WO2021036197A1

WO2021036197A1 - Preparation method for starch-based adhesive

Info

Publication number: WO2021036197A1
Application number: PCT/CN2020/072867
Authority: WO
Inventors: 杨桂花; 刘欢欢; 陈嘉川; 林兆云
Original assignee: 齐鲁工业大学
Priority date: 2019-08-30
Filing date: 2020-01-17
Publication date: 2021-03-04
Also published as: CN110452634B; DE112020000426T5; CN110452634A

Abstract

The present disclosure relates to the technical field of starch-based adhesives, and in particular, to a preparation method for a starch-based adhesive. Conventional starch-based adhesives have poor flowability, poor film-forming property, low bonding strength, and great limitations in use. Aiming at the above-mentioned shortcomings of the starch-based adhesives, the present disclosure provides a starch-based adhesive and a preparation method therefor. Oxidized corn starch is used as a matrix, and polyvinyl alcohol (PAV)/glycerol is used as a compound plasticizer. The starch-based adhesive is obtained by adding borax and alkali liquor to oxidized corn starch milk and then heating those. Rheological property tests show that the rheological property of the oxidized corn starch is remarkably improved, and a polyhydroxy structure formed by compounding of PVA and glycerol provides richer hydrogen bonding, so that the adhesive is more stable, has remarkably improved water resistance, and is thus a starch adhesive having excellent performance.

Description

Method for preparing starch-based adhesive

Technical field

The present disclosure belongs to the technical field of starch-based adhesives, and specifically relates to a corn starch/polyvinyl alcohol/glycerin composite adhesive and a preparation method of the adhesive.

Background technique

Disclosure of the background information is only intended to increase the understanding of the overall background of the present disclosure, and is not necessarily regarded as an acknowledgement or any form of suggestion that the information constitutes the prior art known to those of ordinary skill in the art.

Starch is a low-priced, easily degradable, environmentally friendly, purely natural renewable resource. It is used as an adhesive to produce no pollution to the environment, and its production process is simple, equipment investment is small, production costs are low, and sources and uses are wide. , Has been widely used in the bonding of corrugated cardboard, packaging cartons, etc., and has become one of the most promising adhesive varieties. However, traditional starch-based adhesives have poor fluidity, poor film-forming properties, poor water resistance, perishable and low bonding strength, and have greater limitations in use. How to increase the adhesive strength and fluidity of starch has become an urgent need for solutions. Is an important issue.

In recent years, with the continuous search for environmentally friendly materials, composite materials based on starch have gradually been favored. The performance of starch-based adhesive materials mainly depends on its functional properties, especially rheological properties. The application performance can be evaluated by studying the rheological properties of the substrate, thereby improving its processing performance and producing high-quality products.

Polyvinyl alcohol (PVA) is an easily degradable water-soluble polymer material with a wide range of uses. It has the characteristics of excellent resistance to organic solvents, good thermal stability and high bonding strength, and it can interact with starch after being hydrolyzed. Joint condensation to improve the adhesive strength of starch. However, PVA/starch composite materials have disadvantages such as difficult processing, long degradation cycle and poor rheology, which limit their application range. How to improve the comprehensive performance of PVA/starch composite adhesives and prepare better functional, biodegradable and environmentally friendly Materials have become an important research direction in the study of starch composite adhesive materials.

Summary of the invention

In order to achieve the above technical effects, the present disclosure provides the following technical solutions:

In the first aspect of the present disclosure, a starch-based composite adhesive is provided. The adhesive uses oxidized corn starch as a matrix, and polyvinyl alcohol and glycerin as a compound plasticizer.

Preferably, the mass ratio of polyvinyl alcohol to glycerin is 5-10:3-7; the amount of polyvinyl alcohol in the adhesive is 5.0-20.0 wt%.

Preferably, the oxidized corn starch adopts a strong oxidizer/pro-oxidant system as the oxidant; further, the strong oxidant is sodium hypochlorite, and the pro-oxidant is nano microcrystalline cellulose.

