CN115569440A - Filter medium for heterogeneous separation and preparation method thereof - Google Patents

Abstract

The application relates to the technical field of filtration and separation, in particular to a filter medium for heterogeneous phase separation and a preparation method thereof, wherein the filter medium comprises a fiber composite structure formed by nanoscale interception fibers, micron-sized fibers and cross-linked fibers; the weight ratio of the nano-scale trapped fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micron-scale fibers in the fiber composite structure are sequentially increased; the melting points of the nano-scale interception fiber and the micron-scale fiber are both higher than those of the cross-linking fiber; the method comprises the following steps: mixing the nanoscale interception fibers, the micron-sized fibers and the crosslinked fibers according to a preset weight ratio, performing fiber dissociation treatment, and uniformly mixing to obtain a fiber suspension; carrying out wet sheet-making molding treatment on the fiber suspension, and dehydrating and drying to obtain an initial filter medium; carrying out surface high-temperature instantaneous plasticizing treatment and surface function modification treatment on the initial filter medium to obtain a filter medium for heterogeneous phase separation; the application can effectively improve the medium interception precision and the utilization rate of effective components.

Description

Filter medium for heterogeneous phase separation and preparation method thereof

Technical Field

The application relates to the technical field of filtration and separation, in particular to a filter medium for heterogeneous phase separation and a preparation method thereof.

Background

The heterogeneous separation is based on the difference of physical properties among dispersoids, can separate heterogeneous mixtures such as solid, liquid, gas and liquid, or gas and solid by mechanical action, is an indispensable technical link in the fields of solid-liquid separation, gas and solid separation, water treatment and the like in industrial production, and comprises a filtration method, a precipitation method, a centrifugal separation method and the like. The filter medium is a core element determining the separation effect in the separation process, needs to bear conditions such as complex chemical working condition environment, extremely high working pressure and the like, and is required to have high mechanical strength, filtration and interception precision and separation efficiency. The existing filter media applied to heterogeneous separation generally adopt various forms of filter cloth, such as high interception precision filter cloth, but the filter cloth can realize effective filtration only after continuous feeding and filter cake formation in the filtration process, the average effective component loss rate is more than 30%, the filtration effect is poor, and a large amount of material particles are lost; in addition, the filtration and interception precision of the existing filter medium can only reach 3-5 microns, and can not reach the nanometer precision, and the nanometer-level high-precision separation of heterogeneous separation in industrial application can not be realized.

Disclosure of Invention

In view of the above problems in the prior art, the present application provides a filter medium for heterogeneous separation and a preparation method thereof, and the specific technical scheme is as follows:

in one aspect, the present application provides a filter media for heterogeneous separations comprising a fibrous composite structure formed of nano-sized retaining fibers, micro-sized fibers, and cross-linked fibers;

the weight ratio of the nano-scale interception fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micro-scale fibers in the fiber composite structure are increased in sequence; the melting points of the nanoscale intercepting fibers and the micron-sized fibers are higher than those of the crosslinked fibers.

Specifically, the filter medium comprises a interception surface layer and a diversion surface layer, the interception surface layer and the diversion surface layer are crosslinked, and the crosslinked fibers form a hot-melt crosslinking point structure in the filter medium;

the mass ratio of the nano-scale interception fibers in the interception surface layer is higher than that of the micron-scale fibers and that of the cross-linking fibers, and the mass ratio of the micron-scale fibers in the diversion surface layer is higher than that of the nano-scale interception fibers.

In another aspect, the present application provides a method for preparing a filter medium for heterogeneous separation, applied to the filter medium for heterogeneous separation as described above, the method comprising the steps of:

s21: mixing nanoscale interception fibers, micron-sized fibers and cross-linked fibers according to a preset weight ratio to prepare an initial suspension, wherein the weight ratio of the nanoscale interception fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micron-sized fibers are increased in sequence;

s22: performing fiber dissociation treatment on the initial suspension, and uniformly mixing to obtain a fiber suspension;

s23: carrying out wet sheet making and forming treatment on the fiber suspension, and dehydrating and drying to obtain an initial filter medium;

s24: and carrying out surface high-temperature instantaneous plasticizing treatment and surface function modification treatment on the initial filter medium to obtain the filter medium for heterogeneous separation.

Specifically, the preset weight ratio is 1 (5-50) to 2-48.

Specifically, the wet sheet forming process performed on the fiber suspension in S23 includes:

s231: performing gravity dehydration and sedimentation treatment on the fiber suspension to obtain an initial fiber laminar medium;

s232: and carrying out suction filtration and dehydration treatment on the initial fiber laminated medium to obtain the fiber laminated medium to be subjected to heat setting and drying.

S233: and carrying out moisture extrusion and heat setting drying on the fiber layered medium to obtain the initial filter medium.

Specifically, before the S21, the method further includes:

s11: carrying out fiber opening treatment on the sea-island micron-sized fiber filament in an alkaline solution to obtain a sea-island fiber filament;

s12: and cutting the sea-island fiber filaments into short fibers to obtain the micron-sized fibers.

Specifically, the nano-scale interception fibers are made of cellulose microfibers, the micro-scale fibers are made of one or more of terylene and chinlon, and the cross-linking fibers are made of one or more of terylene and chinlon.

