarbyl groups used herein may be unsubstituted or optionally substituted with suitable substituents, for example, halogen, nitro, hydroxy, cyano, alkyl and the like groups.

As used herein, the term "alkyl" refers to a compound derived from the general formula C_nH_2n+2And can be linear or branched. Of alkyl groupsExamples are, but not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, second butyl, third butyl, C₅Alkyl and isomers, C₆Alkyl and isomers, C₇Alkyl and isomers, alkyl containing 8 or more than 8 carbon atoms and isomers thereof.

The term "cycloalkyl" as used herein refers to a group derived from a fully saturated hydrocarbon molecule having a ring in its structure. Examples of cycloalkyl groups include monocycloalkyl groups such as, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, methylcyclobutyl, cyclohexyl, and other cycloalkyl groups containing 6 or more carbon atoms and isomers thereof; bicycloalkyl or polycycloalkyl, and the like, for example, isobornyl.

The term "aryl" as used herein refers to a group derived from a hydrocarbon molecule having aromatic character. Examples of the carbon aromatic group may be a monocyclic group such as phenyl, tolyl, xylyl, or the like; bicyclic groups such as biphenyl, naphthyl, and the like; or polycyclic groups such as anthracyl, phenanthryl, and the like.

As used herein, "extensor" or "subvertion" refers to a hydrocarbon group divalent ly linked to another structure. For example, "alkylene" refers to a divalent group derived from an alkane molecule.

The term "alcohol" as used herein refers to a molecule having at least one-OH group in its molecular structure. The term "polyol" refers to a molecule that contains 2 or more than 2-OH groups in its structure. For convenience of expression, the terms "diol", "triol", and the like are also used to specifically refer to the number of-OH groups contained in the molecule.

The term "polybasic acid" as used herein means a molecule having at least 2-COOH groups in its molecular structure, or a molecule having a structure derived from-COOH in its molecular structure and capable of generating at least 2-COOH by hydrolysis or the like; such derivatized structures are, for example, esters or anhydrides. For convenience of expression, the terms "diacid," "triacid," and the like are also used to specifically refer to the number of-OH groups contained in the molecule.

As used herein, the term "acrylic acid" refers to acrylic acid or methacrylic acid; the term "(meth) acrylic monomer" refers to "acrylic monomer or methacrylic monomer"; the remaining related terms may be analogized.

The definitions of the groups or molecules are named in the order of importance of the functional groups if there are conflicting points; the rules of nomenclature may also be referred to in the rules promulgated by the International Union of Pure and Applied Chemistry (IUPAC).

1. Polyester prepolymer

Polyesters are generally prepared by the condensation dehydration polymerization (i.e., polycondensation) of one or more polyols with one or more polyacids (anhydrides or esters) comprising units derived from a polyester prepolymer and a naphthenic dibasic acid monomer.

The present invention is a polyester prepolymer prepared by polycondensation using reactants comprising the following monomers: pentaerythritol (A-1), trihydric alcohol (A-2), dihydric alcohol (A-3), and polybasic organic acid monomer (A-4), esters thereof, or anhydrides thereof. At least one of the above-mentioned monomers (A-2), (A-3) and (A-4) has a double bond, and therefore a (meth) acrylic monomer obtained in a subsequent step is grafted onto the polyester by reacting with the double bond.

The kind and amount of the monomers constituting the polyester prepolymer are described below.

Monomer (A-1) pentaerythritol

The inventors have found that the degree of branching of the polyester can be increased and the chemical structure of the resulting coating can be strengthened by introducing pentaerythritol (monomer (A-1); 2, 2-bis (hydroxymethyl) -1, 3-propanediol) into the polyester backbone. Because the branching degree is improved, the reticular structure of the coating is more compact, water molecules are not easy to penetrate into the coating structure, the effects of inhibiting hydrolysis and improving the surface adhesive force of the coating and an article can be achieved, and particularly, the crosslinking density can be further improved in the implementation mode that polyester and a curing agent are used together, and the effect is better.

However, if the amount of pentaerythritol is too large, the resin is too much in the amount of cross-linking during the synthesis process, and gelation (gel) is liable to occur, and if the amount of pentaerythritol is not sufficient, part of ester bonds in the polyester structure of the coating layer may be broken by hydrolysis during the cooking process, and the gloss and solvent resistance are not good, and in one embodiment, the amount of the monomer (a-1) is about 0.07 to about 3 mol%, preferably about 0.1 to about 2.5 mol%, and more preferably about 0.2 to about 1.26 mol%, based on the total number of moles of the monomers forming the acrylic modified polyester resin. If the content is less than 0.07 mol%, the branched disproportionation degree of the coating structure is insufficient, a compact network cannot be formed, the water resistance characteristic is poor, and the glossiness of the coating film is reduced after a boiling test; if the content is more than 3 mol%, the resin may be coagulated or gelled during the synthesis process.

Monomer (A-2) triol

By simultaneously introducing pentaerythritol (monomer (A-1)) and trihydric alcohol (monomer (A-2)) into the polyester main chain, the monomer (A-2) can exert synergistic effect, even if partial ester bonds in the polyester structure of the coating are hydrolyzed and damaged in the boiling water and cooking processes, the structure is still not disintegrated to cause the coating to fall off, and good glossiness is kept. The ratio of the amount of the monomer (A-1) to the amount of the monomer (A-2) can be adjusted according to the desired ratio, and in some embodiments of the present invention, the ratio of the amount of the monomer (A-1) to the amount of the monomer (A-2) (by mole) is about 0.02 to about 0.9, preferably about 0.04 to about 0.6, and more preferably about 0.05 to about 0.37. If the ratio of the amount of the monomer (A-1) to the amount of the monomer (A-2) is less than 0.02, the initial gloss of the coating film is poor, the gloss after a cooking test is greatly reduced, and the storage stability is deteriorated; if the ratio of the amount of the monomer (A-1) to the amount of the monomer (A-2) is higher than 0.9, the resin is gelled and does not flow because the ratio of the pentaerythritol monomer is too high.

