Extinction powder coating composition as well as preparation method and application thereof

Abstract

The invention discloses a matting powder coating composition which comprises the following raw materials: high-activity polyester resin, high-leveling polyester resin, a curing cross-linking agent and a matting agent, the acid value of the high-activity polyester resin is 60-80 mgKOH / g, the reactivity at 160 DEG C is 120-300 s, and the melt viscosity at 160 DEG C is less than or equal to 10000 mPa.s; the acid value of the high-leveling polyester resin is 40-60mgKOH / g, the reactivity at 160 DEG C is 480-900s, and the melt viscosity at 160 DEG C is less than or equal to 5000mPa. S. The low-temperature curing matting powder coating composition can be fully cured under the curing condition of 160 DEG C, a cured coating can obtain an ideal matting effect, meanwhile, excellent appearance flatness and fineness are obtained, and in addition, the coating has good physical and chemical properties such as impact resistance, bending resistance and chemical resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of powder coatings, and in particular relates to a matte powder coating composition and a preparation method and application thereof. Background Art

[0002] As a kind of environmentally friendly coating with zero VOC emission, thermosetting powder coating has the advantages of low comprehensive cost, low energy consumption, convenient construction and excellent performance. It is rapidly replacing traditional solvent-based coatings in the field of coating of metal substrates. The rapid growth of the domestic economy in the past decade has driven the vigorous development of the automotive industry. Under the requirements of environmental protection policies, more and more auto parts are coated with powder coatings, among which the primer of automotive aluminum wheels is basically coated with matte powder coatings. At present, powder coatings for aluminum wheel coating generally require a higher curing temperature (180-200℃) to ensure sufficient curing. Too high curing temperature will cause the toughness of aluminum wheels to decrease, bringing a certain degree of safety hazards. Therefore, aluminum wheel manufacturers hope to reduce the curing temperature of powder coatings to 150-160℃. The lower curing temperature can not only improve the safety of aluminum wheels, but also save energy consumption and reduce the production cost of enterprises.

[0003] In addition to meeting the basic requirements for protective performance, powder coatings for aluminum wheels also have extremely high requirements for decorative performance. Not only is the coating required to have a good matte effect (coating gloss is not higher than 30%), but the coating is also required to have a good appearance leveling (PC I leveling grade ≥ 7). Although the existing low-temperature curing powder coatings can achieve a curing temperature below 160°C, they have poor matting effects and poor appearance leveling of the coating after matting, which cannot meet the requirements for aluminum wheel coating. Since the low-temperature curing, matting and leveling used in the prior art have mutually inhibiting or conflicting mechanisms of action, the low-temperature curing high-leveling matte powder coating composition products have been in a blank state in the current market. Summary of the invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, one of the purposes of the present invention is to provide a matte powder coating composition. The second purpose of the present invention is to provide a method for preparing the matte powder coating composition. The third purpose of the present invention is to provide an application of the matte powder coating composition. The fourth purpose of the present invention is to provide a metal substrate.

[0005] In the prior art, the problems of low-temperature curing, matting and leveling are mainly solved by using a polyester, but since the three are mutually restricted or contradictory in the mechanism of action, the prior art cannot solve the problem of taking all three into account from the fundamental reason. The present invention uses two polyesters with different performance characteristics for compounding to solve the problem that low-temperature curing, matting and leveling cannot be taken into account at the same time, wherein the high-activity polyester can provide good reactivity and matting performance at low temperature, and the high-leveling polyester resin can provide good leveling performance at low temperature, and the high-leveling polyester resin has lower reactivity than the high-activity polyester. The powder coating prepared by compounding the two polyesters has a variety of reaction systems with different curing rates during curing. This difference in curing rate can destroy the continuity of the coating film, which is conducive to further improving the matting effect of the system. After adding a certain amount of matting agent to the powder formula, the addition of the matting agent will further increase the complexity of the curing reaction, and the coating film can obtain an ideal matte effect.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The first aspect of the present invention provides a matte powder coating composition, comprising the following raw materials: a high-activity polyester resin, a high-leveling polyester resin, a curing cross-linking agent and a matting agent;

[0008] The high-activity polyester resin has an acid value of 60-80 mgKOH / g, a reactivity of 120-300 s at 160° C., and a melt viscosity of ≤10000 mPa.s at 160° C.;

[0009] The high-leveling polyester resin has an acid value of 40-60 mgKOH / g, a reactivity of 480-900 s at 160° C., and a melt viscosity of ≤5000 mPa.s at 160° C.;

[0010] The molecular structural formula of the highly active polyester resin is:

[0011]

[0012] The molecular structure formula of the high-leveling polyester resin is:

[0013]

[0014] Among them, R1, R2, R3, R4, R5, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 Each independently represents unsubstituted or substituted C 1-20 Alkyl or C 6-20 Aryl;

[0015] The mass ratio of the high-activity polyester resin to the high-leveling polyester resin is (1-4):1.

