CN111455566A - Composite nanofiber membrane and preparation method thereof - Google Patents

Abstract

The invention provides a composite nanofiber membrane and a preparation method thereof. First, the thermoplastic polymer master batch and the vinyl alcohol-ethylene copolymer master batch are subjected to bi-component melt spinning to prepare bi-component composite fibers with a special-shaped structure, and forming treatment to obtain a composite non-woven fabric base; then, vinyl alcohol- The ethylene copolymer masterbatch and the cellulose acetate butyrate masterbatch are blended, and the PVA‑co‑PE nanofibers are prepared by the melt extrusion phase separation method; finally, the PVA‑co‑PE nanofibers are prepared into a suspension, which is passed through the air pressure After the atomization is preliminarily combined with the composite non-woven fabric base layer, it is subjected to hot pressing treatment to obtain a composite nanofiber membrane. The preparation method adopts the same material as the polymer material of the two-layer structure in the nanofiber membrane composite structure, and performs thermocompression bonding. The prepared composite nanofiber membrane has excellent mechanical strength, and the interface bonding stability of the two-layer structure is stable. High, high adhesion fastness, not easy to separate.

Description

Composite nanofiber membrane and preparation method thereof

technical field

The invention relates to the field of nanofiber membrane preparation, in particular to a composite nanofiber membrane and a preparation method thereof.

Background technique

With the rapid development of the economy, industries such as metallurgy, steel, electricity and cement emit a large amount of fine particles into the atmosphere, causing serious air pollution. Fine particles have the characteristics of small particle size, long residence time in the atmosphere carrying a large amount of toxic substances, and long transportation distance, and become the primary pollutants that endanger human beings. Among them, aerosol particles with a diameter of less than 2.5 μm will not only cause various respiratory diseases in the human body, but also may cause various cardiovascular and cerebrovascular diseases, and even lead to heart failure and pulmonary heart disease.

Nanofibers have the characteristics of small pore size, large specific surface area and high porosity, so they have unparalleled advantages in the field of high-efficiency air filtration. However, as the thickness of the nanofiber membrane increases, it has the defects of low strength and easy delamination, and cannot be used as a filter material alone. Therefore, nanofibers are usually supported on the substrate to form a composite filter material, that is, two or more independent The single-layer filter material is combined into a whole, and this method can combine the advantages of different layers of filter material. At the same time, the arrangement of nanofibers is related to the surface morphology of the substrate. A substrate with a relatively uniform and flat surface and a relatively low thickness can obtain a uniform nanofiber film, thereby obtaining a composite material with good uniformity. Woven fabrics, non-woven fabrics and other forming base fabrics are the most commonly used substrates, but the composite with nanofiber membrane belongs to surface-to-surface composite, and there is a problem of poor composite firmness, which cannot meet the needs of practical applications. When the nanofiber is directly compounded with the base cloth, the adhesion fastness between the two is often small. In actual use, the nanofiber membrane and the base cloth are easily separated under the action of external force.

The invention patent with the application number CN201410193018.8 discloses a high-adsorption nanofiber composite filter material and a preparation method thereof. The composite filter material is composed of a non-woven fabric base material and a nanofiber membrane coated on its surface, and the nanofibers forming the nanofiber membrane are composed of a thermoplastic polymer in a continuous phase and nano active particles in a dispersed phase. The preparation process adopts twin-screw extrusion and granulation of nano-active particles and thermoplastic polymers in proportion to prepare a composite material, and then blends with cellulose acetate butyrate in proportion to melt-spin, and through solvent extraction, to prepare a composite material containing nanometers. The thermoplastic nanofibers of the active particles are finally coated with the ethanol suspension of the thermoplastic nanofibers on the surface of the non-woven fabric base material, and after drying, the high-adsorption nanofiber composite filter material is obtained. However, the disadvantage of this method is that the mechanical properties of the filter material and the interfacial stability between the nanofiber matrix and the non-woven substrate have not been greatly improved.

The lamination composite process combines materials with various functions by thermocompression bonding, which is an effective means to obtain multifunctional composite fibers. The invention patent with the application number CN201310390081.6 discloses a method for enhancing electrospinning nanofiber membranes. The method adopts several thermoplastic high polymers or low melting point thermoplastic polymers and non-thermoplastic polymers with melting points at least 20°C lower than other components to carry out interphase mixed electrospinning, and the fibers are randomly staggered; After hot-rolling treatment, the hot-pressing temperature is slightly higher than the initial melting temperature of the low-melting polymer, and the thermoplastic low-melting polymer is partially melted after hot-pressing, forming point bonds at the intersections of the nanofibers. However, the disadvantage of this method is that the strength of nanofibers has not been greatly improved, and the electrospinning process is not suitable for mass production, which limits its application range.

