Cationic guar gum and preparation method thereof

Abstract

The invention belongs to the technical field of polymers, and discloses a preparation method of cationic guar gum, which comprises the following steps: under the condition of no organic solvent, taking guar endosperm tablets as raw materials, carrying out alkalization reaction and cationic etherification reaction to obtain cationic etherification modified guar endosperm tablets, washing the cationic etherification modified guar endosperm tablets with water, and drying to obtain the cationic guar gum. Preparing cationic guar gum by taking the washed guar endosperm slices as a raw material; the surfaces of the guar bean endosperm slices are subjected to cross-linking modification treatment by adopting a cross-linking agent before the alkalization reaction; or, between the alkalization reaction and the etherification reaction, a cross-linking agent is adopted to carry out cross-linking modification treatment on the surfaces of the guar bean endosperm tablets; according to the method, guar endosperm tablets are used as raw materials for alkalization and etherification, and a cross-linking agent is adopted for surface cross-linking of the guar endosperm tablets before etherification, so that swelling of the guar endosperm tablets in the subsequent washing process is inhibited, the basic shape of the guar endosperm tablets is reserved, and processing after washing is facilitated. The cationic guar gum prepared by the method disclosed by the invention and the cationic guar gum prepared by a traditional organic solvent-containing water washing scheme have the same performance. The production cost of the cationic guar gum is reduced, and the environmental protection property of the production process is improved. The invention further provides the water-phase cationic guar gum.

Description

Technical Field

[0001] The invention discloses a cationic guar gum and a preparation method of the guar gum, belonging to the technical field of polymer materials. Background Art

[0002] Guar gum is a polysaccharide composed of galactose and mannan units, in which the ratio of galactose to mannose is about 1:2. Guar gum has three free hydroxyl groups on each monosaccharide structure, which can quickly form stable hydrogen bonds with water, so it has strong hydrophilicity, and its viscosity increases greatly after mixing with water. It is often used as a thickener in the food industry, but guar gum has problems such as difficult to control viscosity, easy to be degraded by microorganisms, and high content of water-insoluble matter.

[0003] Therefore, cationic modification of guar gum has become a research hotspot for scholars. The modified aqueous cationic guar gum contains quaternary ammonium salt fragments, so it can react with negatively charged substances, thus playing an important role in various applications.

[0004] The method for cationic modified guar gum is generally to alkalize the guar gum powder and then slowly drip a cationic etherifying agent to carry out etherification. The crude product is washed with an alcohol-water mixed solution for multiple times to remove impurities, and then dried and crushed to obtain the cationic guar gum.

[0005] In the prior art, guar gum powder or guar bean endosperm slices are used as raw materials, and then alkalized and etherified to prepare cationic modified guar gum. However, during the preparation process, organic solvent washing is required to remove residual etherifying agent and other impurities, which results in excessively high solvent recovery costs and serious environmental pollution.

[0006] The technical problem solved by the invention is how to reduce the recovery difficulty and cost of the washing solvent in the preparation process of the cationic guar gum. Summary of the invention

[0007] In view of the above-mentioned shortcomings, the first object of the present invention is to provide a method for preparing cationic guar gum, which uses guar bean endosperm slices as raw materials for alkalization and etherification, and uses a cross-linking agent to perform surface cross-linking on the guar bean endosperm slices before etherification, so as to inhibit the swelling of the guar bean endosperm slices in the subsequent washing process, so that the basic shape of the guar bean endosperm slices can be retained, which is conducive to the processing after washing. The cationic guar gum prepared by the method of the present invention is no different from the cationic guar gum obtained by the traditional solution of washing with organic solvents in terms of performance. The present invention reduces the production cost of cationic guar gum and improves the environmental protection of the production process.

[0008] The second object of the present invention is to provide a cationic guar gum.

