Powder coating composition and preparation method therefor, matte coating and preparation method therefor, and product comprising matte coating

Abstract

A powder coating composition and a preparation method therefor, a matte coating and a preparation method therefor, and a product comprising the matte coating. The powder coating composition comprises: a component A in the form of power, wherein the component A comprises at least one epoxy functional acrylic resin (a) and a crosslinking agent used for the epoxy functional acrylic resin; and a component B in the form of powder, wherein the component B comprises at least one epoxy functional acrylic resin (b) and a crosslinking agent used for the epoxy functional acrylic resin. The powder of the component B is different the powder of the component A, the arithmetic mean epoxy equivalent of the at least one epoxy functional acrylic resin (a) in the component A is higher than the arithmetic mean epoxy equivalent of the at least one epoxy functional acrylic resin (b) in the component B, and the difference between the arithmetic mean epoxy equivalent of the component A and the arithmetic mean epoxy equivalent of the component B is at least 50 g / eq.

Description

Powder coating composition and preparation method thereof, matte coating and preparation method thereof, and product having the matte coating Technical Field

[0001] The invention relates to a powder coating composition and a preparation method thereof, a matte coating and a preparation method thereof, and a product having the matte coating. Background Art

[0002] Powder coatings are free-flowing dry powders that are typically applied to substrates by a spraying process.

[0003] Curing is usually carried out in a separate step after the initial deposition of the powder coating particles. Typically, powder coatings are heat-curable. However, UV-curing systems and mixed heat / UV-curing systems are also possible.

[0004] The advantage of powder coatings is that they contain no solvents, which means they are not associated with VOC emissions, which are becoming increasingly regulated.

[0005] Typically, in powder coating particles, both the resin and curing agent are present in the same powder / coating particle. The particles are typically prepared by melt extrusion of the component compounds (i.e., resin, curing agent (crosslinker), and other additives), followed by crushing and sieving to the appropriate size. Two-component systems feature two separate dry-blended, post-blended, or co-ground powder particles containing different resins or curing agents, or varying relative amounts of the constituent components. Separate dry-blended additive particles may also be added to one- or two-component systems to enhance various properties.

[0006] Powder coatings have been used to provide matte finishes. A matte finish is one that has a low gloss after curing. The concept of gloss is a visual impression created by surface evaluation using a gloss meter.

[0007] However, the polyester matte coating formed by the polyester powder coating composition in the prior art, especially the matte polyester coating on aluminum alloy wheels or vehicle decorative parts, may have silver streaks.

[0008] Therefore, it is necessary to provide a powder coating composition that can form a matte coating after curing, wherein the matte coating does not have silver streaks and has good other properties, such as stability.

[0009] Summary of the Invention

[0010] In response to the shortcomings of the prior art, the present invention provides a powder coating composition, which forms a matte coating after curing, and the matte coating does not have silver streaks, and also has good corrosion resistance, weather resistance, water resistance and adhesion. In addition, the powder coating composition also has other good properties, such as good storage stability, low curing temperature and short curing time.

[0011] In one aspect, the present invention relates to a powder coating composition comprising:

[0012] Component A in powder form, wherein Component A comprises at least one epoxy-functional acrylic resin (a) and a crosslinker for the epoxy-functional acrylic resin; and

[0013] Component B in powder form, wherein Component B comprises at least one epoxy-functional acrylic resin (b) and a crosslinker for the epoxy-functional acrylic resin;

[0014] The powder of component B is different from the powder of component A, and the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (a) in component A is higher than the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (b) in component B, and the difference in the arithmetic average epoxy equivalents in component A and component B is at least 50 g / eq.

[0015] In another aspect, the present invention relates to a method for preparing a powder coating composition of the present invention, comprising:

[0016] (i) mixing, extruding and crushing the ingredients in component A to obtain component A in powder form;

[0017] (ii) mixing, extruding and crushing the ingredients of component B to obtain component B in powder form; and

[0018] (iii) Components A and B are optionally mixed uniformly.

[0019] In another aspect, the present invention relates to a matte coating formed from the powder coating composition of the present invention.

