Preparation method of low-cost potato hydroxypropyl starch ether

Abstract

The invention belongs to the technical field of hydroxypropyl starch ether, and relates to a preparation method of low-cost potato hydroxypropyl starch ether.The preparation method comprises the steps that an alkalizing agent, a solvent and an inhibitor are fully mixed, then potato starch is added for alkalization, then an etherifying agent is added, heating is conducted for modification, potato hydroxypropyl starch ether is obtained, and after a reaction product is subjected to desolvation, the potato hydroxypropyl starch ether is obtained. And drying is not needed, and crushing can be directly carried out. The preparation method has the advantages of small solvent addition amount, high utilization rate of the alcohol solvent and the etherifying agent, low reaction temperature and expansion pressure control, safety, high efficiency, small environmental pollution, improvement of the production stability and great reduction of the production cost; the produced product has the advantages of high hydroxypropyl content, high viscosity, high solution transparency, low ash content and the like; the process is simple, the cost is low, industrial production is facilitated, and the market prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of hydroxypropyl starch ether preparation methods, and relates to a method for preparing hydroxypropyl starch ether using potato as a raw material. The method can prepare high-quality hydroxypropyl starch ether with little solvent and phosphating agent, and has simple process and low cost. Background Art

[0002] Hydroxypropyl starch ether (HPS) is a non-ionic mixed ether obtained from natural starch through alkalization and etherification. It is widely used in the building materials industry, food industry, pharmaceutical industry, daily chemical industry, etc. Especially in my country's building decoration materials industry, it is used in large quantities and is an important building material admixture.

[0003] Potato is one of the main non-cereal crops in my country. It is widely planted and has a large yield in my country, making it an important cash crop. Most of the hydroxypropyl starch ethers produced in China use corn starch and cassava starch as raw materials. There are relatively few studies on the hydroxypropylation of potato starch or the production cost is too high. Potato hydroxypropyl starch ether is an etherification reaction between propylene oxide and starch, replacing the hydroxyl groups in the polymer structure of starch to become a high-end etherified starch. Compared with hydroxypropyl starch ethers made from corn, cassava and other starch raw materials, it has the advantages of better polymerization degree and higher viscosity.

[0004] At present, the domestic production process of potato hydroxypropyl starch ether generally adopts solvent method and wet method, which consumes a lot of raw materials, is not environmentally friendly, and has complex procedures and high production costs. The patent application publication number CN113444185A discloses a method for preparing potato hydroxypropyl starch ether by solvent method, in which potato starch is suspended in ethanol, an alkaline catalyst is added, and propylene oxide is added. After the reaction is completed, the solvent is removed, washed and dried. The ratio of potato starch to ethanol is 10:50-200. Although this method has a high yield, it consumes a large amount of ethanol, which is not environmentally friendly and increases production costs; and the temperature of the potato starch etherification stage in this method is as high as 70-80°C. At this temperature, potato starch is very easy to gelatinize, and the material state is difficult to control. The patent with application publication number CN106543293A discloses a method for preparing potato hydroxypropyl starch ether by wet method, which is to dissolve potato starch in water to obtain a starch emulsion with a concentration of 30%, add anhydrous sodium sulfate, sodium hydroxide, propylene oxide, stir and seal, react at a constant temperature for 12 hours, add sulfuric acid to neutralize the pH value, and then filter, wash, and dry for 8 hours to obtain potato hydroxypropyl starch ether. This method consumes a lot of water, has complex production steps, many factors affecting production stability, and high time cost. The finished product produced by this preparation method is difficult to meet market demand.

[0005] Therefore, in view of the problem that the production cost of potato hydroxypropyl starch ether is too high, there is an urgent need for a preparation method that can reduce the cost without affecting the quality of the finished product. Summary of the invention

[0006] The purpose of the invention is to solve the problem that the production cost of the existing potato hydroxypropyl starch ether is too high, optimize the preparation method under the premise of ensuring the quality of the finished product, reduce the production cost, improve the production stability, and make the product better meet the market demand.

[0007] In order to achieve the above object, the present invention provides a low-cost preparation method of potato hydroxypropyl starch ether, wherein the raw materials are as follows by weight: 10 parts of potato starch, 3-5 parts of etherifying agent, 1.5-2.5 parts of solvent, 0.2-0.3 parts of alkalizing agent, and 1.0-1.5 parts of inhibitor; the specific preparation method comprises the following steps: (1) Raw material mixing: add 0.2-0.3 parts of alkalizer, 1.5-2.5 parts of solvent and 1.0-1.5 parts of inhibitor into the reaction kettle, and stir and disperse the mixture at 40°C for 0.5 hours; (2) Alkalization: Add 10 parts of potato starch into the reactor under constant stirring, keep the temperature at 40-45°C, continue stirring, and alkalize for 0.8-1.2 hours; (3) Etherification: Add 3-5 parts of etherifying agent into the reactor under continuous stirring, control the temperature at 45-55°C, and stir the reaction for 6-9 hours; (4) Recovering the solvent: Open the vacuum condensation recovery device to recover the solvent. The material recovered by the solvent is the crude product; (5) Screening: The crude product is sent to a micronizer for crushing to obtain the finished product of potato hydroxypropyl starch ether.

