A paper-plastic composite material for packaging boxes and its preparation method

Abstract

This invention discloses a paper-plastic composite material for packaging boxes and its preparation method. The paper-plastic composite material for packaging boxes is obtained by roll pressing a film layer and a paper layer. The film layer is prepared from raw materials including 40-60 parts by weight of water-soluble polyvinyl alcohol; 20-30 parts by weight of polylactic acid resin; 3-5 parts by weight of diethanolamine; 1-4 parts by weight of dispersant; 2-4 parts by weight of leveling agent; and 10-25 parts by weight of filler. The film layer prepared by this invention incorporates a self-made polymer product with a unique structure. During the preparation process, a complex is introduced through epoxy resin monomers, which acts as a bridging agent during subsequent curing. This solves the problem of insufficient adhesion between the film layer and the paper layer, and also gives the paper-plastic composite material prepared by this invention better mechanical properties, abrasion resistance, and burst resistance.

Description

Technical Field

[0001] This invention relates to the field of plastic preparation technology, specifically to a paper-plastic composite material for packaging boxes and its preparation method. Background Technology

[0002] Paper-plastic composite packaging materials are packaging materials composed of two or more materials with different properties, mainly through the combination of paper and plastic substrates. Paper is widely used as a substrate in composite packaging materials primarily because of its broad applicability in production and application: ① Paper possesses a certain thickness, dimensional stability, and high folding endurance, properties that improve the molding and dimensional stability of paper-plastic composites and give them a better texture. ② Due to the polarity and porous nature of cellulose, paper has excellent ink-receptive properties, resulting in good printing effects for most paper-plastic composites. Furthermore, this property allows it to easily absorb adhesives, facilitating lamination with other plastic substrates and significantly reducing lamination process costs. ③ Paper is non-toxic, harmless, and hygienic, thus improving environmental performance and making it suitable for various commodity packaging, including food packaging.

[0003] Paper-plastic composite packaging materials generally consist of an outer layer, an adhesive layer, a barrier layer, and an inner layer. The outer layer typically uses materials with good mechanical strength and printability. The inner layer, which comes into contact with the product, is generally made of odorless, non-toxic, oil-resistant, water-resistant (moisture-proof), chemical-resistant, and easily heat-sealed materials, such as PP and PE. The barrier layer in paper-plastic composites is usually located close to the product. Its function is to prevent damage to the product from external substances such as oxygen and moisture. Commonly used barrier materials include aluminized film, PVA, PVDC, and EVOH.

[0004] Currently, there are two main methods for implementing paper-plastic composite processes: dry paper-plastic lamination and water-based cold lamination. Dry paper-plastic lamination uses a composite emulsion-type acrylic adhesive, which is applied to a plastic film. After drying, the adhesive is heated by rollers, causing it to flow into a viscous state. This promotes a tighter and more solid bond between the plastic and paper materials, truly integrating the printed paper. This method offers advantages such as strong adaptability, high production efficiency, good lamination effect, and low production cost.

[0005] As plastics are gradually phased out due to their polluting nature, paper-plastic composite materials are finding increasingly wider applications in our lives, ranging from packaging for everyday consumer goods to the medical field, clothing industry, and electrical components. Paper-plastic composite packaging is also widely used in paper trays, microwave oven dishes, and inner liners formed by molds in various cavities, providing better shock resistance, moisture resistance, lower cost, enhanced functionality, and improved hygiene. With technological advancements, paper-plastic composite packaging materials will be used in more and more fields, gradually replacing plastics.

[0006] Chinese Patent CN 113322716 A discloses an environmentally friendly coating for paper-plastic composite materials, comprising the following components in parts by weight: 40-60 parts water-soluble polyvinyl alcohol; 40-60 parts polylactic acid resin; 10-20 parts starch; 20-40 parts modified dammar resin; 10-20 parts plasticizer; 5-10 parts diethanolamine; 1-5 parts dispersant; 1-3 parts leveling agent; 0.3-1 part antibacterial and antifungal agent; and 150-200 parts water. The paper-plastic composite material includes cardboard and a coating applied to one or both sides of the cardboard. The coating is obtained by applying the environmentally friendly coating for paper-plastic composite materials described in this invention. The environmentally friendly paper-plastic composite material of this invention has the advantages of being environmentally friendly and biodegradable, and also possesses excellent heat-sealing performance.

