Epoxy resin finish paint coating composition

Abstract

The invention relates to an epoxy resin topcoat coating composition. The epoxy resin topcoat coating composition comprises a main agent part and an auxiliary agent part, wherein the main agent part comprises bisphenol A type unmodified epoxy resin, fatty acid modified epoxy resin, pigment and a solvent; and a curing agent part containing a cured resin including one or more resins selected from the group consisting of amine resins and amide resins, and a butadiene-based rubber resin, the butadiene-based rubber resin having an active hydrogen equivalent (AHEW) of 800 to 1,000 g / eq.

Description

Technical Field

[0001] The present invention relates to an epoxy resin coating composition which has low volatile organic compound (VOC) content and good environmental protection, excellent composition operability and excellent impact resistance, chemical resistance and weather resistance of the prepared coating film, and is very suitable as a topcoat for iron structures such as containers. Background Art

[0002] Conventional container painting usually involves only zinc spraying or epoxy zinc primer coating on the iron base material such as the frame, followed by epoxy intermediate coating and acrylic or urethane topcoat. In this case, acrylic or urethane paints with excellent weather resistance are used as topcoat paints to minimize changes in color and gloss when the coating film is exposed to external environments such as sunlight.

[0003] For example, Korean Patent No. 1619099 (Patent Document 1) discloses a steel coating construction process, which includes: a step of applying a water-soluble epoxy resin antirust coating containing a main agent of a water-soluble epoxy resin and an amine curing agent; and a step of applying a polyurethane antirust coating containing a water-dispersible acryl urethane resin. However, as for the coating film prepared with the antirust coating disclosed in Patent Document 1, although it has excellent weather resistance, it has the disadvantage that the coating film is fragile when impacted.

[0004] In addition, in order to improve the mechanical properties of the coating film, so as to store the loaded goods more safely and improve the rust resistance of the coating film, epoxy resin topcoat is also applied. However, environmental protection regulations have been strengthened in the Chinese market, which accounts for more than 95% of the world's container production. Therefore, the paint used inside the ordinary dry container production line has been fully converted to water-based paint since April 2017. In addition, from the second half of 2021, in order to reduce the volatile organic compounds (VOC) generated in the production process of refrigerated containers, the use of traditional oil-based paints will be stopped in other processes except pre-treatment, and low-VOC environmentally friendly paints such as water-based paints or high-solid content paints will be used. However, there is no water-based product for traditional epoxy resin topcoats, so oil-based epoxy resin topcoats are used.

[0005] Therefore, there is a real need to develop an epoxy resin topcoat coating that can form a coating film of the same quality as conventional oil-based coatings, has a low VOC content and is environmentally friendly, and has excellent flexibility and impact resistance.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Korean Patent No. 1619099 (Published on May 2, 2016) Summary of the invention

[0009] (Problems to be solved by the invention)

[0010] Therefore, the object of the present invention is to provide an epoxy resin coating composition which has a low volatile organic compound (VOC) content and good environmental performance, has excellent operability of the composition, and has excellent impact resistance, chemical resistance and weather resistance of the prepared coating film, thereby being very suitable as a topcoat for steel structures such as containers.

[0011] (Measures taken to solve the problem)

[0012] The present invention provides an epoxy top-coat coating composition, comprising:

[0013] A main agent part, which comprises bisphenol A type unmodified epoxy resin, fatty acid modified epoxy resin, pigment and solvent; and

[0014] a curing agent part containing a curing resin of one or more resins selected from the group consisting of amine resins and amide resins and a butadiene rubber resin,

[0015] The butadiene-based rubber resin has an active hydrogen equivalent weight (AHEW) of 800 to 1,000 g / eq.

[0016] (Effects of the Invention)

[0017] According to the epoxy resin topcoat coating composition of the present invention, its volatile organic compound (VOC) content is low and environmentally friendly and excellent in operability. In addition, with regard to the coating film prepared by the epoxy resin topcoat coating composition, its impact resistance, chemical resistance and weather resistance are excellent, thereby being very suitable as the topcoat of steel structures such as containers. DETAILED DESCRIPTION

[0018] The present invention is described in detail below.

[0019] In the present invention, functional group values ​​such as “epoxide equivalent weight (EEW)”, “active hydrogen equivalent weight (AHEW)” and “amine value (AmV)” can be measured by methods known in the art, for example, values ​​measured by titration or the like.

[0020] In the present specification, the "weight average molecular weight" can be measured by a method known in the art, and may be, for example, a value measured by a GPC (gel permeation chromatograph) method.

[0021] The epoxy resin topcoat coating composition according to the present invention comprises:

[0022] A main agent part, which comprises bisphenol A type unmodified epoxy resin, fatty acid modified epoxy resin, pigment and solvent; and

[0023] The curing agent portion contains a curing resin of one or more resins selected from the group consisting of amine resins and amide resins, and a butadiene-based rubber resin.

[0024] In particular, the active hydrogen equivalent (AHEW) of the butadiene rubber resin is 800 to 1,000 g / eq. The topcoat coating composition of the present invention includes a butadiene rubber resin having an active hydrogen equivalent in the specific range as described above, thereby having an effect of increasing the flexibility of the produced coating film.

[0025] The common bisphenol epoxy resin used in container coatings can form a high crosslinking density with the amine resin as a curing resin, so that the manufactured coating film has excellent rust resistance, etc., but the flexibility is low and there is a problem of poor impact resistance such as cracking of the coating film when subjected to external impact. Therefore, the present invention includes a butadiene rubber resin, thereby compensating for the above-mentioned problems caused by the high crosslinking density of the bisphenol epoxy resin. Specifically, the butadiene rubber resin is a liquid rubber that can react with the epoxy resin at room temperature. The butadiene rubber resin can be dispersed into a network structure during the curing reaction of the epoxy resin. The elastic region of the rubber resin can play a role in reducing the crosslinking density of the epoxy bond, thereby having the effect of imparting flexibility to the epoxy bond.