In a second aspect of the present disclosure, there is provided a method for preparing a starch-based composite adhesive. The preparation method includes the following steps: adding water to dissolve oxidized corn starch to obtain oxidized corn starch milk, and adding the mixed polyvinyl alcohol/glycerin to the oxidized starch milk , Then add borax solution and lye, heat and stir to obtain the adhesive.

Preferably, the preparation process of the oxidized corn starch adhesive is as follows: add water to the oxidized corn starch to dissolve it, then add borax and lye, stir evenly and place it in a water bath for heating and gelatinization.

More preferably, the oxidized corn starch: water is added at a ratio of 2g: 15～64ml.

More preferably, the borax is a 2% borax solution (relative to the absolute dry mass of oxidized corn starch).

More preferably, the lye is a 10% sodium hydroxide solution (relative to the absolute dry mass of the oxidized corn starch).

More preferably, the reaction time is 1.5-2.5h; or the reaction temperature is 85-95°C.

Preferably, the ratio of the oxidized corn starch to water is 2g:15-64ml.

Preferably, the mass ratio of the polyvinyl alcohol to glycerin is 5-10:3-7.

Preferably, the borax solution is an aqueous solution of sodium tetraborate decahydrate of 1.5% to 2.5% (relative to the mass of PVA).

Preferably, the lye is 5% to 15% NaOH solution (relative to the mass of oxidized corn starch).

Preferably, the heating is water bath heating.

Preferably, the heating temperature is 85-95°C.

Preferably, the heating time is 1.5-2.5h.

Preferably, the preparation method includes the step of ultrasonic defoaming, and the starch-based adhesive is obtained by ultrasonic defoaming after heating and stirring are completed.

Preferably, the oxidized corn starch is obtained by oxidizing corn starch with an oxidizing agent.

Further, the oxidant is a strong oxidant/pro-oxidant system, the strong oxidant is sodium hypochlorite, and the pro-oxidant is nanocrystalline cellulose.

In some specific embodiments, the amount of the nanocrystalline cellulose is 0.5-5 wt% (relative to the amount of corn starch).

In some specific embodiments, the fiber length of the nanocrystalline cellulose is 100-500 nm.

The oxidized corn starch used in the present disclosure is the research result of the inventor's research team, and the related technical solutions are recorded in the prior patent CN108410024A. In order to provide a starch-based viscose with better performance, the present disclosure has made corresponding optimization adjustments to the preparation of oxidized corn starch in the previous patent to adapt to the preparation of the viscose.

The preparation method of the oxidized corn starch is as follows:

Take corn starch and add water to make starch emulsion, add nano microcrystalline cellulose, stir to mix evenly; add NaClO to obtain a mixed solution, add lye to the mixed solution to adjust the pH to 8-10, heat and stir for a period of time and then add acid And sodium thiosulfate, centrifugal drying to obtain oxidized corn starch.

Further, the mass fraction of the starch emulsion is 8-12 wt%.

Further, the added amount of the NaClO is 8wt% NaClO (relative to the absolute dry starch).

Compared with the prior art, the beneficial effects of the present disclosure are:

1. In the previous study, the inventor provided a scheme for oxidizing corn starch by using nanocrystalline cellulose/NaClO. As a follow-up study in the present disclosure, it is found that the oxidized corn starch as a viscose base can significantly improve the bonding strength. It can also be known from the static rheological test results that the viscose using oxidized corn starch as the base has better rheological properties than the native starch viscose.

2. In view of the poor rheological properties of starch/polyvinyl alcohol adhesives in the prior art, the present disclosure provides a starch-based adhesive that uses oxidized corn starch as the base and polyvinyl alcohol/glycerin as the compound plasticizer . Studies have shown that the adhesive of this formula has good stability and bonding strength; by adjusting the ratio of polyvinyl alcohol/glycerin, it can also obtain good waterproof performance and has good application value.

detailed description

It should be pointed out that the following detailed descriptions are all illustrative and are intended to provide further descriptions of the present disclosure. Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs.