In view of this, it is urgent to develop a composite nanofiber membrane, which not only has excellent filtration performance and mechanical strength, but also can make the combination between the substrate and the fiber membrane tight and firm, so as to meet the needs of practical applications and expand Scope of application of nanofiber membranes.

SUMMARY OF THE INVENTION

In view of the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a composite nanofiber membrane and a preparation method thereof.

In order to achieve the above purpose of the invention, the present invention provides a preparation method of a composite nanofiber membrane, comprising the following steps:

S1, the preparation of composite non-woven base layer: according to a predetermined ratio, the thermoplastic polymer master batch and vinyl alcohol-ethylene copolymer master batch are subjected to bi-component melt spinning to obtain bi-component composite fibers; The component composite fibers are subjected to fiber forming treatment to prepare a composite non-woven base layer;

S2. Preparation of PVA-co-PE nanofibers: blend the vinyl alcohol-ethylene copolymer masterbatch and the cellulose acetate butyrate masterbatch according to a predetermined mass ratio to obtain a mixed masterbatch, and melt the mixed masterbatch for spinning. , to prepare PVA-co-PE/CAB composite nanofibers; extract the PVA-co-PE/CAB composite nanofibers with acetone to obtain PVA-co-PE nanofibers;

S3. Preparation of composite nanofiber membrane: the PVA-co-PE nanofibers prepared in step S2 are prepared into a suspension; the suspension is mixed with the composite non-woven fabric prepared in step S1 through a pneumatic atomization process. The base layer is preliminarily compounded to obtain a composite film composed of the PVA-co-PE nanofiber film layer and the composite non-woven base layer; then, the composite film is subjected to hot pressing to make the composite nonwoven The cloth base layer and the vinyl alcohol-ethylene copolymer in the PVA-co-PE nanofiber film layer are partially melted and bonded to obtain a composite nanofiber film.

Preferably, the bi-component composite fiber has a side-by-side structure, a skin-core structure or an orange-lobed structure.

Preferably, the bicomponent composite fiber has a sheath-core structure, and the sheath layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer.

Preferably, the bi-component composite fiber has an orange-lobed structure; the preparation of the bi-component composite fiber with the orange-lobed structure includes a splitting pretreatment process.

Preferably, the cleavage pretreatment process refers to soaking the bi-component composite fibers with chemical additives to reduce the interfacial adhesion between the two-component fibers to separate them, so as to obtain a split cross section Shaped ultra-fine nanofibers; or the cleavage pretreatment process refers to mechanically splitting the bi-component composite fibers using the mechanical energy of the high-pressure water flow generated by the spunlace method to obtain the split cross-section shaped ultra-fine fibers Nanofibers.

Preferably, in the hot-pressing process of step S3, the hot-pressing temperature is 150-210° C., the hot-pressing pressure is 1-5 MPa, and the hot-pressing time is 5-30 s.

Preferably, in the air pressure atomization process described in step S3, the atomization air pressure is 0.1-0.5 MPa.

Preferably, in step S1, the fiber forming process is one of spunlace, heat-sealing, SMS, wet-laid, spunbond, pulp air-laid, melt-blown, and needle punching. A sort of.

Preferably, in step S1, the mass ratio of the thermoplastic polymer masterbatch and the vinyl alcohol-ethylene copolymer masterbatch is 20-80%: 20-80%.

Preferably, the thermoplastic polymer is one or more of PET, PP and PE.

In order to achieve the above purpose of the invention, the present invention also provides a composite nanofiber membrane prepared by the above preparation method. The composite nanofiber membrane is formed by preliminarily compounding the PVA-co-PE nanofiber suspension with the composite non-woven base layer through an air pressure atomization process, and then reinforced and composited by hot pressing treatment; the composite non-woven fabric Both the base layer and the PVA-co-PE nanofiber film layer have vinyl alcohol-ethylene copolymer; the mass ratio of the PVA-co-PE nanofiber film layer and the composite non-woven base layer is 5-20% : 80-95%; the breaking strength of the composite nanofiber membrane is 80-250N/5cm, and the 90° peel strength is 0.05-5KN/m.

