Lignin polyurethane synthetic leather, preparation method and application thereof

Abstract

The present application provides a kind of lignin polyurethane synthetic leather and its preparation method and application, the lignin polyurethane synthetic leather includes the foaming layer, adhesive layer and base cloth arranged in turn, the raw material of foaming layer and adhesive layer all includes phenolated lignin, petrochemical polyol and isocyanate;Since the phenolated lignin is used as the main raw material of foaming layer and adhesive layer, and is matched with specific petrochemical polyol, the obtained lignin polyurethane synthetic leather has good sweat resistance, excellent room temperature folding resistance and high peel strength, can effectively avoid the problem that skin is peeled off due to accelerated aging of leather surface after being eroded by sweat, suitable for being used as waistband leather, and also has the characteristics of sustainable development.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a lignin polyurethane synthetic leather, its preparation method, and its application. Background Technology

[0002] Currently, polyurethane belt leather, whether made from natural leather or polyurethane synthetic leather, exhibits defects such as surface damage and belt breakage after prolonged use. This aging process is particularly rapid in hot summer months due to the corrosive effects of human sweat. Therefore, improving the sweat resistance of polyurethane belt leather has become a key research focus in order to mitigate its aging rate and extend its lifespan.

[0003] In recent years, lignin has received a great deal of attention, especially in the context of the booming bio-based industry. Lignin is a complex and abundant natural polymer and a basic component of plants and trees. Lignin contains a complex three-dimensional structure with a variety of functional groups, including carbonyl, aliphatic, phenolic hydroxyl and methoxy groups.

[0004] Lignin can replace polyols in the reaction with isocyanates to synthesize polyurethane materials, yielding lignin-based polyurethane elastomers, foams, coatings, and adhesives. CN105001391A discloses a method for preparing lignin-based polyurethane prepolymer-modified phenolic foam. The method involves uniformly mixing polyol and lignin, heating and reacting in the presence of a catalyst, followed by vacuum dehydration to obtain a lignin-based polyol. Isocyanate is then added dropwise under a nitrogen atmosphere to obtain a lignin-based polyurethane prepolymer. The lignin-based polyurethane prepolymer is added to phenolic resin, and surfactants, foaming agents, and curing agents are added and stirred until homogeneous. The mixture is then poured into a mold and heated to cure, resulting in lignin-based polyurethane prepolymer-modified phenolic foam. The mechanical properties of the resulting phenolic foam insulation material are significantly improved. Furthermore, the introduction of a benzene ring structure into the polyurethane prepolymer mitigates the problem of decreased foam thermal stability caused by the introduction of urethane into the phenolic foam. CN112175558A discloses a modified lignin weather-resistant adhesive and its preparation method. The method modifies conventional phenolic resin by first phenolizing the acidic lignin with components such as acidic lignin, resorcinol, acetone, and concentrated sulfuric acid to obtain phenolic lignin. Phenolic lignin contains more phenolic hydroxyl groups and free reaction sites, which can replace part of the phenol in the reaction with formaldehyde to obtain phenolic resin. This step not only effectively reduces costs but also reduces the content of free phenol and free formaldehyde, improving the adhesive's performance. The resulting adhesive not only has excellent heat resistance and flame retardant properties but also cures at room temperature, exhibits good adhesion and is not easily detached, while its water resistance and flame retardancy are also improved. It is low-cost and highly practical.

[0005] However, although phenolic lignin has shown better reactivity and solubility, it has not been widely studied as a substitute for traditional polyols, especially in the field of polyurethane synthetic leather. There is even less research on integrating phenolic lignin into belt leather. Therefore, developing a lignin polyurethane synthetic leather is still a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a lignin polyurethane synthetic leather, its preparation method and application. The lignin polyurethane synthetic leather has excellent room temperature folding resistance, high peel strength and excellent resistance to sweat corrosion, and the raw material cost is low and the preparation process is simple, so it can be used as belt leather.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a lignin polyurethane synthetic leather, the lignin polyurethane synthetic leather comprising a foaming layer, an adhesive layer and a base fabric arranged sequentially.

[0009] The raw materials for both the foaming layer and the adhesive layer include phenolic lignin, petrochemical polyols, and isocyanates.

