CN111234455B - Preparation method for preparing phenolic foam by enzymatic modification of lignin - Google Patents

Preparation method for preparing phenolic foam by enzymatic modification of lignin Download PDF

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CN111234455B
CN111234455B CN202010222026.6A CN202010222026A CN111234455B CN 111234455 B CN111234455 B CN 111234455B CN 202010222026 A CN202010222026 A CN 202010222026A CN 111234455 B CN111234455 B CN 111234455B
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lignin
phenolic foam
enzymatic
parts
phenolic
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CN111234455A (en
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朱晨杰
高成
应汉杰
李明
韩耀颖
胡有钦
庄伟�
陈彦君
欧阳平凯
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Nanjing Tech University
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    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/14Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent organic
    • C08J9/141Hydrocarbons
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08GMACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G8/00Condensation polymers of aldehydes or ketones with phenols only
    • C08G8/28Chemically modified polycondensates
    • C08G8/34Chemically modified polycondensates by natural resins or resin acids, e.g. rosin
    • CCHEMISTRY; METALLURGY
    • C12BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12PFERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P1/00Preparation of compounds or compositions, not provided for in groups C12P3/00 - C12P39/00, by using microorganisms or enzymes
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00Foams characterized by the expanding agent
    • C08J2203/14Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08JWORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2361/00Characterised by the use of condensation polymers of aldehydes or ketones; Derivatives of such polymers
    • C08J2361/04Condensation polymers of aldehydes or ketones with phenols only
    • C08J2361/06Condensation polymers of aldehydes or ketones with phenols only of aldehydes with phenols
    • C08J2361/14Modified phenol-aldehyde condensates

Abstract

The invention discloses a preparation method of phenolic foam by enzymatic modification of lignin, which comprises the steps of preparing phenolic foam heat-insulating material by phenolic resin prepared by enzymatic modification of lignin, a foaming agent, a curing agent and a surfactant; the preparation method of the enzymatic modified lignin comprises the steps of mixing lignin and a biocatalyst in a solvent, and reacting to obtain the enzymatic modified lignin. Compared with the existing lignin-based phenolic foam, the method for preparing the phenolic foam by modifying lignin by the enzyme method has the advantages of simple and convenient operation and environmental protection, and the prepared phenolic foam has lower heat conductivity coefficient, better compressive strength and bending strength and higher oxygen index.

Description

Preparation method for preparing phenolic foam by enzymatic modification of lignin
Technical Field
The invention belongs to the field of heat insulation materials, and particularly relates to a preparation method for preparing phenolic foam by enzymatic modification of lignin.
Background
Phenolic foam plastic is a novel flame-retardant, fireproof and corrosion-resistant heat-insulating material developed in recent years. It features fire-retarding, high-temp and corrosion-resisting properties. The foam plastic type heat-insulating material overcomes the defects of inflammability, deformation when being heated and easy corrosion of the original foam plastic type heat-insulating material, and keeps the characteristics of light weight, convenient construction and the like of the original foam plastic type heat-insulating material. And the phenolic foam plastic has rich raw material sources, low price, simple production and processing and wide product application. It is suitable for large cold storage, storage tank, ship, various heat insulating pipes and building industry. If the material is used for factories, mines and mechanical equipment with strict fire protection requirements, the characteristics of flame resistance and high temperature resistance can be more prominent, such as: the heat preservation of steamships, warships, trains and armored vehicles, the papermaking, the chemical industry, the pharmacy and the like.
Lignin is a crosslinked aromatic polymer composed of three different phenylpropane monomers, and due to a similar crosslinked network structure to phenolic resins, the preparation of phenolic resins instead of petroleum-derived phenols has been considered as an added value option for lignin applications, and phenolic resin foams have excellent flame retardancy, low thermal conductivity, high thermal stability compared to other polymeric foams, and are widely used in fields where fire resistance is critical, such as high-rise buildings, airplanes, and chemical pipelines. However, lignin has low reactivity compared to phenol. Therefore, increasing the reactivity of lignin is a key process for preparing phenolic foams with superior properties.
