Oil-absorbing oil-proof paper

Abstract

This invention discloses an oil-absorbing, oil-resistant paper. The oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 20-100 g / m³. 2 The paper comprises a permeable layer composed of fiber material P3 and nanocellulose N1 (500-1000 nm in diameter), an oil-storing layer composed of P3, oil-absorbing material, and nanocellulose N2 (200-500 nm in diameter, 0.6-1.0 mmol / g carboxyl content), a transition layer composed of N2, and an oil-proof layer composed of nanocellulose N3 (10-100 nm in diameter, 1.2-2.0 mmol / g carboxyl content). The oil absorption capacity of the oil-proof paper's oil-absorbing surface is 20-500 g / m². 2 The oil-resistant paper kit has an oil resistance rating of 10-12 and is heat-resistant. This invention utilizes a dynamic forming method, which is simple and can be mass-produced. The resulting oil-resistant paper can absorb excess oil from the surface of fried foods, reducing oil intake, and also possesses excellent oil-resistant properties, making it suitable for packaging high-fat foods.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to an oil-absorbing and oil-resistant paper. Background Technology

[0002] Fried foods such as fried dough sticks, fried chicken, French fries, and fried bread are high in oil. To prevent oil stains during storage and consumption, they are generally packaged in greaseproof paper. Greaseproof paper has a plastic film or is coated with an oil-resistant agent to prevent oil penetration and absorption. Oil-resistant agents mainly include fluorinated and non-fluorinated agents. Recent studies have found that fluorinated oil-resistant agents can be harmful to human health. Therefore, non-fluorinated oil-resistant agents have received widespread attention and research. In addition, fried foods have a high oil content, and an oil-absorbing paper is usually placed underneath to absorb excess oil. However, oil-absorbing paper is not oil-proof; oil can still seep through and contaminate the utensils or containers below. Therefore, there is a need to develop a paper that is both oil-absorbing and oil-resistant. On the one hand, it can prevent oil penetration and maintain a clean appearance; on the other hand, by absorbing excess oil, it can reduce the amount of oil ingested, making it relatively healthier.

[0003] Patent CN108999024A discloses an oil-absorbing and grease-resistant paper, comprising a substrate paper with a hydrophobic oil-retaining layer. This layer is a composite film composed of two combinations selected from ethylene alcohol-ethylene-vinyl acetate terpolymer, ethylene alcohol-ethylene-fatty acid ethylene terpolymer, cationic starch, and polyvinyl alcohol, along with hydrophobic oil-retaining particles. The particles are formed by coupling modification of layered inorganic materials with one or two of stearic acid, stearate, and stearate esters. The mass of the oil-retaining layer per square meter of substrate paper is 0.1-1.8 g. This invention effectively blocks grease from entering the substrate paper through the hydrophilicity of the hydrophilic resin in the hydrophobic oil-retaining layer, exhibiting significant oil absorption and grease diffusion prevention characteristics, resulting in excellent oil-repellent performance. Patent CN109056409A discloses a biodegradable oil-absorbing and grease-proof paper, comprising a substrate paper with a hydrophobic oil-retaining layer. This layer is a composite film composed of hydrophobic oil-retaining particles and a composite resin. The hydrophobic oil-retaining particles are formed by coupling modification of inorganic substances with one or two of fatty acids, fatty acid salts, and fatty acid esters. The composite resin is formed by combining two of chitosan, carboxymethyl cellulose, sodium alginate, and cationic starch with polyvinyl alcohol-microcrystalline cellulose. The mass of the oil-retaining layer on each square meter of substrate paper is 0.3-2.0 g. This invention utilizes the hydrophobic oil-retaining particles and composite resin to form a hydrophobic oil-retaining layer, exhibiting significant oil absorption, blocking oil diffusion, and biodegradability, resulting in good oil-proof performance. It can be used for packaging high-fat fried foods, etc. However, the oil-retaining layer mass in the oil-absorbing and grease-proof papers disclosed in both patents is 2.0 g / m². 2 Within this range, the ability to absorb oil is very limited, and the oil absorption and repellency performance mainly depends on the coating; the base paper itself cannot absorb or repel oil.

[0004] It is evident that improving the absorption of grease and enhancing the oil absorption and repellency of the base paper are technical problems that need to be solved in the field of oil-absorbing and oil-resistant paper. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide an oil-absorbing and oil-resistant paper. This oil-absorbing and oil-resistant paper can be prepared through a papermaking process, without the need for surface coating. The base paper material alone can achieve both oil absorption and oil resistance, exhibiting high oil absorption capacity, a high oil resistance rating, and resistance to hot oil.