It should be noted that the terms used here are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and/or combinations thereof.

As introduced in the background art, in the prior art, PVA/starch composite processing is difficult, the degradation cycle is long, and the rheology is insufficient. In order to solve the above technical problems, the present disclosure proposes a starch-based adhesive.

In order to enable those skilled in the art to understand the technical solutions of the present disclosure more clearly, the technical solutions of the present disclosure will be described in detail below in conjunction with specific embodiments and comparative examples.

In the following embodiments:

Static rheological test:

Take an appropriate amount of sample and analyze the static rheological characteristics in a rheometer (ARES-G2, TA, USA). The steady-state shear conditions are set as follows: choose a flat plate (steel plate) with a diameter of 50mm, a plate spacing of 1.0mm, and a temperature of 25℃, the shear rate is 0.1-100s ^-1 ; the thixotropy test condition is set as: 25℃, the shear rate is ^{increased from 0.1s -1} to 100s ^-1 in 120s, and then reduced ^{from 100s -1 to 100s -1 in 120s} 0.1s ^-1 .

Model fitting:

The flow curve is model-fitted. Among them, "Newtonian fluid" is called a rational liquid. Its flow curve is a straight line. The ratio of the shear stress to the shear rate of this straight line is a fixed value, which means that the viscosity is not affected by it. The effect of shear rate. "Non-Newtonian fluids" do not have such "ideal" flow characteristics. Therefore, the Ostwald-de-Waele model is used to calculate and determine the flow fluid model.

Ostwald-de-Waele flow fluid model fitting:

τ=k*γn

In the formula: τ is the shear stress, Pa; k is the consistency coefficient; γ is the shear rate, s ^-1 ; n is the flow index (related power law index, dimensionless).

Dynamic rheological test:

First detect the linear viscoelastic zone of the composite adhesive, set the frequency to 1Hz, and perform a 0.1-10% strain sweep to determine the strain range of the linear viscoelastic zone; in the linear viscoelastic zone, the fixed strain is 6%, and at frequency 1 The frequency sweep of the composite adhesive is performed within ~100Hz.

Bond strength test: Use electronic universal testing machine to test, test 5 times, take the average value, and stretch rate 0.3mm/min.

Water resistance test: Drop water droplets on the completely dry film and measure the time it takes for the water droplets to penetrate the other side of the paper to test the water resistance.

Solid content test: Measure according to GB/T14074.5-1993 standard, temperature 105±2℃.

Example 1 Preparation of oxidized corn starch

Take 10g corn starch and 90ml water to make a starch emulsion, add 0.5wt% nano-microcrystalline cellulose (based on the quality of corn starch), mechanically stir in a water bath for 0.5h to make it evenly mixed, and then add 0.8g sodium hypochlorite for oxidation. After adjusting the pH to 9 with 0.1 mol/L sodium hydroxide solution, keeping the temperature of the water bath at 90°C, mechanically stirring for 4 hours, adding sodium thiosulfate solution to terminate the reaction, washing and centrifuging, adding hydrochloric acid to adjust the pH to neutral, and drying. The oxidized corn starch is obtained.

Example 2

Weigh 2g of oxidized corn starch and dissolve it with 38ml of deionized water, add 2.0% sodium tetraborate decahydrate (borax) solution and 10% NaOH solution (both are relative to the mass of oxidized corn starch), stir with a glass rod Pour into a 250ml three-necked flask, adjust the temperature of the water bath to 90°C, and mechanically stir for 2h. The oxidized corn starch paste changes from thinning to thick, and the color changes from milky white to light yellow. After cooling to room temperature, an oxidized corn starch adhesive is obtained.