In the prior art, researches and reports have been made that lignin can be applied to phenolic resin, however, the untreated lignin has low phenolic hydroxyl content and low reaction activity, so that the condensation reaction with formaldehyde is poor, and the prepared phenolic resin has the defects of low activity and high viscosity, thereby greatly hindering the stability and uniformity of foaming and further reducing the mechanical property, the heat preservation property and the flame retardant property of foam. In the prior art, the modification of lignin requires higher temperature and pressure and longer reaction time, and chemical reagents which affect the environment are required to modify the lignin, so that the modification process is complex and the industrial application is difficult. For example, chinese application CN105754527A discloses a method for preparing phenol formaldehyde adhesive by using demethylated lignin to replace part of phenol, which comprises, first, performing demethylation modification on lignin by in situ generated lewis acid, and polymerizing the obtained demethylated modified lignin with phenol, formaldehyde, etc. to obtain the demethylated lignin phenol formaldehyde adhesive, wherein the lignin needs to be demethylated and modified at a higher temperature (145 ℃). Anxinnan and the like take alkali lignin black liquor as a main raw material, utilize sulfur as a modifier, heat lignin for reaction for 30min at a reaction temperature of 225-235 ℃, and then carry out cooling, acidification, extraction and separation to obtain modified lignin with the methoxyl content reduced to 5%. Therefore, the modification of lignin in the prior art needs high-temperature and high-pressure reaction conditions, and the organic reagent used in the process has the defects of bad smell and unfriendly environment.
Therefore, the method for preparing the phenolic resin by using the enzymatic method modified lignin has the advantages of simple and convenient operation and environmental protection, avoids using chemical reagents which are not friendly to the environment and reaction conditions which need high temperature and high pressure, and can achieve the aims of obviously improving the phenolic hydroxyl content of the lignin and improving the reaction activity of the lignin and formaldehyde. Meanwhile, the phenolic resin prepared by taking the enzymatic modified lignin as the raw material has the advantages of short gelling time, high activity, low free formaldehyde and the like, and the phenolic foam prepared by taking the enzymatic modified lignin-based phenolic resin has lower heat conductivity coefficient, better compressive strength and bending strength and higher oxygen index.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems in the prior art, the preparation method for preparing the phenolic foam by using the enzymatic modified lignin is provided.
The invention idea is as follows: the untreated lignin has low reaction activity due to the obstruction of methoxy groups on aromatic rings, and has poor polymerization reaction with formaldehyde, and the prepared phenolic resin has the defects of low activity and high viscosity, so that the foaming stability and uniformity of the phenolic resin are greatly hindered, and the mechanical property, the heat insulation property and the flame retardant property of foam are further reduced. The demethylation of lignin reported in the prior art needs higher temperature and pressure and longer reaction time, and needs chemical reagents to modify lignin, thus having great influence on environment, complex preparation process and difficult industrial application.
In order to solve the technical problem, the invention discloses a preparation method of phenolic foam by using enzymatic modified lignin, which is characterized in that phenolic foam heat-insulating material is prepared from phenolic resin prepared by using enzymatic modified lignin, a foaming agent, a curing agent and a surfactant;
the preparation method of the enzymatic modified lignin comprises the steps of mixing lignin and a biocatalyst in a solvent, reacting, filtering the mixed solution to obtain a solid, and washing the solid with water to be neutral to obtain the enzymatic modified lignin.
Wherein the lignin is any one or combination of several of enzymolysis lignin, soda lignin, alkali lignin, lignosulfonate and organic solvent lignin.
Wherein the biocatalyst is any one of phenol monooxygenase (EC1.14.13.7), naphthalene dioxygenase (EC1.14.12.12), tyrosinase (EC1.14.18.1) and ferrous iron oxidase (EC1.16.3.1); the specific enzyme activities are 41.8U/mg of phenol monooxygenase, 33.6U/mg of naphthalene dioxygenase, 35.2U/mg of tyrosinase and 29.1U/mg of ferrous iron oxidase respectively. Enzyme activity is defined as the amount of enzyme required to convert 1 micromole of substrate in 1 minute under a particular condition as one activity unit (U). The specific enzyme activity refers to the enzyme activity per milligram of enzyme protein, U/mg.
Preferably, the biocatalyst is phenol monooxygenase (EC1.14.13.7).
Wherein the solvent is any one of water, phosphate buffer solution, Tris-HCl buffer solution, HEPES buffer solution, MOPS buffer solution and barbital sodium-hydrochloric acid buffer solution; preferably, the solvent is potassium phosphate buffer solution with pH of 6.0-8.0; more preferably, the solvent is potassium phosphate buffer, ph 7.0.
Wherein the concentration of the lignin is 5-80 g/L (preferably 10-30 g/L, more preferably 10 g/L); the dosage of the biocatalyst is 10-100000U/L.
Wherein the reaction is carried out at room temperature to 50 ℃ for 4 to 12 hours; preferably, the reaction is carried out at 30-50 ℃ for 12-24 h.
