A method for preparing regenerated cellulose fiber using waste cotton products and fiber

Abstract

The present invention discloses a method for preparing regenerated cellulose fiber using old cotton products and the fiber, comprising: (1) pre-treating, alkali treating, washing, pressing and crushing the old cotton products in sequence to obtain alkali cellulose; (2) aging, yellowing and dissolving the alkali cellulose obtained in step (1) to obtain spinning dope; (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fiber; the alkali treatment comprises immersing the pre-treated old cotton products in a mixed solution containing alkali and a catalyst, and heating and keeping the mixture warm. The preparation method prepares the pre-treated old cotton products into alkali cellulose with a high alkali content by a shorter alkali treatment process, so as to facilitate the subsequent yellowing process to prepare more cellulose xanthate, and shorten the overall process while reducing the probability of side reactions.

Description

Technical Field

[0001] The invention belongs to the field of regenerated cellulose production, and in particular relates to a method for preparing regenerated cellulose fibers by utilizing old cotton products and the fibers. Background Art

[0002] Regenerated cellulose fiber has good moisture absorption, air permeability, easy dyeing, and low static electricity. The fabric is smooth and soft, has a silky feel, feels smooth, has excellent dyeing properties, and is not easy to fade. Short fibers can be spun pure or blended with other textile fibers. It is mainly used in various textiles, clothing, blanket decorations, etc. It is an indispensable raw material in human life.

[0003] The main preparation process of regenerated cellulose fiber is to use cotton linters, wood, bamboo and other plants as raw materials, and then go through the processes of cooking, beating, bleaching, sand removal, and papermaking to make pulp, and then go through the processes of impregnation, pressing, crushing, aging, yellowing, filtering, spinning, etc. The long production cycle is a major disadvantage of it, and shortening the production cycle is a problem that needs to be solved.

[0004] The main component of regenerated cellulose fiber is cellulose. Among the three plant raw materials mentioned above, cotton linter has the highest cellulose content, which is over 90%, while the cellulose content of bamboo and wood is between 30% and 50%. Therefore, cotton linter is the best raw material for regenerated cellulose fiber.

[0005] At the same time, my country produces 20 million tons of waste textiles every year. At present, only a small part of the waste textiles are recycled, a small part is incinerated and landfilled, and the vast majority are discarded at will. The recycling rate of China's waste textiles is less than 20%. In addition, the incineration of waste textiles will produce a large amount of carbon dioxide and toxic substances, causing serious environmental pollution problems.

[0006] The main component of cotton waste fabric is cotton, and cotton lint is the fur still attached to cotton seeds after the cotton seed is ginned and de-linted. The cellulose content of cotton is higher than that of cotton lint, so cotton waste fabric is also one of the better raw materials for preparing regenerated cellulose fiber. How to use cotton waste fabric to prepare regenerated cellulose fiber is a problem that needs to be solved.

[0007] Chinese patent application number 2011310079782.8 discloses a method for preparing cotton staple fiber, which is a method for producing fibers using cotton linters, but its main process still uses the traditional pulping process, that is, the cotton linters are prepared by sample preparation, steaming, bleaching, and washing to make pulp, and then the pulp is dissolved with NMMO.

[0008] Chinese patent application number 201710314043.0 discloses a linter pulping process, which is also a process for producing fibers from cotton linters, wherein the cotton linters are heated below 85°C, 2.5-3.5% alkali is added, and the cooking time is 25-35 minutes, or the cotton linters are directly bleached without cooking (the bleaching method used is chlorine bleaching, which is not environmentally friendly) to make pulp, which is then dissolved with NMMO and the fibers are prepared by a dry-jet wet spinning process.

[0009] Chinese patent application number 201610647354.4 discloses a method for preparing cotton pulp and viscose fiber. Although the method adopts a cooking process of mixing alkali and hydrogen peroxide, the alkali rate in the scheme is low, the bound alkali content in the intermediate product is low, and the pulping and spinning still adopt traditional processes.

