Preparation of regenerated polysaccharides

Abstract

The present invention relates to a process for preparing high-purity regenerated polysaccharide, wherein the dissolved polysaccharide is precipitated by reacting a solvent with an organic carbonate. The process is healthier, more environmentally friendly and safer than a conventional process. A material made from the produced regenerated polysaccharide is also provided.

Description

Technical Field

[0001] The invention relates to a process for producing regenerated polysaccharide, regenerated polysaccharide produced by the process, and products made from the regenerated polysaccharide. Background Art

[0002] Polysaccharides are polymeric carbohydrates consisting of at least eleven monosaccharides linked by glycosidic bonds. The most common polysaccharide found in nature is cellulose. Cellulose is used as a raw material in the paper industry, the construction industry, the textile industry and the chemical industry. In addition, over the past few decades, cellulose and its derivatives have been used in many areas such as environmental technology, filtration and medical applications.

[0003] Cellulose is a biopolymer synthesized by plants. For the purpose of processing or producing products, natural crystalline cellulose is often converted into synthetic regenerated cellulose. Regenerated cellulose is understood here to mean cellulose that has been dissolved and reprecipitated. This treatment modifies the crystal lattice structure of natural cellulose by swelling and dissolving processes without causing any changes in the cellulose molecular structure. Since regenerated cellulose is the most thermodynamically stable form of cellulose, this conversion process is irreversible. Cellulose can also be synthesized chemically.

[0004] For more than a century, the mainstream processing routes for processing cellulose to produce regenerated cellulose fibers and films have been the rayon route (cellophane cellulose) and the cuprammonium route (copper imitation film cellulose). However, such processes have serious environmental pollution and are accompanied by several economic problems. Therefore, a more environmentally friendly, simpler and more energy-saving process is needed.

[0005] In the past few years, various industrial and non-industrial processes for the manufacture of regenerated cellulose have been developed. Among them, the solvents used include non-derivatized solvents such as lithium chloride / dimethylacetamide (DMAc), nitrogen methyl nitrogen oxide morpholine (NMMO, Lyocell process), alkali / urea or thiourea. In addition to water-intolerant ionic liquids, aqueous solvent mixtures are also used, such as sodium hydroxide (NaOH) together with highly toxic carbon disulfide (CS2). However, most solvents have undesirable properties such as high toxicity or high volatility, and / or are relatively expensive. In contrast, more advantageous are electrolyte solutions, for example, electrolyte solutions of quaternary onium hydroxides such as tetrabutylammonium hydroxide (TBAH) or tetrabutylphosphonium hydroxide (TBPH), which have low toxicity and are therefore more environmentally acceptable and do not cause problems in handling.

[0006] Standard membrane preparation methods rely on the introduction of cellulose membranes in an antisolvent, or by evaporation of the solvent. Ammonium electrolytes such as TBAH can be used to make cellulose membranes by "aging" (over a specific, extended period of time) on a PTFE surface. Such membranes are unable to achieve separations on other surfaces, such as glass.

[0007] US2014 / 0212670A1 discloses a process for producing regenerated cellulose by using phosphonium electrolytes such as TBPH. In this process, cellulose is precipitated in the form of small flakes or fibers, films, pellets or particles by using a solvent that is more volatile than the solvent used in the dissolution step. This process replaces water and TBPH. However, in fact, according to the applicant's research, the products formed are all regenerated cellulose fine powder. The problem solved by the present invention is to develop a reliable process for providing various forms of regenerated polysaccharides and products. Summary of the invention

[0008] This problem is solved by a process having the features of claim 1. Advantageous embodiments and configurations of the invention are evident from the dependent and subclaims, the drawings and the working examples. Embodiments of the invention can be combined with one another in an advantageous manner.

[0009] The first aspect of the present invention relates to a process for producing a solid-state regenerated polysaccharide, comprising the following steps:

[0010] -S1) provides polysaccharides;

[0011] - S2) dissolving the polysaccharide in at least one electrolytic solvent, wherein the electrolytic solvent used is a quaternary onium hydroxide having a weight content of about 40 to 80% in water;

[0012] - S3) precipitating the polysaccharide in the form of a gel by contacting the polysaccharide solution with an electrophilic reagent, wherein the electrophilic reagent used is at least one organic carbonate, or a mixture of different organic carbonates, or at least one organic carbonate polymer, or a mixture of different organic carbonate polymers, or a mixture of at least one organic carbonate and at least one organic carbonate polymer;

[0013] -S4) washing the regenerated polysaccharide.