Preferably, the preparation process of the modified lignin further comprises any one or two combinations of a hydrogen donor and a coenzyme; that is, one or two of hydrogen donor and coenzyme, lignin and biocatalyst are mixed together into solvent for reaction.
When the biocatalyst is phenol monooxygenase, a hydrogen donor and a coenzyme need to be added, the hydrogen donor reduces FAD to FADH2, and then the hydrogen donor is coupled with the coenzyme to catalyze lignin hydroxylation; when the biocatalyst is naphthalene dioxygenase, only hydrogen donor needs to be added; when the biocatalyst is tyrosinase or ferrous oxidase, no hydrogen donor and coenzyme are needed to be added.
Wherein, the hydrogen donor is natural nicotinamide cofactor or artificial nicotinamide cofactor.
Wherein the natural Nicotinamide cofactor is Nicotinamide Adenine Dinucleotide (NADH) or Nicotinamide Adenine Dinucleotide Phosphate (NADPH).
Wherein, the artificial nicotinamide cofactor is shown in formula I:
wherein R is1Is selected from-CN, -CONH2、-COOH、-CSNH2、-COCH3、-COOCH3-CHO, -CONHEt, -CONHPh, -H or-CH3
R2Is selected from-CnHn+2(n=1~8)、-Ph、-CH3、-CH2CH3、-(CH2)2CH3、-CH2Ph、-(CH2)2Ph、-(CH2)2OH、-(CH2)2Cl、-(CH2)3Ph、-(CH2)3OH、-(CH2)2COOH、-CH2PhCOOH、-CH2PhSO3H、-CH2PhOCH3or-CH2PhCF3(ii) a Wherein, said-CH2PhCOOH、-CH2PhSO3H、-CH2PhOCH3、-CH2PhCF3The groups connected with the benzene ring in the groups do not distinguish para position, meta position and ortho position; that is, the group attached to the benzene ring may be para, meta or metaOrtho position.
R3Is selected from-H, -CH3or-Br.
Preferably, R1Is selected from-CN, -CONH2、-COOH、-CSNH2or-COCH3;R2Is selected from-CnHn+2(n=1~8)、-CH3、-CH2Ph、-(CH2)2Ph or-CH2PhCOOH;R3Is selected from-H or-CH3. Wherein, said-CH2The groups connected with the benzene ring in the PhCOOH group do not distinguish para position, meta position and ortho position, namely the groups connected with the benzene ring can be para position, meta position or ortho position.
Wherein the coenzyme is flavin adenine dinucleotide.
Wherein the solvent is potassium phosphate buffer solution with pH of 6.0-8.0.
Wherein the concentration of the hydrogen donor is 5-100 mM; the concentration of the coenzyme is 0.1 to 2 mM.
Performing post-treatment after the reaction to obtain solid modified lignin, specifically, filtering the reaction solution, washing the obtained solid (washing to be neutral), and drying to obtain the solid modified lignin; or directly applied to the preparation of the phenolic resin without drying.
Wherein the pH value of the phenolic resin is 8-10, the solid content is 70-85 wt%, the viscosity is 1800-8000 cp, and the gel time is 75-120 s; preferably, the pH value is 8.3-8.6, the solid content is 75-80 wt%, the viscosity is 1800-5000 cp, and the gel time is 75-100 s (150 ℃).
The phenolic resin is prepared from the following raw materials in parts by weight:
wherein, the alkali catalyst is any one or a combination of more of sodium hydroxide, potassium hydroxide, magnesium hydroxide, triethylamine, magnesium oxide and calcium oxide.
The preparation method of the phenolic resin comprises the following steps:
(1) mixing phenol, enzymatic modified lignin, part of paraformaldehyde, part of an alkali catalyst and part of water in parts by mass, and reacting:
(2) and (2) adding the residual paraformaldehyde, the residual alkali catalyst and the residual water into the reaction solution obtained in the step (1), reacting, and cooling to obtain the phenolic resin prepared from the enzymatic modified lignin.
In the step (1), the dosage of the partial paraformaldehyde is 40-60% (preferably 50%) of the total mass of the paraformaldehyde; the dosage of the partial alkali catalyst is 40-60% (preferably 50%) of the total mass of the total alkali catalyst; the dosage of the part of water is 40 to 60 percent (preferably 50 percent) of the total mass of the water; the reaction temperature is 80-90 ℃, and the reaction time is 1-2 h.
In the step (2), the reaction temperature is 70-90 ℃, and the reaction time is 0.5-1 h; cooling to 40-70 deg.C (preferably 65 deg.C).
