A starch-based adhesive and a method for preparing the same

Abstract

The present application relates to a kind of starch-based adhesives and its preparation method, belong to adhesive technical field, the present application with maleic anhydride and phosphate compound as raw material, using the double bond of maleic anhydride and the phosphorus hydrogen bond of phosphate compound phosphorus hydrogen bond occurs Michael addition reaction to obtain a starch modifier, then starch is gelatinized, precipitated, separated after with starch modifier esterification to obtain modified starch, the number of hydroxyl in the molecule of the modified starch of the present application is reduced after esterification, while introducing water-absorbing hydroxyl, effectively reduce the water absorption of starch-based adhesive, avoid the interface adhesion failure problem caused by moisture penetration;Modified starch is introduced with flame-retardant effect phosphate group, effectively improve the stability and dispersibility of flame-retardant component in starch-based adhesive, reduce the migration and precipitation of flame-retardant component, realize efficient flame-retardant.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of adhesives, and in particular relates to a starch-based adhesive and a preparation method thereof, and more particularly relates to a starch-based adhesive for ceramic processing and a preparation method thereof. BACKGROUND

[0002] Al2O3 corundum ceramics have excellent performance and are widely used. In the production process of corundum ceramics, a certain viscosity is added to the slurry to improve the strength of the ceramic green body. At present, most manufacturers use PVA as an adhesive. PVA causes serious environmental pollution. To solve the problem of environmental damage caused by PVA adhesives, it is imperative to use degradable, renewable and non-polluting starch-based adhesives to replace PVA adhesives.

[0003] The starch-based adhesive mainly has the following technical problems. First, there are a large number of hydrophilic hydroxyl groups on the surface of starch, which leads to the defect of strong moisture absorption of the starch-based adhesive. In a humid environment, the moisture absorption and swelling of the starch-based adhesive will cause cracks in the glue layer, thereby significantly reducing the adhesive strength. Second, the surface of the ceramic matrix is dense and has a large number of hydroxyl groups, which cannot form effective bonding with the starch-based adhesive. In addition, the starch-based adhesive is a flammable material. In order to make the adhesive itself have flame retardancy, an external flame retardant is needed. Phosphate flame retardants are safe and smokeless, but the addition amount is large. Adding a large amount of phosphate flame retardant will cause the adhesive strength and shear strength to decrease to varying degrees. To solve the above technical defects, the present application prepares a starch-based adhesive by modifying starch. SUMMARY

[0004] The present application aims to provide a starch-based adhesive and a preparation method thereof to solve the problems mentioned in the background.

[0005] The purpose of the present application can be achieved by the following technical solutions.

[0006] A starch-based adhesive comprises the following raw materials in mass fraction: modified starch 10-12 parts, oxidizing agent 0.1-0.6 parts, defoaming agent 0.01-0.03 parts, and water 16-20 parts.

[0007] Further, the oxidizing agent is one or a mixture of more than one of sodium hypochlorite, hydrogen peroxide and ammonium persulfate.

[0008] Further, the defoaming agent is tributyl phosphate.

[0009] Further, the modified starch is prepared by the following steps:

[0010] The first step, maleic anhydride, phosphate ester compound, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene are dissolved in dichloromethane in a four-necked flask, a condenser and a thermometer are installed, mechanical stirring is started, and the reaction is carried out at room temperature for 10-30 min. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and dried to obtain a starch modifier.

[0011] The second step, starch and water are mixed in a four-necked flask and reacted at a temperature of 80-100°C for 1-2 h. Then, the mixture is cooled to room temperature to obtain a gelatinous starch. The gelatinous starch and anhydrous ethanol are mixed and centrifuged in a centrifuge. The obtained precipitate is activated starch particles, which are used as needed.

[0012] The third step, the activated starch particles and the ethanol solution are mixed in a four-necked flask. Then, the pH is adjusted to 8-10 with sodium hydroxide solution. Then, the starch modifier is added to the four-necked flask, and the reaction is carried out at a temperature of 40-60°C for 4-6 h. After the reaction is completed, the pH is adjusted to 5-7 with dilute hydrochloric acid. The reaction solution is centrifuged in a centrifuge. Then, the precipitate is washed with deionized water and ethanol solution and dried to obtain modified starch.

