WO2021248464A1 - Non-woven fabric used as supporting layer of water treatment membrane, preparation method therefor and water treatment membrane - Google Patents

Abstract

A non-woven fabric used as a supporting layer of a water treatment membrane, a preparation method therefor and a water treatment membrane. The non-woven fabric comprises: backbone fibers, first binding fibers and second binding fibers, wherein the backbone fibers have a diameter within the range of 5-13 µm; the first binding fibers and the second binding fibers both have a diameter within the range of 7-16 µm; and the melting point or softening point of the first binding fibers is at least 15ºC higher than that of the second binding fibers, and the melting point or softening point of the backbone fibers is at least 20ºC higher than that of the first binding fibers. In the non-woven fabric, the binding fibers bind all the fibers together to form a three-dimensional network structure, followed by curing to form a microfine concave-convex structure on the surface of the non-woven fabric. The microfine concave-convex structure allows a coating solution to be embedded in the microfine concave pores on the surface of the non-woven fabric, producing an extremely strong binding strength, and thus ensuring a high liquid flux and a high filtering performance of the water treatment membrane.

Description

Non-woven fabric used as water treatment membrane support layer, preparation method thereof and water treatment membrane Technical field

This application relates to the field of water treatment, and in particular to a non-woven fabric used as a support layer of a water treatment membrane, a preparation method thereof, and a water treatment membrane.

Background technique

Water treatment membrane technology is currently mainly used in sewage treatment, water supply purification, seawater desalination, and pure water preparation. According to the different manufacturing materials, water treatment membranes can be divided into inorganic membranes and organic membranes. Inorganic membranes are mainly ceramic membranes, glass membranes and metal membranes, which have low filtration accuracy and low selectivity. Organic membrane selects cellulose resin, polyvinyl alcohol resin, polysulfone resin, polyamide resin, polyimide resin and other polymer materials as raw materials according to different separation purposes. It has high filtration accuracy and large selectivity, and is widely used in water resources. Chemical industry and industrial special separation and other fields.

Taking the reverse osmosis membrane in the organic water treatment membrane (hereinafter referred to as the "water treatment membrane") as an example, the reverse osmosis membrane usually consists of three layers: a polyamide ultra-thin layer, a polysulfone intermediate support layer and a polyester-reinforced non-woven fabric. The non-woven fabric mainly provides the support strength of the membrane structure. The polysulfone porous layer has extremely high porosity and rigidity, which can resist compaction under the membrane operating conditions. The polyamide ultra-thin layer has high water flux and salt rejection rate. And chemical stability.

Among them, the polyamide ultra-thin layer is a functional layer that really plays a role of separation in the water treatment process. However, due to the extremely low mechanical strength of the polyamide ultra-thin layer, it cannot be separately prepared into a film and must be compounded with a support layer to form a film. The current conventional method is to use a non-woven fabric and a polyamide ultra-thin layer to compound, the non-woven fabric is used as a support layer, and the functional layer is coated on the non-woven fabric.

However, water treatment membranes require high liquid throughput and high filtration performance. Therefore, the non-woven fabric and the functional layer are required to have good consistency. Generally, the uniformity of the non-woven fabric and the smoothness of the coated surface should be considered. However, this often leads to low adhesiveness of the non-woven fabric, resulting in weak bonding between the organic coating layer and the non-woven fabric, and the phenomenon of delamination and peeling between the coating and the non-woven fabric is prone to occur. This will cause the coating liquid to not well infiltrate the surface of the non-woven fabric, and the air bubbles remain in the pores so that the coating liquid is elevated at the pores of the non-woven fabric, reducing the actual contact area between the coating liquid and the non-woven fabric. Water treatment membrane filtration performance is significantly reduced and other serious problems.

Summary of the invention

The purpose of the embodiments of the present application is to provide a non-woven fabric used as a support layer of a water treatment membrane, a preparation method thereof, and a water treatment membrane.

In the first aspect, the present application provides a non-woven fabric used as a support layer of a water treatment film. The non-woven fabric includes: backbone fibers, first bonding fibers, and second bonding fibers; first bonding fibers and second bonding fibers. The material of the fiber is not the same;

The diameters of the backbone fiber, the first bonding fiber and the second bonding fiber are all in the range of 5-16μm;

The backbone fiber, the first bonding fiber and the second bonding fiber all include a crystalline polymer and/or an amorphous polymer; the melting point or softening point of the first bonding fiber is higher than the melting point or softening point of the second bonding fiber It is at least 15°C higher, and the melting point or softening point of the backbone fiber is at least 20°C higher than the melting point or softening point of the first binding fiber.

