CN109206589B

CN109206589B - Preparation method of pyrolysis lignin and lignin-based polyurethane rigid foam

Info

Publication number: CN109206589B
Application number: CN201710532398.7A
Authority: CN
Inventors: 谭天伟; 段伊静; 曹辉; 方云明; 邱石; 姜志国; 张成彬
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2017-07-03
Filing date: 2017-07-03
Publication date: 2021-08-06
Anticipated expiration: 2037-07-03
Also published as: CN109206589A

Abstract

The invention provides a cracked lignin which is obtained by hydrocatalytically cracking wood fibers. The invention also provides a preparation method of the lignin-based polyurethane rigid foam, and the cracked lignin provided by the invention replaces part of petroleum-based polyol. The lignin-based polyurethane rigid foam prepared by the preparation method disclosed by the invention is excellent in performance, degradable, reproducible and environment-friendly, and has great industrial application prospects.

Description

Preparation method of pyrolysis lignin and lignin-based polyurethane rigid foam

Technical Field

The invention belongs to the field of macromolecules, and particularly relates to a preparation method of a cracking lignin and lignin-based polyurethane hard foam.

Background

Polyurethane rigid foams are widely used as heat insulating materials for general buildings and the like because of their excellent heat insulating properties. Generally, polyurethane rigid foams are prepared using the following method: the polyisocyanate component liquid and the mixed liquid are mixed, after which the polyisocyanate component liquid and the mixed liquid are foamed in a short time and then cured.

With the gradual decrease of the total amount of non-renewable resources such as petroleum and coal, the transformation of plant and microorganism resources into new materials, high calorific value energy and new chemical raw materials is becoming a development trend. Lignin, a phenolic polymer with a very complex molecular structure, is widely present in plant cell tissues and is the second most abundant fiber polymer on earth.

CN 102206320B discloses a preparation method of straw-based biomass polyurethane foam. The method has the following disadvantages: the biomass waste is prepared by mixing corn straws, rice straw straws, cotton stalks and the like, has complex components, is not beneficial to treatment, has small addition amount, and has great influence on the performance of polyurethane foam; the biomass material liquefaction reagent is concentrated hydrochloric acid or concentrated sulfuric acid, the temperature reaches 200 ℃, the energy consumption is large, and the industrialization is not facilitated; the biomass waste and the lignosulfonate are added into the polyurethane, so that the particle size, the molecular weight and the hydroxyl value of the components are greatly different, the blending and foaming of the polyurethane components are complicated and the product performance is unstable.

Disclosure of Invention

In a first aspect of the invention, a cracked lignin is provided, which is obtained by subjecting wood fibres to a hydrocatalytic cracking. The cracked lignin provided by the invention is in a liquid state at normal temperature (usually 15-40 ℃), and can be directly used for synthesizing biomass materials.

According to the present invention, the wood fiber may be wood fiber generally used in the art, preferably having a particle size of 40 to 100 mesh.

According to some preferred embodiments of the present invention, the catalytic cracking is carried out in the presence of a supported ruthenium metal catalyst.

According to some preferred embodiments of the invention, the catalytic cracking is carried out using an initial pressure of from 1MPa to 3MPa, preferably from 1MPa to 2 MPa.

According to some preferred embodiments of the invention, the catalytic cracking is carried out at a temperature of 230 ℃ to 250 ℃, preferably 240 ℃ to 250 ℃. In one embodiment, the temperature is 250 ℃.

According to some preferred embodiments of the invention, the catalytic cracking is carried out for a time ranging from 1 to 6 hours, preferably from 3 to 6 hours, more preferably from 3 to 4 hours.

According to some preferred embodiments of the invention, the catalytic cracking is carried out in the presence of a solvent. The solvent is preferably selected from one or more of methanol, ethanol, tetrahydrofuran and dioxane.

According to some preferred embodiments of the present invention, the wood fiber has a particle size of 40 mesh or less.

The second invention of the invention provides a preparation method of lignin-based polyurethane rigid foam. The preparation method synthesizes the biomass polyurethane foam by using the cracked lignin as a polyol component to replace petroleum-based polyol, has simple synthesis method and convenient operation, and has reference significance for further developing and researching biomass materials.

The preparation method of the lignin-based polyurethane rigid foam provided by the invention comprises the following steps:

step 1): mixing the cracked lignin, the petroleum-based polyol, the catalyst and the foaming agent to obtain a pre-mixed component;

step 2): adding isocyanate into the premixed component to foam.

