KR100220144B1 - Highsolid type acryl resin composition - Google Patents

Abstract

A high solid acrylic resin composition having excellent appearance quality, excellent mechanical properties such as hardness and workability as well as a low pollution type is disclosed. An acrylic resin composition composed of an acrylic resin copolymer and an initiator obtained from a monomer mixture composed of an organic acid group-containing monomer, at least two hydroxyl group-containing monomers, an aromatic nonfunctional unsaturated monomer and an aliphatic nonfunctional unsaturated monomer is provided. Despite its low molecular weight, it has excellent mechanical and chemical properties such as appearance quality, hardness, flex resistance, and acid resistance, so it is excellent for coating metals such as refrigerators, vending machines, and general home appliances.

Description

High Solid Acrylic Resin Composition

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high solid acrylic resin composition, and more particularly, to a high solid acrylic resin composition having excellent appearance quality, excellent mechanical properties such as hardness and workability, and a low pollution type.

Recently, in developed countries, the emission allowance for volatile organic solvents is strictly regulated and further strengthened in relation to the air pollution problem. Therefore, such environmental regulations are expected to be raised in Korea in the future. In this situation, as a suitable alternative to environmental regulations, a low pollution type paint based on a high solid resin that can relatively lower the content of volatile organic solvents has been developed and attracts great attention. Such a high solid resin can be manufactured using existing resin and paint manufacturing equipment, and the research is more important because it can be used as it is a coating line.

In the conventional high solid acrylic resin, in order to increase the nonvolatile content (solid content), a method of lowering the molecular weight of the resin to a low molecular weight or a method of reducing the amount of high volatile organic solvent used has been used. The main reason for this is to lower the molecular weight increase factor due to the absolute concentration of the resin when it is high-solidified so that there is no problem in spray workability when applying the paint.

However, due to the reduction of the crosslinking density due to the low molecular weight, coating properties such as impact resistance, hardness, and acid resistance are poor, adhesion is low, and problems such as yellowing of the coating film are revealed.

In addition, in the field of using a paint prepared using a conventional high solid acrylic resin, natural gas is mainly used as a heat source. In this case, various types of acid gases generated by incomplete combustion, such as carbon monoxide, nitrogen oxides, and sulfurous acid, are used. Gas and the like influenced the hardening of the coating film, resulting in deterioration of quality.

An object of the present invention is to select a suitable monomer in order to satisfy the required physical properties in view of the problems of the conventional high solid-based acrylic resin composition described above, thereby improving the function of the coating film excellent in impact resistance, hardness, adhesion and acid resistance. It is to provide a high-solid acrylic resin composition excellent in appearance quality as well as maintaining and not affected by acid gas.

In order to achieve the above-described present invention, an acrylic resin composition composed of an acrylic resin copolymer and an initiator obtained from a monomer mixture composed of an organic acid group-containing monomer, a hydroxyl group-containing monomer, an aromatic non-functional unsaturated monomer and an aliphatic non-functional unsaturated monomer is Is provided.

The resin composition of the present invention is a high solid with a low content of volatile organic solvent, and has a low molecular weight, as compared with conventional thermosetting acrylic resins. When the resin composition of the present invention is applied to a paint, it can be used to paint metals such as refrigerators, vending machines, and general appliances, which emphasizes the excellent appearance quality and the mechanical properties such as impact resistance, hardness, adhesion, and acid resistance. have.

Hereinafter, the present invention will be described in detail.

The resin composition according to the present invention can be synthesized according to a radical addition solution polymerization method by an initiator of monomers having a vinyl double bond. The composition of the monomer having a vinyl double bond is 0.5 to 5% by weight of the organic acid group-containing monomer, 20 to 50% by weight of the hydroxyl group-containing monomer, 5 to 40% by weight of the aromatic nonfunctional unsaturated monomer and aliphatic based on the total monomer weight. It consists of 10-60 weight% of nonfunctional unsaturated monomers.

The acrylic resin composition according to the present invention has an acid value of 2 to 25 mg KOH / g, a hydroxyl content of 1 to 5%, a glass transition temperature of 10 to 60 ° C, a nonvolatile content of 60% or more, and a Gardner viscosity of T to Y at 25 ° C. The number average molecular weight is 1,000 to 6,000, the weight average molecular weight is 2,000 to 15,000, and the molecular weight distribution is 2.5 or less.

The acrylic resin composition according to the invention preferably has an acid value of 5 to 9 mg KOH / g and a glass transition temperature in the range of 15 to 50 ° C.

