CN113001821B - Recovery method and recycling method of aramid fiber supporting tube in ultrafiltration membrane - Google Patents

Recovery method and recycling method of aramid fiber supporting tube in ultrafiltration membrane Download PDF

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Publication number
CN113001821B
CN113001821B CN202110172376.0A CN202110172376A CN113001821B CN 113001821 B CN113001821 B CN 113001821B CN 202110172376 A CN202110172376 A CN 202110172376A CN 113001821 B CN113001821 B CN 113001821B
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China
Prior art keywords
aramid
support tube
ultrafiltration membrane
fiber
washing
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CN113001821A (en
Inventor
朱俊强
赵开荣
曹煜彤
王蓉
王倩
宋向阳
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Sinochem High Performance Fiber Material Co Ltd
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Sinochem High Performance Fiber Material Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/08—Cleaning involving contact with liquid the liquid having chemical or dissolving effect
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B08—CLEANING
    • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
    • B08B3/00—Cleaning by methods involving the use or presence of liquid or steam
    • B08B3/04—Cleaning involving contact with liquid
    • B08B3/10—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration
    • B08B3/12—Cleaning involving contact with liquid with additional treatment of the liquid or of the object being cleaned, e.g. by heat, by electricity or by vibration by sonic or ultrasonic vibrations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B29B17/02—Separating plastics from other materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
    • B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
    • B29B17/02—Separating plastics from other materials
    • B29B2017/0203—Separating plastics from plastics
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

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  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)

Abstract

The invention provides a method for recycling an aramid fiber supporting tube in an ultrafiltration membrane and a method for recycling the aramid fiber supporting tube in the ultrafiltration membrane. The method comprises the step of separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube by using a wire stripper. The invention realizes the full play of the residual available value of the aramid support tube, and the recycled aramid support tube can be used for preparing the aramid pulp, the aramid yarn and the aramid long fiber with excellent performance.

Description

Recovery method and recycling method of aramid fiber supporting tube in ultrafiltration membrane
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to a recycling method and a recycling method of an aramid fiber supporting tube in an ultrafiltration membrane.
Background
Poly (p-phenylene terephthalamide) (PPTA), also known as para-aramid, has excellent properties of ultra-high strength, high modulus, high temperature resistance, acid and alkali resistance, light weight, etc., and has the strength of 5-6 times of steel wire, the modulus of 2-3 times of steel wire or glass fiber, the toughness of 2 times of steel wire, and the weight of only about 1/5 of steel wire, and does not decompose or melt at 560 ℃. The fiber is very suitable for being used as a lining reinforcing layer of an ultrafiltration membrane due to the characteristics of ultrahigh strength, modulus, excellent acid and alkali resistance, corrosion resistance, high temperature resistance, easiness in processing and the like of para-aramid fiber.
The reinforced pipe woven by the para-aramid fiber has high strength (more than or equal to 1000N), acid and alkali resistance (pH 0-14), high temperature resistance (can be used in an environment of 200 ℃ for a long time), is suitable for treating high-difficulty waste water such as chemical industry, printing and dyeing, electroplating, medicine, landfill leachate and the like, and can effectively avoid the conditions that the ultrafiltration membrane cannot be used such as damage, fracture, degradation and the like in the processes of installation, use and back flushing.
In general, the ultrafiltration membrane can be treated as solid waste after being used, so that the waste of high-performance aramid fiber is avoided, the use cost of enterprises is increased, and the environmental treatment burden is increased. No one has proposed recycling of the aramid support tubes in the ultrafiltration membrane. Patent CN111514757a discloses a recycling and harmless treatment method of an organic filter membrane regenerated ultrafiltration membrane, which mainly comprises the steps of crushing a membrane to be used as a solidified filler in epoxy anti-corrosion construction. The method has low recycling value and cannot fully exert the residual available value of para-aramid.
Therefore, there is a need in the art for a method of recycling an aramid support tube in an ultrafiltration membrane that is capable of fully exploiting the utilizable value of the aramid and a method of recycling the same.
Disclosure of Invention
Aiming at the problems, the invention separates the outer layer material of the ultrafiltration membrane from the lining reinforced aramid support tube, and then carries out resource recycling treatment on the aramid support tube. The invention realizes the full play of the residual available value of the aramid support tube, and the recycled aramid support tube can be used for preparing the aramid pulp, the aramid yarn and the aramid long fiber with excellent performance.
Specifically, the invention provides a method for recycling an aramid support tube in an ultrafiltration membrane, which comprises the following steps: and separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube by using a wire stripper.
In one or more embodiments, the composite ultrafiltration membrane is soaked with a softener selected from one or more of castor oil, silicone oil, and paraffin wax to soften the outer membrane and partially separate it from the inner aramid support tube prior to separating the aramid support tube using a wire stripper.
In one or more embodiments, the softener is castor oil and/or silicone oil.
In one or more embodiments, the bubble time is from 1 to 5 hours.
In one or more embodiments, the soaking temperature is 40-80 ℃.
In one or more embodiments, the soaking treatment is performed simultaneously with the ultrasonic and/or bubbling treatment.
In one or more embodiments, the composite ultrafiltration membrane is dried after soaking and then placed in a wire stripper.
In one or more embodiments, the feed tank of the wire stripper has a diameter that is 100% -120% of the outer diameter of the ultrafiltration membrane.
In one or more embodiments, the wire stripper has dual blades in parallel.
In one or more embodiments, the pressure of the wire stripper is set to 10-60N when the aramid support tube is separated using the wire stripper.
In one or more embodiments, a high pressure air purge device is disposed behind the discharge chute of the wire stripper.
In one or more embodiments, the method comprises: putting the composite ultrafiltration membrane into a wire stripper, cutting off the outer membrane, and simultaneously blowing by using high-pressure air to separate the outer membrane from the aramid fiber supporting tube; the pressure of the high-pressure air is preferably more than or equal to 0.05MPa.
In one or more embodiments, the method further comprises: the separated aramid support tube is cleaned, including acid washing, alkali washing, strong oxidizer washing, ultrasonic washing, and optional back washing.
In one or more embodiments, the backwashing includes backwashing with high pressure water.
In one or more embodiments, the acid washing includes using an acid solution, such as H, at a concentration of 5 to 20wt% 2 SO 4 And (5) cleaning by using an aqueous solution.
In one or more embodiments, the alkaline wash includes washing with an alkaline solution, such as an aqueous NaOH solution, having a concentration of 2-16 wt.%.
In one or more embodiments, the strong oxidizer purge includes a purge using an aqueous NaClO solution, which preferably has an effective chlorine content of 10-16%.
In one or more embodiments, the cleaning further comprises a surfactant cleaning, preferably selected from one or more of triethanolamine oleic soap, ethoxylated sodium alkyl sulfate, and sodium dodecyl sulfate.
