Preparation method and preparation device of electret material and electret material
阅读说明：本技术 驻极体材料的制备方法、制备装置和驻极体材料 (Preparation method and preparation device of electret material and electret material ) 是由 丁伊可 蓝文权 宣晓雅 洪贤良 肖爱菊 于 2019-11-06 设计创作，主要内容包括：本发明提供了一种驻极体材料的制备方法、制备装置和驻极体材料,涉及驻极方法及装置领域。该驻极体材料的制备方法,包括以下步骤：提供基体材料；向基体材料的一侧表面喷射驻极液体,并向基体材料的另一侧表面第一次施加负压,能够使驻极液体浸润到基体材料的厚度方向上,且驻极液体能够与基体材料发生相对摩擦；然后向基体材料进行第二次施加负压,使驻极液体沿着垂直于无纺布表面的方向抽离,且驻极液体能够与基体材料再次发生相对摩擦；干燥,得到驻极体材料。本发明可对不同克重、厚度和材质的基体材料进行简单、高效的驻极处理,得到含有大量静电荷的高效驻极体滤材。(The invention provides a preparation method and a preparation device of an electret material and the electret material, and relates to the field of electret methods and devices. The preparation method of the electret material comprises the following steps: providing a base material; spraying electret liquid on the surface of one side of the base material, and applying negative pressure on the surface of the other side of the base material for the first time, so that the electret liquid can be soaked in the thickness direction of the base material, and the electret liquid and the base material can generate relative friction; then, negative pressure is applied to the base material for the second time, so that the electret liquid is pumped away along the direction vertical to the surface of the non-woven fabric, and the electret liquid and the base material can generate relative friction again; and drying to obtain the electret material. The invention can carry out simple and efficient electret treatment on base materials with different gram weights, thicknesses and materials to obtain the efficient electret filter material containing a large amount of static charges.)
1. A preparation method of an electret material is characterized by comprising the following steps:
(a) providing a base material;
(b) spraying electret liquid on the surface of one side of the base material, and applying negative pressure on the surface of the other side of the base material for the first time, so that the electret liquid can be soaked in the thickness direction of the base material, and the electret liquid and the base material can generate relative friction;
(c) applying negative pressure to the base material obtained in the step (b) for the second time to enable the electret liquid to be drawn away along the direction vertical to the surface of the non-woven fabric, and enabling the electret liquid and the base material to generate relative friction again;
(d) and drying to obtain the electret material.
2. The method of claim 1, wherein the second application of negative pressure is a negative pressure applied to one side surface of the base material or a negative pressure applied to the other side surface of the base material;
preferably, the steps (b) and (c) are performed one or more times.
3. The method for producing an electret material as claimed in claim 1, wherein the electret liquid is sprayed to one side surface of the base material by a liquid spraying device; applying negative pressure to the other side surface of the base material for the first time by using a first negative pressure device; applying negative pressure to the base material for the second time by using a second negative pressure device;
preferably, the liquid spraying device comprises a nozzle, and the distance between the nozzle and the base material is 5-20 cm, preferably 10-15 cm;
the spraying pressure of the liquid spraying device is 0.1-5 MPa, preferably 0.1-1 MPa;
the jet flow of the liquid spraying device is 0.1-10 m3Preferably 0.5 to 5 m/h3/h；
Preferably, the pressure applied by the first negative pressure device is in the range of 0.01-0.05 MPa, preferably 0.01-0.03 MPa;
preferably, the first negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm, preferably 20-40 mm;
preferably, the pressure applied by the second negative pressure device is in the range of 0.01-0.1 MPa, preferably 0.01-0.05 MPa;
preferably, the second negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm, preferably 1-10 mm.
4. A method for producing an electret material according to any of claims 1 to 3, wherein the drying is carried out at a temperature of 110 ℃ or less, preferably 100 ℃ or less.
5. A method of producing an electret material according to any of claims 1 to 3, wherein the electret liquid comprises water;
preferably, the electret liquid further comprises an electrolyte, and the electrolyte is preferably a weakly acidic substance or a weakly alkaline substance;
preferably, the pH value of the electret liquid is 4-10, and the conductivity is 0.1-500 us/cm.
6. The method for producing an electret material as claimed in any one of claims 1 to 3, wherein the base material comprises a nonwoven fabric or a composite material comprising a nonwoven fabric;
preferably, the manufacturing process of the non-woven fabric comprises at least one of melt-blowing, spun-bonding, needle-punching or hydro-punching;
preferably, the non-woven fabric comprises at least one of polyethylene, polypropylene, polyethylene terephthalate or polylactic acid;
preferably, the base material is preheated before step (b).
