A method for producing a barrier paper-based material using a multi-layer spraying technique

Abstract

The application belongs to the technical field of light industry and discloses a preparation method of barrier paper-based material by adopting a multilayer spraying technology, wherein the barrier paper-based material comprises, from bottom to top, a base paper layer, a starch layer, a TOCNF layer and a CNC layer; the total spraying amount of the starch layer, the TOCNF layer and the CNC layer is 60-80 g / m 2 The paper-based material produced by the application has good oxygen resistance, moisture resistance and mechanical properties, the spraying materials (starch, nanocellulose TOCNF and CNC) used are all biomass-based materials, are green and environmentally friendly, are biodegradable, have less harm to the environment and human bodies and have important significance in the field of paper replacing plastic packaging materials.

Description

Technical Field

[0001] This invention belongs to the field of light industry science and technology, and specifically relates to a method for preparing a barrier paper-based material using multi-layer spraying technology. Background Technology

[0002] Polyethylene (PE) and polypropylene (PP) are widely used as packaging materials due to their low cost and good mechanical and barrier properties. However, the use of these petroleum-derived polymers is accompanied by serious problems, including resource depletion and environmental pollution, as these materials are not easily biodegradable and accumulate in the environment. Against this backdrop, biodegradable and renewable biological resources are receiving increasing attention.

[0003] Currently, replacing plastic with paper has become a research hotspot. Paper, as one of the main modern packaging materials, is primarily made from renewable and biodegradable biomass. However, compared to plastics, paper-based materials have hydrophilicity, breathability, and a loose, porous structure, resulting in inferior barrier properties compared to plastic products. This limits their application in the packaging field. Current research has explored modifying the amphiphilicity and porosity of paper materials through sizing, coating, or chemical modification to enhance oil resistance. Paper and paperboard have been used as packaging materials for various food categories, such as dried foods, frozen or liquid foods, and even fresh foods.

[0004] Using sprayed nanocellulose layers for membrane development is an innovative approach, offering a rapid method for preparing self-supporting nanocellulose membranes. Spraying can produce thin, uniform nanocellulose membranes on a variety of substrates, and by controlling spraying parameters such as spraying rate, nozzle distance, and solution concentration, the membrane thickness and morphology can be customized for specific applications. Self-supporting nanocellulose membranes are used in flexible electronics, biomedical devices, sensors, and barrier materials due to their transparency, mechanical strength, and barrier properties. Furthermore, spraying can be used as a nanocellulose barrier coating on paper. Spraying can also be used to apply nanocellulose-based barrier coatings to paper substrates to enhance their properties; the nanocellulose coating improves the paper's barrier properties against moisture, oxygen, and oils, thereby extending the shelf life of packaged products. In summary, spraying is a versatile manufacturing method for producing self-supporting nanocellulose membranes and applying barrier coatings to paper substrates, providing opportunities for developing sustainable packaging materials with enhanced barrier properties.

[0005] Starch, as a natural, biodegradable polymer, boasts advantages such as abundant resources and low cost, making it suitable as a substitute for traditional plastics in molding and packaging materials. In the paper industry, it is widely used as an additive in coated paper. It can improve the surface properties of paper, such as smoothness, gloss, and printability. Starch can partially replace latex to improve the performance of coated paper due to its good film-forming and adhesive properties, while also being relatively inexpensive and environmentally friendly. In summary, the application of starch in paper coating not only improves the physical properties of paper but also provides an environmentally friendly solution, aligning with current sustainable development requirements. With technological advancements, the future application of starch in paper coating is likely to become even more widespread and efficient.

[0006] Existing methods for preparing paper-based packaging materials using starch typically require the combined use of other polymeric materials. Chinese patent CN117364541A describes a biodegradable, high-barrier (water, oil, oxygen, water vapor) paper-based packaging material and its preparation method, comprising five layers: a base paper layer, a starch layer, a polyethylene layer, a polyepoxy oleoresin layer, and a polyacrylic acid resin layer. While this paper-based packaging material improves the product's biodegradability, the use of polyethylene, polyepoxy oleoresin, and polyacrylic acid resin in its preparation leads to some environmental pollution during degradation. Therefore, improvements in oxygen permeability and biodegradability are still needed. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing barrier paper-based materials using multi-layer spraying technology. The starch, nanocellulose TOCNF, and nanocellulose CNC used are all biomass-based materials, which are renewable, green, environmentally friendly, biodegradable, and have little harm to the environment and human body. Furthermore, the materials are sprayed layer by layer in strict order of the original paper layer, starch layer, TOCNF layer, and CNC layer. Through the mutual penetration and filling of each layer, the oxygen barrier rate, durability, and mechanical properties are synergistically improved.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] The first aspect of this invention provides a method for preparing a barrier paper-based material using multi-layer spraying technology, comprising the following steps:

