Salt-tolerant carbomer and method for preparing the same

Abstract

The application belongs to the technical field of functional polymer materials, and particularly relates to a salt-resistant carbomer and a preparation method thereof. The salt-resistant carbomer is prepared from acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, a crosslinking agent, an initiator and a solvent; the mass ratio of the acrylic acid to the 2-acrylamide-2-methylpropanesulfonic acid, the crosslinking agent and the solvent is 1:(0.12-0.6):(0.016-0.04):(2.4-3.2); the initiator is composed of ammonium persulfate and sodium bisulfite at a mass ratio of 2:1, and the mass ratio of the acrylic acid to the ammonium persulfate is 1:(0.00004-0.0002). The salt-resistant carbomer prepared by the application has good stability, excellent viscosity and good salt resistance, and solves the technical problems of poor salt resistance of the existing carbomer resin, viscosity reduction caused by water absorption when the carbomer resin meets salt, and serious decrease or even failure of thickening capacity.

Description

Technical Field

[0001] This invention relates to the field of functional polymer materials technology, specifically to a salt-resistant carbomer and its preparation method. Background Technology

[0002] Carbomer is an important polyacrylic acid thickener, obtained by chemical crosslinking of acrylic acid or acrylate with allyl ether. Carbomer is a very important rheology modifier with excellent thickening, suspending, and emulsifying properties, and is widely used as an adhesive, chelating agent, suspending agent, or pharmaceutical excipient, thus finding wide application in the pharmaceutical, cosmetic, and other fields.

[0003] Carbomer has a thickening capacity of tens of thousands of times in pure water, but carbomer resin has poor salt resistance and easily absorbs water when it comes into contact with salt, resulting in a decrease in viscosity to 2%-10% of the original, and a serious reduction or even failure of thickening capacity; this greatly limits the application of carbomer.

[0004] Furthermore, currently, most carbomer production utilizes precipitation polymerization in organic solvents. These solvents are primarily benzene, xylene, tetrahydronaphthalene, hexane, carbon tetrachloride, chloroform, and chloroform, all of which are toxic and harmful substances. Solvent residues are easily left behind, and the residual solvents in the prepared carbomer products are harmful to human health. Although some companies use organic solvents such as ethyl acetate and cyclohexane to replace harmful solvents like benzene in carbomer synthesis, these solvents still possess a certain degree of toxicity; moreover, the solvents require recycling, increasing production costs. Therefore, there is an urgent need to research a carbomer production method that offers good salt tolerance and is environmentally friendly. Summary of the Invention

[0005] In view of the problems and shortcomings of the existing technology, the purpose of this invention is to provide a salt-tolerant carbomer and its green and environmentally friendly preparation method.

[0006] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0007] The first aspect of this invention provides a salt-resistant carbomer, which is prepared from acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid, the crosslinking agent, and the solvent is 1:(0.12-0.6):(0.016-0.04):(2.4-3.2); the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid to ammonium persulfate is 1:(0.00004-0.0002).

[0008] According to the above-mentioned salt-resistant carbomer, preferably, the solvent is water.

[0009] According to the above-mentioned salt-resistant carbomer, preferably, the crosslinking agent is N-maleylated chitosan. More preferably, the relative molecular mass of the N-maleylated chitosan is 250,000 to 300,000.

[0010] According to the above-mentioned salt-resistant carbomer, preferably, the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, and solvent is 1:0.2:0.024:2.8, and the mass ratio of acrylic acid to ammonium persulfate is 1:0.00012.

[0011] A second aspect of the present invention provides a method for preparing the salt-tolerant carbomer described in the first aspect above, comprising the following steps:

[0012] (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, ammonium persulfate, sodium bisulfite and solvent according to the composition of salt-resistant carbomer, and set aside;

[0013] (2) Under a protective gas atmosphere, add solvent, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and crosslinking agent to the reaction vessel, stir and mix evenly to obtain a mixture; cool the mixture to 10-20℃, add ammonium persulfate and sodium bisulfite to the mixture, then heat the mixture to 60-80℃, keep it at the temperature for 1.5-3h to obtain the reaction product;

[0014] (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

[0015] According to the above preparation method, preferably, in step (2), acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid need to be pretreated before being added to the reaction vessel. The pretreatment operation is as follows: dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in a partial solvent to obtain a mixed solution, add a certain amount of activated carbon and epichlorohydrin to the mixed solution, stir for 1-4 hours, and filter. More preferably, the amount of activated carbon is 10% of the total mass of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid, and the amount of epichlorohydrin is 1.7% of the total mass of 2-acrylamide-2-methylpropanesulfonic acid.