[0010] The lignin-based polyurethane synthetic leather provided by this invention comprises a foaming layer, an adhesive layer, and a base fabric arranged sequentially. The raw materials of the foaming layer and the adhesive layer both include phenolic lignin, petrochemical polyol, and isocyanate. Because the phenolic lignin is used as the main raw material of the foaming layer and the adhesive layer, combined with specific petrochemical polyol, the resulting polyurethane synthetic leather has good sweat resistance. When used as belt leather, it can effectively avoid the problem of accelerated aging and peeling of the leather surface due to sweat erosion. At the same time, it also has excellent room temperature folding resistance, high peel strength, and better sustainability.

[0011] It should be noted that the "petrochemical polyol" mentioned in this invention refers to polymer polyols obtained from petroleum and petrochemical products through a series of chemical reactions.

[0012] Preferably, the raw materials of the foam layer and the adhesive layer each independently comprise the following components in parts by weight:

[0013] 14-18 parts by weight of phenolic lignin;

[0014] 36-40 parts by weight of petrochemical polyols;

[0015] 24 to 28 parts by weight of isocyanate.

[0016] The amount of phenolic lignin used is 14 to 18 parts by weight, such as 14 parts by weight, 14.5 parts by weight, 15 parts by weight, 15.5 parts by weight, 16 parts by weight, 16.5 parts by weight, 17 parts by weight, 17.5 parts by weight, or 18 parts by weight.

[0017] The amount of the petrochemical polyol used is 36 to 40 parts by weight, such as 36 parts by weight, 36.5 parts by weight, 37.5 parts by weight, 38 parts by weight, 38.5 parts by weight, 39 parts by weight, 39.5 parts by weight, or 40 parts by weight.

[0018] The amount of isocyanate used is 24 to 28 parts by weight, for example, 24 parts by weight, 24.5 parts by weight, 25 parts by weight, 25.5 parts by weight, 26 parts by weight, 26.5 parts by weight, 27 parts by weight, 27.5 parts by weight, or 28 parts by weight.

[0019] Preferably, the hydroxyl value of the phenolic lignin is 26-30 mg KOH / g, such as 26 mg KOH / g, 26.5 mg KOH / g, 27 mg KOH / g, 27.5 mg KOH / g, 28 mg KOH / g, 28.5 mg KOH / g, 29 mg KOH / g, 29.5 mg KOH / g, or 30 mg KOH / g.

[0020] Preferably, the acid value of the phenolic lignin is ≤0.5mg KOH / g, such as 0.5mg KOH / g, 0.4mg KOH / g, 0.3mg KOH / g, 0.2mg KOH / g or 0.1mg KOH / g, etc.

[0021] Preferably, the raw materials for the phenolic lignin include lignin, phenol, catalyst, pH adjuster, and solvent.

[0022] Preferably, the phenolic lignin raw material comprises the following components in parts by weight:

[0023]

[0024] The amount of lignin used is 0.3 to 0.7 parts by weight, for example, 0.3 parts by weight, 0.35 parts by weight, 0.4 parts by weight, 0.45 parts by weight, 0.5 parts by weight, 0.55 parts by weight, 0.6 parts by weight, 0.65 parts by weight, or 0.7 parts by weight.

[0025] The amount of phenol used is 0.8 to 1.1 parts by weight, for example, 0.8 parts by weight, 0.85 parts by weight, 0.9 parts by weight, 0.95 parts by weight, 1 part by weight, 1.05 parts by weight, or 1.1 parts by weight.

[0026] The catalyst is used in an amount of 0.03 to 0.06 parts by weight, for example, 0.03 parts by weight, 0.035 parts by weight, 0.04 parts by weight, 0.045 parts by weight, 0.05 parts by weight, 0.055 parts by weight, or 0.06 parts by weight.

[0027] The amount of the pH adjuster is 75 to 90 parts by weight, for example, 75 parts by weight, 77 parts by weight, 79 parts by weight, 81 parts by weight, 83 parts by weight, 85 parts by weight, 87 parts by weight, 89 parts by weight, or 90 parts by weight.

[0028] The amount of solvent used is 8 to 11 parts by weight, for example, 8 parts by weight, 8.5 parts by weight, 9 parts by weight, 9.5 parts by weight, 10 parts by weight, 10.5 parts by weight or 11 parts by weight, etc.

[0029] The lignin is preferably derived from any one of beech, poplar, or pine.