[0010] (1) Heat a starch solution containing 2-4% solids in a water bath at 90-95°C for 0.4-0.6 hours. After gelatinization, spray it evenly onto the surface of the base paper layer and dry it for 25-35 minutes to obtain a paper-based material composed of the base paper layer and the starch layer.

[0011] (2) After mixing 1-2% of nanocellulose TOCNF and glycerol, the mixture is uniformly sprayed onto the starch layer of the paper base material in step (1) and dried to obtain a paper base material composed of the original paper layer, starch layer and TOCNF layer.

[0012] (3) After mixing 1-2% nanocellulose CNC and glycerol, the mixture is uniformly sprayed onto the TOCNF layer of the paper base material in step (2), and dried to obtain a paper base material composed of the original paper layer, starch layer, TOCNF layer and CNC layer.

[0013] (4) Dry the paper-based material obtained in step (3) and calender the paper sample to obtain a barrier paper-based material.

[0014] Furthermore, the starch solution is prepared by adding oven-dried starch to water and then adding glycerol, wherein the mass ratio of starch to glycerol is 1 to 5:1.

[0015] Furthermore, the amount of starch layer sprayed is 5–30 g / m². 2 The starch layer is dried at a temperature of 45–55℃ for 8–15 minutes.

[0016] Furthermore, the mass ratio of the nanocellulose TOCNF / nanocellulose CNC to glycerol is 1:4 to 1:5.

[0017] Furthermore, the coating amount of the TOCNF layer and CNC layer is 15-30 g / m². 2 The coating drying time is 35-45 minutes, and the drying temperature is 75-90℃.

[0018] Furthermore, the starch layer is made of one or more of the following materials: ordinary cassava starch, waxy cassava starch, potato starch, 40% high amylose cassava starch, and 40% high amylose sweet potato starch.

[0019] Furthermore, the material used in the TOCNF layer is TOCNF with a solid content of 1-2% nanocellulose.

[0020] Furthermore, the material used in the CNC layer is CNC nanofiber with a solid content of 1-2%.

[0021] Furthermore, the base paper layer uses bagasse pulp as raw material for papermaking, and the paper basis weight is 220-240 g / m³. 2 .

[0022] Another aspect of the present invention provides a barrier paper-based material prepared by the aforementioned preparation method, comprising: a base paper layer, a starch layer, a TOCNF layer, and a CNC layer arranged sequentially from bottom to top; the total basis weight of the starch layer, TOCNF layer, and CNC layer is 60–80 g / m³. 2 .

[0023] Cellulose nanocrystal (CNC) is a cellulose material with nanoscale dimensions, extracted from natural cellulose through chemical, physical, or biological methods. CNC possesses properties such as high strength, lightweight, renewable, and biodegradable. As a paper coating, CNC can improve the strength, toughness, and durability of paper.

[0024] TOCNF (TEMPO-oxidized cellulose nanofibril) is a type of nanocellulose treated with TEMPO oxidation. Its surface contains numerous carboxyl groups, enhancing its hydrophilicity and reactivity. TOCNF exhibits high strength and toughness, significantly improving the tear resistance and abrasion resistance of paper. Due to its porous structure, coated paper better blocks moisture and gas penetration, enhancing its moisture-proof and preservation properties.

