A fully cellulose-based uncoated greaseproof paper

Abstract

This invention discloses an all-cellulose-based uncoated greaseproof paper. This greaseproof paper is formed by dynamic forming of pulp A (freezing degree 10-50°SR), pulp B (freezing degree 90-97°SR), pulp C (fiber diameter 1-10μm, length 200-600μm), and pulp D (fiber diameter 100-1000nm, length 10-500μm, aspect ratio ≥100) with specific freeness or fiber dimensions, with a basis weight of 10-100 g / m³. 2 Its outer pulp layer (D side) achieves a kit oil resistance rating of 10-12 without any coating and is resistant to hot oil at 80℃. The preparation process of this invention requires no sizing or coating, making it simple, efficient, and environmentally friendly. The resulting product is made from 100% pulp fiber, is recyclable, biodegradable, healthy, and safe, and is suitable for packaging oily foods.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a fully cellulose-based uncoated oil-resistant paper. Background Technology

[0002] Oil-resistant paper is a special type of paper that prevents grease penetration. It mainly includes three categories: coated paper, fluorinated oil-resistant coated paper, and non-fluorinated oil-resistant coated paper. Coated paper is non-recyclable and difficult to biodegrade, while fluorinated oil-resistant agents produce toxic perfluorooctanesulfonamides when heated, posing a threat to human health. Therefore, non-fluorinated oil-resistant agents, especially bio-based biodegradable non-fluorinated oil-resistant agents, have received widespread attention and research. Nanocellulose, a fiber with a diameter at the nanometer level prepared from plant fibers, has a large specific surface area due to its small size effect, resulting in high tensile strength, Young's modulus, and barrier properties, and can be used to prepare non-fluorinated oil-resistant paper.

[0003] Patent CN114808543A discloses a method for preparing a high-performance food-grade greaseproof paper base material containing a nanofiber cellulose composite coating. The method involves mixing a nanofiber cellulose suspension prepared by the Tempo oxidation homogenization method with a propylene glycol alginate solution, coating the mixture onto the surface of food packaging paper, and then drying it thoroughly at room temperature. This method can improve the greaseproofness of the paper, achieving a maximum greaseproof rating of 9. However, in addition to nanofiber cellulose, the coating solution also requires the addition of propylene glycol alginate solution, resulting in a large number of components and a low solid content. Achieving the required coating amount can put pressure on the coating process. Furthermore, the drying method is room temperature drying, which takes a long time. Patent CN111395044A discloses a biodegradable food packaging greaseproof paper and its preparation method. This method involves sequentially coating paper with a nanofiber cellulose solution and a guar gum solution, followed by drying at room temperature for 12-24 hours. The resulting greaseproof paper is biodegradable. When the two solutions are sequentially coated and repeated three times, the resulting greaseproof paper achieves a greaseproof rating of 10. This method uses a solution with a low solid content and requires multiple coating processes, making the process relatively complex. The drying method is room temperature drying, which is time-consuming. Patent CN111304967A discloses a low-basis-weight food packaging paper with added nanocellulose and its manufacturing method. It involves adding nanocellulose to pulp, a surface sizing agent, and a surface coating liquid. The surface sizing agent consists of nanocellulose, starch, and an oil-resistant agent, while the surface coating liquid consists of nanocellulose and edible gelatin. The resulting oil-resistant paper can achieve an oil-resistant rating of 8 or higher. This method requires sizing and coating, involves multiple processes, and requires the addition of an oil-resistant agent to achieve an oil-resistant effect of 8 or higher.

[0004] It is evident that when nanocellulose is used in oil-proof paper, it is mainly used in the surface coating liquid and needs to be combined with other substances, making the process relatively complex and cumbersome. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a fully cellulose-based uncoated greaseproof paper. This greaseproof paper is made from 100% pulp, requiring no additives, and has a basis weight of 10-100 g / m³. 2 Furthermore, the outer oil-resistant surface has an oil resistance rating of 10 or higher and is resistant to hot oil. The oil-resistant paper is obtained through a preparation method that does not require surface sizing or coating. This method has a fast drying speed, simple process, and is suitable for large-scale production.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A type of all-cellulose-based uncoated greaseproof paper, characterized in that the basis weight of the greaseproof paper is 10-100 g / m³. 2 It consists of slurry A, slurry B, slurry C and slurry D, wherein the basis weight of slurry A is 0-90 g / m 2 The basis weight of slurry B is 0-30 g / m², and the basis weight of slurry C is 0-10 g / m². 2 The quantitative amount of slurry D is 1-6 g / m³. 2 The slurry D is located on the outer layer of the greaseproof paper, forming an oil-proof surface. The oil-proof surface has an oil-proof rating of 10-12, and hot oil does not penetrate the surface after being dripped onto it for 10 minutes.

