CN112616316A

CN112616316A - Degumming and scouring of bast materials for textile and pulp quality fiber production

Info

Publication number: CN112616316A
Application number: CN201980037888.7A
Authority: CN
Inventors: 迈克尔·S·朗
Original assignee: Fuxing Fiber Co ltd
Current assignee: Fuxing Fiber Co ltd
Priority date: 2018-04-09
Filing date: 2019-04-09
Publication date: 2021-04-06
Also published as: AU2019251227A1; WO2019199823A1; EP3765659A4; US20210148009A1; MX2020010328A; CA3096348A1; EP3765659A1

Abstract

A method for degumming bast fibres, the method comprising soaking a source of bast fibres in a salt solution. The source of bast fibers may be soaked in a saline solution at a concentration in a range of between less than 1 to about 200 thousandths of a year. The salt concentration can be varied while soaking the bast fiber source, or by alternating the bast fibers between aqueous solutions of different ion concentrations. In one embodiment, the source of bast fibres is immersed in seawater, wherein the salt concentration is varied by alternating salinity with the tide. The source of bast fibers may be hemp.

Description

Degumming and scouring of bast materials for textile and pulp quality fiber production

Background

Cellulose bast fibres harvested from plants like hemp, flax and sisal are composed of most undesired materials other than cellulose including: lignin, pectin, and hemicellulose, collectively referred to as pectin. The gum used as a natural adhesive to bind the cellulose fibers together provides structural rigidity to the plant. For cellulose and fiber manufacturing purposes, gums are undesirable. Its presence is detrimental to manufacturing equipment and product quality and compromises the efficient conversion of virgin bast to marketable cellulose fibers.

Processing bast-derived cellulose fibers requires removal of the gums by chemical and mechanical means, also known as degumming. Chemical treatments attempt to target non-cellulosic molecules with minimal damage to the cellulosic polymer that makes up the fiber itself. Mechanical treatment is intended to enhance chemical transport as well as physically separate the gum from its cellulosic structure. Historically and commonly, bast fiber degumming utilizes natural processes and environmental conditions to extract and separate the original cellulose fibers from the rest of the plant, known as impregnation. Impregnation takes various forms, but typically degummed using natural microbial and chemical activity. For field steeping, the cut stalks are exposed to the field for a period of time. In water immersion, the stalks are placed in ponds or streams.

Both methods do not guarantee a stable production of marketable textile fibers, which brings uncertainty to the market. Recently, on page D3 of the wale Street Journal (Wall Street Journal) of 4.4.2019, the professor of the textile research of the new york fashion technical institute, the chairman jeffey schilberman (Jeffrey Silberman), required a special type of handling equipment to turn hemp into fibres, and this type of machinery was still scarce. To cite him: "to my knowledge, the state of new york has no processing equipment for it. I have not found spinning (spinning) plants that can handle hemp. "

The fibers obtained by conventional field and water immersion yield silver gray colored fibers due to the by-products and contamination of the biological treatment. Enzymatic and other chemical processes produce slightly yellow fibers or fibers that are gold to white.

Industrial scale quality control degumming involves the formulation of chemical reagents and catalysts to target exclusively gums and may generate problematic waste products as well as difficult to handle fibers.

There is a need in the art for a process whose effluent is easily reusable, or which can be reduced to an environmentally benign (inert, neutral, ineffective, non-functional) form with minimal impact on water quality. Successful process execution should yield consistent quality, suitable cellulosic fibers over a wide range of control parameters.

Disclosure of Invention

The present invention meets one or more of these needs in the art by providing a method for degumming bast fibers (to remove structural non-cellulosic materials) comprising soaking a source of bast fibers in a salt solution or an ionic solution. The source of bast fibers may be hemp.

In one embodiment, the source of bast fibers is soaked in a saline solution having a concentration in a range between about 1 to up to about 200 thousandths of a year. When a source of bast fibers is soaked in a salt solution, the ionic concentration of the salt solution may change. This step can be performed without the need for an electrolytic solution.

In one embodiment, the source of bast fibers is soaked in seawater. In another embodiment, the water source is soaked in brackish water. The salt concentration may be time varying; for example, the ion concentration can be fluctuated either using natural (tidal) or artificial (alternate salt bath). Since the ion or salt concentration in water in an estuaries (estuaries: estuary, trigonal bay) varies with tidal fluctuations, the submersion of a source of bast fibres in an estuary for a series of tidal cycles can provide salinity variations.

The saline solution may be modified for the agent using a gum.

The method can include soaking bast fibers in a solution containing a base to degrade lignin into a water soluble form for removal from water. Alkaline salt solutions of bases having a pH of about 7 to about 14 may be used.

