Environment-friendly waterproof carton and preparation method thereof

Abstract

The application discloses an environment-friendly waterproof carton and a preparation method thereof, and relates to the technical field of waterproof cartons. The environment-friendly waterproof carton is prepared by coating a waterproof coating emulsion on the surface of a paperboard, solidifying, and folding; the waterproof coating emulsion comprises the following raw material components in a weight ratio: 30-40 parts of modified polyvinyl alcohol, 15-20 parts of modified starch, 6-10 parts of epoxy soybean oil, 0.2-0.4 parts of alkyl polyglycoside, and 40-50 parts of deionized water; wherein the modified polyvinyl alcohol is prepared by esterification modification grafting of polyvinyl alcohol with unsaturated fatty acyl chloride and saturated fatty acyl chloride, and then grafting with polycaprolactone-sulfhydryl through a sulfhydryl-alkene click reaction; and the modified starch is prepared by esterification modification grafting of starch with saturated fatty acyl chloride, and then carboxymethylation treatment.

Description

Technical Field

[0001] This invention relates to the field of waterproof cardboard box technology, specifically to an environmentally friendly waterproof cardboard box and its preparation method. Background Technology

[0002] Currently, the common waterproof cardboard boxes on the market mainly adopt the following methods: (1) Polyethylene coated or laminated cardboard boxes: A layer of polyethylene plastic film is covered on the surface of the cardboard. This method has a good waterproof effect, but the polyethylene film is difficult to separate from the paper, which leads to the cardboard box needing to undergo complicated treatment during recycling. At the same time, polyethylene itself is non-degradable, and it will cause "white pollution" after being discarded, resulting in poor environmental performance. (2) Cardboard boxes with surface sprayed waterproofing agent: Fluorine or silicon-based chemical reagents are used for spraying. This type of cardboard box can usually only prevent splashing water. When it is continuously soaked or rubbed, the waterproof effect drops rapidly. At the same time, the waterproofing agent cannot be completely biodegradable, which also has the problem of poor environmental performance. (3) Wax-impregnated cardboard boxes: Mainly used for fruit and vegetable packaging, but they are easy to get greasy, have low strength, and are easy to get dirty, so they are not practical.

[0003] Based on this, the present invention provides a method for preparing an environmentally friendly waterproof cardboard box, which can effectively prevent water and moisture, is easy to recycle and biodegradable, and is of great significance. Summary of the Invention

[0004] The purpose of this invention is to provide an environmentally friendly waterproof cardboard box and its preparation method, so as to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: An environmentally friendly waterproof cardboard box is prepared by coating the surface of cardboard with a waterproof emulsion, curing, and folding.

[0006] Furthermore, the cardboard is formed by bonding together structural components including but not limited to face paper, liner paper, core paper, and corrugated paper; wherein the face paper, liner paper, and core paper are all wood pulp kraft paper.

[0007] Furthermore, the waterproof coating emulsion comprises the following raw material components in parts by weight: 30-40 parts modified polyvinyl alcohol, 15-20 parts modified starch, 6-10 parts epoxidized soybean oil, 0.2-0.4 parts alkyl glycoside, and 40-50 parts deionized water.

[0008] Furthermore, the method for preparing the modified polyvinyl alcohol is as follows: (1) Under light-protected conditions, polyvinyl alcohol, triethylamine, and 4-methoxyphenol were added to dimethylformamide and stirred to dissolve. Then, unsaturated fatty acyl chloride and saturated fatty acyl chloride were slowly added to the solution and stirred at room temperature for 24-48 hours. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. The precipitate was filtered, washed, and vacuum dried to constant weight to obtain unsaturated fatty chain modified polyvinyl alcohol. (2) Under nitrogen protection, unsaturated aliphatic chain modified polyvinyl alcohol and polycaprolactone-mercapto-dimethylformamide were added to dimethylformamide, stirred and dissolved, and then a photoinitiator was added. The mixture was then subjected to 365nm ultraviolet light at 20~40mW / cm². 2 Under light intensity, the reaction was stirred for 1-3 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying to constant weight, modified polyvinyl alcohol was obtained.