[0014] The term "regenerated polysaccharide" refers to polysaccharides that have been dissolved and reprecipitated. This treatment modifies the crystalline structure of the native polysaccharide through a swelling and dissolution process without causing any change in the molecular structure of the polysaccharide.

[0015] In the context of the present invention, the term "gel form" is understood to mean a fixed form, also called a solidified form. In the process of the present invention, a solid is formed in step S3.

[0016] In the process of the present invention, it is advantageous to use an electrophilic reagent for precipitation. However, this does not involve the replacement of the solvent (a standard practice in industrial processes or US2014 / 212670A1). Instead, the polysaccharide is directly precipitated by the reaction of the electrophilic reagent with the hydroxide ions in the solvent. When TBPH is used as a solvent, after the polysaccharide is dissolved, hydrogen bonds are formed between the polysaccharide and the [TBP]+ and [OH]- ions, and when in contact with the electrophilic reagent, the hydrogen bonds are broken again due to the reaction with the hydroxide groups. No reaction occurs between the reagent and the polysaccharide. The advantage of this process is that powders and films can be easily manufactured within seconds without using toxic chemicals. This means that the process is economical and feasible in terms of time and materials, and is environmentally friendly in terms of environmental protection. The regenerated polysaccharide manufactured by this process has a high purity. This means that the present invention provides a simple and fast process in which regenerated polysaccharides are manufactured by using non-toxic, recyclable, and water-resistant chemicals.

[0017] The polysaccharide to be regenerated can be provided in microcrystalline form, but can also be provided in any other form, for example in a synthetic or amorphous form, or in a form produced from biomass.

[0018] The polysaccharide may be, for example, cellulose, starch, chitin, chitosan or glycogen.

[0019] The polysaccharide used in this process is more preferably cellulose. Cellulose and its derivatives can be used in a variety of ways. The advantage of this process is that it can produce high-quality regenerated cellulose. The film produced by this process shows extremely high homogeneity both inside and on the surface of the film, and the surface is very smooth. These two points indicate that the organic carbonate penetrates uniformly and quickly into the dissolved cellulose.

[0020] The cellulose to be regenerated can be provided in microcrystalline form, but can also be provided in any other form, for example in synthetic or amorphous form, or in a form produced from biomass.

[0021] The electrolytic solvent used in this process is a quaternary onium hydroxide having a weight content (weight percentage) of about 40 to 80% in water. Here, it is preferred to use at least a phosphonium-containing and / or ammonium-containing onium hydroxide. Here, TBPH is particularly preferred. In addition, TBAH can also be used, in which case the amount of polysaccharide dissolved is less and the dissolution takes longer than when TBPH is used.

[0022] The quaternary onium hydroxide may be, for example, the quaternary onium hydroxide described in US 2014 / 212670 A1.

[0023] The quaternary onium hydroxide may be, for example, a tetraalkylphosphonium hydroxide whose alkyl component has 2 to 8 carbon atoms, such as tetraethylphosphonium hydroxide, tetrapropylphosphonium hydroxide, tetrabutylphosphonium hydroxide, tetrapentylphosphonium hydroxide or tetrahexylphosphonium hydroxide. The quaternary onium hydroxide may be, for example, tetraphenylphosphonium hydroxide. The quaternary onium hydroxide may be, for example, a substituted or unsubstituted alkyltriphenylphosphonium hydroxide, such as ethyltriphenylphosphonium hydroxide, butyltriphenylphosphonium hydroxide, pentyltriphenylphosphonium hydroxide, 2-dimethylaminoethyltriphenylphosphonium hydroxide or methoxymethyltriphenylphosphonium hydroxide.

[0024] The quaternary onium hydroxide may be, for example, a tetraalkylammonium hydroxide having an alkyl component having 2 to 6 carbon atoms, such as tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide or tetrapentylammonium hydroxide.

[0025] The quaternary onium hydroxide is used, for example, in a 50% by weight content in water.

[0026] The weight proportion of the polysaccharide in the solution is, for example, 20%.

[0027] The polysaccharide can be dissolved, for example, by stirring the polysaccharide solution, for example, at room temperature (23° C.) for about 30 min.