[0010] The solutions provided by the above patents all require cotton fabrics to be made into pulp before being used, which results in a long and complicated process, and is not conducive to the utilization of waste cotton products.

[0011] In view of this, the present invention is proposed. Summary of the invention

[0012] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing regenerated cellulose fibers using old cotton products, in which the pretreated old cotton products are processed into alkali cellulose with a higher alkali content through a shorter alkali treatment process, so as to facilitate the subsequent yellowing process to produce more cellulose xanthate, thereby reducing the probability of side reactions and shortening the overall process.

[0013] In order to solve the above technical problems, the basic concept of the technical solution adopted by the present invention is:

[0014] The present invention provides a method for preparing regenerated cellulose fibers by using waste cotton products, comprising:

[0015] (1) pre-treating, alkali treating, washing, pressing and crushing old cotton products in sequence to obtain alkali cellulose;

[0016] (2) aging, yellowing and dissolving the alkali cellulose obtained in step (1) to obtain a spinning solution;

[0017] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers;

[0018] The alkali treatment comprises immersing the pretreated old cotton products in a mixed solution containing alkali and a catalyst, and heating and keeping the mixture warm.

[0019] In the above scheme, the alkali treatment process specifically includes that the cellulose is treated with a high-concentration alkali solution, and then it is violently expanded, the diameter of the fiber increases and the length shrinks, so that the hemicellulose and some impurities therein are dissolved; under the action of the catalyst contained in the mixed solution, the molecular weight of the cellulose is reduced, so that the reaction efficiency is improved, thereby generating a new compound alkali cellulose; at the same time, under the bleaching action of hydrogen peroxide in the mixed solution, the fiber whiteness is improved to a certain extent. In addition, due to the long time and high temperature of the high-concentration alkali solution treatment, the bound alkali of the prepared alkali cellulose is higher than the bound alkali level of normal alkali cellulose, which is more conducive to the reaction of carbon disulfide and alkali cellulose in the subsequent yellowing process, thereby generating more cellulose sulfonate and reducing the occurrence of side reactions.

[0020] In the above scheme, the scheme provided by the present invention combines the three processes of cooking, bleaching and alkali soaking into one process of alkali treatment. There is no need to carry out the pulping process commonly used in traditional processes (i.e., the step of making pulp is eliminated), and the size adjustment of the fiber can be achieved by pressing and crushing after alkali treatment.

[0021] A further solution of the present invention is: the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, the alkali agent is selected from sodium hydroxide or calcium hydroxide; the concentration of the alkali agent in the mixed solution is 180-280 g / L, preferably 210-250 g / L; the amount of hydrogen peroxide added to the mixed solution is 1-10% of the mass of the old cotton products, preferably 3-6%.

[0022] In the above scheme, the present invention adds hydrogen peroxide as a bleaching agent to the mixed solution used for alkali treatment, which can effectively remove the colored groups of cellulose and old cotton products and improve the fiber whiteness; on the other hand, under the action of heating, the purpose of further reducing the fiber polymerization degree can be achieved, which is beneficial to improving the quality of the prepared glue solution, thereby improving the spinning performance.

[0023] A further embodiment of the present invention is: the catalyst is selected from manganese-containing compounds and / or cobalt-containing compounds, the manganese-containing compound is selected from at least one of potassium permanganate and manganese sulfate, the cobalt-containing compound is selected from at least one of cobalt chloride and cobalt sulfate, preferably cobalt chloride; the catalyst is added in an amount of 200 to 600 ppm in the mixed solution, preferably 300 to 400 ppm.

[0024] In the above scheme, the degree of polymerization of cotton linters is usually above 3000, the degree of polymerization of old cotton fabrics is even higher, and the degree of polymerization of regenerated cellulose fibers is only between 300 and 400. However, it is difficult to achieve the purpose of significantly reducing the degree of polymerization of cellulose in old cotton products by relying solely on the alkali component of the mixed solution. To solve this problem, a catalyst is further added to the mixed solution provided by the present invention, and the catalyst can accelerate the decomposition of cellulose in an aerobic environment to achieve the depolymerization of old cotton products in the alkali treatment.