[0016] Preferably, the high-activity polyester resin is prepared from the following raw materials: polyol 1, polyacid 1, acidulant 1, esterification catalyst, cross-linking catalyst; the polyol 1 is aliphatic and / or alicyclic diol; the polyacid 1 is aromatic dibasic acid and aliphatic dibasic acid; the acidulant 1 is aromatic polyacid anhydride; the molar ratio of the polyol 1 to the polyacid 1 is 1:(1-1.3); the molar ratio of the polyol 1 to the acidulant 1 is 1:(0.05-0.2).

[0017] More preferably, the high-activity polyester resin is prepared from the following raw materials in molar parts: 90-110 parts of polyol 1, 100-125 parts of polyacid 1, 10-20 parts of acidulant 1, 0.05-0.2 parts of esterification catalyst, and 2-4 parts of cross-linking catalyst.

[0018] More preferably, the acidolysis agent 1 is selected from one of trimellitic anhydride and pyromellitic anhydride or a combination thereof.

[0019] The invention uses a highly active acid anhydride with a functional group ≥3 to perform terminal carboxylation to obtain the highly active polyester resin. The highly active acid anhydride at the end of the polyester main chain can not only improve the reaction activity of the polyester, but also improve the crosslinking density of the coating film, thereby giving the coating film good mechanical properties.

[0020] More preferably, the polyol 1 is at least one selected from neopentyl glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 2-butyl-2-ethyl-1,3-propylene glycol, pentanediol, hexanediol, and 1,4-cyclohexanedimethanol.

[0021] More preferably, the polyol 1 is composed of neopentyl glycol and other aliphatic and / or alicyclic polyols, and the molar ratio of the neopentyl glycol to the other aliphatic and / or alicyclic polyols is (1-4):1.

[0022] More preferably, the polyol 1 is composed of neopentyl glycol, ethylene glycol, diethylene glycol and 2-methyl-1,3-propanediol, wherein the molar percentage of neopentyl glycol is 50-80 mol%.

[0023] More preferably, the aromatic dibasic acid in the polyacid 1 is selected from at least one of terephthalic acid, isophthalic acid, phthalic anhydride, and trimesic acid, and the aliphatic dibasic acid in the polyacid 1 is selected from at least one of succinic acid, adipic acid, glutaric acid, and 1,4-cyclohexanedicarboxylic acid.

[0024] More preferably, the molar ratio of the aromatic dibasic acid to the aliphatic dibasic acid in the polyacid 1 is (4-20):1.

[0025] Preferably, the high-leveling polyester resin is prepared from the following raw materials: polyol 2, polyacid 2, acidulant 2, esterification catalyst, cross-linking catalyst; the polyol 2 is aliphatic and / or alicyclic diol and aliphatic triol; the polyacid 2 is an aromatic dibasic acid; the acidulant 2 is an aromatic dibasic acid and an aliphatic dibasic acid; the mass ratio of the polyol 2 to the polyacid 2 is 1:(0.85-1); the mass ratio of the polyol 2 to the acidulant 2 is 1:(0.1-0.25).

[0026] More preferably, the high-leveling polyester resin is prepared from the following raw materials in molar parts: 90-110 parts of polyol 2, 85-100 parts of polyacid 2, 10-23 parts of acidulant 2, 0.05-0.2 parts of esterification catalyst, and 0.4-0.8 parts of crosslinking catalyst.

[0027] More preferably, the aliphatic dibasic acid in the acidolysis agent 2 is at least one selected from succinic acid, adipic acid, and glutaric acid.

[0028] The present invention utilizes a dibasic acid to perform terminal carboxylation to obtain the high-leveling polyester resin. The dibasic acid at the end of the polyester main chain can control the reaction activity of the polyester and reduce the reaction rate with the curing agent, so that the powder coating has sufficient time to melt and level during the curing process, thereby giving the coating film good leveling performance. At the same time, the addition of a small amount of triol can ensure that the curing system can form a certain spatial network structure, so that the coating film has certain mechanical properties.

[0029] More preferably, the aliphatic and / or alicyclic diol in the polyol 2 is selected from at least one of neopentyl glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, pentanediol, hexanediol, and 1,4-cyclohexanedimethanol, and the aliphatic triol in the polyol 2 is selected from at least one of trimethylolpropane, trimethylolethane, and pentaerythritol.

[0030] More preferably, the polyol 2 is composed of neopentyl glycol, other aliphatic and / or alicyclic polyols and aliphatic triols.

