Stain-resistant odorless water-based acrylate emulsion and preparation method thereof

Abstract

The invention discloses a stain-resistant odorless water-based acrylate emulsion and a preparation method thereof, the odorless water-based acrylate emulsion comprises the following main components: synthetic wax and modified polyacrylate of which the side chain contains imidazole and derivative groups thereof, and the odorless water-based acrylate emulsion has strong cohesion, good stability, strong stain resistance and high transparency after film formation; in the synthesis process, imidazole and a derivative thereof are subjected to an addition reaction with residual acrylate monomers to generate an odorless, odorless, non-volatile and low-surface-tension compound which is used as an efficient base material wetting agent to obviously improve the wettability of an emulsion to a base material, and meanwhile, as an interface agent, one end of the compound tightly acts on the base material to improve the surface tension of the emulsion. And a small amount of polyethylene wax is added in the emulsification process to form synthetic wax, so that the effect of the fatting agent can be improved, and the surface antifouling and oil-resistant effects are achieved.

Description

Technical Field

[0001] This invention belongs to the field of water-based coatings technology, specifically relating to a stain-resistant and odor-neutralizing water-based acrylic emulsion and its preparation method. Background Technology

[0002] With increasing environmental awareness, low-VOC (VOC, volatile organic compounds; "low-VOC" refers to paints with low VOC content, commonly known as environmentally friendly products) and even zero-VOC, non-toxic, and pollution-free new materials have gained widespread recognition and rapid development. Water-based coatings have therefore become highly sought after. Water-based coatings are made by adding water-based additives and pigments to water-based emulsions using water as a carrier. They have high surface tension, making them unsuitable for both indoor and outdoor use due to poor surface stain resistance and weak adhesion to substrates, severely impacting the coating's aesthetics. During the synthesis of water-based emulsions, as the reaction rate increases, the effects of cage effect, glass transition effect, and monomer competition rate become increasingly significant, inhibiting further monomer polymerization. Furthermore, the low concentration of free monomers significantly reduces the probability of collisions with free radicals. Therefore, conventional water-based emulsions contain a certain amount of monomers, resulting in an unpleasant odor, affecting emulsion performance, and potentially harming consumer health.

[0003] To improve the spreadability and stain resistance of water-based coatings on substrates, researchers often add wetting agents with low surface tension to enhance the adhesion of water-based coatings to substrates. However, for certain substrates, such as polyethylene, polypropylene, or substrates containing release agents, adding wetting agents still cannot meet customer needs.

[0004] Another approach is to introduce low surface tension groups, such as organosilicon segments, during the synthesis process to reduce the interfacial tension of latex particles and improve stain resistance. However, since latex particles spread and diffuse on the substrate surface less rapidly than small molecule wetting agents, some substrates, especially those with a large number of micropores or depressions on the surface, do not have good stain resistance.

[0005] Technicians have developed various methods to remove monomer residues: distillation, stripping, initiator addition, redox system, and alkaline substance conversion.

[0006] (1) Distillation and stripping methods are methods of distilling or steam extraction to volatilize monomers into the system. Both require a large amount of heat and extend the production cycle. At the same time, since both require operation at high temperatures, they have a certain impact on the performance of the emulsion and the effect is not good.

[0007] (2) The method of adding initiator in the later stage increases the concentration of free radicals in the system to achieve full polymerization. Since there are not many residual monomers, if too much initiator is added, it may not be completely decomposed within the limited reaction time and remain in the system, which may have a great impact on the later performance and storage stability of the emulsion.

[0008] (3) The redox system method involves adding oxidants and reductants to generate free radicals through redox reactions, thereby increasing the free radical concentration and reducing monomer residues. Compared to the initiator addition method, the redox system method can ultimately achieve a solution without oxidants and reductants, having little impact on the later performance and storage stability of the emulsion. This method is now the standard for most emulsion synthesis processes. Commonly used redox systems include hydrogen peroxide-sodium formaldehyde sulfoxylate, tert-butyl hydrogen peroxide-sodium formaldehyde sulfoxylate, tert-butyl hydrogen peroxide-FF6M, hydrogen peroxide-ascorbic acid, and hydrogen peroxide-sodium bisulfite. However, due to the short lifespan of the free radicals generated by the redox system, their reaction efficiency with residual monomers is low, often failing to completely eliminate residual monomers and affecting product quality.

