Degradable packaging paper for tableware and preparation method of degradable packaging paper

Abstract

The invention discloses degradable packaging paper for tableware and a preparation method of the degradable packaging paper, and belongs to the technical field of packaging materials. The preparation method of the packaging paper comprises the following steps: respectively carrying out modification treatment on bamboo fibers and straw fibers, and carrying out blending modification by using nano silicon dioxide, chitosan-polylactic acid and an auxiliary agent, so as to obtain modified paper pulp; conveying the modified paper pulp into a headbox, forming in a forming net to obtain a wet paper sheet, squeezing and dehydrating, drying in a drying cylinder, coating the surface with the modified coating liquid through roller type coating, curing and calendering to obtain the degradable packaging paper for the tableware. The modified coating liquid is prepared by emulsifying poly (3-hydroxybutyric acid-hexanoate) and polylactic acid, and blending and modifying the emulsified poly (3-hydroxybutyric acid-hexanoate) and polylactic acid. The packaging paper prepared by the preparation method disclosed by the invention has good mechanical property, antibacterial property and antioxidant property, and can be biodegraded after being used.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and in particular relates to degradable packaging paper for dining utensils and a preparation method thereof. Background Art

[0002] The rapid development of the catering industry has led to the extensive use of packaging materials. As an important component of catering utensil packaging, packaging paper plays a key role in protecting products, facilitating transportation and improving user experience. However, traditional packaging paper has many limitations. Most traditional packaging papers are made of non-degradable materials, such as coated paper containing a large amount of plastic components. After use, these packaging papers are difficult to decompose in the natural environment, and long-term accumulation will lead to ecological problems such as soil pollution and water pollution. According to statistics, the amount of garbage generated by catering packaging is huge every year, among which a large amount of non-degradable packaging paper has become an important source of "white pollution", causing serious damage to the ecological balance. The production of traditional packaging paper often relies on limited resources, such as wood. The large-scale felling of trees for papermaking not only destroys forest resources, but also affects the carbon cycle and biodiversity of the ecosystem. In addition, the recycling rate of non-degradable packaging paper is low, which further aggravates the waste of resources.

[0003] As consumers' environmental awareness continues to improve, the demand for green and environmentally friendly products is growing. In catering consumption, consumers are more inclined to choose products using degradable packaging paper. Therefore, the present invention develops degradable packaging paper for catering utensils and a preparation method thereof, which is used to solve the technical problems in the prior art that packaging paper causes great environmental pollution, serious waste of resources, and has no further refined preparation process and no addition of improved additives to improve the waterproof, oil-proof and fresh-keeping effect of packaging paper. Summary of the invention

[0004] The purpose of the present invention is to provide degradable packaging paper for tableware and a preparation method thereof, so as to solve the technical problems in the prior art that the packaging paper has great environmental pollution, serious waste of resources, and no further refinement of the preparation process and improvement of the surface treatment to enhance the waterproof, oil-proof and fresh-keeping effect of the packaging paper.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing degradable packaging paper for tableware comprises the following steps: (1) The bamboo fiber and the straw fiber are modified respectively, and nano-silicon dioxide, chitosan-polylactic acid and additives are used for blending and modification to obtain modified pulp; (2) The modified pulp is conveyed to a headbox, formed in a forming net to obtain a wet paper sheet, squeezed for dehydration, dried in a drying cylinder, and coated on the surface with a modified coating liquid by roller coating, solidified, and calendered to obtain a degradable packaging paper for tableware; the modified coating liquid is prepared by emulsifying and blending poly 3-hydroxybutyric acid-hexanoate and polylactic acid and then modifying them.

[0006] Furthermore, the method for preparing the degradable tableware wrapping paper comprises the following steps in step (1): S1, dispersing bamboo fiber in water, using a disc mill to decompose, filter, ultrasonicate, and steam explode to obtain modified bamboo fiber; placing straw fiber in an enzymatic hydrolysis solution for enzymolysis, filtering, controlling moisture, and plasma treatment to obtain modified straw fiber; S2. The modified bamboo fiber and the modified straw fiber are pulped and mixed separately to obtain a fiber suspension, a nano-silicon dioxide dispersion is added to blend, and then a chitosan-polylactic acid crosslinking liquid and an auxiliary agent are added to blend to obtain a modified pulp.