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

[0007] An oil-absorbing and greaseproof paper, characterized in that the greaseproof paper is composed of a permeable layer, an oil-retaining layer, a transition layer, and an oil-repellent layer, with a basis weight of 20-100 g / m³. 2 The permeable layer accounts for 2-5 g / m 2 The oil reservoir accounts for 16.5-91 g / m³ 2 The transition layer accounts for 1-3 g / m 2 The oil-resistant layer accounts for 0.5-1g / m². 2 The oil-proof paper absorbs oil on one side, with an absorption capacity of 20-500g / m². 2 The other side is oil-resistant, with an oil resistance rating of 10-12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0008] The permeable layer is composed of fiber raw material P3 and nanocellulose N1, the oil storage layer is composed of fiber raw material P3, oil-absorbing material and nanocellulose N2, the transition layer is composed of nanocellulose N2, and the oil-proof layer is composed of nanocellulose N3.

[0009] The nanocellulose N1 has an average fiber diameter of 500-1000 nm and an average length of 100-500 μm; the nanocellulose N2 has an average fiber diameter of 200-500 nm, an average length of 100-500 μm, and a carboxyl content of 0.6-1.0 mmol / g; the nanocellulose N3 has an average fiber diameter of 10-100 nm, an average length of 1-10 μm, and a carboxyl content of 1.2-2.0 mmol / g.

[0010] The present invention also provides a method for preparing the above-mentioned oil-absorbing and greaseproof paper, characterized by comprising the following steps:

[0011] (1) Preparation of nanocellulose: Nanocellulose N1 is obtained by mechanically dissociating fiber raw material P1, nanocellulose N2 is obtained by chemical pretreatment and mechanical dissociation of fiber raw material P2, and nanocellulose N3 is obtained by further dissociation of N2.

[0012] (2) Raw material preparation: Fiber raw material P3 and nanocellulose N1 are mixed and diluted in a certain proportion to serve as the permeable layer raw material. Fiber raw material P3 is mixed and diluted in a certain proportion with oil-absorbing material and nanocellulose N2 to serve as the oil storage layer raw material. Nanocellulose N2 is diluted to serve as the transition layer raw material and nanocellulose N3 is diluted to serve as the oil-proof layer raw material.

[0013] (3) Forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out sequentially using a dynamic paper forming device at a certain drum speed and rotating spray pressure to form a wet paper web. After vacuum dehydration and drying in a drying cylinder, an oil-absorbing oil-proof paper is obtained.

[0014] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 20-100 g / m³. 2 The permeable layer accounts for 2-5 g / m 2 The oil reservoir accounts for 16.5-91 g / m³ 2 The transition layer accounts for 1-3 g / m 2 The oil-resistant layer accounts for 0.5-1g / m². 2 The oil-proof paper absorbs oil on one side, with an absorption capacity of 20-500g / m². 2 The other side is oil-resistant, with an oil resistance rating of 10-12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0015] The fiber raw material P1 is bleached or unbleached softwood pulp, and the fiber raw material P2 is bleached or unbleached hardwood pulp; the average fiber diameter of nanocellulose N1 is 500-1000 nm, and the average length is 100-500 μm; the average fiber diameter of nanocellulose N2 is 200-500 nm, the average length is 100-500 μm, and the carboxyl content is 0.6-1.0 mmol / g; the average fiber diameter of nanocellulose N3 is 10-100 nm, the average length is 1-10 μm, and the carboxyl content is 1.2-2.0 mmol / g.

[0016] The mechanical dissociation equipment used for nanocellulose N1 includes one or more combinations of conical refiners, cylindrical refiners, disc refiners, and high-consistency refiners; the chemical pretreatment methods used for nanocellulose N2 and nanocellulose N3 are one of TEMPO oxidation, carboxymethylation, and carboxyethylation, and the mechanical dissociation equipment used includes one or more combinations of disc mills, fine grinders, ball mills, and high-pressure homogenizers.

[0017] The fiber raw material P3 is one or more of the following: unbleached hardwood chemimechanical pulp, bamboo chemimechanical pulp, wheat straw pulp, reed pulp, and sugarcane pulp; the oil-absorbing material is one or more of the following: wood chips, talc, clay, calcium carbonate, silica, zeolite, dibenzyl sorbitol, magnesium stearate, calcium stearate, polypropylene fiber, polyethylene fiber, polyester fiber, alkyl ethylene polymer fiber, long-chain alkyl methacrylate fiber, and polyurethane foam particles.