[0009] (4) The alkaline reaction method utilizes the addition reaction between alkaline substances and the double bonds in acrylic acid monomers to combine the acrylic acid monomers with the alkaline substances, thereby eliminating odors. Commonly used alkaline substances include ammonia, organic amines, and hydrazine hydrate. Ammonia and organic amines require very high temperatures to react with residual monomers in the system, which may cause problems such as emulsion bursting and demulsification, and cannot completely eliminate residual monomers. Hydrazine hydrate has high reactivity with acrylate monomers under heating conditions and has a better effect, but due to the high toxicity and volatility of hydrazine hydrate itself, improper storage may cause serious consequences such as explosions. Furthermore, residual hydrazine hydrate cannot be removed from the system by conventional separation methods, and the dosage must be accurate during post-emulsion polymerization treatment. In practical applications, large-scale mass production cannot be achieved.

[0010] Therefore, research on stain-resistant and odor-neutralizing water-based acrylic emulsions has a promising market prospect. Summary of the Invention

[0011] The purpose of this invention is to provide a stain-resistant and odor-neutralizing water-based acrylic emulsion and its preparation method. The post-processing of the obtained stain-resistant and odor-neutralizing water-based acrylic emulsion is simple, green and efficient.

[0012] The stain-resistant and odor-neutralizing water-based acrylic emulsion of this invention is composed of compounds with the following general structural formula:

[0013]

[0014] Where af is a degree of aggregation value: a = integer from 0 to 200, b = integer from 0 to 200, c = integer from 0 to 200, d = integer from 0 to 200, e = integer from 20 to 125, f = integer from 20 to 125, and at most one of a, b, c, and d is allowed to be 0;

[0015] R1-R4 are combinations of several of H, methyl, ethyl, 1-butyl, and 2-ethyl-1-hexyl, with only one of them being H, and when the substituent is H, the corresponding degree of polymerization is an integer between 5 and 30.

[0016] R5-R8 are combinations of one or both of H and methyl;

[0017] R9 is One of them.

[0018] This invention also relates to a method for preparing the above-mentioned stain-resistant and odor-neutralizing water-based acrylic emulsion, comprising the following steps:

[0019] 1) By molar amount, 1 part of allyl acrylate and 1.05-1.13 parts of imidazole or imidazole derivative are stirred evenly under nitrogen protection, 0.05-0.10 parts of catalyst and 0.03-0.05 parts of co-catalyst are added, the temperature is raised to 40-60℃, kept at the temperature for 3-8 hours, and then cooled to 15-25℃ to obtain allyl imidazole modified propionate.

[0020] 2) Mix 4-30 parts of acrylate by weight until homogeneous to obtain a monomer composition;

[0021] Dissolve 0.1-0.8 parts of emulsifier in 4-40 parts of deionized water. After complete dissolution, add 10-15 parts of synthetic wax and monomer composition to the aqueous solution containing emulsifier and disperse at high speed for 0.5-1.0 hours to obtain a stable pre-emulsion.

[0022] Add 0.4-6.0 parts of pre-emulsion and 0.05-0.80 parts of initiator to the reactor, heat to 75-90℃, react for 0.5-1.0 hours until the system shows blue light, add the remaining pre-emulsion dropwise over 2-4 hours at the set temperature of 75-90℃, keep warm for 0.5-2.0 hours, cool down to 40-47℃ to obtain acrylic precursor emulsion;

[0023] 3) Take 100 parts by weight of the acrylic precursor emulsion obtained in step 2), add 0.5-1.2 parts of initiator, add 10-50 parts of the allyl imidazole modified propionate obtained in step 1) within 2-4 hours, stir at 75-90℃ for 1-2 hours, cool down to 30-40℃, add 30-40 parts of macroporous mixed bed resin, stir for 0.5-1.0 hours, filter to separate the macroporous mixed bed resin, add pH adjuster to the system pH=6-8, and obtain a stain-resistant and odor-neutralizing waterborne acrylic emulsion;

[0024] The allyl-containing acrylate in step 1) is one of allyl acrylate and allyl methacrylate; the imidazole or imidazole derivative is one of imidazole, 4-methylimidazolium, and 4-nitroimidazolium.

