An Extinction Agent for HAA Powder Coating and Its Preparation Method

Abstract

The present invention relates to a matting agent for HAA powder coatings and a preparation method thereof. The matting agent is a matting polymer containing special groups such as hydroxyl and epoxy groups with significantly different activities. The matting polymer is mainly prepared from glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, 2-methyl-3-butene-2-ol, dicyclopentadiene dioxide, a hydroxyl polyester resin, and an accelerator. Due to the presence of hydroxyl and epoxy groups of varying activities in its structure, supplemented by the accelerator and the physical dispersion effect during the preparation process, the product has excellent matting ability and good storage and matting stability. It can reduce the gloss of HAA system powder coatings to 3-10%.

Description

Technical Field

[0001] The present invention relates to the field of HAA powder coating additives, and in particular to a matting agent for HAA powder coatings and a preparation method thereof. Background Art

[0002] At present, the powder coatings for outdoor systems are mainly TGIC curing systems and HAA curing systems. HAA system powder coatings have the advantages of being non-toxic and low cost, but they also have shortcomings such as difficulty in matting. At present, the industry mostly adopts dry mixing method to prepare HAA matting powder coatings, but the dry mixing matting process is cumbersome and the matting stability is poor, making it difficult to apply on a large scale. The matting agents on the market currently mainly use wax powder and other added materials, which have poor matting stability and it is difficult to meet the matting requirements. With the increasing application of HAA powder coatings, customers require HAA powder coatings to achieve the matting effect of TGIC, which is 5-10%. It is difficult for current market products to achieve this stably. CN201910838549.0 has also developed an HAA matting agent product, but it requires the use of a liquid emulsifier, resulting in poor storage stability of the matting agent, and the gloss of the matting agent can only be matted to 20-30%, which cannot achieve the matting target of less than 10%. CN202011443527.3 and 202110960545.7 are both prepared by mixing carboxyl compounds and epoxy compounds. The defect is that carboxyl and epoxy are easily cured during storage, especially in the presence of external catalysts, resulting in poor storage stability. On the other hand, its solution adopts a physical mixing method, which makes it difficult to achieve uniformity of batch materials, resulting in poor matting stability. Therefore, it is difficult to achieve large-scale application.

[0003] To address the above shortcomings, this proposal provides a matting agent for HAA powder coatings and a preparation method thereof. The matting polymer contains special groups such as hydroxyl and epoxy groups with significantly different reactivity. The matting polymer is mainly prepared from raw materials such as glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, 2-methyl-3-butene-2-ol, dicyclopentadiene dioxide, hydroxyl polyester resin, and accelerator. Glycidyl methacrylate, butyl methacrylate, norbornene-2-methanol, and 2-methyl-3-butene-2-ol are first polymerized to obtain a polymer containing epoxy groups and different hydroxyl structures. The polymer has a softening point controlled at 108-115°C. The polymer is then physically crushed and mixed with dicyclopentadiene, hydroxyl polyester resin, and accelerator to obtain a powdered matting agent product. Because the product contains hydroxyl and epoxy groups with different activities in its own structure, and the auxiliary accelerator and the physical dispersion effect in the preparation process, the product has excellent matting ability and good storage and matting stability, which can reduce the gloss of HAA system powder coatings to 3-10%. Summary of the Invention

[0004] The present invention relates to a matting agent for HAA powder coating and a preparation method thereof. The matting agent is a matting polymer containing special groups such as hydroxyl groups and epoxy groups with different activities, and specifically comprises the following raw materials in parts by weight:

[0005]

[0006] The raw materials also include initiators and accelerators.

[0007] Preferably, the initiator is benzoyl peroxide (BPO) or azobisisobutyronitrile (AIBN), and the amount used is 2-5% of glycidyl methacrylate;

[0008] Preferably, the accelerator is zinc chloride or manganese acetate, and the amount used is 0.1-0.2% of the total mass of the raw materials;

[0009] The dicyclopentadiene dioxide is also called dicyclopentadiene epoxide, CAS No. 81-21-0, and is commonly available in the market.

[0010] The hydroxyl polyester resin has a hydroxyl value of 25-35 mgKOH / g and can be purchased from Anhui Shenjian New Materials Co., Ltd., for example, model SJ1108.

