Slow-release coated thermosettable powder coating catalyst composition, powder coating and preparation method thereof

Abstract

The present invention relates to the field of powder coatings, and specifically discloses a slow-release coated heat-curable powder coating catalyst composition, a powder coating and a preparation method thereof. Among them, the slow-release coated heat-curable powder coating catalyst composition includes: i) Component A, which is a core coating material and contains at least one basic catalyst that can promote the ring-opening reaction of epoxy resin; ii) Component B, which is a coating shell and contains at least one crystalline solid unsaturated polyester resin or semi-crystalline solid unsaturated polyester resin; iii) Component C, which is a coating medium and contains at least one paraffin wax. By using the present invention, ultra-low temperature curing can be achieved, the curing temperature is as low as 90-120 °C, and the storage time of low-temperature powder coatings can be effectively extended to meet the requirements of normal powder coating processes.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coatings, and particularly relates to a slow-release coated thermosettable powder coating catalyst composition, a powder coating and a preparation method thereof. Background Art

[0002] Since powder coatings do not use organic solvents in traditional solvent-based coatings and have almost no VOCs emissions to the atmosphere, they belong to environmentally friendly coatings; at the same time, oversprayed powder coatings can be recycled, and the usage efficiency is close to 100%, eliminating the problem of difficult recycling and treatment of solid hazardous waste generated by overspray of liquid coatings. Therefore, powder coatings, as green environmental protection coatings for source control of air pollution and solid hazardous waste, have been vigorously developed.

[0003] Powder coatings can be thermosetting or thermoplastic. The present invention relates to the catalyst field of thermosetting powder coatings. Thermosetting powder coatings refer to a mixture of multiple components, which has the ability to form an irreversible cross-linked network after thermosetting without the need for a thermal free radical initiator to initiate free radicals.

[0004] Since the 1990s, people have been continuously researching the application of powder coatings on heat-sensitive substrates such as wood and plastics. The earliest realization was to use ultraviolet radiation-cured powder coatings on the wood surface, heat level at 100 - 130°C for 3 - 5 minutes, and then cure into a coating under ultraviolet radiation. However, for powder coatings with high coloring requirements, ultraviolet radiation is difficult to penetrate, resulting in uneven curing of the powder coating, and ultraviolet radiation is also likely to cause the coating color to turn yellow; radiation curing cannot be achieved on complex 3D workpieces. Therefore, ultraviolet-cured powder coatings have not been commercially applied on a large scale for more than 30 years.

[0005] Under the promotion of a catalyst, traditional thermosetting polyester-epoxy mixed systems or thermal free radical initiation can achieve thermosetting at 110 - 150°C. Technical personnel in the powder industry are familiar with traditional epoxy / polyester hybrid powder coatings that can be thermoset at low temperatures below 120°C. Since they need to add more amine or onium salt catalysts and belong to the ionic ring-opening polymerization mechanism of epoxy groups, the epoxy groups will partially undergo ring-opening reactions during the storage of powder coatings at room temperature of 23°C, resulting in loss of gloss of the powder coating, and in severe cases, pre-reaction phenomena such as sanding and non-curing will occur. Traditional low-temperature thermosettable epoxy / polyester hybrid powder coatings need to be stored under refrigeration at 4 - 20°C, and the shelf life does not exceed 15 days. They are prone to loss of gloss and failure at room temperature, making it difficult to recycle under normal powder coating painting processes at room temperature of 23 - 40°C.

[0006] To solve the problem of pre-reaction and short storage period of ultra-low temperature powder coatings at room temperature caused by excessive catalyst addition, a large number of technicians have developed latent or coated catalysts. However, the currently developed latent catalysts have very high deblocking temperatures, all above 130 °C. The coated capsule catalysts are difficult to meet the process requirements of melting, extrusion and pulverization of thermosetting powder coatings. Moreover, the packaging materials used for coating cannot participate in the chemical reactions of powder coatings, and the residues of packaging materials have a relatively large impact on the coating properties. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a slow-release coated thermosettable powder coating catalyst composition and a preparation method thereof, which can achieve ultra-low temperature curing, with a curing temperature as low as 90 - 120 °C, and effectively extend the storage time of low-temperature powder coatings.

[0008] The technical problem to be solved by the present invention is also to provide a slow-release coated thermosettable powder coating catalyst composition and a preparation method thereof, in which the catalyst is isolated from the main reaction components at room temperature and cannot participate in chemical cross-linking reactions, and has good stability.

[0009] The technical problem to be solved by the present invention is also to provide a slow-release coated thermosettable powder coating catalyst composition and a preparation method thereof, which can be deblocked and activated at a low temperature close to the melting point of the packaging material, 90 °C, and catalyze the main chemical reactions of ultra-low temperature powder coatings at a temperature of 95 - 120 °C.

[0010] The technical problem to be solved by the present invention is also to provide a slow-release coated thermosettable powder coating catalyst composition and a preparation method thereof. After melting and activating the catalyst, the packaging material used for coating the catalyst is itself one of the main reaction resin components of the powder coating and can participate in chemical cross-linking reactions to form a cured coating.

[0011] The technical problem to be solved by the present invention is also to provide a thermosettable powder coating and a preparation method thereof, which can achieve low-temperature curing, have a long storage time, good stability, can be applied industrially on a large scale, and have a low cost.

[0012] To achieve the above technical effects, the present invention provides a slow-release coated thermosettable powder coating catalyst composition, comprising:

[0013] i) Component A, which is an inner core coated material and contains at least one basic catalyst that can promote the ring-opening reaction of epoxy resin;

[0014] ii) Component B, which is a coating shell and contains at least one crystalline solid unsaturated polyester resin or semi-crystalline solid unsaturated polyester resin;

[0015] iii) Component C, which is a coating medium and contains at least one paraffin wax.

[0016] As an improvement to the above solution, the component A contains at least one basic catalyst that can promote the ring-opening reaction of epoxy resin at 70 - 130 °C.

[0017] As an improvement to the above solution, the component A contains at least one organic amine catalyst, organic phosphonium salt catalyst or imidazole catalyst that can promote the ring-opening reaction of epoxy resin.

[0018] As an improvement to the above solution, the component A contains at least one anionic copolymerization Lewis base catalyst that can promote the ring-opening reaction of epoxy resin.

[0019] As an improvement to the above solution, the component A contains at least one organic onium salt catalyst that can promote the ring-opening reaction of epoxy resin.

[0020] As an improvement to the above solution, the average particle size of the component A is 0.8 - 1.5 microns.

[0021] As an improvement to the above solution, the component B is a product obtained by reacting a crystalline polyester or semi-crystalline polyester containing a carboxyl group with a methacrylic monomer and / or its derivatives.

[0022] As an improvement to the above solution, the component B satisfies at least one of the following conditions:

[0023] a. The number-average molecular weight Mn of the component B is 100 - 10000 Da;

[0024] b. The melting point of the component B is 50 - 120 °C, and the crystallization point is 40 - 90 °C;

[0025] c. The viscosity of the component B at 100 °C is 0.01 - 20 Pa·s.

[0026] As an improvement to the above solution, the component C contains at least one straight-chain paraffin wax.

