Plastic-free wood fiber high-barrier transparent paper film

Abstract

The invention relates to the technical field of transparent paper films, in particular to a plastic-free wood fiber high-barrier transparent paper film which comprises a paper film body, a base layer is arranged in the paper film body, the top of the base layer is coated with an outer barrier coating, the other side of the outer barrier coating is coated with an outer waterproof coating, and the other side of the outer waterproof coating is coated with an outer layer. The inner and outer waterproof coatings and the inner and outer barrier coatings are arranged on the outer side of the base layer, the barrier effect of the base layer on substances such as oxygen is improved under the action of the inner and outer barrier coatings, and the performance during food packaging is guaranteed; according to the transparent paper film, the inner and outer barrier coatings are protected under the action of the inner and outer waterproof coatings, entering of water vapor is reduced, the performance of the transparent paper film is further improved, and the transparent paper film is made of a plastic-free material, cannot be decomposed in actual use, guarantees food safety, can be degraded after being used, and avoids environmental pollution.

Description

Technical Field

[0001] The invention relates to the technical field of transparent paper films, in particular to a plastic-free wood fiber high-barrier transparent paper film. Background Art

[0002] Transparent paper film is a thin film product made from natural fibers (such as cotton pulp and wood pulp) through a special process. It is highly transparent, non-toxic, odorless, and naturally degradable in soil, making it a green packaging material. This type of material is FSC-certified and suitable for use in applications with high environmental requirements. With technological advancements, traditional transparent paper films are no longer able to meet user needs. To improve the performance of transparent paper films, process or material innovations are often used to create transparent films with special functions.

[0003] In the packaging field, transparent paper films are also widely used. Traditional transparent paper films cannot block substances such as water vapor and oxygen when used, which makes them unable to be widely used in the field of food packaging. Most transparent paper films commonly used in food packaging contain plastic. Although they have good waterproof effects, plastics are prone to decomposition, affecting food safety. For this reason, we propose a plastic-free wood fiber high-barrier transparent paper film. Summary of the Invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a plastic-free wood fiber high-barrier transparent paper film, which can effectively solve the problems raised in the background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0006] The present invention provides a plastic-free wood fiber high-barrier transparent paper film, comprising a paper film main body, a base layer arranged inside the paper film main body, an outer barrier coating coated on the top of the base layer, an outer waterproof coating coated on the other side of the outer barrier coating, an outer layer coated on the other side of the outer waterproof coating, an inner barrier coating coated on the bottom of the base layer, an outer barrier coating coated on the other side of the inner barrier coating, and an antibacterial layer coated on the other side of the outer barrier coating.

[0007] Preferably, the base layer is prepared from wood fiber or plant fiber through a viscose method, and the thickness is set to 12-28 μm.

[0008] Preferably, the viscose method comprises the following steps:

[0009] S1. Pulping

[0010] Pure α-cellulose pulp made from wood or cotton linters;

[0011] S2, Aging & Yellowing

[0012] The pulp is treated with concentrated alkali solution to produce alkali cellulose, which then reacts with carbon disulfide to produce a viscous solution of cellulose xanthate;

[0013] S3, maturation & filtration degassing

[0014] The glue solution is matured, filtered and degassed;

[0015] S4, Molding

[0016] The viscose is squeezed through a slit die into a coagulation bath containing acid (such as sulfuric acid) and salt (such as sodium sulfate), where the cellulose xanthate decomposes and the cellulose regenerates and precipitates to form a film;

[0017] S5. Post-processing

[0018] The film is washed, bleached, desulfurized, plasticized and dried.

[0019] Preferably, the outer barrier coating and the inner barrier coating are coated respectively with chitosan and its derivatives and nitrocellulose through a roller coating process, and the thickness is set to 2-5 μm.

[0020] Preferably, the outer waterproof coating and the outer barrier coating are both prepared by a bio-wax / oil-based coating or chitosan and its derivatives through a micro-gravure roller coating process.

[0021] Preferably, the outer layer is a decorative layer, coated with nano calcium carbonate or a special primer, and has a thickness of 3-6 μm.

[0022] Preferably, the antibacterial layer is a natural active substance coating, specifically containing one of plant essential oil, chitosan and rosemary extract, and the thickness is set to 2-5 μm.