[0020] In another aspect, the present invention relates to a method for preparing a matte coating, comprising:

[0021] (1) applying the powder coating composition of the present invention to a substrate; and

[0022] (2) The applied powder coating composition is cured. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 shows the silver streaks of coatings formed from the clear coating composition of Comparative Example 3 and the powder coating composition of Example 8 for comparison. DETAILED DESCRIPTION

[0024] Powder coating composition

[0025] The present invention relates to a powder coating composition comprising:

[0026] Component A in powder form, wherein Component A comprises at least one epoxy-functional acrylic resin (a) and a crosslinker for the epoxy-functional acrylic resin; and

[0027] Component B in powder form, wherein Component B comprises at least one epoxy-functional acrylic resin (b) and a crosslinker for the epoxy-functional acrylic resin;

[0028] The powder of component B is different from the powder of component A, and the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (a) in component A is higher than the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (b) in component B, and the difference in the arithmetic average epoxy equivalents in component A and component B is at least 50 g / eq.

[0029] The weight ratio of component A to component B can be 1:7-7:1 (e.g., 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1 or 6:1), preferably 1:5-5:1, more preferably 1:3-3:1 or 1:2-2:1.

[0030] Those skilled in the art will appreciate that in the powder coating composition, component A and component B are not present in the same powder, ie, are not present in the same powder particles. In one embodiment, component A and component B are prepared separately.

[0031] The arithmetic average epoxy equivalent weight is calculated for each epoxy-functional acrylic resin and their ratio. For example, if Component A contains two epoxy-functional acrylic resins with epoxy equivalent weights of 700 g / eq and 500 g / eq, respectively, in a 1:1 weight ratio, the arithmetic average epoxy equivalent weight is: 700 / 2 + 500 / 2 = 600 g / eq. Of course, if Component A contains only one epoxy-functional acrylic resin, the arithmetic average epoxy equivalent weight is the epoxy equivalent weight of that single epoxy-functional acrylic resin.

[0032] The difference in arithmetic average epoxy equivalent weight between component A and component B is at least 50 g / eq, and the difference in arithmetic average epoxy equivalent weight can be, for example, 80 g / eq, 100 g / eq, 120 g / eq, 150 g / eq, 180 g / eq, 200 g / eq, 220 g / eq, 250 g / eq, 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, 480 g / eq, 500 g / eq, 520 g / eq or 550 g / eq. In one embodiment, the difference in arithmetic average epoxy equivalent weight between component A and component B is at least 80 g / eq, or at least 120 g / eq, or at least 150 g / eq, or at least 180 g / eq, or at least 200 g / eq, or at least 220 g / eq. In one embodiment, the difference in the arithmetic mean epoxy equivalent weight between component A and component B is 50-550 g / eq, or 120-500 g / eq, or 150-500 g / eq, or 180-480 g / eq, or 200-480 g / eq.

[0033] In one embodiment, component A and / or component B comprises two or more epoxy-functional acrylic resins, wherein the difference in epoxy equivalent weight between the epoxy-functional acrylic resin with the highest epoxy equivalent weight in component A and the epoxy-functional acrylic resin with the lowest epoxy equivalent weight in component B is at least 50 g / eq, for example, 80 g / eq, 100 g / eq, 120 g / eq, 150 g / eq, 180 g / eq, 200 g / eq, 220 g / eq, 250 g / eq, 300 g / eq, 350 g / eq, 400 g / eq, 450 g / eq, 480 g / eq, 500 g / eq, 520 g / eq or 550 g / eq.

[0034] Increasing the difference in the arithmetic mean epoxy equivalent weight between component A and component B helps reduce gloss and improve matte properties. In a preferred embodiment, the difference in the arithmetic mean epoxy equivalent weight between component A and component B is at least 150 g / eq, or at least 180 g / eq, or at least 200 g / eq, for example, 150-550 g / eq, 150-500 g / eq, 180-500 g / eq, or 200-480 g / eq.

[0035] In one embodiment, the epoxy equivalent weight of the at least one epoxy-functional acrylic resin (a) in component A is at least 500 g / eq, at least 520 g / eq, at least 550 g / eq, at least 600 g / eq, or at least 650 g / eq, preferably no more than 900 g / eq, no more than 850 g / eq, no more than 820 g / eq, or no more than 800 g / eq. In an embodiment, all epoxy-functional acrylic resins in component A have an epoxy equivalent weight of at least 500 g / eq. The epoxy equivalent weight of the at least one epoxy-functional acrylic resin (b) in component B is no more than 550 g / eq, no more than 520 g / eq, no more than 500 g / eq, or no more than 480 g / eq, preferably at least 250 g / eq, at least 280 g / eq, or at least 300 g / eq. In an embodiment, all epoxy-functional acrylic resins in component B have an epoxy equivalent weight of no more than 550 g / eq.

