CN108219151B - Method for grafting polymer on surface of lignin - Google Patents
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- CN108219151B CN108219151B CN201810031853.XA CN201810031853A CN108219151B CN 108219151 B CN108219151 B CN 108219151B CN 201810031853 A CN201810031853 A CN 201810031853A CN 108219151 B CN108219151 B CN 108219151B
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- C08G81/00—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers
- C08G81/02—Macromolecular compounds obtained by interreacting polymers in the absence of monomers, e.g. block polymers at least one of the polymers being obtained by reactions involving only carbon-to-carbon unsaturated bonds
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Abstract
The invention discloses a method for grafting a polymer on the surface of lignin, which comprises the steps of putting 60-99 parts of epoxy group polymer, 1-40 parts of lignin and 0.5-5 parts of zinc ion catalyst into a drying oven, drying for 4-6 hours at the temperature of 60-80 ℃, and then adding into a high-speed mixer to be mixed uniformly; adding the uniformly mixed materials into a double-screw extruder or an internal mixer for reaction and blending, wherein the reaction temperature is 200-230 ℃, the reaction time is 5-15 minutes, and the rotating speed is 10-100 r/min. The invention provides an industrialized, efficient and environment-friendly method for grafting lignin with macromolecules, so that the modified lignin has good solubility in an organic solvent and good compatibility with a polymer, and the modified lignin can be widely applied to the field of modification of macromolecules.
Description
Technical Field
The invention relates to a method for modifying lignin by a polymer, in particular to a method for grafting an epoxy polymer on the surface of lignin by melt reaction blending.
Background
As a natural, renewable and degradable high molecular material, lignin is the second most renewable biomass resource next to cellulose, accounts for about 30% of non-fossil energy on earth, has a three-dimensional reticular rigid molecular structure, and is a strong supporting material. However, it is difficult to chemically modify and reform lignin molecules to obtain a product of high utility value due to their rigid and complex three-dimensional network structure, which makes them difficult to dissolve in conventional solvents. Thus, lignin is often discarded as a by-product of the wood hydrolysate and paper industry and is considered a serious environmental pollution.
Therefore, finding an effective method to improve the structure of lignin and increase the added value thereof is the focus of the current lignin research. In the last 50 years, the compatibility of the lignin modified by high molecules is improved by preparing the lignin modified by high molecules through graft copolymerization, the application field of the lignin is expanded to the modification field of high molecule materials, and the purpose of changing waste into valuable is realized. Many works have realized the graft copolymerization of lignin and radical polymerization monomers such as styrene and acrylic acid by methods such as irradiation, chemistry, electrochemistry, enzyme catalysis and Atom Transfer Radical Polymerization (ATRP), and synthesized lignin graft copolymer with specific structure and function (Chinese patent 201310506131.2; published by high molecular letters 2015,12,1363-. In addition, graft copolymerization of polymers such as polylactic acid and polyacrylonitrile with lignin has also been studied. However, these reactions start from polymer monomers, and the process route is complicated, which is not suitable for industrial production.
The method for directly carrying out graft copolymerization reaction on macromolecules and lignin is a novel and economic method for realizing lignin modification. The research report of the method is very rare at present, and the solution grafting reaction of isocyanate-based polyacrylate and lignin is reported in documents (university of Jinggang, Nature science edition, 2016,1, 34-38). Because the solubility of the lignin in the organic solvent is not high, the reaction uniformity is poor, only the lignin with low molecular weight participates in the reaction, and the use of a large amount of solvent brings secondary pollution to the environment.
Chinese patent application No. 2006100183313 discloses a method for preparing a high boiling point alcohol lignin graft copolymer by reactive extrusion, which comprises the steps of mixing high boiling point alcohol lignin or a high boiling point alcohol lignin derivative, a graft polymerization initiator, a high molecular monomer or polymer, a high polymer modified filler and a high polymer modified auxiliary agent, and then carrying out reactive extrusion by an extruder to obtain the high boiling point alcohol lignin reactive extrusion graft copolymer. Although this document achieves grafting of copolymers onto high-boiling alcohol lignins without using solvents, it still has the following two drawbacks:
firstly, because it is a free radical reaction, the copolymerization of monomer or polymer and lignin is initiated by means of a free radical initiator, the grafting rate is not high, and from the grafting rate described in its example, the highest grafting rate is 10.57%, and the reason that the grafting rate is not high is that ① generates the copolymer of lignin and monomer or polymer only when the free radical of lignin and the free radical of polymer collide and combine, because lignin is difficult to form free radical under the action of general free radical initiator, the probability of collision is low, and the grafting rate is not high, ② when the copolymerization of two is initiated by free radical, the combination between the free radicals of high polymer is obviously prior to the combination of lignin and free radical of lignin, so the yield of non-grafted free polymer is greater than the content of polymer grafted to the surface of lignin.