[0031] More preferably, the polyol 2 is composed of neopentyl glycol, ethylene glycol, diethylene glycol, 2-methyl-1,3-propanediol and trimethylolpropane, wherein the molar percentage of neopentyl glycol is 40-70 mol%.

[0032] More preferably, the polyacid 2 is at least one selected from terephthalic acid, isophthalic acid, and phthalic acid.

[0033] More preferably, the esterification catalyst is selected from at least one of monobutyltin oxide, monobutyltin chloride and tetrabutyl titanate.

[0034] More preferably, the cross-linking catalyst is selected from at least one of benzyltrimethylammonium chloride, triphenylphosphine, triphenylethylphosphonium bromide and tert-butylamine.

[0035] More preferably, the highly active polyester resin is prepared by a preparation method comprising the following steps:

[0036] A1: polyol 1, polyacid 1 and an esterification catalyst are mixed to carry out an esterification reaction to obtain an esterification product 1;

[0037] A2: adding an acidulant 1 to the esterification product 1 to carry out an acidolysis reaction to obtain an acidified product 1;

[0038] A3: The acidified product 1 reacts with a cross-linking catalyst to obtain a highly active polyester resin.

[0039] Further preferably, in A1, the acid value of the esterification product 1 is 15-26 mgKOH / g.

[0040] More preferably, in A1, the reaction temperature of the esterification reaction is 230-245°C.

[0041] Further preferably, in A1, the esterification reaction is carried out under a protective atmosphere.

[0042] Further preferably, A1 further comprises: subjecting the esterification product 1 to vacuum polycondensation.

[0043] Further preferably, in A2, the reaction temperature of the acid hydrolysis reaction is 215-225°C.

[0044] Further preferably, in A2, the acid value of the acidified product 1 is 60-80 mgKOH / g.

[0045] More preferably, in A3, the reaction temperature of the reaction is 170-190°C.

[0046] More preferably, the high-leveling polyester resin is prepared by a preparation method comprising the following steps:

[0047] B1: Mixing polyol 2, polyacid 2 and an esterification catalyst to carry out an esterification reaction to obtain an esterification product 2;

[0048] B2: adding acidulant 2 to the esterification product 2 to carry out acidolysis reaction to obtain acidified product 2;

[0049] B3: The acidified product 2 reacts with a cross-linking catalyst to obtain a high-leveling polyester resin.

[0050] Further preferably, in B1, the acid value of the esterification product 2 is 8-26 mgKOH / g.

[0051] More preferably, in B1, the reaction temperature of the esterification reaction is 230-245°C.

[0052] Further preferably, in B1, the esterification reaction is carried out under a protective atmosphere.

[0053] Further preferably, in B2, the reaction temperature of the acidolysis reaction is 220-235° C., and the reaction temperature of the acidolysis reaction is lower than the reaction temperature of the esterification reaction.

[0054] Further preferably, B2 further comprises: subjecting the acidified product 2 to vacuum polycondensation.

[0055] Further preferably, in B2, the acid value of the acidified product 1 is 55-70 mgKOH / g.

[0056] Further preferably, in B3, the reaction temperature of the reaction is 170-190°C.

[0057] Preferably, the curing cross-linking agent is an epoxy resin curing agent.

[0058] More preferably, the epoxy resin curing agent is bisphenol A epoxy resin.

[0059] More preferably, the bisphenol A epoxy resin has a softening point of 70-95° C. and an epoxy equivalent of 650-950 g / mol.

[0060] Preferably, the mass ratio of the high-activity polyester resin to the curing cross-linking agent is 1:(1-2.5).

[0061] Preferably, the matting agent is selected from a physical matting agent, a chemical matting agent or a combination thereof.

[0062] Preferably, the mass ratio of the high-activity polyester resin to the matting agent is 1:(0.1-0.2).

[0063] Preferably, the matte powder coating composition further comprises at least one of a leveling control agent, a degassing agent, and a pigment or filler.

[0064] More preferably, the polyester resin composition for matte powder coating comprises the following raw materials in parts by mass: 150-400 parts of high-activity polyester resin, 80-160 parts of high-leveling polyester resin, 250-500 parts of curing cross-linking agent, 20-50 parts of matting agent, 10-15 parts of leveling control agent, 2-6 parts of degassing agent, and 50-350 parts of pigments and fillers.

[0065] More preferably, the pigment filler is selected from at least one of titanium dioxide, iron oxide, zinc oxide, metal hydroxide, metal powder, sulfide, sulfate, carbonate, silicate, carbon black, talc, china clay, barite, iron blue, lead blue, organic red and organic purple.

[0066] The second aspect of the present invention provides a method for preparing the matte powder coating composition of the first aspect, comprising the following steps: mixing, extruding, kneading and grinding the components to obtain the matte powder coating composition.