According to some preferred embodiments of the present invention, the petroleum-based polyol is selected from the group consisting of polyether polyols and polyester polyols. Preferably, the polyether polyol is selected from one or more of EP3600, PTMG-1000 (polytetrahydrofuran ether glycol), PPG-1000 (polypropylene glycol) and PEG (polyethylene glycol). Preferably, the polyester polyol is selected from one or more of PBT (polybutylene terephthalate), PBA (polybutyl acrylate), PEA (polyacrylate) and PCL (polycaprolactone polyol).

According to some preferred embodiments of the present invention, the isocyanate is selected from one or more of polymethylene polyphenyl isocyanates, toluene diisocyanate and diphenylmethane diisocyanate.

According to some preferred embodiments of the present invention, the mass ratio of the cracked lignin to the petroleum-based polyol is 1:9 to 7:3, preferably 1:9, 1:1, 3:7, etc. The cracked lignin of the present invention can replace 10 wt% to 70 wt% (e.g., 10 wt%, 20 wt%, 30 wt%, 50 wt%, 60 wt%, 70 wt%) of petroleum-based polyols.

According to some preferred embodiments of the invention, the blowing agent is selected from one or more of water, blowing agent ADC (azodicarbonamide) and sodium and ammonium bicarbonate.

According to some preferred embodiments of the present invention, the catalyst is selected from one or more of stannous octoate, potassium acetate, dibutyl tin dilaurate, N-dimethylcyclohexyl, triethanolamine, triethylamine, and N, N-dimethylethanolamine.

The present invention has the following advantageous effects.

(1) The liquid cracked lignin is obtained by the catalytic degradation of the wood fiber, and can be directly used for the synthesis of biomass materials.

(2) The pyrolysis lignin is used as a polyol component to replace part of petroleum-based polyols (for example, 10-70 wt% of petroleum-based polyols) to synthesize the biomass polyurethane foam, the synthesis method is simple, the operation is convenient, and the reference significance is provided for further development and research of biomass materials.

(3) The lignin-based polyurethane rigid foam synthesized by the preparation method has the advantages of lower process cost, stable performance and certain improvement of the performance compared with pure polyurethane foam (namely, the polyurethane foam prepared by taking petroleum-based polyol as polyol component instead of cracking lignin), and the product has degradable and reproducible environmental protection performance and has great industrial application prospect.

Drawings

FIG. 1 is an IR spectrum of a rigid polyurethane foam prepared in examples 1 to 3 and comparative example 1.

FIG. 2 is an electron micrograph of the rigid polyurethane foam prepared in comparative example 1.

FIG. 3 is an electron micrograph of the rigid polyurethane foam prepared in example 1.

FIG. 4 is an electron micrograph of the rigid polyurethane foam prepared in example 2.

FIG. 5 is an electron micrograph of the rigid polyurethane foam prepared in example 3.

FIG. 6 is a DTG graph of the rigid polyurethane foams prepared in examples 1 to 3 and comparative example 1.

Detailed Description

The present invention will be described in detail below with reference to the drawings and examples, but the present invention is not limited to the examples.

Example 1

Crushing the wood fiber, sieving the crushed wood fiber by a standard sieve of 80 meshes to obtain the wood fiber with uniform particle size, and drying the crushed wood fiber for 3 hours at the temperature of 60 ℃ by a vacuum constant-temperature drying oven. Taking a certain amount of wood fiber, placing into an autoclave, checking the tightness of the autoclave before reaction, sealing, and adding 1MPa H₂Pressurizing to make the air pressure of the whole system reach 2MPa, and slowly heating to 250 ℃. The reaction is carried out for 4h by using a supported ruthenium metal catalyst, and methanol is used as a solvent for catalytic cracking reaction. And taking the liquid lignin and methanol on the upper layer of the product, carrying out rotary evaporation at 40 ℃ under reduced pressure, and removing the methanol to obtain the liquid cracked lignin.

Adding 2g of prepared pyrolysis lignin into a beaker, and mixing the lignin according to a mass ratio of 1:9 adding corresponding polyether polyol 5110, adding 0.5g of catalyst A33, 0.5g of stannous octoate T9, 0.8g of foam stabilizer, 0.6g of crosslinking agent L580, 1g of foaming agent water and the like into a beaker, and uniformly mixing by using an electric stirrer at room temperature, wherein the rotating speed is set as 600 r/min. Adding polymethylene polyphenyl isocyanate PMDI, stirring to mix uniformly, and setting the rotation speed at 600 r/min. When bubbles are observed to be emitted in the mixture and the bubbles are whitened, the mixture is immediately injected into an automatic mold to be freely foamed and expanded for molding. The obtained foam was left at room temperature for 12 hours to conduct post-curing treatment, so that the incomplete reaction therein proceeded to obtain a lignin-based polyurethane rigid foam L10 PU.

