KR20150087923A - Resin for powder paint having excellent storage stability and corrosion resistance and powder paint composition comprising the same - Google Patents

Abstract

The present invention relates to a copolymer resin for powder coating having excellent storage stability and corrosion resistance and a powder coating composition including the same and, more specifically, to an acrylic copolymer resin for powder coating and a powder coating composition including the same, wherein acrylic copolymer resin comprises only monomers having glass transition temperature (Tg) of a homopolymer of 25°C or more as a polymerized unit and has excellent storage stability, improved attachment properties between a substrate and a paint, strong resistance to thread-shaped corrosion and excellent chemical resistance, thereby being usefully applied to car components and an aluminum substrate.

Description

Technical Field [0001] The present invention relates to a resin for a powder coating material excellent in storage stability and corrosion resistance, and a powder coating composition containing the same,

The present invention relates to an acrylic copolymer resin for powder coatings excellent in storage stability and corrosion resistance, and a powder coating composition containing the same. More specifically, the present invention relates to an acrylic copolymer resin having excellent storage stability and improved adhesion between a substrate and a coating material, Which is excellent in chemical resistance and can be applied to automobile parts and aluminum foils, and a powder coating composition containing the same.

In general, the aluminum wheel clear coating system can be roughly divided into a three-coating system consisting of primer-base-clear and a single coating system. 3-Coating System is the most common method, which uses powder primer, solvent base and solvent clear, and the single coating system is to coat the base after coating to the base. Feature.

Such a single coating system is coated to the base, then the diamond is cut on the upper surface, and then the clear coat is applied, so that the corrosion resistance and the chemical resistance are lower than that of the multilayer system. Therefore, in order to be suitable for coating with a single coating system, clear corrosion resistance, chemical resistance and leveling must be excellent. However, solvent type clear coating is not suitable for a single coating system because there is a problem that a coating film is thinly coated and an edge cover is weak and corrosion resistance is weak. Therefore, many paint companies have been working to apply powder clear to a single coating system. Conventionally, there is a polyester type clear as a powder coating to be developed and used as a clear coat, but a polyester type clear is not only poor in weatherability but also a new type of paint is required because the appearance is much lower than that of a solvent type clear.

The solution to this problem is acrylic powder clear. Acrylic powder clear is superior in weatherability and chemical resistance due to the characteristics of acrylic resin itself and is known to be comparable in terms of appearance and curing conditions as compared with conventional solvent clear.

Filiform corrosion is the most recognized problem in developing acrylic powder coatings for aluminum. Seal corrosion is one of long-term properties, and it is one of the properties that is well recognized both in domestic and overseas automobile manufacturers. It is generally known that acrylic type is more susceptible to thread-like corrosion than polyester type. Further, it is known that acrylic powder resin is poor in storage property unlike liquid resin. Particularly, when the temperature of the paint increases due to the high temperature in the summer, the paint tends to cling to each other, which greatly affects appearance and workability.

Accordingly, there is a demand for development of an acrylic resin for a powder coating material having excellent storage stability and a strong corrosion resistance against yarn-shaped corrosion, and a powder coating material utilizing the same.

The present invention has been made to solve the problems of the prior art as described above, and it is an object of the present invention to provide a copolymer resin for a powder coating material having excellent storage stability and corrosion resistance (particularly, a strong corrosion resistance against thread- The technical problem is to provide.

In order to solve the above-mentioned technical problems, the present invention provides a copolymer resin comprising, as polymerized units, only monomers having a glass transition temperature (Tg) of 25 ° C or higher of a homopolymer.

According to another aspect of the present invention, there is provided a powder coating composition comprising the copolymer resin.

The powder coating composition containing the copolymer resin according to the present invention is excellent in corrosion resistance (particularly, corrosion resistance against thread-like corrosion) and storage stability in a high temperature and high humidity environment, and is also excellent in chemical resistance, As shown in FIG.

Hereinafter, the present invention will be described in detail.

The copolymer resin of the present invention contains, as polymerized units, only monomers which provide a homopolymer having a glass transition temperature (Tg) of 25 DEG C or higher, more preferably 30 DEG C or higher, and even more preferably 35 DEG C or higher. That is, all of the monomers constituting the copolymer resin of the present invention are homopolymers each of which provides a homopolymer having a Tg of 25 DEG C or higher, more preferably 30 DEG C or higher, even more preferably 35 DEG C or higher, to be. There is a problem that the coating composition using the copolymer resin containing as a polymerization unit the monomer which does not satisfy the above condition (that is, the Tg of the homopolymer is lower than 25 占 폚) has poor storage stability and corrosion resistance. In the present invention, monomers having a homopolymer Tg of 25 ° C to 350 ° C may be used. Monomers having a homopolymer Tg of 30 ° C to 200 ° C may be used, more preferably homopolymers having a Tg Lt; 0 > C to 150 < 0 > C.

