Environmentally friendly high-barrier packaging paper and method for preparing the same

Abstract

The application discloses an environment-friendly high-barrier packaging paper and a preparation method thereof, and belongs to the technical field of paper product manufacturing. The method comprises the following steps: dispersing bleached kraft softwood pulp in a TEMPO and NaBr aqueous solution, adding NaClO solution and adjusting pH to perform reaction, washing and high-pressure homogenization of a product obtained through the reaction to obtain TEMPO-oxidized nanocellulose (TOCNF); mixing bleached kraft softwood chemical pulp, hardwood pulp and viscose fibers, performing beating and papermaking to obtain original paper; then mixing the TOCNF and water-based epoxy-modified acrylic emulsion to obtain a mixed coating; and finally coating the coating on the surface of the original paper according to a certain mass ratio, and performing hot-pressing and curing to obtain the environment-friendly high-barrier packaging paper. The packaging paper has excellent mechanical properties, strong barrier property, good surface evenness and printing property, and is environment-friendly, biodegradable, simple to prepare and low in cost.

Description

Technical Field

[0001] This invention belongs to the technical field of paper product manufacturing, specifically relating to an environmentally friendly high-barrier packaging paper and its preparation method. Background Technology

[0002] Packaging materials play a crucial role in protecting products from external environmental influences. As consumers increasingly demand higher product quality, packaging materials need to possess excellent barrier properties against substances such as water vapor, oxygen, oils, and volatile organic compounds.

[0003] Currently, most common packaging materials are lightweight, inexpensive, corrosion-resistant, and mechanically strong petroleum-based plastics. These materials have significant drawbacks, such as poor biodegradability and difficulty in recycling, which seriously impacts sustainable development and human health. While using paper packaging materials as alternatives can reduce environmental pollution and the consumption of non-renewable resources, ordinary paper materials have poor barrier properties, failing to prevent the penetration of oxygen, water vapor, and grease, making it difficult to guarantee the preservation quality of the contents. Furthermore, ordinary paper packaging materials have relatively low mechanical strength, making them prone to tearing, punctures, and other damage when holding heavy or sharp products, thus limiting their application range.

[0004] Therefore, there is a need to provide a method for preparing environmentally friendly packaging paper materials with excellent mechanical properties and high barrier properties. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to overcome the deficiencies of paper packaging materials, such as poor barrier properties and mechanical properties, and to provide a method for preparing environmentally friendly high-barrier packaging paper.

[0006] To achieve the above objectives, the present invention discloses the following technical solutions: In a first aspect, the present invention provides a method for preparing environmentally friendly high-barrier packaging paper, the method comprising the following steps: (1) Bleached sulfate softwood pulp was dispersed in an aqueous solution of TEMPO and NaBr to obtain a fiber / TEMPO / NaBr system. NaClO solution and NaOH solution were added to the system to adjust the pH of the solution so that the reaction could be fully carried out and the reaction product was obtained. The product was washed and homogenized under high pressure to obtain TEMPO oxidized nanocellulose. (2) Bleached sulfate softwood chemical pulp, bleached sulfate hardwood pulp and viscose fiber are mixed at an oven-dry fiber mass ratio of (70-75):(20-30):5, and the raw paper is obtained through pulping, pulping, papermaking, pressing and drying steps. (3) Mix the TEMPO oxidized nanocellulose obtained in step (1) with the waterborne epoxy modified acrylic emulsion and stir evenly to obtain the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating. (4) The waterborne epoxy modified acrylic emulsion-TOCNF mixed coating obtained in step (3) is uniformly coated on the surface of the paper obtained in step (2). After coating, the paper sample is hot-pressed and cured to obtain the environmentally friendly high barrier packaging paper.

[0007] Preferably, in step (1), the mass ratio of bleached sulfate softwood pulp oven-dried fiber, TEMPO and NaBr is 1:(0.012-0.016):(0.08-0.10).

[0008] More preferably, in step (1), the mass ratio of bleached sulfate softwood pulp oven-dried fiber, TEMPO and NaBr is 1:0.016:0.1.

[0009] Preferably, in step (1), NaOH solution is added to adjust the pH of the system to 10.0 to 10.5.

[0010] More preferably, in step (1), NaOH solution is added to adjust the pH of the system to 10.0.

[0011] Preferably, the amount of NaClO solution added in step (1) is calculated according to the mass-volume ratio of bleached sulfate softwood pulp oven-dried fiber to NaClO solution of 1:6.67 g / mL; The active chlorine content in the NaClO solution is 6-14%.

[0012] Preferably, the washing in step (1) involves washing with deionized water three or more times until no other liquid residue remains.

