EP2760923A2

EP2760923A2 - Interconnected microcellular material made of industrial lignin and method for preparing same

Info

Publication number: EP2760923A2
Application number: EP12775776.3A
Authority: EP
Inventors: Hervé DELEUZE; Claire FORGACZ; Marc Birot
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite de Bordeaux
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite de Bordeaux
Priority date: 2011-09-29
Filing date: 2012-09-27
Publication date: 2014-08-06
Also published as: US20140228460A1; WO2013045848A3; FR2980797B1; CA2846782A1; FR2980797A1; JP2014530275A; WO2013045848A2; US9290633B2

Abstract

The invention relates to an interconnected microcellular material, to a method for preparing said material using low-value waste from the paper industry, such as industrial lignin, and to the use thereof for the production of items such as catalysts, filters or absorbent elements.

Description

Interconnected microcellular material made from lignin

process and its preparation process

The invention relates to a microcellular material, a process for preparing this material from residues of the paper industry of low value, as well as its use for the manufacture of articles such as catalysts, filters or absorbent elements.

The microcellular materials according to the invention are porous monoliths of centimeter size whose porosity is characterized by the presence of spherical cavities also called "cells", which have a diameter generally ranging between 1 and 100 μm, in particular about 2 μm. pm at about 50 μητι, and preferably from about 5 μm to about 20 μm. These cells are generally all interconnected with their close neighbors by openings or "windows" smaller than them. These interconnect windows are of variable size and have a diameter of from about 0.5 to about 10 μm, particularly from about 50 nm to about 1000 nm, and preferably from about 250 nm to about 500 nm.

The interconnected microcellular materials according to the invention have a particularly low density of 0.02 to 0.2 gcm- ³ .

The existing interconnected microcellular materials are generally obtained by the polyHIPE (Polymerization of a Hg /? Internai Phase Emulsion) process. Such materials are, for example, described in application FR 2 932 184.

The polyHIPE process consists in the polymerization of a highly concentrated emulsion which is composed of a dispersed internal phase whose volume percentage is greater than that of the dispersant external phase. The volume percentage of the dispersed internal phase must theoretically be greater than or equal to 74% relative to the total volume of the emulsion. This threshold of 74% corresponds to the maximum volume occupied by spherical drops internal phase uniforms dispersed and arranged so that they do not undergo deformation. Above 74%, the drops are compressed against each other. In the case of an emulsion having a wide drop size distribution (ie a polydisperse emulsion), the threshold for obtaining, after polymerization, an interconnected porous structure may be less than the theoretical value of 74%.

The outer dispersing phase of the polyHIPE process constitutes the continuous phase and mainly comprises monomers capable of polymerizing and a surfactant in solution in a solvent. The dispersed inner phase consists mainly of a solvent immiscible with the monomers and / or the solvent of the continuous phase.

After polymerization and removal of the solvent from the dispersed inner phase, interconnected microcellular materials are obtained.

Due to their structure and physical properties, interconnected microcellular materials are of increasing interest and their use has been proposed in many areas, including the manufacture of disposable absorbent articles, thermal, acoustic, electrical or mechanical insulation of membranes, filters or carriers for inks, dyes and catalysts.

However, the interconnected microcellular materials, described today, are obtained from polymerizable precursors mainly of petroleum origin or of synthetic origin, that is to say non-plant and non-renewable raw materials. In view of the decline in global oil reserves, the recovery of renewable materials to replace them has become a priority.

There is therefore a need for interconnected microcellular materials prepared from renewable raw materials and processes for preparing these materials, including polyHIPE processes, which use renewable raw materials. It is also important to favor a sustainable development approach by valuing waste from industry, without having a negative impact on other priority uses of such waste. resources, such as food or feed, and without additional environmental impact.

The object of the invention is therefore to provide an interconnected microcellular material, preferably from the polyHIPE process, while meeting certain sustainable development concerns and retaining the advantageous properties of current polyHIPE materials.

The present invention therefore relates to a process for preparing this interconnected microcellular material using as raw material lignin. This raw material is derived from lignocellulosic biomass.

Lignocellulosic biomass is one of the most abundant renewable resources on earth. Lignin is of significant interest because of its abundance and is the subject of much research for valuations other than its current uses in lumber and fuels.

In general, lignin results from the oxidative polymerization of at least three types of phenolic alcohols: p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. However, its structure depends on the botanical origin, the age of the plant, the type of tissue, the cells and the parietal layers in which it is found. This strong natural variability associated with variations in analytical methods makes it difficult to present the structure of lignins.