The monomer (A-2) used in the present invention is a triol, and examples thereof include, but are not limited to: an alkyl triol, an alkenyl triol, a cycloalkyl triol, or a combination thereof; preferably an alkyl triol, an alkenyl triol, or a combination thereof.

Examples of alkyl triols include, but are not limited to: glycerol, butanetriol, pentanetriols (e.g. 1,1, 1-trimethylolethane), hexanetriols (e.g. 1,1, 1-trimethylolpropane) and triols of the straight or branched alkane type having from 7 to 10 carbon atoms.

Examples of alkenyl triols include, but are not limited to: butenetriol, pentenetriol, hexenetriol, and straight or branched alkene triols having 7 to 10 carbon atoms.

Cycloalkyl triols include, but are not limited to: cyclohexanetriols, 1,2, 3-cyclopentanetriols (e.g. 1,3, 5-cyclohexanetriols) and cycloalkanetriols having from 7 to 10 carbon atoms.

In one embodiment of the present invention, the triol (monomer (A-2)) used in the present invention is an alkyltriol, preferably hexanetriol (e.g., 1,1, 1-trimethylolpropane), in order that the coating is less likely to foam and peel in boiling water and is excellent in adhesion.

In one embodiment, the amount of monomer (A-2) is about 0.1 to about 10 mol%, preferably about 1 to about 5 mol%, and more preferably about 3 to about 4 mol%, based on the total moles of monomers forming the acrylic modified polyester resin. If the content of the monomer (A-2) is less than 0.1 mol%, the branched disproportionation degree of the structure of the coating is insufficient, a dense network cannot be formed, the water resistance characteristic is poor, and the glossiness of the coating film is reduced after a boiling test; if the content is more than 10 mol%, the resin may be gelled during the synthesis.

Monomer (A-3) diol

The monomer (A-3) used in the present invention is a diol, and examples thereof include, but are not limited to: an alkyl diol, an alkenyl diol, a cycloalkyl diol, or a combination thereof; preferably an alkyl diol, an alkenyl diol, or a combination thereof.

Examples of alkyl diols include, but are not limited to: ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-butylene glycol, 1, 4-butylene glycol, pentanediol (e.g., neopentyl glycol), hexanediol (e.g., 1, 6-hexanediol), and a straight or branched alkane diol having 7 to 10 carbon atoms (e.g., 2-butyl-2-ethyl-1, 3-propanediol).

Examples of alkenyl diols include, but are not limited to: butene diols (e.g., 1, 4-butene diol), pentene diols (e.g., methylbutene diols including isopentene diol and the like), hexene diols (e.g., 3-hexene-2, 5-diol), and straight or branched alkene diols having 7 to 10 carbon atoms.

Cycloalkyl diols include, but are not limited to: cyclobutanediol (e.g., 2,4,4, -tetramethyl-1, 3-cyclobutanediol), cyclopentanediol, cyclohexanediol (e.g., 1, 4-cyclohexanedimethanol), and cycloalkane diols having from 7 to 10 ring carbon atoms.

In one embodiment, the amount of the monomer (a-3) is about 20 to about 60 mol%, preferably about 35 to about 50 mol%, and more preferably about 30 to about 40 mol%, based on the total number of moles of the monomers forming the acrylic modified polyester resin.

Monomer (A-4) polybasic organic acid monomer, ester thereof or anhydride thereof

The polyvalent organic acid monomer, ester thereof or acid anhydride thereof (monomer (A-4)) used in the present invention has a functionality of at least 2 (carboxyl group or carboxyl group-generable group), and can be used for producing a polyester prepolymer by polycondensation with the aforementioned alcohol monomers (A-1), (A-2), (A-3)). The polybasic organic acid is selected from aromatic polybasic acid, alkane polybasic acid, and alkene polybasic acid.

Examples of the above aromatic polybasic acids, esters or anhydrides include, but are not limited to: terephthalic acid, isophthalic acid, phthalic acid, methylbenzenedicarboxylic acid (e.g., 1, 4-dimethylterephthalic acid or 1, 3-dimethylisophthalic acid), 1,2, 4-benzenetricarboxylic acid, diphenyl-4, 4 '-dicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, 2, 7-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 1, 5-naphthalenedicarboxylic acid, diphenoxyethane-4, 4' -dicarboxylic acid, diphenylsulfone-4, 4 '-dicarboxylic acid, diphenylether-4, 4' -dicarboxylic acid, trimellitic acid, or an ester or anhydride of the foregoing acid.

Examples of the above-mentioned alkane polybasic acids, esters or anhydrides include, but are not limited to: oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, lauric acid, or esters or anhydrides thereof.

Examples of the above alkenyl polybasic acids, esters or anhydrides include, but are not limited to: butenedioic acids (e.g., maleic acid or fumaric acid), pentenedioic acids (e.g., itaconic acid), hexenedioic acid, or esters or anhydrides thereof.

According to some embodiments of the present invention, the monomer (A-4) of the present invention may further comprise other polybasic organic acid monomers, esters thereof, or anhydrides thereof, such as, but not limited to, cycloaliphatic polybasic acids, esters, or anhydrides. The above-mentioned cycloaliphatic polybasic acids, esters or anhydrides may be naphthenic or cycloalkenylpolybasic acids or esters or anhydrides of the foregoing acids, examples of which include, but are not limited to: cyclopropane dicarboxylic acids, cyclobutane dicarboxylic acids, cyclopentane dicarboxylic acids, cyclohexane dicarboxylic acids (e.g., 1, 4-cyclohexane dicarboxylic acid), cyclohexane tricarboxylic acids (e.g., 1,2, 5-cyclohexane tricarboxylic acid or 1,2, 4-cyclohexane tricarboxylic acid), or esters or anhydrides of the foregoing acids.