The invention also provides an aramid support tube recovered by the method of any one of the embodiments.
In one or more embodiments, the aramid support tube has an impurity content of 2wt% or less;
in one or more embodiments, the intrinsic viscosity of the aramid support tube is greater than or equal to 4dl/g.
The invention also provides a method for recycling the aramid fiber supporting tube in the ultrafiltration membrane, which comprises the following steps:
(1) Separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube;
(2) Cleaning the separated aramid support tube, wherein the cleaning comprises acid washing, alkali washing, strong oxidant cleaning, ultrasonic cleaning and optional back flushing; and
(3) And (3) preparing aramid pulp, aramid yarn or aramid long fiber by using the aramid support tube treated in the step (2).
In one or more embodiments, in step (1), the aramid support tube is separated from the composite ultrafiltration membrane having an aramid support tube using the method of recovering an aramid support tube in an ultrafiltration membrane described in any of the embodiments herein.
In one or more embodiments, step (2) has one or more of the following features:
the back flushing comprises back flushing by using high-pressure water;
the acid washing includes the use of an acid solution, such as H, at a concentration of 5-20wt% 2 SO 4 Washing with aqueous solution;
the alkaline washing comprises washing with an alkaline solution, such as an aqueous NaOH solution, having a concentration of 2-16 wt%;
the strong oxidizer purge comprises a purge with an aqueous NaClO solution, preferably having an effective chlorine content of 10-16%; and
the cleaning also includes a surfactant cleaning, preferably selected from one or more of triethanolamine oleic soap, ethoxylated sodium alkyl sulfate, and sodium dodecyl sulfate.
In one or more embodiments, in step (3), preparing the aramid pulp includes: cutting the aramid support tube into chopped fibers with the length of 3-12mm, preferably 5-10mm by using a fiber pulverizer, preparing the chopped fibers into aqueous dispersion, adding the aqueous dispersion into a pulp pulverizing pump, pulverizing, and drying and opening after pulverizing.
In one or more embodiments, the fiber pulverizer employs multistage cyclic pulverization.
In one or more embodiments, the outlet of the fiber pulverizer is provided with a 10-12mm screen.
In one or more embodiments, the dispersion has an aramid content of 0.5 to 5wt%, preferably 1 to 2wt%.
In one or more embodiments, the time of comminution using the pulp comminution pump is from 2 to 20 minutes, preferably from 5 to 10 minutes.
In one or more embodiments, in step (3), preparing the aramid yarn comprises: the aramid support tube is cut into short fibers of 30-51mm using a fiber cutter, and then the short fibers are spun alone or in combination with other fibers.
In one or more embodiments, in step (3), preparing the aramid long fiber comprises: adding the aramid support tube into concentrated sulfuric acid, preparing Cheng Fangguan slurry, and preparing the aramid long fibers from the aramid slurry by adopting a dry-wet method; preferably, before adding the aramid support tube into the concentrated sulfuric acid, the aramid support tube is soaked in a hot water bath, then dried, and the dried aramid support tube is added into the concentrated sulfuric acid.
In one or more embodiments, the hot water bath is at a temperature of 60 to 100 ℃ for a time of 30 to 120 minutes.
In one or more embodiments, the ultrasound treatment is performed simultaneously with the hot water bath.
In one or more embodiments, the drying is at a temperature of 70-200 ℃ for a time of 0.5-3 hours.
In one or more embodiments, the drying is drying in a vacuum oven.
In one or more embodiments, the concentrated sulfuric acid has a concentration of 90 to 102wt%.
In one or more embodiments, the aramid pulp has a solids content of 12 to 20 weight percent.
Drawings
Fig. 1 is a schematic structural diagram of a wire stripper suitable for the present invention, wherein 1 is a wire stripper shell, 2 is a feed chute, 3 is a discharge chute, 4 is an upper roller, 5 is a lower roller, and 6 is a cutter head.
Fig. 2 is a schematic structural diagram of another wire stripper applicable to the present invention, wherein 1 is a wire stripper shell, 2 is a feed chute, 3 is a discharge chute, 4 is an upper roller, 5 is a lower roller, 6 is a cutter head, 7 is a high-pressure air blowing device, and 8 is an air outlet pipe of the high-pressure air blowing device.
Fig. 3 is a schematic flow chart of some embodiments of a method for recycling an aramid support tube in an ultrafiltration membrane of the present invention.
Detailed Description
So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.
The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.
Herein, "comprising," "including," "having," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., where "a comprises B and C" is disclosed herein, "a consisting of B and C" should be considered as having been disclosed herein.
In this document, all features such as values, amounts, and concentrations that are defined as ranges of values or percentages are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.
Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.
In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.
The ultrafiltration membrane suitable for the present invention is a composite ultrafiltration membrane having an aramid support layer. In this context, a composite ultrafiltration membrane has the meaning customary in the art, and is an ultrafiltration membrane comprising a support layer (also known as reinforcement layer) and a surface layer (also known as separation layer, outer membrane). The ultrafiltration membrane suitable for use in the present invention is preferably a hollow fiber ultrafiltration membrane. The hollow fiber ultrafiltration membrane is an ultrafiltration membrane using hollow fibers as a support layer. The support layer of the hollow fiber ultrafiltration membrane is also called a support tube. The material of the support layer or support tube suitable for the ultrafiltration membrane of the present invention is preferably an aramid, such as para-aramid. The aramid support tube refers to a support tube made of aramid. Therefore, the ultrafiltration membrane suitable for the present invention is preferably a composite hollow fiber ultrafiltration membrane using an aramid support tube as a support layer. It will be appreciated that the ultrafiltration membrane treated in accordance with the present invention is typically a used ultrafiltration membrane, but may also be an unused ultrafiltration membrane.
The material of the skin layer of the ultrafiltration membrane suitable for the present invention is typically a polymer, for example including, but not limited to, one or more of Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), polyamide, polysulfone, cellulose acetate, etc. In some embodiments, the material of the ultrafiltration membrane surface layer is PTFE. The term "composite type aramid PTFE hollow fiber ultrafiltration membrane" as used herein refers to a composite type hollow fiber ultrafiltration membrane which uses an aramid support tube as a support layer and PTFE as a surface layer material.
The wire stripper is a machine for stripping the plastic sheath and the metal core wrapped outside the wire. The wire stripper has not been used in the recovery of aramid support tubes prior to the present invention. The invention creatively applies the wire stripper to separate the outer membrane of the composite ultrafiltration membrane and the aramid support tube. The basic construction of the wire stripper applicable to the present invention is the same as that of a conventional wire stripper. The wire stripping machine includes feed chute and blown down tank, is used for feeding and ejection of compact respectively. The diameter of the feed chute used in the invention is slightly larger than the outer diameter of the composite ultrafiltration membrane, so that the ultrafiltration membrane is convenient to feed. In some embodiments, the diameter of the stripper feed tank is greater than the outer diameter of the composite ultrafiltration membrane while not exceeding 120% of the outer diameter of the composite ultrafiltration membrane, e.g., the stripper feed tank may have a diameter of 110±5% of the outer diameter of the composite ultrafiltration membrane.