[0027] As an improvement to the above solution, the component C contains at least one paraffin wax containing 15 - 35 carbon atoms.

[0028] As an improvement to the above solution, the component C contains at least one paraffin wax with a melting point of 30 - 70 °C.

[0029] As an improvement to the above solution, the sum of the addition amounts of the component A, component B and component C is 100 wt%;

[0030] The addition amount of the component A is 20 - 60 wt% of the total amount of the component A, component B and component C;

[0031] The addition amount of the B component is 30 - 70 wt% of the total amount of the A component, B component and C component;

[0032] The addition amount of the C component is 10 - 45 wt% of the total amount of the A component, B component and C component.

[0033] Correspondingly, the present invention also discloses a preparation method of a slow - release coated thermosettable powder coating catalyst composition, including:

[0034] Heat up the C component to make it completely molten and turn into a liquid state;

[0035] Crush the A component;

[0036] Add the crushed A component into the liquid C component, stir and mix evenly to obtain a first premix;

[0037] Heat the first premix to above the melting point of the B component, add the B component into the first premix, and stir to make the B component completely molten to obtain a second premix;

[0038] Cool down the second premix and stir at a low speed until the C component forms two distinct layers, the upper layer is the separate C component, and the lower layer is the mixed phase with the B component coating the A component;

[0039] Suck out the upper layer and cool and crush it;

[0040] Crush the lower layer to obtain a slow - release coated thermosettable powder coating catalyst composition.

[0041] As an improvement of the above - mentioned scheme, heat up the C component to T 1 , the melting point of the C component is T C , T 1 - T C = 2℃ - 8℃.

[0042] As an improvement of the above - mentioned scheme, crush the A component to an average particle size of 0.1 - 5 microns.

[0043] As an improvement of the above - mentioned scheme, crush the A component to an average particle size of 0.8 - 1.5 microns.

[0044] As an improvement of the above - mentioned scheme, heat the first premix to T 2 , the melting point of the B component is T B , T 2 - T B = 12℃ - 20℃.

[0045] As an improvement of the above - mentioned scheme, cool down the second premix to T3 The melting point of the component B is T B The melting point of the component C is T C , T 3 -T C = 2°C to 8°C, and T B -T 3 = 12°C to 20°C.

[0046] As an improvement of the above solution, the lower layer phase is pulverized to an average particle size of 0.5 - 5 microns to obtain a slow-release coated thermosettable powder coating catalyst composition.

[0047] As an improvement of the above solution, the lower layer phase is pulverized to an average particle size of 1 - 3 microns to obtain a slow-release coated thermosettable powder coating catalyst composition.

[0048] Correspondingly, the present invention also provides a thermosettable powder coating, including the slow-release coated thermosettable powder coating catalyst composition as described above; or, the slow-release coated thermosettable powder coating catalyst composition prepared by the preparation method as described above.

[0049] As an improvement of the above solution, it further includes a resin, and the resin is selected from one or more of epoxy resin and polyester resin.

[0050] As an improvement of the above solution, the addition amount of the slow-release coated thermosettable powder coating catalyst composition is 1wt% - 20wt%;

[0051] The addition amount of the resin is 80wt% - 99wt%.

[0052] As an improvement of the above solution, it further contains one or more of fillers, pigments, and additives.

[0053] Correspondingly, the present invention also provides a preparation method of a thermosettable powder coating, including:

[0054] Mixing the resin and the slow-release coated thermosettable powder coating catalyst composition to obtain a preliminary powder coating mixture;

[0055] Melting and mixing the preliminary powder coating mixture, and cooling it to room temperature to obtain a mixture;

[0056] Pulverizing the cooled mixture to obtain a powder coating.

[0057] As an improvement of the above solution, melting and mixing the preliminary powder coating mixture includes:

[0058] Melting and extruding the preliminary powder coating mixture through an extruder.

[0059] The implementation of the present invention has the following beneficial effects:

[0060] 1. The slow-release coated heat-curable powder coating catalyst composition of the present invention comprises component A, component B and component C, wherein component A is a core coating, which comprises at least one alkaline catalyst that can promote the ring-opening reaction of epoxy resin; component B is a coating shell, which comprises at least one crystalline solid unsaturated polyester resin or semi-crystalline solid unsaturated polyester resin; component C is a coating medium, which comprises at least one alkane wax.

[0061] Among them, (1) Component A is the core coating, which contains at least one alkaline catalyst that can promote the ring-opening reaction of epoxy resin. The molecular polarity difference between the coating medium alkane wax of component C and the (semi-) crystalline solid polyester resin of component B is used to make the two completely insoluble, so that component B can be suspended and dispersed in the coating medium of component C, and the basic conditions required for coating are achieved. Then, the melting point temperature difference between the coating medium alkane wax of component C and the (semi-) crystalline solid polyester resin of component B is used to separate them into two obvious phases, thereby achieving the purpose of coating and separation.

[0062] (2) The catalyst composition of the present invention is applied to powder coatings to achieve ultra-low temperature curing, with the curing temperature as low as 90-120°C. Moreover, it can effectively prolong the storage time of low-temperature powder coatings from the original 7 days to more than 30 days at room temperature, meeting the requirements of normal powder coating processes.

[0063] (3) The catalyst coated with a packaging material with a melting point higher than 50°C at room temperature is isolated from the main components of the reaction and cannot participate in the chemical cross-linking reaction, thus having good stability.

[0064] (4) The catalyst composition of the present invention is decapsulated and activated at a low temperature close to the melting point of the packaging material at 90°C, and catalyzes the main chemical reaction of the ultra-low temperature powder coating at a temperature of 95-120°C.

[0065] (5) After the catalyst composition of the present invention is melt-activated, the packaging material used to coat the catalyst is itself one of the main reaction resin components of the powder coating and can participate in the chemical cross-linking reaction to form a cured coating.

[0066] (6) The coating medium C component of the catalyst composition of the present invention is easy to separate and can be recycled and reused. The coating process is green and environmentally friendly, and no three wastes are generated. This solves the problems of the conventional coating technology, such as the complex separation of the coating medium, the difficulty in reuse, and the easy generation of wastewater and harmful organic matter.

[0067] 2. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition of the present invention is simple, highly operable, and easy to control, and can obtain a powder coating catalyst composition with good quality and stability.

[0068] 3. After the powder coating of the present invention is thermally cured, a powder coating with good balance of properties such as leveling property, adhesion, flexibility and hardness is obtained, and it has high colorability, and can be applied to non-thermosensitive or thermosensitive materials such as metals, woods, plastics, calcium silicates, etc., and even 3D complex workpieces, with a wide application range and good decorative effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is the differential scanning calorimetry (DSC) chart of the thermosettable powder coating of the present invention.

[0070] Figure 2 is the flow chart of the preparation method of the catalyst composition of the thermosettable powder coating of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0071] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below.

[0072] The present invention provides a slow-release coated thermosettable powder coating catalyst composition, comprising:

[0073] i) Component A, which is a core coating material and contains at least one basic catalyst that can promote the ring-opening reaction of epoxy resin;

[0074] ii) Component B, which is a coating shell and contains at least one crystalline solid unsaturated polyester resin or semi-crystalline solid unsaturated polyester resin;

[0075] iii) Component C, which is a coating medium and contains at least one paraffin wax.