[0009] To achieve the above object, the first technical solution provided by the present invention is as follows:

[0010] A method for preparing cationic guar gum comprises the following steps: using guar bean endosperm slices as raw materials, performing alkalization reaction and cationic etherification reaction to obtain cationic etherified guar bean endosperm slices without organic solvent, washing the cationic etherified guar bean endosperm slices with water, and using the washed guar bean endosperm slices as raw materials to prepare cationic guar gum;

[0011] Using a cross-linking agent to perform cross-linking modification on the surface of the guar endosperm slices before the alkalization reaction; or

[0012] Between the alkalization reaction and the cationic etherification reaction, a cross-linking agent is used to carry out cross-linking modification treatment on the surface of the guar endosperm slices.

[0013] The invention carries out surface cross-linking modification on the guar bean endosperm slices before etherification, so that a cross-linking network is formed on the surface of the guar bean endosperm slices, and the binding force of the surface of the guar bean endosperm slices to the inside of the guar bean endosperm slices is improved. After the etherification modification, the excessive swelling of the guar bean endosperm slices in water is suppressed, so that the guar bean endosperm slices maintain a basic and complete shape, which is beneficial to subsequent drying, milling and other operations.

[0014] If the surface cross-linking modification is not carried out before etherification, the surface will absorb water quickly during water washing after etherification, turning the entire system into a viscous gel system, making subsequent drying and powdering operations impossible.

[0015] Through the optimization of the present invention, water can be used to wash the cationic etherified guar bean endosperm slices. The guar bean endosperm slices can maintain their basic shape during the water washing operation after etherification, which is beneficial to the subsequent rolling, drying and crushing powder making processes, avoiding the problem of solvent recovery caused by the use of organic solvents for washing operations in traditional processes, and effectively reducing the difficulty and cost of recovering the washing solvent.

[0016] In the above preparation method, the crosslinking agent is one or more combinations of glyoxal, glutaraldehyde, maleimide, diacetyl, silica, epoxy resin, epichlorohydrin, acrylic acid, citric acid, itaconic acid, maleic acid, tartaric acid, borax, and diethylenetriamine borate.

[0017] In the above preparation method, the weight ratio of the guar endosperm slices to the cross-linking agent is 150-120:1.

[0018] In the above preparation method, the temperature of the cross-linking modification is 40 to 60° C., and the time is 20 to 60 minutes.

[0019] In the present invention, any cross-linking agent and process that can realize the cross-linking of guar gum can be used for the surface cross-linking treatment of the guar bean endosperm slices of the present invention. Under the conditions of conventional reaction time, reaction temperature and the amount of cross-linking agent, the guar bean endosperm slices are treated with the cross-linking agent, and most of the cross-linking positions are located on the surface of the guar bean endosperm slices; before etherification, the absorption and swelling speed of the guar bean endosperm slices for water is limited, and the cross-linking agent is difficult to quickly enter the interior of the guar bean endosperm slices for cross-linking reaction; after the small amount of cross-linking agent that enters the interior of the guar bean endosperm slices reacts with the guar gum, the cross-linking amount is also very small, and the impact on the final application performance of the product is minimal.

[0020] In the above preparation method, the alkalizing agent used in the alkalization reaction is one or more of potassium hydroxide, sodium hydroxide, sodium carbonate, and potassium carbonate; the guar bean endosperm slices react with an alkaline solution containing the alkalizing agent, and the concentration of the alkaline solution is 1 to 7 wt %; the weight ratio of the guar bean endosperm slices to the alkaline solution is 1:0.3 to 0.8.

[0021] In the above preparation method, the etherifying agent used in the cationic etherification reaction is 3-chloro-2-hydroxypropyltrimethylammonium chloride or 3-epoxypropyltrimethylammonium chloride; the guar endosperm slices after alkalization are reacted with an etherifying solution containing the etherifying agent, the concentration of the etherifying solution is 55-75wt%, and the weight ratio of the guar endosperm slices to the etherifying solution is 1:0.17-0.54.

[0022] In the above preparation method, the temperature of the alkalization reaction is 40-60°C, and the time of the alkalization reaction is 1-3 hours; the temperature of the cationic etherification reaction is 50-90°C, and the time of the cationic etherification reaction is 0.5-2 hours.