The wire stripper comprises a cutter head, which is originally used for cutting off a plastic wrapping wrapped outside the wire, and is used for cutting off an outer membrane of the composite ultrafiltration membrane. The wire stripper may be a known drum stripper comprising at least one pair of oppositely disposed drums, the oppositely disposed drums rotating in opposite directions, respectively, and the cutter head may be disposed on one or both of the drums. The cutter heads are generally disposed along the circumference of the drum. The material (such as electric wire) is led into the gap between two rollers arranged oppositely by the feeding groove, and passes through the gap under the drive of the rollers, meanwhile, the wrapping of the material is scratched by the cutter head on the rollers, and then the material is discharged by the discharging groove. In a preferred embodiment, the wire stripper of the present invention includes multiple cutting heads, e.g., double cutting heads, in parallel to facilitate adequate scoring of the outer membrane of the composite ultrafiltration membrane.
The wire stripper used in the present invention optionally or preferably further comprises a high pressure air purge device. Conventional wire strippers do not include high pressure air purge devices. According to the invention, the high-pressure air blowing device is arranged on the wire stripping machine, and the separation of the outer membrane of the composite ultrafiltration membrane and the aramid support tube is promoted by blowing high-pressure air. The high-pressure air blowing device is arranged behind the discharge chute of the wire stripper. And an air outlet of the high-pressure air purging device is communicated with the discharge chute. The high pressure air purge device may be a known purge device capable of providing high pressure air of 0.05MPa or more.
Fig. 1 shows a construction of a wire stripper suitable for use in the present invention. The wire stripper comprises a shell 1, a feed chute 2, a discharge chute 3, an upper roller 4, a lower roller 5 and a cutter head 6. The upper roller 4 and the lower roller 5 are oppositely disposed in the housing 1 to rotate in opposite directions, respectively. The cutter heads 6 are disposed on the upper drum 4 and are arranged along the circumferential direction of the drum. The feed chute 2 and the discharge chute 3 are aligned with a gap between the upper drum 4 and the lower drum 5, which are disposed near both ends of the gap, respectively.
Fig. 2 shows a construction of another wire stripper suitable for use in the present invention. The wire stripper differs from the wire stripper shown in fig. 1 in that it further comprises a high pressure air purge device 7. The high pressure air purge device 7 includes an air outlet duct 8. The discharge chute 3 can be communicated with an air outlet pipe 8 of the high-pressure air purging device 7, so that the high-pressure air purges the materials after the foreskin is peeled.
The traditional composite ultrafiltration membrane tube separation process uses manual cutting, an outer membrane (such as a PTFE membrane and a PVDF membrane) is scratched by a steel knife, and an aramid support tube wrapped inside is taken out. Compared with manual stripping, the separation efficiency of separating the aramid fiber supporting tube from the outer membrane in the ultrafiltration membrane by adopting the wire stripper can be improved by more than 10 times, and the process is stable and is not easy to scratch the aramid fiber supporting tube.
The present inventors have found that when the wire stripper is used to separate the aramid support tube, setting the pressure of the wire stripper to 10 to 60N, for example, 10N, 12N, 15N, 18N, 20N, 25N, 30N, 40N, 50N, 60N or in the range of any two of these pressures helps to avoid the cutter head of the wire stripper from scratching the aramid support tube and improves the quality of the product (for example, aramid pulp) produced from the recovered aramid support tube. The manner in which the stripper pressure is set is conventional, for example, in the case of a drum stripper, the stripper pressure can be adjusted by controlling the amount of gap between two oppositely disposed drums.
The method for recovering the aramid support tube in the ultrafiltration membrane comprises the step of separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube by using a wire stripper.
In general, the method of recovering an aramid support tube in an ultrafiltration membrane of the present invention comprises: the composite ultrafiltration membrane (e.g., an aramid PTFE hollow fiber ultrafiltration membrane) is placed in a wire stripper to slit the outer membrane (e.g., PTFE layer) while optionally or preferably purging with high pressure air to separate the outer membrane (e.g., PTFE layer) from the aramid support tube. The pressure of high-pressure air during purging is preferably more than or equal to 0.05MPa, which is favorable for separating the outer membrane of the composite ultrafiltration membrane from the aramid support tube.
The invention discovers that before the composite ultrafiltration membrane is put into a wire stripping machine, the composite ultrafiltration membrane is soaked in a softening agent, so that an outer membrane can be softened, and the outer membrane is partially separated from an inner aramid support tube. Softeners suitable for use in the present invention are one or more selected from castor oil, silicone oil, paraffin wax, etc., preferably castor oil and/or silicone oil. The soaking time may be 1-5 hours, for example 2.+ -. 0.5 hours. The soaking temperature may be 40-80 ℃, for example 60+ -10 ℃. And taking out the composite ultrafiltration membrane after soaking, drying, and then putting the composite ultrafiltration membrane into a wire stripping machine. The drying may be air-drying, for example, with nitrogen gas at a low pressure of 0.02.+ -. 0.01 MPa. According to the invention, the ultrafiltration membrane is soaked by using the softening agent, and the softening agent plays a role in lubricating and softening, so that the aramid support tube and the outer membrane are partially separated, and the separation efficiency of separating the aramid support tube from the outer membrane by using a wire stripper in the subsequent process can be effectively improved. The composite ultrafiltration membrane is preferably subjected to ultrasonic and/or bubbling treatment simultaneously with the soaking treatment with the softener, which facilitates partial separation of the outer membrane from the aramid support tube.
The method for recycling the aramid fiber supporting tube in the ultrafiltration membrane comprises the following steps:
(1) Membrane tube separation: separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube;
(2) Cleaning: cleaning the separated aramid fiber supporting tube;
(3) And (3) recycling: and (3) preparing aramid pulp, aramid yarn or aramid long fiber by using the aramid support tube treated in the step (2).
In the pipe die separation step, the aramid support tube is preferably separated from the composite ultrafiltration membrane with the aramid support tube by using a wire stripper. In some embodiments, the membrane tube separation comprises: the composite ultrafiltration membrane (e.g., an aramid PTFE hollow fiber ultrafiltration membrane) is placed in a wire stripper to slit the skin (e.g., PTFE layer) while the skin (e.g., PTFE layer) and the aramid support tube are separated, preferably or preferably, by purging with high pressure air. Wherein the pressure of high-pressure air during purging is preferably more than or equal to 0.05MPa. Before the composite ultrafiltration membrane is placed in the wire stripper, the composite ultrafiltration membrane is preferably soaked in a softening agent, and the outer membrane is softened and partially separated from the inner aramid support tube, optionally or preferably in combination with ultrasonic and/or bubbling treatment. The softener is one or more selected from castor oil, silicone oil, paraffin, etc., preferably castor oil and/or silicone oil. The soaking time may be 1-5 hours, for example 2.+ -. 0.5 hours. The soaking temperature may be 40-80 ℃, for example 60+ -10 ℃. And taking out the composite ultrafiltration membrane after soaking, drying, and then putting the composite ultrafiltration membrane into a wire stripping machine. The drying may be air-drying, for example, with nitrogen gas at a low pressure of 0.02.+ -. 0.01 MPa.
