CN113122946A

CN113122946A - Preparation method and product of regenerated acrylic fibers

Info

Publication number: CN113122946A
Application number: CN201911393444.5A
Authority: CN
Inventors: 徐佳威; 申增路; 段志国; 马军峰; 李振峰; 梁栋栋; 李清海; 曹冉曦; 尹安吉; 郭振宇; 申佳; 马磊; 吴兴乐
Original assignee: Hebei Aikerui Fiber Co ltd
Current assignee: Hebei Aikerui Fiber Co ltd
Priority date: 2019-12-30
Filing date: 2019-12-30
Publication date: 2021-07-16

Abstract

The invention belongs to the field of recycling of acrylic fiber products, and discloses a preparation method of regenerated acrylic fiber and a product, wherein the preparation method comprises the following steps in sequence: screening raw materials, removing impurities, separating, washing with water, drying, swelling at low temperature, stirring, heating, dissolving, filtering, purifying, spinning, washing with water, drafting, drying, shaping and obtaining a finished product; the invention also provides a regenerated acrylic product, wherein the breaking strength of the regenerated acrylic product is more than or equal to 3.0CN/dtex, the elongation at break is more than or equal to 35 percent, and the moisture regain is 1.8-2.3 percent. The preparation method realizes the recovery, separation and reutilization of the acrylic fabric, adopts the mode of dissolving after low-temperature swelling, can greatly shorten the high-temperature dissolving time and greatly reduce the energy consumption, and the performance of the prepared regenerated acrylic fiber is similar to that of the non-regenerated acrylic fiber.

Description

Preparation method and product of regenerated acrylic fibers

Technical Field

The invention belongs to the field of acrylic fiber recovery, and particularly relates to a preparation method and a product of regenerated acrylic fiber.

Background

Acrylic fiber, a scientific name of polyacrylonitrile fiber, is a fiber obtained by copolymerizing acrylonitrile as a main monomer (the content is more than 85%) and a small amount of other monomers and spinning. It is mainly characterized by that its appearance, hand feeling, elasticity and heat-insulating property are similar to those of wool, so that it is called "synthetic wool". The acrylic fiber has wide application, rich raw materials and fast development speed, is one of three synthetic fibers at present, and has the output second to that of terylene and nylon. 0.9 ton of acrylonitrile is required for producing 1 ton of acrylon, while the propylene required for synthesizing acrylonitrile is derived from petroleum by-products. However, with the global exhaustion of petroleum resources, new countermeasures are urgently needed for the production of acrylon.

The acrylic fiber is widely applied in daily life, and is mainly applied to the fields of spinning clothes, indoor decoration and part of industry in daily life. When people deal with articles such as clothes made of waste acrylic fiber raw materials, the articles are basically thrown away directly as garbage. The acrylic fiber raw material belongs to aromatic polymer materials and is hardly degraded, so that a large amount of waste is caused, and huge environmental pressure is increased. The processing method of the prior acrylic fiber downstream market semi-finished products and finished products is as follows:

(1) the downstream market semi-finished products of the acrylic fibers comprise acrylic wool tops, yarns and the like. Mainly comprises natural color or colored 100 percent pure spinning acrylic fiber material, natural color or colored acrylic fiber and other types of fiber blended material; generally, semi-finished products are sold to low-end customers at a reduced price, low-end consumable products are produced, and the semi-finished products are directly thrown away after use, so that waste is caused, and environmental pressure is increased.

(2) The downstream market finished products of the acrylic fibers comprise daily life consumables such as clothes, carpets and indoor home textiles and part of industrial fields. One part of the disposable sanitary towel belongs to a disposable article, and the disposable sanitary towel is thrown away after being used once, most of the sanitary towel is replaced after being used for a plurality of months and 2-3 years, and finally the sanitary towel is thrown away. The finished product comprises natural color or color 100% pure spinning acrylic fiber material, natural color or color acrylic fiber and other types of fiber blended material.

In summary, the reason why the current acrylic fabric cannot be largely recycled and re-dissolved for recycling is as follows:

(1) the clothes have complex components and small pure spinning proportion, particularly more than 80 percent of the acrylic fabric is blended and is doped with various miscellaneous fibers such as cotton, hemp, wool, terylene and the like, and the recovery, dissolution and re-separation are difficult;

(2) at present, the concentration of the dissolved acrylic fiber is between 5 and 11 percent, the concentration of a stock solution which is normally suitable for spinning is at least more than 24 percent, a regenerated solution after dissolution cannot be purely spun or can only be mixed with a fresh stock solution in a very small proportion (maximum 8 percent) for spinning, and large-scale industrial production cannot be realized, so that the technical bottleneck that spinning cannot be performed due to low concentration of the dissolved solution exists;

(3) the recycled raw material fiber is seriously damaged, and the regenerated acrylic fiber prepared by the recycled raw material has poor mechanical property and cannot be widely applied.

The present invention has been made in view of this situation.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects of the prior art and provide a preparation method and a product of regenerated acrylic fibers.