The method can include soaking the bast fiber source in a sulfur-containing solution (S has an oxidation number of VI) to sulfonate lignin for removal from water from the bast fiber source.

The bast fiber source may be soaked in an oxidizing solution to scour lignin, pectin, and hemicellulose for removal from the bast fiber source by water.

The method can include rinsing the bast fiber source with a detergent and a surfactant to further remove lignin, pectin, and hemicellulose from the bast fiber source. The source of bast fibers may be mechanically agitated (agitate: shaking, stirring). For example, the bast fiber source may be tumbled.

The present invention may also be considered to be a method for degumming hemp fibres from a hemp plant, the method comprising: soaking a cannabis plant in a salt solution; soaking a hemp plant in a sulfur solution to sulfonate lignin for removal from hemp fibers in the hemp plant; and rinsing the hemp fiber with a detergent to further remove lignin, pectin, and hemicellulose from the hemp fiber.

The method may include soaking the hemp fibers in an oxidizing solution to remove lignin, pectin, and hemicellulose and partially oxidized intermediates thereof from the hemp fibers. For example, hemp fibers can be soaked in a hydrogen peroxide solution. Hydrogen peroxide and other oxidizing sources may be generated in situ, e.g. via electrolysis. The hemp fibers can be soaked in an oxidizing solution having a pH between about 6 and about 14 and a temperature below the boiling point of the oxidizing solution. This step can be performed without the need for an electrolytic solution.

In one embodiment, the hemp fibers can be soaked in a sulfur solution having a pH between about 6 and about 14 and a temperature between ambient temperature (20 to 30 ℃) and about 95 ℃.

In one embodiment, immersing the cannabis plant in the salt solution comprises immersing the cannabis plant directly into or within a container connected to natural, tidal scoured (scoured, flushed) coastal waters such that the ionic composition of the solution proximate to the cannabis plant and the associated alkalinity, acidity and density vary with tidal fluctuations.

The resulting fiber is suitable for spinning into textile quality yarn using conventional textile methods and machinery, wherein the treatment is selected from the group consisting of: yarns are made by spinning, yarns are made by weaving, yarns are made by felting, such as nonwoven fabrics by needle punching, and more than one of them. Eliminating the potentially toxic by-products inherently produced by this process does not require the use of bleaching or oxidation and allows the bast material to retain its original natural green elements. The thus degummed fiber (chlorophyll-containing fiber) retains at least some of its green color and is substantially free of lignin, pectin, and hemicellulose, and the fiber can be treated in conventional textile machinery, wherein the treatment is selected from the group consisting of: yarns are made by spinning, yarns are made by weaving, yarns are made by felting, such as nonwoven fabrics by needle punching, and more than one of them. The green color of bast fibers is usually imparted to bast fibers by chlorophyll. The bast fiber may be hemp.

The green source of bast fibers, when extracted into a solvent, can show a photometric absorption spectrum indicative of the general chlorophyll pigments (chlorophyll a, b, and c). Such as in Jeffrey and Humphrey, "New Spectrophotometric Equations for Determining chlorophenyls a, b, c₁、c₂The data from the wavelengths 750, 664, 647 and 630nm can be used to calculate chlorophyll concentration directly from the appropriate absorption spectra, as described in the high her Plants, Algae and Natural Phytoplankton ", biochem. For example, a 500mg sample of green colored, degummed hemp fiber produced according to an embodiment of the method was soaked in 100mL of deionized water for 12 hours and filtered through a 0.45 μm super membrane. Data from absorption spectra according to Jeffrey and Humphrey (1975) show that the total chlorophyll in the extract is 1.6mg/L, corresponding to at least 0.03% by mass of chlorophyll in the fiber sample.

Drawings

The invention will be better understood from a reading of the detailed description of embodiments of the invention and a review of the accompanying drawings, in which:

figure 1 is a black and white photograph of four samples.

Detailed Description

The present invention is directed to a method for treating plants including bast fibers to remove lignin, pectin, and hemicellulose (collectively "gums") and other undesirable materials. The result is a cellulose fiber that is partially, largely, or completely free of gums, such that it can be used for conversion into a marketable material, such as textile fiber. The bast fibres may be hemp, flax or sisal. Jute and other fibers are also known as bast fibers.

