Salt-tolerant carbomer, and preparation method and application thereof

Abstract

The present application relates to a kind of salt-tolerant carbomer and its preparation method and application, the preparation raw material of the carbomer includes the following weight parts of component: acrylic monomer 8-12 parts, cyclohexane 30-70 parts, ethyl acetate 30-70 parts, thickening agent 0.12-0.8 parts, initiator 0.01-0.2 parts and crosslinking agent 0.05-0.3 parts.The salt-tolerant carbomer prepared by the present application has certain salt tolerance, can be better applied in solid preparation, semi-solid preparation and liquid preparation in medicine and daily chemical product, mainly used as adhesive, suspending agent, thickening agent etc., has great application value and scientific research significance.

Description

Technical Field

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

[0002] Carbomer, also known as polycarboxy-polymethleme (CP), is a high molecular weight polymer crosslinked from acrylic acid and allyl sucrose. When dissolved in water, water molecules gradually diffuse into the interior of the polymer particles, causing the carbomer molecules to swell and disperse uniformly in the water. While the diffusion of water molecules into the particles takes a considerable amount of time, the gel network remains loose, resulting in excellent swelling properties in water. After a certain period, it forms a highly viscous gel.

[0003] Carbomer is an important rheology modifier and an excellent gel matrix in the pharmaceutical industry, commonly used in solid, semi-solid, and liquid formulations, primarily as a binder, suspending agent, and thickener. However, traditional carbomer is easily compressed when it comes into contact with salt in formulations, causing the gel viscosity to decrease to 2%-10% of its original value. This problem limits the widespread application of carbomer.

[0004] Therefore, it is of great significance to provide a salt-resistant carbomer with good stability so that it can be widely used in the production of various pharmaceuticals and daily chemical products. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a salt-resistant carbomer, its preparation method, and its applications. The salt-resistant carbomer provided by this invention exhibits excellent salt resistance, high viscosity, and good stability, and can be applied to pharmaceutical products and daily chemical products in solid, semi-solid, and liquid formulations, meeting the needs for its use as a binder, suspending agent, and thickener.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a salt-resistant carbomer, wherein the raw materials for preparing the carbomer comprise the following components in parts by weight:

[0008]

[0009] The weight percentages of the acrylic monomer can be, for example, 8.2 parts, 8.5 parts, 8.8 parts, 9 parts, 9.5 parts, 10 parts, 10.5 parts, 11 parts, or 11.5 parts.

[0010] The weight parts of the cyclohexane may be, for example, 32 parts, 35 parts, 38 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, or 65 parts.

[0011] The weight parts of the ethyl acetate can be, for example, 32 parts, 35 parts, 38 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, or 65 parts.

[0012] The thickener may be present in parts by weight of, for example, 0.15 parts, 0.18 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, 0.6 parts, or 0.7 parts.

[0013] The initiator may be present in parts by weight of, for example, 0.02 parts, 0.04 parts, 0.06 parts, 0.08 parts, 0.1 parts, 0.12 parts, 0.14 parts, 0.16 parts, or 0.18 parts.

[0014] The weight percentage of the crosslinking agent can be, for example, 0.06 parts, 0.07 parts, 0.08 parts, 0.09 parts, 0.1 parts, 0.15 parts, 0.2 parts, or 0.25 parts.

[0015] In this invention, a specific amount of acrylic monomer, thickener, initiator, and crosslinking agent are compounded in a specific ratio system of cyclohexane and ethyl acetate. The crosslinking agent can form multi-site crosslinks between the polymer backbone, thereby forming a network structure. After the gel is prepared, the thickener interpenetrates with the network polymer. In the entire reaction system, the components work together to exert a synergistic effect, resulting in a relatively uniform and stable network structure in the generated polymer. This gives the resulting carbomer good stability and salt resistance, thus solving the technical problem in the prior art where carbomer has poor salt resistance, is easily squeezed by salt, leading to a decrease in viscosity and a serious reduction in thickening ability.

[0016] Preferably, the acrylic monomer includes any one or a combination of at least two of acrylic acid, methyl acrylate, butyl acrylate or methyl methacrylate.

[0017] Preferably, the thickener includes SAB and / or a food-grade thickener, preferably SAB.