In the non-woven fabric used as the support layer of the water treatment membrane, the melting point or softening point of the first bonding fiber is at least 15°C higher than the melting point or softening point of the second bonding fiber, and the melting point or softening point of the backbone fiber is higher than that of the first bonding fiber. The melting point or softening point of the bonding fiber is at least 20°C higher. When heat-pressed into a non-woven fabric, the second bonding fiber will first melt and form a discontinuous fine uneven structure on the surface of the non-woven fabric, and then the first bonding The fiber is partially melted, while the backbone fiber hardly melts. The melted bonding fibers bond the fibers together to form a three-dimensional network structure, and after solidification, a fine uneven structure is formed on the surface of the non-woven fabric. Using this non-woven fabric as a water treatment membrane support layer, this fine concave-convex structure can form an "anchor effect" between the coating solution of the functional layer and the non-woven fabric The same), so that the coating solution is embedded in the fine cavities on the surface of the non-woven fabric. After the coating is cured, the meshing force is generated in the interface area and cannot be moved, resulting in extremely strong bonding strength, thereby ensuring the high pass of the water treatment film Liquid volume and high filtration performance.

In the second aspect, the present application provides a method for preparing the above-mentioned non-woven fabric used as a support layer of a water treatment membrane, including:

The main fiber, the first bonding fiber and the second bonding fiber are formed into fiber base paper, and then the fiber base paper is hot-calendered, so that the second bonding fiber is melted in the main fiber and the first bonding fiber during the hot calendering process. The surface of the knotted fiber forms a bumpy structure;

The temperature at which the fiber base paper is thermally calendered is not lower than the melting point or softening point temperature of the second binding fiber minus 10°C, and not higher than the melting point or softening point temperature of the main fiber.

When hot-pressed into a non-woven fabric, because the melting point or softening point of the second bonding fiber is low, the second bonding fiber will melt first and form a discontinuous fine uneven structure on the surface of the non-woven fabric during hot pressing. The bonding fiber is partially melted; while the melting point or softening point of the backbone fiber is higher than the hot calendering temperature, the dimensional stability is high during the hot pressing process, so it does not melt; the partially or completely melted bonding fiber will make the non-woven fabric The fibers adhere to each other and form a three-dimensional network structure of the non-woven fabric after cooling and solidification, so that the surface of the non-woven fabric obtains a fine uneven structure. Using this non-woven fabric as a water treatment membrane support layer, this fine uneven structure can form an "anchor effect" between the functional layer and the non-woven fabric, so that the coating solution is embedded in the fine cavities on the surface of the non-woven fabric, making After the coating is cured, it cannot move, resulting in extremely strong bonding strength, thereby ensuring the high liquid flow rate and high filtration performance of the water treatment membrane.

In a third aspect, the present application provides a water treatment membrane, which includes the aforementioned non-woven fabric used as a support layer of the water treatment membrane; and

Functional layer, the functional layer is coated on the surface of the non-woven fabric.

The water treatment membrane is provided with the aforementioned non-woven fabric used as the support layer of the water treatment membrane, so that the organic functional coating and the non-woven fabric have high bonding strength, thereby ensuring the high liquid flow rate and high filtration performance of the water treatment membrane .

Description of the drawings

In order to explain the technical solutions of the implementation of this application more clearly, the following will briefly introduce the drawings that need to be used in the implementation. It should be understood that the following drawings only show some embodiments of the application, and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative work.

Fig. 1 shows the surface topography of the non-woven fabric used as the supporting layer of the water treatment membrane prepared in Example 1 of the present application.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments These are a part of the embodiments of this application, but not all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various different configurations.

Therefore, the following detailed description of the embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

In addition, the terms "first", "second", "third", etc. are only used for distinguishing description, and cannot be understood as indicating or implying relative importance.

The inventor found that the method for compounding an organic functional layer on a non-woven fabric support layer is usually to first prepare a coating solution, and then apply the coating solution to the surface of the non-woven fabric, and then solidify the coating through phase separation. The binding force between the functional layer and the non-woven fabric is the result of the interaction between the interfaces of different materials. The influencing factors are complex and may be affected by the interfacial tension between the functional layer and the non-woven fabric, surface free energy, and functional groups. The influence of properties, inter-interface reaction, etc. Based on mechanical theory, the bonding force between the functional layer and the non-woven fabric is mainly caused by the coating liquid penetrating into the pores or bumps on the surface of the non-woven fabric. Similar to the role of tree roots in the soil, the essence of this connection force is friction. By applying this meshing force or increasing the friction force, the bonding force between the functional layer and the non-woven fabric can be improved.