Example 2

Crushing the wood fiber, sieving the crushed wood fiber by a 100-mesh standard sieve to obtain the wood fiber with uniform particle size, and drying the crushed wood fiber for 2 hours at the temperature of 100 ℃ by a vacuum constant-temperature drying oven. Taking a certain amount of wood fiber, putting into an autoclave, checking the tightness of the autoclave before reaction, sealing, pressurizing with 1MPa H2 to make the pressure of the whole system reach 3MPa, and slowly heating to 240 ℃. The reaction is carried out for 5h by using a supported ruthenium metal catalyst, and the catalytic cracking reaction is carried out by using methanol as a solvent. And (3) taking the liquid lignin and methanol on the upper layer of the product, carrying out rotary evaporation at 40 ℃ under reduced pressure, and removing the methanol to obtain the liquid cracked lignin.

6g of prepared pyrolysis lignin is added into a beaker, and the mass ratio of the lignin is 3:7 adding corresponding PEG (polyethylene glycol), adding 0.5g of catalyst A33, 0.5g of stannous octoate T9, 0.8g of foam stabilizer, 0.6g of cross-linking agent L580 and 1g of foaming agent water into a beaker, and uniformly mixing by using an electric stirrer at room temperature, wherein the rotating speed is set as 700 r/min. Adding toluene diisocyanate, stirring to mix uniformly, setting the rotating speed at 700 r/min. When bubbles are observed to be generated in the mixture and the foam body is whitish, the mixture is immediately injected into a self-made mould to be freely foamed and expanded for forming. The obtained foam was left at room temperature for 24 hours to be post-aged, so that the incomplete reaction therein proceeded, to obtain a lignin-based polyurethane rigid foam L30 PU.

Example 3

Crushing the wood fiber, sieving the crushed wood fiber by a 40-mesh standard sieve to obtain the wood fiber with uniform particle size, and drying the crushed wood fiber for 3 hours at the temperature of 80 ℃ by a vacuum constant-temperature drying oven. Taking a certain amount of wood fiber, putting into an autoclave, checking the tightness of the autoclave before reaction, sealing, pressurizing with 1MPa H2 to make the pressure of the whole system reach 1MPa, and slowly heating to 230 ℃. The reaction is carried out for 3h by using a supported ruthenium metal catalyst, and the catalytic cracking reaction is carried out by using methanol as a solvent. And (3) taking the liquid lignin and methanol on the upper layer of the product, carrying out rotary evaporation at 40 ℃ under reduced pressure, and removing the methanol to obtain the liquid cracked lignin.

Adding 10g of prepared pyrolysis lignin into a beaker, and mixing the lignin according to a mass ratio of 1:1 adding corresponding PPG-1000 (polypropylene glycol), adding 0.5g of catalyst A33, 0.5g of stannous octoate T9, 0.8g of foam stabilizer, 0.6g of cross-linking agent L580, 1g of foaming agent water and the like into a beaker, and uniformly mixing by using an electric stirrer at room temperature, wherein the rotating speed is set as 800 r/min. Adding the diphenylmethane diisocyanate, and stirring to uniformly mix the diphenylmethane diisocyanate at the rotating speed of 800 r/min. When bubbles are observed to be generated in the mixture and the foam body is whitish, the mixture is immediately injected into a self-made mould to be freely foamed and expanded for forming. The obtained foam was left at room temperature for 8 hours to conduct post-curing treatment, in which the incomplete reaction was continued, to obtain a lignin-based polyurethane rigid foam L50 PU.

Comparative example 1

20g of polyether polyol 5110, 0.5g of catalyst A33, 0.5g of stannous octoate T9, 0.8g of foam stabilizer, 0.6g of crosslinking agent L580 and 1g of foaming agent water are added into a beaker, and the mixture is uniformly mixed by an electric stirrer at room temperature, wherein the rotating speed is set to be 700 r/min. Then 39.67g of PMDI (polymethylene polyphenyl polyisocyanate) is added and stirred to be uniformly mixed, and the rotating speed is set to be 700 r/min. When bubbles are observed to be generated in the mixture and the foam body is whitish, the mixture is immediately injected into a self-made mould to be freely foamed and expanded for forming. The resulting foam was left at room temperature for 24 hours to conduct post-curing treatment, in which incomplete reaction was allowed to proceed, to obtain pure polyurethane rigid foam L0 PU.

