CN112175096B

CN112175096B - Carboxymethyl-like chitosan and one-step synthesis process

Info

Publication number: CN112175096B
Application number: CN202011075164.2A
Authority: CN
Inventors: 尹应武; 陈思瑞; 师雪琴; 吐松; 叶李艺; 高玉兴; 张文军; 张海双; 马杜媚
Original assignee: INNER MONGOLIA AUTONOMOUS REGION ACADEMY OF FORESTRY SCIENCES; Th Unis Insight Co ltd; Xiamen University
Current assignee: INNER MONGOLIA AUTONOMOUS REGION ACADEMY OF FORESTRY SCIENCES; Th Unis Insight Co ltd; Xiamen University
Priority date: 2020-10-09
Filing date: 2020-10-09
Publication date: 2022-04-26
Anticipated expiration: 2040-10-09
Also published as: CN112175096A

Abstract

The invention relates to a quasi-carboxymethyl chitosan polymer, a new process for synthesizing the polymer in one step and a composition containing the polymer, and provides a new method for synthesizing the quasi-carboxymethyl chitosan polymer in one step by taking cellulose sulfate monoester salt or bio-based mixed sulfate monoester salt as a raw material and carrying out substitution reaction with calcium glycinate in a water or alcohol-water system. The breakthrough technology makes low-cost and large-scale production of the carboxymethyl chitosan mimetic possible, and the carboxymethyl chitosan mimetic polymer with high cost performance is promoted to be widely applied in the fields of water retention agents, slow and controlled release fertilizers, liquid foliar fertilizers, adhesives and the like.

Description

Carboxymethyl-like chitosan and one-step synthesis process

Technical Field

The invention belongs to the field of biomass deep processing industry, particularly belongs to the field of polysaccharide derivative production, and more particularly relates to a wide-application carboxymethyl chitosan prepared by using a sulfonated product of a biomass material as a raw material, a composition containing the carboxymethyl chitosan, and a method for synthesizing the carboxymethyl chitosan by a one-step method.

Background

The carboxymethyl chitosan is a derivative of chitosan, has better film forming property, water solubility, flocculation property, antibacterial property and biocompatibility, and can be widely applied to industries such as industry, agriculture, environmental protection, medical treatment and the like. However, the existing production process has the restriction factors of difficult collection of natural raw materials, high production cost and the like, and the development of the industry is limited.

The prior carboxymethyl chitosan adopts a process route of firstly extracting chitosan from shrimp and crab shells as raw materials and then carrying out carboxymethylation to produce carboxymethyl chitosan, has the series problems of difficult raw material collection, high production cost, complex and long synthesis process, high acid and alkali consumption, low yield, large production amount of waste acid, waste alkali and waste salt organic water, difficult treatment, difficult raw material collection, high production cost and the like which seriously restrict the large-scale application of the waste acid, waste alkali and waste salt organic water, and has the annual output of less than 10 ten thousand tons in the world at present. Therefore, a new method is developed to find out that the water-soluble high molecular compound similar to carboxymethyl chitosan is synthesized by taking the cheap and easily obtained bio-based sulfuric acid monoester salt converted from natural biomass such as cellulose or hemicellulose as a raw material through simple substitution reaction.

Cellulose, starch, hemicellulose, lignin and other natural biological macromolecules all have hydroxyl groups and can form sulfuric acid monoester salt with sulfur trioxide. Cellulose differs from N-carboxymethyl chitosan only in the 2-position, the former being hydroxyl and the latter being carboxymethyl amino substituted.

Cellulose is a natural polymer with the largest content and the widest distribution in nature, and plants in nature can produce 2 multiplied by 10 through photosynthesis every year¹²Ton, but only 2.5% of them are effectively utilized. The preliminary stage of the subject group invents a new process capable of selectively sulfating the hydroxyl at the 6 th position in the cellulose molecule. The characteristic that sulfate radical in cellulose sulfate monoester salt or bio-based mixed sulfate monoester salt is easy to leave and can form calcium sulfate precipitate with calcium ions is utilized, and the direct substitution synthesis of 6-substituted carboxymethyl chitosan or the composition by using glycine calcium salt is a simple and convenient process worthy of being explored.

The subject group invents the synthesis and ammonia substitution reaction of biomacromolecule sulfuric acid monoester salt such as cellulose, straw, starch and the like in special ZLCN103539865A, ZL201610302468.5, ZL201710383270.9, ZL201810358713.3 and the like, establishes a new method for synthesizing chitosan analogue, develops series products such as green surfactant, water-retaining agent, adhesive and the like, and lays the technical foundation of a process route for synthesizing carboxymethyl chitosan by carboxymethylation. However, the synthetic process of the pseudo-chitosan has a series of problems of low substitution degree and yield, high reaction temperature, long time, serious side reactions of polymerization such as disubstituted reaction, high production cost and the like, and further optimization of process conditions is needed.

The process for synthesizing the pseudocarboxymethyl chitosan by using cellulose sulfate monoester calcium (or called as 'cellulose calcium sulfonate') and calcium glycinate in one step is most explored. Because glycinate has larger steric hindrance than ammonia, stronger nucleophilicity and repulsion between a secondary amino structure and negative charges of a substitution product, the glycinate is likely to be easier to substitute than ammonia and is more favorable for reducing polymerization byproducts, the attraction of divalent calcium ions can help raw material molecules to approach, the precipitation of calcium ions and sulfate radicals can help to leave sulfate radicals, but the o-group participation effect of glycine can lead to the fact that the reaction of hydrolysis and molecular degradation of bio-based sulfuric acid monoester must be inhibited.

Disclosure of Invention

In order to solve the above problems, the present invention provides a pseudocarboxymethyl chitosan, characterized in that the pseudocarboxymethyl chitosan has a B unit represented by the following formula:

c of beta-D-glucopyranosyl group in unit B₆The hydroxyl group of (A) is substituted by a carboxymethyl amino group.

In the above pseudocarboxymethyl chitosan, the degree of substitution of carboxymethyl amino groups in the pseudocarboxymethyl chitosan is 0.06 to 0.63, and is particularly preferred, and the degree of substitution of carboxymethyl amino groups in the pseudocarboxymethyl chitosan is 0.18 to 0.63, and is particularly preferred, and the degree of substitution of carboxymethyl amino groups in the pseudocarboxymethyl chitosan is 0.31 to 0.63.