The phenolic foam comprises the following components in parts by weight:
wherein, the foaming agent is any one or the combination of more of n-pentane, n-butane, isopentane, petroleum ether, polyvinyl alcohol aqueous solution and diisopropyl ether.
Wherein, the curing agent is any one or the combination of a plurality of sulfuric acid, hydrochloric acid, phosphoric acid, hydrobromic acid, benzenesulfonic acid, p-toluenesulfonic acid and naphthalenesulfonic acid.
Wherein the surfactant is any one or combination of more of polysiloxane, polyoxyethylene ether, polyoxypropylene, polyoxyethylene polyoxypropylene, polyethylene sorbitan fatty acid, polydimethylsiloxane and tween series.
Preferably, the phenolic foam further comprises any one or a combination of several of a toughening agent, a plasticizer and a flame retardant.
The toughening agent is any one or a combination of more of polyurethane prepolymer, polyethylene glycol, polyvinyl alcohol, polyester polyol, nitrile rubber and epoxy resin.
Wherein, the flame retardant is one or the combination of more of brominated cresol glycidyl ester, magnesium hydroxide, aluminum hydroxide, halogenated phosphate ester and zinc borate.
The preparation method of the phenolic foam comprises the steps of uniformly mixing all the components, pouring the mixture into a mould, and heating and foaming the mixture.
The step of uniformly mixing is that firstly, phenolic resin prepared by modifying lignin with an enzyme method and a surfactant are uniformly mixed at the rotating speed of 500-2500 rpm, then a foaming agent is added into the mixed system and uniformly mixed at the rotating speed of 500-1500 rpm, and finally a curing agent is added into the mixed system and uniformly mixed at the rotating speed of 1000-2500 rpm.
Wherein the foaming temperature is 70-90 ℃ and the time is 0.3-3 h.
The phenolic foam prepared by the method is also within the protection scope of the invention.
Has the advantages that: compared with the prior art, the invention has the following advantages:
the phenolic foam prepared by the method has the advantages of lower heat conductivity coefficient (reduced by 21-42%), stronger mechanical property (the compressive strength is improved by 31-63%, the tensile strength is improved by 31-54%) and higher oxygen index (improved by 17-29%) than that of unmodified lignin-based phenolic foam, has the mechanical property and the heat conductivity coefficient equivalent to those of phenolic foam prepared by chemically modified lignin, and has market application prospect.
Drawings
FIG. 1 is a graph of compressive strength of phenolic foam.
FIG. 2 is a graph of thermal conductivity relationship for phenolic foam.
FIG. 3 is a graph of oxygen index for phenolic foam.
FIG. 4 is a standard curve of phenol concentration versus absorbance.
Detailed Description
The invention will be better understood from the following examples. However, those skilled in the art will readily appreciate that the description of the embodiments is only for illustrating the present invention and should not be taken as limiting the invention as detailed in the claims.
The detection method of each parameter in the following implementation is as follows:
gel time: the national standard GB/T33315-2016;
pH: the national standard GB T32364-2015;
free formaldehyde: the national standard GBT 32684-2016;
solid content, viscosity: GBT 14074-;
properties of the foam: national standard GBT 20974-2014.
Content of lignin phenolic hydroxyl group: the method for preparing the forskolin phenol reagent comprises the following steps
The standard curve drawing method comprises the following steps: 0.2013g of phenol was accurately weighed and placed in a 1000mL glass volumetric flask, and ultrapure water was added to the flask for constant volume. 10mL of the solution was aspirated by a pipette and placed in a 100mL volumetric flask, and the volume was fixed with ultrapure water to obtain an aqueous phenol solution having a concentration of 0.02013 g/L. 0mL, 1mL, 2 mL, 4mL, 8 mL, 10mL and 14mL of the prepared solution are respectively sucked by a pipette gun and added into 750 mL volumetric flasks, the corresponding phenol concentrations are respectively 0, 4.278, 8.556, 17.112, 34.224, 42.780 and 59.892 mu mol/L, 3mL of Folin phenol reagent is added into each volumetric flask, and the volumetric flasks are placed for 10min after being sufficiently shaken and evenly shaken. After the completion of the standing, 10mL of the prepared 20 wt% Na was added2CO3Adding magnetons into the solution and ultrapure water after constant volume, and magnetically stirring the solution at room temperature for 2 hours for reaction. After the reaction, the absorbance of the product at a wavelength of 760nm was measured using an ultraviolet spectrophotometer (UV), and a standard curve was plotted (FIG. 4).
