CN1184364C - Preparation process of spinning dope for producing cellulose fiber by solvent method - Google Patents

Abstract

The preparing invention relates to a preparation technology for producing a spinning stock solution of cellulose fibers by a solvent method, which is characterized in that fiber powder crushed by a pulp crusher is dried for 6 to 12h under the conditions that the vacuum degree is from-9*10<4> to-5*10<4>Pa and a temperature is from 30 to 50 DEG C; the water content of the powder is from 2% to 4%; a water solution of N-methyl-morpholine oxide (NMMO) is treated by inspissation under an alkali pressure condition, and the water content of the solution is equal to or smaller than 15%; the powder and NMMO are stirred for 10 to 30 min in a mixer in certain proportion at 70 90 DEG C to form a yellowish pasty substance; the pasty substance is fed in a double-screw extruder of which the screw length-diameter ratio is from 1:42 to 1:52 for dissolution and deaeration for 3 to 15 min; and then the produced maple transparent solution can be used for spinning. By adopting the technology, not only the dissolution time is shortened, but also the mixing and the dissolution of materials are sufficient. The present invention achieves the purpose of energy saving, high efficiency, degradation reduction, and improvement of the quality of spinning stock solutions.

Description

Preparation process of spinning dope for producing cellulose fiber by solvent method

technical field

The invention relates to a preparation process of a spinning stock solution for producing cellulose fiber by a solvent method in chemical fiber manufacturing industry. The fiber prepared from the spinning stock solution is widely used in industrial textiles and textiles for decorative clothing.

Background technique

Because cellulose fiber products have good hygroscopicity and moisture permeability, are comfortable to wear, and are rich in raw materials, product waste can be naturally degraded and decomposed into carbon dioxide and water by enzymes. Therefore, the production of this fiber material has attracted much attention in recent years. The traditional cellulose fiber is mainly produced by the viscose route, which uses carbon disulfide and a large amount of acid and alkali, which causes serious pollution to the environment, and the wet strength of the obtained viscose fiber is low. Fiber development.

As early as the 1930s, it was proposed that tertiary amine oxides could be used to directly dissolve cellulose to prepare fibers, and thus formed a basic patent (USP-2,179,181). Since the 1970s, Courtaulds and Lenzing have done a lot of research in this field and applied for hundreds of patents, among which EP-A-0553070, EP-A-0356419, DE-A-2913589, WO93/ 19230, WO95/04173, DD-A-218121, EP-A-0574870, AT-B-397392, GB-A-1,017,855, WO92/14871, WO92/07124, DE-A-4219658, WO96/18760, US- A-4,246,221, USP-2,179,181, and Chinese patent applications 96197127, 96191362, 96191361, 95193763, 95193716, 94192192, 94192048, 98801167, 98800540, 97190439, 19619334, etc. In the above-mentioned patents, thin-film evaporators are mostly used to dissolve cellulose. There is also a film extrusion machine (DE-OS-2011493) manufactured by Buss AG, Switzerland. In order to save energy and increase output, each patent proposes different devices and processes to improve the efficiency of cellulose dissolution, but these devices are relatively complicated. Such as: the dissolving device described in WO94/28217 is a large horizontal cylinder with a rotor inside and stirring units arranged along the shaft. The device has a complex structure and is inconvenient to operate. It is also suggested to prefabricate the granules of cellulose mixed with solvent before dissolving (USP 4,211,579).

Classifying all patents, it can be considered that the dissolution methods are divided into two categories:

1. Indirect dissolution method. The cellulose is swollen in NMMO with a water content greater than 22%. After the cellulose is fully swollen, the excessive water is sucked out under vacuum while raising the temperature, so that the cellulose finally dissolves.

2. Direct dissolution method. Control the moisture in NMMO below 15%, so that it can be directly mixed with cellulose, and can be quickly dissolved by raising the temperature.

A large number of patents fall into category 1. Type 1 dissolvers are easy to scale up and have good dissolution quality, but the residence time of the solvent in the dissolver is often longer, which makes NMMO and cellulose easy to degrade, and at the same time, a large amount of solvent-containing cellulose exists at high temperatures. big security risk.

In the second type of direct dissolution method, the easiest method is the twin-screw method.

Korea Institute of Science and Technology proposed a patent (WO97/47790) in 1996, utilizing twin screws to dissolve cellulose. In this method, the twin-screw used is not specially modified, and the cellulose and molten NMMO are injected into the twin-screw in different regions. Although this method greatly simplifies the entire dissolution process, greatly shortens the dissolution time, and reduces material storage, it has special requirements for cellulose raw material particles. Even so, the spinning solution prepared by this method often contains Gel generation that is not conducive to spinning.

Although also mentioned twin-screw in the patent (application number 97107819.X) applied by domestic Yibin City Chemical Fiber Factory, the effect of its twin-screw is not clearly stated. Judging from the claims of the application, the cellulose dissolving time needs to be 6-12 hours, which shows that the twin-screw used in it does not play a dissolving role but only plays a transporting role. Moreover, the dissolving time of 6-12 hours not only reduces the production efficiency, but also easily causes the degradation of cellulose and solvent.

Contents of the invention

The problem to be solved by the present invention is to provide a direct dissolution method that can make the preparation of spinning dope more efficient and more stable in quality.

