Alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and application

Abstract

The invention provides alcohol-resistant and acid-alkali-resistant acrylic resin, a preparation method and application, and aims to solve the technical problems of high comprehensive cost and poor environmental protection performance of modified acrylic resin in the prior art. The invention relates to an alcohol-resistant, acid-resistant and alkali-resistant acrylic resin as well as a preparation method and application thereof. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin is prepared from the following components in percentage by mass: 15 to 30 percent of fluorine-containing monomer, 22 to 37 percent of siloxane monomer, 4 to 8 percent of functional monomer, 0.05 to 0.15 percent of thermal initiator and 0.05 to 0.1 percent of photoinitiator, the preparation method of the acrylic resin comprises the following steps: carrying out free radical polymerization reaction for 4-8 hours at 50-65 DEG C in an inert atmosphere; after siloxane monomers are added, grafting reaction is carried out under ultraviolet irradiation, and the viscosity is controlled to be 3800-4500 cP; oscillating in a buffer solution with the pH value of 4.5-5.5 at 50-60 DEG C for 12-36 hours to form a core-shell structure; the prepared acrylic resin has alcohol resistance, acid resistance and alkali resistance and is used for preparing environment-friendly water-based ink.

Description

Technical Field

[0001] The present invention relates to the technical field of water-based inks and also to the technical field of acrylic resin modification, and particularly relates to an alcohol- and acid-alkali-resistant acrylic resin, a preparation method and uses thereof. Background Art

[0002] As an environmentally friendly printing material, water-based ink usually consists of a water-dispersible resin matrix, coloring pigments, additives and deionized water. Because its VOC content is significantly lower than that of solvent-based inks, it is widely used in printing scenarios with strict hygiene and safety requirements such as food packaging, pharmaceutical labels and children's toys. Among them, acrylate copolymers have become the mainstream choice for water-based ink resins due to their excellent film-forming properties and water-soluble dispersion characteristics. However, traditional acrylate resins generally have the following technical defects when contacting ethanol-based cleaners or acid-base media: 1) The hydrophilic carboxyl groups (-COOH) in the molecular chain swell in polar solvents, resulting in the destruction of the cross-linking network; 2) The contact angle of non-fluorine-modified resins is insufficient (<90°), and an effective chemical barrier layer cannot be formed. This causes the printed marks to be prone to ink layer peeling or color attenuation during disinfection, transportation and other links, and is more likely to fail especially in the ethanol environment (60% vol) of wine packaging.

[0003] In the technical practice of this field, there have been several explorations on the chemical resistance modification of acrylic resins. For example, Chinese invention patent CN115636897A discloses a graft modification method using octafluoropentyl methacrylate (C5H3F8), and fluorocarbon chain segments are introduced into the resin through a two-step solution polymerization method. However, through industrial verification, this technical solution has the following significant defects: First, the C5H3F8 monomer itself is expensive, and the combined raw material and production cost increases significantly compared with conventional acrylic resins due to the stepwise addition polymerization process; second, this process relies on toluene as a solvent carrier, and benzene series substances remain in the final product, which not only cannot meet the migration limit requirements of food contact materials, but also has the environmental risk of excessive VOCs release.

[0004] Aiming at the above technical limitations, the purpose of the present invention is to prepare a modified acrylic resin by a simple preparation method, so that it can have good alcohol- and acid-alkali-resistant properties, lower comprehensive cost and better environmental protection performance. Summary of the Invention

[0005] The present invention provides an alcohol- and acid-alkali-resistant acrylic resin, a preparation method and uses thereof to solve the technical problems of relatively high comprehensive cost and poor environmental protection performance of modified acrylic resins in the prior art.

[0006] To solve the above technical problems, the present invention adopts the following technical solutions: An alcohol- and acid / alkali-resistant acrylic resin, its preparation method and uses, which by mass percentage include: 15-30% fluorine-containing monomer, 22-37% siloxane monomer, 4-8% functional monomer, 0.05-0.15% thermal initiator and 0.05-0.1% photoinitiator; the preparation method of the acrylic resin is: under an inert atmosphere, carry out free radical polymerization reaction at 50-65°C for 4-8 h; after adding the siloxane monomer, carry out grafting reaction under ultraviolet irradiation, and control the viscosity at 3800-4500 cP; oscillate in a buffer solution with pH 4.5-5.5 at 50-60°C for 12-36 h to form a core-shell structure; the prepared acrylic resin has alcohol- and acid / alkali-resistance and is used for preparing environment-friendly water-based ink.