[0025] The catalyst mentioned in step 1) is 1-butyl-3-methylimidazolium hydroxide;

[0026] The cocatalyst mentioned in step 1) is selected from one of benzyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetrabutylammonium bromide, and trioctylmethylammonium bromide;

[0027] The synthetic wax mentioned in step 2) is selected from polyethylene wax;

[0028] Step 2) The acrylate is selected from one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, (2-ethylhexyl) acrylate, and (2-ethylhexyl) methacrylate.

[0029] The emulsifier mentioned in step 2) is selected from one of CM-30, AES, SDS and T-80;

[0030] The initiator mentioned in step 2) is selected from potassium persulfate and ammonium persulfate;

[0031] The pH adjuster mentioned in step 3) is selected from one of sodium hydroxide, ammonia, triethylamine, and N,N-dimethylethanolamine.

[0032] In this invention:

[0033] The macroporous mixed bed resin mentioned in step 3) is MB424, after filtering out the system, the residual polymer was dissolved in acetone, and then eluted with 1 mol / L hydrochloric acid ethanol solution. The eluent was then mixed with excess concentrated ammonia to obtain a mixture of catalyst, co-catalyst, imidazole and derivatives.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] 1. The stain-resistant and odor-neutralizing waterborne acrylic emulsion prepared by the method of the present invention has the following main components: synthetic wax and modified polyacrylate containing imidazole and its derivative groups in the side chain. It has strong cohesion, good stability, high transparency after film formation, and good adhesion to low surface substrates.

[0036] 2. The method for preparing a stain-resistant and odor-neutralizing waterborne acrylic emulsion according to the present invention involves an addition reaction between imidazole and its derivatives and residual acrylic monomers during the synthesis process to generate an odorless, tasteless, non-volatile compound with low surface tension. This compound serves as a highly efficient substrate wetting agent, significantly improving the wettability of the emulsion to the substrate. Simultaneously, it acts as an interface agent, bonding tightly to the substrate at one end and combining with the acrylic polymer containing an imidazole structure at the other end, thereby improving the stain resistance of the polymer surface.

[0037] 3. The post-processing of the stain-resistant and odor-neutralizing water-based acrylic emulsion obtained by this invention is simple, green, and efficient. Detailed Implementation

[0038] The specific embodiments of the present invention will be further described below with reference to examples.

[0039] Example 1:

[0040] A method for preparing a stain-resistant and odor-neutralizing water-based acrylic emulsion includes the following steps:

[0041] 1) By molar amount, 1 mol of allyl acrylate and 1.05 mol of 4-nitroimidazole were stirred evenly under nitrogen protection, 0.1 mol of 1-butyl-3-methylimidazole catalyst and 0.03 mol of tetrabutylammonium bromide co-catalyst were added, the temperature was raised to 60℃, kept at the temperature for 6 hours, and then cooled to 15℃ to obtain 3-(4-nitroimidazole)propionate allyl acrylate;

[0042] 2) Mix 400g of 15g acrylic acid, 137g methyl methacrylate, 155g butyl methacrylate, 93g (2-ethylhexyl) acrylate, and 10g synthetic wax until homogeneous to obtain a monomer composition.

[0043] 10g of emulsifier CM-30 was dissolved in 400g of deionized water. After complete dissolution, the monomer composition was added to the aqueous solution of the emulsifier and dispersed at high speed for 0.5 hours to obtain a white, viscous, stable pre-emulsion. 50g of the pre-emulsion and 5g of initiator ammonium persulfate were added to a reaction vessel and heated to 75°C. After reacting for 0.5 hours, the system showed blue light. The remaining pre-emulsion was added dropwise at 75°C over 2 hours. After maintaining the temperature for another 2 hours, the temperature was lowered to 40°C to obtain an acrylic precursor emulsion.