[0016] According to the above preparation method, preferably, in step (2), ammonium persulfate and sodium bisulfite are added to the reaction vessel in solution form, and the concentration of the ammonium persulfate solution is 1% and the concentration of the sodium bisulfite solution is 1%.

[0017] According to the above preparation method, preferably, in step (2), the mixture is heated to 80°C and kept at that temperature for 2 hours.

[0018] According to the above preparation method, preferably, the freeze-drying temperature in step (3) is -25 to -15℃.

[0019] A third aspect of the present invention provides the application of the salt-resistant carbomer described in the first aspect above in adhesives, cosmetics or pharmaceutical excipients.

[0020] Compared with the prior art, the positive and beneficial effects achieved by the present invention are as follows:

[0021] (1) This invention uses acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid as polymeric monomers. Acrylic acid provides hydration groups, a polymer backbone, and crosslinking carboxyl groups, while 2-acrylamide-2-methylpropanesulfonic acid provides a polymer backbone and sulfonic acid groups. A redox initiation system composed of ammonium persulfate and sodium bisulfite is used to generate free radicals, activating the acrylic acid monomer and the 2-acrylamide-2-methylpropanesulfonic acid monomer for copolymerization. Simultaneously, N-maleicylated chitosan is used as a crosslinking agent. Because N-maleicylated chitosan contains a large number of hydroxyl and amide groups, it has strong reactivity. Therefore, after copolymerization and crosslinking, a crosslinking agent is formed... This invention presents a stable three-dimensional network polymer. This three-dimensional network polymer exhibits good stability and excellent viscosity. Furthermore, the presence of numerous amide and sulfonic acid groups in the network structure significantly enhances its salt resistance. Experiments have shown that when the salt-resistant carbomer prepared according to this invention is diluted with distilled water to a 0.5% aqueous solution and neutralized with triethanolamine, its viscosity reaches 50.3 Pa·s. When the salt-resistant carbomer prepared according to this invention is diluted with a 5% sodium chloride aqueous solution to a 0.5% solution and neutralized with triethanolamine, its viscosity still reaches 35.1 Pa·s. Therefore, the salt-resistant carbomer of this invention exhibits good stability, excellent viscosity, and good salt resistance, solving the technical problems of poor salt resistance, easy water absorption upon contact with salt leading to viscosity reduction, and severely diminished or even ineffective thickening ability of existing carbomer resins.

[0022] (2) The salt-resistant carbomer of the present invention is prepared by using water as a solvent without adding any organic solvent. The preparation method is green and environmentally friendly. The prepared salt-resistant carbomer product is safe and non-toxic and can meet the safe use requirements of the pharmaceutical and cosmetic fields. Detailed Implementation

[0023] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below in conjunction with specific embodiments and accompanying drawings. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention.

[0024] Unless otherwise specified, the experimental methods described in the following embodiments are conventional techniques in this technical field or are performed according to the conditions recommended by the manufacturer; the reagents, materials and instruments used, unless otherwise specified by the manufacturer, are all conventional products that can be obtained commercially.

[0025] Example 1: Experimental Study on the Mass Ratio of Acrylic Acid to 2-Acrylamide-2-methylpropanesulfonic Acid

[0026] To investigate the effect of the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid on the performance of carbomer preparation, Examples 1-1 to 1-7 were conducted in this invention.

[0027] Example 1-1:

[0028] A salt-resistant carbomer is prepared from acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid is 1:0; the crosslinking agent is N-maleicylated chitosan, and the mass ratio of acrylic acid to N-maleicylated chitosan is 1:0.024; the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid to ammonium persulfate is 1:0.00012; the solvent is water, and the mass ratio of acrylic acid to water is 1:2.8.

