Preparation method of clean high-whiteness chlorine-free bleached viscose fiber

Abstract

The invention discloses a preparation method of clean high-whiteness chlorine-free bleached viscose fibers. The preparation method comprises the following steps: preparing a viscose spinning solution, spinning viscose fibers and carrying out aftertreatment on the viscose fibers, chlorine-free bleaching dissolved wood pulp is selected as a raw material in the preparation of the viscose spinning stock solution; in the step of viscose fiber post-treatment, viscose staple fiber flocks discharged from a fluff groove are fed into a refiner and are subjected to primary washing, desulfurization, secondary washing, bleaching, tertiary washing, final washing, oiling and drying, and then the clean high-whiteness chlorine-free bleached viscose fibers are prepared. A bleaching solution adopted in the bleaching process comprises hydrogen peroxide, an activating agent, a penetrating agent, a stabilizing agent and a defoaming agent, and the penetrating agent is an aqueous solution compounded by fatty alcohol-polyoxyethylene ether and urea; oil bath liquid adopted in the oiling procedure is formed by mixing an oil agent and hydrogen peroxide, and the concentration of the hydrogen peroxide in the oil bath liquid is 0.8-1.2 g / L. The clean high-whiteness chlorine-free bleached viscose fiber prepared by the invention has the advantages of low consumption of hydrogen peroxide, small concentration fluctuation, less foam in the bleaching liquid and low cost.

Description

Technical Field

[0001] This invention relates to the field of chemical fiber processing technology, and in particular to a method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber. Background Technology

[0002] Clean, high-whiteness viscose staple fibers have been widely used in the nonwoven fabric manufacturing industry. To improve the whiteness of finished viscose fiber products, sodium hypochlorite or hydrogen peroxide is often used to bleach the fibers in the post-processing of viscose fibers. However, when using sodium hypochlorite for bleaching, the content of adsorbable organic halogens (hereinafter referred to as "AOX") in the finished fibers is difficult to meet the AOX limit requirements specified in the national standard GB / T 30133-2022 Surface Layers for Disposable Sanitary Products. Therefore, it is necessary to study a chlorine-free bleaching process for fibers.

[0003] In the prior art, in order to improve the whiteness of fibers, patent ZL201010501442.6 discloses a method for preparing a completely chlorine-free high-whiteness cellulose fiber, which mainly improves the whiteness of fibers by adding fluorescent whitening agents. However, this raises the question of whether the fluorescent substances in the finished product exceed the standard.

[0004] Patent ZL201210469572.5 discloses a method for bleaching cotton stalk cellulose fibers, employing a two-stage bleaching process using sodium hydrosulfite and hydrogen peroxide. This produces cotton stalk cellulose fibers with good whiteness, improved hand feel and softness, and enhanced spinning performance. The auxiliaries used in this patent include urea, magnesium sulfate, and penetrants, with a bleaching time of 45-55 minutes. In contrast, the bleaching process in viscose fiber post-treatment involves spraying bleaching solution onto the surface of the viscose staple fiber, allowing it to penetrate from the surface to the lower layers for bleaching. The total bleaching time for viscose fibers is approximately 3-4 minutes. However, this process uses sodium hydrosulfite and has a long bleaching time, making it unsuitable for viscose fibers.

[0005] Patent ZL201910126110.5 discloses a chlorine-free bleached high-whiteness viscose fiber and its preparation method. By adopting a low-temperature activated oxygen bleaching process, it is beneficial to reduce energy consumption, reduce damage to fiber mechanical properties, and achieve a comprehensive balance between improving fiber mechanical properties and whiteness. However, when increasing production capacity, problems arise in the continuous bleaching process at high spinning speed, such as excessive hydrogen peroxide consumption, large fluctuations in hydrogen peroxide concentration, and too much foam in the bleaching solution, which prevents further increases in production capacity.

[0006] Patent application 201911273229.1 discloses a method for manufacturing modal fibers, which uses TCF to dissolve slurry as cellulose raw material and uses a bleaching agent without chlorine atoms for bleaching. However, the patent application does not disclose the whiteness index of the finished fiber, nor does it address how to solve the aforementioned problems that occur during continuous bleaching at high spinning speeds.