[0025] The barrier paper-based material of this invention is prepared by spraying layers in strict order: base paper layer, starch layer, TOCNF layer, and CNC layer. The starch layer serves as the base coating of the paper, filling the pores between paper fibers and providing a smooth interface for the next layer. Nanocellulose TOCNF and nanocellulose CNC are then sprayed onto the starch layer layer by layer. Because the surface of nanocellulose TOCNF has a large number of carboxyl groups, it can form hydrogen bonds with the starch layer and CNC layer. The three layers permeate and fill each other, synergistically improving the barrier properties against oxygen and also having a good effect on preventing water vapor transmission. At the same time, it also provides good mechanical properties for the paper-based material.

[0026] The advantages and beneficial effects of this invention are:

[0027] (1) The barrier paper-based material produced by this invention is sprayed layer by layer in strict order of the original paper layer, starch layer, TOCNF layer and CNC layer. The mutual penetration and filling between the starch layer, TOCNF layer and CNC layer are utilized to synergistically improve the performance. The spraying materials (starch and nanocellulose) used are all biomass-based materials, which are green and environmentally friendly, food contactable, have a high biodegradability rate, and are less harmful to the environment and human body. It is of great significance in the field of paper-based plastic packaging materials and has a certain degree of substitution for the current fluorine-based barrier coatings and silicon-based barrier coatings.

[0028] (2) The preparation process of the barrier paper-based material using multi-layer spraying technology of the present invention is simple, practical, green and environmentally friendly, and easy to promote. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Example 1

[0031] A method for preparing a barrier paper-based material using multi-layer spraying technology includes:

[0032] (1) Coating with starch layer:

[0033] Add 3g of oven-dried 40% high amylose sweet potato starch to 100g of water, then add 1.5g of glycerol, heat in a water bath at 95℃ for 0.5h to gelatinize, and prepare a gelatinized 40% high amylose sweet potato starch solution with a solid content of 3%.

[0034] At a quantitative concentration of 240 g / m 2 One side of the paper is 5g / m 2 A quantitative spray of a gelatinized solid solution containing 3% high amylose sweet potato starch (40%) was applied and dried at 50°C for 10 minutes. Care was taken to avoid wrinkling and to keep the paper surface as flat as possible.

[0035] (2) Coating of the TOCNF layer:

[0036] Add 1g of nanocellulose TOCNF to 100g of water, then add 5g of glycerol and mix well to obtain a nanocellulose TOCNF solution with a solid content of 1%.

[0037] A solution containing 1% nanocellulose TOCNF was prepared at 27.5 g / m³. 2 The amount of material is sprayed onto the starch coating and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0038] (3) Coating of the CNC layer:

[0039] Add 1g of nanocellulose CNC to 100g of water, then add 5g of glycerol and mix well to obtain a nanocellulose CNC solution with a solid content of 1%.

[0040] A CNC solution containing 1% nanocellulose was prepared at 27.5 g / m³. 2 The quantitative method involves spraying and drying the TOCNF coating at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process, thus preparing a barrier paper-based material.

[0041] Example 2

[0042] A method for preparing a barrier paper-based material using multi-layer spraying technology includes:

[0043] (1) Coating with starch layer:

[0044] A gelatinized 40% high amylose sweet potato starch solution with a solid content of 3% was used in Example 1, at a concentration of 240 g / m³. 2 One side of the paper is 10g / m 2 A quantitative spray of a gelatinized solid solution containing 3% high amylose sweet potato starch (40%) was applied and dried at 50°C for 10 minutes. Care was taken to avoid wrinkling and to keep the paper surface as flat as possible.

[0045] (2) Coating of the TOCNF layer:

[0046] The TOCNF solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 25 g / m³. 2 The amount of material is sprayed onto the starch coating and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0047] (3) Coating of the CNC layer:

[0048] The CNC solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 25 g / m³. 2 The amount of paper is sprayed onto the TOCNF coating and then dried at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0049] Example 3

[0050] A method for preparing a barrier paper-based material using multi-layer spraying technology includes:

[0051] (1) Coating with starch layer:

[0052] A gelatinized 40% high amylose sweet potato starch solution with a solid content of 3% was used in Example 1, at a concentration of 240 g / m³. 2 One side of the paper is 15g / m 2 A quantitative spray of a gelatinized solid solution containing 3% high amylose sweet potato starch (40%) was applied and dried at 50°C for 10 minutes. Care was taken to avoid wrinkling and to keep the paper surface as flat as possible.

