Low-temperature-resistant casein starch glue and preparation method thereof

Abstract

The invention 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 is prepared from, by weight, 100 parts of casein, 20-46 parts of starch acetate, 18-40 parts of polyvinyl alcohol, 35-50 parts of urea, 2-6 parts of siloxane cross-linking agent and the like. The siloxane cross-linking agent contains a large amount of epoxy groups and can react with amino groups of casein, hydroxyl groups of starch acetate and hydroxyl groups of polyvinyl alcohol, so that the cross-linking degree and cohesion of the casein starch glue are improved, and the adhesive has higher peel strength and adhesive property. After low-temperature and high-humidity treatment, the casein starch glue still has higher peel strength and excellent low-temperature and moisture resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesives, in particular to a low-temperature-resistant casein starch adhesive and a preparation method thereof. BACKGROUND

[0002] The casein starch adhesive is mainly composed of casein, starch, additives and the like, has the advantages of green environmental protection, high safety, biodegradability and low cost, and is widely applied in labels, food packaging, wooden furniture and the like. The ordinary starch-based adhesive has poor low-temperature resistance and poor water resistance and humidity resistance, which limits the application field of the starch-based adhesive.

[0003] Siloxane substances have good water resistance, high and low temperature resistance, flexibility and the like, and are widely applied in coatings, adhesives and the like. The patent with the publication number CN114395079B discloses a starch modification method and an adhesive, and the adhesive is prepared by taking starch, sodium lignosulfonate, trimethylolpropane trimethacrylate, vinyltriethoxysilane and polyvinyl alcohol as raw materials, and has good water resistance and the like, but the patent does not improve the low-temperature resistance of the starch-based adhesive. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a low-temperature-resistant casein starch adhesive and a preparation method thereof, and solves the problems of poor low-temperature resistance, water resistance and the like of the casein starch adhesive.

[0005] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows: 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, 2-6 parts by weight of a siloxane crosslinking agent and 0.8-1.4 parts by weight of a defoaming agent.

[0006] The preparation method of the low-temperature-resistant casein starch adhesive comprises the following steps: (1) adding allyl glycidyl ether, chloroplatinic acid-isopropyl alcohol solution and phenyldichlorosilane into toluene, heating to a reaction temperature, stirring and reacting, reducing pressure and concentrating, recrystallizing the product in ethyl acetate, and obtaining propyl glycidyl ether phenyldichlorosilane, and the reaction formula is as follows:

[0007] (2) adding triethylamine, alkyl glycol, dimethyldichlorosilane and propyl glycidyl ether phenyldichlorosilane into toluene, stirring and reacting, reducing pressure and concentrating, washing the product with water and petroleum ether, and drying to obtain a siloxane crosslinking agent, and the reaction formula is as follows:

[0008] (3) adding polyvinyl alcohol into water, heating and stirring, then cooling, adding acetoacetate starch, urea, defoaming agent, stirring, then adding pH regulator, casein, stirring, then adding siloxane crosslinking agent, ethanol, stirring, to obtain low-temperature-resistant casein starch glue.

[0009] Preferably, the ratio of allyl glycidyl ether to phenyl dichlorosilane in (1) is 1 mol:(1.5-1.6) mol.

[0010] Preferably, the reaction temperature in (1) is 80-90℃, and the reaction time is 2-4h.

[0011] Preferably, the ratio of triethylamine, alkyl glycol, dimethyl dichlorosilane, 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.

[0012] Preferably, the structure of alkyl glycol in (2) is , and a is any integer from 6 to 12.

[0013] Preferably, the reaction temperature in (2) is 50-65℃, and the reaction time is 12-18h.

[0014] Preferably, in (3), the pH of the solution is adjusted to 7.5-8 by adding pH regulator.

[0015] Preferably, in (3), the pH regulator includes sodium hydroxide and ethanolamine.