[0028] In step S2, an additional solvent is preferably used. In this way, the additional solvent can be used in addition to the at least one electrolytic solvent mentioned above. Among them, the additional solvent can be added before the polysaccharide is dissolved, added at the same time as the electrolytic solvent, or added after the polysaccharide is dissolved. The ratio of the additional solvent to the electrolytic solvent can be, for example, 1:1. Particularly preferably, dimethyl sulfoxide (DMSO) is used as an additional solvent. The addition of DMSO can reduce the viscosity of the regenerated polysaccharide solution and improve the coating property of the polysaccharide solution during film formation. In addition, solidification can also be accelerated. Compared with when DMSO is not used, the film manufactured when DMSO is used is more flexible and transparent.

[0029] In this process, the electrophilic reagent used is (i) at least one organic carbonate, or (ii) a mixture of different organic carbonates, or (iii) at least one organic carbonate polymer, or (iv) a mixture of different organic carbonate polymers, or (v) a mixture of at least one organic carbonate and at least one organic carbonate polymer. In the present invention, organic carbonate is particularly effective. Organic carbonate makes the polysaccharide solution solidify immediately without destroying the overall structure. When the polysaccharide solution contacts with organic carbonate, a chemical reaction occurs between the hydroxyl anion in the solvent and the organic carbonate, releasing glycol and carbon dioxide, which partially dissolves in the form of carbonate. In theory, the solvent and glycol can be recycled in subsequent steps and recovered therefrom. Polysaccharide does not react. The formed product is a regenerated polysaccharide.

[0030] The organic carbonate may be, for example, propylene carbonate, vinylethylene carbonate, butyl carbonate or ethylene carbonate.

[0031] The organic carbonate can be cyclic or non-cyclic organic carbonate. The cyclic organic carbonate can be, for example, propylene carbonate, vinyl ethylene carbonate, butyl carbonate, ethylene carbonate or vinyl carbonate. The non-cyclic organic carbonate can be, for example, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, dibenzyl carbonate, diphenyl carbonate or tert-butylphenyl carbonate.

[0032] The organic carbonate used in this process is preferably propylene carbonate. Propylene carbonate is particularly advantageous because it is a carbonate that is liquid at room temperature and can be produced essentially from biomass, and is therefore easy to use. In addition, propylene carbonate has a low cost.

[0033] The organic carbonate polymer may, for example, have 2 to 1,000,000 monomer units.

[0034] The organic carbonate polymer may be, for example, polypropylene carbonate.

[0035] The mixture of at least one organic carbonate and at least one organic carbonate polymer may be, for example, a mixture of propylene carbonate and polypropylene carbonate.

[0036] In the present process, the solid organic carbonate is preferably dissolved before use, for example in DMSO. DMSO is particularly suitable here. The same applies to the organic carbonate polymer. The polymer is a polymer that is solid at room temperature.

[0037] Preferably, at least one organic carbonate or a mixture of different organic carbonates is used in the process.

[0038] In step S3, the electrophilic reagent is used at a concentration of 10-100%, especially 80-100%. Step S3 is preferably carried out at a temperature in the range of 0-100°C for 0.01-100 hours, especially preferably at 23°C for 0.01-10 minutes, and even more preferably at 23°C for 0.01-6 minutes. This means that the process has the advantage of operating at room temperature. In addition, the process is very fast.

[0039] The regenerated polysaccharide purification performed in step S4 is preferably achieved by water, which can effectively remove impurities, especially water-soluble impurities, and the formed organic compounds (propylene glycol) and solvents. The advantage of this approach is that it can achieve extremely high purity and extremely uniform regenerated polysaccharide homogeneous structure.

[0040] In a preferred embodiment of the process, in an additional step S2a, the regenerated polysaccharide is made into a film (also called foil) by applying the polysaccharide solution after step S2 onto a surface with a coating medium (such as a doctor blade) having a determined height. In this way, a polysaccharide / solvent layer with a uniform and determined thickness can be obtained. In step S3, after contact with an organic carbonate (such as propylene carbonate), for example by immersion in a propylene carbonate bath, the layer is converted into a film. In this way, an opaque and whitish film can be obtained. As mentioned above, a transparent film can also be produced by adding DMSO.

[0041] It has been demonstrated that the average surface potential (zeta potential) of the film produced by this process is -20 mV in the pH range of 5.0 to 9.0.

[0042] By introducing an electrophilic agent and leaching the solvent from the polysaccharide solution, a permeable (porous) microfibrillated structure is formed in the regenerated polysaccharide film prepared by the process. It has been demonstrated that the properties of such films are comparable to those of films prepared by existing methods.

[0043] The film can be stored in a neutral, slightly alkaline or slightly acidic medium. It has been shown that the film can maintain printing stability during such storage. The printing stability of the film was tested in a flow reactor at a pressure between 1 and 3 bar.

