阅读说明：本技术 由大米生产下脚料碎米制备造纸施胶剂用变性淀粉的方法 (Method for preparing modified starch for papermaking sizing agent from broken rice leftover in rice production ) 是由 朱同贵 王必华 于 2019-10-09 设计创作，主要内容包括：本发明公开了一种由大米生产下脚料碎米制备造纸施胶剂用变性淀粉的方法,涉及大米副产品加工技术领域,包括以下制备步骤：(1)大米淀粉的制备；(2)大米淀粉的物理变性；(3)大米淀粉的化学变性；本发明以碎米为原料,由碱处理和酶解制得大米淀粉,再经物理变性和化学变性制得变性淀粉,不仅实现了碎米的合理再利用,提高了碎米的再利用价值；并且所制变性淀粉适用于制备造纸施胶剂,通过对纸张的表面施胶来改善纸张的使用性能。(The invention discloses a method for preparing modified starch for a papermaking sizing agent from broken rice which is leftover in rice production, which relates to the technical field of rice byproduct processing and comprises the following preparation steps: (1) preparing rice starch; (2) physical denaturation of rice starch; (3) chemical modification of rice starch; the method takes broken rice as a raw material, prepares rice starch by alkali treatment and enzymolysis, and prepares modified starch by physical modification and chemical modification, thereby not only realizing reasonable reutilization of the broken rice, but also improving the reutilization value of the broken rice; the prepared modified starch is suitable for preparing a papermaking sizing agent, and the use performance of paper is improved by sizing the surface of the paper.)

1. The method for preparing the modified starch for the papermaking sizing agent from the broken rice leftover in the rice production is characterized by comprising the following preparation steps:

(1) preparing rice starch: soaking broken rice in water, grinding with colloid mill, adding dilute alkali solution, soaking, removing soaking solution, washing with water, centrifuging, removing supernatant to obtain wet starch; adding water into wet starch, stirring, adjusting pH to 9 with dilute alkali solution, adding alkaline protease, performing enzymolysis under heat preservation, centrifuging, and removing supernatant to obtain wet starch after enzymolysis; washing, centrifuging, drying the lower layer starch to obtain powder to obtain rice starch;

(2) physical denaturation of rice starch: adding water into rice starch to prepare starch slurry, placing the starch slurry in a high-pressure ultrasonic microwave synergistic combination device, performing high-pressure ultrasonic microwave synergistic treatment, performing centrifugal separation, and drying lower-layer starch to prepare powder;

(3) chemical modification of rice starch: adding water into physically modified rice starch to prepare starch slurry, adding 2-bromothiazole-5-carboxylic acid, adjusting the pH value to 9 by using a dilute alkali solution, heating to 85-95 ℃, preserving the temperature to perform etherification reaction, performing centrifugal separation after the reaction is finished, removing supernatant, washing lower-layer starch with water, and drying to prepare powder, thus obtaining the modified starch.

2. The method of claim 1, wherein: the dilute alkali solution is sodium hydroxide aqueous solution.

3. The method of claim 1, wherein: the dosage of the alkaline protease is 0.1-0.5 wt% of the broken rice.

4. The method of claim 1, wherein: the enzymolysis temperature is 30-40 ℃.

5. The method of claim 1, wherein: the condition parameters of the high-pressure ultrasonic wave and microwave synergistic combination equipment are as follows: the high pressure is 15-25MPa, the microwave frequency is 2450MHz, the microwave power is 300-.

6. The method of claim 1, wherein: the using amount of the 2-bromothiazole-5-carboxylic acid is 5-15 wt% of the mass of the rice starch prepared in the step (1).

7. A sizing agent for papermaking, characterized in that: the modified starch of claim 1, which is prepared by esterification of one molecule of pyridine-3, 5-diol with two molecules of lauric acid, with pyridine laurate as the auxiliary and water as the diluent.

8. A papermaking size according to claim 7, characterised in that: the amount of the modified starch accounts for 5-10 wt% of the total amount of the sizing agent, and the amount of the pyridine laurate accounts for 0.5-2 wt% of the total amount of the sizing agent.

The technical field is as follows:

the invention relates to the technical field of rice byproduct processing, in particular to a method for preparing modified starch for a papermaking sizing agent from rice production leftovers broken rice.

