阅读说明：本技术 一种吸水性淀粉及其制备方法和应用 (Water-absorbing starch and preparation method and application thereof ) 是由 刘鹏 张娜 李颖 尚小琴 汪黎明 于 2019-11-07 设计创作，主要内容包括：本发明属于淀粉改性领域,公开了一种吸水性淀粉及其制备方法和应用。该吸水性淀粉的制备方法包括以下步骤：将天然淀粉在水中分散形成淀粉乳,然后加入到无机盐溶液中分散溶解,得到均匀的淀粉/盐溶液,再向淀粉/盐溶液中加水静置使溶解的淀粉沉降下来,将沉降后的淀粉用水洗涤、离心、干燥、研磨,即可得到吸水性淀粉。本发明以绿色工艺为目标,通过对原淀粉的改性,生产一种吸水性淀粉,其吸水倍率可达原淀粉的3倍。(The invention belongs to the field of starch modification, and discloses water-absorbing starch and a preparation method and application thereof. The preparation method of the water-absorbing starch comprises the following steps: dispersing natural starch in water to form starch milk, adding the starch milk into an inorganic salt solution for dispersing and dissolving to obtain a uniform starch/salt solution, adding water into the starch/salt solution, standing to settle the dissolved starch, washing the settled starch with water, centrifuging, drying and grinding to obtain the water-absorbent starch. The invention aims at a green process, and produces the water-absorbing starch by modifying the original starch, wherein the water absorption capacity of the water-absorbing starch can reach 3 times of that of the original starch.)

1. A preparation method of water-absorbing starch is characterized by comprising the following steps:

dispersing natural starch in water to form starch milk, adding the starch milk into an inorganic salt solution for dispersing and dissolving to obtain a uniform starch/salt solution, adding water into the starch/salt solution, standing to settle the dissolved starch, washing the settled starch with water, centrifuging, drying and grinding to obtain the water-absorbent starch.

2. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the mass percentage of the natural starch in the starch milk is lower than 50 percent;

the mass percentage of the inorganic salt in the inorganic salt solution is 28-65%;

the dosage of the starch milk and the inorganic salt solution meets the following requirements: the mass percentage of inorganic salt in the obtained starch/salt solution is 25-65%.

3. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the natural starch is cassava starch, corn starch and potato starch.

4. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the inorganic salt solution is zinc chloride aqueous solution, calcium chloride aqueous solution or magnesium chloride aqueous solution; the mass percentage of the inorganic salt in the inorganic salt solution is 28-65%.

5. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the mass ratio of the natural starch to the water in the starch milk is 4: 6;

the mass percentage of the inorganic salt in the inorganic salt solution is 28-65%;

the dosage of the starch milk and the inorganic salt solution meets the following requirements: the mass percent of salt in the obtained starch/salt solution is 25-57%.

6. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the dispersing and dissolving is to dissolve for 30-120 min at 45-60 ℃.

7. The method for preparing water-absorbent starch according to claim 1, characterized in that:

the amount of the water added in the water adding station to the starch/salt solution is such that the mass percentage of the salt in the starch/salt solution is reduced to 5-20%.

8. A water-absorbing starch prepared according to the method of any one of claims 1 to 7.

9. Use of the water-absorbent starch according to claim 8 for the preparation of talcum powders, cat litters and paper diapers.

Technical Field

The invention belongs to the field of starch modification, and particularly relates to water-absorbing starch as well as a preparation method and application thereof.

Background

Starch is a raw material of many industrial products, but the nature of natural starch cannot meet the requirements of industrial production, and the natural starch needs to be modified, namely, the composition structure of starch granules is changed by a physical or chemical method, and some unique properties are endowed to adapt to the industrial production.

The starch-based water-absorbing material is modified starch, can absorb water which is many times of the self weight, still has good water retention performance under certain pressure, and is widely applied to the fields of super water-absorbing materials, adhesives, papermaking and the like. In the early 70 s of the 20 th century, people have utilized a free radical chain polymerization method to graft-copolymerize starch and vinyl monomers to obtain hydrophilic groups with a large number of carboxyl groups, amino groups and the like on side chains, and starch-based water-absorbing materials have been prepared.