[0029] The specific steps of the above-mentioned method for preparing salt-tolerant carbomer are as follows:

[0030] (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, N-maleic chitosan, ammonium persulfate, sodium bisulfite, and water according to the composition of the salt-tolerant carbomer. Prepare a 1% ammonium persulfate aqueous solution and a 1% sodium bisulfite aqueous solution for later use;

[0031] (2) Dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in part of water to obtain a mixed solution. Add activated carbon (10% of the total mass of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid) and epichlorohydrin (1.7% of the total mass of 2-acrylamide-2-methylpropanesulfonic acid) to the mixed solution, stir for 2 hours, filter and add to a reaction vessel. Under a nitrogen atmosphere, add N-maleicylated chitosan and the remaining water to the reaction vessel, stir and mix evenly to obtain a mixed solution. Cool the mixed solution to 15°C, then add ammonium persulfate aqueous solution and sodium bisulfite aqueous solution to the mixed solution, gradually raise the temperature to 80°C, keep the temperature for 2 hours and obtain the reaction product.

[0032] (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

[0033] Examples 1-2 to 1-7 are basically the same as Example 1-1, except that the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid is different. In Examples 1-2 to 1-6, the mass ratios of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid are 1:0.12, 1:0.2, 1:0.32, 1:0.44, 1:0.6, and 1:0.8, respectively.

[0034] The salt tolerance of the carbomers prepared in Examples 1-1 to 1-7 was tested, and the test results are shown in Table 1.

[0035] Test method for carbomer's salt tolerance: Dissolve 1g of carbomer in 200ml of 5% sodium chloride aqueous solution to prepare a 0.5% carbomer-sodium chloride aqueous solution. Then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity. For comparison, simultaneously prepare a 0.5% carbomer distilled aqueous solution using distilled water, then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity.

[0036] Table 1. Experimental Results on the Mass Ratio of Acrylic Acid to 2-Acrylamide-2-methylpropanesulfonic Acid

[0037]

[0038] As shown in Table 1, without AMPS, the viscosity of the prepared carbomer in distilled water can reach 71 Pa·s, but in 5% saline, its viscosity is only 5% of that in distilled water (3.2 Pa·s). With the increase of AMPS, the viscosity of the prepared carbomer in distilled water gradually decreases, but the viscosity in 5% saline gradually increases. When the mass ratio of AA to AMPS is 1:0.2, the viscosity of carbomer in 5% saline reaches its maximum (35.1 Pa·s). Further increasing the mass of AMPS does not significantly change the viscosity of carbomer in 5% saline. Therefore, the preferred mass ratio of AA to AMPS is 1:(0.12~0.6), and more preferably 1:0.2.

[0039] Example 2: Experiment exploring the mass ratio of acrylic acid to crosslinking agent

[0040] To investigate the effect of the mass ratio of acrylic acid to crosslinking agent on the performance of prepared carbomer, Examples 2-1 to 2-5 of this invention were conducted.

[0041] Example 2-1:

[0042] A salt-resistant carbomer is prepared from acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid is 1:0.2; the crosslinking agent is N-maleylchitosan, and the mass ratio of acrylic acid to N-maleylchitosan is 1:0; the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid to ammonium persulfate is 1:0.00012; the solvent is water, and the mass ratio of acrylic acid to water is 1:2.8.

[0043] The specific steps of the above-mentioned method for preparing salt-tolerant carbomer are as follows:

[0044] (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, N-maleic chitosan, ammonium persulfate, sodium bisulfite, and water according to the composition of the salt-tolerant carbomer. Prepare a 1% ammonium persulfate aqueous solution and a 1% sodium bisulfite aqueous solution for later use;

[0045] (2) Dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in part of water to obtain a mixed solution. Add activated carbon (the amount of activated carbon accounts for 10% of the total mass of acrylic acid monomer and 2-acrylamide-2-methylpropanesulfonic acid) and epichlorohydrin (the amount of epichlorohydrin accounts for 1.7% of the total mass of 2-acrylamide-2-methylpropanesulfonic acid) to the mixed solution, stir for 2 hours, filter and add to the reaction vessel; under a nitrogen atmosphere, add N-maleicylated chitosan and the remaining water to the reaction vessel, stir and mix evenly to obtain a mixed solution; cool the mixed solution to 15°C, then add ammonium persulfate aqueous solution and sodium bisulfite aqueous solution to the mixed solution, gradually raise the temperature to 80°C, keep the temperature for 2 hours to obtain the reaction product;