[0018] The permeable layer has the following component mass ratios: P3 is 95-99%, N1 is 1-5%, the sum of their component mass percentages is 100%, and the dilution concentration is 0.1-0.5 wt%; the oil reservoir layer has the following component mass ratios: P3 is 30-68%, oil-absorbing material is 30-50%, N2 is 2-10%, the sum of their component mass percentages is 100%, and the dilution concentration is 0.1-1.0 wt%; the transition layer N2 has a dilution concentration of 0.05-0.2 wt%; and the oil-resistant layer N3 has a dilution concentration of 0.05-0.3 wt%.

[0019] The drum speed is 800-1500 m / min, and the rotary spraying pressure is 0.1-0.3 MPa. The drying temperature is 80-120℃, and the drying time is 1-10 min.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. This invention provides an oil-absorbing greaseproof paper and its preparation method. The greaseproof paper is formed by dynamic forming and papermaking, eliminating the need for surface sizing or coating. The process is simple and can be scaled up to papermaking machines with multi-layer wire forming, making it suitable for large-scale production. The oil-absorbing greaseproof paper obtained by this method absorbs oil on one side and is oil-resistant on the other, with an oil absorption capacity of 20-500 g / m³. 2 The kit has an oil resistance rating of 10-12 and is resistant to hot oil.

[0022] 2. This invention provides an oil-absorbing and greaseproof paper and its preparation method. The resulting oil-absorbing and greaseproof paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-proof layer. By adjusting the content and ratio of each component, the oil absorption and oil-proof properties can be controlled to meet the packaging requirements of different fried foods. The oil-absorbing surface can absorb excess oil from fried foods, reducing oil intake and making it relatively healthier. The oil-proof surface can prevent oil from permeating, keeping containers or hands clean.

[0023] 3. This invention provides an oil-absorbing greaseproof paper and its preparation method. The main raw material P3 used in the permeation layer of the obtained oil-absorbing greaseproof paper is one or more combinations of unbleached hardwood chemimechanical pulp, bamboo chemimechanical pulp, wheat straw pulp, reed pulp, and sugarcane pulp. The raw materials have a high lignin content, and the oleophilic groups such as phenylpropane in the lignin can reduce the surface tension of oil on the paper surface, which is conducive to the wetting and penetration of oil. Secondly, the pulp with a high lignin content is relatively stiff, and the paper after papermaking has a high bulk and porosity, which is also conducive to the penetration and absorption of oil. Furthermore, the paper made from these raw materials has a yellowish color, which helps to distinguish it visually from the white oil-absorbing surface. In addition, in order to increase strength, a small amount of slender nanocellulose N1 is added to the permeation layer. This form of nanocellulose can not only increase the hydrogen bonding between fiber raw materials, but also will not clog the mesh of the forming wire or reduce the porosity of the permeation layer. In addition to facilitating the penetration and absorption of oils, the permeable layer also acts as a barrier, preventing direct contact between food and the oil-absorbing material, and preventing the oil-absorbing material from overflowing and contaminating the food. Therefore, it makes the oil-absorbing paper safer and healthier.

[0024] 4. This invention provides an oil-absorbing, greaseproof paper and its preparation method. The oil-absorbing layer of the resulting oil-absorbing, greaseproof paper is composed of fiber raw material P3, oil-absorbing material, and nanocellulose N2. The three-dimensional network structure formed by fiber raw material P3 in this layer can effectively accommodate and disperse the oil-absorbing material, and the pores between its fibers also provide channels for further penetration and diffusion of oil. Nanocellulose N2 plays a reinforcing role in this layer. Compared with nanocellulose N1, nanocellulose N2 has smaller size and higher carboxyl content, which is beneficial for bonding the oil-absorbing material with fiber raw material P3, and the reinforcing effect is more significant than that of nanocellulose N1. The three-dimensional network structure provided by fiber raw material P3 and the adhesive effect of nanocellulose N2 enable the mass percentage of oil-absorbing material in the oil-absorbing layer to be as high as 30-50%. By controlling the type and amount of oil-absorbing material, high-oil-absorbing, greaseproof paper can be prepared.