The method comprises soaking a plant as a source of bast fibers in a salt solution. The bast fiber source may be soaked and stirred in a solution of strong brine (brine, salt water). The bast fiber source may be soaked and agitated in an alkaline solution. The source of bast fibers can be soaked and stirred in a solution with a pH > 6 and this is usually performed without the need for an electrolytic solution. In one embodiment, the solution is comprised of water and inorganic salts, wherein the total salinity is in the range of less than 1 to about 200 parts per thousand (ppt). Salinity sources may include those naturally occurring salinities such as those found in tidal scoured estuaries, bays (reeek: bays, harbors), coastal waters and seawater. Natural fresh water may be used, but ions that are discharged into the fresh water flow field should be taken into account. Typically, fresh water has a salinity in the range of about 0 to about 0.5ppt, brackish water has a salinity in the range of about 0.5ppt to about 30ppt, and seawater has a salinity in the range of about 30ppt to about 50 ppt.

The bast fiber source is immersed in an aqueous solution, allowing water and aqueous ions to be absorbed into the interstices between the cellulose fibers and the gum and into the cellulose matrix due to the wetting and capillary action of the cellulose. This imparts pressure on the cellulosic structure, causing it to expand. The presence of ions in solution within the cellulose matrix changes the wetting characteristics of the cellulose, changes the capillary and pore pressures, and enhances interstitial transport and swelling. Swelling imparts mechanical stress on the bast structure, helps expose the bulk of the fiber to the agent, increases substrate surface area, delivers the agent for subsequent steps, and enhances fiber separation. Conversely, a decrease in ion concentration decreases the swelling characteristics, enhances the diffusion output of the dissolved material from the cellulosic matrix (effectively scouring it), and imparts stress on the fibrous matrix, further enhancing separation. This process may be enhanced by additional mechanical processing. The interstitial pressure gradient may be maintained by periodically increasing and decreasing the ion concentration in the solution by the addition or dilution of salt or concentrated brine, and will enhance fiber separation and enhance exposure of the gum to the agent. The use of a tidal flushed estuary water source allows the use of naturally available and undisturbed sea salt as a source of interstitial pressure. The use of tidal scoured water in estuary also safely removes pectin and/or its partially oxidized intermediates from bast fibres by scouring.

Exposing the bast fiber source to a change in ion concentration can be performed at elevated temperatures and pressures to enhance diffusion and reaction rates and increase the interstitial pressure.

The method may further comprise exposing lignin present in the bast fibers to a degumming agent. This may include alkali to depolymerize the lignin into smaller, lighter weight, soluble lignin products. Alkaline salt solutions of bases having a pH of about 7 to about 14 may be used.

The method can further include sulfonating lignin present on the bast fibers to produce water soluble products that can be removed by scouring the bast fibers with water. Neutral to alkaline solutions of strong bases and sulfur anions having a pH of about 7 to about 14 may be used. The sulfur in the neutral to alkaline solution will react with the ring structure in the lignin to yield sulfonated soluble products that are easily removed from the plant material by scouring. Sufficient sulfur is provided to account for the range of lignin content of the bast fiber source (lignin is typically 5 to 15% by mass for virgin fiber and less for impregnated or otherwise pretreated fiber). The bast fiber source may be soaked in the sulfonation solution at a pressure in the range of ambient pressure to 10 atmospheres for 10 minutes to several hours. The temperature may vary with pressure according to the Clausius-Clapyeron relationship.

Bast fibers may also be soaked in oxidizing solutions to bleach the fibers and scour the remaining gums. The oxidizing agent may be added directly to the solution or generated in situ (e.g., by electrolysis). In some embodiments, the addition of an oxidation stabilizer may be included. The desired water temperature and soaking time depend on the oxidant used. An aqueous solution having a pH in the range of about 8 to about 12 is made using a combination of a strong base and a buffer. As a non-limiting example of a ratio, 50mL of 3% H₂O₂Added to 2g/L NaOH and 1g/L NaHCO₃The solution of (1). The hemp fibers are soaked for about 0.1 to about 1 hour at a temperature below the boiling point of the solution. Since some naturally occurring heavy metals (Fe, Mg) interfere with colloidal H₂O₂Oxidation (see, e.g., Fenton's reagent), so the addition of chelating agents can be used to prevent or minimize their interference.

Additional steps may also be added to further degum the bast fibers. For example, the cleaning agent may be used to rinse and remove any remaining soluble, partially soluble, or insoluble (but mobile) gums in the bast fibers. Pectinase or other natural enzymes (either added directly or produced biologically in situ) can be used as an optional ingredient to assist in removing pectin from bast fibers. These steps may include mechanical agitation. The mechanical agitation may be tumbling, stirring, or other agitation.