Preferable examples of the monomer that can be contained as the polymerization unit in the copolymer resin of the present invention include N-methylol acrylamide, 2-hydroxypropyl methacrylate, propyl methacrylate, t-butylaminoethyl methacrylate, di Cyclopentenyloxyethyl methacrylate, acrylic acid dimer, glycidyl methacrylate, hexanediol diacrylate, t-butyl acrylate, triisopropylsilyl acrylate, benzyl methacrylate, hydroxyethyl methacrylate phthalate , 2-hydroxyethyl methacrylate, trimethylol propane triacrylate, tripropylene glycol diacrylate, ethyl methacrylate, diacetone acrylamide, isobutyl methacrylate, hydroxyisopropyl methacrylate, isopropyl Methacrylate, cyclohexyl methacrylate, triisopropylsilyl Acrylonitrile, methyl methacrylate, acrylic acid, t-butyl methacrylate, isobornyl methacrylate, meta-methyl methacrylate, methacrylonitrile, methacrylonitrile, methacrylonitrile, But are not limited to, acrylonitrile, methacrylonitrile, acrylonitrile, methacrylonitrile, acrylonitrile, methacrylonitrile, methacrylonitrile, Vinyl acetate, vinyl pyrrolidone, vinyl chloride, vinyl alcohol, vinyl toluene, styrene, t-butyl styrene, and the like, but are limited to those exemplified above no. Preferably, at least two kinds (more preferably three kinds or more) selected from the group consisting of glycidyl methacrylate, t-butyl acrylate, benzyl methacrylate, isobutyl methacrylate, styrene and methyl methacrylate Or more, and more preferably four or more monomers) can be used.

The copolymer resin of the present invention preferably has a solid content of 95% or more, a melt viscosity (200 ° C) of 100 cPs to 6,000 cPs, a glass transition temperature of 30 ° C to 105 ° C, Is preferably 3,000 to 40,000. The resin may be a thermosetting resin or a thermoplastic resin. When the resin is a thermosetting resin, the resin may contain at least one functional group selected from the group consisting of a carboxylic acid functional group, an epoxy functional group, a hydroxy functional group, an isocyanate functional group, an amino functional group and an unsaturated functional group can do.

In the copolymer resin of the present invention, if the solid content is less than 95%, the storage stability and workability may be deteriorated. If the melt viscosity (200 ° C) of the resin is less than 100 cPs, it may be difficult to form a coating film, and if it exceeds 6,000 cPs, the flowability and appearance may be deteriorated. If the glass transition temperature of the resin is less than 30 캜, the storage stability may deteriorate. If the glass transition temperature exceeds 105 캜, the appearance may be deteriorated and the coating film may be broken. If the weight average molecular weight of the resin is less than 3,000, the corrosion resistance, weather resistance, and chemical resistance may be deteriorated. If the weight average molecular weight exceeds 40,000, gelation and appearance, transparency, and dispersibility may be deteriorated.

The copolymer resin of the present invention can be produced by a conventional polymerization method and then recovering the solvent by using a solvent recovery apparatus so that the solvent content in the synthesized resin becomes 5% or less. For example, by heating the monomers listed above in the presence of an initiator at a temperature of 60 to 180 DEG C to synthesize a liquid resin, and then reducing the solvent content in the liquid resin to 5% or less by using a solvent recovery apparatus, To obtain the resulting copolymer resin.

Examples of initiators that can be used to prepare the copolymer resin according to the present invention include 2,2'-azobis (2-methylbutylonitrile), 2,2'-azobisisobutylonitrile, dibenzoyl peroxide, t Butyl peroxybenzoate, ditertiary butyl peroxide, t-butyl peroxy-2-ethyl hexanoate, t-butyl peroxyacetate, t-amylperoxy-2-ethylhexanoate, Oxide, dicumyl peroxide, or t-butyl hydroperoxide. However, the initiator that can be used in the present invention is not limited to those exemplified above.