[0026] In addition, the value of the active hydrogen equivalent (AHEW) of the butadiene rubber resin affects the crosslinking density of the reaction with the epoxy resin, so that the physical properties of the prepared coating film, such as flexibility and impact resistance, may change. When the active hydrogen equivalent (AHEW) of the butadiene rubber resin is 800 to 1,000 g / eq, the viscosity of the coating containing it is appropriate, the operability is excellent, and the flexibility of the manufactured coating film can be improved. On the contrary, when the active hydrogen equivalent (AHEW) of the butadiene rubber resin is less than 800 g / eq, the mutual binding force between the molecules in the resin is high, so the viscosity of the coating containing it is high and the operability is insufficient, and the flexibility of the prepared coating film is insufficient. In addition, when the active hydrogen equivalent (AHEW) of the butadiene rubber resin exceeds 1,000 g / eq, the viscosity of the coating containing it is too low and the operability is insufficient. Although the prepared coating film can be given flexibility, the drying speed of the coating is too slow and the operability may be insufficient.

[0027] <Main Ingredients>

[0028] The main agent part includes bisphenol A type unmodified epoxy resin and fatty acid modified epoxy resin.

[0029] Unmodified bisphenol A epoxy resin has a symmetrical structure. Therefore, when the coating only contains unmodified bisphenol A epoxy resin, the mechanical properties such as hardness and rust resistance of the coating film can be improved due to the increase in crosslinking density. However, there are limitations such as insufficient flexibility and insufficient durability such as impact resistance.

[0030] Fatty acid-modified epoxy resin is a resin obtained by modifying epoxy resin with a low-viscosity fatty acid. It has a lower viscosity than the unmodified resin, but contains an acid and can form a salt. The rust resistance of the prepared coating film is low. When it is contained alone, the rust resistance of the prepared coating film will deteriorate.

[0031] On the contrary, the coating composition of the present invention comprises a mixture of a bisphenol A type unmodified epoxy resin and a fatty acid modified epoxy resin in an appropriate ratio to solve the above-mentioned problems. Due to the use of the bisphenol A type unmodified epoxy resin, the mechanical properties and rust resistance of the coating film are improved, and due to the use of the fatty acid modified epoxy resin, the flexibility of the coating film is improved, thereby having an effect of improving durability such as impact resistance.

[0032] Bisphenol A type unmodified epoxy resin

[0033] The unmodified bisphenol A epoxy resin is contained in the main agent of the coating composition, and plays a role in regulating the main physical properties of the prepared coating film, such as rust resistance and mechanical properties. In particular, the hydrophobic hydrocarbon groups in the unmodified bisphenol A epoxy resin are arranged toward the surface of the prepared coating film, and the hydrophilic epoxy groups and / or hydroxyl groups in the resin are arranged toward the surface of the substrate of the coating film, thereby improving the adhesion and rust resistance of the prepared coating film.

[0034] The bisphenol A type unmodified epoxy resin is not particularly limited as long as it is an epoxy resin generally applicable as a main agent of an anti-rust paint.

[0035] In addition, the bisphenol A type unmodified epoxy resin has an epoxy equivalent (EEW) of 100 to 300 g / eq or 150 to 250 g / eq. When the epoxy equivalent of the bisphenol A type unmodified epoxy resin is out of the range, the viscosity of the composition becomes high, which may cause the dispersion and airless spraying operability of the coating to be inappropriate. Specifically, the lower the equivalent of the bisphenol A type unmodified epoxy resin, the lower the viscosity, the higher the cross-linking density, and the excellent chemical resistance of the prepared coating; the higher the equivalent, the higher the molecular weight, and the excellent flexibility and impact resistance of the prepared coating, but the viscosity of the coating containing it becomes too high, which may cause the problem of insufficient operability.

[0036] The viscosity of the unmodified bisphenol A epoxy resin at 25° C. is 8,000 to 20,000 cP or 10,000 to 15,000 cP. When the viscosity of the unmodified bisphenol A epoxy resin is within the range, a coating film having excellent adhesion to a substrate can be prepared. In addition, when the viscosity of the unmodified bisphenol A epoxy resin at 25° C. is less than the range, the coating composition containing the unmodified bisphenol A epoxy resin has a problem of poor fluidity; when it exceeds the range, the coating composition containing the unmodified bisphenol A epoxy resin has a problem of poor coating operability.

[0037] In addition, the weight average molecular weight (Mw) of the bisphenol A type unmodified epoxy resin may be 200 to 500 g / mol, 300 to 450 g / mol, or 350 to 400 g / mol. When the weight average molecular weight of the bisphenol A type unmodified epoxy resin is less than the range, the flexibility and impact resistance of the prepared coating film may be reduced; when it exceeds the range, the chemical resistance of the prepared coating film may be reduced.

[0038] The coating composition may include bisphenol A type unmodified epoxy resin and fatty acid modified epoxy resin in a weight ratio of 3.5: 1 to 6.5: 1, a weight ratio of 4.0: 1 to 6.0: 1, or a weight ratio of 4.5: 1 to 5.5: 1. When the weight ratio of the bisphenol A type unmodified epoxy resin to the fatty acid modified epoxy resin is less than the range, that is, when a small amount of bisphenol A type unmodified epoxy resin is included relative to the weight of the fatty acid modified epoxy resin, the viscosity of the coating composition is high and the rust resistance of the prepared coating film may be reduced; when it exceeds the range, that is, when an excessive amount of bisphenol A type unmodified epoxy resin is included relative to the weight of the fatty acid modified epoxy resin, the flexibility of the prepared coating film is insufficient and may cause a reduction in bendability and impact resistance.