Weighing 0.10g of absolutely dry lignin in a 1000mL glass volumetric flask, adding ultrapure water for constant volume, and accurately preparing into 0.1g/L aqueous solution, if the dissolution is difficult, adding a trace amount of NaOH solid to promote the dissolution. Accurately sucking 1mL of solution by using a pipette, placing the solution in a 50mL volumetric flask, adding 3mL of LFC reagent and 30mL of ultrapure water, fully shaking uniformly, and standing for 10 min. After the completion of the standing, 10mL of the prepared 20 wt% Na was added2CO3Adding magneton after the solution and ultrapure water have constant volume, magnetically stirring at room temperatureStirring for 2h to react. After the reaction is finished, an ultraviolet spectrophotometer (UV) is used for measuring the ultraviolet absorbance of the product at the wavelength of 760nm, the lignin phenolic hydroxyl group content (mmol/g) can be calculated according to a standard curve, the product is multiplied by the hydroxyl molecular weight (17g/mol), and the product is divided by 1000 to be converted into a mass ratio (%).
Example 1
30mL of 50mM potassium phosphate buffer pH7.0 was added with alkali lignin 0.3g, FAD 1mM, and C15H15NO3100mM, and finally 70U/mL phenol monooxygenase was added. The mixture is placed in a shaking table at 50 ℃ and 200rpm for reaction, and the reaction solution is communicated with the outside air. After 24 hours of reaction, the reaction solution is filtered and washed to be neutral, the reaction solution is dried to constant weight in a vacuum oven at the temperature of 80 ℃, the enzymatic modified lignin is obtained after drying, and the product is weighed, wherein the yield is 85 percent, the phenolic hydroxyl content of the unmodified alkali lignin is 2.45 percent, the phenolic hydroxyl content of the enzymatic modified alkali lignin is 5.24 percent, and the phenolic hydroxyl content is increased by 2.79 percent.
Taking 100 parts of phenol, adding 10 parts of enzymatic modified lignin, adding 40 parts of paraformaldehyde, 2 parts of alkaline catalyst (sodium hydroxide) and 20 parts of water in two batches, adding 40% by mass of paraformaldehyde, 40% by mass of alkaline catalyst and 40% by mass of water for the first time, heating to 80 ℃ for reaction for 1h, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 0.5h at 70 ℃, and cooling to 40 ℃ to obtain the phenolic resin prepared from the enzymatic modified lignin; the pH value of the phenolic resin is 8.3, the solid content is 76 wt%, the viscosity is 2130cp, and the gel time (150 ℃) is 75 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 2 parts of polyoxyethylene ether, and stirring for 60 seconds at 500rpm of a mechanical stirrer until the mixture is uniformly stirred. 5 parts of n-butane is added, and the mixture is stirred for 30s at 500rpm by a mechanical stirrer until the mixture is uniformly stirred. Adding 15 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring for 30s at 1000rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 0.3h at 70 ℃ to obtain the enzymatic modified lignin-based phenolic foam material.
Example 2
50mL of 50mM potassium phosphate buffer pH7.0 was added with 1.5g of lignin, FAD 2mM, and C as organic solvents14H14N2O3100mM, and finally 50U/mL phenol monooxygenase was added. The mixture is placed in a shaking table at 50 ℃ and 200rpm for reaction, and the reaction solution is communicated with the outside air. After reacting for 15h, filtering and washing the reaction solution to be neutral, drying the reaction solution to be constant weight in a vacuum oven at the temperature of 80 ℃, drying the reaction solution to obtain hydroxylated modified lignin, weighing the product, wherein the yield is 81 percent, the phenolic hydroxyl content of the unmodified organic solvent lignin is 2.52 percent, the phenolic hydroxyl content of the hydroxylated modified lignin is 5.17 percent, and the phenolic hydroxyl content is increased by 2.65 percent.
Taking 100 parts of phenol, adding 30 parts of enzymatic modified lignin, adding 45 parts of paraformaldehyde, 6 parts of alkaline catalyst (sodium hydroxide) and 30 parts of water in two batches, adding 50% by mass of paraformaldehyde, 50% by mass of alkaline catalyst and 50% by mass of water for the first time, heating to 85 ℃, reacting for 1.5 hours, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 0.75 hours at 80 ℃, and cooling to 55 ℃, thus obtaining the phenolic resin prepared from the enzymatic modified lignin; the phenolic resin has a pH value of 8.6, a solid content of 78 wt%, a viscosity of 3480cp and a gel time (150 ℃) of 80 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 6 parts of polydimethylsiloxane (DC-193), and stirring for 60 seconds at 1500rpm of a mechanical stirrer until the mixture is uniformly stirred. 10 parts of n-pentane is added, and the mixture is stirred for 30 seconds at 1000rpm of a mechanical stirrer until the mixture is uniformly stirred. Adding 20 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring at 1750rpm of a mechanical stirrer for 30s until the mixture is uniformly stirred, introducing the mixture into a mold, and curing at 80 ℃ for 2h to obtain the enzymatic modified lignin-based phenolic foam material.
