Method for preparing multi-scale nanolignin waterproof and oil-proof agent by alkali pulping black liquor and application

Abstract

The application discloses a method for preparing a multi-scale nanolignin waterproof and oil-proof agent by using alkaline pulping black liquor and application thereof, and belongs to the technical field of bio-based waterproof and oil-proof agents. The multi-scale nanolignin waterproof and oil-proof agent is prepared by using alkaline pulping black liquor as raw material, directly preparing multi-scale nanolignin with a particle size of 200-1500 nm through an acid precipitation method, and compounding the multi-scale nanolignin with starch. The multi-scale nanolignin waterproof and oil-proof agent is double-coated on paper, so that the Cobb 60 value of the base paper is reduced from 62.14 g / m 2 to 17.71 g / m 2 , the Kit value is increased from 0 to 10, and the tensile index is increased from 41.11 Nm / g to 55.96 Nm / g, so that the waterproofness, oil-proofness and mechanical properties of the paper coating are significantly improved. The preparation method is simple, the raw material source is wide, and the method meets the major strategic demand of sustainable development of the material industry in China.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bio-based waterproof and oil-proof agent, and more particularly relates to a method for preparing a multi-scale nanolignin waterproof and oil-proof agent from alkaline pulping black liquor and application thereof. BACKGROUND

[0002] In some application fields using paper as a base material, the paper often needs to be endowed with barrier properties due to insufficient barrier properties to water, air and grease. The commonly used method is to use paper waterproof and oil-proof agent to internally penetrate and fill capillary holes, or to reduce its interfacial energy through surface treatment. However, the traditional fluorine-containing waterproof and oil-proof agent uses the special surface energy of fluorine materials to achieve the purpose of preventing water and grease from penetrating, which has high persistence and bioaccumulation in the environment and can cause harm to the human body.

[0003] At present, there are many related researches on new type of non-toxic and environment-friendly waterproof and oil-proof agent using bio-based polymers (such as polysaccharides, proteins, lipids, etc.) as main raw materials. Bio-based waterproof and oil-proof agent mainly includes chitosan, hemicellulose, microfibrillated cellulose and starch, etc. Although these materials are biologically friendly, they still have high hydrophilicity, and the film made of these materials usually has high moisture absorption, resulting in the loss of part of the barrier performance under high humidity conditions. Lignin, as a typical biomass macromolecule, is cheap and easy to obtain, environment-friendly, biodegradable and has good hydrophobicity. On the one hand, there are few studies on lignin as a paper waterproof and oil-proof agent. On the other hand, China's paper industry produces a large amount of black liquor every year, which contains a large amount of lignin. According to statistics, more than 95% of lignin is discarded as waste in the pulping and papermaking process, and most of it is burned after the alkali recovery process, without being well utilized.

[0004] Patent CN 108532362 A provides a preparation method of a lignin sizing agent, but it modifies lignin and then performs surface sizing on corrugated paper together with starch, which is complicated to operate and has higher cost. It can improve the waterproofness of corrugated paper, but does not mention the oil-proof effect.

[0005] Chinese patent CN 115821628 A discloses a preparation method and application of a cationized starch-based nanocellulose oil-proof agent, but it is complicated to operate through three times of pulp treatment, and only has oil-proof performance.

[0006] Patent CN 105899628 A discloses a lignin-based waterproof coating, which forms a lignin solution by dissolving lignin in a solvent, and coats the lignin solution on a substrate to enhance the waterproofness of the substrate, but does not mention the oil-proof performance.

[0007] In Wu Wei's "Influence of Starch on Water and Oil Resistance of Oil-proof Paper", it is mentioned that by using oxidized starch, cationic starch and cassava starch to compound a certain amount of oil-proof agent and polyvinyl alcohol to prepare a sizing agent for coating oil-proof paper, the oil-proof grade can reach 7 level and the water contact angle can reach 90.6°. However, the polyvinyl alcohol in it is petroleum-based plastic, non-renewable, difficult to degrade and has limited oil-proof effect.