[0008] Wherein, the freeness of pulp A is 10-50°SR, the freeness of pulp B is 90-97°SR, the average fiber diameter of pulp C is 1-10μm, the average length is 200-600μm, the average fiber diameter of pulp D is 100-1000nm, the average length is 10-500μm, and the average aspect ratio is ≥100.

[0009] The present invention also provides a method for preparing the above-mentioned all-cellulose-based uncoated oleophobic paper, characterized by comprising the following steps:

[0010] (1) Raw material preparation: The pulp raw material is first pulped in a pulping equipment to obtain pulp A, then pulped a second time to obtain pulp B, then pulped a third time to obtain pulp C, and pulp C is dissociated in a mechanical dissociation device to obtain pulp D;

[0011] (2) Dynamic forming: The pulps A, B, C and D are diluted to a certain concentration. A dynamic paper forming device is used to spray the pulps in sequence and at intervals under a certain drum speed and rotating spray pressure to form a wet paper web, which is then vacuum dewatered.

[0012] (3) Post-processing: The dehydrated wet paper web is dried in a drying cylinder and then calendered to obtain a full cellulose-based uncoated greaseproof paper;

[0013] The raw material used for the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 10-100 g / m³. 2 Slurry A accounts for 0-90 g / m 2 Slurry B accounts for 0-30g / m 2 Slurry C content is 0-10 g / m 2 Slurry D accounts for 1-6 g / m 2 The outer layer of slurry, surface D, is an oil-resistant surface with an oil resistance rating of 10-12. Hot oil droplets applied to the surface will not penetrate after 10 minutes.

[0014] The pulp raw material is at least one of bleached or unbleached softwood pulp, hardwood pulp, cotton pulp, bamboo pulp, wheat straw pulp, hemp pulp, reed pulp, or sugarcane pulp.

[0015] The pulping equipment includes one or more combinations of a trough pulper, a cone refiner, a cylindrical refiner, a disc refiner, and a high-consistency refiner; the first and second pulping methods are long-fiber viscous pulping, and the third pulping method is short-fiber viscous pulping.

[0016] The dissociation equipment includes one or more combinations of disc mills, fine grinding mills, ball mills, and high-pressure homogenizers; wherein the slurry mass concentration of the disc mill and fine grinding treatment is 3-5 wt%, the gap between the grinding discs is -100-0 μm, and the grinding disc rotation speed is 1500-2000 rpm; the slurry mass concentration of the ball mill treatment is 3-5 wt%, and the speed is 300-700 rpm; the slurry mass concentration of the high-pressure homogenizer treatment is 0.5-1 wt%, and the pressure is 500-1500 Bar.

[0017] The freeness of pulp A is 10-50°SR; the freeness of pulp B is 90-97°SR; the average fiber diameter of pulp C is 1-10μm and the average length is 200-600μm; the average fiber diameter of pulp D is 100-1000nm, the average length is 10-500μm, and the average aspect ratio is ≥100.

[0018] The slurry concentration is 0.01-0.5%, the drum speed is 600-1700 m / min, and the rotary spraying pressure is 0.1-0.3 MPa.

[0019] The slurry spraying sequence is at least one of the following: A→B→C→D, A→B→D, A→C→D, B→C→D, B→D, C→D, D→A→B→C→D, D→A→B→D, D→A→C→D, D→B→C→D, D→B→D, or D→C→D; the interval between each slurry is 0-120s.