[0016] Preferably, in (3), when heating and stirring and then cooling, the heating temperature is controlled to be 90-95℃, and the cooling temperature is 60-65℃.

[0017] The present application has the beneficial technical effects that: the alkyl glycol, dimethyl dichlorosilane, propyl glycidyl ether phenyl dichlorosilane are subjected to siloxane reaction, and a siloxane crosslinking agent is obtained by polymerization, and then the siloxane crosslinking agent is compounded with casein, acetoacetate starch, polyvinyl alcohol, etc., to obtain casein starch glue. The siloxane crosslinking agent contains a large number of epoxy groups, which can react with the amino group of casein, the hydroxyl group of acetoacetate starch, and the hydroxyl group of polyvinyl alcohol, so as to cause chemical crosslinking reaction of casein, acetoacetate starch and polyvinyl alcohol, improve the crosslinking degree and cohesion of casein starch glue, and make the adhesive have higher peel strength and bonding performance.

[0018] The siloxane crosslinking agent of the present application is chemically crosslinked with casein, starch and the like, and the hydrophobic siloxane, benzene ring and alkyl chain are chemically bonded into the adhesive matrix to form a hydrophobic crosslinking network, which is beneficial to improve the water resistance and waterproof performance of the casein starch adhesive, and the low temperature resistance of the siloxane structure is strong, and the casein starch adhesive still has higher peel strength and excellent low temperature resistance and moisture resistance after low temperature and high humidity treatment. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application. Example 1

[0020] (1) 10 mmol of allyl glycidyl ether, 250 μL of isopropyl alcohol solution containing 4.8 mg of chloroplatinic acid, 15 mmol of phenyl dichlorosilane were added into 50 mL of toluene, heated to 90°C, stirred for 2h, concentrated under reduced pressure, and the product was recrystallized in ethyl acetate to obtain propyl glycidyl ether phenyl dichlorosilane.

[0021] (2) 200 mmol of triethylamine, 106 mmol of 1,10-decanediol were added into 150 mL of toluene, 95 mmol of dimethyl dichlorosilane, 5 mmol of propyl glycidyl ether phenyl dichlorosilane were added, heated to 50°C, stirred for 18h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried to obtain a siloxane crosslinking agent.

[0022] (3) 230 g of polyvinyl alcohol was added into 2.5 L of water, heated to 90°C, stirred and cooled to 65°C, 380 g of acetate starch, 420 g of urea, 9 g of defoaming agent (Huashun BSM1148, Hebei Huashun Chemical Co., Ltd., same below) were added, stirred, then sodium hydroxide was added to adjust the pH of the solution to 8, 1 kg of casein was added, stirred, then 20 g of siloxane crosslinking agent, 50 mL of ethanol was added, stirred and mixed to obtain a low temperature resistant casein starch adhesive. Example 2

[0023] (1) 10 mmol of allyl glycidyl ether, 250 μL of isopropyl alcohol solution containing 4.8 mg of chloroplatinic acid, 16 mmol of phenyl dichlorosilane were added into 50 mL of toluene, heated to 80°C, stirred for 4h, concentrated under reduced pressure, and the product was recrystallized in ethyl acetate to obtain propyl glycidyl ether phenyl dichlorosilane.

[0024] (2) To 200 mL of toluene, 220 mmol of triethylamine, 110 mmol of 1,6-hexanediol, 90 mmol of dimethyldichlorosilane, and 10 mmol of propyl glycidyl ether phenyl dichlorosilane were added, heated to 60°C, stirred for 12 h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried, and a siloxane crosslinking agent was obtained.

[0025] (3) To 2 L of water, 180 g of polyvinyl alcohol was added, heated to 90°C, stirred, and cooled to 60°C, 460 g of acetate starch, 350 g of urea, and 14 g of an antifoaming agent were added, stirred, 3:1 mass ratio of sodium hydroxide and ethanolamine was added, the pH of the solution was adjusted to 7.5, 1 kg of casein was added, stirred, 30 g of a siloxane crosslinking agent, and 100 mL of ethanol were added, stirred, and a low-temperature resistant casein starch adhesive was obtained. Example 3

[0026] (1) Propyl glycidyl ether phenyl dichlorosilane was prepared according to the method of Example 1.