[0044] The film can be stored in water, ethanol or acetone, for example. Preferably, the film is stored in water.

[0045] In another preferred embodiment of the process, the regenerated polysaccharide is made into a pellet form by mechanically pulverizing it in an additional step S4a after step S4. By pulverizing the solid composed of the regenerated polysaccharide formed after the polysaccharide solution is contacted with an organic carbonate (such as propylene carbonate) and then subjected to a washing step, a high-purity polysaccharide material in the form of pellets, such as a powder, can be obtained.

[0046] The second aspect of the present invention relates to a regenerated polysaccharide produced by the process of the present invention according to the above embodiments. The regenerated polysaccharide is preferably regenerated cellulose.

[0047] The regenerated polysaccharide is preferably provided as a film. Among them, preferably a regenerated cellulose film is provided. Such films show high homogeneity both inside the film and on the surface. The surface of such films is very smooth. The distance (pores) between the fibrils (fibers) is extremely small, preferably 10 to 100 nm, and is correspondingly selective for a specific particle size. The film of the present invention can be used, for example, as a purification membrane or film in the selective purification of drinking water. In addition, negatively charged ions can also be selectively separated from positively charged ions. In addition, such films can be used to produce sheets and nanotubes.

[0048] Likewise, the regenerated polysaccharide is preferably provided in the form of pellets. The pellets (as in powder form) can be used, for example, as an additive in nutritional or pharmaceutical preparations, or in the construction chemical industry or in ceramic applications.

[0049] The regenerated cellulose films and pellets produced according to the present invention are characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, X-ray diffraction, thermal analysis, atomic force microscopy, scanning electron microscopy, transmission electron microscopy, UV / visible spectroscopy and size exclusion chromatography.

[0050] A third aspect of the present invention relates to a product consisting of the polysaccharide regenerated according to the present invention. Such a product is, for example, a membrane, a film, a sheet, a nanotube or a combination with other materials.

[0051] As long as it is not limited to the process technology alone, the advantages of the regenerated polysaccharide produced by this process and the products composed of the regenerated polysaccharide correspond to the advantages of this process.

[0052] The public contents are as follows:

[0053] 1. A solid-state regenerated polysaccharide manufacturing process comprising the following steps:

[0054] -S1) provides polysaccharides;

[0055] - S2) dissolving the polysaccharide in at least one electrolytic solvent;

[0056] -S3) by mixing the polysaccharide solution with a

[0057]

[0058] Or formula (II)

[0059]

[0060] or a mixture of electrophilic reagents of formula I and / or II, so that the polysaccharide is precipitated in the form of a gel,

[0061] wherein X is a C=O, C=S, C=NR functional group, Y and Z are identical or different and are selected independently of each other and consist of O, NH, NR, S, CR groups, wherein R is hydrogen and / or a substituted or unsubstituted hydrocarbon group, and M is a bridging group consisting of 0 to 20 carbon atoms and a substituted or unsubstituted straight or branched hydrocarbon group;

[0062] - S4) washing the regenerated polysaccharide.

[0063] 2. The process according to item 1, wherein the polysaccharide used is cellulose.

[0064] 3. The process according to item 1 or 2, wherein the electrolytic solvent used is a quaternary onium hydroxide having a weight content of about 40 to 80% in water.

[0065] 4. A process according to Disclosure Item 3, wherein at least one phosphonium-containing and / or at least one ammonium-containing onium hydroxide is used.

[0066] 5. The process according to Disclosure Item 4, wherein tetrabutylphosphonium hydroxide is used.

[0067] 6. The process according to any one of the preceding disclosures, wherein an additional solvent is used in step S2.

[0068] 7. The process according to Disclosure Item 6, wherein dimethyl sulfoxide is used as an additional solvent.

[0069] 8. The process according to any one of the preceding disclosures, wherein the electrophilic agent is used at a concentration of 80-100%.

[0070] 9. The process according to any one of the preceding disclosures, wherein the electrophilic reagent used in step S3 is at least one organic carbonate or a mixture of different organic carbonates.

[0071] 10. The process according to Disclosure Item 9, wherein the organic carbonate used in step S3 is propylene carbonate.

[0072] 11. The process according to any one of Disclosure Items 1 to 8, wherein the electrophilic reagent used in step S3 is at least one organic carbonate polymer, or a mixture of different organic carbonate polymers, or a mixture of at least one organic carbonate and at least one organic carbonate polymer.