[0008] Therefore, it is necessary to develop a new type of non-toxic and harmless, degradable, water-proof and oil-proof paper agent with enhanced mechanical properties using lignin extracted from pulp black liquor as raw material, which has important social value. SUMMARY

[0009] In view of the above problems existing in the prior art, the technical problems to be solved by the present application are to provide a method for preparing a multi-scale nanolignin water-proof and oil-proof agent from alkali pulping black liquor, which has a wide source of raw materials, a simple preparation method and low cost. Another technical problem to be solved by the present application is to provide a multi-scale nanolignin water-proof and oil-proof agent prepared by the above method, which can form a dense barrier coating on the surface of paper. The present application also solves a technical problem to provide the application of the above multi-scale nanolignin water-proof and oil-proof agent in the preparation of water-proof and oil-proof paper base materials.

[0010] In order to solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0011] A method for preparing a multi-scale nanolignin water-proof and oil-proof agent from alkali pulping black liquor, which uses alkali pulping black liquor as raw material and directly prepares multi-scale nanolignin by acid precipitation method. The multi-scale nanolignin is compounded with starch to prepare a multi-scale nanolignin water-proof and oil-proof agent. The particle size of the multi-scale nanolignin is 200-1500 nm.

[0012] As a preferred embodiment, the specific process of the acid precipitation method is as follows: after the alkali pulping black liquor is stirred and heated, the pH value of the solution is adjusted with acid, and after standing and settling, it is centrifuged and washed to neutral, freeze-dried, ground and vacuum dried to obtain multi-scale nanolignin particles.

[0013] As a preferred embodiment, the stirring speed is 100-1000 rpm and the temperature is raised to 20-100℃.

[0014] As a preferred embodiment, when the pH value of the solution is adjusted to 1-5, the acid addition is stopped and the stirring is continued for 30-150 min.

[0015] As a preferred embodiment, the acid is selected from any one of sulfuric acid, hydrochloric acid and phosphoric acid.

[0016] As a preferred embodiment, the starch is selected from any one of table glue starch, raw starch, oxidized starch and cationic starch.

[0017] Preferably, the mass ratio of the multi-scale nanolignin to starch is 0.5-2:2.

[0018] Preferably, the starch concentration is 5%-8%.

[0019] The method for preparing the multi-scale nanolignin waterproof and oil-proof agent from alkaline pulping black liquor comprises the following steps:

[0020] 1) The alkaline pulping black liquor is mechanically stirred, and acid is added dropwise while stirring until the pH value of the black liquor is 1-5, then the acid addition is stopped, and the stirring is continued after heat preservation, then the mixture is statically settled, centrifugally washed to neutral, freeze-dried, ground, and vacuum-dried to obtain multi-scale nanolignin particles;

[0021] 2) The multi-scale nanolignin particles prepared in step 1), starch, and pure water are mixed and gelatinized to prepare the multi-scale nanolignin waterproof and oil-proof agent, which is used after heat preservation at 60 DEG C.

[0022] The method for preparing the multi-scale nanolignin waterproof and oil-proof agent from alkaline pulping black liquor prepares the multi-scale nanolignin waterproof and oil-proof agent.

[0023] The multi-scale nanolignin waterproof and oil-proof agent is applied to the preparation of a waterproof and oil-proof paper base material.

[0024] In the application, the preparation process is as follows: a rod coater is used to perform double-layer coating on the surface of A4 paper with a basis weight of 80 g / m 2 , the coating amount is 5 g / m 2 , a layer of the multi-scale nanolignin waterproof and oil-proof agent is coated on the surface of the paper, the paper coated with the layer is placed into a 60 DEG C constant-temperature oven and dried for 2 min, then the second layer of starch is coated, and the paper is placed into the 60 DEG C constant-temperature oven and dried for 5 min, and finally the treated A4 paper is balanced in a constant-temperature and constant-humidity chamber for 24 h.

[0025] Compared with the prior art, the application has the following beneficial effects:

[0026] (1) The multi-scale nanolignin particles are directly extracted from the alkaline pulping black liquor by the acid precipitation method, the nanomaterial characteristics and the hydrophobicity of the lignin are utilized, the nanolignin waterproof and oil-proof agent is prepared by compounding the nanolignin with starch, and the waterproof and oil-proof performance of the paper is improved by sizing on the surface of the paper;

[0027] (2) The size of the lignin nanoparticles of different scales is regulated, a dense multi-layer space network structure is constructed on the surface of the paper, the hydrophobic and oleophobic performance of the paper is improved, the porosity is reduced, and the waterproof and oil-proof performance of the paper is improved;

[0028] (3) The multi-scale nanolignin waterproof and oil-proof agent prepared by the application is applied to paper-based materials to improve waterproof and oil-proof performance, which can reduce the Cobb 60 value of the raw paper from 62.14 g / m 2 to 17.71 g / m 2 , increase the Kit value from 0 level to 10 level, and increase the tensile index from 41.11 Nm / g to 55.96 Nm / g, so that the waterproof, oil-proof and mechanical properties of the paper coating can be significantly improved.