The embodiment of the present application provides a non-woven fabric used as a support layer of a water treatment film, the non-woven fabric includes: backbone fibers, first bonding fibers, and second bonding fibers; materials of the first bonding fibers and second bonding fibers Are not the same;

In terms of mass fraction, the weight of the backbone fiber accounts for 60-80wt% of the total weight of the backbone fiber, the first bonding fiber and the second bonding fiber; the second bonding fiber accounts for the first bonding fiber and the second bonding fiber 10-40wt% of the total fiber weight;

The diameters of the backbone fiber, the first bonding fiber and the second bonding fiber are all in the range of 5-16μm;

The backbone fiber, the first bonding fiber and the second bonding fiber all include a crystalline polymer and/or an amorphous polymer; the melting point or softening point of the first bonding fiber is higher than the melting point or softening point of the second bonding fiber It is at least 15°C higher, and the melting point or softening point of the backbone fiber is at least 20°C higher than the melting point or softening point of the first binding fiber.

In the non-woven fabric used as the support layer of the water treatment membrane, the melting point or softening point of the first bonding fiber is at least 15°C higher than the melting point or softening point of the second bonding fiber, and the melting point or softening point of the backbone fiber is higher than that of the first bonding fiber. The melting point or softening point of the bonding fiber is at least 20°C higher. When hot-pressed into a non-woven fabric, the second bonding fiber has a lower melting point or softening point. The surface of the non-woven fabric forms a discontinuous micro-concave-convex structure, while the first bonding fiber is partially melted; the melting point or softening point of the backbone fiber is higher than the hot-calendering temperature, and the dimensional stability is high during the hot-pressing process, so it does not occur Melting; The partially or completely melted bonding fibers adhere the fibers of the non-woven fabric to each other, and form a three-dimensional network structure of the non-woven fabric after cooling and solidification, so that the surface of the non-woven fabric has a fine uneven structure. Using this non-woven fabric as a water treatment membrane support layer, this fine concave-convex structure can form an "anchor effect" between the coating solution of the functional layer and the non-woven fabric The same), so that the coating solution is embedded in the fine cavities on the surface of the non-woven fabric, so that the coating cannot move after curing, resulting in extremely strong bonding strength, thereby ensuring the high liquid flow rate and high filtration performance of the water treatment membrane.

In some embodiments of the present application, the lengths of the backbone fiber, the first bonding fiber, and the second bonding fiber are all in the range of 3-10 mm.

By setting the length of the backbone fiber, the first bonding fiber, and the second bonding fiber in the range of 3-10 mm, the strength of the non-woven fabric can be ensured. If the fiber length is less than 3mm, the strength of the non-woven fabric is likely to be too low; if the fiber length is greater than 10mm, the excessively long fibers are easy to agglomerate and entangle, causing serious defects in the appearance and performance of the non-woven fabric.

Further optionally, the lengths of the backbone fiber, the first bonding fiber, and the second bonding fiber are all in the range of 3.5 to 9.5 mm.

Further optionally, the lengths of the backbone fiber, the first bonding fiber and the second bonding fiber are all in the range of 4-9 mm.

Exemplarily, the length of the backbone fiber, the first bonding fiber, and the second bonding fiber are all 5 mm; or the length of the backbone fiber, the first bonding fiber, and the second bonding fiber are all 8 mm; or the length of the backbone fiber, the first bonding fiber is 8 mm. The length of the first bonding fiber and the second bonding fiber are both 4 mm.

In other optional embodiments of the present application, the lengths of the above-mentioned backbone fiber, the first bonding fiber, and the second bonding fiber can also be selected to be different. For example, the length of the backbone fiber is 5 mm, and the length of the first bonding fiber is 5 mm. The length of the fiber is 6 mm, and the length of the second bonding fiber is 4.5 mm.

Further, the diameter of the backbone fiber is in the range of 5 to 13 μm; the diameter of the first bonding fiber and the second bonding fiber are both in the range of 7 to 16 μm.