[0020] The drying temperature is 80-120℃, the drying time is 1-15min; the calendering pressure is 50-300N / mm, and the number of calendering cycles is 1-6.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] 1. This invention provides a fully cellulose-based uncoated greaseproof paper and its preparation method. The greaseproof paper is formed by dynamic forming and papermaking, without the need for surface sizing or coating. It dries quickly, has a simple process, and can be scaled up to papermaking machines with multi-layer wire forming, making it suitable for large-scale production. The uncoated greaseproof paper obtained by this method uses 100% pulp as raw material, without the need for adding other substances. It achieves an oil resistance rating of 10-12, and 1 mL of 80°C soybean oil is not penetrated after 10 minutes on the surface of the greaseproof paper, demonstrating heat and oil resistance.

[0023] 2. This invention provides an all-cellulose-based uncoated greaseproof paper and its preparation method. The pulp used consists of pulps with different beating degrees and mechanical dissociation degrees. By controlling the type of pulp raw materials, beating conditions (including beating concentration, beating method, and beating degree), and spraying conditions (pulp dilution concentration, drum speed, rotary spraying pressure, spraying sequence, and spraying interval), a multilayer structure of 2-5 layers is constructed. Pulp A, with a lower beating degree and larger fiber size, acts as a base layer. Its larger pores between fibers provide the required thickness for the greaseproof paper while reducing its density and cost. Pulps B or C, with a higher beating degree and finer fibers, act as a support layer. The network structure they form is more compact. Spraying pulp D onto their surface reduces the thickness and amount of pulp D required. Furthermore, pulp C has finer fibers than pulp B. Using pulp C to prepare pulp D makes the mechanical dissociation process smoother and reduces dissociation energy consumption. In the multi-layered structure, the finer fiber size of slurry D acts as an oil barrier. Its fibers are very tightly packed with small pores, reducing the chance of oil penetration. In addition, the dense surface formed by slurry D has a fine micro-rough structure, which can support oil droplets, reduce the contact area between oil droplets and the surface, and reduce the wetting performance of oil on the surface.

[0024] 3. This invention provides a fully cellulose-based uncoated greaseproof paper and its preparation method. All pulps are formed in the same equipment, and no single pulp needs to be processed and formed in an additional device before lamination. The advantages of multi-layer forming in the same equipment include a simpler process and a very strong bond between layers, preventing delamination after drying or during folding and crumpling. By adjusting the spraying conditions, reasonable fiber interlacing areas are created between different pulps. The thickness of these interlacing areas is strictly controlled, ensuring that adjacent layers are tightly bonded together by hydrogen bonds formed by fiber interlacing, while preventing excessive penetration of fine fiber pulp into the pores of larger fiber pulp due to excessive interlacing thickness, thus avoiding an increase in the amount of fine fiber pulp needed to achieve the same greaseproof effect. Therefore, by effectively controlling the pulp size and spraying conditions, the goals of good interlayer bonding, material saving, low cost, and good greaseproof effect are achieved.

[0025] 4. This invention provides a fully cellulose-based uncoated greaseproof paper and its preparation method. The slurry D with the best greaseproof effect is constructed by papermaking rather than coating. Its advantage lies in that during papermaking, most of the water in slurry D is removed during rotary spraying and subsequent vacuum dewatering. Before drying, the solid content of slurry D in the wet paper web is above 15%, allowing it to directly enter the drying cylinder for drying. Furthermore, the content of slurry D is relatively low, resulting in a shorter drying time. In contrast, commonly used spraying or coating methods require, on the one hand, small nanocellulose sizes to avoid clogging the nozzles or affecting the coating process; and on the other hand, low nanocellulose concentrations to prevent the coating from becoming too viscous, which is also detrimental to the coating process. Generally, the solid content of nanocellulose in the coating solution does not exceed 2%, and the 98% water content not only severely reduces drying efficiency but also reduces the amount coated per pass, often requiring multiple coatings and complicating the process. In this invention, the slurry D has a larger average diameter and length than nanocellulose, which facilitates rapid water filtration during papermaking. Most of the water can be removed through the papermaking and dewatering process, forming a dense layer and reducing drying time. The entire process is simple and fast.