In some embodiments of the present invention, the amount of monomer (a-4) is from about 5 mol% to about 35 mol%, preferably from about 10 mol% to about 30 mol%, and more preferably from about 15 mol% to about 25 mol%, based on the total moles of monomers forming the acrylic modified polyester resin.

According to some embodiments of the invention, the resulting polyester prepolymer has an acid number of no greater than 10mgKOH/g, for example, 10mgKOH/g, 8mgKOH/g, 6mgKOH/g, 4mgKOH/g, or 2mgKOH/g, preferably no greater than 6 mgKOH/g.

2. Polyester

As mentioned above, the present invention is to prepare a polyester prepolymer by a polycondensation reaction using monomers comprising pentaerythritol, a triol, a diol, and a polybasic organic acid monomer, an ester thereof, or an anhydride thereof; preferably, after the polyester prepolymer is produced, a naphthenic dibasic acid (monomer (B)) is further added to perform polycondensation with the alcohol groups remaining on the polyester prepolymer to produce a polyester.

The kind and amount of the monomer (B) are described below.

Monomer (B) naphthenic dibasic acid

The present inventors have further found that, in addition to strengthening the chemical structure of the coating layer by introducing pentaerythritol into the main chain of the polyester, the hydrolysis resistance of the polyester can be further strengthened by using a naphthenic dibasic acid (monomer (B)) to perform polycondensation with a polyester prepolymer, and the resulting polyester is not easily hydrolyzed even when subjected to high temperatures. The inventors believe, without being bound by theory, that this may result from the naphthenic dibasic acid acting as an electron donating group on the ester linkage of the polyester prepolymer, which may act synergistically with the pentaerythritol in the polyester prepolymer, thereby further inhibiting the hydrolysis reaction and increasing the stability of the coating.

In some embodiments of the invention, naphthenic diacid monomer systems are used as linking groups (linking groups) for the polyester prepolymer. In some embodiments of the invention, naphthenic dibasic acids are used as end groups (end groups) of the polyester prepolymer.

Examples of naphthenic dibasic acid monomers include, but are not limited to: cyclopropane dicarboxylic acid, cyclobutane dicarboxylic acid, cyclopentane dicarboxylic acid, cyclohexane dicarboxylic acid (e.g., 1, 4-cyclohexane dicarboxylic acid), hexahydrophthalic anhydride, and the like.

In one embodiment, the amount of monomer (B) is about 5 to about 15 mol%, preferably about 6 to about 13 mol%, and more preferably about 8 to about 11 mol%, based on the total moles of monomers forming the acrylic modified polyester resin. If the content of the monomer (B) is less than 5 mol%, ester bonds cannot be protected by sufficient electron-donating groups, and the resin diluted by water is easy to have poor stability and generate a layering phenomenon; if the content of the monomer (B) is more than 15 mol%, the coating layer formed from the resin may have problems such as poor mechanical properties and insufficient hardness.

According to some embodiments of the invention, the resulting polyester has an acid number of no greater than 15mgKOH/g, for example, 15mgKOH/g, 12mgKOH/g, 10mgKOH/g, 8mgKOH/g, 6mgKOH/g, 4mgKOH/g, or 2mgKOH/g, preferably no greater than 10mgKOH/g, and more preferably no greater than 8 mgKOH/g.

3. Acrylic acid modified polyester resin

As described above, since at least one of the monomers (a-2), (a-3) and (a-4) constituting the polyester prepolymer has a double bond and the resulting polyester has a double bond available for addition reaction, the acrylic modified polyester resin can be produced by further reacting the double bond with a (meth) acrylic monomer (C)). The monomer having a double bond includes, but is not limited to, an alkenyl triol, an alkenyl diol, an alkenyl polyacid, an ester, or an anhydride. The amount of the monomer having a double bond introduced may affect the polyester modification effect, and the content of the monomer having a double bond is about 1 mol% to about 4.1 mol%, preferably about 2.5 mol% to about 3.5 mol%, and more preferably about 2 mol% to about 3 mol%, based on the total number of moles of the monomers forming the acrylic modified polyester resin. If the content is less than 1 mol%, the self-polymerization phenomenon of the acrylic monomer is extremely easy to occur, so that the resin contains two macromolecules of polyester and polyacrylic acid, and the appearance of the resin is easy to appear white haze because the polyester and the polyacrylic acid are not good in compatibility; if the content is more than 4.1 mol%, a large amount of double bonds form self-crosslinking, the viscosity of the resin is rapidly increased, and the resin is easy to be gelatinized in the synthesis process.

Monomer (C) (meth) acrylic monomer

The acrylic modified polyester resin of the present invention is formed by using a (meth) acrylic monomer as a modifying monomer (C)) and grafting the (meth) acrylic monomer onto a polyester by reacting a double bond on the polyester with a double bond of the monomer (C), thereby improving the mechanical strength and resistance of a coating layer, and at the same time, improving hydrolysis resistance.

The (meth) acrylic monomer used in the present invention includes (meth) acrylic acid, alkyl (meth) acrylates, or a combination thereof. Examples of alkyl (meth) acrylates suitable for use in the present invention include, but are not limited to: (meth) acrylic acid C₁-C₁₂Alkyl esters, wherein the alkyl group may optionally be further substituted with a hydroxy group.

In one embodiment, the amount of monomer (C) is about 20 to about 60 mol%, preferably about 35 to about 50 mol%, and more preferably about 30 to about 40 mol%, based on the total moles of monomers forming the acrylic modified polyester resin.

In one embodiment, examples of (meth) acrylic monomers useful in the present invention include, but are not limited to: acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, and the like.

