UV-LED curing spraying agent for furniture and preparation method thereof

Abstract

The invention relates to the technical field of epoxy resin, and discloses a UV-LED curing spraying agent for furniture and a preparation method thereof.The spraying agent comprises, by weight, 100 parts of UV curing waterborne epoxy resin, 5-20 parts of sulfydryl waterborne polyurethane, 1.6-2.4 parts of a neutralizing agent, 0.6-1 part of a defoaming agent and 4.2-5.4 parts of a photoinitiator; under the action of a photoinitiator, a large amount of sulfydryl contained in a side chain of waterborne polyurethane and alkenyl in waterborne epoxy resin are subjected to a sulfydryl-alkene light click reaction, chemical crosslinking modification of polyurethane on the epoxy resin is achieved, a flexible polyurethane molecular chain is chemically grafted into the epoxy resin, and an excellent toughening effect is achieved; the flexibility, the impact resistance and the elongation at break of a paint film of the epoxy resin spraying agent are improved. The obtained spraying agent has good practical application in the aspects of furniture, building materials and the like.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy resins, in particular to a UV-LED-cured spray agent for furniture and a preparation method thereof. Background Art

[0002] Epoxy resin has excellent anti-corrosion properties and high mechanical strength, and is widely used in coatings, sprays, adhesives, etc. UV-curable water-based epoxy resin uses water as a solvent, is green and environmentally friendly, and contains chemical olefins, which can be UV-cured, with good curing effect and fast curing speed. Usually, epoxy resin is reacted with acrylic acid to open the ring, olefins and hydroxyl groups are introduced, and the hydroxyl groups react with maleic anhydride to generate carboxyl hydrophilic groups, thereby giving the epoxy resin good water-based and UV-curing properties.

[0003] Traditional UV-curable waterborne epoxy resin has problems such as poor toughness, so it needs to be toughened and modified. Common toughening agents include polyurethane, nitrile rubber, polyacrylate core-shell particles, etc. Patent CN105440252B discloses a UV-curable waterborne polyurethane modified epoxy itaconic acid resin and a preparation method thereof, wherein epoxy resin and itaconic acid are reacted to obtain UV-curable epoxy itaconic acid resin A, which is then reacted with an isocyanate-terminated polyurethane semi-adduct, and the obtained ultraviolet light UV-curable waterborne polyurethane modified epoxy itaconic acid resin has the advantages of good flexibility and green environmental protection. Compared with the modified epoxy itaconic acid resin of the patent, the UV-curable waterborne epoxy resin spraying agent of the present invention has higher tensile strength, elongation at break and other properties. Summary of the invention

[0004] (I) Technical problems to be solved: The present invention solves the problem of poor toughness of epoxy resin.

[0005] (ii) Technical solution: A method for preparing a UV-LED-cured spray for furniture, comprising 100 parts by weight of a UV-curable waterborne epoxy resin, 5-20 parts by weight of a mercapto waterborne polyurethane, 1.6-2.4 parts by weight of a neutralizer, 0.6-1 parts by weight of a defoamer, and 4.2-5.4 parts by weight of a photoinitiator.

[0006] The preparation method comprises the following steps: adding UV-curable waterborne epoxy resin, mercapto waterborne polyurethane, a neutralizer and a defoamer into water, stirring and dispersing the mixture, and then adding a photoinitiator to obtain a UV-LED-curable spray for furniture.

[0007] Preferably, the neutralizing agent is triethylamine, and the photoinitiator is benzoin dimethyl ether or 2-hydroxy-2-methyl-1-phenylpropanone.

[0008] Preferably, the preparation method of the mercapto waterborne polyurethane is:

[0009] (1) Dry and dehydrated polyether polyol, diisocyanate and dibutyltin dilaurate are stirred in a nitrogen atmosphere at 70-75° C. for reaction for 2.5-3 h, then acetone and chloropropyl waterborne chain extender are added, and the mixture is reacted at 40-45° C. for 40-60 min. The acetone is removed by drying to obtain chloropropyl waterborne polyurethane.