[0007] Furthermore, the mass ratio of bamboo fiber to water in S1 is 1:100-120, the decomposition speed is 1000-3000r / min, the decomposition time is 10-30min, the filter mesh aperture is 40-80μm, the ultrasonic frequency is 20-40kHz, the power density is 0.5-1.0W / cm², and the ultrasonic treatment time is 10-20min; 5-10% of carbon dioxide by volume is mixed into the steam, the steam explosion temperature is 180-200℃, the pressure is 1.5-2.0MPa, and the maintenance time is 3-5min; the mass of straw fiber and enzymatic hydrolysate The ratio is 1:5, the enzymatic hydrolysis liquid is a mixture of cellulase, hemicellulase, xylanase, laccase, activator and water, the activator is a mixture of magnesium sulfate and calcium chloride, the mass ratio of cellulase, hemicellulase, xylanase, laccase, magnesium sulfate, calcium chloride and water is 5-6:3-4:2:1:0.5:0.3:1000, the enzymatic hydrolysis temperature is 45-55°C, the enzymatic hydrolysis time is 2-3h, and the enzymatic hydrolysis stirring speed is 100-200r / min; the plasma gas is air or nitrogen, the processing power is 50-100W, and the processing time is 5-15min.

[0008] Furthermore, in S2, the beating degree is 30-45°SR, the mass ratio of modified bamboo fiber to modified straw fiber is 1-2:1; the nano-silicon dioxide dispersion is obtained by ultrasonically dispersing nano-silicon dioxide powder in deionized water, the mass concentration of the nano-silicon dioxide dispersion is 1-3wt%, the volume ratio of the fiber suspension to the nano-silicon dioxide dispersion is 3-5:1, the stirring reaction speed is 40-60r / min, the stirring time is 1-2h, the reaction temperature is 40-50℃; the blending time is 1-2h; the chitosan-polylactic acid cross-linking liquid is composed of 1-2wt% chitosan A chitosan acetic acid aqueous solution and a 2-3wt% polylactic acid dichloromethane solution are mixed in a volume ratio of 1:1, and 2-5vt% glutaraldehyde is added to react at 50-60°C for 2-3h for cross-linking. The volume ratio of the fiber suspension to the chitosan-polylactic acid cross-linking liquid is 3-5:1. The auxiliary agent is prepared by ultrasonic dispersion of nano bamboo charcoal powder, lavender essential oil, tea tree essential oil, natural rosin emulsion sizing agent and polydimethylsiloxane in an amount ratio of 1-2g:1g:1g:6-8mL:2-3mL. The volume ratio of the fiber suspension to the auxiliary agent is 1:0.1-0.15.

[0009] Furthermore, the method for preparing the modified coating liquid comprises the following steps: Q1, adding poly 3-hydroxybutyric acid-caproate and polylactic acid to tetrahydrofuran, stirring and dissolving in an oil bath, adding deionized water dropwise for emulsification, adding sorbitan monooleate for stirring and emulsification, and removing tetrahydrofuran by vacuum distillation to obtain an aqueous emulsion; Q2. Add food-grade water-based polyurethane emulsion and water-based emulsion into a reaction kettle, add nano zinc oxide dispersion, and then add tea polyphenol-sodium carboxymethyl cellulose composite liquid to obtain a coating mixture, add polydimethylsiloxane, heat and stir to obtain a modified coating liquid.

[0010] Furthermore, in Q1, the mass ratio of poly 3-hydroxybutyric acid-caproate to polylactic acid is 1:1-1.5, the mass ratio of tetrahydrofuran to poly 3-hydroxybutyric acid-caproate is 1:10-20, the mass ratio of deionized water to tetrahydrofuran is 1-3:1, and the mass ratio of sorbitan monooleate to poly 3-hydroxybutyric acid-caproate is 3-10:100; in Q2, the volume ratio of food-grade aqueous polyurethane emulsion to aqueous emulsion is 2:1; the amount of nano zinc oxide dispersion added is 2-5% of the total volume of the emulsion, and the nano zinc oxide dispersion consists of 1 part by weight of nano zinc oxide powder and 0.01-0.03 parts by weight of sodium polyacrylate are dispersed in 10-20 parts by weight of deionized water; the tea polyphenol-sodium carboxymethyl cellulose composite liquid is added in an amount of 6-10% of the total volume of the emulsion, and the tea polyphenol-sodium carboxymethyl cellulose composite liquid is obtained by mixing tea polyphenol and 2-4wt% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 1:5-10; the amount of polydimethylsiloxane added is 0.1-0.3% of the total volume of the emulsion, the heating temperature is 55-65°C, the stirring speed is 600-900r / min, and the stirring time is 4-6h.