In order to improve the compatibility of the modified polyester resin obtained by the invention with water, the monomer (C) may comprise a proper amount of a monomer having a hydrophilic group, such as a carboxylic acid group or a sulfonic acid group, and the hydrophilic group helps to make the acrylic modified polyester resin obtained by the invention disperse in water more stably, so that the acrylic modified polyester resin can be used as a water-dilutable acrylic modified polyester resin, and meets the environmental protection specifications and current trends more. The above-mentioned monomer having a hydrophilic group is, for example, (meth) acrylic acid monomer. The (meth) acrylic monomers include, but are not limited to: acrylic acid, methacrylic acid. Acrylic having a low glass transition temperature (Tg) combines flexibility (softness) and toughness (toughnesss), prevents a coating from being broken when it is impacted, maintains a high degree of gloss of a curved surface, and the like, and is suitable for use in outer cans including food cans, beverage cans, trash cans, paint cans, and the like. In one embodiment, the (meth) acrylic monomer is present in an amount of about 0.5 to about 1.2 mole percent, preferably about 0.7 to about 1 mole percent, and most preferably about 0.8 to about 0.9 mole percent, based on the total moles of monomers used to form the acrylic modified polyester resin. If the content of the (meth) acrylic acid monomer is less than 0.5 mol%, the introduced hydrophilic group is insufficient, and the polyester resin cannot be stably dispersed in water; if the content of the (meth) acrylic acid monomer is more than 1.2 mol%, the excessive hydrophilic property may increase the hydrolysis phenomenon of ester bonds, resulting in poor water resistance, boiling resistance and stability.

Properties of acrylic-modified polyester resin

The acrylic modified polyester resin provided by the present invention has a number average molecular weight (Mn) of about 500g/mol to about 5,000g/mol, preferably about 1,000g/mol to about 3,000g/mol, more preferably about 1,000g/mol to about 2,000g/mol, and particularly preferably about 1,000g/mol to about 1,500 g/mol. If the number average molecular weight of the acrylic modified polyester resin is too low (for example, less than 500g/mol), the branching ratio of the resin is low, the reactive functional group is insufficient, the crosslinking density is too low when reacting with the curing agent, the boiling resistance or steaming resistance when being used as a coating film is affected, and the finished product is easy to have a light loss phenomenon after being boiled in water; on the other hand, when the number average molecular weight of the acrylic modified polyester resin is too high (for example, higher than 5,000g/mol), there is a problem that the viscosity of the resin is too high and the resin is gelled and difficult to apply for coating.

The polydispersity index (PDI) is the ratio (Mw/Mn) of the weight average molecular weight (Mw) divided by the number average molecular weight (Mn), with larger PDI indicating a broader molecular weight distribution and a higher branching ratio. In a preferred embodiment of the present invention, the acrylic modified polyester resin provided by the present invention has a polydispersity index (PDI) in the range of 8 to 30, preferably 8 to 20. When the PDI of the resin is less than 8, the branching ratio of the resin is too low, and the formed coating layer has poor resistance to boiling and steaming; when the PDI of the resin is more than 30, the viscosity of the resin is high, the crosslinking density is too high, and the coating construction is difficult.

The acid value of the acrylic modified polyester resin provided by the invention is 20mgKOH/g to 60mgKOH/g, preferably 35mgKOH/g to 55mgKOH/g, and more preferably 40mgKOH/g to 50 mgKOH/g. Carboxyl in the resin can increase the compatibility with a water solvent and a reaction functional group with a curing agent, if the acid value is more than 60mgKOH/g, the water resistance of a coating film is poor, and the storage stability of the resin diluted by water is poor; if the acid value is less than 20mgKOH/g, the bearable water dilution capability of the resin is weaker due to insufficient hydrophilic functional groups after the resin is transferred to water, and the VOC of the coating cannot be effectively reduced.

On the other hand, in the pattern obtained by analyzing the acrylic modified polyester resin by the PY-GC-MS method, the ratio of the signal integral value of pentaerythritol to the signal integral value of trihydric alcohol in the acrylic modified polyester resin is 0.05 to 0.35, preferably 0.06 to 0.33, and more preferably 0.07 to 0.3. The coating formed by using the acrylic modified polyester resin has good glossiness, for example, the 60-degree glossiness tested by GB/T9754-2007 standard is at least 76, and the 60-degree glossiness after the boiling resistance test can still maintain more than 67.

The composition and content of the acrylic modified polyester resin of the present invention were analyzed by Pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS). Thermal cracking gas chromatography mass spectrometry is one of the analytical methods commonly used in the art for analyzing polymer composition, in which a polymer is cracked into volatile small molecules at a high temperature, and then introduced into a mass spectrometer (e.g., a gas chromatography mass spectrometer) for analysis, and the structure/composition of the polymer and the content of each component can be known from the obtained spectrum. The thermal cracking temperature used in the present invention is a temperature commonly used by those skilled in the art, and is generally between 400 ℃ and 900 ℃, preferably between 500 ℃ and 600 ℃.

Preparation method of acrylic acid modified polyester resin

The invention provides a method for preparing acrylic acid modified polyester resin, which comprises the following steps:

(1) forming a polyester by a polycondensation reaction of monomers (A-1), (A-2), (A-3), (A-4) and a naphthenic dibasic acid, wherein at least one of the monomers (A-2), (A-3) and (A-4) has a double bond; and

(2) (meth) acrylic monomers are added and grafted onto the polyester by reaction with the double bonds to form an acrylic modified polyester resin.

The method of the step (1) of preparing the acrylic modified polyester resin of the present invention may be a one-pot process in which the monomers (a-1), (a-2), (a-3), (a-4) and the naphthenic dibasic acid are polycondensed together to form the polyester, or a stepwise process in which the monomers (a-1), (a-2), (a-3) and (a-4) are polycondensed to form a polyester prepolymer, and then the naphthenic dibasic acid is added as a monomer providing an ester bond protection function to polycondensed with the residual alcohol groups on the polyester prepolymer to form the polyester. The operation of the one-pot method is simple. The stepwise method is generally applied to the synthesis method, and in some examples of the present invention, the stability of the obtained polymer in water is superior by using the stepwise method.