[0007] Chinese Patent CN 107419597 A discloses a paper-plastic composite material and its preparation method, comprising: 1) mixing and cooking wood pulp, bark, hemp, straw, glass fiber, inorganic filler, and lime water in a weight ratio of 100:20-30:1-5:2-5:5-15:15-25:200-300 to obtain pulp; washing, bleaching, beating, papermaking, pressing, and baking the pulp to obtain composite paper; 2) heating and coating a low-density polyethylene film onto the surface of the composite paper to form a plastic layer to obtain the paper-plastic composite material. This paper-plastic composite material not only possesses excellent mechanical strength but also good antibacterial properties.

[0008] However, paper-plastic composites are composite materials made by laminating plastics onto paper-based materials; they have advantages such as good water resistance and high strength and are widely used in packaging materials such as cardboard boxes and shopping bags. However, existing coatings still have problems such as low adhesion and poor abrasion and tear resistance, so there is a need to develop a new material for paper-plastic composite packaging. Summary of the Invention

[0009] In view of the above-mentioned shortcomings in the prior art, the technical problem to be solved by the present invention is to provide a paper-plastic composite material for packaging boxes and a method for preparing the same.

[0010] A paper-plastic composite material for packaging boxes is made by rolling a film layer and a paper layer together.

[0011] Preferably, the film layer is prepared from raw materials including water-soluble polyvinyl alcohol; polylactic acid resin; diethanolamine; dispersant; leveling agent and filler.

[0012] Preferably, the film layer is prepared from the following components in parts by weight: 40-60 parts of water-soluble polyvinyl alcohol, 20-30 parts of polylactic acid resin, 3-5 parts of diethanolamine, 1-4 parts of dispersant, 2-4 parts of leveling agent, and 10-25 parts of filler.

[0013] Preferably, the paper material is one of the following: paper bag paper, kraft paper, chicken skin paper, striped kraft paper, kraft cardboard, linerboard, boxboard, corrugated paper, and honeycomb paperboard.

[0014] Furthermore, the thickness of the paper layer is 100–500 μm.

[0015] Preferably, the dispersant is hexadecyltrimethylammonium bromide.

[0016] Preferably, the leveling agent is a water-based leveling agent BYK-333.

[0017] Furthermore, the filler is prepared using the following method:

[0018] Add 10-15 parts by weight of the polymerization product to 100-150 parts by weight of water, stir at 55-60°C for 2-3 hours, then sonicate at 300-400W, 35-40kHz for 10-15 minutes, then add 18-22 parts by weight of octadecylmethyldihydroxyethylammonium bromide, and maintain the reaction at 58-60°C for 2-3 hours. Centrifuge the suspension at 3000-4000rpm for 15-20 minutes, remove the supernatant, wash with water 2-3 times, dry at 102-105°C for 24-48 hours, grind into powder, and pass through a 200-240 mesh sieve to obtain the filler.

[0019] The polymer product is prepared by the following method: 1-2 parts by weight of emulsifier are added to 100-150 parts by weight of water at 600-750 rpm, and then stirred until viscous. Next, 1-2 parts by weight of tributyl phosphate, 0.5-1 parts by weight of sodium bicarbonate, and 0.2-0.4 parts by weight of sodium dodecyl sulfonate are added. Then, a mixed solution consisting of 2-3 parts by weight of methyl methacrylate, 2.6-3 parts by weight of butyl acrylate, and 10-13 parts by weight of 1H,1H,2H,2H-perfluorodecyl acrylate is added at 600-700 rpm. The mixture is stirred for 0.5-1 h. After raising the reaction temperature to 75-80°C, 12-15 parts by weight of an aqueous solution containing 1.3-1.5 wt% potassium persulfate is added. Subsequently, 10-14 parts by weight of aqueous epoxy resin and 5-7 parts by weight of curing agent are added. Finally, the polymer is obtained by polymerization under nitrogen protection.

[0020] Furthermore, the emulsifier is OP-10.

[0021] Furthermore, the polymerization reaction temperature is 80–85°C, and the reaction time is 4–5 hours.

[0022] Furthermore, the waterborne epoxy resin is waterborne epoxy resin EPIKOTE3510-W-60A.

[0023] Furthermore, the curing agent is a water-based amine epoxy curing agent, EPIKURE8537-WY-60.

[0024] Furthermore, the thickness of the thin film layer is 5–40 μm.

