RU2786924C1 - Spinneret pack, method for heating of spinneret pack and process of production of lyocell - Google Patents

Abstract

FIELD: cellulose industry.

SUBSTANCE: invention relates to a spinneret pack and to a method for the production of lyocell, in which such a spinneret pack is used. The spinneret pack is made of a rectangular shape, with the ratio of sides of more than 2, and it contains at least a cover, a case of the spinneret pack, a distribution lattice, and, optionally, separate spinneret plates in the case of the spinneret pack. Moreover, at least the cover and/or the case of the spinneret pack are heated using vapor with a temperature in the range from 105 to 138°C and pressure from 1.0 to 4 bar, and the distribution lattice is made of material with specific heat conductivity of more than 50 W/(m*K), preferably 80 W/(m*K).

EFFECT: specified spinneret pack, especially with high throughput capacity and high speed, provides proper uniformity of elementary threads.

14 cl, 1 ex, 1 tbl, 2 dwg

Description

The field of technology to which the present invention relates

[0001] The present invention relates to a spunbond assembly and a method for heating a spunbond assembly used for spinning cellulosic filaments from a solution of cellulose in a solvent. The present invention also relates to a lyocell production process using such a spin pack.

Background of the Invention

[0002] Spunbond kits are used to produce fibers and filaments of various chemical natures, including cellulose-derived fibers and filaments. One example of such a spunbond assembly is a spunbond assembly which is used in the lyocell production process, such as a spunbond assembly comprising a plurality of spunbond plates, each of which contains a plurality of holes for spinning filaments, and the spunbond plates are arranged in a four-sided housing surrounding them on all sides. sides. Such a spinneret assembly is known, for example, from EP-A-0756025 or from EP-A-0700456.

[0003] Another example is the spin pack disclosed in WO 03/014429. This document discloses a spunbond assembly with a plurality of flat perforated metal plates each containing a plurality of holes for spinning filaments. The perforated plates in this case are mounted on all sides in a section of the stainless steel body. These spunbond assemblies can, for example, be used to produce lyocell fibers and filaments.

[0004] Prior to spinning, the cellulosic feedstock for the lyocell process is known to be dissolved in an appropriate solvent at an elevated temperature, typically from about 70 to 130° C., to form a spinning mass. This solution, after optional additional process steps, for example, to remove impurities and ensure a high degree of uniformity, is then sent to a spunbond set to obtain fibers and filaments. At this stage of the production process, it is necessary to control the temperature distribution in the spinning mass, since temperature fluctuations in the spinning mass can lead to undesirable deviations in the resulting fibers and filaments. While such variation may not be critical in the production of staple fibers, variations in the resulting filaments result in inhomogeneities in the resulting filament yarn that adversely affect the continued use of the filament yarn.

[0005] Thus, for the production of filaments, it is important to ensure proper temperature control so that any changes in the temperature of the spunbond are within the smallest possible range. In this context, the shape of the spin pack is an important factor to consider.

[0006] In general, it is possible to achieve negligible temperature fluctuations in the spinning mass in round spunbond assemblies (with an aspect ratio of 1) or spunbond assemblies having an aspect ratio close to 1 (square spunbond assemblies). One example of a round die set is disclosed in CN 205241867 U. Another example is provided in US 3130448. In these cases it is sufficient to heat the die set with hot water or by means of electrical heating elements. However, when using spin packs with an aspect ratio greater than 2, such as the spin pack disclosed in WO 03/14429 described above, problems arose.

[0007] However, these types of spunbond kits have proven to be of commercial importance, in particular for high-speed filament production, as they allow the production of a large number of filaments (by using multiple spunbond plates in a spunbond kit body) while making optimum use of the housing capacity (in particular , for rectangular cases). However, the incentive to use such spunbond kits comes from the disadvantage that, in order to obtain filaments, in which the filament property spread must be as small as possible to ensure high product quality, the necessary temperature control and regulation in the spunbond kit is no longer possible when using hot water or electrical heating means. The requirements for the uniformity of the filaments are such that the variation in linear density within a given batch of filaments must be within +/-5%, preferably within +/- 2.5%.

