Preparation method of packaging paper

Abstract

The invention relates to a preparation method of paper, in particular to a preparation method of packaging paper. According to the invention, the paraffin hollow microspheres are prepared to replace traditional paraffin, and the paraffin hollow microspheres are coated on the surface of the raw paper, so that micropores of the paraffin hollow microspheres are utilized to realize a ventilation function, the ventilation performance of the packaging paper is improved on the basis of ensuring the waterproof and oil-proof functions, and the strength of the packaging paper is further improved through compounding of the aluminized BOPP film.

Description

Technical Field

[0001] The invention relates to a method for preparing paper, in particular to a method for preparing packaging paper. Background Art

[0002] As an important medium for product protection and display, wrapping paper has a wide range of applications, covering almost all areas of products that require packaging. From food and daily necessities to electronic products and artworks, wrapping paper, with its varied materials, rich colors and patterns, provides the necessary physical protection for products and greatly enhances the market appeal and added value of products. Especially in the modern consumer market, wrapping paper not only carries the basic information of the product, but also becomes an important means to convey brand culture and stimulate consumers' desire to buy. Whether it is exquisite gift packaging, convenient express packaging, or environmentally friendly degradable packaging, wrapping paper plays an irreplaceable role in the circulation and consumption of goods with its unique charm and practicality.

[0003] In many application fields of packaging paper, water and oil resistance is often a crucial technical indicator. Especially in the field of food packaging, such as fast food, baked food, fried food, etc., because the food itself may contain oil or moisture, and the environmental humidity and temperature changes during transportation and storage, the packaging paper must have excellent water and oil resistance. Water and oil resistance can not only protect food from external environmental pollution, extend the shelf life and freshness of food, but also keep the inside of the package clean and enhance the consumer experience. Therefore, the development of packaging paper with efficient water and oil resistance has become the key to meeting market demand and improving product competitiveness.

[0004] As a common waterproof and oil-proof agent, paraffin is often used to enhance the waterproof and oil-proof properties of packaging paper. However, although applying paraffin on the surface of packaging paper can improve its waterproof and oil-proof ability to a certain extent, it often leads to a decrease in air permeability. This is because the paraffin coating will cover the pores and fiber structure on the surface of the packaging paper during the formation process, forming a relatively dense film. Although this film can effectively block the penetration of water and grease, it also hinders the permeation of gas, resulting in a decrease in the air permeability of the packaging paper. To this end, the applicant tried to use paraffin hollow microspheres to coat the surface of the base paper, and use hot pressing treatment so that the paraffin microspheres can better penetrate and fix in the paper, and can also improve the flatness and tightness of the paper. However, the applicant found that the above scheme makes the paraffin hollow microspheres reduce the bonding force between the base paper fibers, thereby causing a decrease in the strength of the paper. Especially in packaging applications that need to maintain a certain air permeability and strength, such as the packaging of fresh fruits and vegetables, and the packaging of commodities that need to bear a certain weight, the decrease in air permeability and strength caused by the paraffin hollow microsphere coating may become a key factor restricting its application. Therefore, how to ensure the waterproof and oil-proof properties while taking into account the air permeability and strength of the packaging paper has become an important issue that needs to be urgently solved in current packaging technology. Summary of the invention

[0005] In order to solve the above technical problems, the present invention prepares hollow paraffin microspheres to replace traditional paraffin, and coats them on the surface of base paper, thereby utilizing the micropores of the hollow paraffin microspheres to achieve a breathable function, thereby improving the breathability of the packaging paper while ensuring the waterproof and oil-proof functions, and further improving the strength of the packaging paper by compounding with an aluminum-plated BOPP film.

[0006] Specifically, the present invention provides a method for preparing packaging paper, which comprises the following steps: (1) preparing hollow paraffin microspheres: mixing paraffin, surfactant, foaming agent and solvent in a mass ratio of 3-7:0.3-0.7:0.05-0.15:30-70, dispersing by ultrasonic wave, and then performing rotary evaporation to volatilize the solvent to form hollow paraffin microspheres; (2) Treating the natural color base paper: calendering the natural color base paper, and then immersing the natural color base paper in a suspension containing the above-mentioned hollow paraffin microspheres; (3) Hot pressing treatment: hot pressing the impregnated natural base paper; (4) Composite treatment: The natural color base paper after heat pressing treatment and the aluminum-coated BOPP film are corona treated and then composited, and then vacuum dried to obtain the packaging paper.

[0007] Specifically, in step (1), the paraffin wax is food grade paraffin wax with a melting point range of 55-65°C and a purity of not less than 90%; the solvent is xylene or toluene; the surfactant is a non-ionic surfactant, such as polyoxyethylene ether; and the foaming agent is azodicarbonamide (ADC).

[0008] Specifically, in step (1), the power range of ultrasonic dispersion is 50-200 W, and the time is 10-30 minutes; the temperature range of rotary evaporation is 40-80° C., the speed range is 50-200 rpm, and the time range is 1-5 hours.

[0009] Specifically, the particle size of the paraffin hollow microspheres formed in step (1) is 2-10 μm.