Preferably, the fibers of the composite non-woven base layer are bicomponent composite fibers, and the bicomponent composite fibers have a skin-core structure, and the skin layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer; Or the bi-component composite fiber has an orange-lobed structure, which includes a plurality of split ultrafine nanofibers with special-shaped cross-sections obtained through the splitting pretreatment process; or the bi-component composite fiber has a side-by-side structure.

Compared with the prior art, the beneficial effects of the present invention are:

1. The preparation method of the composite nanofiber film provided by the present invention, the two-layer structure of the composite non-woven fabric base layer and the PVA-co-PE nanofiber film layer is subjected to a two-step composite process of air pressure atomization preliminary composite and thermocompression bonding reinforcement composite , so that the mechanical strength of the prepared composite nanofiber membrane has been greatly improved, and further solves the disadvantage that the interfacial bonding force of the nanofiber membrane is not strong enough. This is mainly due to:

1) The base layer of the composite non-woven fabric is made of thermoplastic polymer and vinyl alcohol-ethylene copolymer to form a two-component composite fiber with a special structure. The thermoplastic polymer has excellent mechanical strength, which can make up for the insufficient strength of vinyl alcohol-ethylene copolymer. , endows the special-shaped structure bicomponent fiber with unique combined properties, improves the overall mechanical strength of the fiber, and further improves the mechanical properties of the composite non-woven base.

2) The base layer of the composite non-woven fabric adopts a bi-component composite fiber with a special structure. The two components of the thermoplastic polymer used for spinning and the vinyl alcohol-ethylene copolymer are incompatible with each other and have similar melt viscosity and similar melt viscosity. At the same time, the two polymer components have weak adhesion to each other; at the same time, the vinyl alcohol-ethylene copolymer and the polymer of the PVA-co-PE nanofiber in the bicomponent composite fiber with the heterostructure are the same material , which provides the basis for interfacial bonding between the two-layer structures for the second-step thermocompression bonding reinforcement composite process.

3) In the present invention, the PVA-co-PE nanofiber suspension is preliminarily compounded with the non-woven base through air pressure atomization, and then processed by hot pressing to reinforce the composite molding, and the vinyl alcohol-ethylene copolymer on the surface of the composite non-woven base fiber is polymerized. It is the same polymer material as the fibers of the PVA-co-PE nanofiber film layer. The composite effect is strengthened by hot-pressing fusion bonding, which greatly improves the bonding stability of the two-layer structure of the composite nanofiber film. . This is mainly because: in the hot pressing process of the composite non-woven base layer and the PVA-co-PE nanofiber film layer (the second step of reinforcement and composite process), the fibers of the composite non-woven base layer are vinyl alcohol-ethylene copolymer. The fiber structure is mixed with thermoplastic polymer, and the hot-pressing temperature is set slightly higher than the melting temperature of vinyl alcohol-ethylene copolymer. The nanofiber connections and intersections in the interface of the two-layer structure form polymer face-to-face bonds (skin-core structure) or point-to-point bonds (orange flap structure and side-by-side structure), namely PVA-co-PE The vinyl alcohol-ethylene copolymer in the nanofiber film layer forms point/surface contact with the vinyl alcohol-ethylene copolymer on the surface of the composite non-woven base layer, thereby making the two interfaces of the composite non-woven base layer and the nanofiber film layer meet. The vinyl alcohol-ethylene copolymer in the molten state of the layers is bonded, realizing the point/surface bonding enhanced structure between the nanofibers, improving the overall mechanical strength of the nanofiber film, and the interfacial bonding force between the two-layer structures, The bonding stability of the two-layer structure of the composite nanofiber membrane is greatly improved, and the bonding fastness between the two is large. Under the action of external force, the nanofiber membrane and the base cloth are tightly combined and stable, and are not easy to separate.

4) The combined stability of the composite non-woven base layer and the nanofiber film layer in the composite nanofiber film prepared by the present invention is far higher than the stability of the double-layer composite structure obtained by the traditional coating method, which is mainly due to: the present invention By using vinyl alcohol-ethylene copolymer as the main material of the polymer thermocompression bonding on the surface of the two-layer structure in the nanofiber membrane composite structure, after the thermocompression treatment, the adhesive fastness between the two-layer structures is large, and the external force Under the action, the PVA-co-PE nanofiber membrane layer and the composite non-woven base layer are closely and stably combined, and are not easy to separate.