In order to solve the technical problems, the invention adopts the technical scheme that:

the first purpose of the invention is to provide a preparation method of recycled acrylon, which comprises the following steps:

(1) removing impurities from the recovered raw materials, washing with water, and drying to obtain regenerated dissolved raw materials;

(2) mixing the regenerated dissolving raw material with a solvent for swelling to obtain mixed regenerated slurry;

(3) squeezing and extruding the mixed regenerated slurry to remove the unswollen remainder to obtain regenerated slurry;

(4) dissolving, filtering and purifying the regenerated slurry to obtain a regenerated acrylic fiber solution;

(5) spinning the regenerated acrylic fiber solution to obtain nascent acrylic fiber, and then forming and drying to obtain regenerated acrylic fiber.

In the invention, the raw material is 100 percent acrylic fiber and products thereof and one or more than two blended textile products of the acrylic fiber and fibers such as terylene, cotton, wool and the like. The acrylic fiber pure spinning or blended spinning product comprises wool, woolen yarn, a blanket, sportswear, overcoat, artificial fur, plush, bulked yarn, hose, parasol cloth, curtain cloth, tarpaulin, plush toy and the like. The principle of raw material selection is that the higher the content ratio of the acrylic fiber components in the recovered raw material is, the higher the priority is, but the acrylic fiber and the product with acrylonitrile AN and vinyl acetate VA as the first monomer and the second monomer are selected most preferentially. Because the components of the prior textile are complex, the pure spinning proportion is small, especially more than 80 percent of the acrylic fabric is blended products which are doped with various miscellaneous fibers such as cotton, hemp, wool, terylene and the like, and the recovery, dissolution and separation are difficult. The invention extracts the acrylic fibers from the acrylic fiber blended product as the raw material and prepares 100 percent regenerated acrylic fibers, thereby solving the problem that the existing acrylic fiber blended product can not be recycled.

In the scheme, the impurity removal in the step (1) is to remove doffing paper tubes in recovered products, buttons made of various materials on clothes, decorative articles and other doped foreign matters before washing; the washing is to purify the fabric and remove various finishing agents in the recycled fabric, and the washing conditions are as follows: desalting water at 90-100 ℃, and circularly heating for 90-120 minutes; the drying is to further remove the moisture in the recovered raw materials, so as to reach the requirement of dissolved moisture, avoid the influence on dissolution and product quality due to overhigh moisture, and the drying conditions are as follows: and (3) heating the continuous chain plate dryer by using low-pressure steam, wherein the low-pressure steam pressure is 0.45-0.6 Mpa, the temperature is 160-170 ℃, and the drying temperature is controlled to be 75-80 ℃.

Further, the water washing process in the step (1) is added with an alkaline accelerator, which comprises sodium hydroxide, potassium hydroxide, water glass, trisodium phosphate, tripotassium phosphate, sodium sulfide, ammonia water and calcium hydroxide, preferably sodium hydroxide;

the alkaline accelerant accounts for 0.05-0.15% of the washing solution by mass, and preferably 0.08-0.1%;

in the scheme, the alkaline promoter is added in the washing process, and the washing solution is alkaline, so that partial cations or acid dyes and finishing auxiliaries added in the after-finishing process of the recycled raw materials can be removed more favorably, and meanwhile, the prehydrolysis effect on the acrylic fibers is achieved, and CN groups in the acrylic fibers are hydrolyzed. The washing conditions are as follows: a drum-type washing circulating heating method is adopted, desalted water is heated at 90-100 ℃, and circulating heating time is 90-120 minutes.

In a further scheme, the step (1) further comprises raw material sorting, wherein the raw material sorting is carried out according to the proportion of the acrylic fibers in the recovered raw materials, 100% of natural color acrylic fibers and products are separately classified, 100% of colored acrylic fibers and products are separately classified, the blending proportion of the acrylic fibers and other types of fibers is greater than 50%, and the blending proportion of the acrylic fibers and other types of fibers is less than 50%; dewatering can be carried out before drying in the step (1), wherein the dewatering is to remove alkaline moisture of the recovered raw materials in the washing process to the maximum extent, reduce the steam consumption of drying in the next procedure and avoid the influence of alkali liquor; in addition, when the recycled raw materials are 100% acrylic fibers and products, the acrylic fibers are required to be crushed after being dried in the step (1), and the crushing enables the acrylic fibers to be more fully dissolved in the subsequent dissolving process. It should be noted that, when the recycled raw material is a blended product of acrylic fibers and other fibers, in order to better filter and separate the acrylic fiber solution from other undissolved fibers, a crushing step is not needed after drying.

In the step (2), the regenerated dissolved raw material and the solvent are mixed in proportion, and the mass fraction of the mixed regenerated dissolved raw material is 10-28%; preferably, the mass fraction of the regenerated and dissolved raw material is 15-20%.

Within the mass fraction range, the solvent can better enter the regeneration raw material, and a better swelling effect can be achieved.

In the step (2), after the regenerated dissolving raw material is mixed with the solvent, the mixture is soaked and swelled at the temperature of 16-24 ℃, and the soaking time is 120-420 min.

