Preparation method of fluoride-free degradable oil-proof packaging paper

Abstract

The invention relates to the technical field of functional paper and food packaging, in particular to a preparation method of fluoride-free degradable oil-proof packaging paper. The preparation method comprises the following steps: (1) preparing polydopamine modified palygorskite particles; (2) uniformly dispersing the polydopamine modified palygorskite in a solution containing glycerol or emulsified silicone oil and glutaraldehyde to obtain a coating A; (3) preparing a chitosan solution as a coating B; and (4) selecting different paper sheets, firstly dipping the paper sheets in the coating A solution, then dipping the paper sheets in the coating B solution after drying, and obtaining the fluoride-free degradable oil-proof paper after drying. The oil-proof packaging paper prepared by the preparation method has the advantages that the normal-temperature and high-temperature oil-proof performance is improved, the mechanical property and the barrier property are excellent, the application range of the oil-proof paper is expanded, and the service cycle is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of functional paper and food packaging, and in particular to a method for preparing fluorine-free, degradable and oil-proof packaging paper. Background Art

[0002] With the development of the food industry and the rise of the takeout industry, the use of grease-proof paper is increasing. However, due to the large number of hydrophilic hydroxyl groups and tiny pores distributed on the surface of traditional paper, it has poor performance in blocking water, oil and other molecules, limiting its further development and application in the food packaging industry.

[0003] At present, this problem is mainly solved by laminating paper or using fluorinated oil-proofing agents. Plastic lamination uses polyolefin polymers, which have good barrier properties and low cost, but their difficult-to-degrade properties cause great pollution and harm to the environment. Fluorinated oil-proofing agents are generally copolymerized by fluorinated monomers and non-fluorinated monomers. Fluorinated substances have low surface energy and can shield the hydroxyl groups on the surface of cellulose. Then the fluorinated substances with low surface tension are arranged in a directional manner to form an oil-proof layer. However, this type of fluorinated compound is not only difficult to decompose, causing damage to the ozone layer, but also threatening human health. It has now been banned in most countries. With the strengthening of environmental awareness and the demand for health, the development of non-toxic, degradable, and environmentally friendly oil-proof paper is imminent.

[0004] The patent application "A water-based coating with waterproof and oil-proof properties, its preparation method and application" WO2023088018A1 discloses a water-based coating for waterproof and oil-proof coatings, which is mainly made of water-in-oil type Pickering emulsions and oil-proof ingredients such as natural polysaccharides, providing a green, environmentally friendly and safe waterproof and oil-proof coating with hydrophobic, waterproof and oil-proof properties. Patent "A method for preparing super-hydrophobic and oil-proof baking paper with a bionic lotus leaf surface structure" 2023101460177 discloses a method for preparing a hydrophobic, oil-proof, fluorine-free and environmentally friendly high-performance baking paper, which uses healthy chemicals as raw materials and is assembled layer by layer to provide high-performance baking paper with a bionic lotus leaf surface structure.

[0005] The present invention selects natural palygorskite and chitosan to construct a network structure and utilizes micropores to store food-grade emulsified silicone oil. The materials involved are non-toxic, pollution-free, degradable, and environmentally friendly, meeting the requirements of green development and achieving more significant innovation over existing oil-proof packaging paper. Summary of the invention

[0006] In order to make up for the deficiencies of the prior art, the present invention provides a method for preparing fluorine-free biodegradable oil-proof packaging paper. The oil-proof paper prepared by the preparation method has improved room temperature and high temperature oil-proof properties, excellent mechanical properties and barrier properties, expands the application range of the oil-proof paper, extends the service life, and solves the problems existing in the prior art.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is:

[0008] A method for preparing fluorine-free biodegradable oil-proof packaging paper comprises the following steps:

[0009] (1) Modification of palygorskite

[0010] Weigh 0.5g-2g of palygorskite and disperse it in 50ml Tris solution with pH 7.5-9.0, and perform ultrasonic dispersion for 30min; add 50mg-200mg dopamine, stir magnetically, and react for 8h-24h; then centrifuge for 5min, with the speed controlled at 6000r / min-10000r / min; wash twice with deionized water, and obtain polydopamine-modified palygorskite particles after drying;

[0011] (2) Preparation of coating A

[0012] 0.5 g to 2 g of the polydopamine-modified palygorskite particles prepared in step (1) were added to a beaker, and then 24.5 mL of deionized water was added, and ultrasonic dispersion was performed for 30 min; 0.6 g to 2 g of emulsified silicone oil or glycerol and 3% to 7% of glutaraldehyde solution by mass of palygorskite were added, and magnetic stirring was performed to fully mix the solution to obtain coating A;