[0044] 3) Take 300g of the acrylic precursor emulsion obtained in step 2), add 3.55g of ammonium persulfate, and slowly add 150g of allyl 3-(4-nitroimidazolyl)propionate dropwise over 4 hours. After incubating at 75℃ for 2 hours, cool to 38℃ and add... MB424, stirred for 1 hour, then filtered and separated. MB424, with the addition of ammonia to bring the system pH to 8, yields a stain-resistant and odor-neutralizing waterborne acrylic emulsion.

[0045] Example 2:

[0046] A method for preparing a stain-resistant and odor-neutralizing water-based acrylic emulsion includes the following steps:

[0047] 1) By molar amount, 1 mol of allyl methacrylate and 1.13 mol of imidazole were stirred evenly under nitrogen protection, 0.05 mol of 1-butyl-3-methylimidazolium hydroxide catalyst and 0.04 mol of trioctylmethylammonium bromide co-catalyst were added, the temperature was raised to 40℃, kept at the temperature for 3 hours, and then cooled to 25℃ to obtain 2-methyl-3-imidazolylpropionate allyl acrylate;

[0048] 2) Add 100g of 2-methyl-3-imidazolyl propionate to 1300g of a mixture of 64g acrylic acid, 533g methyl acrylate, 250g ethyl acrylate, 268g butyl methacrylate, 185g (2-ethylhexyl) methacrylate, 15g synthetic wax, and 12g synthetic wax. Stir and mix thoroughly to obtain the monomer composition.

[0049] 48g of emulsifier AES was dissolved in 1400g of deionized water. After complete dissolution, the monomer composition was added to the aqueous solution of the emulsifier and dispersed at high speed for 1 hour to obtain a stable pre-emulsion. 300g of the pre-emulsion and 25g of initiator potassium persulfate were added to a reaction vessel and heated to 90°C. The reaction was carried out for 0.5 hours until the system showed blue light. The remaining pre-emulsion was added dropwise over 2 hours at 90°C. After maintaining the temperature for another 0.5 hours, the temperature was lowered to 47°C to obtain an acrylic precursor emulsion.

[0050] 3) Take 300g of the acrylic precursor emulsion obtained in step 2), add 1.5g of potassium persulfate, and slowly add 30g of allyl 2-methyl-3-imidazolium propionate dropwise over 1 hour. After maintaining the temperature at 90℃ for 1 hour, cool to 30℃, stir for 1 hour, and then filter to separate. MB424, with the addition of triethylamine as a pH adjuster to pH 6, yields a stain-resistant and odor-neutralizing waterborne acrylic emulsion.

[0051] Example 3:

[0052] A method for preparing a stain-resistant and odor-neutralizing water-based acrylic emulsion includes the following steps:

[0053] 1) By molar amount, 1 mol of allyl acrylate and 1.10 mol of 4-methylimidazole were stirred evenly under nitrogen protection, 0.08 mol of 1-butyl-3-methylimidazole catalyst and 0.03 mol of benzyltrimethylammonium bromide co-catalyst were added, the temperature was raised to 55℃, kept at the temperature for 8 hours, and then cooled to 20℃ to obtain 3-(4-nitroimidazolyl)propionate allyl acrylate;

[0054] 2) Mix 400g of 15g acrylic acid, 137g methyl methacrylate, 155g butyl methacrylate, 93g methyl acrylate, and 10g synthetic wax evenly to obtain a monomer composition.