[0036] The epoxy-functional acrylic resin (a) and the epoxy-functional acrylic resin (b) can have a melt index at 125°C of 4-80 g / 10 min (e.g., 5, 6, 8, 10, 20, 30, 40, 50, 60, 70, or 80 g / 10 min), or 5-70 g / 10 min, or 5-60 g / 10 min.

[0037] The glass transition temperature (Tg) of the epoxy-functional acrylic resin (a) and the epoxy-functional acrylic resin (b) may be at least 38°C, or at least 40°C, or at least 45°C (e.g., 50°C or 60°C), for example, 38-110°C, or 40-100°C, or 40-90°C, or 45-80°C.

[0038] The epoxy-functional acrylic resin may include, in polymerized form, an epoxy-functional unsaturated monomer and at least one other comonomer. It will be understood by those skilled in the art that the other comonomer is different from the epoxy-functional unsaturated monomer.

[0039] The epoxy functional unsaturated monomer is H2C=C(R 8 )C(O)OR 9 (Meth) acrylate glycidyl ester monomer, wherein R 8 is H or methyl, and R 9 The compound of formula (I) is an alkylene residue having 1 to 4 carbon atoms and ending in a glycidyl group. For example, the compound of formula (I) may be glycidyl acrylate, glycidyl methacrylate, and 1,2-epoxybutyl acrylate, preferably glycidyl (meth)acrylate.

[0040] The amount of epoxy-functional unsaturated monomer may be 10 to 40 weight percent (eg, 10, 20, 30, or 40 weight percent) based on the total weight of all monomers in the epoxy-functional acrylic resin.

[0041] The comonomer may be selected from C1-C 20 (Cyclo)alkyl esters, methacrylic acid C1-C 10 Hydroxyalkyl esters and vinyl aromatic monomers.

[0042] The C1-C 20 The (cyclo)alkyl ester can be a C1-C1 20 Alkyl esters and (meth) acrylic acid C3-C 20 Cycloalkyl esters.

[0043] C1-C 20 (Cyclo)alkyl esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, eicosyl (meth)acrylate, cetyl (meth)acrylate, and tridecyl (meth)acrylate, and mixtures thereof.

[0044] C1-C 20 The amount of (cyclo)alkyl ester may be 10-70 wt% (e.g., 10, 20, 30, 40, 50, 60, or 70 wt%), based on the total weight of all monomers in the epoxy-functional acrylic resin.

[0045] (Meth)acrylic acid C1-C 10 The hydroxyalkyl ester may include hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxypentyl acrylate, 6-hydroxynonyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 2-hydroxypentyl methacrylate, 5-hydroxypentyl methacrylate, 7-hydroxyheptyl methacrylate and 5-hydroxydecyl methacrylate, and mixtures thereof. Specifically, the hydroxyalkyl (meth)acrylate may be, for example, hydroxyethyl acrylate or hydroxyethyl methacrylate.

[0046] (Meth)acrylic acid C1-C 10 The amount of hydroxyalkyl ester may range from 0.5 to 20 weight percent (eg, 1, 5, 10, 20, 30, or 40 weight percent), based on the total weight of all monomers in the epoxy-functional acrylic resin.

[0047] Suitable vinyl aromatic monomers may be selected from styrene, α-methylstyrene, α-ethylstyrene and other α-alkyl substituted styrenes, vinyltoluene and mixtures thereof. The most preferred vinyl aromatic monomer comprises styrene.

[0048] The amount of vinyl aromatic monomer can range from 0.5 to 40 weight percent (e.g., 1, 5, 10, 20, 30, or 40 weight percent), based on the total weight of all monomers in the epoxy-functional acrylic resin.

[0049] The epoxy-functional acrylic resin can be prepared by polymerizing the monomers. The polymerization can be carried out by conventional polymerization methods in the presence of a polymerization initiator.

[0050] In addition to the epoxy-functional acrylic resin, component A and / or component B may optionally contain other resins. The other resins may be epoxy resins, for example bisphenol epoxy resins, such as bisphenol A epoxy resin, bisphenol F epoxy resin, or novolac epoxy resin. In another embodiment, the other resins may be acrylic resins, polyether resins, polyester resins, polyurea resins, polyurethane resins, or any mixtures thereof of two or more thereof. However, the amount of the other resins is typically no more than 10 weight percent, preferably no more than 5 weight percent, more preferably no more than 3 weight percent, in each case based on the total weight of the component. In one embodiment, component A and / or component B, in addition to the epoxy-functional acrylic resin, do not contain other resins.