Thus, the term lignin is a generic name which denotes a set of polyphenolic polymers of high molecular mass, composition and variable and complex structure.

In chemical pulping processes, lignins are separated from cellulose by chemical processes that significantly alter their structure. The residual lignins, henceforth referred to as "industrial lignins", are present in dissolved form in cooking liquors which may also comprise hemicellulose monomers. These cooking liquors are either strongly basic in the Kraft process or in acidic solutions comprising sulfonated derivatives in the case of the bisulphite process. Industrial lignins can be mined and are a by-product of a significant amount of waste with more than 50,000 tonnes per year worldwide.

Several types of industrial lignin are available and can be used in the context of the invention, for example:

- Kraft lignin, which is derived from the papermaking process of the same name and accounts for more than 80% of the world's paper production;

lignosulphonates from the bisulphite process;

organosolines lignins resulting from an extraction process using organic oxidants;

- lignins from biorefineries using other sources of biomass than wood for the preparation of biofuel such as ethanol.

In particular, the raw material of the process according to the invention is one of the main by-products of the paper industry, currently available in very large quantities and very poorly valued, namely the "black liquor".

Black liquor or Kraft black liquor is the baking liquor from Kraft paper making. It is in the form of a strongly basic aqueous solution consisting mainly of Kraft lignin and hemicellulose residues dissolved from the pulp, as well as other inorganic chemical compounds used in the dissolution process. Black liquor is mainly used locally as a liquid fuel to supply energy to paper mills.

The subject of the invention is therefore a process for preparing an interconnected microcellular material by polymerization of a concentrated emulsion comprising:

an outer dispersant phase comprising, in a solvent, a surfactant and a solution comprising at least one polymerizable monomer contained in industrial lignin, and

a dispersed internal phase comprising a solvent immiscible with said polymerizable monomer and / or with the solvent of the dispersant external phase. By "at least one polymerizable monomer contained in industrial lignin" is meant a polymerizable monomer which originates from industrial lignins as defined above.

Once the outer dispersing phase of the concentrated emulsion is polymerized to a solid material, the solid material is preferably subjected to one or more washing and drying steps.

The invention also relates to interconnected microcellular materials, obtainable by the polymerization of a concentrated emulsion as described above.

In particular, the volume percentage of the dispersed inner phase of the concentrated emulsion is greater than or equal to about 55%. Thus, microcellular materials having an interconnected porous structure according to the invention are capable of being obtained by polymerization of a concentrated emulsion comprising a percentage by volume in dispersed internal phase less than the theoretical threshold of 74% of the polyHIPE emulsions.

The concentrated emulsion according to the invention is preferably an "oil-in-water" emulsion, that is to say having as dispersant outer phase an aqueous phase and dispersed organic phase an organic phase.

The outer dispersing phase comprises a solution containing the monomers contained in the industrial lignin, as described above, which will then polymerize. This solution can be a cooking liquor, especially the black liquor itself. Indeed, Kraft lignin is the main constituent of the black liquor, which makes it possible to use it in a privileged manner as main constituent of the dispersant external phase of a concentrated oil-in-water type emulsion according to the invention, and that without prior modification. In cases where the solution containing the monomers contained in the industrial lignin is a cooking liquor, in particular black liquor, the solvent of the dispersing external phase is derived from this liquor.

In particular, the raw material used in the context of the invention is black liquor comprising in particular from about 20% to about 80% by weight of dry matter, preferably from about 40% to about 60% mass of dry matter. The preferred mass percentage for obtaining interconnected microcellular materials according to the invention is 45% by mass of dry matter in the black liquor.

The dispersed internal phase of the emulsion according to the invention can be formed of any oil, and in particular, an oil soluble in common solvents and inexpensive to facilitate the washing of solids. Other types of oil can be used as the dispersed internal phase of the emulsion according to the invention. Thus, oils having a melting point between about 10 ° C and about 40 ° C and preferably close to room temperature may also be used.

When black liquor is used, the monomers capable of polymerization come from Kraft lignin and hemicelluloses.

The polymerizable monomers contained in the outer dispersant phase may be crosslinked to obtain a rigid solid. The outer phase of the concentrated emulsion may then further comprise a crosslinking agent, such as, for example, epichlorohydrin and cyanuric chloride.

The crosslinking makes it possible to create covalent bonds between the polymer chains by means of the reactive chemical functions present on the lignin chains (aliphatic alcohols and phenols) as well as on the hemicellulose chains possibly present (aliphatic alcohols only), in aqueous basic medium and at a moderate temperature. Under these conditions, the preferred crosslinking agent is epichlorohydrin. The reaction of epichlorohydrin with Kraft lignin from black liquor has the advantage of being catalyzed in a strong basic medium at a moderate temperature of 60.degree.