[0013] (3) Preparation of coating B

[0014] Prepare 50 ml of 2%-5% acetic acid aqueous solution or formic acid aqueous solution, take 1 g of chitosan and dissolve it in the acetic acid aqueous solution or formic acid aqueous solution to obtain a chitosan solution with a mass fraction of 1%-3%, i.e. coating B;

[0015] (4) Preparation of degradable oil-proof paper

[0016] The paper is immersed in the coating A solution for 30s-120s, then hung in an oven at 80-100°C to dry for 20min-40min, and this step is repeated 2-5 times; then immersed in the coating B solution for 30s-120s, hung in an oven at 80°C-100°C to dry for 20min-40min, and repeated 1-3 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0017] Furthermore, in step (1), the mass of the palygorskite particles is 0.8 g-1.5 g; the amount of dopamine is 100 mg-150 mg; the pH range is 7.5-8.5; and the reaction time is 12 h-15 h.

[0018] Furthermore, the mass of palygorskite particles is 1.0 g, dopamine is 100 mg, pH is 8.5, and the reaction time is 12 h.

[0019] Furthermore, in step (2), the amount of polydopamine-modified palygorskite is 0.5 g, the mass of emulsified silicone oil is 1 g, and the amount of glutaraldehyde solution added is 60 mg.

[0020] Furthermore, in step (3), the molecular weight of chitosan is 500 kDa-1000 kDa, and the mass fraction is 1%; the content of formic acid or acetic acid in the formic acid aqueous solution or the acetic acid aqueous solution is 2%.

[0021] Furthermore, the paper selected in step (4) is filter paper, cardboard, corrugated paper, kraft paper or paperboard.

[0022] Furthermore, in step (4), the immersion time of coating A and coating B is 1 min respectively, the temperature in the oven is 100° C., and the drying time is 30 min; the number of immersions in the coating A solution is 3 times.

[0023] Beneficial effects of the present invention:

[0024] The present invention uses polydopamine to modify palygorskite, which helps to reduce the electrostatic effect and hydrogen bond adsorption between palygorskite crystals and improve its dispersibility; at the same time, amino groups are introduced into the surface, which can react with glutaraldehyde to form a Schiff base, so that the palygorskite forms a solid mesh structure. Emulsified silicone oil can be stored in the mesh grid, and the capillary force of the micropores also helps to fix the stored emulsified silicone oil to form an oil-proof layer. Excess glutaraldehyde can also react with chitosan to form a solid chitosan shell to protect the emulsified silicone oil oil-proof layer. Both palygorskite and chitosan are natural materials, environmentally friendly and non-toxic. Chitosan can be degraded under natural conditions. The oil-proof paper obtained by the present invention has a room temperature oil-proof performance KIT>9, a 70°C hot oil oil-proof performance KIT>5, and mechanical properties such as the tensile index and tear index of the paper are also improved. DETAILED DESCRIPTION

[0025] In order to clearly illustrate the technical features of this solution, the present invention is described in detail below through specific implementation methods. The scope of the present invention is not limited to the following embodiments. Professionals in the field can understand that various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention.

[0026] The instruments, reagents, materials, etc. involved in the following embodiments, unless otherwise specified, are all conventional instruments, reagents, materials, etc. in the prior art and can be obtained through regular commercial channels. The experimental methods, detection methods, etc. involved in the following embodiments, unless otherwise specified, are all conventional experimental methods, detection methods, etc. in the prior art.

[0027] Example 1

[0028] A method for preparing fluorine-free biodegradable oil-proof packaging paper, comprising the following steps:

[0029] Step 1: Weigh 1.0g of palygorskite and disperse it in 50ml Tris solution at pH 8.5, use ultrasonic disperser to sonicate for 30min, add 100mg dopamine, stir magnetically, and react for 12h. Then centrifuge at a speed of 8000r / min for 5min. Wash twice with deionized water and dry to obtain polydopamine-modified palygorskite particles;

[0030] Step 2: Add 0.5 g of the modified palygorskite particles obtained in step 1 into a beaker, then add 24.5 mL of deionized water, and ultrasonically disperse for 30 min. Add 1 g of emulsified silicone oil and 60 mg of glutaraldehyde solution, and stir magnetically to fully mix the solution. In this step, coating A is obtained;

[0031] Step 3: First prepare 50 ml of 2% acetic acid aqueous solution, then take 1 g of chitosan and dissolve it in the acetic acid aqueous solution to obtain a 2% chitosan solution. This step obtains coating B;