[0025] 5. The present invention provides an oil-absorbing type of oil-proof paper and its preparation method. The transition layer of the obtained oil-absorbing type of oil-proof paper is composed of nanocellulose N2. This layer mainly plays a transition role between the oil storage layer and the oil-proof layer. Nanocellulose N2 has abundant hydroxyl and carboxyl hydrophilic groups. The dense network structure formed by it can reduce the penetration of oil into the oil-proof layer. At the same time, the dense structure fills the large pores on the surface of the oil storage layer, which is beneficial to reduce the amount of oil-proof layer material used.

[0026] 6. The present invention provides an oil-absorbing greaseproof paper and its preparation method. The oil-absorbing greaseproof paper has an oil-proof layer composed of nanocellulose N3. Compared with nanocellulose N2, nanocellulose N3 has a smaller size and a higher carboxyl content, thus forming a denser membrane structure that blocks the permeation of oil and has a high oil-proof rating. This allows the oil-absorbing greaseproof paper to absorb oil without allowing it to pass through, which is beneficial for packaging high-oil fried foods.

[0027] 7. The present invention provides an oil-absorbing greaseproof paper and its preparation method. The method uses dynamic paper forming to construct a four-layer structure of oil-absorbing greaseproof paper in the same equipment. No additional sizing or surface coating is required in the process. The vacuum dehydration and drying cylinder used are also common methods in the papermaking industry. Therefore, it can be scaled up to papermaking machines with multi-layer wire forming and is suitable for large-scale production.

[0028] 8. This invention provides an oil-absorbing greaseproof paper and its preparation method. The resulting oil-absorbing greaseproof paper has adjacent layers tightly bonded together by hydrogen bonds formed through fiber interweaving. The layers are firmly bonded, and even if folded or crumpled during use, it will not separate, thus maintaining its oil absorption and grease-repellent effects. Furthermore, the resulting oil-absorbing greaseproof paper is food-safe and can absorb excess oil while exhibiting excellent grease-repellent properties. It is suitable for packaging high-fat foods such as fried dough sticks, twisted dough sticks, French fries, and fried chicken. Attached Figure Description

[0029] 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:

[0030] Figure 1 This is a schematic diagram of the structure of an oil-absorbing, greaseproof paper.

[0031] The parts referred to by the numbers in the attached diagram are as follows: 1 - Permeable layer, 2 - Oil reservoir layer, 3 - Transition layer, 4 - Oil-proof layer, 21 - Oil-absorbing material. Detailed Implementation

[0032] 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.

[0033] Example 1

[0034] (1) Preparation of nanocellulose: Unbleached softwood pulp was mechanically dissociated using a high-consistency refiner to obtain nanocellulose N1, with an average fiber diameter of 800 nm and an average length of 300 μm; Unbleached hardwood pulp was pretreated with carboxyethylation and mechanically dissociated using a fine mill to obtain nanocellulose N2, with an average fiber diameter of 300 nm, an average length of 200 μm, and a carboxyl content of 0.8 mmol / g; N2 was further dissociated using a high-pressure homogenizer to obtain nanocellulose N3, with an average fiber diameter of 100 nm, an average length of 5 μm, and a carboxyl content of 1.4 mmol / g;

[0035] (2) Raw material preparation: Unbleached hardwood cellulose pulp and nanocellulose N1 are mixed at a mass ratio of 96:4 and diluted to 0.3wt% as the raw material for the permeation layer. Unbleached hardwood cellulose pulp, polypropylene fiber and nanocellulose N2 are mixed at a mass ratio of 48:50:2 and diluted to 0.5wt% as the raw material for the oil storage layer. Nanocellulose N2 is diluted to 0.2wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.1wt% as the raw material for the oil-resistant layer.

[0036] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming machine at a drum speed of 1500m / min and a rotary spraying pressure of 0.2Mpa to form a wet paper web. After vacuum dehydration and drying in a 105℃ drying cylinder for 15min, an oil-absorbing oil-proof paper is obtained.

