Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/10—Esters of organic acids, i.e. acylates
  • C08L1/12—Cellulose acetate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/045—Reinforcing macromolecular compounds with loose or coherent fibrous material with vegetable or animal fibrous material
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  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/04—Reinforcing macromolecular compounds with loose or coherent fibrous material
  • C08J5/06—Reinforcing macromolecular compounds with loose or coherent fibrous material using pretreated fibrous materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/12—Chemical modification
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/12—Chemical modification
  • C08J7/14—Chemical modification with acids, their salts or anhydrides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/10—Esters of organic acids, i.e. acylates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L1/00—Compositions of cellulose, modified cellulose or cellulose derivatives
  • C08L1/08—Cellulose derivatives
  • C08L1/10—Esters of organic acids, i.e. acylates
  • C08L1/14—Mixed esters, e.g. cellulose acetate-butyrate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L97/00—Compositions of lignin-containing materials
  • C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M13/00—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment
  • D06M13/10—Treating fibres, threads, yarns, fabrics or fibrous goods made from such materials, with non-macromolecular organic compounds; Such treatment combined with mechanical treatment with compounds containing oxygen
  • D06M13/184—Carboxylic acids; Anhydrides, halides or salts thereof
  • D06M13/188—Monocarboxylic acids; Anhydrides, halides or salts thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/10—Esters of organic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/10—Esters of organic acids
  • C08J2301/12—Cellulose acetate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
  • C08J2301/08—Cellulose derivatives
  • C08J2301/14—Mixed esters
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2397/00—Characterised by the use of lignin-containing materials
  • C08J2397/02—Lignocellulosic material, e.g. wood, straw or bagasse
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2205/00—Polymer mixtures characterised by other features
  • C08L2205/14—Polymer mixtures characterised by other features containing polymeric additives characterised by shape
  • C08L2205/16—Fibres; Fibrils
• • D—TEXTILES; PAPER
  • D06—TREATMENT OF TEXTILES OR THE LIKE; LAUNDERING; FLEXIBLE MATERIALS NOT OTHERWISE PROVIDED FOR
  • D06M—TREATMENT, NOT PROVIDED FOR ELSEWHERE IN CLASS D06, OF FIBRES, THREADS, YARNS, FABRICS, FEATHERS OR FIBROUS GOODS MADE FROM SUCH MATERIALS
  • D06M2101/00—Chemical constitution of the fibres, threads, yarns, fabrics or fibrous goods made from such materials, to be treated
  • D06M2101/02—Natural fibres, other than mineral fibres
  • D06M2101/04—Vegetal fibres
  • D06M2101/06—Vegetal fibres cellulosic

Definitions

• the present invention relates to novel cellulose / cellulose composites and methods for their manufacture.
• Thermoplastic composites are conventionally made with a mixture of reinforcing fibers (glass, Kevlar, etc.) and a thermoplastic matrix.
• the field of thermoplastics offers numerous examples of substitution of mineral fibers by cellulose fibers (Michaud, F. 2003).
• the mechanical properties requirements are indeed lower than in the case of thermosets and water sensitivity problems related to the hydrophilic nature of the cellulose fibers can be overcome by a strategy of encapsulation of the fibers by the polymer matrix. This operation is made possible by the current low cost of polymer matrices, but this situation could change with the long-term evolution of oil prices.
• the results obtained, however, are poor mainly because of the poor accounting between the hydrophilic surface of the fibers and the hydrophobic polymer matrix.
• thermoplastic applications there is one which stands out in particular and which is cellulose acetate (Zugenmaier, P. 2004).
• the latter compound has a long history as a thermoplastic and is still an important industrial product in the field of membranes (Cerqueira, DA, et al., 2008) and cigarette filters in particular. It is, in fact, a family of products since are also marketed specialties of propionate, butyrate and cellulose acetate butyrate.
• Cellulose acetates are not considered to be truly biodegradable, which in many cases is actually an advantage but they are clearly recyclable by the conventional alkaline regeneration of cellulose acetate to cellulose.
• This regeneration is particularly advantageous in the case of cellulosic materials because the recycling of printed papers takes place precisely in alkaline conditions.