[0025] The present invention also provides a method for preparing the paper-plastic composite material for packaging boxes, comprising the following steps:

[0026] S1 involves extruding and granulating 40-60 parts by weight of water-soluble polyvinyl alcohol, 20-30 parts by weight of polylactic acid resin, 3-5 parts by weight of diethanolamine, 1-4 parts by weight of dispersant, 2-4 parts by weight of leveling agent, and 10-25 parts by weight of filler in a twin-screw extruder, followed by drying to obtain a mixed material.

[0027] S2 involves casting the mixed material, and then rolling the resulting film with a paper layer in a molten state to obtain a paper-plastic composite material.

[0028] In step S1, the die head temperature of the twin-screw extruder is 170–185°C, and the screw speed is 220–300 rpm.

[0029] In step S2, the screw speed for casting is 50 to 280 rpm.

[0030] Cardboard boxes are the most widely used packaging products. Depending on the materials used, there are corrugated cardboard boxes, single-layer cardboard boxes, etc., and they come in various specifications and models. Cardboard boxes commonly have three or five layers, while seven-layer boxes are less common. Each layer consists of linerboard, corrugated paper, core paper, and face paper. Face paper can be made of kraft paper or kraft paper, while the core paper is made of corrugated paper. The colors and textures of various types of paper are different, and the paper produced by different manufacturers is also different. As an indispensable part of modern logistics, packaging cardboard boxes bear the important responsibility of containing, protecting, and presenting products. Therefore, the demand for packaging cardboard boxes is increasing day by day.

[0031] As people's living standards improve, the requirements for cardboard boxes are no longer limited to the simple packaging boxes of the past; there are also different demands for the appearance and quality of cardboard boxes. Cardboard packaging should exhibit a multi-functional development trend, moving towards diversification, in order to better adapt to market needs.

[0032] Paper-plastic composites are composite materials made by laminating plastics onto a paper-based material. They are widely used in packaging materials such as cardboard boxes and shopping bags due to their advantages of good water resistance and high strength. However, existing coatings still suffer from problems such as low adhesion and poor abrasion and tear resistance. Therefore, it is necessary to develop a new material for paper-plastic composite packaging.

[0033] This invention first prepares a polymer product with a unique structure. During the preparation process, a complex is introduced through epoxy resin monomers, which acts as a bridging agent during subsequent curing, solving the problem of insufficient adhesion between the film layer and the paper layer. Furthermore, the film layer, through the complex combination of latex and epoxy resin, effectively reduces defects and increases the energy consumption of the molecular chains under alternating action, resulting in high wear and tear resistance. In addition, the inventors discovered that the degradation of the paper layer in the paper box material generates more free -OH groups, which can enhance the surface polarity of the paper layer. Therefore, it is necessary to improve the outer layer of the paper-plastic composite material. This invention introduces dihydroxyl groups into the prepared polymer by treating it with octadecylmethyldihydroxyethylammonium bromide, thus enabling better bonding with the paper layer and improving its stability and practicality. Detailed Implementation

[0034] Description of raw materials in the examples:

[0035] Polyvinyl alcohol, PVA1788, 120 mesh powder, purchased from Wuhan Runxingyuan Technology Co., Ltd.

[0036] Polylactic acid resin, grade L105, purchased from Shanghai Lexuan Plastics Co., Ltd.

[0037] Diethanolamine, CAS: 111-42-2, purchased from Shandong Yousheng Chemical Co., Ltd.;

[0038] The water-based leveling agent BYK-333, with a density of 1.04 g / mL, was purchased from Buding Chemical.

[0039] Emulsifier OP-10, product number YJ13, purchased from Jinan Yinju Chemical Co., Ltd.

[0040] Waterborne epoxy resin EPIKOTE 3510-W-60A, purchased from Xiamen Aikema Chemical Co., Ltd.

[0041] The water-based amine epoxy curing agent EPIKURE 8537-WY-60 was purchased from Xiamen Aikema Chemical Co., Ltd.

[0042] Potassium aluminum silicate, powder, 3000 mesh, purchased from Guangzhou Liben Rubber Raw Material Trading Co., Ltd.

[0043] Octadecylmethyldihydroxyethylammonium bromide, CAS: 97508-23-1, purchased from Shanghai Denoli Biotechnology Co., Ltd.