[0011] The preparation method of the matting agent for HAA powder coating comprises the following steps:

[0012] A. Mix the formulated amount of glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, 2-methyl-3-butene-2-ol, and initiator at room temperature, and then pump them into a high-level tank for standby use;

[0013] B. Add the formulated amount of solvent xylene into a stainless steel reactor, heat it to 105-125°C and keep it warm, then start adding the mixed monomer and initiator solution in the header tank dropwise to carry out polymerization reaction. After the addition is complete, continue to keep it warm for reaction;

[0014] C. When the softening point of the polymer reaches 108-115°C, add the formulated amount of dicyclopentadiene dioxide and hydroxy polyester resin, raise the temperature to 130-135°C and keep warm, stir thoroughly to fully dissolve, then start the vacuum system to reduce pressure and remove the xylene solvent to obtain the matt resin;

[0015] D. When the volatile matter reaches less than 1%, stop the vacuum, stir evenly, discharge the material, cool, crush, add the formulated amount of accelerator and physically mix to obtain the HAA matting agent product.

[0016] Preferably, in step B, the dropping time is controlled at 2-2.5 h; in step C, the vacuum degree is controlled at -0.096 to -0.098 MPa; in step D, the particle size of the matting agent product is controlled at 80-120 mesh.

[0017] For example, the preparation method comprises the following steps:

[0018] A. Mix the formulated amount of glycidyl methacrylate, methyl methacrylate, butyl acrylate, norbornene-2-methanol, 2-methyl-3-butene-2-ol, and initiator at room temperature, then pump them into a high-level tank for standby use;

[0019] B. Add the formulated amount of solvent xylene into a stainless steel reactor, heat it to 105-125°C and keep it warm, then start adding the mixed monomer and initiator solution in the header tank dropwise to carry out polymerization reaction. The addition time is controlled within 2-2.5 hours. After the addition is completed, continue to keep warm and react;

[0020] C. When the softening point of the polymer reaches 108-115°C, add the formulated amount of dicyclopentadiene and hydroxy polyester resin, raise the temperature to 130-135°C and keep warm, stir thoroughly to fully dissolve, then start the vacuum system to reduce pressure and remove the xylene solvent to obtain the matt resin; the vacuum degree is controlled at -0.096 to -0.098 MPa;

[0021] D. When the volatile matter reaches less than 1%, stop the vacuum, stir evenly, discharge, cool, crush, add the formulated amount of accelerator and physically mix to obtain the HAA matting agent product. The particle size of the matting agent product is controlled at 80-120 mesh.

[0022] The obtained product has the appearance of white powder, an epoxy equivalent of 340-400 g / mol, a hydroxyl value of 110-140 mgKOH / , and a softening point of 110-120°C.

[0023] The present invention also relates to a matte HAA system powder coating system, which can be obtained, for example, using pure polyester resin, HAA, the matting agent prepared above, titanium dioxide, matting barium sulfate, leveling agent, matting agent, benzoin, etc. According to the above polyester powder coating formula, the various materials are mixed, extruded, tableted, and crushed using a twin-screw extruder, and then the tablets are crushed and sieved (150-180 mesh) to form a powder coating. The powder coating is sprayed on a surface-treated tinplate substrate using an electrostatic spray gun with a spray thickness of 70-80 μm and cured at 180°C / 15 minutes to obtain a powder coating film.

[0024] Beneficial effects:

[0025] (1) The present invention obtains hydroxyl and epoxy groups of different activities by copolymerizing glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, and 2-methyl-3-butene-2-ol. The hydroxyl and epoxy groups achieve extinction during subsequent curing due to the difference in curing speed with the carboxyl polyester resin.

[0026] (2) The present invention specifically selects dicyclopentadiene dioxide, a diepoxy compound with a high melting point and strong rigidity, as a matting agent to provide differentiated epoxy, and uses a high-temperature dissolution and dispersion preparation process to uniformly disperse it in the polymer system, thereby avoiding the problem of poor matting stability caused by process stability in the physical mixing method. The epoxy group of dicyclopentadiene dioxide and the epoxy group introduced into the polymer by glycidyl methacrylate have a large difference in activity, resulting in a significant matting effect; and the introduction of dicyclopentadiene dioxide also enhances the rigidity and water boiling resistance of the cured coating film;

[0027] (3) The hydroxy polyester resin specially selected in the present invention is introduced into the polymer system by means of external dissolution and uniform dispersion, thereby avoiding the problem of poor extinction stability caused by process stability in the physical mixing method. In addition, the hydroxy polyester resin is different from the hydroxyl group in the polymer. Moreover, the hydroxy polyester resin is an independent resin system. When introduced within a suitable dosage range, it can enhance the extinction effect without causing defects in the coating film.