Example 3
To 30mL of 50mM potassium phosphate buffer, pH7.0, was added 0.6g of lignin as an organic solvent and 50U/mL of ferrous oxidase. The mixture is placed in a shaking table at 35 ℃ and 200rpm for reaction, and the reaction liquid is communicated with the outside air. After 24h of reaction, the reaction solution is filtered and washed to be neutral, the reaction solution is dried to constant weight in a vacuum oven at 80 ℃, the enzymatic modified lignin is obtained after drying, and the product is weighed, the yield is 80%, the phenolic hydroxyl content of the unmodified organic solvent lignin is 2.52%, the phenolic hydroxyl content of the enzymatic modified lignin is 4.78%, and the phenolic hydroxyl content is increased by 2.26%.
Taking 100 parts of phenol, adding 50 parts of enzymatic lignin, adding 50 parts of paraformaldehyde, 8 parts of alkaline catalyst (sodium hydroxide) and 40 parts of water in two batches, adding 60% by mass of paraformaldehyde, 60% by mass of alkaline catalyst and 60% by mass of water for the first time, heating to 90 ℃ for reaction for 2 hours, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 1 hour at 90 ℃, and cooling to 70 ℃ to obtain enzymatic modified lignin-based phenolic resin; the pH value of the phenolic resin is 8.4, the solid content is 80 wt%, the viscosity is 3920cp, and the gel time (150 ℃) is 85 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 10 parts of polyoxypropylene, and stirring for 60 seconds at 2500rpm of a mechanical stirrer until the mixture is uniformly stirred. Adding 15 parts of isopentane, and stirring for 30s at 1500rpm of a mechanical stirrer until the mixture is uniformly stirred. Adding 25 parts of curing agent (p-toluenesulfonic acid: phosphoric acid: water: 7: 3: 3), 10 parts of polyethylene glycol and 10 parts of aluminum hydroxide, stirring for 30s at 2500rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 3h at 90 ℃ to obtain the enzymatic modified lignin-based phenolic foam material.
Example 4
To 30mL of 50mM potassium phosphate buffer, pH7.0, was added alkali lignin 0.3g, FAD 0.1mM, BNAH100mM, and finally phenol monooxygenase 100U/mL. The mixture is placed in a shaking table at 50 ℃ and 200rpm for reaction, and the reaction solution is communicated with the outside air. And (3) reacting for 24 hours, filtering the reaction solution, washing to be neutral, drying in a vacuum oven at 80 ℃ to constant weight, drying to obtain the enzymatic modified lignin, and weighing the product, wherein the yield is 85%, the phenolic hydroxyl content of unmodified alkali lignin is 2.66%, the phenolic hydroxyl content of the enzymatic modified lignin is 5.59%, and the phenolic hydroxyl content is increased by 2.93%.
Taking 100 parts of phenol, adding 20 parts of enzymatic modified lignin, adding 45 parts of paraformaldehyde, 8 parts of alkaline catalyst (sodium hydroxide) and 35 parts of water in two batches, adding 50% by mass of paraformaldehyde, 50% by mass of alkaline catalyst and 50% by mass of water for the first time, heating to 80 ℃ for reaction for 1h, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 0.5h at 80 ℃, and cooling to 65 ℃ to obtain the phenolic resin prepared from enzymatic modified lignin; the pH value of the phenolic resin is 8.5, the solid content is 76 wt%, the viscosity is 2520cp, and the gel time (150 ℃) is 80 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 3 parts of polydimethylsiloxane (DC-193), and stirring at 1500rpm of a mechanical stirrer for 60 seconds until the mixture is uniformly stirred. 9 parts of n-pentane was added thereto, and the mixture was stirred with a mechanical stirrer at 1000rpm for 30 seconds until the mixture was uniformly stirred. Adding 17 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring for 30s at 2000rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 2h at 70 ℃ to obtain the lignin-based phenolic foam material.