The step of degumming the bast fibers may vary depending on the chemical and physical conditions of the water source. Potential sources of water for soaking bast fibers include most natural waters as well as municipal water and purified water. Since the method utilizes a salt solution, a natural saline source can be advantageously used.

Raw water (non-municipal or other untreated water, salt water, brackish or fresh water) may be used for one or more steps. Some natural water sources contain ingredients that can be utilized as reagents for one or more of the steps described above. For example, water that can be obtained from wetlands contains naturally abundant sulfur (i.e., has an oxidation number less than or equal to VI), which can be used to sulfonate lignin. The presence of naturally available reactants or reagent components within the water source may be taken into account when formulating the desired reagent components. For example, naturally available chelating agents may be used instead of those added artificially. The natural salinity of the water source can be taken into account in all steps and its natural salinity variation (due to tides or other factors) can be used as an enthalpy source for physical and chemical treatments. Naturally available sources of alkaline water may also be used for certain treatments, wherein the pH of the solution is in the range of about 8 to about 12.

Furthermore, certain steps of the method may vary for several reasons. For example, bast fibers may be pretreated or decorticated, thus requiring less aggressive treatment. If the operator determines that the results of one or more steps are deemed inadequate, certain steps may be repeated (with or without the use of more aggressive reagents). In some embodiments, the plant stem may still be intact (i.e., the bast is not separated from the entire plant), requiring additional steps/iterations to remove additional gums. On the other hand, some bast fiber sources may have been partially treated ("impregnated") and require less aggressive treatment, allowing one or more steps to be omitted. A particular quality of material may also be desired due to the variable control available for the process.

The effluent of the degumming process may be the following solutions and mixtures: gums, their partially oxidized intermediates, and their oxidation by-products, residual cellulose fibers lost due to agitation, and inorganic salts, residual reagents, detergents, and chelating agents. Post-treatment of the effluent includes additional oxidation (by addition of oxidant and/or generation of oxidant in situ) or biological activity, in accordance with standard municipal water treatment protocols. Residual fiber, lignin and sulfonated lignin can be recovered from the effluent as marketable material. The suitable, detoxified effluent may be used as a nutritional additive to agricultural soils. Inorganic ions may be added to the effluent to adjust the ionic ratio and salinity to match the ionic ratio and salinity of the surface water into which the effluent is to be discharged. The alkalinity or acidity of the effluent may be neutralized by titration with a suitable acid or base.

The fibers obtained by the above process are high quality, discrete, soft, spinnable fibers. Bast fibers are sufficiently free of lignin, pectin, and hemicellulose so that the fibers can be processed in conventional textile machinery. Such processing may include: manufacturing yarns by spinning, weaving, felting; and nonwoven fabrics made, for example, by needle punching.

The bast fibers may remain green. The color can be determined by extracting the bast fibres into a solvent, showing a photometric absorption spectrum indicative of the general chlorophyll pigments (chlorophyll a, b and c). Such as in Jeffrey and Humphrey, "New Spectrophotometric Equations for Determining chlorophenyls a, b, c₁、c₂The data from the wavelengths 750, 664, 647 and 630nm can be used to calculate chlorophyll concentration directly from the appropriate absorption spectra, as described in the high her Plants, Algae and Natural Phytoplankton ", biochem. For example, a 500mg sample of green colored, degummed, spinnable hemp fiber produced according to an embodiment of the method is soaked in 100mL of deionized water for 12 hours and filtered through a 0.45 μm super membrane. Data from absorption spectra according to Jeffrey and Humphrey (1975) show that the total chlorophyll in the extract is 1.6mg/L, corresponding to at least 0.03% by mass of chlorophyll in the fiber sample. The following results were obtained by evaluation using the methods of Jeffrey and Humphrey (1975):

wavelength (nm)	750	664	647	630
					Absorption of	0.015	0.047	0.059	0.058

When the bast fiber source is treated without bleaching or oxidation, the production of potentially toxic byproducts is substantially eliminated and the green color can be retained.

Figure 1 is a black and white photograph of four samples. From left to right, these samples are:

original green hemp (unglued)

Degummed hemp fibre, which shows a slight green colour remaining (actual sample for chlorophyll extraction, for UV-VIS scanning)

Degummed fibres (different kinds-the original fibres are green) are slightly dark green

Degummed fibre-no green (original fibre not green)

Certain modifications and improvements will occur to those skilled in the art upon a reading of the foregoing description. For example, the methods disclosed herein are not limited to the above order. In certain embodiments, the above steps may be omitted, repeated, combined, or performed in a different order. For example, limited resources may require combining steps, or reusing effluent from one step in another step. In some embodiments, the sequence of steps, parameters, and iterations can be modified to enhance or attenuate the properties or composition of a particular fiber, or to unify the properties of the final product relative to the untreated bast. It will be understood that all such modifications and improvements have been omitted for the sake of brevity and readability, but are properly within the scope of the appended claims.