[0039] The bisphenol A type unmodified epoxy resin can be contained in the composition in an amount of 15 to 40 parts by weight, 20 to 40 parts by weight, or 20 to 30 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the content of the bisphenol A type unmodified epoxy resin is within the range, the hardness and rust resistance of the prepared coating film are improved. In addition, when the content of the bisphenol A type unmodified epoxy resin is less than the range, the crosslinking density of the prepared coating film is reduced, thereby reducing the mechanical properties of the coating film such as hardness and rust resistance; when the range is exceeded, the coating composition may have insufficient coating operability or the prepared coating film may have insufficient flexibility.

[0040] Fatty acid modified epoxy resin

[0041] The fatty acid modified epoxy resin is included in the main agent of the epoxy resin coating composition, which plays a role in improving the adhesion and flexibility of the prepared coating film. Specifically, the fatty acid modified epoxy resin is included in the coating composition, and the hydrophobic hydrocarbon group is arranged toward the surface of the coating film, and the hydrophilic epoxy group or hydroxyl group is arranged toward the surface of the coating substrate, thereby improving the adhesion. In addition, the fatty acid modified epoxy resin can be a high molecular weight resin, and the flexibility of the prepared coating film can also be improved at this time.

[0042] The fatty acid modified epoxy resin is a resin modified by using fatty acid to modify epoxy resin. At this time, the epoxy resin is not particularly limited as long as it is a resin commonly used in coating compositions, and can include, for example, one or more selected from the group consisting of bisphenol epoxy resin, alicyclic epoxy resin, aliphatic chain epoxy resin, phenol novolac epoxy resin, cresol novolac epoxy resin, diglycidyl ether of bisphenol, diglycidyl ether of naphthalene diol, diglycidyl ether of phenols, diglycidyl ether of alcohols, multifunctional epoxy resin and heterocyclic epoxy resin. Specifically, the epoxy resin of the fatty acid modified epoxy resin can be one or more selected from the group consisting of bisphenol A epoxy resin, bisphenol F epoxy resin and bisphenol S epoxy resin, or bisphenol A (BPA) epoxy resin.

[0043] In addition, the fatty acid can be monobasic fatty acid, polybasic fatty acid or their mixture.For example, the fatty acid can include one or more selected from the group consisting of dimer acid (dimer acid), soybean oil fatty acid, tall oil fatty acid, castor oil fatty acid, rice bran oil fatty acid, linseed oil fatty acid, coconut oil fatty acid, lauric acid, linoleic acid, benzoic acid, acrylic acid, methacrylic acid, oleic acid, nonanoic acid, abietic acid, phthalic anhydride, maleic anhydride, isophthalic acid, adipic acid, tetrahydrophthalic anhydride, terephthalic acid, azelaic acid, sebacic acid, fumaric acid, succinic acid and citric acid.Specifically, the fatty acid can include one or more selected from the group consisting of soybean oil fatty acid, tall oil fatty acid, castor oil fatty acid, rice bran oil fatty acid, linseed oil fatty acid, coconut oil fatty acid, lauric acid and linoleic acid.More specifically, the fatty acid can be a mixture of monobasic fatty acid and polybasic fatty acid.

[0044] Specifically, the fatty acid-modified epoxy resin may be a resin obtained by modifying a bisphenol A type epoxy resin with a mixture of a monobasic fatty acid and a polybasic fatty acid. As described above, when the resin modified with a mixture of a monobasic fatty acid and a polybasic fatty acid is included, the flexibility of the coating film prepared from the coating composition is further improved, thereby having the effect of improving the bendability and impact resistance.

[0045] The fatty acid modification rate of the fatty acid-modified epoxy resin may be 5 to 40% by weight or 10 to 30% by weight relative to the total solid content of the fatty acid-modified epoxy resin. When the fatty acid modification rate of the fatty acid-modified epoxy resin is less than the above range, the adhesion of the prepared coating film may be deteriorated; when it exceeds the above range, the physical properties of the prepared coating film, such as water resistance and flexibility, may be reduced.

[0046] In addition, the epoxy equivalent weight (EEW) of the fatty acid modified epoxy resin can be 200 to 350 g / eq or 240 to 300 g / eq. When the epoxy equivalent weight of the fatty acid modified epoxy resin is within the range, the storage property of the coating composition is excellent. In addition, when the epoxy equivalent weight of the fatty acid modified epoxy resin is less than the range, the rust resistance of the prepared coating film may be poor; when exceeding the range, the flexibility of the prepared coating film may be deteriorated.

[0047] The viscosity of the fatty acid-modified epoxy resin at 25° C. is 2,000 to 8,000 cP or 3,000 to 7,000 cP. When the viscosity of the fatty acid-modified epoxy resin is within the range, the prepared coating film has an excellent effect of adhesion to the substrate. In addition, when the viscosity of the fatty acid-modified epoxy resin at 25° C. is less than the range, there is a problem of poor fluidity of the coating composition; when it exceeds the range, there may be a problem of poor coating operability of the coating composition.