[0018] In this invention, the specifically selected SAB and food-grade thickener not only have good compatibility, which is conducive to the uniform dispersion of each raw material component, making the reaction system more stable and facilitating cross-linking during monomer polymerization, thereby forming a stable network structure and improving salt resistance; but also have a highly efficient thickening effect. When the addition amount is 1%-10% of the acrylic monomer, the required viscosity of the hydrogel system can be achieved, with high thickening efficiency; at the same time, it also has high safety and can be better applied in pharmaceuticals and daily chemical products.

[0019] SAB is an alkali-swellable thickener. Its structure contains a large number of hydrophilic EO segments, which form numerous hydrogen bonds with water to achieve a good thickening effect while reducing the compression of the electric double layer by ions in salt-containing systems, thus achieving better viscosity retention and resulting in products with excellent salt resistance. On the other hand, SAB also contains hydrophobic segments and -COOH groups. The -COOH groups ensure good compatibility with carbomer molecules, while the hydrophobic segments provide molecular rigidity, which helps reduce the compression of the carbomer molecule structure by ions, further improving the product's salt resistance.

[0020] Preferably, the food-grade thickener includes any one or a combination of at least two of gelatin, sodium caseinate, gum arabic, tamarind gum, guar gum, agar, sodium alginate, or carrageenan;

[0021] Preferably, the initiator comprises any one or a combination of at least two of azobisisobutyrate, azobisisoheptanenitrile, or azoisobutylcyanoformamide, with azobisisobutyrate being the most preferred.

[0022] In this invention, the selected specific azo initiators, dimethyl azobisisobutyrate (AIBME), azobisisoheptanenitrile (ABVN), and azoisobutylcyanoformamide (CABN), not only possess good initiation activity but also offer greater advantages for long-term stable and safe production compared to commonly used initiators. Common initiators such as azobisisobutyronitrile (AIBN) decompose to form solid tetramethylsuccinate, which is not only harmful to human health but also prone to clogging equipment and pipelines during long-term production. Furthermore, the decomposition of dilauryl peroxide (LPO) generates oxygen, which not only inhibits polymerization and affects the reaction but also compromises production safety.

[0023] Among them, dimethyl azobisisobutyrate (AIBME) has a decomposition temperature of 65℃-85℃, which is suitable for the preparation reaction of salt-resistant carbomer in this invention. Moreover, its decomposition rate is less affected by solvent changes, which is beneficial to improving the stability of the entire reaction system. At the same time, dimethyl azobisisobutyrate has moderate initiation activity, which makes the polymerization reaction easy to control, the polymerization process leaves no residue, the product conversion rate is high, and the decomposition products are harmless.

[0024] Preferably, the crosslinking agent comprises any one or a combination of at least two of bis-tert-butylperoxyisopropylbenzene, dicumyl peroxide, divinylbenzene, diisocyanate or N,N-methylenebisacrylamide, and is preferably bis-tert-butylperoxyisopropylbenzene and / or dicumyl peroxide.

[0025] In this invention, unlike common crosslinking agents that require linking linear polymers through crosslinking agent molecules, the crosslinking agents used in this invention, bis(tert-butylperoxyisopropylbenzene) (BIPB) and di(diisopropylbenzene peroxide) (DCP), can generate chemical bonds between linear molecules, allowing the linear molecules to be linked together by C-C bonds through the carbon atoms of the main chain to form a network structure. This improves the strength and elasticity of the resulting carbomer, reduces the possibility of chain breakage, and thus produces a good salt resistance effect.

[0026] Under the specific solvent ratio system of this invention, the initiator dimethyl azobisisobutyrate and the crosslinking agent bis(tert-butylperoxyisopropylbenzene) (BIPB) have basically the same half-life at 55℃-75℃, which can meet the requirement that the monomer polymerization rate and the main chain crosslinking rate are uniform and controllable during the reaction process. The resulting polymer structure is relatively uniform, which is beneficial to improving the stability and salt resistance of the product.

[0027] Preferably, the mass ratio of cyclohexane to ethyl acetate is (3:7)-(7:3), for example, it can be 3:7, 4:6, 4.5:5.5, 5:5, 5.5:4.5, 6:4 or 7:3, etc.

