A method for preparing high-whiteness viscose fiber

Abstract

The present invention relates to a method for preparing high-whiteness viscose fiber, which mainly comprises the following steps performed in sequence: (1) preparing a bleaching aid; (2) preparing viscose staple fibers; and (3) preparing high-whiteness viscose fibers. This invention overcomes the shortcomings of existing methods for preparing high-whiteness viscose fibers, such as increased bleaching agent consumption and high production costs to ensure high fiber whiteness. The invention dilutes a compounded aid containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water to prepare a bleaching aid, which is then mixed with a sodium hypochlorite solution to prepare a bleaching solution. The invention synergizes with other preferred reagents and the specific steps and process parameters of the method for preparing high-whiteness viscose fibers to achieve the goal of effectively reducing bleaching agent consumption while ensuring high whiteness. The invention has the advantages of easy operation, environmental friendliness, and cost savings.

Description

Technical Field

[0001] The invention relates to a method for preparing high-whiteness viscose fiber, which is applied in the field of viscose fiber production. Background Art

[0002] Clean, high-white viscose fiber is a differentiated type of viscose fiber widely used in nonwovens, medical and sanitary products, and other fields. Whiteness is a key evaluation metric for clean, high-white viscose fiber. The industry standard "FZT 54032-2010 Clean, High-Whiteness Viscose Staple Fiber" stipulates that the whiteness center value of cotton-type viscose staple fiber must not be less than 85%. To improve fiber whiteness, viscose fiber production currently primarily involves bleaching with sodium hypochlorite or hydrogen peroxide. For example, Patent ZL200410092441.5 discloses a high-white viscose staple fiber for sanitary products and its production process, using a sodium hypochlorite concentration of 0.5-1.2 g / L for bleaching. Patent ZL201610743740.3 discloses a high-white viscose staple fiber and its preparation method, using a sodium hypochlorite concentration of 0.5-5 g / L for bleaching. Patent application CN202011590640.4 discloses a clean, high-white matt viscose fiber and a preparation method thereof, in which the sodium hypochlorite concentration used for bleaching is 5.0-6.0 g / L. The amount of sodium hypochlorite used is related to the output of viscose fiber. As the output of viscose fiber increases, the amount of sodium hypochlorite used in the bleaching process of viscose fiber post-treatment will also increase accordingly. However, none of the above patent documents mentions how to effectively reduce the amount of sodium hypochlorite used. Therefore, it has become an urgent task to provide a preparation method for high-whiteness viscose fiber that is easy to operate, can effectively reduce the consumption of bleaching agents while ensuring high whiteness, is environmentally friendly, and saves costs. Summary of the Invention

[0003] In order to overcome the shortcomings of existing high-whiteness viscose fiber preparation methods, such as increased bleaching agent consumption and high production costs caused by ensuring high fiber whiteness, the present invention provides a method for preparing high-whiteness viscose fiber. The method comprises diluting a composite auxiliary agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water to prepare a bleaching auxiliary agent, and then mixing the bleaching auxiliary agent with a sodium hypochlorite solution to prepare a bleaching solution. By combining the combined effects of other preferred reagents and the specific steps and process parameters of the high-whiteness viscose fiber preparation method, the method achieves the goal of effectively reducing bleaching agent consumption while ensuring high whiteness. The method has the advantages of easy operation, environmental protection, and cost savings.

[0004] The technical solutions of the present invention are as follows:

[0005] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0006] (1) Prepare bleaching aids:

[0007] A bleaching agent is prepared by mixing a compounding agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water in a mass ratio of 1:50 to 1:100; the mass ratio of fatty alcohol polyoxyethylene ether to fatty alcohol polyoxyethylene ether sodium sulfate in the compounding agent is 2:1 to 6:1;

[0008] (2) Preparation of viscose staple fibers:

[0009] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6:100 to 7:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution and ripening; the viscose spinning stock solution is then uniformly mixed with a titanium dioxide dispersion, and the mixture is fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:4 to 1:6; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.5:100 to 0.7:100;

[0010] (3) Preparation of high whiteness viscose fiber:

[0011] The viscose staple fiber is fed into the scouring machine and goes through the following processes: first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying to obtain high-whiteness viscose fiber.