[0007] Therefore, providing a method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber has become an urgent task. Summary of the Invention

[0008] In view of this, this application provides a method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber with low hydrogen peroxide consumption, small hydrogen peroxide concentration fluctuation, less foam in the bleaching solution, and low cost. This preparation method optimizes the bleaching process in the post-treatment steps of viscose fiber by using a bleaching solution composed of an activator, penetrant, stabilizer, defoamer, and hydrogen peroxide in the bleaching process, combined with the use of high-whiteness, chlorine-free bleached pulp and the addition of an appropriate concentration of hydrogen peroxide in the oiling process. This results in low hydrogen peroxide consumption, small hydrogen peroxide concentration fluctuation, less foam in the bleaching solution, and reduced cost, thus producing high-whiteness, chlorine-free bleached viscose fiber.

[0009] To achieve the above objectives, this application employs the following technical solution:

[0010] A method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber includes the following steps: preparing viscose spinning solution, viscose spinning, and viscose fiber post-treatment; the step of preparing the viscose spinning solution involves selecting chlorine-free bleached dissolved wood pulp with a whiteness of 89% or higher and a methyl cellulose content of 90% or higher as raw material, and preparing the viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution, and maturation; the step of viscose fiber post-treatment involves sending viscose short fibers from the fluffing tank into a refining machine, and obtaining clean, high-whiteness, chlorine-free bleached viscose fiber through a first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling, and drying processes; characterized in that:

[0011] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer.

[0012] The penetrant is an aqueous solution composed of fatty alcohol polyoxyethylene ether and urea, wherein the mass concentration of fatty alcohol polyoxyethylene ether in the aqueous solution is 58-63% and the mass concentration of urea is 1-4%.

[0013] The bleaching solution contains hydrogen peroxide at a concentration of 3-6 g / L, an activator at a concentration of 0.4-1.2 g / L, a penetrant at a concentration of 0.05-0.1 g / L, a stabilizer at a concentration of 0.1-0.2 g / L, and an antifoamer at a concentration of 0.1-1 g / L.

[0014] The oiling process involves applying an oil bath solution at 70-75°C to the viscose staple fiber. The oil bath solution is a mixture of an oil agent and hydrogen peroxide, with a hydrogen peroxide concentration of 0.8-1.2 g / L. The pH value of the oil bath solution is adjusted to 3-4 using sulfuric acid.

[0015] This invention uses chlorine-free bleaching to dissolve wood pulp, ensuring that the fibers meet the AOX limit requirements specified in the national standard GB / T 30133-2022 "Topcoat for Disposable Hygiene Products". Adding an appropriate concentration of hydrogen peroxide during the oiling process helps extend the bleaching time, improve fiber whiteness, and also helps avoid fiber strength loss caused by excessive hydrogen peroxide concentration.

[0016] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0017] The technical parameters of the clean, high-whiteness, chlorine-free bleached viscose fiber obtained by this invention are as follows: linear density 1.70–1.80 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness ≥87.0%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0018] Specifically, the activator is an amide compound, the stabilizer is a non-silicone bleaching stabilizer containing 1-4% by mass of acrylamide / sodium acrylate copolymer, and the defoamer is a dispersion containing 90-99% by mass of polyoxyethylene polyoxypropylene ether.

[0019] The penetrant added during the bleaching process in this invention contains urea, which promotes the uniform dissolution of fatty alcohol polyoxyethylene ether and the decomposition of hydrogen peroxide, further improving bleaching efficiency. Additionally, the penetrant itself helps reduce the surface tension of the solution, accelerating the penetration of the bleaching agent into the fiber, thus synergistically improving fiber whiteness. The fatty alcohol polyoxyethylene ether penetrant added during the bleaching process is non-ionic and added in low amounts, which helps reduce foam formation. Adding a certain proportion of an activator containing amide groups during the bleaching process allows it to react with hydrogen peroxide to generate substances with higher oxidizing activity, enabling bleaching to be carried out at lower temperatures, which helps reduce damage to the fiber's mechanical properties. The stabilizer added during the bleaching process contains acrylamide / sodium acrylate copolymer, which has excellent dispersing properties, effectively dispersing solid particles in the liquid and preventing particle aggregation and sedimentation. Its molecular chains ionize in water, forming high-molecular-weight anions and sodium ions. These ions adsorb onto the particle surface, giving the particles the same charge, thus generating electrostatic repulsion and preventing particle flocculation. Simultaneously, the steric hindrance effect of the polymer chains also hinders particle proximity, achieving stable dispersion. A non-silicone bleaching stabilizer containing 1-4% by mass of acrylamide / sodium acrylate copolymer helps inhibit the ineffective decomposition of hydrogen peroxide, stabilizes the hydrogen peroxide concentration, and facilitates the removal of impurities from the fiber surface. The defoamer added during the bleaching process is preferably a non-silicone defoamer, which helps reduce bleach foam, ensures smooth continuous bleaching, and also helps avoid the formation of silica scale, reducing the defect content of the finished fiber.