[0025] A further scheme of the present invention is: the alkali treatment includes two heating and insulation steps, the first heating and insulation temperature is 80-120°C, the insulation time is 30-60min, preferably the first heating and insulation temperature is 90-100°C, the insulation time is 40-50min; the second heating and insulation temperature is 130-160°C, the insulation time is 60-120min, preferably the second heating and insulation temperature is 135-145°C, the insulation time is 90-100min.

[0026] In the above scheme, the heating and heat preservation includes two processes of heating and heat preservation. First, the alkali-treated mixed liquid soaked with old cotton products is heated to 80-120°C, then kept at this temperature for a certain period of time, and then a subsequent second heating and heat preservation is carried out based on the temperature of the first heat preservation.

[0027] A further embodiment of the present invention is that the washing in step (1) comprises washing the product after the alkali treatment with an alkali solution having a concentration similar to that of the mixed solution used for the alkali treatment.

[0028] A further solution of the present invention is that the concentration of the alkali solution used for washing is 160-240 g / L, preferably 180-200 g / L.

[0029] In the above scheme, the fiber product after alkali treatment, cooking and insulation still contains a lot of hemicellulose and other impurities. The present invention uses the principle of like dissolves like and uses alkali solution with a similar alkali concentration to the mixed solution for washing after alkali treatment to wash out the hemicellulose and impurities, thereby purifying the alkali cellulose.

[0030] A further embodiment of the present invention is as follows: the alkali cellulose obtained in step (1) has a methylcellulose content of 30-36%, a viscosity of 5-15 mPas, a total alkali content of 15-25%, and a combined alkali content of 13-22%. Preferably, the alkali cellulose has a methylcellulose content of 32-34%, a viscosity of 6-8 mPas, a total alkali content of 18-20%, and a combined alkali content of 15-18%.

[0031] In the above scheme, the bound alkali of alkali cellulose in the traditional process is generally in the range of 8-10%. In the present invention, the fiber is washed with alkali solution of similar concentration after alkali treatment, so that the bound alkali content in the prepared alkali cellulose is higher. The higher the bound alkali in the alkali cellulose, the more conducive it is to the subsequent yellowing in the positive reaction direction, so that carbon disulfide and alkali cellulose react to generate more cellulose sulfonate, thereby reducing the occurrence of side reactions.

[0032] A further embodiment of the present invention is as follows: the aging temperature in step (2) is 25-70°C and the aging time is 20-100 min; preferably the aging temperature is 40-60°C and the aging time is 30-60 min.

[0033] In the above scheme, the degradation of alkali cellulose is relatively rapid in the initial stage, but the degradation rate will continue to decrease over time, so the aging time can be appropriately shortened. As the aging temperature increases, the degree of polymerization of cellulose and the viscosity of the glue solution gradually decrease, and the hemicellulose content increases. Therefore, the selection of the aging temperature is very important to the quality of the glue solution. The present invention comprehensively considers the influence of the two to obtain more appropriate process parameters.

[0034] A further solution of the present invention is that the old cotton products are selected from cotton linters or cotton fabrics, and the pretreatment includes opening cotton and removing impurities when cotton linters are selected, and includes cutting cotton when cotton fabrics are selected; the cotton cutting includes cutting the cotton fabric into fabrics not larger than 10mm*10mm, preferably cutting into fabrics not larger than 5mm*5mm.

[0035] A further solution of the present invention is that the cotton linters are first or second grade of Class II or Class III linters, preferably first or second grade of Class III linters, and the impurity content of the cotton linters after impurities removal is not more than 4%. The grade standard of the cotton linters is detailed in GB / T 20223-2018.

