Skin-touch frosted powder coating based on resin reaction kinetics regulation and preparation method

Abstract

The invention relates to a resin reaction kinetics regulation-based skin-touch frosted powder coating and a preparation method thereof, and belongs to the technical field of powder coating preparation, the resin reaction kinetics regulation-based skin-touch frosted powder coating comprises the following components by mass: 30-40% of epoxy resin, 10-17% of polyester resin, 10-17% of acrylic resin, and 32-45% of an auxiliary agent. Local microphase separation in a cross-linked network is formed and a uniform micron-sized concave-convex structure is generated by utilizing differential reaction rates of the epoxy resin, the polyester resin and the acrylic resin, so that a fine and smooth uneven texture state similar to sand texture powder is formed on the surface of the coating, and the sand texture with the sand texture powder is visually observed; the surface is fine and smooth in the low-gloss state, the hand feeling is smooth, the manufacturing mode that a fluorine-containing sand texturing agent is used for a common sand texturing powder product is changed, and good application prospects are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of powder coating preparation, and specifically to a skin-friendly matte powder coating based on resin reaction kinetics regulation and a preparation method thereof. Background Art

[0002] Traditional sand pattern powder coatings generally use polytetrafluoroethylene-based sanding agents (such as PTFE) to form surface textures. Such powder coatings have the following defects. First, their environmental friendliness is poor, and fluorine-containing substances do not meet the requirements of EU environmental protection regulations. Second, their touch is rough, the surface particle feeling formed by low-gloss sand pattern powder is obvious, and the fineness is insufficient. Moreover, their mechanical properties are weak, the scratch resistance of low-gloss sand pattern powder is poor, and scratches are likely to appear after long-term use. In response to the above problems, the prior art adjusts the dosage of the sanding agent to improve the texture, but it cannot effectively solve the problems. Therefore, it is urgent to break through the traditional technical bottleneck by innovating the resin compatibility system. Summary of the Invention

[0003] The purpose of the present invention is to provide a skin-friendly matte powder coating based on resin reaction kinetics regulation and a preparation method thereof, which can at least partially solve the technical problems mentioned in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solutions:

[0005] The first aspect of the present invention provides a skin-friendly matte powder coating based on resin reaction kinetics regulation, which includes the following components by mass percentage:

[0006] Epoxy resin 30-40%, polyester resin 10-17%, acrylic resin 10-17%, additives 32-45%.

[0007] In a preferred embodiment, the epoxy resin is bisphenol A type epoxy resin, and the epoxy equivalent is 700-900 g / mol.

[0008] In a preferred embodiment, the polyester resin is a carboxyl-terminated polyester, and the acid value is 45-55 mg KOH / g.

[0009] In a preferred embodiment, the acrylic resin is a carboxyl-terminated acrylic resin, and the acid value is 140-160 mg KOH / g.

[0010] In a preferred embodiment, the mass ratio of the polyester resin to the epoxy resin is (1-1.5):1.

[0011] In a preferred embodiment, the mass ratio of the acrylic resin to the epoxy resin is 1:(1.5-2).

[0012] In a preferred embodiment, the auxiliaries include barium sulfate for matting, benzoin, brightening agent, leveling agent, defoaming agent, conductive agent, curing accelerator, and pigment.

[0013] In a preferred embodiment, by mass percentage, the barium sulfate for matting is 30 - 40%, benzoin is 0.3 - 0.5%, brightening agent is 0.5 - 0.8%, leveling agent is 0.8 - 1%, defoaming agent is 0.5 - 0.8%, conductive agent is 0.2 - 0.4%, curing accelerator is 0.1 - 0.2%, and pigment is 0.6 - 1%.

[0014] The second aspect of the present invention provides a preparation method of a skin - feeling matte powder coating based on resin reaction kinetics regulation, comprising the following steps:

[0015] Pre - mix the epoxy resin, polyester resin, acrylic resin and auxiliaries, melt and knead the pre - mixture evenly, then perform tablet pressing, crushing, and carry out grading and screening to form a powder coating.

[0016] In a preferred embodiment, a twin - screw extruder is used to melt and knead the pre - mixture, the temperature of the extruder is 100 - 105°C, and the screw frequency is 40 - 50 HZ.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The skin - feeling matte powder coating based on resin reaction kinetics regulation provided by the present invention forms local micro - phase separation in the cross - linked network through the different reaction rates of epoxy resin and polyester / acrylic resin (the reaction rate of polyester and epoxy > the reaction rate of acrylic and epoxy), generating a uniform micron - level uneven structure, making the surface of the coating form a delicate uneven texture state similar to sand - like powder, and meeting the fluorine - free requirements of EU products. Further, through a specific resin compatibility ratio, it can ensure its surface flatness and 60° glossiness, with a delicate surface and smooth hand feeling in a low - gloss state, and having better mechanical properties. Description of the Drawings

[0019] Figure 1 A is the coating effect of the powder coating provided in Comparative Example 1 of the present invention;

[0020] Figure 1 B is the coating effect of the powder coating provided in Example 1 of the present invention. Detailed Embodiments

[0021] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0022] Unless otherwise specified, the raw materials used in the present invention are all commercially available products in the art.