Setting the diameters of the main fiber, the first bonding fiber, and the second bonding fiber within the above range can ensure the high liquid flow rate and high filtration performance of the water treatment membrane. If the diameter of the backbone fiber is higher than 13μm and the diameter of the bonding fiber is higher than 16μm, the thickness of the resulting non-woven fabric will be too large. For a certain size of water treatment membrane module, the larger the thickness of the non-woven fabric means the larger the area of the water treatment membrane. Small, it also leads to a reduction in the filtration efficiency of the water treatment membrane module; at the same time, the thick fiber also increases the possibility of large holes in the non-woven fabric, which does not help to obtain the desired pore size and distribution, and easily causes the organic coating liquid to pass through the through holes. It penetrates from the upper layer to the lower layer, thereby increasing the possibility of defects such as pinholes in the coating layer. If the diameter of the backbone fiber is less than 5 μm and the diameter of the bonding fiber is less than 7 μm, the use of too thin fibers will weaken the overall strength of the non-woven fabric, and the thinner the fiber, the higher the cost.

Further optionally, the diameter of the backbone fiber is in the range of 5.5 to 12.5 μm; the diameter of the first bonding fiber and the second bonding fiber are both in the range of 7.5 to 15.5 μm.

Further optionally, the diameter of the backbone fiber is in the range of 6-12 μm; the diameter of the first bonding fiber and the second bonding fiber are both in the range of 8-15 μm.

Illustratively, the diameter of the backbone fiber is 7.13 μm, the diameter of the first bonding fiber is 10.08 μm, and the second bonding fiber is 14.55 μm. Or the diameter of the main fiber is 7.70 μm, the diameter of the first bonding fiber is 12.00 μm, and the second bonding fiber is 13.01 μm. Or the diameter of the backbone fiber is 6.51 μm, the diameter of the first bonding fiber is 12.00 μm, and the second bonding fiber is 14.55 μm.

Further, the melting point or softening point of the second bonding fiber is in the range of 100 to 200°C.

Further optionally, the melting point or softening point of the second bonding fiber is in the range of 100 to 170°C.

Further optionally, the melting point or softening point of the second bonding fiber is in the range of 105 to 165°C.

Further, the melting point or softening point of the first bonding fiber is at least 15°C higher than the melting point or softening point of the second bonding fiber, and the melting point or softening point of the backbone fiber is higher than the melting point or softening point of the first bonding fiber At least 20°C.

If the melting point or softening point of the second bonding fiber is too low, it is easy to be over-melted during the hot pressing process, and the sticking is serious. If the melting point or softening point of the second bonding fiber is too high, it cannot be melted in time during hot pressing. Therefore, it is difficult to obtain the desired fine concavo-convex structure on the surface of the non-woven fabric. Setting the backbone fiber, the first bonding fiber, and the second bonding fiber within the above range can effectively ensure that a non-woven fabric with a fine concave-convex structure on the surface is obtained, thereby improving the adhesion between the non-woven fabric and the organic functional coating. The resultant effect, thereby ensuring the high liquid flow rate and high filtration performance of the water treatment membrane.

Exemplarily, when the second bonding fiber, the first bonding fiber and the backbone fiber are all selected crystalline polymers; when the melting point of the second bonding fiber is 110°C, the melting point of the first bonding fiber is at least 125°C , The melting point of the backbone fiber is at least 130°C.

Illustratively, when amorphous polymers are selected for the second and first bonding fibers, crystalline polymers are selected for the backbone fibers; when the softening point of the second bonding fibers is 120°C, the first bonding fibers The softening point is at least 135°C, and the melting point of the backbone fiber is at least 140°C.

Further, in terms of mass fraction, the weight of the backbone fiber accounts for 60 to 80 wt% of the total weight of the backbone fiber, the first bonding fiber, and the second bonding fiber; the second bonding fiber accounts for the first bonding fiber and the second bonding fiber. 10-40wt% of the total weight of the knotted fiber.

By setting the mass fractions of the backbone fiber, the first bonding fiber, and the second bonding fiber within the above range, it can be ensured that the subsequently prepared water treatment membrane has high liquid flow capacity and high filtration performance. The second bonding fiber accounts for 10-40% by weight of the total weight of the first bonding fiber and the second bonding fiber. If the second bonding fiber accounts for less than 10%, it is difficult to form a fine uneven structure on the surface of the non-woven fabric, and vice versa. If the proportion of the second bonding fiber is higher than 40%, the excessive low-melting polymer melts on the surface of the non-woven fabric, which is likely to cause serious pore blockage, and it is difficult to obtain the desired pore structure. The mass fraction of the backbone fiber is 60-80wt%. If the content of the backbone fiber as the main body of the structure is less than 60%, it is difficult to maintain sufficient mechanical strength. On the contrary, if the content is higher than 80%, the content of the bonding fiber is too small, and the fibers cannot be fully connected. Adhesion is solid, the structure of the non-woven fabric is loose, and the mechanical strength of the non-woven fabric is also difficult to guarantee.