Specifically, the length of the nano-scale interception fiber is more than or equal to 100 μm, the length of the micron-scale fiber is 1-3mm, and the length of the cross-linked fiber is 1-5mm.

Specifically, the average diameter of the nanometer grade interception fiber is 10-100nm, the average diameter of the micron grade fiber is less than or equal to 2.5 μm, and the average diameter of the cross-linked fiber is 10-25 μm.

Specifically, the grammage of the filter medium is greater than or equal to 50g/m ² The filtration interception precision of the filter medium is 10-100nm.

In another aspect, the present application provides a filter device comprising a filter medium for heterogeneous separation as described above.

In another aspect, the present application provides the use of a filter medium as described above for heterogeneous separation.

Based on the technical scheme, the method has the following beneficial effects:

1. according to the method, a fiber composite structure formed by nanoscale interception fibers, micron-sized fibers and cross-linked fibers is formed in a filter medium, the weight ratio of the nanoscale interception fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micron-sized fibers are controlled to be sequentially increased, the filter medium with heterogeneous separation can reach the nanoscale filtration precision, and the micron-sized fibers and the cross-linked fibers provide the filtration precision of up to 0.1-1MPa/cm ² The above working pressure bearing capacity; in addition, the melting points of the nano-scale interception fibers and the micro-scale fibers are higher than those of the cross-linking fibers, so that the melting plasticizing treatment in the preparation process is facilitated, the supporting strength and the cross-linking strength of the filter medium are further improved, and the fiber units in the filter medium are ensured to be in liquidThe cross-linking force in the environment is correspondingly used to avoid the separation and disintegration between fibers.

2. According to the preparation method, the suspension of the nanoscale interception fibers, the micron-sized fibers and the crosslinking fibers is mixed and prepared according to the preset weight proportion, fiber dissociation treatment is carried out to form single fibers, forming treatment is carried out by a wet-method sheet making method to form a fiber composite structure, the filter medium is obtained after surface treatment, any chemical additive component is not required to be added in each preparation link of the whole process chain, process water can be recycled, and the preparation method is environment-friendly and pollution-free. Moreover, the crosslinking fibers can form a dense hot melting crosslinking point structure in the filter medium through surface high-temperature instantaneous plasticizing treatment and surface function modification treatment, and the prepared filter medium not only can reach the nanoscale interception precision, but also can bear 0.1-1MPa/cm ² The above operating pressure.

Drawings

In order to more clearly illustrate the technical solution of the present application, the drawings used in the description of the embodiment or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the application, and that for a person skilled in the art, other drawings can also be derived from them without inventive effort.

FIG. 1 is a schematic flow diagram of a method for preparing a filter media for heterogeneous separation as provided in an embodiment of the present application;

2-4 are TEM images of filter media for heterogeneous separation provided by embodiments of the present application;

fig. 5 is a process flow diagram of a method of making a filter media for heterogeneous separation as provided in an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making creative efforts shall fall within the protection scope of the present application.

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. All numerical values, whether explicitly indicated or not, are herein defined as modified by the term "about". The term "about" generally refers to a range of values that one of ordinary skill in the art would consider equivalent to the recited values in order to produce substantially the same properties, functions, results, etc. A numerical range indicated by a low value and a high value is defined to include all numbers subsumed within the numerical range and all subranges subsumed within the numerical range.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the accompanying drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be implemented in sequences other than those illustrated or described herein. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover a non-exclusive inclusion.

Before further detailed description of the embodiments of the present application, terms and expressions referred to in the embodiments of the present application will be described, and the terms and expressions referred to in the embodiments of the present application will be used for the following explanation.

Heterogeneous phase: it means that there are different phase interfaces in the system, and the material properties on both sides of the phase interface are significantly different, and have different physical properties. Systems composed of a dispersed phase and a continuous phase having different physical properties are referred to as heterogeneous systems or heterogeneous mixtures. Heterogeneous systems are divided into two categories depending on the state of the continuous phase: gaseous heterogeneous systems such as dust-containing gases, mist-containing gases, and the like; liquid heterogeneous systems such as suspensions, emulsions and foams.

It will be appreciated that the higher the filtration rejection, the lower the filtration flux. The existing woven filter cloth is usually woven by warps and wefts alternately to form a fabric organization structure, wherein almost all warp and weft interlacing points are shielding areas which can not realize filtration completely, the denser the fabric density is, the higher the filtration interception precision is, but the more the warp and weft interlacing points are, the less the effective filtration area is, the lower the filtration separation efficiency is, and the existing woven filter cloth can not realize nano-scale fine filtration no matter the physical limitation of weaving units in the fabric or the requirement of the effective filtration area.

The filter media for heterogeneous separation provided by the embodiments of the present application, including a fiber composite structure formed of nano-sized trapping fibers, micro-sized fibers, and cross-linked fibers, is described below; the weight ratio of the nano-scale trapped fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micro-scale fibers in the fiber composite structure are sequentially increased; the melting points of the nanometer-level interception fiber and the micron-level fiber are both higher than those of the cross-linking fiber.