[0044] Example 1

[0045] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0046] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0047] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0048] The filler was prepared using the following method:

[0049] 12 kg of the polymerization product was added to 120 kg of water and stirred at 60 °C for 3 h. Then, it was sonicated at 400 W and 40 kHz for 15 min. Then, 20 kg of octadecylmethyldihydroxyethylammonium bromide was added, and the reaction was maintained at 60 °C for 3 h. The suspension was then centrifuged at 4000 rpm for 20 min, the supernatant was removed, and the product was washed three times with water. The product was then dried at 105 °C for 48 h, ground into powder, and passed through a 200 mesh sieve to obtain the filler.

[0050] The polymer product was prepared by the following method: 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2 kg of methyl methacrylate, 2.7 kg of butyl acrylate and 12 kg of 1H,1H,2H,2H-perfluorodecyl acrylate was added at 600 rpm. The mixture was stirred for 1 hour. After raising the reaction temperature to 80°C, 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Then, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the mixture was polymerized at 85°C for 5 hours under nitrogen protection to obtain the polymer product.

[0051] Example 2

[0052] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0053] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0054] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0055] The filler was prepared using the following method:

[0056] 12 kg of the polymerization product was added to 120 kg of water and stirred at 60 °C for 3 h. Then, it was sonicated at 400 W and 40 kHz for 15 min. Then, 20 kg of octadecylmethyldihydroxyethylammonium bromide was added, and the reaction was maintained at 60 °C for 3 h. The suspension was then centrifuged at 4000 rpm for 20 min, the supernatant was removed, and the product was washed three times with water. The product was then dried at 105 °C for 48 h, ground into powder, and passed through a 200 mesh sieve to obtain the filler.

[0057] The polymer product was prepared by the following method: 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2.7 kg of butyl acrylate and 12 kg of 1H,1H,2H,2H-perfluorodecyl acrylate was added at 600 rpm. The mixture was stirred for 1 h. After raising the reaction temperature to 80 °C, 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Then, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the mixture was polymerized at 85 °C for 5 h under nitrogen protection to obtain the polymer product.

[0058] Example 3

[0059] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0060] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0061] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0062] The filler was prepared using the following method:

[0063] 12 kg of the polymerization product was added to 120 kg of water and stirred at 60 °C for 3 h. Then, it was sonicated at 400 W and 40 kHz for 15 min. Then, 20 kg of octadecylmethyldihydroxyethylammonium bromide was added, and the reaction was maintained at 60 °C for 3 h. The suspension was then centrifuged at 4000 rpm for 20 min, the supernatant was removed, and the product was washed three times with water. The product was then dried at 105 °C for 48 h, ground into powder, and passed through a 200 mesh sieve to obtain the filler.

[0064] The polymer product was prepared by the following method: 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2 kg of methyl methacrylate and 12 kg of 1H,1H,2H,2H-perfluorodecyl acrylate was added at 600 rpm. The mixture was stirred for 1 h. After raising the reaction temperature to 80 °C, 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Then, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the mixture was polymerized at 85 °C for 5 h under nitrogen protection to obtain the polymer product.

[0065] Example 4

[0066] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0067] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0068] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0069] The filler was prepared using the following method:

[0070] 12 kg of the polymerization product was added to 120 kg of water and stirred at 60 °C for 3 h. Then, it was sonicated at 400 W and 40 kHz for 15 min. Then, 20 kg of octadecylmethyldihydroxyethylammonium bromide was added, and the reaction was maintained at 60 °C for 3 h. The suspension was then centrifuged at 4000 rpm for 20 min, the supernatant was removed, and the product was washed three times with water. The product was then dried at 105 °C for 48 h, ground into powder, and passed through a 200 mesh sieve to obtain the filler.

[0071] The polymer product was prepared by the following method: 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2 kg of methyl methacrylate and 2.7 kg of butyl acrylate was added at 600 rpm and stirred for 1 h. After raising the reaction temperature to 80 °C, 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Then, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the polymer was obtained by reacting at 85 °C for 5 h under nitrogen protection.

[0072] Example 5

[0073] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0074] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0075] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0076] The filler was prepared using the following method:

[0077] 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate, and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2 kg of methyl methacrylate, 2.7 kg of butyl acrylate, and 12 kg of 1H,1H,2H,2H-perfluorodecyl acrylate was added at 600 rpm. The mixture was stirred for 1 hour. The reaction temperature was raised to 80°C, and then 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Subsequently, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the mixture was polymerized at 85°C for 5 hours under nitrogen protection to obtain the polymer product. The polymer product was then dried at 60°C for 12 hours to obtain the filler.