[0051] In one embodiment, the amount of the at least one epoxy-functional acrylic resin (a) is 50-95 wt % (e.g., 60, 70, 80, or 90 wt %), preferably 60-90 wt %, or 70-90 wt %, or 80-90 wt %, based on the total weight of component A; and / or the amount of the at least one epoxy-functional acrylic resin (b) is 50-95 wt % (e.g., 60, 70, 80, or 90 wt %), preferably 60-90 wt %, or 70-85 wt %, based on the total weight of component B.

[0052] crosslinking agent

[0053] Component A and component B comprise a cross-linking agent for the epoxy-functional acrylic resin. The cross-linking agent has epoxy-reactive groups, in particular at least two epoxy-reactive groups. The cross-linking agent comprises, for example, a dicarboxylic acid, a polycarboxylic acid or an anhydride thereof. In a preferred embodiment, the cross-linking agent is selected from a dicarboxylic acid or an anhydride thereof having 4 to 20 (e.g., 6, 8, 10, 12, 14, 16 or 18) carbon atoms, preferably 6 to 18 carbon atoms. The cross-linking agent can preferably be selected from adipic acid, azelaic acid, sebacic acid and dodecanedioic acid and anhydrides thereof.

[0054] In component A, the stoichiometric ratio of the crosslinker to the at least one epoxy-functional acrylic resin (a) is from 0.9:1 to 1:0.9, preferably from 0.95:1 to 1:0.95, for example, from 0.98:1 to 1:0.98, or from 1:0.9 to 1:0.995, or from 1:0.95 to 1:0.995, or from 1:0.98 to 1:0.995; and in component B, the stoichiometric ratio of the crosslinker to the at least one epoxy-functional acrylic resin (b) is from 0.9:1 to 1:0.9, preferably from 0.95:1 to 1:0.95, for example, from 0.98:1 to 1:0.98, or from 1:0.9 to 1:0.995, or from 1:0.95 to 1:0.995, or from 1:0.98 to 1:0.995. In this regard, if the crosslinking agent is a dicarboxylic acid, the stoichiometric ratio is the ratio of carboxyl groups of the crosslinking agent to epoxy groups of the epoxy-functional acrylic resin.

[0055] In one embodiment, the stoichiometric ratio of all crosslinkers to all epoxy-functional acrylic resins in the powder coating composition is 0.9:1-1:0.9, preferably 0.95:1-1:0.95, for example 0.98:1-1:0.98, or 1:0.9-1:0.995, or 1:0.95-1:0.995, or 1:0.98-1:0.995.

[0056] In one embodiment, in the powder coating composition, the weight ratio of all epoxy functional acrylic resins to crosslinker is 3:1 to 10:1 (e.g., 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1), preferably 4:1 to 8:1.

[0057] Accelerators and other additives

[0058] Component A and / or component B of the powder coating composition may further comprise at least one curing accelerator. Examples of the accelerator include tertiary amines, imidazoles, organic acids, phenols, and organic phosphines.

[0059] Examples of suitable tertiary amines are triethanolamine, dialkylaminoethanol, triethylenediamine, 1,4-diazabicyclo[2.2.2]octane, 1,8-diazabicyclo[5.4.0]undec-7-ene and 2,4,6-tris(dimethylaminomethyl)phenol.

[0060] Examples of suitable imidazoles are 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole and 2-heptadecylimidazole.

[0061] Examples of suitable organic acids are benzoic acid derivatives, such as salicylic acid.

[0062] Examples of suitable organic phosphines are tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine and phenylphosphine.

[0063] Examples of suitable phenols are alkylphenols such as nonylphenol and Novares LS500.

[0064] Preferred accelerators are organic phosphines, especially triphenylphosphine.

[0065] In component A, the amount of accelerator can be 0-10 wt %, or 0.1-8 wt %, or 0.5-5 wt %, based on the total weight of component A. In component B, the amount of accelerator can be 0-10 wt %, or 0.1-8 wt %, or 0.5-5 wt %, based on the total weight of component B. In one embodiment, component B does not contain an accelerator. In one embodiment, both component A and component B do not contain an accelerator.

[0066] Component A and / or component B of the powder coating composition may further comprise at least one plasticizer, such as 1,4-cyclohexanedimethanol dibenzoate, tetraethylene glycol dimethyl ether, and triethylene glycol mono(2-hexylhexanoate). In component A, the amount of the plasticizer may be 0.1-5% by weight, or 0.5-3% by weight, or 0.5-2% by weight, based on the total weight of component A. In component B, the amount of the plasticizer may be 0.1-5% by weight, or 0.5-3% by weight, or 0.5-2% by weight, based on the total weight of component B.