Result: Through the static rheological test, when the shear rate increases, the shear viscosity of the oxidized starch paste shows a downward trend, while the shear stress shows an increase trend, that is, the oxidized starch paste belongs to a shear thinning non-Newtonian fluid. And when the shear rate is increased to 40.0s ^-1 , the shear viscosity of the oxidized starch paste is 0.2Pa.s. Compared with starch paste (comparative test 1), the shear viscosity of oxidized starch paste decreases, indicating that the molecular mobility of oxidized modified corn is increased, the flow resistance between molecules is reduced, and the fluidity of starch paste is improved.

Oxidized starch paste has thixotropic rings. The thixotropic ring area of oxidized starch paste is 19.4. Compared with starch paste, the thixotropy of oxidized starch paste is smaller. This indicates that after the shearing force is removed, the oxidized starch paste needs to restore its original structure. Time is shorter,

It can be seen from model fitting that, compared with starch paste, the n value of oxidized corn starch paste is greater than starch paste, but the consistency coefficient k of oxidized corn starch paste is smaller than corn starch paste, which strongly shows that oxidative modification causes corn starch molecules to occur. The oxidized starch adhesive can be used in papermaking, packaging, textile and food industries.

After the bonding strength test, the bonding strength of the oxidized starch adhesive is 0.48 MPa. Therefore, the bonding ability of the starch gum can be improved through oxidative modification.

After the water resistance test, the water resistance time of oxidized starch is 42 minutes. Compared with the original starch adhesive, oxidation modification does not significantly improve the water resistance of the adhesive.

Example 3

Weigh 2g of oxidized corn starch and dissolve it with deionized water to prepare 3%, 5%, 8%, and 10% starch emulsions respectively, and then add 2.0% sodium tetraborate decahydrate (borax) solution and 10% NaOH solution, (All relative to the quality of oxidized starch), put it in a 250ml three-necked flask, adjust the temperature of the water bath to 90℃, mechanically stir for 2h, the oxidized corn starch paste will change from thin to thick, and the color will change from milky white to light yellow. Cool to At room temperature, different concentrations of oxidized corn starch adhesive can be obtained.

Results: The static rheological test shows that at the same temperature, as the mass fraction of the oxidized starch paste increases, the initial viscosity of the oxidized starch paste increases, the shear thinning effect is more obvious, and the yield stress value increases. The apparent viscosity of the oxidized starch paste at a concentration of 10.0 wt% is 30.1 Pa.s at the highest. Therefore, the oxidized starch paste with a mass fraction of 10.0 wt% has the highest initial viscosity, the strongest cohesive force, and the prepared adhesive is the most stable.

The thixotropy test shows that the thixotropic ring area and thixotropy increase as the concentration of the oxidized starch paste increases, and the thixotropic ring area of the oxidized starch paste at a concentration of 10.0 wt% is 424.0. Therefore, the higher the concentration of oxidized starch paste, the better the thixotropy and the higher the stability, and the longer the system needs to recover its original structure.

It can be known from the model fitting that as the concentration of oxidized starch paste increases, the flow index n of the sample gradually decreases and reaches the minimum value, and the consistency coefficient k gradually increases. The smaller the flow index n, the more obvious the degree of shear thinning of the system, and the stronger the non-Newtonian fluid behavior.

Through the dynamic rheological test, the elastic modulus G'of starch paste and oxidized starch paste are both greater than the viscosity modulus G". The viscosity and elastic modulus of starch paste increase gradually with the increase of scanning frequency, and the elastic modulus of starch paste is in The low frequency internal change is almost 0, and the viscous modulus is gradually increasing and higher than the oxidized starch paste, indicating that the viscoelastic properties of the starch paste are more obvious, and the internal structure is more stable. After oxidation, the starch structure is destroyed, and the particles are partially generated. Degradation, the introduction of carboxyl and aldehyde groups, resulting in poor structural stability, and reduced viscosity modulus and elastic modulus.

After the cementation strength test, the cementation strength increases with the increase in the quality of oxidized starch, that is, the cohesive force increases. When the mass of oxidized starch increases to 10wt%, the cementation strength reaches 0.72MPa.