• These compounds are therefore extremely attractive for use as a thermoplastic matrix provided that the problem of compatibility of the cellulose acetate / cellulose fiber matrix interface is solved. Indeed, although they are both made of cellulose, these two materials do not have the same chemical and physicochemical properties and they even a priori very poor compatibility.
• the conventional use as a cellulose acetate filler of vegetable cellulosic materials is for example described in the patent FR 519 822. However, cellulose fibers and cellulose acetate have a very poor compatibility.
• GB 570,529 discloses a molding powder containing a synthetic resin and cellulose acetate fibers.
• Cellulose acetate fibers were obtained by partial acetylation of the cellulose under fibrous conditions to maintain the fiber structure.
• This document essentially concerns the substitution of cellulosic reinforcing fibers with acetylated cellulose reinforcement fibers. This document does not specify the nature of the synthetic resin used.
• DE 295 22 229 describes a material based on cellulose acetate and natural cellulose fibers.
• the cellulose fibers are used without special pretreatment and the relative incompatibility of the cellulose fibers and the cellulose acetate matrix is therefore not resolved.
• US patent application 2003/0124937 discloses a material comprising native cellulose fibers and cellulose ester fibers. This material does not include a thermoplastic matrix in which reinforcing fibers are dispersed.
• acetylated whiskers can only have very short cellulose acetate oligomer chains on their surface.
• polycaprolactone oligomer of sufficient molecular weight on the surface of the microf ⁇ briUes Our hypothesis is that the cellulose acetate ohgomer chains present on the surface of the whiskers would not be long enough to interact effectively with the cellulose acetate matrix.
• the invention lies at this level. Instead of attempting to solve the problem of dimensional instability by eliminating the amorphous parts of the fibers by acidic hydrolysis or other means, the invention is to make them lose their sensitivity to water by taking advantage of their obvious more high chemical reactivity and transforming them via appropriate chemical modification into high molecular weight cellulose acetate oligomers capable of effectively interacting with a polymeric matrix of cellulose acetate.
• This operation would be pointless if the oligomers thus synthesized were, as a result of the chemical modification in question, detached from the structure of the fiber. It is essential, in fact, that the formed cellulose acetate oligomer chains remain firmly bonded by covalent bonding to the main structure of the fiber. It is therefore essential to choose mild acylation conditions preserving the glycosidic bonds of cellulose or in other words not leading to hydrolysis of these cellulose molecules.
• acylation or acetylation of cellulose are known from the prior art.
• the acylation of the cellulose is generally carried out in the presence of a catalyst such as a strong acid.
• This acylation leads not only to the acylation of the cellulose but also to a cut in the fibers of the celluloses.
• the product obtained - typically cellulose acetate - thus has a reduced DP following the hydrolysis of the cellulose molecules. It then becomes soluble in organic solvents such as chloroform or acetone while the cellulose is not soluble in these solvents.
• This acylation can also take place under fibrous conditions. In all cases, however, the acylation is accompanied by hydrolysis of the cellulose molecules.
• No. 2,535,919 discloses that the cellulose fibers comprise amorphous cellulose as well as crystalline cellulose and this document describes the partial acetylation of these cellulose fibers.
• the acetylation conditions used include impregnation of the fibers with glacial acetic acid followed by reaction with acetic anhydride in the presence of a strong acid. This acetylation is conducted in fibrous conditions in the absence of solvent, but it is nonetheless a "hard” acetylation condition leading to cleavage of the cellulose chains. This is illustrated by the fact that the formed cellulose acetate is soluble in the methylene chloride used in this document to make the fibers sticky.
• the acylation process used in the present invention is based on activation and selective acylation of the amorphous zones of the cellulose fibers under conditions that preserve the glycosidic bonds of the cellulose molecules. These conditions were already described in the literature (Fraizy, J. 1966, Nagai, K. and Saito, M. 1960).
• the invention therefore consists in achieving two important objectives by carrying out a single key operation, the peracetylation of all the amorphous zones of the cellulose fibers.