[0048] In addition, the weight average molecular weight (Mw) of the fatty acid modified epoxy resin may be 500 to 800 g / mol or 400 to 700 g / mol. When the weight average molecular weight of the fatty acid modified epoxy resin is less than the range, the prepared coating film may have poor flexibility; when the range is exceeded, the drying speed of the coating containing the fatty acid modified epoxy resin may be too long or the hardness of the prepared coating film may be poor.

[0049] The fatty acid-modified epoxy resin may be contained in the composition in an amount of 1 to 15 parts by weight, 1 to 10 parts by weight, or 2 to 8 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the content of the fatty acid-modified epoxy resin is within the range, the prepared coating film has an excellent adhesion to the substrate. In addition, when the content of the fatty acid-modified epoxy resin is less than the range, the coating operability of the coating composition may be insufficient or the flexibility of the prepared coating film may be insufficient; when the content exceeds the range, the adhesion of the prepared coating film to the substrate may be insufficient or the cross-linking density of the prepared coating film may be reduced, resulting in a problem of reduced mechanical properties such as hardness and rust resistance of the coating film.

[0050] pigment

[0051] The pigment serves to impart color to the prepared coating film or to increase hardness.

[0052] The pigment may be, for example, a coloring pigment, an extender pigment or a mixture thereof.

[0053] The coloring pigment plays the role of ensuring the hiding power and giving color to the coating film. At this time, the coloring pigment can be a black pigment, a white pigment or a mixture thereof. The coloring pigment can also include blue, red, yellow, purple and other pigments.

[0054] At this time, the black pigment is used without any particular restriction as long as it is a common known black pigment, for example, carbon black, graphite, iron oxide or a mixture thereof, etc. In addition, the white pigment is used without any particular restriction as long as it is a common known white pigment, for example, titanium dioxide (TiO2) etc. can be used.

[0055] In addition, the extender pigment plays a role in improving the hardness of the prepared coating film. The extender pigment can be used without limitation as long as it is a commonly known component. For example, feldspar, talc, calcium carbonate, barium sulfate, calcium silicate, silicon dioxide or a mixture thereof can be used.

[0056] The pigment is contained in an amount of 30 to 60 parts by weight, 35 to 55 parts by weight, or 35 to 50 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the content of the pigment is less than the range, the weather resistance or hardness of the prepared coating film may be reduced; when it exceeds the range, the appearance characteristics of the prepared coating film may be reduced.

[0057] Specifically, the coating composition may contain 5 to 20 parts by weight or 6 to 13 parts by weight of coloring pigments and 25 to 50 parts by weight or 30 to 45 parts by weight of extender pigments relative to 100 parts by weight of the topcoat coating composition. When the content of the coloring pigment is less than the range, the shielding power of the prepared coating film is insufficient; when it exceeds the range, the effect obtained by comparing the content of the coloring pigment is small and the economy is reduced. In addition, when the content of the extender pigment is less than the range, the hardness of the prepared coating film may be reduced; when it exceeds the range, the appearance characteristics and weather resistance of the prepared coating film may be reduced.

[0058] Solvents

[0059] The solvent plays a role in adjusting the viscosity of the composition, improving the drying property, and improving the appearance and spreadability of the prepared coating film. The solvent does not participate in the reaction with the curing resin, and remains in the coating film, thereby affecting the physical properties of the coating film.

[0060] In addition, the solvent is not particularly limited as long as it is commonly used in epoxy resin coating compositions, and for example, it may include one or more selected from the group consisting of methyl isobutyl ketone, dimethyl carbonate, acetone, parachlorobenzotrifluoride, propylene carbonate, xylene, toluene, methoxypropanol, methyl ethyl ketone, butyl acetate, butanol, isopropanol, propylene glycol monomethyl ether, tert-butyl acetate and 2-amino-2methyl-1-propanol.

[0061] The solvent may be included in the composition in an amount of 1 to 15 parts by weight or 3 to 13 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the solvent is included in the range, the viscosity of the coating composition is appropriate, which has the effect of improving operability and dryness. When the content of the solvent is less than the range, there is a problem of poor operability due to the high viscosity of the coating composition; when it exceeds the range, the content of volatile organic compounds (VOC) of the coating composition is too high, resulting in insufficient environmental protection or poor fluidity.

[0062] First Additive

[0063] The main agent portion can be supplemented with a first additive. At this time, the first additive is used without particular restrictions as long as it is an additive that can be usually used for the epoxy resin topcoat coating composition, for example, it can be a reactive diluent, a tackifier, a dispersant, a defoamer, an adhesion promoter, a surface modifier and a light stabilizer etc.

[0064] <Curing Agent Section>

[0065] The curing agent part includes: a curing resin containing one or more resins selected from the group consisting of amine resins and amide resins; and a butadiene-based rubber resin.

[0066] Amine resin

[0067] The amine resin functions to react with the epoxy resin to cure the coating composition.

[0068] The amine resin may be, for example, an aliphatic amine compound, an aromatic amine compound, a heterocyclic amine compound, a Mannich modified compound, etc. Specifically, the amine resin may include, for example, an alicyclic amine compound.