After the water resistance test, as the amount of oxidized starch added increases, the water resistance time decreases. This is because the oxidized modified starch adhesive contains a large number of hydrophilic hydroxyl and carboxyl groups, and the water resistance is poor. Therefore, the content of oxidized starch The larger the value, the worse the water resistance.

Through the determination of the solid content of the adhesive with different oxidized starch addition, it is found that as the addition of oxidized starch increases from 3.0wt% to 10wt%, the solid content of the adhesive increases, from 3.1953% to 36.3216%, the higher the solid content , The greater the initial tack of the adhesive, the fewer times of gluing.

Example 4

Weigh 2g of oxidized cornstarch and dissolve it with 18ml of deionized water, stir with a glass rod and pour it into a 250ml three-necked flask, place the three-necked flask in a constant temperature water bath at 90℃, and mix the mass ratio of polyvinyl alcohol ( PVA) and glycerin (GL) are mixed and then added to the oxidized starch milk, wherein the mass ratio of PVA to oxidized starch is 5.0wt%, and 2.0% sodium tetraborate decahydrate (borax) solution is added (relative to the mass of PVA) ) And 10% NaOH solution, (relative to the quality of starch), stir the mixed solution under 90℃ water bath heating for 2h, then ultrasonic defoams, the oxidized starch composite film-forming solution changes from thin to thick, and the color changes from milky white to light Yellow, oxidized starch composite adhesive is obtained.

Results: Through the static rheological test, it can be seen that the oxidized starch-based composite adhesive is a shear thinning fluid. Compared with the starch-based composite adhesive (Comparative Test 2), its shear viscosity and shear stress are lower than those of the starch-based composite adhesive. . This shows that after oxidative modification, its viscosity decreases and fluidity increases.

Oxidized starch composite adhesives have thixotropy. Compared with starch-based composite adhesives, starch-based composite adhesives have a larger thixotropic ring area, that is, it takes longer to restore the original structure.

It can be seen from the model fitting that the correlation coefficient R ^{2 of the} sample is above 0.97. Compared with the native starch adhesive, the oxidized starch-based composite adhesive has a larger flow index n and a smaller consistency coefficient k, indicating that the oxidized starch-based composite adhesive has low viscosity and fluidity. Strong. The oxidized starch/polyvinyl alcohol composite adhesive has low viscosity and weak thixotropy, and its recovery degree is better after being subjected to external force, which is beneficial to industrial production.

Through the dynamic rheological test, the elastic modulus G'of the composite adhesive is higher than the viscosity modulus G". Compared with starch glue, the modulus of oxidized starch-based adhesives is higher than that of starch-based adhesives. PVA and GL are much higher. The hydroxyl structure makes it easier to form hydrogen bonds, forming a network structure with high strength and high stability.

After the cementation strength test, after adding PVA, the cementation strength increases. This is because the polar groups in the PVA molecule and the -OH, -COOH and other groups in the starch molecule undergo cross-linking reaction under alkaline conditions to make the starch The hydrophobic properties of the base adhesive increase. The film-forming properties of PVA are good. After being blended with starch, a film will be formed. When it is coated on the cardboard, it can prevent the penetration of water and improve the drying speed and initial adhesion of the adhesive. Compared with starch-based composite adhesives, oxidized starch-based composite adhesives have a higher bonding strength, with a bonding strength of 1.85MPa.

After water resistance test, after adding PVA, the water resistance of starch-based composite adhesive increases, and the water resistance time is 33h.