[0026] 5. This invention provides a fully cellulose-based uncoated greaseproof paper and its preparation method. The raw material used is only pulp, and the entire process is similar to papermaking. The white water used in papermaking can be completely reused, and no wastewater or waste gas is generated. The resulting greaseproof paper is 100% cellulose-based material, containing no greaseproof agents, adhesives, wet strength agents, or other chemicals, and can be recycled. Therefore, the preparation method provided by this invention is a green, environmentally friendly, and eco-friendly method. The resulting greaseproof paper is recyclable, biodegradable, healthy, safe, and food-contact, and has excellent greaseproof properties, making it suitable for packaging oily foods such as fried dough sticks, twisted dough sticks, French fries, popcorn, and fried chicken. Attached Figure Description

[0027] The accompanying drawings are provided to further illustrate the invention and form part of the specification, but do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 This is a scanning electron microscope image of the surface of an all-cellulose-based uncoated greaseproof paper, magnified at ×200 (inset magnification is ×10,000), showing a relatively dense network structure.

[0029] Figure 2 This is a scanning electron microscope image of a cross-section of an all-cellulose-based uncoated greaseproof paper (the pulp is sprayed out in the order of A→B→D), showing that the layers are tightly bonded together.

[0030] Figure 3 Digital photographs taken from an uncoated, oleophobic paper made entirely of cellulose. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments, but this is not intended to limit the present invention.

[0032] Example 1

[0033] (1) Raw material preparation: Bleached hardwood pulp is first beaten with long fibers in a high-consistency refiner to obtain pulp A with a freeness of 35°SR. Then, it is beaten with long fibers in a second long fiber viscous process to obtain pulp B with a freeness of 97°SR. Then, it is beaten with short fibers in a third short fiber viscous process to obtain pulp C with an average fiber diameter of 5μm and an average fiber length of 400μm. Pulp C is then dissociated in a fine refiner with a pulp mass concentration of 5wt%, a gap between the refiner discs of -100μm, and a refiner disc rotation speed of 2000rpm to obtain pulp D with an average fiber diameter of 200nm, an average fiber length of 50μm, and an average aspect ratio of 250.

[0034] (2) Dynamic forming: Pulp B is diluted to a concentration of 0.15% and pulp D is diluted to a concentration of 0.1%. A dynamic paper forming device is used. At a drum speed of 1000m / min and a rotary spraying pressure of 0.2Mpa, the pulp is sprayed out in the order of B→D with an interval of 5s to form a wet paper web, and then vacuum dewatered.

[0035] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 105℃ for 5 minutes, and then calendered once under a pressure of 100N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0036] The raw material used in the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 10 g / m³. 2 Of which slurry B accounts for 8 g / m 2Slurry D accounts for 2g / m 2 The outer layer of slurry, surface D, is an oil-resistant surface with an oil resistance rating of 12. Hot oil droplets applied to the surface will not penetrate after 10 minutes.

[0037] Example 2

[0038] (1) Raw material preparation: Bleached softwood pulp is first beaten with long fibers in a high-consistency refiner to obtain pulp A with a freeness of 50°SR. Then, it is beaten with long fibers a second time to obtain pulp B with a freeness of 97°SR. Then, it is beaten with short fibers a third time to obtain pulp C with an average fiber diameter of 8μm and an average fiber length of 550μm. Pulp C is dissociated in a high-pressure homogenizer with a pulp mass concentration of 0.8wt% and a pressure of 800Bar to obtain pulp D1 with an average fiber diameter of 500nm, an average fiber length of 450μm, and an average aspect ratio of 900. Pulp D1 is dissociated in a high-pressure homogenizer with a pulp mass concentration of 0.5wt% and a pressure of 1200Bar to obtain pulp D2 with an average fiber diameter of 200nm, an average fiber length of 40μm, and an average aspect ratio of 200.

[0039] (2) Dynamic forming: Dilute pulp D1 to a concentration of 0.15%, pulp C to a concentration of 0.18%, and pulp D2 to a concentration of 0.09%. Using a dynamic paper forming device, at a drum speed of 1400 m / min and a rotary spraying pressure of 0.15 MPa, the pulp is sprayed out in the order of D1→C→D2, with a 2-second interval between D1 and C and a 4-second interval between C and D2, to form a wet paper web, which is then vacuum dewatered.

