Preparation method of ultraviolet curing modified coating

Abstract

The invention discloses a preparation method of an ultraviolet curing modified coating, which comprises the following steps: synthesizing PUA and an organic silicon prepolymer, compounding the three prepolymers in the presence of an emulsifier, and initiating crosslinking curing of the prepolymers through a photoinitiator. Organosilicone acrylate is good in low-temperature performance, resistant to heat and hydrophobic, but poor in mechanical performance; polyurethane acrylate is good in elasticity and soft, but not high in strength; epoxy acrylate is high in strength and good in adhesion to glass, but high in modulus and poor in low-temperature performance, and by combining the three kinds of resin according to a proper proportion, the defect that the performance of single resin is poor is overcome. The viscosity, curing speed, hardness, glass transition temperature and other performance parameters are wide, and the expected performance can be achieved by properly adjusting the proportion. The light-cured resin with excellent performance is formed and has the characteristics of wear resistance, yellowing resistance, high temperature resistance and high curing speed.

Description

Technical Field

[0001] The present invention relates to the technical field of light curing, and in particular to a method for preparing an ultraviolet light curing modified coating. Background Art

[0002] UV-curable coatings offer numerous advantages, such as ease of use and rapid curing. However, they also have significant performance deficiencies that require continuous improvement. These include curing being hindered by oxygen in the air, poor coating flexibility, and weak adhesion to substrates. Building on previous research, this present invention investigates the curing mechanisms of polyurethane acrylate, silicone MQ resin, and epoxy acrylate resin (EA) under UV light, focusing on both prepolymer composition and UV curing conditions. The aim is to identify the optimal combination and ratio of coating prepolymers for UV curing, aiming to develop a UV-curable system that rapidly cures in air without compromising the coating's excellent properties. Excess diisocyanate first reacts with a polyol to extend the chain, producing molecules with a higher molecular weight. Hydroxyalkyl acrylate is then added to the reaction to produce a dicapped PUA prepolymer. The acrylate enters the reaction system relatively late, resulting in a relatively short residence time. Half the reaction heat is released before the addition of the acrylate, significantly reducing double-bond free radical polymerization and significantly improving adhesion.

[0003] The reaction process is sensitive to temperature, and the preparation process needs to control temperature fluctuations. The operations in the relevant stages are relatively complicated:

[0004] 1. During the prepolymer synthesis preparation stage, isocyanate and polyether polyol react violently. After the two are mixed, the temperature of adding the catalyst should be controlled. If the reaction temperature is too high, cross-linking will be generated to form a resin with a higher molecular weight, resulting in a wider molecular weight distribution of the resin. After the chain extension is completed, the end-capping reaction is carried out, and the reaction is mild.

[0005] 2. Emulsification and compounding stage of prepolymer.

[0006] During the compounding process, attention should be paid to the order of adding materials and the speed of adding materials should not be too fast. Under the action of the emulsifier, the system will have a wrapping process to form certain micelles. If the compounding effect is good at this stage, the molecular weight of the subsequent photocuring will be uniform and the mechanical properties will be excellent. Summary of the Invention

[0007] In order to solve the problems mentioned in the above background technology, the present invention provides a method for preparing a UV-curable resin, which obtains a coating with relatively complete performance by compounding three prepolymers. Since the structure of PUA is very easy to adjust, the performance variation range is relatively wide, and it can be designed as a high-strength or high-toughness structure; the cost of EA is relatively low, because EA usually contains a benzene structure and has greater rigidity; MQ resin has higher strength, faster curing speed, and lower glass transition temperature. By adjusting the mixing ratio and emulsifying the three prepolymers, a chemical curing method is used to form a three-dimensional network structure film at room temperature through a chemical cross-linking reaction. In the present invention, the coating prepolymer undergoes chemical curing and is cured by double bond cross-linking. The comprehensive performance of the coating is improved, such as water permeability, glass strength, curing speed, viscosity and fracture growth rate.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] The specific preparation method of UV-curable modified coating is as follows:

[0010] 1. PUA prepolymer modification synthesis stage:

[0011] S1. Add IPDI into a three-necked flask and stir evenly. Use a constant pressure dropper. All equipment must be dried before use.

[0012] S2, add PPG4000 to S1 and stir evenly, heat to 40℃, and add DBTDL catalyst when the temperature reaches 40℃;

[0013] S3. Continue heating to 45°C and keep the reaction for 2 hours. Take samples to test the NCO value. If the NCO value is between 1.7% and 1.9%, proceed to the next step. If it is greater than 1.9, take samples every 30 minutes to measure the NCO value until it reaches between 1.7% and 1.9%. If it is less than 1.7%, repeat from S1.