[0011] Furthermore, in step (2), the lip opening of the headbox is 1-3 mm, the slurry flow rate is 0.5-2 m / s, the mesh speed of the forming mesh is 50-300 m / min, the pressing adopts 3-5 pressings, the first pressing pressure is 0.1-0.3 MPa, the second pressing pressure is 0.3-0.5 MPa, the last pressing pressure is 0.5-1.5 MPa, the pressing time is 1-5 s, the drying temperature of the drying cylinder is 100-130°C, the steam pressure of the drying cylinder is 0.2-0.6 MPa, the drying time is 1-5 min, the coating roller pressure is 0.05-0.2 MPa, the coating amount is 5-20 g / m², the curing temperature is 60-100°C, the curing time is 1-5 min, the calendering pressure is 1-5 MPa, the temperature is 50-80°C, and the calendering speed is 50-200 m / min.

[0012] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The present invention can effectively destroy the structure of the fibers, increase the specific surface area of ​​the fibers, and improve the reaction activity of the fibers by modifying the bamboo fibers and straw fibers; the nano-silicon dioxide dispersion has a high specific surface area and activity, which can enhance the strength and barrier properties of the paper and form a tighter structure; the chitosan-polylactic acid cross-linking liquid can form chemical bonds between the fibers through the cross-linking reaction of chitosan and polylactic acid, thereby further enhancing the strength and stability of the paper.

[0013] 2. The present invention achieves a good balance between strength and flexibility by mixing poly 3-hydroxybutyrate-caproate and polylactic acid and compounding them with an aqueous polyurethane emulsion; nano zinc oxide has excellent antibacterial properties, can destroy bacterial cell walls and cell membranes, and inhibit bacterial growth and reproduction; tea polyphenols, as antioxidants, can effectively remove free radicals, prevent oxidation and deterioration of oils, pigments and other ingredients in food, and maintain the color and flavor of food; a variety of biodegradable materials are used in the preparation process, which meets environmental protection requirements. DETAILED DESCRIPTION

[0014] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1:

[0015] This embodiment discloses a method for preparing a modified coating liquid, comprising the following steps: Q1, 100g poly 3-hydroxybutyric acid-caproate and 100g polylactic acid were added to 1kg tetrahydrofuran, stirred and dissolved in an oil bath, 1kg deionized water was added dropwise for emulsification, and 3g sorbitan monooleate was added for stirring and emulsification, and tetrahydrofuran was removed by vacuum distillation to obtain an aqueous emulsion; Q2. Add 2L of food-grade aqueous polyurethane emulsion and 1L of aqueous emulsion into a reactor, add 60mL of nano zinc oxide dispersion, the nano zinc oxide dispersion is obtained by dispersing 1 part by weight of nano zinc oxide powder and 0.01 parts by weight of sodium polyacrylate in 10 parts by weight of deionized water, then add 180mL of tea polyphenol-sodium carboxymethyl cellulose composite liquid, the tea polyphenol-sodium carboxymethyl cellulose composite liquid is obtained by mixing tea polyphenol and 2wt% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 1:5, obtain a coating mixture, add 3mL of polydimethylsiloxane, heat and stir, the heating temperature is 55°C, the stirring speed is 600r / min, and the stirring time is 4h to obtain a modified coating liquid.

[0016] This embodiment discloses a method for preparing degradable packaging paper for tableware, comprising the following steps: (1) The bamboo fiber and the straw fiber are modified respectively, and nano-silicon dioxide, chitosan-polylactic acid and additives are used for blending and modification to obtain modified pulp; (2) The modified pulp is conveyed to a headbox with a lip opening of 1 mm and a pulp flow rate of 0.5-2 m / s. The paper is formed in a forming net with a net speed of 50 m / min to obtain a wet paper sheet. The paper is pressed and dehydrated in three passes. The first pass has a pressure of 0.13 MPa, the second pass has a pressure of 0.3 MPa, and the last pass has a pressure of 0.5 MPa. The pressing time is 1 s. The paper is dried in a drying cylinder at a drying temperature of 100°C and a drying cylinder steam pressure of 0.2 MPa. The drying time is 1 min. The modified coating liquid is coated on the surface by roller coating at a coating roller pressure of 0.05 MPa and a coating amount of 5 g / m². The paper is cured at a curing temperature of 60°C and a curing time of 1 min. The paper is calendered at a calendering pressure of 1 MPa, a temperature of 50°C, and a calendering speed of 50 m / min to obtain a degradable packaging paper for tableware.