[0030] Preferably, the catalyst comprises concentrated sulfuric acid, which refers to an aqueous solution of sulfuric acid with a mass fraction greater than or equal to 70%.

[0031] Preferably, the pH adjuster includes dilute sulfuric acid with a pH value of 0.5 to 2, such as 0.7, 0.9, 1, 1.2, 1.4, 1.6 or 1.8.

[0032] Preferably, the solvent comprises a mixture of acetone and water.

[0033] Preferably, the volume ratio of acetone to water is (9-11):1, for example, 9, 9.2:1, 9.4:1, 9.6:1, 9.8:1, 10:1, 10.2:1, 10.4:1, 10.6:1 or 10.8:1, etc.

[0034] Preferably, the phenolic lignin is prepared by the following method, which includes: first reacting lignin, phenol and a catalyst, then dissolving the resulting reaction product in a solvent and adding it together to a pH adjuster for precipitation, and finally filtering, washing and drying to obtain the phenolic lignin.

[0035] Preferably, the reaction temperature is 100-120°C, such as 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, or 118°C.

[0036] Preferably, the reaction time is 20 to 50 minutes, such as 25 minutes, 30 minutes, 35 minutes, 40 minutes, or 45 minutes.

[0037] Preferably, the polymer ultrafiltration membrane used for filtration includes any one of polyethersulfone ultrafiltration membrane, polyester ultrafiltration membrane, or polytetrafluoroethylene ultrafiltration membrane.

[0038] Preferably, the pore size of the polymer ultrafiltration membrane is 0.3 to 0.5 μm, such as 0.3 μm, 0.32 μm, 0.34 μm, 0.36 μm, 0.38 μm, 0.4 μm, 0.42 μm, 0.44 μm, 0.46 μm, 0.48 μm or 0.5 μm.

[0039] Preferably, the drying is carried out in the presence of a desiccant, which includes any one or a combination of at least two of phosphorus pentoxide, anhydrous calcium chloride, anhydrous magnesium sulfate, or silica gel.

[0040] Preferably, the drying is vacuum drying, the vacuum drying temperature is 60-80℃ (e.g., 65℃, 70℃ or 75℃, etc.), and the vacuum drying time is 10-15h (e.g., 11h, 12h, 13h or 14h, etc.).

[0041] Preferably, the hydroxyl value of the petrochemical polyol is 54-58 mg KOH / g, such as 54.5 mg KOH / g, 55 mg KOH / g, 55.5 mg KOH / g, 56 mg KOH / g, 56.5 mg KOH / g, 57 mg KOH / g, or 57.5 mg KOH / g.

[0042] Preferably, the acid value of the petrochemical polyol is ≤0.5mg KOH / g, such as 0.5mg KOH / g, 0.4mg KOH / g, 0.3mg KOH / g, 0.2mg KOH / g, or 0.1mg KOH / g.

[0043] Preferably, the petrochemical polyol includes any one or a combination of at least two of the following: polytetrahydrofuran ether diol, polyoxypropylene ether diol, polymethyl propylene glycol succinate diol, or diethylene glycol succinate diol.

[0044] Preferably, the isocyanate comprises 4,4-diphenylmethane diisocyanate and / or toluene diisocyanate.

[0045] Preferably, the raw materials of both the foaming layer and the adhesive layer also include a catalyst.

[0046] Preferably, the catalyst content in the raw materials of the foaming layer and the adhesive layer is 0.004 to 0.008 parts by weight, such as 0.005 parts by weight, 0.006 parts by weight, 0.007 parts by weight or 0.008 parts by weight.

[0047] Preferably, the catalyst comprises any one or a combination of at least two of dibutyltin dilaurate, stannous octoate, or bismuth carboxylate.

[0048] Preferably, the raw materials of both the foaming layer and the adhesive layer also include organic solvents.

[0049] Preferably, the content of organic solvent in the raw materials of the foaming layer and the adhesive layer is 17 to 21 parts by weight, such as 17.5 parts by weight, 18 parts by weight, 18.5 parts by weight, 19 parts by weight, 19.5 parts by weight, 20 parts by weight or 20.5 parts by weight, etc.

[0050] Preferably, the organic solvent includes any one or a combination of at least two of ethyl acetate, dimethyl carbonate, or butanone.