Claims

1. A method for degumming bast fibers, the method comprising: immersing a source of bast fibers in an aqueous solution; and varying the ion concentration of the aqueous solution in which the bast fiber source is immersed such that the varying ion concentration of the solution applies a varying interstitial pressure within the bast fiber source to assist in releasing pectin from the cellulose fibers in the bast fiber source.

2. The method of claim 1, wherein varying the ionic concentration of the solution has an effect selected from the group consisting of: delivering an agent to the source of bast fibers; scouring pectin and reacted byproducts from the bast fibers; imparting structural stress on the source of bast fibers; increasing the surface area of the gum as a reaction substrate; separating the bast fibers free of gums; and more than one of them.

3. The method of claim 1, wherein the bast fiber source is soaked in an ionic solution without electrolyzing the ionic solution.

4. The method of claim 1, wherein the ionic solution is a saline solution having a concentration in the range of less than 1 to about 200 thousandths.

5. The method of claim 4, comprising varying the ion concentration of a water-soaking solution in which the bast fiber source is not soaked.

6. The method of claim 1, wherein submerging the source of bast fibers comprises soaking the source of bast fibers in seawater.

7. The method of claim 1, wherein submerging the bast fiber source comprises soaking the bast fiber source in brackish water.

8. The method of claim 5, wherein varying the concentration of the aqueous solution comprises exposing the bast fiber source to water having a salinity that varies over time.

9. The method of claim 1, comprising: soaking the bast fiber source in a sulfur solution to sulfonate lignin for removal from bast fibers in the bast fiber source.

10. The method of claim 1, comprising: soaking the source of bast fibers in an oxidizing solution to remove lignin, pectin, and hemicellulose from the bast fibers in the source of bast fibers.

11. The method of claim 1, comprising: rinsing the source of bast fibers with water to further remove lignin, pectin, and hemicellulose from the bast fibers in the source of bast fibers.

12. The method of claim 1, comprising: rinsing the source of bast fibers with a detergent and water to further remove lignin, pectin, and hemicellulose from the bast fibers in the source of bast fibers.

13. The method of claim 1, wherein the source of bast fibers is hemp.

14. A method for removing lignin, pectin, and hemicellulose from cellulosic fibers in a hemp plant, the method comprising:

soaking the cannabis plant in a salt solution;

soaking the cannabis plant in a sulfur solution to sulfonate lignin for removal from the cannabis plant; and

rinsing the cannabis plant with an aqueous solution to further remove lignin, pectin, and hemicellulose and their partially oxidized intermediates from cellulose fibers in the cannabis plant.

15. The method of claim 14, comprising: soaking the hemp plant in an oxidizing solution to remove lignin, pectin, and hemicellulose from the cellulosic fibers.

16. The method of claim 15, wherein soaking the cannabis plant in an oxidizing solution comprises soaking the cannabis plant in a hydrogen peroxide solution.

17. The method of claim 16, comprising generating hydrogen peroxide as the oxidizing solution using electrolysis.

18. The method of claim 15, wherein soaking the cannabis plant in an oxidizing solution comprises: soaking the cannabis plant in the oxidizing solution at a pH between about 6 to about 12 and at a temperature below the boiling point of the oxidizing solution.

19. The method of claim 14, wherein soaking the cannabis plant in a sulfur solution comprises: soaking the cannabis plant in a sulfate solution having a pH between about 6 and about 12 and a temperature between about 20 ℃ and about 90 ℃.

20. The method of claim 14, wherein soaking the cannabis plant in a salt solution comprises: immersing the cannabis plant in water flushed through a tidal floor such that the salinity of the solution proximate to the cannabis plant varies as the tide fluctuates.

21. A bast fibre having a green colour which is sufficiently free of lignin, pectin and hemicellulose such that the fibre can be processed in conventional textile machinery.

22. The bast fiber of claim 21, wherein the bast fiber has a green color imparted to the bast fiber by chlorophyll.

23. The bast fiber of claim 21, wherein the treatment in conventional textile machinery is selected from the group consisting of: spinning; weaving; felting; making a nonwoven fabric, such as by needle punching; and more than one of them.

24. The bast fiber of claim 21, wherein the bast fiber is hemp.

25. The bast fiber of claim 21, wherein the green color of the bast fiber is extractable and has an absorption spectrum indicative of the presence of chlorophyll in the extract.