Low-temperature resistant casein starch glue and preparation method thereof

Abstract

The application relates to the technical field of adhesives, and discloses a low-temperature-resistant casein starch adhesive and a preparation method thereof. The low-temperature-resistant casein starch adhesive comprises 100 parts by weight of dry casein, 20-46 parts by weight of acetate starch, 18-40 parts by weight of polyvinyl alcohol, 35-50 parts by weight of urea and 2-6 parts by weight of a siloxane crosslinking agent. The siloxane crosslinking agent contains a large amount of epoxy groups, can react with the amino groups of the casein, the hydroxyl groups of the acetate starch and the hydroxyl groups of the polyvinyl alcohol, improves the crosslinking degree and the cohesion of the casein starch adhesive, and makes the adhesive have higher peeling strength and bonding performance. After the casein starch adhesive is treated at low temperature and high humidity, the adhesive still has higher peeling strength and excellent low-temperature resistance and moisture resistance.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a low-temperature resistant casein starch adhesive and its preparation method. Background Technology

[0002] Casein starch adhesive is mainly composed of casein, starch, and additives. It boasts advantages such as being environmentally friendly, highly safe, biodegradable, and inexpensive, making it widely used in labels, food packaging, and wooden furniture. However, ordinary starch-based adhesives suffer from poor low-temperature resistance and water / moisture resistance, limiting their application areas.

[0003] Siloxanes possess excellent water resistance, high and low temperature resistance, and flexibility, making them widely used in coatings and adhesives. Patent CN114395079B discloses a starch modification method and adhesive, using starch, sodium lignosulfonate, trimethylolpropane trimethacrylate, vinyltriethoxysilane, and polyvinyl alcohol as raw materials. The resulting adhesive exhibits good water resistance, but this patent does not improve the low-temperature resistance of starch-based adhesives. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low-temperature resistant casein starch adhesive and its preparation method, solving the problems of poor low-temperature resistance and water resistance of casein starch adhesive.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a low-temperature resistant casein starch adhesive and its preparation method, the low-temperature resistant casein starch adhesive comprising: 100 parts by weight of casein, 20-46 parts by weight of acetate starch, 18-40 parts by weight of polyvinyl alcohol, 35-50 parts by weight of urea, 2-6 parts by weight of siloxane crosslinking agent, and 0.8-1.4 parts by weight of defoamer.

[0006] Preparation method of low-temperature resistant casein starch gum:

[0007] (1) Allyl glycidyl ether, chloroplatinic acid-isopropanol solution, and phenyl dichlorosilane were added to toluene, heated to the reaction temperature, stirred, concentrated under reduced pressure, and the product was recrystallized in ethyl acetate to obtain propyl glycidyl ether phenyl dichlorosilane. The reaction formula is as follows:

[0008] (2) Triethylamine, alkyl glycol, dimethyl dichlorosilane, and propyl glycidyl ether phenyl dichlorosilane were added to toluene, and the mixture was stirred and reacted. After concentration under reduced pressure, the product was washed with water and petroleum ether and dried to obtain a siloxane crosslinking agent. The reaction formula is as follows:

[0009] (3) Add polyvinyl alcohol to water, heat and stir, then cool, add acetate starch, urea, and defoamer, stir, then add pH adjuster and casein, stir, then add siloxane crosslinking agent and ethanol, stir and mix well to obtain low-temperature resistant casein starch glue.

[0010] Preferably, the ratio of allyl glycidyl ether to phenyl dichlorosilane in (1) is 1 mol: (1.5-1.6) mol.

[0011] Preferably, in (1), the reaction temperature is 80-90℃ and the reaction time is 2-4h.

[0012] Preferably, the ratio of triethylamine, alkyl diol, dimethyl dichlorosilane, and propyl glycidyl ether phenyl dichlorosilane in (2) is (2-2.2) mol: (1.04-1.1) mol: (0.8-0.95) mol: (0.05-0.2) mol.

[0013] Preferably, the structural formula of the alkyl diol in (2) is: , where a is any integer from 6 to 12.

[0014] Preferably, the reaction temperature in (2) is 50-65℃ and the reaction time is 12-18h.

[0015] Preferably, in (3), a pH adjuster is added to adjust the pH of the solution to 7.5-8.

[0016] Preferably, in (3), the pH adjuster includes sodium hydroxide and ethanolamine.

[0017] Preferably, in (3), when heating and stirring and then cooling, the heating temperature is controlled at 90-95℃ and the cooling temperature is controlled at 60-65℃.