In the scheme, the regenerated dissolved raw materials are firstly subjected to a low-temperature soaking swelling process, the interaction force of solvent molecules and the regenerated dissolved raw material molecules is greater than the cohesive force among the solvent molecules, so that the regenerated raw material molecules are separated from each other and dissolved in the solvent, the solvent molecules can be diffused into the regenerated raw materials due to the movement of high molecular chain segments while being separated from each other on the surfaces of the regenerated raw materials, the internal chain segments are gradually solvated, and the high molecular solute is expanded.

More specifically, in the scheme, the regenerated dissolving raw material obtained in the step (1) is placed into a container, then the solvent is injected into the container and mixed according to a certain proportion, the regenerated dissolving raw material accounts for 13-33 percent, the solvent accounts for 87-67 percent, the temperature of the solvent is controlled to 15-24 ℃ for soaking, and the mixture is stirred for 10 minutes every 1-1.5 hours. The soaking time is 2-8 hours. Therefore, after the low-temperature soaking and swelling process, the molecules in the regenerated dissolving raw material are loose, so that the regenerated dissolving raw material is easier to dissolve at high temperature, the dissolving time is greatly shortened, and meanwhile, the energy consumption and the cost are reduced.

In a further scheme, in the step (2), the solvent comprises dimethylacetamide, dimethylformamide and dimethyl sulfoxide;

preferably, the solvent is dimethylacetamide.

In the scheme, the solvent is selected according to the principle of polarity similarity (namely polar polymer is dissolved in a polar solvent, nonpolar polymer is dissolved in a nonpolar solvent, polymer with large polarity is dissolved in a solvent with large polarity, and polymer with small polarity is dissolved in a solvent with small polarity) and the principle of solvation, cohesive energy density or tolerance parameter similarity; when the recycled raw material is a blended product of acrylic fibers and other fibers, the acrylic fiber solution and other undissolved fibers can be separated to obtain an acrylic fiber solution with the purity close to 100 percent only by simple filtration because other fibers cannot be dissolved in dimethylacetamide, dimethylformamide and dimethyl sulfoxide; dimethylacetamide is particularly preferred.

Further, in the step (2), a penetrating agent is added in the swelling process, wherein the penetrating agent accounts for 0.3-1% of the mass of the recovered raw materials, and preferably 0.5-0.8%;

preferably, the osmotic agent comprises sodium hydroxide, potassium hydroxide, water glass, trisodium phosphate, tripotassium phosphate, sodium sulfide, ammonia water, calcium hydroxide, preferably sodium hydroxide.

In the scheme, the swelling speed of the acrylic fiber can be increased under the alkaline condition, because the main component of the acrylic fiber is polyacrylonitrile, CN in acrylic fiber molecules is easier to hydrolyze under the action of a strong alkaline medium, and CN groups are hydrolyzed into-CONH 2 firstly and then are further hydrolyzed into-COOH and-COONa groups. Therefore, the addition of a penetrating cosolvent, such as sodium hydroxide, potassium hydroxide, water glass, trisodium phosphate, tripotassium phosphate, sodium sulfide, ammonia water, calcium hydroxide and the like, can be beneficial to swelling, and sodium hydroxide is generally used as a promoter most frequently. Due to the addition of the penetration cosolvent, on one hand, the generated hydrolytic groups improve the hydrophilicity of polyacrylonitrile, and simultaneously, the surface roughening of the polyacrylonitrile in the spinning process is facilitated.

In the present application, the amounts of the penetrant and the antioxidant are added in a mass ratio to the recycled raw material, which is the recycled raw material in step (1).

Further, step (3) is to press and separate the obtained mixed rejuvenated slurry to remove unswollen portions. Specifically, the swollen material is extruded out of the swollen slurry by an extruder with a screen hole of 0.5-2mm, and the unswollen material is cured or dissolved again.

In a preferred embodiment, in the step (3), a solvent is added into the non-swelled residue, stirring and heating are carried out to 70-95 ℃, stirring is stopped, heat preservation is carried out for 40-60 min, and filtration is carried out to obtain a residue dissolved solution.

Further, mixing the residual material dissolving solution obtained in the step (3) with the dissolving solution obtained in the step (4), filtering and purifying; wherein the mass percentage of the residual material dissolving solution obtained in the step (3) in the combined solution is 5-30%. The scheme can achieve the purpose of fully extracting and recovering the raw materials, and simultaneously ensures that the concentration of the combined solution is higher.

In the step (4), stirring the regenerated slurry, heating to 70-95 ℃, stopping stirring, and keeping the temperature for 35-50min to obtain a dissolved solution;

preferably, the stirring speed is 600-1200 rpm;

preferably, the heating rate is 0.6-2 ℃/min, preferably 0.6-1.6 ℃/min.

In the scheme, high-speed stirring and heating are applied in the dissolving process, oligomers in the dissolving solution can be subjected to self-polymerization in the heating process to form a chain segment with higher molecular weight, and even can be grafted to other polyacrylonitrile molecular chains, so that the molecular weight of the acrylic chain segment in the acrylic fiber recovery solution is increased, the intermolecular acting force is increased, the strength of the fiber after spinning can be improved to a certain extent, and in addition, part of low-molecular substances which do not undergo self-polymerization can increase the intermolecular distance of high polymers in the acrylic fiber spinning process and weaken the entanglement effect among the molecular chain segments, so that the plasticizing effect is achieved, and the breaking elongation of the regenerated acrylic fiber is also improved.