[0023] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0024] 1. The present invention provides inner and outer waterproof coatings and inner and outer barrier coatings on the outside of the base layer. The inner and outer barrier coatings enhance the base layer's barrier effect against substances such as oxygen, thereby ensuring performance during food packaging. Furthermore, the inner and outer waterproof coatings are provided on the outside of the inner and outer barrier coatings to protect the inner and outer barrier coatings, thereby reducing the ingress of water vapor and further improving the performance of the transparent paper film. Furthermore, the transparent paper film is made of a plastic-free material and will not decompose during actual use, thereby ensuring food safety. The transparent paper film can be degraded after use to avoid environmental pollution.

[0025] 2. The present invention provides an outer layer and an antibacterial layer. The outer layer is made of nano-calcium carbonate or a special primer. When packaging food, it can help improve smoothness, ink adhesion and color vividness, and facilitate the printing of icons. In addition, an antibacterial layer of natural active substances is provided on the surface in contact with food to prevent the entry of bacteria and protect the food. At the same time, it can be degraded and composted after use, further meeting the needs of food packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0027] Figure 1 This is a schematic diagram of the overall structure of the plastic-free wood fiber high-barrier transparent paper film of the present invention;

[0028] Figure 2 This is a schematic diagram of the explosion structure of the plastic-free wood fiber high-barrier transparent paper film of the present invention.

[0029] The numbers in the figure represent:

[0030] 1. Paper film body; 101. Base layer; 102. External waterproof coating; 103. External barrier coating; 104. External barrier coating; 105. Internal barrier coating; 106. Antibacterial layer; 107. External layer. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Example 1:

[0034] Reference Figure 1-2, which is the first embodiment of the present invention, discloses a plastic wood fiber-free high-barrier transparent paper film, including a paper film body 1, a base layer 101 is arranged inside the paper film body 1, the top of the base layer 101 is coated with an outer barrier coating 103, the other side of the outer barrier coating 103 is coated with an outer waterproof coating 102, the other side of the outer waterproof coating 102 is coated with an outer layer 107, the bottom of the base layer 101 is coated with an inner barrier coating 105, the other side of the inner barrier coating 105 is coated with an outer barrier coating 104, and the other side of the outer barrier coating 104 is coated with an antibacterial layer 106.

[0035] Specifically, the base layer 101 is prepared by a viscose method using wood fiber or plant fiber, and the thickness is set to 12 μm.

[0036] Material: A high-transmittance regenerated cellulose film (essentially an upgraded version of cellophane) made from high-purity wood fiber (such as coniferous wood and hardwood dissolving pulp) or non-wood plant fiber (such as cotton linter, bamboo, and sugarcane bagasse dissolving pulp) through the viscose process.

[0037] Function: As the core skeleton of the entire paper film, it provides the main mechanical strength (tensile strength, stiffness), transparency and bio-based basis. Its high purity is the key to achieving excellent transparency and subsequent coating adhesion.

[0038] Specifically, the viscose method includes the following steps:

[0039] S1. Pulping

[0040] Pure α-cellulose pulp made from wood or cotton linters;

[0041] Dissolving pulp replaces ordinary pulp: Use dissolving pulp with an α-cellulose content greater than 90% (such as hardwood / coniferous wood dissolving pulp) to reduce impurities such as lignin and hemicellulose.

[0042] Low-consistency pulping & headbox optimization: ensure uniform fiber dispersion (concentration < 0.1%) and reduce flocculation.

[0043] S2, Aging & Yellowing

[0044] The pulp is treated with concentrated alkali solution to produce alkali cellulose, which then reacts with carbon disulfide to produce a viscous solution of cellulose xanthate;

[0045] Chlorine-free bleaching (ECF / TCF) is used to achieve higher whiteness (ISO 90+) and reduce the risk of yellowing.

[0046] S3, maturation & filtration degassing

[0047] The glue solution is matured, filtered and degassed;

[0048] S4, Molding

[0049] The viscose is squeezed through a slit die into a coagulation bath containing acid (such as sulfuric acid) and salt (such as sodium sulfate); the cellulose xanthate decomposes and the cellulose regenerates and precipitates to form a film;

[0050] S5. Post-processing

[0051] The film is washed, bleached, desulfurized, plasticized and dried.