[0023] The above-mentioned alkalization reaction and cationic etherification reaction are conventional means for preparing cationic guar gum. The parameters such as the relevant reagents, reaction temperature, time, etc. used in the alkalization reaction and cationic etherification reaction of the present invention are not limited to the above ranges. In the art, any means for alkalization and etherification of guar gum can be applied to the present invention.

[0024] In the above preparation method, the water used for washing is equivalent to 3 to 5 times the weight of the guar bean endosperm slices; the washing times are 1 or more times, 2, 3 or 4 times, and the purpose of washing is to remove the residual etherifying agent and other impurities; therefore, washing can be carried out according to the conventional washing operation guidance in the art.

[0025] In the above preparation method, the washed guar endosperm slices are crushed, dried and pulverized to obtain cationic guar gum powder.

[0026] Crushing can be done by crusher or by rolling; the purpose of crushing is to break it into smaller particles to facilitate drying.

[0027] Drying is carried out using a dryer or oven, and drying to a moisture content of less than 10wt% can meet the requirements of subsequent pulverization operations;

[0028] The crushing is carried out by a crusher, and the crushing mesh size is controlled at 80-100 meshes according to customer needs.

[0029] Finally, the invention discloses a cationic guar gum powder, which is prepared by any of the above methods.

[0030] Compared with the prior art, the technical solution provided by the present invention has the following technical advantages:

[0031] 1. The present invention uses guar bean endosperm slices as raw materials for alkalization and etherification, and uses a cross-linking agent to inhibit the swelling of the guar bean endosperm slices during the subsequent water washing process, so that the basic shape of the guar bean endosperm slices can be retained, which is beneficial for processing after water washing. The problem of solvent recovery and environmental pollution caused by the need to use organic solvents in the washing process of producing cationic guar gum in the prior art is solved.

[0032] 2. There is no difference in application performance between the cationic guar gum produced by the process of the present invention and the cationic guar gum produced by the applicant using the traditional process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a photograph of the washing operation in step 4 of Example 1;

[0034] Figure 2 is a photograph of the pulverized cationic modified guar gum powder of step 5 of Example 1;

[0035] Figure 3 This is a photograph of Comparative Example 1 after washing. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with specific implementation methods, but those skilled in the art should understand that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the technical solution of the present invention, and these modifications and replacements all fall within the scope of protection of the present invention.

[0037] The first part is cross-linking process after alkalization

[0038] Embodiment 1 to Embodiment 8

[0039] A kind of aqueous phase cationic guar gum, it is prepared by the following method:

[0040] Step 1: 30 g of guar bean endosperm slices (the endosperm part of the seeds of the leguminous plant guar bean after peeling and removing the germ, with a moisture content of ≤8%, and the raw material specifications of all subsequent guar bean endosperm slices are the same as the guar bean endosperm slices of this embodiment) and 15 g of alkali solution are mixed and stirred at 50° C. for 1 hour to obtain alkalized guar bean slices; the alkali solution is a sodium hydroxide aqueous solution with a concentration of 2.7wt%;

[0041] Step 2: preparing a crosslinking agent solution, and adding the crosslinking agent solution to the mixture in step 1 for surface crosslinking treatment;

[0042] Step 3: Raise the temperature of the mixture obtained in step 2 to 60° C., slowly drop 10 g of a cationic etherifying agent solution to carry out a cationic etherification reaction, and stir for 2 h;

[0043] The cationic etherifying agent solution is a 60wt% 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution;

[0044] Step 4: Cool the mixture obtained in step 3 to room temperature, filter out the guar bean endosperm slices in step 3, soak and stir and wash them with 90 g of deionized water, and wash them twice, each time consuming 45 g of water;

[0045] Step 5: rolling, drying and crushing to obtain cationic modified guar gum powder;

[0046] Mash until flat and mashed potatoes form;

[0047] After the rolled material is shaken or broken up, it is dried in an oven at a drying temperature of 60°C for 12 hours, and the moisture content after drying is less than 10wt%;

[0048] The mixture was crushed by a pulverizer and passed through an 80-mesh sieve to obtain cationic modified guar gum powder.