Secondly, the following steps: when a polymer is used for grafting by reacting with lignin, the free radical initiator can also cause severe degradation of the polymer in the process of forming free radicals from the polymer, and the amount of byproducts is too much, so that the uncontrollable property of the product structure is increased.
Therefore, there is a need to find a new way to directly graft lignin via macromolecules. Compared with the free radical graft polymerization reaction with poor controllability, the method for preparing the graft copolymer by adopting the esterification reaction between carboxyl or hydroxyl and epoxy group in the artificially synthesized Polymer material is a method with higher controllability (Polymer,2009,50, 747-751; RSC adv.,2015,5, 96353). However, unlike synthetic polymers, rigid natural polymers are much less reactive than flexible synthetic polymers. We imagine that if a proper catalyst can be selected, the conditions of melt blending reaction are controlled, and a large amount of active hydroxyl and carboxyl on the surface of lignin are utilized through a grafting method of 'graft-onto', so that macromolecules are directly combined with covalent bonds of the lignin in a non-solvent environment, the grafting efficiency and grafting controllability are improved, and the method is a new way for grafting a copolymer on the surface of the lignin.
Disclosure of Invention
In order to overcome the defects of low grafting rate and too many byproducts of grafting a macromolecular polymer on lignin in the prior art, the invention provides an industrialized, efficient and environment-friendly method for grafting the lignin on the macromolecule, so that the modified lignin has good solubility in an organic solvent and good compatibility with a polymer, and the modified lignin can be widely applied to the field of macromolecular modification.
In order to achieve the purpose, the invention prepares the copolymer of the epoxy polymer grafted lignin by using the zinc ion catalyst and adopting the epoxy polymer and the lignin and blending the epoxy polymer and the lignin through a melting reaction to realize the reaction of the epoxy group and the hydroxyl and carboxyl on the surface of the lignin. The method specifically comprises the following steps:
firstly, respectively weighing 60-99 parts of epoxy group polymer, 1-40 parts of lignin and 0.5-5 parts of zinc ion catalyst according to parts by weight, putting into a drying oven, and drying at the temperature of 60-80 ℃ for 4-6 hours; taking out, adding into a high-speed mixer, and mixing uniformly;
secondly, adding the uniformly mixed materials into a melting processing device for reaction and blending, wherein the reaction temperature is 200-230 ℃, the time is 5-15 minutes, the rotating speed is 10-100r/min, and the reaction product is as follows: epoxy-polymer grafted lignin and a small excess of polymer or lignin.
If the above products need to be characterized, the reaction products can be taken out, dissolved in organic solvents such as tetrahydrofuran, chloroform, DMF and the like, and the purification of the grafting products is realized by a Soxhlet extraction process at 60 ℃. If the graft product is used for modifying polymers, it can be used without extraction.
The zinc ion catalyst is preferably: one of organic zinc salts such as zinc acrylate, zinc methacrylate, zinc dimethacrylate, etc.
The above epoxy-based polymer is preferably: long chain aliphatic glycidyl ethers, or epoxy acrylic polymers: such as polyglycidyl methacrylate (PGMA) or polyethylene-glycidyl methacrylate (EGMA), and the like. The epoxy groups in the polymers can be copolymerized with carboxyl and hydroxyl of lignin at high temperature under the catalytic action of zinc ions, so that the grafting reaction of the epoxy group polymers on the surface of the lignin is realized.
The lignin is any one of needle lignin, broad leaf lignin or herbaceous lignin.
The melting processing equipment comprises: single screw extruders, twin screw extruders, multiple screw extruders or internal mixers.
The invention has the positive effects that:
1. according to the invention, the esterification reaction between the hydroxyl or carboxyl of lignin and the epoxy group positioned on the side group or the end group on the polymer is utilized, so that the main chain molecular chain is not broken, and therefore, the molecular weight of the polymer is not reduced after grafting, and the controllability of the grafting reaction is improved.