In the above-mentioned carboxymethylchitosan, the degree of substitution of sulfonic acid groups in the carboxymethylchitosan polymer is 0.06 to 1.02, preferably, the degree of substitution of sulfonic acid groups in the carboxymethylchitosan polymer is 0.57 to 1.02, and particularly preferably, the degree of substitution of sulfonic acid groups in the carboxymethylchitosan polymer is 0.59 to 0.89.

The invention also provides a quasi-carboxymethyl chitosan polymer prepared by taking cellulose as a raw material, which is characterized in that the ratio of the substitution degree of carboxymethyl amino groups to the substitution degree of sulfonic groups in the polymer is (0.02-0.63) to (0.06-1.02), preferably, the ratio of the substitution degree of carboxymethyl amino groups to the substitution degree of sulfonic groups in the polymer is (0.18-0.63) to (0.57-1.02), and preferably, the ratio of the substitution degree of carboxymethyl amino groups to the substitution degree of sulfonic groups in the polymer is (0.31-0.61) to (0.59-0.89).

The carboxymethyl chitosan-like polymer contains a sulfonic acid group substituted cellulose unit and a carboxymethyl amino group substituted cellulose unit, wherein the representative structure of the sulfonic acid group substituted cellulose unit is an A unit of the following structure, and the representative structure of the carboxymethyl amino group substituted cellulose unit is a B unit of the following structure:

the carboxymethyl chitosan mimetic polymer generally comprises a C unit, and the structure of the C unit is as follows:

wherein the C unit is an unsubstituted unit.

Preferably, in the above carboxymethyl chitosan mimetic polymer, the Degree of Substitution (DS) of carboxymethyl amino group in the carboxymethyl chitosan mimetic polymer_N) From 0.02 to 0.63, the degree of substitution of sulfonic acid groups in the pseudo-carboxymethyl chitosan polymer being from 0.06 to 1.02, preferably, the degree of substitution of carboxymethyl amino groups in the pseudo-carboxymethyl chitosan polymer being from 0.18 to 0.63, the degree of substitution of sulfonic acid groups in the pseudo-carboxymethyl chitosan polymer being from 0.57 to 1.02, and particularly preferably, the degree of substitution of carboxymethyl amino groups in the pseudo-carboxymethyl chitosan polymer (DS)_N) 0.31-0.61, and the substitution degree of sulfonic acid group in the carboxymethyl chitosan polymer is 0.59-0.89.

Preferably, in the above carboxymethyl chitosan mimetic polymer, the synthesis method of the polymer is as follows:

the carboxymethyl chitosan analog polymer is prepared by heating and reacting cellulose sulfate monoester salt or bio-based mixed sulfate monoester salt containing the cellulose sulfate monoester salt serving as a raw material with calcium glycinate in water or an alcohol-water system.

Preferably, in the carboxymethyl chitosan mimetic polymer, the molar ratio of the sulfuric acid monoester salt in the cellulose sulfuric acid monoester salt or the bio-based mixed sulfuric acid monoester salt containing the cellulose sulfuric acid monoester salt to the glycine anion in the calcium glycine is 1: 1 to 1: 5, and the mass percentage of water in the alcohol-water system is 1 to 30%.

Preferably, in the above carboxymethyl chitosan mimetic polymer, in the alcohol-water system, the alcohol is selected from one or more of methanol, ethanol, propanol, n-butanol, and isobutanol, and preferably, the alcohol is n-butanol.

Preferably, in the above carboxymethyl chitosan mimetic polymer, the reaction conditions of the reaction are: the reaction temperature is 60-200 ℃, the reaction time is 8-30h, preferably, the reaction temperature is 110-150 ℃, and the reaction time is 8-24 h.

Preferably, in the carboxymethyl chitosan mimetic polymer, the bio-based mixed sulfuric acid monoester salt is prepared from pure cellulose, or the bio-based mixed sulfuric acid monoester salt is prepared from one or more plant raw materials of bleached pulp containing cellulose, hemicellulose and lignin, cotton, straws or natural color bamboo pulp, and the salt of the cellulose sulfuric acid monoester salt or the bio-based mixed sulfuric acid monoester salt containing the cellulose sulfuric acid monoester salt is a calcium salt.

The invention also provides a composition containing the pseudo-carboxymethyl chitosan polymer, wherein the mass percentage of the pseudo-carboxymethyl chitosan polymer in the composition is 0.5-99% of the mass of the composition.

Preferably, in the composition, the cellulose sulfate monoester is contained in the composition, and the mass ratio of the carboxymethyl chitosan-like polymer to the cellulose sulfate monoester is 1: 4 to 4: 1.

Preferably, in the composition, the carboxymethyl chitosan can be compounded with raw materials according to needs, or the content of calcium glycinate in the reaction process can be adjusted to obtain the composition with the needed performance.

Preferably, in the composition, the composition further comprises one or more of calcium glycinate, hemicellulose sulfuric acid monoester salt, lignin sulfuric acid monoester salt, polymer of hemicellulose sulfuric acid monoester salt substituted by carboxymethyl amino group, and polymer of lignin sulfuric acid monoester salt substituted by carboxymethyl amino group.

The invention also provides a method for preparing the carboxymethyl chitosan mimetic polymer, which comprises the following steps:

the carboxymethyl chitosan-like polymer is prepared by heating and reacting cellulose sulfate monoester salt or bio-based mixed sulfate monoester salt containing the cellulose sulfate monoester salt serving as a raw material with calcium glycinate in water or an alcohol-water system, wherein the molar ratio of the sulfate monoester group in the cellulose sulfate monoester salt or the bio-based mixed sulfate monoester salt containing the cellulose sulfate monoester salt to the glycine anion in the calcium glycinate is 1: 1-1: 5, the mass percent of water in the alcohol-water system is 1-30%, in the alcohol-water system, the alcohol is selected from one or more of methanol, ethanol, propanol, n-butanol and isobutanol, the reaction temperature is 60-200 ℃, the reaction time is 8-30h, and preferably, the reaction time is 8-24 h.

Preferably, in the above method, the bio-based mixed monoester sulfate is prepared from pure cellulose, or the bio-based mixed monoester sulfate is prepared from one or more plant raw materials of bleached pulp containing cellulose, hemicellulose and lignin, cotton, straw or natural color bamboo pulp, the salt in the cellulose monoester sulfate or the bio-based mixed monoester sulfate containing the cellulose monoester sulfate is calcium salt, the alcohol is n-butanol, and the reaction temperature is 110-150 ℃.