[0020] Specifically, the bleaching solution is preferably heated to 65-68°C and the pH is 9.8-10.4, and the bleaching time is preferably 3-3.5 min.

[0021] Specifically, the viscose spinning process includes the following steps: the viscose spinning solution and titanium dioxide dispersion are mixed evenly and fed into a spinning machine, then ejected from the spinneret by a metering pump, reacting with a coagulation bath in an acid bath to coagulate and regenerate nascent fibers; the coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength, then cut and fed into a pile trough; steam bubbles ejected through small holes in the steam jet pipe at the bottom of the pile trough disperse the fibers to make the fiber layer thickness uniform;

[0022] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose monoxide in the viscose spinning solution is 0.5~0.7:100;

[0023] The spinning speed of the spinning machine is 57~60 m / min;

[0024] The inlet steam pressure of the fluff trough is 1.0-1.5 bar.

[0025] This invention optimizes spinning speed and appropriately increases linear density, thereby further improving production capacity and reducing costs. Under steam pressure, steam bubbles are ejected from small holes in the steam jet pipe at the bottom of the fluffing tank and burst on the liquid surface, dispersing the fibers and making the fiber layer thickness uniform. In addition, the high-temperature steam removes acidic gases and CS2 from the fibers and then enters the condensation recovery system, thereby significantly reducing the residual sulfur content in the fibers.

[0026] Specifically, the first water wash temperature is 70-75℃, the second water wash temperature is 69-75℃, the third water wash temperature is 45-50℃, and the final water wash temperature is 70-75℃. This invention, by increasing the water temperature of the second water wash, helps to reduce temperature fluctuations in the bleaching solution, thereby improving the bleaching effect.

[0027] Specifically, the desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1-2 g / L, and the concentration of sodium hydroxide is 3.0-3.3 g / L. The desulfurization temperature is 84-85℃. Adding an appropriate concentration of sodium sulfide during the desulfurization process enhances the desulfurization effect and improves the whiteness of the fibers before bleaching.

[0028] Specifically, the drying temperature is 135-145°C. This preferred drying temperature is beneficial for removing moisture and sulfur-containing volatiles from the viscose fiber product.

[0029] Compared with the prior art, this invention application has the following advantages:

[0030] (1) The present invention prepares a novel clean, high-whiteness, chlorine-free bleached viscose fiber with extremely low defect content, very low residual sulfur content, low surface active matter content, and low water-soluble matter content, which can be used in various non-woven fabrics and medical sanitary materials.

[0031] (2) The present invention uses hydrogen peroxide bleaching process to avoid the problem of excessive AOX content in finished fiber.

[0032] (3) The present invention adopts a low-temperature activation bleaching process, which is beneficial to reduce energy consumption, reduce fiber performance damage, and improve bleaching effect compared with the traditional hydrogen peroxide high-temperature bleaching process.

[0033] (4) In the bleaching process, the present invention adds a non-silicone bleaching stabilizer containing 1-4% mass concentration of acrylamide / sodium acrylate copolymer, which helps to inhibit the ineffective decomposition of hydrogen peroxide, stabilize the hydrogen peroxide concentration, and help remove impurities from the fiber surface.

[0034] (5) The addition of a non-silicone defoamer during the bleaching process in this invention helps to reduce foam in the bleaching liquid, ensures the smooth progress of continuous bleaching, and also helps to avoid the formation of silicone scale and reduce the defect content of the finished fiber.

[0035] (6) The fatty alcohol polyoxyethylene ether penetrant added during the bleaching process in this invention is non-ionic and the amount added is low, which is beneficial to reduce foam generation; and the addition of urea to the penetrant is beneficial to promote uniform dissolution of the penetrant and decomposition of hydrogen peroxide, and synergistically improves fiber whiteness.