[0036] The method for preparing regenerated cellulose fiber using waste cotton products provided by the present invention specifically comprises the following steps:

[0037] (1) Pre-treating old cotton products in sequence, and then adding the pre-treated old cotton products into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 180-280 g / L, the amount of hydrogen peroxide added is 1-10% of the mass of the old cotton products, and the amount of the catalyst added is 200-600 ppm; the first heating and heat preservation temperature is 80-120° C., the heat preservation time is 30-60 min, and the second heating and heat preservation temperature is 130-160° C., the heat preservation time is 60-120 min; washing the alkali-treated fiber product with an alkali solution with a concentration of 160-240 g / L, and then squeezing and crushing to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 30-36%, a viscosity of 5-15 mPas, a total alkali content of 15-25%, and a combined alkali content of 13-22%;

[0038] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 25 to 70° C. and the time is 20 to 100 min;

[0039] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers;

[0040] The present invention also provides a regenerated cellulose fiber prepared by the method as described above, wherein the dry breaking strength of the regenerated cellulose fiber is not less than 2.15 cN / dtex, the coefficient of variation of dry strength is not greater than 12.0%, the wet breaking strength is not less than 1.10 cN / dtex, and the whiteness is 67-75%; preferably, the dry breaking strength of the regenerated cellulose fiber is not less than 2.3 cN / dtex, the coefficient of variation of dry strength is not greater than 10.5%, and the wet breaking strength is not less than 1.2 cN / dtex.

[0041] In the above scheme, the coefficient of variation of dry strength (dry strength CV value), i.e., the coefficient of variation of yarn unevenness, is one of the test indicators of yarn evenness. The smaller the coefficient of variation of dry strength, the better the uniformity. The whiteness of the regenerated cellulose fiber prepared in the present application is high, and the numerical difference is small, which further illustrates the stability of the preparation method of the present application.

[0042] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0043] 1. The method for preparing regenerated cellulose fiber using waste cotton products provided by the present invention effectively solves the problem of long production cycle of viscose fiber, especially using waste cotton fabrics to produce regenerated cellulose fiber, which increases the available resources of the textile industry and realizes the value-added of waste textiles; at the same time, the mechanical properties of the regenerated cellulose fiber obtained by the preparation method of the present invention can meet the production requirements, and further enriches the diversity of products;

[0044] 2. The preparation method provided by the present invention combines the three processes of cooking, bleaching and alkali leaching into one process of alkali treatment, and does not require the pulping process commonly used in traditional processes; at the same time, due to the long time and high temperature of the high-concentration alkali solution treatment, the bound alkali of the prepared alkali cellulose is higher than the bound alkali level of normal alkali cellulose, which is more conducive to the reaction of carbon disulfide and alkali cellulose in the subsequent yellowing process, thereby generating more cellulose sulfonate and reducing the occurrence of side reactions;

[0045] 3. The preparation method provided by the present invention further adds a catalyst to the alkali-treated mixed solution, and the catalyst can accelerate the decomposition of cellulose in an aerobic environment to achieve the degradation of the old cotton products during the alkali treatment.

[0046] The specific embodiments of the present invention are described in further detail below. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing regenerated cellulose fiber using waste cotton linters, wherein the cotton linters are selected to be the first grade of Class III linters, and the method comprises the following steps:

[0050] (1) opening and removing impurities from old cotton linters to reduce the impurity content to less than 4%, and then adding the pretreated old cotton linters into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 210 g / L, the amount of hydrogen peroxide added is 6% of the mass of the old cotton product, and the amount of the catalyst added is 400 ppm; the first heating and heat preservation temperature is 90° C., the heat preservation time is 40 min, and the second heating and heat preservation temperature is 135° C., the heat preservation time is 100 min; washing the alkali-treated fiber product with an alkali solution of 180 g / L concentration, and then squeezing and crushing to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 32%, a viscosity of 6 mPas, a total alkali content of 18%, and a combined alkali content of 15%;

[0051] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 40° C. and the time is 60 min;

[0052] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

[0053] Example 2

[0054] This embodiment provides a method for preparing regenerated cellulose fiber using old cotton linters, wherein the cotton linters are selected to be the first grade of Class II linters, and the method comprises the following steps:

[0055] (1) opening and removing impurities from old cotton linters to reduce the impurity content to less than 4%, and then adding the pretreated old cotton linters into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 250 g / L, the amount of hydrogen peroxide added is 3% of the mass of the old cotton product, and the amount of the catalyst added is 300 ppm; the first heating and heat preservation temperature is 100° C., the heat preservation time is 50 min, and the second heating and heat preservation temperature is 160° C., the heat preservation time is 60 min; the alkali-treated fiber product is washed with an alkali solution with a concentration of 200 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 34%, a viscosity of 8 mPas, a total alkali content of 20%, and a combined alkali content of 18%;

[0056] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 70° C. and the time is 20 min;

[0057] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

[0058] Example 3

[0059] This embodiment provides a method for preparing regenerated cellulose fiber using old cotton linters, using old cotton fabric as raw material, comprising the following steps:

[0060] (1) Cutting old cotton fabric into fabrics not larger than 10 mm*10 mm, then adding the pretreated old cotton linters into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 180 g / L, the amount of hydrogen peroxide added is 10% of the mass of the old cotton product, and the amount of the catalyst added is 600 ppm; the first heating and heat preservation temperature is 80° C., the heat preservation time is 60 min, and the second heating and heat preservation temperature is 130° C., the heat preservation time is 120 min; washing the alkali-treated fiber product with an alkali solution of 160 g / L concentration, and then squeezing and crushing to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 30%, a viscosity of 5 mPas, a total alkali content of 15%, and a combined alkali content of 13%;

[0061] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 25° C. and the time is 100 min;

[0062] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

[0063] Example 4

[0064] This embodiment provides a method for preparing regenerated cellulose fiber using old cotton linters, using old cotton fabric as raw material, comprising the following steps:

[0065] (1) Cutting old cotton fabric into fabrics not larger than 5 mm*5 mm, then adding the pretreated old cotton linters into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 280 g / L, the amount of hydrogen peroxide added is 1% of the mass of the old cotton product, and the amount of the catalyst added is 200 ppm; the first heating and heat preservation temperature is 120° C., the heat preservation time is 30 min, and the second heating and heat preservation temperature is 145° C., the heat preservation time is 90 min; washing the alkali-treated fiber product with an alkali solution of 240 g / L concentration, and then squeezing and crushing to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 36%, a viscosity of 15 mPas, a total alkali content of 25%, and a combined alkali content of 22%;

[0066] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 60° C. and the time is 30 min;

[0067] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

[0068] Example 5

[0069] This embodiment provides a method for preparing regenerated cellulose fibers using old cotton linters, wherein the second-grade cotton linters among the Class II linters are selected, and the method comprises the following steps:

[0070] (1) opening and removing impurities from old cotton linters to reduce the impurity content to less than 4%, and then adding the pretreated old cotton linters into an alkali treatment mixed solution for heating and heat preservation twice; the mixed solution comprises an alkali agent, hydrogen peroxide and a catalyst, wherein the concentration of the alkali agent is 230 g / L, the amount of hydrogen peroxide added is 5% of the mass of the old cotton product, and the amount of the catalyst added is 350 ppm; the first heating and heat preservation temperature is 95° C., the heat preservation time is 45 min, and the second heating and heat preservation temperature is 140° C., the heat preservation time is 95 min; the alkali-treated fiber product is washed with an alkali solution with a concentration of 190 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 33%, a viscosity of 7 mPas, a total alkali content of 18.9%, and a combined alkali content of 16.2%;

[0071] (2) subjecting the alkali cellulose obtained in step (1) to aging, xanthation and dissolution to obtain a spinning dope, wherein the aging temperature is 55° C. and the time is 50 min;

[0072] (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

[0073] Example 6

[0074] This embodiment is based on Example 5, and the concentration of the alkali solution in the washing process in step (1) is adjusted. The difference from Example 5 is that:

[0075] In step (1), the alkali-treated fiber product is washed with an alkali solution having a concentration of 170 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the total alkali content of the alkali cellulose is 17.2% and the combined alkali content is 14.7%.