The concentration of the dissolving solution obtained in the step (4) is 22-32%, preferably 24-28%;

or after the residual material dissolving solution obtained in the step (3) and the dissolving solution obtained in the step (4) are combined, the concentration is 22-32%, and preferably 24-28%.

In the step (4), an antioxidant is added in the dissolving process;

preferably, the antioxidant stabilizer comprises oxalic acid and/or citric acid, preferably citric acid, and the antioxidant accounts for 0.1-2% of the mass of the recycled raw materials, preferably 0.2-2%, and more preferably 0.3-0.6%.

In the invention, the temperature in the swelling step is lower, the solution is stable, and the swelling speed is accelerated by adopting a penetrant; in the dissolving process, the temperature is higher, and in order to ensure the stability of the solution, a certain amount of antioxidant stabilizer needs to be added, so that the hydrolysis of the polymer in the recovered fabric due to long-time heating and pH value increase in the dissolving process is effectively prevented, namely the generation of yellow miazines is prevented, the whiteness of the regenerated liquid is improved, and meanwhile, the NaOH solution in the solution is neutralized and removed. Because citric acid is relatively weak in acidity, low in corrosivity and good in thermal stability, the addition amount of citric acid is preferably 0.1-2%, preferably 0.2-2%, and more preferably 0.3-0.6% of the amount of raw materials in a batch.

In the further scheme, in the step (4), the solution obtained after the regenerated slurry is dissolved is subjected to multi-stage filtration, and the solution obtained after the regenerated acrylic fiber solution is recovered is subjected to multi-stage filtration to remove insoluble foreign fibers and insoluble particles. The filtration conditions are as follows: the filtration precision is less than 3 μm.

Filtering in the step (4) by adopting a three-stage filtering method, wherein the primary filtering method adopts a basket type coarse filter for filtering, the filtering pressure is 0.1-0.2 Mpa, and the filtering precision is 20-120 mm; the second-stage filtration adopts a candle filter for filtration, the filtration pressure is 0.3-0.4 Mpa, and the filtration precision is 0.5-1 mm; and the third-stage filtration is carried out by adopting a plate-and-frame filter, the filtration pressure is 0.5-0.7 Mpa, and the filtration precision is 3-5 mu m. In the scheme, the solution of the recycled and regenerated acrylic fiber solution is subjected to multistage filtration to remove insoluble foreign fibers and insoluble particles. The filtration conditions are as follows: the filtration precision is less than 3 μm, the solid content of the filtrate is less than 26%, and the viscosity is less than 16000 deberthing (cp).

Further, the step (5) and the purification process comprise:

(1) a first temperature rise stage: the heating rate is 0.5-2 ℃/min, the heating time is 30-90 min, the target temperature is 100-120 ℃,

(2) the first constant temperature stage, wherein the constant temperature time is 90-120 min

(3) In the second temperature rise stage, the temperature rise rate is 0.5-1 ℃/min, the temperature rise time is 60-180 min, and the temperature rise target temperature is 150-190 ℃;

(4) and a second constant temperature stage: the constant temperature time is 60-90 mim;

(5) and (3) cooling: the cooling rate is 1-2 ℃/min, and the target temperature of cooling is 70-100 ℃;

the vacuum degree in the purification process is-20 to-90 kPa;

preferably, (1) the first temperature raising stage: the heating rate is 0.5-1 ℃/min, the heating time is 40-60 min, the target temperature is 100-110 ℃,

(2) the first constant temperature stage, constant temperature time is 100-115 min

(3) In the second temperature rise stage, the temperature rise rate is 0.8-1 ℃/min, the temperature rise time is 90-120 min, and the temperature rise target temperature is 120-170 ℃;

(4) and a second constant temperature stage: the constant temperature time is 75-85 mim;

(5) and (3) cooling: the cooling rate is 1.5-2 ℃/min, and the target temperature of cooling is 80-90 ℃;

the vacuum degree in the purification process is-50 to-90 kPa.

In the scheme, the purification treatment is carried out on the regenerated acrylic fiber solution by adopting a stepped temperature rising mode. In the first temperature rise stage, the temperature of the regenerated acrylic fiber solution is gradually raised, and the cold glue phenomenon in the high-concentration solution is destroyed in the temperature rise process, so that the solution is uniformly dispersed; when the temperature rises to 100-120 ℃, keeping the constant temperature, entering a first constant temperature stage, and gradually evaporating the water in the solution in the process, so that the distance between polymer molecules is reduced, and the polymerization degree between the polymer molecules is improved; keeping the constant temperature for 90-120 min, then entering a second temperature rising stage, wherein in the process, along with the continuous rising of the temperature, free radicals are generated among the molecules of the high polymer, on one hand, the free radicals can generate self-polymerization, partial grafting or slight crosslinking reaction, so that the molecular weight of the high polymer is increased, the chain length is increased, and branched chains are generated, therefore, the molecules are easier to tangle, the acting force among the molecules is larger, the molecular chain is relatively difficult to stretch and deform, the breaking strength of the spun fiber is increased to a certain extent, the molecular weight is increased, the viscosity of the regenerated acrylic fiber solution is also increased, and the spinnability of the regenerated acrylic fiber solution is improved; on the other hand, as the water content is gradually reduced, the contact probability between the high molecular polymer and the low molecular substance in the solution is increased, and the free radical in the high polymer can abstract an atom from the low molecular substance to stop the self-polymerization reaction, thereby preventing the conditions that the self-polymerization reaction causes the overlarge molecular weight and the overhigh viscosity to reduce the spinnability. And when the temperature is raised to 150-190 ℃, entering a second constant temperature stage, wherein the low molecular substances dissolved in the solution and a small amount of solvent are gradually evaporated in the process, so that the content of the solvent and the low molecular substances in the fiber after spinning is reduced, the concentration of the recovered acrylic fiber solution is improved, the spinnability is improved, and the adverse effect of the solvent and the low molecular substances in the fiber after spinning on the performance of the fiber is reduced. And finally, entering a temperature reduction stage, and reducing the temperature of the regenerated acrylic fiber solution to a temperature capable of spinning.

