Preparation method of modified lignin and application thereof

Abstract

A modified lignin preparation method is characterized in that the following raw materials are included: lignin 100 parts, methacrylic acid 2-5 parts, N, N-dimethyl acrylamide ethylenediamine 1-5 parts, allyl polyethylene glycol 5-10 parts by mass, and initiator 3-8 parts. The application also provides a modified lignin preparation step and application thereof in the field of rubber processing. The modified lignin obtained by the application has good dispersion effect in the rubber matrix and excellent reinforcing effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a modified lignin preparation method and its application, belonging to the technical field of material chemistry. BACKGROUND

[0002] Lignin is a non-crystalline, highly branched three-dimensional network of aromatic ring-containing phenolic biopolymer. Lignin widely exists in higher plant cells in nature, and is the second largest renewable natural polymer in the world, only next to cellulose. It is estimated that about 5 x 10 8 -36 x 10 8 tons can be produced every year. In the plant body, lignin, cellulose, hemicellulose and other substances together constitute a supramolecular system. Lignin binds cellulose to enhance the mechanical strength of the plant body. Lignin has a complex structure. So far, the complete structure of natural lignin has not been known. However, through years of research, it has been shown that lignin has active groups such as aromatic group, phenolic hydroxyl group, alcoholic hydroxyl group and double bond. At the same time, its specific surface area is large, and it can be widely used to replace carbon black as a reinforcing agent to fill rubber. Compared with carbon black filled rubber material, lignin can achieve high content filling, and after filling, it has the advantages of small density, high gloss, good wear resistance, enhanced flex resistance, etc. The complex polar groups on the surface of lignin fine particles, on the one hand, make them adsorb together by hydrogen bonding, and are difficult to disperse, on the other hand, the polarity is strong, and the compatibility with non-polar rubber is poor, so it is difficult to effectively disperse in non-polar rubber by traditional mixing method, which limits its application field.

[0003] CN108299657B provides a preparation method of highly dispersed modified lignin and its application, and particularly relates to a preparation of highly dispersed modified lignin for functional modification of rubber material. The lignin used is papermaking pulping black liquor, and an alkoxyl donor is added to the black liquor for hydroxymethylation modification to reduce the polarity of phenolic hydroxyl group. Then, long-chain fatty acid is added to coat, isolate and reduce the mutual adhesion between lignin particles, so as to improve the dispersion performance of the modified lignin product. After spray drying, part of the carboxylic acid groups are esterified with hydroxymethyl through stirring and heating, to further reduce the surface polarity of lignin. However, the maximum tensile strength of the modified lignin filled styrene-butadiene rubber vulcanized rubber is only 17.5 MPa.

[0004] CN106117675A provides a preparation method of silane coupling agent modified lignin reinforced emulsion polymerized styrene-butadiene rubber, in which the lignin is first modified by a silane coupling agent to contain two different active groups, amino and oxy, in the molecule to couple with the lignin and enhance the adhesion of the lignin. Then, the modified lignin reinforced emulsion polymerized styrene-butadiene rubber is prepared by a stepwise flocculation-coagulation method. However, the lignin in the rubber cannot be fully dispersed.

[0005] The present invention focuses on improving the dispersion effect of lignin in rubber through modification, thereby improving the reinforcing performance of lignin on rubber products. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides solutions as follows.

[0007] A method for preparing modified lignin comprises the following raw materials in parts by mass: 100 parts of lignin, 2-5 parts of methacrylic acid, 1-5 parts of N,N-dimethylacryloylethylenediamine, 5-10 parts by mass of allyl polyethylene glycol, and 3-8 parts by mass of an initiator.

[0008] Preferably, the initiator is one or more of ammonium persulfate, sodium persulfate, potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, and diisopropyl peroxydicarbonate.

[0009] A method for preparing modified wood, comprising the following steps:

[0010] (1) Add lignin to a reactor, stir and disperse it evenly with deionized water at room temperature, then add some methacrylic acid, N,N-dimethylacryloylethylenediamine, and allyl polyethylene glycol, and expel excess air from the reactor to maintain an inert atmosphere;

[0011] (2) Raise the temperature to 80-100°C, keep warm for 30 minutes, then add part of the initiator and react for 1-2 hours;

[0012] (3) Add the remaining monomers and initiator, continue to raise the temperature to 150-180°C, and keep the temperature for another 2-3 hours;

[0013] (4) After cooling to room temperature, the material is released, filtered, washed with water, dried, ground and crushed to obtain modified lignin.

[0014] Preferably, in step (1), the amount of methacrylic acid added is 70-90% of the total amount of methacrylic acid.

[0015] Preferably, in step (2), the amount of the initiator added is 80-90% of the total amount of the initiator.