[0023] On the one hand, the present invention discloses a skin-feeling matte powder coating based on the regulation of resin reaction kinetics, which includes the following components by mass percentage: 30-40% of epoxy resin, 10-17% of polyester resin, 10-17% of acrylic resin, and 32-45% of additives.

[0024] Among them, by mass percentage, the additives include 30-40% of extinction barium sulfate, 0.3-0.5% of benzoin, 0.5-0.8% of brightening agent, 0.8-1% of leveling agent, 0.5-0.8% of defoaming agent, 0.2-0.4% of conductive agent, 0.1-0.2% of curing accelerator, and 0.6-1% of pigment.

[0025] In the present invention, the leveling agent is a silica adsorbed polyacrylate leveling agent; the brightening agent is an acrylic copolymer containing polar groups; the defoaming agent is micronized polyamide wax; the conductive agent is one or more of castor oil alkanolamide borate, polyamide wax, and fumed alumina; the curing accelerator is one or more of 2-methylimidazole, 2-phenylimidazoline, and ammonium chloride; the pigment is carbon black or titanium white, etc.

[0026] Furthermore, in the present invention, the epoxy resin is bisphenol A type epoxy resin with an epoxy equivalent of 700-900 g / mol;

[0027] The polyester resin is a carboxyl-terminated polyester with an acid value of 45-55 mg KOH / g;

[0028] The acrylic resin is a carboxyl-terminated acrylic resin with an acid value of 140-160 mg KOH / g.

[0029] The above model setting and range setting will cause the epoxy group and the carboxyl group to react to form a stable network structure, and the three work together to balance hardness and impact resistance, so as to achieve the best physical properties and texture effects.

[0030] Specifically, the high crosslinking density of epoxy resin stems from the rapid crosslinking reaction between its epoxy groups and the curing accelerator, forming a three-dimensional network structure. An excessively high epoxy equivalent will lead to a reduction in epoxy groups and insufficient crosslinking density, thereby affecting its mechanical strength. While an excessively low epoxy equivalent is prone to causing overly tight crosslinking, increasing brittleness and affecting its impact resistance. The carboxylic acid groups of the polyester resin react partially with the epoxy groups of the epoxy resin to form an epoxy-polyester interpenetrating network. Its long-chain structure disperses stress, enhancing flexibility and impact resistance. A low ratio of polyester can avoid overly reducing the crosslinking density and maintain the balance between hardness and flexibility. At the same time, the rigid benzene ring of bisphenol A provides a high crosslinking density, and the flexible chain segments of the polyester disperse stress through IPN, enhancing the impact strength. The acrylic resin induces phase separation during curing through surface tension differences, enhancing the matting effect. Moreover, its low melt viscosity improves the powder flowability, reduces coating defects, and enhances surface uniformity.

[0031] Furthermore, in the present invention, the reaction between the polyester resin and the epoxy resin consumes a part of the epoxy resin in a mass ratio of (1 - 1.5):1; the reaction between the acrylic resin and the epoxy resin consumes a part of the epoxy resin in a mass ratio of 1:(1.5 - 2). The sum of the amounts of epoxy consumed by the two is the total amount of epoxy resin used. The reaction rate between the polyester resin and the epoxy resin is greater than the reaction rate between the acrylic resin and the epoxy resin. The present invention utilizes the differential reaction rates of the epoxy resin with the polyester resin and the acrylic resin to form local microphase separation in the crosslinked network, generating a uniform micron-level concave-convex structure, and making the coating surface form a delicate concave-convex texture state similar to that of sand-like powder. Among them, by appropriately increasing the mass of the polyester resin, the reaction is accelerated, and the crosslinked skeleton is preferentially formed. However, if the mass of the polyester resin is too high, the epoxy groups will be consumed prematurely, resulting in insufficient reaction of the acrylic resin and insufficient crosslinking degree of the coating, and a decrease in mechanical strength. The reaction rate between the carboxyl group of the acrylic resin and the epoxy group is relatively slow. Therefore, a higher epoxy ratio is required to ensure the completion of the reaction. If the mass of the acrylic resin is too low, there will be an excess of epoxy groups, and unreacted epoxy groups may remain, leading to brittleness of the coating.