Purpose of the invention

[0008] Accordingly, it is an object of the present invention to provide a method for providing the necessary linear density in a spinning kit for spinning cellulosic filaments from a solution of cellulose in a solvent, said spinning kit, especially at high throughput and high speed, provides proper uniformity of filaments and lessen the problems associated with prior art spunbond assemblies.

Brief summary of the present invention

[0009] Unexpectedly, this problem is solved by the spunbond kit according to item 1, the method for providing temperature control of the spinning mass in the spunbond kit according to item 4, and the method for producing lyocell filaments according to item 5. Preferred embodiments are given in the dependent claims, as well as in the following description .

Description of figures

[0010] The present invention is further described with reference to the accompanying drawings, in which Fig. 1 schematically shows a spunbond block providing an embodiment of a spunbond kit according to the present invention in section, and Fig. 2 schematically shows an embodiment of a spunbond kit according to the present invention in top view.

Detailed disclosure of the present invention

[0011] In accordance with the present invention, the term "spunbond kit" is used to refer to the part of the apparatus for producing lyocell, which provides for the formation of a spinning mass or a spinning solution to obtain filaments, and which, in particular, contains a body of a spunbond kit, and optionally separate spunbond the plates are located in the housing, and a cover covering the housing of the spunbond assembly to form a space into which the spinning mass/solution is introduced before the formation of the filaments. In the context of the present invention, the terms "die set", "die block", etc. can be used interchangeably. The aspect ratio, which is an integral part of the definition of the spunbond assembly according to the present invention, however, refers to the aspect ratio of the portion of the spunbond assembly that forms the spunbond section of the spunbond assembly (ie, the portion that defines the area through which the filaments are extruded).

[0012] In the framework of the present invention, the production of lyocell filaments begins with the preparation of a spinning solution or spinning mass by dissolving cellulose in a solvent. The preferred solvent used in the preparation of lyocell filaments is a tertiary amine N-oxide and optionally water mixed with it. A solution of cellulose in tertiary amine N-oxide and optionally water is then hot extruded by a spinneret kit and shaped (molded) during the extrusion process. For the production of filaments, in particular the high-speed production of filaments, proper control of the temperature of the spinning mass is required. Such temperature control should ensure that the spinning mass exhibits only a slight temperature fluctuation, so that in the filaments thus obtained there is no unfavorable deviation in the properties of the filaments, in particular the linear density of the filaments, which could have a negative effect on the properties of the final product (such like yarn from elementary filaments).

As indicated above, this problem is particularly relevant when using die assemblies that may contain multiple filament extrusion die plates and are generally rectangular in shape with an aspect ratio greater than 2. The present invention as set forth in the claims and as further described herein , solves these problems by using steam to heat the spunbond assembly, thereby ensuring the necessary uniformity of the temperature profile of the spinning mass before exiting the spinning holes.

[0013] In accordance with the principles of the present invention, a spunbond assembly for producing multiple filaments, preferably a spunbond assembly comprising a plurality of spunbond plates arranged in a rectangular body, has an aspect ratio greater than 2. By conducting a series of tests with spunbond assemblies with different aspect ratios, it was it has been proven that a spunbond assembly can have aspect ratios of up to 10 or more, such as 12 or more and even 15 or more. If the spin pack is suitable for providing heating of the spinning stock in the spin pack by means of steam, preferably by providing channels, which are preferably micro-channels in the cover of the spin pack and/or the body of the spin pack, for uniform heating of the spin pack by supplying steam to these channels can be the required homogeneity was ensured in the production of elementary filaments.

Examples of providing steam heating are providing channels and microchannels (1 mm diameter or more) in the die set body, die plates or even closer to individual holes, for example by providing channels in close proximity to individual holes. If these channels can be provided in the appropriate part of the spinneret set without compromising mechanical integrity, then such channels can be provided. As a rule, the lid is not heated by introducing steam into the channels, but by providing the lid with suitable means to provide steam heating of the main parts of its inner surface, for example, through double-walled parts and heating jackets.

[0014] Reference is now made to Figures 1 and 2 depicting the present invention. Figure 1 shows a spunbond kit with an inlet 1 for a spinning solution. The spinning solution is fed into the center of the heated upper part 2 (cover) of the spinning unit. In accordance with one embodiment of the present invention, means are provided in at least this cover to allow steam heating of the housing to control the temperature of the spinning mass. A wire mesh 3 is connected to the cover 2, which is located on the distribution grid 4.

