Oil-proof label paper and preparation method thereof

Abstract

The invention belongs to the technical field of label paper, and provides oil-proof label paper and a preparation method thereof.The oil-proof label paper sequentially comprises an oil-proof layer, a plane material layer and a release layer from top to bottom; the oil-proof layer is prepared from the following raw material components in parts by weight: 25 to 40 parts of modified chitosan, 2 to 5 parts of modified polyvinyl alcohol, 3 to 6 parts of nano silicon dioxide, 0.5 to 2 parts of polyacrylamide and 0.05 to 1 part of carboxymethyl cellulose. The preparation method of the oil-proof label paper comprises the following steps: mixing the modified chitosan, the modified polyvinyl alcohol, the nano silicon dioxide, the polyacrylamide and the carboxymethyl cellulose in proportion, and uniformly stirring to obtain a mixed solution; and uniformly coating one surface of the surface material layer with the mixed solution, drying after coating is completed, and compounding the other surface, which is not coated, of the surface material layer on the release layer after drying to prepare the oil-proof label paper, and the prepared label paper has excellent oil-proof and water-proof effects and can be widely applied to the field of food packaging.

Description

Technical Field

[0001] The invention belongs to the technical field of label paper, and in particular relates to an oil-proof label paper and a preparation method thereof. Background Art

[0002] Paper labels are increasingly favored by the market for their good decorativeness, economy and good environmental sustainability. As an environmentally friendly material, they are widely used in the packaging of various products, such as cigarette packages, wine packages, cosmetics, food, etc. They are also used in laser anti-counterfeiting labels, labels, signs and other products.

[0003] Oil-proof label paper is a special kind of label paper with excellent oil-proof performance. It can maintain the clarity and integrity of the label in an environment where it comes into contact with liquids such as grease. At present, oil-proof labels usually use film labels, such as labels made of polyester or polyethylene film, which can effectively prevent the erosion of oil and water. In addition, coated labels are also often used, generally using polyethylene (PE) particles for coating. Although film labels or coated labels can play a certain role in oil prevention, these types of products have problems such as migration of harmful substances, difficulty in degradation, and environmental pollution. In the field of packaging paper, it is common to achieve oil-proof effect by applying a coating on the surface of base paper. For example, the most commonly used fluorinated oil-proof agent, although it can bring good oil-proof effect, is easy to produce harmful substances such as perfluorooctane sulfonic acid (PFOS) or perfluorooctane amide (FOSE), which brings health problems. In particular, the risk of application in the field of food packaging is higher. Polysaccharide oil-proof agents are safe and degradable, but in order to achieve a good oil-proof effect, they require high concentrations and high viscosity, which is not conducive to coating and has poor feasibility. When the aforementioned oil-proof agents are applied to label paper, corresponding problems will also be introduced, thereby restricting their use and promotion.

[0004] Therefore, how to prepare an oil-proof label paper with good oil-proof effect is a technical problem that needs to be solved urgently. Summary of the invention

[0005] The object of the present invention is to provide an oil-proof label paper and a preparation method thereof, so as to solve the problem that the oil-proof performance of the label paper prepared in the prior art is poor.

[0006] The purpose of the present invention can be achieved through the following technical solutions: The first aspect of the present invention provides an oil-proof label paper, which comprises an oil-proof layer, a surface material layer and a release layer from top to bottom; the raw materials of the oil-proof layer comprise the following components in parts by weight: 25-40 parts of modified chitosan, 2-5 parts of modified polyvinyl alcohol, 3-6 parts of nano-silicon dioxide, 0.5-2 parts of polyacrylamide, and 0.05-1 part of carboxymethyl cellulose.

[0007] As a further embodiment of the present invention, the modified chitosan is prepared by the following steps: Chitosan was added to the acetic acid solution and stirred until completely dissolved, glutaraldehyde solution was added, stirring was continued for 1.0-1.5 hours, montmorillonite was added, stirring was continued for 12-24 hours, and modified chitosan was obtained after vacuum drying.

[0008] As a further solution of the present invention, the usage ratio of chitosan, acetic acid solution, glutaraldehyde solution and montmorillonite is 1.0-1.2g:50mL:2.5-3.0mL:0.3-0.5g; wherein the volume fraction of the acetic acid solution is 2%, and the volume fraction of the glutaraldehyde solution is 2.5%.