Thus, by forming a fiber composite structure including three kinds of fiber units and controlling the weight ratio of three kinds of fiber components, it is possible to achieve nano-scale filtration accuracy of a heterogeneous separation filter medium and provide up to 0.1 to 1MPa/cm based on micro-scale fibers and cross-linked fibers ² The above working pressure bearing capacity; in addition, the melting points of the nano-scale interception fibers and the micron-scale fibers are higher than those of the cross-linking fibers, so that the melting plasticizing treatment in the preparation process is facilitated, the cross-linking fibers form a cross-linking reinforced structure, the supporting strength and the cross-linking strength of the filter medium are further improved, the cross-linking acting force of fiber units in the filter medium in a liquid-phase application environment is ensured, and the separation and disintegration among the fibers are avoided.

Wherein, the micron-sized fiber is obtained by splitting sea-island micron-sized fiber filament in an alkaline solution; the filter medium is obtained by sequentially carrying out fiber dissociation, wet forming, heat setting and surface high-temperature instantaneous plasticizing treatment on suspension of nano-scale interception fibers, micron-scale fibers and cross-linking fibers. The wet forming may be specifically wet sheet forming. In the wet sheet-making forming process, a fiber layer is formed by gravity dehydration and sedimentation for primary forming, and then the vacuum filtration residual water is assisted to complete the final forming.

Specifically, the fiber composite structure is formed by mutually crosslinking and combining nanoscale interception fibers, micron-sized fibers and crosslinking fibers. The filter medium is formed by crosslinking and combining nanoscale interception fibers, micron-sized fibers and crosslinking fibers through a non-woven method, and the overall performance of the filter medium is enhanced by combining fiber units with different functions.

Specifically, in the filter medium, micron-sized fibers form a medium skeleton structure, the medium skeleton structure is provided with skeleton hydrophobic channels to play a skeleton supporting role, and a skeleton bridge formed by the micron-sized fibers can not only increase the strength of the filter medium, but also increase flow guide channels to play a role in bridging and flow guiding, so that the separation efficiency is improved; the nanometer grade interception fiber is crosslinked in the filtering medium to form interception pores so as to improve the filtering and interception precision of the filtering medium; the cross-linked fibers are meltable fibers, form a hot-melt cross-linked point structure in the filter medium so as to enhance the cross-linking strength between different layers and different fiber units in the medium, and improve the tolerable working pressure of the medium through fiber cross-linking among the micron-sized fibers, the nano-sized trapped fibers and the cross-linked fibers and the hot-melt cross-linked point structure.

Specifically, the filter medium comprises an interception surface layer and a diversion surface layer, wherein the interception surface layer is crosslinked with the diversion surface layer, and the interception surface layer is crosslinked with the diversion surface layer through fibers of nanoscale interception fibers, micron-sized fibers and crosslinked fibers and is simultaneously crosslinked through a hot-melt crosslinking point structure.

Specifically, the mass ratio of the nanoscale interception fibers in the interception surface layer is higher than that of the micron-sized fibers and that of the cross-linked fibers, and the filtration and interception functions are mainly achieved; the mass ratio of the micron-sized fibers in the flow guide surface layer is higher than that of the nanometer-sized interception fibers, so that the micro-sized fibers are used for supporting and forming a skeleton hydrophobic channel. During heterogeneous separation, suspended matters firstly contact with a retention surface layer taking nano-scale retention fibers as main components to form primary particulate matter material interception, so that nano-scale retention precision is achieved, and separated liquid passes through the nano-scale retention fibers of the retention surface layer to enter a framework drainage channel of a flow guide surface layer so as to form rapid flow guide and complete the whole separation process.

In some embodiments, the nanoscale entrapment fibers are cellulose microfibers (microfibrillated cellulose), and the nanoscale entrapment fibers used in the filtration media are made based on a total bio-based material, are non-toxic, environmentally friendly, and can be suspended in an aqueous solvent, and can be 3D-cellulose microfibers. In addition, the nanoscale interception fiber has functional OH groups and a high available surface area, and can further resist extreme environments such as pH value, temperature, salt, solvent and the like. Specifically, the Cellulose microfibrils used in the nanoscale trapped fiber can be microfibrillated Cellulose (MFC), which is a degradable nanoscale trapped Cellulose functional material, is highly swollen colloidal Cellulose, and is non-toxic and harmless.

In some embodiments, the material of the micron-sized fiber includes one or more of terylene and nylon. The micron-sized fiber is sea-island fiber, is obtained by alkali-method fiber opening treatment, plays a role of a basic skeleton in a medium, and forms a bridging effect to realize high interception precision and high separation efficiency of the filter medium cooperatively.

In some embodiments, the material of the cross-linked fiber includes one or more of terylene and nylon. The cross-linked fiber is meltable fiber, can be in a full-melting type or a sheath-core type, and forms dense hot-melting cross-linking points among different fiber units through heat setting and surface high-temperature instantaneous plasticizing treatment, so that the mechanical strength of the filter medium is improved, and the breaking strength of the filter medium is up to more than 30N/cm. Specifically, the melting point temperature of the crosslinked fibers may be 150 to 180 ℃.