[0009] Furthermore, the preparation of the unsaturated fatty chain modified polyvinyl alcohol includes the following raw material components in parts by weight: 45-55 parts of polyvinyl alcohol, 3-5 parts of unsaturated fatty acyl chloride, 6-10 parts of saturated fatty acyl chloride, 5-8 parts of triethylamine, 0.1-0.2 parts of 4-methoxyphenol, and 120-180 parts of dimethylformamide.

[0010] Furthermore, the modified polyvinyl alcohol preparation comprises the following raw material components in parts by weight: 45-55 parts of unsaturated aliphatic chain modified polyvinyl alcohol, 4-6 parts of polycaprolactone-mercapto, 0.5-1.5 parts of photoinitiator, and 80-120 parts of dimethylformamide.

[0011] Furthermore, the polyvinyl alcohol has a molecular weight of 20,000 to 40,000 and a degree of hydrolysis of 78 to 88%.

[0012] Furthermore, the unsaturated fatty acyl chloride is oleoyl chloride.

[0013] Furthermore, the carbon chain length of the saturated fatty acyl chloride is C12~C18, specifically including but not limited to one or more combinations of lauroyl chloride, myristoyl chloride, palmitoyl chloride, and stearoyl chloride.

[0014] Furthermore, the molecular weight of the polycaprolactone-thiol group is 1000~3000.

[0015] Furthermore, the modified starch is prepared by: (1) Add starch to dimethylformamide and stir at 70~80℃ for 1~2h; then add lithium chloride and continue stirring for 20~40min, and set aside. (2) Under nitrogen protection, saturated fatty acyl chloride and triethylamine were added to (1), and the mixture was stirred at room temperature for 6-18 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying to constant weight, fatty chain modified starch was obtained. (3) Add the fatty chain modified starch to a 50 v / v% isopropanol aqueous solution with pH=9~11, stir and mix at 50~60℃ for 0.5~1h, then add sodium chloroacetate and continue stirring and mixing for 2~6h. Finally, add dilute hydrochloric acid solution to adjust the pH to 6.5~7, filter, wash, and vacuum dry to constant weight to obtain modified starch.

[0016] Furthermore, the preparation of the fatty chain modified starch includes the following raw material components in parts by weight: 20-25 parts starch, 4-6 parts lithium chloride, 6-10 parts saturated fatty acyl chloride, 4-6 parts triethylamine, and 80-100 parts dimethylformamide.

[0017] Furthermore, the modified starch preparation includes the following raw material components in parts by weight: 20-25 parts of aliphatic chain modified starch, 4-6 parts of sodium chloroacetate, and 80-100 parts of isopropanol aqueous solution.

[0018] Further, the preparation method of the environmentally friendly waterproof cardboard box is as follows: (1) According to the formula ratio, the modified polyvinyl alcohol, modified starch, epoxidized soybean oil, alkyl glycoside and deionized water are mixed evenly to obtain a waterproof coating emulsion; (2) The waterproof coating emulsion is coated on the surface of the cardboard, dried and cured at 100~110℃, and folded into a box to obtain an environmentally friendly waterproof cardboard box.

[0019] Furthermore, the coating thickness is 10~50μm.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are: (1) In this invention, polyvinyl alcohol is modified by esterification and grafting with unsaturated fatty acyl chloride and saturated fatty acyl chloride, followed by grafting with polycaprolactone-mercaprolactone via a mercapto-olefin click reaction to obtain modified polyvinyl alcohol containing long carbon chains and polycaprolactone segments. The long carbon chains and polycaprolactone segments can both impart certain hydrophobic properties to polyvinyl alcohol, thereby solving the problems of poor water resistance and easy water absorption of ordinary polyvinyl alcohol. In addition, the long carbon chains and polycaprolactone segments can reduce the molecular crystallinity of polyvinyl alcohol, thereby significantly improving the toughness and extensibility of the film layer, so as to avoid the film layer from falling off and play a role in providing long-term waterproof performance to the carton. In this invention, the hydroxyl groups in polyvinyl alcohol are not completely reacted. On the one hand, the retained hydroxyl groups can ensure the adhesion of the waterproof coating. On the other hand, the presence of hydroxyl groups also avoids the excessive hydrophobicity of polyvinyl alcohol, which would lead to agglomeration and flocculation when preparing the waterproof coating emulsion in the later stage, so as to better prepare a uniform and stable water-based environmentally friendly waterproof coating emulsion.