• This modification makes it possible to eliminate the dimensional sensitivity of the cellulose fibers by transforming the hydrophilic amorphous zones into hydrophobic apolar zones (40% reduction in the water uptake of the acetylated fibers).
• Cellulose acetate oligomers are thus generated which represent between 30 and 50% of the starting cellulosic material. These oligomers obtained without any cleavage of glycosidic bonds are therefore necessarily of high molecular weight and will thus be able to establish a very good interaction with cellulose acetate matrices.
• the quality of the accounting obtained by the acetylation of the amorphous zones with respect to thermoplastic matrices of cellulose acetate was determined by dispersion tests of partially acetylated fibers in cellulose acetate matrices.
• the improvement of the mechanical properties was determined by the measurement of the Young's modulus which shows a significant increase of 21%.
• the quality of the compatibilization obtained was also characterized by the regeneration of the acetylated cellulose fiber / cellulose acetate composites in a basic medium. It is known that it is possible to regenerate cellulose II by alkaline treatment of cellulose acetate. This is notably the process for obtaining Fortisan fibers (Kim, I.S., et al., 2002, Koh, J., et al., 2004).
• Heat-stable composites are conventionally obtained by in situ polymerization processes and lead to crosslinked assemblies in all three dimensions.
• a major disadvantage of these composites is their almost total absence of recycling properties (apart from thermal recovery or to make charges).
• thermostable composites recyclable. These are prepared from cellulose matrix reinforced with cellulose fibers. They are prepared for example by using the solvent power towards the cellulose of certain solutions like DMAc / LiCl. As the solubilization is a progressive phenomenon, it suffices to block it by dilution after a defined period thus leading to a cellulose / cellulose composite in which the fibers not yet solubilized constitute the reinforcing part, the matrix being constituted by the regenerated cellulose . What characterizes this type of cellulose / cellulose composites is the fact that the crosslinking is no longer carried out through irreversible covalent chemical bonds but via reversible hydrogen bonds.
• thermostable composites by this method comes from the fact that the precursor composites are thermoplastic composites which can therefore be prepared industrially with conventional tools.
• the improvement of the mechanical properties was measured by the significant increase of the Young's modulus of 25%.
• thermostable composites not completely saponified with different properties such as less dimensional instability or greater plasticity related to the presence of residual acetates.
• thermoplastic polymeric matrix chosen from cellulose acetates, cellulose proprionates, cellulose butyrates, cellulose acetobutyrates and mixtures thereof, e) Optionally, shaping the composite material obtained in the previous step by hot molding, hot injection and / or hot pressing.
• the activation of the amorphous areas of the cellulose fibers by an alkaline treatment is carried out with an aqueous alkaline solution of sodium hydroxide or potassium hydroxide.
• activation of the amorphous areas of the cellulose fibers by alkaline treatment is carried out with potassium acetate or sodium acetate.
• the acylation of the amorphous areas of the cellulose fibers comprises contacting the cellulose fibers with an acylating agent under neutral conditions.
• the acylating agent is selected from acetic anhydride, butyric anhydride, propionic anhydride, mixed anhydrides, acetic acid chloride, propionic acid chloride, butyric acid chloride, activated acetates, activated propionates, activated butyrates and mixtures thereof.
• step d) comprises the addition of 1% to 50% by weight of thermoplastic matrix relative to the weight of the cellulose fibers.
• step d) comprises immersing the cellulose fibers in the form of braided yarns in the matrix followed by drying the fibers.
• step d) comprises dispersing the cellulose fibers in the thermolastic matrix.
• the cellulose fibers are chosen from fibers of rayon, abaca, bamboo, hemp, coir, coconut, cotton, originating from the seed, broom, stem broth , gucca, jute, kapok, kennaf, flax, shackle, nettle, straw, ramie, raffia or sisal or mixtures thereof.
• the cellulose fibers are rayon fibers and the thermoplastic polymeric matrix is cellulose triacetate.
• the method further comprises a step of partial or total saponification of the cellulose-based composite material obtained in step d) or in step e).
• the saponification comprises treating the material with sodium hydroxide solution followed by washing and drying the material.
• the subject of the invention is also a thermoplastic composite material based on cellulose which can be obtained by the process according to the invention.