According to the invention, the concentrated emulsion can be polymerized at a temperature below 100 ° C and preferably from about 40 ° C to about 80 ° C.

To form a stable oil-in-water emulsion, a surfactant having a strong hydrophilic character is preferably added to the dispersant outer phase. The surfactant may thus be selected from hydrophilic anionic surfactants and nonionic hydrophilic surfactants. For example, an anionic surfactant will be used, the hydrophilic head may be a carboxylate, sulfate or sulfonate group. The apolar part may consist of a long linear or branched alkyl chain, simple or functionalized, or a long linear or branched alkylbenzene chain. Thus, sodium dodecyl sulphate (SDS), triethanolamine stearate, sodium lauryl sulphate and triethanolamine lauryl sulphate can be used, for example, to form the emulsion according to the invention.

Preferably, SDS will be used because it is inexpensive and can be used in a wide variety of formulations.

According to the invention, the surfactant may also be selected from nonionic surfactants. A wide variety of high hydrophilic-lipophilic balance (HLB) surfactants can be envisioned, including alkyl polyethoxylates, ethoxylated alkylphenols, polyethylene and polypropylene oxide complex polymers, octylphenols, and the like. polyethylene oxides, polyethylene oxide nonylphenols, polyethylene oxide and polypropylene oxide block copolymers, sorbitan fatty acid monoesters and polyesters, glycerol monoesters and polyesters of fatty acids, and their mixtures.

The porous morphology of the interconnected microcellular materials according to the invention can be characterized by the porosity but also by the distribution of the mean diameters of the cells, the average diameter of the windows of the interconnections or the specific surface. The analysis of this porous morphology also includes the determination of the origin of the porosity which comes from the imprint of the dispersed internal phase or the elimination of the water possibly contained in the dispersant external phase.

An indicator of the dispersion of the distribution of the U-cell diameters can in particular be used to determine whether this distribution is polydisperse or even monodisperse. This factor U is defined by the following expression:

U = (1 / d *) x (Σ | d * - di | x nidi ³ / Σnidi ³ )

where ri, is the number of cells of diameter d and d * the median diameter, namely the diameter for which the volume fraction of the smaller sizes is equal to 0.5. It is generally considered that a monodisperse distribution (i.e. where the cell diameters are homogeneous) is obtained when U is less than or equal to 0.3.

This porous morphology can be, in particular, modulated according to the nature and the amount of surfactant or the emulsification time. The interconnected microcellular material according to the invention then has a polydisperse or monodisperse distribution.

To determine the parameters influencing the porous morphology, different analysis techniques are used. Scanning Electron Microscopy (SEM) allows, from microphotographs, to establish a statistical analysis of the average cell diameter of the material. The porosimetry by mercury intrusion makes it possible to determine the porosity of the solid, the average diameter of the interconnections as well as the apparent density of the final solid. Finally, the measurement of the specific surface area of the interconnected microcellular materials is carried out by nitrogen adsorption and data processing by the BET method (Brunauer-Emmet-Teller).

The modulation of the experimental parameters thus makes it possible to obtain interconnected microcellular materials according to the invention having a more or less broad distribution of cell diameters (monodisperse or polydisperse).

The invention also relates to the interconnected microcellular materials, obtainable by the method described above.

These interconnected microcellular materials may in particular have a porosity greater than or equal to about 60%. This porosity value is sufficient to obtain high permeability materials while maintaining the mechanical strength required for the intended applications.

The invention also relates to the use of a concentrated emulsion comprising at least one polymerizable monomer contained in industrial lignin, as defined above, for the preparation of an interconnected microcellular material. The industrial lignin as described above may, in particular, be present in a cooking liquor, in particular black liquor. The invention also relates to an emulsion useful for the preparation of a microcellular material as defined above. This emulsion is preferably monodisperse.

The emulsion according to the invention comprises:

a dispersed internal phase comprising a solvent immiscible with said monomer and / or with the solvent of the dispersant external phase.

In addition, the invention relates to any article consisting of all or part of the interconnected microcellular material described above such as, for example, a filter, a thermal insulation article, an acoustic insulation article, an insulation article. electric or mechanical, a disposable absorbent article, or a carrier for inks, dyes and catalysts.

The present invention is illustrated by the examples described below, to which it is however not limited.

Example 1 relates to the preparation of concentrated emulsions based on black liquor.