In order to solve this problem, the following technical solutions are adopted:

1. The cellulose wood pulp or cotton pulp with a degree of polymerization (DP) of 400 to 1000 is pulverized into cellulose powder with a pulp crusher of a common viscose fiber factory. The powder is dried at a vacuum degree of -9×10 ⁴ ~-5×10 ⁴ Pa and 30-50°C for 6-12 hours, so that the moisture content reaches 2%-4%;

The aqueous solution of N-methylmorpholine oxide (NMMO) was evaporated under reduced pressure to make the water content equal to or less than 15%.

Mix the above pulverized powder and NMMO aqueous solution in a certain proportion in a mixer with a stirrer, and stir at 70-90°C for 10-30 minutes until a light yellow paste is formed. The mixing ratio of powder and NMMO is the weight ratio 7:93～15:85.

2. Make the following corrections to the general high-speed co-rotating reactive twin-screw extruder: (A) Close the two vacuum ports. (B) Increase the aspect ratio to 1:42 to 1:52. The one-way transfer of materials between the two screws of the co-rotating twin-screws is used to complete the temperature rise of the materials (to make the temperature reach the control temperature), transportation, full mixing and degassing. And use its self-cleaning ability to achieve the plunger flow of materials. As the materials alternately flow in the two screw grooves, the materials are fully stirred and mixed. The increase of screw length-to-diameter ratio can make materials have more opportunities to mix and dissolve. In this mixing process, due to the continuous renewal of its surface, the volatile substances or water vapor in the material can be discharged, and the quality of the solution can be improved.

3. Feed the light yellow paste in the above-mentioned 1 into the twin-screw of the above-mentioned 2, control the temperature and speed of each zone of the twin-screw, and after 3-15 minutes of dissolution and defoaming, the formation temperature is 90-130°C and the viscosity is Light brown transparent solution with 400～1200Pa·s and refractive index of 1.480～1.488. The solution is pressurized by a booster pump, then enters a metering pump through a pre-filter, and is sprayed out from a spinneret with 1,000 to 6,000 holes. After solidification, washing, cutting, and drying, cellulose fibers can be obtained. The temperature control range of the twin-screw is 80-130°C: the temperature ranges of each zone are 80-120°C, 80-120°C, 85-125°C, 90-130°C; the speed range of the screw is 30-100r/min.

4. In order to obtain a spinning stock solution without bubbles, the pressure strength of the head of the extruder should be controlled at 295-785N/cm ² to ensure that the stock solution has sufficient defoaming.

The advantage of the present invention is that the spinning dope preparation process provided is based on the existing twin-screw extruder dissolving technology, and the twin-screw with increased aspect ratio not only only takes 3 to 15 minutes to dissolve the cellulose, but also saves It saves energy, reduces cost, and the device is very simple. More importantly, it strengthens the mixing and dissolving of materials in the twin-screw; and because the cellulose and solvent stay in the screw at high temperature for a short time, it can avoid or reduce the material The degradation phenomenon is beneficial to the recovery of the solvent and the improvement of the quality of the fiber. The present invention adds a mixer before the twin-screw, so that the dry cellulose powder and NMMO with a water content of 15% or less are fully mixed before entering the twin-screw, which is beneficial to the uniformity of the spinning stock solution and the spinning quality improvement.

Detailed ways

The wood pulp with a DP of 700 is pulverized by a common pulverizer in a viscose production plant, and dried under reduced pressure (to -7×10 ⁴ Pa) and 50°C for 6 hours, and the obtained pulp (ie, cellulose Powder) has a water content of 2%;

The NMMO aqueous solution was evaporated under reduced pressure to make the water content equal to 13% (that is, the concentration of NMMO was 87%).

Place 7.2kg of the above pulp and 82.8kg of 87% NMMO aqueous solution in a mixer with a stirrer, stir and blend at 80°C for 10min, and add 90g of propyl citrate before mixing to prevent oxidation ;

The blended material is continuously fed into a twin-screw extruder with a screw length-diameter ratio of 1:48 for dissolution. The pressure intensity at the head (namely the outlet) is controlled at 490N/cm ² , and a transparent and uniform spinning dope with a refractive index of 1.4840 can be obtained after 5 minutes, and its spinnability is good.

Claims (4)

1. the preparation technology of the spinning dope of cellulose fiber produced by solvent method, it is characterized in that: The cellulose wood pulp or cotton pulp with a degree of polymerization of 400-1000 is crushed into cellulose powder with an ordinary pulp mill, and the powder is placed in a vacuum of -9×10 ⁴ ～-5×10 ⁴ Pa and 30 Dry at ~50°C for 6-12 hours to make the moisture content reach 2%-4%; Concentrating the aqueous solution of N-methylmorpholine oxide under reduced pressure so that its water content is equal to or less than 15%; Mix the above-mentioned cellulose powder and N-methylmorpholine oxide aqueous solution in a weight ratio of 7:93 to 15:85 in a mixer with a stirrer, and stir at 70 to 90°C for 10 to 30 minutes until A light yellow paste formed. 2. The preparation process as claimed in claim 1, characterized in that the formed pale yellow paste is fed into two co-rotating reaction machines with closed vacuum ports and screw length-to-diameter ratios of 1:42 to 1:52. Dissolving and defoaming treatment in a twin-screw extruder for 3 to 15 minutes to generate a light brown transparent solution with a temperature of 90 to 130°C, a viscosity of 400 to 1200Pa·s, and a refractive index of 1.480 to 1.488. Spinning after pressurization, filtration and metering. 3. The preparation process according to claim 2, characterized in that the head pressure strength of the extruder is 295-785 N/cm ² . 4. The preparation process according to claim 2 or 3, characterized in that the temperature ranges of each zone of the twin-screw extruder are 80-120°C, 80-120°C, 85-125°C, 90-130°C.