A cellulose glassine coating, its preparation method and use

Abstract

This invention discloses a cellulose cellophane coating, its preparation method, and its application, comprising: 1) dissolving polyvinyl alcohol in water and heating to obtain a polyvinyl alcohol coating solution; 2) dissolving an acidic substance in water to obtain a first solution, and dissolving a barrier substance and a dispersant in water to obtain a second solution; wherein the mass ratio of the barrier substance to the dispersant is 15-45:72; 3) mixing the first and second solutions and adding them to the polyvinyl alcohol coating solution, and performing a chemical crosslinking reaction to obtain a composite coating solution; 4) uniformly coating the composite coating solution onto the surface of a cellulose film and drying to obtain a cellulose cellophane coating. The chemical crosslinking method produces a heat-sealable, biodegradable, highly transparent cellulose coating film, which not only improves the water resistance of PVA materials but also enhances the water vapor barrier properties of the film by adding mica powder. The resulting cellulose cellophane coating is environmentally friendly and exhibits excellent oxygen and water vapor barrier properties in high-humidity environments.

Description

Technical Field

[0001] This invention belongs to the technical field of heat-sealable packaging materials, specifically relating to a cellulose cellophane coating, its preparation method, and its application. Background Technology

[0002] Cellulose is a recognized environmentally friendly material, and it has become a solution due to its low cost, abundant sources, easy degradation and renewability.

[0003] Waterborne PVA coatings possess excellent film-forming properties, transparency, and superior oxygen barrier performance, and are fully compatible with coating equipment used for PVDC films. In low-humidity environments, PVA exhibits exceptional oxygen barrier capabilities, even surpassing current barrier resins such as ethylene-vinyl alcohol copolymer (EVOH) and polyvinylidene chloride (PVDC). However, the presence of numerous hydrophilic hydroxyl groups on the PVA molecular chain makes it prone to swelling upon contact with water, resulting in poor water resistance.

[0004] Therefore, developing a heat-sealable, biodegradable, and water vapor-resistant highly transparent cellulose coating film that can be applied to the food packaging industry still faces significant challenges. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a cellulose cellophane coating, its preparation method, and its application. The cellulose cellophane coating obtained by this method is not only environmentally friendly and biodegradable, but also exhibits excellent oxygen barrier, water resistance, water vapor barrier, and heat-sealing properties in high-humidity environments.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a cellulose cellophane coating includes the following steps:

[0008] 1) Dissolve polyvinyl alcohol in water and heat to obtain a polyvinyl alcohol coating solution;

[0009] 2) Dissolve the acidic substance in water to obtain a first solution, and dissolve the barrier substance and dispersant in water to obtain a second solution; the mass ratio of the barrier substance to the dispersant is 15-45:72;

[0010] 3) Mix the first solution and the second solution, add them to the polyvinyl alcohol coating solution, and perform a chemical cross-linking reaction to obtain a composite coating solution;

[0011] 4) The composite coating liquid is uniformly coated on the surface of the cellulose film and dried to obtain a cellulose cellophane coating;

[0012] The barrier material is selected from one or more of mica powder, montmorillonite, hydrotalcite compounds, and organic modified clay; preferably, it is mica powder.

[0013] In one embodiment of the present invention, the mass ratio of the barrier substance to the dispersant is 25 to 45:72.

[0014] In one embodiment of the present invention, step 1) includes:

[0015] Dissolve polyvinyl alcohol in water and heat in an oil bath at 85–95°C for 0.5–3.5 hours;

[0016] For example, heat in an oil bath at 95°C for 2 hours.

[0017] In one embodiment of the present invention, the mass concentration of the polyvinyl alcohol is 10wt% to 15wt%.

[0018] For example, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%.

[0019] In one embodiment of the present invention, the acidic substance is selected from one or more of maleic acid, boric acid, sodium tetraborate, polyacrylic acid, and glutaraldehyde.

[0020] Preferably, the maleic acid is food-grade maleic acid.