[0076] To better elaborate the present technical solution, some technical terms are defined herein:

[0077] "Room temperature" herein refers to 23 °C.

[0078] "Normal temperature" herein refers to 23 °C - 35 °C.

[0079] "Curing to an acceptable degree at low temperature" means that when cured at up to 110 °C for up to 10 minutes, the powder coating can resist at least 100 times of two-way acetone friction.

[0080] "Good adhesion" herein means that according to the cross-cut test of ISO2409, among the grades from 0 (best) - 5 (worst), the adhesion of the powder coating is within the range of 0 - 2 grades, and more preferably within the range of 0 - 1 grades.

[0081] "Curing" as used herein refers to the process in which a coating forms an irreversible cross-linked network after a chemical reaction, where the material no longer flows, melts or dissolves. In this text, "curing" and "cross-linking" can be used interchangeably. The thermosettable powder coating of the present invention uses heating for curing, which is called "thermal curing", and does not include curing caused by ultraviolet (UV), electron beam, or thermal free radical initiators.

[0082] "Good leveling property" as used herein refers to the leveling property of conventional powder coatings, which is divided into a grade range of 1 (worst leveling) - 10 (best leveling). The leveling property of a good powder coating needs to be equal to or higher than grade 3, more preferably equal to or higher than grade 4, even more preferably equal to or higher than grade 5, and most preferably equal to or higher than grade 6.

[0083] "Resin" as used herein can be understood to have the same meaning as understood by those of ordinary skill in the art of thermosetting polymer chemistry, a polymer having reactive groups, which can be thermoset and cross-linked. The molecular weight of the resin can be characterized by the number average molecular weight (Mn) or weight average molecular weight (Mw) well-known to those of ordinary skill in the art of thermosetting polymer chemistry.

[0084] "Composition" as used herein refers to a combination and / or mixture of different chemical substances and / or components, which forms an integral whole.

[0085] "Powder" as used herein refers to a fine, loose particulate state, which does not agglomerate and has good fluidity at room temperature of 23°C - 40°C, and can be coated by traditional electrostatic powder coating processes; where the size of individual particles is at most 130 microns at room temperature and atmospheric pressure, and the method for measuring the particle size of the granular material according to the present invention is sieving.

[0086] "Thermosettable powder coating" as used herein refers to a composition in powder form, which has the ability to be cured by heating. The composition of the present invention is a thermosettable composition.

[0087] "Slow-release coated thermosettable powder coating catalyst composition" as used herein refers to a composition of a powder catalyst, which has the ability to catalyze the heating and curing of a powder coating.

[0088] "Unsaturated resin" as used herein refers to a resin containing an ethylenic unsaturated group.

[0089] "Powder coating" as used herein refers to a partially or fully cured form of the thermosettable powder coating of the present invention.

[0090] In addition, the glass transition temperature Tg, melting point (Tm), and crystallization temperature (Tc) described herein can be measured by differential scanning calorimetry (DSC).

[0091] Unless otherwise specified, "viscosity" in this article refers to the melt viscosity at 160°C (in Pa.s). Viscosity was measured using a rotational rheometer Brookfield CAP2000+, with a rotation speed of 200 rpm and a 5# rotor of 19.07 mm.

[0092] In a preferred embodiment, the slow-release coated heat-curable powder coating catalyst composition comprises:

[0093] i) Component A, wherein the component A is a core coating, and comprises at least one alkaline catalyst capable of promoting the ring-opening reaction of epoxy resin at 70-130° C.;

[0094] ii) a B component, wherein the B component is a coating shell comprising at least one crystalline solid unsaturated polyester resin or a semi-crystalline solid unsaturated polyester resin;

[0095] iii) a C component, wherein the C component is a coating medium comprising at least one alkane wax.

[0096] Under room temperature dry storage conditions, the lower the curing temperature of the powder coating of the traditional polyester epoxy mixed reaction system, the easier it is to lose gloss. The powder coating cured below 120°C will lose gloss within 7 days. The present invention includes component A, component B, and component C, and realizes the coating of the alkaline catalyst of component A by the (semi-) crystalline olefinic unsaturated polyester resin solid of component B. At room temperature, the catalyst coated with the crystalline packaging material with a melting point higher than 50°C is physically isolated from the main components of the reaction and cannot participate in the chemical cross-linking reaction. It is unsealed and activated at a low temperature of 90°C, which is close to the melting point of the packaging material, and catalyzes the main chemical reaction of the ultra-low temperature powder coating at a temperature of 95-120°C. Therefore, under the premise of not affecting the low-temperature curing of the powder coating, the embodiment of the present invention can significantly extend the storage period of the ultra-low temperature powder coating at room temperature, meet the process requirements of normal powder coating, and solve the problem of the traditional ultra-low temperature powder losing gloss within 7 days of storage. Preferably, the curing temperature of the powder coating of the present invention is 95-115°C, and more preferably 100-110°C.

[0097] Specifically, this embodiment uses the C component coating medium alkane wax and the B component (semi) crystalline solid polyester resin to coat the A component containing an alkaline catalyst that promotes the epoxy resin ring-opening reaction at 70-130°C, and the coating is achieved by utilizing the difference in miscibility caused by different molecular polarities.

[0098] First, the alkaline catalyst particles of component A are suspended and dispersed in the alkane wax of component C as a coating medium, so that the alkaline catalyst particles of component A are coated by component C;

[0099] Then, the B-component (semi)crystalline solid polyester resin is melt-dispersed into the dispersion emulsion of the C-component and the A-component. Due to the difference in miscibility caused by the different molecular polarities of the C-component alkane wax and the B-component (semi)crystalline solid polyester resin with respect to the basic catalyst that promotes the ring-opening reaction of the epoxy resin at 70-130°C, the coating medium C-component on the outer layer of the A-component is displaced by the B-component, and is divided into two distinct phases due to the differences in melting point and polarity, achieving the purpose of coating and separation.

[0100] The following further elaborates on each component of the thermosettable powder coating catalyst composition of the present invention.

[0101] In some embodiments, the A-component comprises at least one organic amine catalyst or organic phosphonium salt catalyst that can promote the ring-opening reaction of the epoxy resin, and its structural general formula is X(R)n, where X is the element N or P, R is the same or different alkyl, aryl or aralkyl containing 1-18 carbon atoms, and n can be the number 3 or 4.

[0102] Or, the A-component is an imidazole catalyst.

[0103] In some embodiments, the A-component comprises at least one anionic copolymerization Lewis base catalyst that can promote the ring-opening reaction of the epoxy resin, and its structural general formula is X(R)nY, where X is the element N or P, R is the same or different alkyl, aryl or aralkyl containing 1-18 carbon atoms, Y can be the halogen element chlorine (Cl) or bromine element (Br); n can be the number 3 or 4.

[0104] In some embodiments, the A-component comprises at least one organic onium salt catalyst that can promote the ring-opening reaction of the epoxy resin, such as DTMeAB, NBu 4 Br, NBu 4 Cl, PPh 4 Br, PPh 4 Cl, PPNCl and other onium salts.