[0017] Wherein, the method for preparing the degradable packaging paper for tableware, step (1) comprises the following process: S1. Disperse 10kg of bamboo fiber in 1000kg of water, use a disc mill for decomposition, the decomposition speed is 1000r / min, the decomposition time is 10min, filter, the filter mesh aperture is 40μm, ultrasound, ultrasound frequency is 20kHz, power density is 0.5W / cm², ultrasound treatment time is 10min, steam explosion, mix 5% volume ratio of carbon dioxide in steam, steam explosion temperature is 180℃, pressure is 1.5MPa, and maintenance time is 3min to obtain modified bamboo fiber; place 10kg of straw fiber in 50kg enzymatic hydrolysis enzymolysis in liquid, the enzymolysis liquid is a mixture of cellulase, hemicellulase, xylanase, laccase, activator and water, the activator is magnesium sulfate and calcium chloride, the mass ratio of cellulase, hemicellulase, xylanase, laccase, magnesium sulfate, calcium chloride and water is 5:3:2:1:0.5:0.3:1000, the enzymolysis temperature is 45°C, the enzymolysis time is 2h, the enzymolysis stirring speed is 100r / min, filtering, controlling the moisture, plasma treatment, the plasma gas is air, the processing power is 50W, the processing time is 5min, and the modified straw fiber is obtained; S2, 1kg modified bamboo fiber and 1kg modified straw fiber were pulped separately, the beating degree was 30°SR, mixed, and fiber suspension was obtained, 300mL fiber suspension was added to 100mL 1wt% nano-silicon dioxide dispersion, the stirring reaction speed was 400r / min, the stirring time was 1h, the reaction temperature was 40℃, the blending time was 1h, and then 100mL chitosan-polylactic acid crosslinking liquid and 30mL auxiliary agent were added to blend to obtain modified pulp. Chitosan-polylactic acid crosslinking liquid was mixed by 1wt% chitosan acetic acid aqueous solution and 2wt% polylactic acid dichloromethane solution in a volume ratio of 1:1, and 2vt% glutaraldehyde was added at 50℃, stirred for 2h to crosslink, and the auxiliary agent was obtained by ultrasonic dispersion of nano bamboo charcoal powder, lavender essential oil, tea tree essential oil, natural rosin emulsion sizing agent and polydimethylsiloxane in a ratio of 1g:1g:1g:6mL:2mL. Embodiment 2:

[0018] This embodiment discloses a method for preparing a modified coating liquid, comprising the following steps: Q1, 100g poly 3-hydroxybutyric acid-caproate and 130g polylactic acid were added to 1.5kg tetrahydrofuran, stirred and dissolved in an oil bath, 3kg deionized water was added dropwise for emulsification, and 6g sorbitan monooleate was added for stirring and emulsification, and tetrahydrofuran was removed by vacuum distillation to obtain an aqueous emulsion; Q2. Add 2L of food-grade aqueous polyurethane emulsion and 1L of aqueous emulsion into a reactor, add 100mL of nano zinc oxide dispersion, the nano zinc oxide dispersion is obtained by dispersing 1 part by weight of nano zinc oxide powder and 0.02 parts by weight of sodium polyacrylate in 15 parts by weight of deionized water, then add 220mL of tea polyphenol-sodium carboxymethyl cellulose composite liquid, the tea polyphenol-sodium carboxymethyl cellulose composite liquid is obtained by mixing tea polyphenol and 3wt% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 1:7, obtain a coating mixture, add 6mL of polydimethylsiloxane, heat and stir, the heating temperature is 60°C, the stirring speed is 800r / min, and the stirring time is 5h to obtain a modified coating liquid.

[0019] This embodiment discloses a method for preparing degradable packaging paper for tableware, comprising the following steps: (1) The bamboo fiber and the straw fiber are modified respectively, and nano-silicon dioxide, chitosan-polylactic acid and additives are used for blending and modification to obtain modified pulp; (2) The modified pulp is conveyed to the headbox with a lip opening of 2 mm and a pulp flow rate of 1 m / s. The pulp is formed in a forming net with a net speed of 100 m / min to obtain a wet paper sheet, which is then pressed and dehydrated. The pressing process adopts 4 passes, with the first pass having a pressure of 0.2 MPa, the second pass having a pressure of 0.4 MPa, the third pass having a pressure of 0.6 MPa, and the last pass having a pressure of 1 MPa. The pressing time is 3 s and the paper is dried on a drying cylinder. , the drying temperature of the drying cylinder is 120℃, the steam pressure of the drying cylinder is 0.4MPa, the drying time is 3min, the modified coating liquid is coated on the surface by roller coating, the coating roller pressure is 0.1MPa, the coating amount is 10g / m², curing, the curing temperature is 80℃, the curing time is 1-5min, calendering, the calendering pressure is 3MPa, the temperature is 60℃, and the calendering speed is 100m / min to obtain degradable packaging paper for tableware.