[0051] Preferably, the raw materials of both the foaming layer and the adhesive layer also include color paste.

[0052] In a second aspect, the present invention provides a method for preparing lignin-polyurethane synthetic leather as described in the second aspect, the method comprising the following steps:

[0053] (1) Phenolic lignin, petrochemical polyol and optionally catalyst are mixed in an organic solvent, and isocyanate is added to react to obtain polyurethane resin slurry.

[0054] (2) The polyurethane resin paste obtained in step (1) is coated on the surface of the release paper, and then dried, cured and foamed to obtain a foamed layer;

[0055] (3) A layer of polyurethane resin paste obtained in step (1) is coated on the surface of the foamed layer obtained in step (1), and then bonded to the base fabric. After drying and curing, the lignin polyurethane synthetic leather is obtained.

[0056] The method for preparing lignin polyurethane synthetic leather provided by this invention adopts a dry foaming process, which is different from the traditional wet-process synthetic leather that requires coagulation foaming. The process is simpler and lower in cost, and can ensure that the prepared lignin polyurethane synthetic leather has excellent sweat resistance, room temperature folding resistance and sustainable development.

[0057] Preferably, the reaction temperature in step (1) is 70 to 90°C, for example, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C or 88°C.

[0058] Preferably, the reaction time in step (1) is 1 to 3 hours, for example, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours or 2.8 hours.

[0059] Preferably, the coating thickness in step (2) is 0.5 to 0.9 mm, such as 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm or 0.85 mm.

[0060] Preferably, the drying, curing and foaming temperature in step (2) is 80-110℃ (e.g., 85℃, 90℃, 95℃, 100℃ or 105℃, etc.), and the time is 15-30min (e.g., 17min, 19min, 21min, 23min, 25min, 27min or 29min, etc.).

[0061] Preferably, the coating thickness in step (3) is 0.5 to 0.9 mm, such as 0.55 mm, 0.6 mm, 0.65 mm, 0.7 mm, 0.75 mm, 0.8 mm or 0.85 mm.

[0062] Preferably, the drying and curing temperature in step (3) is 80-110℃ (e.g., 85℃, 90℃, 95℃, 100℃ or 105℃, etc.), and the time is 15-30min (e.g., 17min, 19min, 21min, 23min, 25min, 27min or 29min, etc.).

[0063] Thirdly, the present invention provides an application of lignin polyurethane synthetic leather as described in the first aspect as belt leather.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] The lignin polyurethane synthetic leather provided by this invention comprises a foaming layer, an adhesive layer, and a base fabric arranged sequentially. The raw materials of the foaming layer and the adhesive layer both include phenolic lignin, petrochemical polyol, and isocyanate. By using phenolic lignin as the main raw material for the foaming layer and the adhesive layer, and combining it with specific petrochemical polyol, the resulting lignin polyurethane synthetic leather has good sweat resistance, excellent room temperature folding resistance, and high peel strength. It can effectively avoid the problem of accelerated aging and peeling of the leather surface due to sweat erosion, making it suitable for use as belt leather. It also has the characteristics of sustainable development. Detailed Implementation

[0066] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0067] Unless otherwise specified, the raw materials involved in the specific embodiments of this invention are all conventional materials in the art and can be purchased commercially.

[0068] Preparation Example 1

[0069] A phenolic lignin with a hydroxyl value of 28 mg KOH / g and an acid value of 0.4 mg KOH / g;

[0070] The method for preparing the phenolic lignin includes the following steps:

[0071] (1) Add 0.3 parts by weight of lignin derived from beech wood, 0.8 parts by weight of phenol and 0.03 parts by weight of concentrated sulfuric acid (mass fraction of 98.3%) to a reaction flask and react at 100°C for 50 min. Dissolve the resulting reaction product in a mixture of 8 parts by weight of acetone and water (volume ratio of acetone to water is 9:1) to obtain a mixture.

[0072] (2) The mixture obtained in step (1) is added to 75 parts by weight of dilute sulfuric acid (pH value is 1) for precipitation. The collected precipitate is filtered through a polyethersulfone membrane with a pore size of 0.3 μm, then washed with water until the pH is neutral, and then dried in the presence of phosphorus pentoxide under vacuum at 60°C for 15 h to obtain the phenolic lignin.