The solvent which can be used in the polymerization reaction is not particularly limited as long as it does not adversely affect the reaction. Examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, , Ketone solvents such as methyl isobutyl ketone and methylaryl ketone, solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, methyl cellosolve acetate, cellosolve acetate, butyl cellosolve acetate, Ester solvents such as toluene and toluene, and alcohol solvents such as n-propanol, isopropanol, n-butanol, isobutanol, and t-butanol.

According to another aspect of the present invention, there is provided a powder coating composition comprising the above-described copolymer resin of the present invention.

In the powder coating composition of the present invention, the copolymer resin may be contained in an amount of 40 to 95 parts by weight, more preferably 60 to 90 parts by weight, based on 100 parts by weight of the coating composition. If the content of the copolymer resin in 100 parts by weight of the coating composition is less than 40 parts by weight, there may be a problem that gloss, leveling, adhesion and the like are lowered, and if it exceeds 95 parts by weight, there is a problem that hardness and weather resistance are lowered.

The powder coating composition of the present invention may further contain a curing agent. As the curing agent, a curing agent generally used for powder coating can be used without any particular limitation, and examples thereof include oxalic acid, malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, Dodecanoic acid, dodecanedioic acid, maleic acid, terephthalic acid, and the like, but not limited thereto. In the powder coating composition of the present invention, the acrylic copolymer resin may be contained in an amount of 5 to 60 parts by weight, more preferably 10 to 40 parts by weight, based on 100 parts by weight of the coating composition. When the content of the curing agent in 100 parts by weight of the coating composition is less than 5 parts by weight, there may be a problem that the hardness and the weather resistance are lowered, and when it exceeds 60 parts by weight, there is a problem that gloss, leveling and adhesion are lowered.

The powder coating composition of the present invention may further comprise at least one additive selected from the group consisting of a leveling agent, a pinhole inhibitor, a flow control agent, an ultraviolet absorber, an antioxidant and a coupling agent.

The leveling agent is used for improving the appearance of the coating film and can be used without any particular limitations as long as it is a leveling agent usually used in powder coating materials and is preferably selected from the group consisting of polyether-modified polydimethylsiloxane and polyester-modified polysiloxane More than one can be used. Preferably, the leveling agent may be included in the coating composition in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the coating composition. If the content of the leveling agent in the composition is too low, crating may occur, and if it is excessively large, the birth of the coating film may occur.

The pinhole preventing agent is also used for releasing volatile substances from the coating film during curing. Any pinhole preventing agent usually used for powder coating can be used without any particular limitation, and benzoin and the like can be preferably used. Preferably, the pinhole inhibitor may be included in the coating composition in an amount of 0.2 to 1 part by weight based on 100 parts by weight of the coating composition. If the content of the pinhole inhibitor in the composition is too small, the appearance may deteriorate, and if it is excessively large, the haze phenomenon may occur.

As the ultraviolet absorber (or light stabilizer), an ultraviolet absorber generally used in powder coating can be used without any particular limitation. Specifically, Tinuvin and IRGANOX series of Ciba Co. can be used have. Preferably, the ultraviolet absorber may be included in the coating composition in an amount of 1 to 5 parts by weight based on 100 parts by weight of the coating composition.

In addition to the above-mentioned additives, a catalyst for controlling the curing rate, a catalyst for controlling the calcination temperature, and the like may be additionally used as needed. Such additives may be included in an amount of less than 10 parts by weight based on 100 parts by weight of the coating composition.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the scope of the present invention is not limited to these examples.

[ Example  And Comparative Example ]

Comparative Example  One

A thermometer and a condenser was charged with 300 g of toluene in a nitrogen atmosphere, and the mixture was heated to 110 DEG C and refluxed. 270 g of styrene (homopolymer Tg: 100 占 폚), 270 g of methyl methacrylate (homopolymer Tg: 105 占 폚), 210 g of n-butyl methacrylate (homopolymer Tg: 22 占 폚) 250 g of acrylate (homopolymer Tg: 41 DEG C), 70 g of t-butyl peroxyacetate as an initiator and 250 g of toluene was uniformly added dropwise over 5 hours. Subsequently, the mixture was maintained at 110 ° C for 2 hours under reflux, and the solvent was recovered in vacuo at elevated temperature (210 ° C) and reduced pressure (-700 mmHg) to obtain a solid content of 95% or more. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 1,400 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 66.4 DEG C and a weight average molecular weight of 9,500.