[0016] Preferably, in step (4), the washing and filtration times are 2-5 times, and the drying temperature is 60-90°C.

[0017] A modified lignin is prepared by the above preparation method.

[0018] The present invention also provides an application of the modified lignin as a reinforcing agent in the field of rubber processing.

[0019] The advantages of the present invention compared to the prior art are as follows:

[0020] 1. The dispersion effect of modified lignin in the rubber matrix is ​​improved;

[0021] 2. The modified lignin has a stronger reinforcing function. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The microscopic morphology of the dispersion of the modified lignin obtained in the examples in rubber processing, wherein (1-4) correspond to Examples 1-4 respectively;

[0023] Figure 2 This is a microscopic morphology of the dispersion of lignin used in Comparative Example 1 during rubber processing. DETAILED DESCRIPTION

[0024] The present invention is further described with reference to the following examples, but the protection scope of the present invention is not limited thereto.

[0025] Example 1

[0026] A modified lignin specifically comprises the following raw materials in parts by mass: 100 parts of lignin, 2 parts of methacrylic acid, 3 parts of N,N-dimethylacryloylethylenediamine, 8 parts of allyl polyethylene glycol, 1 part of ammonium persulfate, 2 parts of sodium persulfate, and 2 parts of potassium persulfate.

[0027] A method for preparing modified wood, comprising the following steps:

[0028] (1) Add lignin to a stainless steel high-pressure closed reactor (304 material or above) and fix the reaction equipment. Use deionized water to disperse it evenly at room temperature, then add 70% methacrylic acid, N,N-dimethylacryloylethylenediamine, and allyl polyethylene glycol. Use nitrogen to expel excess air in the reactor to maintain an inert atmosphere.

[0029] (2) Raise the temperature to 80°C, keep warm for 30 minutes, then add 80% initiator and react for 1.5 hours;

[0030] (3) Add the remaining 30% of methacrylic acid and the remaining 20% ​​of the initiator, raise the temperature to 170°C, and keep the reaction at this temperature for another 2.5 hours;

[0031] (4) After cooling to room temperature, the material was discharged, filtered, washed with water three times, dried at 60°C, and then ground to obtain modified lignin.

[0032] Example 2

[0033] A modified lignin specifically comprises the following raw materials in parts by mass: 100 parts of lignin, 3 parts of methacrylic acid, 1 part of N,N-dimethylacryloylethylenediamine, 5 parts of allyl polyethylene glycol, 1 part of azobisisobutyronitrile, 1 part of benzoyl peroxide, and 1 part of diisopropyl peroxydicarbonate.

[0034] A method for preparing modified wood, comprising the following steps:

[0035] (1) Add lignin to a stainless steel high-pressure closed reactor (304 material or above) and fix the reaction equipment. Use deionized water to disperse it evenly at room temperature, then add 80% methacrylic acid, N,N-dimethylacryloylethylenediamine, and allyl polyethylene glycol. Use nitrogen to expel excess air in the reactor to maintain an inert atmosphere.

[0036] (2) Raise the temperature to 90°C, keep warm for 30 minutes, then add 80% initiator and react for 1 hour;

[0037] (3) Add the remaining 20% ​​of methacrylic acid and the remaining 20% ​​of initiator, raise the temperature to 150°C, and keep the temperature to react for another 2 hours;

[0038] (4) After cooling to room temperature, the material was discharged, filtered, washed with water twice, dried at 90°C, and then ground to obtain modified lignin.

[0039] Example 3

[0040] A modified lignin specifically comprises the following raw materials in parts by mass: 100 parts of lignin, 5 parts of methacrylic acid, 5 parts of N,N-dimethylacryloylethylenediamine, 10 parts of allyl polyethylene glycol, 4 parts of ammonium persulfate, and 4 parts of sodium persulfate.

[0041] A method for preparing modified wood, comprising the following steps:

[0042] (1) Add lignin to a stainless steel high-pressure closed reactor (304 material or above) and fix the reaction equipment. Use deionized water to disperse it evenly at room temperature, then add 90% methacrylic acid, N,N-dimethylacryloylethylenediamine, and allyl polyethylene glycol. Use nitrogen to expel excess air in the reactor to maintain an inert atmosphere.

[0043] (2) Raise the temperature to 100°C, keep warm for 30 minutes, then add 90% initiator and react for 2 hours;

[0044] (3) Add the remaining 10% of methacrylic acid and the remaining 10% of initiator, raise the temperature to 180°C, and keep the temperature to react for another 3 hours;

[0045] (4) After cooling to room temperature, the material was discharged, filtered, washed with water 5 times, dried at 70°C, and then ground to obtain modified lignin.