[0073] Preparation Example 2

[0074] A phenolic lignin with a hydroxyl value of 28 mg KOH / g and an acid value of 0.4 mg KOH / g;

[0075] The method for preparing the phenolic lignin includes the following steps:

[0076] (1) Add 0.5 parts by weight of lignin derived from poplar wood, 1 part by weight of phenol and 0.05 parts by weight of concentrated sulfuric acid (mass fraction of 98.3%) into a reaction flask, react at 110°C for 30 min, and dissolve the resulting reaction product in a mixture of 10 parts by weight of acetone and water (volume ratio of acetone to water is 10:1) to obtain a mixture.

[0077] (2) The mixture obtained in step (1) is added to 80 parts by weight of dilute sulfuric acid (pH value is 1) for precipitation. The collected precipitate is filtered through a polyester membrane with a pore size of 0.4 μm, then rinsed with water until the pH is neutral, and then dried in a vacuum environment at 70°C for 12 h in the presence of phosphorus pentoxide to obtain the phenolic lignin.

[0078] Preparation Example 3

[0079] A phenolic lignin with a hydroxyl value of 28 mg KOH / g and an acid value of 0.4 mg KOH / g;

[0080] The method for preparing the phenolic lignin includes the following steps:

[0081] (1) Add 0.7 parts by weight of lignin derived from pine wood, 1.1 parts by weight of phenol and 0.06 parts by weight of concentrated sulfuric acid (mass fraction of 98.3%) to a reaction flask and react at 120°C for 20 min. Dissolve the resulting reaction product in a mixture of 11 parts by weight of acetone and water (volume ratio of acetone to water is 11:1) to obtain a mixture.

[0082] (2) The mixture obtained in step (1) is added to 90 parts by weight of dilute sulfuric acid (pH value is 1) for precipitation. The collected precipitate is filtered through a polytetrafluoroethylene membrane with a pore size of 0.5 μm, then rinsed with water until the pH is neutral, and then dried in the presence of phosphorus pentoxide under vacuum at 80°C for 15 h to obtain the phenolic lignin.

[0083] Preparation Example 4

[0084] A phenolic lignin, which differs from Preparation Example 1 in that the precipitate collected in step (2) is not filtered through a polyethersulfone membrane with a pore size of 0.3 μm, but is directly rinsed with water until the pH is neutral. Other materials, amounts and steps are the same as in Preparation Example 1.

[0085] Preparation Example 5

[0086] A phenolic lignin differs from Preparation Example 1 in that 0.03 parts by weight of 85% formic acid is used instead of 0.03 parts by weight of 98.3% concentrated sulfuric acid, while the other substances, amounts, and preparation methods are the same as in Preparation Example 1.

[0087] Example 1

[0088] A lignin-polyurethane synthetic leather, comprising a foaming layer, an adhesive layer, and a base fabric arranged sequentially;

[0089] The raw materials for preparing the foaming layer and the adhesive layer include: 14 parts by weight of phenolic lignin (Preparation Example 1), 36 parts by weight of polytetrahydrofuran ether diol (hydroxyl value of 56 mg KOH / g, purchased from Hyosung Chemical, brand name PTMG-2000) and 0.004 parts by weight of dibutyltin dilaurate dissolved in 17 parts by weight of ethyl acetate, stirred evenly, and 24 parts by weight of 4,4-diphenylmethane diisocyanate added. The mixture was reacted at 70°C for 3 hours. After the reaction was completed, the mixture was cooled and packaged to obtain polyurethane resin slurry.

[0090] (2) The polyurethane resin slurry prepared in step (1) is mixed with 1 part by weight of black slurry (purchased from Jiangxi Sanyue Chemical, brand name PW-987A) and then coated on the surface of the release paper with a coating thickness of 0.5 mm. Then it is placed in an 80℃ oven to dry, cure and foam for 30 min to obtain a foamed layer.

[0091] (3) A layer of polyurethane resin slurry prepared in step (1) is coated on the surface of the foamed layer dried in step (1) with a coating thickness of 0.05 mm. Then, a microfiber base cloth (purchased from Tongda Microfiber) is attached, compacted, and placed in an 80°C oven to dry for 30 min to obtain the lignin polyurethane synthetic leather.