Comparative Example  2

An acrylic resin was prepared in the same manner as in Comparative Example 1, except that 320 g of styrene, 320 g of methyl methacrylate, 110 g of n-butyl methacrylate and 250 g of glycidyl methacrylate were used as monomers. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 3,200 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 75.0 DEG C and a weight average molecular weight of 8,700.

Comparative Example  3

Except that 100 g of methyl vinyl ether (homopolymer Tg: -31 占 폚) as the monomer, 550 g of methyl methacrylate, 100 g of n-butyl methacrylate and 250 g of glycidyl methacrylate were used. Acrylic resin. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 1,600 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 60.0 DEG C and a weight average molecular weight of 8,300.

Example  One

An acrylic resin was prepared in the same manner as in Comparative Example 1, except that 250 g of styrene, 250 g of methyl methacrylate, 250 g of t-butyl acrylate (homopolymer Tg: 107 DEG C) and 250 g of glycidyl methacrylate were used as monomers Respectively. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 2,200 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 69.6 DEG C and a weight average molecular weight of 6,700.

Example  2

An acrylic resin was prepared in the same manner as in Comparative Example 1, except that 250 g of styrene, 250 g of methyl methacrylate, 250 g of benzyl methacrylate (homopolymer Tg: 54 DEG C) and 250 g of glycidyl methacrylate were used as monomers . The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 2,200 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 72.7 DEG C and a weight average molecular weight of 6,200.

Example  3

An acrylic resin was prepared in the same manner as in Comparative Example 1 except that 250 g of styrene, 250 g of methyl methacrylate, 250 g of isobutyl methacrylate (homopolymer Tg: 67 DEG C) and 250 g of glycidyl methacrylate were used as monomers Respectively. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 2,400 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 76.3 DEG C and a weight average molecular weight of 6,300.

Example  4

Except for using 250 g of styrene as a monomer, 250 g of isopropyl methacrylate (homopolymer Tg: 81 DEG C), 250 g of ethyl methacrylate (homopolymer Tg: 65 DEG C) and 250 g of glycidyl methacrylate, To prepare an acrylic resin. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 2,000 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 70.4 DEG C and a weight average molecular weight of 6,300.

Example  5

Except that 250 g of vinyltoluene (homopolymer Tg: 112 DEG C), 250 g of methyl methacrylate, 250 g of vinyl t-butylbenzoate (homopolymer Tg: 101 DEG C) and 250 g of glycidyl methacrylate were used as monomers An acrylic resin was prepared in the same manner as in Example 1. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 3,500 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 87.3 DEG C and a weight average molecular weight of 7,500.

Example  6

Except that 250 g of vinyl acetate (homopolymer Tg: 30 DEG C), 250 g of vinylcyclohexanoate (homopolymer Tg: 76 DEG C), 250 g of vinyl t-butylbenzoate and 250 g of glycidyl methacrylate were used as monomers An acrylic resin was prepared in the same manner as in Comparative Example 1. The obtained acrylic resin was a transparent powdery resin having a solid content of 99%, a melt viscosity (200 DEG C) of 2,400 cPs, an epoxy equivalent of 568 g / eq., A glass transition temperature of 76.3 DEG C and a weight average molecular weight of 7,000.

Comparative Example  4 to 6 and Example  7-12: Preparation of Coating Composition

The raw ingredients were compounded in the compositions shown in Table 1 below, premixed for 5 minutes in a mixer, and the premixed composition was extruded twice at 100 占 폚 using Exturder (ZSK 25, Werner & Pleider) Lt; / RTI > The resulting melt mixture was cooled in a cooling roller, followed by pulverization using a hammer mill and filtering to prepare powder coating compositions of Examples and Comparative Examples.

Experimental Example : Measurement of Physical Properties of Powder Coating Composition

The powder coating compositions prepared in the above Examples and Comparative Examples were electrostatically coated on an aluminum plate pretreated with a solution containing no chromium and cured under the conditions of 160 ° C * 20 minutes (substrate surface temperature) 80 탆. Each of the prepared coating films was tested for the following items. Specific test conditions are as follows, and the test results are shown in Table 2 below.