Background art:

broken rice is an inevitable processing leftover in the rice production process. In order to further improve the utilization value of the broken rice, the inventor wants to use the broken rice to prepare modified starch, and the prepared modified starch is used as the main raw material of a papermaking sizing agent.

The papermaking sizing agent comprises an internal sizing agent and a surface sizing agent, and the surface sizing agent can obviously improve the surface performance of paper, such as surface strength, water resistance, poor two surfaces, smoothness, printability and the like. Common surface sizing agents are mainly modified and unmodified starches, and modified and unmodified polyvinyl alcohols.

Starch has outstanding properties of good cohesion and film formation and environmental protection and is therefore frequently used for the preparation of surface sizing agents, but native starch has a viscosity which is too high at the concentrations usually used (5-15% solids), and if it is diluted with water to the desired working viscosity, large amounts of water are added, which leads to a loss of the adhesive effect of the starch. In addition, the aqueous solution of native starch is prone to have a reducing effect during aging, and has the disadvantages of poor fluidity, easy agglomeration, and the like. In order to solve the above problems, it is urgently necessary to modify native starch.

The modified starch is a modified starch, and can be divided into four types of physical modified starch, chemical modified starch, enzymatic modified starch and composite modified starch according to the treatment modes, wherein the physical modification and the chemical modification belong to two common starch modification treatment modes, and the two modification treatment modes have advantages respectively. Therefore, how to optimize the use performance of starch as the main component of the surface sizing agent for papermaking by a combined treatment of physical denaturation and chemical denaturation becomes a research hotspot at present.

The invention content is as follows:

the technical problem to be solved by the invention is to provide a method for preparing modified starch for a papermaking sizing agent from broken rice which is leftover in rice production, so that reasonable recycling of the broken rice is realized, the economic value of the broken rice is improved, and the surface performance of paper can be obviously improved after the prepared modified starch is used as the main component of the papermaking sizing agent.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

the method for preparing the modified starch for the papermaking sizing agent from the broken rice leftover in the rice production comprises the following preparation steps:

(1) preparing rice starch: soaking broken rice in water, grinding with colloid mill, adding dilute alkali solution, soaking, removing soaking solution, washing with water, centrifuging, removing supernatant to obtain wet starch; adding water into wet starch, stirring, adjusting pH to 9 with dilute alkali solution, adding alkaline protease, performing enzymolysis under heat preservation, centrifuging, and removing supernatant to obtain wet starch after enzymolysis; washing, centrifuging, drying the lower layer starch to obtain powder to obtain rice starch;

(2) physical denaturation of rice starch: adding water into rice starch to prepare starch slurry, placing the starch slurry in a high-pressure ultrasonic microwave synergistic combination device, performing high-pressure ultrasonic microwave synergistic treatment, performing centrifugal separation, and drying lower-layer starch to prepare powder;

(3) chemical modification of rice starch: adding water into physically modified rice starch to prepare starch slurry, adding 2-bromothiazole-5-carboxylic acid, adjusting the pH value to 9 by using a dilute alkali solution, heating to 85-95 ℃, preserving the temperature to perform etherification reaction, performing centrifugal separation after the reaction is finished, removing supernatant, washing lower-layer starch with water, and drying to prepare powder, thus obtaining the modified starch.

The dilute alkali solution is sodium hydroxide aqueous solution.

The dosage of the alkaline protease is 0.1-0.5 wt% of the broken rice.

The enzymolysis temperature is 30-40 ℃.

The condition parameters of the high-pressure ultrasonic wave and microwave synergistic combination equipment are as follows: the high pressure is 15-25MPa, the microwave frequency is 2450MHz, the microwave power is 300-.

The using amount of the 2-bromothiazole-5-carboxylic acid is 5-15 wt% of the mass of the rice starch prepared in the step (1).

The invention applies the high-pressure ultrasonic wave microwave synergistic treatment mode to the physical modification treatment of the starch for the first time, and changes the properties and structural parameters of the surface appearance, the molecular weight, the paste viscosity, the crystallinity and the like of the starch in a short time by the high-pressure ultrasonic wave microwave synergistic treatment mode, thereby changing the application performance of the starch.