In the washing step, the washing may include one or more or all selected from aqueous, acid washing, alkali washing, strong oxidizer washing, ultrasonic washing, surfactant washing, and back washing. The water washing is carried out by water. In the present invention, the water is preferably pure water. Pickling is by using acid, e.g. H 2 SO 4 The aqueous solution (which may be at a concentration of 5-20wt%, for example 10.+ -. 2 wt%) is subjected to washing. The acid washing can react iron oxides such as scale and rust with an acid solution to form salts which are dissolved in the acid solution and removed.Alkaline washing is a washing with an alkaline solution, such as an aqueous NaOH solution (the concentration may be 2-16wt%, for example 10.+ -. 5 wt%). The alkaline washing can soften, loosen, emulsify and disperse sediment and remove greasy dirt. The surfactant cleaning is cleaning with a solution containing a surfactant, for example, cleaning with an aqueous solution containing a surfactant. Surfactant cleaning is preferably included to facilitate cleaner cleaning. The surfactant concentration of the surfactant-containing solution may be 1-5wt%. Surfactants suitable for use in the present invention may be one or more selected from triethanolamine oleic soap, sodium ethoxylated alkyl sulfate and sodium lauryl sulfate. The surfactant cleaning can be performed simultaneously with the alkaline cleaning, i.e. some surfactant (such as triethanolamine oleic soap with concentration of 1-5 wt%) can be added during the alkaline cleaning to enhance the cleaning effect. Strong oxidizer cleaning is a cleaning using a strong oxidizer aqueous solution, such as NaClO aqueous solution (available chlorine content may be 10-16%, such as 13±2%) for disinfection and bleaching. Ultrasonic cleaning is to soak a base film in a cleaning liquid and apply ultrasonic waves for thoroughly washing away residual dirt left by previous cleaning. The invention discovers that ultrasonic cleaning is carried out on the separated aramid support tube, which is beneficial to improving the cleaning effect, thereby improving the performance of the product manufactured by the recycled aramid support tube. The cleaning liquid used in ultrasonic cleaning can be water, acid liquor, alkali liquor, solution containing surfactant and strong oxidant aqueous solution, i.e. ultrasonic cleaning can be carried out simultaneously with water cleaning, acid cleaning, alkali cleaning, surfactant cleaning and strong oxidant cleaning. The stirring may be performed while washing with water, washing with acid, washing with alkali, washing with a surfactant, and washing with a strong oxidizing agent. The back flushing is performed by using water (e.g., high-pressure water) to wash away dirt on the surface of the support tube. The back flushing is preferably included, which is advantageous for cleaning cleaner. In some embodiments, the cleaning comprises water washing, acid washing, alkaline washing, strong oxidizer washing, ultrasonic washing, optional backwash, and optional surfactant washing. The final step of the washing is preferably water washing. Preferably, the washing is carried out in the last step of washing until the pH of the washing liquid reaches neutral. In the invention, after the aramid support tube is cleaned, the aramid support tube is usually dried, And carrying out the resource utilization step of the aramid fiber supporting tube. The cleaned aramid support tube can be dried in a drying mode.
In some embodiments, the cleaning comprises: acid washing, preferably with H in a concentration of 5-20wt%, for example 10.+ -. 2wt% 2 SO 4 Washing with aqueous solution; alkali washing, preferably with 2-16wt%, such as 10+ -5wt% NaOH aqueous solution, and optionally adding surfactant (such as triethanolamine oleate soap, with concentration of 1-5wt%); strong oxidizer cleaning, preferably with an aqueous NaClO solution having an effective chlorine content of 10-16%, for example 13±2%; washing with water, preferably finally until the pH value reaches neutrality; and optionally back flushing. Wherein, the washing can be carried out firstly, then the alkali washing is carried out, and then the strong oxidant is used for washing. Water washing may be performed between acid washing and alkali washing, between alkali washing and strong oxidizer washing. In the invention, the pickling, alkaline washing and strong oxidizer cleaning can be realized by immersing the aramid support tube in acid solution, alkali solution or strong oxidizer aqueous solution. The soaking time may be 30-120min, for example 60+ -20 min. Stirring can be performed during soaking. Preferably, the soaking is performed with ultrasonic treatment. The stirring and the ultrasonic treatment may be performed simultaneously or sequentially, for example, stirring may be performed for 15 to 60 minutes, for example, 30.+ -. 10 minutes, followed by ultrasonic treatment for 15 to 60 minutes, for example, 30.+ -. 10 minutes, respectively, during the acid washing, the alkali washing and the strong oxidizer washing.
The impurity content of the aramid fiber supporting tube recovered by the method is less than or equal to 3wt%, preferably less than or equal to 2wt%, such as less than or equal to 1.8wt% and less than or equal to 0.9wt%, so that the aramid fiber supporting tube has higher purity. The impurity content of the aramid support tube refers to the firing margin. The aramid support tube recovered by the method has the intrinsic viscosity of more than or equal to 4dl/g, such as more than or equal to 4.4dl/g, more than or equal to 4.6dl/g, more than or equal to 4.8dl/g and more than or equal to 4.9dl/g, and therefore has higher molecular weight.
In the present invention, preparing the aramid pulp may include: cutting the aramid support tube into chopped fibers with the length of 3-12mm, preferably 5-10mm, for example 6-8mm by using a fiber pulverizer, adding water to prepare chopped fiber aqueous dispersion, pulverizing the dispersion by a pulp pulverizing pump, and drying and opening the pulverized dispersion to prepare the aramid finished pulp. Wherein the fiber pulverizer preferably adopts multistage circulation pulverization, and the outlet of the fiber pulverizer is preferably provided with a 10-12mm screen, for example 11+/-0.5 mm screen, so as to ensure that the chopped fibers after pulverization are uniform in length (between 3-12mm, preferably 6-10 mm). The aramid content of the aqueous dispersion of chopped fibers may be 0.5 to 5% by weight, preferably 1 to 2% by weight. The time for pulverizing the dispersion using the pulp pulverizing pump may be 2 to 20 minutes, preferably 5 to 10 minutes, for example, 7.+ -. 1 minute.