[0007] Further, the fluorine-containing monomer is a low-fluorine monomer, preferably tetrafluoropropyl methacrylate.

[0008] Further, the siloxane monomer is vinyltrimethoxysilane; the functional monomer is 2-hydroxyethyl methacrylate.

[0009] Further, the mass percentage of tetrafluoropropyl methacrylate is preferably 22%, and the mass percentage of vinyltrimethoxysilane is preferably 30%.

[0010] Further, the thermal initiator is azobis(isobutyramidine) dihydrochloride, and the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide; the working wavelength range of the photoinitiator is 315-400 nm, and the cumulative irradiation dose is 25-30 J / cm2.

[0011] Further, the preparation method of the acrylic resin is as follows: S11: In a nitrogen glove box, add TEPMA, HEMA and V-50 initiator into a reaction kettle containing deionized water, and disperse at a speed of 400 rpm for 30 min; S12: Heat up to 60±0.5°C, turn on mechanical stirring, maintain the nitrogen flow rate at 20 mL / min, and react for 6 h; S13: Cool down to 25°C, add VTMS and Irgacure 819, stir and pre-emulsify for 15 min, turn on the 365 nm UV light source, irradiate under continuous stirring for 1.5 h, and measure the viscosity of the system in real time until it reaches 4200 cP±200 cP; S14: Transfer to a constant temperature oscillator, add a buffer solution with pH = 5, and oscillate at 55°C±1°C for 24 h to obtain a milky semi-transparent dispersion.

[0012] Further, the water-based ink includes: acrylic resin dispersion, dispersant, wetting agent, defoaming agent.

[0013] Furthermore, by mass percentage, it contains: 60 - 70% of acrylic resin dispersion, 2 - 3% of polycarboxylate dispersant, 0.1 - 0.3% of silicone defoamer, and 0.3 - 0.7% of wetting agent.

[0014] Furthermore, the dispersant is BYK - 190, the wetting agent is Surfynol 465, and the defoamer is Tego 8020.

[0015] Furthermore, the preparation method of the water - based ink is as follows: Stir the acrylic resin dispersion at room temperature until it is completely uniform; separately take an independent container to mix the following additives: pre - disperse the BYK - 190 dispersant for 20 min, stir and dissolve Surfynol 465 and then add the Tego 8020 defoamer after mixing; slowly add the well - dispersed acrylic resin dispersion into the above - mentioned mixed solution, with a stirring speed of 400 rpm and a mixing time of 30 min.

[0016] Compared with the prior art, the present invention has the following beneficial effects: a. The present invention uses C3 - F to replace C8 - F, and uses tetrafluoropropyl methacrylate with a shortened carbon chain to greatly reduce the raw material cost. At the same time, it uses siloxane and utilizes the synergistic effect with fluorine - containing monomers to enhance the alcohol - resistance, acid - resistance, and alkali - resistance of the modified acrylate. The number of times it can withstand wiping with 75% ethanol reaches 800 - 1000 times, the number of times it can withstand 5% H2SO4 reaches 180 - 200 times, and the number of times it can withstand 5% NaOH reaches 220 - 250 times. b. The present invention adopts a benzene - free reaction system, with low VOC emissions, PFOA / PFOS detection below the detection limit, avoiding the pollution risk of "forever chemicals", and the heavy metal migration meets the hygiene standards for food - contact materials, and the residual methanol of by - products is lower than the national standard; its green process is conducive to environmental protection and can be safely used in food packaging. c. The present invention adopts a synergistic "one - pot" process of thermal polymerization and photopolymerization. Its overall reaction temperature is relatively low. Compared with the traditional 80 - 120°C, the reaction temperature of the present invention is about 60°C, which has lower energy consumption and is safer in operation. Specific Embodiments

[0017] The technical solutions of the present invention will be described in detail through examples below.

[0018] Based on Patent CN115636897A, by selecting fluorine - containing monomers with low fluorine content to replace high - fluorine monomers, and establishing a composite system through siloxane to maintain the alcohol - resistance, acid - resistance, and alkali - resistance of the acrylic resin. In addition, the preparation process is optimized to reduce steps to meet the requirements of industrial production, thereby reducing the production cost. Example 1

[0019] Experimental reagents: Tetrafluoropropyl methacrylate (TEPMA), industrial grade ≥ 99%; Vinyltrimethoxysilane (VTMS), industrial grade ≥ 98.5%; 2-Hydroxyethyl methacrylate (HEMA), industrial grade ≥ 97%; 2,2'-Azobis(2-methylpropionamidine) dihydrochloride (V-50), industrial grade ≥ 98%; Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure 819), industrial grade ≥ 96%.