[0010] (2) Add chloropropyl waterborne polyurethane to N-methylpyrrolidone, stir and then add potassium thioacetate, stir and react at 15-25°C for 3-6h, add ethanol, precipitate in an ice water bath, filter and add the precipitate to a sodium hydroxide aqueous solution, stir and react at 40-50°C for 5-8h, then add to a hydrochloric acid solution for acidification, wash the product with ethanol, and dry to obtain a mercapto waterborne polyurethane. The preparation reaction mechanism is:

[0011]

[0012] Preferably, the amount of polyether polyol in (1) is 100 parts by weight, the amount of diisocyanate is 42-46 parts by weight, the amount of dibutyltin dilaurate is 0.07-0.08 parts by weight, and the amount of chloropropyl water-based chain extender is 28-33 parts by weight.

[0013] Preferably, the polyether polyol is polyethylene glycol or polypropylene glycol, and the diisocyanate is toluene diisocyanate or isophorone diisocyanate.

[0014] Preferably, the preparation method of the chloropropyl water-based chain extender is: add 100 parts by weight of β-alanine to 208-212 parts by weight of epichlorohydrin, add sodium hydroxide aqueous solution, control the pH of the reaction solution to 8-9, react at 50-55°C for 15-30 minutes, drop concentrated hydrochloric acid to neutralize the solution to pH 7, add saturated sodium chloride solution and dichloromethane, shake and stand for stratification, take the organic layer, concentrate and dry, and obtain the chloropropyl water-based chain extender. The preparation reaction formula is:

[0015]

[0016] Preferably, the amount of chloropropyl waterborne polyurethane in (2) is 100 parts by weight and the amount of potassium thioacetate is 22-30 parts by weight.

[0017] Preferably, the mass fraction of the sodium hydroxide aqueous solution in (2) is 12-15%.

[0018] Preferably, the mass fraction of the hydrochloric acid solution in (2) is 3-5%.

[0019] (III) Technical effect: The present invention utilizes β-alanine and epichlorohydrin to carry out a ring-opening addition reaction to obtain a chloropropyl water-based chain extender, which is then subjected to a polymerization chain extension reaction with a polyether polyol and a diisocyanate to obtain a chloropropyl water-based polyurethane, which is then reacted with potassium thioacetate and hydrolyzed to generate a thiol group to obtain a thiol water-based polyurethane.

[0020] The invention uses UV curing waterborne epoxy resin as a spray film-forming substance and mercapto waterborne polyurethane as a curing crosslinking agent. Under the action of photoinitiators such as 2-hydroxy-2-methyl-1-phenylacetone, a large number of mercapto groups in the side chain of the waterborne polyurethane react with the alkenyl groups in the waterborne epoxy resin to undergo mercapto-alkenyl photoclick reaction, thereby achieving chemical crosslinking modification of the polyurethane to the epoxy resin, chemically grafting the flexible polyurethane molecular chain to the epoxy resin, improving the bonding performance between the two, enabling the polyurethane to play an excellent toughening role, and improving the flexibility, impact resistance and elongation at break of the epoxy resin spray paint film.

[0021] The thiol waterborne polyurethane of the present invention contains a carboxyl hydrophilic group, has good compatibility in the epoxy resin spray agent aqueous solution, excellent dispersibility, no stratification, no precipitation, and good storage stability. It uses water as a solvent, is green, environmentally friendly and pollution-free, and has good practical applications in furniture and building materials. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The epoxy resin model of the present invention is bisphenol A epoxy resin E44, produced by Jinan Yanglan New Material Technology Co., Ltd.

[0024] The preparation method of UV-curable water-based epoxy resin is as follows: 100g of epoxy resin and acrylic acid are mixed in a molar ratio of n (epoxy group): n (acrylic acid) = 1:1, 0.65g of catalyst triethylamine and 0.62g of inhibitor p-hydroxyanisole are added, reacted at 110°C for 5h, cooled, and UV-curable acrylic epoxy resin is obtained.