[0040] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 105℃ for 5 minutes, and then calendered twice under a pressure of 260N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0041] The raw material used in the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 10 g / m³. 2 Of which, slurry D1 accounts for 4 g / m 2 Slurry C accounts for 4g / m 2 Slurry D2 accounts for 2g / m 2 The outer slurry surfaces D1 and D2 are oil-resistant, and their oil resistance rating is 12. Hot oil droplets can be dropped onto the surface for 10 minutes without penetrating.

[0042] Example 3

[0043] (1) Raw material preparation: Unbleached bamboo pulp is first beaten with long fibers in a trough beater to obtain pulp A1 with a freeness of 38°SR. Cotton pulp is first beaten with long fibers in a disc refiner to obtain pulp A2 with a freeness of 40°SR. Then, it is beaten with long fibers in a second long fiber beater to obtain pulp B with a freeness of 97°SR. Then, it is beaten with short fibers in a third short fiber beater to obtain pulp C with an average fiber diameter of 4μm and an average fiber length of 500μm. Pulp C is further dissociated in a disc refiner with a pulp mass concentration of 4%, a disc gap of -50μm, and a disc rotation speed of 1500rpm to obtain pulp D with an average fiber diameter of 300nm, an average fiber length of 50μm, and an average aspect ratio of 167.

[0044] (2) Dynamic forming: Slurry A1 is diluted to a concentration of 0.2%, slurry B to a concentration of 0.1%, and slurry D to a concentration of 0.1%. A dynamic paper forming device is used. At a drum speed of 1200 m / min and a rotary spraying pressure of 0.2 MPa, the slurries are sprayed out in the order of A1→B→D, with an interval of 5 s between A1 and B and an interval of 2 s between B and D, to form a wet paper web, which is then vacuum dewatered.

[0045] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 105℃ for 7 minutes, and then calendered 4 times under a pressure of 200N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0046] The raw material used for the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 20 g / m³. 2 Of which, slurry A1 accounts for 14 g / m 2 Slurry B accounts for 4g / m 2 Slurry D accounts for 1g / m 2 The outer layer of slurry, surface D, is an oil-resistant surface with an oil resistance rating of 10. Hot oil droplets applied to the surface will not penetrate after 10 minutes.

[0047] Example 4

[0048] (1) Raw material preparation: Bleached reed pulp was subjected to a first long-fiber viscous beating in a conical refiner to obtain pulp A1 with a freeness of 40°SR. Bleached hemp pulp was subjected to a first long-fiber viscous beating in a cylindrical refiner to obtain pulp A2 with a freeness of 45°SR. A second long-fiber viscous beating was then performed to obtain pulp B with a freeness of 96°SR. A third short-fiber viscous beating was then performed to obtain pulp C with an average fiber diameter of 8μm and an average fiber length of 500μm. Pulp C was then... The slurry was dissociated in a fine grinding mill with a mass concentration of 5%, a gap of -100 μm between grinding discs, and a grinding disc rotation speed of 1800 rpm to obtain slurry D1, which has an average fiber diameter of 350 nm, an average length of 200 μm, and an average aspect ratio of 571. Slurry D1 was then dissociated in a high-pressure homogenizer with a mass concentration of 1 wt% and a pressure of 1300 Bar to obtain slurry D2, which has an average fiber diameter of 150 nm, an average length of 60 μm, and an average aspect ratio of 400.

[0049] (2) Dynamic forming: Pulp A1 is diluted to a concentration of 0.25%, pulp B to a concentration of 0.18%, pulp D1 to a concentration of 0.1%, and pulp D2 to a concentration of 0.1%. A dynamic paper forming device is used. At a drum speed of 1150 m / min and a rotary spraying pressure of 0.15 MPa, the pulp is sprayed out in the order of D1→A1→B→D2. The interval between D1 and A1 is 1 s, the interval between A1 and B is 6 s, and the interval between B and D2 is 2 s to form a wet paper web, which is then vacuum dewatered.

[0050] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 105℃ for 10 min, and then calendered 4 times under a pressure of 300 N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0051] The raw material used in the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 40 g / m³. 2 Of which, slurry D1 accounts for 2 g / m 2 Slurry A1 accounts for 32g / m 2 Slurry B accounts for 5g / m 2 Slurry D2 accounts for 1g / m 2 The outer slurry surfaces D1 and D2 are oil-resistant, with an oil resistance rating of 10. Hot oil droplets applied to the surface do not penetrate after 10 minutes.