[0069] At this time, the aliphatic amine compound can be exemplified by: alkylene polyamines such as methylenediamine, ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-diaminopentane, 1,6-hexanediamine, 1,7-diaminoheptane, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, and trimethylhexamethylenediamine; polyalkylene polyamines such as diethylenetriamine, dipropylenetriamine, triethylenetetramine, tripropylenetetramine, tetraethylenepentamine, tetrapropylenepentamine, pentaethylenehexamine, nonaethylenedecylamine, and bis(hexamethylene)triamine; tetra(aminomethyl)methane (tetra(aminomethyl)methane)

[0043] Alkylamines such as 2,2'-[ethylenebis(iminotrimethyleneimino)]bis(ethaneamine), tetrakis(2-aminoethylaminomethyl)methane, 1,3-bis(2'-aminoethylamino)propane, diethylene glycol di(3-aminopropyl) ether, 2,2'-[ethylenebis(iminotrimethyleneimino)]bis(ethaneamine), tris(2-aminoethyl)amine, and bis(cyanoethyl)diethylenetriamine; and alicyclic amines such as 1,3-bisaminomethylcyclohexane, 1,4-cyclohexanediamine, 4,4'-methylenebis(cyclohexylamine), 4,4'-isopropyldicyclohexylamine, norbornane diamine, bis(aminomethyl)cyclohexane, isophorone diamine, and menthane diamine (MDA, menthanediamine).

[0070] The aromatic amine compounds can be exemplified by phenylenediamine, naphthalene diamine, diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 2,2'-dimethyl-4,4'-diaminodiphenylmethane, 2,4'-diaminobiphenyl, 2,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, o-phenylenediamine, m-phenylenediamine (MXDA), p-phenylenediamine, bis(aminomethyl)naphthalene, bis(aminoethyl)naphthalene, and the like.

[0071] Examples of the heterocyclic amine compounds include N-methylpiperazine, morpholine, 1,4-bis-(3-aminopropyl)piperazine, 1,4-diazacycloheptane, 1-(2'-aminoethyl)piperazine, 1-[2'-(2"-aminoethylamino)ethyl]piperazine, 1,11-diazacycloeicosane, 1,15-diazacyclooctacosane, and the like.

[0072] Examples of the Mannich modified product include Mannich modified aliphatic polyamine, phenalkamine, phenalkamide, and the like.

[0073] Amide resin

[0074] The amide resin reacts with the epoxy resin to cure the coating composition to form a coating film.

[0075] Examples of the amide resin include amide addition resins, polyamides, and amides in the form of alicyclic amines containing hydrogenated aniline or aromatic amines to which methylene groups are bonded.

[0076] The active hydrogen equivalent (AHEW) of the curing resin may be 50 to 150 g / eq or 80 to 120 g / eq. When the active hydrogen equivalent of the curing resin is less than the range, the reactivity of the coating composition is fast, and it may be difficult to predict the drying time and the operation time; when the active hydrogen equivalent exceeds the range, the reactivity of the coating composition becomes slow, and thus the productivity may be reduced.

[0077] In addition, the amine value (AmV) of the curing resin may be 100 to 400 mgKOH / g or 130 to 390 mgKOH / g. When the amine value of the curing resin is less than the range, the reactivity of the coating composition becomes slow, which may lead to reduced productivity; when the amine value exceeds the range, the drying time and curing time of the coating composition are too fast, which may lead to reduced operability.

[0078] The curing resin may be contained in an amount of 1 to 30 parts by weight or 5 to 20 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the content of the curing resin is less than the range, the curing time of the coating composition may be slowed down and the weather resistance of the prepared coating film may be deteriorated; when the content exceeds the range, the pot life of the coating composition may be shortened, which may cause the mechanical properties of the prepared coating film to deteriorate.

[0079] In addition, the topcoat coating composition contains a curing resin and a butadiene rubber resin in a weight ratio of 5:1 to 8:1, or a weight ratio of 5.5:1 to 7.5:1. When the weight ratio of the curing resin to the butadiene rubber resin is less than the above range, that is, when the curing resin is contained in a small amount relative to the weight of the butadiene rubber resin, the viscosity of the coating containing it is too high, and there are problems such as poor coating workability or poor hardness of the prepared coating film; when it exceeds the above range, that is, when an excessive amount of the curing resin is contained relative to the weight of the butadiene rubber resin, the prepared coating film may have poor flexibility and impact resistance.

[0080] On the contrary, when the curing agent portion of the topcoat coating composition only comprises a cured resin, that is, when only comprising amine resins and / or amide resins, the hardness, fast drying rate, and low viscosity of the coating are obtained by the formation of short crosslinks, but the pot life of the coating is too short, which may cause insufficient operability or insufficient flexibility of the prepared coating. In addition, when the curing agent portion of the topcoat coating composition only comprises a butadiene rubber resin, that is, when not comprising amines and / or amide resins, flexibility of the coating can be given by the formation of long crosslinks, but the viscosity of the coating is too high, and insufficient operability or slow drying rate and insufficient productivity may occur.

[0081] Butadiene rubber resin

[0082] The butadiene rubber resin serves to impart flexibility to the coating film.

[0083] In addition, the butadiene-based rubber resin may include at least one selected from the group consisting of acrylonitrile-butadiene rubber resin, styrene-butadiene rubber resin, and polybutadiene. Specifically, the butadiene-based rubber resin may include acrylonitrile-butadiene rubber resin.

[0084] The acrylonitrile-butadiene rubber resin may include at least one selected from the group consisting of amineterminated butadiene acrylonitrile (ATBN) and carboxylterminated butadiene acrylonitrile (CTBN).

[0085] For example, the butadiene-based rubber resin may include an amine group. When the butadiene-based rubber resin includes an amine group, the curing reaction with the epoxy resin and the compatibility with other resins may be improved.

[0086] In addition, the weight average molecular weight (Mw) of the butadiene rubber resin may be 1,400 to 2,500 g / mol, 1,500 to 2,300 g / mol, or 1,800 to 2,000 g / mol. When the weight average molecular weight of the butadiene rubber resin is less than the above range, there is a problem that it is difficult to give flexibility to the prepared coating film; when it exceeds the above range, the viscosity of the coating containing it is high, which may cause poor operability or insufficient hardness of the prepared coating film.