Table 1 shows the properties of the rigid polyurethane foams prepared in examples 1 to 3 and comparative example 1

TABLE 1

It is evident from the infrared of fig. 1 that polyurethane is formed and that the addition of depolymerized lignin does not significantly change the chemical structure of the polyurethane foam.

Thermal analysis of polyurethane rigid foam L0PUL10PU L30PU L50PU

The thermal degradation temperature range of all samples is about 200-450 ℃, the thermal weight loss decomposition is divided into two stages, 200-345 ℃ is the first degradation stage, and the temperature when the thermal weight loss of the samples is 5 wt% is generally defined as the thermal degradation starting temperature TOD of the composite material. The higher thermal degradation onset temperatures (247 ℃, 257 ℃) of L10PU, L0PU compared to samples L30PU, L50PU (225 ℃), indicate that the addition of the cleaved lignin slightly lowers the initial degradation temperature of the polyurethane material.

The second stage of thermal weight loss occurs at 345-450 ℃ and mainly results from the degradation of the urethane structure of polyurethane rigid foam materials [19 ]. L10PU, L30PU had a higher rate of second stage thermal degradation than L0PU, and although the cracked lignin had a higher hydroxyl number, had lower accessibility to the isocyanate, resulting in insufficient crosslinking, and therefore less urethane linkages than pure polyurethane foam. It is clear that L50PU has a very high second stage thermal degradation rate, indicating that the addition of too much cleaved lignin further hinders the reaction with isocyanate groups. In addition, the derivative thermal mass curve is shown in fig. 6, and the four groups of samples all reach the maximum thermal degradation rate at about 325 ℃; the maximum weight loss values for samples L0PU, L30PU were nearly identical (325 deg.C), while L10PU, L50PU were elevated to 329 deg.C, and the addition of the cleaved lignin increased the thermal stability of the polyurethane foam due to the higher thermal decomposition temperature of lignin compared to polyurethane.

Limiting oxygen index of polyurethane rigid foam L0PUL10PU L30PU L50PU

According to the formula, after the lignin is added, the hard polyurethane foam is changed from inflammable to inflammable.

While the invention has been described with reference to certain embodiments, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the various features of the various embodiments of the invention disclosed may be used in any combination, provided that no structural conflict exists, and the combination is not exhaustively described in this specification merely for the sake of brevity and resource conservation. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a lignin-based rigid polyurethane foam, comprising:

step 1): mixing the cracked lignin, the petroleum-based polyol, the catalyst and the foaming agent to obtain a premixed component;

step 2): adding isocyanate into the premixed component for foaming;

the cracking lignin is obtained by carrying out hydrocatalytic cracking on wood fibers, the particle size of the wood fibers is 40-100 meshes, and the cracking lignin is in a liquid state at normal temperature;

wherein the mass ratio of the cracked lignin to the petroleum-based polyol is 1:9-7: 3.

2. The method of claim 1, wherein the petroleum-based polyol is selected from at least one of a polyester polyol and a polyether polyol.

3. The method according to claim 2, wherein the polyether polyol is selected from one or more of EP3600, polytetrahydrofuran ether glycol, polypropylene glycol and polyethylene glycol.

4. The method of claim 2, wherein the polyester polyol is selected from one or more of polybutylene terephthalate, polybutylacrylate, polyethylacrylate, and polycaprolactone polyol.

5. A process according to any one of claims 1 to 4, characterised in that the isocyanate is selected from one or more of polymethylene polyphenyl isocyanate, toluene diisocyanate and diphenylmethane diisocyanate; and/or the blowing agent is selected from water, blowing agent ADC and one or more of sodium bicarbonate and ammonium carbonate; the catalyst is selected from one or more of stannous octoate, potassium acetate, dibutyltin dilaurate, N-dimethyl cyclohexyl, triethanolamine, triethylamine and N, N-dimethyl ethanolamine.

6. The method of claim 1, wherein the mass ratio of the cracked lignin to the petroleum-based polyol is 1:9, 3:7, or 1: 1.

7. The process of claim 1, wherein the catalytic cracking is carried out in the presence of a supported ruthenium metal catalyst.

8. The method of claim 1, wherein the catalytic cracking is conducted at an initial pressure of 1 to 3 MPa; the temperature is 230 ℃ and 250 ℃, and the reaction time is 3-6 hours.

9. The method of claim 8, wherein the catalytic cracking is carried out at an initial pressure of 1-2MPa, a temperature of 250 ℃ and a reaction time of 3-4 hours.

10. The method of claim 1, wherein the catalytic cracking is performed in the presence of a solvent selected from one or more of methanol, ethanol, tetrahydrofuran, and dioxane.