1. Leveling: Visual determination of smoothness of film

2. Gloss: 60 ° Reflectivity measurement using BYK Gloss meter (Higher is better)

3. Tape Attachment: Measuring the adherence of the substrate and the film (100 marks with the number of cuts per 100 cuts, the better the less the number of cuts cut)

4. Salt spray: Creep back measurement (GMW3286) after spraying at 35 ± 1 ℃ and 5% NaCl solution (pH 6.5 ~ 7.2) * 100 hours after X-cut on the coating film )

5. CASS: After the X-cut in film 35 ± 1 ℃, NaCl 5% + Cupric chloride (CuCl 2 H 2 O): 1 ± 0.1g / gallon + Glacial acetic acid 5.5ml / gallon (pH 3.1 ~ 3.3 ) * Creep back measurement after 168 hours spray (GMW14458) (smaller measurement value is better)

6. Chipping: -18 ℃ * After 4 hours 473 ± 10mm Gravel, hit the film at 70psi air pressure (GMW14700) (Higher GM rating is better)

7. Filiform: Crease-back measurement (GMW15287) after holding straight for 6 hours at 60 ° C * 85RH% for 672 hours after cutting straight on the coating film (smaller measurement value is better)

8. Stability of paint storage: After coating the paint in a vial bottle and keeping it at 35 ℃, observe the occurrence of blocking, and show the elapsed days since the first blocking occurred (better the longer the days passed)

The fill test, which is evaluated over a long period of time in a high temperature and high humidity environment, should be excellent in moisture resistance, corrosion resistance, and interlayer adhesion. As can be seen from the above Table 2, the powder coating compositions of the present examples were superior to the comparative examples in all the test items, and in particular, the corrosion resistance (salt spray, CASS, fill test) Excellent results were obtained.

Claims (11)

Wherein the homopolymer comprises only the monomers having a glass transition temperature (Tg) of 25 DEG C or higher as polymerization units. The copolymer resin according to claim 1, wherein the homopolymer comprises only the monomers having a glass transition temperature (Tg) of 30 DEG C or higher as polymerization units. The copolymer resin according to claim 1, wherein only the monomers having a glass transition temperature (Tg) of 35 占 폚 or higher of the homopolymer are contained as polymerization units. The positive photosensitive composition as claimed in claim 1, wherein the monomer is selected from the group consisting of N-methylol acrylamide, 2-hydroxypropylmethacrylate, propylmethacrylate, t-butylaminoethylmethacrylate, dicyclopentenyloxyethylmethacrylate, , Glycidyl methacrylate, hexanediol diacrylate, t-butyl acrylate, triisopropylsilyl acrylate, benzyl methacrylate, hydroxyethyl methacrylate phthalate, 2-hydroxyethyl methacrylate, trimethyl Diisopropyl methacrylate, isopropyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, trioctyl acrylate, diisopropyl acrylate, isobutyl methacrylate, isopropyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, Isopropyl silyl methacrylate, isobornyl acrylate, t-butylcyclohexyl Acrylate, methacrylate, trimethylcyclohexyl methacrylate, acrylonitrile, methyl methacrylate, acrylic acid, t-butyl methacrylate, isobonyl methacrylate, methacrylonitrile, methacrylic acid, acrylamide, methacrylamide Methylstyrene, phenylenevinyl ketone, vinyl t-butyl benzoate, vinyl cyclohexanoate, vinyl ethers such as acetoxystyrene, chlorostyrene, cyclohexyl vinyl ether, dimethyl styrene, ethoxystyrene, fluorostyrene, methoxystyrene, Wherein the copolymer resin is at least two kinds selected from the group consisting of acetate, vinylpyrrolidone, vinyl chloride, vinyl alcohol, vinyltoluene, styrene, and t-butylstyrene. The resin composition according to claim 1, wherein the monomer is at least two kinds selected from the group consisting of glycidyl methacrylate, t-butyl acrylate, benzyl methacrylate, isobutyl methacrylate, styrene and methyl methacrylate . The copolymer resin according to claim 1, which has a solid content of 95% or more, a melt viscosity (200 ° C) of 100 cPs to 6,000 cPs, a glass transition temperature of 30 ° C to 105 ° C, and a weight average molecular weight of 3,000 to 40,000. The copolymer resin according to claim 1, which is a thermosetting resin or a thermoplastic resin. The copolymer resin according to claim 7, wherein the thermosetting resin is a thermosetting resin comprising at least one functional group selected from the group consisting of carboxylic acid functional group, epoxy functional group, hydroxy functional group, isocyanate functional group, amino functional group and unsaturated functional group. A powder coating composition comprising the copolymer resin according to any one of claims 1 to 8. The powder coating composition of claim 9, further comprising a curing agent. The powder coating composition according to claim 9, further comprising at least one additive selected from the group consisting of a leveling agent, an anti-pinhole agent, a flow control agent, an ultraviolet absorber, an antioxidant and a coupling agent.