In the step (1), the cross-linking density of the polyester can be improved and the structure of the polyester can be strengthened by introducing the monomer (A-1) pentaerythritol into the polyester main chain, so that the polyester cannot be disintegrated due to partial hydrolysis to cause coating shedding; meanwhile, because the crosslinking density is improved, water molecules are not easy to penetrate into the polyester structure, and the effect of inhibiting hydrolysis can be achieved.

In some embodiments, the ratio of the total moles of polyol monomers (i.e., monomers (A-1), (A-2), and (A-3)) to the total moles of polyacid monomers (A-4), and (B)) making up the polyester is from about 0.8 to about 1.60, preferably from about 0.95 to about 1.40, and more preferably from about 1.05 to 1.25.

In addition, through the acrylic modified monomer added in the step (2), the solubility and the compatibility of the resin to water can be increased, the aim of reducing the VOC of the resin is fulfilled, and the hardness and the crosslinking density of the coating can also be increased, so that the coating has better boiling resistance and steaming resistance than pure polyester resin.

Through the combination, the acrylic modified polyester resin prepared by the invention has good boiling resistance, can resist high-temperature boiling and has good adhesion to a base material.

The operating temperature in the above steps (1) to (2) is not particularly limited as long as the reaction can be smoothly carried out and completed. For example, in a step-by-step process, the polycondensation reaction to form the polyester prepolymer can be conducted at a temperature of about 150 to 230 ℃, preferably 170 to 230 ℃; then, a naphthenic dibasic acid is added thereto to conduct polycondensation at a temperature of about 150 to 230 ℃, preferably 170 to 230 ℃. Step (2) may be carried out at a temperature of 135 to 145 ℃, preferably 138 to 142 ℃.

In step (1), an esterification catalyst and a solvent may be added as required. Examples of esterification catalysts are for example but not limited to: an organotin catalyst, an organotitanium catalyst, or an organozinc catalyst. Commonly used catalysts include zinc acetate, zinc propionate, dibutyltin oxide, dibutyltin dilaurate, butyl titanate, and isobutyl titanate, among others.

In step (2), a radical initiator may be added as necessary, such as, but not limited to: azo compounds, such as Azobisisobutyronitrile (AIBN), azobiscyanovaleric acid (ACVA), 1' -azobis (cyclohexanecarbonitrile) (ACHN), α -phenylazotriphenylmethane; peroxides, such as dibenzoyl peroxide, dicumyl peroxide, diacetyl peroxide, dilauroyl peroxide, di-t-butyl peroxide, t-butyl peroxybenzoic acid; persulfates, for example ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate.

Coating compositions comprising acrylic modified polyester resins

The invention also provides a coating composition which comprises the acrylic modified polyester resin. In some embodiments, the coating composition of the present invention comprises an acrylic modified polyester resin as described above, a solvent, and optionally additives. In some embodiments, the aforementioned coating composition is an aqueous coating composition.

The aforementioned solvent may be water, alcohol ethers or a combination thereof. Examples of alcohol ethers include, but are not limited to, ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, and the like.

Optional additives may be, for example, pigments, crosslinking agents, curing agents, neutralizing agents, etc., and one or more additives may be added as required.

The foregoing pigment may be an inorganic pigment or an organic pigment, examples including, but not limited to, phthalocyanine blue, phthalocyanine green, permanent yellow, red iron oxide, yellow iron oxide, black iron oxide, zinc phosphate, titanium dioxide, calcium carbonate, barium sulfate, aluminum oxide, silicon oxide, carbon black, metal powder.

The curing agent is generally an amine-based resin or an aziridine curing agent.

The neutralizing agent can be N, N-dimethylethanolamine, N-diethylethanolamine, triethylamine,

2-amino-2-methyl-1-propanol, triethanolamine, diethanolamine, aqueous ammonia or combinations thereof.

Use of aqueous coating compositions

The coating layer obtained from the aqueous coating composition of the present invention has good adhesion to the surface of the article to be coated (hereinafter referred to as "substrate surface"). Such substrates are exemplified by, but not limited to: a metal substrate, a plastic substrate, a glass substrate, preferably a metal substrate. The kind of the metal substrate is not particularly limited, and may be, for example, iron, steel, aluminum, tin, or an alloy material made of one or more metals.

In summary, compared to the prior art, the present invention has at least one or more of the following advantages:

(1) the cross-linking density is improved by introducing pentaerythritol into the polyester main chain, water molecules are less prone to penetrate into the polyester structure, and the hydrolysis inhibiting effect can be achieved.

(2) By introducing pentaerythritol and trihydric alcohol into the polyester main chain, the cross-linking density of the polyester can be improved and the coating structure can be strengthened under the regulation and control of a certain proportion, and the resin is not gelled due to overhigh cross-linking density in the reaction process. During boiling and steaming, even if partial ester bonds in the polyester structure of the coating are hydrolyzed and damaged, the structure is still not disintegrated to cause the coating to fall off.

(3) By introducing naphthenic dibasic acid into the polyester main chain, the effect of electron donating groups is exerted on ester bonds of the polyester prepolymer, the hydrolysis reaction can be inhibited, and the storage stability of the coating and the stability of the coating are improved.

(4) By further adding naphthenic dibasic acid after the preparation of the polyester prepolymer, the storage stability of the obtained polymer in water is excellent.

The acrylic acid modified polyester resin prepared by the invention has good hydrolysis resistance, can resist high temperature and has good adherence to the surface of a coated article, so that the acrylic acid modified polyester resin can be applied to a coating composition to provide protection and decoration effects; in addition, the acrylic modified polyester resin prepared by the invention has good compatibility with water, so the acrylic modified polyester resin is particularly suitable for water-based coating compositions and can further meet the requirement of environmental protection. The coating prepared by the coating composition has good glossiness and chemical resistance, high hardness, high adhesion and high temperature and boiling water resistance, and can maintain the high glossiness and the high adhesion even if the coating is exposed in a high-temperature and high-humidity environment for a long time or is disinfected by boiling water, the coating cannot crack due to hydrolysis. Therefore, the paint has wide application, such as food field, automobile coating field and building field, and is especially suitable for being applied to water-based outer tank paint as a base coat or a gloss oil layer.