The fiber length of the aramid pulp prepared by the method can be more than or equal to 0.8mm, preferably more than or equal to 1.0mm, for example more than or equal to 1.1mm, and the specific surface area can be more than or equal to 5m 2 /g, preferably not less than 6m 2 /g, e.g.gtoreq.6.5 m 2 The freeness can reach 20SR, for example 23SR.
In the present invention, preparing the aramid yarn may include: cutting the aramid support tube into short fibers of 30-51mm, such as 38+ -5 mm and 38-51mm by using a fiber cutter, and spinning the aramid short fibers or mixing the aramid short fibers with other fibers to obtain yarns. The length of the other fibers used for blending may be 38-51mm, e.g., 38+ -5 mm, 38-51mm. In some embodiments, the aramid support tube is a para-aramid support tube, and the cut staple fibers are para-aramid staple fibers. The para-aramid staple fiber and meta-aramid staple fiber are mixed and spun to prepare fireproof yarn for fireproof clothing, blanket and other fireproof articles. During blending, the mass ratio of the short fibers cut by the aramid support tube to other short fibers can be 1:10 to 10:1, for example 1: 9. 1: 8. 1: 7. 1: 6. 1: 5. 1: 4. 1: 3. 1: 2. 1:1.
the length deviation rate of the aramid yarn prepared by the method can be less than or equal to 5%, such as less than or equal to 4 percent and less than or equal to 3 percent, the ultra-long fiber rate can be less than or equal to 0.1%, such as less than or equal to 0.07 percent and less than or equal to 0.06 percent and less than or equal to 0.05 percent, the double length fiber content can be less than or equal to 5mg/100g, such as less than or equal to 4mg/100g, less than or equal to 3mg/100g and less than or equal to 2mg/100g, the linear density deviation rate can be less than or equal to 5%, such as less than or equal to 4.9 percent and less than or equal to 4.8 percent, less than or equal to 4.7 percent and less than or equal to 4.6 percent, and the chlorine and bromine content can be less than or equal to 3000ppm, preferably less than or equal to 1000ppm, such as less than or equal to 500ppm, less than or equal to 400ppm and 321ppm.
In the present invention, the preparation of the aramid long fiber may include: the aramid support tube is added into concentrated sulfuric acid (the concentration of the concentrated sulfuric acid can be 90-102wt%, such as 100+ -2 wt%, 90-100 wt%) to prepare Cheng Fangguan slurry (the solid content can be 12-20wt%, such as 15-20wt%, 19.5+ -0.5 wt%) for preparing the aramid long fiber. The aramid pulp can be prepared into aramid long fibers by adopting a dry-wet method. The prepared aramid long fiber can be used for weaving an aramid reinforced pipe. In a preferred embodiment, the aramid support tube is immersed in a hot water bath prior to adding the aramid support tube to the concentrated sulfuric acid. The hot water bath temperature may be 60-100deg.C, such as 70.+ -. 10 ℃ and 70.+ -. 5 ℃. The hot water bath time may be 30-120min, for example 60+ -20 min. Stirring and/or ultrasonic treatment can be carried out during the hot water bath; the stirring and the ultrasonic treatment may be performed simultaneously or sequentially, for example, stirring may be performed for 15 to 60 minutes, for example, 30.+ -. 10 minutes, followed by ultrasonic treatment for 15 to 60 minutes, for example, 30.+ -. 10 minutes. Deep cleaning is carried out on the aramid fiber support tube through a hot water bath, intermolecular van der Waals acting force is enhanced, and viscosity of the aramid fiber support tube is improved. The ultrasonic treatment may be performed while the hot water bath is being performed. And after the hot water bath, drying the aramid support tube, and then adding the aramid support tube into concentrated sulfuric acid. The aramid support tube after hot water bath can be dried in a vacuum oven. The drying temperature may be 70-200deg.C, such as 80-150deg.C, 90-120deg.C, 105+ -5deg.C. The drying time may be 0.5 to 3 hours, preferably 60.+ -. 20 minutes. Compared with the method for preparing the aramid fiber slurry by directly adding the recovered aramid fiber support tube into the concentrated sulfuric acid, the method provided by the invention has the advantages that the recovered aramid fiber support tube is subjected to hot water bath treatment, and then the concentrated sulfuric acid is added to prepare the aramid fiber slurry, so that the strength and the modulus of the aramid fiber long fiber prepared from the aramid fiber slurry are effectively improved.
The linear density of the aramid fiber long fiber prepared by the method can reach more than or equal to 1100dtex, preferably more than or equal to 1100dtex, for example more than or equal to 1116dtex, the linear density deviation rate can reach less than or equal to +/-5%, the strength can reach more than or equal to 16cN/dtex, for example more than or equal to 17cN/dtex, preferably more than or equal to 18cN/dtex, for example more than or equal to 18.6cN/dtex, the modulus can reach more than or equal to 600cN/dtex, preferably more than or equal to 650cN/dtex, for example more than or equal to 676cN/dtex, and the elongation can reach 2.5-5%, preferably 2.5-4%, for example 2.5-3.6%.
Fig. 3 is a schematic flow chart of some embodiments of a method for recycling an aramid support tube in an ultrafiltration membrane of the present invention. As shown in fig. 3, in some embodiments, the present invention first separates an ultrafiltration membrane into an outer membrane (e.g., a PTFE membrane) and an aramid support tube, then washes and dries the separated aramid support tube, then pulverizes the aramid support tube into pulp fibers, opens to make pulp, or secondarily washes the aramid support tube, spins into aramid long fibers, then weaves the aramid support tube, or cuts the aramid support tube into short fibers, and blends the other fibers into yarns.
In some embodiments, the method for recycling the aramid support tube in the ultrafiltration membrane comprises the following steps:
(1) Membrane tube separation: immersing the composite aramid PTFE hollow fiber ultrafiltration membrane in a softener, preferably simultaneously carrying out ultrasonic wave and bubbling treatment, so as to soften the outer membrane and partially separate the outer membrane from the inner aramid support tube, wherein the softener is one or more selected from castor oil, silicone oil and paraffin, preferably castor oil and/or silicone oil, the immersing time can be 1-5h, such as 2+/-0.5 h, and the immersing temperature can be 40-80 ℃, such as 60+/-10 ℃; drying the composite ultrafiltration membrane after soaking, then putting the composite ultrafiltration membrane into a wire stripper, and scribing the outer membrane PTFE layer, preferably simultaneously blowing by using high-pressure air, so that the PTFE layer and the aramid support tube are separated; the diameter of the feed chute of the wire stripper is preferably slightly larger than the outer diameter of the composite ultrafiltration membrane; the pressure of the high-pressure air is preferably more than or equal to 0.05MPa;
(2) Cleaning: cleaning the separated aramid support tube, wherein the cleaning comprises the following steps:
acid washing: for example, H is used in a concentration of 5-20wt%, for example 10.+ -. 2wt% 2 SO 4 Washing with aqueous solution;
alkali washing: for example, washing with 2-16wt%, such as 10+ -5wt% NaOH aqueous solution, and optionally adding surfactant (such as triethanolamine oleic soap, 1-5wt%);
and (3) cleaning with a strong oxidant: for example, using an aqueous NaClO solution having an effective chlorine content of 10-16%, for example 13+ -2%;
Washing with water, preferably finally until the pH value reaches neutrality; and
optionally back flushing;
preferably, the cleaning includes ultrasonic cleaning, which may be performed simultaneously with acid washing, alkali washing, and/or enhancer washing;
(3) And (3) recycling: the aramid pulp, aramid yarn or aramid long fiber is prepared using the separated aramid support tube, wherein the method of preparing the aramid pulp, aramid yarn and aramid long fiber may be as described in any of the embodiments herein.