[0032] Step 4: Soak the filter paper in the coating A solution for 1 minute, then hang it in a 100°C oven to dry for 30 minutes, and repeat this step 4 times. Then immerse it in the coating B solution for 1 minute, hang it in a 100°C oven to dry for 30 minutes, and repeat this step 4 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0033] Example 2

[0034] A method for preparing fluorine-free biodegradable oil-proof packaging paper, comprising the following steps:

[0035] Step 1: Weigh 0.8g of palygorskite and disperse it in 50ml Tris solution at pH 7.5, use ultrasonic disperser to sonicate for 30min, add 80mg of dopamine, stir magnetically, and react for 15h. Then centrifuge at a speed of 10000r / min for 5min. Wash twice with deionized water and dry to obtain polydopamine-modified palygorskite particles;

[0036] Step 2: Add 0.8g of modified palygorskite particles obtained in step 1 into a beaker, add 24.5mL of deionized water, and ultrasonically disperse for 30min. Add 1.2g of emulsified silicone oil and 40mg of glutaraldehyde solution, stir magnetically, and mix the solution thoroughly. This step obtains coating A;

[0037] Step 3: First prepare 50 ml of 1.2% acetic acid aqueous solution, then take 1.2 g of chitosan and dissolve it in the acetic acid aqueous solution to obtain a 2.4% chitosan solution. This step obtains coating B;

[0038] Step 4: Soak the cardboard in the coating A solution for 40 seconds, then hang it in a 100°C oven to dry for 40 minutes, and repeat this step 5 times. Then immerse it in the coating B solution for 1 minute, hang it in a 100°C oven to dry for 30 minutes, and repeat this step 5 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0039] Example 3

[0040] A method for preparing fluorine-free biodegradable oil-proof packaging paper, comprising the following steps:

[0041] Step 1: Weigh 1.2g of palygorskite and disperse it in 50ml Tris solution of pH 8.0, use ultrasonic disperser to sonicate for 30min, add 150mg dopamine, stir magnetically, and react for 12h. Then centrifuge at a speed of 7000r / min for 5min. Wash twice with deionized water and dry to obtain polydopamine-modified palygorskite particles;

[0042] Step 2: Add 1.2 g of modified palygorskite particles obtained in step 1 into a beaker, add 24.5 mL of deionized water, and perform ultrasonic dispersion for 30 min. Add 1.5 g of glycerol and 48 mg of glutaraldehyde solution, stir magnetically, and mix the solution thoroughly. This step produces coating A;

[0043] Step 3: First prepare 50 ml of 1.5% formic acid aqueous solution, then take 2 g of chitosan and dissolve it in the formic acid aqueous solution to obtain a 4% chitosan solution. This step obtains coating B;

[0044] Step 4: Soak the corrugated paper in the coating A solution for 80 seconds, then hang it in a 100°C oven to dry for 40 minutes, and repeat this step 3 times. Then immerse it in the coating B solution for 80 seconds, hang it in a 100°C oven to dry for 40 minutes, and repeat this step 3 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0045] Example 4

[0046] A method for preparing fluorine-free biodegradable oil-proof packaging paper, comprising the following steps:

[0047] Step 1: Weigh 1.5g of palygorskite and disperse it in 50ml Tris solution of pH 9.0, use ultrasonic disperser to sonicate for 30min, add 200mg of dopamine, stir magnetically, and react for 12h. Then centrifuge at a speed of 6000r / min for 5min. Wash twice with deionized water and dry to obtain polydopamine-modified palygorskite particles;

[0048] Step 2: Add 1.5g of modified palygorskite particles obtained in step 1 into a beaker, then add 24.5mL of deionized water, and ultrasonically disperse for 30min. Add 2g of emulsified silicone oil and 70mg of glutaraldehyde solution, stir magnetically, and mix the solution thoroughly. This step obtains coating A;

[0049] Step 3: First prepare 50 ml of 1.8% formic acid aqueous solution, then take 1.8 g of chitosan and dissolve it in the formic acid aqueous solution to obtain a 3.6% chitosan solution. This step obtains coating B;

[0050] Step 4: Soak the filter paper in the coating A solution for 1 minute, then hang it in a 100°C oven to dry for 30 minutes, and repeat this step 3 times. Then immerse it in the coating B solution for 1 minute, hang it in a 100°C oven to dry for 30 minutes, and repeat this step 3 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0051] Example 5

[0052] A method for preparing fluorine-free biodegradable oil-proof packaging paper, comprising the following steps:

[0053] Step 1: Weigh 1.8g of palygorskite and disperse it in 50ml Tris solution at pH 8.5, use ultrasonic disperser to sonicate for 30min, add 180mg of dopamine, stir magnetically, and react for 12h. Then centrifuge at a speed of 7000r / min for 5min. Wash twice with deionized water and dry to obtain polydopamine-modified palygorskite particles;