The following examples illustrate embodiments of the present invention and illustrate technical features of the present invention, but are not intended to limit the scope of the present invention. Any modifications or equivalent arrangements which may occur to those skilled in the art are intended to be included within the scope of the present invention as defined in the appended claims.

Examples of the invention

< preparation of acrylic modified polyester resin >

Example 1:

according to the mixture ratio shown in Table 2, monomer (A-1), monomer (A-2), monomer (A-3), monomer (A-4) and a catalyst are put into a reaction kettle, nitrogen is introduced, the temperature is slowly raised to 230 ℃ under stirring to carry out esterification reaction until the acid value is less than 6mgKOH/g of resin, and the temperature is cooled to 140 ℃.

And then putting the monomer (B) into a reaction kettle, continuously introducing nitrogen, slowly heating to 230 ℃ under stirring to perform esterification until the acid value is less than 8mg KOH/g of resin, adding butyl cellosolve to dilute, wherein the solid content of the obtained polyester is about 70 wt%, the viscosity is Z5-Z7, and cooling the resin to 135-145 ℃.

And (3) respectively and slowly dripping the monomer (C) and the initiator into the reaction kettle, finishing dripping within about 2 hours, and keeping the temperature at 140 ℃ for 2 hours to react until the viscosity is not increased any more, so as to obtain the acrylic modified polyester resin, wherein the acid value of the obtained acrylic modified polyester resin is 40-50mgKOH/g of resin, and the solid content is about 65 +/-1 wt%.

Examples 2 to 5 and comparative examples 1 to 4, 6 and 8

Acrylic modified polyester resins of examples 2 to 5 and comparative examples 1 to 4, 6 and 8 were prepared in the manner described in example 1 and in the formulation shown in Table 2.

Comparative example 5

According to the proportion shown in Table 2, monomer (A-1), monomer (A-2), monomer (A-3), monomer (A-4), monomer (B), solvent and catalyst are put into a reaction kettle, nitrogen is introduced, the temperature is slowly raised to 230 ℃ under stirring to carry out esterification reaction until the acid value is less than 8mg KOH/g of resin, a proper amount of ethylene glycol butyl ether is added for dilution, the solid content of the obtained polyester is about 70 wt%, the viscosity is Z5-Z7, and the resin is cooled to 135-145 ℃.

And (3) respectively and slowly dripping the monomer (C) and the initiator into the reaction kettle, finishing dripping for about 2 hours, and keeping the temperature at 140 ℃ for 2 hours for reaction until the viscosity is not increased any more, thereby obtaining the acrylic modified polyester resin.

Comparative example 7

According to the mixture ratio shown in Table 2, monomer (A-2), monomer (A-3), monomer (A-4), solvent and catalyst were put into a reaction kettle, nitrogen was introduced, the temperature was slowly raised to 230 ℃ under stirring to perform esterification reaction until the acid value was less than 6mg KOH/g resin, and the temperature was cooled to 140 ℃.

And adding tertiary (tertiary) glycidyl carbonate to react until the acid value is less than 8mgKOH/g of resin, then adding a proper amount of ethylene glycol butyl ether to dilute, wherein the solid content of the obtained polyester is about 70 wt%, the viscosity is Z5-Z7, and cooling the resin to 135-145 ℃.

And (3) respectively and slowly dripping the monomer (C) and the initiator into the reaction kettle, finishing dripping for about 2 hours, and keeping the temperature at 140 ℃ for 2 hours for reaction until the viscosity is not increased any more, thereby obtaining the acrylic modified polyester resin.

Comparative example 9

Commercially available polyester resins: ETERKYD 5050-B-75(Eternal Materials)

< preparation of coating composition >

36 g of the acrylic modified polyester resin obtained in examples 1 to 5 and comparative examples 1 to 8 or the commercial polyester resin of comparative example 9, 2.4 g of N, N-diethylethanolamine, 2.5 g of the cosolvent Butyl glycol monobutyl ether (Butyl Cellosove; Dow chemical Co., Ltd., USA), 15 g of reverse osmosis water and 20 g of titanium dioxide (R902 +/DuPont) were stirred at 3000rpm for 2 hours, and after confirming sufficient mixing, 6 g of the curing agent was added

303; cyanohydrin corporation, usa) to prepare a coating composition.

< preparation of coating layer >

The tinplate is used as a base material, a NO.55 roller rod (the wire winding diameter is 1.4m/m, the wet film thickness is 128.73 mu m) is used for coating the coating on the base material in a rolling coating mode, the base material is placed in a 120 ℃ oven for baking for 30 minutes, the temperature is raised to 200 ℃ for baking for 10 minutes, and the thermosetting film forming is completed.

< resin Property test >

Determination of the solid content

The aluminum dish blank weight is finely weighed as W0, then 0.45-0.55 g of resin is evenly placed in the aluminum dish to be flattened and weighed, and the obtained weight is recorded as W1 after the blank weight of the aluminum dish is subtracted. The aluminum dish with the resin was then placed in an oven at 150 ℃ for 15 minutes to remove the solvent, the dish was removed and cooled to room temperature before weighing, and the weight was recorded as W2.

Solid content (%) - (W2-W0) × 100%/W1

Determination of molecular weight (Mw, Mn) and molecular weight distribution (polydispersity index: PDI ═ Mw/Mn)

M_WAnd M_nThe measurement of (2) was carried out by Gel Permeation Chromatography (GPC) (Waters 1515Isocratic, high pressure pump system Waters 717, Waters International, Inc., liquid chromatography and autosampler Waters 717; detector Waters 2414) as a solvent, THF (tetrahydrofuran) as a Column, Waters Styragel Column, HR 4E, HR 3, HR 1, HR 0.5 as a Column, which were connected in series and used at a Column temperature of 40 ℃ and a flow rate of 0.6 ml/min. The weight average molecular weight (Mw) and the molecular weight distribution (Mw/Mn) are in terms of polystyrene standards.