[0009] As a further embodiment of the present invention, the modified polyvinyl alcohol is prepared by the following steps: Add polyvinyl alcohol to deionized water, heat to 90-95℃, stir until uniform, keep warm for 1.0-1.5h, cool to room temperature, add citric acid, heat to 75-80℃, stir to react for 2-3h, cool to room temperature, and obtain modified polyvinyl alcohol. Polyvinyl alcohol has the characteristics of being soluble in water, biodegradable and having excellent film-forming properties. It can be mixed with other raw materials to improve the barrier properties of label paper. However, since polyvinyl alcohol molecules have a large number of hydroxyl groups, are highly hydrophilic, easily absorb moisture in the air, swell and even dissolve when exposed to water, citric acid is used to modify polyvinyl alcohol. The carboxyl group of citric acid can react with the hydroxyl group of polyvinyl alcohol under certain conditions to form an ester bond, so that a stable structure is formed between the molecular chains of polyvinyl alcohol. The modified polyvinyl alcohol has excellent film-forming properties and can form a dense coating on the surface of the surface material layer, thereby reducing the air permeability of the label paper and preventing the penetration of grease.

[0010] As a further embodiment of the present invention, the usage ratio of polyvinyl alcohol, deionized water and citric acid is 1.50-1.55 g:30 mL:0.60-0.65 g.

[0011] As a further solution of the present invention, the particle size of the nano silicon dioxide is 60-85 nm. The addition of nano silicon dioxide in the raw material helps to form a rough surface and reduce the surface energy of the oil-proof layer, thereby achieving a certain hydrophobic effect.

[0012] As a further solution of the present invention, the thickness of the oil-proof layer is 15-20 μm, the thickness of the surface material layer is 10-25 μm, and the thickness of the release layer is 60-100 μm.

[0013] As a further solution of the present invention, the surface material layer is one of offset paper, thermal paper, polypropylene film, polyethylene film, polyester film and polyvinyl alcohol film.

[0014] As a further solution of the present invention, the release layer is silicon-coated paper.

[0015] A second aspect of the present invention provides a method for preparing oil-proof label paper, comprising the following steps: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0016] Beneficial effects of the present invention: 1. The label paper provided by the present invention is composed of an oil-proof layer, a surface material layer and a release layer from top to bottom, has excellent oil-proof and waterproof effects, and can be widely used in the field of food packaging. Among them, the oil-proof layer raw material is evenly coated on the surface of the surface material layer to form a dense barrier film, which reduces the surface energy of the surface material layer, thereby enhancing the oil-proof performance of the label paper. At the same time, chitosan is the main raw material, has good degradability and environmental friendliness, and has broad application prospects.

[0017] 2. The oil-proof layer of the present invention is formed by coating after modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose are mixed in proportion by weight, and has excellent oil-proof and water-proof properties. 2 Once the film is formed and comes into contact with liquids such as water, it will absorb a large amount of water, thus destroying the oil-proof coating. At the same time, chitosan has the disadvantage of low mechanical strength. Therefore, glutaraldehyde is used to crosslink chitosan. The aldehyde group of glutaraldehyde reacts with the primary amino group (-NH 2 ) undergoes a cross-linking reaction to form a Schiff base. The cross-linking reaction leads to a reduction in free amino groups, which reduces the ability of chitosan to form hydrogen bonds with water molecules, thereby effectively reducing the hydrophilicity of chitosan. Then, montmorillonite is added to the mixed solution, and a solution intercalation reaction occurs, so that the montmorillonite is evenly dispersed in the chitosan. On the one hand, it can improve the mechanical properties of chitosan. On the other hand, due to the layered structure of montmorillonite, it can produce a significant barrier effect, increase the path length of water molecules penetrating the oil-proof layer, reduce the diffusion rate of water molecules, and further improve the oil and water resistance of the oil-proof layer.

[0018] 3. The oil-proof label paper prepared in the present invention The method for preparing the oil-proof label paper of the present invention has the advantages of simple operation, easy availability of raw materials, low production cost, and is suitable for large-scale production. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] Obviously, the following description is only some examples or embodiments of the present application. For those of ordinary skill in the art, the present application can also be applied to other similar scenarios without creative work. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for those of ordinary skill in the art related to the content disclosed in the present application, some changes such as design, manufacturing or production based on the technical content disclosed in the present application are only conventional technical means, and should not be understood as insufficient content disclosed in the present application. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the following description is provided for those skilled in the art to fully understand the present application and is not intended to limit the subject matter recorded in the claims.

[0021] Chitosan used in the examples and comparative examples of the present invention has a deacetylation degree of ≥95% and was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; montmorillonite was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; glutaraldehyde was purchased from Shanghai Adamas Reagent Co., Ltd.; polyvinyl alcohol was purchased from Shanghai MacLean Biochemical Technology Co., Ltd. The remaining reagents without indicating the manufacturer are all conventional products that can be purchased commercially.