[0053] (2) Coating of the TOCNF layer:

[0054] The TOCNF solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 22.5 g / m³. 2 The amount of material is sprayed onto the starch coating and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0055] (3) Coating of the CNC layer:

[0056] The CNC solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 22.5 g / m³. 2 The amount of paper is sprayed onto the TOCNF coating and then dried at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0057] Example 4

[0058] A method for preparing a barrier paper-based material using multi-layer spraying technology includes:

[0059] (1) Coating with starch layer:

[0060] A gelatinized 40% high amylose sweet potato starch solution with a solid content of 3% was used in Example 1, at a concentration of 240 g / m³. 2 One side of the paper is 20g / m 2 A quantitative spray of a gelatinized solid solution containing 3% high amylose sweet potato starch (40%) was applied and dried at 50°C for 10 minutes. Care was taken to avoid wrinkling and to keep the paper surface as flat as possible.

[0061] (2) Coating of the TOCNF layer:

[0062] The TOCNF solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 20 g / m³. 2 The amount of material is sprayed onto the starch coating and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0063] (3) Coating of the CNC layer:

[0064] The CNC solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 20 g / m³. 2 The amount of paper is sprayed onto the TOCNF coating and then dried at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0065] Comparative Example 1 (without starch layer)

[0066] A method for preparing a barrier paper-based material using multi-layer spraying technology includes:

[0067] (1) Coating of the TOCNF layer:

[0068] The TOCNF solution containing 1% nanocellulose was prepared in the same manner as in Example 1, with a quantitative concentration of 240 g / m³. 2 One side of the paper is 30g / m 2 Apply a quantitative amount of coating and dry it at a temperature of 80℃ for 40 minutes. Take care to avoid wrinkling and keep the paper surface as flat as possible during the process.

[0069] (2) Coating of CNC layer:

[0070] The CNC solution containing 1% nanocellulose was prepared in the same manner as in Example 1, but at a concentration of 30 g / m³. 2 The amount of paper is sprayed onto the TOCNF coating and then dried at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0071] Comparative Example 2 (Two TOCNF Layers)

[0072] The difference from Example 1 is only in step (3), where the 1% solid content of nanocellulose TOCNF solution is added at 27.5 g / m 2 The quantitative method involves spraying and drying the TOCNF coating at a temperature of 80°C for 40 minutes, while keeping the paper surface as flat as possible during the process, thus preparing a barrier paper-based material.

[0073] Comparative Example 3 (Two CNC Layers)

[0074] The only difference from Example 1 is that in step (2), the CNC solution containing 1% nanocellulose is used at 27.5 g / m³. 2 The amount of material is sprayed onto the starch coating and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0075] Comparative Example 4

[0076] The only difference from Example 1 is that steps (2) and (3) are different.

[0077] (2) Coating of CNC layer:

[0078] A CNC solution containing 1% nanocellulose was prepared at 27.5 g / m³. 2 The amount of material is sprayed onto the starch layer and then dried at a temperature of 80℃ for 40 minutes, while keeping the paper surface as flat as possible during the process.

[0079] (3) Coating of the TOCNF layer:

[0080] A solution containing 1% nanocellulose TOCNF was prepared at 27.5 g / m³. 2 The quantitative coating is sprayed onto the CNC layer and dried at a temperature of 80°C for 40 minutes. During the process, the paper surface is kept as flat as possible to prepare a barrier paper-based material.

[0081] The oxygen and moisture barrier properties of the barrier paper-based materials prepared in the examples and comparative examples were tested:

[0082] Oxygen permeability refers to the amount of oxygen that permeates through a unit area of ​​a sample within a specified pressure difference and time period, and is measured in cm². 3 / cm 2 The test principle is as follows: The sample is clamped between the upper and lower test chambers of the testing instrument. First, the lower chamber (low-pressure chamber) is evacuated, and then the entire system is evacuated. After a certain period of time, the lower chamber is closed, and high-purity oxygen (99.99% purity) at a certain pressure is introduced into the upper chamber (high-pressure chamber). A constant pressure difference is maintained between the two sides of the sample. Under the action of the pressure gradient, oxygen permeates from the high-pressure side to the low-pressure side. By monitoring the pressure in the low-pressure side, the oxygen permeability of the tested sample is obtained.