• the invention also relates to a process for recycling a cellulose-based thermoplastic composite material in which the material is subjected to complete acetylation in the presence of a strong acid.
• the invention also relates to a thermostable composite material based on cellulose obtainable by the method according to the invention comprising a saponification step.
• the subject of the invention is a cellulose-based composite material comprising: cellulose fibers comprising crystalline zones and at least 20% of amorphous zones, at least 80% of these amorphous zones being acylated by low-weight fatty acids; molecular compounds selected from acetate, propionate, butyrate and mixtures thereof;
• thermoplastic polymer matrix chosen from cellulose acetates, cellulose proprionates, cellulose butyrates and cellulose acetate butyrates, and mixtures thereof.
• the cellulose-based composite material comprises from 1% to 50% by weight of thermoplastic matrix.
• the cellulose-based composite material comprises from 50% to 99% by weight of cellulose fibers.
• the cellulose fibers are selected from rayon, abaca, bamboo, hemp, coir, coconut, cotton, seed, broom, cottons with rods of rush, gucca, jute, kapok, kennaf, flax, manila, nettle, straw, ramie, raffia, sisal or their mixtures.
• the cellulose-based composite material comprises partially acetylated rayon fibers having a degree of acetylation of between 20% and 40% by weight.
• thermoplastic polymeric matrix is cellulose triacetate.
• the composite material is at least partially saponified.
• Another object of the invention is a method of manufacturing a composite material based on cellulose comprising the following steps:
• the partial acylation of the cellulose fibers comprises:
• the activation of the amorphous zones of the cellulose fibers by an alkaline treatment is carried out by impregnating the cellulose fibers with an aqueous alkaline solution of sodium hydroxide or potassium hydroxide.
• the activation of the amorphous zones of the cellulose fibers by an alkaline treatment is carried out by impregnating the cellulose fibers with potassium acetate or sodium acetate.
• the acylating agent is chosen from acetic anhydride, butyric anhydride, propionic anhydride, mixed anhydrides, acetic acid chloride, propionic acid chloride and acid chloride.
• butyric acid activated acetates, activated propionates, activated butyrates and mixtures thereof.
• the cellulose fibers are selected from rayon, abaca, bamboo, hemp, coir, coconut, cotton, seed, broom, cottons with rods of rush, gucca, jute, kapok, kennaf, flax, manila, nettle, straw, ramie, raffia or sisal or their mixtures.
• the cellulose fibers are preferably rayon fibers and the thermoplastic polymeric matrix is preferably cellulose triacetate.
• step b) comprises the addition of 1% to 50% by weight of thermoplastic matrix relative to the weight of the cellulose fibers.
• step b) comprises immersing the cellulose fibers in the form of braided yarns in the matrix followed by drying the fibers.
• step b) comprises dispersing the cellulose fibers in the matrix.
• the methods according to the invention further comprise a step of partial or total saponification of the cellulose-based composite material obtained in step b) or in step c).
• this saponification comprises treating the material with sodium hydroxide solution followed by washing and drying the material.
• the invention also relates to cellulose-based thermoplastic composite materials that can be obtained by the methods according to the invention.
• the invention also relates to thermostable composite materials based on cellulose that can be obtained by the processes according to the invention.
• the invention thus relates to processes for the manufacture of various cellulose-based composites and in particular cellulose / cellulose acetate composite materials and cellulose / cellulose composite materials.
• acylation and especially cellulose acetylation processes use a strong acid as a catalyst such as sulfuric acid, perchloric acid or phosphoric acid, under these conditions, acetylation and hydrolysis of the molecules. cellulose then leads to a cellulose acetate dissolved in various organic solvents such as chloroform and acetone, for example.
• milder reaction conditions permit selective acylation of the amorphous areas of the cellulose not accompanied by hydrolysis of the glycosidic linkages of the cellulose molecules.
• the integrity of the cellulose molecules and in particular glycosidic bonds of the cellulose molecules is maintained.
• This selective acetylation of the amorphous areas of the cellulose is not carried out in the presence of a catalyst such as a strong acid and therefore a prior step of activating the amorphous areas of the cellulose fibers is generally required.