[0076] Other implementations of this embodiment are the same as those of Embodiment 5.

[0077] Example 7

[0078] This embodiment is based on Example 5, and the concentration of the alkali solution in the washing process in step (1) is adjusted. The difference from Example 5 is that:

[0079] In step (1), the alkali-treated fiber product is washed with an alkali solution having a concentration of 210 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the total alkali content of the alkali cellulose is 19.3% and the combined alkali content is 16.8%.

[0080] Other implementations of this embodiment are the same as those of Embodiment 5.

[0081] Example 8

[0082] This embodiment is based on Example 5, and the concentration of the alkali solution in the washing process in step (1) is adjusted. The difference from Example 5 is that:

[0083] In step (1), the alkali-treated fiber product is washed with an alkali solution having a concentration of 220 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the total alkali content of the alkali cellulose is 20.1% and the combined alkali content is 17.2%.

[0084] Other implementations of this embodiment are the same as those of Embodiment 5.

[0085] Example 9

[0086] This embodiment is based on Example 5, and the concentration of the alkali solution in the washing process in step (1) is adjusted. The difference from Example 5 is that:

[0087] In step (1), the alkali-treated fiber product is washed with an alkali solution having a concentration of 230 g / L, and then pressed and crushed to obtain alkali cellulose, wherein the total alkali content of the alkali cellulose is 21% and the combined alkali content is 20.5%.

[0088] Other implementations of this embodiment are the same as those of Embodiment 5.

[0089] Comparative Example 1

[0090] This comparative example is based on Example 5, except that the alkaline solution used in the washing process in step (1) is adjusted to deionized water for washing. The other implementation methods of this comparative example are the same as those of Example 5.

[0091] Comparative Example 2

[0092] This comparative example is based on Example 5, except that the catalyst added during the alkali treatment in step (1) is adjusted to be added during the subsequent pulverization process. The other implementation methods of this comparative example are the same as those of Example 5.

[0093] Comparative Example 3

[0094] This comparative example is based on Example 5, except that the catalyst added during the alkali treatment in step (1) is removed. The other implementation methods of this comparative example are the same as those of Example 5.

[0095] Experimental Example 1

[0096] In this experimental example, the dry breaking strength, dry strength variation coefficient, wet breaking strength and whiteness of the regenerated cellulose fibers prepared in Examples 1 to 9 and Comparative Examples 1 and 2 were measured, and the results are shown in the following table:

[0097]

[0098] It can be seen from the above table that the regenerated cellulose fibers provided in Examples 1 to 9 of the present invention, under the premise of omitting the preparation of pulp, adopt a process method in which a catalyst is used for degradation during alkali treatment and the solution is subjected to relatively low-concentration alkali washing, so that the bound alkali level of the prepared alkali cellulose is higher than the bound alkali level of normal alkali cellulose, which is more conducive to the reaction of carbon disulfide and alkali cellulose in the subsequent yellowing process, reduces side reactions, and improves the uniformity of the prepared fibers, so that the fibers have good mechanical properties and better whiteness performance.

[0099] Among them, Comparative Example 1 is based on Example 5, and the washing after alkali treatment is adjusted to water washing. Since the pH of the system changes rapidly during water washing, the combined alkali content is greatly reduced, which is not only not conducive to the degradation of cellulose, but also causes more side reactions in the subsequent yellowing reaction, affecting the uniformity and related mechanical properties of the fiber. Comparative Example 2 adjusts the position of adding the catalyst, and adds the catalyst in the crushing step after alkali treatment and washing. Although the catalyst plays a certain role, making the mechanical properties of the fiber closer to the requirements of the present invention than the comparative example 3 without adding the catalyst, the catalyst lacks the synergistic effect of the components in the mixed solution when not treated with alkali, so that it has a larger dry strength variation coefficient than Example 5; while Comparative Example 3 does not add the catalyst, and the fiber performance parameters obtained are not as good as those of Comparative Example 2, indicating that the catalyst plays a more important role in the adjustment of fiber performance, and also indirectly illustrates that the catalyst and other components in the alkali-treated mixed solution play a better synergistic role in cellulose degradation.