[0105] It should be noted that the types of the A-component are diverse, as long as it can promote the ring-opening reaction of the epoxy resin at a temperature of 70-130°C.

[0106] The average particle size of the A-component is preferably 0.8-1.5 microns, specifically it can be 0.8 microns, 0.9 microns, 1.0 microns, 1.1 microns, 1.2 microns, 1.3 microns, 1.4 microns, 1.5 microns, etc., but not limited thereto.

[0107] In some embodiments, the Group B component is a product obtained by reacting a crystalline polyester or semi-crystalline polyester containing a carboxyl group with a methacrylic monomer and / or its derivatives. Its crystallinity can be adjusted using one or more of diacids and diols. Among them, diacids include but are not limited to succinic acid, adipic acid, sebacic acid, dodecanedioic acid, and diols include but are not limited to hexanediol, ethylene glycol, butanediol, and ethylidene glycol.

[0108] In this embodiment, the included (semi)-crystalline polyester resin generally refers to the polycondensation product of polyols and polyacids, preferably the polycondensation product of dibasic acids, diols (diols) and / or trifunctional alcohols and trifunctional carboxylic acids.

[0109] The polyacid is preferably a polycarboxylic acid, and the polycarboxylic acids include but are not limited to isophthalic acid, terephthalic acid, phthalic acid, tetrahydrophthalic acid, hexahydroterephthalic acid, azelaic acid, adipic acid, sebacic acid, succinic acid, trimellitic acid, 2-methyl-2-butenedioic acid, 2-butenedioic acid, itaconic acid and their derivatives, etc. These exemplary polyacids can be used in their acid form, or in the form of acid anhydrides, acyl chlorides or lower alkyl esters, or as a mixture of polyacids, and hydroxycarboxylic acids and lactones can also be used.

[0110] Polyols can undergo polycondensation reactions with the above-mentioned carboxylic acids and their derivatives to prepare polyester resins. Examples of polyols include but are not limited to aliphatic diols, 2,2-dimethylpropane-1,3-diol (neopentyl glycol), propane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butane-1,2-diol, 2,3-butanediol.

[0111] The polyester resin can be prepared by well-known esterification reactions and / or transesterification reactions. Organic tin catalysts commonly used in esterification reactions can be used, and by adjusting the ratio of COOH to OH, the desired polyester resin product can be obtained.

[0112] In this embodiment, the methacrylated unsaturated polyester resin is an unsaturated polyester containing an ethylenic unsaturated functional group with a methyl group, and the ethylenic unsaturated functional group is derived from a methacrylic monomer and its derivatives. In the methacrylated polyester resin, its methyl ethylenic unsaturated functional group is generally at the end of the unsaturated polyester resin. The methacrylated polyester resin can be prepared, for example, by first using a common polyester manufacturing method to prepare a (semi)-crystalline polyester intermediate, and then reacting the (semi)-crystalline polyester intermediate with a methacrylic monomer and its derivatives to form an unsaturated polyester resin with a methyl ethylenic unsaturated functional group at the end.

[0113] In some embodiments, the Group B component satisfies at least one of the following conditions:

[0114] a. The number-average molecular weight Mn of the B component is 100 - 10,000 Da;

[0115] b. The melting point of the B component is 50 - 120 °C, and the crystallization point is 40 - 90 °C;

[0116] c. The viscosity of the B component at 100 °C is 0.01 - 20 Pa·s.

[0117] Furthermore, regarding the B component, it contains at least one (semi)crystalline ethylenically unsaturated polyester resin, whose number-average molecular weight Mn is at least 100 Da, preferably at least 500 Da, more preferably at least 1500 Da, and further preferably at least 2500 Da. The B component containing the (semi)crystalline ethylenically unsaturated polyester resin has a number-average molecular weight Mn of at most 10,000 Da, preferably at most 8000 Da, more preferably at most 5000 Da, and further preferably at most 4000 Da.

[0118] The B component containing at least one (semi)crystalline ethylenically unsaturated polyester resin has a melting point of at least 50 °C, preferably at least 55 °C, more preferably at least 60 °C, and further preferably 65 °C. The B component containing at least one (semi)crystalline ethylenically unsaturated polyester resin has a melting point of at most 120 °C, preferably at most 110 °C, more preferably at most 105 °C, and further preferably at most 100 °C.

[0119] The B component containing at least one (semi)crystalline ethylenically unsaturated polyester resin has a viscosity at 100 °C of at least 0.01 Pa·s, preferably at least 0.05 Pa·s, more preferably at least 0.1 Pa·s, and further preferably at least 0.5 Pa·s. The B component containing at least one (semi)crystalline ethylenically unsaturated polyester resin has a viscosity at 100 °C of at most 20 Pa·s, preferably at most 15 Pa·s, more preferably at most 10 Pa·s, and further preferably at most 5 Pa·s, and particularly preferably at most 1 Pa·s.

[0120] In some embodiments, the C component contains at least one straight-chain paraffin wax.

[0121] In some embodiments, the C component contains at least one alkane wax having 15 - 35 carbon atoms, and preferably one or more of C16 alkane, C18 alkane, C22 alkane, C28 alkane, isomeric C20 alkane, and cyclic C25 alkane, but is not limited thereto.

[0122] In some embodiments, the C component contains at least one alkane wax having a melting point of 30 - 70 °C, and more preferably an alkane wax having a melting point of 50 - 70 °C.

[0123] Further, regarding the contents of each component, the sum of the addition amounts of the A component, the B component, and the C component is 100 wt%; the addition amount of the A component is 20 - 60 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the B component is 30 - 70 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the C component is 10 - 45 wt% of the total amount of the A component, the B component, and the C component.

[0124] Preferably, regarding the contents of each component, the sum of the addition amounts of the A component, the B component, and the C component is 100 wt%; the addition amount of the A component is 30 - 50 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the B component is 40 - 60 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the C component is 10 - 30 wt% of the total amount of the A component, the B component, and the C component.

[0125] More preferably, regarding the contents of each component, the sum of the addition amounts of the A component, the B component, and the C component is 100 wt%; the addition amount of the A component is 30 - 50 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the B component is 30 - 50 wt% of the total amount of the A component, the B component, and the C component; the addition amount of the C component is 10 - 25 wt% of the total amount of the A component, the B component, and the C component.

[0126] Correspondingly, as Figure 2 shown, the present invention also discloses a preparation method of a slow-release coated thermosettable powder coating catalyst composition, including:

[0127] S101. Heat up the C component to make it completely molten and turn into a liquid state;

[0128] Preferably, heat up the C component to T 1 , the melting point of the C component is T C , T 1 - T C = 2°C to 8°C. Further preferably, heat up the C component to T 1 , the melting point of the C component is T C , T 1 - T C = 4°C to 6°C. More preferably, heat up the C component to T 1 , the melting point of the C component is T C , T 1 - T C = 5°C. In this step, heating up the C component to T 1 can make it completely molten and obtain a uniform liquid.

[0129] S102. Crush the A component;

[0130] Preferably, the component A is pulverized to an average particle size of 0.1 - 5 μm. More preferably, the component A is pulverized to an average particle size of 0.8 - 1.5 μm.