Preferably, in the above method, the method further comprises the optimization steps of filtering, washing, concentrating, drying and the like. The mother liquor can be recycled and can not be used as a raw material of the liquid fertilizer.

Specifically, after the reaction is finished, a crude product of the carboxymethyl chitosan is obtained through layering or filtering and drying, and the carboxymethyl chitosan can be directly used as raw materials such as an adhesive, a water-retaining agent, a liquid fertilizer and the like. The pure quasi-carboxymethyl chitosan product can be obtained by filtering, recrystallizing and drying the crude quasi-carboxymethyl chitosan product, and the pure quasi-carboxymethyl chitosan product can be used as raw materials of adhesives, water-retaining agents, liquid fertilizers and the like. When the crude or pure carboxymethyl chitosan mimetic is used as the adhesive, the concentration of the crude or pure carboxymethyl chitosan mimetic is 10-100%, and when the concentration of the crude or pure carboxymethyl chitosan mimetic in the composition containing the crude or pure carboxymethyl chitosan mimetic is less than 100%, the pH of the composition is more than 2, preferably, the pH is more than 6, and particularly preferably, the pH is more than 8.

Purifying the pure product of the pseudocarboxymethyl chitosan by a dialysis method: and after the reaction is finished, putting the reaction mixture into a dialysis bag with the molecular weight cutoff of 100-500, dialyzing for 48h to remove impurities, replacing water once every 6h, removing inorganic salt, drying the product, and drying at 60 ℃ to obtain a pure carboxymethyl chitosan-like solid product for analysis characterization and performance evaluation.

The characteristic that the by-product is easy to form precipitate is utilized to be firstly filtered and removed, because the molecular weight of the raw materials such as glycine and the like is below 200, the raw materials can be completely removed through dialysis, the influence of the raw materials on the conversion rate of the raw materials is eliminated, then the raw materials are concentrated and dried to obtain a product, and the product is weighed, so that the conversion rate of the raw materials can be calculated.

The invention also provides the application of the polymer, and the polymer is used for one or more products of water retention agents, controlled release fertilizers, liquid foliar fertilizers and adhesives, and improves the water retention property, water absorption property or viscosity property of the products. Preferably, the slow release fertilizer is a slow release fertilizer which does not contain a foliar liquid fertilizer, or a root slow release fertilizer or a soil slow release fertilizer.

In the context of the present invention, the term "cellulose sulphate monoester salt" is used, which is prepared by neutralisation of cellulose sulphate monoester with an alkaline substance, the cellulose sulphate monoester being obtained by substitution of cellulose by sulphonic acid groups. Cellulose sulphate monoester salts, also called fibre sulphates or cellulose sulphate salts, relate to the term "cellulose calcium sulphate monoesters", also called cellulose calcium sulphate, i.e. cellulose calcium sulphate monoesters prepared by reacting cellulose sulphate monoesters with a calcium-containing alkaline substance, also called cellulose calcium sulphate or cellulose calcium sulphonate.

The invention has the advantages of

1. In the prepared pseudo-carboxymethyl chitosan of the invention,carboxymethyl amino substituted beta-D-glucopyranosyl C₆The hydroxyl groups form nitrogen-substituted units, and the process is realized by the substitution of sulfate groups on cellulose sulfate monoester salt, but the obtained pseudocarboxymethyl chitosan has viscosity, water absorption and water retention.

2. The degree of substitution of carboxymethyl amino groups and the degree of substitution of sulfonic groups of the carboxymethyl chitosan-like polymer have reasonable proportion, and beneficial effects in the aspects of water retention, viscosity and the like can be embodied.

3. The invention relates to a method for preparing pseudocarboxymethyl chitosan by adopting a one-step synthesis method, which creates a new method for synthesizing a pseudocarboxymethyl chitosan polymer by taking cellulose sulfate monoester salt or bio-based mixed sulfate monoester salt as a raw material and performing substitution reaction by using calcium glycinate in an alcohol-water system in one step, can produce the pseudocarboxymethyl chitosan with higher conversion rate and higher substitution degree in shorter time and at lower temperature, has simple and convenient synthesis process, less byproducts, high substitution degree and easy separation and purification.

4. The invention has the characteristics, and the quasi-carboxymethyl chitosan prepared by the method has excellent performances in the aspects of viscosity, water absorption rate and water retention rate, and the high cost performance advantage can promote the quasi-carboxymethyl chitosan to be widely applied in the fields of water retention agents, slow-release fertilizers, liquid foliar fertilizers, amino acid fertilizers, adhesives and the like.

5. The quasi-carboxymethyl chitosan prepared by the invention can form an interpenetrating network system with cellulose sulfate monoester salt, and shows good water absorption and retention performance.

Drawings

FIG. 1 is a flow chart of a preparation process of a pseudo-carboxymethyl chitosan.

FIG. 2 is an infrared spectrum of calcium cellulose sulfonate.

FIG. 3 is a scanning electron microscope analysis chart of calcium cellulose sulfonate.

FIG. 4 is an infrared spectrum of a carboxymethyl chitosan mimetic.

FIG. 5 is the nuclear magnetic resonance carbon spectrum of the pseudocarboxymethyl chitosan.

FIG. 6 is a scanning electron microscope analysis chart of the carboxymethyl chitosan mimetic.

Figure 7 is a standard XRD pattern of the reaction by-product.

FIG. 8 is a scanning electron micrograph of a reaction by-product.

Detailed Description

The following examples further illustrate the present invention, and the following examples reflect the effects of the present invention under different conditions of temperature, time and water content, and the effects of the present invention in the application of adhesives and water-retaining agents. These examples are intended to illustrate the invention only and are not intended to limit the scope of the invention.

According to the preparation process flow chart of the pseudocarboxymethyl chitosan shown in fig. 1, the following conclusions can be obtained through a large number of experiments and process searches: the optimized process conditions for preparing the pseudo-carboxymethyl chitosan are as follows: the temperature is below 200 ℃ (preferably 80-160 ℃), the reaction time is 6-24h (preferably 8-16h), the mixture of pseudocarboxymethyl chitosan with the substitution degree DS about 0.6, carboxymethyl amino substituted hemicellulose and the like can be synthesized, and the process has few degradation products and byproducts.