Example 2 describes the preparation of microcellular materials interconnected by the polymerization of the outer dispersant phase of the emulsions prepared in Example 1.

Example 3 relates to the analysis of the porous morphology of the microcellular materials obtained in Example 2, in particular as a function of the nature and amount of the surfactant.

Example 4 relates to the analysis of the porous morphology of microcellular materials obtained in Example 2 as a function of the emulsification time.

Example 1 Preparation of concentrated emulsions based on black liquor

The emulsification is carried out using a system consisting of a metal tube of 10 mm diameter divided into two chambers connected by a small diameter channel (1 mm), and closed at both ends by pistons waterproof. The tube is immobilized on a bench. A regular back and forth motion is applied to the pistons that close the tube by a crank / crank system operated by a motor. The mixture to be emulsified is thus forced to pass alternately from one chamber to another through the small junction channel. This creates a strong shear of the mixture to be emulsified, which is favorable for obtaining monodisperse emulsions.

In the metal tube constituting the mixing chamber of the emulsifier system, the following are introduced:

- black liquor with a known dry matter content (Smurfit Kappa Cellulose of Pine),

surfactant: Triton® X-405 (polyoxoethylene (35) -octylphenyl ether, HLB = 17.0) (Sigma Aldrich) or Cremophor® EL (polyethoxylated castor oil (35), HLB = 16-18) (Sigma Aldrich),

the crosslinking agent: epichlorohydrin (Acros Organics), and

castor oil (Acros Organics) as a solvent for the dispersed internal phase.

The metal tube is closed using the two pistons and fixed with screws on the bench. The mixture to be emulsified is then stirred by reciprocating the pistons for 80 min at a constant speed of 15 rpm.

Φ is defined as the volume percentage approximated in the internal phase dispersed in the emulsion.

Four types of emulsion are made using this protocol. The results are reported in Table 1 below:

Table 1

Example 2 Preparation of microcellular materials

The emulsions of Example 1 are molded into hermetically sealed 2.80 cm × 4.30 cm polytetrafluoroethylene (PTFE) molds and are heated to a temperature of 60 ° C. for 48 hours. The rigid solids obtained after this step are placed with their mold in an ethanol bath at room temperature for 24 hours. During this period, a portion of the castor oil constituting the dispersed phase of the emulsion and a portion of the water of the outer dispersant phase are entrained by the ethanol. This causes a slight contraction of the solid which allows easy demolding and without risk of deterioration of the solid. Once unmolded, the solids are placed in a Soxhlet extractor and continuously extracted with ethanol for four days to completely remove castor oil remaining in the solid. Once washed, the solids are placed in an ether bath for 24 hours at room temperature in order to exchange the ethanol contained in the solid with this more volatile solvent. Finally, the solids are dried in ambient air for four days.

Example 3 Analysis of the Porous Morphology of the Microcellular Materials

A mercury intrusion porosimetry analysis of the interconnected microcellular materials obtained according to Example 2 is carried out. The results are shown in Table 2 below. This analysis makes it possible to determine the porosity of the materials obtained, as well as the average diameter of the interconnections or "windows". SEM images of the prepared materials are made. Thus, FIG. 1 corresponds to the image obtained for the interconnected microcellular material A based on 4% by mass of Triton X-405. FIG. 2 corresponds to the image obtained from the interconnected microcellular material C based on 4% by mass of Cremophor EL.

An image analysis of the interconnected microcellular materials obtained according to Example 2, completed by a statistical analysis on a significant sample of cells (between 100 and 150 cells) are also carried out. This study makes it possible to determine the mean diameter of the cells, as well as the dispersion factor of these U diameters. The results are shown in Table 2 below.

Nitrogen adsorption analysis followed by BET data processing allowed access to the specific surfaces of the microcellular materials prepared. The results are also shown in Table 2 below.

Table 2

The results show that the nature of the surfactant and its amount have little influence on the measured porosity. This is greater than percentage of dispersed phase, Φ = 55% for all samples. This phenomenon can be attributed to the presence of water in the black liquor constituting the aqueous dispersant external phase of the emulsion. Elimination of this water during the treatment of interconnected microcellular materials contributes to porosity. Thus, from 10 to 15% of the porosity of the samples can be attributed to the initial presence of this water.

The nature of the surfactant has an influence on the average diameter of the interconnections. This is 300 nm for microcellular materials A and B, Triton® X-405, and 800 nm for microcellular materials C and D, Cremophor® EL.