[0100] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A method for preparing regenerated cellulose fibers using waste cotton products, characterized in that: include: (1) pre-treating old cotton products, where the old cotton products are selected from cotton linters or cotton fabrics, wherein the pre-treatment includes opening and removing impurities when cotton linters are selected, and cutting cotton when cotton fabrics are selected; The pretreated old cotton products are immersed in a mixed solution containing an alkali agent, hydrogen peroxide and a catalyst, and are heated and kept warm twice. The first heating and keeping warm temperature is 80-120°C, and the keeping warm time is 30-60 minutes; the second heating and keeping warm temperature is 130-160°C, and the keeping warm time is 60-120 minutes; the concentration of the alkali agent in the mixed solution is 180-280 g / L, and the amount of the catalyst added to the mixed solution is 200-600 ppm; The alkali treated product is washed, squeezed and crushed with an alkali solution having a concentration of 180-200 g / L to obtain alkali cellulose, wherein the alkali cellulose has a methylcellulose content of 30-36%, a viscosity of 5-15 mPas, a total alkali content of 15-25%, and a combined alkali content of 13-22%; (2) aging, xanthating and dissolving the alkali cellulose obtained in step (1) to obtain a spinning dope; (3) filtering and spinning the spinning dope obtained in step (2) to obtain regenerated cellulose fibers.

2. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 1, characterized in that: The alkaline agent is selected from sodium hydroxide or calcium hydroxide; the concentration of the alkaline agent in the mixed solution is 210-250 g / L.

3. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 2, characterized in that: The amount of hydrogen peroxide added to the mixed solution is 1-10% of the mass of the old cotton products.

4. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 3, characterized in that: The amount of hydrogen peroxide added to the mixed solution is 3-6% of the mass of the old cotton products.

5. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 2, characterized in that: The catalyst is selected from manganese-containing compounds and / or cobalt-containing compounds. The manganese-containing compound is selected from at least one of potassium permanganate and manganese sulfate, and the cobalt-containing compound is selected from at least one of cobalt chloride and cobalt sulfate.

6. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 5, characterized in that: The catalyst is cobalt chloride; the amount of the catalyst added to the mixed solution is 300-400 ppm.

7. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 1, characterized in that: The first heating and insulation temperature is 90-100°C, and the insulation time is 40-50min; the second heating and insulation temperature is 135-145°C, and the insulation time is 90-100min.

8. The method for preparing regenerated cellulose fiber using waste cotton products according to any one of claims 1 to 7, characterized in that: The alkali cellulose prepared in step (1) has a methyl cellulose content of 32-34%, a viscosity of 6-8 mPas, a total alkali content of 18-20%, and a combined alkali content of 15-18%.

9. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 1, characterized in that: The aging temperature in step (2) is 25-70° C. and the aging time is 20-100 min.

10. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 9, characterized in that: The aging temperature in step (2) is 40-60° C. and the aging time is 30-60 min.

11. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 1, characterized in that: The cotton cutting comprises cutting the cotton fabric into fabrics not larger than 10 mm*10 mm.

12. The method for preparing regenerated cellulose fiber using waste cotton products according to claim 11, characterized in that: The cotton cutting comprises cutting the cotton fabric into fabrics not larger than 5 mm*5 mm.

13. A regenerated cellulose fiber prepared by the method according to any one of claims 1 to 12, characterized in that: The regenerated cellulose fiber has a dry breaking strength of not less than 2.15 cN / dtex, a dry strength variation coefficient of not more than 12.0%, a wet breaking strength of not less than 1.10 cN / dtex, and a whiteness of 67-75%.

14. The regenerated cellulose fiber according to claim 13, characterized in that The dry breaking strength of the regenerated cellulose fiber is not less than 2.3 cN / dtex, the dry strength variation coefficient is not greater than 10.5%, and the wet breaking strength is not less than 1.20 cN / dtex.

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