• the acylation reaction is therefore conducted under neutral conditions and in particular under ionically neutral conditions.
• the acylation conditions are therefore neither acidic nor basic.
• This partial acylation of the cellulose fibers preserving the integrity of the cellulose molecules is based on the use of cellulose fibers having a large amorphous phase, the latter being more reactive than the crystalline phase. Acylation under mild reaction conditions is therefore limited to acylation of the amorphous regions of the fiber leading to partial acylation of the cellulose without hydrolysis of the glycosidic linkages.
• the almost total absence of hydrolysis of the cellulose is illustrated by the fact that the acetylated cellulose fibers obtained according to the invention do not comprise Extractable fraction with solvents such as chloroform or acetone corresponding to cellulose acetate of lower DP and thus soluble in these solvents.
• thermoplastic polymeric matrices consisting of cellulose acyls.
• the composite materials thus obtained may be totally or partially saponified to lead to thermostable materials.
• the invention thus relates to new composite materials consisting of two elements having exceptional complementarity:
• a fibrous reinforcement structure constituted by cellulose fibers whose amorphous part has been selectively acylated by low molecular weight fatty acids under mild conditions which do not lead to the hydrolysis of the cellulose acyl chains thus produced.
• This selective acylation makes it possible to reduce the dimensional instability of the cellulose fibers and to generate a high density of pendant cellulose acyl chains.
• thermoplastic polymeric matrix consisting of perfectly soluble cellulose acyl matrices with the cellulose acyl chains present on the cellulose fibers.
• acylation is performed under neutral conditions to preserve the integrity of the glycosidic linkages of the cellulose molecules.
• the invention also describes a variant of these new composite materials where all or part of the acyl groups has been removed by alkaline treatment to produce a thermostable material.
• the invention thus relates to composite materials based on cellulose comprising:
• cellulose fibers comprising crystalline zones and at least 20% of amorphous zones, at least 80% of these amorphous zones being acylated by low molecular weight fatty acids chosen from acetate, propionate and butyrate, and mixtures thereof; ;
• thermoplastic polymer matrix chosen from cellulose acetates, cellulose proprionates, cellulose butyrates and cellulose acetate butyrates, and mixtures thereof.
• the cellulose fibers are partially acylated under mild conditions (neutral conditions) leading to selective acylation of the amorphous areas of the cellulose and not accompanied by hydrolysis of the glycosidic linkages of the cellulose. cellulose.
• the amorphous areas of cellulose fibers are selectively acetylated.
• the cellulose fibers comprise at least 10, 20, 30 or 40% amorphous areas.
• the cellulose fibers therefore have a degree of crystallinity of less than 90, 80, 70 or 60%.
• the amorphous areas of the cellulose being acylated to at least 80%>, 85% or 90%. In other embodiments, the amorphous areas of the cellulose are fully acylated.
• the cellulose fibers selected from rayon, abaca, bamboo, hemp, coir, coconut, cotton, from seed, broom, cottons rods of rush, gucca, jute, kapok, kennaf, flax, manila, nettle, straw, ramie, raffia, sisal or their mixtures.
• the cellulose fibers are rayon and linen fibers.
• the cellulose fibers have an acylation level of between 10% and 50% by weight and preferably between 20% and 40% by weight.
• the cellulose fibers have an acetylation level of between 10% and 50% by weight and preferably between 20% and 40% by weight.
• the cellulose fibers used in the materials of the present invention are rayon fibers having a level of acylation, and preferably acetylation, of between 20% and 40% by weight.
• the second component of the materials is a thermoplastic polymeric matrix selected from cellulose acetate, cellulose propionates, cellulose butyrates, cellulose acetate butyrates and mixtures thereof.
• thermoplastic matrix is meant a matrix that melts or softens under the effect of heat. Typically, the melting temperature of a thermolplastic material is lower than its decomposition temperature.
• the thermoplastic matrices are chosen from the following matrices: cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose acetate butyrate (commercial product CAB: 13.5% by weight of acetate and 38% mass of butyrate, molar ratio approximately 1 acetate for 2 butyrates), cellulose tributyrate.