[0022] Example 1 This embodiment provides a modified chitosan, and the preparation steps are as follows: Add 1.0 g of chitosan to 50 mL of acetic acid solution (volume fraction 2%) and stir until completely dissolved, add 2.5 mL of glutaraldehyde solution (volume fraction 2.5%), continue stirring for 1.0 h, add 0.3 g of montmorillonite, continue stirring for 18 h, and finally place in a 50°C vacuum drying oven and dry for 8 h to obtain modified chitosan.

[0023] Example 2 This embodiment provides a modified chitosan, and the preparation steps are as follows: 1.2 g of chitosan was added to 50 mL of acetic acid solution (volume fraction 2%) and stirred until completely dissolved, 2.6 mL of glutaraldehyde solution (volume fraction 2.5%) was added, stirring was continued for 1.0 h, 0.5 g of montmorillonite was added, stirring was continued for 18 h, and finally, it was placed in a vacuum drying oven at 50 °C and dried for 8 h to obtain modified chitosan.

[0024] Example 3 This embodiment provides a modified polyvinyl alcohol, and the preparation steps are as follows: Add 1.50 g of polyvinyl alcohol to 30 mL of deionized water, heat to 90 ° C and stir until uniform, keep warm for 1.0 h, cool to room temperature, add 0.60 g of citric acid, heat to 75 ° C, stir and react for 2 h, cool to room temperature to obtain modified polyvinyl alcohol.

[0025] Example 4 This embodiment provides a modified polyvinyl alcohol, and the preparation steps are as follows: Add 1.55 g of polyvinyl alcohol to 30 mL of deionized water, heat to 90 ° C and stir until uniform, keep warm for 1.0 h, cool to room temperature, add 0.65 g of citric acid, heat to 75 ° C, stir and react for 2 h, cool to room temperature to obtain modified polyvinyl alcohol.

[0026] Example 5 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0027] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0028] Example 6 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 2, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0029] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0030] Example 7 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 4, 3 parts of nano silicon dioxide (particle size is 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0031] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0032] Example 8 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 40 parts of modified chitosan in Example 1, 5 parts of modified polyvinyl alcohol in Example 3, 6 parts of nano silicon dioxide (particle size is 60 nm), 2 parts of polyacrylamide, and 1 part of carboxymethyl cellulose.

[0033] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0034] Example 9 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 30 parts of modified chitosan in Example 1, 4 parts of modified polyvinyl alcohol in Example 3, 4 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0035] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0036] Example 10 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 40 parts of modified chitosan in Example 1, 3.5 parts of modified polyvinyl alcohol in Example 3, 4 parts of nano silicon dioxide (particle size of 60 nm), 0.8 parts of polyacrylamide, and 0.06 parts of carboxymethyl cellulose.

[0037] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0038] Embodiment 11 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (thickness of 20 μm), a surface material layer (using double-sided paper, thickness of 20 μm) and a release layer (using silicon-coated paper, thickness of 80 μm); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0039] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0040] Example 12 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (thickness of 20 μm), a surface material layer (using double-sided paper, thickness of 25 μm) and a release layer (using silicon-coated paper, thickness of 60 μm); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0041] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0042] Embodiment 13 This example provides an oil-proof label paper, which includes, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (using offset paper, 10 μm thick) and a release layer (using silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 80 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0043] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0044] Comparative Example 1 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the modified chitosan in Example 1 is replaced by chitosan (deacetylation degree ≥ 95%, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.).

[0045] An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of chitosan, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0046] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0047] Comparative Example 2 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the modified polyvinyl alcohol in Example 3 is replaced by polyvinyl alcohol (purchased from Shanghai MacLean Biochemical Technology Co., Ltd.).

[0048] An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of polyvinyl alcohol, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0049] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0050] Comparative Example 3 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the modified chitosan in Example 1 is replaced by chitosan (deacetylation degree ≥ 95%, purchased from Shanghai McLean Biochemical Technology Co., Ltd.), and the modified polyvinyl alcohol in Example 3 is replaced by polyvinyl alcohol (purchased from Shanghai McLean Biochemical Technology Co., Ltd.).