[0049] In step 2, the reaction temperature, reaction time, selection and use of the cross-linking agent can refer to Table 1;

[0050] Table 1 Process parameters

[0051]

[0052] Example 1 Photo reference during washing Figure 1 ;

[0053] Example 1: Photograph of pulverized cationic modified guar gum powder Figure 2 .

[0054] Embodiment 9 to Embodiment 12

[0055] A kind of aqueous phase cationic guar gum, it is prepared by the following method:

[0056] Step 1: Mix and stir 30 g of guar bean endosperm slices with alkali solution at a set temperature for a period of time to obtain alkalized guar bean slices;

[0057] Step 2: prepare a crosslinking agent solution (a 9.1wt% aqueous solution of glyoxal, used in an amount of 5.5g), add the crosslinking agent solution to the mixture of step 1 for surface crosslinking treatment, the reaction temperature is 50°C, and the reaction time is 50min;

[0058] Step 3: raising the temperature of the mixture obtained in step 2 to a set temperature, slowly dropping a cationic etherifying agent solution to carry out a cationic etherification reaction, and stirring for a period of time;

[0059] Step 4: Cool the mixture obtained in step 3 to room temperature, filter the guar bean endosperm slices in step 3, and soak and stir the slices with 90 g of deionized water for washing, which is divided into 2 washings, and each washing consumes 45 g of water;

[0060] Step 5: rolling into a flat mashed potato shape, drying, and crushing to obtain cationic modified guar gum powder;

[0061] After shaking or breaking up the rolled material, drying it in an oven at a drying temperature of 60°C for 12 hours, with a moisture content of less than 10wt% after drying;

[0062] The mixture was crushed by a pulverizer and passed through an 80-mesh sieve to obtain cationic modified guar gum powder.

[0063] The relevant parameters of the alkalization reaction and the cationic etherification reaction in step 1 and step 3 are shown in Table 2 below;

[0064] Table 2 Process parameters

[0065]

[0066] Embodiment 13

[0067] The method is substantially the same as Example 1, except that the washing water is 120 g, and the washing is divided into 3 times, each washing time is 40 g, and the crushing mesh size after washing is 90 mesh.

[0068] Embodiment 14

[0069] The method is substantially the same as Example 1, except that the washing water is 150 g, and the washing is divided into 3 times, each washing time is 50 g, and the crushing mesh size after washing is 100 mesh.

[0070] Embodiment 15

[0071] The method is substantially the same as Example 1, except that the washing water is 80 g, the washing is performed once, and the crushing size after washing is 80 meshes.

[0072] Comparative Example 1

[0073] The method is similar to Example 1, except that the cross-linking modification treatment in step 2 is not used. Step 3 is performed directly after step 1 is completed. The temperature is then lowered to room temperature and washed with water. When 90 g of deionized water is used for washing, the endosperm sheet quickly absorbs water and swells, and it is difficult to retain the complete structure of the endosperm sheet. The whole body is in a gel state and cannot be washed. When water is added to about 300 ml, the body still is in a gel state and cannot be washed. Figure 3 .

[0074] Performance Testing

[0075] The samples obtained in the above Examples 1 to 15 and a commercially available product (commercial product information: produced by Guangzhou Tianci High-tech Materials Co., Ltd., cationic guar gum, brand: GUAR 14S, cationic guar gum prepared by an organic solvent washing method) were subjected to the following performance tests.

[0076] 1) Appearance: visual inspection;

[0077] 2) Viscosity: The viscosity of a 1 wt% cationic guar gum aqueous solution was tested using an RVT viscometer, using a No. 4 rotor at a speed of 20 rpm;

[0078] 3) Nitrogen content: Kjeldahl method;

[0079] 4) Loss on drying: 1.5 g of cationic guar gum powder was spread on a halogen moisture analyzer (VM-E01) to test the weight loss. The average value was taken after three tests.

[0080] 5) pH value: The pH value of a 1% cationic guar gum aqueous solution was tested using a pH meter at 25°C.