[0025] 100 g of curable acrylic epoxy resin and maleic anhydride were mixed in a molar ratio of n (hydroxyl group): n (anhydride group) = 1:1, 1.27 g of triethylamine and 0.69 g of inhibitor p-hydroxyanisole were added, the mixture was reacted at 75° C. for 1 h, and the mixture was cooled to obtain a UV-curable waterborne epoxy resin.

[0026] Embodiment 1:

[0027] (1) 5 g of β-alanine was added to 10.6 g of epichlorohydrin, and a 2% by mass sodium hydroxide aqueous solution was added to control the pH of the reaction solution to 8. The reaction was carried out at 50° C. for 30 min, and concentrated hydrochloric acid was added dropwise to neutralize the solution to pH 7. A saturated sodium chloride solution and dichloromethane were added, and the mixture was allowed to stand for stratification after shaking. The organic layer was collected, concentrated and dried to obtain a chloropropyl water-based chain extender.

[0028] (2) 50 g of dried and dehydrated polyethylene glycol 1000, 23 g of isophorone diisocyanate, and 0.035 g of dibutyltin dilaurate were stirred in a nitrogen atmosphere at 70° C. for reaction for 3 h, and then 30 mL of acetone and 15.6 g (56.93 mmol) of a chloropropyl water-based chain extender were added, and the mixture was reacted at 45° C. for 40 min. The acetone was removed by drying to obtain a chloropropyl water-based polyurethane.

[0029] (3) 60 g of chloropropyl waterborne polyurethane was added to 200 mL of N-methylpyrrolidone, and 13.2 g of potassium thioacetate was added after stirring. The mixture was stirred at 20° C. for 3 h, and ethanol was added. The mixture was precipitated in an ice-water bath. After filtering, the precipitate was added to 300 mL of a 12% sodium hydroxide aqueous solution, and stirred at 50° C. for 5 h. The mixture was then added to 200 mL of a 5% hydrochloric acid solution for acidification for 30 min. The product was washed with ethanol and dried to obtain a thiol waterborne polyurethane.

[0030] (4) Add 500 g of UV-curable waterborne epoxy resin, 25 g of mercapto waterborne polyurethane, 8 g of neutralizer triethylamine, and 4 g of defoamer BYK019 to 600 mL of water, stir and disperse, and then add 21 g of photoinitiator 2-hydroxy-2-methyl-1-phenylacetone to obtain a UV-LED-cured spray for furniture.

[0031] Comparative Example 1:

[0032] (1) Prepare chloropropyl waterborne polyurethane according to the method of Example 1.

[0033] (2) Add 500 g of UV-curable waterborne epoxy resin, 25 g of chloropropyl waterborne polyurethane, 8 g of neutralizer triethylamine, and 4 g of defoamer BYK019 to 600 mL of water, stir and disperse, and then add 21 g of photoinitiator 2-hydroxy-2-methyl-1-phenylpropanone to obtain a UV-LED-cured spray for furniture.

[0034] Comparative Example 2:

[0035] (1) 50 g of dried and dehydrated polyethylene glycol 1000, 23 g of isophorone diisocyanate, and 0.035 g of dibutyltin dilaurate were stirred in a nitrogen atmosphere at 70° C. for reaction for 3 h, and then 30 mL of acetone and 7.63 g (56.93 mmol) of 2,2-dimethylolpropionic acid were added and reacted at 45° C. for 40 min. The acetone was removed by drying to obtain a waterborne polyurethane.

[0036] (2) Add 500 g of UV-curable waterborne epoxy resin, 25 g of waterborne polyurethane, 8 g of neutralizer triethylamine, and 4 g of defoamer BYK019 to 600 mL of water, stir and disperse, and then add 21 g of photoinitiator 2-hydroxy-2-methyl-1-phenylacetone to obtain a UV-LED-cured spray for furniture.

[0037] Comparative Example 3

[0038] (1) 50 g of dried and dehydrated polyethylene glycol 1000, 23 g of isophorone diisocyanate, and 0.035 g of dibutyltin dilaurate were stirred in a nitrogen atmosphere at 70° C. for reaction for 3 h, and then 30 mL of acetone and 6.29 g (56.93 mmol) of 3-chloro-1,2-propylene glycol were added and reacted at 45° C. for 40 min. The acetone was removed by drying to obtain chlorinated polyurethane.