[0037] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 100 g / m³. 2 The permeable layer accounts for 3g / m 2 The oil reservoir accounts for 94g / m 2 The transition layer accounts for 2g / m 2 Oil-resistant layer accounts for 1g / m 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 500g / m². 2 The other side is oil-resistant, with an oil resistance rating of 12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0038] Example 2

[0039] (1) Preparation of nanocellulose: Bleached softwood pulp was mechanically dissociated using a disc refiner to obtain nanocellulose N1, with an average fiber diameter of 500 nm and an average length of 200 μm; Bleached hardwood pulp was pretreated with carboxymethylation and mechanically dissociated using a ball mill to obtain nanocellulose N2, with an average fiber diameter of 200 nm, an average length of 100 μm, and a carboxyl content of 1.0 mmol / g; N2 was further dissociated using a high-pressure homogenizer to obtain nanocellulose N3, with an average fiber diameter of 60 nm, an average length of 1 μm, and a carboxyl content of 1.6 mmol / g;

[0040] (2) Raw material preparation: Unbleached bamboo slurry and nanocellulose N1 are mixed at a mass ratio of 95:5 and diluted to 0.4wt% as the raw material for the permeation layer. Unbleached bamboo slurry, talc powder and nanocellulose N2 are mixed at a mass ratio of 55:40:5 and diluted to 0.3wt% as the raw material for the oil storage layer. Nanocellulose N2 is diluted to 0.15wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.2wt% as the raw material for the oil-proof layer.

[0041] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming device at a drum speed of 1000m / min and a rotary spraying pressure of 0.1Mpa to form a wet paper web. After vacuum dehydration and drying in a 105℃ drying cylinder for 5min, an oil-absorbing oil-proof paper is obtained.

[0042] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 50 g / m³. 2 The permeable layer accounts for 5g / m 2 The oil reservoir accounts for 43g / m 2 The transition layer accounts for 1 g / m 2 Oil-resistant layer accounts for 1g / m 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 100g / m². 2 The other side is oil-resistant, with an oil resistance rating of 12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0043] Example 3

[0044] (1) Preparation of nanocellulose: Bleached softwood pulp was mechanically dissociated using a conical refiner to obtain nanocellulose N1, with an average fiber diameter of 800 nm and an average length of 300 μm; Unbleached hardwood pulp was pretreated with TEMPO and mechanically dissociated using a disc mill to obtain nanocellulose N2, with an average fiber diameter of 400 nm, an average length of 200 μm, and a carboxyl content of 0.9 mmol / g; N2 was further dissociated using a ball mill to obtain nanocellulose N3, with an average fiber diameter of 80 nm, an average length of 2 μm, and a carboxyl content of 1.8 mmol / g;

[0045] (2) Raw material preparation: Unbleached wheat straw pulp and nanocellulose N1 are mixed at a mass ratio of 97:3 and diluted to 0.3wt% as the raw material for the permeation layer. Unbleached wheat straw pulp, magnesium stearate and nanocellulose N2 are mixed at a mass ratio of 62:35:3 and diluted to 0.2wt% as the raw material for the oil storage layer. Nanocellulose N2 is diluted to 0.1wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.1wt% as the raw material for the oil-resistant layer.

[0046] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming device at a drum speed of 1200m / min and a rotary spraying pressure of 0.3Mpa to form a wet paper web. After vacuum dehydration and drying in a 110℃ drying cylinder for 1min, an oil-absorbing oil-proof paper is obtained.

[0047] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 20 g / m³. 2 The permeable layer accounts for 2g / m 2 The oil reservoir accounts for 15g / m 2 The transition layer accounts for 2g / m 2 Oil-resistant layer accounts for 1g / m 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 50g / m². 2 The other side is oil-resistant, with an oil resistance rating of 12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0048] Example 4

[0049] (1) Preparation of nanocellulose: Unbleached softwood pulp was mechanically dissociated using a cylindrical refiner to obtain nanocellulose N1, with an average fiber diameter of 600 nm and an average length of 500 μm; bleached hardwood pulp was pretreated with carboxyethylation and mechanically dissociated using a high-pressure homogenizer to obtain nanocellulose N2, with an average fiber diameter of 300 nm, an average length of 400 μm, and a carboxyl content of 0.6 mmol / g; N2 was further dissociated using a ball mill to obtain nanocellulose N3, with an average fiber diameter of 100 nm, an average length of 5 μm, and a carboxyl content of 1.2 mmol / g;

[0050] (2) Raw material preparation: Unbleached reed pulp and nanocellulose N1 are mixed at a mass ratio of 96:4 and diluted to 0.4wt% as the raw material for the penetrating layer. Unbleached reed pulp, sawdust, and nanocellulose N2 are mixed at a mass ratio of 45:45:10 and diluted to 0.3wt% as the raw material for the oil storage layer. Nanocellulose N2 is diluted to 0.2wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.1wt% as the raw material for the oil-resistant layer.