[0131] In some embodiments, in this step, a supersonic pulverizer can be used to pulverize the component A to a D50 of 0.1 - 5 μm, but it is not limited thereto.

[0132] S103. Add the pulverized component A to the component C in a liquid state, and stir and mix evenly to obtain a first premix;

[0133] After adding the pulverized component A to the component C in a liquid state and stirring evenly, a uniform emulsion-like liquid first premix can be obtained. In this step, the basic catalyst particles of the component A are suspended and dispersed in the alkane wax of the component C coating medium, forming a coating of the component C on the basic catalyst particles of the component A.

[0134] S104. Heat the first premix to a temperature above the melting point of the component B, add the component B to the first premix, and stir to completely melt the component B to obtain a second premix;

[0135] Preferably, heat the first premix to T 2 , the melting point of the component B is T B , T 2 - T B = 12°C to 20°C. Further preferably, heat the first premix to T 2 , the melting point of the component B is T B , T 2 - T B = 13°C to 18°C. More preferably, heat the first premix to T 2 , the melting point of the component B is T B , T 2 - T B = 15°C.

[0136] In this step, heat the first premix to a temperature above the melting point of the component B, add the component B to the first premix, and stir to completely melt the component B. The (semi)-crystalline solid polyester resin of the component B is melted and dispersed into the dispersion emulsion of the component C and the component A. By utilizing the molecular polarity difference between the alkane wax of the component C coating medium and the (semi)-crystalline solid polyester resin of the component B, the two are completely immiscible, satisfying the basic condition that the component B can be suspended and dispersed in the component C coating medium to achieve coating.

[0137] S105. Cool down the second premix and stir it at a low speed until the C component forms two distinct layers. The upper layer is the separate C component, and the lower layer is the mixed phase with the B component coating the A component.

[0138] Preferably, cool down the second premix to T 3 , the melting point of the B component is T B , the melting point of the C component is T C , T 3 -T C = 2°C to 8°C, and T B -T 3 = 12°C to 20°C. Further preferably, cool down the second premix to T 3 , the melting point of the B component is T B , the melting point of the C component is T C , T 3 -T C = 3°C to 6°C, and T B -T 3 = 13°C to 18°C. More preferably, cool down the second premix to T 3 , the melting point of the B component is T B , the melting point of the C component is T C , T 3 -T C = 5°C, and T B -T 3 = 15°C.

[0139] The (semi)-crystalline solid polyester resin of the B component is melt-dispersed into the dispersion emulsion of the C component and the A component. Due to the difference in the molecular polarity of the C component and the B component towards the basic catalyst, resulting in a difference in the miscibility degree, the C component, which is the coating medium covering the A component, is replaced by the B component, and is separated into two distinct phases using the differences in melting point and polarity, achieving the purpose of coating and separation.

[0140] S106. Suck out the upper layer and cool and crush it.

[0141] In this step, the upper layer can be sucked out and crushed into powder particles for reuse, improving environmental protection. The upper layer is mainly the coating medium C component, and its separation is simple and can be recycled. The coating process is green and environmentally friendly, without the generation of three wastes, solving the problems in common coating technologies such as the complex separation of the coating medium, difficulty in reuse, and easy generation of wastewater and harmful organic substances.

[0142] S107. Crush the lower layer to obtain a slow-release coated heat-curable powder coating catalyst composition.

[0143] Preferably, the lower phase is crushed to an average particle size of 0.5-5 microns to obtain a slow-release coated heat-curable powder coating catalyst composition. More preferably, the lower phase is crushed to an average particle size of 1-3 microns to obtain a slow-release coated heat-curable powder coating catalyst composition.

[0144] The sustained-release coated heat-curable powder coating catalyst composition is isolated from the main reaction components by the catalyst coated by the packaging material with a melting point higher than 50°C at room temperature, and cannot participate in the chemical cross-linking reaction, and has good stability. The catalyst composition is low-temperature unsealed and activated at a temperature close to the melting point of the packaging material at 90°C, and catalyzes the main chemical reaction of the ultra-low temperature powder coating at a temperature of 95-120°C. In addition, after the catalyst composition is melt-activated, the packaging material used to coat the catalyst is itself one of the main reaction resin components of the powder coating, and can participate in the chemical cross-linking reaction to form a cured coating.

[0145] Correspondingly, the present invention also provides a heat-curable powder coating, comprising the above-mentioned slow-release coated heat-curable powder coating catalyst composition; or, the slow-release coated heat-curable powder coating catalyst composition prepared by the above-mentioned preparation method.

[0146] A preferred embodiment of the heat-curable powder coating comprises a resin and a slow-release coated heat-curable powder coating catalyst composition.

[0147] The resin may be one or more of epoxy resin and polyester resin;

[0148] The slow-release coated heat-curable powder coating catalyst composition is added in an amount of 1wt%-20wt%, and the resin is added in an amount of 80wt%-99wt%. Preferably, the slow-release coated heat-curable powder coating catalyst composition is added in an amount of 2wt%-15wt%, and the resin is added in an amount of 85wt%-98wt%. More preferably, the slow-release coated heat-curable powder coating catalyst composition is added in an amount of 3wt%-10wt%, and the resin is added in an amount of 90wt%-97wt%.

[0149] Another preferred embodiment of the heat-curable powder coating comprises a resin, a slow-release coated heat-curable powder coating catalyst composition, a filler, a pigment, and an additive.

[0150] The resin may be one or more of epoxy resin and polyester resin;

[0151] The slow-release coated heat-curable powder coating catalyst composition is added in an amount of 1wt%-20wt%; the resin is added in an amount of 70wt%-98wt%; the filler is added in an amount of 0.1wt%-10wt%; the pigment is added in an amount of 0.1wt%-10wt%; and the auxiliary agent is added in an amount of 0.1wt%-10wt%.

[0152] Accordingly, the present invention also provides a method for preparing a heat-curable powder coating, comprising:

[0153] Mixing a resin and a slow-release coated heat-curable powder coating catalyst composition to obtain a powder coating preliminary mixture;

[0154] Melting and mixing the powder coating preliminary mixture, and cooling to room temperature to obtain a mixture;

[0155] The cooled mixture is pulverized to obtain a powder coating.

[0156] Preferably, the powder coating preliminary mixture is melt mixed, which may be performed by melt extruding the powder coating preliminary mixture through an extruder, or by melt mixing through other methods for preparing powder coating.

[0157] See also Figure 1 , Figure 1 is a differential scanning calorimetry (DSC) graph of the heat-curable powder coating of the present invention, Figure 1 The heating curves under different heating rates are shown, including, from top to bottom, curve 1 is a heating curve with a heating rate of 3°C / min, curve 2 is a heating curve with a heating rate of 5°C / min, curve 3 is a heating curve with a heating rate of 8°C / min, and curve 4 is a heating curve with a heating rate of 10°C / min.

[0158] It can be seen from the DSC curve that the glass transition temperature (inflection point) of the present invention is 95-105°C, that is, the starting temperature of the reaction is 95-105°C, and the peak temperature of the reaction is 118-129°C. Therefore, the prepared powder coating can be desealed and activated at a low temperature of 90°C, which is close to the melting point of the packaging material, and catalyze the main chemical reaction of the ultra-low temperature powder coating at a temperature of 95-120°C for curing.