[0028] In this invention, cyclohexane and ethyl acetate are used as a mixed solvent in a specific mass ratio. Ethyl acetate has excellent solubility, dries quickly, and has low toxicity, which facilitates post-processing. Cyclohexane is highly miscible with ethyl acetate. Using both as a common solvent makes it easy to adjust the polarity of the entire solvent, so that the low molecular weight primary polymer has good stability and does not precipitate out of the solvent too early or too late. If the volume ratio of the two solvents decreases or increases, the chain length of the polymerization intermediate will be too short or too long, failing to reach the predetermined molecular weight, which in turn reduces the viscosity and salt resistance of the final product.

[0029] Preferably, the mass ratio of the thickener to the acrylic monomer is (0.025-0.067):1, for example, it can be 0.028:1, 0.03:1, 0.035:1, 0.04:1, 0.045:1, 0.05:1, 0.055:1, 0.06:1 or 0.065:1, etc.

[0030] In this invention, when the mass ratio of thickener to acrylic monomer is within a specific range, the resulting carbomer exhibits good viscosity and salt resistance. When the mass ratio is below 0.025:1, the thickening effect is not significant due to the low content of thickener, thus failing to effectively improve the compatibility and stability of the system, and consequently failing to significantly improve the salt resistance of the resulting carbomer. When the mass ratio is above 0.067:1, with the increase of thickener content, the resulting carbomer exhibits non-swelling in water, which is detrimental to the stability and uniformity of its viscosity.

[0031] Preferably, the mass ratio of the crosslinking agent to the acrylic monomer content is (0.015-0.022):1, for example, it can be 0.0155:1, 0.016:1, 0.0165:1, 0.017:1, 0.0175:1, 0.018:1 or 0.02:1, etc.

[0032] In this invention, when the mass ratio of crosslinking agent to acrylic monomer is within a specific range, the resulting carbomer exhibits good viscosity and salt resistance. When the mass ratio is below 0.015:1, the crosslinking agent content is too low, resulting in a low degree of crosslinking between polymer molecules. Although the initial viscosity of the prepared hydrogel system is high, the lack of rigidity in the polymer molecules makes the molecular structure easily compressed after the addition of salt, thus reducing salt resistance. When the mass ratio is above 0.022:1, the crosslinking agent content is too high, increasing the crosslinking density. However, excessively high crosslinking density reduces the maximum water absorption ratio of the polymer, severely restricting the extension of the polymer molecular chains in the solution, which leads to reduced water swelling. This prevents the carbomer from fully swelling in water, forming a precipitate, thus significantly reducing its initial viscosity and failing to meet the usage requirements.

[0033] In a second aspect, the present invention provides a method for preparing salt-tolerant carbomer as described in the first aspect, the method comprising the following steps:

[0034] Acrylic monomer, thickener, initiator and crosslinking agent are added to a mixed solvent and reacted to obtain the salt-resistant carbomer.

[0035] Preferably, the reaction is carried out under stirring.

[0036] Preferably, the reaction temperature is 55℃-75℃, for example, it can be 57℃, 60℃, 62℃, 65℃, 68℃, 70℃ or 72℃, etc.

[0037] In this invention, when the reaction temperature is below 55°C, the initiator decomposes at a low rate, failing to form a sufficient amount of free radicals for monomer polymerization, resulting in low polymerization efficiency. The free radicals are easily deactivated by external influences, only generating small-molecule oligomers, and the reaction cannot proceed normally, resulting in a product with low viscosity. When the reaction temperature is above 75°C, the system generates a large number of free radicals, the monomer reaction rate is too fast and uncontrollable, and explosive polymerization is likely to occur. The resulting polymer has a wide molecular weight distribution and a non-uniform structure, which reduces the viscosity of the carbomer and consequently leads to poor salt resistance.

[0038] Preferably, the reaction time is 7-9 hours, for example, 7 hours, 7.5 hours, 8 hours, 8.5 hours or 9 hours.

[0039] Preferably, the reaction is carried out under a protective gas atmosphere.

[0040] Preferably, the protective gas includes any one or a combination of at least two of nitrogen, argon, or helium.

[0041] Preferably, after the reaction is completed, a post-processing step is also included.