The reaction equation for the preparation of the starting material is as follows:

the reaction equation for preparing the pseudo-carboxymethyl chitosan is as follows:

see table 1 for relevant test and analysis methods.

Table 1: analysis content and analysis method of product

Analyzing content	Analytical method
		Degree of substitution	Elemental analysis
Structural analysis	¹²C NMR
		Functional group analysis	FT-IR
Product yield	Gravimetric method
		Topography characterization	SEM
Product solution viscosity analysis	Digital display viscometer DV-C

EXAMPLE 1 preparation of starting cellulose Monosulfate salt

Weighing microcrystalline cellulose 0.486g, adding DCE 3.75ml for swelling cellulose, adding SO 1mol/L₃/DCE sulfonation reagents, based on cellulose building blocks and SO₃Feeding materials according to the molar ratio of 3: 5, stirring in an ice bath for 15min, then placing the reaction solution at room temperature for reacting for 2h to obtain cellulose sulfate monoester (the cellulose sulfate monoester is used in examples 12 and 13), adding 10ml of water and lime mixed solution, stirring and neutralizing until the pH value is 7, filtering out solid, wherein the filtrate is cellulose calcium sulfonate, and dialyzing, concentrating and drying are carried out to obtain a solid product 2.66g, the product yield is 54.8%, and the test sulfonation substitution degree is 1.2, wherein the infrared spectrogram of the cellulose sulfonate is shown in figure 2, and the scanning electron microscope analysis figure is shown in figure 3. Using the cellulose calcium sulfonate (CaCS) as a reaction raw material to carry out carboxyl reactionPreparation of methyl chitosan, calcium cellulose sulfonate with a degree of sulfonated substitution of 1.2 was used in examples 2-8 below.

The Degree of Substitution (DS) is the average number of substitutions of functional groups on the glucose structural unit in the cellulose. In the following examples, C, N, S analysis was performed on a sample by an element analyzer, and the degree of substitution of the sample was calculated by the following formula, and the degree of substitution of sulfur element (degree of substitution with sulfonic acid group) in the sample was calculated by the following formula:

wherein: s means sulfur content% in elemental analysis.

C means% carbon content in elemental analysis.

The calculation formula of the substitution degree (carboxymethyl amino substitution degree) of nitrogen element in the sample is as follows:

wherein: n means the% nitrogen content in the elemental analysis.

C means% carbon content in elemental analysis.

Example 2 yield and degree of substitution of carboxymethyl-like chitosan in Water System at different reaction times

0.281g of calcium cellulose sulfonate (CaCS) was added to an autoclave, and an appropriate amount of calcium glycinate was added thereto, changing the equivalence ratio of glucose units in calcium glycinate and calcium cellulose sulfonate to 2: adding 35ml of deionized water into the solution, changing the reaction time at the reaction temperature of 180 ℃, separating solid from liquid after the reaction is finished, obtaining the yield of pure products after the liquid is dialyzed, concentrated and dried, and calculating the substitution degree through element analysis.

Table 2: substitution degree and yield of pseudo-carboxymethyl chitosan in different reaction times in water system

Reaction time (h)	Degree of Substitution (DSN)	Degree of substitution (DSS)	Pure yield (%)
				4	0.09	0.45	44.2
8	0.25	0.30	21.6
				12	0.28	0.26	14.1
16	0.36	0.22	17.6
				20	0.40	0.19	14.5
24	0.48	0.20	7.9

As can be seen from Table 2, in an aqueous system, at a reaction temperature of 180 ℃, the degree of substitution increases gradually, but the yield of the product decreases seriously, and shortening the reaction time is advantageous for ensuring the yield, but the degree of substitution decreases if the reaction time is too short.

Example 3 yield and degree of substitution of carboxymethyl-like chitosan in different reaction equivalents in aqueous systems

Adding 0.281g of calcium cellulose sulfonate (CaCS) into a high-pressure reaction kettle, adding a proper amount of calcium glycinate into the high-pressure reaction kettle, changing the equivalent ratio of glucose units in the calcium glycinate and the calcium cellulose sulfonate to be 1: 1, 3: 1, 5: 1, 7: 1, 9: 1 and 11: 1, adding 35ml of deionized water into the high-pressure reaction kettle, reacting at the temperature of 180 ℃ for 24 hours, separating solid from liquid after the reaction is finished, obtaining the yield of pure products after the liquid is dialyzed, concentrated and dried, and calculating the substitution degree through element analysis. The test results are as follows.

Table 3: substitution degree and yield of pseudo-carboxymethyl chitosan with different reaction equivalents in water system

Equivalence ratio	Degree of substitution of the product (DsN)	Degree of substitution of the product (DsS)	Pure yield (%)
				1：1	0.59	0.18	3.4
3∶1	0.48	0.20	7.9
				5∶1	0.56	0.15	7.8
7∶1	0.53	0.19	5.8
				9∶1	0.52	0.15	9.4
11∶1	0.67	0.15	6.1

As can be seen from Table 3, in the water system, no matter how the mixture ratio is changed at the reaction temperature of 180 ℃, the substitution degree and the pure product yield are very low, and the hydrolysis and degradation of the product and the raw material are accelerated probably because the ortho-group participates in the catalysis, so that the process conditions need to be further optimized.

Example 4 yield and degree of substitution of carboxymethyl-like chitosan in Water System at different reaction temperatures

0.281g of calcium cellulose sulfonate (CaCS) was added to an autoclave, and an appropriate amount of calcium glycinate was added thereto, changing the equivalence ratio of glucose units in calcium glycinate and calcium cellulose sulfonate to 2: adding 35ml of deionized water into the solution, changing the reaction temperature, reacting for 24 hours, separating solid from liquid after the reaction is finished, obtaining the yield of pure products after the liquid is dialyzed, concentrated and dried, and calculating the substitution degree through element analysis.

Table 4: substitution degree and yield of pseudo-carboxymethyl chitosan in water system at different reaction temperatures

Reaction temperature (. degree.C.)	Degree of Substitution (DSN)	Degree of substitution (DSS)	Pure yield (%)
				120	0.03	0.40	78.3
140	0.02	0.42	63.6
				160	0.10	0.31	49.7
170	0.04	0.30	36.6
				180	0.42	0.15	7.9
190	0.63	0.06	3.9

As shown in Table 4, in the aqueous system, the degree of substitution increased significantly with the increase in reaction temperature, but the product yield decreased sharply. The reaction temperature is reduced, so that the product with low substitution degree requirement and high yield can be obtained.