[0029] (4) The multi-scale nanolignin particles prepared by the application are extracted from black liquor of alkaline pulping, which not only has a wide source of raw materials, but also can achieve waste recycling and environmental protection, meet the major strategic needs of sustainable development of the material industry in China, and has a simple preparation method, low cost and wide industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The infrared spectrum of the multi-scale nanolignin particles prepared in Examples 1-6 is shown in the figure.

[0031] Figure 2 The particle size scale diagram of the multi-scale nanolignin particles prepared in Examples 1-6 is shown in the figure. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described below in combination with specific examples. Unless otherwise specified, the technical means used in the following examples are conventional means known to those skilled in the art. If no specific conditions are noted in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If no manufacturer of the reagent or instrument is noted, it is a conventional product that can be purchased on the market.

[0033] The performance test method used in the application is as follows:

[0034] 1. Water resistance test of paper: refer to Determination of Water Absorption of Paper and Paperboard GB / T 1540-2002;

[0035] 2. Oil resistance test of paper: refer to Determination of Grease Resistance of Paper and Paperboard GB / T 22805.2-2008;

[0036] 3. Tensile index and elongation test of paper: refer to Determination of Tensile Index of Paper and Paperboard GB / T 453-2002.

[0037] 4. Particle size scale measurement: Zetasizer Nano-Zs dynamic light scattering nanolaser particle size instrument, Malvern Company, UK.

[0038] The alkali pulping black liquor and raw starch used in the following examples were provided by APP; the table glue starch, oxidized starch and cationic starch were provided by Ekin Silicone (Shanghai) Co., Ltd. The mixer used was a JB300-D electric mechanical mixer, purchased from Shanghai Jin'an Industrial Technology Co., Ltd.

[0039] Example 1

[0040] A method for preparing a multi-scale nanolignin waterproof and oil-proof agent using alkali pulping black liquor, comprising the following steps:

[0041] 1) 500g of alkali pulping black liquor was added to a beaker and mechanically stirred at 100rmp at 20℃, while adding sulfuric acid dropwise until the pH value of the black liquor was 1, then stopping the acid addition, continuing to stir for 30min, and then standing overnight, centrifugal washing to neutral, freezing drying for 48h, grinding, and vacuum drying at 40℃ for 24h, to obtain 24.65g of multi-scale nanolignin particles, denoted as L1;

[0042] 2) After 0.5g of multi-scale nanolignin particles prepared in step 1), 2g of table glue starch and 23g of pure water were gelatinized at 90℃ for 1h, a multi-scale nanolignin waterproof and oil-proof agent was obtained, and the mixture was stored at 60℃ for standby use.

[0043] Example 2

[0044] A method for preparing a multi-scale nanolignin waterproof and oil-proof agent using alkali pulping black liquor, comprising the following steps:

[0045] 1) 500g of alkali pulping black liquor was added to a beaker and mechanically stirred at 500rmp at 60℃, while adding sulfuric acid dropwise until the pH value of the black liquor was 3, then stopping the acid addition, continuing to stir for 90min, and then standing overnight, centrifugal washing to neutral, freezing drying for 48h, grinding, and vacuum drying at 40℃ for 24h, to obtain 25.89g of multi-scale nanolignin particles, denoted as L2;

[0046] 2) After 0.5g of multi-scale nanolignin particles prepared in step 1), 2g of cationic starch and 23g of pure water were gelatinized at 90℃ for 1h, a multi-scale nanolignin waterproof and oil-proof agent was obtained, and the mixture was stored at 60℃ for standby use.

[0047] Example 3

[0048] A method for preparing a multi-scale nanolignin waterproof and oil-proof agent using alkali pulping black liquor, comprising the following steps:

[0049] 1) 500 g of alkaline pulping black liquor was added to a beaker and mechanically stirred at 1000 rpm at 100°C, while adding sulfuric acid dropwise until the pH of the black liquor was 5, then the acid was stopped, and the stirring was continued for 150 min, then it was left overnight, centrifuged and washed to neutral, frozen and dried for 48 h, ground, and vacuum dried at 40°C for 24 h, to obtain 23.11 g of multi-scale nanolignin particles, denoted as L3;

[0050] 2) After 0.5 g of multi-scale nanolignin particles prepared in step 1), 2 g of surface glue starch and 23 g of pure water were gelatinized at 90°C for 1 h, a multi-scale nanolignin waterproof and oil-proof agent was obtained, and it was used at 60°C.