[0013] Further, the phosphate ester compound is one or more of dimethyl phosphite, diethyl phosphite, and diphenyl phosphite.

[0014] Further, the amount ratio of maleic anhydride, phosphate ester compound, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene, and dichloromethane used in the first step is 0.98-1.08:1.10-2.34:0.14-0.28:6-10.

[0015] Further, the starch is one or more of corn starch, cassava starch, potato starch, and wheat starch.

[0016] Further, the mass fraction ratio of starch, water, and anhydrous ethanol used in the second step is 8-10:40-100:120-200.

[0017] Further, the volume fraction of the ethanol solution in the third step is 80-90%.

[0018] Further, the mass fraction ratio of activated starch particles, ethanol solution, and starch modifier used in the third step is 5-6:200-300:0.4-1.

[0019] Further, the centrifugation conditions in the second and third steps are 3000-4000 rpm for 8-15 min.

[0020] A method for preparing a starch-based adhesive, comprising the following steps:

[0021] After mixing the modified starch and water, the oxidant is added and oxidized at a temperature of 30-60 DEG C for 30-90 min, then a defoaming agent is added to the system, stirred uniformly and discharged to obtain the starch-based adhesive.

[0022] The beneficial effects of the present application are:

[0023] The present application uses maleic anhydride and phosphate ester compound as raw materials, and a Michael addition reaction occurs between the double bond of maleic anhydride and the phosphorus-hydrogen bond of the phosphate ester compound to obtain a starch modifier, and then the starch is gelatinized, precipitated, separated and subjected to an esterification reaction with the starch modifier to obtain modified starch. The number of hydroxyl groups in the modified starch is reduced after the esterification reaction, and a hydrophobic ester group is introduced, which effectively reduces the water absorption performance of the starch-based adhesive and avoids the problem of interface adhesion failure caused by water penetration.

[0024] The modified starch of the present application introduces carboxyl and phosphate ester structures. The carboxyl group can undergo esterification with the hydroxyl group on the surface of the ceramic matrix to form a chemical bond, and the phosphorus atom can form a coordination bond with the metal atoms (such as aluminum and zirconium) on the surface of the ceramic group. The two work together to significantly improve the bonding performance of the starch-based adhesive to the surface of the ceramic matrix.

[0025] The modified starch of the present application introduces phosphate ester groups with flame-retardant effect, effectively improving the stability and dispersibility of the flame-retardant component in the starch-based adhesive, reducing the migration and precipitation of the flame-retardant component, and achieving efficient flame retardation. The flame-retardant component is introduced through chemical bonding, which can maintain the mechanical properties of the adhesive while playing a flame-retardant effect, and solve the problem of mechanical property degradation caused by the addition of flame retardant. DETAILED DESCRIPTION

[0026] It should be understood that the expression "one or more of something" includes each of the objects recited after the expression and various combinations of two or more of the recited objects, unless otherwise understood from the context and usage. The expression "and / or" in combination with three or more recited objects should be understood to have the same meaning, unless otherwise understood from the context.

[0027] The terms "comprising", "having", or "including", or their grammatical variants thereof, when used in the specification, generally should be understood to be open-ended and non-limiting, for example, not excluding other unrecited elements or steps, unless otherwise specifically stated or understood from the context.

[0028] It should be understood that the order of steps or order for performing certain actions is immaterial so long as the present application remains operable. Moreover, two or more steps or actions can be conducted simultaneously.

[0029] The use of any and all examples, or exemplary language (e.g., "such as" or "including") provided herein, is intended merely to better illuminate the application and does not pose a limitation on the scope of the application unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the application.

[0030] Embodiment 1, a starch-based adhesive, comprising the following raw materials in mass fraction: modified starch 10 parts, oxidizing agent 0.1 part, defoaming agent 0.01 part, water 16 parts;

[0031] The oxidizing agent is sodium hypochlorite, the defoaming agent is tributyl phosphate, and the modified starch is prepared by the following steps:

[0032] In the first step, 0.98 parts of maleic anhydride, 1.10 parts of a phosphate ester compound, and 0.14 parts of 1,5,7-triazabicyclo-[4.4.0]dec-5-ene are dissolved in 6 parts of dichloromethane in a four-necked flask, a condenser and a thermometer are installed, mechanical stirring is started, and the reaction is carried out at room temperature for 10 minutes. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and dried to obtain a starch modifier.