Example 5 yield and degree of substitution of carboxymethyl-like chitosan in different alcohol-water systems

0.281g of calcium cellulose sulfonate (CaCS) is added into an autoclave, a proper amount of calcium glycinate is added into the autoclave, the equivalent ratio of glucose units in the calcium cellulose sulfonate to the calcium glycinate is 1: 2, 35ml of alcohol-water mixed solvent is added into the autoclave, the reaction temperature is 140 ℃, the reaction time is 12 hours, and the water content in the alcohol-water mixed solvent is 14 percent by weight. After the reaction is finished, solid-liquid separation is carried out, the solid is dissolved in pure water, the liquid is taken out after centrifugation, the yield of the liquid after dialysis, concentration and drying is the yield of a pure product, and the substitution degree can be calculated through element analysis.

Table 5: substitution degree and yield of pseudo-carboxymethyl chitosan in different alcohol-water systems

Alcohols	Methanol	Ethanol	Isopropanol (I-propanol)	N-butanol
					Crude product yield (%)	53.4	65.8	67.5	67.2
Pure yield (%)	48.2	59.6	63.1	63.5
					Degree of nitrogen substitution in pure form	0.21	0.25	0.30	0.61

As can be seen from Table 5, the yield in the water system is low, the degree of substitution is small, the degradation is severe, the degree of substitution and the yield of the product can be greatly increased in the alcohol-water system, the reaction time and the reaction temperature can be greatly reduced, and the product yield and the degree of substitution are highest particularly in the n-butanol-water system.

EXAMPLE 6 yield and degree of substitution of carboxymethyl-like chitosan in solvent systems of different alcohol content

0.281g of calcium cellulose sulfonate (CaCS) is added into an autoclave, and an appropriate amount of calcium glycinate is added into the autoclave, wherein the equivalent ratio of glucose units to calcium glycinate in the calcium cellulose sulfonate is 1: 2, adding 35ml of mixed n-butanol-water solvent, reacting at 140 ℃ for 12h, and changing the water content of the mixed solvent. After the reaction is finished, solid-liquid separation is carried out, the solid is dissolved in pure water, the liquid is taken out after centrifugation, the yield of the liquid after dialysis, concentration and drying is the yield of a pure product, and the substitution degree can be calculated through element analysis. And finding out an influence rule according to the substitution degree and the product yield of the carboxymethyl chitosan to determine the optimized process condition. The infrared spectrogram of the prepared carboxymethyl-like chitosan with the water content of 20 percent is shown in figure 4, the nuclear magnetic resonance carbon spectrogram is shown in figure 5, and the scanning electron microscope analytic map is shown in figure 6.

Measurement of Degree of Substitution (DS) of carboxymethyl amino group of quasi-carboxymethyl chitosan_S) Degree of substitution of sulfonic acid group (DS)_S) See table 6 below.

Table 6: substitution degree and yield of quasi-carboxymethyl chitosan in different water-containing systems

Water content (%)	Degree of Substitution (DS)_N)	Degree of Substitution (DS)_S)	Pure yield (%)	Crude product yield (%)
					5	0.41	0.79	42.3	43.7
8	0.50	0.70	52.2	53.4
					11	0.58	0.62	62.4	63.9
14	0.61	0.59	63.5	67.2
					17	0.37	0.83	67.4	69.1
20	0.31	0.89	71.1	73.5

As can be seen from Table 6, the water/butanol solvent system can achieve very good results in the water/alcohol mixed solvent.

The substitution degree of the product is increased and then decreased along with the increase of the water content, and the yield of the product is increased along with the increase of the water content because when the water content is too low, reaction raw materials are not dissolved in n-butyl alcohol, so that the reaction polymerization is serious, the reaction yield is decreased, and the water content is increasedThe degree of substitution is increased, and the increase in the water content to some extent leads to the aggravation of hydrolysis and degradation, resulting in a decrease in the degree of substitution. As can be seen from Table 6, the Degree of Substitution (DS) of the carboxymethyl amino group_N) Between 0.31 and 0.61.

Example 7 yield and degree of substitution of carboxymethyl-like chitosan at different temperatures

0.281g of calcium cellulose sulfonate (CaCS) was charged into an autoclave, 35ml of water or a mixed n-butanol aqueous solvent was added thereto to give a water content of 14%, and calcium glycinate was added thereto in an equivalent ratio of 1: 2 to glucose units in the calcium cellulose sulfonate. Changing the reaction temperature, wherein the reaction time is 12h, separating solid from liquid after the reaction is finished, dissolving the solid in pure water, centrifuging, taking the liquid, dialyzing, concentrating and drying to obtain the yield of a pure product, and calculating the substitution degree by element analysis, wherein the experimental result is as follows.

Table 7: influence of different reaction temperatures on degree of substitution and yield of carboxymethyl chitosan mimetic

Reaction temperature (. degree.C.)	Degree of Substitution (DS)_N)	Degree of Substitution (DS)_S)	Pure yield (%)	Crude product yield (%)
					100	0.31	0.89	83.6	84.0
120	0.54	0.66	71.8	73.6
					140	0.61	0.59	63.5	67.2
160	0.56	0.64	55.8	57.1
					180	0.54	0.66	34.9	36.5

As can be seen from Table 7, in the 14% alcohol-water system, the degree of substitution of the product increased with increasing temperature, which ranged from 0.31 to 0.61. The improvement of the substitution degree can obviously reduce the yield of the product, and the increase of the temperature can aggravate the hydrolysis of the raw materials and the product, so the yield is reduced.

Example 8 yield and degree of substitution of carboxymethyl-like chitosan under different reaction time conditions

0.281g of calcium cellulose sulfonate (CaCS) is added into an autoclave, the reaction equivalent ratio of the calcium cellulose sulfonate to the calcium glycinate is 1: 2, 35ml of water or a mixed n-butanol hydrosolvent is added into the autoclave, and the water content is 14 percent. The reaction temperature is 140 ℃, the reaction time is changed, solid-liquid separation is carried out after the reaction is finished, the solid is dissolved in pure water, the liquid is taken out after centrifugation, the yield of the liquid after dialysis, concentration and drying is the yield of a pure product, the substitution degree can be calculated through element analysis, and the experimental result is as follows.