[0159] The present invention is further described below with specific embodiments

[0160] Example 1

[0161] 1. Formula:

[0162] i) Component A, using an organic amine catalyst, with an amount of 20wt%;

[0163] ii) Component B, which is a product obtained by reacting a crystalline polyester or semi-crystalline polyester containing a carboxyl group with a methacrylic monomer and / or its derivative, with a dosage of 40 wt%. Among them, Component B is prepared by the following method:

[0164] Add 192 g of ethylene glycol, 803 g of 1,12-dodecanedioic acid, 4100 catalyst (0.15 mmol), antioxidant (0.6 g), and water (4 g) into a four-necked flask equipped with a thermometer, a stirrer, and a distillation device. Under nitrogen protection, stir and heat to 140 °C to distill out water. Then continue to heat up to 220 °C without releasing water, and keep vacuum polymerization at 220 °C to obtain a crystalline polyester with an acid value of 56 mgKOH / g, a hydroxyl value lower than 3 mgKOH / g, and a number-average molecular weight of Mn of 2000. Then cool the crystalline polyester to 140 °C, and slowly add dropwise a mixture of 112 g of glycidyl methacrylate, 5.6 g of ethyltriphenylphosphonium bromide, and 0.7 g of 2,5-di-tert-butyl-1,4-hydroquinone at normal pressure. Maintain stirring reaction at 140 °C for 1 hour to obtain the final product, an ethylenically unsaturated solid polyester resin capped with methacrylic acid, with a number-average molecular weight of 2220, a viscosity at 100 °C of 200 mPa·s, an acid value of 1.0 mgKOH / g, a melting point Tm of 75 °C, and a hydroxyl value of 54 mgKOH / g.

[0165] iii) Component C, which is C16 alkane wax, with a dosage of 40 wt%.

[0166] (II) Preparation method:

[0167] 1) Heat and raise the temperature of Component C by 5 degrees above its melting point, and keep it warm until it is completely melted and becomes a liquid state;

[0168] 2) Grind Component A to D50 of 0.8 - 1.5 microns using a supersonic airflow pulverizer;

[0169] 3) Add the ground Component A in step 2) to the Component C that has become a liquid in step 1), and stir and mix evenly to obtain a uniform milky liquid as the first premix;

[0170] 4) Heat the first premix in step 3) to 15 degrees above the melting point of Component B, add Component B to the first premix, and stir to ensure that Component B is completely melted to form a uniform mixture, obtaining the second premix;

[0171] 5) Cool the second premix in step 4) to 5 degrees above the melting point of component C and below 15 degrees below the melting point of component B, and keep stirring the second premix at a low speed until component C forms two distinct layers. Completely suck out: the upper layer is the transparent liquid of pure component C, and the lower layer is the mixed phase of component B coating component A, obtaining the third premix;

[0172] 6) Suck out the component C in the upper layer of the third premix in step 5), cool and crush it into powder particles for reuse;

[0173] 7) Cool and crush the mixture of component B coating component A in the lower layer of the third premix in step 5) to D50 of 1 - 3 microns, becoming a slow-release coated thermosettable powder coating catalyst composition.

[0174] Example 2

[0175] (I) Formulation:

[0176] i) Component A, select an anionic copolymerization Lewis base catalyst, with a dosage of 35 wt%;

[0177] ii) Component B, select the product obtained by reacting a crystalline polyester or semi-crystalline polyester containing carboxyl groups with a methacrylic acid monomer and / or its derivatives, with a dosage of 35 wt%. Among them, component B is prepared by the following method:

[0178] Add 192 g of ethylene glycol, 803 g of 1,12-dodecanedioic acid, 4100 catalyst (0.15 mmol), antioxidant (0.6 g), and water (4 g) into a four-necked flask equipped with a thermometer, stirrer, and distillation device. Under nitrogen protection, stir and heat to 140 °C to distill out water. Continue to heat up to 220 °C without releasing water, and keep vacuum polymerization at 220 °C to obtain a crystalline polyester with an acid value of 56 mgKOH / g, a hydroxyl value lower than 3 mgKOH / g, and a number average molecular weight of Mn of 2000. Then cool the crystalline polyester to 140 °C, and slowly dropwise add a mixture of 112 g of glycidyl methacrylate, 5.6 g of ethyltriphenylphosphonium bromide, and 0.7 g of 2,5-di-tert-butyl-1,4-hydroquinone at normal pressure. Maintain stirring and reaction at 140 °C for 1 hour to obtain the final product, a methacrylic acid-terminated ethylenically unsaturated solid polyester resin, with a number average molecular weight of 2220, a viscosity of 200 mPa.s at 100 °C, an acid value of 1.0 mgKOH / g, a melting point Tm of 75 °C, and a hydroxyl value of 54 mgKOH / g.

[0179] iii) Component C, select C18 paraffin wax, with a dosage of 30 wt%.

[0180] (II) Preparation method:

[0181] 1) Heat component C to a temperature 6 degrees above its melting point and keep it at this temperature to ensure complete melting and turn it into a liquid state.

[0182] 2) Grind component A using a supersonic airflow mill to a D50 of 0.8 - 1.5 microns.

[0183] 3) Add the ground component A from step 2) to the liquid component C from step 1) and stir to mix evenly to obtain a homogeneous milky liquid as the first pre - mixture.

[0184] 4) Heat the first pre - mixture from step 3) to a temperature 18 degrees above the melting point of component B, add component B to the first pre - mixture, and stir to ensure complete melting of component B to form a homogeneous mixture, obtaining the second pre - mixture.

[0185] 5) Cool the second pre - mixture from step 4) to a temperature 5 degrees above the melting point of component C and 15 degrees below the melting point of component B, and keep it at this temperature while stirring at a low speed until component C forms two distinct layers. Completely suck out: the upper layer is the transparent liquid of pure component C, and the lower layer is the mixed phase with component B coating component A, obtaining the third pre - mixture.

[0186] 6) Suck out the component C from the upper layer of the third pre - mixture in step 5), cool it, grind it into powder particles for reuse.

[0187] 7) Cool and grind the mixture with component B coating component A in the lower layer of the third pre - mixture in step 5) to a D50 of 1 - 3 microns to obtain a slow - release coated thermosettable powder coating catalyst composition.

[0188] Example 3

[0189] (I) Formulation:

[0190] i) For component A, select an organic onium salt catalyst with a dosage of 50 wt%.