In some embodiments, the weight ratio of the nanoscale retention fibers, the weight ratio of the micron-sized fibers, and the weight ratio of the crosslinked fibers in the filter media satisfy 1 (5-50): 2-48), preferably, the weight ratio satisfies 1 (9-17): 3-10. By controlling the weight ratio of the three functional fibers in the range, the micron-sized fibers and the cross-linked fibers can form an effective supporting and cross-linked structure, meanwhile, the nano-sized interception fibers form dense filtration pores and a proper effective filtration area, a rich and cross-linked and entangled three-dimensional network structure is formed in a medium, and the requirements on interception precision, bearing strength and breaking strength are balancedAnd excellent strength, interception precision and filtering efficiency are achieved. The filtering precision of the filtering medium can reach 10-100nm, and the bearable working pressure can reach 0.1-1MPa/cm ² As described above.

In some embodiments, the nanoscale trapping fibers have an average diameter of 10-100nm, preferably, the nanoscale trapping fibers have an average diameter of 10-70nm; the average diameter of the micron-sized fibers is less than or equal to 2.5 μm, preferably, the average diameter of the micron-sized fibers is greater than or equal to 1.5 and less than or equal to 2.5 μm, and the average diameter of the crosslinked fibers is 10-25 μm, preferably, the average diameter of the crosslinked fibers is 13-21 μm. Specifically, the fineness of the micron-sized fibers is 0.05-1D before the opening treatment. Thus, the radial sizes of the three different functional fiber units are respectively controlled to be within the range, the fiber width gradation is formed, and the nanoscale dense pores with high interception precision are formed while the supporting strength is ensured; in addition, the radial dimension of the nanoscale interception fiber is controlled to be within the range, so that the interception precision of the medium can be ensured to be less than 100nm, preferably less than 70nm, the size is too high, the interception precision is not favorably improved, and the size is too small, so that the dispersion and the forming in the preparation process are not favorably realized; the average diameter of the micron-sized fibers is controlled to be within the range, so that the requirements of support strength and interception precision can be balanced, interception precision is easy to reduce when the average diameter is too high, and medium strength is not favorably improved when the average diameter is too low; the single titer of the cross-linked fibers is controlled to be within the range, a hot-melt cross-linked point structure with a proper size can be formed, the hot-melt cross-linked point structure is too large easily due to overlarge size, the effective filtering area is reduced, the hot-melt cross-linked point structure is too small and not dense enough due to undersize, and the cross-linking strength is reduced.

In some embodiments, the length of the nanoscale trapping fibers is greater than or equal to 100 μm, preferably greater than or equal to 110 μm; the length of the micron-sized fiber is 1-3mm, and preferably, the length of the micron-sized fiber is 1.5-2mm; the crosslinked fibers have a fiber length of 1 to 5mm, and preferably, the crosslinked fibers have a fiber length of 2 to 4mm. Therefore, by adjusting the fiber lengths of the three different functional fibers to the range, the fiber length gradation is formed while the width gradation is formed, so that a rich and cross-linked entangled network structure is formed, and the strength and the interception precision of the medium are ensured. The length of the fibers of the nanoscale interception fiber unit is controlled to be within the range, so that the fibers are uniformly distributed in the filter medium and are crosslinked with each other to form dense and uniform interception pores, and if the length of the fibers is too short, the crosslinking strength is not improved, and if the length of the fibers is too long, the nanoscale interception fibers are easily agglomerated, so that the dispersion difficulty is increased, and the porosity is reduced; the length of the micron-sized fiber is controlled to be within the range, a continuous framework structure and a stretched and communicated hydrophobic channel can be formed, a proper bridge structure is formed, the strength and the filtering efficiency of the medium are improved, too short, the fracture of the framework is easy to increase, the cross-linking strength is reduced, too high, the dispersion difficulty is easy to increase, the fiber is not uniformly agglomerated and dispersed, and the weak point of the bridge is formed, so that the overall strength is reduced; the fiber length of the cross-linked fibers is controlled to be in the range, so that hot-melt cross-linked points can be increased, the cross-linked strength is ensured, if the length of the cross-linked fibers is too long, the formed hot-melt cross-linked points are too few and are not uniformly distributed under the condition of the same addition amount and fineness, the strength is reduced, and the cross-linked fibers are easy to curl and overlap in the radial direction; if the length of the cross-linked fiber is too short, the cross-linking gap is increased, and the content of effective hot-melting cross-linking points is reduced.

In some embodiments, the filter media has a grammage of 50g/m or greater ² Preferably, the grammage is 120g/m or more ² And 300g/m or less ² Thus, by reaching the gram weight value, the strength of the medium can be improved, and the industrial application of heterogeneous phase separation is facilitated; the filtration interception precision of the filter medium can reach 10-100nm, and preferably, the filtration interception precision is 10-70nm; the breaking strength of the filter medium is more than or equal to 30N/cm.

Specifically, the surface of the filter medium has hydrophilic groups obtained by subjecting the formed initial filter medium to a surface functional modification treatment, which enables the filtration separation efficiency to be improved.