[0027] (2) To 200 mL of toluene, 200 mmol of triethylamine, 104 mmol of 1,16-hexadecanediol, 85 mmol of dimethyldichlorosilane, and 15 mmol of propyl glycidyl ether phenyl dichlorosilane were added, heated to 65°C, stirred for 12 h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried, and a siloxane crosslinking agent was obtained.

[0028] (3) To 3 L of water, 400 g of polyvinyl alcohol was added, heated to 95°C, stirred, and cooled to 65°C, 200 g of acetate starch, 500 g of urea, and 12 g of an antifoaming agent were added, stirred, sodium hydroxide was added, the pH of the solution was adjusted to 8, 1 kg of casein was added, stirred, 45 g of a siloxane crosslinking agent, and 140 mL of ethanol were added, stirred, and a low-temperature resistant casein starch adhesive was obtained. Example 4

[0029] (1) Propyl glycidyl ether phenyl dichlorosilane was prepared according to the method of Example 1.

[0030] (2) To 200 mL of toluene, 210 mmol of triethylamine, 110 mmol of 1,1,2-decanediol, 80 mmol of dimethyldichlorosilane, and 20 mmol of propyl glycidyl ether phenyl dichlorosilane were added, heated to 50°C, stirred for 18 h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried, and a siloxane crosslinking agent was obtained.

[0031] (3) To 2.5 L of water, 320 g of polyvinyl alcohol was added, heated to 95 °C, stirred and cooled to 60 °C, 270 g of acetylated starch, 380 g of urea, 14 g of defoaming agent were added, stirred and then ethanolamine was added, the pH of the solution was adjusted to 7.5, 1 kg of casein was added, stirred and then 60 g of silicone crosslinking agent, 200 mL of ethanol were added, stirred and mixed uniformly to obtain a low-temperature resistant casein starch glue.

[0032] Comparative Example 1 (1) To 2.5 L of water, 230 g of polyvinyl alcohol was added, heated to 90 °C, stirred and cooled to 65 °C, 380 g of acetylated starch, 420 g of urea, 9 g of defoaming agent were added, stirred and then sodium hydroxide was added, the pH of the solution was adjusted to 8, 1 kg of casein was added, stirred and then 20 g of polyethylene glycol diglycidyl ether (CAS No. 39443-66-8, Shandong Suihua Biological Technology Co., Ltd.), 50 mL of ethanol were added, stirred and mixed uniformly to obtain a casein starch glue.

[0033] Comparative Example 2 (1) To 2.5 L of water, 230 g of polyvinyl alcohol was added, heated to 90 °C, stirred and cooled to 65 °C, 380 g of acetylated starch, 420 g of urea, 9 g of defoaming agent were added, stirred and then sodium hydroxide was added, the pH of the solution was adjusted to 8, 1 kg of casein was added, stirred and then 20 g of polyethylene glycol diglycidyl ether (CAS No. 39443-66-8, Shandong Suihua Biological Technology Co., Ltd.), 50 mL of ethanol were added, stirred and mixed uniformly to obtain a casein starch glue.

[0034] Comparative Example 3 (1) To 150 mL of toluene, 200 mmol of triethylamine, 106 mmol of 1,10-decanediol were added, 100 mmol of dimethyldichlorosilane was added, heated to 50 °C, stirred for 18 h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried to obtain a silicone crosslinking agent.

[0035] (2) To 2.5 L of water, 230 g of polyvinyl alcohol was added, heated to 90 °C, stirred and cooled to 65 °C, 380 g of acetylated starch, 420 g of urea, 9 g of defoaming agent were added, stirred and then sodium hydroxide was added, the pH of the solution was adjusted to 8, 1 kg of casein was added, stirred and then 20 g of silicone crosslinking agent, 50 mL of ethanol were added, stirred and mixed uniformly to obtain a casein starch glue.