2. The preparation method of the composite nanofiber membrane provided by the present invention adopts the melt extrusion phase separation method to prepare the nanofibers, which does not need to use a solvent, reduces the production cost, and has no pollution to the environment; the melt phase separation method can ensure that the stretching into During the silk process, the two component filaments are radially separated. When the matrix is removed by dissolving, the radial composition of the nanofibers remains unchanged, and no breakage occurs, thereby improving the stability of the fibers.

3. The preparation method of the composite nanofiber membrane provided by the present invention is simple and controllable, has low cost, and has great commercial promotion value.

Description of drawings

FIG. 1 is an electron microscope image of the composite nanofiber membrane provided in Example 1 of the present invention, and the scale is 1 μm.

Detailed ways

The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

The invention provides a preparation method of a composite nanofiber membrane, comprising the following steps:

S1, the preparation of composite non-woven base layer: according to a predetermined ratio, the thermoplastic polymer master batch and vinyl alcohol-ethylene copolymer master batch are subjected to bi-component melt spinning to obtain bi-component composite fibers; The component composite fibers are subjected to fiber forming treatment to prepare a composite non-woven base layer;

S2. Preparation of PVA-co-PE nanofibers: blend the vinyl alcohol-ethylene copolymer masterbatch and the cellulose acetate butyrate masterbatch according to a predetermined mass ratio to obtain a mixed masterbatch, and melt the mixed masterbatch for spinning. , to prepare PVA-co-PE/CAB composite nanofibers; extract the PVA-co-PE/CAB composite nanofibers with acetone to obtain PVA-co-PE nanofibers;

S3. Preparation of composite nanofiber membrane: the PVA-co-PE nanofibers prepared in step S2 are prepared into a suspension; the suspension is mixed with the composite non-woven fabric prepared in step S1 through a pneumatic atomization process. The base layer is preliminarily compounded to obtain a composite film composed of the PVA-co-PE nanofiber film layer and the composite non-woven base layer; then, the composite film is subjected to hot pressing to make the composite nonwoven The cloth base layer and the vinyl alcohol-ethylene copolymer in the PVA-co-PE nanofiber film layer are partially melted and bonded to obtain a composite nanofiber film.

Further, the bi-component composite fiber has a side-by-side structure, a skin-core structure or an orange-lobed structure.

Further, the bicomponent composite fiber has a skin-core structure, and the skin layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer.

Further, the bi-component composite fiber has an orange-lobed structure; the preparation of the bi-component composite fiber with the orange-lobed structure also includes a splitting pretreatment process.

Further, the cleavage pretreatment process refers to soaking the bi-component composite fibers with chemical additives to reduce the interfacial adhesion between the two-component fibers to separate them, so as to obtain a split cross-section. Shaped ultra-fine nanofibers; or the cleavage pretreatment process refers to mechanically splitting the bi-component composite fibers using the mechanical energy of the high-pressure water flow generated by the spunlace method to obtain the split cross-section shaped ultra-fine fibers Nanofibers. Further, in the hot-pressing process of step S3, the hot-pressing temperature is 150-210° C., the hot-pressing pressure is 1-5 MPa, and the hot-pressing time is 5-30 s.

Further, in the air pressure atomization process described in step S3, the atomization air pressure is 0.1-0.5 MPa.

Further, in step S1, the process of the fiber forming treatment is spunlace process, heat sealing process, SMS process, wet process, spunbond process, pulp airlaid process, meltblown process, needle punching process. A sort of.

Further, in step S1, the mass ratio of the thermoplastic polymer master batch and the vinyl alcohol-ethylene copolymer master batch is 20-80%: 20-80%.

Further, the thermoplastic polymer is one or more of PET, PP, and PE.

90° peeling effect test method: reference standard GB8808-1988.

Breaking Strength Test Method: Reference Standard ISO 9073-3.

The preparation method of the composite nanofiber membrane provided by the present invention will be further described in detail below through specific examples.

Example 1

Preparation method of composite nanofiber membrane:

S1. Preparation of composite non-woven base layer: The thermoplastic polymer PE masterbatch and vinyl alcohol-ethylene copolymer masterbatch with a mass ratio of 50%: 50% are respectively subjected to bi-component melt spinning through a screw extruder to prepare A melt-blown composite non-woven fabric base layer with a skin-core structure is obtained; wherein, the skin layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer.