[0021] (2) The modified starch in this invention is prepared by grafting starch with saturated fatty acyl chloride esterification and then carboxymethylation. The modified starch is also endowed with a certain degree of hydrophobicity by introducing long carbon chains; the purpose of carboxymethylation is that: on the one hand, the carboxyl group can undergo cross-linking reaction with the relevant groups in the coating system to improve the density of the coating and enhance the water barrier performance; on the other hand, the carboxyl group itself is a hydrophilic polar group, which can play a role in emulsification, dispersion and stabilization, reduce the interfacial tension of the system, promote the uniform dispersion of each component, avoid agglomeration and stratification, and make the waterproof coating emulsion more stable and the coating more uniform.

[0022] (3) Modified polyvinyl alcohol and modified starch can form a dense coating through hydrogen bonding and cross-linking, which can significantly improve the aging resistance of the coating, while the coating also has excellent adhesion properties.

[0023] (4) In order to further enhance the performance of the waterproof coating emulsion and improve the hydrophobicity of the coating, epoxidized soybean oil was added to this invention. It can crosslink and plasticize with modified polyvinyl alcohol and modified starch, which can improve the density and toughness of the coating. At the same time, epoxidized soybean oil can also improve the aging resistance of the coating and increase the coating life.

[0024] (5) In this invention, all raw material components in the waterproof coating emulsion are natural biodegradable materials and environmentally friendly degradable materials modified from natural biodegradable materials. They do not contain harmful substances such as benzene and aldehydes, and can achieve full biodegradation without causing environmental pollution. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] It should be noted that the following quantities are by weight, and there are no special restrictions on the suppliers of all raw materials involved in this invention. Exemplary examples include: In the following examples, polyvinyl alcohol with a molecular weight of 30,000 and a degree of hydrolysis of 80%; stearoyl chloride (CAS No. 112-76-5); oleoyl chloride (CAS No. 112-77-6); triethylamine; 4-methoxyphenol (CAS No. 150-76-5); dimethylformamide; corn starch; photoinitiator 819; lithium chloride; sodium chloroacetate; epoxidized soybean oil; alkyl glycoside (APG-0810); all-wood pulp kraft paper; and starch adhesive were all commercially available. Polycaprolactone-mercaprolactone, catalog number R-PCL-SH, molecular weight 2000, purchased from Xi'an Ruixi Biotechnology Co., Ltd. Each serving is 50g.

[0027] Preliminary preparations: Preparation of paperboard: Use 100% wood pulp kraft paper as the face paper and liner paper, 3mm high B-type corrugated paper as the middle corrugated paper, and glue them together with starch adhesive. After cutting and unpacking, a three-layer B-type corrugated paperboard of the size of a No. 1 postal carton is obtained.