[0012] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber, and then penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber (the viscose staple fiber takes about 3-4 minutes to go through the bleaching process); the bleaching solution has a temperature of 58-62°C and a pH of 9-10, a sodium hypochlorite concentration of 0.8-1.6 g / L, and a bleaching agent concentration of 0.1-0.2 g / L;

[0013] The oiling process is to use an oil bath liquid at 74 to 76° C. to oil the viscose staple fibers. The oil bath liquid is a mixture of an oil agent and hydrogen peroxide. The concentration of hydrogen peroxide in the oil bath liquid is 0.5 to 0.8 g / L, and the pH value of the oil bath liquid is adjusted to 3 to 4 using sulfuric acid.

[0014] The preparation method of the high-whiteness viscose fiber of the present application is to dilute a compounded auxiliary agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water to prepare a bleaching auxiliary agent, and then mix it with a sodium hypochlorite solution to prepare a bleaching solution. The combined effect of other preferred reagents and the specific steps and process parameters of the preparation method of the high-whiteness viscose fiber is coordinated to achieve the goal of effectively reducing the consumption of bleaching agent while ensuring high whiteness, and has the advantages of easy operation, environmental protection, and cost savings. Among them, in this scheme, an auxiliary agent compounded with a nonionic surfactant (fatty alcohol polyoxyethylene ether) and an anionic surfactant (fatty alcohol polyoxyethylene ether sodium sulfate) is used, and the two types of surfactants form mixed micelles in the mixed system. Wherein, the oxygen atom in the oxyethylene chain in the fatty alcohol polyoxyethylene ether nonionic surfactant can be combined with the hydrogen atom in the water by hydrogen bonding, so that this nonionic surfactant molecule has some positive charge, thereby weakening the electrical repulsion between the anionic surfactant ions, more easily forming micelles, making the critical micelle concentration (CMC value) of the mixture solution decline, so the nonionic surfactant selected by the application and the anionic surfactant compatibility have stronger synergistic effect. Because described composite auxiliary agent is a kind of alkali-resistant, oxidation-resistant efficient environmentally friendly surfactant, it has stronger synergistic effect, it is added in sodium hypochlorite solution as bleaching aid after diluting with water, is conducive to reducing the surface tension of liquid, can accelerate the penetration of bleaching agent to fiber interior, so synergistic effect is played to improving fiber whiteness. The application adds a small amount of environmentally friendly bleaching aid in the bleaching process, and when ensuring that fiber whiteness is up to standard, is conducive to reducing the consumption of sodium hypochlorite bleaching agent. Adding hydrogen peroxide to the oiling process as bleaching agent can carry out secondary bleaching to fiber.

[0015] This method for producing high-whiteness viscose fiber reduces sodium hypochlorite consumption by approximately 6-10 kg per ton of fiber compared to existing processes. The high-whiteness viscose fiber produced by this method has low residual sulfur content and high whiteness, and can be used in non-woven fabrics and medical and sanitary materials. The fiber exhibits the following technical parameters: fineness of 1.65-1.75 dtex, length of 38-40 mm, dry breaking strength ≥2.15 cN / dtex, dry breaking elongation of 19.0%-22.0%, whiteness ≥88.5%, and residual sulfur content ≤4 mg / 100 g.

[0016] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60-61 m / min.

[0017] The preferred higher spinning speed is beneficial to reducing production costs.

[0018] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 75 to 80° C., wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1 to 2 g / L and the concentration of sodium hydroxide is 3 to 3.5 g / L.