[0067] Component A and / or Component B of the powder coating composition may further comprise one or more hydrophobic submicron particles, such as inorganic oxides (e.g., metal oxides or silica) and organosilicon compounds (e.g., fumed silica treated with polydimethylsiloxane (PDMS)). The amount of the hydrophobic submicron particles may be 0-1.5 wt%.

[0068] The coating composition may further comprise one or more additives such as fillers, antioxidants, matting agents, pigments, corrosion inhibitors, wear resistant particles, flow control agents, dispersants, surfactants, adhesion promoters, thixotropic agents, light stabilizers, and the like.

[0069] Component A and component B are prepared separately. Component A and component B can be in the form of a dry-blended homogeneous mixture (sometimes also referred to as a "dry blend") or in the form of separate packages. If component A and component B are in the form of separate packages, component A and component B are uniformly mixed before use.

[0070] Characteristics of powder compositions and methods of preparing powder coating compositions

[0071] One aspect of the present invention relates to a method for preparing the powder coating composition of the present invention, comprising:

[0072] (i) mixing, extruding and crushing the ingredients in component A to obtain component A in powder form;

[0073] (ii) mixing, extruding and crushing the ingredients of component B to obtain component B in powder form; and

[0074] (iii) Components A and B are optionally mixed homogeneously, preferably by dry blending.

[0075] For example, in steps (i) and (ii), the ingredients may be blended and then extruded to obtain an extrudate, for example, by melt mixing and extruding the molten mixture. After extrusion, the extrudate is cooled. The extrudate is then crushed (e.g., ground), and the crushed (e.g., ground) powder is sieved, if necessary.

[0076] The particle size (D90) of the powder may be 5-200 μm, such as 25-200 μm, or 75-150 μm. Said particle size is preferred for electrostatic spraying.

[0077] Matt coating, article having matte coating, and method for preparing matte coating

[0078] One aspect of the present invention relates to a method for preparing a matte coating, comprising:

[0079] (1) applying the powder coating composition of the present invention to a substrate; and

[0080] (2) The applied powder coating composition is cured.

[0081] The powder coating composition may be applied by conventional means such as electrostatic spraying.

[0082] The curing in step (2) can be performed by thermal curing. The curing temperature may not exceed 200° C., for example, not exceed 180° C. The curing time may not exceed 20 minutes, for example, not exceed 15 minutes.

[0083] Suitable substrates may include aluminum, wrought alloys, iron, steel, magnesium alloys, and brass or organic substrates such as polymers. Aluminum substrates may include aluminum silicon alloys, aluminum lithium alloys, aluminum magnesium, aluminum zinc, aluminum manganese, and aluminum copper-based alloys (e.g., aluminum bronze).

[0084] One aspect of the present invention relates to a matte coating formed from the powder coating composition of the present invention. Matte, as used herein, is understood to mean a gloss of no more than 60%, preferably no more than 55%, and more preferably no more than 50% at 60°. The gloss is measured at 60° on a polyester epoxy black basecoat using a gloss meter from Sheen.

[0085] One aspect of the present invention relates to an article having the matte coating of the present invention, preferably the article is a wheel hub or a decorative article.

[0086] In one embodiment, the matte coating of the present disclosure has a gloss of 30-40%, wherein the gloss is measured using a gloss meter from Sheen on a polyester epoxy black basecoat at an angle of 60°.

[0087] The following examples are provided to illustrate but not to limit the present invention. The amounts of the various substances in the examples are based on parts by weight.

[0088] Example

[0089] raw material

[0090] ALMATEX MT2780: Epoxy-functional acrylic resin (GMA acrylic resin) with an epoxy equivalent weight (EEW) of 785 g / eq, a melt index (g / 10 min @ 125°C) of 6-10, and a glass transition temperature (Tg) of 56-60°C. Available from Anderson Development.

[0091] PD7610-J: Epoxy-functional acrylic resin (GMA acrylic resin) with an epoxy equivalent weight (EEW) of 535 g / eq, a melt index (g / 10 min @ 125°C) of 46-54, and a glass transition temperature (Tg) of 45-50°C. Available from Anderson Development.

[0092] PD6300-J: Epoxy-functional acrylic resin (GMA acrylic resin) with an epoxy equivalent weight (EEW) of 535 g / eq, a melt index (g / 10 min @ 125°C) of 10-16, and a glass transition temperature (Tg) of 58-63°C. Available from Anderson Development.