[0033] In the second step, 8 parts of starch and 40 parts of water are mixed in a four-necked flask and reacted at a temperature of 80°C for 2 hours. Then the temperature is cooled to room temperature to obtain a gelatinous starch. The gelatinous starch is mixed with 120 parts of anhydrous ethanol and centrifuged in a centrifuge at a speed of 3000 rpm for 15 minutes. The obtained precipitate is activated starch particles, which are ready for use.

[0034] In the third step, 5 parts of activated starch particles and 200 parts of 90% ethanol solution are mixed in a four-necked flask. Then, the pH is adjusted to 8 with sodium hydroxide solution. Then, 0.4 parts of the starch modifier is added to the four-necked flask, and the reaction is carried out at a temperature of 40°C for 6 hours. After the reaction is completed, the pH is adjusted to 7 with dilute hydrochloric acid. The reaction solution is centrifuged in a centrifuge at a speed of 3000 rpm for 15 minutes. Then, the precipitate is washed with deionized water and ethanol solution and dried to obtain modified starch.

[0035] The phosphate ester compound is dimethyl phosphite, and the starch is corn starch.

[0036] A method for preparing a starch-based adhesive, comprising the following steps:

[0037] The modified starch and water are mixed, the oxidizing agent is added and oxidized at a temperature of 30°C for 30 minutes. Then, the defoaming agent is added to the system, stirred uniformly, and discharged to obtain the starch-based adhesive.

[0038] Example 2, a starch-based adhesive, comprising the following raw materials in mass fraction: modified starch 11 parts, oxidizing agent 0.35 parts, defoaming agent 0.02 parts, water 18 parts;

[0039] The oxidizing agent is ammonium persulfate, the defoaming agent is tributyl phosphate, and the modified starch is prepared by the following steps:

[0040] In the first step, 1.03 parts of maleic anhydride, 1.38 parts of a phosphate ester compound, and 0.21 parts of 1,5,7-triazabicyclo-[4.4.0]dec-5-ene are dissolved in 8 parts of dichloromethane in a four-necked flask, a condenser and a thermometer are installed, mechanical stirring is started, and the reaction is carried out at room temperature for 20 minutes. After the reaction is completed, the solvent is removed by rotary evaporation, and the remaining solid is washed with deionized water and dried to obtain a starch modifier.

[0041] In the second step, 9 parts of starch and 70 parts of water are mixed in a four-necked flask and reacted at a temperature of 90°C for 1.5 hours. Then the temperature is cooled to room temperature to obtain a gelatinous starch. The gelatinous starch is mixed with 160 parts of anhydrous ethanol and centrifuged in a centrifuge at a speed of 3500 rpm for 11.5 minutes. The obtained precipitate is activated starch particles, which are ready for use.

[0042] In the third step, 5.5 parts of activated starch particles and 250 parts of an ethanol solution with a volume fraction of 85% are mixed in a four-necked flask. Then, the pH is adjusted to 9 with a sodium hydroxide solution. Then, 0.7 parts of the starch modifier is added to the four-necked flask, and the reaction is carried out at a temperature of 50°C for 5 hours. After the reaction is completed, the pH is adjusted to 6 with dilute hydrochloric acid. The reaction solution is placed in a centrifuge and centrifuged at a speed of 3500 rpm for 11.5 minutes. Then, the precipitate is washed with deionized water and an ethanol solution and dried to obtain modified starch.

[0043] The phosphate ester compound is diethyl phosphite, and the starch is cassava starch.

[0044] A method for preparing a starch-based adhesive, comprising the following steps:

[0045] The modified starch and water are mixed, an oxidizing agent is added, and the system is oxidized at a temperature of 45°C for 60 minutes. Then, a defoaming agent is added, the mixture is stirred uniformly, and the starch-based adhesive is obtained.