[0087] The butadiene rubber resin may be included in an amount of 0.5 to 10 parts by weight, 0.8 to 8 parts by weight, or 1 to 5 parts by weight relative to 100 parts by weight of the topcoat coating composition. When the content of the butadiene rubber resin is less than the above range, there is a problem of poor flexibility and impact resistance of the prepared coating film; when it exceeds the above range, the viscosity of the coating containing it is too high, which may cause problems of insufficient operability or poor chemical resistance of the prepared coating film.

[0088] Second additive

[0089] The curing agent part may be supplemented with a second additive including one or more selected from the group consisting of an organic solvent and a non-reactive diluent. In this case, the organic solvent and the non-reactive diluent are not particularly limited as long as they are respectively commonly used in epoxy resin coating compositions.

[0090] <2-component type>

[0091] The epoxy resin topcoat coating composition is a two-component coating material comprising a main agent part and a curing agent part, and the main agent part and the curing agent part can be mixed before coating.

[0092] The solid content (NV) of the epoxy resin topcoat coating composition is 87 to 96% by weight or 90 to 93% by weight. When the solid content of the coating composition is within the range, the solid content is high and the solvent content is low, so the VOC content is low and the environmental protection is good, and the harmfulness to the operator during construction is low and the construction can be safe.

[0093] As mentioned above, according to the epoxy resin topcoat coating composition of the present invention, its VOC content is low and environmental protection is good, and workability and storage stability are also excellent. In addition, the coating film prepared with the epoxy resin topcoat coating composition has excellent impact resistance, chemical resistance and weather resistance, thereby the coating composition is very suitable as the topcoat coating of steel structures such as containers.

[0094] The present invention is further described in detail below by way of examples, but these examples are only for the purpose of helping to understand the present invention and do not have any limiting meaning, and the scope of the present invention is not limited by these examples.

[0095] [Example]

[0096] Examples 1 to 14 and Comparative Examples 1 to 5 Preparation of Coating Compositions According to the compositions described in Tables 1 to 3, the components were mixed to prepare a main agent part and a curing agent part.

[0097]

Table 1

[0098]

[0099]

[0100]

Table 2

[0101]

[0102]

[0103]

Table 3

[0104]

[0105]

[0106] The manufacturers, product names, physical properties, etc. of the components used in the comparative examples and examples are shown in Table 4 below, where EEW represents epoxy equivalent, Mw represents weight average molecular weight, vis(25°C) represents viscosity at 25°C, AHEW represents active hydrogen equivalent, and AmV represents amine value.

[0107]

Table 4

[0108]

[0109]

[0110]

[0111] Experimental Example 1: Evaluation of basic physical properties

[0112] After applying an oil-based epoxy resin primer (manufacturer: KCC, product name: EP170 (QD)) with a dry coating thickness of 10 μm on an iron plate, the coatings of the examples and comparative examples were applied with a dry coating thickness of 135±10 μm to prepare coating test pieces.

[0113] The prepared coating film test piece was placed at room temperature for 10±2 minutes, dried in an oven at 80° C. for 20 minutes, and placed at room temperature again for 7 days to completely cure, thereby preparing the final coating film.

[0114] Thereafter, the physical properties of the topcoat coating compositions of Examples and Comparative Examples and the final coating films prepared were measured according to the following methods. The results are shown in Tables 5 to 7.

[0115] (1) Storage stability

[0116] After the coating composition was allowed to stand at 25°C for 7 days, precipitation and phase separation of the pigment in the coating composition were evaluated visually.

[0117] Specifically, the evaluation was excellent (◎) when there was no increase in the viscosity of the coating after storage, no precipitation of the pigment, and no phase separation; the evaluation was good (○) when the pigment precipitation was soft; the evaluation was fair (△) when the pigment precipitation was hard; and the evaluation was poor (×) when the pigment precipitation was hard and phase separation occurred.

[0118] (2) Curing and drying properties

[0119] After applying the topcoat coating composition, the time required for curing and drying was measured at 80° C. according to the method described in ASTM D1640. The time required for hard curing was measured as the time when the coating film was pressed hard by hand and twisted left and right without causing an indentation.

[0120] (3) Pencil hardness

[0121] The hardness of the coating film was measured by the pencil hardness method according to ASTM D3363. Specifically, the maximum hardness without damaging the coating film was measured using 3B, 2B, B, HB, F, H, 2H and 3H pencils (3B, 2B, B, HB, F, H, 2H, 3H: difference Excellent).

[0122] (4) Adhesion

[0123] According to the method described in ASTM D3359, 25 squares (2 mm horizontally and 2 mm vertically) were scratched horizontally and vertically on the final coating film with a knife blade, and the adhesion was measured by tape peeling. At this time, the adhesion was expressed by the amplitude ratio of the peeled area, and the case of no peeling was evaluated as 5B, the case of peeling area less than 5 area% was evaluated as 4B, the case of 5 area% or more and less than 15 area% was evaluated as 3B, the case of 15 area% or more and less than 35 area% was evaluated as 2B, the case of 35 area% or more and less than 65 area% was evaluated as 1B, and the case of 65 area% or more was evaluated as 0B.

[0124] (5) Impact resistance

[0125] The coating film was coated according to the method described in ASTM D2794, and an impact was applied at room temperature (25°C) to measure whether the coating film cracked or peeled. At this time, the impact conditions were evaluated under 100 lbs·in, 80 lbs·in, 60 lbs·in, and 55 lbs·in. The impact condition in which the coating film cracked or peeled was shown as impact resistance, and the case in which the coating film cracked or peeled under the condition of 55 lbs·in was evaluated as "failure", and the other cases were evaluated as "pass".