[0013] Preferably, in step (1), the homogenization pressure of high-pressure homogenization is 50-70 MPa, and the number of homogenization cycles is 5-10.

[0014] Preferably, the degree of dissolution of the bleached sulfate softwood chemical pulp and the bleached sulfate hardwood pulp in step (2) is 55-60°SR.

[0015] Preferably, the mass concentration of the waterborne epoxy-modified acrylic emulsion in step (3) is 30%; In step (3), TEMPO oxidized nanocellulose and waterborne epoxy modified acrylic emulsion are mixed at a content mass ratio of (5-7):1 and stirred at 15-40℃ and 450-550r / min for 5-20min to obtain the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating.

[0016] Preferably, in step (4), the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating is applied to the surface of the original paper at a mass ratio of (10-13):60.

[0017] More preferably, the waterborne epoxy-modified acrylic emulsion-TOCNF mixed coating is applied to the surface of the original paper at a mass ratio of 12:60.

[0018] Preferably, the hot-press curing temperature in step (4) is 95-105°C and the hot-pressing time is 15-20 min.

[0019] More preferably, the hot-press curing temperature in step (4) is 105°C and the hot-pressing time is 15 min.

[0020] In a second aspect, the present invention provides an environmentally friendly high-barrier packaging paper, which is prepared by the preparation method described in the first aspect.

[0021] The present invention has the following advantages and effects compared with the prior art: (1) This invention provides an environmentally friendly high-barrier packaging paper, which is mainly composed of softwood fiber, hardwood fiber, viscose fiber and water-based epoxy modified acrylic emulsion-TOCNF mixed coating. The high-barrier packaging paper has excellent mechanical properties and gas barrier properties, and can effectively resist the penetration of water vapor, oxygen and other substances. At the same time, the raw materials meet the requirements of green environmental protection and natural degradation. (2) The present invention has the advantages of simple overall manufacturing method, low processing cost and quick processing, which improves the operability of preparing high barrier paper packaging with high barrier performance and mechanical properties, which is efficient, economical and environmentally friendly, and the resulting packaging material can meet the needs of many packaging scenarios. (3) This invention uses various fiber blends to make paper and TEMPO oxidized nanocellulose TOCNF as a coating material. TOCNF is rich in functional groups such as hydroxyl and carboxyl groups and has excellent mechanical properties, which helps to improve the tensile strength, tear resistance and other properties of packaging paper and improve the durability of packaging. Attached Figure Description

[0022] To further understand the present invention, the invention will be described in more detail below with reference to the accompanying drawings: Figure 1 This is a comparison chart of the water vapor transmission rate of the barrier packaging paper prepared in Example 1 and Comparative Examples 1-3; Figure 2The image shows a comparison of the screen printing performance of the barrier packaging paper prepared in Example 1 and Comparative Examples 1 and 3, where from left to right are Comparative Example 1, Comparative Example 3, and Example 1. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0024] Unless otherwise specified, the experimental methods described in the following examples are generally performed under standard experimental conditions. Unless otherwise stated, all reagents and raw materials used in this invention are commercially available.

[0025] In the following examples, unless otherwise specified, all figures are by mass; all raw materials used are commercially available, and conventional equipment is employed.

[0026] TEMPO (≥98%), NaOH (≥97%), NaBr (≥99%), NaClO sodium hypochlorite solution (6-14% active chlorine basis), and anhydrous ethanol (≥99.5%) used were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd. The waterborne epoxy-modified acrylic emulsion used was purchased from Wanhua New Materials Co., Ltd., with a mass concentration of 30%.

[0027] Preparation of Example 1 1. Preparation of TEMPO-oxidized cellulose nanoparticles (TOCNF) 1.1 Weigh 0.16g TEMPO and 1.0g NaBr respectively and add them to 500mL of deionized water. Stir until the drugs are completely dissolved. Take 10g of bleached sulfate softwood pulp with an oven-dry fiber mass and disperse it in the TEMPO / NaBr aqueous solution to obtain the fiber / TEMPO / NaBr system. 1.2 Add 66.7 mL of NaClO solution to the fiber / TEMPO / NaBr system and stir. Then add 0.5 mol / L NaOH solution to adjust the pH of the solution to about 10.0 until it no longer changes. Stir the reaction for 5 h. After completion, add 100 mL of anhydrous ethanol to terminate the reaction. Centrifuge to obtain the reaction product. 1.3 The product was centrifuged and washed three times with deionized water. The washed oxidized cellulose was homogenized 10 times with a high pressure homogenizer at a pressure of 60 MPa to obtain a uniformly dispersed TEMPO oxidized nanocellulose (TOCNF) solution, wherein the mass fraction of TEMPO oxidized nanocellulose in the solution was 1.0%.