[0019] Adding an appropriate concentration of sodium sulfide in the desulfurization process can enhance the desulfurization effect and improve the whiteness of the fiber before bleaching.

[0020] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 70-75°C, the second washing temperature is 60-65°C, the third washing temperature is 55-60°C, the final washing temperature is 73-77°C, and the drying temperature is 135-145°C.

[0021] The preferred second wash water temperature is beneficial to reducing the temperature fluctuation of the bleaching solution and can further improve the bleaching effect.

[0022] The bleaching process also includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 120 to 240 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 20 to 40 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 0.8 to 1.6 g / L and the bleaching aid concentration at 0.1 to 0.2 g / L. When bleaching viscose staple fibers, the bleaching liquid in the bleaching liquid circulation barrel is transported to the leaching tank via a bleaching liquid delivery pump, and then the bleaching liquid is poured onto the fiber surface layer. After the bleaching liquid passes through the fiber surface layer and the fiber lower layer, it flows back into the bleaching liquid circulation barrel; at the same time, an appropriate amount of sodium hypochlorite mother liquor and bleaching aid are added to the bleaching liquid circulation barrel to replenish the sodium hypochlorite and bleaching aid consumed during the bleaching process.

[0023] The recycling of bleaching liquid helps to reduce losses and save costs.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1) The method for preparing high-whiteness viscose fiber of the present application comprises diluting a compounded auxiliary agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water to prepare a bleaching auxiliary agent, which is then mixed with a sodium hypochlorite solution to prepare a bleaching solution. The bleaching solution is then combined with hydrogen peroxide, another bleaching agent, and the combined effects of other preferred reagents, as well as the specific steps and process parameters of the method for preparing high-whiteness viscose fiber, thereby achieving the goal of effectively reducing the consumption of bleaching agent while ensuring high whiteness. The method has the advantages of easy operation, environmental protection, and cost savings.

[0026] 2) The preferred higher spinning speed is beneficial to reduce production costs;

[0027] 3) Adding an appropriate concentration of sodium sulfide during the desulfurization process can enhance the desulfurization effect and improve the whiteness of the fiber before bleaching;

[0028] 4) The preferred second wash water temperature is beneficial to reducing the temperature fluctuation of the bleaching solution and can further improve the bleaching effect. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described in detail below in conjunction with various embodiments.

[0030] Example 1

[0031] The method for preparing high-whiteness viscose fiber of the present invention mainly comprises the following steps performed in sequence:

[0032] (1) Prepare bleaching aids:

[0033] A bleaching aid is prepared by mixing a compounding agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water in a mass ratio of 1:50; the mass ratio of fatty alcohol polyoxyethylene ether to fatty alcohol polyoxyethylene ether sodium sulfate in the compounding agent is 6:1;

[0034] (2) Preparation of viscose staple fibers:

[0035] A method of preparing viscose staple fibers comprises the following steps: selecting coniferous wood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methylcellulose content of ≥90%, and first mixing the coniferous wood dissolving pulp and the hardwood dissolving pulp at a mass ratio of 6:100; then preparing a viscose spinning stock solution through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; then uniformly mixing the viscose spinning stock solution with a titanium dioxide dispersion, and feeding the mixture into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:4; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.7:100;

[0036] (3) Preparation of high whiteness viscose fiber:

[0037] The viscose staple fiber is fed into the scouring machine and goes through the following processes: first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying to obtain high-whiteness viscose fiber.

[0038] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 58°C and a pH of 9, a sodium hypochlorite concentration of 0.8g / L, and a bleaching agent concentration of 0.2g / L;

[0039] The oiling process is to oil the viscose staple fibers using an oil bath at 74° C. The oil bath is a mixture of an oil agent and hydrogen peroxide. The concentration of hydrogen peroxide in the oil bath is 0.5 g / L, and the pH value of the oil bath is adjusted to 4 using sulfuric acid.

[0040] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60 m / min.