In the invention, the waste clothes have oligomers such as the breakage, degradation and the like of acrylic fibers due to abrasion and the like, the oligomers form a high molecular chain by self polymerization in the temperature rising process and are grafted to other polyacrylonitrile molecular chains, the molecular weight of a high polymer in an acrylic fiber recovery solution is increased, the acting force among molecules is increased, the strength of the fibers spun by the recovered acrylic fiber solution is improved to a certain extent, in addition, a small amount of low molecular substances remained in the acrylic fiber solution are recovered, the distance among the molecules of the high polymer is increased in the acrylic fiber spinning process, the entanglement among the molecules is relatively weakened, the molecular chain segments have enough stretching space relatively, so that the plasticizing effect is realized, the stretching is easy and the retraction is easy, and the breaking elongation of the regenerated acrylic fibers is also improved.

The invention adopts a step heating purification mode, avoids the situation that the viscosity of the solution is increased sharply when the temperature is directly raised to the target temperature, and simultaneously, the water is continuously evaporated and bubbles appear in the solution in the process, thereby damaging the polymerization degree among molecules and causing the phenomenon that a large number of holes appear in the fiber after spinning to influence the performance of the fiber.

Further, the purification method comprises a vacuum jet circulation heating purification method, an embedded coil heating evaporator vacuum purification method, a jacket heating continuous stirring evaporator vacuum purification method and a distillation tower heating purification method, and the jacket heating continuous stirring evaporator vacuum purification method is preferably selected according to comprehensive consideration of purification effect and cost.

In a further scheme, when the colorless acrylic fiber recycled raw material is dissolved, a color correcting agent needs to be added, so that the recycled acrylic fiber after spinning is closer to the natural color. The color correcting agent is a carbazole color correcting agent, preferably carbazole violet blue, and the mass percentage of the carbazole violet blue in the recovered raw materials is 0.04-0.13%, preferably 0.047-0.07%.

Further, the steps (2) to (4) further comprise a solvent recovery process, and the temperature of cooling water during solvent recovery is less than 30 ℃.

In the scheme, the solvent in the purification process can be recycled as the dissolved solvent; in addition, if the preparation method adopts a wet spinning process, the spinning solution can also be used as a coagulating bath for wet spinning. By recycling the solvent, the waste of the solvent is reduced, and the resources are saved.

Further spinning in the step (5) is directly spinning the regenerated acrylic fiber solution; or the regenerated acrylic fiber solution in the step (5) is mixed with the fresh spinning stock solution and then spun; the raw materials of the fresh spinning solution comprise 90.1-94.25% of acrylonitrile in the spinning solution and 5.75-9.15% of vinyl acetate in the spinning solution.

In the scheme, because the spinning can be directly carried out when the concentration of the spinning solution is more than 25 percent, the concentration of the dissolved solution is 10-28 percent, preferably 24-27 percent, and the spinning can be directly carried out within the concentration range after purification without adding the solution into fresh spinning solution.

Further, when the regenerated acrylic fiber solution and the fresh spinning solution are mixed for spinning, the mass ratio of the regenerated acrylic fiber solution to the fresh spinning solution is more than 0.5:1, preferably more than 1: 1.

In the above scheme, if the regenerated spinning solution needs to be added into the fresh spinning solution for spinning, the regenerated spinning solution can be added into the fresh spinning solution in a large proportion due to the high concentration of the regenerated spinning solution, and the addition ratio of the regenerated spinning solution to the fresh spinning solution is greater than 0.5:1, preferably greater than 1: 1.

In a further scheme, the regenerated acrylic fiber spinning solution needs to be subjected to precise filtration to remove more tiny impurities in the spinning solution, and the influence of blockage of a spinneret plate by the impurities on spinning spinnability and fiber quality in the spinning process is reduced. The precise filtering conditions are as follows: the temperature is 85-90 ℃, the filtration precision is less than or equal to 3 microns, and the pressure difference is 0-1 Mpa. The regenerated acrylic fiber solution is precisely filtered and then injected into the fresh spinning solution in a pre-spinning injection mode.

Further, the spinning in the step (5) is dry spinning or wet spinning, preferably wet spinning.