[0126] (6) Pot life (hr)

[0127] After adding 12±2 wt% of dilution water to the total amount of the topcoat coating composition, stirring was continued at 30°C at a speed of 1,000RPM, and the viscosity change of the coating was measured using Zahn Cup 3 as a reference and measured for a total of 3 hours at 1 hour intervals, thereby measuring the pot life by evaluating the viscosity change of the coating. At this time, the pot life is represented by the time when the viscosity change of the coating is less than 15%.

[0128] (7) Sagging

[0129] After adding 12±2 wt% of the total weight of the dilution water to the topcoat coating composition, the coating was applied on a 30 cm x 30 cm test piece with a wet film thickness (WFT) of 150 μm by airless spraying. At this time, the airless coating machine used a pump ratio of 45:1, an input pressure of 4 bar, and a tip size of 815.

[0130] After coating, the test piece was placed vertically at room temperature (25° C.) and the fluidity of the coating was evaluated by visual observation. At this time, WFT measurement was performed using a BYK WFT gauge, and the evaluation was performed according to the following criteria.

[0131] Specifically, no flow of the paint is evaluated as level 1, waving at the boundary line is evaluated as level 2, slight sagging of the paint is evaluated as level 3, severe sagging of the paint is evaluated as level 4, and severe flow of the paint with complete overlap at the boundary line is evaluated as level 5.

[0132] (8) Appearance-1: Pinhole

[0133] After adding 12±2 wt% of dilution water to the total amount of the topcoat coating composition, the topcoat coating composition was applied on a 30 cm x 30 cm test piece with a wet film thickness (WFT) of 125 μm using an airless spray method. At this time, the airless coating machine used a pump ratio of 45:1, an input pressure of 4 bar, and a tip size of 815.

[0134] After coating, the coating was left at room temperature (25°C) for about 7 minutes, dried in a 60°C oven for 30 minutes, and then the pinholes on the coating surface were observed with a 15x magnifying glass for evaluation. The evaluation criteria were as follows: the lower the number, the better the pinhole characteristics.

[0135] Level 1: No pinholes observed

[0136] Level 2: The average number of pinholes is 1 to 4

[0137] Level 3: The average number of pinholes is 5 to 10

[0138] Level 4: The average number of pinholes is more than 10 and less than 20

[0139] Level 5: The average number of pinholes is more than 20

[0140] (9) Appearance-2: Leveling

[0141] After coating in the same manner as in item (8), the smoothness of the coating film was visually observed and evaluated according to the following evaluation criteria (1 to 5).

[0142] Level 1: The coating is smooth and has a glossy appearance

[0143] Level 2: The coating smoothness is slightly lower but still good

[0144] Level 3: The smoothness of the coating is so poor that gaps can be seen

[0145] Level 4: The coating is not smooth enough and has many gaps

[0146] Level 5: The coating is so uneven that it cannot be painted.

[0147] (10) Chemical resistance-1: NaOH

[0148] After the final coating film was exposed to a 10 wt % sodium hydroxide aqueous solution for 168 hours, the degree of blister generation on the flat surface of the coating film was evaluated according to the evaluation method of ASTM D714. The evaluation was performed as follows based on the frequency of blister generation.

[0149] Specifically, the size of the blisters was evaluated in four levels: tiny (8), small (6), medium (4), and large (2), and the frequency of blisters was evaluated in four levels: few (FEW, F), medium (MEDIUM, M), slightly many (MEDIUM DENSE, MD), and many (DENSE, D). In addition, the case of no blisters was evaluated as 10, and the case of final coating peeling was evaluated as 0.

[0150] (11) Chemical resistance-2: H2SO4

[0151] After the final coating film was exposed to a 10 wt % sulfuric acid aqueous solution for 168 hours, the degree of blistering of the flat coating film was evaluated according to the evaluation method of ASTM D714. The evaluation was performed as follows based on the frequency of blistering.

[0152] Specifically, the size of the blisters was evaluated using 4 levels: tiny (8), small (6), medium (4), and large (2), and the frequency of the blisters was evaluated using 4 levels: few (FEW, F), medium (MEDIUM, M), slightly many (MEDIUM DENSE, MD), and many (DENSE, D). In addition, the case of no blisters was evaluated as 10, and the case of final coating peeling was evaluated as 0.

[0153] (12) Salt water resistance-1: Rust formation

[0154] The final coating film which was completely cured by standing at 60°C for one day after topcoat application was tested in a salt spray resistance tester (35±2°C, 5 wt% NaCl aqueous solution) for 600 hours according to ASTM B117, and the generation of rust was measured to evaluate the salt water resistance.

[0155] At this time, regarding the evaluation criteria, according to ASTM D610, when no rust is generated, it is evaluated as 10, when the rust generation area is less than 0.03 area%, it is evaluated as 9, when it is 0.03 area% or more and less than 0.1 area%, it is evaluated as 8, when it is 0.1 area% or more and less than 0.3 area%, it is evaluated as 7, when it is 0.3 area% or more and less than 1 area%, it is evaluated as 6, when it is 1 area% or more and less than 3 area%, it is evaluated as 5, and when it is 3 area% or more, it is evaluated as 4.

[0156] (13) Salt water resistance-2: Formation of blisters

[0157] The prepared coating test piece was placed at room temperature for 10±2 minutes, dried in an oven at 80°C for 20 minutes and placed at room temperature again for 7 days to completely cure the final coating. After testing in a salt spray resistance tester (35±2°C, 5 wt% NaCl aqueous solution) for 600 hours according to ASTM D610, the formation of blisters was observed with the naked eye to evaluate the salt water resistance.