The four-sided die plates 5 are located in the body 7 of the die set, which, again according to one embodiment of the present invention, can preferably be heated by means of steam. The spunbond plates are separated from each other by sections 6. These sections 6 at the same time serve as the reinforcement of the distribution grid 4. According to the present invention, it is also preferable if these sections are connected to the body of the spunbond set and, in addition, it is preferable if these sections also suitable for steam heating.

[0015] Figure 2 shows a top view of the body 7 of the spunbond set and the spunbond plates 5. In addition, rows 8 of holes for spinning filaments and columns 9 of these holes of the spunbond set are shown. Lines 7a and 7b define the area available for actual spinning of the filaments and define the aspect ratio accordingly.

[0016] As stated above, it has been found effective if the die set allows for steam heating of the die set cover or die set body, but also steam heating adjacent to the individual die plates as well as the cover, for example by providing channels for steam heating , also inside the body in which the individual die plates are located (the die set body), or, if present, also in any parts of the die set body forming separate die plate bodies in the larger die set body (as a result of which each die plate is surrounded by a separate body, which can be advantageous in terms of pressure resistance of the entire construction of the die set, i.e. sections (6)).

[0017] Surprisingly, it has been found that by using steam as the heating medium, a very uniform temperature within the spinning mass can be achieved, resulting in uniform filaments.

[0018] the Term "steam" in the context of this document refers to water in the gaseous phase, and preferably means dry steam (ie, steam containing no water droplets) and supercritical steam. The steam temperature is preferably in the range of 105 to 138°C, preferably 110 to 130°C, at a pressure of 1.0 to 4 bar, preferably 1.2 to 3.8 bar, more preferably 1.5 to 3 .4 bar (i.e. not low pressure steam, but overpressure steam, preferably from 0.2 to 2.8, in particular from 0.5 to 2.4 bar). Preferably the steam is saturated steam. As shown in particular in the examples, an increase in the uniformity of the resulting filaments can surprisingly be achieved by using excess pressure.

[0019] The present invention, of course, also provides for a combination of types of heating, such as steam heating of the lid and electric heating of the body of the spinneret set, etc. If the spin pack used in accordance with the present invention provides for the possibility of steam heating at least the cover, you can use any combination of ways to provide heating.

[0020] The individual parts of the spunbond kit can be made from common materials used in the art, such as (stainless) steel. Since it is an object of the present invention to provide adequate temperature control (including, in particular, satisfactory heat transfer), materials that provide satisfactory heat transfer are preferred for the manufacture of the respective parts of the spunbond assembly.

[0021] The type and shape of the individual die plates are not critical, for example, those disclosed in WO 03/014429 can be used. Likewise, the number of die plates disposed in the body of the multi-die plate set is generally not limited. However, for the die sets according to the present invention, it is preferred that up to 100, preferably 30 to 60 die plates are located in the housing. The number of holes in the die plates is also not limited. However, it is generally preferred that the individual spunbond plates, in the case of the claimed spunbond assemblies, comprise 3 to 1000, preferably 20 to 300, more preferably 30 to 120 filament spinning holes.

[0022] The present invention in a preferred embodiment provides a spin pack that includes a steam-heated cover, a mesh nozzle, a distributing grid, and a spin pack (a spin pack body and optional separate die plates located in the build if the build is not already a spinning orifice for complex spinning). threads) according to the present invention, with a certain aspect ratio. Preferably, only one spinning pump supplies material to the spinneret block, i. e. the supply of the cellulose solution to the spinneret block is carried out by one pump. Each spinneret plate in a spinneret set in this case corresponds to one yarn or a multifilament yarn consisting of several filaments obtained from several spinning holes in this spinneret plate.

[0023] As a rule, the spinning mass (spinning solution) is filtered before moving to the spinning block. In the filtration process, candle filters, such as metal wool filters with a filtration fineness of 5 to 50 pm, have proven themselves well. Other media such as textile or fabric filters (sheets, nets, etc.) may also be used, provided that the fineness of the filtration is appropriate for the lyocell process. Candle filters are preferred. The preparation of cellulosic dope solutions in suitable solvents, for example tertiary amine N-oxide and optionally water, is known to those skilled in the art and is described, for example, in WO 98/06754 and the literature cited therein, so it will not be further described in this document.