Further, in some preferred embodiments of the present application, the above-mentioned backbone fiber is selected as a crystalline polymer. By selecting the backbone fiber as a crystalline polymer, the prepared non-woven fabric can have better mechanical strength.

Further optionally, the weight of the backbone fiber accounts for 65 to 75 wt% of the total weight of the backbone fiber, the first bonding fiber, and the second bonding fiber; the second bonding fiber accounts for the total weight of the first bonding fiber and the second bonding fiber. 13-40wt% of the weight.

Exemplarily, in terms of mass fraction, the non-woven fabric used as the support layer of the water treatment membrane includes 65 wt% of the backbone fiber, 28 wt% of the first bonding fiber, and 7 wt% of the second bonding fiber. Or in terms of mass fraction, the non-woven fabric used as the support layer of the water treatment membrane includes 75 wt% of the backbone fiber, 18.5% of the first bonding fiber, and 6.5 wt% of the second bonding fiber. Or in terms of mass fraction, the non-woven fabric used as the support layer of the water treatment membrane includes 80 wt% of the backbone fiber, 15 wt% of the first bonding fiber, and 5 wt% of the second bonding fiber.

Further, the average pore diameter of the non-woven fabric used as the water treatment membrane support layer is not more than 4.5 μm, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 5.

By using the above-mentioned non-woven fabric as the support layer of the water treatment membrane, the average pore diameter is not more than 4.5μm, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 5, which can ensure that the subsequently prepared water treatment membrane has a high liquid permeability Volume and high filtration performance.

Further, when the average pore diameter is greater than 4.5 μm and the maximum pore diameter/average pore diameter ratio is greater than 5, the coating liquid is likely to penetrate from the coating surface to the back of the non-woven fabric, resulting in through holes in the coating layer, and finally the coating liquid adheres On the surface of the guide roller, causing contamination by foreign matter. In addition, when the maximum pore diameter/average pore diameter ratio is greater than 5, the air entrained by the non-woven fabric exchanges with water at an uneven rate during the phase separation process, which will affect the uniformity of the coating layer curing into a film.

Further, the backbone fiber is selected from at least one of polyester fiber, polyolefin fiber, polyamide fiber, polyimide fiber, polytetrafluoroethylene fiber, polyphenylene sulfide fiber, polyacrylonitrile fiber or aramid fiber kind.

Further, the material of the polyester fiber includes: polyethylene terephthalate and polybutylene terephthalate;

Polyolefin fiber materials include: polyethylene, polypropylene, polyvinyl chloride, ES;

The material of polyamide fiber includes: PA66.

Further, both the first bonding fiber and the second bonding fiber are selected from:

Polyethylene terephthalate undrawn fiber, polybutylene terephthalate undrawn fiber, polyolefin fiber, copolyester fiber, low melting point copolyamide fiber, low melting point polyolefin as the skin layer At least one of the core-skin structure composite fiber, the core-skin structure composite fiber with a low melting point copolyester as the skin layer, or the skin-core structure composite fiber with a low melting point copolyamide as the skin layer.

Further, the materials of polyolefin fibers include: polyethylene, polypropylene, and polyvinyl chloride;

The raw materials of copolymerized polyester fiber include: CoPET, CoPBT;

The materials of low melting point copolyamide fiber include: PA6/6, PA6/66, PA6/66/12, PA6/66/69, PA6/66/610, PA6/66/69/12, PA6/612/12, PA6 /610/12;

The low-melting-point polyolefin skin layer materials of the skin-core composite fiber include: PE, PP;

The low melting point copolyester skin layer materials of the skin-core composite fiber include: CoPET, CoPBT;

The low melting point copolyamide skin layer materials of the core structure composite fiber include: PA6/66/12, PA6/66/69, PA6/66/610, PA6/66/69/12, PA6/612/12, PA6/610/ 12.

Some embodiments of the application also provide a method for preparing a non-woven fabric used as a support layer of a water treatment membrane,

The main fiber, the first bonding fiber and the second bonding fiber are formed into fiber base paper, and then the fiber base paper is hot-calendered, so that the second bonding fiber is melted in the main fiber and the first bonding fiber during the hot calendering process. The surface of the knotted fiber forms an uneven structure.