[0093] A705: epoxy-functional acrylic resin (GMA acrylic resin) with an epoxy equivalent weight (EEW) of 425 g / eq, a melt index (g / 10 min @ 125°C) of 30-40, and a glass transition temperature (Tg) of 50°C; from DIC Corporation.

[0094] WSR120 (A707): epoxy-functional acrylic resin (GMA acrylic resin) with an epoxy equivalent weight (EEW) of 330 g / eq, a melt index (g / 10 min @ 125°C) of 50, and a glass transition temperature (Tg) of 55°C; from DIC Corporation.

[0095] Additol TMP964 (hereinafter referred to as P964): 95% carboxyl polyester resin masterbatch + 5% triphenylphosphine (accelerator), from Allnex;

[0096] Benzoflex: 1,4-cyclohexanedimethanol dibenzoate (plasticizer);

[0097] DDDA: dodecanedioic acid (cross-linking agent);

[0098] URALAC P800 is a saturated carboxyl polyester resin with an acid number of 26-30 mg KOH / g, a viscosity (Brookfield) of 21-41 Pa·s, and a glass transition temperature of about 61°C; it is available from DSM.

[0099] URALAC P 5500 is a saturated carboxyl polyester resin with an acid number of 46-54 mg KOH / g, a viscosity (Brookfield) of 37-67 Pa·s, and a glass transition temperature of about 58° C.; it is from DSM.

[0100] method

[0101] Crazing Test Method (determines the relative resistance of a clear powder coating to crazing when exposed to isopropyl alcohol): Apply the powder coating to a bare aluminum Type AQ-aluminum panel, 76.2 mm x 152.4 mm x 0.60 mm (3 in x 6 in x 0.25 in), from Q-Lab, Cleveland, Ohio, and cure the panel under appropriate conditions (see Table 7). Bend the panel 30 to 45 degrees from horizontal and apply isopropyl alcohol to the coating at the point of maximum curvature. Immediately thereafter, observe the treated area for crack formation. Observe the reference point of the crack perpendicular to the axis. One minute after applying the isopropyl alcohol; observe and report the extent of cracking. Only one or two drops of isopropyl alcohol are required.

[0102] Gloss: The gloss of the cured coating was measured by light reflection at an angle of 60° using a gloss meter from Sheen.

[0103] Storage stability: GBT 21782[1].8-2008, with some modifications based on the standard and in practice, the powder composition is stored at 23±2°C and inspected every 2 or 4 weeks. The main inspections are gel time, appearance, and gloss changes.

[0104] Full cure: Full cure is achieved when the coating is insoluble in the organic solvent (methyl ethyl ketone) after immersion.

[0105] Example 1

[0106] The ingredients of component A (or B) were weighed (see Table 1) and mixed together, and then extruded in a ZSK-26 (coperion) extruder at 120°C. The molten mixture was cooled and coarsely ground, then milled and sieved, with the D90 of each component controlled to less than 70 μm. This yielded the final individual components A and B.

[0107] The final powder coating composition was obtained by dry blending Component A and Component B in the weight ratio shown in Table 1 and ensuring uniform mixing.

[0108] The final powder coating composition was applied to the metal sheet or polyester-epoxy black basecoat by electrostatic spraying with a film thickness of 80-120 μm. Finally, the coating was cured in a convection oven (conditions see Table 1).

[0109] Table 1

[0110] Examples 2 and 3

[0111] The preparation of the powder coating compositions in Examples 2 and 3, and the coating preparation were made with reference to Example 1, wherein the ingredients used, curing conditions and results are shown in Table 2.

[0112] Table 2

[0113] Compared to Example 1, PD6300-J, which has a lower EEW than ALMATEX MT2780, was added to Component A of Example 3, resulting in a lower average EEW of the epoxy-functional acrylic resin in Component A of Example 3. Because Component B of Example 3 and Example 1 is the same, the arithmetic mean EEW difference in Example 3 is lower than that in Example 1, and the gloss of the resulting coating is increased.

[0114] Examples 4 and 5

[0115] The preparation of the powder coating compositions in Examples 4 and 5, and the coating preparation were made with reference to Example 1, wherein the ingredients used, curing conditions and results are shown in Table 3.

[0116] Table 3

[0117] The difference in arithmetic average epoxy equivalent weights of the epoxy resins of components A and B in Example 5 is greater than that of the epoxy resins of components A and B in Example 4. The resulting coating of Example 5 has lower gloss.