2. According to the invention, the epoxy polymer is adopted to modify lignin, and the preparation of the graft polymer on the surface of the lignin is realized by utilizing the reaction of epoxy group, carboxyl and hydroxyl at high temperature; the use of a large amount of organic solvent in the conventional grafting reaction process is avoided, and the green reaction is realized to prepare the lignin graft copolymer; on the other hand, the method has the advantages of short process flow, relatively simple requirement on equipment, convenient operation and easy control of process parameters, thereby having lower production cost and being easy for industrial production.
3. The lignin grafted epoxy polymer prepared by the reaction realizes full contact between lignin and the polymer through shearing action in the process of melting the blend, and has uniform reaction and high grafting rate. In addition, a large amount of hydroxyl and carboxyl on the lignin ensure the grafting activity, further improve the grafting rate and finally make the grafting rate reach 43.5 percent.
4. The lignin grafted epoxy polymer prepared by the reaction improves the compatibility of lignin and other high polymer materials, and can be widely used as a compatilizer of lignin modified polymers.
Drawings
FIG. 1a is a photograph of the solubility of the reaction mixture of lignin/EGMA in tetrahydrofuran, wherein the photograph of the solubility of the reaction mixture after standing for 0h and 24h is taken from left to right;
FIG. 1b is a photograph of the solubility in tetrahydrofuran of an unkneaded reference material of the same composition as in the example, wherein from left to right are photographs of the solubility after standing for 0h and 24h, respectively;
FIG. 2a is a photograph showing the solubility of the reaction mixture of the lignin/polyethylene glycol glycidyl ether melt-kneaded in chloroform in the example, wherein the photograph shows the solubility after standing for 0h and 24h from left to right;
FIG. 2b is a photograph showing the solubility of an unkneaded reference material having the same composition as in example two in chloroform, wherein the photographs are taken from left to right after standing for 0h and 24h, respectively;
FIG. 3 is an infrared spectrum of lignin, PGMA and the reaction and blending product of lignin and PGMA of example;
FIG. 4 is a thermogravimetric plot of lignin, EGMA and copolymers of the two before and after the four-graft reaction of the example.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Example one
Preparing raw materials: weighing the following components in parts by weight: 90 parts of ethylene-glycidyl methacrylate copolymer (EGMA), 10 parts of lignin and 1 part of zinc acrylate;
the preparation method comprises the following steps: putting the raw materials into an oven, and drying for 4-6 hours at the temperature of 70 ℃; taking out, adding into a high-speed mixer together, and mixing uniformly;
and adding the uniformly mixed materials into an internal mixer, and internally mixing for 8 minutes at 200 ℃ at the rotating speed of 30rpm to obtain a reaction product.
The results of dissolving the reaction mixture obtained in the example after melt kneading in tetrahydrofuran and leaving it for 0h and 24h are shown in FIG. 1 a.
The results of the dissolution of the unkneaded reference material of the same composition as in the example in tetrahydrofuran after 0h and 24h of standing are shown in FIG. 1 b.
Comparing fig. 1a and 1b, it can be seen that the lignin and EGMA mixture was dispersed in tetrahydrofuran, both of which were initially dispersed in the solvent. However, after 24h of standing, the reaction-blended sample precipitated only a little below (fig. 1a, right panel), but the mixture that did not melt-react precipitated entirely at the bottom of the sample vial (fig. 1b, right panel). This shows that, in the melting and banburying process, the epoxy-based polymer and lignin are subjected to a chemical reaction, and a graft copolymerization reaction on the surface of the lignin is realized.
Example two
Preparing raw materials: weighing the following components in parts by weight: 80 parts of polyethylene glycol glycidyl ether, 20 parts of lignin and 3 parts of zinc acrylate;
the preparation method comprises the following steps: putting lignin, polyethylene glycol glycidyl ether and zinc acrylate into an oven, and drying at 60 ℃ for 4-6 hours; taking out, adding into a high-speed mixer together, and mixing uniformly;
and adding the uniformly mixed materials into a double-screw extruder, and staying in double screws for 4 minutes at 230 ℃ to obtain a reaction product.
The reaction product obtained by melt extrusion of example two was dissolved in chloroform and the solubility results after standing for 0h and 24h are shown in fig. 2 a.
The results of the dissolution of the unkneaded reference material having the same composition as in example two in chloroform after 0h and 24h of standing are shown in FIG. 2 b.
Comparing fig. 2a and 2b, it can be seen that the lignin and polyethylene glycol glycidyl ether mixture was dispersed in chloroform, both of which were initially dispersed in the solvent. However, after 24h of standing, the reaction-blended sample had only a few agglomerates above (fig. 2a, right), but the mixture that had not been melt-reacted floated entirely above the solvent (fig. 2b, right). This indicates that, during the melt extrusion reaction, the polyethylene glycol glycidyl ether chemically reacts with the lignin, and the graft copolymerization reaction on the surface of the lignin is realized.