[0018] The beneficial technical effects of this invention are as follows: This invention involves the siloxaneation reaction of alkyl diol, dimethyl dichlorosilane, and propyl glycidyl ether phenyl dichlorosilane to obtain a siloxane crosslinking agent. This agent is then compounded with casein, acetate starch, and polyvinyl alcohol to obtain casein starch adhesive. The siloxane crosslinking agent contains a large number of epoxy groups, which can react with the amino groups of casein, the hydroxyl groups of acetate starch, and the hydroxyl groups of polyvinyl alcohol, thereby chemically crosslinking casein, acetate starch, and polyvinyl alcohol. This improves the crosslinking degree and cohesive force of the casein starch adhesive, resulting in higher peel strength and bonding performance.

[0019] After the siloxane crosslinking agent of the present invention is chemically crosslinked with casein, starch, etc., the hydrophobic siloxane, benzene ring and alkyl chain are chemically bonded to the adhesive matrix to form a hydrophobic crosslinking network, which is beneficial to improving the water resistance and waterproof performance of casein starch adhesive. In addition, the siloxane structure has strong low temperature resistance. After the casein starch adhesive is treated with low temperature and high humidity, it still has higher peel strength and excellent low temperature and humidity resistance. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0021] (1) Add 10 mmol of allyl glycidyl ether, 250 μL of isopropanol solution containing 4.8 mg of chloroplatinic acid, and 15 mmol of phenyl dichlorosilane to 50 mL of toluene, heat to 90 °C, stir for 2 h, concentrate under reduced pressure, and recrystallize the product in ethyl acetate to obtain propyl glycidyl ether phenyl dichlorosilane.

[0022] (2) Add 200 mmol of triethylamine and 106 mmol of 1,10-decanediol to 150 mL of toluene, add 95 mmol of dimethyl dichlorosilane and 5 mmol of propyl glycidyl ether phenyl dichlorosilane, heat to 50 °C, stir and react for 18 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0023] (3) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer (Hua Shun BSM1148, Hebei Hua Shun Chemical Co., Ltd., the same below), stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of siloxane crosslinking agent and 50mL of ethanol, stir and mix well to obtain low temperature resistant casein starch glue. Example 2

[0024] (1) Add 10 mmol of allyl glycidyl ether, 250 μL of isopropanol solution containing 4.8 mg of chloroplatinic acid, and 16 mmol of phenyl dichlorosilane to 50 mL of toluene, heat to 80 °C, stir for 4 h, concentrate under reduced pressure, and recrystallize the product in ethyl acetate to obtain propyl glycidyl ether phenyl dichlorosilane.

[0025] (2) Add 220 mmol of triethylamine and 110 mmol of 1,6-hexanediol to 200 mL of toluene, add 90 mmol of dimethyl dichlorosilane and 10 mmol of propyl glycidyl ether phenyl dichlorosilane, heat to 60 °C, stir and react for 12 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0026] (3) Add 180g of polyvinyl alcohol to 2L of water, heat to 90℃, stir and cool to 60℃, add 460g of acetate starch, 350g of urea and 14g of defoamer, stir and add sodium hydroxide and ethanolamine in a mass ratio of 3:1, adjust the pH of the solution to 7.5, add 1kg of casein, stir and add 30g of siloxane crosslinking agent and 100mL of ethanol, stir and mix well to obtain low-temperature resistant casein starch glue. Example 3

[0027] (1) Propyl glycidyl ether phenyl dichlorosilane was prepared according to the method of Example 1.

[0028] (2) Add 200 mmol of triethylamine and 104 mmol of 1,16-hexadecyl alcohol to 200 mL of toluene, add 85 mmol of dimethyl dichlorosilane and 15 mmol of propyl glycidyl ether phenyl dichlorosilane, heat to 65 °C, stir and react for 12 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0029] (3) Add 400g of polyvinyl alcohol to 3L of water, heat to 95℃, stir and cool to 65℃, add 200g of acetate starch, 500g of urea and 12g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 45g of siloxane crosslinking agent and 140mL of ethanol, stir and mix well to obtain low-temperature resistant casein starch glue. Example 4

[0030] (1) Propyl glycidyl ether phenyl dichlorosilane was prepared according to the method of Example 1.

[0031] (2) Add 210 mmol of triethylamine and 110 mmol of 1,1,2-dodecanediol to 200 mL of toluene, add 80 mmol of dimethyl dichlorosilane and 20 mmol of propyl glycidyl ether phenyl dichlorosilane, heat to 50 °C, stir and react for 18 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0032] (3) Add 320g of polyvinyl alcohol to 2.5L of water, heat to 95℃, stir and cool to 60℃, add 270g of acetate starch, 380g of urea and 14g of defoamer, stir and add ethanolamine, adjust the pH of the solution to 7.5, add 1kg of casein, stir and add 60g of siloxane crosslinking agent and 200mL of ethanol, stir and mix well to obtain low-temperature resistant casein starch glue.