[0052] Example 5

[0053] (1) Raw material preparation: Unbleached wheat straw pulp was subjected to a first long-fiber viscous pulping process in a trough pulper to obtain pulp A1 with a freeness of 32°SR. Unbleached sugarcane pulp was subjected to a first long-fiber viscous pulping process in a high-consistency refiner to obtain pulp A2 with a freeness of 50°SR. A second long-fiber viscous pulping process was then performed to obtain pulp B with a freeness of 95°SR. A third short-fiber viscous pulping process was then performed to obtain pulp C with an average fiber diameter of 7μm and an average fiber length of 400μm. Material C is dissociated in a fine grinding mill with a slurry concentration of 4%, a grinding disc gap of -100μm, and a grinding disc rotation speed of 1500rpm to obtain slurry D1, which has an average fiber diameter of 320nm, an average length of 160μm, and an average aspect ratio of 500. Slurry D1 is then dissociated in a high-pressure homogenizer with a slurry concentration of 1wt% and a pressure of 800Bar to obtain slurry D2, which has an average fiber diameter of 200nm, an average length of 70μm, and an average aspect ratio of 350.

[0054] (2) Dynamic forming: Slurry A1 is diluted to a concentration of 0.23%, slurry C to a concentration of 0.15%, slurry D1 to a concentration of 0.1%, and slurry D2 to a concentration of 0.1%. A dynamic paper forming device is used. At a drum speed of 1350 m / min and a rotary spraying pressure of 0.25 MPa, the slurries are sprayed out in the order of D1→A1→C→D2. The interval between D1 and A1 is 2 s, the interval between A1 and C is 10 s, and the interval between C and D2 is 4 s to form a wet paper web, which is then vacuum dewatered.

[0055] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 110°C for 10 min, and then calendered three times under a pressure of 200 N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0056] The raw material used for the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 60 g / m³. 2 Of which, slurry D1 accounts for 3g / m 2 Slurry A1 accounts for 51.5 g / m 2 Slurry C accounts for 4g / m 2 Slurry D2 accounts for 1.5g / m 2 The outer slurry surfaces D1 and D2 are oil-resistant, and their oil resistance rating is 11. Hot oil droplets can be dropped onto the surface for 10 minutes without penetrating.

[0057] Example 6

[0058] (1) Raw material preparation: Bleached hardwood pulp is first beaten with long fibers in a high-consistency refiner to obtain pulp A with a freeness of 30°SR. Then, it is beaten with long fibers a second time to obtain pulp B with a freeness of 93°SR. Then, it is beaten with short fibers a third time to obtain pulp C with an average fiber diameter of 10μm and an average fiber length of 600μm. Pulp C is dissociated in a high-pressure homogenizer with a pulp mass concentration of 0.5wt% and a pressure of 1000Bar to obtain pulp D1 with an average fiber diameter of 1000nm, an average fiber length of 500μm, and an average aspect ratio of 500. Pulp D1 is concentrated to a mass concentration of 3% and further dissociated in a ball mill at a speed of 700rpm to obtain pulp D2 with an average fiber diameter of 300nm, an average fiber length of 40μm, and an average aspect ratio of 130.

[0059] (2) Dynamic forming: Pulp A is diluted to a concentration of 0.3%, pulp B to a concentration of 0.2%, pulp C to a concentration of 0.17%, pulp D1 to a concentration of 0.12%, and pulp D2 to a concentration of 0.1%. A dynamic paper forming device is used, with a drum speed of 1500 m / min and a rotary spraying pressure of 0.3 MPa. The pulp is sprayed out in the order of D1→A→B→C→D2, with a 2s interval between D1 and A, a 30s interval between A and B, a 10s interval between B and C, and a 7s interval between C and D2 to form a wet paper web, which is then vacuum dewatered.

[0060] (3) Post-treatment: The dehydrated wet paper is dried in a drying cylinder at 120°C for 15 minutes, and then calendered 6 times under a pressure of 300 N / mm to obtain a whole cellulose-based uncoated oil-proof paper.