[0052] High-temperature hot air penetrates and dries, which can quickly set the shape and prevent the fiber from rebounding and forming pores.

[0053] Specifically, the outer barrier coating 103 and the inner barrier coating 105 are respectively coated with chitosan and its derivatives and nitrocellulose through a roller coating process, and the thickness is set to 2 μm.

[0054] Material: It is a compound of chitosan and its derivatives (providing film-forming properties and basic barrier) and nitrocellulose.

[0055] Function: One of the core barrier layers. It primarily provides excellent barrier properties against oxygen, carbon dioxide, and various volatile organic compounds (VOCs). Chitosan has excellent film-forming and gas barrier properties (especially for O2), while nitrocellulose significantly enhances the barrier properties against oils, aromas, and specific gases. The two work synergistically to achieve high barrier properties.

[0056] Process: Roller coating process is used to ensure the coating is dense and defect-free.

[0057] Specifically, the outer waterproof coating 102 and the outer barrier coating 104 are both prepared by a micro-gravure roller coating process using a bio-wax / oil-based coating or chitosan and its derivatives.

[0058] Material: Bio-wax / oil-based coating (such as carnauba wax, rice bran wax modifications) or chitosan and its derivatives (such as hydrophobic chitosan esters).

[0059] Function: Forms the first waterproof barrier, effectively resisting liquid water and condensation in the environment, preventing water from directly penetrating and eroding the internal structure. Biowax / oil provides excellent hydrophobicity, while chitosan derivatives have both waterproofness and certain biological activity.

[0060] Process: Thin and uniform coating is achieved through high-precision micro-gravure roller coating process to ensure optical clarity.

[0061] Specifically, the outer layer 107 is a decorative layer coated with nano calcium carbonate or a special primer, and has a thickness of 3 μm.

[0062] Coating with nano calcium carbonate or special primer can provide basic protection and printability. Nano calcium carbonate can enhance surface hardness, smoothness and glossiness, providing an ideal substrate for subsequent printing (such as water-based ink) or hot stamping. The primer can optimize the adhesion with the upper layer (such as ink or subsequent composite layer).

[0063] Specifically, the antibacterial layer 106 is a natural active substance coating, specifically containing one of plant essential oil, chitosan and rosemary extract, and the thickness is set to 2 μm.

[0064] Material: Functional coating loaded with natural active substances, the core ingredients are selected from: plant essential oils (such as thymol, carvacrol, cinnamaldehyde), chitosan (which has broad-spectrum antibacterial properties), and rosemary extract (rich in antioxidant and antibacterial ingredients such as carnosic acid and rosmarinic acid).

[0065] Function: Provides contact and non-volatile antimicrobial / microbial inhibition. Particularly suitable for applications requiring high hygiene standards, such as fresh foods, ready-to-eat products, and medical supplements, it effectively inhibits the growth of surface microorganisms (bacteria and mold), extending product shelf life and enhancing safety. Its natural origin ensures consistency with the product's "plastic-free" and "fully biodegradable" properties.

[0066] Application Areas

[0067] Food packaging:

[0068] Candy (twist-tie packaging, bags), chocolate (inner packaging), baked goods (dry), tea, coffee (inner bags), dry goods (rice, flour, nuts, biscuits - often require compounding / coating), sausage casings (as an alternative to collagen casings).

[0069] Example 2:

[0070] Reference Figure 1-2 , which is the second embodiment of the present invention:

[0071] The plastic-free wood fiber high-barrier transparent paper film includes a paper film body 1, a base layer 101 is arranged inside the paper film body 1, an outer barrier coating 103 is coated on the top of the base layer 101, an outer waterproof coating 102 is coated on the other side of the outer barrier coating 103, an outer layer 107 is coated on the other side of the outer waterproof coating 102, an inner barrier coating 105 is coated on the bottom of the base layer 101, an outer barrier coating 104 is coated on the other side of the inner barrier coating 105, and an antibacterial layer 106 is coated on the other side of the outer barrier coating 104.