[0020] Wherein, the method for preparing the degradable packaging paper for tableware, step (1) comprises the following process: S1. Disperse 10kg of bamboo fiber in 1100kg of water, use a disc mill for debonding, the debonding speed is 2000r / min, the debonding time is 20min, filter, the filter mesh aperture is 60μm, ultrasound, ultrasound frequency is 30kHz, power density is 0.8W / cm², ultrasonic treatment time is 15min, steam explosion, mix 7% volume ratio of carbon dioxide in steam, steam explosion temperature is 190℃, pressure is 1.8MPa, and maintenance time is 4min to obtain modified bamboo fiber; place 10kg of straw fiber in 50kg of enzymatic hydrolysis solution for enzymolysis The enzymatic hydrolysis liquid is a mixture of cellulase, hemicellulase, xylanase, laccase, an activator and water, the activator is magnesium sulfate and calcium chloride, the mass ratio of cellulase, hemicellulase, xylanase, laccase, magnesium sulfate, calcium chloride and water is 5.5:3.5:2:1:0.5:0.3:1000, the enzymatic hydrolysis temperature is 50°C, the enzymatic hydrolysis time is 2.5h, the enzymatic hydrolysis stirring speed is 150r / min, filtration, water is controlled, plasma treatment is performed, the plasma gas is nitrogen, the processing power is 80W, and the processing time is 10min, to obtain modified straw fiber; S2. 1.5 kg of modified bamboo fiber and 1 kg of modified straw fiber were pulped separately with a beating degree of 40°SR, mixed to obtain a fiber suspension, 400 mL of the fiber suspension was added into 100 mL of 2 wt% nano-silicon dioxide dispersion for blending, the stirring reaction speed was 50 r / min, the stirring time was 1.5 h, the reaction temperature was 45°C, the blending time was 1.5 h, and then 100 mL of chitosan-polylactic acid cross-linking liquid and 50 mL of auxiliary agent were added for blending to obtain modified pulp. Chitosan-polylactic acid cross-linking liquid is prepared by mixing 1.5wt% chitosan acetic acid aqueous solution and 2.5wt% polylactic acid dichloromethane solution in a volume ratio of 1:1, adding 4vt% glutaraldehyde and stirring at 55°C for 2.5h to obtain cross-linking. The auxiliary agent is prepared by ultrasonic dispersion of nano bamboo charcoal powder, lavender essential oil, tea tree essential oil, natural rosin emulsion sizing agent and polydimethylsiloxane in a ratio of 1.5g:1g:1g:7mL:2.5mL. Embodiment 3:

[0021] This embodiment discloses a method for preparing a modified coating liquid, comprising the following steps: Q1, 100g poly 3-hydroxybutyric acid-caproate and 50g polylactic acid were added to 2kg tetrahydrofuran, stirred and dissolved in an oil bath, 6kg deionized water was added dropwise for emulsification, and 10g sorbitan monooleate was added for stirring and emulsification, and tetrahydrofuran was removed by vacuum distillation to obtain an aqueous emulsion; Q2. Add 2L of food-grade aqueous polyurethane emulsion and 1L of aqueous emulsion into a reactor, add 150mL of nano zinc oxide dispersion, the nano zinc oxide dispersion is obtained by dispersing 1 part by weight of nano zinc oxide powder and 0.03 parts by weight of sodium polyacrylate in 20 parts by weight of deionized water, then add 300mL of tea polyphenol-sodium carboxymethyl cellulose composite liquid, the tea polyphenol-sodium carboxymethyl cellulose composite liquid is obtained by mixing tea polyphenol and 4wt% sodium carboxymethyl cellulose aqueous solution in a mass ratio of 1:10, obtain a coating mixture, add 9mL of polydimethylsiloxane, heat and stir, the heating temperature is 65°C, the stirring speed is 900r / min, and the stirring time is 6h to obtain a modified coating liquid.

[0022] This embodiment discloses a method for preparing degradable packaging paper for tableware, comprising the following steps: (1) The bamboo fiber and the straw fiber are modified respectively, and nano-silicon dioxide, chitosan-polylactic acid and additives are used for blending and modification to obtain modified pulp; (2) The modified pulp was transported to the headbox with a lip opening of 3 mm and a pulp flow rate of 2 m / s. The pulp was formed in a forming net with a net speed of 300 m / min to obtain a wet paper sheet, which was then pressed and dehydrated. The pressing process was performed in five stages. The first stage had a pressure of 0.3 MPa, the second stage had a pressure of 0.5 MPa, the third stage had a pressure of 0.7 MPa, the fourth stage had a pressure of 1 MPa, and the last stage had a pressure of 1.5 MPa. The pressing time was 5 s, drying with a drying cylinder drying temperature of 130°C, a drying cylinder steam pressure of 0.6MPa, and a drying time of 5min, applying the modified coating liquid on the surface by roller coating, with a coating roller pressure of 0.2MPa and a coating amount of 20g / m², curing with a curing temperature of 100°C and a curing time of 5min, calendering with a calendering pressure of 5MPa, a temperature of 80°C, and a calendering speed of 200m / min, to obtain degradable packaging paper for tableware.