[0191] ii) For component B, select the product obtained by reacting a crystalline polyester or semi - crystalline polyester containing carboxyl groups with a methacrylic monomer and / or its derivatives, with a dosage of 35 wt%. Among them, component B is prepared by the following method:

[0192] 192 g of ethylene glycol, 803 g of 1,12-dodecanedioic acid, 4100 catalyst (0.15 mmol), antioxidant (0.6 g), and water (4 g) were added to a four-necked flask equipped with a thermometer, a stirrer, and a distillation device. Under nitrogen protection, the mixture was stirred and heated to 140 °C to distill out water. Then, the temperature was further raised to 220 °C without releasing water, and vacuum polymerization was carried out at 220 °C to obtain a crystalline polyester with an acid value of 56 mgKOH / g, a hydroxyl value below 3 mg KOH / g, and a number-average molecular weight of Mn of 2000. Then, the crystalline polyester was cooled to 140 °C, and a mixture of 112 g of glycidyl methacrylate, 5.6 g of ethyltriphenylphosphonium bromide, and 0.7 g of 2,5-di-tert-butyl-1,4-hydroquinone was slowly added dropwise under atmospheric pressure. The mixture was stirred at 140 °C for 1 hour to obtain the final product, an ethylenically unsaturated solid polyester resin capped with methacrylic acid, with a number-average molecular weight of 2220, a viscosity of 200 mPa·s at 100 °C, an acid value of 1.0 mg KOH / g, a melting point Tm of 75 °C, and a hydroxyl value of 54 mg KOH / g.

[0193] iii) Component C, C22 alkane wax was selected, and the dosage was 15 wt%.

[0194] (II) Preparation method:

[0195] 1) Heat and raise the temperature of Component C by 8 degrees above its melting point, and keep it warm until it is completely melted and becomes a liquid state;

[0196] 2) Grind Component A to D50 of 0.8 - 3 microns using a supersonic airflow mill;

[0197] 3) Add the ground Component A in step 2) to the already liquid Component C in step 1) and stir to mix evenly to obtain a uniform milky liquid as the first pre-mixture;

[0198] 4) Heat the first pre-mixture in step 3) to 20 degrees above the melting point of Component B, add Component B to the first pre-mixture, and stir to ensure that Component B is completely melted to form a uniform mixture to obtain the second pre-mixture;

[0199] 5) Cool the second pre-mixture in step 4) to 5 degrees above the melting point of Component C and below 15 degrees below the melting point of Component B, and keep it warm and stir the second pre-mixture in step 4) at a low speed until Component C forms two distinct layers. Completely suck out: the upper layer is the transparent liquid of Component C alone, and the lower layer is the mixed phase of Component B coating Component A to obtain the third pre-mixture;

[0200] 6) Suck out the upper layer of Component C in the third pre-mixture in step 5), cool and grind it into powder particles for repeated use;

[0201] 7) Cool and pulverize the mixture in which component B of the third premix lower layer in step 5 coats component A to D50 of 1 - 3 μm to obtain a slow - release coated heat - curable powder coating catalyst composition.

[0202] Perform storage performance tests on the slow - release coated heat - curable powder coating catalyst compositions prepared in Examples 1 - 3, and the results are shown in Table 1 below:

[0203] Table 1 Test results of the powder coating catalyst compositions of Examples 1 - 3

[0204]

[0205] Example 4

[0206] Mix 85 wt% epoxy resin and 15 wt% of the slow - release coated heat - curable powder coating catalyst composition obtained in Example 1 to obtain a powder coating premix;

[0207] Melt - extrude the powder coating premix through an extruder and cool it to room temperature to obtain an extrudate;

[0208] Pulverize the cooled extrudate to obtain a powder coating.

[0209] Spray the powder coating prepared in Example 4 onto a medium - density fiberboard (MDF) with a thickness of 15 mm using an electrostatic spray gun at a voltage of 60 kv. Put the sprayed MDF board into an infrared baking oven, set the temperature to 120 °C, and the residence time to 4 minutes. Label it as sample 1.

[0210] Spray the powder coating prepared in Example 4 onto a bamboo charcoal board with a thickness of 15 mm using an electrostatic spray gun, and set the voltage to 50 kv. Put the sprayed bamboo charcoal board into an infrared baking oven, set the temperature to 90 °C, and the time to 5.5 minutes. Label it as sample 2.

[0211] Spray the powder coating prepared in Example 4 onto a fiberglass sample with a thickness of 3 mm using an electrostatic spray gun at a voltage of 50 kv. Put the sprayed fiberglass board into an infrared baking oven, set the temperature to 100 °C, and the residence time to 4 minutes. Label it as sample 3.

[0212] Test the above three samples, and the test results are shown in Table 2 below:

[0213] Table 2 Test results of the powder coating of Example 4

[0214]

[0215] As can be seen from Table 2, the gelling time of the powder coating in Example 4 tested at 120°C is 59 seconds, the gelling time tested at 100°C is 80 seconds, and the gelling time tested at 90°C is 110 seconds. Therefore, the powder coating of this example can be cured at 90 - 120°C. Other performance indicators, including gloss, hardness, adhesion, film-forming properties (bubbles, dimensional deformation), etc., can all meet the performance requirements of the coating.

[0216] Example 5

[0217] Mix 92 wt% epoxy resin and 8 wt% of the slow-release coated thermosettable powder coating catalyst composition obtained in Example 2 to obtain a preliminary powder coating mixture;

[0218] Melt-extrude the preliminary powder coating mixture through an extruder and cool it to room temperature to obtain an extrudate;

[0219] Crush the cooled extrudate to obtain a powder coating.

[0220] Spray the powder coating prepared in Example 5 onto a medium-density fiberboard (MDF) with a thickness of 15 mm using an electrostatic spray gun at a voltage of 60 kv. Place the sprayed MDF board in an infrared baking oven, set the temperature to 100°C, and the dwell time to 4 minutes. Label it as Specimen 1.

[0221] Spray the powder coating prepared in Example 5 onto a bamboo charcoal board with a thickness of 15 mm using an electrostatic spray gun, and set the voltage to 50 kv. Place the sprayed bamboo charcoal board in an infrared baking oven, set the temperature to 90°C, and the time to 5.5 minutes. Label it as Specimen 2.

[0222] Spray the powder coating prepared in Example 5 onto a fiberglass specimen with a thickness of 3 mm using an electrostatic spray gun at a voltage of 50 kv. Place the sprayed fiberglass board in an infrared baking oven, set the temperature to 100°C, and the dwell time to 5 minutes. Label it as Specimen 3.

[0223] Test the above three specimens, and the test results are shown in Table 3 below:

[0224] Table 3 Test Results of the Powder Coating in Example 5

[0225]

[0226] As can be seen from Table 3, the gelling time of the powder coating in Example 5 tested at 120°C is 63 seconds, the gelling time tested at 100°C is 85 seconds, and the gelling time tested at 90°C is 120 seconds. Therefore, the powder coating of this example can be cured at 90 - 120°C. Other performance indicators, including gloss, hardness, adhesion, film-forming properties (bubbles, dimensional deformation), etc., can all meet the performance requirements of the coating.

[0227] Example 6

[0228] Mix 95 wt% epoxy resin with 5 wt% of the slow-release coated thermosettable powder coating catalyst composition obtained in Example 3 to obtain a preliminary powder coating mixture.

[0229] Melt-extrude the preliminary powder coating mixture through an extruder and cool it to room temperature to obtain an extrudate.

[0230] Crush the cooled extrudate to obtain a powder coating.

[0231] Spray the powder coating prepared in Example 6 onto a medium-density fiberboard (MDF) with a thickness of 15 mm using an electrostatic spray gun at a voltage of 60 kv. Place the sprayed MDF board in an infrared baking oven, set the temperature to 100 °C, and the dwell time to 4 minutes. Label it as Specimen 1.