[0028] 2. Environmentally friendly high-barrier packaging paper 2.1 Weigh a certain mass of bleached sulfate softwood pulp and bleached sulfate hardwood pulp boards. After soaking, loosening, and balancing the moisture content of the pulp boards, adjust the pulp concentration to 10%. Use a PFI disc mill to increase the pulp freeness to 60°SR. Weigh out the beaten bleached sulfate softwood chemical pulp, bleached sulfate hardwood pulp, and viscose fiber separately and mix them. The mass ratio of the three raw materials is 75:20:5 (octane dry fiber mass). Use a sheet forming machine to form sheets, and then perform press drying and constant temperature and humidity equilibration treatment to obtain a basis weight of 60 g / m³. 2 The base paper; 2.2 The aforementioned 1% TEMPO oxidized nanocellulose (TOCNF) solution and 30% waterborne epoxy modified acrylic emulsion were mixed at a content-to-content ratio of 5:1 and stirred at 500 r / min for 10 min at room temperature to obtain a waterborne epoxy modified acrylic emulsion-TOCNF mixed coating. 2.3 at 12g / m 2 The coating amount is determined by uniformly coating the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating from step 2.2 onto the surface of the base paper obtained in step 2.1 using a coating machine. After coating, the paper sample is placed in a hot press and hot-pressed at 105°C for 15 minutes to cure the coating and obtain environmentally friendly high-barrier packaging paper.

[0029] Preparation of Example 2 The preparation method of Example 1 is as follows: The difference from Example 1 is that the mass ratio of the three raw materials in step 2.1, namely bleached sulfate softwood chemical pulp, bleached sulfate hardwood pulp and viscose fiber, is adjusted to 70:25:5 of oven-dry fiber mass. The other steps, parameters and conditions are the same as in Example 1.

[0030] Preparation of Example 3 The preparation method of Example 1 is as follows: The difference from Example 1 is that the mass ratio of the three raw materials in step 2.1, namely bleached sulfate softwood chemical pulp, bleached sulfate hardwood pulp and viscose fiber, is adjusted to 70:30:0 of ​​oven-dried fiber mass. The other steps, parameters and conditions are the same as in Example 1.

[0031] Preparation of Example 4 The preparation method of Example 1 is the same as that of Example 1. The difference is that the mass ratio of TEMPO oxidized nanocellulose (TOCNF) solution to the contents of aqueous epoxy modified acrylic emulsion in step 2.2 is adjusted to 6:1. The parameters and conditions of the other steps are the same as those of Example 1.

[0032] Preparation of Example 5 The preparation method of Example 1 is the same as that of Example 1. The difference is that the mass ratio of TEMPO oxidized nanocellulose (TOCNF) solution to aqueous epoxy modified acrylic emulsion in step 2.2 is adjusted to 7:1. The parameters and conditions of the remaining steps are the same as those of Example 1.

[0033] Preparation of Example 6 The preparation method is the same as in Example 1: the difference is that the coating amount of the waterborne epoxy-modified acrylic emulsion-TOCNF mixed coating in step 2.3 is adjusted to 6 g / m². 2 The remaining steps, parameters, and conditions are the same as in Example 1.

[0034] Preparation of Example 7 The preparation method is the same as in Example 1: the difference is that the coating amount of the waterborne epoxy-modified acrylic emulsion-TOCNF mixed coating in step 2.3 is adjusted to 9 g / m². 2 The remaining steps, parameters, and conditions are the same as in Example 1.

[0035] Preparation of Comparative Example 1 The quantitative 60 g / m³ prepared according to step 2.1 of Example 1 2 The paper.

[0036] Preparation of Comparative Example 2 The preparation method is the same as in Example 1: the difference is that it is prepared at 12 g / m 2 The coating amount is directly obtained by uniformly coating the TEMPO oxidized nanocellulose solution onto the paper surface obtained in step 2.1 using a coating machine. After coating, the paper sample is placed in a hot press and hot-pressed at 105℃ for 15 min to obtain TOCNF surface-coated paper.

[0037] Preparation of Comparative Example 3 The preparation method is the same as in Example 1: the difference is that it is prepared at 12 g / m 2 The coating amount is directly applied by uniformly coating the waterborne epoxy modified acrylic emulsion onto the surface of the paper obtained in step 2.1 using a coating machine. After coating, the paper sample is placed in a hot press and hot-pressed at 105℃ for 15 min to obtain the waterborne epoxy modified acrylic emulsion surface coated paper.