[0073] 12. The process according to any one of the preceding disclosures, wherein the regenerated polysaccharide is manufactured as a thin film by applying the polysaccharide solution after step S2 to a surface in an additional step S2a.

[0074] 13. The process according to any one of Disclosures 1 to 12, wherein the regenerated polysaccharide is manufactured into a powder or pellet form by mechanically crushing it in an additional step S4a after step S4.

[0075] 14. A regenerated polysaccharide produced by the process according to any one of Disclosures 1 to 13.

[0076] 15. The regenerated polysaccharide according to Disclosure Item 14, provided in the form of a film.

[0077] 16. The regenerated polysaccharide according to Disclosure 14, provided in the form of pellets.

[0078] 17. A product made from the regenerated polysaccharide according to any one of Disclosures 14 to 16.

[0079] Unless otherwise stated, the features and examples described for the process for producing the regenerative polysaccharide of the present invention, the regenerative polysaccharide of the present invention produced by the process, and the products of the present invention made from the regenerative polysaccharide are equally applicable to the corresponding features of each disclosed item.

[0080] Substituted or unsubstituted hydrocarbon groups encompassed by R are especially alkyl or aryl groups, such as alkyl groups having 1 to 20 carbon atoms or having 1 to 8 carbon atoms. R is preferably methyl, ethyl or n-propyl.

[0081] Compounds that are explicitly excluded from use as electrophilic agents are compounds disclosed in the publication US2014 / 212670A1 for the precipitation of regenerated cellulose. This aspect particularly relates to alcohols having 1 to 4 carbon atoms such as methanol, ethanol, 2-propanol, and ketones such as acetone. In other words, the use of such compounds is excluded from the disclosure scope of disclosure 1.

[0082] In the context of the present disclosure, "electrolytic solvent" is understood to mean a dissolved solid composed of ionic crystals, which are composed of hydroxide ions as negatively charged anions and positively charged cations. The electrolytic solvent used in the process of the present disclosure is preferably a quaternary onium hydroxide having a weight content (weight percentage) in water of about 40 to 80%. In addition, other protic solvents and aprotic solvents may also be tolerated, which can achieve improved fluidity and processability.

[0083] Further disclosures include the following:

[0084] 1. A solid-state regenerated polysaccharide manufacturing process comprising the following steps:

[0085] -S1) provides polysaccharides;

[0086] - S2) dissolving the polysaccharide in at least one electrolytic solvent;

[0087] -S3) contacting the polysaccharide solution with an electrophilic reagent to precipitate the polysaccharide in the form of a gel, wherein the electrophilic reagent used is: at least one having the formula

[0088]

[0089] A reagent wherein X and Y are O, S or NR functional groups, Y and Z are the same or different and are independently selected from each other. wherein R is hydrogen and / or a substituted or unsubstituted straight or branched hydrocarbon group;

[0090] or at least one having the formula

[0091]

[0092] A reagent, wherein X and Y are O, S or NR functional groups, X and Y are the same or different and are independently selected from each other, wherein R is hydrogen and / or a substituted or unsubstituted straight or branched hydrocarbon group, and B is a bridging group consisting of a substituted or unsubstituted straight or branched hydrocarbon group having 1 to 20 carbon atoms;

[0093] or a mixture of agents having formula I and / or II;

[0094] or at least one polymer having 2 to 1,000,000 monomer units, wherein the monomer units correspond to agents having formula I and / or formula II;

[0095] or a mixture of polymers each having 2 to 1,000,000 monomer units, wherein the monomer units correspond to agents having formula I and / or formula II;

[0096] or a mixture of at least one agent having formula I and / or formula II and at least one polymer having 2 to 1,000,000 monomer units, wherein the monomer units correspond to the agent having formula I and / or formula II;

[0097] - S4) washing the regenerated polysaccharide.

[0098] 2. The process according to item 1, wherein the polysaccharide used is cellulose.

[0099] 3. The process according to item 1 or 2, wherein the electrolytic solvent used is a quaternary onium hydroxide having a weight content of about 40 to 80% in water.

[0100] 4. A process according to Disclosure Item 3, wherein at least one phosphonium-containing and / or at least one ammonium-containing onium hydroxide is used.

[0101] 5. The process according to Disclosure Item 4, wherein tetrabutylphosphonium hydroxide is used.

[0102] 6. A process according to any one of the preceding disclosures, wherein an additional solvent is used in step S2.

[0103] 7. The process according to Disclosure Item 6, wherein dimethyl sulfoxide is used as an additional solvent.

[0104] 8. The process according to any one of the preceding disclosures, wherein the electrophilic agent is used at a concentration of 80-100%.