• CAB 13.5% by weight of acetate and 38% mass of butyrate, molar ratio approximately 1 acetate for 2 butyrates
• cellulose tributyrate Among the cellulose acetobutyrates, mention will be made in particular of CAB comprising 13.5% by weight of acetate and 38% by weight of butyrate (molar ratio of about 1 acetate for 2 butyrates). This product is commercially available.
• These thermoplastic matrices are well known to those skilled in the art.
• thermoplastic matrices typically have a sufficiently low DP to be soluble in organic solvents such as acetone or chloroform.
• a "compatible" matrix is meant a matrix that is soluble with the acyl chains of the partially acylated cellulose fibers.
• the compatible matrices are for example chosen from triacetates and cellulose diacetate.
• the compatible matrices are for example chosen from cellulose propionates.
• the compatible matrices are for example chosen from cellulose acetate butyrate and cellulose tributyrate.
• the cellulose-based composite material comprises rayon fibers having a degree of acetylation of between 20% and 40% by weight, preferably between 25% and 35% by weight and a cellulose triacetate matrix.
• the composite material comprises flax fibers with an acylation level with a mixture of acetate and butyrate (1 acetate for 2 butyrates) of between 30 and 50% by weight and as matrix an acetobutyrate and in particular CAB comprising 13.5% by weight of acetate and 38% by weight of butyrate.
• the compatibility between the matrix and the fiber makes it possible to reduce the amount of matrix in the composite materials of the present invention.
• the composite materials comprise 1%, 5%, 10%, 20%, 30%, 40% to 50% by weight of thermoplastic matrix.
• the composite materials according to the invention comprise less than 50%, 40%, 30%, 20%, 10% or less than 5% by weight of thermoplastic matrix.
• the composite materials according to the invention thus comprise 50%, 60%, 70%,
• the materials according to the invention comprise more than 50%, 60%, 70%, 80%, 90% or more than 95% of partially acylated cellulose fibers.
• the invention also relates to composite materials as described above partially or totally saponified. This saponification makes the composite material thermostable.
• the invention also relates to processes for producing a cellulose-based composite material comprising the following steps:
• thermoplastic polymeric matrix chosen from cellulose acetate, cellulose propionates, cellulose butyrates, cellulose acetobutyrates and mixtures thereof,
• the acylation is carried out under neutral conditions to preserve the integrity of the glycoside bonds of the cellulose molecules. Only the amorphous zones of the previously activated cellulose are acylated at this stage without hydrolyzing the cellulose.
• the first step of the processes according to the invention is a partial acylation step of the cellulose fibers and preferably a partial acetylation step of the cellulose fibers.
• the invention relates to processes for manufacturing a cellulose-based composite material comprising the following steps:
• thermoplastic polymeric matrix chosen from cellulose acetate, cellulose propionates, cellulose butyrates, cellulose acetobutyrates and mixtures thereof,
• the cellulose fibers used in the processes of the present invention have an amorphous phase, preferably this zone or amorphous phase represents at least 10%, 20%, 30% or 40% of the cellulose fibers.
• the cellulose fibers obtained have an acylation level of between 10% and 50% by weight and preferably between 20% and 40% by weight.
• the cellulose fibers obtained have an acetylation level of between 10% and 50% by weight and preferably between 20% and 40% by weight.
• the partial acylation of the cellulose fibers is carried out under mild conditions - typically neutral conditions - according to techniques known to those skilled in the art. Partial acylation of the cellulose fibers under these conditions leads selectively to the acylation of the amorphous zones of the cellulose fibers without hydrolysis of the cellulose.
• partial acetylation under mild reaction conditions preserves the integrity of the cellulose molecules.
• the partial acylation of the cellulose fibers comprises a first step of activating the cellulose fibers by an alkaline treatment.
• This alkaline treatment may include impregnating the cellulose fibers with an aqueous alkaline solution of sodium hydroxide or potassium hydroxide.
• this alkaline treatment may comprise impregnation of the cellulose fibers with potassium acetate or sodium acetate.