Comparative example 1
5g of alkali lignin, 28g of phenol, 1.98g of sodium hydroxide and 66g of water are added into a reaction bottle, the reaction is carried out for 1h at 90 ℃, and the reaction is rapidly cooled to room temperature after the reaction is finished. 3mol/L hydrochloric acid solution is added into the reaction liquid until the pH value is 1, and 5 times of equivalent volume of water is added to assist precipitation. And filtering and washing the precipitate until the washing liquid is neutral, drying in vacuum, and grinding in a grinding bowl to obtain the alkaline phenolated lignin. The phenolic hydroxyl content of the unmodified enzymatic hydrolysis lignin is 2.45 percent, the phenolic hydroxyl content of the phenolic modified lignin is 3.26 percent, and the phenolic hydroxyl content is increased by 0.81 percent.
Taking 100 parts of phenol, 10 parts of alkaline catalyst (sodium hydroxide), 20 parts of phenolated modified lignin, reacting for 2 hours at 90 ℃ to obtain phenolated modified lignin liquid, adding 45 parts of paraformaldehyde, 8 parts of alkaline catalyst (sodium hydroxide) and 35 parts of water in two batches, adding 50% of paraformaldehyde, 50% of alkaline catalyst and 50% of water in mass fraction for the first time, heating to 80 ℃ for reaction for 1 hour, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction liquid again, reacting for 0.5 hour at 80 ℃, and cooling to 65 ℃ to obtain phenolic resin prepared from phenolated modified lignin; the pH value of the phenolic resin is 8.1, the solid content is 76 wt%, the viscosity is 3610cp, and the gel time (150 ℃) is 95 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 3 parts of polydimethylsiloxane (DC-193), and stirring at 1500rpm of a mechanical stirrer for 60 seconds until the mixture is uniformly stirred. 9 parts of n-pentane was added thereto, and the mixture was stirred with a mechanical stirrer at 1000rpm for 30 seconds until the mixture was uniformly stirred. Adding 17 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring for 30s at 2000rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 2h at 80 ℃ to obtain the phenolic modified lignin-based phenolic foam material.
Comparative example 2
Taking 100 parts of phenol, adding 20 parts of organic solvent lignin, adding 45 parts of paraformaldehyde, 8 parts of alkaline catalyst (sodium hydroxide) and 35 parts of water in two batches, adding 50% by mass of paraformaldehyde, 50% by mass of alkaline catalyst and 50% by mass of water for the first time, heating to 80 ℃, reacting for 1h, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 0.5h at 80 ℃, and cooling to 65 ℃ to obtain lignin-based phenolic resin; the pH value of the phenolic resin is 8.3, the solid content is 76 wt%, the viscosity is 4920cp, and the gel time (150 ℃) is 150 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 4 parts of polydimethylsiloxane (DC-193), and stirring for 60 seconds at 1500rpm of a mechanical stirrer until the mixture is uniformly stirred. 9 parts of n-pentane was added thereto, and the mixture was stirred with a mechanical stirrer at 1000rpm for 30 seconds until the mixture was uniformly stirred. Adding 17 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring for 30s at 2000rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 2h at 75 ℃ to obtain the lignin-based phenolic foam material.
Comparative example 3
Taking 100 parts of phenol, adding 45 parts of paraformaldehyde, 8 parts of alkaline catalyst (sodium hydroxide) and 35 parts of water in two batches, adding 50% of paraformaldehyde, 50% of alkaline catalyst and 50% of water in mass fraction for the first time, heating to 80 ℃, reacting for 1h, adding the rest paraformaldehyde, alkaline catalyst and water into the reaction solution again, reacting for 0.5h at 80 ℃, and cooling to 65 ℃ to obtain pure phenolic resin; the phenolic resin has a pH value of 8.2, a solid content of 76 wt%, a viscosity of 1420cp and a gel time (150 ℃) of 95 s.
And (3) taking 100 parts of the hairstyle phenolic resin and 4 parts of polydimethylsiloxane (DC-193), and stirring for 60 seconds at 1500rpm of a mechanical stirrer until the mixture is uniformly stirred. 9 parts of n-pentane was added thereto, and the mixture was stirred with a mechanical stirrer at 1000rpm for 30 seconds until the mixture was uniformly stirred. Adding 17 parts of curing agent (p-toluenesulfonic acid: sulfuric acid: 1), 10 parts of polyethylene glycol and 10 parts of brominated cresol glycidyl ester, stirring for 30s at 2000rpm of a mechanical stirrer until the mixture is uniformly stirred, introducing the mixture into a mold, and curing for 2h at 75 ℃ to obtain the pure phenolic foam material.