[0028] Example 1: A method for preparing an environmentally friendly waterproof cardboard box: 1. Preparation of modified polyvinyl alcohol: (1) Under light protection, 50 parts of polyvinyl alcohol (molecular weight 30000), 6.5 parts of triethylamine, and 0.15 parts of 4-methoxyphenol were added to 150 parts of dimethylformamide and stirred to dissolve. Then, 4 parts of oleoyl chloride and 8 parts of stearoyl chloride were slowly added to the solution and stirred at room temperature for 36 hours. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. The precipitate was filtered, washed, and vacuum dried at 60°C to constant weight to obtain unsaturated aliphatic chain modified polyvinyl alcohol; (2) Under nitrogen protection, 50 parts of unsaturated aliphatic chain modified polyvinyl alcohol and 5 parts of polycaprolactone-mercapto (molecular weight 2000) were added to 100 parts of dimethylformamide and stirred to dissolve. Then, 1 part of photoinitiator 819 was added to the solution and the solution was heated with 365nm ultraviolet light at 30mW / cm 2 Under light intensity, the reaction was stirred for 2 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying at 60°C to constant weight, modified polyvinyl alcohol was obtained. 2. Preparation of modified starch: (1) 22.5 parts of corn starch were added to 90 parts of dimethylformamide and stirred at 75°C for 1.5 h; then 5 parts of lithium chloride were added and stirred for 30 min for later use; (2) Under nitrogen protection, 8 parts of stearoyl chloride and 5 parts of triethylamine were added to (1) and stirred at room temperature for 12 h. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. After filtration, washing, and vacuum drying at 60°C to constant weight, fatty chain modified starch was obtained; (3) 22.5 parts of fatty chain modified starch were added to 50 v / v% isopropanol aqueous solution with pH=10 and stirred at 55°C for 1 h. Then 5 parts of sodium chloroacetate were added and stirred for 4 h. Finally, dilute hydrochloric acid solution was added to adjust the pH to 6.6. After filtration, washing, and vacuum drying at 60°C to constant weight, modified starch was obtained. 3. (1) Mix 35 parts of modified polyvinyl alcohol, 17.5 parts of modified starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0029] Example 2: A method for preparing an environmentally friendly waterproof cardboard box: Example 2 is based on Example 1, but with adjustments made to the amount of raw material components in the waterproof coating emulsion, while other processes remain unchanged. Specifically: 3. (1) Mix 30 parts of modified polyvinyl alcohol, 15 parts of modified starch, 6 parts of epoxidized soybean oil, 0.2 parts of APG-0810 alkyl glycoside and 40 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 20 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0030] Example 3: A method for preparing an environmentally friendly waterproof cardboard box: Example 3 is based on Example 1, but with adjustments made to the amount of raw material components in the waterproof coating emulsion, while keeping other processes unchanged. Specifically: 3. (1) Mix 40 parts of modified polyvinyl alcohol, 20 parts of modified starch, 10 parts of epoxidized soybean oil, 0.4 parts of APG-0810 alkyl glycoside and 50 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 20 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0031] The following is a control experiment based on Example 1, with comparative examples 1 to 7, as detailed below: Comparative Example 1: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 1 is based on Example 1, with the following adjustment: no modification treatment of polyvinyl alcohol is performed, while other processes remain unchanged. Specifically: 1. Preparation of modified starch: (1) 22.5 parts of corn starch were added to 90 parts of dimethylformamide and stirred at 75°C for 1.5 h; then 5 parts of lithium chloride were added and stirred for 30 min for later use; (2) Under nitrogen protection, 8 parts of stearoyl chloride and 5 parts of triethylamine were added to (1) and stirred at room temperature for 12 h. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. After filtration, washing, and vacuum drying at 60°C to constant weight, fatty chain modified starch was obtained; (3) 22.5 parts of fatty chain modified starch were added to 50 v / v% isopropanol aqueous solution with pH=10 and stirred at 55°C for 1 h. Then 5 parts of sodium chloroacetate were added and stirred for 4 h. Finally, dilute hydrochloric acid solution was added to adjust the pH to 6.6. After filtration, washing, and vacuum drying at 60°C to constant weight, modified starch was obtained. 2. (1) Mix 35 parts of polyvinyl alcohol (molecular weight 30000), 17.5 parts of modified starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of B-type corrugated cardboard with a coating thickness of 30μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of No. 1 postal cardboard box.