[0036] (7) The present invention adds an appropriate concentration of hydrogen peroxide in the oiling process, which is beneficial to prolong the bleaching time, improve the whiteness of the fiber, and also to avoid the loss of fiber strength caused by excessive hydrogen peroxide concentration. Detailed Implementation

[0037] The exemplary embodiments of the present invention are described in more detail below. These embodiments are intended to provide a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art. While exemplary embodiments of the present invention are shown, it should be understood that the invention should not be limited to the embodiments set forth herein.

[0038] Example 1

[0039] Prepare clean, high-whiteness, chlorine-free bleached viscose fibers using the following steps:

[0040] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 90% and a methyl cellulose content of 91% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0041] (2) Viscose spinning:

[0042] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0043] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.7:100;

[0044] The spinning speed of the spinning machine is 57 m / min;

[0045] The inlet steam pressure of the fluff trough is 1.0 bar.

[0046] (3) Post-treatment of viscose fibers:

[0047] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0048] The first water wash temperature is 70℃, the second water wash temperature is 69℃, the third water wash temperature is 45℃, and the final water wash temperature is 70℃.

[0049] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.3 g / L, and the desulfurization temperature is 84℃.

[0050] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The concentrations of hydrogen peroxide, activator, penetrant, stabilizer, and defoamer in the bleaching solution are as follows: hydrogen peroxide 3 g / L; activator 0.4 g / L; penetrant 0.05 g / L; stabilizer 0.1 g / L; and defoamer 0.1 g / L. The activator is an amide compound; the penetrant is an aqueous solution of 58% (w / w) fatty alcohol polyoxyethylene ether and 1% (w / w) urea; the stabilizer is a non-silicone bleaching stabilizer containing 1% (w / w) acrylamide / sodium acrylate copolymer; and the defoamer is a dispersion containing 90% (w / w) polyoxyethylene polyoxypropylene ether. The bleaching solution is set at 65°C and pH 9.8, and the bleaching time is 3.5 min.

[0051] The oiling process involves applying oil to viscose staple fibers using an oil bath at 70°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 0.8 g / L. The pH of the oil bath is adjusted to 4 using sulfuric acid.

[0052] The drying temperature is 135°C.

[0053] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.80 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 87.2%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0054] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0055] Example 2

[0056] Prepare clean, high-whiteness, chlorine-free bleached viscose fibers using the following steps:

[0057] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 89% and a methyl cellulose content of 90% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0058] (2) Viscose spinning:

[0059] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0060] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.5:100;

[0061] The spinning speed of the spinning machine is 60 m / min;

[0062] The inlet steam pressure of the fluff trough is 1.5 bar.

[0063] (3) Post-treatment of viscose fibers:

[0064] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0065] The first water wash temperature is 75℃, the second water wash temperature is 75℃, the third water wash temperature is 50℃, and the final water wash temperature is 75℃.

[0066] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 2 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.0 g / L, and the desulfurization temperature is 85℃.

[0067] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The concentrations of hydrogen peroxide, activator, penetrant, stabilizer, and defoamer in the bleaching solution are as follows: hydrogen peroxide concentration 6 g / L; activator concentration 1.2 g / L; penetrant concentration 0.1 g / L; stabilizer concentration 0.2 g / L; and defoamer concentration 1 g / L. The activator is an amide compound; the penetrant is an aqueous solution of 63% (w / w) fatty alcohol polyoxyethylene ether and 4% (w / w) urea; the stabilizer is a non-silicone bleaching stabilizer containing 4% (w / w) acrylamide / sodium acrylate copolymer; and the defoamer is a dispersion containing 99% (w / w) polyoxyethylene polyoxypropylene ether. The bleaching solution is set at 68°C and pH 10.4, and the bleaching time is 3 minutes.

[0068] The oiling process involves applying oil to viscose staple fibers using an oil bath at 75°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 1.2 g / L. The pH of the oil bath is adjusted to 3 using sulfuric acid.

[0069] The drying temperature is 145°C.

[0070] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.70 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 87.0%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0071] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0072] Example 3

[0073] Prepare clean, high-whiteness, chlorine-free bleached viscose fibers using the following steps:

[0074] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 89% and a methyl cellulose content of 90% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0075] (2) Viscose spinning:

[0076] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0077] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.6:100;

[0078] The spinning speed of the spinning machine is 59 m / min;

[0079] The inlet steam pressure of the fluff trough is 1.2 bar.