[0020] Experimental procedures: S11: In a nitrogen glove box, add TEPMA, HEMA and V-50 initiator into a reaction kettle containing deionized water, and disperse at a speed of 400 rpm for 30 min; S12: Heat up to 60 ± 0.5 °C, start mechanical stirring, maintain the nitrogen flow rate at 20 mL / min, and react for 6 h; S13: Cool down to 25 °C, add VTMS and Irgacure 819, stir for pre-emulsification for 15 min, turn on the 365 nm UV light source, irradiate under continuous stirring for 1.5 h, and measure the viscosity of the system in real time until it reaches 4200 cP ± 200 cP; S14: Transfer to a constant temperature oscillator, add a buffer solution with pH = 5, and shake at 55 °C ± 1 °C for 24 h to obtain a milky translucent dispersion.

[0021] Among them, the dosage of reagents: TFPMA is 22 wt%, VTMS is 30 wt%, HEMA is 5 wt%, V-50 is 0.1 wt%, Irgacure 819 is 0.08 wt%, deionized water is 200 mL, and the buffer solution is 80 mL; The mechanical stirring speed in S12 is 1.2 m / s, the stirring speed in S13 is 200 rpm, and the viscosity is measured with Brookfield DV2T and rotor LV-3; the cumulative irradiation dose in step S13 is 27 J / cm2; an acetic acid-sodium acetate buffer solution is used in step S14.

[0022] After the reaction in step S12, the conversion rate of TEMPA is tested by the iodometric method. The specific operation is as follows: Take 1 g of the reaction solution and add it to a centrifuge tube containing 5 mL of methanol. Add 0.5 g of solid sodium thiosulfate under magnetic stirring to terminate the free radical chain growth. Transfer the terminated sample to a conical flask, add 20 mL of 0.1 mol / L iodine solution, and let it stand in the dark for 30 min. Titrate with 0.05 mol / L sodium thiosulfate solution until it turns light yellow, add 2 mL of starch indicator, and titrate until the blue color disappears as the end point. Record the consumed volume V1. Parallelly determine the blank sample (the unreacted TFPMA stock solution), and record the consumed volume as V0. Through calculation, the conversion rate of TEPMA in this example is 93.2%.

[0023] In this example, thermal polymerization is carried out first, then UV grafting of siloxane is carried out, and finally hydrolysis and condensation are carried out to form a Si-O-Si crosslinked network, forming a core-shell structure to enhance the alcohol and acid-base resistance performance.

[0024] In this example, a tetrafluoro monomer with a shortened carbon chain is used to replace the high-fluorine monomer, and a lower reaction temperature is adopted. Both the raw material cost and the production cost are significantly reduced. Although the experiment in this example is at the laboratory level, it should be understood that when scaled up to industrial production, its production cost and raw material cost will be further reduced. The main manifestations are that the dispersion time in the production process will be shortened by 1 / 3, the nitrogen protection cost will decrease by 60%, the reaction time of S12 can be shortened by 25%, the overall energy consumption can be reduced by more than 80%, and the manual intervention rate is reduced from 15 times / batch to 0.3 times / batch.

[0025] Use the acrylate obtained in this example to prepare water-based ink. The preparation method of the water-based ink is as follows: Stir the acrylate resin prepared above at room temperature until it is completely uniform. Separately take an independent container to mix the following additives: Pre-disperse the BYK-190 dispersant for 20 min, stir and dissolve Surfynol 465 and then add the Tego 8020 defoamer after mixing; Slowly add the dispersed acrylate resin to the above mixture, with a stirring speed of 400 rpm and a mixing time of 30 min.

[0026] Among them, the dosage of each component in the ink is: acrylate resin dispersion 65 wt%, BYK-190 dispersant 2.5 wt%, Tego 8020 defoamer 0.2 wt%, Surfynol 465 wetting agent 0.5 wt%, and the balance is deionized water.

[0027] The environmental protection performance of the acrylate resin obtained in this example is tested. The test contents include: VOC emission test, fluorine pollutants, methanol test, and heavy metal migration amount.