[0021] In one embodiment of the present invention, the concentration of the first solution obtained after the acidic substance is dissolved in water is 23wt% to 60wt%; preferably 23wt% to 45wt%, more preferably 31wt% to 37.5wt%.

[0022] For example, 23wt%, 25wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, or any value within any range of any two of the above points.

[0023] In one embodiment of the present invention, the mica powder accounts for 1 wt% to 10 wt% of the mass of polyvinyl alcohol, preferably 3 wt% to 4 wt% of the mass of polyvinyl alcohol.

[0024] In one embodiment of the present invention, the dispersant is BYK-190 and / or GS-9297.

[0025] In one embodiment of the present invention, in step 4), a 4-6 μm scraper is used to uniformly coat the composite coating liquid onto the surface of the cellulose film, which is then placed in a forced-air drying oven and dried at 60-80°C for 10-20 minutes to obtain a cellulose cellophane coating.

[0026] The present invention also provides a cellulose glass paper coating, which is obtained by the above-described method for preparing cellulose glass paper coating.

[0027] In one embodiment of the present invention, the water absorption rate of the cellulose glassine coating is 125-155%; the water vapor transmission rate of the cellulose glassine coating is as low as 197.72 g / (m²). 2. 24h).

[0028] This invention also provides an application of cellulose cellophane coating in food packaging and preservation; particularly its application in cellulose sealed bags for packaging items.

[0029] The beneficial effects of this invention are:

[0030] Existing cellulose films lack heat-sealing properties and have poor water resistance and water vapor barrier performance. This invention employs a chemical crosslinking method, simultaneously adding maleic acid and mica powder during the preparation process to synthesize a maleic acid crosslinked PVA / mica composite coating liquid, which improves the water vapor barrier properties of cellophane. When the coating liquid is applied to the surface of cellophane, the cellophane achieves heat-sealing properties at 175°C with a pressing time of 1 second.

[0031] This invention uses a chemical crosslinking method to prepare a heat-sealable and biodegradable highly transparent cellulose film. The resulting cellulose cellophane coating is not only environmentally friendly and biodegradable, but also has excellent oxygen barrier, water vapor barrier and heat-sealability in high humidity environments. Attached Figure Description

[0032] Figure 1 This is a SEM image of the cellulose cellophane coating prepared in Example 1;

[0033] Figure 2 This is a SEM image of the cellulose cellophane coating prepared in Comparative Example 3. Detailed Implementation

[0034] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0035] Example 1

[0036] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 95℃ for 2h to obtain polyvinyl alcohol coating liquid;

[0037] (2) Dissolve 2.25g of maleic acid in 5g of water to obtain the first solution, and dissolve 0.45g of mica powder and 0.72g of dispersant in 20g of water to obtain the second solution;

[0038] (3) The first solution containing maleic acid and the second solution containing mica powder and dispersant are mixed and added to the polyethanol coating solution, and the chemical cross-linking reaction is carried out for 4 hours to obtain the composite coating solution.

[0039] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then placed in a forced-air drying oven and dried at 80℃ for 15min to obtain a cellulose cellophane coating.

[0040] Example 2

[0041] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 85℃ for 3h to obtain polyvinyl alcohol coating liquid;

[0042] (2) Dissolve 3g of maleic acid in 5g of water to obtain the first solution, and dissolve 0.45g of mica powder and 0.72g of dispersant in 20g of water to obtain the second solution;

[0043] (3) The first solution containing maleic acid and the second solution containing mica powder and dispersant are mixed and added to the polyethanol coating solution, and the chemical cross-linking reaction is carried out for 4 hours to obtain the composite coating solution.

[0044] (4) The composite coating liquid was uniformly coated on the surface of the cellulose film using a 4μm scraper and dried in a forced-air drying oven at 80℃ for 15min to obtain a cellulose cellophane coating.