• This activation is typically performed by dipping or impregnating the fibers with a potassium acetate solution having a concentration of 20% (g / g) at 60 ° C-80 ° C.
• the fibers are usually dewatered and dried according to usual techniques.
• the acylation is carried out by contacting the activated fibers with an acylating agent preferably chosen from acetic anhydride, butyric anhydride, propionic anhydride, mixed anhydrides, acetic acid chloride, propionic acid chloride, butyric acid chloride, activated acetates, activated propionates, activated butyrates and mixtures thereof.
• an acylating agent preferably chosen from acetic anhydride, butyric anhydride, propionic anhydride, mixed anhydrides, acetic acid chloride, propionic acid chloride, butyric acid chloride, activated acetates, activated propionates, activated butyrates and mixtures thereof.
• This bringing into contact is carried out under neutral conditions and more particularly at ionically neutral conditions. Catalysts such as strong acids are not used at this stage.
• This step comprises, for example, immersing the previously activated fibers in acetic anhydride heated at 100 ° C. for a variable time ranging from a few minutes to a few hours.
• the acetylation rate then varies according to the reaction time.
• the partially acetylated fibers are generally washed and dried.
• the cellulose fibers are rayon fibers and their degree of acetylation is between 25 and 35% by weight.
• thermoplastic matrix is added to the fibers.
• thermoplastic matrices based on cellulose are described above.
• This step preferably comprises immersing the cellulose fibers in the form of braided yarns in the matrix followed by drying the fibers.
• acetylated fibers in the form of braided yarns are immersed in a triacetate solution (for example a 5% solution in chloroform). After incubation, the fibers are removed, excess solution is removed and the threads are dried. The son obtained are much more rigid because of the cohesion between the fibers provided by the cellulose acetate.
• a triacetate solution for example a 5% solution in chloroform.
• this step comprises dispersing the cellulose fibers in the matrix.
• partially acetylated fibers are dispersed in a solution of cellulose triacetate (2% cellulose triacetate solution in chloroform, for example). After evaporation, cellulose acetate films containing reinforcing fibers are obtained.
• the cellulose fibers are partially acetylated rayon fibers and the thermoplastic polymeric matrix is cellulose triacetate.
• the processes according to the invention comprise the addition of 1% to 50% by weight of thermoplastic matrix relative to the weight of the cellulose fibers and preferably the addition of less than 50%, 40%,> 30% >, 20%>, 10%> or less than 5% by weight of thermoplastic matrix.
• the composite materials obtained are distinguished by improved mechanical properties (measured by the Young's Modulus) and a decrease in water intake (water sensitivity).
• the invention also relates to a process for recycling a cellulose-based thermoplastic composite material in which the material is subjected to complete acetylation in the presence of a strong acid.
• Cellulose acetate-cellulose composite materials have low potential for biodegradation but can be fully recycled. Unlike other composite materials requiring a separation of their components as a prerequisite for recycling, thermoplastic cellulose-matrix composite materials according to the present invention are directly and fully recyclable including complete acylation of the composite material. Two recycling paths are conceivable: regeneration (alkaline treatment) when all the acyl groups are removed and the cellulose acetate of the composite material is converted into cellulose or nonfibrous acetylation when the cellulose of the composite material is completely transformed into triacetate of cellulose and fibers lose their fibrous appearance.
• regeneration alkaline treatment
• a cellulose-cellulose acetate composite according to the invention can be directly converted into cellulose acetate in conventional industrial cellulose acetylation chains, which implement so-called non-fibrous or homogeneous acylation conditions.
• These use a strong acid as a catalyst such as sulfuric acid or perchloric acid and comprise two steps: the pretreatment during which the composite material, acetic acid and catalyst are intimately mixed before adding the reagent.
• acetylation acetic anhydride, for example
• the actual treatment when the material reacts with the reagent added to the reaction medium.
• the cellulose of the composite material is converted into cellulose acetate which is soluble in the reaction medium.
• the acetate formed is then recovered by filtration, after its precipitation following the addition to the mixture of a aqueous solution of acetic acid.
