Spinning solution for producing regenerated cellulosic material

Abstract

The invention relates to a spinning solution for producing a regenerated cellulosic material. The spinning solution has improved stability. The spinning solution comprises a cellulosic material, an aqueous alkaline solution and ammonium ions. The invention further relates to a method of producing a spinning solution. Furthermore, the invention relates to a method of producing a regenerated cellulosic material.

Description

Technical Field

[0001] This specification relates to a spinning solution for producing regenerated cellulose materials and a method for producing the spinning solution. It also relates to a method for producing regenerated cellulose materials. Background Technology

[0002] Regenerated cellulose materials refer to cellulose materials prepared by dissolving or suspending cellulose materials or converting cellulose materials into soluble cellulose derivatives, and then regenerating the cellulose materials into, for example, fibers (e.g., fibers for textile industry purposes) or films.

[0003] The long-term stability of alkaline spinning solutions containing dissolved or suspended cellulose materials can be challenging. Currently, spinning solution stability has only been achieved for 5 to 6 days. After this period, the cellulose material in the spinning solution forms a gel, thus preventing extrusion using the spinning solution. Therefore, improvements in the stability of spinning solutions are needed. Summary of the Invention

[0004] The purpose of this specification is to provide a novel spinning solution with improved stability for the production of regenerated cellulose materials suitable for applications such as textiles. The spinning solution comprises cellulose material, an aqueous alkaline solution, and ammonium ions. The ammonium ions act as a stabilizer to delay or even prevent gelation within the spinning solution.

[0005] The improved stability of the spinning solution provided by the addition of ammonium ions enables the production of larger volumes of spinning solution in a single batch, as it is not necessary to use all the prepared spinning solution immediately after preparation. Furthermore, the longer storage time achieved through improved stability represents a significant improvement in logistics.

[0006] Furthermore, a method for producing a spinning solution as described herein is provided. The method includes: providing an aqueous alkaline solution containing ammonium ions, cooling the aqueous alkaline solution containing ammonium ions to a lower temperature, and dissolving a cellulose material into the alkaline solution containing ammonium ions at a temperature of -30°C to 50°C to form a spinning solution.

[0007] Furthermore, a method for producing regenerated cellulose materials is provided. The method includes: providing a spinning solution as described herein, and extruding the spinning solution into a regeneration solution to form a regenerated cellulose material. Attached Figure Description

[0008] Figure 1 The graphs show the stability of the spinning solution for various samples. Detailed Implementation

[0009] This solution will be described in more detail below with reference to some implementation methods, but should not be regarded as a limitation.

[0010] In this specification and claims, unless otherwise stated, percentage values ​​relating to the amount of material are weight percentages (wt%). Thickness units expressed in micrometers correspond to µm. Temperature units expressed in degrees Celsius correspond to °C.

[0011] Cellulose is a polysaccharide composed of linear chains of hundreds to thousands of β(1→4)-linked D-glucose units. Cellulose is an important structural component of the primary cell walls of green plants, various forms of algae, and oomycetes. Natural cellulose is cellulose I, and its structure is I. α and I β Regenerated (i.e., artificial) cellulose is cellulose II. The conversion of cellulose I to cellulose II is irreversible.

[0012] Cellulose can be obtained from pulp. Pulp refers to lignocellulosic material separated from wood, fiber crops, waste paper, or rags by chemical and / or mechanical means. Wood and other plant materials used for pulping contain cellulose fibers, lignin, and hemicellulose. Raw materials for wood pulp can be derived from, for example, birch, bamboo, beech, eucalyptus, softwood (i.e., spruce or pine), maple, or aspen. Pulp can be pretreated. For example, pulp can be hydrolyzed.

[0013] Regenerated cellulose materials can be made from cellulose materials extracted from pulp. Alternatively or additionally, the cellulose material can be derived from, for example, hemp, flax, sisal, jute, kenaf, bamboo, agricultural fibers, or recycled fibers (e.g., recycled cotton and cotton lint). The cellulose material may or may not contain hemicellulose. The cellulose material is chemically dissolved to form a colloidal suspension, i.e., a spinning solution, which is then extruded, for example, into continuous filaments or films.

[0014] In the context of this specification, the term "spinning solution" refers to cellulose material or cellulose-like material in an aqueous alkaline solution, i.e., cellulose material or cellulose-like material in dissolved form. Spinning solution may also be called spinning dope. Spinning solutions are suitable for coagulating into regenerated cellulose-like materials (cellulose type II structure) in a regeneration solution.