[0078] Comparative Example 1

[0079] A method for preparing a paper-plastic composite material for packaging boxes includes the following steps:

[0080] S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180℃ and the screw speed is 260 rpm. After drying at 80℃ for 10 hours, a mixed material is obtained.

[0081] S2 casts the mixed material to obtain a film with a thickness of 30 μm. Then, the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm.

[0082] The filler is potassium aluminum silicate.

[0083] Test Example 1

[0084] The thin film layers prepared in Examples 1-5 and Comparative Example 1 were dried at 150°C for 5 min. The thermal conductivity was tested using ASTM-E2584-20, and the tensile strength and elongation at break were tested using ASTM-D638-14. The sample width was 10 mm, the length was 100 mm, and the tensile rate was 300 mm / min. The test results are shown in Table 1.

[0085] Table 1. Test Results of Thin Film Layer Performance

[0086]

[0087] As shown in Table 1, the film layer prepared in Example 1 has better thermal insulation performance and mechanical strength. The film layer in Example 1 contains a polymer with a unique structure. During the preparation process, a complex is introduced through epoxy resin monomers, which plays a bridging role in the subsequent curing process. This solves the problem of insufficient adhesion between the film layer and the paper layer. The film layer has stronger mechanical properties after being combined with a complex mixture of latex and epoxy resin.

[0088] Test Example 2

[0089] The paper-plastic composite materials prepared in Examples 1-5 and Comparative Example 1 were subjected to bursting performance tests according to GB / T 454-2020, and the bursting index (kPa·m) was obtained. 2 / g), the specific test results are shown in Table 2.

[0090] Table 2. Results of Bursting Resistance Test for Paper-Plastic Composites

[0091]

[0092]

[0093] As shown in Table 2, the paper-plastic composite material prepared in the examples exhibits the best burst resistance. In Example 1 of this invention, a polymer product was first prepared. This polymer product has a unique structure. During the preparation process, a complex was introduced through epoxy resin monomers, which act as a bridging agent during subsequent curing, solving the problem of insufficient adhesion between the film layer and the paper layer. In addition, the film layer is bonded by a complex mixture of latex and epoxy resin. The molecular chains effectively reduce defects under alternating action, increasing the energy consumption of the molecular chains and thus giving the film layer high wear and burst resistance. Furthermore, as the paper layer in the paper box material degrades, more free -OH groups are generated, which can enhance the surface polarity of the paper layer. Therefore, it is necessary to improve the outer layer of the paper-plastic composite material. In Example 1, the prepared polymer was treated with octadecylmethyldihydroxyethylammonium bromide to introduce dihydroxyl groups into the polymer, thus enabling better bonding with the paper layer and improving its stability and practicality.

Claims

1. A paper-plastic composite material for packaging boxes, characterized in that: It is obtained by rolling a film layer and a paper layer, wherein the film layer is prepared from water-soluble polyvinyl alcohol, polylactic acid resin, diethanolamine, dispersant, leveling agent and filler; The film layer is prepared from the following components in parts by weight: 40-60 parts of water-soluble polyvinyl alcohol, 20-30 parts of polylactic acid resin, 3-5 parts of diethanolamine, 1-4 parts of dispersant, 2-4 parts of leveling agent, and 10-25 parts of filler. The filler was prepared by the following method: 10-15 parts by weight of the polymer product were added to 100-150 parts by weight of water, stirred at 55-60°C for 2-3 hours, then sonicated at 300-400W and 35-40kHz for 10-15 minutes, and then 18-22 parts by weight of octadecylmethyldihydroxyethylammonium bromide were added. The reaction was maintained at 58-60°C for 2-3 hours, and then the suspension was centrifuged at 3000-4000rpm for 15-20 minutes. After removing the supernatant, the solution was washed with water 2-3 times, dried at 102-105°C for 24-48 hours, ground into powder, and passed through a 200-240 mesh sieve to obtain the filler. The polymer product is prepared by the following method: 1-2 parts by weight of emulsifier are added to 100-150 parts by weight of water at 600-750 rpm, and then stirred until viscous. Next, 1-2 parts by weight of tributyl phosphate, 0.5-1 parts by weight of sodium bicarbonate, and 0.2-0.4 parts by weight of sodium dodecyl sulfonate are added. Then, a mixed solution consisting of 2-3 parts by weight of methyl methacrylate, 2.6-3 parts by weight of butyl acrylate, and 10-13 parts by weight of 1H,1H,2H,2H-perfluorodecyl acrylate is added at 600-700 rpm. The mixture is stirred for 0.5-1 h. After raising the reaction temperature to 75-80°C, 12-15 parts by weight of an aqueous solution containing 1.3-1.5 wt% potassium persulfate is added. Subsequently, 10-14 parts by weight of aqueous epoxy resin and 5-7 parts by weight of curing agent are added. Finally, the polymer is obtained by polymerization under nitrogen protection.