[0028] (4) The present invention selects a special accelerator variety to promote the cross-linking and curing of the polyester resin at the curing temperature, while achieving a curing difference capability with the HAA curing agent. DETAILED DESCRIPTION

[0029] The present invention is further described below with reference to the accompanying drawings and examples. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0030] The raw materials described in the present invention are all commercially available; for example, the hydroxy polyester resin has a hydroxyl value of 25-35 mgKOH / g and can be purchased from Anhui Shenjian New Materials Co., Ltd., model SJ1108.

[0031] Preparation Example 1

[0032] A matting agent for HAA powder coating, specifically comprising the following raw materials in parts by weight:

[0033]

[0034]

[0035] The initiator is benzoyl peroxide (BPO), the dosage is 3% of glycidyl methacrylate;

[0036] The accelerator is zinc chloride, and the dosage is 0.1% of the total mass of the raw materials;

[0037] The preparation method comprises the following steps:

[0038] A. Mix the formulated amount of glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, 2-methyl-3-butene-2-ol, and initiator at room temperature, and then pump them into a high-level tank for standby use;

[0039] B. Add the formulated amount of solvent xylene into a stainless steel reactor, heat it to 120°C and keep it warm, then start adding the mixed monomer and initiator solution in the header tank dropwise to carry out polymerization reaction. The addition time is controlled within 2.5 hours. After the addition is completed, continue to keep it warm for reaction;

[0040] C. When the softening point of the polymer reaches the expected value, add the formulated amount of dicyclopentadiene and hydroxy polyester resin, raise the temperature to 132°C and keep warm, stir thoroughly to fully dissolve, then start the vacuum system to reduce pressure and remove the xylene solvent to obtain the matt resin; the vacuum degree is controlled at -0.096Mpa;

[0041] D. When the volatile matter reaches less than 1%, stop the vacuum, stir evenly, discharge, cool, crush, add the formulated amount of accelerator and physically mix to obtain the HAA matting agent product. The particle size of the matting agent product is controlled at 80 mesh.

[0042] The product has the appearance of white powder, epoxy equivalent: 352g / mol, hydroxyl value: 122mgKOH / g, and softening point: 112℃.

[0043] Preparation Example 2

[0044] A matting agent for HAA powder coating, specifically comprising the following raw materials in parts by weight:

[0045]

[0046]

[0047] The initiator is azobisisobutyronitrile (AIBN), the dosage is 5% of glycidyl methacrylate;

[0048] The accelerator is manganese acetate, and the dosage is 0.2% of the total mass of the raw materials;

[0049] The preparation method is the same as that of Preparation Example 1.

[0050] The product has the appearance of white powder, epoxy equivalent: 369g / mol, hydroxyl value: 130mgKOH / g, and softening point: 118℃.

[0051] Preparation Example 3

[0052] A matting agent for HAA powder coating, specifically comprising the following raw materials in parts by weight:

[0053]

[0054] The initiator is benzoyl peroxide (BPO), the dosage is 5% of glycidyl methacrylate;

[0055] The accelerator is manganese acetate, and the dosage is 0.2% of the total mass of the raw materials;

[0056] The preparation method is the same as that of Preparation Example 1.

[0057] The product has the appearance of white powder, epoxy equivalent: 364g / mol, hydroxyl value: 129mgKOH / g, and softening point: 116℃.

[0058] Preparation Example 4

[0059] A matting agent for HAA powder coating, specifically comprising the following raw materials in parts by weight:

[0060]

[0061] The initiator is benzoyl peroxide (BPO), the dosage is 5% of glycidyl methacrylate;

[0062] The accelerator is zinc chloride, and the dosage is 0.1% of the total mass of the raw materials;

[0063] The preparation method is the same as that of Preparation Example 1.