Further, the temperature at which the fiber base paper is subjected to thermal calendering treatment is not lower than the melting point or softening point temperature of the second binding fiber minus 10° C., and is not higher than the melting point or softening point temperature of the main fiber. The second bonding fiber has a low melting point or softening point, so the second bonding fiber will melt first and form a discontinuous fine uneven structure on the surface of the non-woven fabric when hot pressing is performed, while the first bonding fiber is partially melted; and The melting point or softening point of the backbone fiber is higher than the hot calendering temperature, and the dimensional stability is high during the hot-pressing process, so it will not melt; the partially or completely melted bonding fiber will adhere the fibers of the non-woven fabric to each other, and after cooling and solidification A three-dimensional network structure of the non-woven fabric is formed, so that the surface of the non-woven fabric obtains a fine uneven structure. Using this non-woven fabric as a water treatment membrane support layer, this fine uneven structure can make the organic coating layer and the non-woven fabric form an "anchor effect" ("anchor effect" refers to an anchor hooking a recess on the seabed Same), so that the coating solution is embedded in the fine cavities on the surface of the non-woven fabric, so that the coating cannot move after curing, resulting in extremely strong bonding strength, thereby improving the high liquid flow rate and high filtration performance of the water treatment membrane.

It should be noted that the above-mentioned method of making the main fiber, the first bonding fiber and the second bonding fiber into the fiber base paper can adopt the conventional non-woven fabric preparation method in the art.

Some embodiments of the present application also provide a water treatment membrane, which includes the non-woven fabric used as the support layer of the water treatment membrane provided in the foregoing embodiments and a functional layer.

Further, the functional layer is coated on the surface of the non-woven fabric.

Since the water treatment membrane is provided with the aforementioned non-woven fabric used as the support layer of the water treatment membrane, the bonding strength of the coating layer of the water treatment membrane to the support layer is significantly improved.

Further, in some embodiments of the present application, the water treatment membrane is a reverse osmosis membrane, and the reverse osmosis membrane is provided with the aforementioned non-woven fabric used as a support layer of the water treatment membrane. A polysulfone layer was coated on the outer surface of the non-woven fabric used as the support layer of the water treatment membrane. In terms of mass fraction, the composition of the coating solution is: 7.5% polysulfone and 92.5% N-methylpyrrolidone. After coating, it was immersed in water for phase separation, and after 10 minutes, it was taken out and dried at room temperature to obtain a water treatment membrane.

The features and performance of the present application will be described in detail below in conjunction with examples and comparative examples.

Example 1

Provide a water treatment membrane, which is prepared as follows:

The fiber base paper with an areal density of 75g/m2 is made from each raw material using an inclined wire paper machine, and then the fiber base paper is subjected to hot calendering treatment. The temperature of the hot calendering treatment is not lower than the melting point or softening point temperature of the second bonding fiber minus 10°C , And not higher than the melting point or softening point temperature of the main fiber, the hot press uses a steel roller/steel roller combination to prepare a non-woven fabric used as a support layer of a water treatment film.

Next, the non-woven fabric prepared above was cut out into an A4 paper size sample, and the outer surface of the upper layer was coated with a polysulfone layer. In terms of mass fraction, the composition of the coating solution is: 7.5% polysulfone and 92.5% N-methylpyrrolidone. After coating, it was immersed in water for phase separation, and after 10 minutes, it was taken out and dried at room temperature to obtain a water treatment membrane.

The specific parameters of each raw material fiber are shown in Table 1.

Example 2

A water treatment film is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material fiber are different. The second bonding fiber is a skin-core composite with CoPET as the skin and PET as the core. Fiber, the specific parameters of each raw material are shown in Table 1.

Example 3

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different. The second bonding fiber is a sheath-core composite fiber with PE as the skin and PP as the core. , The specific parameters of each raw material are shown in Table 1.

Example 4

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different, and the specific parameters of each raw material are shown in Table 1.

Comparative example 1

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different (Comparative Example 1 The melting point or softening point temperature of the second binding fiber is lower than 100°C) , The specific parameters of each raw material fiber are shown in Table 1.

Comparative example 2

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different (Comparative Example 2 The main fiber and the first bonding fiber have the same melting point/softening point temperature) , The specific parameters of each raw material fiber are shown in Table 1.

Comparative example 3

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different (Comparative Example 3 The melting point or softening point of the first bonding fiber is higher than that of the second bonding fiber. The melting point or softening point of the fiber is higher than 15°C). The specific parameters of each raw fiber are shown in Table 1.

Comparative example 4

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different (the mass fraction of the main fiber in Comparative Example 4 is greater than 80% by weight), and the specific raw material fiber Parameters are shown in Table 1.

Comparative example 5

A water treatment membrane is provided, which is the same as the preparation method of Example 1, except that the specific parameters of each raw material are different (the second binding fiber is not added in Comparative Example 5), and the specific parameters of each raw fiber See Table 1.

