A method for evaluating the spinnability of pulp for Tencel

Abstract

The present invention discloses a method for evaluating the spinnability of pulp for Tencel. The evaluation is carried out respectively from the dissolution performance, spinnability and strength performance of the pulp. By simulating the preparation process of Tencel fibers, qualitative and quantitative analysis is performed on the fiber strength after pulp dissolution, spinning jet and spinning, effectively connecting the pulp performance with the spinning process. The operation is simple and has good practical value.

Description

Technical Field

[0001] The present invention relates to a method for evaluating the spinnability of pulp for Tencel, and specifically to the technical field of Tencel fiber technology. Background Art

[0002] As an upgraded product of viscose fiber, Tencel fiber is a fiber produced by a solvent spinning method using dissolving pulp, cotton fiber, etc. as the main raw materials and N-methylmorpholine-N-oxide (NMMO) as the solvent. Since no chemical reagents such as carbon disulfide need to be added during production, no toxic and harmful wastewater, waste gas, and waste residue are generated, only NMMO is used as the solvent, and production is carried out by physical methods, and the fiber can be naturally degraded in the soil within 3 to 6 months. Therefore, Tencel fiber is called the "green fiber" of the 21st century.

[0003] Tencel fiber combines the advantages of natural fibers and synthetic fibers, has the moisture absorption and air permeability and comfort of cotton fiber, and at the same time, its strength performance is much higher than that of cotton and ordinary viscose fibers, approaching that of polyester fiber. Moreover, Tencel fiber also has a fibrillation effect, and can produce a surface effect similar to peach skin that cannot be obtained by conventional fibers. Based on the excellent natural fiber and synthetic fiber characteristics of Tencel fiber, a variety of high-value-added woven and knitted products have been developed and widely used in the fields of clothing, textiles, as well as industrial fields such as non-woven fabrics, industrial filter cloths, industrial yarns, and special papers.

[0004] The upstream of the Tencel fiber industry is mainly pulp such as wood pulp and bamboo pulp and solvents, and the downstream is the textile industry. Among them, the upstream product pulp is the key factor restricting the development of Tencel fiber. At present, the import dependence of pulp raw materials is high, and domestic pulp generally has problems such as a relatively low average quality level and general processing performance. Under the background of the trade war, import policies will gradually become stricter. Developing high-quality and low-cost domestic pulp products is the key to achieving a breakthrough in the production capacity of the Tencel fiber industry.

[0005] The influence of pulp on the production of Tencel fibers and product quality is mainly summarized in two aspects: one is the impurities contained in the pulp other than cellulose, such as hemicellulose, lignin, extractives, metal ions, etc. Most of these impurities have a negative impact. As the pulp enters the spinning solution system, they cannot be removed in the spinning solution filtration process and affect the spinnability of the spinning solution. At the same time, with the recycling of the solvent, the impurity concentration in the system continuously increases, which will also affect the solvent recovery. The other is the internal structure of the pulp, such as crystallinity, molecular weight distribution, etc., which affect its swelling effect in the NMMO solution system, and then affect the properties of the spinning solution. In terms of product quality evaluation, different from viscose fibers, there is no established evaluation system for the dissolution performance of Tencel fibers in China. Existing dissolution pulp indexes, such as alpha cellulose content, alkali solubility, extractives content, metal ion content, etc., cannot be used as the criteria for evaluating the quality of pulp for Tencel. Therefore, it is impossible to effectively connect the upstream pulp products of Tencel fibers with the downstream spinning performance. Therefore, it is necessary to establish a spinnability evaluation system for pulp for Tencel fibers, so as to refine and improve the existing pulp targeted, so as to meet the standards of pulp for Tencel. Summary of the Invention

[0006] Aiming at the problems existing in the existing evaluation system for pulp for Tencel fibers, the present invention provides a method for evaluating the spinnability of pulp for Tencel fibers. The method provided by the present invention can well combine the upstream pulp raw materials with the downstream spinning industry, and provide a reference for realizing the upgrading of pulp for Tencel fibers.

[0007] The present invention provides a method for evaluating the spinnability of pulp for Tencel, comprising the following steps:

[0008] (1) Evaluation of dissolution performance: Tear the pulp into small pieces, mix it with 50% NMMO solution in a certain proportion, and form an amber homogeneous spinning solution under reduced pressure distillation. Record the dissolution time, and observe the spinning solution with a polarized light microscope to check if there are undissolved fibers. The pulp with a shorter dissolution time and no undissolved fibers in the spinning solution is a better pulp.

[0009] (2) Evaluation of the spinnability of the spinning solution: For the homogeneous spinning solution prepared in step (1), under the steady-state shear flow mode, use a rheometer to measure the zero-shear viscosity, Newtonian index, viscous flow activation energy, and structural viscosity index of the spinning solution; the lower the zero-shear viscosity, the higher the Newtonian index, and the lower the viscous flow activation energy and structural viscosity index of the spinning solution of the pulp measured, the better the spinnability of the slurry and the easier the fiber formation.