[0092] Example 2

[0093] A lignin-polyurethane synthetic leather, comprising a foaming layer, an adhesive layer, and a base fabric arranged sequentially;

[0094] The raw materials for preparing the foaming layer and the adhesive layer include: 16 parts by weight of phenolic lignin (Preparation Example 2), 38 parts by weight of polyoxypropylene ether glycol (hydroxyl value of 56 mg KOH / g, purchased from Wanhua Chemical, brand name C2020D) and 0.006 parts by weight of stannous octoate dissolved in 19 parts by weight of dimethyl carbonate, stirred evenly, 26 parts by weight of toluene diisocyanate added, reacted at 80°C for 2 hours, and after the reaction was completed, the material was cooled and packaged to obtain polyurethane resin slurry;

[0095] (2) The polyurethane resin slurry prepared in step (1) is mixed with 1 part by weight of black slurry (purchased from Jiangxi Sanyue Chemical, brand name PW-987A) and then coated on the surface of the release paper with a coating thickness of 0.7 mm. Then it is placed in a 90℃ oven to dry, cure and foam for 20 min to obtain a foamed layer.

[0096] (3) A layer of polyurethane resin slurry prepared in step (1) is coated on the surface of the foamed layer dried in step (1) with a coating thickness of 0.08 mm. Then, a microfiber base cloth (purchased from Tongda Microfiber) is attached, compacted, and placed in a 90°C oven to dry for 20 min to obtain the lignin polyurethane synthetic leather.

[0097] Example 3

[0098] A lignin-polyurethane synthetic leather, comprising a foaming layer, an adhesive layer, and a base fabric arranged sequentially;

[0099] The raw materials for preparing the foaming layer and the adhesive layer include: 18 parts by weight of phenolic lignin (Preparation Example 3), 40 parts by weight of polymethyl propylene glycol succinate (hydroxyl value of 56 mg KOH / g, purchased from Asahikawa Chemical), and 0.008 parts by weight of bismuth carboxylate dissolved in 21 parts by weight of butanone, stirred evenly, 28 parts by weight of toluene diisocyanate added, reacted at 90°C for 1 h, and after the reaction was completed, the material was cooled and packaged to obtain polyurethane resin slurry;

[0100] (2) The polyurethane resin slurry prepared in step (1) is mixed with 1 part by weight of black slurry (purchased from Jiangxi Sanyue Chemical, brand name PW-987A) and then coated on the surface of the release paper with a coating thickness of 0.9 mm. Then it is placed in an oven at 110℃ to dry and cure for 15 min to obtain a foamed layer.

[0101] (3) A layer of polyurethane resin slurry prepared in step (1) is coated on the surface of the foamed layer dried in step (1) with a coating thickness of 0.1 mm. Then, a microfiber base cloth (purchased from Tongda Microfiber) is attached, compacted, and placed in an oven at 110°C for 15 min to obtain the lignin polyurethane synthetic leather.

[0102] Examples 4-5

[0103] A lignin-polyurethane synthetic leather, which differs from Example 1 in that the phenolic lignin provided in Preparation Examples 4-5 is used instead of the phenolic lignin provided in Preparation Example 1, while the other materials, amounts and preparation methods are the same as in Example 1.

[0104] Example 6

[0105] A lignin-polyurethane synthetic leather differs from Example 1 in that the amount of phenolic lignin added to the raw materials for preparing the foam layer and the adhesive layer is 30 parts by weight, and the amount of polytetrahydrofuran diol added is 11 parts by weight. Other materials, amounts, and preparation methods are the same as in Example 1.

[0106] Example 7

[0107] A lignin-polyurethane synthetic leather differs from Example 1 in that the amount of phenolic lignin added as a raw material for preparing the foam layer and adhesive layer is 9 parts by weight, and the amount of polytetrahydrofuran diol added is 41 parts by weight. Other materials, amounts, and preparation methods are the same as in Example 1.

[0108] Comparative Example 1

[0109] A lignin-polyurethane synthetic leather differs from Example 1 in that the raw materials for preparing the foam layer and the adhesive layer do not contain polytetrahydrofuran diol, and the amount of phenolic lignin added is 50 parts by weight. Other materials, amounts, and preparation methods are the same as in Example 1.