[0033] Comparative Example 1

[0034] (1) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of polyethylene glycol diglycidyl ether (CAS No. 39443-66-8, Shandong Suihua Biotechnology Co., Ltd.) and 50mL of ethanol, stir and mix well to obtain casein starch gel.

[0035] Comparative Example 2

[0036] (1) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of epoxypropoxypropyl-terminated polydimethylsiloxane (CAS No. 102782-97-8, Wuhan Camic Technology Co., Ltd.) and 50mL of ethanol, stir and mix well to obtain casein starch gel.

[0037] Comparative Example 3

[0038] (1) Add 200 mmol of triethylamine and 106 mmol of 1,10-decanediol to 150 mL of toluene, add 100 mmol of dimethyldichlorosilane, heat to 50 °C, stir and react for 18 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0039] (2) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of siloxane crosslinking agent and 50mL of ethanol, stir and mix well to obtain casein starch gel.

[0040] Comparative Example 4

[0041] (1) Add 200 mmol of triethylamine and 106 mmol of 1,10-decanediol to 150 mL of toluene, add 95 mmol of dimethyldichlorosilane and 5 mmol of methylphenyldichlorosilane, heat to 50 °C, stir and react for 18 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0042] (2) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of siloxane crosslinking agent and 50mL of ethanol, stir and mix well to obtain casein starch gel.

[0043] Comparative Example 5

[0044] (1) Add 10 mmol of allyl glycidyl ether, 250 μL of isopropanol solution containing 4.8 mg of chloroplatinic acid, and 15 mmol of methyldichlorosilane to 50 mL of toluene. Heat to 90 °C and stir for 2 h. Concentrate under reduced pressure to remove low-boiling substances to obtain propyl glycidyl ether methyldichlorosilane, with the structural formula: .

[0045] (2) Add 200 mmol of triethylamine and 106 mmol of 1,10-decanediol to 150 mL of toluene, add 95 mmol of dimethyl dichlorosilane and 5 mmol of propyl glycidyl ether methyl dichlorosilane, heat to 50 °C, stir and react for 18 h, concentrate under reduced pressure, wash the product with water and petroleum ether, and dry to obtain siloxane crosslinking agent.

[0046] (3) Add 230g of polyvinyl alcohol to 2.5L of water, heat to 90℃, stir and cool to 65℃, add 380g of acetate starch, 420g of urea and 9g of defoamer, stir and add sodium hydroxide to adjust the pH of the solution to 8, add 1kg of casein, stir and add 20g of siloxane crosslinking agent and 50mL of ethanol, stir and mix well to obtain casein starch gel.

[0047] The 180° peel strength F was tested according to GB / T 2790-1995 standard. The test sample was a polypropylene sheet-tinplate, the curing temperature was 90℃, and the curing time was 3h.

[0048] The polypropylene sheet-tinplate test specimen bonded with casein starch adhesive was placed in a high and low temperature test chamber at 2°C and 95% relative humidity for 240 hours. The specimen was then removed, left at room temperature for 1 hour, and the 180° peel strength F1 was tested again.

[0049] Table 1 Properties of Casein Starch Gum

[0050]

[0051] After testing, the casein starch adhesives prepared in each embodiment showed higher peel strength, mainly because the added siloxane crosslinking agent contained a large number of epoxy groups. During the high-temperature curing process, these groups could react with the amino groups of casein, the hydroxyl groups of acetate starch, and the hydroxyl groups of polyvinyl alcohol, thereby chemically crosslinking casein, acetate starch, and polyvinyl alcohol. This improved the crosslinking degree and cohesive force of the casein starch adhesive, resulting in higher peel strength and bonding performance. At the same time, after chemical crosslinking, the siloxane crosslinking agent chemically bonded the hydrophobic siloxane, benzene ring, and alkyl chain into the adhesive matrix, forming a hydrophobic crosslinking network. This improved the water resistance and waterproof performance of the casein starch adhesive. Furthermore, the siloxane structure exhibited strong low-temperature resistance, and the casein starch adhesive still showed higher peel strength and excellent low-temperature and moisture resistance after low-temperature and high-humidity treatment.