[0046] Example 4

[0047] A modified lignin, specifically comprising the following raw materials by mass: lignin 100 parts, methacrylic acid 3 parts, N,N-dimethyl acrylamide ethylenediamine 1 part, allyl polyethylene glycol 5 parts, azobisisobutyronitrile 2 parts, benzoyl peroxide 3 parts, diisopropyl peroxide carbonate 1 part.

[0048] A modified lignin preparation method, the specific steps comprising:

[0049] (1) Put the lignin into a stainless steel high-pressure sealed reaction kettle (304 material above type) and fix the reaction equipment. After uniform dispersion at room temperature using deionized water, add 80% methacrylic acid, N,N-dimethyl acrylamide ethylenediamine, and allyl polyethylene glycol. Use nitrogen to exhaust the excess air in the reaction kettle and maintain an inert atmosphere for the reaction;

[0050] (2) Heat to 80°C and keep for 30 min, then add 80% initiator and react for 1 h;

[0051] (3) Add the remaining 20% methacrylic acid and the remaining 20% initiator, and increase the temperature to 150°C. Keep reacting for another 1.3 h;

[0052] (4) After cooling to room temperature, discharge the material and perform water washing twice. Dry at 80°C, then grind and crush to obtain modified lignin.

[0053] Comparative Example 1

[0054] Unmodified lignin sample.

[0055] Implementation effect:

[0056] The modified lignin obtained in the above examples and the lignin of the comparative example are applied in the rubber processing field according to the formulations described in Table 1.

[0057] Table 1

[0058]

[0059] Rubber is plasticized at 60°C for 1 min, and additive 1 is mixed for 4 min (40 s rolling and 1 min 20 s rolling). Discharge; adjust the roller distance to the minimum, pass the mill 5 times, adjust the roller distance to 4 mm, and discharge the sheet after opening. Store for 12 h;

[0060] Set the mill temperature to 60°C. After rolling the rubber, add the vulcanization aid, and then roll and open for 5 times. Set the thickness and discharge the sheet;

[0061] Pressurize and vulcanize at 150°C for 50 min. The thickness of the vulcanized sheet is 2 mm ± 0.1 mm.

[0062] The tensile strength test is carried out by cutting samples according to the dumbbell-shaped type 1 sample test in the national standard GB / T528-2009, and the mechanical properties test is carried out in accordance with the standard; the tear strength test is carried out by cutting samples according to the right-angle sample test in GB / T529-2009 and the mechanical properties test is carried out.

[0063] Table 2

[0064] sample Tensile strength (MPa) Tear strength (MPa) Example 1 28.8 45.0 Example 2 29.4 45.9 Example 3 29.1 48.1 Example 4 28.1 47.2 Comparative Example 1 25.2 36.8

[0065] from Figure 1-2 It can be seen that the modified lignin of the present invention has a better dispersion effect in rubber, while there is obvious unevenness in Comparative Example 1 (as shown in the circle).

[0066] It can be seen from Table 2 that, compared with the unmodified lignin in the comparative example, the tensile strength and tear strength of the rubber products processed using the modified lignin are significantly improved.

[0067] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing modified lignin, characterized in that: The specific steps include: (1) Add lignin to a reactor, stir and disperse it evenly with deionized water at room temperature, then add some methacrylic acid, N,N-dimethylacryloylethylenediamine, and allyl polyethylene glycol, and expel excess air from the reactor to maintain an inert atmosphere; (2) Raise the temperature to 80-100°C, keep warm for 30 minutes, then add part of the initiator and react for 1-2 hours; (3) Add the remaining monomers and initiator, continue to raise the temperature to 150-180°C, and keep the temperature for another 2-3 hours; (4) After cooling to room temperature, the material is released, filtered, washed with water, dried, ground and pulverized to obtain modified lignin; The raw materials include, by weight, 100 parts of lignin, 2-5 parts of methacrylic acid, 1-5 parts of N,N-dimethylacryloylethylenediamine, 5-10 parts by weight of allyl polyethylene glycol, and 3-8 parts of initiator.

2. The method for preparing modified lignin according to claim 1, wherein The initiator is one or more of ammonium persulfate, sodium persulfate, potassium persulfate, azobisisobutyronitrile, benzoyl peroxide, and diisopropyl peroxydicarbonate.

3. The method for preparing modified lignin according to claim 1, wherein: In the step (1), the amount of methacrylic acid added is 70-90% of the total amount of methacrylic acid.

4. The method for preparing modified lignin according to claim 1, wherein: In the step (2), the amount of the initiator added is 80-90% of the total amount of the initiator.

5. The method for preparing modified lignin according to claim 1, wherein: In the step (4), the washing and filtration times are 2-5 times, and the drying temperature is 60-90°C.

6. The modified lignin prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the modified lignin as claimed in claim 6 in the field of rubber processing.

Images