[0042] Preferably, the post-processing steps include: cooling, washing and filtering, drying, and pulverizing and sieving;

[0043] Preferably, the drying is vacuum drying.

[0044] Preferably, the vacuum drying temperature is 80℃-90℃, for example, it can be 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃ or 90℃, etc.

[0045] Preferably, the vacuum drying time is 9-11 hours, for example, 9 hours, 9.2 hours, 9.5 hours, 9.7 hours, 10 hours, 10.2 hours, 10.5 hours, 10.7 hours or 11 hours.

[0046] Preferably, the sieve used for crushing and sieving has a mesh size of 40.

[0047] Preferably, the preparation method of the salt-tolerant carbomer specifically includes the following steps:

[0048] (1) Mix cyclohexane and ethyl acetate to obtain a mixed solvent;

[0049] (2) Under a protective gas atmosphere, add acrylic monomer, thickener, initiator and crosslinking agent to the mixed solvent in step (1), and stir the reaction at 55℃-75℃ for 7-9h.

[0050] (3) Cool the reaction solution from step (2) to 25°C, wash and filter, vacuum dry at 80°C-90°C for 9-11 hours, grind into powder and pass through a 40-mesh sieve to obtain the salt-resistant carbomer.

[0051] In this invention, a blending preparation method is adopted, which is simple, easy to operate, and has low requirements for preparation conditions, making it suitable for large-scale industrial production.

[0052] Thirdly, the present invention provides the application of salt-resistant carbomer as described in the first aspect in pharmaceuticals or daily chemical products.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects:

[0054] (1) In a specific ratio system of cyclohexane and ethyl acetate, the present invention combines a specific amount of acrylic monomer, thickener, initiator and crosslinking agent to generate a polymer with a relatively uniform network structure, thereby giving the obtained carbomer good stability and salt resistance, thus solving the technical problem in the prior art that carbomer has poor salt resistance, is easily squeezed by salt, resulting in reduced viscosity and severely reduced thickening ability;

[0055] (2) By optimizing the raw materials for carbomer preparation, the present invention enables the obtained carbomer to have high viscosity and stability as well as good salt resistance, and its viscosity retention rate measured at 25°C can reach 56.8%.

[0056] (3) The present invention uses a small amount of thickener, initiator and crosslinking agent, which not only reduces production costs, but also helps to improve the safety of the obtained salt-resistant carbomer. Detailed Implementation

[0057] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0058] The following is some information about the raw materials involved in the specific implementation method:

[0059] SAB was purchased from Wanhua Chemical Group Co., Ltd., and its brand name is Vesmody A401.

[0060] Dimethyl azobisisobutyrate was purchased from Liaoning Shuangqi Fine Chemical Co., Ltd.

[0061] The bis-tert-butylperoxyisopropylbenzene (BIPB) was purchased from Tianmen Hengchang Chemical Co., Ltd.

[0062] Gelatin G6317 was purchased from Maclean's Reagents Ltd.

[0063] The gum arabic was purchased from Maclean's Reagents Ltd., brand name Acacia A800707.

[0064] Example 1

[0065] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0066]

[0067] The method for preparing the salt-resistant carbomer is as follows:

[0068] (1) Mix cyclohexane and ethyl acetate according to the formula to obtain a mixed solvent;

[0069] (2) Under a nitrogen atmosphere, the mixed solvent in step (1) was added to a slanted four-necked flask, and then acrylic acid, SAB, dimethyl azobisisobutyrate and bis-tert-butylperoxyisopropylbenzene were added in sequence according to the formula. The mixture was stirred at 65°C for 8 hours.

[0070] (3) Cool the reaction solution from step (2) to 25°C, wash and filter, vacuum dry at 85°C for 10 hours, grind into powder and pass through a 40-mesh sieve to obtain white, fine, and light salt-resistant carbomer powder.

[0071] Example 2

[0072] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0073]

[0074] The preparation method of the salt-tolerant carbomer is the same as that in Example 1.

[0075] Example 3

[0076] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0077]

[0078] The preparation method of the salt-tolerant carbomer is the same as that in Example 1.

[0079] Example 4

[0080] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0081]

[0082] The preparation method of the salt-tolerant carbomer is the same as that in Example 1.