[0010] (3) Evaluation of spinning strength performance: The uniform spinning solution prepared in step (1) is evenly coated on paper and placed in an oven to dry to a constant weight. Then, it is cut into standard sizes, and the strength of the paper samples is measured on a paper tensile strength tester. By comparing the tensile strengths of the paper samples under the same coating amount, the higher the measured strength, the better the performance of the pulp and the higher the strength of the spun fibers.

[0011] Preferably, the pulp in step (1) is one or more of hardwood pulp, softwood pulp, bamboo pulp, cotton pulp, hemp pulp, etc.

[0012] Preferably, the size of the small pieces of pulp in step (1) is 1 - 5 cm 2 ;

[0013] Preferably, the mixing ratio of the pulp in step (1) and the 50% NMMO solution is 1 - 10%.

[0014] Preferably, the vacuum distillation temperature in step (1) is 50 - 99 °C.

[0015] Preferably, the coating method in step (3) can be one or more of knife coating, rod coating, and curtain coating.

[0016] Preferably, the drying temperature in step (3) is 80 - 115 °C.

[0017] Preferably, the cut size in step (3) is 100 - 200 mm in length and 15 mm in width.

[0018] The characteristics of the present invention are as follows: The present invention simulates the preparation process of Tencel fibers, qualitatively and quantitatively analyzes the fiber strength after pulp dissolution, spinning, and spinning, effectively connects the pulp performance with the spinning process, is simple to operate, and has good practical value. Detailed implementation methods

[0019] To facilitate the understanding of the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0020] Example 1:

[0021] A method for evaluating the spinnability of pulp for Tencel, the method comprising the following steps:

[0022] (1) Evaluation of dissolution performance: Pulp A and pulp B are torn into small pieces with a size of about 1 cm 2 , mixed with the 50% NMMO solution at a ratio of 3%, and a amber-colored uniform spinning solution is formed at a vacuum distillation temperature of 95 °C. Record the dissolution time, and observe the spinning solution with a polarized light microscope to check if there are undissolved fibers.

[0023] (2) Spinnability evaluation of spinning solution: For the homogeneous spinning solutions A and B prepared in step (1), under the steady-state shear flow mode, use a rheometer to measure the zero-shear viscosity, Newtonian index, viscous flow activation energy, and structural viscosity index of the spinning solution;

[0024] (3) Spinning strength performance evaluation: The homogeneous spinning solutions A and B prepared in step (1) are evenly coated on printing paper and placed in an oven at 105 °C to dry to a constant weight. Then, it is cut into a standard size of 180 mm in length × 15 mm in width, and the strength of the paper sample is measured on a paper tensile strength tester, and the tensile strength of the paper sample under the same coating amount is compared;

[0025] Compare the spinning solutions A and B prepared in Example 1, and the results are shown in Table 1.

[0026]

[0027] It can be seen from Table 1 that a method for evaluating the spinnability of pulp for Tencel fibers provided by the present invention is used to evaluate pulps A and B, and among them, pulp A is superior to pulp B in terms of dissolution performance, spinnability, and strength performance.

[0028] The applicant declares that the present invention uses the above examples to illustrate the process parameters and process flow of the present invention, but the present invention is not limited to the above detailed process parameters and process flow, that is, it does not mean that the present invention must rely on the above detailed process parameters and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating the spinnability of pulp for Tencel, characterized in that, It includes the following steps: (1)Tear the pulp into small pieces, mix it with 50% NMMO solution in a certain proportion, and form a amber homogeneous spinning solution under reduced pressure distillation for standby; the pulp is any one of hardwood pulp, softwood pulp, bamboo pulp, cotton pulp, and ramie pulp, and the size of the pulp is 1-5 cm 2 , the temperature of reduced pressure distillation is 50-99 °C; record the dissolution time, and observe the spinning solution with a polarized light microscope to check whether there are undissolved fibers. The pulp with a shorter dissolution time and no undissolved fibers in the spinning solution is a better pulp; (2) Measuring the zero-shear viscosity, Newtonian index, viscous flow activation energy, and structural viscosity index of the spinning solution prepared in step (1) by a rheometer under a steady-state shear flow mode; the lower the zero-shear viscosity, the higher the Newtonian index, and the lower the viscous flow activation energy and structural viscosity index of the measured pulp spinning solution, the better the spinnability of the slurry and the easier the fiber formation; (3) Coating the spinning solution prepared in step (1) and quantitatively coating the paper strength performance; The operation method of coating is as follows: the uniform spinning solution prepared in step (1) is evenly coated on the paper, placed in an oven and dried to a constant weight, then cut into standard sizes, and the strength of the paper sample is measured on a paper tensile strength tester; the coating method is any one of blade coating, rod coating, and curtain coating, the drying temperature is 80-115°C, and the cut size is 100-200 mm in length and 15 mm in width; comparing the tensile strength of the paper samples under the same coating amount, the higher the measured strength, the better the performance of the pulp and the higher the strength of the spun fiber.

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