[0008] The etherifying agent of the present invention is one or more of chloroacetic acid, methyl chloride, ethyl chloride, propylene glycol ether, propylene oxide and ethylene oxide; the solvent is alcohol, specifically one or more of methanol, ethanol, isopropanol, n-butanol, tert-butanol, acetone and diethylene glycol; the alkalizing agent is granular alkali metal hydroxide or powdered alkali metal hydroxide; the inhibitor is any one of anhydrous sodium sulfate, anhydrous sodium carbonate, anhydrous sodium bicarbonate and anhydrous sodium chloride or a mixture of several of them.

[0009] The alkalizing agent of the present invention is preferably sodium hydroxide.

[0010] Compared with the prior art, the invention has the advantages of less solvent addition, high utilization rate of alcohol solvent and etherifying agent, relatively low controlled reaction temperature and expansion pressure, safety and high efficiency, low environmental pollution, improved production stability, greatly reduced production cost of potato hydroxypropyl starch ether, and the reaction product can be directly crushed without drying after desolventizing; the produced finished product has the advantages of high hydroxypropyl content, high viscosity, high solution transparency, low ash content, etc.; the process is simple, the cost is low, it is conducive to industrial production, and the market prospect is broad. DETAILED DESCRIPTION

[0011] The technical solution of the present invention is described in detail below through specific embodiments.

[0012] Example 1 The present embodiment relates to a method for preparing potato hydroxypropyl starch ether, wherein the raw materials are as follows by weight: 10 parts of potato starch, 3 parts of propylene oxide, 1.5 parts of ethanol, 0.2 parts of sodium hydroxide and 1.0 parts of anhydrous sodium sulfate; the propylene oxide is an etherifying agent, the ethanol is a solvent, the sodium hydroxide is an alkalizing agent, and the anhydrous sodium sulfate is an inhibitor; the specific preparation steps are as follows: (1) Raw material mixing: add 0.2 parts of sodium hydroxide, 1.5 parts of ethanol and 1.0 parts of anhydrous sodium sulfate into a reaction kettle, and stir and disperse at 40°C for 0.5 hours; (2) Alkalization: Add 10 parts of potato starch into the reactor under constant stirring, keep the temperature at 40°C, continue stirring, and alkalize for 0.8 hours; (3) Etherification: Add 3 parts of propylene oxide into the reactor under continuous stirring, control the temperature at 45°C, and stir the reaction for 6 hours; (4) Recovery: Open the vacuum condensation recovery device to recover the solvent; (5) Screening: The dried material is sent to a micronizer, where it is crushed to an 80-mesh sieving rate of more than 99%. After passing the inspection, it is packaged and stored.

[0013] The hydroxypropyl content, moisture, ash content, light transmittance and viscosity of the potato hydroxypropyl starch ether prepared in Example 1 were tested by conventional testing methods in the art. The results are shown in Table 1.

[0014] Table 1

[0015] Example 2 The present embodiment relates to a method for preparing potato hydroxypropyl starch ether, wherein the raw materials are as follows by weight: 10 parts of potato starch, 4 parts of propylene oxide, 2 parts of ethanol, 0.25 parts of sodium hydroxide and 1.5 parts of anhydrous sodium sulfate; the propylene oxide is an etherifying agent, the ethanol is a solvent, the sodium hydroxide is an alkalizing agent, and the anhydrous sodium sulfate is an inhibitor. The preparation steps are as follows: (1) Raw material mixing: Add 0.25 parts of sodium hydroxide, 2 parts of ethanol and 1.5 parts of anhydrous sodium sulfate into a reaction kettle, and stir and disperse at 40°C for 0.5 hours; (2) Alkalization: Add 10 parts of potato starch into the reactor under constant stirring, keep the temperature at 50°C, continue stirring, and alkalize for 1 hour; (3) Etherification: Add 5 parts of propylene oxide into the reactor under continuous stirring, control the temperature at 50°C, and stir to react for 8 hours; (4) Recovery: Open the vacuum condensation recovery device to recover the solvent; (5) Screening: The dried material is sent to a micronizer, where it is crushed to an 80-mesh sieving rate of more than 99%. After passing the inspection, it is packaged and stored.

[0016] The hydroxypropyl content, moisture, ash content, light transmittance and viscosity of the potato hydroxypropyl starch ether prepared in Example 2 were detected by conventional detection methods in the art. The results are shown in Table 2.