[0036] Comparative Example 4 (1) To 150 mL of toluene, 200 mmol of triethylamine, 106 mmol of 1,10-decanediol were added, 95 mmol of dimethyldichlorosilane, 5 mmol of methylphenyldichlorosilane were added, heated to 50 °C, stirred for 18 h, concentrated under reduced pressure, and the product was washed with water and petroleum ether, dried to obtain a silicone crosslinking agent.

[0037] (2) To 2.5 L water, 230 g of polyvinyl alcohol was added, heated to 90 °C, cooled to 65 °C after stirring, 380 g of acetylated starch, 420 g of urea, 9 g of defoaming agent were added, sodium hydroxide was added after stirring, the pH of the solution was adjusted to 8, 1 kg of casein was added, 20 g of siloxane crosslinking agent, 50 mL of ethanol was added after stirring, and the mixture was stirred to obtain a casein starch adhesive.

[0038] Comparative Example 5 (1) To 50 mL of toluene, 10 mmol of allyl glycidyl ether, 250 μL of isopropyl alcohol solution containing 4.8 mg of chloroplatinic acid, 15 mmol of methyl dichlorosilane were added, heated to 90 °C, stirred for 2 h, and the low boiling point was removed by vacuum concentration to obtain propyl glycidyl ether methyl dichlorosilane, the structure is .

[0039] (2) To 150 mL of toluene, 200 mmol of triethylamine, 106 mmol of 1,10-decanediol were added, 95 mmol of dimethyl dichlorosilane, 5 mmol of propyl glycidyl ether methyl dichlorosilane were added, heated to 50 °C, stirred for 18 h, and the product was washed with water and petroleum ether after vacuum concentration and drying to obtain a siloxane crosslinking agent.

[0040] (3) To 2.5 L water, 230 g of polyvinyl alcohol was added, heated to 90 °C, cooled to 65 °C after stirring, 380 g of acetylated starch, 420 g of urea, 9 g of defoaming agent were added, sodium hydroxide was added after stirring, the pH of the solution was adjusted to 8, 1 kg of casein was added, 20 g of siloxane crosslinking agent, 50 mL of ethanol was added after stirring, and the mixture was stirred to obtain a casein starch adhesive.

[0041] The 180° peeling strength F was tested according to GB / T 2790-1995 standard, the test sample was polypropylene sheet-steel, the curing temperature was 90 °C, and the curing time was 3 h.

[0042] The polypropylene sheet-steel test sample bonded with the casein starch adhesive was placed in a high and low temperature test chamber, the temperature was 2 °C, the relative humidity was 95%, and the sample was placed for 240 h. The sample was taken out, placed at room temperature for 1 h, and then the 180° peeling strength F1 was tested.

[0043] Table 1 Properties of casein starch adhesive

[0044] The casein starch adhesive prepared by each embodiment has higher peeling strength, mainly because the siloxane crosslinking agent added contains a large amount 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 during high-temperature curing, thereby causing chemical crosslinking reaction of casein, acetate starch and polyvinyl alcohol, improving the crosslinking degree and cohesion of the casein starch adhesive, and making the adhesive have higher peeling strength and bonding performance. At the same time, after chemical crosslinking of the siloxane crosslinking agent, the hydrophobic siloxane, benzene ring and alkyl chain are chemically bonded into the adhesive matrix to form a hydrophobic crosslinking network, which is beneficial to improve the water resistance and waterproof performance of the casein starch adhesive. In addition, the siloxane structure has strong low-temperature resistance, and the casein starch adhesive still has higher peeling strength after low-temperature and high-humidity treatment, and has excellent low-temperature and moisture resistance.