[0046] (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

[0047] Examples 2-2 to 2-5 are basically the same as Example 2-1, except that the mass ratio of acrylic acid to N-maleicyl chitosan is different. In Examples 2-2 to 2-5, the mass ratios of acrylic acid to N-maleicyl chitosan are 1:0.008, 1:0.016, 1:0.032, and 1:0.04, respectively.

[0048] The carbomers prepared in Examples 2-1 to 2-5 were subjected to performance tests, and the test results are shown in Table 2.

[0049] Test method for carbomer's salt tolerance: Dissolve 1g of carbomer in 200ml of 5% sodium chloride aqueous solution to prepare a 0.5% carbomer-sodium chloride aqueous solution. Then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity. For comparison, simultaneously prepare a 0.5% carbomer distilled aqueous solution using distilled water, then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity.

[0050] Table 2. Experimental results of mass ratio of acrylic acid to N-maleyl chitosan.

[0051]

[0052] Table 2 shows that the carbomer prepared without N-maleicchitosan has low viscosity in both distilled water and brine. This is because the prepared carbomer product is a highly water-soluble linear polymer of polyacrylic acid, which does not possess the rheological properties of carbomer resin. With increasing N-maleicchitosan content, the viscosity of carbomer in distilled water and brine increases accordingly. When the mass ratio of acrylic acid to N-maleicchitosan is 1:0.024, the viscosity of the prepared carbomer in both distilled water and brine reaches its maximum. Further increasing the amount of N-maleicchitosan actually decreases the viscosity of carbomer. This is because while excessive crosslinking of the crosslinking agent leads to sufficient crosslinking, it also reduces the maximum water absorption ratio of the polymer. The extension of the polymer molecular chains in the solution is severely restricted, resulting in limited swelling of the formed hydrogel particles rather than complete dissolution, thus significantly reducing the viscosity of the carbomer. Therefore, the preferred mass ratio of acrylic acid to N-maleyl chitosan is 1:(0.016-0.04), and more preferably 1:0.024.

[0053] Example 3: Experiment to explore the mass ratio of acrylic acid to ammonium persulfate

[0054] To investigate the effect of the mass ratio of acrylic acid to ammonium persulfate on the performance of carbomer preparation, Examples 3-1 to 3-6 of this invention were conducted.

[0055] Example 3-1:

[0056] A salt-resistant carbomer is prepared from acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid is 1:0.2; the crosslinking agent is N-maleicylated chitosan, and the mass ratio of acrylic acid to N-maleicylated chitosan is 1:0.024; the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid to ammonium persulfate is 1:0.00001; the solvent is water, and the mass ratio of acrylic acid to water is 1:2.8.

[0057] The specific steps of the above-mentioned method for preparing salt-tolerant carbomer are as follows:

[0058] (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, N-maleic chitosan, ammonium persulfate, sodium bisulfite, and water according to the composition of the salt-tolerant carbomer. Prepare a 1% ammonium persulfate aqueous solution and a 1% sodium bisulfite aqueous solution for later use;

[0059] (2) Dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in part of water to obtain a mixed solution. Add activated carbon (10% of the total mass of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid) and epichlorohydrin (1.7% of the total mass of 2-acrylamide-2-methylpropanesulfonic acid) to the mixed solution, stir for 2 hours, filter and add to a reaction vessel. Under a nitrogen atmosphere, add N-maleicylated chitosan and the remaining water to the reaction vessel, stir and mix evenly to obtain a mixed solution. Cool the mixed solution to 15°C, then add ammonium persulfate aqueous solution and sodium bisulfite aqueous solution to the mixed solution, gradually raise the temperature to 80°C, keep the temperature for 2 hours and obtain the reaction product.