EXAMPLE III
Preparing raw materials: weighing the following components in parts by weight: 60 parts of poly glycidyl methacrylate copolymer (PGMA), 40 parts of lignin and 5 parts of zinc methacrylate;
the preparation method comprises the following steps: putting the raw materials into an oven, and drying for 4-6 hours at the temperature of 70 ℃; taking out, adding into a high-speed mixer together, and mixing uniformly;
and adding the uniformly mixed materials into an internal mixer, and mixing for 10 minutes at 220 ℃ and the rotating speed of 80rpm to obtain a reaction product.
The reaction product of example three was purified by soxhlet extraction and then subjected to infrared detection, and the obtained results are shown in fig. 3. As can be seen from FIG. 3, the reaction product of PGMA and lignin after the reaction was 3440cm relative to lignin-1The strength of the lignin is obviously reduced, which indicates that the hydroxyl of the lignin participates in the copolymerization reaction. In addition, the reaction mass was 1600cm relative to pure PGMA-1Characteristic bands of carbon-carbon double bonds of lignin are formed. This indicates that the grafting reaction of lignin with PGMA was successfully achieved.
Example four
Preparing raw materials: weighing the following components in parts by weight: 90 parts of ethylene-glycidyl methacrylate copolymer (EGMA), 10 parts of lignin and 2 parts of zinc acrylate;
the preparation method comprises the following steps: putting the raw materials into an oven, and drying for 4-6 hours at the temperature of 80 ℃; taking out, adding into a high-speed mixer together, and mixing uniformly;
and adding the uniformly mixed materials into an internal mixer, carrying out internal mixing for 12 minutes at the rotation speed of 20rpm at the temperature of 240 ℃, and melting to obtain a reaction product.
The reaction product of example four was subjected to soxhlet extraction purification and thermogravimetric analysis, and the results are shown in fig. 4. As can be seen from fig. 4, the initial decomposition temperature of lignin after the reaction was increased from 180 ℃ to 380 ℃, and the thermal stability was significantly improved. Comparing the weight difference between lignin and the grafted product at 550 deg.c, it can be seen that the grafting ratio of lignin is 43.5%.
Claims (4)
1. A method for grafting a polymer on the surface of lignin is characterized by comprising the following steps:
firstly, respectively weighing 60-99 parts of epoxy group polymer, 1-40 parts of lignin and 0.5-5 parts of zinc ion catalyst according to parts by weight, putting into a drying oven, and drying at the temperature of 60-80 ℃ for 4-6 hours; taking out, adding into a high-speed mixer, and mixing uniformly;
secondly, adding the uniformly mixed materials into a melting processing device for reaction and blending, wherein the reaction temperature is 200-230 ℃, the time is 5-15 minutes, the rotating speed is 10-100r/min, and the reaction product is as follows: epoxy polymer grafted lignin and excess polymer or lignin;
the lignin is any one of coniferous lignin, broadleaf lignin or herbaceous lignin;
the catalyst is as follows: any one of zinc acrylate, zinc methacrylate or zinc dimethacrylate organic zinc salt.
2. The method for grafting a polymer on the surface of lignin according to claim 1, wherein the epoxy polymer is a long-chain aliphatic glycidyl ether or an epoxy acrylic polymer.
3. The method for grafting a polymer on the surface of lignin according to claim 2, wherein the epoxy acrylic polymer is poly glycidyl methacrylate or polyethylene-glycidyl methacrylate.
4. The method for grafting a polymer on the surface of lignin according to claim 1, wherein the reactive blending equipment is a single screw extruder, a twin screw extruder, a multi-screw extruder or an internal mixer.
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| US9409823B2 (en) * | 2013-02-15 | 2016-08-09 | Deborah D. L. Chung | Microstructured high-temperature hybrid material, its composite material and method of making |
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| CN102690422A (en) * | 2012-05-18 | 2012-09-26 | 江苏博特新材料有限公司 | Lignin asphalt emulsifier with high emulsifying property, and preparation method and application thereof |
| CN103709409A (en) * | 2013-11-29 | 2014-04-09 | 华南理工大学 | Lignin based polyoxyethylene ether, preparation method and application thereof |
| CN104163977A (en) * | 2014-07-09 | 2014-11-26 | 华南理工大学 | Red lignin/polyolefin composite material and preparation method thereof |
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