[0014] S4. After passing the test, add 2,6-di-tert-butylphenol (BHT) as polymerization inhibitor, and add HEA and HPA using a constant pressure dropper for 40 minutes;

[0015] S5. Raise the temperature to 75°C, keep the temperature for reaction for 3 hours, take samples every 30 minutes to measure the NCO value, and when the measured value is less than 0.03%, the preparation of PUA prepolymer is completed;

[0016] 2. Preparation stage of compound prepolymer:

[0017] S6. Cool the prepolymer prepared in S5 to 50°C, then add 2‰ of the mass of the synthesized prepolymer, Disponil A 3065 emulsifier, introduce nitrogen gas at 1 L / min, stir evenly, and then slowly add a certain amount of silicone MQ resin and / or epoxy acrylate EA resin according to the specific application ratio, maintaining the temperature at 57±2°C;

[0018] 3. Preparation stage of coating:

[0019] S7, after stirring, slowly add diluent, then add silicone acrylate, 3g of 2,4,6-trimethylbenzoyl diphenyl phosphine oxide (TPO);

[0020] S8. After all the dissolution is completed, keep warm at 60℃ for 2 hours and filter the material with a 300-mesh filter cloth.

[0021] The prepolymer of the present invention is prepared by firstly carrying out a chain extension reaction and then carrying out an end-capping reaction.

[0022] Preferably, the compound prepolymer is formed by compounding PUA resin and MQ resin in a mass ratio of 6:1.

[0023] Preferably, the compound prepolymer is formed by compounding PUA resin and EA resin in a mass ratio of 5:1.

[0024] Preferably, the compound prepolymer is formed by compounding PUA resin, MQ resin and EA resin in a mass ratio of 7:1:2.

[0025] Preferably, the diluent in S7 is a mixture of vinyl pyrrolidone (NVP) and tripropylene glycol diacrylate (TPGDA) in a mass ratio of 1:1.

[0026] Preferably, the entire preparation process needs to be carried out in the dark, as light will cause the coating to crosslink and solidify.

[0027] The preparation mechanism of PUA is as follows:

[0028]

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] PUA and silicone prepolymers are first synthesized, then compounded in the presence of an emulsifier, and crosslinked and cured using a photoinitiator. Silicone acrylates offer excellent low-temperature performance, heat resistance, and hydrophobicity, but suffer from poor mechanical properties; polyurethane acrylates offer excellent elasticity and flexibility, but low strength; and epoxy acrylates offer high strength and good glass adhesion, but high modulus and poor low-temperature performance. By combining these three resins in appropriate proportions, the shortcomings of individual resins are overcome.

[0031] Its performance parameters, such as viscosity, curing speed, hardness, and glass transition temperature, are relatively wide, and the desired performance can be achieved by appropriately adjusting the ratio. This results in a superior light-curable resin with enhanced wear resistance, yellowing resistance, high temperature resistance, and rapid curing speed. This performance has applications in a wide range of fields, such as wood, plastics, metal, and optical fiber. This method offers a safe, stable, and environmentally friendly production process, making it an environmentally friendly coating.

[0032] The present invention has a fast curing speed and can complete all curing in a relatively short time without reducing the product performance. Since the mechanization speed is already very high now, the curing speed can determine the level of output. The environmental performance is good. The present invention does not volatilize solvents during curing and is an environmentally friendly polymer material. The present invention has excellent performance and good adjustability. It is a compounded light-curing resin with good mechanical properties, such as high hardness, wear resistance and high flexibility. At the same time, it has good chemical stability and resistance to corrosion by organic solvents such as acids and alkalis. Since it is compounded, more performance requirements can be met by adjusting the compounding ratio. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0035] Example 1

[0036] Prepolymer system with PUA and MQ (6:1)

[0037] Add 45g of IPDI to a dried three-necked flask with stirring, and add 410g of PPG4000 dropwise at normal pressure using a constant pressure dropping device at a dropping rate of 8.2g / min. Raise the temperature to 40℃, add 0.2g of DBTDL catalyst when the temperature reaches 40℃, raise the temperature to 45℃ and start timing. After keeping the temperature for 2h, take samples to test the NCO value. If the NCO value is between 1.7% and 1.9%, proceed to the next step; if it is greater than 1.9, take samples every 30 minutes to measure the NCO value until it reaches between 1.7% and 1.9%. After the reaction reaches the corresponding range, add 0.2g of 2,6-di-tert-butylphenol (BHT) as a polymerization inhibitor, and add 13.2g of HEA and 15g of HPA using a constant pressure dropper for 40 minutes; raise the temperature to 75°C, keep the temperature for reaction for 3 hours, and then take samples every 30 minutes to measure the NCO value. When the measured value is less than 0.03%, the prepolymer preparation is complete;

[0038] The prepolymer prepared above was cooled to 50°C, 360g was taken out and added to another clean three-necked flask, stirred and kept warm at 50°C, then 0.72g of emulsifier Disponil A 3065 was added, nitrogen was introduced into the liquid at 1 L / min, and after stirring evenly, 60g of silicone MQ resin was slowly added, maintaining the temperature at 57±2°C. After stirring evenly, 72g each of diluent NVP and TPGDA were slowly added dropwise, followed by 1g of leveling agent and 3g of TPO; after all the dissolution was completed, the mixture was kept warm at 60°C for 2 hours, and the material was filtered with a 300-mesh filter cloth to obtain the prepared UV-curable modified coating.