[0046] Example 3, a starch-based adhesive, comprising the following raw materials in mass fraction: modified starch 12 parts, oxidizing agent 0.6 parts, defoaming agent 0.03 parts, water 20 parts;

[0047] The oxidizing agent is a 30% hydrogen peroxide aqueous solution, the defoaming agent is tributyl phosphate, and the modified starch is prepared by the following steps:

[0048] The first step, according to the mass fraction, 1.08 parts of maleic anhydride, 2.34 parts of phosphate compound, 0.28 parts of 1,5,7-triazabicyclo-[4.4.0]dec-5-ene are dissolved in a four-necked flask with 10 parts of dichloromethane, equipped with a condenser and a thermometer, start mechanical stirring, react at room temperature for 30 min, after the reaction is completed, remove the solvent by rotary evaporation, wash the remaining solid with deionized water and dry to obtain a starch modifier;

[0049] The second step, according to the mass fraction, 10 parts of starch and 100 parts of water are mixed in a four-necked flask, and reacted at a temperature of 100°C for 1h, then cooled to room temperature to obtain a colloidal starch, then the colloidal starch and 200 parts of anhydrous ethanol are mixed and centrifuged in a centrifuge at a speed of 4000 rpm for 8 min, and the obtained precipitate is activated starch particles for use;

[0050] The third step, according to the mass fraction, 6 parts of activated starch particles and 300 parts of 80% ethanol solution by volume are mixed in a four-necked flask, then the pH is adjusted to 10 with sodium hydroxide solution, then 1 part of starch modifier is added to the four-necked flask, and reacted at a temperature of 60°C for 4h, after the reaction is completed, the pH is adjusted to 5 with dilute hydrochloric acid, and the reaction solution is placed in a centrifuge and centrifuged at a speed of 4000 rpm for 8 min, then the precipitate is washed with deionized water and ethanol solution and dried to obtain modified starch;

[0051] The phosphate compound is diphenyl phosphite, and the starch is a mixture of potato starch and wheat starch in a mass ratio of 4:6.

[0052] A preparation method of a starch-based adhesive, comprising the following steps:

[0053] The modified starch and water are mixed, an oxidizing agent is added and oxidized at a temperature of 60°C for 90 min, then a defoaming agent is added to the system, stirred uniformly and discharged to obtain a starch-based adhesive.

[0054] Comparative Example 1:

[0055] A starch-based adhesive, comprising the following mass fractions of raw materials: activated starch particles 10 parts, oxidizing agent 0.1 part, defoaming agent 0.01 part, flame retardant 0.8 part, water 16 parts;

[0056] The starch is corn starch, the oxidizing agent is sodium hypochlorite, the defoaming agent is tributyl phosphate, the flame retardant is DOPO, and the activated starch particles are prepared by the following steps:

[0057] 8 parts of corn starch and 40 parts of water were mixed in a four-necked flask, and reacted at a temperature of 80 DEG C for 2 hours, and then cooled to room temperature to obtain a gelatinous starch, and then the gelatinous starch and 120 parts of anhydrous ethanol were mixed and centrifuged in a centrifuge at a speed of 3000 rpm for 15 minutes, and the obtained precipitate was activated starch particles for standby.

[0058] A preparation method of a starch-based adhesive, comprising the following steps:

[0059] After the activated starch particles and water were mixed, an oxidizing agent was added and oxidized at a temperature of 30 DEG C for 30 minutes, and then a defoaming agent and a flame retardant were added to the system, and after stirring uniformly, the starch-based adhesive was obtained.

[0060] Comparative Example 2:

[0061] A starch-based adhesive, comprising the following mass parts of raw materials: activated starch particles 10 parts, oxidizing agent 0.1 part, defoaming agent 0.01 part, water 16 parts;

[0062] The oxidizing agent is sodium hypochlorite, the defoaming agent is tributyl phosphate, and the activated starch particles are prepared by the following steps:

[0063] 8 parts of corn starch and 40 parts of water were mixed in a four-necked flask, and reacted at a temperature of 80 DEG C for 2 hours, and then cooled to room temperature to obtain a gelatinous starch, and then the gelatinous starch and 120 parts of anhydrous ethanol were mixed and centrifuged in a centrifuge at a speed of 3000 rpm for 15 minutes, and the obtained precipitate was activated starch particles for standby.