[0060] (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

[0061] Examples 3-2 to 3-6 are basically the same as Example 3-1, except that the mass ratio of acrylic acid to ammonium persulfate is different. The mass ratios of acrylic acid to ammonium persulfate in Examples 3-2 to 3-6 are 1:0.00004, 1:0.00008, 1:0.00016, 1:0.0002, and 1:0.00024, respectively.

[0062] The carbomers prepared in Examples 3-1 to 3-6 were subjected to performance tests, and the test results are shown in Table 3.

[0063] Test method for carbomer's salt tolerance: Dissolve 1g of carbomer in 200ml of 5% sodium chloride aqueous solution to prepare a 0.5% carbomer-sodium chloride aqueous solution. Then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity. For comparison, simultaneously prepare a 0.5% carbomer distilled aqueous solution using distilled water, then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity.

[0064] Table 3. Experimental results of the mass ratio of acrylic acid to ammonium persulfate.

[0065]

[0066] Table 3 shows that the salt-tolerant carbomer viscosity reaches its maximum when the ammonium persulfate ratio is 1:0.00012. It also indicates that the product viscosity is lower when the ammonium persulfate content is low. This is because insufficient ammonium persulfate results in a slow polymer reaction rate, hindering chain growth and leading to incomplete polymerization and a high content of free monomers. As the ammonium persulfate content increases, the number of free radicals in the system increases, the initiation rate accelerates, the relative molecular mass of the polymer increases, and the product viscosity gradually increases. However, when the ammonium persulfate ratio exceeds 1:0.00012, the product viscosity shows a decreasing trend. This is because increasing the ammonium persulfate content increases the number of primary free radicals generated, increases the initiation rate, intensifies the reaction, increases chain transfer, and also leads to excessively high crosslinking density in the polymer network, causing a decrease in viscosity. Therefore, the preferred mass ratio of acrylic acid to ammonium persulfate is 1:(0.00004~0.0002), and more preferably 1:0.00012.

[0067] Example 4: Experiment to explore reaction temperature

[0068] To investigate the effect of the mass ratio of acrylic acid to ammonium persulfate on the performance of carbomer preparation, Examples 4-1 to 4-4 of this invention were conducted.

[0069] Example 4-1:

[0070] A salt-resistant carbomer is prepared from acrylic acid (AA), 2-acrylamide-2-methylpropanesulfonic acid (AMPS), a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid is 1:0.2; the crosslinking agent is N-maleylchitosan, and the mass ratio of acrylic acid monomer to N-maleylchitosan is 1:0.024; the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid monomer to ammonium persulfate is 1:0.00012; the solvent is water, and the mass ratio of acrylic acid monomer to water is 1:2.8.

[0071] The specific steps of the above-mentioned method for preparing salt-tolerant carbomer are as follows:

[0072] (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, N-maleic chitosan, ammonium persulfate, sodium bisulfite, and water according to the composition of the salt-tolerant carbomer. Prepare a 1% ammonium persulfate aqueous solution and a 1% sodium bisulfite aqueous solution for later use;

[0073] (2) Dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in part of water to obtain a mixed solution. Add activated carbon (10% of the total mass of acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid) and epichlorohydrin (1.7% of the total mass of 2-acrylamide-2-methylpropanesulfonic acid) to the mixed solution, stir for 2 hours, filter and add to a reaction vessel. Under a nitrogen atmosphere, add N-maleicylated chitosan and the remaining water to the reaction vessel, stir and mix evenly to obtain a mixed solution. Cool the mixed solution to 15°C, then add ammonium persulfate aqueous solution and sodium bisulfite aqueous solution to the mixed solution, gradually raise the temperature to 50°C, keep the temperature for 2 hours, and obtain the reaction product.

[0074] (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

[0075] Examples 4-2 to 4-4 are basically the same as Example 4-1, except that the reaction temperatures are different. The reaction temperatures in Examples 4-2 to 4-4 are 60℃, 70℃, and 90℃, respectively.

[0076] The carbomers prepared in Examples 4-1 to 4-4 were subjected to performance tests, and the test results are shown in Table 4.

[0077] Test method for carbomer's salt tolerance: Dissolve 1g of carbomer in 200ml of 5% sodium chloride aqueous solution to prepare a 0.5% carbomer-sodium chloride aqueous solution. Then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity. For comparison, simultaneously prepare a 0.5% carbomer distilled aqueous solution using distilled water, then adjust the pH of the solution to 7.3-7.8 with triethanolamine and measure its viscosity.