[0038] Preparation of Comparative Example 4 The preparation method is the same as in Example 1: the difference from Example 1 is that, firstly, at 11.92 g / m 2 The TOCNF solution was evenly coated onto the paper surface obtained in step 2.1 using a coating machine. After coating, the paper sample was placed in a hot press and cured at 105°C for 15 minutes. Then, the solution was applied at a rate of 0.08 g / m². 2The coating amount was determined by uniformly coating the water-based epoxy-modified acrylic emulsion onto the surface of the TOCNF layer using a coating machine, placing it in a hot press, and curing it at 105℃ for 15 min to obtain the coating paper of Comparative Example 4.

[0039] Performance testing 1. Various mechanical properties were tested on the paper materials prepared in Examples 1-7 and Comparative Examples 1-4, including tensile strength (kN·m). -1 The tensile strength, elongation (%), bursting strength (kPa), and tear strength (mN) were tested. The tensile strength and elongation were tested according to GB / T 12914-2018 "Determination of Tensile Strength of Paper and Paperboard", the bursting strength was tested according to GB / T 6545 "Determination of Bursting Strength of Corrugated Board", and the tear strength was tested by three replicates. The average value of the test results was selected. The results are shown in Table 1.

[0040] 2. The surface uniformity (μm) and softness (mN) of the paper materials prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were tested. The experiment was repeated three times, and the average value of the test results was selected. The results are shown in Table 2.

[0041] 3. The air permeability (μm·(Pa·s)) of the paper materials prepared in Examples 1-7 and Comparative Examples 1-4 above was measured. -1 ) and water vapor transmission rate (g·(m 2 ·d) -1 The test results are shown in Table 3. Figure 1 .

[0042] 4. The printing performance of the paper materials prepared in Example 1 and Comparative Examples 1 and 3 was compared and tested. The results are shown in the figure. Figure 2 .

[0043] Table 1 Example 1 4.59 5.45 358.6 1069.3 Example 2 4.42 5.33 351.3 1032.6 Example 3 4.38 5.40 349.5 1030.3 Example 4 4.63 5.58 360.3 1073.6 Example 5 4.71 5.63 366.2 1075.5 Example 6 4.13 3.88 338.5 1009.3 Example 7 4.21 4.02 342.6 1023.3 Comparative Example 1 4.03 3.54 329.0 953.0 Comparative Example 2 5.32 6.85 356.1 1083.3 Comparative Example 3 4.68 5.01 374.3 1077.6 Comparative Example 4 5.01 6.05 359.7 1075.3 Table 2 Example 1 421 1.08 Example 2 425 1.07 Example 3 430 1.05 Example 4 421 1.05 Example 5 419 1.04 Example 6 424 1.23 Example 7 421 1.14 Comparative Example 1 425 1.37 Comparative Example 2 398 1.02 Comparative Example 3 593 1.04 Comparative Example 4 401 1.02 Table 3 Example 1 0.0181 18.7 Example 2 0.0195 23.8 Example 3 0.0212 27.6 Example 4 0.0299 43.9 Example 5 0.0283 60.2 Example 6 0.0833 49.5 Example 7 0.0626 37.7 Comparative Example 1 6.70 171.2 Comparative Example 2 0.486 169.3 Comparative Example 3 0.688 12.0 Comparative Example 4 0.594 143.6 Results analysis: Comparing Examples 1-7 with Comparative Example 1 (uncoated base paper), it can be seen that the coated packaging paper has significantly improved tensile strength, elongation, bursting strength and tear resistance, indicating that the coating of waterborne epoxy modified acrylic emulsion-TOCNF mixed coating effectively enhances the mechanical properties of the paper.

[0044] As the mass ratio of TOCNF to waterborne epoxy-modified acrylic emulsion increased from 5:1 in Example 1 to 7:1 in Example 5, the tensile strength increased from 4.59 kN·m. -1 Increased to 4.71 kN·m-1 The elongation increased from 5.45% to 5.63% and the bursting strength increased from 358.6 kPa to 366.2 kPa, showing a gradual upward trend. This indicates that increasing the TOCNF ratio can enhance the bonding force between the coating and the fiber, and further optimize the mechanical properties.

[0045] The air permeability of Examples 1-7 is much lower than that of Comparative Example 1, which has a permeability of 6.70 μm·(Pa·s). -1 This indicates that the mixed coating effectively blocked the pores of the paper and significantly reduced air permeability; among them, Example 1 had the lowest air permeability, reaching 0.0181 μm·(Pa·s). -1 This indicates 12g / m 2 The coating amount and the 5:1 coating ratio can form a dense barrier structure. The water vapor permeability of Example 1 is significantly reduced compared to Comparative Example 1, demonstrating the excellent waterproof vapor permeability of the mixed coating. Figure 1 It can be seen that the longer the time, the higher the water vapor permeability of the mixed coating.