[0064] A preparation method of a starch-based adhesive, comprising the following steps:

[0065] After the activated starch particles and water were mixed, an oxidizing agent was added and oxidized at a temperature of 30 DEG C for 30 minutes, and then a defoaming agent and a flame retardant were added to the system, and after stirring uniformly, the starch-based adhesive was obtained.

[0066] Experimental Example:

[0067] The starch-based adhesives in Examples 1-3 and Comparative Examples 1-2 were tested for bonding strength, tensile shear strength, and flame retardant performance, and the test results are shown in Table 1:

[0068] Bonding strength test: test the bonding strength in dry and humid environments according to national standard GB / T 44549-2024;

[0069] Tensile shear strength test: test according to national standard GB / T 6328-2021;

[0070] Flame-retardant performance: test limited oxygen index according to national standard GB / T 2406.3-2022, the higher the limited oxygen index, the stronger the flame-retardant performance;

[0071]

[0072] As can be seen from Table 1, the adhesives prepared by using the modified starch of the application in Examples 1-3 have good flame-retardant performance, good adhesive strength and tensile shear strength, and the adhesive strength is less affected in a humid environment. Comparative Example 2 is an adhesive prepared by using conventional starch, and it can be seen that the adhesive strength of the adhesive with the ceramic matrix surface is poor, and the shear strength is also not as good as that of the adhesives in Examples 1-3. Comparative Example 1 is a control experiment using a conventional flame retardant, and it can be seen that, compared with Comparative Example 2, the adhesive strength and tensile shear strength of Comparative Example 1 after adding the flame retardant have decreased to different degrees.

[0073] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A starch-based adhesive, characterized in that, The raw materials include the following parts by weight: 10-12 parts modified starch, 0.1-0.6 parts oxidant, 0.01-0.03 parts defoamer, and 16-20 parts water; The modified starch is prepared by the following steps: Maleic anhydride, phosphate ester compound, and 1,5,7-triazabicyclo-[4.4.0]dec-5-ene were dissolved in dichloromethane and reacted at room temperature to obtain a starch modifier for later use. Then, starch and water were mixed and reacted at 80-100℃ to obtain gelatinous starch. The gelatinous starch was mixed with anhydrous ethanol and centrifuged to obtain activated starch granules. The activated starch granules were mixed with anhydrous ethanol and the pH was adjusted to 8-10. Then, the starch modifier was added and reacted at 40-60℃. After the reaction was completed, the pH was adjusted to 5-7. The reaction solution was then centrifuged to obtain a precipitate, which was washed and dried to obtain modified starch. The phosphate ester compound is one or more of dimethyl phosphite, diethyl phosphite, and diphenyl phosphite.

2. The starch-based adhesive according to claim 1, characterized in that, The oxidant is one or a mixture of sodium hypochlorite, hydrogen peroxide, and ammonium persulfate.

3. The starch-based adhesive according to claim 1, characterized in that, The defoamer is tributyl phosphate.

4. The starch-based adhesive according to claim 1, characterized in that, Starch can be one or more of the following: corn starch, tapioca starch, potato starch, and wheat starch.

5. The starch-based adhesive according to claim 1, characterized in that, The ratio of maleic anhydride, phosphate ester compound, 1,5,7-triazabicyclo-[4.4.0]dec-5-ene, and dichloromethane used in the preparation of modified starch is 0.98~1.08:1.10~2.34:0.14~0.28:6~10.

6. The starch-based adhesive according to claim 1, characterized in that, The mass ratio of starch, water, and anhydrous ethanol used in the preparation of modified starch is 8–10:40–100:120–200.

7. The starch-based adhesive according to claim 1, characterized in that, The volume fraction of the ethanol solution used to prepare the modified starch is 80-90%, and the mass ratio of the activated starch granules, ethanol solution, and starch modifier is 5-6:200-300:0.4-1.

8. The starch-based adhesive according to claim 1, characterized in that, The centrifugation conditions are 3000-4000 rpm for 8-15 minutes.

9. A method for preparing a starch-based adhesive as described in any one of claims 1 to 8, characterized in that, Includes the following steps: After mixing modified starch and water, an oxidant is added and oxidized at a temperature of 30-60℃ for 30-90 minutes. Then, an antifoaming agent is added to the system, and after stirring evenly, the starch-based adhesive is discharged.

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