[0118] Examples 6 and 7

[0119] The preparation of the powder coating compositions in Examples 6 and 7, and the coating preparation were made in accordance with Example 1, wherein the ingredients used, curing conditions and results are shown in Table 4.

[0120] Table 4

[0121] The difference in arithmetic average epoxy equivalent weights of the epoxy resins of components A and B in Example 7 is greater than that of the epoxy resins of components A and B in Example 6, and the glossiness of the coating obtained in Example 7 is lower.

[0122] Examples 8 and 9 and Comparative Examples 1 and 2

[0123] The powder coating compositions of Examples 8 and 9 and Comparative Examples 1 and 2 were prepared, and the coating was prepared in Reference Example 1, wherein the ingredients used, curing conditions and results are shown in Table 5.

[0124] The powder coating composition of Comparative Example 1 contains only component B of Example 8, and the powder coating composition of Comparative Example 2 contains only component A of Example 8. See Table 5 for the results.

[0125] Table 5

[0126] Comparative Examples 1 and 2 show that since two epoxy acrylates having an EEW difference of more than 50 g / eq (here 230 g / eq and 90 g / eq, respectively) are not present in the two components respectively, the resulting powder coating composition can only produce a high-gloss coating.

[0127] The powder coating composition of Example 8 can be stably stored at 6° C. for 6-8 months.

[0128] Example 10

[0129] The preparation of the powder coating composition in Example 10 and the coating preparation were made with reference to Example 1, wherein the ingredients used, curing conditions and results are shown in Table 6.

[0130] Table 6

[0131] Comparative Example 3

[0132] The clear coating composition of Comparative Example 3 is based on a carboxyl polyester and triglycidyl isocyanurate. Component A of Comparative Example 3 contains 90.144% URALAC P800 and 5.754% TGIC (triglycidyl isocyanurate), with the balance being additives. Component B of Comparative Example 3 contains 86.053% URALAC P5500 and 9.545% TGIC, with the balance being additives. The powder coating composition of Comparative Example 3 was prepared similarly to that of Example 1. The weight ratio of Component A to Component B was 1:1.

[0133] Characterization 1: Characterization of the powder coating composition of Example 8 and the clear coating composition of Comparative Example 3

[0134] Table 7

[0135] Photographs of silver streaks of the powder coating composition of Example 8 and the clear coating composition of Comparative Example 3 are shown in Figure 1. The results show that the coating formed from the clear coating composition of Comparative Example 3 exhibits silver streaks, while the coating formed from the powder coating composition of Example 8 does not.

[0136] Characterization 2: Characterization of the powder coating composition of Example 8 and commercially available products

[0137] The commercially available product is a high-gloss clear coating based on glycidyl methacrylate acrylic resin and DDDA.

[0138] Table 8

[0139] 1) The test piece was immersed in 40°C hot water for 240 hours. It was then removed from the water and stored at room temperature for 30 minutes before being inspected for film color and gloss, swelling, peeling, and wrinkling. A secondary adhesion test was then performed according to ISO 2409.

[0140] 2) The CASS test is conducted according to ISO9227 for 6 hours + / - 15 minutes, with a 3-second immersion wash in running deionized water, and then the test piece is placed in a cabinet at 60°C and 85% relative humidity for 672 hours. The maximum filament length on one side is recorded weekly, and the result of week 4 is used as the final result at the end of the test.

[0141] The results in Table 8 show that the powder coating composition of the present invention passed the water resistance, CASS and filiform corrosion tests.

[0142] Characterization 3: Xenon lamp aging

[0143] Table 9 shows the xenon arc aging results of the coatings formed from the powder coating composition of Example 8 on the substrate A356 (aluminum alloy).

[0144] Table 9 - On substrate A356 (aluminum alloy)

[0145] 3) First, a 3000-hour weathering test was performed according to SAE J2527-2017 Boro / Boro. Then, the color, gloss, adhesion, and water resistance tests shown in Table 9 were performed.

[0146] Table 10 shows the xenon arc aging results of coatings formed from the powder coating composition of Example 8 on a highly weatherable polyester based black primer.

[0147] Table 10 - On a black primer based on highly weatherable polyester

[0148] The results in Tables 9 and 10 show that the coatings formed from the powder coating compositions of the present invention have excellent weather resistance.