[0045] The comparative example 1 uses a conventional polyethylene glycol diglycidyl ether as a crosslinking agent, which only contains epoxy groups at both ends and has a low content, and has poor crosslinking effect on casein, acetate starch and polyvinyl alcohol, and does not contain benzene ring and siloxane structure, resulting in low peeling strength of the casein starch adhesive, and a large decrease in peeling strength after low-temperature and high-humidity treatment.

[0046] The comparative example 2 uses an epoxy propoxy propyl-terminated polydimethylsiloxane as a crosslinking agent, which only contains epoxy groups at both ends and has a low content, and has poor crosslinking effect on casein, acetate starch and polyvinyl alcohol, and does not contain benzene ring structure, resulting in low peeling strength of the casein starch adhesive.

[0047] Compared with the example 1, the comparative example 3 polymerizes 1,10-decanediol and dimethyldichlorosilane to obtain a siloxane crosslinking agent which does not contain epoxy groups and cannot react with casein, acetate starch and polyvinyl alcohol, resulting in low peeling strength of the casein starch adhesive, and a large decrease in peeling strength after low-temperature and high-humidity treatment. The comparative example 4 polymerizes 1,10-decanediol, dimethyldichlorosilane and methylphenyldichlorosilane to obtain a siloxane crosslinking agent which does not contain epoxy groups and cannot react with casein, acetate starch and polyvinyl alcohol, resulting in low peeling strength of the casein starch adhesive, and a large decrease in peeling strength after low-temperature and high-humidity treatment.

[0048] Compared with the example 1, the comparative example 5 polymerizes 1,10-decanediol, dimethyldichlorosilane and propyl glycidyl ether methyl dichlorosilane to obtain a siloxane crosslinking agent which does not contain benzene ring structure, and the peeling strength of the casein starch adhesive is significantly reduced after low-temperature and high-humidity treatment, has a low retention rate and poor low-temperature and moisture resistance.

[0049] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A low temperature resistant casein starch glue, characterized in that, The low-temperature-resistant casein starch glue comprises the following components: 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, 2-6 parts by weight of siloxane crosslinking agent, 0.8-1.4 parts by weight of defoaming agent. The preparation method of the siloxane crosslinking agent is as follows: triethylamine, alkyl glycol, dimethyl dichlorosilane, propyl glycidyl ether phenyl dichlorosilane are added into toluene, stirring reaction, vacuum concentration, then the product is washed, dried, to obtain the siloxane crosslinking agent.

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

3. The low temperature resistant casein-starch glue according to claim 1, characterized in that, The ratio of the triethylamine, alkyl glycol, dimethyl dichlorosilane, 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 glue according to claim 1, characterized in that, The alkyl glycol has a structural formula of , and a is any integer from 6 to 12.

5. The low temperature resistant casein-starch glue according to claim 1, characterized in that, The preparation method of the propyl glycidyl ether phenyl dichlorosilane is as follows: allyl glycidyl ether, chloroplatinic acid-isopropyl alcohol solution, phenyl dichlorosilane are added into toluene, heated to 80-90℃, stirring reaction for 2-4h, vacuum concentration, the product is recrystallized to obtain the propyl glycidyl ether phenyl dichlorosilane.

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

7. A process for the preparation of a low temperature resistant casein-starch glue according to any one of claims 1 to 6, said process comprising: Polyvinyl alcohol is added into water, heated and stirred, then cooled, acetate starch, urea, defoaming agent are added, stirred, then pH regulator, casein are added, stirred, then siloxane crosslinking agent, ethanol are added, stirred, to obtain the low-temperature-resistant casein starch glue.

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 the pH regulator.

9. The method for preparing low-temperature resistant casein starch gum according to claim 8, characterized in that, The pH regulator comprises sodium hydroxide, ethanolamine. The pH of the solution is adjusted to 7.5-8 by adding the pH regulator. The pH regulator comprises sodium hydroxide, ethanolamine.

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