2. The paper-plastic composite material for packaging boxes as described in claim 1, characterized in that: The paper material is one of the following: paper bag paper, kraft paper, chicken skin paper, striped kraft paper, kraft cardboard, linerboard, boxboard, corrugated paper, and honeycomb cardboard.

3. The paper-plastic composite material for packaging boxes as described in claim 1, characterized in that: The thickness of the paper layer is 100–500 μm.

4. The paper-plastic composite material for packaging boxes as described in claim 1, characterized in that: The emulsifier is OP-10.

5. The paper-plastic composite material for packaging boxes as described in claim 1, characterized in that: The waterborne epoxy resin is EPIKOTE 3510-W-60A, and the curing agent is EPIKURE 8537-WY-60, an amine-based epoxy curing agent.

6. The paper-plastic composite material for packaging boxes as described in claim 1, characterized in that: The polymerization reaction temperature is 80–85°C, and the reaction time is 4–5 hours.

7. A method for preparing a paper-plastic composite material for packaging boxes as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Extruding and granulating 40-60 parts by weight of water-soluble polyvinyl alcohol, 20-30 parts by weight of polylactic acid resin, 3-5 parts by weight of diethanolamine, 1-4 parts by weight of dispersant, 2-4 parts by weight of leveling agent, and 10-25 parts by weight of filler in a twin-screw extruder, and drying the mixture to obtain a mixed material; S2. Casting the mixed material, and rolling the film obtained by casting with a paper layer in a molten state to obtain a paper-plastic composite material.

8. A method for preparing a paper-plastic composite material for packaging boxes as described in any one of claims 1-6, characterized in that, Includes the following steps: S1 granulates 50 kg of water-soluble polyvinyl alcohol, 25 kg of polylactic acid resin, 4 kg of diethanolamine, 3 kg of hexadecyltrimethylammonium bromide, 3 kg of water-based leveling agent BYK-3333, and 20 kg of filler in a twin-screw extruder. The die temperature of the twin-screw extruder is 180°C and the screw speed is 260 rpm. After drying at 80°C for 10 hours, a mixed material is obtained. S2 The mixed material is cast to obtain a film with a thickness of 30 μm. Then the film is rolled and laminated with linerboard in a molten state to obtain a paper-plastic composite material with a linerboard thickness of 470 μm. The filler was prepared using the following method: 12 kg of the polymerization product was added to 120 kg of water and stirred at 60 °C for 3 h. Then, it was sonicated at 400 W and 40 kHz for 15 min. Then, 20 kg of octadecylmethyldihydroxyethylammonium bromide was added, and the reaction was maintained at 60 °C for 3 h. The suspension was then centrifuged at 4000 rpm for 20 min, the supernatant was removed, and the product was washed with water three times. The product was then dried at 105 °C for 48 h, ground into powder, and passed through a 200 mesh sieve to obtain the filler. The polymer product was prepared by the following method: 2 kg of emulsifier OP-10 was added to 120 kg of water at 750 rpm and stirred until viscous. Then, 2 kg of tributyl phosphate, 0.5 kg of sodium bicarbonate and 0.3 kg of sodium dodecyl sulfonate were added. Then, a mixed solution consisting of 2 kg of methyl methacrylate, 2.7 kg of butyl acrylate and 12 kg of 1H,1H,2H,2H-perfluorodecyl acrylate was added at 600 rpm. The mixture was stirred for 1 hour. After raising the reaction temperature to 80°C, 12 kg of an aqueous solution containing 1.5 wt% potassium persulfate was added. Then, 13 kg of waterborne epoxy resin EPIKOTE 3510-W-60A and 6 kg of waterborne amine epoxy curing agent EPIKURE 8537-WY-60 were added. Finally, the mixture was polymerized at 85°C for 5 hours under nitrogen protection to obtain the polymer product.

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