[0067] The third aspect of the present invention provides use of the matte powder coating composition of the first aspect in protecting the surface of a workpiece.

[0068] Preferably, the matte powder coating composition is used in the protection of the surface of a metal workpiece.

[0069] Preferably, the matte powder coating composition is used in the surface protection of metal aluminum workpieces.

[0070] The fourth aspect of the present invention provides a metal substrate, the surface of which is coated with a coating formed by curing the low-temperature curing matte powder coating composition of the first aspect.

[0071] Preferably, the metal substrate is prepared by the following steps: a low-temperature curing powder coating composition is deposited on a substrate by using an electrostatic or friction-charged spray gun, or a low-temperature curing powder coating composition is deposited on a substrate by using a fluidized bed technology, and then heated and melted to form a coating.

[0072] More preferably, the curing temperature is 150-160°C.

[0073] The beneficial effects of the present invention are:

[0074] (1) The present invention provides a matte powder coating composition, which is compounded with two polyesters with different performance characteristics to solve the problem that low-temperature curing, matting and leveling cannot be taken into account at the same time, wherein the high-activity polyester can provide good reactivity and matting performance at low temperatures, and the high-leveling polyester resin can provide good leveling performance at low temperatures. At the same time, the high-leveling polyester resin has lower reactivity than the high-activity polyester. The powder coating prepared by compounding the two polyesters has a plurality of reaction systems with different curing rates during curing. The difference in curing rates can destroy the continuity of the coating film, which is beneficial to further improve the matte effect of the system. After a certain amount of matting agent is added to the powder formula, the addition of the matting agent will further increase the chaos of the curing reaction, and the coating film can obtain an ideal matte effect.

[0075] (2) Compared with the prior art, the low-temperature curing matte powder coating composition of the present invention can be fully cured under the curing condition of 160°C. The cured coating can not only obtain an ideal matte effect (the glossiness of the coating film is not higher than 30%), but also obtain excellent appearance flatness (PCI leveling grade ≥7) and fineness. In addition, the coating has good physical and chemical properties such as impact resistance, bending resistance and chemical resistance, while conventional polyester / epoxy low-temperature curing powder coatings cannot take into account both matte and appearance leveling. DETAILED DESCRIPTION

[0076] The present invention is further described in detail below through specific examples. The raw materials used in the following examples, unless otherwise specified, can be obtained from conventional commercial sources or prepared and separated by simple synthesis; the processes used, unless otherwise specified, are conventional processes in the art.

[0077] Example 1

[0078] This embodiment provides a highly active polyester resin, and the synthesis steps are as follows:

[0079] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 1 in Table 1, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 235° C. to carry out esterification polycondensation reaction until the acid value of the reactant is detected to be 15-20 mgKOH / g;

[0080] The second stage: the kettle temperature is lowered to 230°C, and the esterification polycondensation reactants are subjected to vacuum polycondensation reaction at a vacuum degree of -0.094 MPa for 120 minutes. After the vacuum is released, the acid value of the polycondensation product is detected to be 5-10 mgKOH / g;

[0081] The third stage: the kettle temperature is further lowered to 225°C and trimellitic anhydride is added for acidification reaction until the acid value of the reactant is detected to be 63.8 mgKOH / g;

[0082] Stage 4: Continue to lower the reaction temperature to 190°C, add the cross-linking catalyst, stir for 25 minutes, and then discharge the material, which is recorded as HAPE1.

[0083] Example 2

[0084] This embodiment provides a highly active polyester resin, and the synthesis steps are as follows:

[0085] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 2 in Table 1, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 238° C. to carry out esterification polycondensation reaction until the acid value of the reactant is detected to be 18-24 mgKOH / g KOH / g;

[0086] The second stage: the kettle temperature is lowered to 230°C, and the esterification polycondensation reactants are subjected to vacuum polycondensation reaction at a vacuum degree of -0.094 MPa for 100 minutes. After the vacuum is released, the acid value of the polycondensation product is detected to be 8-14 mgKOH / g;

[0087] The third stage: the kettle temperature is further lowered to 220°C and trimellitic anhydride is added for acidification reaction until the acid value of the reactant is detected to be 66.1 mgKOH / g;

[0088] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HAPE2.

[0089] Example 3

[0090] This embodiment provides a highly active polyester resin, and the synthesis steps are as follows:

[0091] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 3 in Table 1, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 240° C. to carry out esterification polycondensation reaction until the acid value of the reactant is detected to be 20-25 mgKOH / g;

[0092] The second stage: the kettle temperature is lowered to 230°C, and the esterification polycondensation reactants are subjected to vacuum polycondensation reaction at a vacuum degree of -0.094 MPa for 90 minutes. After the vacuum is released, the acid value of the polycondensation product is detected to be 10-15 mgKOH / g;

[0093] The third stage: the kettle temperature is further lowered to 215°C and trimellitic anhydride is added for acidification reaction until the acid value of the reactant is detected to be 68.4 mgKOH / g;

[0094] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HAPE3.