[0081] Table 3 Performance test results

[0082] Appearance Viscosity / mPa·s Nitrogen content / % Loss on drying / % pH Example 1 Yellow powder 4800 1.35 7.50 8.90 Example 2 Yellow powder 4574 1.57 6.37 8.75 Example 3 Yellow powder 5072 1.45 8.64 8.32 Example 4 Yellow powder 4274 1.37 9.75 8.14 Example 5 Light yellow powder 5836 1.00 7.37 8.63 Example 6 Light yellow powder 5735 1.12 6.28 8.36 Example 7 Yellow powder 4938 1.50 8.47 8.42 Example 8 Yellow powder 4594 1.75 8.33 9.12 Example 9 Light yellow powder 5622 1.27 8.53 9.15 Example 10 Light yellow powder 5238 1.24 9.32 8.75 Embodiment 11 Yellow powder 4948 1.30 9.37 8.21 Example 12 Yellow powder 5742 1.37 9.58 7.96 Example 13 Light yellow powder 5046 1.40 8.55 9.03 Embodiment 14 Light yellow powder 4826 1.39 8.36 8.34 Embodiment 15 Light yellow powder 4742 1.46 8.65 7.37 Commercially available products Light yellow powder 4942 1.46 8.42 8.10

[0083] According to Table 3 and Figure 1 and Figure 2 It can be seen that the cationic guar gum provided by the present invention has a light yellow powder appearance, and the viscosity of the product aqueous solution is between 4274 and 5836 mPa·s, which is moderate and meets market demand; the nitrogen content is between 1% and 1.75%, indicating that it has a high protein content, the drying loss is 6.28% to 9.75%, the drying stability is good, and the pH value is 7.96 to 9.15, indicating that it has good acid-base stability.

[0084] In order to verify the residual solvent content of the technical solution provided in this application, the applicant tested the residual content of common organic solvents on the cationic guar gum prepared in the embodiment and commercially available products. The detection method of all organic solvents adopts gas chromatography, which is as follows:

[0085] Using a gas chromatography-mass spectrometry detector (Shimadzu GCMS-QP2010 SE gas chromatography-mass spectrometry), the sample is first separated by a gas chromatography column and then enters the mass spectrometer for ionization and mass spectrometry analysis; since different molecules produce different signals on the spectrum, the chemical composition of the sample can be determined. By comparing the peak intensity of the organic solvent in the sample with the peak intensity of the standard sample, the residual amount of organic solvent in the sample is calculated; the specific test results are shown in Table 4:

[0086] Table 4 Residue test results

[0087]

[0088] It can be seen from Table 4 that the residual amounts of ethanol, isopropanol, ethylene glycol, acetone and butanone in the technical solution provided by the present application are all 0 ppm, and no organic solvent remains.

[0089] Part 2 Cross-linking process before alkalization

[0090] Example 16 to Example 19

[0091] A kind of aqueous phase cationic guar gum, it is prepared by the following method:

[0092] Step 1: 30 g of guar bean endosperm slices were mixed with a crosslinking agent solution to perform surface crosslinking treatment;

[0093] Step 2: Add 15 g of alkali solution to the mixture obtained in step 1, mix and stir at 50° C. for 1 hour to obtain alkalized guar bean slices; the alkali solution is a sodium hydroxide aqueous solution with a concentration of 2.7 wt%;

[0094] Step 3: Raise the temperature of the mixture obtained in step 2 to 60° C., slowly drop 10 g of a cationic etherifying agent solution to carry out a cationic etherification reaction, and stir for 2 h;

[0095] The cationic etherifying agent solution is a 60wt% 3-chloro-2-hydroxypropyltrimethylammonium chloride aqueous solution;

[0096] Step 4: Cool the mixture obtained in step 3 to room temperature, filter the guar bean endosperm slices in step 3, and soak and stir the slices with 90 g of deionized water for washing, which is divided into 2 washings, and each washing consumes 45 g of water;

[0097] Step 5: rolling into a flat mashed potato shape, drying, and crushing to obtain cationic modified guar gum powder;

[0098] After shaking or breaking up the rolled material, drying it in an oven at a drying temperature of 60°C for 12 hours, with a moisture content of less than 10wt% after drying;

[0099] The mixture was crushed by a pulverizer and passed through an 80-mesh sieve to obtain cationic modified guar gum powder.