The invention has the following advantages:
1. the method for recycling the aramid support tubes in the ultrafiltration membrane has high recycling efficiency, fully exerts the available value of the aramid support tubes, and has good quality of aramid pulp, aramid yarns and aramid long fibers prepared from the recycled aramid support tubes;
2. the separation efficiency of separating the aramid fiber supporting tube from the outer membrane in the ultrafiltration membrane by adopting the wire stripper is high, the process is stable, and the aramid fiber supporting tube is not easy to scratch;
3. according to the invention, the ultrafiltration membrane is soaked by using the softening agent, and the softening agent plays a role in lubrication and softening, so that the aramid support tube and the outer membrane are partially separated, and the separation efficiency of separating the aramid support tube and the outer membrane by using the wire stripper can be further improved;
4. The aramid fiber support tube recovered by the method has good quality, low impurity content and high intrinsic viscosity.
The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods, reagents and materials used in the examples are those conventional in the art unless otherwise indicated. The starting compounds in the examples are all commercially available. The composite aramid PTFE hollow fiber ultrafiltration membranes used in the examples and comparative examples were derived from medium-high-fiber, meta-aramid short-fiber was derived from san euro.
Example 1
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare aramid pulp:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 15N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. Cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube in the solution after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in 10wt% NaOH solution, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, soaking in NaClO (effective chlorine content 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the resulting aramid support tube had an impurity content (balance burned) of 1.8% and an intrinsic viscosity of 4.9dl/g, and the intrinsic viscosity test method herein was GB/T1632.
3. Preparing aramid pulp: cutting the aramid support tube obtained in the step 2 into 6mm chopped fibers by using a fiber pulverizer, wherein the fiber pulverizer adopts multistage circulation pulverization, and an 11mm screen is arranged at the outlet of the fiber pulverizer; adding water to prepare an aramid fiber dispersion liquid with the solid content of 1wt%, adding the dispersion liquid into an aramid fiber crushing pump to crush for 7min, and drying and opening the crushed aramid fiber pulp to prepare the para-aramid fiber finished pulp fiber.
The performance of the aramid pulp prepared in example 1 was tested according to FZ/T51015-2018, the textile industry standard of the people's republic of China, and the results are shown in Table 1. The requirements of the aramid pulp on the qualified products are as follows: the length of the fiber is more than or equal to 0.8mm, and the specific surface area is more than or equal to 5m 2 And/g, and the beating degree is more than or equal to 20SR. The aramid pulp prepared in example 1 satisfies the conditions of the aramid pulpAnd (5) the requirements of the lattice product.
Example 2
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare aramid pulp:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 80N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube in the solution after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in 10wt% NaOH solution, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, soaking in NaClO (effective chlorine content 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 2.6 percent, and the intrinsic viscosity is 4.6dl/g.
3. Preparing aramid pulp: cutting the aramid support tube obtained in the step 2 into 6mm chopped fibers by using a fiber pulverizer, wherein the fiber pulverizer adopts multistage circulation pulverization, and an 11mm screen is arranged at the outlet of the fiber pulverizer; adding water to prepare an aramid fiber dispersion liquid with the solid content of 1wt%, adding the dispersion liquid into an aramid fiber crushing pump to crush for 7min, and drying and opening the crushed aramid fiber pulp to prepare the para-aramid fiber finished pulp fiber.
The performance of the aramid pulp prepared in example 2 was tested according to FZ/T51015-2018, the textile industry standard of the people's republic of China, and the results are shown in Table 1.
Table 1: properties of the aramid pulp of examples 1-2
Example 3
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare aramid yarns:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 20N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. Cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in an aqueous solution of 10wt% NaOH and 2wt% triethanolamine oleic soap, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, soaking in a NaClO (effective chlorine content of 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 0.9%, and the intrinsic viscosity is 4.8dl/g.
3. Preparing aramid yarn: cutting the aramid support tube obtained in the step 2 into short fibers with the length of 38mm by using a fiber cutter, and then mixing the short fibers with the meta-aramid short fibers with the length of 38mm according to the following ratio of 1:9, mixing and spinning the materials according to the mass ratio to prepare the aramid fiber finished flame-retardant yarn.
The flame-retardant yarn prepared in example 3 was subjected to performance tests according to the GB/T14335 chemical fiber short fiber linear density test method and the GB/T14336 chemical fiber short fiber length test method, and the results are shown in Table 2. The requirements of the flame-retardant yarn on the superior products are as follows: the length deviation rate is less than or equal to 5%, the ultra-long fiber rate is less than or equal to 0.1%, the double-long fiber content is less than or equal to 5mg/100g, the linear density deviation rate is less than or equal to 5%, and the chlorine and bromine content is less than or equal to 1000ppm. The flame-retardant yarn prepared in example 3 meets the requirements of high-grade flame-retardant yarns.
Example 4
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare aramid yarns:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 20N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube after stirring at high speed for 30min, soaking in an aqueous solution of 10wt% NaOH and 2wt% triethanolamine oleic soap after rinsing with clear water, taking out the support tube after stirring at high speed for 30min, soaking in a NaClO (effective chlorine content 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 2.9%, and the intrinsic viscosity is 4.4dl/g.
3. Preparing aramid yarn: cutting the aramid support tube obtained in the step 2 into short fibers with the length of 38mm by using a fiber cutter, and then mixing the short fibers with the meta-aramid short fibers with the length of 38mm according to the following ratio of 1:9, mixing and spinning the materials according to the mass ratio to prepare the aramid fiber finished flame-retardant yarn.
The flame-retardant yarn prepared in example 4 was subjected to performance tests according to the GB/T14335 chemical fiber staple linear density test method and the GB/T14336 chemical fiber staple length test method, and the results are shown in Table 2. The requirements of the flame-retardant yarn on the qualified products are as follows: the length deviation rate is less than or equal to 5 percent, the ultra-long fiber rate is less than or equal to 0.1 percent, the double-long fiber content is less than or equal to 5mg/100g, the linear density deviation rate is less than or equal to 5 percent, and the chlorine and bromine content is less than or equal to 3000ppm. The flame-retardant yarn prepared in example 4 meets the requirements of qualified flame-retardant yarns.