[0052] Comparative Example 1 used conventional polyethylene glycol diglycidyl ether as a crosslinking agent. It only contains epoxy groups at both ends, and the content is low. It has poor crosslinking effect on casein, acetate starch and polyvinyl alcohol. In addition, it does not contain benzene ring and siloxane structure, resulting in low peel strength of casein starch glue. After low temperature and high humidity treatment, the peel strength decreased significantly.

[0053] Comparative Example 2 used epoxypropyl-terminated polydimethylsiloxane as a crosslinking agent. It only contains epoxy groups at both ends, and the content is low. It has poor crosslinking effect on casein, acetate starch and polyvinyl alcohol, and does not contain benzene ring structure, resulting in low peel strength of casein starch adhesive.

[0054] Compared to Example 1, Comparative Example 3, which polymerized 1,10-decanediol and dimethyldichlorosilane, produced a siloxane crosslinking agent that lacked epoxy groups. This agent could not crosslink with casein, acetate starch, and polyvinyl alcohol, resulting in a casein starch adhesive with low peel strength, which decreased significantly after low-temperature, high-humidity treatment. Comparative Example 4, which polymerized 1,10-decanediol, dimethyldichlorosilane, and methylphenyldichlorosilane, also produced a siloxane crosslinking agent that lacked epoxy groups. This agent could not crosslink with casein, acetate starch, and polyvinyl alcohol, resulting in a casein starch adhesive with low peel strength, which decreased significantly after low-temperature, high-humidity treatment.

[0055] Compared with Example 1, Comparative Example 5 polymerized 1,10-decanediol, dimethyldichlorosilane and propyl glycidyl ether methyldichlorosilane. The resulting siloxane crosslinking agent did not contain a benzene ring structure. After low temperature and high humidity treatment, the peel strength of the casein starch adhesive was significantly reduced, the retention rate was low, and the low temperature and humidity resistance was poor.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-temperature resistant casein starch gum, characterized in that, The low-temperature resistant casein starch adhesive comprises the following components: 100 parts by weight of casein, 20-46 parts by weight of starch acetate, 18-40 parts by weight of polyvinyl alcohol, 35-50 parts by weight of urea, 2-6 parts by weight of siloxane crosslinking agent, and 0.8-1.4 parts by weight of defoamer. The preparation method of the siloxane crosslinking agent is as follows: triethylamine, alkyl diol, dimethyl dichlorosilane, and propyl glycidyl ether phenyl dichlorosilane are added to toluene, the mixture is stirred and reacted, the product is concentrated under reduced pressure, washed, and dried to obtain the siloxane crosslinking agent.

2. The low-temperature resistant casein starch adhesive according to claim 1, characterized in that, The reaction temperature is 50-65℃, and the reaction time is 12-18h.

3. The low-temperature resistant casein starch adhesive according to claim 1, characterized in that, The ratio of triethylamine, alkyl diol, dimethyl dichlorosilane, and propyl glycidyl ether phenyl dichlorosilane is (2-2.2) mol: (1.04-1.1) mol: (0.8-0.95) mol: (0.05-0.2) mol.

4. The low-temperature resistant casein starch adhesive according to claim 1, characterized in that, The structural formula of the alkyl diol is: , where a is any integer from 6 to 12.

5. The low-temperature resistant casein starch adhesive according to claim 1, characterized in that, The preparation method of the propyl glycidyl ether phenyl dichlorosilane is as follows: add allyl glycidyl ether, chloroplatinic acid-isopropanol solution and phenyl dichlorosilane to toluene, heat to 80-90℃, stir and react for 2-4 hours, concentrate under reduced pressure, and recrystallize the product to obtain propyl glycidyl ether phenyl dichlorosilane.

6. The low-temperature resistant casein starch gum according to claim 5, characterized in that, The ratio of allyl glycidyl ether to phenyl dichlorosilane is 1 mol: (1.5-1.6) mol.

7. A method for preparing low-temperature resistant casein starch gum as described in any one of claims 1-6, the method comprising: Polyvinyl alcohol is added to water, heated and stirred, then cooled. Acetate starch, urea, and defoamer are added, and after stirring, pH adjuster and casein are added. After stirring, siloxane crosslinking agent and ethanol are added, and the mixture is stirred until homogeneous to obtain low-temperature resistant casein starch gel.

8. The method for preparing low-temperature resistant casein starch gum according to claim 7, characterized in that, The pH of the solution is adjusted to 7.5-8 by adding a pH adjuster.

9. The method for preparing low-temperature resistant casein starch gum according to claim 8, characterized in that, The pH adjuster includes sodium hydroxide and ethanolamine.

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