[0080] (3) Post-treatment of viscose fibers:

[0081] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0082] The first water wash temperature is 72℃, the second water wash temperature is 72℃, the third water wash temperature is 48℃, and the final water wash temperature is 72℃.

[0083] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1.5 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.2 g / L, and the desulfurization temperature is 84.5℃.

[0084] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The concentrations of hydrogen peroxide, activator, penetrant, stabilizer, and defoamer in the bleaching solution are as follows: hydrogen peroxide 4 g / L; activator 0.9 g / L; penetrant 0.06 g / L; stabilizer 0.15 g / L; and defoamer 0.3 g / L. The activator is an amide compound; the penetrant is an aqueous solution of 62% (w / w) fatty alcohol polyoxyethylene ether and 2% urea; the stabilizer is a non-silicone bleaching stabilizer containing 2% (w / w) acrylamide / sodium acrylate copolymer; and the defoamer is a dispersion containing 95% (w / w) polyoxyethylene polyoxypropylene ether. The bleaching solution is kept at 66°C and pH 10.2, with a bleaching time of 3.3 min.

[0085] The oiling process involves applying oil to viscose staple fibers using an oil bath at 72°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 1.0 g / L. The pH of the oil bath is adjusted to 3.3 using sulfuric acid.

[0086] The drying temperature is 140°C.

[0087] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.76 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 87.7%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0088] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0089] Comparative Example 1

[0090] Prepare chlorine-free bleached viscose fibers using the following steps:

[0091] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 89% and a methyl cellulose content of 90% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0092] (2) Viscose spinning:

[0093] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0094] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.6:100;

[0095] The spinning speed of the spinning machine is 59 m / min;

[0096] The inlet steam pressure of the fluff trough is 1.2 bar.

[0097] (3) Post-treatment of viscose fibers:

[0098] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0099] The first water wash temperature is 72℃, the second water wash temperature is 72℃, the third water wash temperature is 48℃, and the final water wash temperature is 72℃.

[0100] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1.5 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.2 g / L, and the desulfurization temperature is 84.5℃.

[0101] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The concentrations of hydrogen peroxide, activator, penetrant, stabilizer, and defoamer in the bleaching solution are as follows: hydrogen peroxide 4 g / L; activator 0.9 g / L; penetrant 0.06 g / L; stabilizer 0.15 g / L; and defoamer 0.3 g / L. The activator is an amide compound, the penetrant is a high-concentration fatty alcohol polyoxyethylene ether, the stabilizer is a non-silicone bleaching stabilizer containing 2% by mass of acrylamide / sodium acrylate copolymer, and the defoamer is a dispersion containing 95% by mass of polyoxyethylene polyoxypropylene ether. The bleaching solution is prepared at 66°C with a pH of 10.2, and the bleaching time is 3.3 min.

[0102] The oiling process involves applying oil to viscose staple fibers using an oil bath at 72°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 1.0 g / L. The pH of the oil bath is adjusted to 3.3 using sulfuric acid.

[0103] The drying temperature is 140°C.

[0104] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.76 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 86.7%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0105] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0106] The main difference between Comparative Example 1 and Example 3 of this application is that the penetrant used in the bleaching solution of Comparative Example 1 does not contain urea, resulting in lower whiteness of the finished fiber.

[0107] Comparative Example 2

[0108] Prepare clean, high-whiteness, chlorine-free bleached viscose fibers using the following steps:

[0109] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 89% and a methyl cellulose content of 90% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0110] (2) Viscose spinning:

[0111] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0112] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.6:100;

[0113] The spinning speed of the spinning machine is 59 m / min;

[0114] The inlet steam pressure of the fluff trough is 1.2 bar.

[0115] (3) Post-treatment of viscose fibers:

[0116] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0117] The first water wash temperature is 72℃, the second water wash temperature is 72℃, the third water wash temperature is 48℃, and the final water wash temperature is 72℃.

[0118] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1.5 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.2 g / L, and the desulfurization temperature is 84.5℃.