[0083] Example 5

[0084] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0085]

[0086] The method for preparing the salt-resistant carbomer is as follows:

[0087] (1) Mix cyclohexane and ethyl acetate according to the formula to obtain a mixed solvent;

[0088] (2) Under a nitrogen atmosphere, the mixed solvent in step (1) was added to a slanted four-necked flask, and then methyl methacrylate, gelatin, azoisobutyl cyanoformamide and dicumyl peroxide were added in sequence according to the formula. The mixture was stirred at 55°C for 7 hours.

[0089] (3) Cool the reaction solution from step (2) to 25°C, wash and filter, vacuum dry at 80°C for 9 hours, grind into powder and pass through a 40-mesh sieve to obtain white, fine, and light salt-resistant carbomer powder.

[0090] Example 6

[0091] This embodiment provides a salt-resistant carbomer, the raw materials for which include the following components in parts by weight:

[0092]

[0093] The method for preparing the salt-resistant carbomer is as follows:

[0094] (1) Mix cyclohexane and ethyl acetate according to the formula to obtain a mixed solvent;

[0095] (2) Under a nitrogen atmosphere, the mixed solvent in step (1) was added to a slanted four-necked flask, and then butyl acrylate, gum arabic, azobisisobutyronitrile and dicumyl peroxide were added in sequence according to the formula. The mixture was stirred at 75°C for 9 hours.

[0096] (3) Cool the reaction solution from step (2) to 25°C, wash and filter, dry under vacuum at 90°C for 11 hours, grind into powder and pass through a 40-mesh sieve to obtain white, fine, and light salt-resistant carbomer powder.

[0097] Example 7

[0098] The difference between this embodiment and Embodiment 1 is that the weight of SAB is adjusted to 0.2 parts, while the other components, contents and preparation methods are the same as in Embodiment 1.

[0099] Example 8

[0100] The difference between this embodiment and Example 1 is that the weight of SAB is adjusted to 0.25 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0101] Example 9

[0102] The difference between this embodiment and Embodiment 1 is that the weight of SAB is adjusted to 0.67 parts, while the other components, contents and preparation methods are the same as in Embodiment 1.

[0103] Example 10

[0104] The difference between this embodiment and Embodiment 1 is that the weight of SAB is adjusted to 0.7 parts, while the other components, contents and preparation methods are the same as in Embodiment 1.

[0105] Example 11

[0106] The difference between this embodiment and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.12 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0107] Example 12

[0108] The difference between this embodiment and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.15 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0109] Example 13

[0110] The difference between this embodiment and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.22 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0111] Example 14

[0112] The difference between this embodiment and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.25 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0113] Comparative Example 1

[0114] The difference between this comparative example and Example 1 is that the weight parts of cyclohexane are adjusted to 20 parts and the weight parts of ethyl acetate are adjusted to 80 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0115] Comparative Example 2

[0116] The difference between this comparative example and Example 1 is that SAB is not added, the weight of acrylic acid is adjusted to 10.48 parts, and the other components, amounts and preparation methods are the same as in Example 1.

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 1 is that the weight of SAB is adjusted to 0.1 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0119] Comparative Example 4

[0120] The difference between this comparative example and Example 1 is that the weight of SAB is adjusted to 0.9 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0121] Comparative Example 5

[0122] The difference between this comparative example and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.04 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0123] Comparative Example 6

[0124] The difference between this comparative example and Example 1 is that the weight of bis-tert-butylperoxyisopropylbenzene is adjusted to 0.32 parts, while the other components, contents and preparation methods are the same as in Example 1.

[0125] Comparative Example 7

[0126] The difference between Comparative Example 1 and Example 1 is that the reaction temperature in step (2) of the preparation method of Comparative Example 1 is 50°C.

[0127] Comparative Example 8

[0128] The difference between Comparative Example 1 and Example 1 is that the reaction temperature in step (2) of the preparation method of Comparative Example 1 is 80°C.