Determination of viscosity

Viscosity was measured using a bubble-type viscosity tube (gauge) standard method (GARDNER). The resin sample was poured into a special viscosity tube (GARDNER tube, D ═ 10.65 ± 0.25mm) to the lower mark position, then the orifice was sealed with a cork stopper and pressed to the upper mark of the viscosity tube. Then, the viscosity tube (sample tube) containing the resin and the viscosity tube of the standard product are placed in a constant temperature water tank at 25 ℃ for about 20 minutes. Then, the sample tube and the standard viscosity tube are aligned and inverted by 180 degrees rapidly, the rising speed of the bubble in the sample tube and the standard viscosity tube is compared, the mark closest to the standard viscosity tube is used to represent, and the mark and the viscosity are converted as shown in Table 1.

Mark mark	Z1	Z2	Z3	Z4	Z5	Z6	Z7
								Viscosity (stoke)	27	34	46.3	62	93.5	148	200

Measurement of acid value

About 1 g of the sample was weighed and dissolved in 20 ml of a neutral solution of toluene in alcohol (toluene: alcohol ═ 1:1), and after shaking to completely dissolve the sample, a phenolphthalein indicator was added. Titration was then carried out with an ethanol solution containing 0.1N potassium hydroxide until the solution appeared reddish.

Acid value (mgKOH/g) (titrated milliliters (mL) × 0.1N × 56.1)/(sample weight (g) × solid content (%))

Method for analyzing mass spectrum (PY-GC-MS) of thermally cracked peaches by sample deformation

The acrylic modified polyester resins prepared in examples and comparative examples were analyzed by JHP-5 thermal cracking gas chromatography mass spectrometer of JAI, Japan. The analytical methods are detailed below:

mixing l-2mg sample and 0.5ml tetramethyl ammonium hydroxide (Sigma-Aldrich 334901), heating to 536 deg.C in metal foil (such as nickel, cobalt, nickel or their alloy), thermally cracking for 10 s, folding the metal foil in half, and folding the sample in half; then, the sample in the metal foil is detected by an online thermal cracking-gas chromatography-mass spectrometer (PY-GC-MS).

The temperature rising procedure of the gas chromatograph is as follows: the injection port temperature was 280 deg.C, the initial temperature was 40 deg.C, held for 2min, then ramped to 60 deg.C at 4 deg.C/min, held for 0.5min, then ramped to 300 deg.C at 10 deg.C/min, held for 20 min.

Optionally, the parameters are controlled as follows: for example, the temperature for instantaneous thermal cracking of the sample can be 500-550 ℃; setting the temperature of the Curie point thermal cracker to be 250 ℃, and keeping the sample after thermal cracking in a gas phase; the operating conditions of the gas chromatograph may be set to a carrier gas flow rate of 12psi helium at constant pressure mode, and the split ratio may be 80: 1-100: 1; the working conditions of the mass spectrometer can be detected by adopting an EI source in a positive ion mode, wherein the electron energy is 70eV, the ion source temperature is 230 ℃, the mass spectrum interface temperature is 280 ℃, the scanning mode is a full scanning mode (29-650 amu), and the solvent delay is 1.9 min.

Data analysis and sample identification: comparing and calculating the total ion chromatographic data and mass spectrum data obtained by detection to obtain the composition and relative content of the alcohol in the sample, dividing the signal integral sum of the pentaerythritol by the signal integral sum of the trihydric alcohol (1,1, 1-trimethylolpropane) to obtain the ratio of the signal integral values of the pentaerythritol and the trihydric alcohol, and recording the ratio in table 3.

FIG. 2 is the thermal cracking mass spectrum of pentaerythritol and triol (1,1, 1-trimethylolpropane) standard.

FIG. 3 is total ion chromatography data according to thermal cracking mass spectrometry for the acrylic modified polyester resin of example 1.

FIG. 4 is total ion chromatography data according to thermal cracking mass spectrometry for the acrylic modified polyester resin of comparative example 1.

< test of coating Property >

Gloss of the coating

Measured according to the method GB/T9754-2007 determination of the specular gloss of pigmented paint films which do not contain metallic pigments.

Hardness of the coating

Measured according to the method of GB/T6739-2006 "determination of paint film hardness by the pencil method of colored paint and varnish".

Adhesion of coatings to substrate surfaces

Measured according to the method of GB/T9286-1998 test for marking test of paint films of paints and varnishes.

Flexibility of the coating

Measured according to the method of GB/T1731-1993 Standard for paint film flexibility measurements.

Solvent resistance test

Using a MEK Abrasion tester (Abrasion Test A20-339), a back-and-forth rubbing Test was performed on the coating using a 1000 gram weight of cotton cloth soaked in butanone solvent. Observing whether the coating is damaged or falls off due to friction. One of them was recorded once back and forth, and if the number of back and forth rubs was higher than 100 without damaging the coating or dropping the surface, "> 100" was recorded.

Steaming resistance test

And (3) putting the base material coated with the coating into a high-temperature sterilization pot (TM-328), cooking for 30 minutes at the temperature of 121 ℃, then decompressing, and cooling to room temperature.

< test on the stability of coating composition >

Adding about 2 g of N, N-diethylethanolamine into 35 g of the coating composition at normal temperature, adding 35 g of reverse osmosis water, uniformly stirring, sealing the mixed solution in a flat port, and placing the mixed solution in an oven at 60 ℃ to observe the change of the resin.

TABLE 2 (in moles)

TABLE 2-CONTINUOUS (in MOL)

TABLE 3

TABLE 3 continuation

Evaluation results

As shown in FIG. 1, the coating layer (a) formed by using the commercially available polyester resin of comparative example 9 and the coating layer (b) formed by using the acrylic-modified polyester resin of comparative example 1 both exhibited a significant peeling phenomenon after the retort resistance test and exhibited poor gloss. On the contrary, the coating layer (c) formed by using the acrylic modified polyester resin of example 1 of the present invention has good adhesion to the substrate, no peeling phenomenon in the retort resistance test, and good gloss can be maintained.