[0078] Table 4 Experimental results of polymerization reaction temperature

[0079]

[0080] Table 4 shows that, under the same polymerization conditions, when the reaction temperature is below 60℃, the viscosity of the prepared carbomer in distilled water and brine is low. This is because at low temperatures, the monomer activity is low, the initiator decomposition rate is low, the polymerization rate decreases, the polymerization process is difficult to carry out, the polymerization is incomplete, and the product viscosity is low. As the reaction temperature increases, the decomposition of the initiator is accelerated, thereby increasing the polymerization rate, and the product viscosity gradually increases. When the reaction temperature is raised to 80℃, the viscosity of the prepared carbomer in both distilled water and brine reaches its maximum; however, when the reaction temperature exceeds 80℃, the excessively high reaction temperature will accelerate the decomposition of the initiator, thereby accelerating the polymerization rate, and at the same time promoting side reactions, such as the cleavage of macromolecules, which increases the number of active centers and accelerates the chain termination rate, resulting in a decrease in the molecular weight and viscosity of the reaction product. Therefore, the preferred reaction temperature is 60–80℃, and more preferably 80℃.

[0081] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may use the above technical content as inspiration to make changes or modifications. These are equivalent embodiments with similar variations. However, any simple modifications, equivalent variations, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the technical concept of the present invention still fall within the protection scope of the claims of the present invention.

Claims

1. A salt-resistant carbomer, characterized in that, The salt-resistant carbomer is prepared from acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, a crosslinking agent, an initiator, and a solvent; the mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid, the crosslinking agent, and the solvent is 1:(0.12-0.6):(0.016-0.04):(2.4-3.2); the initiator is composed of ammonium persulfate and sodium bisulfite in a mass ratio of 2:1, and the mass ratio of acrylic acid to ammonium persulfate is 1:(0.00004-0.0002); the crosslinking agent is N-maleylated chitosan; and the solvent is water.

2. The salt-tolerant carbomer according to claim 1, characterized in that, The mass ratio of acrylic acid to 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, and solvent is 1:0.2:0.024:2.8, and the mass ratio of acrylic acid to ammonium persulfate is 1:0.00012.

3. The salt-tolerant carbomer according to claim 2, characterized in that, The relative molecular mass of N-maleylated chitosan is 250,000 to 300,000.

4. A method for preparing the salt-tolerant carbomer according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Weigh out acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, crosslinking agent, ammonium persulfate, sodium bisulfite and solvent according to the composition of salt-resistant carbomer, and set aside; (2) Under a protective gas atmosphere, add solvent, acrylic acid, 2-acrylamide-2-methylpropanesulfonic acid and crosslinking agent to the reaction vessel, stir and mix evenly to obtain a mixture; cool the mixture to 10-20°C, add ammonium persulfate and sodium bisulfite to the mixture, then heat the mixture to 60-80°C, keep it at the temperature for 1.5-3 hours to obtain the reaction product; (3) The reaction product obtained in step (2) is frozen, granulated, freeze-dried and ground to obtain salt-resistant carbomer.

5. The preparation method according to claim 4, characterized in that, In step (2), acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid need to be pretreated before being added to the reaction vessel. The pretreatment operation is as follows: dissolve acrylic acid and 2-acrylamide-2-methylpropanesulfonic acid in a partial solvent to obtain a mixed solution, add activated carbon and epichlorohydrin to the mixed solution, stir for 1 to 4 hours, and filter.

6. The preparation method according to claim 5, characterized in that, In step (2), ammonium persulfate and sodium bisulfite are added to the reaction vessel in solution form. The concentration of the ammonium persulfate solution is 1%, and the concentration of the sodium bisulfite solution is 1%.

7. The preparation method according to claim 6, characterized in that, In step (2), the mixture is heated to 80°C and kept at that temperature for 2 hours.

8. The use of the salt-resistant carbomer according to any one of claims 1 to 3 in adhesives, cosmetics or pharmaceutical excipients.

Images