In the scheme, the concentration range of wet spinning is 23-25%, the concentration of dry spinning is more than 25%, and the concentration range of the purified fiber is 10-28%, preferably 24-27%, so that dry spinning or wet spinning can be adopted.

The wet spinning is carried out in a spinning coagulating bath for DMAC wet two-step spinning, wherein the mass percentage of a solvent in the spinning coagulating liquid accounts for 40-60% of water, and the temperature of the coagulating bath is 30-50 ℃. Compared with NaSCN wet spinning and dry DMF acrylic fiber spinning processes, the process has the advantages of short spinning process route, small occupied area, flexible operation, high production efficiency, low energy consumption, low production cost and the like, so the wet process is preferred. The solvent used in the wet spinning coagulation bath may be the solvent recovered in steps (2), (3), and (4).

In a further scheme, when the spinning mode is wet spinning, the regenerated acrylic fiber dissolved solution prepared by filtering is fully mixed by 2 homogenizing static mixers to carry out wet two-step spinning, and the wet two-step spinning process comprises the following steps: the concentration of the solvent in the coagulating bath liquid is 40-60%, the temperature of the coagulating bath is 30-50 ℃, and the nascent fiber sprayed out of the coagulating bath is subjected to double diffusion forming, water washing, oiling, drying and curling, wherein the drawing multiple is 4-10 times.

The second purpose of the invention is to provide the regenerated acrylic fibers prepared by the preparation method of any one or the combination of the schemes, wherein the breaking strength of the regenerated acrylic fibers is more than or equal to 3.0CN/dtex, the elongation at break is more than or equal to 35 percent, and the moisture regain is 1.8-2.3 percent;

preferably, the cross section of the regenerated acrylic fiber has a kidney-shaped section, the edge of the section is provided with burrs, at least one side of the waist is provided with dents, the surface of the fiber is rough, and a small amount of grooves and/or depressions exist.

In the scheme, the regenerated acrylic fibers manufactured by the method disclosed by the invention are soft in handfeel and soft in color, have specific colors, are determined by the colors of the acrylic fibers recycled in batches and products thereof, do not need to be dyed, avoid the pollution of subsequent dyeing procedures to the environment, and are energy-saving and environment-friendly. The breaking strength is more than or equal to 3.0CN/dtex, the elongation at break is more than or equal to 35 percent, the index is close to that of the conventional acrylic fiber, and the fiber has the characteristics different from that of the conventional fiber. The regenerated acrylic fiber can be spun purely and can be blended with other fibers according to any proportion, and the fiber fabric prepared by the method can be widely applied to the fields of spinning, carpets and various indoor decorations.

In the scheme, the raw materials for manufacturing the regenerated acrylic fibers are acrylic fibers and products or blended products of the acrylic fibers and other fibers, the spinning solution after dissolution and purification still contains a very small amount of small molecular substances and trace impurities, a small amount of grooves and/or depressions are formed on the surface of the acrylic fibers after filamentation, the moisture absorption of the fibers is enhanced, the defects that the original acrylic fibers are poor in moisture absorption and easy to generate static electricity are obviously improved, and in addition, the defects that the acrylic fibers are not easy to color are improved to a certain extent due to the existence of the grooves and/or the depressions.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. in the original method for preparing the regenerated acrylic fiber solution, the regenerated raw material is dissolved for 8 to 12 hours at high temperature, the time is long, and the energy consumption is large. The preparation method of the invention firstly carries out low-temperature swelling and then high-temperature heating dissolution on the basis of the original preparation method of the regenerated acrylic fiber solution, not only can greatly shorten the high-temperature dissolution time, but also can improve the dissolution effect, reduce the energy consumption, and also can obtain the regenerated acrylic fiber with improved mechanical property, thereby solving the defects of long dissolution time and low efficiency of the previous acrylic fiber, and the raw material of the invention can form the regenerated stock solution after being heated and stirred for 2 hours after swelling.

2. In the original preparation method of the regenerated acrylic fiber solution, the dissolving process is long in time and high in temperature, and the penetrant and the antioxidant are added in the dissolving process at the same time.

3. The performance indexes of the regenerated acrylic fibers produced by the method are close to those of conventional fibers, the breaking strength is more than or equal to 3.0CN/dtex, the elongation at break is more than or equal to 35 percent, and the regenerated acrylic fibers are different from the regenerated acrylic fibers of the conventional fibers.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments are clearly and completely described below, and the following embodiments are used for illustrating the present invention and are not used for limiting the scope of the present invention.

Example 1

Regenerated acrylic fiber with 100% of natural color acrylic fiber as raw material

The preparation method comprises the following steps:

(1) removing foreign matters such as a yarn bobbin from the recovered raw material, and then washing with water under the following washing conditions: desalting water at 90-100 ℃, and circularly heating for 90-120 minutes; adding a sodium hydroxide alkaline promoter accounting for 0.05-0.15% of the mass of the washing solution in the washing process, and finally drying the washed raw materials, wherein the drying conditions are as follows: heating by using low-pressure steam in a continuous chain plate dryer, wherein the low-pressure steam pressure is 0.45-0.6 Mpa, the temperature is 160-170 ℃, and the drying temperature is controlled to be 75-80 ℃ to obtain a regenerated dissolving raw material; in order to facilitate the subsequent steps, the regenerated dissolved raw material is crushed.