The preparation process of the starch-based water absorbing material proposed by the predecessor comprises the following steps: gelatinizing starch under heating, cooling to the temperature near the copolymerization reaction temperature, and sequentially adding an initiator, a monomer and a cross-linking agent for reaction; and then extracting to remove unreacted monomers and homopolymers, and drying the product to obtain the starch-based water-absorbing material.

As can be seen from the background art, the production process of the starch-based water-absorbing material in the market is mature at present, but a large amount of chemical reagents are needed, and the process steps are multiple.

Disclosure of Invention

In order to overcome the disadvantages and shortcomings of the prior art, the invention aims to provide a preparation method of water-absorbing starch.

The invention also aims to provide the water-absorbing starch prepared by the method.

The invention also aims to provide application of the water-absorbing starch.

The purpose of the invention is realized by the following scheme:

a method for preparing water-absorbing starch, comprising the following steps:

dispersing natural starch in water to form starch milk, adding the starch milk into an inorganic salt solution for dispersing and dissolving to obtain a uniform starch/salt solution, adding water into the starch/salt solution, standing to settle the dissolved starch, washing the settled starch with water, centrifuging, drying and grinding to obtain the water-absorbent starch.

The variety of the natural starch is preferably cassava starch, corn starch, potato starch and the like, and more preferably the cassava starch;

the inorganic salt solution is preferably an inorganic salt chloride aqueous solution such as zinc chloride (CAS NO.7646-85-7), calcium chloride (CAS NO.10043-52-4), magnesium chloride (CAS NO.7786-30-3) and the like, and is preferably a magnesium chloride aqueous solution; the mass percentage of the inorganic salt in the inorganic salt solution is 28-65%, preferably 28-33%;

the mass ratio of the natural starch to the water in the starch milk is less than 1:1, preferably 4: 6;

the dosage of the starch milk and the inorganic salt solution meets the following requirements: the mass percent of the inorganic salt in the obtained starch/salt solution is 25-65%, preferably 25-57%, and more preferably 25-30%;

the dispersing and dissolving is to dissolve at 45-60 ℃ for 30-120 min, preferably at 50 ℃ for 60 min;

the amount of the water added in the water adding station to the starch/salt solution is such that the mass percentage of the salt in the starch/salt solution is reduced to 5-20%, preferably 10%. The starch/salt solution after the starch is separated out can be concentrated to improve the mass concentration of the salt in the solution to 28-65%, preferably 28-33%, and is continuously mixed with the starch milk for recycling.

A water-absorbing starch prepared by the method.

The water-absorbing starch is applied to the preparation of products such as toilet powder, cat litter, paper diapers and the like.

The mechanism of the invention is as follows:

some inorganic salt solutions (zinc chloride, magnesium chloride and calcium chloride) can depolymerize the complex structure of the starch granules at a certain concentration, and molecular chains are thoroughly dispersed. The salt ion concentration in the solution reaches a certain degree, the salt ion can permeate into the starch granules, the protonation effect of anions weakens intermolecular and intramolecular hydrogen bonds of the starch, and cations can form coordination compounds with hydroxyl groups on the starch molecules to further break the hydrogen bonds and promote the deconstruction of the starch granules. In this process, the concentration of the salt solution is critical, there being a minimum concentration. Below this concentration, only the starch granules swell and cannot be dissolved. When the concentration of the salt solution is reduced, the starch molecules originally dispersed in the salt solution are bound by hydrogen bonds again and settle down. The starch after sedimentation has a loose structure and a large amount of active hydroxyl groups, so the starch has certain water absorption capacity.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the inorganic salt solution does not need to be pretreated and activated for dissolving the starch, so that the use of chemical reagents is reduced, and the treatment of the raw starch is direct and convenient.

(2) In the whole process, the product can be obtained only by adjusting the concentration of salt ions, the diluted salt solution can improve the concentration of the salt ions through reduced pressure evaporation, the natural starch is dissolved again and recycled, and the generated three wastes are few, so that the method belongs to a green production process.

(3) The water absorption capacity of the water-absorbent starch obtained by the process can reach 3 times of that of the original starch.

Drawings

FIG. 1 is a diagram of a water-absorbent starch product prepared in example 1.

FIG. 2 is an X-ray diffraction diagram of the water-absorbent starch product obtained in example 1.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.