Table 8: degree of substitution and yield of pseudo-carboxymethyl chitosan under different reaction time conditions

Reaction time (h)	Degree of Substitution (DS)_N)	Degree of Substitution (DS)_S)	Pure yield (%)	Crude product yield (%)
					6	0.18	1.02	73.2	76.1
8	0.24	0.96	71.1	74.8
					10	0.42	0.78	65.5	66.3
12	0.61	0.59	63.5	67.2
					14	0.59	0.61	61.2	63.1
16	0.63	0.57	56.9	58.4

As can be seen from Table 8, the degree of substitution increased with increasing reaction time, but the yield decreased, and after 12 hours the degree of substitution did not increase significantly, but the yield decreased significantly. Possibly with concomitant hydrolysis and degradation of the feedstock. As can be seen from Table 8, the Degree of Substitution (DS) of the carboxymethyl amino group_N) A reaction time of 16 hours can reach 0.63.

Example 9 Effect of pH on viscosity of carboxymethyl-like Chitosan

The carboxymethyl-like chitosan (substitution degree 0.61, reaction conditions were 14% water content in mixed n-butanol aqueous solvent, reaction temperature 140 ℃ C., reaction time 12 hours, that is, the carboxymethyl-like chitosan prepared in example 8 by reaction for 12 hours (the carboxymethyl-like chitosan in examples 10 to 15 below was tested by preparing a sample using this condition), was dissolved with pure water, 1mol/L hydrochloric acid solution or 1mol/L sodium hydroxide solution was added to the carboxymethyl-like chitosan to adjust pH, 30% by mass aqueous solution was adjusted, viscosity value in the solution was measured with a digital display viscometer DV-C, the temperature of the solution was controlled to 25 ℃ using a constant temperature water bath, and the results of the relevant measurements are shown in Table 9.

Table 9: effect of pH on viscosity of carboxymethyl chitosan mimetic

pH	2	6	8	10
					viscosity/MPa.s	217.12	233.78	271.54	362.8

As can be seen from table 9, when the concentration of the pseudocarboxymethyl chitosan was 30%, the viscosity was the greatest at pH 10, and it can be seen that the solution viscosity increased with the increase in pH.

Example 10 Effect of the mass fraction of a pseudocarboxymethyl chitosan on its viscosity

Since the viscosity of the product is the maximum at pH 10, the above-mentioned aqueous solutions of pseudocarboxymethyl chitosan, which have different mass fractions under the condition of pH 10, were selected and tested for viscosity values in the solution at a temperature of 25 ℃ with a digital viscometer DV-C. See table 10 for relevant experimental results. Wherein the preparation process of the carboxymethyl chitosan is as follows.

The shrimp and crab shell powder is used as raw material, the steps of decalcification and deproteinization are omitted, and the chitosan or carboxymethyl chitosan is directly prepared in an alcohol-alkali-water mixed system by a one-pot method under the conditions of heating and stirring. The steps are sequentially

1) The dried shrimp and crab shell solid is crushed into powder with more than 200 meshes (48 percent of calcium carbonate, 15 percent of chitin, 35 percent of lipid and protein and 2 percent of water) for later use.

2) Adding solid NaOH into an isopropanol-water mixed system, stirring to form a white pasty liquid, weighing a certain amount of powder, adding the powder into the mixed solution, stirring for a period of time at 70 ℃, fully deacetylating chitin, fully degrading proteins, washing and filtering the solid after the reaction is finished to obtain a chitosan-calcium carbonate mixture, dissolving the chitosan and calcium carbonate in the mixture by hydrochloric acid, performing ethanol reverse precipitation to obtain chitosan, and repeatedly washing with 70% ethanol aqueous solution to remove calcium chloride to obtain the pure chitosan.

3) After the chitin is fully deacetylated, chloroacetic acid is added into the system for 3 times, and carboxymethylation reaction of chitosan is carried out at 60 ℃.

4) Washing the product with 70% ethanol solution for 3 times, filtering, and drying the solid to obtain pure carboxymethyl chitosan.

Table 10: influence of mass fraction of quasi-carboxymethyl chitosan on viscosity in different preparation processes

As can be seen from table 10, the viscosity of the aqueous solution of the one-step synthesized pseudocarboxymethyl chitosan increases with the increase of the mass fraction and is higher than that of the aqueous solution of carboxymethyl chitosan.

Example 11 Effect of temperature on viscosity of carboxymethyl-like Chitosan

The carboxymethyl chitosan was dissolved in water at a mass fraction of 40% and a pH of 10, and the viscosity value in the solution was measured with a digital display viscometer DV-C, the measurement environment temperature was changed, and the influence of the measurement temperature on the viscosity was measured, and the experimental results are shown in Table 11.

Table 11: effect of temperature on viscosity of carboxymethyl-like Chitosan

As can be seen from Table 11, the viscosity of the pseudocarboxymethyl chitosan rapidly decreased as the temperature increased.

Example 12 Effect of the ratio of carboxymethyl chitosan mimetic to cellulose sulphate monoester on viscosity

The synthesized pseudo-carboxymethyl chitosan was compounded with the raw material cellulose sulfate monoester, and the compounding ratio was changed, with the results shown in table 12.

Table 12: influence of ratio of carboxymethyl chitosan to cellulose sulfate monoester on viscosity

As can be seen from Table 12, when the mass ratio of the pseudocarboxymethyl chitosan to the cellulose sulfate monoester is 1: 1 (pH is 7 at this time), the viscosity is the highest, and the viscosity of the compounded product is higher than that of the pure product, which indicates that the two are neutralized to form the interpenetrating network polymer.

Example 13 influence of different ratios of carboxymethyl chitosan and cellulose sulfate monoester on Water absorption Capacity

The carboxymethyl chitosan and cellulose sulfate monoester were compounded in the following ratio as shown in table 13, and the water absorption of the compounded product was measured according to the following methods:

mixing 50g of soil dried to constant weight with 1g of water-retaining agent after synthesis and compounding uniformly, loading into a chromatographic column, weighing the mass, and recording as W_aSlowly adding clear water into the chromatographic column until water drops out from the lower part, stopping adding water, standing until no water drops out from the lower end of the chromatographic column, weighing the mass, and recording as W₀。

The calculation formula of the water absorption rate of the water-retaining agent is as follows: w_H＝(W₀-W_a)/1g

The results of the related experiments and the control experiments are shown in Table 13.