Example 5
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare aramid yarns:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 20N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. Cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube in the solution after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in 10wt% NaOH solution, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, soaking in NaClO (effective chlorine content 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 1.8%, and the intrinsic viscosity is 4.9dl/g.
3. Preparing aramid yarn: cutting the aramid support tube obtained in the step 2 into short fibers with the length of 38mm by using a fiber cutter, and then mixing the short fibers with the meta-aramid short fibers with the length of 38mm according to the following ratio of 1:9, mixing and spinning the materials according to the mass ratio to prepare the aramid fiber finished flame-retardant yarn.
The flame-retardant yarn prepared in example 5 was subjected to performance tests according to the GB/T14335 chemical fiber short fiber linear density test method and the GB/T14336 chemical fiber short fiber length test method, and the results are shown in Table 2. The flame-retardant yarn prepared in example 5 meets the requirements of qualified flame-retardant yarns.
Table 2: performance of the flame retardant yarns of examples 3-5
Example 6
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare the aramid long fibers:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 18N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 Taking out the support tube in the solution after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in 10wt% NaOH solution, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, soaking in NaClO (effective chlorine content 13%) solution after rinsing with clear water, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 1.8%, and the intrinsic viscosity is 4.9dl/g.
3. Hot water bath: soaking the aramid fiber supporting tube obtained in the step 2 in pure water at 70 ℃, stirring at a high speed for 30min and carrying out ultrasonic treatment for 30min, taking out the aramid fiber supporting tube, and drying the aramid fiber supporting tube in a drying oven at 105 ℃ for 1h;
4. preparing aramid fiber long fibers: and (3) dissolving the aramid support tube obtained in the step (3) in 100wt% of concentrated sulfuric acid to prepare aramid slurry with the solid content of 19.5wt%, and preparing the aramid long fiber by adopting a dry-wet method.
The performance of the aramid long fiber prepared in example 6 was tested according to ASTM D1907 and ASTM D885, and the results are shown in table 3. The requirements of the aramid fiber long fiber on the superior products are as follows: the deviation rate of linear density is less than or equal to +/-5%, the strength is more than or equal to 18cN/dtex, the modulus is more than or equal to 650cN/dtex, and the elongation is 2.5-4%. The aramid long fiber prepared in the example 6 meets the requirements of superior products of the aramid long fiber.
Examples 7 to 9
Examples 7-9 para-aramid support tubes were separated from a composite para-aramid PTFE hollow fiber ultrafiltration membrane by using the method for recycling the aramid support tubes in the ultrafiltration membrane of the present invention, and the separated para-aramid support tubes were used to prepare long aramid fibers:
1. soaking the softening agent: soaking a hollow fiber ultrafiltration membrane in a softener, wherein the softener is castor oil (example 7), silicone oil (example 8) or paraffin (example 9), the soaking time is 2 hours, the soaking temperature is 60 ℃, ultrasonic waves and bubbling are matched while soaking, so that an outer membrane is softened, the outer membrane is partially separated from an inner aramid support tube, and the hollow fiber ultrafiltration membrane is taken out after soaking and is air-dried by using low-pressure nitrogen gas of 0.02 MPa;
2. A wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane treated in the step 1 into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 18N; the separation efficiencies of examples 7, 8 and 9 are respectively 2.5kg, 2.4kg and 2.2kg of hollow fiber ultrafiltration membranes which can be peeled off by one machine per hour;
3. cleaning: at room temperature, 100g of the aramid support tube obtained in the step 2 is soaked in 10wt% H 2 SO 4 In the solution, the supporting tube is taken out after stirring for 30min at high speed and ultrasonic for 30min, and is soaked in 10wt% NaO after rinsing with clear waterTaking out the support tube in the H solution after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water, soaking in NaClO (effective chlorine content 13%) solution, taking out the support tube after stirring at high speed for 30min and ultrasonic for 30min, rinsing with clear water for multiple times, testing the pH value of the aqueous solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 1.8%, and the intrinsic viscosity is 4.9dl/g.
4. Hot water bath: soaking the aramid fiber supporting tube obtained in the step 3 in pure water at 70 ℃, stirring at a high speed for 30min and carrying out ultrasonic treatment for 30min, taking out the aramid fiber supporting tube, and drying the aramid fiber supporting tube in a drying oven at 105 ℃ for 1h;
5. Preparing aramid fiber long fibers: and (3) dissolving the aramid support tube obtained in the step (4) in 100wt% of concentrated sulfuric acid to prepare aramid slurry with the solid content of 19.5wt%, and preparing the aramid long fiber by adopting a dry-wet method.
The performance of the aramid long fibers prepared in examples 7 to 9 was tested according to ASTM D1907 and ASTM D885, and the results are shown in Table 3. The aramid long fibers prepared in examples 7-9 meet the requirements of superior aramid long fiber products.
Example 10
In the embodiment, the method for recycling the aramid support tubes in the ultrafiltration membrane is adopted to separate the para-aramid support tubes from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separated para-aramid support tubes are utilized to prepare the aramid long fibers:
1. a wire stripper with the structure shown in figure 1 is used for separating PTFE outer membranes and aramid support tubes in the hollow fiber ultrafiltration membrane: placing the hollow fiber ultrafiltration membrane into a wire stripping machine, cutting off an outer membrane to separate the outer membrane from an aramid fiber supporting tube, wherein the diameter of a feeding groove of the wire stripping machine is 110% of the outer diameter of the ultrafiltration membrane, and the pressure of the wire stripping machine is set to be 18N; the separation efficiency is that one person can peel 2kg hollow fiber ultrafiltration membrane per hour by one machine;
2. cleaning: at room temperature, 100g of the aramid support tube obtained in the step 1 is soaked in 10wt% H 2 SO 4 In the solution, the supporting tube is taken out after stirring for 30min at high speed and ultrasonic for 30min, and is soaked in 10wt% NaOH solution after rinsing with clear water, and stirring for 30min at high speedMixing for 30min, taking out the support tube after ultrasonic treatment, rinsing with clear water, soaking in NaClO (effective chlorine content 13%) solution, stirring at high speed for 30min, taking out the support tube after ultrasonic treatment for 30min, rinsing with clear water for multiple times, testing pH value of the water solution to be neutral, and drying for later use; the impurity content of the obtained aramid fiber supporting tube is 1.8%, and the intrinsic viscosity is 4.9dl/g.
3. Preparing aramid fiber long fibers: and (3) dissolving the aramid support tube obtained in the step (2) in 100wt% of concentrated sulfuric acid to prepare aramid slurry with the solid content of 19.5wt%, and preparing the aramid long fiber by adopting a dry-wet method.