Example 5

Weigh 2g of oxidized cornstarch and dissolve it with 18ml of deionized water, stir with a glass rod and pour it into a 250ml three-necked flask, place the three-necked flask in a constant temperature water bath at 90℃, and mix the mass ratio of polyvinyl alcohol ( PVA) is mixed with glycerin (GL) and then added to the oxidized starch milk. Among them, the mass ratio of PVA to starch is 5.0wt%, 10.0wt%, 15.0wt%, 20.0wt%, adding 2.0% sodium tetraborate decahydrate (borax) solution (relative to the mass of PVA) and 10% NaOH solution , (Relative to the quality of oxidized starch), stir the mixed solution in a water bath at 90°C for 2 hours and then ultrasonically defoam. The oxidized starch composite adhesive changes from thinning to thick, and the color changes from milky white to light yellow, and the oxidized starch adhesive is obtained. .

Result: Through the static rheological test, it can be known that the apparent viscosity decreases with the increase of the shear speed, and the change trend of the shear stress is exactly the opposite of the apparent viscosity. The amount of PVA is 15.0% by weight. The apparent viscosity and shear stress of the composite adhesive are the largest, and the rheological properties are the highest. When the amount of PVA is greater than 15.0% by weight, the viscosity decreases. The possible reasons are: (1) the blending ratio of PVA and oxidized starch is reversed; (2) the flow mechanism of the blending system of PVA and oxidized starch has changed; (3) the increase of GL content destroys the combination of PVA and starch . It can be found that the comprehensive performance of the modified composite adhesive is good. When the amount of PVA in the film-forming liquid is 15.0wt%, the viscosity is the highest (9.9 Pa.s) and the bonding effect is the best.

It can be seen from the thixotropy that when the amount of PVA is 15.0wt%, the area of the thixotropic ring is the largest, the area is 206.4, the fluid stability is the highest, and the time it takes to restore the initial structure is the longest.

It can be seen from the model fitting that with the increase of the amount of PVA, the increasing trend of the consistency coefficient k of the composite adhesive becomes more obvious. When the amount of PVA is 15.0wt%, the consistency coefficient k of the film-forming liquid adhesive is the largest and the flow index is the smallest.

Through the dynamic rheological test, the elastic modulus G'of the composite adhesive is higher than the viscosity modulus G". Compared with starch glue, the modulus of oxidized starch-based adhesives is higher than that of starch-based adhesives. PVA and glycerin are more common. The hydroxyl structure makes it easier to form hydrogen bonds, forming a network structure with high strength and high stability.

After the bonding strength test, as the PVA content increases, the bonding strength first increases and then decreases. When the PVA addition amount is 15.0wt%, the bonding strength of the oxidized starch-based composite adhesive is the largest, and the maximum value is 2.48Mpa.

After the water resistance test, as the PVA content increases, its water resistance first increases and then decreases. When the PVA addition amount is 15.0wt%, the water resistance of the oxidized starch-based composite adhesive increases, and the water resistance time is 97 hours.

Through the determination of the solid content of the adhesive with different PVA content, it is found that with the increase of PVA content, the solid content first increases and then decreases. When the PVA content is 15.0wt%, the solid content of the adhesive reaches the maximum value. The content was 79.6587%, and then the solid content decreased and stabilized. For adhesives with high solid content, the greater the initial tack, the fewer times of gluing.

Comparative example 1

The preparation method of the raw corn starch adhesive: weigh 2g raw corn starch and dissolve it with 38ml deionized water, add 2.0% sodium tetraborate decahydrate (borax) solution and 10% NaOH solution, (both are relative to the original corn starch In terms of quality), stir with a glass rod and pour it into a 250ml three-necked flask. Adjust the temperature of the water bath to 90℃ and mechanically stir for 2h. The starch paste will change from thin to thick, and the color will change from milky white to light yellow. Cool to room temperature to obtain Corn starch adhesive.

Preferably, the mass-volume ratio of the raw corn starch and water is 2g:38ml; the reaction time is 2h, and the reaction conditions are 90°C.

Results: Through the static rheological test, when the shear rate increases, the shear viscosity of starch shows a downward trend, while the shear stress shows an increasing trend, that is, starch paste belongs to a shear thinning non-Newtonian fluid. When the speed increases to 10.9s ^-1 , the shear viscosity of starch paste tends to a constant value of 0.8Pa.s

The starch paste has a thixotropic ring. The calculated area of the thixotropic ring of starch paste is 116.6, and the flow index n value of corn starch paste is 0.7.