[0051] Example 4

[0052] A method for preparing a multi-scale nanolignin waterproof and oil-proof agent using alkaline pulping black liquor, comprising the following steps:

[0053] 1) 500 g of alkaline pulping black liquor was added to a beaker and mechanically stirred at 1000 rpm at 100°C, while adding sulfuric acid dropwise until the pH of the black liquor was 5, then the acid was stopped, and the stirring was continued for 150 min, then it was left overnight, centrifuged and washed to neutral, frozen and dried for 48 h, ground, and vacuum dried at 40°C for 24 h, to obtain 23.11 g of multi-scale nanolignin particles, denoted as L3;

[0054] 2) After 0.5 g of multi-scale nanolignin particles prepared in step 1), 2 g of surface glue starch and 23 g of pure water were gelatinized at 90°C for 1 h, a multi-scale nanolignin waterproof and oil-proof agent was obtained, and it was used at 60°C.

[0055] Example 5

[0056] A method for preparing a multi-scale nanolignin waterproof and oil-proof agent using alkaline pulping black liquor, comprising the following steps:

[0057] 1) 500 g of alkaline pulping black liquor was added to a beaker and mechanically stirred at 1000 rpm at 100°C, while adding sulfuric acid dropwise until the pH of the black liquor was 5, then the acid was stopped, and the stirring was continued for 150 min, then it was left overnight, centrifuged and washed to neutral, frozen and dried for 48 h, ground, and vacuum dried at 40°C for 24 h, to obtain 23.11 g of multi-scale nanolignin particles, denoted as L3;

[0058] 2) After 0.5 g of multi-scale nanolignin particles prepared in step 1), 2 g of surface glue starch and 23 g of pure water were gelatinized at 90°C for 1 h, a multi-scale nanolignin waterproof and oil-proof agent was obtained, and it was used at 60°C.

[0059] Example 6

[0060] A method for preparing multi-scale nano-lignin waterproof and oil-resistant agents using alkaline pulping black liquor includes the following steps:

[0061] 1) Add 500g of black liquor from alkaline pulping to a beaker and mechanically stir at 200rpm at 40℃. While stirring, add phosphoric acid dropwise until the pH of the black liquor is 2. Stop adding acid, keep warm and continue stirring for 60min, let stand overnight, centrifuge and wash until neutral, freeze dry for 48h, grind, and vacuum dry at 40℃ for 24h to obtain 22.02g of multi-scale nano-lignin particles, denoted as L6;

[0062] 2) Gelatinize 0.5g of the multi-scale nano-lignin particles prepared in step 1), 2g of native starch and 23g of purified water at 90℃ for 1h to obtain a multi-scale nano-lignin waterproof and oil-repellent agent, and keep it at 60℃ for later use.

[0063] Depend on Figure 1 It can be seen that the basic structure of lignin nanoparticles (LNPs) at different scales remains unchanged, and the types of functional groups remain consistent. In the 1300–1000 cm⁻¹ range... -1 The peaks are relatively dispersed, mainly due to the stretching vibrations of CO and the tensile vibrations of its secondary structure. (833 cm⁻¹) -1 The location is the benzene ring CH bending vibration, 1220 cm⁻¹ -1 The point is the stretching vibration of CO on the benzene ring, 1600 cm⁻¹. -1 The point represents the C=C stretching vibration of the benzene ring. 2930 cm⁻¹ -1 The absorption peak at 3413 cm⁻¹ is attributed to the asymmetric vibrations of the methyl (-CH₃) and methylene (-CH₂) groups. -1 The peak at this point corresponds to the vibration of the hydroxyl group (-OH).

[0064] The particle size of the multi-scale nano-lignin particles prepared in Examples 1-6 above was measured, and the results are shown in Table 1 and... Figure 2 As shown.

[0065]

[0066]

[0067] Comparative Example 1

[0068] Mix 2g of surface starch and 23g of purified water and place them in a four-necked flask equipped with an electric stirrer, a condenser and a thermometer. Then place the flask in a constant temperature water bath and heat it to 90℃ for 1 hour to carry out a gelatinization reaction to obtain surface starch sizing agent. Keep it at 60℃ for later use.