[0105] 9. A process according to any one of the aforementioned disclosures, wherein the electrophilic reagent used in step S3 is at least one organic carbonate, or a mixture of different organic carbonates, or at least one organic carbonate polymer, or a mixture of different organic carbonate polymers, or a mixture of at least one organic carbonate and at least one organic carbonate polymer.

[0106] 10. The process according to Disclosure Item 9, wherein an organic carbonate is used in step S3.

[0107] 11. The process according to Disclosure Item 10, wherein the organic carbonate used in step S3 is propylene carbonate.

[0108] 12. The process according to any one of the preceding disclosures, wherein the regenerated polysaccharide is manufactured as a thin film by applying the polysaccharide solution after step S2 to a surface in an additional step S2a.

[0109] 13. The process according to any one of Disclosures 1 to 12, wherein the regenerated polysaccharide is manufactured into a powder or pellet form by mechanically crushing it in an additional step S4a after step S4.

[0110] 14. A regenerated polysaccharide produced by the process according to any one of Disclosures 1 to 13.

[0111] 15. The regenerated polysaccharide according to Disclosure Item 14, provided in the form of a film.

[0112] 16. The regenerated polysaccharide according to Disclosure 14, provided in the form of pellets.

[0113] 17. A product made from the regenerated polysaccharide according to any one of disclosures 14 to 16.

[0114] Unless otherwise stated, the features and examples described for the process for producing the regenerative polysaccharide of the present invention, the regenerative polysaccharide of the present invention produced by the process, and the products of the present invention made from the regenerative polysaccharide are equally applicable to the corresponding features of each disclosed item.

[0115] Substituted or unsubstituted hydrocarbon groups encompassed by R are especially alkyl or aryl groups, such as alkyl groups having 1 to 20 carbon atoms or having 1 to 8 carbon atoms. R is preferably methyl, ethyl or n-propyl.

[0116] Compounds that are explicitly excluded from use as electrophilic agents are compounds disclosed in the publication US2014 / 212670A1 for the precipitation of regenerated cellulose. This aspect particularly relates to alcohols having 1 to 4 carbon atoms such as methanol, ethanol, 2-propanol, and ketones such as acetone. In other words, the use of such compounds is excluded from the disclosure scope of disclosure 1.

[0117] In the context of the present disclosure, "electrolytic solvent" is understood to mean a dissolved solid composed of ionic crystals, which are composed of hydroxide ions as negatively charged anions and positively charged cations. The electrolytic solvent used in the process of the present disclosure is preferably a quaternary onium hydroxide having a weight content (weight percentage) in water of about 40 to 80%. In addition, other protic solvents and aprotic solvents may also be tolerated, which can achieve improved fluidity and processability. BRIEF DESCRIPTION OF THE DRAWINGS

[0118] The present invention is described in detail below with reference to the accompanying drawings.

[0119] Figure 1 is a general embodiment flow chart of the process of the present invention for producing regenerated cellulose;

[0120] Figure 2 Another embodiment of the process of the present invention for manufacturing a thin film is a flow chart;

[0121] Figure 3 A flow chart of one embodiment of the process of the present invention for making pelletized material;

[0122] Figure 4 Based on Figure 2 Permeability analysis graph of the manufactured regenerated cellulose membrane;

[0123] Figure 5 Based on Figure 2 Quality and structural analysis of regenerated cellulose of manufactured films ( 13 C nuclear magnetic resonance spectroscopy analysis) diagram, wherein Cmcell: commercially available microcrystalline cellulose.

[0124] Figure 6 Based on Figure 2 Pore ​​size analysis of the fabricated regenerated cellulose membrane.

[0125] Figure 7 Based on Figure 3 Structural analysis of regenerated cellulose of the produced pellet material: A) FT-IR spectrum, B) X-ray diffraction; and C) NMR spectrum.

[0126] Figure 8 Based on Figure 3 Comparative analysis of the structures of pelletized regenerated cellulose made from four different organic carbonates: A) FT-IR and B) X-ray diffraction patterns.

[0127] Fig. 9 Based on Figure 2 Optical micrograph of a cross section of the fabricated regenerated cellulose membrane.