[0054] Step 2: Add 1.8g of modified palygorskite particles prepared in step 1 into a beaker, add 24.5mL of deionized water, and ultrasonically disperse for 30min. Add 1.6g of emulsified silicone oil and 90mg of glutaraldehyde solution, stir magnetically, and mix the solution thoroughly. This step obtains coating A;

[0055] Step 3: First prepare 50 ml of 3% acetic acid aqueous solution, then take 2.2 g of chitosan and dissolve it in the acetic acid aqueous solution to obtain a 4.4% chitosan solution. This step obtains coating B;

[0056] Step 4: Soak the filter paper in the coating A solution for 120 seconds, then hang it in a 100°C oven to dry for 30 minutes, and repeat this step twice. Then immerse it in the coating B solution for 120 seconds, hang it in a 100°C oven to dry for 30 minutes, and repeat this step twice to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

[0057] The fluorine-free, biodegradable and oil-proof packaging paper prepared in the above embodiments has been tested to have a room temperature oil-proof performance KIT>9 and a 70°C hot oil-proof performance KIT>5.

[0058] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any substitution, improvement or change made to the implementation manner of the present invention falls within the protection scope of the present invention.

[0059] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A method for preparing fluorine-free, degradable and oil-proof packaging paper, characterized in that: The steps are as follows: (1) Modification of palygorskite Weigh 0.5g-2g of palygorskite and disperse it in 50ml Tris solution with pH 7.5-9.0, and perform ultrasonic dispersion for 30min; add 50mg-200mg dopamine, stir magnetically, and react for 8h-24h; then centrifuge for 5min, with the speed controlled at 6000r / min-10000r / min; wash twice with deionized water, and obtain polydopamine-modified palygorskite particles after drying; (2) Preparation of coating A Take 0.5 g to 2 g of the polydopamine-modified palygorskite particles prepared in step (1), add 24.5 mL of deionized water, and ultrasonically disperse for 30 min; add 0.6 g to 2 g of emulsified silicone oil or glycerol and 3% to 7% of glutaraldehyde solution by weight of palygorskite, stir magnetically, and mix the solution thoroughly to obtain coating A; (3) Preparation of coating B Prepare 50 ml of 2%-5% acetic acid aqueous solution or formic acid aqueous solution, take 1 g of chitosan and dissolve it in the acetic acid aqueous solution or formic acid aqueous solution to obtain a chitosan solution with a mass fraction of 1%-3%, i.e. coating B; (4) Preparation of degradable oil-proof paper The paper is immersed in the coating A solution for 30s-120s, then hung in an oven at 80-100°C to dry for 20min-40min, and this step is repeated 2-5 times; then immersed in the coating B solution for 30s-120s, hung in an oven at 80°C-100°C to dry for 20min-40min, and repeated 1-3 times to obtain palygorskite-based fluorine-free biodegradable oil-proof paper.

2. The method for preparing fluorine-free, degradable and oil-proof packaging paper according to claim 1, characterized in that: In step (1), the mass of palygorskite particles is 0.8g-1.5g; the amount of dopamine is 100mg-150mg, the pH range is 7.5-8.5, and the reaction time is 12h-15h.

3. The method for preparing the fluorine-free, degradable and oil-proof packaging paper according to claim 2, characterized in that: The mass of palygorskite particles is 1.0 g, dopamine is 100 mg, pH is 8.5, and the reaction time is 12 h.

4. The method for preparing fluorine-free, degradable and oil-proof packaging paper according to claim 1, characterized in that: In step (2), the mass of polydopamine-modified palygorskite is 0.5 g, the mass of emulsified silicone oil is 1 g, and the amount of glutaraldehyde solution added is 60 mg.

5. The method for preparing fluorine-free, degradable and oil-proof packaging paper according to claim 1, characterized in that: In step (3), the molecular weight of chitosan is 500kDa-1000kDa, and the mass fraction is 1%; the content of formic acid or acetic acid in the formic acid aqueous solution or the acetic acid aqueous solution is 2%.

6. The method for preparing fluorine-free, degradable and oil-proof packaging paper according to claim 1, characterized in that: The paper selected for use in step (4) is filter paper, cardboard, corrugated paper, kraft paper or cardboard.

7. The method for preparing fluorine-free, degradable and oil-proof packaging paper according to claim 1, characterized in that: In step (4), the immersion time of coating A and coating B is 1 min respectively, the temperature in the oven is 100° C., and the drying time is 30 min; the number of immersions in the coating A solution is 3 times.