[0095] Example 4

[0096] This embodiment provides a highly active polyester resin, and the synthesis steps are as follows:

[0097] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 4 in Table 1, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 243° C. to carry out esterification polycondensation reaction until the acid value of the reactant is detected to be 22-26 mgKOH / g;

[0098] The second stage: the kettle temperature was lowered to 230°C, and the esterification polycondensation reactants were subjected to vacuum polycondensation reaction at a vacuum degree of -0.094 MPa for 80 minutes. After the vacuum was released, the acid value of the polycondensation product was detected to be 11-17 mgKOH / g;

[0099] The third stage: the kettle temperature is further lowered to 220°C, and trimellitic anhydride and pyromellitic anhydride are added to carry out acidification reaction until the acid value of the reactant is detected to be 73.3 mgKOH / g;

[0100] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HAPE4.

[0101] Example 5

[0102] This embodiment provides a highly active polyester resin, and the synthesis steps are as follows:

[0103] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 5 in Table 1, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 245° C. to carry out esterification polycondensation reaction until the acid value of the reactant is detected to be 23-28 mgKOH / g;

[0104] The second stage: the kettle temperature was lowered to 230°C, and the esterification polycondensation reactants were subjected to vacuum polycondensation reaction at a vacuum degree of -0.094 MPa for 90 minutes. After the vacuum was released, the acid value of the polycondensation product was detected to be 14-18 mgKOH / g;

[0105] The third stage: the kettle temperature is further lowered to 215°C, and trimellitic anhydride and pyromellitic anhydride are added to carry out acidification reaction until the acid value of the reactant is detected to be 76.4 mgKOH / g;

[0106] The fourth stage: the reaction temperature was further lowered to 180°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HAPE5.

[0107] The raw materials and quality of each stage are shown in Table 1.

[0108] Table 1 Input amount of each raw material (unit: mol)

[0109]

[0110] Example 6

[0111] This embodiment provides a high-leveling polyester resin, and the synthesis steps are as follows:

[0112] The first stage: the polyol and the esterification catalyst were mixed according to the ratio of Example 6 in Table 2, heated to melt, and then the polyacid was added, nitrogen was passed through and the temperature was gradually raised to 232°C for esterification polycondensation reaction. After the material was clear, the acid value of the reactant was detected to be 8-12 mgKOH / g;

[0113] The second stage: After the kettle temperature is lowered to 230°C, an acidolysis agent is added and the reaction is carried out for 150 minutes. After the material is clear, the acid value of the reactant is detected to be 55-59 mgKOH / g;

[0114] The third stage: the temperature in the kettle was maintained at 230°C, and the acidified product was subjected to vacuum polycondensation reaction at a vacuum degree of -0.095 MPa for 90 minutes. After the vacuum was released, the acid value of the polycondensation product was detected to be 45.1 mgKOH / g;

[0115] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HLPE1.

[0116] Example 7

[0117] This embodiment provides a high-leveling polyester resin, and the synthesis steps are as follows:

[0118] The first stage: the polyol and the esterification catalyst are mixed according to the ratio of Example 7 in Table 2, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 235°C for esterification polycondensation reaction. After the material is clear, the acid value of the reactant is detected to be 10-14 mgKOH / g;

[0119] The second stage: After the kettle temperature is lowered to 230°C, an acidolysis agent is added and the reaction is carried out for 180 minutes. After the material is clear, the acid value of the reactant is detected to be 57-61 mgKOH / g;

[0120] The third stage: the temperature in the kettle was maintained at 230°C, and the acidified product was subjected to vacuum polycondensation reaction at a vacuum degree of -0.095 MPa for 100 minutes. After the vacuum was released, the acid value of the polycondensation product was detected to be 47.3 mgKOH / g;

[0121] The fourth stage: the reaction temperature is further lowered to 185°C, a cross-linking catalyst is added, and the mixture is stirred for 25 minutes before discharging the mixture, which is recorded as HLPE2.