[0129] The carbomers provided in Examples 1-14 and Comparative Examples 1-8 were subjected to salt tolerance tests, and the test methods are as follows:

[0130] A 0.5% carbomer hydrogel was prepared at 25°C, and the pH was adjusted to 7.35-7.45 using an 18% sodium hydroxide solution. Its viscosity η was measured using a Borelfeld DV2 viscometer. 水 Then, sodium chloride was added at a ratio of 1%, and the viscosity η after adding NaCl was measured using a Bollerfeld DV2 viscometer. 盐 The viscosity retention rate μ of carbomer was calculated using formula (1):

[0131] μ=(η 盐 ÷η 水 )×100% (1)

[0132] The larger the μ value, the better its salt resistance.

[0133] The test results are shown in Table 1:

[0134] Table 1

[0135]

[0136] The test results show that:

[0137] (1) As can be seen from Examples 1-14, the present invention optimizes the selection of components and content in the raw materials of carbomer, so that the obtained salt-resistant carbomer has good viscosity and salt resistance. At 25°C, its viscosity retention rate can reach 56.8%.

[0138] (2) By comparing Example 1 with Examples 7-10, it can be seen that when the weight of SAB is 0.48 parts, the mass ratio of SAB to acrylic acid is 0.048:1, and the resulting carbomer has the best salt resistance. When the mass ratio of SAB to acrylic acid is 0.02:1, the thickening effect is not obvious due to the low content of SAB, which cannot improve the compatibility and stability of the system, and thus cannot significantly improve the salt resistance of the resulting carbomer. When the mass ratio of SAB to acrylic acid is 0.07:1, the carbomer does not swell in water due to the high content of SAB, which is not conducive to the stability and uniformity of its viscosity. Therefore, when the mass ratio of SAB to acrylic acid exceeds the preferred mass ratio of the present invention (0.025-0.067):1, the viscosity and viscosity retention rate of the resulting salt-resistant carbomer decrease, that is, the salt resistance is poor.

[0139] (3) By comparing Example 1 with Examples 11-14, it can be seen that when the weight of di-tert-butylperoxyisopropylbenzene is 0.16 parts, the mass ratio of di-tert-butylperoxyisopropylbenzene to acrylic acid is 0.016:1, and the resulting carbomer has the best salt resistance. When the mass ratio of the two is 0.012:1, the content of di-tert-butylperoxyisopropylbenzene is too low, and the degree of cross-linking between polymer molecules is low. Although the initial viscosity of the prepared hydrogel system is high, the lack of rigidity of polymer molecules leads to the easy compression of molecular structure after the addition of salt, which in turn reduces the salt resistance. When the mass ratio of the two is 0.025:1, the content of di-tert-butylperoxyisopropylbenzene is too high, and the cross-linking density increases. However, the excessively high cross-linking density will reduce the maximum water absorption ratio of the polymer, and the extension of the polymer molecular chain in the solution will be severely restricted, which will reduce the water swelling capacity. As a result, the carbomer cannot fully swell in water and form a precipitate, which will significantly reduce its initial viscosity and fail to meet the requirements for use. Therefore, when the mass ratio of the two exceeds the preferred mass ratio of the present invention (0.015-0.022):1, the viscosity and viscosity retention of the obtained salt-resistant carbomer decrease, that is, the salt resistance is poor.

[0140] (4) A comparison between Example 1 and Comparative Example 1 shows that the content of cyclohexane and ethyl acetate exceeds the specific range of this invention, and the mass ratio of the two is less than 3:7, resulting in poor salt resistance of the obtained salt-resistant carbomer. In this invention, the polarity of the entire solvent system is adjusted by adjusting the mass ratio between cyclohexane and ethyl acetate, so that the low molecular weight primary polymer has good stability and does not precipitate from the solvent too early or too late. A decrease or increase in the mass ratio of the two solvents will cause the chain length of the polymerization intermediate to be too short or too long, failing to reach the predetermined molecular weight, thereby reducing the viscosity and salt resistance of the final product.

[0141] (5) By comparing Example 1 with Comparative Examples 3 and 4, it can be seen that when the content of thickener is less than 0.12 parts, the salt resistance of the obtained carbomer is poor; when the content is greater than 0.8 parts, the salt resistance is higher, but the viscosity of the product is significantly worse, which is not conducive to the actual application of the product.