[0128] Fig.10 Based on Figure 2 Transmission electron micrograph of a cross section of the fabricated regenerated cellulose membrane. DETAILED DESCRIPTION

[0129] In accordance with Figure 1 In a general embodiment of the process of the present invention, regenerated cellulose is manufactured. Wherein, in the first step S1, natural cellulose in microcrystalline form is provided. However, as an alternative, the cellulose can also be provided in any other possible form of cellulose, for example, a synthetic or amorphous form, or a form made from biomass. In the second step S2, in a suitable container, 20% (200 mg) of microcrystalline cellulose by weight (%) is dissolved in a 50% aqueous solution (1 ml) of TBPH. This process involves stirring the resulting cellulose solution at room temperature (23° C.) for about 30 minutes. In the third step S3, the liquid is mixed with propylene carbonate to achieve coagulation. This operation instantly converts the cellulose / solvent layer into regenerated cellulose. In the fourth step S4, the regenerated cellulose is washed with water to remove the solvent and the organic compounds formed, thereby obtaining high-purity regenerated cellulose.

[0130] In accordance with Figure 2 In one embodiment of the process of the invention for producing a regenerated cellulose film / foil, the process is carried out in the same manner as Figure 1 Similarly, the difference is that in the additional step S2a, the transparent solution is applied to the glass plate, for example with a doctor blade, so as to obtain a cellulose / solvent layer with a specific preset thickness (e.g. 300 μm). In the third step S3, the applied liquid is immersed in a propylene carbonate bath for solidification. This step allows the cellulose / solvent layer to be instantly converted into a regenerated cellulose film. In the fourth step S4, the regenerated cellulose film is washed with water to remove the solvent and the organic compounds formed, so as to obtain a high-purity cellulose film. Immediately thereafter, the film is peeled off the glass plate and stored in water for later use.

[0131] However, during the above-mentioned conversion process, the optical properties do not change. The cellulose film is whitish and opaque, so that the conversion of the cellulose / solvent layer into a cellulose film cannot be visually detected. In another embodiment of the process of the present invention, in step S2, DMSO is added as an additional solvent to the dissolved cellulose (preferably the solvent / DMSO ratio is 1:1). In this way, a transparent cellulose film is produced in step S3. Again, the conversion process cannot be visually detected. The use of DMSO also has an effect on the permeability of the film. This can be shown in Figure 4In the experiment, the film was used as an osmotic membrane and subjected to a water flow test. The water flow rate depends in principle on the size and distribution of the pores in the osmotic membrane. The first membrane was manufactured without DMSO (RC1), while the second membrane was manufactured with DMSO (RC2). For the first membrane RC1, the water permeability varied from 1.6 L*m to 2.1 L*m in a pressure range of 0.5 to 2.1 bar. -2 *h -1 Increased to 5.4L*m -2 *h -1 (Square data points). For the second membrane RC2, the water permeability changes from 3.7 L*m to 1.1 L*m in a pressure-dependent manner within the pressure range of 0.5 to 1.1 bar. -2 *h -1 Increased to 7.8L*m -2 *h -1 (Circular data points) The increase in permeability shown in the graph indicates that DMSO has a significant diluting effect on the regenerated cellulose.

[0132] Figure 5 The purification effect of the novel process and the improvement in the quality of the produced films are shown. The abbreviation au represents arbitrary units. No impurities (sharp signals) were observed in the films. Furthermore, the chemical structure of the membrane RC2 (membrane 2, top line) and membrane RC1 (membrane 1, second line from the top) corresponds to commercial microcrystalline cellulose (abbreviated Cmcell., second line from the bottom). The bottom line is related to the solvent (TBPH, 50%).

[0133] Figure 6 The pore distribution in the two membranes is shown in Figure 1. The pore size is 10-70 nm, which is much smaller than the pore size of commercially available regenerated cellulose membranes (200-500 nm).

[0134] In accordance with Figure 3 In another embodiment of the process of the present invention, pelletized material is produced from regenerated cellulose. Steps S1 and S2 are carried out in accordance with Figure 1 The process is performed in the same manner. In step S3, propylene carbonate is added directly to the cellulose solution (preferably propylene carbonate is added in excess in a ratio of 10:1), so that the regenerated cellulose is instantly gelled / solidified. The solidified regenerated cellulose can be washed with water in step S4, for example, by repeatedly skimming off the supernatant or repeatedly centrifuging when the cellulose is deposited at the bottom of a container containing cellulose and solvent. The regenerated cellulose is preferably dried at 30-100°C and stored in the form of pellets for subsequent use. Optionally, the pellet material can be mechanically crushed in step S4a, for example by a pestle or mortar. Figure 3In the process shown, the size of the pellet particles formed can be varied, so that a powder or a more coarse pellet material can be produced. The size of the pellet material can be adjusted by suitable pulverizing equipment and pulverizing intensity (applied force, applied duration).