[0041] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 75°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1 g / L and the concentration of sodium hydroxide is 3 g / L.

[0042] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 70°C, the second washing temperature is 60°C, the third washing temperature is 55°C, the final washing temperature is 73°C, and the drying temperature is 135°C.

[0043] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 120 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 40 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 0.8 g / L and the bleaching aid concentration at 0.2 g / L.

[0044] The technical parameters of the high-whiteness viscose fiber obtained in this embodiment are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 89.0%, and residual sulfur ≤4 mg / 100 g.

[0045] Example 2

[0046] The method for preparing high-whiteness viscose fiber of the present invention mainly comprises the following steps performed in sequence:

[0047] (1) Prepare bleaching aids:

[0048] A bleaching aid is prepared by mixing a compounding agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water in a mass ratio of 1:80; the mass ratio of fatty alcohol polyoxyethylene ether to fatty alcohol polyoxyethylene ether sodium sulfate in the compounding agent is 2:1;

[0049] (2) Preparation of viscose staple fibers:

[0050] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 7:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then uniformly mixed with a titanium dioxide dispersion, and fed into a spinning machine to produce viscose staple fibers; wherein the titanium dioxide dispersion is prepared with a mass ratio of titanium dioxide to water of 1:6; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to the methylcellulose in the viscose spinning stock solution is 0.5:100;

[0051] (3) Preparation of high whiteness viscose fiber:

[0052] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0053] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber, and then penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 62°C and a pH of 10, a sodium hypochlorite concentration of 1.4g / L, and a bleaching agent concentration of 0.1g / L;

[0054] The oiling process is to oil the viscose staple fibers using an oil bath at 76°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.8 g / L, and the pH value of the oil bath is adjusted to 3 using sulfuric acid.

[0055] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 61 m / min.

[0056] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 75°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 2 g / L and the concentration of sodium hydroxide is 3.5 g / L.

[0057] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 75°C, the second washing temperature is 65°C, the third washing temperature is 60°C, the final washing temperature is 77°C, and the drying temperature is 145°C.

[0058] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 210 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 20 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 1.4 g / L and the bleaching aid concentration at 0.1 g / L.

[0059] The technical parameters of the high-whiteness viscose fiber obtained in this embodiment are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 89.5%, and residual sulfur ≤4 mg / 100 g.

[0060] Example 3

[0061] The method for preparing high-whiteness viscose fiber of the present invention mainly comprises the following steps performed in sequence:

[0062] (1) Prepare bleaching aids:

[0063] A bleaching aid is prepared by mixing a compounding agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water in a mass ratio of 1:100; the mass ratio of fatty alcohol polyoxyethylene ether to fatty alcohol polyoxyethylene ether sodium sulfate in the compounding agent is 3:1;

[0064] (2) Preparation of viscose staple fibers:

[0065] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6.5:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then evenly mixed with a titanium dioxide dispersion, and fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:5; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.6:100;

[0066] (3) Preparation of high whiteness viscose fiber:

[0067] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0068] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 60°C and a pH of 9.5, a sodium hypochlorite concentration of 1.6g / L, and a bleaching agent concentration of 0.15g / L;

[0069] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0070] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0071] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0072] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0073] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 240 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 30 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 1.6 g / L and the bleaching aid concentration at 0.15 g / L.

[0074] The technical parameters of the high-whiteness viscose fiber obtained in this embodiment are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 90.0%, and residual sulfur ≤4 mg / 100 g.