S2. Preparation of PVA-co-PE nanofibers: blend the vinyl alcohol-ethylene copolymer masterbatch and the cellulose acetate butyrate masterbatch in a mass ratio of 20:80, and dry to obtain a mixed masterbatch. The master batch is poured into the screw extruder for melt blending and spinning, and the PVA-co-PE/CAB composite nanofibers are prepared, wherein the temperature of the first zone to the sixth zone of the twin-screw extruder is respectively set to 160, 180, 200, 210, 215, and 225° C.; then, the PVA-co-PE/CAB composite nanofibers were extracted with acetone, and the matrix phase acetate butyrate fibers were removed to obtain PVA-co-PE nanofibers.

S3. Preparation of composite nanofiber membrane: the PVA-co-PE nanofibers prepared in step S2 are prepared into a suspension through air pressure atomization (the atomization pressure is 0.1-0.5MPa) and the composite non-woven fabric prepared in step S1 The spun base layer is composited, and then subjected to hot pressing treatment to obtain the composite nanofiber membrane; in the hot pressing process, the hot pressing temperature is 150° C., the hot pressing pressure is 1 MPa, and the hot pressing time is 10 s.

Please refer to FIG. 1 , after the composite nanofiber film prepared in Example 1 is subjected to hot pressing, the nanofiber layer and the partially melted part of the PVA-co-PE in the base layer are bonded and are in close contact. The skin-core structure fiber is composed of two components that are covered with each other layer by layer and composited along the fiber axis. Since the skin layer of the bi-component composite fiber is thin, the skin layer components are melted during the hot pressing process, so the bonding between the non-woven fabric base layer and the nanofiber membrane layer is fine, uniform and stable.

In the composite nanofiber film prepared in Example 1, the thickness of the PVA-co-PE nanofiber film layer is 0.2 μm, and the thickness of the composite non-woven base layer is 0.2 mm; the PVA-co-PE nanofiber The mass ratio of the film layer to the composite non-woven base layer is 1:10.

The composite nanofiber membrane prepared in Example 1 has a filtration efficiency of 100% with a gram weight of 66 g/m ² and excellent filtration performance. The fracture strength of the composite nanofiber membrane is 210N/5cm, and the 90° peel strength is 3KN/m, indicating that it has excellent mechanical strength, and the interfacial bonding between its double-layer structures is firm and stable.

Example 2-5

The difference from Embodiment 1 is that the setting of the hot-pressing temperature in step S3 is different, and other steps are the same as those of Embodiment 1, which will not be repeated here.

Example Hot pressing temperature (℃) Breaking Strength (N/5cm) Peel Strength(KN/m) Example 1 150 210 3.0 Example 2 160 213 3.4 Example 3 170 216 3.6 Example 4 180 220 3.9 Example 5 210 224 4.5

The effect of hot pressing temperature on the strength of composite nanofiber membrane:

Under the same other conditions, with the increase of the hot pressing temperature, the more the PVA-co-PE in the nanofiber layer and the non-woven base layer is partially melted, and the more the nanofiber layer and the base layer are in contact after hot pressing. Tight, so the bonding strength is higher, and further, the overall strength of the composite membrane is also enhanced.

Examples 6-8

The difference from Embodiment 1 is that the setting of the hot-pressing pressure in step S3 is different, and other steps are the same as those of Embodiment 1, which will not be repeated here.

Example Hot pressing pressure (MPa) Breaking Strength (N/5cm) Peel Strength(KN/m) Example 1 1 210 3.0 Example 6 2 214 3.3 Example 7 3 222 4.0 Example 8 5 225 5.0

The effect of hot pressing pressure on the strength of composite nanofiber membrane:

Under the same other conditions, with the increase of hot pressing pressure, the contact between the nanofiber layer and the partially melted part of the PVA-co-PE in the non-woven fabric base layer is closer, so the bonding strength is higher, and further, also The overall strength of the composite membrane is enhanced.

Examples 9-11

The difference from Embodiment 1 is that the setting of the hot-pressing time in step S3 is different, and other steps are the same as those of Embodiment 1, which will not be repeated here.

Example Hot pressing time (s) Breaking Strength (N/5cm) Peel Strength(KN/m) Example 1 10 210 3.0 Example 9 5 201 1.8 Example 10 15 218 3.5 Example 11 30 225 4.0

The effect of hot pressing time on the strength of composite nanofiber membrane:

Under the same other conditions, with the extension of the hot pressing time, the more molten parts of the PVA-co-PE in the nanofiber layer and the non-woven base layer are partially melted, the longer the contact time, and the tighter the bonding after hot pressing. , so the higher the bonding strength, and further, the overall strength of the composite membrane is also enhanced.