[0039] Example 2

[0040] Prepolymer system with PUA and EA (5:1)

[0041] Add 45g of IPDI to a dried three-necked flask with stirring, and add 410g of PPG4000 dropwise at normal pressure using a constant pressure dropping device at a dropping rate of 8.2g / min. Raise the temperature to 40°C. When the temperature reaches 40°C, add 0.2g of DBTDL catalyst. Raise the temperature to 45°C and start timing. Keep the temperature at 45°C for 2h, then take samples to test the NCO value. If the NCO value is between 1.7% and 1.9%, proceed to the next step; if it is greater than 1.9, take samples every 30 minutes to measure the NCO value until it reaches between 1.7% and 1.9%. After the reaction reaches the corresponding range, add 0.2g of 2,6-di-tert-butylphenol (BHT) as a polymerization inhibitor, and add 13.2g of HEA and 15g of HPA using a constant pressure dropper for 40 minutes; raise the temperature to 75°C, keep the temperature for reaction for 3 hours, and then take samples every 30 minutes to measure the NCO value. When the measured value is less than 0.03%, the prepolymer preparation is complete;

[0042] The prepolymer prepared above was cooled to 50°C, 350g was taken out and added to another clean three-necked flask, stirred and kept warm at 50°C, then 0.7g of emulsifier Disponil A 3065 was added, nitrogen was introduced into the liquid at 1 L / min, and after stirring evenly, 70g of epoxy acrylate EA resin was slowly added, maintaining the temperature at 57±2°C. After stirring evenly, 72g of diluent NVP and TPGDA were slowly added dropwise, followed by 1g of leveling agent and 3g of TPO; after all the dissolution was completed, the mixture was kept warm at 60°C for 2 hours, and the material was filtered with a 300-mesh filter cloth to obtain the prepared UV-curable modified coating.

[0043] Example 3

[0044] Prepolymer system of PUA, MQ and EA (7:1:2)

[0045] Add 45g of IPDI to a dried three-necked flask with stirring, and add 410g of PPG4000 dropwise at normal pressure using a constant pressure dropping device at a dropping rate of 8.2g / min. Raise the temperature to 40°C. When the temperature reaches 40°C, add 0.2g of DBTDL catalyst. Raise the temperature to 45°C and start timing. Keep the temperature at 45°C for 2h, then take samples to test the NCO value. If the NCO value is between 1.7% and 1.9%, proceed to the next step; if it is greater than 1.9, take samples every 30 minutes to measure the NCO value until it reaches between 1.7% and 1.9%. After the reaction reaches the corresponding range, add 0.2g of 2,6-di-tert-butylphenol (BHT) as a polymerization inhibitor, and add 13.2g of HEA and 15g of HPA using a constant pressure dropper for 40 minutes; raise the temperature to 75°C, keep the temperature for reaction for 3 hours, and then take samples every 30 minutes to measure the NCO value. When the measured value is less than 0.03%, the prepolymer preparation is complete;

[0046] The prepolymer prepared above was cooled to 50°C, 294g was taken out and added to another clean three-necked flask, stirred and kept warm at 50°C, then 0.588g of emulsifier Disponil A 3065 was added, nitrogen was introduced into the liquid at 1 L / min, and after stirring evenly, 42g of silicone MQ resin and 84g of epoxy acrylate EA resin were slowly added, maintaining the temperature at 57±2°C. After stirring evenly, 72g of diluent NVP and TPGDA were slowly added dropwise, followed by 1g of leveling agent and 3g of TPO; after all the dissolution was completed, the mixture was kept warm at 60°C for 2 hours, and the material was filtered with a 300-mesh filter cloth to obtain the prepared UV-curable modified coating.

[0047] Performance testing and comparative experiments

[0048] (1) Determine the curing speed of the sample

[0049] The filtered coating was applied to a tinplate substrate to a 100 μm film thickness using a 1000W medium-pressure mercury lamp with an 80W / cm2 lamp at a distance of 12 cm. The time required for the coating to no longer feel sticky was measured. The results are shown in Table 1.