[0028] VOC Release Test: The acrylic resin was coated on a polyester film (dry film thickness: 30 μm), and after curing at 80 °C, a 10 cm² specimen was cut. It was equilibrated in a sealed container at 40 °C for 24 h, and headspace sampling was performed (heated at 80 °C for 30 min). The test results are shown below. Fluorine-containing Pollutant Test: The resin film was subjected to Soxhlet extraction (methanol: water = 80:20, 8 h), and enriched by a C18 solid-phase extraction column. The mobile phase was acetonitrile / 2 mM ammonium acetate (gradient elution), and multiple reaction monitoring (MRM) was used. For PFOA, m / z 413→369, and for PFOS, m / z 499→80. The test results are shown below: By-product Methanol Test: The resin dispersion was distilled, and the distillate was directly injected for GC analysis. The calibration curve range was 1 - 500 mg / L (R² = 0.9998); Test Results: The methanol residue was 0.7 mg / L, lower than the migration limit of GB 31604.1 - 2015 (<5 mg / kg) Heavy Metal Migration Test: The resin film (6 dm²) was immersed in 100 mL of simulated solution (4% acetic acid) (40 °C × 24 h); The test results are as follows. Benzene series, PFOA / PFOS were not detected, and the heavy metal migration amount was far lower than the limit, meeting the requirements for food contact materials; The VOC release amount of 31.5 g / L met the environmental label product certification conditions; The methanol by-product was 0.7 mg / L, and no halogen-containing solvents were used, meeting the green chemical process standards.

[0029] Test Example 1: The alcohol resistance of the water-based ink prepared in Example 1 and the water-based ink prepared from a commercially available water-based acrylic resin was tested. In the control group, except for using a commercially available water-based acrylic resin (Primal E - 3310), the types, dosages, and mixing methods of the other inks were the same as those in the example. In this test example, the wiping method was used to test the durability of the water-based ink under the combined action of dynamic friction and alcohol swelling.

[0030] Test Conditions: Test Procedure: Use an automatic dropping device to add 0.1 mL of alcohol every 20 cycles to keep the test area moist; Replace the new wiping cloth every 50 cycles to avoid fiber wear interfering with the results.

[0031] Termination Conditions: The coating was completely exposed (visible area of the substrate ≥ 3 mm²); or the color difference ΔE ≥ 3.0 (measured under a D65 light source); or the adhesion degraded to ≤ 3B (ASTM D3359).

[0032] Comparison of Test Results: Dynamic swelling rate: The slope of the change in coating thickness with the number of wiping times was measured by a laser confocal microscope (Keyence VK-X3000).

[0033] Due to its crosslinked structure and solvent resistance, the modified acrylate ink has significantly better tolerance to high-concentration ethanol than Primal E-3310 and also has a higher number of tolerance cycles to low-concentration ethanol.

[0034] Test Example 2: This test example was a test of the acid and alkali resistance of the water-based ink prepared from the acrylic resin in Example 1 and the control group. The wiping method was used for the test to measure the acid and alkali resistance of the water-based ink under the combined action of dynamic mechanical friction and chemical corrosion.

[0035] Test conditions: Test procedure: Immerse the cotton cloth completely in the acid-base solution for 10 seconds, take it out and control the liquid content to 300 ± 10% by the roller pressing method; fix the impregnated cotton cloth to the friction head to ensure complete contact with the coating surface; make one round trip (i.e., one round trip of the friction head is recorded as one cycle); stop the machine after every 50 cycles, replace the new cotton cloth and replenish the solution.

[0036] Termination conditions: There is continuous exposure of the base material (visible base material) with an area ≥ 3 mm² on the coating; or the adhesion grade drops from the initial 5B to ≤ 3B.

[0037] Comparison of test results: Dynamic corrosion rate: The decrease value of the coating thickness with the number of wiping times was measured by a white light interferometer (Wyko NT9100), and the linear relationship was fitted and calculated.

[0038] It can be clearly seen from the wiping method test that the modified acrylate ink has significantly better tolerance in a dynamic acid-base corrosion environment than Primal E-3310 ink, and is especially suitable for scenarios such as industrial labels and medical device markings that require frequent contact with cleaning agents. Example 2

[0039] On the basis of Example 1, the dosages of TFPMA / VTMS were adjusted to test the effects on alcohol and acid-base resistance. The group number of Example 1 was 1-1. The alcohol and acid-base resistance of Example 2 were tested using the methods of Test Example 1 and Test Example 2, and the comparison results are as follows. Result analysis: In Group 1-1, the fluorine content is relatively high and VTMS provides moderate crosslinking, with extremely strong hydrophobicity and a balance of anti-permeability and mechanical strength; in Group 2-1, the fluorine content is relatively insufficient and is not enough to resist ethanol swelling; in Group 2-2, although the fluorine content is the highest, the degree of crosslinking is decreasing, which may lead to cracking under local stress.