Table 1 Specific parameters of each raw material

1. Test the performance of the water treatment membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 5. The detected properties include: "area density" of non-woven fabric, "density" of non-woven fabric, "thickness" of non-woven fabric, "pore size" of non-woven fabric, "tensile strength" of non-woven fabric, coating The "peel strength" of the layer.

Among them, the "area density" of the non-woven fabric is measured according to the GB/T 451.2-2002 method. The "density" of the non-woven fabric is obtained by dividing the "area density" of the non-woven fabric and the "thickness" of the non-woven fabric. The "thickness" of the non-woven fabric is measured according to the GB/T 451.3-2002 method. The "pore size" of the non-woven fabric is measured according to the GB/T 32361-2015 method. The "tensile strength" of non-woven fabrics is measured according to the GB/T 12914-2008 method. The "peel strength" of the coating layer is measured according to the GB/T 2792-2014 method.

The test results are shown in Table 2 below.

Table 2 Test results

It can be seen from Table 2 that the samples of Examples 1-4 of the present application have good performance, especially the peel strength of the coating layer is significantly higher than the peel strength of the samples of Comparative Examples 1 to 5, indicating that the use of the samples provided by the application The non-woven fabric of the support layer of the water treatment membrane can significantly enhance the bonding strength of the coating layer to the support layer.

The test results of Comparative Example 1 show that when the melting point or softening point of the second bonding fiber used is lower than 105°C, the melting point or softening point of the first bonding fiber is higher than that of the second bonding fiber. When the temperature is less than 15°C, the second bonding fiber is excessively melted during the hot pressing process, and the sticking roller is severe, which affects the surface smoothness of the non-woven fabric, and the fine uneven structure on the surface of the non-woven fabric cannot be formed.

The test result of Comparative Example 2 shows that when the melting point or softening point of the main fiber used is the same as that of the first bonding fiber, that is, the melting point or softening point of the main fiber is less than 20°C higher than the melting point or softening point of the first bonding fiber. At this time, excessive polymer melts on the surface of the non-woven fabric, resulting in serious pore blockage, it is difficult to obtain the desired pore structure, and the fine uneven structure on the surface of the non-woven fabric cannot be formed.

The test results of Comparative Example 3 show that when the melting point or softening point of the first bonding fiber used is less than 15°C higher than the melting point or softening point of the second bonding fiber, the first bonding fiber and the The second bonding fiber melts almost simultaneously, and the fine uneven structure on the surface of the non-woven fabric cannot be formed.

The test results of Comparative Example 4 show that when the mass fraction of the main fiber used is greater than 80wt%, after hot pressing, the fibers cannot be fully bonded and solidified, the structure of the non-woven fabric is loose, and the surface of the non-woven fabric is finely uneven. The structure cannot be formed.

The test results of Comparative Example 5 show that when the second bonding fiber is not used, the fine uneven structure on the surface of the non-woven fabric cannot be formed, the peel strength of the coating is significantly reduced, and the bonding between the coating and the non-woven fabric layer is poor.

2. Using a scanning electron microscope to characterize the surface morphology of the non-woven fabric prepared in Example 1 and used as the support layer of the water treatment membrane.

Figure 1 of the specification shows the surface topography of the non-woven fabric prepared in Example 1 and used as the supporting layer of the water treatment membrane.

It can be seen from Figure 1 that the partially or completely melted bonding fibers in the non-woven fabric used as the support layer of the water treatment membrane prepared in Example 1 adhere each fiber of the non-woven fabric to each other to form a three-dimensional network structure, so that The surface of the non-woven fabric forms a fine uneven structure. Using this non-woven fabric as a water treatment membrane support layer enables the coating liquid to be embedded in the fine pores on the surface of the non-woven fabric, and the coating cannot move after curing, resulting in extremely strong bonding strength, thereby improving the coating layer The bonding strength to the support layer improves the structural stability of the water treatment membrane, thereby improving the water treatment effect.

Industrial applicability

The preparation method of the non-woven fabric used as the support layer of the water treatment membrane of the present application is suitable for large-scale production, thereby improving its practicability and economy.

The foregoing descriptions are only preferred embodiments of the application, and are not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in the protection scope of this application.