If the acid value, which is a resin characteristic value, is 2 mg KOH / g or less, sufficient curing property cannot be exhibited with the crosslinking agent resin, and thus the reaction is delayed, and thus the cured coating film exhibits a lack of hardness, which is not preferable. When the acid value is 25 mg KOH / g or more, since excessive polarity is introduced into the resin, the viscosity of the solution increases during the polymerization, making the manufacturing operation difficult, which is not preferable. In addition, by promoting the activity of the acidic gas (wrinkle) phenomenon and gloss loss occurs, it is difficult to expect excellent appearance quality and shelf life.

When the hydroxyl content is 1% by weight or less, the crosslinking density is low and the molecular weight of the crosslinked coating film is small. Therefore, a coating film having sufficient physical properties cannot be obtained with such a low molecular weight high solid resin. On the contrary, when the hydroxyl content is 5% by weight or more, compatibility with the non-polar solvent as well as the crosslinked resin may be poor, so that excellent appearance quality cannot be expected.

In addition, resin having a glass transition temperature of 10 ° C. or less hardly expects sufficient hardness in the final coating film, and at 60 ° C. or more, the resin viscosity becomes high, and the elasticity and toughness of the coating film remarkably decrease, resulting in poor impact resistance and adhesion.

It is preferable that a number average molecular weight exists in the range of 1,000-6,000. If the number average molecular weight is 1,000 or less, sufficient crosslinking density cannot be obtained, and thus the physical properties of the cured coating film are lowered. If the number average molecular weight is 6,000 or more, a high solid resin having a nonvolatile content of 60% or more cannot be obtained.

Specific examples of the unsaturated monomer that can be used in the synthesis of the high-solid acrylic resin of the present invention include organic acid group-containing monomers such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, and anhydrides thereof. These can be used 1 type or in mixture of 2 or more types, respectively. 2-hydroxy ethyl acrylate, 2-hydroxy ethyl methacrylate, 4-hydroxy butyl acrylate, hydroxypropyl methacrylate etc. are mentioned as a hydroxyl-containing monomer. In addition, these hydroxyl group-containing monomers and epsilon caprolactone ring-opening part are epsilon caprolactone ring-opening derivatives (e.g., Fraxel FM-1, Fraxel FM-2, Fraxel FM-1 (trade name: manufactured by Daicel Chemical Industries, Ltd.)). Can be used. It is particularly preferable to use at least two or more hydroxyl group-containing monomer mixtures containing a ring-opening derivative of 4-hydroxy butyl acrylate or epsilon caprolactone among such hydroxyl group-containing monomers. More preferably, 5 to 20% of epsilon caprolactone ring-opening derivatives are included. As such, by using two or more kinds of hydroxyl monomers having different binding reactivity with the crosslinker resin, the curing reactivity can be shortened more quickly, and the crosslinking density can be increased to improve the mechanical properties and appearance quality.

Examples of the aromatic nonfunctional monomers include styrene and vinyl toluene. Examples of the aliphatic nonfunctional monomers include methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl methacrylate, normal butyl acrylate, and normal. Butyl methacrylate, isobutyl methacrylate, normal hexyl methacrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, cyclohexyl acrylate, vinyl acetate, acrylonitrile and the like. In addition, a monomer having a vinyl double bond can be used. It is especially preferable to use the thing of the form containing 6% or more of long-chain monomers whose carbon number of a substituent of a double bond position is 10 or more among the monomers which have such a vinyl double bond. In this way, excellent appearance and good functionality can be exhibited.

As crosslinking agent resin, there are melamine resin, urethane resin, etc., It is preferable to use 2-10% of urethane resin. If the urethane resin content is 2% or less, the adhesion decreases, and if 10% or more, the compatibility may be poor, so that gloss and clarity of appearance quality cannot be expected.

Examples of the thermal decomposition initiator used in the present invention include general thermal decomposition initiators such as benzoyl peroxide, azoisobutyronitrile and tert-butyl peroxy 2-ethylhexanoate.

As a chain transfer agent used for molecular weight control and a crosslinking function with a crosslinking agent, mercapto acetic acid, a normal dodecyl mercaptan, a mercapto propionic acid, etc. are mentioned. Resin synthesis temperature is 100-130 degreeC which is a general acrylic resin synthesis temperature.

The resin synthesis method proceeds by introducing the mixed solution containing the monomer and initiator described above into the reactor at a uniform rate for 2 to 4 hours. By adding it at such a uniform rate, reflux of the low boiling point solvent is prevented beforehand so that reaction temperature does not fall.

As described above, when the reaction conditions are stably induced, the monomer composition ratio and the functional group distribution are uniform, and the chain transfer agent having the functional group is attached to the terminal of the molecular structure to form a coating film through crosslinking with the crosslinking agent resin. By polymerizing in a linear direction, it is possible to obtain a high solid acrylic resin composition that ultimately exhibits excellent gloss and hardness, and has a good workability.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited thereto.