[0032] Comparative Example 2: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 2 is based on Example 1, with the following adjustment: the corn starch is not modified, while other processes remain unchanged. Specifically: 1. Preparation of modified polyvinyl alcohol: (1) Under light protection, 50 parts of polyvinyl alcohol (molecular weight 30000), 6.5 parts of triethylamine, and 0.15 parts of 4-methoxyphenol were added to 150 parts of dimethylformamide and stirred to dissolve. Then, 4 parts of oleoyl chloride and 8 parts of stearoyl chloride were slowly added to the solution and stirred at room temperature for 36 hours. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. The precipitate was filtered, washed, and vacuum dried at 60°C to constant weight to obtain unsaturated aliphatic chain modified polyvinyl alcohol; (2) Under nitrogen protection, 50 parts of unsaturated aliphatic chain modified polyvinyl alcohol and 5 parts of polycaprolactone-mercapto (molecular weight 2000) were added to 100 parts of dimethylformamide and stirred to dissolve. Then, 1 part of photoinitiator 819 was added to the solution and the solution was heated with 365nm ultraviolet light at 30mW / cm 2 Under light intensity, the reaction was stirred for 2 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying at 60°C to constant weight, modified polyvinyl alcohol was obtained. 2. (1) Mix 35 parts of modified polyvinyl alcohol, 17.5 parts of corn starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0033] Comparative Example 3: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 3 is based on Example 1, with the following adjustments: neither polyvinyl alcohol nor corn starch is modified, while other processes remain unchanged. Specifically: 1. (1) Mix 35 parts of polyvinyl alcohol (molecular weight 30000), 17.5 parts of corn starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0034] Comparative Example 4: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 4 is based on Example 1, with the following adjustment: epoxidized soybean oil is not added, while other processes remain unchanged. Specifically: 3. (1) Mix 35 parts of modified polyvinyl alcohol, 17.5 parts of modified starch, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0035] Comparative Example 5: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 5 is based on Example 1, with the following adjustment: polycaprolactone is not grafted onto the modified polyvinyl alcohol, while other processes remain unchanged. Specifically: A method for preparing an environmentally friendly waterproof cardboard box: 1. Preparation of modified polyvinyl alcohol: Under light-protected conditions, 50 parts of polyvinyl alcohol (molecular weight 30,000), 6.5 parts of triethylamine, and 0.15 parts of 4-methoxyphenol were added to 150 parts of dimethylformamide and stirred to dissolve. Then, 4 parts of oleoyl chloride and 8 parts of stearoyl chloride were slowly added to the solution and stirred at room temperature for 36 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying at 60°C to constant weight, unsaturated aliphatic chain modified polyvinyl alcohol (modified polyvinyl alcohol) was obtained. 2. Preparation of modified starch: (1) 22.5 parts of corn starch were added to 90 parts of dimethylformamide and stirred at 75°C for 1.5 h; then 5 parts of lithium chloride were added and stirred for 30 min for later use; (2) Under nitrogen protection, 8 parts of stearoyl chloride and 5 parts of triethylamine were added to (1) and stirred at room temperature for 12 h. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. After filtration, washing, and vacuum drying at 60°C to constant weight, fatty chain modified starch was obtained; (3) 22.5 parts of fatty chain modified starch were added to 50 v / v% isopropanol aqueous solution with pH=10 and stirred at 55°C for 1 h. Then 5 parts of sodium chloroacetate were added and stirred for 4 h. Finally, dilute hydrochloric acid solution was added to adjust the pH to 6.6. After filtration, washing, and vacuum drying at 60°C to constant weight, modified starch was obtained. 3. (1) Mix 35 parts of modified polyvinyl alcohol, 17.5 parts of modified starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0036] Comparative Example 6: A method for preparing an environmentally friendly waterproof cardboard box: Comparative Example 6 is based on Example 1, with the following adjustments: the starch is not carboxymethylated, while other processes remain unchanged. Specifically: 1. Preparation of modified polyvinyl alcohol: (1) Under light protection, 50 parts of polyvinyl alcohol (molecular weight 30000), 6.5 parts of triethylamine, and 0.15 parts of 4-methoxyphenol were added to 150 parts of dimethylformamide and stirred to dissolve. Then, 4 parts of oleoyl chloride and 8 parts of stearoyl chloride were slowly added to the solution and stirred at room temperature for 36 hours. Finally, excess deionized water was added to the reaction solution and allowed to stand to precipitate. The precipitate was filtered, washed, and vacuum dried at 60°C to constant weight to obtain unsaturated aliphatic chain modified polyvinyl alcohol; (2) Under nitrogen protection, 50 parts of unsaturated aliphatic chain modified polyvinyl alcohol and 5 parts of polycaprolactone-mercapto (molecular weight 2000) were added to 100 parts of dimethylformamide and stirred to dissolve. Then, 1 part of photoinitiator 819 was added to the solution and the solution was heated with 365nm ultraviolet light at 30mW / cm 2 Under light intensity, the reaction was stirred for 2 hours. Finally, excess deionized water was added to the reaction solution, and the precipitate was allowed to stand and precipitate out. After filtration, washing, and vacuum drying at 60°C to constant weight, modified polyvinyl alcohol was obtained. 2. Preparation of modified starch: (1) Add 22.5 parts of corn starch to 90 parts of dimethylformamide and stir and mix at 75°C for 1.5 h; then add 5 parts of lithium chloride and continue stirring and mixing for 30 min, and set aside; (2) Under nitrogen protection, add 8 parts of stearoyl chloride and 5 parts of triethylamine to (1), stir and react at room temperature for 12 h, and finally add excess deionized water to the reaction solution, let it stand to precipitate, filter, wash, and vacuum dry at 60°C to constant weight to obtain aliphatic chain modified starch (modified starch); 3. (1) Mix 35 parts of modified polyvinyl alcohol, 17.5 parts of modified starch, 8 parts of epoxidized soybean oil, 0.3 parts of APG-0810 alkyl glycoside and 45 parts of deionized water evenly to obtain a waterproof coating emulsion; (2) Coat the waterproof coating emulsion on both surfaces of type B corrugated cardboard with a coating thickness of 30 μm, dry and cure at 105℃, fold into a box, and obtain an environmentally friendly waterproof cardboard box of the size of a No. 1 postal cardboard box.