[0075] Experimental data:

[0076] Comparative Example:

[0077] Comparative Example 1:

[0078] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0079] (1) Selecting coniferous wood dissolving pulp and hardwood dissolving pulp with a whiteness of ≥89% and a methyl cellulose content of ≥90%, firstly mixing the coniferous wood dissolving pulp and the hardwood dissolving pulp at a mass ratio of 6.5:100; then preparing a viscose spinning stock solution through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution and ripening; then uniformly mixing the viscose spinning stock solution with a titanium dioxide dispersion, feeding the mixture into a spinning machine to obtain viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:5; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to the methyl cellulose in the viscose spinning stock solution is 0.6:100;

[0080] (2) Preparation of high whiteness viscose fiber:

[0081] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0082] The bleaching process mainly includes the following steps: spraying a sodium hypochlorite solution (i.e., bleaching liquid) on the surface layer of the viscose staple fibers and penetrating through the surface layer of the viscose staple fibers to the lower layer of the viscose staple fibers to bleach the viscose staple fibers; the bleaching liquid has a temperature of 60° C. and a pH of 9.5, and a sodium hypochlorite concentration of 1.6 g / L;

[0083] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0084] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0085] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0086] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0087] The bleaching process also includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with sodium hypochlorite mother liquor with a flow rate of 240 L / h and a concentration of 12% to maintain the sodium hypochlorite concentration in the bleaching liquid at 1.6 g / L.

[0088] The technical parameters of the high-whiteness viscose fiber obtained in Comparative Example 1 are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 87.5%, and residual sulfur ≤5 mg / 100 g.

[0089] The main difference between Comparative Example 1 and Example 3 is that no bleaching aid is added in the bleaching process.

[0090] Comparative Example 2:

[0091] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0092] (1) Prepare bleaching aids:

[0093] The bleaching agent is prepared by mixing an additive containing fatty alcohol polyoxyethylene ether with water in a mass ratio of 1:100;

[0094] (2) Preparation of viscose staple fibers:

[0095] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6.5:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then evenly mixed with a titanium dioxide dispersion, and fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:5; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.6:100;

[0096] (3) Preparation of high whiteness viscose fiber:

[0097] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0098] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 60°C and a pH of 9.5, a sodium hypochlorite concentration of 1.6g / L, and a bleaching agent concentration of 0.15g / L;

[0099] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0100] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0101] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0102] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0103] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 240 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 30 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 1.6 g / L and the bleaching aid concentration at 0.15 g / L.

[0104] The technical parameters of the high-whiteness viscose fiber obtained in Comparative Example 2 are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 87.0%, and residual sulfur ≤5 mg / 100 g.

[0105] The main difference between Comparative Example 2 and Example 3 is that the bleaching aid does not contain the anionic surfactant fatty alcohol polyoxyethylene ether sodium sulfate.

[0106] Comparative Example 3:

[0107] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0108] (1) Prepare bleaching aids:

[0109] The bleaching agent is prepared by mixing an additive containing fatty alcohol polyoxyethylene ether with water in a mass ratio of 1:100;

[0110] (2) Preparation of viscose staple fibers:

[0111] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6.5:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then evenly mixed with a titanium dioxide dispersion, and fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:5; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.6:100;

[0112] (3) Preparation of high whiteness viscose fiber:

[0113] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0114] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 60°C and a pH of 9.5, a sodium hypochlorite concentration of 2.1g / L, and a bleaching agent concentration of 0.15g / L;

[0115] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0116] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0117] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0118] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0119] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 320 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 30 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 2.1 g / L and the bleaching aid concentration at 0.15 g / L.

[0120] The technical parameters of the high-whiteness viscose fiber obtained in Comparative Example 3 are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.10 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 88.0%, and residual sulfur ≤5 mg / 100 g.

[0121] The main difference between Comparative Example 3 and Example 3 is that the bleaching aid does not contain the anionic surfactant fatty alcohol polyoxyethylene ether sodium sulfate.