[0015] In the context of this specification, the term "regenerated cellulose materials" includes fibers, filaments, films, cellulose beads, and 3D objects. The regenerated cellulose fibers / filaments disclosed herein are particularly suitable for use as cellulose textile fibers in the textile industry.

[0016] In the context of this specification, the term "extrusion" refers to the process / technique of forming an object with a fixed cross-sectional profile by pushing material through a die or nozzle with a desired cross-section. Extrusion also includes spinning, which is a special form of extrusion.

[0017] In the context of this specification, the terms "fiber," "filament," "short fiber," and "filament fiber" are used interchangeably to refer to natural or man-made materials whose length is significantly greater than their width. Cellulose fiber or cellulose-like fiber refers to fiber composed primarily of cellulose.

[0018] In the context of this specification, the term "regeneration solution" refers to a solution that causes cellulosic materials to coagulate or form into a desired shape or physical form. A regeneration solution may also be referred to as a regeneration bath, coagulation bath, or spinning bath.

[0019] Typically, methods for producing regenerated cellulose materials include: providing cellulose material and dissolving it in an aqueous alkaline solution, preferably at a lower temperature, to form a suspension. The process of forming the suspension can also be called a cold alkali process.

[0020] As described above, a suspension is formed as a result of the dissolution step. Specifically, the suspension can be a colloidal suspension. A colloidal suspension is a heterogeneous mixture in which one substance, consisting of microscopically dispersed insoluble particles, is suspended in another substance. In other words, a colloidal suspension consists of solid particles uniformly dispersed in a liquid. Therefore, as a result of the dissolution step, cellulose is uniformly dispersed in an aqueous alkaline solution.

[0021] The stability of spinning solutions, especially their long-term stability, is often a challenge. The stability of spinning solutions can be expressed using Brookfield viscosity. An increase in Brookfield viscosity is caused by the gelation of cellulose / cellulose-based materials. Spinning solutions with Brookfield viscosity values ​​higher than 6500 mPa·s are considered unstable or unsuitable for extrusion. In the context of this disclosure, Brookfield viscosity can be measured using a spindle with a range up to 10000 mPa·s (theoretical error ±100, measurement error ±147.87) at a temperature of 4 to 6 °C. The rotation speed is 100 rpm, and the measurement duration is 30 seconds. The spindle must be at least 2 cm away from the wall of the container holding the sample. The sample amount is 60 g to 200 g. The viscometer used can be a model “Brookfield digital viscometer DV1MRVMB0”.

[0022] This specification provides a spinning solution for producing regenerated cellulose materials, the spinning solution having improved stability. The spinning solution comprises cellulose material, an aqueous alkaline solution, and ammonium ions. The ammonium ions act as a stabilizer to delay or even prevent gelation within the spinning solution.

[0023] Ammonium ions are ideal for stabilizing spinning solutions because they are safe and inexpensive to use. Furthermore, they are soluble in alkaline aqueous conditions and in their salt forms. It is speculated that sufficiently large ammonium ions help keep the cellulose polymers separated in aqueous alkaline solutions, thereby delaying or preventing gel formation. In addition, ammonium cations can interact with deprotonated carboxylic acid groups (i.e., the carboxylate groups of cellulose under aqueous alkaline conditions). This may have an effect of enhancing the hydrophilicity of cellulose, thereby preventing hydrophobic interactions in the cellulose polymers.

[0024] Cellulose materials may include or consist of at least one of the following substances: cellulose pulp, pretreated cellulose pulp, hemp fiber, flax fiber, sisal fiber, jute fiber, kenaf fiber, bamboo fiber, agricultural fiber, and recycled fiber.

[0025] In order to dissolve the cellulose material in an aqueous alkaline solution, the degree of polymerization (DP) of the cellulose material is preferably at most 300, for example, 200 to 300.

[0026] The amount of cellulose material can be 5 to 15% of the weight of the spinning solution.

[0027] The aqueous alkaline solution may contain at least one of the following substances as an alkaline component: sodium hydroxide (NaOH), potassium hydroxide (KOH), or lithium hydroxide (LiOH). NaOH may be preferred over the more expensive KOH and LiOH. The amount of the alkaline component may be 5 to 10% by weight of the spinning solution.