Table 13: influence of different proportions of carboxymethyl chitosan and cellulose sulfate monoester on water absorption rate

As can be seen from table 13, the reaction of crude carboxymethyl chitosan mimetic with cellulose sulfate monoester was carried out for 4: the water absorption capacity of the 1-component system can reach 31.83 times, and even if the more economical ratio of 1: 4 is used, the water absorption capacity can reach 30.39.

Example 14 Effect of solution mass fraction on bond Strength of carboxymethyl chitosan mimetic

Pure water is used for dissolving the pseudocarboxymethyl chitosan, aqueous solutions with different mass fractions are prepared according to the experimental requirements in the table 14, the test of the adhesive property is carried out according to the national standard GB7124-2008, the test material is a wood board, the mass difference of the wood board before and after adhesion is the glue application amount, and the related experimental results are shown in the table 14. Wherein, the preparation process of the two-step product is as follows.

Accurately weighing 6-amino cellulose with a certain mass in a round-bottom flask, adding isopropanol and 10mol/L NaOH solution with a certain proportion, uniformly stirring at 60 ℃, adding chloroacetic acid in 5 batches, and reacting for 3 hours. The raw materials are mixed according to the proportion of 6-amino cellulose, isopropanol, NaOH (10M) and chloroacetic acid which are 1g to 10ml to 2.5ml to 1.2 g. After the reaction is finished, the mixture is added with water to be dissolved, the mixture is centrifuged to obtain supernatant, the solid is washed by a small amount of deionized water and then centrifuged again, the process is repeated twice, and the supernatants are combined. Adding 3 times volume of absolute ethyl alcohol for reverse precipitation to obtain solid, washing the solid for 3 times by using the absolute ethyl alcohol, and drying the solid in vacuum at 60 ℃ to obtain the pure carboxymethyl 6-amino cellulose (namely the pseudocarboxymethyl chitosan).

Table 14: influence of solution mass fraction on binding strength of carboxymethyl chitosan mimetic

Solution mass fraction (wt%)	One-step product bonding strength (MPa)	Two-step product bond Strength (MPa)
			9	3.3	0.7
16	4.1	0.8
			28	4.0	1.2
37	5.9	1.2
			50	4.3	1.3

As can be seen from Table 14, as the mass fraction of the solution increases, the tensile shear strength of the aqueous solution of the pseudocarboxymethyl chitosan increases first and then decreases, and the bonding strength of the product synthesized by the one-step method is obviously higher than that of the product synthesized by the two-step method.

EXAMPLE 15 Effect of different addition amounts on tensile shear Strength of styrene-acrylic emulsion

The carboxymethyl chitosan analog is added into the styrene-acrylic emulsion with the solid content of 30 percent, and the enhancement effect of the carboxymethyl chitosan analog on the performance of the styrene-acrylic emulsion is explored. Styrene-acrylic emulsion-carboxymethyl chitosan solution with different mass fractions is prepared according to the experimental requirements in the table 15, the test of the adhesive property is carried out according to the national standard GB7124-2008, the test material is a wood board, and the mass difference of the wood board before and after adhesion is the glue application amount. See example 14 for a two-step product. See table 15 for relevant experimental results.

Table 15: effect of different addition amounts on tensile shear Strength of styrene-acrylic emulsion

Addition amount (wt%)	One-step method product tensile shear strength (Mpa)	Two-step product tensile shear Strength (MPa)
			0	6.5	6.5
10	8.0	8.2
			20	8.8	9.8
30	6.6	10.2
			40	5.3	10.1
60	4.6	9.7

As can be seen from Table 15, when the amount of the pseudocarboxymethyl chitosan added reaches 20 wt%, the tensile shear strength of the styrene-acrylic emulsion can be improved by 34%.

Example 16 analysis of reaction by-products

Washing insoluble by-products with water, drying, measuring XRD and comparing with standard spectrum. The XRD spectrum is shown in FIG. 7, and the electron micrograph of insoluble substances is shown in FIG. 8.

The insoluble matter is a mixture of calcium carbonate and calcium sulfate, and dilute hydrochloric acid solution is added into the insoluble matter. The mass was again weighed after drying and found to decrease, and the elemental analysis data before and after the reaction are shown in Table 16 below.

Table 16: elemental analysis of by-products

As can be seen from table 16, the calcium carbonate was consumed by hydrochloric acid after the addition of hydrochloric acid, leaving a calcium sulfate by-product, which was determined to be a mixture of calcium carbonate and calcium sulfate in combination with the XRD pattern.

Example 17 test of Water absorption and Water retention Properties of carboxymethyl chitosans prepared from straw sulfonate

The straw is used as a substitute for cellulose, the straw calcium sulfonate prepared by the sulfonation process in the embodiment 1 is used for substituting for cellulose sulfate monoester salt in a raw material for preparing the carboxymethyl chitosan, so that the synthesis cost is reduced, the influence of different reaction time, reaction temperature and reaction equivalent on the water retention and water absorption of the carboxymethyl chitosan is studied, the water content is 14% in the process of preparing the straw mixed sulfate monoester salt containing the cellulose sulfate monoester salt, when the reaction time is changed, the reaction temperature is 120 ℃, the reaction equivalent is 1: 1 of the equivalent ratio of the straw sulfonate to calcium glycinate, when the reaction temperature is changed, the reaction time is 12 hours, the reaction equivalent is 1: 1 of the equivalent ratio of the straw sulfonate to the calcium glycinate, and when the reaction equivalent is changed, the reaction temperature is 120 ℃, and the reaction time is 12 hours.

The calculation method of the water absorption multiplying power and the water retention rate comprises the following steps: mixing 50g of soil dried to constant weight with 1g of water-retaining agent after synthesis and compounding uniformly, loading into a chromatographic column, weighing the mass, and recording as W_aSlowly adding clear water into the chromatographic column until water drops out from the lower part, stopping adding water, standing until no water drops out from the lower end of the chromatographic column, weighing the mass, and recording as W₀。

The sample was poured into a watch glass and weighed as W₁And weighing at 60 ℃ after baking for 8h, and recording as W₂. The calculation formula of the water absorption rate of the water-retaining agent is as follows: w_H＝(W₀-W_a)/1g。

The calculation formula of the water retention rate of the water retention agent is as follows: w_R(％)＝(1-(W₁-W₂)/(W₀-W_a))×100％。

See tables 17, 18 and 19 for results of related and control experiments.