[0032] On the other hand, the present invention provides a preparation method of a skin-friendly matte powder coating based on resin reaction kinetics regulation, comprising the following steps:

[0033] Step 1, put the epoxy resin, polyester resin, acrylic resin and additives into a mixing tank according to the corresponding mass percentages for premixing, ensuring that the dosage ratio of the polyester resin to the epoxy resin is (1 - 1.5):1, the dosage of the acrylic resin to the epoxy resin is 1:(1.5 - 2), and the total feeding amount of the epoxy resin is the sum of the above two parts of epoxy resin. The premixing time is 3 - 5 minutes, the rotation speed is 500 r / min, and the working temperature is 20 - 30 °C;

[0034] Step 2: Use a twin-screw extruder to melt and knead the pre-mixed raw materials to make them evenly dispersed and extruded. Among them, the temperature of the extruder is controlled at 100 - 105 °C, and the screw frequency is controlled at 40 - 50 Hz. Then, carry out tablet pressing and crushing.

[0035] Step 3: Use an ACM mill to classify and crush the crushed materials. The main mill frequency is 25 - 35 Hz, and the secondary mill frequency is 25 - 35 Hz.

[0036] Step 4: Screen and classify the finely ground materials with a standard sieve of 160 - 180 meshes to form powder coatings.

[0037] The following further elaborates on the present invention in combination with embodiments. It should also be understood that the following embodiments are only used to further illustrate the present invention and cannot be construed as limiting the protection scope of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the protection scope of the present invention. The specific process parameters and the like in the following examples are also only an example within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, rather than being limited to the specific values in the following examples.

[0038] Example 1

[0039] This example provides a skin-friendly matte powder coating based on resin reaction kinetics regulation. The powder coating is prepared by the preparation method mentioned above. By mass percentage, the powder coating includes the following components:

[0040] Bisphenol A epoxy resin 34%, carboxyl-terminated polyester resin 14%, carboxyl-terminated acrylic resin 13%, extinctor barium sulfate 36%, benzoin 0.3%, brightening agent 0.7%, leveling agent 1%, defoaming agent 0.6%, conductive agent 0.2%, curing accelerator 0.1%, carbon black 0.8%.

[0041] In this example, the mass ratio of acrylic resin to epoxy resin is 1:1.9, consuming about 25 parts of epoxy resin; the mass ratio of polyester resin to epoxy resin is 1.5:1, consuming about 9 parts of epoxy resin.

[0042] Example 2

[0043] This example provides a skin-friendly matte powder coating based on resin reaction kinetics regulation. The powder coating is prepared by the preparation method mentioned above. By mass percentage, the powder coating includes the following components:

[0044] Bisphenol A epoxy resin 32.2%, carboxyl-terminated polyester resin 10%, carboxyl-terminated acrylic resin 17%, matting barium sulfate 30%, benzoin 0.5%, brightening agent 0.5%, leveling agent 0.8%, defoaming agent 0.5%, conductive agent 0.2%, curing accelerator 0.1%, carbon black 1.0%.

[0045] In this example, the mass ratio of acrylic resin to epoxy resin is 1:1.5, and 25.5 parts of epoxy resin are consumed; the mass ratio of polyester resin to epoxy resin is 1.5:1, and about 6.7 parts of epoxy resin are consumed.

[0046] Example 3

[0047] This example provides a skin-friendly matte powder coating based on the regulation of resin reaction kinetics. The powder coating is prepared by the preparation method mentioned above. By mass percentage, the powder coating includes the following components:

[0048] Bisphenol A epoxy resin 37%, carboxyl-terminated polyester resin 17%, carboxyl-terminated acrylic resin 10%, matting barium sulfate 40%, benzoin 0.4%, brightening agent 0.8%, leveling agent 0.9%, defoaming agent 0.8%, conductive agent 0.2%, curing accelerator 0.1%, carbon black 0.6%.

[0049] In this example, the mass ratio of acrylic resin to epoxy resin is 1:2, and 20 parts of epoxy resin are consumed; the mass ratio of polyester resin to epoxy resin is 1:1, and about 17 parts of epoxy resin are consumed.

[0050] Comparative Example 1 (Traditional sand pattern coating)

[0051] The powder coating provided in this comparative example is prepared by the preparation method mentioned above. By mass percentage, the powder coating includes the following components:

[0052] Epoxy resin 24%, polyester resin 36%, PTFE sand pattern agent 0.3%, matting barium 39%, carbon black 0.8%.

[0053] Comparative Example 2 (High polyester resin quality)

[0054] The difference between the powder coating provided in this comparative example and Example 1 is that, by mass percentage, in this powder coating: the carboxyl-terminated polyester resin is 18%.