(2) Putting the regenerated dissolving raw material into a dimethylacetamide solution, wherein the mass fraction of the regenerated dissolving raw material is 10-28%, and soaking and swelling for 120-420min at the temperature of 16-24 ℃; adding sodium hydroxide accounting for 0.3-1% of the mass of the recovered raw materials in the swelling process; obtaining mixed regeneration slurry;

(3) extruding the mixed regenerated slurry through an extruder with a sieve pore of 0.5-2mm to obtain a swelled slurry, and removing the unswollen part to obtain a regenerated slurry;

(4) stirring and heating the regenerated slurry to 70-95 ℃, and preserving the heat for 30-50 min to form a dissolved solution; adding citric acid antioxidant accounting for 0.3 percent of the mass percent of the regenerated dissolving raw material and carbazole violet blue color correcting agent accounting for 0.04 percent of the mass percent of the regenerated dissolving raw material in the dissolving process, filtering the solution after the dissolving is finished,

purifying the filtered solution, wherein the purification stage comprises: a first temperature rise stage: the heating rate is 0.5 ℃/min, the heating time is 90min, and the target temperature is 100-120 ℃; a first constant temperature stage, wherein the constant temperature time is 90 min; in the second temperature rise stage, the temperature rise rate is 0.5 ℃/min, and the temperature rise target temperature is 120-170 ℃; and a second constant temperature stage: the constant temperature time is 90 mim; and (3) cooling: the cooling rate is 1 ℃/min, and the target temperature of cooling is 70 ℃; the vacuum degree in the purification process is-20 to-90 kPa; in order to remove finer impurities, the acrylic fiber can be subjected to precise filtration to obtain a regenerated acrylic fiber solution;

(5) directly spinning the regenerated acrylic fiber solution by adopting a dimethyl acetamide wet method two-step method, and then forming and drying to obtain the nascent acrylic fiber.

In the embodiment, the breaking strength of the prepared regenerated acrylic fiber is 3.0CN/dtex, and the breaking elongation is 35%.

Examples 2-4 were carried out in a similar manner to example 1, and the specific process and performance criteria are shown in Table 1.

TABLE 1

Example 5

The preparation method comprises the following steps:

(1) removing foreign matters such as a yarn bobbin from the recovered raw material, and then washing with water under the following washing conditions: desalting water at 90-100 ℃, and circularly heating for 90-120 minutes; adding a sodium hydroxide alkaline promoter accounting for 0.3 percent of the mass of the washing solution in the washing process, and finally drying the washed raw materials under the drying conditions that: heating by using low-pressure steam in a continuous chain plate dryer, wherein the low-pressure steam pressure is 0.45-0.6 Mpa, the temperature is 160-170 ℃, and the drying temperature is controlled to be 75-80 ℃ to obtain a regenerated dissolving raw material; in order to facilitate the subsequent steps, the regenerated dissolved raw material is crushed.

adding a solvent into the unswollen excess material, stirring, heating to 70-95 ℃, stopping stirring, keeping the temperature for 40-60 min, and filtering to obtain an excess material dissolving solution;

mixing the residual material dissolving solution obtained in the step (3) with the dissolving solution obtained in the step (4), filtering and purifying; wherein, the mass percentage of the residual material dissolving solution obtained in the step (3) in the combined solution is 5-30%;

In the embodiment, the breaking strength of the prepared regenerated acrylic fiber is 3.0CN/dtex, and the breaking elongation is 35%. Examples 6-8 similar to example 5 were used, and the specific process and performance indices are shown in Table 2.

TABLE 2

Comparative example 1

The difference between the comparative example and the example 1 is that the regenerated dissolving raw material is directly dissolved according to the method of the example 1 without swelling treatment in the comparative example 1, the temperature is raised to 70-95 ℃ by stirring during the dissolving process, the dissolving time is 8-12h, and the rest steps are the same as the example 1.

Comparative example 2

This comparative example differs from example 1 in that no penetrant is added during the swelling process of comparative example 2, and the rest of the procedure is the same as example 1.

Comparative example 3

This comparative example employed a two-shot dissolution method, and the specific method refers to the method of example 1 of application No. CN201910223699.0 to prepare regenerated acrylic fiber.

Test example 1

In the test example, the performance parameters of the regenerated acrylic fibers prepared in examples 1 and 5 and comparative examples 1 to 4 are compared in table 3.

TABLE 3

From the above experimental results, it can be seen that the method of swelling at low temperature and then dissolving at high temperature is adopted in example 1, so that the regenerated acrylic fiber solution has good solubility and high concentration, the mechanical properties of the prepared regenerated acrylic fiber are good, the high-temperature dissolving time is greatly shortened, and the energy consumption can be greatly reduced.

In example 5, the excess material squeezed out after swelling is dissolved, and then the mixture is mixed with the solution dissolved by swelling in proportion, so that the mechanical properties of the regenerated acrylic fiber are further improved.