[0039] (2) 60 g of chloropolyurethane was added to 200 mL of N-methylpyrrolidone, and 13.2 g of potassium thioacetate was added after stirring. The mixture was stirred at 20° C. for 3 h, and ethanol was added. The mixture was precipitated in an ice-water bath. After filtering, the precipitate was added to 300 mL of a 12% sodium hydroxide aqueous solution, and stirred at 50° C. for 5 h. The mixture was then added to 200 mL of a 5% hydrochloric acid solution for acidification for 30 min. The product was washed with ethanol and dried to obtain a mercapto polyurethane.

[0040] (3) Add 500 g of UV-curable waterborne epoxy resin, 25 g of mercapto polyurethane, 8 g of neutralizer triethylamine, and 4 g of defoamer BYK019 to 600 mL of water, stir and disperse, and then add 21 g of photoinitiator 2-hydroxy-2-methyl-1-phenylacetone to obtain a UV-LED-cured spray for furniture.

[0041] Embodiment 2:

[0042] (1) 5 g of β-alanine was added to 10.4 g of epichlorohydrin, and a 2% by mass sodium hydroxide aqueous solution was added to control the pH of the reaction solution to 9. The reaction was carried out at 55° C. for 15 min, and concentrated hydrochloric acid was added dropwise to neutralize the solution to pH 7. A saturated sodium chloride solution and dichloromethane were added, and the mixture was allowed to stand for stratification after shaking. The organic layer was collected, concentrated and dried to obtain a chloropropyl water-based chain extender.

[0043] (2) 50 g of dried and dehydrated polypropylene glycol 1000, 23 g of isophorone diisocyanate, and 0.04 g of dibutyltin dilaurate were stirred in a nitrogen atmosphere at 70° C. for reaction for 3 h, and then 30 mL of acetone and 16.5 g of a chloropropyl water-based chain extender were added and reacted at 40° C. for 60 min. The acetone was removed by drying to obtain a chloropropyl water-based polyurethane.

[0044] (3) 60 g of chloropropyl waterborne polyurethane was added to 300 mL of N-methylpyrrolidone, and 15.8 g of potassium thioacetate was added after stirring. The mixture was stirred at 15° C. for 6 h, and ethanol was added. The mixture was precipitated in an ice-water bath. After filtering, the precipitate was added to 300 mL of a 15% by mass sodium hydroxide aqueous solution, and the mixture was stirred at 40° C. for 8 h. The mixture was then added to 200 mL of a 3% by mass hydrochloric acid solution for acidification for 60 min. The product was washed with ethanol and dried to obtain a thiol waterborne polyurethane.

[0045] (4) Add 500 g of UV-curable waterborne epoxy resin, 60 g of mercapto waterborne polyurethane, 11 g of neutralizer triethylamine, and 5 g of defoamer BYK019 to 800 mL of water, stir and disperse, and then add 25 g of photoinitiator 2-hydroxy-2-methyl-1-phenylacetone to obtain a UV-LED-cured spray for furniture.

[0046] Embodiment 3:

[0047] (1) Prepare a chloropropyl water-based chain extender according to the method of Example 1.

[0048] (2) 50 g of dried and dehydrated polyethylene glycol, 21 g of toluene diisocyanate, and 0.035 g of dibutyltin dilaurate were stirred in a nitrogen atmosphere at 75° C. for reaction for 2.5 h, and then 30 mL of acetone and 14 g of a chloropropyl water-based chain extender were added and reacted at 40° C. for 60 min. The acetone was removed by drying to obtain a chloropropyl water-based polyurethane.

[0049] (3) 60 g of chloropropyl waterborne polyurethane was added to 300 mL of N-methylpyrrolidone, and 18 g of potassium thioacetate was added after stirring. The mixture was stirred at 25° C. for 5 h, and ethanol was added. The mixture was precipitated in an ice-water bath. After filtering, the precipitate was added to 300 mL of a 12% sodium hydroxide aqueous solution, stirred at 50° C. for 6 h, and then added to 200 mL of a 3% hydrochloric acid solution for acidification for 60 min. The product was washed with ethanol and dried to obtain a thiol waterborne polyurethane.