The performance of the aramid long fiber prepared in example 10 was tested according to ASTM D1907 and ASTM D885, and the results are shown in table 3. The requirements of the aramid fiber long fiber on the qualified products are as follows: the deviation rate of linear density is less than or equal to +/-5%, the strength is more than or equal to 16cN/dtex, the modulus is more than or equal to 600cN/dtex, and the elongation is 2.5-5%. The aramid long fiber prepared in the embodiment 10 meets the requirements of the qualified aramid long fiber product.
Table 3: properties of the aramid Long fibers of examples 6 to 10
Comparative example 1
The comparative example adopts a manual stripping method to separate the para-aramid support tube from the composite para-aramid PTFE hollow fiber ultrafiltration membrane, and the separation efficiency is 0.2kg of hollow fiber ultrafiltration membrane which can be stripped by one person per hour.
The above examples are only illustrative of the preferred embodiments of the present invention and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art to the technical solution of the present invention should fall within the scope of protection defined by the claims of the present invention without departing from the spirit of the design of the present invention.

Claims (14)

1. A method of recovering an aramid support tube in an ultrafiltration membrane, the method comprising: separating an aramid support tube from a composite ultrafiltration membrane with the aramid support tube by using a wire stripper, wherein the impurity content of the aramid support tube is less than or equal to 2wt%, and the intrinsic viscosity of the aramid support tube is more than or equal to 4dl/g;
before the aramid fiber supporting tube is separated by using a wire stripper, soaking the composite ultrafiltration membrane by using a softening agent, wherein the softening agent is one or more of castor oil and silicone oil, the soaking time is 1-5h, the soaking temperature is 40-80 ℃, ultrasonic wave and bubbling treatment are carried out while the soaking treatment is carried out, and the composite ultrafiltration membrane is dried after the soaking and then is put into the wire stripper;
The method comprises the following steps: putting the composite ultrafiltration membrane into a wire stripper, cutting off the outer membrane, and simultaneously blowing by using high-pressure air to separate the outer membrane from the aramid fiber supporting tube;
the diameter of the feed chute of the wire stripper is 100% -120% of the outer diameter of the ultrafiltration membrane; the wire stripper is provided with double cutter heads connected in parallel; when the wire stripper is used for separating the aramid fiber supporting tubes, the pressure of the wire stripper is set to be 10-60N; a high-pressure air blowing device is arranged behind the discharge chute of the wire stripper; and an air outlet of the high-pressure air purging device is communicated with the discharge chute, and the pressure of the high-pressure air during purging is more than or equal to 0.05MPa.
2. The method of claim 1, wherein the method further comprises: and cleaning the separated aramid support tube, wherein the cleaning comprises acid washing, alkali washing, strong oxidant cleaning, ultrasonic cleaning and back flushing.
3. The method of claim 2, wherein the method has one or more of the following features:
the back flushing comprises back flushing by using high-pressure water;
the acid washing comprises the steps of washing with acid liquor with the concentration of 5-20wt%;
the alkaline washing comprises washing with alkaline solution with concentration of 2-16wt%;
the strong oxidizer purge includes a purge using an aqueous NaClO solution;
The cleaning also includes surfactant cleaning.
4. A method according to claim 3, characterized in that the method has one or more of the following features:
the acid liquor is H 2 SO 4 An aqueous solution;
the alkali liquor is NaOH aqueous solution;
the effective chlorine content of the NaClO water solution is 10-16%;
the surfactant is selected from one or more of triethanolamine oleic soap, ethoxylated alkyl sodium sulfate and sodium dodecyl sulfate.
5. The method for recycling the aramid fiber supporting tube in the ultrafiltration membrane is characterized by comprising the following steps of:
(1) Separating the aramid support tube from the composite ultrafiltration membrane with the aramid support tube by the method of claim 1;
(2) Cleaning the separated aramid support tube, wherein the cleaning comprises acid washing, alkali washing, strong oxidant cleaning, ultrasonic cleaning and back flushing; and
(3) And (3) preparing aramid pulp, aramid yarn or aramid long fiber by using the aramid support tube treated in the step (2).
6. The method of claim 5, wherein step (2) has one or more of the following features:
the back flushing comprises back flushing by using high-pressure water;
The acid washing comprises the steps of washing with acid liquor with the concentration of 5-20wt%;
the alkaline washing comprises washing with alkaline solution with concentration of 2-16wt%;
the strong oxidizer purge includes a purge using an aqueous NaClO solution; and
the cleaning also includes surfactant cleaning.
7. The method of claim 6, wherein the method has one or more of the following features:
the acid liquor is H 2 SO 4 An aqueous solution;
the alkali liquor is NaOH aqueous solution;
the effective chlorine content of the NaClO water solution is 10-16%;
the surfactant is selected from one or more of triethanolamine oleic soap, ethoxylated alkyl sodium sulfate and sodium dodecyl sulfate.
8. The method of claim 5, wherein in step (3), preparing the aramid pulp comprises: cutting the aramid support tube into chopped fibers with the length of 3-12mm by using a fiber pulverizer, preparing the chopped fibers into aqueous dispersion, adding the aqueous dispersion into a pulp pulverizing pump, pulverizing, and drying and opening after pulverizing.
9. The method of claim 8, wherein the method has one or more of the following features:
cutting the aramid support tube into chopped fibers with the length of 5-10mm by using a fiber pulverizer;
The fiber pulverizer adopts multistage circulation pulverization;
the outlet of the fiber pulverizer is provided with a 10-12mm screen;
the content of the aramid fiber in the dispersion liquid is 0.5-5wt%;
the grinding time of the pulp grinding pump is 2-20min.
10. The method of claim 9, wherein the dispersion has an aramid content of 1 to 2wt% and/or the time for pulverizing using a pulp pulverizing pump is 5 to 10min.
11. The method of claim 5, wherein in step (3), preparing an aramid yarn comprises: the aramid support tube is cut into short fibers of 30-51mm using a fiber cutter, and then the short fibers are spun alone or in combination with other fibers.
12. The method of claim 5, wherein in step (3), preparing the aramid long fiber comprises: adding the aramid support tube into concentrated sulfuric acid, preparing Cheng Fangguan slurry, and preparing the aramid long fiber from the aramid slurry by adopting a dry-wet method.
13. The method of claim 12 wherein the aramid support tube is immersed in a hot water bath prior to adding the aramid support tube to the concentrated sulfuric acid, then dried, and then adding the dried aramid support tube to the concentrated sulfuric acid.
14. The method of claim 13, wherein the method has one or more of the following features:
the temperature of the hot water bath is 60-100 ℃ and the time is 30-120min;
the drying temperature is 70-200 ℃ and the drying time is 0.5-3h;
the drying is that the materials are dried in a vacuum oven;
the concentration of the concentrated sulfuric acid is 90-102wt%;
the solid content of the aramid fiber slurry is 12-20wt%.
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