[0024] Before the spinning solution reaches the spin pack, it advantageously passes through a mesh packing, which may, for example, be made of a metal woven fabric with a filtration rating of 15 to 50 pm. This mesh nozzle is located directly on the distribution grid, followed by the actual spunbond set, which consists of the above-described body and spunbond plates. The spunbond plates are preferably welded to the housing. The die block, for example, is made of high quality stainless steel.

[0025] The steam-heated lid of the spin pack is designed to provide uniform distribution of the dope over the entire length and width of the spin pack. In this process, the dope may be fed into the center of the lid, for example by means of a flexible metal tube or a metal channel. Preferably, they can be heated, for example, by providing heating jackets or double-walled structures that allow a heating medium to be supplied. Suitable examples are flexible double-walled tubes which allow, for example, heating by means of water or steam. The volume of the lid is preferably kept small, since the dope at elevated temperatures and long holding times tends to decompose. On the other hand, the holding time must be long enough to keep the dope at a constant temperature throughout its length and width. Thus, a high uniformity of the dope flow is ensured. Thus, the same amount of cellulose solution enters each hole in the spinneret plate, and the resulting filaments or filaments have a very high uniformity. In this regard, as already noted, it is preferable if not only the lid can be heated with steam, but also the body of the die set, including the areas provided for attaching individual die plates.

[0026] One of ordinary skill in the art is able to determine cap dimensions by simple experimentation and appropriate rheological calculations. Under the cover there is usually a distribution grid on which a wire mesh is located. The wire mesh or mesh packing is intended for final filtration before the spin pack and protects the relatively fine spinning holes in the spin plates from contamination. The filament spinning holes preferably have a diameter of 30 to 200 pm, more preferably 60 to 130 pm. In addition, the drop in flow pressure caused by the wire mesh serves to increase the uniformity of the spinning dope in terms of pressure, temperature and uniformity along the length and width of the entire spinneret assembly. The distribution grid also serves to ensure uniformity of the spinning dope in terms of pressure, temperature and uniformity along the length and width of the entire spinneret set, as well as to support the wire mesh.

[0027] According to a preferred embodiment, the distribution grid is made of a material with high thermal conductivity. In contrast to the commonly used distribution grids or support plates, by using materials with high thermal conductivity, the temperature of the spinning dope can be made even at right angles (transverse) to the direction of flow and thus in all spinning positions. In this case, it is preferable to use materials for the distribution grid whose thermal conductivity exceeds about 50 W/(m*K), preferably about 80 W/(m*K). Examples of such materials are silicon carbides (approximately 100 W/(m*K)).

[0028] As mentioned above, the die plates are usually individually welded to the body. The die plates of the die set according to the present invention are preferably flat and have a thickness in this case of 1 to 3 mm, preferably about 1.5 to 2 mm, and are designed for pressures above about 60 bar.

[0029] Due to the uniform distribution of heat in the spin pack according to the present invention, as well as in the spin pack that contains this spin pack, it is possible to produce a large number of cellulosic multifilament yarns very economically with both good quality and process stability. This is especially true at a filament spinning speed of more than 500 m/min, preferably more than 800 m/min. In principle, there are no restrictions on the achievable spinning speeds. Even at speeds of 1500-2000 m/min very good quality filaments are obtained.

[0030] While the present invention has been described above primarily in the context of a steam-heated spin pack/spin pack, one skilled in the art will appreciate that this description also applies to the claimed process for heating the spin pack, as well as the claimed process for producing lyocell filaments. . In particular, in connection with the production of lyocell filaments, one skilled in the art will appreciate that by using steam heating as described herein, improvements can be achieved, in particular with regard to the uniformity of the resulting lyocell filaments, an improvement that is not disclosed. and not proposed in the prior art. The method for producing lyocell filaments according to the present invention generally includes the steps described in paragraphs [0023] and [0024] as well as the usual preparation steps for obtaining a spinning mass/solution in accordance with the process for obtaining lyocell. Spinning is carried out in a typical manner, often using an air gap between the spin pack and the coagulation bath. Typical subsequent steps include washing and post-spinning treatments (application of filament surface treatments, etc.) as well as drying and winding steps.