[0050] (4) Add 500 g of UV-curable waterborne epoxy resin, 100 g of mercapto waterborne polyurethane, 12 g of neutralizer triethylamine, and 5 g of defoamer BYK019 to 800 mL of water, stir and disperse, and then add 27 g of photoinitiator benzoin dimethyl ether to obtain a UV-LED-cured spray for furniture.

[0051] Taking Example 1 as an example, 500 g of UV-curable waterborne epoxy resin, 25 g of mercapto waterborne polyurethane, 8 g of neutralizing agent triethylamine, and 4 g of defoaming agent BYK019 were added to 600 mL of water, and the mixture was stirred and dispersed to obtain a spray. The spray was placed at room temperature in the dark for 30 days to observe the storage stability of the spray solution.

[0052] Spray the spray agent on the surface of the tinplate substrate, irradiate and cure for 3 minutes in a UV-LED curing machine (main wavelength of 365nm, power of 2kW) and dry. Flexibility is tested according to GB / T 1731-2020. Impact resistance is tested according to GB / T 1732-2020.

[0053] Pour the spray into the mold, cure it in a UV-LED curing machine for 5 minutes and dry it, and test the tensile properties according to GB / T1040.1-2018 standard.

[0054] Table 1 Spraying agent performance test

[0055]

[0056] Example 1: A mercapto waterborne polyurethane is used as a crosslinking curing agent, and its side chain contains a large number of mercapto groups. Under the action of the photoinitiator 2-hydroxy-2-methyl-1-phenylacetone, the mercapto groups and the alkenyl groups in the waterborne epoxy resin undergo a mercapto-ene photoclick reaction, thereby achieving chemical crosslinking modification of the epoxy resin by polyurethane, chemically grafting the flexible polyurethane molecular chain to the epoxy resin, improving the bonding performance between the two, making the polyurethane play an excellent toughening role, and improving the flexibility, impact resistance and elongation at break of the epoxy resin spray paint film. In addition, the mercapto waterborne polyurethane contains a carboxyl hydrophilic group, has good compatibility in the epoxy resin spray aqueous solution, excellent dispersibility, and the solution is not stratified and has no precipitation.

[0057] The water-based epoxy resin of the water-based polyurethane in Comparative Example 1 does not contain a thiol group, and cannot undergo a thiol-ene photoclick reaction with the olefin group in the water-based epoxy resin, and cannot achieve chemical cross-linking modification of the epoxy resin by the polyurethane, resulting in poor toughening effect of the polyurethane. The flexibility of the epoxy resin spray paint film is only 3 mm, and the impact resistance and elongation at break are low.

[0058] In Comparative Example 2, conventional 2,2-dimethylolpropionic acid is used as a chain extender. The obtained water-based polyurethane does not contain chloropropyl groups, cannot react with potassium thioacetate to form thiol groups, cannot react with olefin groups in water-based epoxy resins, and cannot achieve chemical crosslinking modification of epoxy resins by polyurethane, resulting in poor toughening effect of polyurethane, flexibility of only 3 mm, and low impact resistance and elongation at break.

[0059] Comparative Example 3 uses 3-chloro-1,2-propylene glycol as a chain extender, and the obtained polyurethane contains chloromethyl, which can react with potassium thioacetate and hydrolyze to generate sulfhydryl. Under the action of the photoinitiator 2-hydroxy-2-methyl-1-phenylacetone, the sulfhydryl can react with the alkenyl in the water-based epoxy resin, so that the polyurethane plays an excellent toughening role, and improves the flexibility, impact resistance and elongation at break of the epoxy resin spray paint film. However, its tensile strength and elongation at break are slightly lower than those in Example 1. It may be that 3-chloro-1,2-propylene glycol contains only one chloromethyl, resulting in less sulfhydryl in the polyurethane, and the cross-linking reaction with the alkenyl in the water-based epoxy resin is insufficient, resulting in poor mechanical properties of the paint film. And the generated sulfhydryl polyurethane does not contain a carboxyl hydrophilic group, has poor compatibility in the epoxy resin spray aqueous solution, poor dispersibility, and the solution has obvious polyurethane precipitates.