After the cementation strength test, the cementation strength of the native starch adhesive is 0.45Mpa; after the water resistance test, the water resistance time of the native starch adhesive is 39min.

Comparative example 2

The preparation method of the raw corn starch composite adhesive: take an appropriate amount of raw starch and place it in a constant temperature water bath for dispersion, mix polyvinyl alcohol and glycerin and add to the oxidized starch milk, add 2.0% sodium tetraborate decahydrate (borax) solution (Relative to the quality of PVA) and 10% NaOH solution (relative to the quality of starch), the original starch composite film-forming liquid changes from thin to thick, and the color changes from milky white to light yellow. After the reaction is completed, ultrasonic defoaming , That is, the original starch composite adhesive.

Preferably, the mass-volume ratio of the raw corn starch and water is 2g:18ml; the mass ratio of polyvinyl alcohol and glycerin is 8:5; the amount of polyvinyl alcohol is 5.0wt%; the reaction time is 2h, and the reaction conditions are 90°C .

Results: The rheological test shows that the native starch composite adhesive is a shear thinning fluid, the composite adhesive has thixotropy, and the area of the thixotropic ring is 283.5. The correlation coefficient R ^{2 of the} sample is above 0.97.

After the cementation strength test, the cementation strength of the native starch composite adhesive is 1.51Mpa; after the water resistance test, the water resistance time of the starch adhesive is 31h.

The foregoing descriptions are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

A starch-based adhesive, characterized in that the adhesive uses oxidized corn starch as a matrix, and polyvinyl alcohol and glycerin as compound plasticizers.
The starch-based adhesive of claim 1, wherein the mass ratio of polyvinyl alcohol to glycerin is 5-10:3-7; the amount of polyvinyl alcohol in the adhesive is 5.0-20.0 wt%.
The starch-based adhesive according to claim 1, wherein the oxidized corn starch uses a strong oxidizer/pro-oxidant system as the oxidant; further, the strong oxidant is sodium hypochlorite, and the pro-oxidant is nanocrystalline cellulose.
A preparation method of starch-based adhesive, characterized in that the preparation method comprises the following steps: adding water to dissolve oxidized corn starch to obtain oxidized corn starch milk, adding the mixed polyvinyl alcohol/glycerin to the oxidized starch milk, and then adding borax The solution and lye are heated and stirred to obtain the adhesive.
The preparation method of starch-based adhesive according to claim 4, characterized in that, the preparation process of the oxidized corn starch milk is as follows: add water to the oxidized corn starch to dissolve it, then add borax and lye, stir evenly and place it in Heat gelatinization in a water bath.
The method for preparing starch-based adhesive according to claim 4, wherein the oxidized corn starch is obtained by oxidizing corn starch through an oxidant; the oxidant is a strong oxidant/pro-oxidant system, the strong oxidant is sodium hypochlorite, and the The pro-oxidant is nano microcrystalline cellulose.
The preparation method of the starch-based adhesive according to claim 4, wherein the ratio of the oxidized corn starch to water is 2g: 15 to 64 ml; or the mass ratio of the polyvinyl alcohol to glycerin is 5 to 10: 3. ~7.
The preparation method of the starch-based adhesive according to claim 4, wherein the borax solution is an aqueous solution of 1.5% to 2.5% sodium tetraborate decahydrate (relative to the mass of PVA); or the lye It is a 5% to 15% NaOH solution (relative to the quality of starch).
The preparation method of starch-based adhesive according to claim 4, wherein the heating is water bath heating; or the heating temperature is 85-95°C; the heating time is 1.5-2.5h.
4. The preparation method of starch-based adhesive according to claim 4, characterized in that, the preparation method comprises the step of ultrasonic defoaming, and the starch-based adhesive is obtained by ultrasonic defoaming after heating and stirring.