[0064] The product has the appearance of white powder, epoxy equivalent: 386g / mol, hydroxyl value: 128mgKOH / g, and softening point: 115℃.

[0065] Application Examples 1-4 (matting agents are prepared from the above Preparation Examples 1-4, respectively):

[0066] Matte HAA system powder coating, the formula in parts by weight is as follows:

[0067]

[0068]

[0069] The polyester resin used is HAA special polyester resin SJ4B produced by Anhui Shenjian New Materials Co., Ltd.

[0070] Paint coating preparation

[0071] According to the polyester powder coating formula, the materials were mixed thoroughly, extruded, tableted, and crushed using a twin-screw extruder. The tablets were then crushed and sieved (150-180 mesh) to produce the powder coating. The powder coating was then applied to the surface-treated tinplate substrate using an electrostatic spray gun to a thickness of 70-80 μm. The coating was then cured at 180°C / 15 minutes to obtain a powder coating film.

[0072] The storage stability test of the matting agent itself and the matting powder coating prepared from it is carried out in accordance with GB / T21782.8-2008 "Powder Coatings Part 8: Evaluation of Storage Stability of Thermosetting Powders". Level 0 means no change, level 1 means slight clumping, and level 2 means obvious clumping.

[0073] The coating index test is based on GB / T 21776-2008 "Guide to the Testing Standards of Powder Coatings and Their Coatings", and the adhesion grade is carried out in accordance with GB / T 9286-1998 "Paint and Varnish Film Grid Test".

[0074] Table 1 Comparison of properties of products after coating in the examples

[0075]

[0076]

[0077] From the data comparison in Table 1 above, it can be seen that the product of the present invention itself and the finished matte powder coating prepared therefrom have excellent storage stability, and there is still no agglomeration phenomenon under the storage conditions of 40°C / 120 days. The matte powder coating prepared therefrom also has excellent comprehensive properties, such as coating film appearance, impact resistance, gloss, boiling water resistance and adhesion.

[0078] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A method for preparing a matting agent for HAA powder coating, characterized in that , including the following raw materials in parts by weight: The raw materials also include initiators and accelerators; Wherein, the accelerator is zinc chloride or manganese acetate, and the amount used is 0.1-0.2% of the total mass of the raw materials; the hydroxyl value of the hydroxy polyester resin is 25-35 mgKOH / g; The preparation method of the matting agent for HAA powder coating comprises the following steps: A. Mix the formulated amount of glycidyl methacrylate, methyl methacrylate, butyl acrylate, 5-norbornene-2-methanol, 2-methyl-3-butene-2-ol, and initiator at room temperature, and then pump them into a high-level tank for standby use; B. Add the formulated amount of solvent xylene into a stainless steel reactor, heat it to 105-125°C and keep it warm, then start adding the mixed monomer and initiator solution in the header tank dropwise to carry out polymerization reaction. After the addition is complete, continue to keep it warm for reaction; C. When the softening point of the polymer reaches 108-115°C, add the formulated amount of dicyclopentadiene dioxide and hydroxy polyester resin, raise the temperature to 130-135°C and keep warm, stir thoroughly to fully dissolve, then start the vacuum system to reduce pressure and remove the xylene solvent to obtain the matt resin; D. When the volatile matter reaches less than 1%, stop the vacuum, stir evenly, discharge the material, cool, crush, add the formulated amount of accelerator and mix to obtain the HAA matting agent product.

2. The method for preparing a matting agent for HAA powder coating according to claim 1, further characterized in that the initiator is benzoyl peroxide or azobisisobutyronitrile, and the amount used is 2-5% of the glycidyl methacrylate.

3. The method for preparing a matting agent for HAA powder coating according to claim 1 or 2, further characterized in that, in step B, the dropping time is controlled to be 2-2.5 hours.

4. The method for preparing a matting agent for HAA powder coating according to claim 1 or 2, further characterized in that, in step C, the vacuum degree is controlled at -0.096 to -0.098 MPa.

5. The method for preparing a matting agent for HAA powder coating according to claim 1 or 2, further characterized in that, in step D, the particle size of the matting agent product is controlled to be 80-120 mesh.

6. A matting agent for HAA powder coating, obtained by the preparation method according to any one of claims 1 to 5.

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