[0023] Wherein, the method for preparing the degradable packaging paper for tableware, step (1) comprises the following process: S1. Disperse 10kg of bamboo fiber in 1200kg of water, use a disc mill for decomposition, the decomposition speed is 3000r / min, the decomposition time is 30min, filter, the filter mesh aperture is 80μm, ultrasound, ultrasound frequency is 40kHz, power density is 1.0W / cm², ultrasonic treatment time is 20min, steam explosion, mix 10% volume ratio of carbon dioxide in steam, steam explosion temperature is 200℃, pressure is 2.0MPa, and maintenance time is 5min to obtain modified bamboo fiber; place 10kg of straw fiber in 50kg of enzymatic hydrolyzate Enzymolysis, wherein the enzymolysis solution is a mixture of cellulase, hemicellulase, xylanase, laccase, an activator and water, the activator is magnesium sulfate and calcium chloride, the mass ratio of cellulase, hemicellulase, xylanase, laccase, magnesium sulfate, calcium chloride and water is 6:4:2:1:0.5:0.3:1000, the enzymolysis temperature is 55°C, the enzymolysis time is 3h, the enzymolysis stirring speed is 200r / min, filtering, controlling the moisture, plasma treatment, the plasma gas is air or nitrogen, the processing power is 100W, and the processing time is 15min, to obtain modified straw fiber; S2, 2kg modified bamboo fiber and 1kg modified straw fiber were pulped separately, the beating degree was 45°SR, mixed to obtain fiber suspension, 500mL fiber suspension was added to 100mL 3wt% nano-silicon dioxide dispersion, the stirring reaction speed was 60r / min, the stirring time was 2h, the reaction temperature was 50℃, the blending time was 2h, and then 100mL chitosan-polylactic acid crosslinking liquid and 75mL auxiliary agent were added to blend to obtain modified pulp. Chitosan-polylactic acid crosslinking liquid was mixed by 2wt% chitosan acetic acid aqueous solution and 3wt% polylactic acid dichloromethane solution in a volume ratio of 1:1, 5vt% glutaraldehyde was added at 60℃, stirred for 3h to crosslink, and the auxiliary agent was obtained by ultrasonic dispersion of nano bamboo charcoal powder, lavender essential oil, tea tree essential oil, natural rosin emulsion sizing agent and polydimethylsiloxane in an amount ratio of 2g:1g:1g:8mL:3mL.

[0024] Comparative Example 1: Comparative Example 1 Compared with Example 3, in the process of preparing the degradable tableware packaging paper in Comparative Example 1, the bamboo fiber is not modified, and other conditions remain unchanged.

[0025] Comparative Example 2: Comparative Example 2 Compared with Example 3, in the process of preparing the degradable tableware wrapping paper in Comparative Example 2, no modification treatment is performed on the straw fiber, and other conditions remain unchanged.

[0026] Comparative Example 3: Comparative Example 3 Compared with Example 3, during the preparation of the degradable tableware packaging paper in Comparative Example 3, no modified coating liquid was added, and other conditions remained unchanged.

[0027] Experimental example: The performance of the degradable tableware packaging paper samples prepared in Examples 1-3 and Comparative Examples 1-3 was tested: 1. Mechanical properties test According to the requirements of GB / T12914-2018 standard, the degradable tableware packaging paper samples prepared in Examples 1-3 and Comparative Examples 1-3 were cut into specimens with a size of 15 mm × 250 mm, with 10 specimens in each group. The test results were averaged, and the results of tensile strength and elongation at break are shown in Table 1: Table 1 Group Tensile strength (kN / m) Elongation at break (%) Example 1 2.8 2.9 Example 2 3.0 3.2 Example 3 3.2 3.4 Comparative Example 1 1.8 1.8 Comparative Example 2 1.9 1.8 Comparative Example 3 1.6 1.5 From the test results in Table 1, it can be seen that the degradable tableware packaging paper prepared in Examples 1-3 of the present invention has good mechanical properties. From the comparison between Comparative Examples 1-3 and Examples 1-3, it can be seen that the tensile strength and elongation at break can be significantly improved by modifying bamboo fiber and straw fiber and adding modified coating liquid.