Claims (10)

1. A non-woven fabric used as a support layer of a water treatment membrane, characterized in that the non-woven fabric comprises: backbone fibers, first bonding fibers, and second bonding fibers; the first bonding fibers and the The material of the second bonding fiber is different;

   In terms of mass fraction, the weight of the backbone fiber accounts for 60 to 80 wt% of the total weight of the backbone fiber, the first bonding fiber, and the second bonding fiber; the second bonding fiber accounts for the 10-40 wt% of the total weight of the first bonding fiber and the second bonding fiber;

   The diameters of the backbone fiber, the first bonding fiber and the second bonding fiber are all in the range of 5-16 μm;

   The backbone fiber, the first bonding fiber and the second bonding fiber all include a crystalline polymer and/or an amorphous polymer; the melting point or softening point of the first bonding fiber is higher than that of the The melting point or softening point of the second binding fiber is at least 15°C higher, and the melting point or softening point of the backbone fiber is at least 20°C higher than the melting point or softening point of the first binding fiber.
2. The non-woven fabric used as a support layer of a water treatment membrane according to claim 1, wherein:

   The melting point or softening point of the second bonding fiber is in the range of 100 to 200°C;

   Optionally, the melting point or softening point of the second bonding fiber is 100-170°C.
3. The non-woven fabric used as a support layer of a water treatment membrane according to claim 1, wherein:

   The lengths of the backbone fiber, the first bonding fiber, and the second bonding fiber are all in the range of 3-10 mm.
4. The non-woven fabric used as a support layer of a water treatment membrane according to any one of claims 1 to 3, wherein:

   The average pore diameter of the non-woven fabric used as the support layer of the water treatment membrane is not more than 4.5 μm, and the ratio of the maximum pore diameter to the average pore diameter is not less than 1 and not more than 5;

   Optionally, the diameter of the backbone fiber is in the range of 5 to 13 μm; the diameter of the first bonding fiber and the second bonding fiber are both in the range of 7 to 16 μm;
5. The non-woven fabric used as a support layer of a water treatment membrane according to claim 1, wherein:

   The backbone fiber is selected from at least one of polyester fiber, polyolefin fiber, polyamide fiber, polyimide fiber, polytetrafluoroethylene fiber, polyphenylene sulfide fiber, polyacrylonitrile fiber or aramid fiber .
6. The non-woven fabric used as a support layer of a water treatment membrane according to claim 5, wherein:

   The material of the polyester fiber includes: polyethylene terephthalate and polybutylene terephthalate;

   The material of the polyolefin fiber includes: polyethylene, polypropylene, polyvinyl chloride, ES;

   The material of the polyamide fiber includes: PA66.
7. The non-woven fabric used as a support layer of a water treatment membrane according to claim 1, wherein:

   Both the first bonding fiber and the second bonding fiber are selected from:

   Polyethylene terephthalate undrawn fiber, polybutylene terephthalate undrawn fiber, polyolefin fiber, copolyester fiber, low melting point copolyamide fiber, low melting point polyolefin as the skin layer At least one of the core-skin structure composite fiber, the core-skin structure composite fiber with a low melting point copolyester as the skin layer, or the skin-core structure composite fiber with a low melting point copolyamide as the skin layer.
8. The non-woven fabric used as a support layer of a water treatment membrane according to claim 7, wherein:

   The material of the polyolefin fiber includes: polyethylene, polypropylene, and polyvinyl chloride;

   The material of the copolyester fiber includes: CoPET, CoPBT;

   The materials of the low melting point copolyamide fiber include: PA6/6, PA6/66, PA6/66/12, PA6/66/69, PA6/66/610, PA6/66/69/12, PA6/612/12 , PA6/610/12;

   The low-melting-point polyolefin skin layer material of the skin-core structure composite fiber includes: PE and PP;

   The low melting point copolyester skin layer material of the skin-core structure composite fiber includes: CoPET and CoPBT;

   The low melting point copolyamide skin layer materials of the skin-core structure composite fiber include: PA6/66/12, PA6/66/69, PA6/66/610, PA6/66/69/12, PA6/612/12, PA6/ 610/12.
9. The method for preparing a non-woven fabric used as a support layer of a water treatment membrane according to any one of claims 1 to 8, characterized in that it comprises:

   The main fiber, the first bonding fiber, and the second bonding fiber are formed into fiber base paper, and then the fiber base paper is hot-calendered so that the second bonding fiber is melted in the heat-calendering process. The surface of the backbone fiber and the first bonding fiber forms a concave-convex structure;

   The temperature at which the fibrous base paper is thermally calendered is not lower than the melting point or softening point temperature of the second binding fiber minus 10° C., and is not higher than the melting point or softening point temperature of the backbone fiber.
10. A water treatment membrane, characterized in that the water treatment membrane comprises the non-woven fabric used as a water treatment membrane support layer according to any one of claims 1 to 8; and

    The functional layer is coated on the surface of the non-woven fabric.

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