[0040] For the comparison of acid and alkali resistance performance, the acid and alkali resistance performance is classified, and the results are compared through classification. Grade A: The film layer has no color change, no blistering, and the adhesion retention rate ≥ 95%; Grade B: Slight color change (ΔE < 1.5), adhesion retention rate ≥ 80%; Grade C: Obvious corrosion (blistering / peeling). Result analysis: The Si-O-Si network formed by a high VTMS content can effectively block the penetration of ions, thus having better acid and alkali resistance; and the addition of fluorine elements further promotes its acid and alkali resistance.

Claims

1. An alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, a preparation method and use thereof, characterized in that: The acrylic resin comprises, by mass percentage, 15-30% of a fluorine-containing monomer, 22-37% of a siloxane monomer, 4-8% of a functional monomer, 0.05-0.15% of a thermal initiator and 0.05-0.1% of a photoinitiator. The preparation method of the acrylic resin is as follows: a free radical polymerization reaction is carried out at 50-65°C for 4-8 hours under an inert atmosphere; after adding the siloxane monomer, a grafting reaction is carried out under ultraviolet light irradiation, and the viscosity is controlled at 3800-4500 cP; the acrylic resin is oscillated at 50-60°C for 12-36 hours in a buffer solution of pH 4.5-5.5 to form a core-shell structure; the prepared acrylic resin is resistant to alcohol and acid and alkali and is used to prepare environmentally friendly water-based inks.

2. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 1, characterized in that: The fluorine-containing monomer is a low-fluorine monomer, preferably tetrafluoropropyl methacrylate.

3. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 2, characterized in that: The siloxane monomer is vinyl trimethoxy silane; and the functional monomer is hydroxyethyl methacrylate.

4. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 3, characterized in that: The mass percentage of the tetrafluoropropyl methacrylate is preferably 22%, and the mass percentage of the vinyltrimethoxysilane is preferably 30%.

5. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 4, characterized in that: The thermal initiator is azobisisobutylamidine hydrochloride, and the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; the working band of the photoinitiator is 315-400nm, and the cumulative irradiation amount is 25-30J / cm 2 .

6. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 5, characterized in that: The preparation method of the acrylic resin is: S11: In a nitrogen glove box, TEPMA, HEMA and V-50 initiator were added into a reactor containing deionized water and dispersed at 400 rpm for 30 min; S12: Raise the temperature to 60±0.5℃, start mechanical stirring, maintain nitrogen flow rate at 20mL / min, and react for 6h; S13: Cool down to 25°C, add VTMS and Irgacure 819, stir and pre-emulsify for 15 minutes, turn on the 365nm UV light source, irradiate for 1.5 hours under continuous stirring, and measure the viscosity of the system in real time until it reaches 4200cP±200cP; S14: Transfer to a constant temperature oscillator, add a buffer solution with pH = 5, and oscillate at 55°C ± 1°C for 24 hours to obtain a milky white translucent dispersion.

7. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 1, characterized in that: The water-based ink comprises: acrylic resin dispersion, dispersant, wetting agent and defoaming agent.

8. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 7, characterized in that: The composition comprises, by mass percentage, 60-70% acrylic resin dispersion, 2-3% polycarboxylate dispersant, 0.1-0.3% organosilicon defoamer, and 0.3-0.7% wetting agent.

9. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 8, characterized in that: The dispersant is BYK-190, the wetting agent is Surfynol 465, and the defoaming agent is Tego 8020.

10. The alcohol-resistant, acid-resistant and alkali-resistant acrylic resin, preparation method and use according to claim 9, characterized in that: The preparation method of the water-based ink is as follows: stirring the acrylic resin dispersion at room temperature until it is completely uniform; mixing the following additives in another independent container: pre-dispersing BYK-190 dispersant for 20 minutes, stirring and dissolving Surfynol 465, and then adding Tego 8020 defoamer after mixing; slowly adding the dispersed acrylic resin dispersion into the above mixed solution, stirring at a speed of 400 rpm, and mixing for 30 minutes.