Comparative Example 1

The difference from Example 1 is that the traditional coating method is used to carry out the compounding of the double-layer structure.

Comparative Example 2

The difference from Example 1 is that in step S1, the base layer of the non-woven fabric is prepared by melt spinning with pure thermoplastic polymer PE, and other steps are the same as those in Example 1, and will not be repeated here.

Examples 12-15

The difference from Example 1 is: in step S1, the setting of the mass ratio of thermoplastic polymer PE and vinyl alcohol-ethylene copolymer (PVA-co-PE) is different, and other steps are the same as in Example 1, here No longer.

Effect of thermoplastic polymer PE and vinyl alcohol-ethylene copolymer (PVA-co-PE) mass ratio on the strength of composite nanofiber membrane:

Under the same conditions, with the increase of the PVA-co-PE content of the substrate, the more the melted part of the PVA-co-PE in the nanofiber layer and the non-woven base layer is partially melted, the more the contact is, and the heat is further increased. The tighter the bond after pressing, the higher the bond strength; however, due to the decrease of PE content, the breaking strength of the composite film decreases.

Examples 16-17

The difference from Example 1 is that the thermoplastic polymer species is set differently.

Example thermoplastic polymer Breaking Strength (N/5cm) Peel Strength(KN/m) Example 1 PE 210 3.0 Example 16 PET 250 2.5 Example 17 PP 230 2.1

Effects of thermoplastic polymer species on the strength of composite nanofiber membranes:

Under the same conditions, the polymer fiber strength is PET>PP>PE, and the affinity with PVA-co-PE is PE>PET>PP, so the corresponding breaking strength of the composite film is PET>PP>PE, and the nanofiber layer and The peel strength of the substrate layer is PE>PET>PP.

Example 18

Preparation method of composite nanofiber membrane:

S1, the thermoplastic polymer PP master batch and vinyl alcohol-ethylene copolymer master batch are respectively added in the screw extruder at a mass ratio of 50%: 50%, and two-component melt spinning is carried out to prepare 32 orange petals The bi-component composite fiber of the structure; then the bi-component composite fiber adopts the spunlace stripping technology, and the orange-lobed bi-component composite fiber is subjected to the split reinforcement process, and finally the spunlace composite non-woven fabric base is prepared. .

S2, the vinyl alcohol-ethylene copolymer master batch and the cellulose acetate butyrate master batch are blended in a mass ratio of 20:80, and the drying treatment obtains the mixed master batch, and the mixed master batch is poured into the screw extruder for carrying out Melt-blend filaments to prepare PVA-co-PE/CAB composite nanofibers, wherein the temperatures of the first zone to the sixth zone of the twin-screw extruder are respectively set at 160, 180, 200, 210, 215, and 225°C; then , the PVA-co-PE/CAB composite nanofibers are extracted with acetone, the matrix phase acetate butyrate fibers are removed, and the /PVA-co-PE nanofibers are obtained by drying.

S3. Preparation of composite nanofiber membrane: the PVA-co-PE nanofibers prepared in step S2 are prepared into a suspension through air pressure atomization (the atomization pressure is 0.1-0.5MPa) and the composite non-woven fabric prepared in step S1 The spun base layer is preliminarily compounded to obtain a composite membrane, and then hot-pressed to obtain a composite nanofiber membrane; in the hot-pressing process, the hot-pressing temperature is 200° C., the hot-pressing pressure is 2MPa, and the hot-pressing time is 20s.

In the composite nanofiber film prepared in Example 18, the thickness of the PVA-co-PE nanofiber film layer is 0.2 μm, and the thickness of the composite non-woven base layer is 0.2 mm; the PVA-co-PE nanofiber The mass ratio of the film layer to the composite non-woven base layer is 1:10.

The composite nanofiber membrane prepared in Example 18 has a filtration efficiency of 100% with a gram weight of 66 g/m ² and excellent filtration performance. The composite nanofiber membrane has a breaking strength of 195N/5cm and a 90° peel strength of 3.5KN/m, indicating that it has excellent mechanical strength, and the interfacial bonding between its double-layer structures is firm and stable.

The bi-component fibers with orange petal structure are used for the splitting treatment process to obtain the split ultrafine nanofibers with special-shaped cross-sections, which are then composited into a nanofiber non-woven base layer. The split bicomponent fiber not only has a great improvement in fiber fineness, but also the special cross-sectional shape of the orange petal structure bicomponent composite fiber greatly improves the superfine fiber and its composite non-woven base. The specific surface area makes it possible for the particles to be separated in the medium to collide or adhere to the fibers in the composite nanofiber filtration membrane during the filtration and separation process, and the filtration performance is more superior. Therefore, this structure improves to a certain extent. Filtration performance of composite nanofiber filtration membranes.