The swelling process of the embodiment 1 and the embodiment 5 is provided with specific heating and strong stirring, so that oligomers in the solution are subjected to self-polymerization to form a chain segment with higher molecular weight, and can even be grafted to other polyacrylonitrile molecular chains, the molecular weight of the acrylic chain segment in the acrylic fiber recovery solution is increased, the intermolecular acting force is increased, the strength of the fiber after spinning can be improved to a certain extent, and in addition, part of low molecular substances which are not subjected to self-polymerization increase the distance between polymer molecules in the acrylic fiber spinning process, weaken the entanglement effect between the molecular chain segments, play a role in plasticization, and improve the elongation at break of the regenerated acrylic fiber.

Comparative example 1 does not adopt swelling treatment, adopts a direct dissolution process, not only needs high-temperature dissolution for 8-12h and consumes a large amount of energy, but also the prepared regenerated acrylic fiber is inferior to that of examples 1 and 5 in mechanical property.

In the comparative example 2, no penetrant is added in the swelling treatment process, so that the swelling time is prolonged, and the mechanical properties of the prepared regenerated acrylic fiber are not as good as those of the regenerated acrylic fiber prepared in the examples 1 and 5.

Comparative example 3 the regenerated acrylic fiber prepared by the method of application No. CN201910223699.0 through two times of dissolution is similar to example 1 in mechanical properties, but the dissolution time at high temperature is long and the energy consumption is large.

Test example 2

In the test example, the ratio of the regenerated dissolving raw material to the solvent is adjusted to explore the influence of the regenerated dissolving raw material to the preparation process of the regenerated acrylic fiber solution.

Specifically, referring to the preparation method of example 1, after mixing the regenerated dissolved raw material with the solvent, the mass fractions of the regenerated dissolved raw material were controlled to be 5%, 10%, 15%, 20%, 25%, 30%, 35%, respectively, and the remaining steps were the same as example 1. The parameters of the recycled acrylic fibers obtained by the preparation are compared, and the results are shown in Table 4.

TABLE 4

From the above results, it can be seen that when the mass fraction of the regenerated soluble raw material is less than 10% or more than 30%, the mechanical properties of the regenerated acrylic fiber are slightly poor, and when the mass fraction is more than 30%, the swelling and dissolving time is obviously increased, and the swelling effect is poor. And when the mass fraction of the regenerated soluble raw material is 15-20%, the prepared regenerated acrylic fiber has better mechanical property.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The preparation method of the recycled acrylon is characterized by comprising the following steps:

2. The method for preparing regenerated acrylic fibers according to claim 1, wherein in the step (2), the regenerated soluble raw material and the solvent are mixed in proportion, and the mass fraction of the mixed regenerated soluble raw material is 10-28%;

preferably, the mass fraction of the regenerated and dissolved raw material is 15-20%.

3. The method for preparing regenerated acrylic fibers as claimed in claim 1 or 2, wherein in the step (2), the regenerated soluble raw material is mixed with the solvent and then soaked and swelled at a temperature of 16-24 ℃ for a period of 120-420 min.

4. The method for producing acrylic fibers for recycling according to any of claims 1 to 3, wherein in the step (2), the solvent comprises dimethylacetamide, dimethylformamide, dimethylsulfoxide;

preferably, the solvent is dimethylacetamide.

5. The method for preparing regenerated acrylon according to any one of claims 1-4, characterized in that in step (2), a penetrant is added in the process of swelling, and the penetrant accounts for 0.3-1% of the mass of the recycled raw material, preferably 0.5-0.8%;

6. The method for preparing recycled acrylon according to claim 1, characterized in that in step (3), the solvent is added into the non-swelled residual material, the temperature is raised to 70-95 ℃ by stirring, the stirring is stopped, the temperature is kept for 40-60 min, and the residual material solution is obtained by filtering.

7. The method for preparing acrylic fibers for recycling according to claim 6, wherein the dissolving solution of the remainder obtained in step (3) is combined with the dissolving solution obtained in step (4), filtered and purified;

wherein the mass percentage of the residual material dissolving solution obtained in the step (3) in the combined solution is 5-30%.

8. The method for preparing acrylic fibers recycled as in any one of claims 1 to 7, wherein in the step (4), the recycled slurry is stirred and heated to 70-95 ℃, the stirring is stopped, and the temperature is kept for 35-50min to obtain a dissolved solution;

preferably, the stirring speed is 600-1200 rpm;

preferably, the heating rate is 0.6-2 ℃/min, preferably 0.6-1.6 ℃/min.

9. The method for preparing recycled acrylon according to any one of claims 1-6, characterized in that in step (4), antioxidant is added in the dissolving process, and the antioxidant accounts for 0.1-2% of the mass of the recycled raw material, preferably 0.2-2%, more preferably 0.3-0.6%;

preferably, the antioxidant stabilizer comprises oxalic acid and/or citric acid, preferably citric acid.

10. The regenerated acrylic fibers prepared by the preparation method of any one of claims 1 to 9 is characterized in that the breaking strength of the regenerated acrylic fibers is more than or equal to 3.0CN/dtex, the elongation at break is more than or equal to 35 percent, and the moisture regain is 1.8 to 2.3 percent;