[0028] 2. Antibacterial and Antioxidant Performance Test Antibacterial rate test: According to GB / T20944.3-2008 "Evaluation of antibacterial properties of textiles Part 3: Oscillation method", the degradable tableware packaging paper samples prepared in Examples 1-3 and Comparative Examples 1-3 were cut into circular specimens with a diameter of 50 mm and sterilized by irradiation with ultraviolet light for 30 min. The sterile filter paper discs were used as the control group. Escherichia coli and Staphylococcus aureus were inoculated in nutrient broth medium, cultured at 37°C for 24 h, and then diluted to 10% with physiological saline. 6 -10 7 cfu / mL, drip 0.2mL of bacterial solution on the surface of each sample, then cover it with sterile polyethylene film to evenly distribute the bacterial solution, put the sample in an incubator, and culture it at 37℃ for 24h, put the cultured sample in a triangular flask containing 20mL of sterile saline, and shake it for 20min to fully elute the bacteria. Then take the eluate for gradient dilution, spread it on the nutrient agar plate, and culture it at 37℃ for 24h, count the number of colonies on the plate A1, and the number of colonies corresponding to the sterile filter paper disc is A0. The calculation formula of antibacterial rate is: antibacterial rate (%) = (A0-A1) / A0×100%.

[0029] DPPH free radical scavenging rate test: The degradable packaging paper samples for tableware prepared in Examples 1-3 and Comparative Examples 1-3 were cut into 50mm×50mm small pieces, 0.1g of sample was weighed, 10mL of anhydrous ethanol was added, and the sample was extracted by shaking at room temperature for 24h, and then filtered to obtain a sample extract; 0.002g of DPPH was weighed, dissolved with anhydrous ethanol and fixed to 100mL to obtain a 0.02mg / mL DPPH solution; 2mL of sample extract was taken, 2mL of DPPH solution was added, and the reaction was carried out at room temperature in the dark for 30min after shaking. Then the absorbance was measured at a wavelength of 517nm (B1). At the same time, 2mL of anhydrous ethanol was used to replace the sample extract, 2mL of DPPH solution was added, and the absorbance (B0) was measured; 2mL of anhydrous ethanol was added to 2mL of sample extract, and the absorbance (B2) was measured.

[0030] The calculation formula for DPPH free radical scavenging rate: DPPH free radical scavenging rate (%) = [1-(A1-A2) / A0] × 100%.

[0031] The test results of antibacterial rate and DPPH free radical scavenging rate are shown in Table 2: Table 2 Group Antibacterial rate (%) DPPH free radical scavenging rate (%) Example 1 91 47 Example 2 92 49 Example 3 93 53 Comparative Example 1 77 31 Comparative Example 2 79 34 Comparative Example 3 61 28 According to the test results in Table 2, the degradable tableware wrapping paper prepared in Examples 1-3 of the present invention has good antibacterial and antioxidant effects. By comparing Comparative Examples 1-3 with Examples 1-3, it can be seen that modifying bamboo fiber and straw fiber and adding modified coating liquid can significantly improve their antibacterial rate and DPPH free radical scavenging rate.

[0032] 3. Biodegradability Test According to GB / T19277.1-2011 "Determination of the ultimate aerobic biodegradability of materials under controlled composting conditions by measuring the released carbon dioxide - Part 1: General method", the degradable tableware packaging paper samples prepared in Examples 1-3 and Comparative Examples 1-3 are cut into small pieces of 50mm×50mm, and the burial mass (m0) is weighed. The samples are buried in soil at a depth of 10-15cm, the soil moisture is maintained at 50-60%, and the temperature is maintained at 25-30°C. The samples are taken out at 1, 3, and 6 months, respectively, rinsed with distilled water, and then dried at 60°C to constant weight, and the mass (m1) is weighed.

[0033] The calculation formula for degradation rate: Degradation rate (%) = (m0-m1) / m0×100%.

[0034] Table 3 Group Degradation rate in the first month (%) Degradation rate at the third month (%) Degradation rate at 6th month (%) Example 1 5.4 24.2 86.5 Example 2 6.2 25.7 87.1 Example 3 7.1 27.8 89.2 Comparative Example 1 2.1 13.4 64.0 Comparative Example 2 2.3 15.1 67.9 Comparative Example 3 5.8 25.9 85.8 According to the test results in Table 3, the degradable tableware wrapping paper prepared in Examples 1-3 of the present invention has good biodegradability. By comparing Comparative Examples 1-3 with Examples 1-3, it can be seen that modifying bamboo fiber and straw fiber can significantly increase the biodegradability, and the modified coating liquid has no significant effect on the wrapping paper.

[0035] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0036] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing degradable packaging paper for tableware, characterized in that: The steps include: (1) The bamboo fiber and the straw fiber are modified respectively, and nano-silicon dioxide, chitosan-polylactic acid and additives are used for blending and modification to obtain modified pulp; (2) The modified pulp is conveyed to a headbox, formed in a forming net to obtain a wet paper sheet, squeezed for dehydration, dried in a drying cylinder, and coated on the surface with a modified coating liquid by roller coating, solidified, and calendered to obtain a degradable packaging paper for tableware; the modified coating liquid is prepared by emulsifying and blending poly 3-hydroxybutyric acid-hexanoate and polylactic acid and then modifying them.