[0010] Specifically, the preparation method of the suspension of paraffin hollow microspheres is: adding the paraffin hollow microspheres and an appropriate amount of dispersant into deionized water, and then using a high-speed stirrer to fully stir until a uniform suspension is formed; the dispersant is sodium carboxymethyl cellulose or polyvinyl alcohol, and its amount is 0.5-2% of the mass of the paraffin hollow microspheres; the mass concentration of the paraffin hollow microspheres in the suspension is 1-10%.

[0011] Specifically, in step (2), the natural color base paper is immersed for 2-6 minutes and immersed 1-4 times.

[0012] Specifically, in step (3), the temperature range of the hot pressing treatment is 140-180° C., the pressure range is 0.3-2.0 MPa, and the time range is 20-60 seconds.

[0013] Specifically, in step (4), the voltage range of the corona treatment is 1-5 kV, and the treatment time is 3-20 seconds.

[0014] Specifically, the thickness of the aluminized BOPP film is 0.01-0.03 mm, and the porosity is 10-20%.

[0015] Specifically, in step (4), the vacuum drying temperature ranges from 40 to 80° C. and the drying time ranges from 0.5 to 5 hours.

[0016] Compared with the prior art, the present invention has the following advantages: Firstly, hollow paraffin microspheres are prepared to replace traditional paraffin, and the paraffin hollow microspheres are coated on the surface of base paper, so that the micropores of the hollow paraffin microspheres are used to achieve air permeability, thereby improving the air permeability of the packaging paper while ensuring the waterproof and oil-proof functions of the packaging paper.

[0017] Secondly, the hot pressing treatment of the present invention not only helps the hollow paraffin microspheres to penetrate and fix better in the paper, but also improves the flatness and tightness of the paper. In order to solve the problem of reduced strength, the present invention improves the strength of the packaging paper by compounding the aluminum-plated BOPP film, and improves the glossiness and aesthetics of the packaging paper.

[0018] In addition, the corona treatment of the present invention can enhance the adhesion between the aluminized BOPP film and the natural color base paper layer, providing good conditions for the subsequent composite steps. DETAILED DESCRIPTION

[0019] Embodiment 1: A method for preparing packaging paper, the specific steps are as follows: Preparation of hollow paraffin microspheres: Food-grade paraffin (melting point 60°C, purity 92%), polyoxyethylene ether surfactant, azodicarbonamide (ADC) foaming agent and xylene solvent were mixed in a mass ratio of 5:0.5:0.1:50.

[0020] Ultrasonic dispersion was performed at a power of 100 W for 20 minutes, and then rotary evaporation was performed at a speed of 100 rpm at 60° C. for 3 hours to form paraffin hollow microspheres with a particle size of about 5 μm.

[0021] Processing of natural paper: The natural base paper is calendered and then immersed in a suspension containing the above-mentioned hollow paraffin microspheres, wherein the suspension is prepared from hollow paraffin microspheres, sodium carboxymethyl cellulose dispersant (the amount used is 1% of the mass of the hollow paraffin microspheres) and deionized water, and the mass concentration of the hollow paraffin microspheres is 5%.

[0022] The dipping time was 4 minutes and the dipping frequency was 2 times.

[0023] Heat pressing treatment: The impregnated natural base paper was hot pressed at 160° C. and a pressure of 1.0 MPa for 40 seconds.

[0024] Composite treatment: The natural base paper after heat pressing and the aluminum-coated BOPP film with a thickness of 0.02 mm and a porosity of 15% were subjected to corona treatment at a voltage of 3 kV and a treatment time of 10 seconds.

[0025] After the two were combined, they were vacuum dried at 60°C for 2 hours.

[0026] Embodiment 2: A method for preparing packaging paper, the specific steps are as follows: Preparation of hollow paraffin microspheres: Food-grade paraffin (melting point 58° C., purity 95%), a nonionic surfactant, azodicarbonamide (ADC) and toluene solvent were mixed in a mass ratio of 7:0.7:0.15:40.

[0027] Ultrasonic dispersion was performed at a power of 150 W for 25 minutes, and then rotary evaporation was performed at a speed of 150 rpm at 70° C. for 4 hours to form paraffin hollow microspheres with a particle size of about 8 μm.

[0028] Processing of natural paper: After calendering, the natural base paper is immersed in a suspension containing the above-mentioned hollow paraffin microspheres. The suspension is prepared from hollow paraffin microspheres, polyvinyl alcohol dispersant (the amount used is 1.5% of the mass of the hollow paraffin microspheres) and deionized water. The mass concentration of the hollow paraffin microspheres is 8%.

[0029] The immersion time was 6 minutes and the immersion frequency was 1 time.

[0030] Heat pressing treatment: The impregnated natural base paper was hot pressed at 170°C and a pressure of 1.5 MPa for 30 seconds.

[0031] Composite treatment: The natural color base paper after heat pressing and the aluminum-coated BOPP film with a thickness of 0.02 mm and a porosity of 15% were subjected to corona treatment with a voltage of 4 kV and a treatment time of 15 seconds.

[0032] After compounding, the composite was dried in vacuum at 70°C for 1.5 hours.