[0122] Example 8

[0123] This embodiment provides a high-leveling polyester resin, and the synthesis steps are as follows:

[0124] The first stage: the polyol and the esterification catalyst were mixed according to the ratio of Example 8 in Table 2, heated to melt, and then the polyacid was added, nitrogen was passed through and the temperature was gradually raised to 238°C for esterification polycondensation reaction. After the material was clear, the acid value of the reactant was detected to be 13-18 mgKOH / g;

[0125] The second stage: After the kettle temperature is lowered to 230°C, an acidolysis agent is added to react for 180 minutes. After the material is clear, the acid value of the reactant is detected to be 60-64 mgKOH / g;

[0126] The third stage: the temperature in the kettle was maintained at 230°C, and the acidified product was subjected to vacuum polycondensation reaction at a vacuum degree of -0.095 MPa for 120 min. After the vacuum was released, the acid value of the polycondensation product was detected to be 49.8 mgKOH / g;

[0127] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the mixture, which was recorded as HLPE3.

[0128] Example 9

[0129] This embodiment provides a high-leveling polyester resin, and the synthesis steps are as follows:

[0130] The first stage: the polyol and the esterification catalyst were mixed according to the proportion of Example 9 in Table 2, heated to melt, and then the polyacid was added, nitrogen was passed through and the temperature was gradually raised to 240°C for esterification polycondensation reaction. After the material was clear, the acid value of the reactant was detected to be 16-21 mgKOH / g;

[0131] The second stage: after the kettle temperature is lowered to 230°C, an acidolysis agent is added to react for 180 minutes. After the material is clear, the acid value of the reactant is detected to be 62-65 mgKOH / g;

[0132] The third stage: the temperature in the kettle was maintained at 230°C, and the acidified product was subjected to vacuum polycondensation reaction at a vacuum degree of -0.095 MPa for 150 minutes. After the vacuum was released, the acid value of the polycondensation product was detected to be 52.8 mgKOH / g;

[0133] The fourth stage: the reaction temperature was further lowered to 185°C, a cross-linking catalyst was added, and the mixture was stirred for 25 minutes before discharging the product, which was recorded as HLPE4.

[0134] Example 10

[0135] This embodiment provides a high-leveling polyester resin, and the synthesis steps are as follows:

[0136] The first stage: the polyol and the esterification catalyst are mixed according to the proportion of Example 10 in Table 2, heated to melt, and then the polyacid is added, nitrogen is passed through and the temperature is gradually raised to 240° C. to carry out esterification polycondensation reaction. After the material is clear, the acid value of the reactant is detected to be 20-25 mgKOH / g;

[0137] The second stage: after the kettle temperature is lowered to 230°C, an acidolysis agent is added to react for 180 minutes. After the material is clear, the acid value of the reactant is detected to be 64-68 mgKOH / g;

[0138] The third stage: the temperature in the kettle was maintained at 230°C, and the acidified product was subjected to vacuum polycondensation reaction at a vacuum degree of -0.095 MPa for 180 min. After the vacuum was released, the acid value of the polycondensation product was detected to be 55.2 mgKOH / g;

[0139] The fourth stage: the reaction temperature is further reduced to 185°C, and then a cross-linking catalyst is added and stirred for 25 minutes before discharging the material, which is recorded as HLPE5. The raw materials and their quality at each stage are shown in Table 2

[0140] Table 2 Input amount of each raw material (unit: mol)

[0141]

[0142]

[0143] In Tables 1 and 2 above:

[0144] The acid value is tested according to GB / T6743-2008;

[0145] Melt viscosity: ICI cone and plate viscosity measured at 160°C according to ASTM D4287-88;

[0146] Reactivity: refers to the time required for the resin and curing agent to react to gel, measured at 160°C according to GB / T 16995-1997.

[0147] Examples 11-20

[0148] The obtained high-activity polyester and high-leveling polyester are mixed with a curing crosslinking agent, a matting agent, a leveling control agent, a degassing agent and a pigment and filler according to the amounts specified in Table 3 and Table 4 and formulated into a powder coating.

[0149] The powder coatings were prepared by first dry blending the different components and then homogenizing them in melt form using a twin-screw extruder at a base temperature of 90-120° C. The homogenized mixture was then cooled and ground in a grinding jar, and the powders were subsequently sieved to obtain a particle size of 10-90 μm, noted as Powder 5 to Powder 14.

[0150] Comparative Examples 1-4

[0151] The obtained high-activity polyester and high-leveling polyester are mixed with a curing crosslinking agent, a matting agent, a leveling control agent, a degassing agent and a pigment and filler according to the amounts specified in Table 3 and formulated into a powder coating.

[0152] The powder coatings were prepared by first dry-blending the different components and then homogenizing them in the form of a melt using a twin-screw extruder at a base temperature of 90-120° C., then cooling the homogenized mixture and grinding it in a grinding jar, and then sieving the powder to obtain a particle size of 10-90 μm, referred to as comparative powder 1 to comparative powder 4.