[0135] The pelletized material produced was subjected to structural examination. The results showed that the regenerated cellulose was not chemically modified by propylene carbonate, that is, the cellulose was not actually reacted with propylene carbonate. Fourier transform infrared spectroscopy (FT-IR) analysis showed that no propylene carbonate was incorporated into the cellulose structure ( Figure 7 A). The upper graph shows propylene carbonate, the middle graph shows regenerated cellulose and the lower graph shows native microcrystalline cellulose. It can be seen that no chemical structural changes occurred during the regeneration of cellulose after dissolution. X-ray diffraction (XRD) analysis of the pelletized material showed that its macrostructure had changed. The additional reflection peaks at 12.1° and 20.6° in the upper graph (regenerated cellulose) compared to the lower graph (native cellulose, crystalline cellulose) indicate the formation of cellulose II structure (regenerated cellulose) ( Figure 7 B). Similarly, in the nuclear magnetic resonance (NMR) analysis, the trajectory of the upper line (regenerated cellulose) is clearly similar to that of the lower line (native cellulose), indicating that no chemical structural changes have occurred ( Figure 7 C). The abbreviation au in the various figures represents arbitrary units.

[0136] As an alternative to the propylene carbonate used above, other organic carbonates can also be used to obtain regenerated cellulose ( Figure 8 ). FT-IR( Figure 8 A) and X-ray diffraction ( Figure 8 B) shows that the regenerated cellulose obtained from vinyl ethylene carbonate (top line), butyl carbonate (second line from the top) and ethylene carbonate (second line from the bottom) has the same structure as the regenerated cellulose obtained from propylene carbonate (bottom line). The abbreviations au in the various figures represent arbitrary units.

[0137] Fig. 9 Shown is based on Figure 2 Optical micrograph of a cross section of a produced regenerated cellulose film. The film (foil) (RC1) shown in the photograph was produced without the use of DMSO as an additional solvent. The thickness of the film is 200 μm. As can be seen from the photograph, the film has excellent homogeneity. As can also be seen from the photograph, there are no bubbles in the film.

[0138] Fig.10 according to Figure 2High-resolution transmission electron micrograph (TEM image) of a cross section of a produced regenerated cellulose membrane. The membrane (foil) (RC1) shown in the photograph was produced without the use of DMSO as an additional solvent. The microfibril structure was visualized by uranyl acetate and lead citrate.

[0139] Materials made from the produced regenerated cellulose can be used in filtration technology. For example, the produced membrane can be used as a purification membrane for the selective purification of drinking water.

Claims

1. A process for producing solid-state regenerated polysaccharide, characterized in that: The steps include: S1) provides polysaccharides; S2) dissolving the polysaccharide in at least one electrolytic solvent, wherein the electrolytic solvent used is a quaternary onium hydroxide having a weight content of 40-80% in water; S3) contacting the polysaccharide solution with an electrophilic reagent to precipitate the polysaccharide in the form of a gel, wherein the electrophilic reagent used is at least one cyclic organic carbonate or at least one cyclic organic carbonate polymer; S4) washing the regenerated polysaccharide; Wherein, the polysaccharide used is cellulose, the quaternary onium hydroxide used is tetrabutylphosphonium hydroxide, the electrophilic reagent used is cyclic organic carbonate, and the cyclic organic carbonate is propylene carbonate.

2. The process according to claim 1, characterized in that In step S2, additional solvent is used.

3. The process according to claim 2, characterized in that Dimethyl sulfoxide was used as an additional solvent.

4. The process according to any one of claims 1 to 3, characterized in that The electrophilic reagent is used at a concentration of 80-100%.

5. The process according to any one of claims 1 to 3, characterized in that In an additional step S2a, the regenerated polysaccharide is manufactured into a thin film by applying the polysaccharide solution after step S2 to a surface.

6. The process according to any one of claims 1 to 3, characterized in that The regenerated polysaccharide is produced in the form of a powder or pellets by mechanically pulverizing it in an additional step S4a after step S4.

7. A regenerated polysaccharide produced by the process according to any one of claims 1 to 6, wherein the regenerated polysaccharide is provided in the form of a film having pores with a pore size of 10 to 100 nm.

8. The regenerated polysaccharide according to claim 7, characterized in that Supplied in film form.

9. The regenerated polysaccharide according to claim 7, characterized in that Supplied in pellet form.

10. A product made from the regenerated polysaccharide according to any one of claims 7 to 9.

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