[0122] Comparative Example 4:

[0123] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0124] (1) Prepare bleaching aids:

[0125] The bleaching agent is prepared by mixing an auxiliary agent containing sodium fatty alcohol polyoxyethylene ether sulfate and water at a mass ratio of 1:100;

[0126] (2) Preparation of viscose staple fibers:

[0127] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6.5:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then evenly mixed with a titanium dioxide dispersion, and fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:5; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.6:100;

[0128] (3) Preparation of high whiteness viscose fiber:

[0129] The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber;

[0130] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 60°C and a pH of 9.5, a sodium hypochlorite concentration of 1.6g / L, and a bleaching agent concentration of 0.15g / L;

[0131] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0132] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0133] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0134] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0135] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 240 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 30 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 1.6 g / L and the bleaching aid concentration at 0.15 g / L.

[0136] The technical parameters of the high-whiteness viscose fiber obtained in Comparative Example 4 are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.15 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 87.5%, and residual sulfur ≤5 mg / 100 g.

[0137] The main difference between Comparative Example 4 and Example 3 is that the bleaching aid does not contain the nonionic surfactant fatty alcohol polyoxyethylene ether.

[0138] Comparative Example 5:

[0139] A method for preparing high-whiteness viscose fiber mainly comprises the following steps performed in sequence:

[0140] (1) Prepare bleaching aids:

[0141] The bleaching agent is prepared by mixing an auxiliary agent containing sodium fatty alcohol polyoxyethylene ether sulfate and water at a mass ratio of 1:100;

[0142] (2) Preparation of viscose staple fibers:

[0143] A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected and first mixed at a mass ratio of 6.5:100. A viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and maturation. The viscose spinning stock solution is then evenly mixed with a titanium dioxide dispersion and fed into a spinning machine to produce viscose staple fibers. The titanium dioxide dispersion is prepared from titanium dioxide and water at a mass ratio of 1:5. The mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.6:100.

[0144] (3) Preparation of high whiteness viscose fiber:

[0145] The viscose staple fiber is fed into the scouring machine and goes through the following processes: first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying to obtain high-whiteness viscose fiber.

[0146] The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 60°C and a pH of 9.5, a sodium hypochlorite concentration of 2.1g / L, and a bleaching agent concentration of 0.15g / L;

[0147] The oiling process is to oil the viscose staple fibers using an oil bath at 75°C, wherein the oil bath is a mixture of an oil agent and hydrogen peroxide, the concentration of hydrogen peroxide in the oil bath is 0.6 g / L, and the pH value of the oil bath is adjusted to 3.3 using sulfuric acid.

[0148] The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60.5 m / min.

[0149] In step (3), the desulfurization process for preparing high-whiteness viscose fiber is to desulfurize the viscose staple fiber using a desulfurizer at 78°C, wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1.8 g / L and the concentration of sodium hydroxide is 3.3 g / L.

[0150] In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 72°C, the second washing temperature is 62°C, the third washing temperature is 56°C, the final washing temperature is 75°C, and the drying temperature is 140°C.

[0151] The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 320 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 30 L / h to maintain the sodium hypochlorite concentration in the bleaching liquid at 2.1 g / L and the bleaching aid concentration at 0.15 g / L.

[0152] The technical parameters of the high-whiteness viscose fiber obtained in Comparative Example 5 are: fineness 1.65-1.75 dtex; length 38-40 mm; dry breaking strength ≥2.10 cN / dtex; dry breaking elongation 19.0%-22.0%; whiteness 88.5%, and residual sulfur ≤5 mg / 100 g.

[0153] The main difference between Comparative Example 5 and Example 3 is that the bleaching aid does not contain the nonionic surfactant fatty alcohol polyoxyethylene ether.

[0154] Detection method:

[0155] Whiteness (%): Refer to national standard GBT 14463 and its referenced corresponding standards.

[0156] The test data is shown in the following table:

[0157] Table 1 Test results of various embodiments and comparative examples

[0158]

[0159] As can be seen from Table 1, the embodiments of the present application can not only effectively reduce the amount of bleaching agent used, but also ensure high whiteness of the product, while the comparative examples cannot achieve both.