[0153] Table 3

[0154]

[0155]

[0156] Table 4

[0157] Powder 7 Powder 8 Powder 9 Powder 10 Powder 11 Powder 12 Powder 13 Powder 14 HAPE1 180 / / / / / / 246 HAPE2 / 220 / / / 200 / / HAPE3 / / 280 / / 286 / HAPE4 / / / 360 / / / / HAPE5 / / / / 160 / / / HLPE1 150 / / / / / / 84 HLPE2 / 144 / / / 120 / / HLPE3 / / 120 / / / 114 / HLPE4 / / / 90 / / / / HLPE5 / / / / 144 / / / E-12 280 316 360 420 316 370 482 452 PM228 332 254 165 46 323 244 44 133 GLP588 14 12 11 10 13 12 10 11 701 6 6 6 6 6 6 6 6 Benzoin 4 4 4 4 4 4 4 4 PE520 6 6 6 6 6 6 6 6 Carbon Black 8 8 8 8 8 8 8 8 3390 20 30 40 50 / / / / X-8 / / / / 20 30 40 50

[0158] In this table:

[0159] E-12 is an epoxy resin curing agent, Sinopec Hunan Petrochemical Co., Ltd.;

[0160] PM228 is a barium sulfate, Guangdong Xinmei Nanotechnology Co., Ltd.;

[0161] GLP588 is a leveling control agent, Ningbo Nanhai Chemical Co., Ltd.;

[0162] 701 is a brightener, Ningbo Nanhai Chemical Co., Ltd.;

[0163] Benzoin is a degassing agent, Ningbo Nanhai Chemical Co., Ltd.;

[0164] PE520 is a wax powder, Clariant Chemicals (China) Co., Ltd.;

[0165] 3390 is a physical matting agent, Guangzhou Zehe Chemical Materials Research and Development Co., Ltd.;

[0166] X-8 is a chemical matting agent. One part of X-8 requires three parts of E-12 epoxy resin. Guangzhou Zehe Chemical Materials Research and Development Co., Ltd.

[0167] Experimental analysis

[0168] The powders obtained in Examples 11-20 and Comparative Examples 1-4 were deposited on cold rolled steel with a thickness of 0.5 mm by an electrostatic spray gun. At a film thickness of 60-80 μm, the panel was transferred to an oven with hot air circulation and cured at a temperature of 160° C. for 15 minutes to obtain a cured coating. The performance test results of the coating are shown in Table 5.

[0169] Table 5

[0170]

[0171] In this Table 5:

[0172] Column 1: indicates the powder formula identification number;

[0173] Column 2: indicates the curing temperature / time of the powder coating;

[0174] Column 3: indicates 60° gloss, tested according to GB / T9754-2007;

[0175] Column 4: Indicates the PCI leveling grade of the coating appearance. Specifically, the coating to be tested is visually compared with the PCI leveling grade control plate (0-10) to determine the corresponding leveling grade of the coating to be tested. This is a common leveling grade determination method in the industry;

[0176] Column 5: indicates the positive and negative impact strength, tested in accordance with GB / T1732-2020, recording the highest impact that will not cause the coating to break, in kg.cm;

[0177] Column 6: Indicates the coating adhesion, tested in accordance with GB / T9286-2021;

[0178] Column 7: indicates the pencil hardness of the coating, tested in accordance with GB / T6739-2022;

[0179] Column 8: Indicates the T-bend performance of the coating, tested in accordance with GB / T 30791-2014.

[0180] It is obvious from the test results in Table 5 that the formula of the comparative powder 1-2 using a single high-activity polyester can achieve a lower matte gloss at low temperatures, but the coating appearance is poor, and the PCI leveling grade is <5. The powder coating prepared by using a single high-leveling polyester in the formula of the comparative powder 3-4 has a coating appearance leveling grade of >8 at low temperatures, but the gloss of the coating is high, and the mechanical properties of the coating are poor. Powders 5-14 prepared by compounding two polyesters have good matte effects at low temperatures, the gloss can be less than 30%, and the leveling grade of the coating is above 7. In addition, the coating has been proven to have good impact resistance, adhesion, hardness and T-bend performance, which can meet the requirements of aluminum wheel coating.

[0181] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A matte powder coating composition, characterized in that: The raw materials include: high-activity polyester resin, high-leveling polyester resin, curing cross-linking agent and matting agent; The high-activity polyester resin has an acid value of 60-80 mgKOH / g, a reactivity of 120-300 s at 160° C., and a melt viscosity of ≤10000 mPa.s at 160° C.; The high-leveling polyester resin has an acid value of 40-60 mgKOH / g, a reactivity of 480-900 s at 160° C., and a melt viscosity of ≤5000 mPa.s at 160° C.; The molecular structural formula of the highly active polyester resin is: The molecular structure formula of the high-leveling polyester resin is: Among them, R1, R2, R3, R4, R5, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 Each independently represents unsubstituted or substituted C 1-20 Alkyl or C 6-20 Aryl; The mass ratio of the high-activity polyester resin to the high-leveling polyester resin is (1-4):

1.