[0045] Example 3

[0046] (1) Dissolve 10g of polyvinyl alcohol in 90g of water and heat in an oil bath at 95℃ for 2h to obtain polyvinyl alcohol coating liquid;

[0047] (2) Dissolve 1.5g of maleic acid in 5g of water to obtain the first solution, and dissolve 0.3g of mica powder and 0.72g of dispersant in 20g of water to obtain the second solution;

[0048] (3) The first solution containing maleic acid and the second solution containing mica powder and dispersant are mixed and added to the polyethanol coating solution, and the chemical cross-linking reaction is carried out for 4 hours to obtain the composite coating solution.

[0049] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then placed in a forced-air drying oven and dried at 80℃ for 15min to obtain a cellulose cellophane coating.

[0050] Example 4

[0051] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 95℃ for 1.5h to obtain a polyvinyl alcohol coating solution;

[0052] (2) Dissolve 2.25g of maleic acid in 5g of water to obtain a mixed solution;

[0053] (3) Maleic acid was added to the polyethanol coating solution and chemical cross-linking reaction was carried out for 4 hours to obtain the composite coating solution.

[0054] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then placed in a forced-air drying oven and dried at 60℃ for 20min to obtain a cellulose cellophane coating.

[0055] Comparative Example 1

[0056] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 95℃ for 2h to obtain polyvinyl alcohol coating liquid;

[0057] (2) Dissolve 0.1g of maleic acid in 5g of water to obtain a mixture, and dissolve 0.15g of mica powder and 0.72g of dispersant in 20g of water;

[0058] (3) Add the mixture of maleic acid, mica powder and dispersant to the polyethanol coating solution and react for 4 hours to obtain the composite coating solution.

[0059] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then dried in a forced-air drying oven at 80℃ for 15min to obtain a cellulose cellophane coating.

[0060] Comparative Example 2

[0061] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 95℃ for 2h to obtain polyvinyl alcohol coating liquid;

[0062] (2) Dissolve 0.1g of maleic acid in 5g of water to obtain a mixture, and dissolve 0.45g of mica powder and 0.72g of dispersant in 20g of water;

[0063] (3) Add the mixture of maleic acid, mica powder and dispersant to the polyethanol coating solution and react for 4 hours to obtain the composite coating solution.

[0064] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then dried in a forced-air drying oven at 80℃ for 15min to obtain a cellulose glass paper alcohol coating.

[0065] Comparative Example 3

[0066] (1) Dissolve 15g of polyvinyl alcohol in 85g of water and heat in an oil bath at 95℃ for 2h to obtain polyvinyl alcohol coating liquid;

[0067] (2) Dissolve 2.25g of maleic acid in 5g of water to obtain a mixture, and dissolve 1.5g of 100-mesh mica powder and 0.72g of dispersant in 20g of water;

[0068] (3) Add the mixture of maleic acid, mica powder and dispersant to the polyethanol coating solution and react for 4 hours to obtain the composite coating solution.

[0069] (4) The coating liquid was uniformly coated on the surface of the cellulose film using a 6μm wire bar, and then dried in a forced-air drying oven at 80℃ for 15min to obtain a cellulose cellophane coating.

[0070] Cellophane water absorption rate and water vapor permeability test:

[0071] Cut the film into 60mm×60mm pieces and soak them in 500mL of distilled water at room temperature for 24 hours. Remove the film sample, quickly absorb the water on the surface with filter paper, weigh it, and the formula for calculating the water absorption rate is shown in (1-1).

[0072]

[0073] In formula (1-1): m1—mass of the film sample before immersion; m2—mass of the film sample after immersion.

[0074] The water vapor barrier properties of the cellophane prepared in Examples 1-4 and Comparative Examples 1-3 were determined according to the national standard GB / T 1037-2021 "Test Method for Water Permeability of Plastic Films and Sheets - Cup Method". The test environment was 38℃±0.5℃ and 90%RH±2%RH. The specific data are shown in Table 1.

[0075] Table 1 Properties of coated cellophane

[0076]

[0077] As can be seen from Table 1, the water absorption rate of the cellulose polyvinyl alcohol coatings prepared in Examples 1-4 is approximately between 125% and 155%. In Comparative Example 1, due to the low content of maleic acid and mica powder, the coatings failed to crosslink with PVA and did not change the water resistance and water vapor barrier properties.