[0051] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming device at a drum speed of 1400m / min and a rotary spraying pressure of 0.2Mpa to form a wet paper web. After vacuum dehydration and drying in a 120℃ drying cylinder for 2min, an oil-absorbing oil-proof paper is obtained.

[0052] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 40 g / m³. 2 The permeable layer accounts for 3g / m 2 The oil reservoir accounts for 34.5 g / m 2 The transition layer accounts for 2g / m 2 The oil-resistant layer accounts for 0.5g / m². 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 80g / m². 2 On the other side, it is oil-resistant, with an oil resistance rating of 11. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0053] Example 5

[0054] (1) Preparation of nanocellulose: Bleached softwood pulp was mechanically dissociated using a disc refiner to obtain nanocellulose N1, with an average fiber diameter of 700 nm and an average length of 400 μm; Unbleached hardwood pulp was pretreated with carboxymethylation and mechanically dissociated using a fine mill to obtain nanocellulose N2, with an average fiber diameter of 400 nm, an average length of 500 μm, and a carboxyl content of 0.7 mmol / g; N2 was further dissociated using a disc refiner to obtain nanocellulose N3, with an average fiber diameter of 100 nm, an average length of 10 μm, and a carboxyl content of 1.3 mmol / g;

[0055] (2) Raw material preparation: Unbleached sugarcane pulp and nanocellulose N1 are mixed at a mass ratio of 95:5 and diluted to 0.2wt% as the raw material for the permeation layer. Unbleached sugarcane pulp, long-chain alkyl methacrylate fiber and nanocellulose N2 are mixed at a mass ratio of 45:50:5 and diluted to 0.2wt% as the raw material for the oil storage layer. Nanocellulose N2 is diluted to 0.1wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.05wt% as the raw material for the oil-resistant layer.

[0056] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming device at a drum speed of 1500m / min and a rotary spraying pressure of 0.3Mpa to form a wet paper web. After vacuum dehydration and drying in a 90℃ drying cylinder for 5min, an oil-absorbing oil-proof paper is obtained.

[0057] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 60 g / m³. 2 The permeable layer accounts for 4.5 g / m 2 The oil reservoir accounts for 54 g / m 2 The transition layer accounts for 1 g / m 2 The oil-resistant layer accounts for 0.5g / m². 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 300g / m². 2 On the other side, it is oil-resistant, with an oil resistance rating of 10. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0058] Example 6

[0059] (1) Preparation of nanocellulose: Unbleached softwood pulp was mechanically dissociated using a disc refiner to obtain nanocellulose N1, with an average fiber diameter of 500 nm and an average length of 150 μm; Unbleached hardwood pulp was TEMPO pretreated and mechanically dissociated using a ball mill to obtain nanocellulose N2, with an average fiber diameter of 200 nm, an average length of 100 μm, and a carboxyl content of 0.9 mmol / g; N2 was further dissociated using a high-pressure homogenizer to obtain nanocellulose N3, with an average fiber diameter of 10 nm, an average length of 2 μm, and a carboxyl content of 1.9 mmol / g;

[0060] (2) Raw material preparation: Unbleached hardwood phenolic pulp and nanocellulose N1 are mixed at a mass ratio of 96:4 and diluted to 0.1wt% as the raw material for the penetrating layer. Unbleached hardwood phenolic pulp, silica and nanocellulose N2 are mixed at a mass ratio of 66:30:4 and diluted to 0.1wt% as the raw material for the oil reservoir layer. Nanocellulose N2 is diluted to 0.1wt% as the raw material for the transition layer. Nanocellulose N3 is diluted to 0.05wt% as the raw material for the oil repellent layer.

[0061] (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming device at a drum speed of 1250m / min and a rotary spraying pressure of 0.2Mpa to form a wet paper web. After vacuum dehydration and drying in an 80℃ drying cylinder for 7min, an oil-absorbing oil-proof paper is obtained.