[0072] Specifically, the base layer 101 is prepared by a viscose method using wood fiber or plant fiber, and the thickness is set to 28 μm.

[0073] Material: A high-transmittance regenerated cellulose film (essentially an upgraded version of cellophane) made from high-purity wood fiber (such as coniferous wood and hardwood dissolving pulp) or non-wood plant fiber (such as cotton linter, bamboo, and sugarcane bagasse dissolving pulp) through the viscose process.

[0074] Function: As the core skeleton of the entire paper film, it provides the main mechanical strength (tensile strength, stiffness), transparency and bio-based basis. Its high purity is the key to achieving excellent transparency and subsequent coating adhesion.

[0075] Specifically, the viscose method includes the following steps:

[0076] S1. Pulping

[0077] Pure α-cellulose pulp made from wood or cotton linters;

[0078] Dissolving pulp replaces ordinary pulp: Use dissolving pulp with an α-cellulose content greater than 90% (such as hardwood / coniferous wood dissolving pulp) to reduce impurities such as lignin and hemicellulose.

[0079] Low-consistency pulping & headbox optimization: ensure uniform fiber dispersion (concentration < 0.1%) and reduce flocculation.

[0080] S2, Aging & Yellowing

[0081] The pulp is treated with concentrated alkali solution to produce alkali cellulose, which then reacts with carbon disulfide to produce a viscous solution of cellulose xanthate;

[0082] Chlorine-free bleaching (ECF / TCF) is used to achieve higher whiteness (ISO 90+) and reduce the risk of yellowing.

[0083] S3, maturation & filtration degassing

[0084] The glue solution is matured, filtered and degassed;

[0085] S4, Molding

[0086] The viscose is squeezed through a slit die into a coagulation bath containing acid (such as sulfuric acid) and salt (such as sodium sulfate); the cellulose xanthate decomposes and the cellulose regenerates and precipitates to form a film;

[0087] S5. Post-processing

[0088] The film is washed, bleached, desulfurized, plasticized and dried.

[0089] High-temperature hot air penetrates and dries, which can quickly set the shape and prevent the fiber from rebounding and forming pores.

[0090] Specifically, the outer barrier coating 103 and the inner barrier coating 105 are respectively coated with chitosan and its derivatives and nitrocellulose through a roller coating process, and the thickness is set to 5 μm.

[0091] Material: It is a compound of chitosan and its derivatives (providing film-forming properties and basic barrier) and nitrocellulose.

[0092] Function: One of the core barrier layers. It primarily provides excellent barrier properties against oxygen, carbon dioxide, and various volatile organic compounds (VOCs). Chitosan has excellent film-forming and gas barrier properties (especially for O2), while nitrocellulose significantly enhances the barrier properties against oils, aromas, and specific gases. The two work synergistically to achieve high barrier properties.

[0093] Process: Roller coating process is used to ensure the coating is dense and defect-free.

[0094] Specifically, the outer waterproof coating 102 and the outer barrier coating 104 are both prepared by a micro-gravure roller coating process using a bio-wax / oil-based coating or chitosan and its derivatives.

[0095] Material: Bio-wax / oil-based coating (such as carnauba wax, rice bran wax modifications) or chitosan and its derivatives (such as hydrophobic chitosan esters).

[0096] Function: Forms the first waterproof barrier, effectively resisting liquid water and condensation in the environment, preventing water from directly penetrating and eroding the internal structure. Biowax / oil provides excellent hydrophobicity, while chitosan derivatives have both waterproofness and certain biological activity.

[0097] Process: Thin and uniform coating is achieved through high-precision micro-gravure roller coating process to ensure optical clarity.

[0098] Specifically, the outer layer 107 is a decorative layer coated with nano calcium carbonate or a special primer, and the thickness is set to 6 μm.

[0099] Coating with nano calcium carbonate or special primer can provide basic protection and printability. Nano calcium carbonate can enhance surface hardness, smoothness and glossiness, providing an ideal substrate for subsequent printing (such as water-based ink) or hot stamping. The primer can optimize the adhesion with the upper layer (such as ink or subsequent composite layer).