[0110] Comparative Example 2

[0111] A polyurethane synthetic leather differs from Example 1 in that phenolic lignin is not added to the raw materials for preparing the foam layer and the adhesive layer, and the amount of polytetrahydrofuran diol added is 50 parts by weight. Other materials, amounts, and preparation methods are the same as in Example 1.

[0112] Performance testing:

[0113] (1) Room temperature flexural endurance: Tested according to the method provided in QB / T 3812.9-1999 standard;

[0114] (2) Peel strength: Tested according to the method provided in GB / T 3903.3-2011 standard;

[0115] (3) Color fastness to perspiration: Tested according to the method provided in GB / T 42165-2022 standard.

[0116] The polyurethane synthetic leathers provided in Examples 1-7 and Comparative Examples 1-2 were tested according to the above test methods. The test results are shown in Table 1.

[0117] Table 1

[0118] Example 1 18 83 Colorfast Example 2 16 77 Colorfast Example 3 15 75 Colorfast Example 4 9 49 Colorfast Example 5 16 51 Slight color fading Example 6 8 62 Colorfast Example 7 19 57 fade Comparative Example 1 7 43 Colorfast Comparative Example 2 16 51 Severe color fading

[0119] According to the data in Table 1:

[0120] (1) The lignin polyurethane synthetic leather provided in Examples 1 to 3 has a room temperature folding resistance of up to 150,000 to 180,000 times, a peel strength of up to 75 to 88 N, and does not fade in the perspiration test. It has excellent room temperature folding resistance, high peel strength and excellent perspiration color fastness.

[0121] (2) Compared with Example 1, the phenolic lignin used in the lignin polyurethane synthetic leather provided in Example 4 was not filtered, which resulted in the presence of impurities such as sulfite lignin in the obtained phenolic lignin, which could not participate in the synthesis reaction of polyurethane resin, thus causing a decrease in the room temperature folding resistance, peeling resistance and sweat resistance of the obtained synthetic leather.

[0122] (3) Compared with Example 1, the lignin polyurethane synthetic leather provided in Example 5 has poor sweat resistance and slight color fading. This is because the catalytic effect of formic acid is worse than that of concentrated sulfuric acid, resulting in poor quality of the obtained phenolic lignin.

[0123] (4) Compared with Example 1, the amount of phenolic lignin added in the lignin polyurethane synthetic leather provided in Example 6 is too high, resulting in excessive crosslinking degree and crystallinity of the obtained polyurethane resin, which further leads to a decrease in the room temperature folding resistance and peel strength of the polyurethane synthetic leather.

[0124] (5) Compared with Example 1, the amount of phenolic lignin added in the lignin polyurethane synthetic leather provided in Example 7 is too small and the amount of petrochemical polyol added is too large, resulting in a low degree of crosslinking and low crystallinity in the prepared polyurethane resin, which further leads to poor peel strength and color fastness to perspiration of the prepared polyurethane synthetic leather.

[0125] (6) Compared with Example 1, the lignin polyurethane synthetic leather provided in Comparative Example 1 uses phenolic lignin, and the degree of crosslinking and crystallinity in the polyurethane resin is too high, resulting in a decrease in its room temperature folding resistance and peel strength.

[0126] (7) Compared with Example 1, the lignin polyurethane synthetic leather provided in Comparative Example 2 uses all petrochemical polyols. The polyurethane resin does not have a cross-linked network structure and has a very low degree of crystallization, resulting in poor peel strength and color fastness to perspiration.

[0127] The applicant declares that this invention illustrates a lignin-polyurethane synthetic leather, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A lignin-polyurethane synthetic leather, characterized in that, The lignin-polyurethane synthetic leather comprises a foaming layer, an adhesive layer, and a base fabric arranged sequentially. The preparation method of the lignin polyurethane synthetic leather adopts a dry foaming process; The raw materials for the foaming layer and the adhesive layer each independently comprise the following components in parts by weight: 14-18 parts by weight of phenolic lignin; 36-40 parts by weight of petrochemical polyols; 24-28 parts by weight of isocyanate; 17-21 parts by weight of organic solvent; The raw materials for the phenolic lignin include lignin, phenol, catalyst, pH adjuster, and solvent; the catalyst includes concentrated sulfuric acid. The petrochemical polyol is selected from any one or a combination of at least two of the following: polytetrahydrofuran ether diol, polyoxypropylene ether diol, polymethyl propylene glycol succinate diol, or polyethylene glycol succinate diol.

2. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The hydroxyl value of the phenolic lignin is 26~30 mg KOH / g.

3. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The acid value of the phenolic lignin is ≤0.5 mg KOH / g.

4. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The raw material for the phenolic lignin comprises the following components in parts by weight: Lignin 0.3~0.7 parts by weight; Phenol 0.8~1.1 parts by weight; Catalyst: 0.03~0.06 parts by weight; 75-90 parts by weight of pH adjuster; Solvent: 8-11 parts by weight.

5. The lignin-polyurethane synthetic leather according to claim 4, characterized in that, The pH adjuster includes dilute sulfuric acid.

6. The lignin-polyurethane synthetic leather according to claim 4, characterized in that, The solvent includes a mixture of acetone and water.

7. The lignin-polyurethane synthetic leather according to claim 6, characterized in that, The volume ratio of acetone to water is (9~11):

1.

8. The lignin-polyurethane synthetic leather according to claim 4, characterized in that, The phenolic lignin is prepared by the following method, which includes: first reacting lignin, phenol and a catalyst, then dissolving the resulting reaction product in a solvent, then adding them together to a pH adjuster for precipitation, and finally filtering, washing and drying to obtain the phenolic lignin.

9. The lignin-polyurethane synthetic leather according to claim 8, characterized in that, The reaction is carried out at a temperature of 100-120°C for a time of 20-50 minutes.

10. The lignin-polyurethane synthetic leather according to claim 8, characterized in that, The polymer ultrafiltration membrane used for filtration includes any one of polyethersulfone ultrafiltration membrane, polyester ultrafiltration membrane, or polytetrafluoroethylene ultrafiltration membrane.

11. The lignin-polyurethane synthetic leather according to claim 10, characterized in that, The pore size of the polymer ultrafiltration membrane is 0.3~0.5 μm.

12. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The hydroxyl value of the petrochemical polyol is 54~58 mg KOH / g.

13. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The acid value of the petrochemical polyol is ≤0.5 mg KOH / g.

14. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The isocyanate includes 4,4-diphenylmethane diisocyanate and / or toluene diisocyanate.

15. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, Both the foaming layer and the adhesive layer contain catalysts in their raw materials.

16. The lignin-polyurethane synthetic leather according to claim 15, characterized in that, The catalyst content in the raw materials of the foaming layer and the adhesive layer is 0.004~0.008 parts by weight.

17. The lignin-polyurethane synthetic leather according to claim 15, characterized in that, The catalyst comprises any one or a combination of at least two of dibutyltin dilaurate, stannous octoate, or bismuth carboxylate.

18. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The organic solvent includes any one or a combination of at least two of ethyl acetate, dimethyl carbonate, or butanone.

19. The lignin-polyurethane synthetic leather according to claim 1, characterized in that, The raw materials for both the foaming layer and the adhesive layer also include color paste.

20. A method for preparing lignin-polyurethane synthetic leather according to any one of claims 1 to 19, characterized in that, The preparation method includes the following steps: (1) Phenolic lignin, petrochemical polyol and optionally catalyst are mixed in an organic solvent, and isocyanate is added to react to obtain polyurethane resin slurry; (2) The polyurethane resin paste obtained in step (1) is coated on the surface of the release paper, and then dried, cured and foamed to obtain a foamed layer; (3) A layer of polyurethane resin paste obtained in step (1) is coated on the film surface of the foamed layer obtained in step (1), and then bonded to the base fabric. After drying and curing, the lignin polyurethane synthetic leather is obtained.

21. The preparation method according to claim 20, characterized in that, The reaction in step (1) is carried out at a temperature of 70~90℃ for 1~3 h.

22. The preparation method according to claim 20, characterized in that, The coating thickness in step (2) is 0.5~0.9mm.

23. The preparation method according to claim 20, characterized in that, The drying, curing, and foaming temperature in step (2) is 80~110℃, and the time is 15~30 min.

24. The preparation method according to claim 20, characterized in that, The coating thickness in step (3) is 0.05~0.1 mm.

25. The preparation method according to claim 20, characterized in that, The drying and curing temperature in step (3) is 80~110℃ and the time is 15~30 min.

26. The use of a lignin-polyurethane synthetic leather as described in any one of claims 1 to 19 as belt leather.

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