[0037] Comparative Example 7: No waterproof coating emulsion was applied to the cardboard.

[0038] Performance Test 1: According to GB / T 450-2008, several 450mm×450mm samples were cut from the environmentally friendly waterproof cartons prepared in Examples 1-3 and Comparative Examples 1-7, and their waterproof performance and aging resistance were tested. The specific test methods are as follows: (1) Waterproof performance test: According to GB / T 1540-2002, at 23℃ and 50%RH, a cross-sectional area of ​​100cm² was used for waterproof performance testing. 2 A Cobb absorbency tester with an inner diameter of 112.8 mm was used to test the Cobb value of a sample after absorbing water for 30 seconds. The test was repeated 5 times and the average value was taken. (2) Aging resistance: The samples corresponding to each example were first baked at 80℃ for 8 hours, then taken out and allowed to return to room temperature, then cooled to -20℃ and frozen for 48 hours, and finally their waterproof performance was tested.

[0039] The test data for the above test items are shown in Table 1 below: Table 1

[0040] Result Analysis 1: As can be seen from the data in Table 1 above, the present invention has prepared an environmentally friendly waterproof cardboard box with excellent waterproof performance, adhesion performance and aging resistance. After aging treatment, its performance did not change significantly.

[0041] Performance Test 2: The waterproof coating emulsion prepared in Example 1 was applied to a polytetrafluoroethylene plate with a coating thickness of 1 mm. After drying and curing at 105°C, it was peeled off and cut into 1 cm × 1 cm fragments for biodegradation testing. The specific test method was as follows: at 25°C and 60%RH, 5 fragments were buried in standard soil (pH = 6.5 ± 0.1, organic matter content of 3.5%) at a depth of 20 cm. After 180 days, the fragments were dug up and removed to test the mass loss of the fragments before and after the test.

[0042] The test data for the above test items are shown in Table 2 below: Table 2

[0043] Result Analysis 2: As can be seen from the data in Table 2 above, the waterproof coating emulsion prepared by this invention has fully biodegradable characteristics and can be completely degraded within 180 days, fundamentally solving the problem of environmental pollution.

[0044] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An environmentally friendly waterproof cardboard box, characterized in that: The coating is prepared by applying a waterproof emulsion to the surface of cardboard, followed by curing and folding. The waterproof coating emulsion comprises the following raw material components in parts by weight: 30-40 parts modified polyvinyl alcohol, 15-20 parts modified starch, 6-10 parts epoxidized soybean oil, 0.2-0.4 parts alkyl glycoside, and 40-50 parts deionized water; The modified polyvinyl alcohol is prepared by grafting polyvinyl alcohol with unsaturated fatty acyl chloride and saturated fatty acyl chloride through esterification modification, and then grafting it with polycaprolactone-mercapto-thiol via a mercapto-olefin click reaction. The modified starch is prepared by grafting starch with saturated fatty acyl chloride esterification, followed by carboxymethylation.