2. The matte powder coating composition according to claim 1, characterized in that: The high-activity polyester resin is prepared from the following raw materials: polyol 1, polyacid 1, acidulant 1, esterification catalyst, and crosslinking catalyst; the polyol 1 is aliphatic and / or alicyclic diol; the polyacid 1 is aromatic dibasic acid and aliphatic dibasic acid; the acidulant 1 is aromatic polyacid anhydride; the molar ratio of the polyol 1 to the polyacid 1 is 1:(1-1.3); the molar ratio of the polyol 1 to the acidulant 1 is 1:(0.05-0.2); And / or, the high-leveling polyester resin is prepared from the following raw materials: polyol 2, polyacid 2, acidulant 2, esterification catalyst, cross-linking catalyst; the polyol 2 is aliphatic and / or alicyclic diol and aliphatic triol; the polyacid 2 is an aromatic dibasic acid; the acidulant 2 is an aromatic dibasic acid and an aliphatic dibasic acid; the molar ratio of the polyol 2 to the polyacid 2 is 1:(0.85-1); the molar ratio of the polyol 2 to the acidulant 2 is 1:(0.1-0.25).

3. The matte powder coating composition according to claim 2, characterized in that: The acidolysis agent 1 is selected from one of trimellitic anhydride and pyromellitic anhydride or a combination thereof; And / or, the aromatic dibasic acid in the acidolysis agent 2 is selected from at least one of terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid, and the aliphatic dibasic acid in the acidolysis agent 2 is selected from at least one of succinic acid, adipic acid, and glutaric acid.

4. The matte powder coating composition according to claim 2, characterized in that: The polyol 1 is at least one selected from neopentyl glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propylene glycol, 2-butyl-2-ethyl-1,3-propylene glycol, pentanediol, hexanediol, and 1,4-cyclohexanedimethanol; And / or, the aliphatic and / or alicyclic diol in the polyol 2 is selected from at least one of neopentyl glycol, ethylene glycol, diethylene glycol, 1,3-propylene glycol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, pentanediol, hexanediol, and 1,4-cyclohexanedimethanol, and the aliphatic triol in the polyol 2 is selected from at least one of trimethylolpropane, trimethylolethane, and pentaerythritol.

5. The matte powder coating composition according to claim 2, characterized in that: The aromatic dibasic acid in the polyacid 1 is selected from at least one of terephthalic acid, isophthalic acid, phthalic anhydride, and trimesic acid, and the aliphatic dibasic acid in the polyacid 1 is selected from at least one of succinic acid, adipic acid, glutaric acid, and 1,4-cyclohexanedicarboxylic acid; And / or, the polyacid 2 is at least one selected from terephthalic acid, isophthalic acid, and phthalic acid.

6. The matte powder coating composition according to claim 2, characterized in that: The esterification catalyst is selected from at least one of monobutyltin oxide, monobutyltin chloride and tetrabutyl titanate; And / or, the cross-linking catalyst is selected from at least one of benzyltrimethylammonium chloride, triphenylphosphine, triphenylethylphosphonium bromide and tert-butylamine.

7. The matte powder coating composition according to any one of claims 2 to 6, characterized in that: The highly active polyester resin is prepared by a preparation method comprising the following steps: A1: polyol 1, polyacid 1 and an esterification catalyst are mixed to carry out an esterification reaction to obtain an esterification product 1; A2: adding an acidulant 1 to the esterification product 1 to carry out an acidolysis reaction to obtain an acidified product 1; A3: The acidified product 1 reacts with a cross-linking catalyst to obtain a highly active polyester resin; And / or, the high-leveling polyester resin is prepared by a preparation method comprising the following steps: B1: Mixing polyol 2, polyacid 2 and an esterification catalyst to carry out an esterification reaction to obtain an esterification product 2; B2: adding acidulant 2 to the esterification product 2 to carry out acidolysis reaction to obtain acidified product 2; B3: The acidified product 2 reacts with a cross-linking catalyst to obtain a high-leveling polyester resin.

8. The matte powder coating composition according to claim 1, characterized in that: The curing cross-linking agent is an epoxy resin curing agent; And / or, the matting agent is selected from a physical matting agent, a chemical matting agent or a combination thereof.

9. The matte powder coating composition according to claim 1, characterized in that: The matte powder coating composition further comprises at least one of a leveling control agent, a degassing agent, a pigment, a dye, and a filler.

10. Use of the matte powder coating composition according to any one of claims 1 to 9 in protecting the surface of a workpiece.

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