Examples

[0031] Lyocell filaments were produced using identical spinning solutions under standard conditions, using spin packs with different aspect ratios, as well as different means of heating the spin pack (heating with water (118°C) or steam (118°C, 1, 9 bar), the heated areas of the die set/die block were the lid and body of the die set). The resulting filaments were evaluated by the linear density of the filaments (average, as well as the minimum and maximum linear density), and the standard deviations were calculated. In the context of the present invention, a standard deviation (STD) of 0.15 or less is considered acceptable, with STD values of less than 0.15, in particular 0.1 or less, being preferred.

[0032] It has been found that for spunbond assemblies with a circular shape (diameter of 50 cm or more), as well as spunbond assemblies having an aspect ratio of less than 2, satisfactory filaments can be obtained, with STD values of approximately 0.15, even when water is used. as a heating agent.

[0033] Using rectangular spunbonds with aspect ratios of 12 and 15, respectively, water heating has produced filaments with STD values greater than 0.15, and in some embodiments, 0.2 or greater. In contrast, under identical conditions, steam heating of the spunbond assembly produced filaments with STD values less than 0.15, in some embodiments even less than 0.1.

[0034] Additional experiments were carried out in accordance with the table below. The values in the columns °C and bar define the temperature of the heating medium used and, in the case of steam, the pressure which, at a given temperature, is necessary to obtain this temperature in saturated steam.

The results again confirm the concept of the present invention, namely that when using steam heating, the uniformity of the obtained filaments is significantly increased for rectangular spunbond assemblies with a certain aspect ratio. Even when both the lid and the body of the spinneret set are heated with water, the uniformity does not reach the level achieved with steam heating. These results also confirm that STD values of 0.14 or less can be achieved in accordance with the present invention, while water heating provides filament uniformity corresponding to STD values of 0.15 or higher.

[0035] Accordingly, the present invention provides a means for ensuring linear density uniformity by controlling the temperature in the spin pack using steam heating.

Claims (20)

1. A spunbond set capable of steam heating, characterized by a rectangular shape with an aspect ratio of more than 2 and containing at least a cover, a spunbond set body, a distribution grid and optionally separate spunbond plates in the spunbond set body, the distribution grid being made of a material with specific with a thermal conductivity above 50 W/(m*K), preferably 80 W/(m*K), at least the lid and/or body of the spinneret set are heated with steam at a temperature in the range of 105 to 138°C and at a pressure of 1 .0 to 4 bar. 2. A spunbond set according to claim 1, wherein the lid and body of the spunbond set are heated with steam. 3. A spunbond kit according to claim 1 or 2, wherein the spunbond kit further comprises additional means for heating other than steam heating. 4. A spunbond set according to any one of the preceding claims, wherein the spunbond set has an aspect ratio between 5 and 25. 5. A spinneret set according to any one of the preceding claims, using steam having a pressure of 1.0 to 3.4 bar. 6. The spunbond set according to any one of the preceding claims, wherein the lid and body of the spunbond set are made of stainless steel. 7. A spunbond kit according to any one of the preceding claims, wherein the distribution grid is configured to be heated with steam. 8. The die set according to any of the preceding claims, wherein the die set is a die set with multiple die plates, the body of the die set comprising portions that are configured to be heated by steam. 9. A method for producing lyocell filaments, including: preparation of a spinning solution by dissolving cellulose in a solvent, feeding the spinning solution into the spinning block, hot extrusion using a die set according to any one of paragraphs. 1-3, wherein the spinneret set is heated with steam at a temperature in the range of 105 to 138°C and at a pressure of 1.0 to 4 bar, spinning of elementary filaments, washing and processing after spinning, drying and winding lyocell filaments. 10. The method according to claim 9, in which the spunbond set is characterized by an aspect ratio of 5 to 25. 11. The method according to paragraphs. 9-10, which use steam, characterized by a pressure of 0.2 to 3.4 bar. 12. The method according to paragraphs. 9-11, in which the cover and body of the spinneret set are made of stainless steel. 13. The method according to paragraphs. 9-12, in which the spinneret block contains a distribution grid, and preferably the distribution grid is made with the possibility of heating with steam. 14. The method according to paragraphs. 9-13, in which the die set is a die set with several die plates, and the body of the die set contains sections that are made with the possibility of steam heating.

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