Various properties of the lignin-based phenolic foam prepared in examples 1-4 and comparative examples 1-3 were characterized as shown in Table 1. By observing examples 1 to 4 and comparative examples 1 to 3, as shown in FIGS. 1 to 3, it was found that the phenolic foam prepared from the enzymatically modified lignin as a starting material had improved compressive strength, tensile strength, and oxygen index and had a lower thermal conductivity as compared with the phenolic foam prepared from the phenolized modified lignin. Compared with the phenolic foam prepared from the unmodified lignin, the phenolic foam prepared from the lignin modified by the enzyme method has greatly improved mechanical property, thermal property and flame retardant property. Compared with pure phenolic foam, the phenolic foam prepared by using the enzymatic method modified lignin as the raw material has the advantages of greatly improved oxygen index, improved flame retardant property, reduced heat conductivity coefficient and improved heat insulation property. The enzymatic modification of lignin shows that the activity of lignin can be greatly improved, the performance of phenolic resin is improved, and the quality of phenolic foam is further improved.
TABLE 1
The method for preparing the phenolic resin and the phenolic foam by using the enzymatic method modified lignin as the raw material increases the phenolic hydroxyl content of the lignin and improves the reaction activity of the lignin. The phenolic resin prepared from the modified lignin has short gelling time and high reaction activity, and the phenolic foam prepared from the phenolic resin has excellent mechanical property, fireproof property and heat preservation property, and has a prospect of large-scale application in the market.
The invention provides a concept of a preparation method of phenolic foam by enzymatic modification of lignin, and a method and a way for implementing the technical scheme are many, the above description is only a preferred embodiment of the invention, and it should be noted that, for those skilled in the art, a plurality of improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications should be regarded as the protection scope of the invention. All the components not specified in the present embodiment can be realized by the prior art.

Claims (10)

1. A preparation method for preparing phenolic foam by enzymatic modification of lignin is characterized in that phenolic foam heat-insulating material is prepared from phenolic resin prepared by enzymatic modification of lignin, a foaming agent, a curing agent and a surfactant;
the preparation method of the enzymatic modified lignin comprises the steps of mixing lignin and a biocatalyst in a solvent, and reacting to obtain the lignin;
wherein the biocatalyst is any one of phenol monooxygenase, naphthalene dioxygenase, tyrosinase and ferrous iron oxidase;
wherein, when the biocatalyst is phenol monooxygenase, hydrogen donor and coenzyme are required to be added; when the biocatalyst is naphthalene dioxygenase, only hydrogen donor needs to be added; when the biocatalyst is tyrosinase or ferrous oxidase, hydrogen donor and coenzyme do not need to be added;
wherein, the hydrogen donor is a natural nicotinamide cofactor or an artificial nicotinamide cofactor;
wherein the coenzyme is flavin adenine dinucleotide.
2. The method for preparing phenolic foam from lignin modified by an enzymatic method according to claim 1, wherein the solvent is any one of water, phosphate buffer, Tris-HCl buffer, HEPES buffer, MOPS buffer and barbital sodium-hydrochloric acid buffer.
3. The preparation method of phenolic foam by using enzymatic modified lignin according to claim 1, wherein the concentration of the lignin is 5-80 g/L; the dosage of the biocatalyst is 10-100000U/L.
4. The method for preparing the phenolic foam by using the enzymatic modified lignin according to claim 1, wherein the reaction in the enzymatic modified lignin is carried out at room temperature to 50 ℃ for 4 to 24 hours.
5. The method for preparing phenolic foam from lignin modified by enzyme method according to claim 1, wherein the natural nicotinamide cofactor is NADH or NADPH.
6. The method for preparing phenolic foam from lignin modified by an enzymatic method according to claim 1, wherein the artificial nicotinamide cofactor is represented by formula I1 or formula I2:
7. the method for preparing the phenolic foam by using the enzymatic modified lignin according to claim 1, wherein the concentration of the hydrogen donor is 5-100 mM; the concentration of the coenzyme is 0.1 to 2 mM.
8. The preparation method of the phenolic foam through enzymatic modification of lignin according to claim 1, wherein the phenolic resin has a pH value of 8-10, a solid content of 70-85 wt%, a viscosity of 1800-8000 cp and a gel time of 75-120 s.
9. The preparation method of the phenolic foam by using the enzymatic modified lignin according to claim 1, wherein the phenolic foam comprises the following components in parts by weight:
100 parts of phenolic resin prepared by modifying lignin by an enzyme method;
5-15 parts of a foaming agent;
15-25 parts of a curing agent;
2-10 parts of a surfactant.
10. Phenolic foam produced by the process of any one of claims 1 to 9.
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