[0069] Comparative Example 2

[0070] 2 g of the original starch and 23 g of pure water were mixed and placed in a four-necked flask equipped with an electric stirrer, a condenser and a thermometer, and then placed in a constant temperature water bath oven, and heated to 90℃ for gelatinization reaction for 1 h to obtain the original starch surface sizing agent, and stored at 60℃.

[0071] Example 7

[0072] After 0.1 g of the multi-scale nanolignin particles prepared in Example 1, 2 g of the surface-sized starch and 38 g of pure water were gelatinized at 90℃ for 1 h, a multi-scale nanolignin water and oil repellent was obtained, and stored at 60℃.

[0073] Example 8

[0074] An A4 paper with a basis weight of 80 g / m 2 was double-coated on the surface using a rod coater, and the coating amount was 5 g / m 2 . The specific process was as follows: first, a layer of the tested agent was coated on the surface of the paper, the paper coated with the layer was placed in a constant temperature oven at 60℃ and dried for 2 min, then the second layer of starch was coated, and after coating, the paper was placed in a constant temperature oven at 60℃ and dried for 5 min, finally, the treated A4 paper was placed in a constant temperature and humidity room for 24 h, and then the physical properties of the paper were tested.

[0075] The multi-scale nanolignin water and oil repellents prepared in Examples 1-7, the surface sizing agent prepared in Comparative Example 1 and the original starch surface sizing agent prepared in Comparative Example 2 were coated on the surface of the paper by the above method, wherein when the second layer of starch was coated, the surface-sized starch of Examples 1-5, 7, Comparative Example 1 was coated, and the original starch of Example 6 and Comparative Example 2 was coated. The paper test results are shown in Table 2. The smaller the Cobb 60 value, the better the water resistance of the paper; the larger the Kit value, the better the oil resistance of the paper.

[0076] Table 2 Physical property results of the coated paper and the original paper of Examples 1-7 and Comparative Examples 1-2

[0077]

[0078]

[0079] As can be seen from Table 2, compared with Comparative Example 1, after being coated with the multi-scale nanolignin water and oil repellent prepared in the application, the Cobb 60 value of the paper decreased from 40.21 g / m 2 to 17.71 g / m 2, Kit value from 1 to 10 levels, 41.11 Nm / g to 55.96 Nm / g, paper coating waterproof, oil resistance and mechanical properties can be significantly improved. This shows that the nano lignin itself has hydrophobic properties, and the effective filling and blocking of the pores between the paper fibers, by compounding with starch on the surface of the paper, the paper surface cavity is covered, the nano lignin particles construct micro-nano structure on the surface of the paper, and a dense nano coating is formed on the surface of the paper, which blocks the penetration of water and oil into the paper.

[0080] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the scope of protection of the present application.

Claims

1. The application of multi-scale nano-lignin waterproofing and oil-repellent agent in the preparation of waterproof and oil-repellent paper-based materials, characterized in that: A rod coater was used to coat a sample with a basis weight of 80 g / m³. 2 The surface of A4 paper is coated with a double layer, with a coating amount of 5g / m². 2 First, coat the paper surface with a multi-scale nano lignin waterproof and oil-resistant agent. After coating the paper with one layer, put it into a 60℃ constant temperature oven and dry it for 2 minutes. Then, coat it with starch and put it into a 60℃ constant temperature oven and dry it for 5 minutes. Finally, let the treated A4 paper stand in a constant temperature and humidity room for 24 hours. The preparation method of the multi-scale nano-lignin waterproof and oil-repellent agent specifically includes the following steps: 1) Add 500g of black liquor from alkaline pulping to a beaker and mechanically stir at 100rpm at 20℃. While stirring, add sulfuric acid dropwise until the pH of the black liquor is 1. Stop adding acid, keep warm and continue stirring for 30min, let stand overnight, centrifuge and wash until neutral, freeze dry for 48h, grind, and vacuum dry at 40℃ for 24h to obtain 24.65g of multi-scale nano-lignin particles with a particle size of 200nm. 2) Gelatinize 0.5g of the multi-scale nano-lignin particles prepared in step 1), 2g of surface starch and 23g of purified water at 90℃ for 1h to obtain a multi-scale nano-lignin waterproof and oil-repellent agent, and keep it at 60℃ for later use.

Images