[0119] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, and a penetrant. The concentration of hydrogen peroxide in the bleaching solution is 4 g / L, the concentration of the activator is 0.9 g / L, and the concentration of the penetrant is 0.06 g / L. The activator is an amide compound, and the penetrant is an aqueous solution of 62% (w / w) fatty alcohol polyoxyethylene ether and 2% (w / w) urea. The bleaching solution is set at a temperature of 66°C and a pH of 10.2, with a bleaching time of 3.3 min.

[0120] The oiling process involves applying oil to viscose staple fibers using an oil bath at 72°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 1.0 g / L. The pH of the oil bath is adjusted to 3.3 using sulfuric acid.

[0121] The drying temperature is 140°C.

[0122] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.76 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 86.6%; defect content ≤1.5 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0123] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0124] The main difference between Comparative Example 2 and Example 3 of this application is that no stabilizer and defoamer are added to the bleaching solution of Comparative Example 2, resulting in more foam in the bleaching area, higher fiber defect content in the finished product, and lower whiteness.

[0125] Comparative Example 3

[0126] Prepare clean, high-whiteness, chlorine-free bleached viscose fibers using the following steps:

[0127] (1) Preparation of viscose spinning solution: Select chlorine-free dissolved wood pulp with a whiteness of 89% and a methyl cellulose content of 90% as raw material, and prepare viscose spinning solution through steps including impregnation, pressing, crushing, aging, xanthation, dissolution and maturation.

[0128] (2) Viscose spinning:

[0129] After the viscose spinning solution and titanium dioxide dispersion are mixed evenly, they are fed into the spinning machine and then ejected from the spinneret by a metering pump. The mixture reacts with the coagulation bath in an acid bath to coagulate and regenerate nascent fibers. The coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength. After being cut, the fibers enter the pile trough. Steam bubbles ejected through the small holes of the steam jet pipe at the bottom of the pile trough disperse the fibers and make the fiber layer thickness uniform.

[0130] The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose methyl ester in the viscose spinning solution is 0.6:100;

[0131] The spinning speed of the spinning machine is 59 m / min;

[0132] The inlet steam pressure of the fluff trough is 1.2 bar.

[0133] (3) Post-treatment of viscose fibers:

[0134] The viscose short fiber fibers coming out of the pile trough are sent into the refining machine and, after a series of processes including first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying, clean, high-whiteness, chlorine-free viscose fibers are obtained.

[0135] The first water wash temperature is 72℃, the second water wash temperature is 72℃, the third water wash temperature is 48℃, and the final water wash temperature is 72℃.

[0136] The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1.5 g / L, the concentration of sodium hydroxide in the desulfurizing agent is 3.2 g / L, and the desulfurization temperature is 84.5℃.

[0137] The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The concentrations of hydrogen peroxide, activator, penetrant, stabilizer, and defoamer in the bleaching solution are as follows: hydrogen peroxide 4 g / L; activator 0.9 g / L; penetrant 0.06 g / L; stabilizer 0.15 g / L; and defoamer 0.3 g / L. The activator is an amide compound, and the penetrant is a 62% (w / w) lipid peroxide solution. An aqueous solution of fatty alcohol polyoxyethylene ether and 2% urea (by mass) is prepared. The stabilizer is a non-silicone bleaching stabilizer containing 2% acrylamide / sodium acrylate copolymer (by mass). The defoamer is a dispersion of polyoxyethylene polyoxypropylene ether (by mass) containing 95% polyoxyethylene polyoxypropylene ether. The stabilizer and penetrant are mixed in the same additive mixing tank according to their respective addition amounts, and then simultaneously added to the bleaching solution. The bleaching solution is prepared at a temperature of 66°C and a pH of 10.2, and the bleaching time is 3.3 min.

[0138] The oiling process involves applying oil to viscose staple fibers using an oil bath at 72°C. The oil bath is a mixture of oil and hydrogen peroxide, with a hydrogen peroxide concentration of 0.5 g / L. The pH of the oil bath is adjusted to 3.3 using sulfuric acid.

[0139] The drying temperature is 140°C.

[0140] The technical parameters of the obtained clean, high-whiteness, chlorine-free bleached viscose fiber are as follows: linear density 1.76 dtex; length 38–41 mm; dry breaking strength ≥2.2 cN / dtex; dry breaking elongation 19.0%–22.0%; whiteness 86.8%; defect content ≤1.0 mg / 100g; residual sulfur content ≤4 mg / 100g; surfactant content ≤3 mm; water-soluble content ≤0.6%.