[0061] The raw material used in the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 100 g / m³. 2 Of which, slurry D1 accounts for 4 g / m 2 Slurry A accounts for 84g / m³ 2 Slurry B accounts for 6g / m 2 Slurry C accounts for 4g / m 2 Slurry D2 accounts for 2g / m 2 The outer slurry surfaces D1 and D2 are oil-resistant, and their oil resistance rating is 12. Hot oil droplets can be dropped onto the surface for 10 minutes without penetrating.

[0062] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing an all-cellulose-based uncoated oleophobic paper, characterized in that, Includes the following steps: (1) Raw material preparation: The pulp raw material is first beating in a beating device to obtain pulp A, then beating a second time to obtain pulp B, then beating a third time to obtain pulp C, and pulp C is dissociated in a mechanical dissociation device to obtain pulp D; the freeness of pulp A is 10-50°SR, the freeness of pulp B is 90-97°SR, the average fiber diameter of pulp C is 1-10μm, the average length is 200-600μm, the average fiber diameter of pulp D is 100-1000nm, the average length is 10-500μm, and the average aspect ratio is ≥100; (2) Dynamic forming: Pulp A, pulp B, pulp C and pulp D are diluted to a concentration of 0.01-0.5% respectively. Using a dynamic paper forming device, the pulp is sprayed out in sequence and at intervals at a drum speed of 600-1700m / min and a rotary spraying pressure of 0.1-0.3MPa to form a wet paper web, which is then vacuum dewatered. (3) Post-processing: The dehydrated wet paper web is dried in a drying cylinder and then calendered to obtain a full cellulose-based uncoated greaseproof paper; The raw material used for the obtained all-cellulose-based uncoated greaseproof paper is 100% pulp, with a basis weight of 10-100 g / m³. 2 The quantitative amount of slurry A is 0-90 g / m³. 2 The quantitative amount of slurry B is 0-30 g / m³. 2 The quantitative amount of slurry C is 0-10 g / m³. 2 The quantitative amount of slurry D is 1-6 g / m³. 2 The slurry D is located on the outer layer of the oil-proof paper to form an oil-proof surface. The oil-proof surface has an oil-proof rating of 10-12, and hot oil does not penetrate the surface after being dripped onto it for 10 minutes.

2. The method for preparing a fully cellulose-based uncoated oleophobic paper according to claim 1, characterized in that, In step (1), the pulp raw material is at least one of bleached or unbleached softwood pulp, broadleaf pulp, cotton pulp, bamboo pulp, wheat straw pulp, hemp pulp, reed pulp, or sugarcane pulp.

3. The method for preparing a fully cellulose-based uncoated oleophobic paper according to claim 1, characterized in that, The pulping equipment used in step (1) includes one or more combinations of a trough pulper, a cone refiner, a cylindrical refiner, a disc refiner, and a high-consistency refiner; the first and second pulping methods are long fiber viscous pulping, and the third pulping method is short fiber viscous pulping.

4. The method for preparing a fully cellulose-based uncoated oleophobic paper according to claim 1, characterized in that, The mechanical dissociation equipment used in step (1) includes one or more combinations of disc mills, fine grinding mills, ball mills, and high-pressure homogenizers; wherein the mass concentration of the slurry treated by disc milling and fine grinding is 3-5 wt%, the gap between the grinding discs is -100 to 0 μm, and the grinding disc rotation speed is 1500-2000 rpm; the mass concentration of the slurry treated by ball milling is 3-5 wt%, and the speed is 300-700 rpm; the mass concentration of the slurry treated by high-pressure homogenization is 0.5-1 wt%, and the pressure is 500-1500 Bar.

5. The method for preparing a fully cellulose-based uncoated oleophobic paper according to claim 1, characterized in that, The slurry spraying sequence in step (2) is at least one of the following: A→B→C→D, A→B→D, A→C→D, B→C→D, B→D, C→D, D→A→B→C→D, D→A→B→D, D→A→C→D, D→B→C→D, D→B→D, or D→C→D; the interval between each slurry is 0-120s.

6. The method for preparing a fully cellulose-based uncoated oleophobic paper according to claim 1, characterized in that, In step (3), the drying temperature is 80-120℃, the drying time is 3-15min, the calendering pressure is 50-300N / mm, and the number of calendering cycles is 1-6.

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