[0083] The moisture barrier performance test measures the water vapor transmission value, and the data is shown in Table 1.

[0084] Table 1. Oxygen permeability and water permeability of the barrier paper-based materials prepared in the examples and comparative examples.

[0085]

[0086] As shown in Table 1, the paper-based material obtained using the spraying scheme of Example 4 exhibits the best oxygen barrier properties. With the gradual increase in the amount of starch coating applied, the oxygen barrier properties are significantly improved, and it also has a positive effect on water vapor barrier. The water vapor permeability of the paper-based material obtained in Example 3 is tested to be 240 g / m³. 2 ·24h.

[0087] The oxygen permeability and water permeability of the paper-based material prepared in Comparative Example 1 without the starch layer were not as good as those in Example 1, indicating that the starch layer played a role in oxygen and moisture barrier. The oxygen and water permeability of the paper-based materials prepared in Comparative Example 2 with two TOCNF layers and Comparative Example 3 with two CNC layers were better than those in Comparative Example 1, but neither was as good as the performance of Example 1. In Example 4, the TOCNF layer was sprayed first and then the CNC layer was sprayed, but the effect was not as good as that in Comparative Example 2 and Comparative Example 3, indicating that the nanocellulose TOCNF reacted with starch and nanocellulose CNC at the same time, and the three layers permeated and filled each other, synergistically improving the oxygen and moisture barrier performance.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and variations.

Claims

1. A method for preparing a barrier paper-based material using multi-layer spraying technology, characterized in that, The steps are as follows: (1) Heat a starch solution with a solid content of 2-4% in a water bath at 90-95℃ for 0.4-0.6h. After gelatinization, spray it evenly on the surface of the base paper and dry it for 25-35min to obtain a paper base material composed of a base paper layer and a starch layer. (2) After mixing 1-2% of nanocellulose TOCNF and glycerol, the mixture is uniformly sprayed onto the starch layer of the paper base material in step (1) and dried to obtain a paper base material composed of the original paper layer, starch layer and TOCNF layer. (3) After mixing 1-2% of nanocellulose CNC and glycerol, the mixture is uniformly sprayed onto the TOCNF layer of the paper base material in step (2), and dried to obtain a paper base material composed of the original paper layer, starch layer, TOCNF layer and CNC layer. (4) Dry the paper-based material obtained in step (3), and calender the paper sample to obtain a barrier paper-based material. The starch solution is prepared by adding dry starch to water and then adding glycerin, wherein the mass ratio of starch to glycerin is 1~5:1; The amount of starch layer sprayed is 5~30g / m². 2 The drying temperature of the starch layer is 45~55℃, and the drying time is 8~15min; the mass ratio of the nanocellulose TOCNF / nanocellulose CNC and glycerol is 1:

5. The coating amount of the TOCNF layer and CNC layer is 15~30g / m². 2 The coating drying time is 35~45 min, and the drying temperature is 75~90℃; The starch layer, TOCNF layer, and CNC layer achieve layer-by-layer penetration and filling through the hydrogen bond network formed between the carboxyl groups on the surface of TOCNF and the starch and CNC layers, thereby synergistically improving the oxygen barrier and water vapor barrier properties of the paper-based material.

2. The preparation method according to claim 1, characterized in that, The starch layer is made of one or more of the following materials: ordinary cassava starch, waxy cassava starch, potato starch, 40% high amylose cassava starch, and 40% high amylose sweet potato starch.

3. The preparation method according to claim 1, characterized in that, The material used in the TOCNF layer is TOCNF with a solid content of 1-2% nanocellulose.

4. The preparation method according to claim 1, characterized in that, The CNC layer uses a material with a solid content of 1-2% nanocellulose CNC.

5. The preparation method according to claim 1, characterized in that, The base paper layer uses bagasse pulp as raw material for papermaking, and the paper basis weight is 220~240g / m³. 2 .

6. A barrier paper-based material prepared by the preparation method according to any one of claims 1 to 5, characterized in that, It includes, from bottom to top, a base paper layer, a starch layer, a TOCNF layer, and a CNC layer; the total basis weight of the starch layer, TOCNF layer, and CNC layer is 60~80g / m³. 2 .

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