(Example 1)

A four-necked flask equipped with a thermometer, condenser, dropping funnel and stirrer was used as the reactor. 55 g of xylene and 14 g of normal butanol were placed in a flask, and then heated to 100 to 130 ° C. while stirring, and then the following monomer and initiator mixtures were added dropwise at a uniform rate over 3 hours while maintaining the temperature of the reaction constant.

After completion of the dropwise addition, the mixture was allowed to react for 1 hour, and then 0.5 g of azoisobutyronitrile was added to the flask to induce unreacted monomers to react, which was further maintained for 2 hours. Thus synthesized, an acrylic resin solution having an acid value of 7.8 mg KOH / g, a hydroxyl content of 1.9%, a glass transition temperature of 35 ° C, a nonvolatile content of 60%, a 25 ° C Gardner viscosity U, a number average molecular weight of 4,700 and a molecular weight distribution of 2.1 was obtained. .

(Example 2)

In the same manner as in Example 1, the following monomer and initiator mixtures were solution polymerized.

After completion of the dropwise addition, the mixture was allowed to react for 1 hour, and then 0.5 g of azoisobutyronitrile was added to the flask to induce unreacted monomers to react, which was further maintained for 2 hours. Thus synthesized to obtain an acrylic resin solution having characteristic values of acid value 7.8 mg KOH / g, hydroxyl group content 3.1%, glass transition temperature 20 ° C, nonvolatile content 60%, 25 ° C Gardner viscosity W, number average molecular weight 6,000, molecular weight distribution 1.9. .

(Example 3)

In the same manner as in Example 1, the following monomer and initiator mixtures were solution polymerized.

After completion of the dropwise addition, the mixture was allowed to react for 1 hour, and then 0.5 g of azoisobutyronitrile was added to the flask to induce unreacted monomers to react, which was further maintained for 2 hours. Thus synthesized, an acrylic resin solution having an acid value of 7.8 mg KOH / g, a hydroxyl content of 3.0%, a glass transition temperature of 43 ° C, a nonvolatile content of 60%, a 25 ° C Gardner viscosity V, a number average molecular weight of 5,500, and a molecular weight distribution of 2.2 was obtained. .

(Comparative Example 1)

80 g of xylene and 20 g of normal butanol were added to the same four-necked flask as in Example 1, and the mixture was heated to 100-130 ° C. while stirring, and then the mixture of the monomers and the initiators were maintained at a uniform speed for 3 hours while keeping the temperature constant. It was dripped.

After completion of the dropwise addition, the mixture was allowed to react for 1 hour, and then 0.5 g of azoisobutyronitrile was added to the flask to induce unreacted monomers to react, which was further maintained for 2 hours. Thus synthesized to obtain an acrylic resin solution having an acid value of 7.8 mg KOH / g, a hydroxyl content of 3.0%, a glass transition temperature of 9.2 ° C, a nonvolatile content of 50%, a 25 ° C Gardner viscosity S, a number average molecular weight of 6,000 and a molecular weight distribution of 2.5. .

(Comparative Example 2)

80 g of xylene and 20 g of normal butanol were added to the same four-necked flask as in Example 1, and then the mixture was heated to 100-130 ° C. while stirring, and then the mixture of the monomers and the initiator was maintained at a uniform speed for 3 hours while maintaining the temperature constant. It was dripped.

After completion of the dropwise addition, the mixture was allowed to react for 1 hour, and then 0.5 g of azoisobutyronitrile was added to the flask to induce unreacted monomers to react, which was further maintained for 2 hours. Thus synthesized to obtain an acrylic resin solution having characteristic values of acid value 5.0 mg KOH / g, hydroxyl content 1.9%, glass transition temperature 11.6 ° C, nonvolatile content 50%, 25 ° C Gardner viscosity M, number average molecular weight 5,000, molecular weight distribution 2.3. . The characteristic values of the acrylic resin obtained in Table 1 below are shown.

Characteristics of Acrylic Resin

TABLE 1

40 to 60% of acrylic resin, melamine resin (trade name (manufactured by Daehan Paint Co., Ltd.): M3) in order to examine the coating film properties of the resins of Examples 1, 2 and 3 and Comparative Examples 1 and 2 obtained as described above. -3333 (melamine formaldehyde resin)) 4-8%, urethane resin (trade name (product of Japan Enfiyu): 3-9% of coronate dish -2507), white pigment (brand name (product of the United States DuPont)): al-960 ) 28-37%, dispersant (Brand name, manufactured by BWK Chemie Co., Ltd .: BWK-161) 0.5-2.0% of solvent and methyl isobutyl ketone, butyl cellosolve, etc. are mixed and dispersed (dispersion particle size: 7 μm or more), here, an anti-cuttering agent, an anti-pinhole agent, etc., which are suitable additives, are used for smoothness, pinholes, and cracking prevention of the coating film appearance. The viscosity of the paint thus prepared was adjusted to 20 seconds at 25 DEG C with Pod Cup No. 4, and then the pre-treated 0.5 T-siaal plate was coated with a dry film thickness of 25 to 35 탆 and heated at 160 DEG C for 20 minutes. It was dried to prepare a coating specimen. After 24 hours, the coated film was evaluated for coating performance.