The filter medium for heterogeneous separation is formed by combining three fibers with different functions according to a certain mass ratio, the filtration interception precision can reach 10-100nm, the breaking strength of the filter medium can reach more than 30N/cm, and the filter medium can be applied to industrial application scenes in the technical field of heterogeneous separation and can be used for realizing the purpose of separating heterogeneous fibers into heterogeneous fibersThe existing hyperfine interception of high concentration solid-liquid ratio reduces the loss of effective components, reaches the filtration interception precision of nanometer level, and can be further applied to the high purity separation application of superfine nano powder particles in the fields of new energy materials, rare earth and the like, such as nano SiO with the average particle size of 50-100 nanometers ₂ And (5) filtering. Meanwhile, the interception surface layer, the supporting framework and the cross-linking structure points are formed by the fibers with different functions, and the filtering medium can bear 0.1-1MPa/cm ² The working pressure is higher, and the medium can be used for a long time at the temperature of 150 ℃, so that the application performance of the medium required by the working condition environment is ensured.

In another aspect, the present application provides a method for preparing a filter medium for heterogeneous separation, applied to the above filter medium for heterogeneous separation, the method comprising the following steps S21 to S24.

S21: mixing the nanoscale interception fibers, the micron-sized fibers and the cross-linked fibers according to a preset weight proportion to prepare an initial suspension, wherein the weight proportion of the nanoscale interception fibers, the weight proportion of the cross-linked fibers and the weight proportion of the micron-sized fibers are increased in sequence.

In some embodiments, the predetermined weight ratio is 1 (5-50): 2-48, and preferably, the predetermined weight ratio is 1 (9-17): 3-10. By controlling the weight ratio of the three functional fibers in the range, the micron-sized fibers and the cross-linked fibers can form an effective supporting and cross-linked structure, meanwhile, the nanoscale interception fibers form dense filtration pores and a proper effective filtration area, a rich and cross-linked and entangled three-dimensional network structure is formed in a medium, the requirements on interception precision, bearing strength and breaking strength are balanced, and excellent strength, interception precision and filtration efficiency are achieved. The filtering precision of the filtering medium can reach 10-100nm, and the bearable working pressure can reach 0.1-1MPa/cm ² As described above.

In some embodiments, the initial suspension has a mass concentration of 0.15-0.5%, preferably, 0.2-0.4%; by controlling the mass concentration of the initial suspension to the range, the dispersion uniformity of various fibers is facilitated, the subsequent fiber settling speed is in a reasonable range, effective crosslinking and layered settling among the nanoscale interception fibers, the micron-sized fibers and the crosslinked fibers are further ensured, and a medium structure with a crosslinked interception surface layer and a crosslinked diversion surface layer is further formed.

In some embodiments, prior to S21, the method further comprises S11-S12:

s11: carrying out fiber opening treatment on the sea-island micron-sized fiber filament in an alkaline solution to obtain a sea-island fiber filament;

s12: cutting the sea island fiber filament into short fibers to obtain micron-sized fibers.

Specifically, sea-island micron-sized fiber filaments are provided and subjected to a continuous ultrasonic alkaline splitting process. Wherein the mass concentration of the alkali liquor is 4-10%, the fiber opening temperature is 95-98 ℃, the fiber opening time is 20-40min, the cleaning time in water after fiber opening treatment is 30-300s, and the drying temperature is 100-120 ℃.

Specifically, the micron-sized fiber filaments of the sea-island type have a sea-island ratio of (2-3): (7-8), preferably 3. In one embodiment, the sea-island type micron-sized fiber filament may be a FDY process terylene sea-island fiber filament, and the single denier may be 0.05-0.2D.

After the fiber filaments of only the rest island fibers are formed, the fiber filaments are rolled and cut to form short fibers with the required fiber length, and the micron-sized fibers adopted by the filter medium are obtained.

In some embodiments, the crosslinked fibers may be staple fibers obtained by cutting FDY crosslinked fiber filaments, and the crosslinked fibers may be all-melt type or sheath-core type.

In some embodiments, the nanoscale entrapment fibers are made of cellulose microfibers (microfibrillated cellulose), the micron fibers are made of one or more of terylene and chinlon, and the cross-linked fibers are made of one or more of terylene and chinlon. Specifically, the nano-scale interception fiber adopted in the filter medium is prepared based on a full bio-based, is non-toxic and environment-friendly, can be suspended in an aqueous solvent, and can be 3D-cellulose microfiber. In addition, the nanoscale interception fiber has functional OH groups and a high available surface area, and can further resist extreme environments such as pH value, temperature, salt and solvent. The Cellulose microfibril adopted by the nanoscale trapped fiber can be microfibrillated Cellulose (MFC), is a degradable nanoscale trapped Cellulose functional material, is highly swollen colloidal Cellulose, and is non-toxic and harmless. The micron-sized fiber plays a role of a basic skeleton in the medium and forms a bridging effect so as to realize high interception precision and high separation efficiency of the filter medium in a synergistic manner. The crosslinking fiber forms dense hot melting crosslinking points among different fiber units, and the mechanical strength of the filter medium is improved, so that the breaking strength of the filter medium reaches more than 30N/cm.

Specifically, the cross-linked fibers may have a melting point temperature of 150 to 180 ℃.

S22: and (4) performing fiber dissociation treatment on the initial suspension, and uniformly mixing to obtain the fiber suspension.

Specifically, mixing the nanoscale trapped fiber, the micron-sized fiber and the crosslinked fiber according to a preset weight ratio, adding deionized water to prepare an initial suspension, dissociating the fiber in the initial suspension into single fibers by using a fiber dissociator, and uniformly mixing to obtain a fiber suspension.