[0160] The method for preparing high-whiteness viscose fiber described in the present invention is not limited to the above embodiments. Any improvement or replacement based on the principles of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing high-whiteness viscose fiber, characterized by: It mainly includes the following steps in order: (1) Prepare bleaching aids: A bleaching agent is prepared by mixing a compounding agent containing fatty alcohol polyoxyethylene ether and fatty alcohol polyoxyethylene ether sodium sulfate with water in a mass ratio of 1:50 to 1:100; the mass ratio of fatty alcohol polyoxyethylene ether to fatty alcohol polyoxyethylene ether sodium sulfate in the compounding agent is 2:1 to 6:1; (2) Preparation of viscose staple fiber: A coniferous wood dissolving pulp and a hardwood dissolving pulp having a whiteness of ≥89% and a methylcellulose content of ≥90% are selected, and the coniferous wood dissolving pulp and the hardwood dissolving pulp are first mixed at a mass ratio of 6:100 to 7:100; a viscose spinning stock solution is then prepared through the steps of impregnation, pressing, crushing, aging, xantholysis, dissolution, and ripening; the viscose spinning stock solution is then uniformly mixed with a titanium dioxide dispersion, and the mixture is fed into a spinning machine to produce viscose staple fibers; wherein the mass ratio of titanium dioxide to water in the titanium dioxide dispersion is 1:4 to 1:6; and the mass ratio of titanium dioxide in the titanium dioxide dispersion to methylcellulose in the viscose spinning stock solution is 0.5:100 to 0.7:100; (3) Preparation of high whiteness viscose fiber: The viscose staple fiber is fed into the scouring machine and goes through the first washing, desulfurization, second washing, bleaching, third washing, final washing, oiling and drying processes in sequence to obtain high-whiteness viscose fiber; The bleaching process mainly includes the following steps: first, mixing a bleaching agent with a sodium hypochlorite solution to prepare a bleaching solution, then spraying the bleaching solution on the surface layer of the viscose staple fiber and penetrating through the surface layer of the viscose staple fiber to the lower layer of the viscose staple fiber to bleach the viscose staple fiber; the bleaching solution has a temperature of 58-62°C and a pH of 9-10, a sodium hypochlorite concentration of 0.8-1.6 g / L, and a bleaching agent concentration of 0.1-0.2 g / L; The oiling process is to oil the viscose staple fibers using an oil bath at 74-76°C, wherein the oil bath is a mixture of oil and hydrogen peroxide, wherein the concentration of hydrogen peroxide in the oil bath is 0.5-0.8 g / L, and the pH value of the oil bath is adjusted to 3-4 using sulfuric acid; The bleaching process further includes a step of recycling the used bleaching liquid, wherein the bleaching liquid is replenished with a sodium hypochlorite mother liquor having a flow rate of 120 to 240 L / h and a concentration of 12% and a bleaching aid obtained in step (1) having a flow rate of 20 to 40 L / h, so as to maintain the sodium hypochlorite concentration in the bleaching liquid at 0.8 to 1.6 g / L and the bleaching aid concentration at 0.1 to 0.2 g / L; In step (3), the desulfurization process for preparing high-whiteness viscose fibers is to desulfurize the viscose staple fibers using a desulfurizer at 75 to 80° C., wherein the desulfurizer is an aqueous solution containing sodium sulfide and sodium hydroxide, wherein the concentration of sodium sulfide is 1 to 2 g / L and the concentration of sodium hydroxide is 3 to 3.5 g / L.

2. The method for preparing high-whiteness viscose fiber according to claim 1, characterized in that: The spinning speed of the spinning machine in step (2) for preparing viscose staple fibers is 60-61 m / min.

3. The method for preparing high-whiteness viscose fiber according to claim 1, characterized in that: In step (3) of preparing high-whiteness viscose fiber, the first washing temperature is 70-75°C, the second washing temperature is 60-65°C, the third washing temperature is 55-60°C, the final washing temperature is 73-77°C, and the drying temperature is 135-145°C.

Images