[0100] Specifically, the antibacterial layer 106 is a natural active substance coating, specifically containing one of plant essential oil, chitosan and rosemary extract, and the thickness is set to 5 μm.

[0101] Material: Functional coating loaded with natural active substances, the core ingredients are selected from: plant essential oils (such as thymol, carvacrol, cinnamaldehyde), chitosan (which has broad-spectrum antibacterial properties), and rosemary extract (rich in antioxidant and antibacterial ingredients such as carnosic acid and rosmarinic acid).

[0102] Function: Provides contact and non-volatile antimicrobial / microbial inhibition. Particularly suitable for applications requiring high hygiene standards, such as fresh foods, ready-to-eat products, and medical supplements, it effectively inhibits the growth of surface microorganisms (bacteria and mold), extending product shelf life and enhancing safety. Its natural origin ensures consistency with the product's "plastic-free" and "fully biodegradable" properties.

[0103] Application Areas

[0104] Food packaging:

[0105] Candy (twist-tie packaging, bags), chocolate (inner packaging), baked goods (dry), tea, coffee (inner bags), dry goods (rice, flour, nuts, biscuits - often require compounding / coating), sausage casings (as an alternative to collagen casings).

[0106] The workflow of the present invention is as follows:

[0107] When preparing the plastic-free wood fiber high-barrier transparent paper film, the base layer 101 is first prepared by a gluing method;

[0108] After the base layer 101 is prepared, a barrier coating is applied using a coating device. The coated base layer 101 is dried in a hot air flotation drying oven. After drying, a waterproof layer is applied again, and then dried again.

[0109] After the drying is completed, the outer layer 107 and the antibacterial layer 106 are coated respectively. After the coating of the outer layer 107 and the antibacterial layer 106 is completed, the film is rolled up.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Plastic-free wood fiber high barrier transparent paper film, characterized by: It includes a paper film body, a base layer is arranged inside the paper film body, the top of the base layer is coated with an outer barrier coating, the other side of the outer barrier coating is coated with an outer waterproof coating, the other side of the outer waterproof coating is coated with an outer layer, the bottom of the base layer is coated with an inner barrier coating, the other side of the inner barrier coating is coated with an outer barrier coating, and the other side of the outer barrier coating is coated with an antibacterial layer.

2. The plastic-free wood fiber high-barrier transparent paper film according to claim 1, characterized in that: The base layer is prepared by using wood fiber or plant fiber through a viscose method, and the thickness is set to 12-28 μm.

3. A method of making the base layer according to claim 2 by viscose method of wood fiber or plant fiber, characterized in that: The viscose method comprises the following steps: S1. Pulping Pure α-cellulose pulp made from wood or cotton linters; S2, Aging & Yellowing The pulp is treated with concentrated alkali solution to produce alkali cellulose, which then reacts with carbon disulfide to produce a viscous solution of cellulose xanthate; S3, maturation & filtration degassing The glue solution is matured, filtered and degassed; S4, Molding The viscose is squeezed through a slit die into a coagulation bath containing acid (such as sulfuric acid) and salt (such as sodium sulfate), where the cellulose xanthate decomposes and the cellulose regenerates and precipitates to form a film; S5. Post-processing The film is washed, bleached, desulfurized, plasticized and dried.

4. The plastic-free wood fiber high-barrier transparent paper film according to claim 1, characterized in that: The outer barrier coating and the inner barrier coating are respectively coated with chitosan and its derivatives and nitrocellulose through a roller coating process, and the thickness is set to 2-5 μm.

5. The plastic-free wood fiber high-barrier transparent paper film according to claim 1, characterized in that: The outer waterproof coating and the outer barrier coating are both prepared by a micro-gravure roller coating process using a bio-wax / grease-based coating or chitosan and its derivatives.

6. The plastic-free wood fiber high-barrier transparent paper film according to claim 1, characterized in that: The outer layer is specifically a decorative layer, which is coated with nano calcium carbonate or a special primer, and has a thickness of 3-6 μm.

7. The plastic-free wood fiber high-barrier transparent paper film according to claim 1, characterized in that: The antibacterial layer is a natural active substance coating, specifically containing one of plant essential oil, chitosan and rosemary extract, and the thickness is set to 2-5 μm.

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