S23: and carrying out wet sheet-making molding treatment on the fiber suspension, and dehydrating and drying to obtain the initial filter medium.

In some embodiments, the wet sheet forming process of the fiber suspension in S23 includes:

s231: carrying out gravity dehydration and sedimentation treatment on the fiber suspension to obtain an initial fiber laminar medium;

s232: carrying out suction filtration and dehydration treatment on the initial fiber laminated medium to obtain a fiber laminated medium to be subjected to heat setting and drying;

s233: and (3) carrying out moisture extrusion and heat setting drying on the fiber laminated medium to obtain an initial filter medium.

Specifically, the nanometer-scale interception fiber, the micron-scale fiber and the cross-linked fiber have size and weight difference, so that different sedimentation speeds are formed, the sedimentation speed of the nanometer-scale interception fiber is low, the sedimentation speed of the micron-scale fiber and the cross-linked fiber is high, a fiber layer is formed by adopting gravity dehydration sedimentation in a wet forming process, namely, self-weight sedimentation dehydration is carried out under the action of gravity without external force, then, vacuum filtration residual water is assisted to complete final forming, the nanometer-scale interception fiber and other two fibers can naturally form an initial fiber layered medium with cross-linking and obvious layering, the fibers in a medium part taking the nanometer-scale interception fiber as a main component are cross-linked and entangled with each other microcosmically, internal fibers in a medium part taking the nanometer-scale interception fiber as a main component are also cross-linked and entangled with each other, and meanwhile, a bottom surface fiber part in the medium part taking the nanometer-scale interception fiber as a main component and a surface layer fiber part in the medium part taking the micrometer-scale fiber and the cross-linked fiber as a main component form a cross-linked and entangled state.

Specifically, the formed filter medium comprises an interception surface layer and a diversion surface layer, wherein the interception surface layer and the diversion surface layer are crosslinked, and the interception surface layer and the diversion surface layer are crosslinked through fibers of nanoscale interception fibers, micron-sized fibers and crosslinked fibers and are simultaneously crosslinked through a hot-melt crosslinking point structure. The nanometer grade interception fiber in the interception surface layer is the main component, and the micrometer grade fiber in the diversion surface layer is the main component. During heterogeneous separation, suspended matters firstly contact an interception surface layer to form primary particulate matter material interception, so that nanoscale interception precision is achieved; the separated liquid passes through the nano fiber and enters the flow guide channel of the flow guide surface layer to form rapid flow guide, so that the integral separation process is completed. The framework bridge frame formed by the micron-sized fibers can not only increase the strength of the filter medium, but also increase the flow guide channels and improve the separation efficiency.

In some embodiments, step S233 may specifically include: and extruding the fiber laminated medium again by using a felt squeezing device, drying and molding by using heat setting equipment to obtain an initial filter medium so as to ensure the shape and dimensional stability of the filter medium.

Specifically, the suction filtration dehydration can be realized by vacuum filtration, the negative pressure of the vacuum filtration can be 0.01-0.04MPa, the heat setting temperature is 150-180 ℃, and the heat setting time is 5-30min.

S24: and carrying out surface high-temperature instantaneous plasticizing treatment and surface function modification treatment on the initial filter medium to obtain the filter medium for heterogeneous separation.

Specifically, the instantaneous plasticizing temperature of the surface high-temperature instantaneous plasticizing treatment is 170-190 ℃, the time of the surface high-temperature instantaneous plasticizing treatment is 1-5s, and the pressure of the surface high-temperature instantaneous plasticizing treatment is 5-10MPa/cm ² So that the crosslinked fibers are melted and cooled to be plasticized to form a hot-melt crosslinking point structure in the filter medium. It is understood that the melting points of the nano-sized trapping fibers and the micro-sized fibers are higher than 170-190 ℃. Thus, the product is changed from a wet state to a dry state through heat setting, the cross-linked fibers are melted through surface high-temperature instantaneous plasticizing treatment to generate polycondensation, and the polycondensation is formed by melting and shrinking the fibers into points and adhering the points among fiber layers to form hot-melt cross-linked points. It is understood that the melt cross-linking points are adhered between the nano-scale entrapment fibers and the micro-scale fibers, and do not form complete blockage, and have negligible effect on the effective filtration area of the media.

Specifically, the surface function modification treatment may be a jet plasma treatment of surface function modification to form hydrophilic groups on the surface of the shaped medium, thereby improving the filtration separation efficiency.

Specifically, the length of the nanometer-level interception fiber is more than or equal to 100 μm, the length of the micron-level fiber is 1-3mm, and the length of the cross-linked fiber is 1-5mm.

Specifically, the average diameter of the nanometer-scale interception fiber is 10-100nm, the average diameter of the micron-scale fiber is less than or equal to 2.5 μm, and the average diameter of the crosslinking fiber is 10-25 μm.

Specifically, the grammage of the filter medium is 50g/m or more ² The filter medium can bear 0.1-1MPa/cm ² The breaking strength reaches more than 30N/cm under the above working pressure, and the filtration and interception precision is 10-100nm.