The nature and proportion of surfactant also influences the average cell diameter and the dispersion of the values of these diameters. The average cell diameter is thus 6 μm and the distribution is monodisperse for Triton® X-405, 4% and 11 μm and the distribution is polydisperse for Triton® X-405, 8%. Similarly, the average cell diameter is 9 μm and the monodisperse distribution for Cremophor® EL 4%; and 16 μm and the polydisperse distribution for Cremophor® EL 8%.

Example 4 Influence of Emulsification Time

Two other emulsions, E and F, were prepared according to the same formulation as for emulsion C of Example 1, with varying emulsification times.

The results are as follows:

Table 3

(*) Relative to the total mass of dispersant outer phase

The results show that the emulsification time has a significant influence on the morphology of the microcellular material obtained.

For the same surfactant, Cremophor® EL, used in the same 4% proportion, the decrease in the emulsification time results in a decrease in the mean diameter of the cells and a greater dispersion of these values (U increases).

Claims

A process for preparing an interconnected microcellular material by polymerizing a concentrated emulsion comprising:

a dispersed internal phase comprising a solvent immiscible with said polymerizable monomer and / or with the solvent of the dispersant external phase.

2. The method of claim 1, wherein the volume percentage of the dispersed inner phase of the concentrated emulsion is greater than or equal to about 55%.

The process according to any one of claims 1 and 2, wherein said dispersant outer phase is an aqueous phase and wherein said immiscible solvent is an oil having a melting point between about 10 ° C and about 40 ° C, preferably close to room temperature.

The method of any one of claims 1 to 3, wherein the industrial lignin is selected from the group consisting of Kraft lignin, lignosulfonates, organosolines lignins and lignins from biorefineries.

The method of any one of claims 1 to 4, wherein the dispersant outer phase further comprises at least one hemicellulose monomer.

6. Process according to any one of claims 1 to 5, wherein the solution comprising at least one polymerizable monomer contained in industrial lignin is a cooking liquor, preferably black liquor.

7. The method of claim 6 wherein said black liquor comprises from about 20% to about 80% by weight of dry matter, preferably from about 40% to about 60% by weight of dry matter.

The method of any one of claims 1 to 7, wherein said dispersant outer phase further comprises a crosslinking agent, preferably epichlorohydrin or cyanuric chloride.

The process according to any one of claims 1 to 8, wherein the emulsion is polymerized at a temperature below 100 ° C, preferably from 40 ° C to 80 ° C.

10. Process according to any one of claims 1 to 9 wherein the surfactant is selected from hydrophilic anionic surfactants and nonionic hydrophilic surfactants.

The method of claim 10 wherein the anionic hydrophilic surfactant is selected from the group consisting of sodium dodecyl sulfate, triethanolamine stearate, sodium lauryl sulfate, and triethanolamine lauryl sulfate.

The process according to claim 10 wherein the nonionic hydrophilic surfactant is selected from the group consisting of alkyl polyethoxylate, ethoxylated alkylphenol, polyethylene oxide and polypropylene oxide complex polymers, octylphenol polyol polyethylene oxide, nonylphenol polyethylene oxide, polyethylene oxide block copolymer and polypropylene oxide, monoester and sorbitan fatty acid polyester, monoesters and glycerol fatty acid polyester, and their mixtures.

13. The method of any one of claims 1 to 12 which further comprises at least one step of washing and drying the solid material obtained.

14. Interconnected microcellular material obtainable by the method according to any one of claims 1 to 13.

The interconnected microcellular material of claim 14, said material having a porosity greater than or equal to about 60%.

The interconnected microcellular material according to any one of claims 14 and 15, wherein the cells have a diameter of from about 2 μm to about 50 μm, preferably from about 5 μm to about 20 μm.

The interconnected microcellular material of any one of claims 14 to 16, wherein the interconnect windows have a diameter of about 50 nm to about 1000 nm, preferably about 250 nm to about 500 nm.

18. Use of a concentrated emulsion comprising at least one polymerizable monomer contained in industrial lignin for the preparation of an interconnected microcellular material.

19. Use according to claim 18 wherein the industrial lignin is selected from the group consisting of Kraft lignin, lignosulfonates, organosolines lignins, lignins from biorefineries.

20. Use according to any one of claims 18 and 19 wherein the industrial lignin is present in a cooking liquor, preferably black liquor.

21. Emulsion useful for the preparation of an interconnected microcellular material, which comprises:

An article which consists of all or part of an interconnected microcellular material according to any one of claims 14 and 17.

23. Article according to claim 22, which is a filter, a thermal insulation article, an acoustic insulation article, an electrical or mechanical insulation article, a disposable absorbent article, or a support for inks, colorants and catalysts.