[0141] The AOX content of the finished fiber obtained by this invention is less than 2 mg / kg.

[0142] The main difference between Comparative Example 3 and Example 3 of this application is that the concentration of hydrogen peroxide in the oil bath of Comparative Example 3 is lower, resulting in lower whiteness of the finished fiber.

[0143] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for the production of clean high brightness chlorine-free bleached viscose fibre comprising the steps of: The method comprises preparing viscose spinning dope, viscose spinning, and viscose fiber post-treatment; the step of preparing the viscose spinning dope involves selecting chlorine-free dissolved wood pulp with a whiteness of 89% or higher and a methyl cellulose content of 90% or higher as raw material, and preparing the viscose spinning dope through steps including impregnation, pressing, crushing, aging, xanthation, dissolution, and maturation; the step of viscose fiber post-treatment involves feeding viscose short fibers from the fluffing tank into a refining mill, and obtaining clean, high-whiteness chlorine-free viscose fibers through a series of processes including primary washing, desulfurization, secondary washing, bleaching, tertiary washing, final washing, oiling, and drying; characterized in that: The bleaching process uses a bleaching solution containing hydrogen peroxide, an activator, a penetrant, a stabilizer, and a defoamer. The penetrant is an aqueous solution composed of fatty alcohol polyoxyethylene ether and urea, wherein the mass concentration of fatty alcohol polyoxyethylene ether in the aqueous solution is 58-63% and the mass concentration of urea is 1-4%. The bleaching solution contains hydrogen peroxide at a concentration of 3-6 g / L, an activator at a concentration of 0.4-1.2 g / L, a penetrant at a concentration of 0.05-0.1 g / L, a stabilizer at a concentration of 0.1-0.2 g / L, and an antifoamer at a concentration of 0.1-1 g / L. The oiling process involves applying an oil bath solution at 70-75°C to the viscose staple fiber. The oil bath solution is a mixture of an oil agent and hydrogen peroxide, with a hydrogen peroxide concentration of 0.8-1.2 g / L. The pH value of the oil bath solution is adjusted to 3-4 using sulfuric acid.

2. A process for the production of clean high brightness chlorine free bleached viscose fibre as claimed in claim 1, wherein: The activator is an amide compound, the stabilizer is a non-silicone bleaching stabilizer containing 1-4% by mass of acrylamide / sodium acrylate copolymer, and the defoamer is a dispersion containing 90-99% by mass of polyoxyethylene polyoxypropylene ether.

3. The method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber according to claim 1, characterized in that: The bleaching solution is heated to 65-68°C and has a pH of 9.8-10.4, with a bleaching time of 3-3.5 minutes.

4. The method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber according to claim 1, characterized in that: The viscose spinning process includes the following steps: the viscose spinning solution and titanium dioxide dispersion are mixed evenly and fed into a spinning machine, then ejected from the spinneret by a metering pump, reacting with a coagulation bath in an acid bath to coagulate and regenerate nascent fibers; the coagulated and regenerated nascent fibers are stretched and oriented to form fibers with a certain strength, then cut and fed into a pile trough; steam bubbles ejected through small holes in the steam jet pipe at the bottom of the pile trough disperse the fibers to make the fiber layer thickness uniform. The mass ratio of titanium dioxide in the titanium dioxide dispersion to cellulose monoxide in the viscose spinning solution is 0.5~0.7:100; The spinning speed of the spinning machine is 57~60 m / min; The inlet steam pressure of the fluff trough is 1.0-1.5 bar.

5. The method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber according to claim 1, characterized in that: The first water wash temperature is 70~75℃, the second water wash temperature is 69~75℃, the third water wash temperature is 45~50℃, and the final water wash temperature is 70~75℃.

6. The method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber according to claim 1, characterized in that: The desulfurizing agent used in the desulfurization process includes sodium sulfide and sodium hydroxide. The concentration of sodium sulfide in the desulfurizing agent is 1-2 g / L, the concentration of sodium hydroxide is 3.0-3.3 g / L, and the desulfurization temperature is 84-85℃.

7. The method for preparing clean, high-whiteness, chlorine-free bleached viscose fiber according to claim 1, characterized in that: The drying temperature is 135-145℃.