In some embodiments, the process flow of preparing the filter medium can be as shown in fig. 5, the sea-island micron-sized fiber filament is placed in a continuous ultrasonic fiber opening device 1 for alkali fiber opening treatment, and then enters a cleaning device 2 for cleaning, and then enters a drying device 3 for drying, and then enters a rolling and cutting device 4 for rolling and cutting to the required length; the obtained product enters a mixing and fiber dissociation device 5 to form an initial suspension with the nanoscale interception fibers and the crosslinked fibers, and the initial suspension is dissociated to obtain single fibers; then, wet sheet forming and dehydration drying treatment are realized through a gravity dehydration settling device 6, a vacuum filtration device 7, a blanket squeezing device 8 and a heat setting device 9; then, the surface is instantaneously plasticized at high temperature and is functionally treated by a high-temperature surface instantaneous plasticizing treatment device 10 and a jet plasma treatment device 11 to obtain a filter medium for heterogeneous separation, and finally, the filter medium is rolled by a rolling device to form a final product.

In summary, suspensions of nano-scale trapped fibers, micro-scale fibers and cross-linked fibers are mixed and prepared according to a preset weight ratio, fiber dissociation treatment is carried out to form single fibers, forming treatment is carried out by a wet-method sheet making method to form a fiber composite structure, a filter medium is obtained after surface treatment, any chemical additive component is not required to be added in each preparation link of the whole process chain, process water can be recycled, and the preparation method is environment-friendly and pollution-free. Moreover, the crosslinking fibers can form a dense hot melting crosslinking point structure in the filter medium through surface high-temperature instantaneous plasticizing treatment and surface function modification treatment, the prepared filter medium can achieve nanoscale interception precision, the filtration interception precision can reach 10-100nm, and the filter medium can bear 0.1-1MPa/cm ² The working pressure is higher, and the device can be used for a long time at the temperature of 150 ℃ and is suitable for severe working conditions. In addition, the material components in the filter medium are all environment-friendly materials, the materials can be recycled and reused, no chemical additive component exists in the whole process chain manufacturing link, the process water can be recycled, and the filter medium is non-toxic and pollution-free, so that the product and the process are environment-friendly.

In another aspect, the present application provides a filter device comprising a filter medium as above for heterogeneous separation.

In another aspect, the present application provides the use of a filter medium as above for heterogeneous separation.

The following describes examples and comparative examples of the present application in conjunction with the above technical solutions.

The filter media for heterogeneous separation in examples and comparative example 2 were prepared by the following method:

s1: carrying out continuous ultrasonic alkaline splitting process treatment on micron-sized fiber filaments with certain filament bundle fineness, wherein the filament bundle fineness, the mass concentration of alkali liquor, the splitting temperature, the splitting time, the cleaning time, the drying temperature and the sea-island ratio are shown in table 1;

the micron-sized fiber filaments can be FDY fiber filaments;

s2: winding and cutting the opened and dried micron-sized fiber filaments into short fibers to obtain micron-sized fibers, wherein the fiber lengths are shown in table 1;

s3: cutting sheath-core or full-melt FDY cross-linked fiber filaments with certain tow fineness into short fibers to obtain cross-linked fibers, wherein the tow fineness, the fiber length and the melting point temperature are shown in table 1;

s4: mixing the nanoscale trapped fiber, the micron-sized fiber and the crosslinked fiber according to a preset mass ratio, adding deionized water to prepare an initial suspension, wherein the mass concentration of the initial suspension is shown in table 1, dissociating the fiber into single fibers by using a fiber dissociator, and uniformly mixing to obtain a fiber suspension;

s5: wet-process sheet forming is carried out on the fiber suspension dissociated in the step S4 by using continuous forming equipment, water is extruded again by a blanket squeezing device and then dried and formed by using heat setting equipment, and the gram weight of the formed initial filter medium, the heat setting temperature and the vacuum suction filtration negative pressure in the wet-process sheet forming process are shown in a table 1;

s6: carrying out surface high-temperature instantaneous plasticizing treatment on the initial filter medium subjected to heat setting, drying and forming, wherein the treatment temperature is shown in table 1;

s7: and (4) performing surface function modified jet plasma treatment on the filter medium treated by the S6, and rolling to obtain the filter medium for heterogeneous separation.

TABLE 1

The titer of each tow is 75D/36F 25 islands, namely the total titer of each tow is 75D, each tow consists of 36 filaments, 25 islands are arranged in each filament, the titer of each island is 75/36/25D, the titer of other tows is similar in meaning, and the description is omitted.

Based on the table 1 and fig. 2-4, it can be seen that the filter media prepared in examples 1-5 form a strong bonding structure with three kinds of fibers cross-linked and entangled, and the working pressure, the interception precision, the breaking strength and the filtration efficiency of examples 1-5 are obviously improved. Where fig. 4 exemplarily indicates one crosslinked fiber (18.297 μm) and two micro-sized fibers (0.889 μm and 1.987 μm), it is understood that the nano-scale cut-off fiber size is not indicated due to image resolution limitations.