[0100] In step 1, the reaction temperature, reaction time, selection and use of the cross-linking agent can refer to Table 5;

[0101] Table 5 Process parameters

[0102]

[0103] The samples obtained in Examples 16 to 19 above were subjected to physical and chemical property tests and residue tests, and the test results are shown in Tables 6 and 7;

[0104] Table 6 Performance test results

[0105]

[0106]

[0107] Table 7 Residue test results

[0108]

[0109] It can be seen from the above Examples 16 to 19 that an ideal product can also be obtained by performing a cross-linking treatment before alkalization.

[0110] In summary, the present invention uses guar bean endosperm slices as raw materials for alkalization and etherification, and uses a cross-linking agent to perform surface cross-linking on the guar bean endosperm slices before etherification, so as to inhibit the swelling of the guar bean endosperm slices in the subsequent washing process, so that the basic shape of the guar bean endosperm slices can be retained, which is beneficial to the processing after washing. The problems of solvent recovery and environmental pollution caused by the organic solvent that must be used in the washing process of producing cationic guar gum in the prior art are solved. At the same time, there is no difference in application performance between the cationic guar gum produced by the process of the present invention and the cationic guar gum produced by the applicant using the traditional process.

Claims

1. A method for preparing cationic guar gum, characterized in that: In the absence of organic solvent, guar bean endosperm slices are used as raw materials, and cation etherification reaction is performed to obtain cationic etherified guar endosperm slices, the cationic etherified guar endosperm slices are washed with water, and the washed guar endosperm slices are used as raw materials to prepare cationic guar gum; Before the alkalization reaction, a cross-linking agent is used to perform cross-linking modification on the surface of the guar endosperm slices; or Between the alkalization reaction and the cationic etherification reaction, a cross-linking agent is used to carry out cross-linking modification treatment on the surface of the guar endosperm slices.

2. The preparation method according to claim 1, characterized in that: The cross-linking agent It is one or more combinations of glyoxal, glutaraldehyde, maleimide, diacetyl, silicon dioxide, epoxy resin, epichlorohydrin, acrylic acid, citric acid, itaconic acid, maleic acid, tartaric acid, borax, and diethylenetriamine borate.

3. The preparation method according to claim 1, characterized in that: The weight ratio of the guar bean endosperm slices to the cross-linking agent is 30 to 150:

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The cross-linking modification temperature is 40-60° C. and the time is 20-60 min.

5. The preparation method according to claim 1, characterized in that: The alkalizing agent used in the alkalization reaction is one or more of potassium hydroxide, sodium hydroxide, sodium carbonate and potassium carbonate; the guar bean endosperm slices react with an alkaline solution containing the alkalizing agent, and the concentration of the alkaline solution is 1-7wt%; the weight ratio of the guar bean endosperm slices to the alkaline solution is 1:0.3-0.

8.

6. The preparation method according to claim 1, characterized in that: The etherifying agent used in the cationic etherification reaction is 3-chloro-2-hydroxypropyltrimethylammonium chloride or 3-epoxypropyltrimethylammonium chloride; the guar bean endosperm slices after alkalization are reacted with an etherifying solution containing the etherifying agent, the concentration of the etherifying solution is 55-75wt%, and the weight ratio of the guar bean endosperm slices to the etherifying solution is 1:0.17-0.

54.

7. The preparation method according to claim 1, characterized in that: The temperature of the alkalization reaction is 40-60° C., and the time of the alkalization reaction is 1-3 hours; the temperature of the cationic etherification reaction is 50-90° C., and the time of the cationic etherification reaction is 0.5-2 hours.

8. The preparation method according to claim 1, characterized in that: The water used for washing is equivalent to 3 to 5 times the weight of the guar bean endosperm slices.

9. The preparation method according to claim 1, characterized in that: The washed guar endosperm slices are crushed, dried and pulverized to obtain cationic guar gum powder.

10. A cationic guar gum powder, characterized in that: The method is prepared by any one of claims 1 to 9.

Images