[0050] Table 1 Sample curing speed test results

[0051] Test samples Example 1 Example 2 Example 3 Imported UV-curing coating (Arkema product PRO33918) Domestic UV-curing coating (DIC's product V-4025-ZS) Curing time / s 20 8 10 9 12

[0052] (2) Determination of sample tensile properties and elongation at break

[0053] The coating was poured into a standard tensile mold and cured. After curing, the specimen was removed and placed at room temperature for 24 hours. The tensile strength and elongation at break of the coating were measured using a universal material testing machine at a tensile rate of 60 mm / min. The test results are shown in Table 2:

[0054] Table 2 Test results of tensile strength and elongation at break of samples

[0055] Test samples Example 1 Example 2 Example 3 Imported UV-curing coating (Arkema product PRO33918) Domestic UV-curing coating (DIC's product V-4025-ZS) Tensile strength / Mpa 35 73 61 63 67 Elongation at break / % 202 73 145 143 148

[0056] (3) Determine the glass transition temperature of the sample

[0057] Take 3-8 mg of the coating cured on the tinplate substrate, grind it into powder, add it to the sample crucible, and place the crucible in the sample cell of the DSC instrument. The heating rate is 5-20℃ / min. The instrument records the DSC curve of the heat flow difference between the sample and the reference as a function of temperature or time. The glass transition temperature is shown in Table 3.

[0058] Table 3 Glass transition temperature test results of samples

[0059] Test samples Example 1 Example 2 Example 3 Imported UV-curing coating (Arkema product PRO33918) Domestic UV-curing coating (DIC's product V-4025-ZS) Glass transition temperature / ℃ 55 187 138 140 137

[0060] (4) Determination of yellowing and aging properties of samples

[0061] The oven aging method was used to cure the coating into a sample and place it in an oven. Different temperature gradients were set and the yellowing temperature values ​​were shown in Table 4.

[0062] Table 4 Yellowing temperature of samples

[0063] Test samples Example 1 Example 2 Example 3 Imported UV-curing coating (Arkema product PRO33918) Domestic UV-curing coating (DIC's product V-4025-ZS) Yellowing temperature ±0.5 (℃) 160 110 160 140 130

[0064] Comparison of the above test results highlights the excellent usability and strong plasticity of Example 3 in terms of cure speed, tensile properties and elongation at break, glass transition temperature, and yellowing and aging performance. These performance parameters can be further optimized with appropriate compounding ratios. The present invention fully utilizes the excellent properties of the silicone resin, polyamino acrylic resin, and epoxy acrylic resin, resulting in a polymer resin with high durability under various environments.

[0065] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a UV-curable modified coating, characterized in that: The following steps are involved:

1. PUA prepolymer modification synthesis stage: S1. Add IPDI into a three-necked flask and stir evenly, equipped with a constant pressure dropper; S2. Add PPG4000 to S1 and stir evenly. When the temperature reaches 40°C, add DBTDL catalyst. S3. Continue heating to 45°C and keep the temperature for 2 hours. Take samples to test the NCO value. If it meets the qualified standard, proceed to the next step. If it fails, take samples every 30 minutes to measure the NCO value until it meets the standard. S4. After passing the test, add HEA, HPA and BHT inhibitor; S5. After heating to 75°C and reacting for 3 hours, take samples every 30 minutes to measure the NCO value. When the measured value is less than 0.03%, the preparation of the PUA prepolymer is completed; 2. Preparation stage of compound prepolymer: S6. Cool the PUA prepolymer in S5 to 50°C, add a nonionic emulsifier, introduce nitrogen into the liquid, stir evenly, and then slowly add a certain proportion of silicone MQ resin and / or epoxy acrylate EA resin, maintaining the temperature at 57±2°C; 3. Preparation stage of coating: S7. After stirring evenly, slowly add diluent, leveling agent, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; S8. After all the dissolution is completed, keep warm at 60℃ for 2 hours and filter the material with a 300-mesh filter cloth.

2. The method for preparing a UV-curable modified coating according to claim 1, wherein: The compound prepolymer is formed by compounding PUA resin and MQ resin in a mass ratio of 6:

1.

3. The method for preparing a UV-curable modified coating according to claim 1, wherein: The compound prepolymer is formed by compounding PUA resin and EA resin in a mass ratio of 5:

1.

4. The method for preparing a UV-curable modified coating according to claim 1, wherein: The compound prepolymer is prepared by compounding PUA resin, MQ resin and EA resin in a mass ratio of 7:1:

2.

5. The method for preparing a UV-curable modified coating according to claim 1, wherein: The leveling agent in S7 is silicone acrylate.

6. The method for preparing a UV-curable modified coating according to claim 1, wherein: The diluent in S7 is a mixture of vinyl pyrrolidone and tripropylene glycol diacrylate in a mass ratio of 1:

1.

7. The method for preparing a UV-curable modified coating according to claim 1, wherein: The entire preparation process needs to be carried out in the dark, as light will cause the coating to crosslink and solidify.

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