During chemical modification, 2-bromothiazole-5-carboxylic acid is used as an etherifying agent to generate etherification reaction with starch, carboxyl and thiazolyl are simultaneously introduced into the molecular structure of the starch, the introduction of the carboxyl can improve the hydrophilicity of the starch, and the introduction of the thiazolyl can improve the viscosity stability, the caking property and the film forming property of the starch. However, the 2-bromothiazole-5-carboxylic acid is not a starch etherifying agent commonly used in the field, 3-chloro-2-hydroxypropyl-trimethyl ammonium chloride is generally adopted as the starch etherifying agent in the field, while the 2-bromothiazole-5-carboxylic acid is structurally different from the conventional starch etherifying agent, namely, the invention realizes the new application of using the 2-bromothiazole-5-carboxylic acid as the starch etherifying agent to improve the starch application performance.

In order to optimize the use performance of the prepared modified starch as the main component of the papermaking sizing agent, the invention also adopts a two-stage physical modification method to replace the physical modification method on the basis of the technical scheme, and the specific technical scheme is as follows:

the method for preparing the modified starch for the papermaking sizing agent from the broken rice leftover in the rice production comprises the following preparation steps:

(1) preparing rice starch: soaking broken rice in water, grinding with colloid mill, adding dilute alkali solution, soaking, removing soaking solution, washing with water, centrifuging, removing supernatant to obtain wet starch; adding water into wet starch, stirring, adjusting pH to 9 with dilute alkali solution, adding alkaline protease, performing enzymolysis under heat preservation, centrifuging, and removing supernatant to obtain wet starch after enzymolysis; washing, centrifuging, drying the lower layer starch to obtain powder to obtain rice starch;

(2) first-stage physical modification of rice starch: heating rice starch to 70-80 ℃ by program heating, then carrying out heat preservation treatment, then transferring the rice starch into a refrigeration house at-15 ℃ to-10 ℃ for freezing treatment, repeating the program heating and freezing for three times, and finally preparing the starch into powder;

(3) secondary physical modification of rice starch: adding water into rice starch to prepare starch slurry, placing the starch slurry in a high-pressure ultrasonic microwave synergistic combination device, performing high-pressure ultrasonic microwave synergistic treatment, performing centrifugal separation, and drying lower-layer starch to prepare powder;

(4) chemical modification of rice starch: adding water into physically modified rice starch to prepare starch slurry, adding 2-bromothiazole-5-carboxylic acid, adjusting the pH value to 9 by using a dilute alkali solution, heating to 85-95 ℃, preserving the temperature to perform etherification reaction, performing centrifugal separation after the reaction is finished, removing supernatant, washing lower-layer starch with water, and drying to prepare powder, thus obtaining the modified starch.

The first-stage physical modification treatment of the rice starch is carried out by adopting circulating temperature programming and freezing, and the internal crystallization of starch molecules is rearranged by the temperature difference treatment mode, so that the application performance of the starch is changed.

The invention also provides a papermaking sizing agent, any modified starch prepared by the method is used as a main component, pyridine laurate is used as an auxiliary agent, water is used as a diluting agent, and the pyridine laurate is prepared by esterification reaction of one molecule of pyridine-3, 5-diol and two molecules of lauric acid.

The amount of the modified starch accounts for 5-10 wt% of the total amount of the sizing agent, and the amount of the pyridine laurate accounts for 0.5-2 wt% of the total amount of the sizing agent.

The synthetic route of the pyridine laurate is as follows:

the invention has the beneficial effects that: the method takes broken rice as a raw material, prepares rice starch by alkali treatment and enzymolysis, and prepares modified starch by physical modification and chemical modification, thereby not only realizing reasonable reutilization of the broken rice, but also improving the reutilization value of the broken rice; the prepared modified starch is suitable for preparing a papermaking sizing agent, and the use performance of paper is improved by sizing the surface of the paper; meanwhile, the prepared modified starch is high in use environmental protection, can be prepared into an aqueous surface sizing agent, and is particularly superior to the conventional pregelatinized starch, oxidized starch and etherified starch in application performance.

The specific implementation mode is as follows:

in order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific embodiments.

Alkaline protease AP-20 alkaline protease available from Angel Yeast Inc.; the pregelatinized starch is purchased from a new chemical company, Inc. in Qinyang city; oxidized starch was purchased from henan Xuanzai chemical Co., Ltd; etherified starch is available from Beijing Kentucky trade, Inc.