2. The method for preparing the degradable tableware wrapping paper according to claim 1, characterized in that: Step (1) includes the following process: S1, dispersing bamboo fiber in water, using a disc mill to decompose, filter, ultrasonicate, and steam explode to obtain modified bamboo fiber; placing straw fiber in an enzymatic hydrolysis solution for enzymolysis, filtering, controlling moisture, and plasma treatment to obtain modified straw fiber; S2. The modified bamboo fiber and the modified straw fiber are pulped and mixed separately to obtain a fiber suspension, a nano-silicon dioxide dispersion is added to blend, and then a chitosan-polylactic acid crosslinking liquid and an auxiliary agent are added to blend to obtain a modified pulp.

3. The method for preparing the degradable packaging paper for tableware according to claim 2, characterized in that: In S1, 5-10% by volume of carbon dioxide is mixed into steam; the mass ratio of straw fiber to enzymatic hydrolysate is 1:5, the enzymatic hydrolysate is a mixture of cellulase, hemicellulase, xylanase, laccase, activator and water, the activator is a mixture of magnesium sulfate and calcium chloride, and the mass ratio of cellulase, hemicellulase, xylanase, laccase, magnesium sulfate, calcium chloride and water is 5-6:3-4:2:1:0.5:0.3:1000.

4. The method for preparing the degradable packaging paper for tableware according to claim 2, characterized in that: The beating degree in S2 is 30-45°SR, the mass ratio of modified bamboo fiber to modified straw fiber is 1-2:1; the mass concentration of nano-silicon dioxide dispersion is 1-3wt%, the volume ratio of fiber suspension to nano-silicon dioxide dispersion is 3-5:1; the volume ratio of fiber suspension to chitosan-polylactic acid crosslinking liquid is 3-5:

1.

5. The method for preparing the degradable packaging paper for tableware according to claim 2, characterized in that: The auxiliary agent is obtained by ultrasonic dispersion of nano bamboo charcoal powder, lavender essential oil, tea tree essential oil, natural rosin emulsion sizing agent and polydimethylsiloxane in a dosage ratio of 1-2g:1g:1g:6-8mL:2-3mL; the volume ratio of the fiber suspension to the auxiliary agent is 1:0.1-0.

15.

6. The method for preparing the degradable packaging paper for tableware according to claim 1, characterized in that: The method for preparing the modified coating liquid comprises the following steps: Q1, adding poly 3-hydroxybutyric acid-caproate and polylactic acid to tetrahydrofuran, stirring and dissolving in an oil bath, adding deionized water dropwise for emulsification, adding sorbitan monooleate for stirring and emulsification, and removing tetrahydrofuran by vacuum distillation to obtain an aqueous emulsion; Q2. Add food-grade water-based polyurethane emulsion and water-based emulsion into a reaction kettle, add nano zinc oxide dispersion, and then add tea polyphenol-sodium carboxymethyl cellulose composite liquid to obtain a coating mixture, add polydimethylsiloxane, heat and stir to obtain a modified coating liquid.

7. The method for preparing the degradable packaging paper for tableware according to claim 6, characterized in that: The mass ratio of poly 3-hydroxybutyric acid-hexanoate and polylactic acid in Q1 is 1:1-1.5, the mass ratio of tetrahydrofuran to poly 3-hydroxybutyric acid-hexanoate is 1:10-20, the mass ratio of deionized water to tetrahydrofuran is 1-3:1, and the mass ratio of sorbitan monooleate to poly 3-hydroxybutyric acid-hexanoate is 3-10:

100.

8. The method for preparing the degradable packaging paper for tableware according to claim 6, characterized in that: The volume ratio of food-grade water-based polyurethane emulsion and water-based emulsion in Q2 is 2:1; the addition amount of nano zinc oxide dispersion is 2-5% of the total volume of the emulsion; the addition amount of tea polyphenol-sodium carboxymethyl cellulose composite liquid is 6-10% of the total volume of the emulsion; and the addition amount of polydimethylsiloxane is 0.1-0.3% of the total volume of the emulsion.

9. The method for preparing the degradable packaging paper for tableware according to claim 1, characterized in that: In step (2), 3-5 pressing steps are adopted, the first pressing step has a pressure of 0.1-0.3 MPa, the second pressing step has a pressure of 0.3-0.5 MPa, and the last pressing step has a pressure of 0.5-1.5 MPa.

10. Degradable packaging paper for tableware, characterized in that: The degradable tableware wrapping paper is prepared by the method for preparing the degradable tableware wrapping paper as described in any one of claims 1 to 9.