[0028] Ammonium ions can be derived from water-soluble ammonium salts. These water-soluble ammonium salts can be any commercially available water-soluble ammonium salt. In one example, the water-soluble ammonium salt is at least one of the following: ammonium hydroxide (NH4OH), ammonium chloride (NH4Cl), ammonium bromide (NH4Br), ammonium iodide (NH4I), or ammonium nitrate (NH4NO3). The amount of water-soluble ammonium salt can be from 0.1 to 20% by weight of the spinning solution, for example, 0.1 to 10% by weight, or 0.1 to 5% by weight, or 0.1 to 1% by weight. When using ammonium hydroxide, the amount of alkaline component in the aqueous alkaline solution can be adjusted to keep the hydroxide concentration constant.

[0029] The spinning solution may also contain additives such as zinc oxide (ZnO), thiourea, and / or urea. The purpose of these additives is to improve the solubility / dispersion of cellulose in aqueous alkaline solutions. Urea can also be used to form cellulose carbamates. The amount of additives can be 0.1 to 3% by weight of the spinning solution.

[0030] For example, the spinning solution may contain 5 to 15% by weight of an alkaline component, 0.1 to 20% by weight of ammonium ions, 0.1 to 3% by weight of additives and 5 to 15% by weight of cellulose material.

[0031] In one specific example, the spinning solution may consist of 5 to 15% by weight of an alkaline component, 0.1 to 20% by weight of ammonium ions, 0.1 to 3% by weight of additives, 5 to 15% by weight of cellulose material, and water.

[0032] In another specific example, the spinning solution contains 5 to 10% by weight of NaOH, 0.1 to 0.5% by weight of ammonium hydroxide and / or ammonium chloride, 0.1 to 3% by weight of ZnO as an additive, and 5 to 15% by weight of cellulose material. The remainder of the spinning solution may consist of water.

[0033] The annual production capacity of spinning solutions can be, for example, 50,000 tons per year. The addition of ammonium ions to provide improved stability in the spinning solution allows for the production of larger volumes of spinning solution in a single batch, as it eliminates the need to use all the prepared spinning solution immediately after preparation. Furthermore, the longer storage time achieved through improved stability represents a significant improvement in logistics.

[0034] A method for producing a spinning solution includes providing an aqueous alkaline solution containing ammonium ions. The aqueous alkaline solution can be provided by dissolving an alkaline component in water to produce the aqueous alkaline solution, and subsequently dissolving ammonium ions in the aqueous alkaline solution. Alternatively, the ammonium ions can be dissolved in water before dissolving the alkaline component. Alternatively, the alkaline component and ammonium ions can be introduced into the water simultaneously. The method may further include dissolving an additive in the aqueous alkaline solution containing ammonium ions.

[0035] The aqueous alkaline solution containing ammonium ions is cooled to a low temperature, for example, to 0 to 15°C. Then, the cellulose material is dissolved in the aqueous alkaline solution containing ammonium ions at a temperature of -30°C to 50°C, or at a temperature of -30°C to 30°C, or at a temperature of -30°C to 15°C, or at a temperature of -30°C to 10°C, or at a temperature of -30°C to 5°C, preferably at a temperature of -15°C to 5°C, to produce a spinning solution. If the produced spinning solution is not immediately used for extrusion after production, it is preferably stored at a temperature of 0 to 10°C.

[0036] In the production of regenerated cellulose materials, the aforementioned spinning solution is extruded into a regeneration solution to form the regenerated cellulose material. The temperature of the spinning solution during extrusion can be 0 to 10°C, for example, 4 to 6°C. The regenerated cellulose material is formed by coagulating (i.e., regenerating) the extruded suspension in the regeneration solution. During coagulation, the cellulose in the spinning solution solidifies into the desired form of the regenerated cellulose material (i.e., fibers, filaments, films, cellulose beads, or 3D objects). The terms "coagulation" and "regeneration" can refer to the precipitation and / or crystallization of cellulose from a dissolved state. Cellulose can at least partially crystallize into cellulose II. Typically, the coagulated cellulose is in the form of cellulose II.

[0037] The regeneration solution can be an acidic, alkaline, or neutral aqueous solution. Only one regeneration solution can be used. Alternatively, a two-stage regeneration system can be used, comprising a first regeneration solution and a second regeneration solution. When only one regeneration solution is used, the regeneration solution is an acidic aqueous solution. In a two-stage regeneration system, the first regeneration solution can be, for example, a neutral or alkaline aqueous solution, in which case the second regeneration solution is an acidic aqueous solution.