Table 17: influence of reaction time on water absorption and water retention of straw ammoniated product

In Table 17, the reaction temperature for preparing the carboxymethyl-like chitosan was 120 ℃, the reaction equivalent was 1: 1, and the water content was 14%. As can be seen from Table 17, the carboxymethyl chitosan prepared by ammoniating straw sulfonate as a raw material also has good water absorption and retention properties, and the water absorption property and the water retention property of the carboxymethyl chitosan are increased with the increase of the reaction time, but the increase rate is slow.

Table 18: influence of reaction temperature on water absorption and water retention of straw ammoniated product

Temperature (. degree.C.)	Residual amount of calcium glycinate (%)	Multiple of water absorption	Water retention (%)	Theoretical degree of nitrogen substitution
					100	62.44	21.3	13.6	0.37
110	46.52	25.6	19.4	0.53
					120	37.79	34.1	26.3	0.62
130	33.82	33.7	24.5	0.66
					140	26.58	32.6	23.9	0.73

In Table 18, the reaction time for preparing the carboxymethyl chitosan mimetic was 12 hours, the reaction equivalent was 1: 1, and the water content was 14%. As can be seen from Table 18, the calcium glycinate content gradually decreases with increasing temperature, and the water absorption and retention properties of the product increase and then decrease, but the water retention and absorption properties are all good in combination.

Table 19: influence of reaction equivalent on water absorbability and water retention rate of straw ammoniated product

Equivalent ratio of straw sulfonate to calcium glycinate	Residual amount of calcium glycinate (%)	Multiple of water absorption	Water retention (%)
				0.5∶1	15.26	23.5	14.6
1∶1	37.79	34.1	26.3
				1∶2	48.10	35.7	27.9

In Table 19, the reaction time for the preparation of the carboxymethyl chitosan was 12 hours, the reaction temperature was 120 ℃ and the water content was 14%. As can be seen from Table 19, the total gain in economic efficiency and water retention and absorption capacity is highest at a reaction equivalent of 1: 1.

Claims

1. A quasi-carboxymethyl chitosan polymer prepared by using cellulose as a raw material is characterized in that the ratio of the substitution degree of carboxymethyl amino groups to the substitution degree of sulfonic groups in the polymer is (0.02-0.63): (0.06-1.02), and the quasi-carboxymethyl chitosan has a B unit with the following formula:

c of beta-D-glucopyranosyl group in unit B₆The hydroxyl is substituted by carboxymethyl amino, and the substitution degree of the carboxymethyl amino in the pseudocarboxymethyl chitosan is 0.06-0.63.

2. The polymer according to claim 1, wherein the ratio of the degree of substitution of carboxymethyl amino groups to the degree of substitution of sulfonic acid groups in the polymer is (0.18-0.63): (0.57-1.02), and the degree of substitution of carboxymethyl amino groups in the pseudocarboxymethyl chitosan is 0.18-0.63.

3. The polymer according to claim 2, wherein the ratio of the degree of substitution of carboxymethyl amino groups to the degree of substitution of sulfonic acid groups in the polymer is (0.31-0.61): (0.59-0.89), and the degree of substitution of carboxymethyl amino groups in the pseudocarboxymethyl chitosan is 0.31-0.63.

4. The polymer according to claim 1, characterized in that the synthesis of the polymer is as follows:

5. Polymer according to claim 4, characterized in that the molar ratio of the sulfate monoester salt of cellulose sulfate monoester salt or of the biobased mixed sulfate monoester salt comprising cellulose sulfate monoester salt to the glycine anion of calcium glycinate is 1: 1-1: 5, the mass percent of water in the alcohol-water system is 1-30%.

6. The polymer according to claim 4, wherein the alcohol is selected from one or more of methanol, ethanol, propanol, n-butanol, and isobutanol.

7. The polymer according to claim 6, characterized in that the alcohol is n-butanol.

8. The polymer according to claim 4, characterized in that the reaction conditions of the reaction are: the reaction temperature is 60-200 ℃, and the reaction time is 8-30 h.

9. The polymer according to claim 8, wherein the reaction temperature is 110 ℃ and 150 ℃ and the reaction time is 8-24 h.

10. The polymer according to claim 4, characterized in that the bio-based mixed monoester sulfate is prepared from pure cellulose, or the bio-based mixed monoester sulfate is prepared from a plant raw material containing one or more of bleached pulp of cellulose, hemicellulose and lignin, cotton, straw or natural color bamboo pulp, and the salt of the cellulose monoester sulfate or the bio-based mixed monoester sulfate containing the cellulose monoester sulfate is calcium salt.

11. A method of preparing a carboxymethylchitosan-like polymer, the method comprising:

the carboxymethyl chitosan-like polymer is prepared by taking cellulose sulfate monoester salt or a biological mixed sulfate monoester salt containing the cellulose sulfate monoester salt as a raw material and heating and reacting the raw material with calcium glycinate in water or an alcohol-water system, wherein the molar ratio of a sulfate monoester in the cellulose sulfate monoester salt or the biological mixed sulfate monoester salt containing the cellulose sulfate monoester salt to a glycine anion in the calcium glycinate is 1: 1-1: 5, the mass percent of water in an alcohol-water system is 1-30%, in the alcohol-water system, the alcohol is selected from one or more of methanol, ethanol, propanol, n-butanol and isobutanol, and the reaction temperature is 60-200 ℃.

12. The process according to claim 11, characterized in that the reaction time is 8-30 h.

13. The process according to claim 12, characterized in that the reaction time is 8-24 hours.

14. The method as claimed in claim 11, wherein the bio-based mixed monoester sulfate is prepared from pure cellulose, or the bio-based mixed monoester sulfate is prepared from one or more plant materials selected from bleached pulp containing cellulose, hemicellulose and lignin, cotton, straw or natural color bamboo pulp, the salt of the cellulose monoester sulfate or the bio-based mixed monoester sulfate containing the cellulose monoester sulfate is calcium salt, the alcohol is n-butanol, and the reaction temperature is 110-.