[0055] 10g of emulsifier SDS was dissolved in 400g of deionized water. After complete dissolution, the monomer composition was added to the aqueous solution of the emulsifier and dispersed at high speed for 0.5 hours to obtain a white, viscous, stable pre-emulsion. 50g of the pre-emulsion and 5g of initiator ammonium persulfate were added to a reaction vessel and heated to 75°C. After reacting for 0.5 hours, the system showed blue light. The remaining pre-emulsion was added dropwise at 75°C over 2 hours. After maintaining the temperature for another 2 hours, the temperature was lowered to 40°C to obtain an acrylic precursor emulsion.

[0056] 3) Take 300g of the acrylic precursor emulsion obtained in step 2), add 3.55g of ammonium persulfate, and slowly add 150g of allyl 3-(4-nitroimidazolyl)propionate dropwise over 4 hours. After maintaining the temperature at 75℃ for 2 hours, cool to 40℃ and add... MB424, stirred for 1 hour, then filtered and separated. MB424, with the addition of sodium hydroxide to bring the pH of the system to 8, yields a stain-resistant and odor-neutralizing water-based acrylic emulsion.

[0057] Example 4:

[0058] A method for preparing a stain-resistant and odor-neutralizing water-based acrylic emulsion includes the following steps:

[0059] 1) By molar amount, 1 mol of allyl methacrylate and 1.12 mol of imidazole were stirred evenly under nitrogen protection. 0.05 mol of 1-butyl-3-methylimidazolium hydroxide catalyst and 0.05 mol of hexadecyltrimethylammonium bromide co-catalyst were added. The mixture was heated to 50°C, kept at that temperature for 4 hours, and then cooled to 25°C to obtain 2-methyl-3-imidazolylpropionate allyl acrylate.

[0060] 2) Add 100g of 2-methyl-3-imidazolyl propionate to 1300g of a mixture of 64g acrylic acid, 533g methyl acrylate, 250g ethyl acrylate, 268g butyl methacrylate, 185g butyl acrylate, and 15g synthetic wax, and stir until homogeneous to obtain the monomer composition.

[0061] 48g of emulsifier T-80 was dissolved in 1400g of deionized water. After complete dissolution, the monomer composition was added to the aqueous solution of the emulsifier and dispersed at high speed for 1 hour to obtain a stable pre-emulsion. 300g of the pre-emulsion and 25g of initiator potassium persulfate were added to a reaction vessel and heated to 90°C. The reaction was carried out for 0.5 hours until the system showed blue light. The remaining pre-emulsion was added dropwise over 2 hours at 90°C. After maintaining the temperature for another 0.5 hours, the temperature was lowered to 47°C to obtain an acrylic precursor emulsion.

[0062] 3) Take 300g of the acrylic precursor emulsion obtained in step 2), add 1.5g of potassium persulfate, and slowly add 30g of allyl 2-methyl-3-imidazolium propionate dropwise over 1 hour. After maintaining the temperature at 90℃ for 1 hour, cool to 30℃, stir for 1 hour, and then filter to separate. MB424 was mixed with N,N-dimethylethanolamine, a pH adjuster, to bring the system pH to 7, resulting in a stain-resistant and odor-neutralizing waterborne acrylic emulsion.

[0063] Experimental example:

[0064] The stain-resistant and odor-neutralizing waterborne acrylic emulsions P1-P4 obtained in Examples 1-4 above and the commercially available waterborne acrylic emulsions P5-P7 were tested for residual monomers according to the gas chromatography method in GB / T 11175-2002, 5.10.2. The results are shown in Table 1.

[0065] Table 1. Residual monomer content in waterborne acrylic emulsions

[0066]

[0067]

[0068] It can be seen that the residual monomer content of the high-adhesion, odorless waterborne acrylic emulsions P1-P4 obtained in Examples 1-4 is all below 100 mg / kg, while the residual monomer content of commercially available conventional waterborne acrylic emulsions P5-P7 all exceeds 300 mg / kg, and P7 even exceeds 1000 mg / kg. The residual monomer content directly affects the odor of the emulsion. Therefore, P1-P4 have low residual monomer content and extremely low odor, and can be considered as odorless emulsions.

[0069] The above description is a detailed description of the preferred embodiments of the present invention. However, the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modifications made under the technical spirit of the present invention should fall within the patent scope covered by the present invention.