[0033] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the traditional paraffin coating method is used to replace the paraffin hollow microspheres.

[0034] Comparative Example 2 The difference between Comparative Example 1 and Example 1 is that the composite aluminized BOPP film has a thickness of 0.05 mm and a porosity of 15%.

[0035] Comparative Example 3 The difference between Comparative Example 1 and Example 1 is that the composite aluminized BOPP film has a thickness of 0.02 mm and a porosity of 5%.

[0036] Characterization In order to comprehensively evaluate the performance of the packaging paper of the present invention, the following characterization methods were used and tested under specific conditions. All tests were conducted under standard laboratory conditions to ensure the accuracy and repeatability of the test results.

[0037] Waterproof and oilproof performance test: Characterization method: Use standard water drop and oil drop test method. Drop a certain amount of water drop and oil drop on the surface of the packaging paper, observe and record their penetration.

[0038] Characterization conditions: The volume of water droplets and oil droplets is 0.1 mL. After dropping, let it stand for 5 minutes and observe the penetration.

[0039] Air permeability test: Characterization method: The air permeability of the packaging paper was measured using an air permeability tester.

[0040] Characterization conditions: test temperature is 25°C, relative humidity is 50%, and test pressure is 100kPa.

[0041] Strength performance test: Characterization method: Tensile strength and tear strength were tested separately using a universal material testing machine.

[0042] Characterization conditions: tensile speed 100 mm / min, tearing speed 50 mm / min, sample size 150 mm × 25 mm.

[0043] The specific characterization data are shown in the following table: Table 1 Characterization results of different embodiments and comparative examples Waterproof test Oil resistance test Air permeability / mL / min Tensile strength / MPa Tear strength / N / mm Example 1 none none 2014 45 8 Example 2 none none 1895 48 7.5 Comparative Example 1 none none 560 43 8.6 Comparative Example 2 none none 1229 51 8.5 Comparative Example 3 none none 1099 48 7 Combined with the data in Table 1, it can be seen that the method adopted by the present invention can improve the air permeability of the packaging film on the basis of ensuring the waterproof and oil-proof performance, and has a certain strength and has a high application potential.

Claims

1. A method for preparing packaging paper, characterized in that The following steps are involved: (1) preparing hollow paraffin microspheres: mixing paraffin, surfactant, foaming agent and solvent in a mass ratio of 3-7:0.3-0.7:0.05-0.15:30-70, dispersing by ultrasonic wave, and then performing rotary evaporation to volatilize the solvent to form hollow paraffin microspheres; (2) Treating the natural color base paper: calendering the natural color base paper, and then immersing the natural color base paper in a suspension containing the above-mentioned hollow paraffin microspheres; (3) Hot pressing treatment: hot pressing the impregnated natural base paper; (4) Composite treatment: The natural color base paper after heat pressing treatment and the aluminum-coated BOPP film are corona treated and then composited, and then vacuum dried to obtain the packaging paper.

2. The method for preparing the packaging paper according to claim 1, characterized in that In step (1), the paraffin is food grade paraffin with a melting point range of 55-65°C and a purity of not less than 90%; the solvent is xylene or toluene; the surfactant is a non-ionic surfactant; and the foaming agent is azodicarbonamide (ADC).

3. The method for preparing the packaging paper according to claim 1, characterized in that In step (1), the power range of ultrasonic dispersion is 50-200 W, and the time range is 10-30 minutes; the temperature range of rotary evaporation is 40-80° C., the speed range is 50-200 rpm, and the time range is 1-5 hours.

4. The method for preparing the packaging paper according to claim 1, characterized in that The particle size of the paraffin hollow microspheres formed in step (1) is 2-10 μm.

5. The method for preparing packaging paper according to claim 1, characterized in that The preparation method of the suspension of paraffin hollow microspheres is as follows: the paraffin hollow microspheres and an appropriate amount of dispersant are added into deionized water, and then fully stirred with a high-speed stirrer until a uniform suspension is formed; the dispersant is sodium carboxymethyl cellulose or polyvinyl alcohol, and the amount thereof is 0.5-2% of the mass of the paraffin hollow microspheres; the mass concentration of the paraffin hollow microspheres in the suspension is 1-10%.

6. The method for preparing packaging paper according to claim 1, characterized in that In step (2), the impregnation time of the natural color base paper is 2-6 minutes, and the number of impregnations is 1-4 times.

7. The method for preparing packaging paper according to claim 1, characterized in that In step (3), the temperature range of the hot pressing treatment is 140-180°C, the pressure range is 0.3-2.0 MPa, and the time range is 20-60 seconds.

8. The method for preparing packaging paper according to claim 1, characterized in that In step (4), the voltage range of the corona treatment is 1-5 kV, and the treatment time is 3-20 seconds.

9. The method for preparing packaging paper according to claim 1, characterized in that The aluminized BOPP film has a thickness of 0.01-0.03 mm and a porosity of 10-20%.

10. The method for preparing packaging paper according to claim 1, characterized in that In step (4), the vacuum drying temperature ranges from 40 to 80° C. and the drying time ranges from 0.5 to 5 hours.