[0046] The surface uniformity of Examples 1-7 is better than that of Comparative Example 3 (593 μm) and close to that of Comparative Example 2, indicating that the mixed coating retains the surface smoothness improvement effect of TOCNF while avoiding the surface roughness problem of emulsion coating alone. The softness of Examples 1-7 is better than that of Comparative Example 1, indicating that the coating treatment enhances performance without significantly reducing paper softness. Increasing the TOCNF ratio to 7:1 can further improve the softness to 1.04 mN. For details, please refer to the data in Example 5.

[0047] Depend on Figure 2 It can be seen that the screen printing effect of Example 1 is better than that of Comparative Example 1 (uncoated base paper) and Comparative Example 3 (emulsion coating alone). This shows that the surface uniformity formed by the mixed coating is higher and the compatibility between the coating and the ink is better, which can reduce printing defects such as missing prints and smudging.

[0048] In summary, this invention achieves a synergistic improvement in the mechanical, barrier, and surface properties of packaging paper by optimizing the fiber ratio of the base paper and using a mixed coating of TOCNF and water-based epoxy-modified acrylic emulsion. Compared with uncoated base paper and single-component coatings, the packaging paper prepared by this invention exhibits high tensile strength, excellent burst strength, low air permeability, low water vapor transmission rate, good surface uniformity, and printability. It solves the problems of poor barrier properties and insufficient mechanical properties in traditional paper packaging, while also using environmentally friendly raw materials, meeting the requirements of sustainable development.

[0049] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly high-barrier packaging paper, characterized in that, The preparation method includes the following steps: (1) Bleached sulfate softwood pulp was dispersed in an aqueous solution of TEMPO and NaBr to obtain a fiber / TEMPO / NaBr system. NaClO solution and NaOH solution were added to the system to adjust the pH of the solution so that the reaction could be fully carried out and the reaction product was obtained. The product was washed and homogenized under high pressure to obtain TEMPO oxidized nanocellulose. (2) Bleached sulfate softwood chemical pulp, bleached sulfate hardwood pulp and viscose fiber are mixed at an oven-dry fiber mass ratio of (70-75):(20-30):5, and the raw paper is obtained through pulping, pulping, papermaking, pressing and drying steps. (3) Mix the TEMPO oxidized nanocellulose obtained in step (1) with the waterborne epoxy modified acrylic emulsion and stir evenly to obtain the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating. (4) The waterborne epoxy modified acrylic emulsion-TOCNF mixed coating obtained in step (3) is uniformly coated on the surface of the paper obtained in step (2). After coating, the paper sample is hot-pressed and cured to obtain the environmentally friendly high barrier packaging paper. The mass fraction of the TEMPO-oxidized nanocellulose was 1.0%. In step (3), the mass concentration of the waterborne epoxy-modified acrylic emulsion is 30%. In step (3), TEMPO oxidized nanocellulose and waterborne epoxy modified acrylic emulsion are mixed at a content mass ratio of (5-7):1 and stirred at 15-40℃ and 450-550r / min for 5-20min to obtain the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of bleached sulfate softwood pulp oven-dried fiber, TEMPO, and NaBr is 1:(0.012-0.016):(0.08-0.10).

3. The preparation method according to claim 1, characterized in that, In step (1), NaOH solution is added to adjust the pH of the system to 10.0 to 10.

5.

4. The preparation method according to claim 1, characterized in that, The amount of NaClO solution added in step (1) is calculated according to the mass-volume ratio of bleached sulfate softwood pulp dry fiber to NaClO solution of 1:6.67 g / mL. The active chlorine content in the NaClO solution is 6-14%.

5. The preparation method according to claim 1, characterized in that, The washing in step (1) involves centrifuging with deionized water 3-4 times.

6. The preparation method according to claim 1, characterized in that, In step (1), the homogenization pressure of high-pressure homogenization is 50-70 MPa, and the number of homogenization cycles is 5-10.

7. The preparation method according to claim 1, characterized in that, In step (4), the waterborne epoxy modified acrylic emulsion-TOCNF mixed coating is applied to the surface of the original paper at a mass ratio of (10-13):

60.

8. The preparation method according to claim 1, characterized in that, In step (4), the hot-press curing temperature is 95-105℃ and the hot-pressing time is 15-20min.

9. An environmentally friendly high-barrier packaging paper, characterized in that, The packaging paper is prepared by the preparation method according to any one of claims 1-8.

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