[0149] Although the present invention is disclosed above with reference to preferred embodiments, the present invention is not limited thereto. Any changes and modifications made by those skilled in the art without departing from the spirit and scope of the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A powder coating composition comprising: Component A in powder form, wherein Component A comprises at least one epoxy-functional acrylic resin (a) and a crosslinking agent for the epoxy-functional acrylic resin; and Component B in powder form, wherein Component B comprises at least one epoxy-functional acrylic resin (b) and a crosslinker for the epoxy-functional acrylic resin; The powder of component B is different from the powder of component A, and the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (a) in component A is higher than the arithmetic average epoxy equivalent of the at least one epoxy-functional acrylic resin (b) in component B, and the difference in the arithmetic average epoxy equivalents in component A and component B is at least 50 g / eq.

2. The powder coating composition according to claim 1, wherein the difference in the arithmetic mean epoxy equivalent weight between component A and component B is at least 80 g / eq, or at least 120 g / eq, or at least 150 g / eq, or at least 180 g / eq.

3. The powder coating composition according to claim 1 or 2, wherein the difference in the arithmetic mean epoxy equivalent weight between component A and component B is 50-550 g / eq, or 120-500 g / eq, or 150-500 g / eq, or 180-480 g / eq.

4. A powder coating composition according to any one of claims 1 to 3, wherein component A comprises two or more epoxy-functional acrylic resins (a) and / or component B comprises two or more epoxy-functional acrylic resins (b).

5. A powder coating composition according to any one of claims 1 to 4, wherein the at least one epoxy-functional acrylic resin (a) in component A has an arithmetic average epoxy equivalent weight of at least 500 g / eq, preferably at least 520 g / eq, and the at least one epoxy-functional acrylic resin (b) in component B has an arithmetic average epoxy equivalent weight of not more than 550 g / eq, preferably not more than 520 g / eq or not more than 500 g / eq.

6. The powder coating composition according to any one of claims 1 to 5, wherein the weight ratio of component A to component B is 1:7 to 7:1, preferably 1:5 to 5:1, more preferably 1:3 to 3:

1.

7. A powder coating composition according to any one of claims 1 to 6, wherein in component A, the stoichiometric ratio of the crosslinker to the at least one epoxy functional acrylic resin (a) is 0.9:1 to 1:0.9, preferably 0.95:1 to 1:0.95; and in component B, the stoichiometric ratio of the crosslinker to the at least one epoxy functional acrylic resin (b) is 0.9:1 to 1:0.9, preferably 0.95:1 to 1:0.

95.

8. The powder coating composition according to any one of claims 1 to 7, wherein in the powder coating composition the stoichiometric ratio of all crosslinkers to all epoxy functional acrylic resins is from 0.9:1 to 1:0.9, preferably from 0.95:1 to 1:0.

95.

9. The powder coating composition according to any one of claims 1 to 8, wherein in the powder coating composition, the weight ratio of all epoxy functional acrylic resins to all crosslinking agents is 3:1 to 10:1, preferably 4:1 to 8:

1.

10. A powder coating composition according to any one of claims 1 to 9, wherein the crosslinking agent is selected from dicarboxylic acids or anhydrides thereof having 4 to 20 carbon atoms, preferably 6 to 18 carbon atoms.

11. A powder coating composition according to any one of claims 1 to 10, wherein the amount of the at least one epoxy-functional acrylic resin (a) is 50-95% by weight, preferably 60-90% by weight, based on the total weight of component A; and the amount of the at least one epoxy-functional acrylic resin (b) is 50-95% by weight, preferably 60-90% by weight, based on the total weight of component B.

12. A powder coating composition according to any one of claims 1 to 11, wherein component A and / or component B comprises at least one plasticizer.

13. A powder coating composition according to any one of claims 1 to 12, wherein component A and component B are in the form of a dry-blended homogeneous mixture or in the form of separate packages.

14. A powder coating composition according to any one of claims 1 to 13, wherein component A and component B are prepared separately.

15. A method for preparing a powder coating composition according to any one of claims 1 to 14, comprising: (i) mixing, extruding and crushing the ingredients in component A to obtain component A in powder form; (ii) mixing, extruding and crushing the ingredients in component B to obtain component B in powder form; and (iii) Optionally, components A and B are uniformly mixed.

16. A matte coating formed from a powder coating composition according to any one of claims 1 to 14.

17. An article, preferably a wheel hub or a trinket, having a matte coating according to claim 16.

18. A method for preparing a matte coating, comprising: (1) applying a powder coating composition according to any one of claims 1 to 14 on a substrate; and (2) Curing the applied powder coating composition.

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