[0232] Spray the powder coating prepared in Example 6 onto a bamboo charcoal board with a thickness of 15 mm using an electrostatic spray gun, and set the voltage to 50 kv. Place the sprayed bamboo charcoal board in an infrared baking oven, set the temperature to 90 °C, and the time to 5.5 minutes. Label it as Specimen 2.

[0233] Spray the powder coating prepared in Example 6 onto a fiberglass specimen with a thickness of 3 mm using an electrostatic spray gun at a voltage of 50 kv. Place the sprayed fiberglass board in an infrared baking oven, set the temperature to 100 °C, and the dwell time to 5 minutes. Label it as Specimen 3.

[0234] Test the above three specimens, and the test results are shown in Table 4 below:

[0235] Table 4 Test Results of the Powder Coating in Example 6

[0236]

[0237] As can be seen from Table 4, the gel time of the powder coating in Example 6 tested at 120 °C is 70 seconds, at 100 °C is 95 seconds, and at 90 °C is 130 seconds. Therefore, the powder coating in this example can be cured at 90 - 120 °C. Other performance indicators, including gloss, hardness, adhesion, film-forming property (bubbles, dimensional deformation), etc., can meet the required performance of the coating.

[0238] It should be noted that the gloss is the glossiness measured on the surface of the coating at an incident angle of 60°.

[0239] The detection basis for adhesion is GB9286, where 0 - 5 indicates the adhesion from good to bad, and the specific grading standard description is: 0 - The cutting edge is completely smooth and none of the grids peel off.

[0240] The pencil hardness is based on ASTM3363.

[0241] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications are also regarded as the protection scope of the present invention.

Claims

1. A sustained-release coated heat-curable powder coating catalyst composition, characterized in that: include: i) Component A, wherein the component A is a core coating, and comprises at least one alkaline catalyst capable of promoting the ring-opening reaction of the epoxy resin; ii) a B component, wherein the B component is a coating shell comprising at least one crystalline solid unsaturated polyester resin or a semi-crystalline solid unsaturated polyester resin; iii) a C component, wherein the C component is a coating medium comprising at least one alkane wax; The component A is suspended and dispersed in the component C, so that the component C covers the component A; then, the component B is melted and dispersed into the dispersion of the component C and the component A.

2. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The A component comprises at least one basic catalyst which can promote the ring-opening reaction of the epoxy resin at 70-130°C.

3. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1 or 2, characterized in that: The component A comprises at least one organic amine catalyst, organic phosphine salt catalyst or imidazole catalyst which can promote the ring-opening reaction of epoxy resin.

4. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1 or 2, characterized in that: The A component contains at least one anionic copolymerization Lewis base catalyst which can promote the ring-opening reaction of the epoxy resin.

5. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1 or 2, characterized in that: The A component contains at least one organic onium salt catalyst which can promote the ring-opening reaction of epoxy resin.

6. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1 or 2, characterized in that: The average particle size of the A component is 0.8-1.5 microns.

7. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The B component is a product of a reaction between a crystalline polyester or a semi-crystalline polyester containing a carboxyl group and a methacrylic acid monomer and / or a derivative thereof.

8. The sustained-release coated heat-curable powder coating catalyst composition according to claim 7, characterized in that: The B component meets at least one of the following conditions: a. The number average molecular weight Mn of the B component is 100-10000Da; b. The melting point of the B component is 50-120°C and the crystallization point is 40-90°C; c. The viscosity of the B component at a temperature of 100° C. is 0.01-20 Pa.s.

9. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The C component comprises at least one straight-chain paraffin wax.

10. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The C component comprises at least one alkane wax containing 15 to 35 carbon atoms.

11. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The C component comprises at least one alkane wax having a melting point of 30-70°C.

12. The sustained-release coated heat-curable powder coating catalyst composition according to claim 1, characterized in that: The total amount of component A, component B and component C added is 100wt%; The amount of component A added is 20-60wt% of the total amount of component A, component B and component C; The amount of component B added is 30-70wt% of the total amount of component A, component B and component C; The added amount of the C component is 10-45 wt % of the total amount of the A component, the B component and the C component.

13. A method for preparing a sustained-release coated heat-curable powder coating catalyst composition according to any one of claims 1 to 12, characterized in that: include: Heat component C to make it melt completely and turn it into a liquid state; Crush component A; Adding the crushed component A to the liquid component C, stirring and mixing evenly to obtain a first premix; The first premix is ​​heated to a temperature above the melting point of component B, component B is added to the first premix, and stirred to completely melt component B to obtain a second premix; The second premix is ​​cooled and stirred at a low speed until the C component forms two distinct layers, the upper phase is the separate C component, and the lower phase is the mixed phase of the B component covering the A component; The upper phase is sucked out, cooled and crushed; The lower phase is pulverized to obtain a slow-release coated heat-curable powder coating catalyst composition.

14. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 13, characterized in that: The C component is heated to T1, and the melting point of the C component is T C , T1-T C =2℃~8℃.

15. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 13, characterized in that: Component A is crushed to an average particle size of 0.8-1.5 microns.

16. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 13, characterized in that: The first premix is ​​heated to T2, the melting point of the B component is T B , T2-T B =12℃~20℃.

17. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 13, characterized in that: The second premix is ​​cooled to T3, and the melting point of the B component is T B , the melting point of the C component is T C , T3-T C =2℃~8℃, and T B -T3=12℃~20℃.

18. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 13, characterized in that: The lower phase is crushed to an average particle size of 0.5-5 microns to obtain a slow-release coated heat-curable powder coating catalyst composition.

19. The method for preparing the sustained-release coated heat-curable powder coating catalyst composition according to claim 18, characterized in that: The lower phase is crushed to an average particle size of 1-3 microns to obtain a slow-release coated heat-curable powder coating catalyst composition.

20. A heat-curable powder coating, characterized in that: A sustained-release coated heat-curable powder coating catalyst composition comprising any one of claims 1 to 12; Alternatively, a sustained-release coated heat-curable powder coating catalyst composition prepared by the preparation method according to any one of claims 13 to 19.

21. The heat-curable powder coating according to claim 20, characterized in that Also includes resin; The resin is selected from one or more of epoxy resin and polyester resin.

22. The heat-curable powder coating according to claim 20, characterized in that The slow-release coated heat-curable powder coating catalyst composition is added in an amount of 1wt%-15wt%; The added amount of the resin is 85wt%-99wt%.

23. The heat-curable powder coating according to claim 20, characterized in that It also contains one or more of fillers, pigments and additives.

24. A method for preparing a heat-curable powder coating according to any one of claims 20 to 23, characterized in that: include: Mixing a resin and a slow-release coated heat-curable powder coating catalyst composition to obtain a powder coating preliminary mixture; Melting and mixing the powder coating preliminary mixture, and cooling to room temperature to obtain a mixture; The cooled mixture is pulverized to obtain a powder coating.

25. The method for preparing a heat-curable powder coating according to claim 24, characterized in that: Melting and mixing the powder coating premix comprises: The powder coating preliminary mixture is melt-extruded through an extruder.

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