Claims

1. A stain-resistant and odor-free water-based acrylic emulsion, characterized in that: It is composed of the compound structure of the following general formula: Wherein af is a degree of polymerization value: a=an integer of 0-200, b=an integer of 0-200, c=an integer of 0-200, d=an integer of 0-200, e=an integer of 20-125, f=an integer of 20-125, and at most one of a, b, c, and d is allowed to be 0; R1-R4 is a combination of H, methyl, ethyl, 1-butyl, 2-ethyl-1-hexyl, one and only one of which is H, and when the substituent is H, the corresponding degree of polymerization is an integer of 5-30; R5-R8 is a combination of one or both of H and methyl; R9 is One of them.

2. The method for preparing a stain-resistant and odor-free aqueous acrylic emulsion according to claim 1, characterized in that: The steps include: 1) Based on the amount of substance, 1 part of allyl-containing acrylate and 1.05-1.13 parts of imidazole or imidazole derivative are stirred evenly under nitrogen protection, 0.05-0.10 parts of catalyst and 0.03-0.05 parts of co-catalyst are added, the temperature is raised to 40-60° C., the temperature is kept constant for 3-8 hours, and the temperature is lowered to 15-25° C. to obtain allyl-containing imidazole-modified propionate; 2) stirring and mixing 4-30 parts by weight of acrylic acid ester to obtain a monomer composition; Dissolve 0.1-0.8 parts of emulsifier in 4-40 parts of deionized water. After the emulsifier is completely dissolved, add 10-15 parts of synthetic wax and monomer composition to the aqueous solution containing the emulsifier and disperse at high speed for 0.5-1.0 hours to obtain a stable pre-emulsion. 0.4-6.0 parts of pre-emulsion and 0.05-0.80 parts of initiator are added into a reaction kettle, heated to 75-90°C, reacted for 0.5-1.0 hour until the system shows blue light, the remaining pre-emulsion is added dropwise at a set temperature of 75-90°C within 2-4 hours, kept warm for 0.5-2.0 hours, and cooled to 40-47°C to obtain an acrylic acid precursor emulsion; 3) Taking 100 parts of the acrylic precursor emulsion obtained in step 2) by weight, add 0.5-1.2 parts of initiator, add 10-50 parts of the allyl-containing imidazole-modified propionate obtained in step 1) within 2-4 hours, keep stirring at 75-90° C. for 1-2 hours, cool to 30-40° C., add 30-40 parts of macroporous mixed bed resin, stir for 0.5-1.0 hours, filter and separate the macroporous mixed bed resin, add pH adjuster to pH = 6-8, and obtain a stain-resistant and odor-free water-based acrylic emulsion; The allyl-containing acrylate in step 1) is one of allyl acrylate and allyl methacrylate; the imidazole or imidazole derivative is one of imidazole, 4-methylimidazole and 4-nitroimidazole; The catalyst in step 1) is 1-butyl-3-methylimidazole hydroxide; The co-catalyst in step 1) is selected from one of benzyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetrabutylammonium bromide and trioctylmethylammonium bromide; The synthetic wax described in step 2) is selected from polyethylene wax; The acrylate in step 2) is selected from one of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, (2-ethylhexyl) acrylate and (2-ethylhexyl) methacrylate: The emulsifier in step 2) is selected from one of CM-30, AES, SDS and T-80; The initiator in step 2) is selected from one of potassium persulfate and ammonium persulfate; The pH regulator in step 3) is selected from one of sodium hydroxide, ammonia water, triethylamine and N,N-dimethylethanolamine.

3. The method for preparing a stain-resistant and odor-free aqueous acrylic emulsion according to claim 1, characterized in that: The macroporous mixed bed resin described in step 3) is MB424, after filtering out the system, the residual polymer is dissolved with acetone, and then eluted with 1 mol / L hydrochloric acid ethanol solution, and excess concentrated ammonia water is added to the eluent to obtain a mixture of catalyst, co-catalyst, imidazole and derivatives.

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