[0142] (6) By comparing Example 1 with Comparative Examples 5 and 6, it can be seen that when the content of crosslinking agent is less than 0.05 parts, although the initial viscosity of the prepared hydrogel system is high, the molecular structure is easily compressed after salt is added due to the lack of rigidity of polymer molecules, which reduces the salt resistance. When the content of crosslinking agent is higher than 0.3 parts, although it obtains high salt resistance, it has poor viscosity value and cannot meet the actual use requirements.

[0143] (7) By comparing Example 1 with Comparative Examples 7 and 8, it can be seen that when the reaction temperature of the system is below 55°C, it has a poor viscosity value. Although the salt resistance increases, it cannot meet the actual use needs. When the temperature of the system is above 75°C, the salt resistance of the product is poor.

[0144] In summary, the present invention, through a specific ratio of cyclohexane and ethyl acetate, and by compounding acrylic monomers, thickeners, initiators, and crosslinking agents in specific amounts, produces a polymer with a relatively uniform network structure. This results in carbomer exhibiting good stability and salt resistance, thereby solving the technical problems of poor salt resistance, easy compression upon contact with salt leading to viscosity reduction, and severely reduced thickening ability of carbomer in the prior art.

[0145] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A salt-resistant carbomer, characterized in that, The raw materials for preparing carbomer include the following components in parts by weight: 8-12 parts of acrylic monomer 30-70 parts of cyclohexane 30-70 parts of ethyl acetate Thickener 0.12-0.8 parts Initiator 0.01-0.2 parts Crosslinking agent 0.05-0.3 parts; The acrylic monomer is acrylic acid; the thickener is SAB; the initiator is dimethyl azobisisobutyrate; and the crosslinking agent is bis-tert-butylperoxyisopropylbenzene. The mass ratio of cyclohexane to ethyl acetate is (3:7)-(7:3); the mass ratio of thickener to acrylic monomer is (0.025-0.067):1; and the mass ratio of crosslinking agent to acrylic monomer content is (0.015-0.022):

1. The carbomer was prepared by the following method, which includes the following steps: mixing cyclohexane and ethyl acetate, adding acrylic monomer, thickener, initiator and crosslinking agent, and reacting at 55℃-75℃ to obtain the salt-resistant carbomer.

2. A method for preparing salt-tolerant carbomer as described in claim 1, characterized in that, The preparation method includes the following steps: Cyclohexane and ethyl acetate were mixed, and acrylic monomer, thickener, initiator and crosslinking agent were added. The mixture was reacted at 55℃-75℃ to obtain the salt-resistant carbomer.

3. The preparation method according to claim 2, characterized in that, The reaction was carried out under stirring.

4. The preparation method according to claim 2, characterized in that, The reaction time is 7-9 hours.

5. The preparation method according to claim 2, characterized in that, The reaction was carried out under a protective gas atmosphere.

6. The preparation method according to claim 5, characterized in that, The protective gas includes any one or a combination of at least two of nitrogen, argon, or helium.

7. The preparation method according to claim 2, characterized in that, After the reaction is completed, a post-processing step is also included.

8. The preparation method according to claim 7, characterized in that, The post-processing steps include: cooling, washing and filtering, drying, and pulverizing and sieving.

9. The preparation method according to claim 8, characterized in that, The drying process is vacuum drying.

10. The preparation method according to claim 9, characterized in that, The vacuum drying temperature is 80℃-90℃.

11. The preparation method according to claim 9, characterized in that, The vacuum drying time is 9-11 hours.

12. The preparation method according to claim 8, characterized in that, The sieve used for crushing and sieving has a mesh size of 40.

13. The preparation method according to any one of claims 2-12, characterized in that, The preparation method specifically includes the following steps: (1) Mix cyclohexane and ethyl acetate to obtain a mixed solvent; (2) Under a protective gas atmosphere, acrylic monomer, thickener, initiator and crosslinking agent are added to the mixed solvent in step (1), and the mixture is stirred at 55℃-75℃ for 7-9 h. (3) Cool the reaction solution from step (2) to 25°C, wash and filter, vacuum dry at 80°C-90°C for 9-11 h, grind it into powder and pass it through a 40-mesh sieve to obtain the salt-resistant carbomer.

14. The use of the salt-resistant carbomer as described in claim 1 in pharmaceuticals or daily chemical products.

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