It should be noted that those skilled in the art should understand that the orange-lobed structure may also be one of 16 petals or 64 petals.

Example 19

Preparation method of composite nanofiber membrane:

S1. Preparation of composite non-woven base layer: The thermoplastic polymer PE masterbatch and vinyl alcohol-ethylene copolymer masterbatch with a mass ratio of 50%: 50% are respectively subjected to bi-component melt spinning through a screw extruder to prepare A needle-punched composite non-woven base layer with a side-by-side structure was obtained.

S2. Preparation of PVA-co-PE nanofibers: blend the vinyl alcohol-ethylene copolymer masterbatch and the cellulose acetate butyrate masterbatch in a mass ratio of 20:80, and dry to obtain a mixed masterbatch. The master batch is poured into the screw extruder for melt blending and spinning, and the PVA-co-PE/CAB composite nanofibers are prepared, wherein the temperature of the first zone to the sixth zone of the twin-screw extruder is respectively set to 160, 180, 200, 210, 215, and 225° C.; then, the PVA-co-PE/CAB composite nanofibers were extracted with acetone, and the matrix phase acetate butyrate fibers were removed to obtain PVA-co-PE nanofibers.

S3. Preparation of composite nanofiber membrane: the PVA-co-PE nanofibers prepared in step S2 are prepared into a suspension through air pressure atomization (the atomization pressure is 0.1-0.5MPa) and the composite non-woven fabric prepared in step S1 The spun base layer is composited, and then subjected to hot pressing treatment to obtain the composite nanofiber membrane; in the hot pressing process, the hot pressing temperature is 170° C., the hot pressing pressure is 2 MPa, and the hot pressing time is 10 s.

In the composite nanofiber film prepared in Example 19, the thickness of the PVA-co-PE nanofiber film layer is 0.4 μm, and the thickness of the composite non-woven base layer is 0.2 mm; the PVA-co-PE nanofiber The mass ratio of the film layer to the composite non-woven base layer is 2:4.

The fracture strength of the composite nanofiber membrane is 180N/5cm, and the 90° peel strength is 3KN/m, indicating that it has excellent mechanical strength, and the interfacial bonding between its double-layer structures is firm and stable.

It should be noted that those skilled in the art should understand that different types of thermoplastic polymers, different structures of bi-component composite fibers, and different melting points, so there will also be differences when setting the melt spinning temperature and hot pressing temperature. Differently, in actual operation, parameters such as melt spinning temperature and hot pressing temperature need to be adjusted and set according to the melting point of the thermoplastic polymer. The fiber forming process of the composite non-woven base layer can also be one of the heat sealing process, the SMS process, the wet process, the spunbond process, and the pulp airlaid process.

In summary, the present invention provides a composite nanofiber membrane and a preparation method thereof. First, the thermoplastic polymer master batch and the vinyl alcohol-ethylene copolymer master batch are subjected to bi-component melt spinning to prepare bi-component composite fibers with a special-shaped structure, and molding to obtain a composite non-woven base; then, vinyl alcohol- Ethylene copolymer masterbatch and cellulose acetate butyrate masterbatch are blended, and the PVA-co-PE nanofibers are prepared by melt extrusion phase separation method; finally, the PVA-co-PE nanofibers are prepared into a suspension, and the After the atomization is preliminarily combined with the composite non-woven fabric base layer, it is subjected to hot pressing treatment to obtain a composite nanofiber membrane. The preparation method adopts the same material as the polymer material of the two-layer structure in the nanofiber membrane composite structure, and performs thermocompression bonding. The prepared composite nanofiber membrane has excellent mechanical strength, and the interface bonding stability of the two-layer structure is stable. High, high adhesion fastness, not easy to separate.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or some or all of the technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims (10)