• Such methods of acylation of cellulose have existed for a long time and are well described in the literature (Malm et al., (1946), Sassi and Chanzy (1995)). More recently, Barud et al. (2008), following the protocol used by Sassi and Chanzy (1995), acetylated bacterial cellulose and obtained, for reaction times ranging from 0.5 h to 24h, 2,3 degrees of substitution. at 2.77.
• the processes according to the invention may further comprise a step of partial or total saponification of the composite material described above.
• This saponification is carried out according to usual techniques well known to those skilled in the art.
• the saponification comprises treating the material with sodium hydroxide solution followed by washing and drying the material.
• the materials obtained are placed in a 0.5 N sodium hydroxide solution for 24 hours at room temperature. The resulting materials are then washed and dried.
• the subject of the invention is also the thermoplastic composite materials obtainable by the processes according to the invention as well as the thermostable composite materials based on cellulose that can be obtained by the processes according to the invention.
• FIGURES are also the thermoplastic composite materials obtainable by the processes according to the invention as well as the thermostable composite materials based on cellulose that can be obtained by the processes according to the invention.
• Figure 1 Selective acetylation of the amorphous zones of cellulose fibers and formation of the composite with exogenous cellulose acetate
• Figure 2 Alkaline treatment of composites Partially acetylated cellulose fibers / cellulose acetate to give a cellulose / cellulose composite
• the cellulose fibers are immersed in a potassium acetate solution at 60-80 ° C, having a concentration of 20% (g / g), for 20 minutes.
• the activated fibers are dewatered and dried at 80 ° C for 2h30. Then, they are immersed in acetic anhydride which is heated at 100 ° C for 20, 40, 80 or 160 minutes. After reaction, the fibers are washed with hot water and acetone, and then dried at 105 ° C for 24 hours.
• the acetylation rate is determined by weighing before and after the acetylation according to the following formula:
• m 2 represents the mass of the rayon fibers after the acetylation, in grams.
• the acetate level is variable depending on the reaction time.
• the maximum value corresponds to the acetylation of the entire amorphous domain of the cellulose fibers.
• the fibers washed with chloroform were analyzed by transmission IR spectrometry.
• the spectra of the acetylated fibers after and before washing with chloroform have a characteristic ester band at 1735 cm -1 if they are stackable.
• the acetylated fibers in the form of braided fibers are immersed in a solution of 5% cellulose triacetate in chloroform. After incubation for one hour, the impregnated fibers are removed, the excess solution is removed and the yarns are dried at room temperature. The son obtained are much more rigid because of the cohesion between the fibers provided by the cellulose acetate. Control samples are prepared with nonacetylated threads.
• Cellulose triacetate films containing rayon fibers were obtained by dispersing about 3 mg of virgin or acetylated rayon fibers in 1.5 ml of a TAC solution in 2% chloroform. After evaporation, cellulose acetate films containing the fibers are obtained.
• the prepared samples were analyzed by light microscopy.
• the results obtained indicate that native rayon fibers are not dispersed at all in cellulose acetate where they are in the form of entangled fiber clusters.
• the acetylated fibers are capable of dispersing in this matrix of cellulose acetate, even going as far as to melt in the latter.
• this is only an optical illusion because an extraction of the cellulose acetate matrix with chloroform restores the starting fibers.
• the facies analysis of the composite wafer, acetylated fibers / cellulose acetate, in electron microscopy confirms the good quality of the fiber matrix interface.
• Example 3 The acetylated fiber / cellulose acetate composites previously obtained in Example 3 are placed in a 0.5 N NaOH solution for 24 hours at room temperature. The resulting composites are then washed with distilled water and dried at 105 ° C for 24 hours.
• Young's modulus was determined for different samples.
• the acetylation of the fibers makes it possible to improve the value of the Young's modulus also at the level of the acetylated fiber / cellulose acetate composites as at the level of the cellulose / cellulose composites.
• FNATAC non acetylated fibers + cellulose triacetate
• FATAC acetylated fibers + cellulose triacetate
• FNATACR non-acetylated fibers + cellulose triacetate after regeneration with sodium hydroxide
• FATACR acetylated fibers + cellulose triacetate after regeneration with sodium hydroxide

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