[0038] Regenerated cellulose materials can be extracted with a self-regenerating solution for their desired applications (e.g., as textile fibers). Before use, regenerated cellulose materials can be washed and dried.

[0039] Example

[0040] The following experiments demonstrated the effect of ammonium ions on the stability of the spinning solution.

[0041] A reference spinning solution was prepared, consisting of 7 wt% cellulose material, 1.3 wt% ZnO, 7.8 wt% NaOH and 83.9 wt% water.

[0042] The spinning solution in Example 1 consisted of 7% cellulose material, 1.3% ZnO, 7.37% NaOH, 0.43% NH4OH and 83.9% water.

[0043] The spinning solution in Example 2 consisted of 7% cellulose material, 1.3% ZnO, 7.37% NaOH, 0.43% NH4Cl and 83.9% water.

[0044] Hydrolyzed slurry was used in all embodiments.

[0045] The prepared spinning solution was stored at approximately 6–8 °C. The stability of the spinning solution was studied by measuring its Brookfield viscosity daily at approximately 5–6 °C. Brookfield viscosity was measured using a DV1MRVMB0 digital Brookfield viscometer. Sample volumes ranged from 60 g to 200 g, with the rotor at least 2 cm away from the container wall containing the sample. A rotor with a range up to 10000 mPa·s (theoretical error ±100, measurement error ±147.87) was used. The rotation speed was 100 rpm, and the measurement duration was 30 seconds.

[0046] The graphs showing the stability of the spinning solution are as follows: Figure 1 As shown. The reference spinning solution showed stability for two days. On the third day, the Brookfield viscosity exceeded 7000 mPa·s, which was therefore too high for the extrusion process. The spinning solution according to Example 1, containing ammonium ions derived from ammonium hydroxide, showed good stability even up to the 23rd day. The Brookfield viscosity of the spinning solution according to Example 2, containing ammonium ions derived from ammonium chloride, showed stability up to the 10th day.

[0047] The results showed that adding ammonium ions to the spinning solution significantly improved its stability. Furthermore, the addition of ammonium ions did not affect the solubility of the cellulose material or the spinnability of the extrusion spinning solution.

Claims

1. A spinning solution for producing regenerated cellulose materials, wherein, - The spinning solution contains cellulose material, an aqueous alkaline solution, and ammonium ions; and - An aqueous alkaline solution contains at least one of the following substances as an alkaline component: sodium hydroxide, potassium hydroxide, or lithium hydroxide.

2. The spinning solution as described in claim 1, wherein, The amount of cellulose material is 5 to 15% of the weight of the spinning solution.

3. The spinning solution as described in claim 1 or 2, wherein, The amount of alkaline component is 5 to 10% of the weight of the spinning solution.

4. The spinning solution as described in any of the preceding claims, wherein, Ammonium ions originate from water-soluble ammonium salts.

5. The spinning solution as described in claim 4, wherein, Water-soluble ammonium salts are at least one of the following substances: ammonium hydroxide, ammonium chloride, ammonium bromide, ammonium iodide, or ammonium nitrate.

6. The spinning solution as described in claim 4 or 5, wherein, The amount of water-soluble ammonium salt is 0.1 to 20% of the weight of the spinning solution.

7. The spinning solution as described in any of the preceding claims, wherein, The spinning solution also contains zinc oxide, thiourea, and / or urea as additives.

8. A method for producing a spinning solution as described in any one of claims 1 to 7, the method comprising: - Provides an aqueous alkaline solution containing ammonium ions; - Cool the aqueous alkaline solution containing ammonium ions to a lower temperature; as well as - At a temperature of -30°C to 50°C, cellulose material is dissolved in an aqueous alkaline solution containing ammonium ions to form a spinning solution, wherein... - An aqueous alkaline solution contains at least one of the following substances as an alkaline component: sodium hydroxide, potassium hydroxide, or lithium hydroxide.

9. The method of claim 8, wherein, The method further includes: - Dissolve the additive in an aqueous alkaline solution containing ammonium ions.

10. A method for producing regenerated cellulose materials, the method comprising: - Provide a spinning solution as described in any one of claims 1 to 7; and - The spinning solution is extruded into the regeneration solution to form regenerated cellulose materials.

11. The method of claim 10, wherein, The temperature of the spinning solution during extrusion is 0 to 10°C.

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