[0017] Table 2

[0018] Example 3 The present embodiment relates to a method for preparing potato hydroxypropyl starch ether, wherein the raw materials are as follows by weight: 10 parts of potato starch, 5 parts of propylene oxide, 2.5 parts of ethanol, 0.3 parts of sodium hydroxide and 1.5 parts of anhydrous sodium sulfate; the propylene oxide is an etherifying agent, the ethanol is a solvent, the sodium hydroxide is an alkalizing agent, and the anhydrous sodium sulfate is an inhibitor; the preparation steps are as follows: (1) Raw material mixing: Add 0.3 parts of sodium hydroxide, 2.5 parts of ethanol and 1.5 parts of anhydrous sodium sulfate into a reaction kettle, and stir and disperse at 40°C for 0.5 hours; (2) Alkalization: Add 10 parts of potato starch into the reactor under constant stirring, keep the temperature at 45°C, continue stirring, and alkalize for 1.2 hours; (3) Etherification: Add 5 parts of propylene oxide into the reactor under continuous stirring, control the temperature at 55°C, and stir the reaction for 9 hours; (4) Recovery: Open the vacuum condensation recovery device to recover the solvent; (5) Screening: The dried material is sent to a micronizer, where it is crushed to an 80-mesh sieving rate of more than 99%. After passing the inspection, it is packaged and stored.

[0019] The hydroxypropyl content, moisture, ash content, light transmittance and viscosity of the potato hydroxypropyl starch ether prepared in Example 3 were detected by conventional detection methods in the art. The results are shown in Table 3.

[0020] Table 3

[0021] Comparative Example: (1) Two types of potato hydroxypropyl starch ethers that are relatively widely circulated in the domestic market are selected. One type is a potato hydroxypropyl starch ether prepared by a solvent method, denoted as type A; the second type is a potato hydroxypropyl starch ether prepared by a wet method, denoted as type B.

[0022] (2) The potato hydroxypropyl starch ether produced in Example 1 of the present invention is selected and recorded as Type C.

[0023] The physical and chemical indicators of potato hydroxypropyl starch ethers of types A, B and C were compared, and the results are shown in Table 4.

[0024] Table 4

[0025] It can be seen from Table 4 that the physicochemical indicators of the potato hydroxypropyl starch ether type C produced in Example 1 of the present invention are similar to those of the potato hydroxypropyl starch ether types A and B circulating on the market, and even some indicators are slightly better than those of the potato hydroxypropyl starch ether types A and B. It can be seen that the potato hydroxypropyl starch ether type C produced in Example 1 is of good quality, has the advantages of high hydroxypropyl content, high viscosity, high solution transparency, low ash content, etc., and can meet the needs of the industry. The preparation method of the present invention greatly reduces the amount of solvent and etherifying agent used, reduces production costs, and is conducive to expanding its production volume and expanding the scope of product use.

Claims

1. A method for preparing low-cost potato hydroxypropyl starch ether, characterized in that: The raw materials include, by weight: 10 parts of potato starch, 3-5 parts of etherifying agent, 1.5-2.5 parts of solvent, 0.2-0.3 parts of alkalizing agent, and 1.0-1.5 parts of inhibitor. The specific preparation steps are: 1) Raw material mixing: add the alkalizer, solvent and inhibitor into the reactor together and stir to make them fully dispersed and mixed; 2) Alkalization: Put potato starch into the kettle and stir it continuously to carry out alkalization reaction to obtain alkalized product; 3) Etherification: Add etherifying agent into the reactor, maintain the temperature at 45-55°C, continue stirring, and carry out etherification reaction; 4) Recover the solvent: Open the vacuum condensation device to recover the solvent. The material recovered by the solvent is the crude product; 5) Preparation of potato hydroxypropyl starch ether: Grind the crude product to obtain the finished potato hydroxypropyl starch ether.

2. The method for preparing low-cost potato hydroxypropyl starch ether according to claim 1, characterized in that: The etherifying agent is one or more of chloroacetic acid, methyl chloride, ethyl chloride, propylene glycol ether, propylene oxide and ethylene oxide; the solvent is an alcohol, specifically one or more of methanol, ethanol, isopropanol, n-butanol, tert-butanol, acetone and diethylene glycol; the alkalizing agent is a granular alkali metal hydroxide or a powdered alkali metal hydroxide; the inhibitor is any one of anhydrous sodium sulfate, anhydrous sodium carbonate, anhydrous sodium bicarbonate and anhydrous sodium chloride or a mixture of several of them.

3. The method for preparing low-cost potato hydroxypropyl starch ether according to claim 1, characterized in that: The alkalizing agent is sodium hydroxide.

4. The method for preparing low-cost potato hydroxypropyl starch ether according to claim 1, characterized in that: In step 1), the mixing temperature is maintained at 40° C. and the stirring and dispersing time is 0.5 hour.

5. The method for preparing low-cost potato hydroxypropyl starch ether according to claim 1, characterized in that: In step 2), the alkalization temperature is maintained at 40°C-45°C, and the alkalization is stirred for 0.8-1.2 hours.

6. The method for preparing low-cost potato hydroxypropyl starch ether according to claim 1, characterized in that: The etherification reaction time in step 2) is 6-9 hours.

7. Low-cost potato hydroxypropyl starch ether prepared according to the preparation method according to any one of claims 1 to 6.

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