Coating performance test was evaluated according to the general coating properties evaluation method. The measured results of the coating film performance test are shown in Table 2 below.

Coating performance test result

TABLE 2

◎: Excellent coating state

1) The non-volatile content is 2.5 to 3.0g of the paint sample was collected by volatilizing the solvent at 105 ℃ for 3 hours and quantified the amount of solid content was expressed as a percentage.

2) Gloss was measured with a 60 ° Glass polisher.

3) The visual appearance evaluated the glossiness, the leveling degree on the coating film, and the fog.

4) Pencil hardness was measured using a Mitsubishi's pencil.

5) Impact resistance indicated the maximum height (in cm) in which the crack of the coating film does not appear when the weight of 500 g is dropped freely at a height of 20 cm.

6) Flexural resistance was measured by the Eriksen tester until the coating film was ruptured.

7) Acid resistance was measured by immersing the coating film in a water bath containing 5% acetic acid (CH ₃ COOH) solution and then swelling, gloss reduction and discoloration of the coating film.

8) The alkali resistance was measured by immersing the coating film in a tank containing 5% NaOH solution and measuring the time when the coating film was swollen, reduced in gloss, and discolored.

The acrylic resins of Examples 1, 2, and 3 are high solids having a nonvolatile content of 60%, and despite low molecular weight, as shown in the coating performance test of Table 2, they exhibit excellent mechanical quality, hardness, bending resistance, and acid resistance, and mechanically. On the other hand, the acrylic resins of Comparative Examples 1 and 2 had a nonvolatile content of 50%, and exhibited undesirable results in mechanical and chemical properties such as appearance quality, hardness, flex resistance and acid resistance. Able to know.

Therefore, according to the present invention, it is possible to obtain a high-solid acrylic resin composition having excellent mechanical properties such as impact resistance, hardness, adhesion, and acid resistance, as well as excellent appearance quality without being affected by acidic gases. have.

The resin composition of the present invention is very excellent for use in coating metals such as refrigerators, vending machines, general home appliances, etc. which require excellent hardness, impact resistance, acid resistance and excellent appearance film quality.

Claims (5)

In an acrylic resin composition formed from a monomer mixture consisting of an organic acid group-containing monomer, at least two hydroxyl group-containing monomers, an aromatic non-functional unsaturated monomer, and an aliphatic non-functional unsaturated monomer, the monomer mixture is based on the weight of the total monomers. 0.5 to 5% by weight of the organic acid group-containing monomer, 20 to 50% by weight of the at least two or more hydroxyl group-containing monomers, 5 to 40% by weight of the aromatic nonfunctional unsaturated monomer and 10 to 60% by weight of the aliphatic nonfunctional unsaturated monomer The acrylic resin composition has an acid value of 2 to 25 mg KOH / g, a hydroxyl content of 1 to 5%, a glass transition temperature of 10 to 60 ° C, a nonvolatile content of 60% or more, and a number average molecular weight of 1,000 to 6,000. The weight average molecular weight is 2,000-15,000, and molecular weight distribution degree is 2.5 or less, The acrylic resin composition characterized by the above-mentioned. The acrylic resin composition according to claim 1, wherein an acid value of the acrylic resin composition is 5 to 9 mg KOH / g, and a glass transition temperature is 15 to 50 ° C. The organic acid group-containing monomer according to claim 1, wherein at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid and anhydrides thereof is used, and as the aromatic nonfunctional unsaturated monomer, At least one of styrene or vinyl toluene is used, and as the aliphatic nonfunctional unsaturated monomer, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl methacrylate, normal butyl acrylate, normal butyl methacrylate, At least one selected from the group consisting of isobutyl methacrylate, normal hexyl methacrylate, lauryl methacrylate, isobornyl acrylate, isobonyl methacrylate, cyclohexyl acrylate, vinyl acetate and acrylonitrile Characterized by using Acrylic resin composition. The method according to claim 1, wherein the hydroxyl group-containing monomer is one selected from the group consisting of 2-hydroxy ethyl acrylate, 2-hydroxy ethyl methacrylate, 4-hydroxy butyl acrylate and hydroxypropyl methacrylate or epsilon. An acrylic resin composition comprising at least two hydroxyl group-containing monomer mixtures, including ring-opening derivatives of caprolactone. The acrylic resin composition according to claim 4, wherein the epsilon caprolactone ring-opening derivative comprises 5 to 20%.