1. A preparation method of a composite nanofiber membrane is characterized by comprising the following steps: the method comprises the following steps:

s1, preparing the composite non-woven fabric base layer: carrying out double-component melt spinning on the thermoplastic polymer master batch and the vinyl alcohol-ethylene copolymer master batch according to a predetermined proportion to obtain double-component composite fiber; then, carrying out fiber forming treatment on the two-component composite fibers to prepare a composite non-woven fabric base layer;

s2, preparation of PVA-co-PE nano-fiber: blending the vinyl alcohol-ethylene copolymer master batch and the cellulose acetate butyrate master batch according to a preset mass ratio to obtain a mixed master batch, and performing melt blending spinning on the mixed master batch to prepare the PVA-co-PE/CAB composite nanofiber; extracting the PVA-co-PE/CAB composite nanofiber by using acetone to obtain PVA-co-PE nanofiber;

s3, preparation of the composite nanofiber membrane: preparing the PVA-co-PE nano-fiber prepared in the step S2 into a suspension; preliminarily compounding the suspension with the composite non-woven fabric base layer prepared in the step S1 through an air pressure atomization process to obtain a composite film formed by mutually compounding a PVA-co-PE nanofiber film layer and the composite non-woven fabric base layer; and then, carrying out hot-pressing treatment on the composite membrane, so that the composite non-woven fabric base layer and the vinyl alcohol-ethylene copolymer in the PVA-co-PE nano fiber membrane layer are partially melted, bonded and reinforced and compounded, and the composite nano fiber membrane is obtained.

2. The method for preparing a composite nanofiber membrane as claimed in claim 1, characterized in that: the bicomponent composite fiber is of a parallel structure, a sheath-core structure or a orange-flap structure.

3. The method for preparing a composite nanofiber membrane as claimed in claim 2, characterized in that: the bicomponent composite fiber is of a sheath-core structure, the sheath layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer.

4. The method for preparing a composite nanofiber membrane as claimed in claim 2, characterized in that: the two-component composite fiber is of a orange petal type structure; the preparation of the two-component composite fiber with the orange petal-shaped structure comprises a cracking pretreatment process.

5. The method of producing a composite nanofiber membrane as claimed in claim 4, characterized in that: the splitting pretreatment process is to soak the two-component composite fiber by using a chemical auxiliary agent to reduce the interface adhesive force between the two-component composite fiber and separate the two-component composite fiber so as to obtain split superfine nano fiber with a special-shaped section; or the cracking pretreatment process is to perform mechanical cracking on the bicomponent composite fiber by using the mechanical energy of high-pressure water flow generated by a water-jet method so as to obtain the cracked superfine nanofiber with the special-shaped section.

6. The method for preparing a composite nanofiber membrane as claimed in claim 1, characterized in that: in the hot pressing process of the step S3, the hot pressing temperature is 150-210 ℃, the hot pressing pressure is 1-5 MPa, and the hot pressing time is 5-30S; in the air pressure atomization process of step S3, the atomization air pressure is 0.1-0.5 MPa.

7. The method for preparing a composite nanofiber membrane as claimed in claim 1, characterized in that: in step S1, the fiber forming process is one of a spunlace process, a heat sealing process, an SMS process, a wet process, a spunbond process, a pulp air-laying process, a melt-blowing process, and a needle-punching process.

8. The method for preparing a composite nanofiber membrane as claimed in claim 1, characterized in that: in step S1, the mass ratio of the thermoplastic polymer masterbatch to the vinyl alcohol-ethylene copolymer masterbatch is 20 to 80%: 20-80%; the thermoplastic polymer is one or more of PET, PP and PE.

9. The composite nanofiber membrane prepared by the method for preparing a composite nanofiber membrane according to any one of claims 1 to 8, wherein: the composite nanofiber membrane is formed by preliminarily compounding PVA-co-PE nanofiber suspension with the composite non-woven fabric base layer through an air pressure atomization process and then reinforcing and compounding through hot pressing; the composite non-woven fabric base layer and the PVA-co-PE nanofiber membrane layer are both provided with a vinyl alcohol-ethylene copolymer; the mass ratio of the PVA-co-PE nanofiber membrane layer to the composite non-woven fabric base layer is 5-20% to 80-95%; the breaking strength of the composite nanofiber membrane is 80-250N/5 cm, and the 90-degree peel strength is 0.05-5 KN/m.

10. The composite nanofiber membrane of claim 9, wherein: the fiber of the composite non-woven fabric base layer is a bi-component composite fiber, the bi-component composite fiber is of a sheath-core structure, the sheath layer is a vinyl alcohol-ethylene copolymer, and the core layer is a thermoplastic polymer; or the two-component composite fiber is of a orange petal type structure and comprises a plurality of split section profiled superfine nano fibers obtained through a splitting pretreatment process; or the bicomponent composite fiber is of a parallel structure.

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