As shown in Table 3, the coating prepared from the acrylic modified polyester resin of the present invention has good gloss and chemical resistance, high hardness, high temperature resistance and boiling water resistance, and even after a boiling resistance test, the coating can maintain good gloss and solvent resistance and is not cracked due to hydrolysis. In addition, the acrylic acid modified polyester resin has good compatibility to water, and can maintain good stability even after being diluted by adding water, so the acrylic acid modified polyester resin can be applied to water-dilutable resins to further solve the problem of environmental protection.

In addition, the PY-GC-MS spectra of the acrylic modified polyester resin of the invention have signal integral values of pentaerythritol and triol in the range of 0.05 to 0.35, and the formed coating has 60 DEG gloss of at least about 76 as measured by GB/T9754-2007 standard, and has 60 DEG gloss of at least 67 as measured by retort resistance. The polyesters of the comparative examples do not satisfy the aforementioned conditions at the same time.

In comparative examples 1 and 7, since pentaerythritol was not used, and in comparative example 3, the amount of pentaerythritol used was too low, the resulting coating was not resistant to boiling, hydrolyzed at high temperature, and had poor gloss and solvent resistance. Comparative example 2 caused gelation due to the addition of excessive pentaerythritol.

Comparative example 4 does not use naphthenic dibasic acid, the stability of the obtained polymer in water is insufficient, hydrolysis occurs, and the appearance of the prepared water-based paint is turbid. Comparative example 5 the naphthenic dibasic acid was added to the polyester prepolymer during the preparation thereof, and the stability of the resulting polymer in water was also poor.

Comparative example 6 using a higher content of maleic anhydride, self-crosslinking was likely to occur due to a large amount of double bonds, the viscosity of the resin rapidly rose, and the prepared water-based paint appeared white turbid in appearance.

Comparative example 7 using a conventional glycidyl tertiary (t) -carbonate, the resulting coating had poor storage stability; and the coating does not contain pentaerythritol, cannot resist boiling, is hydrolyzed at high temperature, and has poor glossiness and solvent resistance.

Comparative example 8, which does not use a triol, cannot provide a proper degree of divergence of the coating structure to form a dense network through the synergistic effect of pentaerythritol and a triol, and thus the gloss and solvent resistance of the coating after retort test are not good.

Claims (12)

1. An acrylic modified polyester resin comprising:

(i) a polyester comprising units derived from a polyester prepolymer and a naphthenic dibasic acid monomer, wherein the polyester prepolymer is prepared from the following monomers by polycondensation:

(A-1) a step of adding pentaerythritol,

(A-2) a trihydric alcohol,

(A-3) a diol, and

(a-4) a polybasic organic acid monomer, an ester thereof, or an anhydride thereof, wherein the polybasic organic acid comprises an aromatic polybasic acid, an alkane polybasic acid, an alkene polybasic acid, or a combination thereof; and

(ii) a (meth) acrylic monomer grafted to the polyester;

wherein at least one of the monomers (A-2), (A-3) and (A-4) has a double bond, and the (meth) acrylic monomer is grafted onto the polyester by reacting with the double bond.

2. The acrylic modified polyester resin according to claim 1, wherein the ratio of the amount of the monomer (A-1) to the amount of the monomer (A-2) is about 0.02 to about 0.9 on a molar basis.

3. The acrylic modified polyester resin as claimed in claim 1, wherein the monomer (a-1) is contained in an amount of 0.07 to 3 mol% based on the total number of moles of the monomers forming the acrylic modified polyester resin.

4. The acrylic-modified polyester resin according to claim 1, wherein said monomer (A-2) is selected from the group consisting of alkyl triol, alkenyl triol, cycloalkyl triol and combinations thereof.

5. The acrylic modified polyester resin according to claim 1, wherein the monomer (a-2) is contained in an amount of 0.1 to 10 mol% based on the total number of moles of the monomers forming the acrylic modified polyester resin.

6. The acrylic modified polyester resin according to claim 1, wherein the naphthenic dibasic acid is selected from the group consisting of: cyclopropane dicarboxylic acid, cyclobutane dicarboxylic acid, cyclopentane dicarboxylic acid, cyclohexane dicarboxylic acid, hexahydrophthalic anhydride, and combinations thereof.

7. The acrylic modified polyester resin as claimed in claim 1, wherein the naphthenic dibasic acid is contained in an amount of 5 to 15 mol% based on the total number of moles of the monomers forming the acrylic modified polyester resin.

8. The acrylic modified polyester resin of claim 1, wherein the (meth) acrylic monomer is acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl methacrylate, or a combination thereof.

9. The acrylic modified polyester resin of claim 1, wherein the (meth) acrylic monomer content is 20 to 60 mol% based on the total number of moles of monomers forming the acrylic modified polyester resin.

10. The acrylic modified polyester resin of claim 1, wherein the ratio of the signal integral values of pentaerythritol to triol is from 0.05 to 0.35 in the spectrum obtained by thermal cracking mass spectrometry analysis of the acrylic modified polyester resin, and wherein the acrylic modified polyester resin forms a coating having a 60 ° gloss of at least 76 as measured by GB/T9754-2007 standard.

11. A method for preparing the acrylic modified polyester resin of any one of claims 1 to 10, comprising the steps of:

(1) forming a polyester by a polycondensation reaction of monomers (A-1), (A-2), (A-3), (A-4) and a naphthenic dibasic acid, wherein at least one of the monomers (A-2), (A-3) and (A-4) has a double bond; and

(2) (meth) acrylic monomers are added and grafted onto the polyester by reaction with the double bonds to form an acrylic modified polyester resin.

12. An aqueous coating composition comprising the acrylic modified polyester resin according to any one of claims 1 to 10.

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