[0055] Comparative Example 3 (Low polyester resin quality)

[0056] The difference between the powder coating provided in this comparative example and Example 1 is that, by mass percentage, in this powder coating: the carboxyl-terminated polyester resin is 7%.

[0057] Comparative Example 4 (Low acrylic resin quality)

[0058] The difference between the powder coating provided in this comparative example and that in Example 1 is that, by mass percentage, in this powder coating: the terminal carboxyl group acrylic resin is 10%.

[0059] Comparative Example 5 (high acrylic resin quality)

[0060] The difference between the powder coating provided in this comparative example and that in Example 1 is that, by mass percentage, in this powder coating: the terminal carboxyl group acrylic resin is 25%.

[0061] Performance tests were carried out on the powder coatings prepared through the above-mentioned examples and comparative examples. The tests were respectively carried out from four dimensions: glossiness, touch (surface roughness), mechanical properties (scratch resistance, the number of visible scratches after rubbing with 500 g load steel wool), and environmental friendliness (fluorine content). The test results are shown in Table 1:

[0062] Table 1 Performance test results of powder coatings in examples and comparative examples

[0063]

[0064] From the above test results, it can be seen that for the three groups of powder coatings provided in Example 1, Example 2 and Example 3, through specific resin compatibility ratios, their glossiness, touch and scratch resistance in mechanical aspects are all maintained in a relatively good state.

[0065] Comparative Example 1 uses a traditional sand pattern coating, whose environmental performance is not ideal, the fluorine-containing substances do not meet the requirements of EU environmental protection regulations, and its surface roughness and mechanical properties are relatively poor.

[0066] In Comparative Example 2, the mass of the polyester resin is too high, which will cause the epoxy group to be consumed prematurely, resulting in insufficient reaction of the acrylic resin, insufficient crosslinking degree of the coating, and a decrease in mechanical strength.

[0067] In Comparative Example 3, the mass of the polyester resin is too low. In this comparative example, the advantage of the polyester reaction rate is weakened, and an insufficiently dense initial crosslinking network cannot be formed, resulting in the mixing of the acrylic phase and the polyester phase, and the microphase separation is not obvious, affecting its mechanical strength and surface texture.

[0068] In Comparative Example 4, the mass of the acrylic resin is too low, which will cause an excess of epoxy groups, and there may be residual unreacted epoxy groups, resulting in brittleness of the coating. At the same time, the acrylic phase cannot form an effective filling, making the sand pattern effect not obvious.

[0069] In Comparative Example 5, the mass of the acrylic resin is too high, resulting in insufficient epoxy groups, the difference in reaction rates is reduced, and the uniformity of the phase separation structure is damaged, affecting the surface texture.

[0070] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A skin-feel matte powder coating based on resin reaction kinetics regulation, characterized in that: According to mass percentage, it includes the following components: Epoxy resin 30-40%, polyester resin 10-17%, acrylic resin 10-17%, additives 32-45%.

2. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 1, characterized in that: The epoxy resin is a bisphenol A type epoxy resin, and the epoxy equivalent is 700-900 g / mol.

3. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 1, characterized in that: The polyester resin is a carboxyl-terminated polyester with an acid value of 45 to 55 mg KOH / g.

4. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 1, characterized in that: The acrylic resin is a carboxyl-terminated acrylic resin with an acid value of 140 to 160 mg KOH / g.

5. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 1, characterized in that: The mass ratio of the polyester resin to the epoxy resin is (1-1.5):

1.

6. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 5, characterized in that: The mass ratio of the acrylic resin to the epoxy resin is 1:(1.5-2).

7. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 1, characterized in that: The auxiliary agents include matting barium sulfate, benzoin, brightener, leveling agent, defoamer, conductive agent, curing accelerator and pigment.

8. The skin-feel matte powder coating based on resin reaction kinetics regulation according to claim 7, characterized in that: According to mass percentage, the matting barium sulfate comprises 30-40%, benzoin 0.3-0.5%, brightener 0.5-0.8%, leveling agent 0.8-1%, defoamer 0.5-0.8%, conductive agent 0.2-0.4%, curing accelerator 0.1-0.2% and pigment 0.6-1%.

9. The method for preparing a skin-feel matte powder coating based on resin reaction kinetics control according to any one of claims 1 to 8, characterized in that: The following steps are involved: The epoxy resin, polyester resin, acrylic resin and auxiliary agent are premixed, and the premixed mixture is melted, kneaded evenly, and then tableted, crushed, and graded and sieved to form a powder coating.

10. The method for preparing a skin-feeling matte powder coating based on resin reaction kinetics regulation according to claim 9, characterized in that: A twin-screw extruder is used to melt and mix the premix, wherein the temperature of the extruder is 100-105° C. and the screw frequency is 40-50 Hz.

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