2. The environmentally friendly waterproof cardboard box according to claim 1, characterized in that: The method for preparing the modified polyvinyl alcohol is as follows: (1) Under light-protected conditions, polyvinyl alcohol, unsaturated fatty acyl chloride, saturated fatty acyl chloride, triethylamine, and 4-methoxyphenol were added to dimethylformamide and stirred at room temperature. Then, excess deionized water was added and allowed to stand to precipitate. After separation and purification, unsaturated fatty chain modified polyvinyl alcohol was obtained. (2) Under nitrogen protection, unsaturated aliphatic chain modified polyvinyl alcohol, polycaprolactone-mercapto, and photoinitiator were added to dimethylformamide and stirred under ultraviolet light. Then, excess deionized water was added, and the precipitate was allowed to stand and precipitate out. After separation and purification, modified polyvinyl alcohol was obtained.

3. The environmentally friendly waterproof cardboard box according to claim 2, characterized in that: The preparation of the unsaturated fatty chain modified polyvinyl alcohol includes the following raw material components in parts by weight: 45-55 parts of polyvinyl alcohol, 3-5 parts of unsaturated fatty acyl chloride, 6-10 parts of saturated fatty acyl chloride, 5-8 parts of triethylamine, 0.1-0.2 parts of 4-methoxyphenol, and 120-180 parts of dimethylformamide. The modified polyvinyl alcohol is prepared by the following raw material components in parts by weight: 45-55 parts of unsaturated aliphatic chain modified polyvinyl alcohol, 4-6 parts of polycaprolactone-mercaprolactone, 0.5-1.5 parts of photoinitiator, and 80-120 parts of dimethylformamide.

4. The environmentally friendly waterproof cardboard box according to claim 3, characterized in that: The unsaturated fatty acyl chloride is oleoyl chloride; The carbon chain length of the saturated fatty acyl chloride is C12~C18, specifically including one or more combinations of lauroyl chloride, myristoyl chloride, palmitoyl chloride, and stearoyl chloride.

5. An environmentally friendly waterproof cardboard box according to claim 3, characterized in that: The polyvinyl alcohol has a molecular weight of 20,000 to 40,000 and a degree of alcoholysis of 78 to 88%. The molecular weight of the polycaprolactone-thiol group is 1000~3000.

6. The environmentally friendly waterproof cardboard box according to claim 1, characterized in that: The method for preparing the modified starch: (1) Add starch to dimethylformamide and stir at 70~80℃; then add lithium chloride and continue stirring and mixing, and set aside. (2) Under nitrogen protection, saturated fatty acyl chloride and triethylamine were added to (1), and the mixture was stirred at room temperature. Then, excess deionized water was added, and the precipitate was allowed to stand and precipitate out. The precipitate was separated and purified to obtain fatty chain modified starch. (3) Add the fatty chain modified starch to a 50 v / v% isopropanol aqueous solution with pH=9~11, stir and mix at 50~60℃, then add sodium chloroacetate, continue stirring and mixing, and finally add dilute hydrochloric acid solution to adjust the pH to 6.5~7, separate and purify to obtain modified starch.

7. An environmentally friendly waterproof cardboard box according to claim 6, characterized in that: The preparation of the fatty chain modified starch includes the following raw material components in parts by weight: 20-25 parts starch, 4-6 parts lithium chloride, 6-10 parts saturated fatty acyl chloride, 4-6 parts triethylamine, and 80-100 parts dimethylformamide. The modified starch preparation comprises the following raw material components in parts by weight: 20-25 parts of aliphatic chain modified starch, 4-6 parts of sodium chloroacetate, and 80-100 parts of isopropanol aqueous solution.

8. A method for preparing an environmentally friendly waterproof cardboard box according to any one of claims 1 to 7, characterized in that: Specifically: (1) According to the formula ratio, the modified polyvinyl alcohol, modified starch, epoxidized soybean oil, alkyl glycoside and deionized water are mixed evenly to obtain a waterproof coating emulsion. (2) Apply the waterproof coating emulsion to the surface of the cardboard, dry and cure it, and fold it into a box to obtain an environmentally friendly waterproof cardboard box.

9. The method for preparing an environmentally friendly waterproof cardboard box according to claim 8, characterized in that: The coating thickness is 10~50μm.

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