[0158] At this time, the evaluation criteria were as follows: the size of the blisters was evaluated in four grades: tiny (8), small (6), medium (4), and large (2), and the frequency of the blisters was evaluated in four grades: few (FEW, F), medium (MEDIUM, M), slightly many (MEDIUM DENSE, MD), and many (DENSE, D) according to ASTM D610. In addition, the case of no blisters was evaluated as 10, and the case of final coating peeling was evaluated as 0.

[0159] (14) Salt water resistance-3: Creep

[0160] The prepared coating test piece was placed at room temperature for 10±2 minutes, dried in an 80°C oven for 20 minutes, and then placed at room temperature for 7 days. A 1 mm wide knife mark was made on the completely cured coating with a knife blade. After testing in a salt spray resistance tester (35±2°C, 5 wt% NaCl aqueous solution) according to ASTM D714 for 600 hours, the distance (mm) of rust penetration from the knife mark was measured to evaluate the salt water resistance.

[0161] (15) Weather resistance-1: Flexibility

[0162] After the prepared coating film specimen was placed at room temperature for 10±2 minutes, it was dried in an oven at 80℃ for 20 minutes, and then placed at room temperature for 7 days to completely cure. The completely cured topcoat coating film was placed on a rod of a certain thickness, and then folded 180° to evaluate whether cracks occurred in the coating film. The average diameter of the rod used at this time was 3mm, 5mm, 8mm or 10mm.

[0163] (16) Weather resistance-2: Adhesion

[0164] Weather resistance was evaluated by adhesion according to ASTM D3359. Specifically, after the coating film was exposed outdoors for 600 hours, adhesion was measured and evaluated in the same manner as in item (4).

[0165] (17) Weather resistance-3: Impact resistance

[0166] Weather resistance was evaluated by impact resistance according to ASTM D2794. Specifically, the coating film was exposed outdoors for 600 hours and then the impact resistance was measured in the same manner as in item (5).

[0167]

Table 5

[0168]

[0169]

[0170]

[0171]

Table 6

[0172]

[0173]

[0174]

Table 7

[0175]

[0176]

[0177] As shown in Tables 5 and 6, it can be seen that the coating films of Examples 1 to 14 are excellent in all physical properties and are therefore very suitable as topcoats for steel structures and the like.

[0178] On the contrary, as shown in Table 7, in Comparative Example 1 not containing a butadiene rubber resin, Comparative Example 2 containing a butadiene rubber resin-3 having a low active hydrogen equivalent (AHEW), and Comparative Example 4 containing only a bisphenol A type unmodified epoxy resin and not containing a fatty acid modified epoxy resin, the pot life of the coating is short and the workability is insufficient, and the bendability of the prepared coating film is also insufficient. In particular, the adhesion of the coating film of Comparative Example 4 is also insufficient. Furthermore, in Comparative Examples 1 and 4, the impact resistance of the prepared coating film is also insufficient, and therefore the weather resistance is also insufficient.

[0179] In addition, in Comparative Example 3 containing butadiene rubber resin-4 having a high active hydrogen equivalent (AHEW), and Comparative Example 5 containing only fatty acid-modified epoxy resin without unmodified epoxy resin, the curing and drying time of the coating was long and productivity was insufficient, and the pencil hardness of the prepared coating film was also insufficient. In particular, in Comparative Example 3, the chemical resistance of the coating film was insufficient, and in Comparative Example 5, the fluidity of the coating film was large and the sagging property was insufficient, and the appearance and salt water resistance of the coating film were also insufficient.

Claims

1. An epoxy resin topcoat coating composition, characterized in that: Include: A main agent part, which comprises bisphenol A type unmodified epoxy resin, fatty acid modified epoxy resin, pigment and solvent; and a curing agent part containing a curing resin and a butadiene rubber resin, wherein the curing resin contains one or more resins selected from the group consisting of amine resins and amide resins, The butadiene-based rubber resin has an active hydrogen equivalent of 800 to 1,000 g / eq.

2. The epoxy resin topcoat coating composition according to claim 1, wherein The bisphenol A type unmodified epoxy resin has an epoxy equivalent of 100 to 300 g / eq, a viscosity of 8,000 to 20,000 cP at 25° C., and a weight average molecular weight of 200 to 500 g / mol.

3. The epoxy resin topcoat coating composition according to claim 1, wherein The fatty acid-modified epoxy resin has a fatty acid modification rate of 5 to 40% by weight relative to the total solid content of the fatty acid-modified epoxy resin, an epoxy equivalent of 200 to 350 g / eq, a viscosity of 2,000 to 8,000 cP at 25° C., and a weight average molecular weight of 500 to 800 g / mol.

4. The epoxy resin topcoat coating composition according to claim 1, wherein The butadiene-based rubber resin includes at least one selected from the group consisting of acrylonitrile-butadiene rubber resin, styrene-butadiene rubber resin, and polybutadiene.

5. The epoxy resin topcoat coating composition according to claim 1, wherein The butadiene-based rubber resin has a weight average molecular weight of 1,400 to 2,500 g / mol, and the butadiene-based rubber resin includes an amine group.

6. The epoxy resin topcoat coating composition according to claim 1, wherein The bisphenol A type unmodified epoxy resin and the fatty acid modified epoxy resin are contained in a weight ratio of 3.5:1 to 6.5:

1.

7. The epoxy resin topcoat coating composition according to claim 1, wherein The curing resin and the butadiene-based rubber resin are contained in a weight ratio of 5:1 to 8:1.

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