[0078] In Comparative Example 2, due to the low content of maleic acid but the appropriate amount of mica powder, it failed to crosslink with PVA and thus did not improve water resistance.

[0079] Figure 1The image shows an SEM image of the cellulose polyvinyl alcohol coating prepared in Example 1. It can be seen that the coating has good uniformity and smoothness. Figure 2 The SEM image of the coating prepared in Comparative Example 3 shows that although the amount of maleic acid added was appropriate, the amount of mica powder was excessive, which affected the uniformity and smoothness of the coating. It can be seen that the mica protruded from the coating and was exposed to the outside. The mica was randomly distributed in the coating and exposed on the surface in the form of aggregates, which also greatly increased the roughness.

[0080] In summary, the cellulose polyvinyl alcohol coatings prepared in Comparative Examples 1-3 have high water absorption rates and poor water resistance and water vapor barrier properties.

[0081] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. 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 a cellulose cellophane coating, characterized in that, Includes the following steps: 1) Dissolve polyvinyl alcohol in water and heat to obtain a polyvinyl alcohol coating solution; 2) Dissolve the acidic substance in water to obtain a first solution, and dissolve the barrier substance and dispersant in water to obtain a second solution; the mass ratio of the barrier substance to the dispersant is 15-45:72; 3) Mix the first solution and the second solution, add them to the polyvinyl alcohol coating solution, and perform a chemical cross-linking reaction to obtain a composite coating solution; 4) The composite coating liquid is uniformly coated on the surface of the cellulose film and dried to obtain a cellulose cellophane coating.

2. The preparation method according to claim 1, characterized in that, The barrier material is selected from one or more of mica powder, montmorillonite, hydrotalcite compounds, and organic modified clay; mica powder is preferred.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the barrier substance to the dispersant is 25–45:

72.

4. The preparation method according to claim 1, characterized in that, Step 1) includes: Dissolve polyvinyl alcohol in water and heat in an oil bath at 85–95°C for 1–3.5 hours; For example, heating in an oil bath at 95°C for 2 hours; Preferably, the polyvinyl alcohol has a mass concentration of 10 wt% to 15 wt%. For example, 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt%.

5. The preparation method according to claim 1, characterized in that, The acidic substance is selected from one or more of maleic acid, boric acid, sodium tetraborate, polyacrylic acid, and glutaraldehyde; Preferably, the maleic acid is food-grade maleic acid; Preferably, the concentration of the first solution obtained after the acidic substance is dissolved in water is 23 wt% to 60 wt%. More preferably, it is 23 wt% to 45 wt%, and most preferably, it is 31 wt% to 37.5 wt%. For example, 23wt%, 25wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 48wt%, 50wt%, 52wt%, 54wt%, 56wt%, 58wt%, 60wt%, or any value within any range of any two of the above points.

6. The preparation method according to claim 1, characterized in that, The barrier material should account for 1%-10% of the mass of polyvinyl alcohol, preferably 3%-4% of the mass of polyvinyl alcohol.

7. The preparation method according to claim 1, characterized in that, The dispersant is BYK-190 and / or GS-9297.

8. The preparation method according to any one of claims 1 to 7, characterized in that, In step 4), a 4-6 μm scraper is used to uniformly coat the composite coating liquid onto the surface of the cellulose film, which is then placed in a forced-air drying oven and dried at 60-80°C for 10-20 minutes to obtain a cellulose cellophane coating.

9. A cellulose cellophane coating, characterized in that, The cellulose glass paper coating is prepared by any one of claims 1 to 7. Preferably, the water absorption rate of the cellulose cellophane coating is 125-155%; the water vapor transmission rate of the cellulose cellophane coating is as low as 197.72 g / (m²).

2. 24h).

10. The application of the cellulose cellophane coating as described in claim 9 in the field of food packaging and preservation; particularly its application in cellulose sealed bags for packaging articles.

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