In conclusion, the application has the following beneficial effects: the filtering medium which is not subjected to heterogeneous separation can reach the nano-scale filtering precision by forming a fiber composite structure formed by nano-scale interception fibers, micro-scale fibers and cross-linked fibers in the filtering medium and controlling the weight ratio of the nano-scale interception fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micro-scale fibers to be sequentially increased, and the filtering medium which is subjected to heterogeneous separation is provided with the filtering precision of 0.1-1MPa/cm based on the micro-scale fibers and the cross-linked fibers ² The above working pressure bearing capacity; in addition, the melting points of the nano-scale interception fibers and the micron-scale fibers are higher than those of the cross-linking fibers, so that the melting plasticizing treatment in the preparation process is facilitated, the supporting strength and the cross-linking strength of the filter medium are further improved, the cross-linking acting force of fiber units in the filter medium in a liquid-phase application environment is ensured, and the separation and disintegration among the fibers are avoided. And moreover, the suspension of the nanoscale trapped fiber, the micron-sized fiber and the crosslinked fiber is mixed and prepared according to a preset weight ratio, fiber dissociation treatment is carried out to form a single fiber, forming treatment is carried out by a wet sheet making method to form a fiber composite structure, a filter medium is obtained after surface treatment, any chemical additive component is not required to be added in each preparation link of the whole process chain, process water can be recycled, and the preparation method is environment-friendly and pollution-free. And, the cross-linked fiber can be formed densely in the filter medium by the surface high-temperature instantaneous plasticizing treatment and the surface function modification treatmentThe hot melting cross-linking point structure can ensure that the prepared filter medium not only can reach the nano-grade interception precision, but also can bear 0.1-1MPa/cm ² The above operating pressure.

The foregoing description has disclosed fully embodiments of the present application. It should be noted that those skilled in the art can make modifications to the embodiments of the present application without departing from the scope of the claims of the present application. Accordingly, the scope of the claims of the present application is not to be limited to the particular embodiments described above.

Claims (10)

1. A filter medium for heterogeneous separation comprising a fibrous composite structure formed of nano-sized retaining fibers, micro-sized fibers and cross-linked fibers;

the weight ratio of the nano-scale interception fibers, the weight ratio of the cross-linked fibers and the weight ratio of the micro-scale fibers in the fiber composite structure are increased in sequence; the melting points of the nanoscale entrapment fibers and the micron-sized fibers are both higher than the cross-linked fibers.

2. The filter media of claim 1, wherein the filter media comprises a retention surface layer and a flow directing surface layer, the retention surface layer and the flow directing surface layer being cross-linked, the cross-linked fibers forming a hot melt cross-linked dot structure in the filter media;

the mass ratio of the nano-scale interception fibers in the interception surface layer is higher than that of the micron-scale fibers and that of the cross-linking fibers, and the mass ratio of the micron-scale fibers in the diversion surface layer is higher than that of the nano-scale interception fibers.

3. A method for preparing a filter medium for heterogeneous separation, applied to the filter medium for heterogeneous separation according to any one of claims 1 to 2, comprising the steps of:

s21: mixing nanoscale interception fibers, micron-sized fibers and cross-linked fibers according to a preset weight proportion to prepare an initial suspension, wherein the weight proportion of the nanoscale interception fibers, the weight proportion of the cross-linked fibers and the weight proportion of the micron-sized fibers are increased in sequence;

s22: performing fiber dissociation treatment on the initial suspension, and uniformly mixing to obtain a fiber suspension;

s23: carrying out wet sheet making and forming treatment on the fiber suspension, and dehydrating and drying to obtain an initial filter medium;

s24: and carrying out surface high-temperature instantaneous plasticizing treatment and surface function modification treatment on the initial filter medium to obtain the filter medium for heterogeneous separation.

4. The method of claim 3, wherein the predetermined weight ratio is 1 (5-50) to 2-48.

5. The method according to claim 3, wherein the wet sheet forming process of the fiber suspension in S23 includes:

s231: performing gravity dehydration and sedimentation treatment on the fiber suspension to obtain an initial fiber laminar medium;

s232: carrying out suction filtration and dehydration treatment on the initial fiber laminated medium to obtain a fiber laminated medium to be subjected to heat setting and drying;

s233: and carrying out moisture extrusion and heat setting drying on the fiber laminated medium to obtain the initial filter medium.

6. The method of claim 3, wherein prior to the step S21, the method further comprises:

s11: carrying out fiber opening treatment on the sea-island micron-sized fiber filament in an alkaline solution to obtain a sea-island fiber filament;

s12: and cutting the sea-island fiber filaments into short fibers to obtain the micron-sized fibers.

7. The method according to any one of claims 3 to 6, wherein the nanoscale intercepting fibers are made of cellulose microfibers, the micron-sized fibers are made of one or more of terylene and chinlon, and the cross-linked fibers are made of one or more of terylene and chinlon.

8. The method according to any one of claims 3 to 6, wherein the nano-sized trapping fibers have a fiber length of 100 μm or more, the micro-sized fibers have a fiber length of 1 to 3mm, and the cross-linked fibers have a fiber length of 1 to 5mm.

9. The method according to any one of claims 3 to 6, wherein the nanoscale retention fibres have an average diameter of 10 to 100nm, the microscale fibres have an average diameter of 2.5 μm or less, and the crosslinked fibres have an average diameter of 10 to 25 μm.

10. The method of any of claims 3-6, wherein the filter media has a grammage of 50g/m or greater ² The filtration interception precision of the filter medium is 10-100nm.

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