[0062] The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 80 g / m³. 2 The permeable layer accounts for 4.8 g / m 2 The oil reservoir accounts for 74 g / m 2 The transition layer accounts for 1 g / m 2 The oil-resistant layer accounts for 0.5g / m². 2 The oil-proof paper absorbs oil on one side, with an oil absorption capacity of 140g / m². 2 On the other side, it is oil-resistant, with an oil resistance rating of 11. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

[0063] 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 oil-absorbing, greaseproof paper, characterized in that, Includes the following steps: (1) Preparation of nanocellulose: Nanocellulose N1 is obtained by mechanically dissociating fiber raw material P1, and nanocellulose N2 is obtained by chemical pretreatment and mechanical dissociation of fiber raw material P2. Nanocellulose N3 is obtained by further dissociation of N2. The fiber raw material P1 is bleached or unbleached softwood pulp, and the fiber raw material P2 is bleached or unbleached hardwood pulp. The average fiber diameter of nanocellulose N1 is 500-1000 nm, and the average length is 100-500 μm. The average fiber diameter of nanocellulose N2 is 200-500 nm, the average length is 100-500 μm, and the carboxyl content is 0.6-1.0 mmol / g. The average fiber diameter of nanocellulose N3 is 10-100 nm, the average length is 1-10 μm, and the carboxyl content is 1.2-2.0 mmol / g. (2) Raw material preparation: Fiber raw material P3 and nanocellulose N1 are mixed and diluted in a certain proportion to serve as the permeation layer raw material; fiber raw material P3 is mixed and diluted in a certain proportion with oil-absorbing material and nanocellulose N2 to serve as the oil storage layer raw material; nanocellulose N2 is diluted to serve as the transition layer raw material; and nanocellulose N3 is diluted to serve as the oil-proof layer raw material; the fiber raw material P3 is one or a combination of unbleached hardwood pulp, bamboo pulp, wheat straw pulp, reed pulp, and sugarcane pulp. (3) Paper forming: The permeation layer material, oil storage layer material, transition layer material and oil-proof layer material are sprayed out in sequence using a dynamic paper forming machine at a drum speed of 800-1500m / min and a rotary spraying pressure of 0.1-0.3MPa to form a wet paper web. After vacuum dehydration and drying in a drying cylinder, an oil-absorbing oil-proof paper is obtained. The resulting oil-absorbing and oil-resistant paper consists of a permeable layer, an oil-retaining layer, a transition layer, and an oil-resistant layer, with a basis weight of 20-100 g / m³. 2 The permeable layer accounts for 2-5 g / m 2 The oil reservoir accounts for 16.5-91 g / m³ 2 The transition layer accounts for 1-3 g / m 2 The oil-resistant layer accounts for 0.5-1g / m². 2 The oil-proof paper absorbs oil on one side, with an absorption capacity of 20-500g / m². 2 The other side is oil-resistant, with an oil resistance rating of 10-12. Hot oil will not penetrate the surface after being dripped on it for 10 minutes.

2. The method for preparing an oil-absorbing, greaseproof paper according to claim 1, characterized in that, The mechanical dissociation equipment used in step (1) for nanocellulose N1 includes one or more combinations of conical refiners, cylindrical refiners, disc refiners, and high-consistency refiners; the chemical pretreatment methods used for nanocellulose N2 and nanocellulose N3 are one of TEMPO oxidation, carboxymethylation, and carboxyethylation, and the mechanical dissociation equipment used includes one or more combinations of disc mills, fine grinders, ball mills, and high-pressure homogenizers.

3. The method for preparing an oil-absorbing, greaseproof paper according to claim 1, characterized in that, The oil-absorbing material in step (2) is one or a combination of wood chips, talc, clay, calcium carbonate, silica, zeolite, dibenzyl sorbitol, magnesium stearate, calcium stearate, polypropylene fiber, polyethylene fiber, polyester fiber, alkyl ethylene polymer fiber, long-chain alkyl methacrylate fiber, and polyurethane foam particles.

4. The method for preparing an oil-absorbing and greaseproof paper according to claim 1, characterized in that, In step (2), the mass ratio of each component in the permeable layer is: P3 is 95-99%, N1 is 1-5%, the sum of the mass percentages of the components is 100%, and the dilution concentration is 0.1-0.5 wt%; the mass ratio of each component in the oil reservoir layer is: P3 is 30-68%, oil-absorbing material is 30-50%, N2 is 2-10%, the sum of the mass percentages of the components is 100%, and the dilution concentration is 0.1-1.0 wt%; the dilution concentration of N2 in the transition layer is 0.05-0.2 wt%; and the dilution concentration of N3 in the oil-resistant layer is 0.05-0.3 wt%.

5. The method for preparing an oil-absorbing, greaseproof paper according to claim 1, characterized in that, In step (3), the drying temperature is 80-120℃ and the drying time is 1-10min.

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