[0060] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A UV-LED-cured spray for furniture, characterized in that: The spraying agent comprises 100 parts by weight of UV curable waterborne epoxy resin, 5-20 parts by weight of mercapto waterborne polyurethane, 1.6-2.4 parts by weight of neutralizer, 0.6-1 parts by weight of defoamer, and 4.2-5.4 parts by weight of photoinitiator; The preparation method of the mercapto waterborne polyurethane is: (1) Dry and dehydrated polyether polyol, diisocyanate, and dibutyltin dilaurate are stirred for reaction in a nitrogen atmosphere, and then acetone and a structural formula of A chloropropyl waterborne chain extender is added, and after the reaction, the acetone is removed by drying to obtain a chloropropyl waterborne polyurethane; (2) Adding chloropropyl water-based polyurethane to N-methylpyrrolidone, adding potassium thioacetate after stirring, stirring to react, adding ethanol, precipitating in an ice-water bath, filtering the precipitate, adding it to an aqueous sodium hydroxide solution, adding it to a hydrochloric acid solution after the reaction to acidify, washing the product, and drying to obtain a thiol water-based polyurethane.

2. The UV-LED-cured spray for furniture according to claim 1, characterized in that: The neutralizing agent in (1) is triethylamine, and the photoinitiator is benzoin dimethyl ether or 2-hydroxy-2-methyl-1-phenylacetone.

3. The UV-LED-cured spray for furniture according to claim 1, characterized in that: The reaction in (1) is first carried out at 70-75°C for 2.5-3h, and then at 40-45°C for 40-60min.

4. The UV-LED-cured spray for furniture according to claim 1, characterized in that: The amount of the polyether polyol in (1) is 100 parts by weight, the amount of the diisocyanate is 42-46 parts by weight, the amount of the dibutyltin dilaurate is 0.07-0.08 parts by weight, and the amount of the chloropropyl water-based chain extender is 28-33 parts by weight.

5. The UV-LED-cured spray for furniture according to claim 4, characterized in that: The polyether polyol is polyethylene glycol or polypropylene glycol, and the diisocyanate is toluene diisocyanate or isophorone diisocyanate.

6. The UV-LED-cured spray for furniture according to claim 4, characterized in that: The preparation method of the chloropropyl water-based chain extender comprises the following steps: adding 100 parts by weight of beta-alanine to 208-212 parts by weight of epichlorohydrin, adding a sodium hydroxide aqueous solution, controlling the pH of the reaction solution to be 8-9, reacting at 50-55° C. for 15-30 minutes, dripping concentrated hydrochloric acid to neutralize the solution to pH 7, adding a saturated sodium chloride solution and dichloromethane, shaking and standing to separate layers, taking an organic layer, concentrating and drying, and obtaining the chloropropyl water-based chain extender.

7. The UV-LED-cured spray for furniture according to claim 1, characterized in that: In the above (2), the amount of chloropropyl waterborne polyurethane used is 100 parts by weight, and the amount of potassium thioacetate used is 22-30 parts by weight.

8. The UV-LED-cured spray for furniture according to claim 1, characterized in that: The reaction in (2) is first carried out at 15-25°C for 3-6 hours, and then at 40-50°C for 5-8 hours.

9. The UV-LED-cured spray for furniture according to claim 1, characterized in that: The mass fraction of the sodium hydroxide aqueous solution in (2) is 12-15%, and the mass fraction of the hydrochloric acid solution is 3-5%.

10. A method for preparing a UV-LED-cured spray for furniture according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: adding UV-curable waterborne epoxy resin, mercapto waterborne polyurethane, a neutralizer and a defoamer into water, stirring and dispersing the mixture, and then adding a photoinitiator to obtain a UV-LED-curable spray for furniture.

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