[0051] An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of chitosan, 2 parts of polyvinyl alcohol, 3 parts of nano silicon dioxide (particle size is 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0052] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0053] Comparative Example 4 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the amount of the oil-proof layer is different: An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 15 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0054] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0055] Comparative Example 5 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the amount of the oil-proof layer is different: An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 20 parts of modified chitosan in Example 1, 1 part of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0056] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0057] Comparative Example 6 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the nano-silicon dioxide particle size is different: An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (15 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 100 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0058] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0059] Comparative Example 7 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the thickness of the oil-proof layer is different: An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (10 μm thick), a surface material layer (adopting double-sided offset paper, 10 μm thick) and a release layer (adopting silicon-coated paper, 60 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0060] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0061] Comparative Example 8 This comparative example provides an oil-proof label paper and a preparation method thereof, which is different from Example 5 only in that the thicknesses of the oil-proof layer, the surface material layer and the release layer are different: An oil-proof label paper, comprising, from top to bottom, an oil-proof layer (10 μm thick), a surface material layer (adopting offset paper, 30 μm thick) and a release layer (adopting silicon-coated paper, 45 μm thick); The raw materials of the oil-proof layer include the following components in parts by weight: 25 parts of modified chitosan in Example 1, 2 parts of modified polyvinyl alcohol in Example 3, 3 parts of nano silicon dioxide (particle size of 60 nm), 0.5 parts of polyacrylamide, and 0.05 parts of carboxymethyl cellulose.

[0062] The preparation steps of the oil-proof label paper are as follows: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

[0063] The following performance tests were conducted on the label papers prepared in Examples 5 to 13 and Comparative Examples 1 to 8: Water permeability: paper samples were cut into 60×60 mm sizes, and samples were taken from the edges greater than 12 cm; a proper amount of water (23° C.) was placed in a watch glass, two drops of blue ink were added, and the mixture was stirred evenly; the front side of the label paper sample (i.e., the side coated with the oil-proof layer) was placed in the water with the front side facing downward (the oil-proof layer contacting the water), and a stopwatch was started from the time the paper sample was placed in the water, and the timing was stopped when the first water permeable point appeared; the minimum number of seconds was recorded by meter reading as the water permeability test result; Oil-proof grade: the test was conducted using the KIT method; the above test results are shown in Table 1: Table 1

[0064] It can be seen from Table 1 that, compared with the label papers prepared in Comparative Examples 1-8 of the present invention, the oil resistance of the label papers prepared in Examples 5-13 can reach level 11 or above, and at the same time have excellent water resistance. It can be seen that the oil-proof label paper and the preparation method thereof provided by the present invention have excellent water resistance and oil resistance, and the preparation method is simple and can be mass-produced.

[0065] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0066] It should be understood that in the various embodiments of the present application, the size of the serial number of each process does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0067] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0068] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An oil-proof label paper, characterized in that: The oil-proof layer comprises an oil-proof layer, a surface material layer and a release layer from top to bottom; the raw materials of the oil-proof layer comprise the following components by weight: 25-40 parts of modified chitosan, 2-5 parts of modified polyvinyl alcohol, 3-6 parts of nano silicon dioxide, 0.5-2 parts of polyacrylamide and 0.05-1 parts of carboxymethyl cellulose; The modified chitosan is prepared by the following steps: Add chitosan to acetic acid solution and stir until completely dissolved, add glutaraldehyde solution, continue stirring for 1.0-1.5h, add montmorillonite, continue stirring for 12-24h, and obtain modified chitosan after vacuum drying; wherein the amount ratio of chitosan, acetic acid solution, glutaraldehyde solution and montmorillonite is 1.0-1.2g:50mL:2.5-3.0mL:0.3-0.5g; wherein the volume fraction of acetic acid solution is 2%, and the volume fraction of glutaraldehyde solution is 2.5%; The modified polyvinyl alcohol is prepared by the following steps: Add polyvinyl alcohol to deionized water, heat to 90-95°C, stir until uniform, keep warm for 1.0-1.5h, cool to room temperature, add citric acid, heat to 75-80°C, stir to react for 2-3h, cool to room temperature to obtain modified polyvinyl alcohol; wherein the amount ratio of polyvinyl alcohol, deionized water and citric acid is 1.50-1.55g:30mL:0.60-0.65g.

2. The oil-proof label paper according to claim 1, characterized in that: The particle size of the nano silicon dioxide is 60-85nm.

3. The oil-proof label paper according to claim 1, characterized in that: The thickness of the oil-proof layer is 15-20 μm, the thickness of the surface material layer is 10-25 μm, and the thickness of the release layer is 60-100 μm.

4. The oil-proof label paper according to claim 1, characterized in that: The surface material layer is one of offset paper, thermal paper, polypropylene film, polyethylene film, polyester film and polyvinyl alcohol film.

5. The oil-proof label paper according to claim 1, characterized in that: The release layer is silicon-coated paper.

6. The method for preparing an oil-proof label paper according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1: Mix modified chitosan, modified polyvinyl alcohol, nano-silicon dioxide, polyacrylamide and carboxymethyl cellulose according to a proportion, stir evenly, and obtain a mixed solution; Step 2: evenly apply the mixed liquid on one side of the surface material layer, dry it after coating, and laminate the other side of the uncoated surface material layer on the release layer after drying to obtain oil-proof label paper.

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