7. A device for preparing electret material, which comprises a liquid electret unit and a drying unit, wherein the liquid electret unit comprises:
a liquid ejecting device for ejecting an electret liquid to a surface of a base material;
at least two negative pressure devices for applying negative pressure to the surface of the base material, respectively;
at least one of the negative pressure device and the liquid spraying device is respectively positioned on two sides of the base material.
8. The apparatus for preparing electret material of claim 8, wherein the negative pressure device comprises a first negative pressure device and a second negative pressure device, and the first negative pressure device and the liquid spraying device are respectively disposed on both sides of the base material;
preferably, the first negative pressure device is vertically opposite to the liquid spraying device;
preferably, the second negative pressure device and the first negative pressure device are positioned on the same side of the base material, or the second negative pressure device and the first negative pressure device are respectively positioned on two sides of the base material;
preferably, the cross section of the negative pressure device is funnel-shaped, the negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm;
preferably, the liquid spraying device is provided with a plurality of parallel nozzles, and the distance between each nozzle and the base material is 5-20 cm.
9. The electret material preparation device according to claim 7 or 8, further comprising an unwinding unit and a winding unit, wherein the unwinding unit, the liquid electret unit, the drying unit and the winding unit are sequentially and continuously arranged;
preferably, the device further comprises a liquid collecting device, wherein the liquid collecting device is used for collecting the redundant electret liquid.
10. An electret material produced by a process comprising the electret material of any one of claims 1-6.
Technical Field
The invention relates to the technical field of electret methods and devices, in particular to a preparation method and a preparation device of an electret material and the electret material.
Background
Currently, with the increasing living standard of people, the requirement on the indoor air quality is higher and higher. Traditional air filter material relies on physical barrier effect filtering particles mostly, like glass fiber filter paper, though have very high filtration efficiency, nevertheless have the shortcoming that the resistance is big, the energy consumption is high. The novel electret filter material is a dielectric material which stores a large amount of stable static charges, mainly captures particles in air under the action of an electrostatic field, has the characteristics of high efficiency and low resistance, and has obvious advantages compared with the traditional air filter material.
Currently, the industry primarily charges electret materials using both corona discharge and liquid electret methods. Corona discharge, which is a method of bombarding and charging a dielectric with an ion beam generated by corona discharge that causes local breakdown of air due to a non-uniform electric field, is one of the most widely used methods in industry. However, corona discharge causes discharge deviation due to precision error of a gap between a high-voltage applying electrode and a grounding electrode, so that the electret material is not uniformly charged, and the electret effect is not ideal; in addition, corona discharge can generate a large amount of ozone to pollute the environment and harm human health in a long-term discharge process; in addition, high voltage equipment is expensive, and there are also great concerns in terms of safe operation and management. In contrast, the liquid electret device is not only cheap, but also has the characteristics of high efficiency, environmental protection and safety.
"spray charging" is the spraying of a stream of water or water droplets onto a thermoplastic microfiber nonwoven substrate at a pressure sufficient to impart an electret charge to the substrate that enhances filtration (CN 1129963A). However, this "liquid-jet charging" method has insufficient penetrating power in the thickness direction, and it is difficult to achieve an ideal electret effect for a substrate having a high grammage and a high thickness. In order to improve the filtration efficiency of the substrate, the flow rate and pressure of the water column or water drop stream or the front and back sides of the substrate need to be increased for multiple times of liquid spraying, so that the cost and complexity of the process equipment are increased.
Chinese patent publication No. CN108744713A discloses an ultrasonic sputtering liquid charging device and method for an electret. The method charges the electret material by controlling the distance between two roll shafts and a bottom liquid groove and changing the inclination of the bottom of the liquid groove and the power of ultrasonic waves at the bottom of the liquid groove. The charging method has strong applicability, and is suitable for electrets formed by mixing long fibers, short fibers or long and short fibers and multi-layer composite electrets with different thicknesses and different materials. And the mechanical strength of the ultrasonic sputtering charging device is small, and the electret with thin thickness and low strength is not easy to damage. However, the ultrasonic power is limited, the mechanical action force is small, so that the electret is not sufficiently soaked by liquid, and the corona charging is still carried out before the liquid is charged for achieving a good electret effect, so that the defect of the corona charging cannot be avoided.
Chinese patent publication No. CN1288681C discloses a method for manufacturing electrets by steam condensation. The method condenses the vapor from the atmosphere of the controlled environment onto the dielectric article and then dries the article to remove the condensate. The method uses a small amount of liquid to electrically charge the article and does not damage the overall structure of the article or unduly compress the porous web fabric. However, this method requires a closed controlled vacuum environment, and the volume, pressure and temperature of the controlled environment are adjusted to condense the vapor in the controlled environment on the article. Charging the article in this way takes a long time, the operation is relatively complicated and the required environmental conditions are not suitable for industrial mass production.
In view of this, the invention is particularly proposed.
Disclosure of Invention
A first object of the present invention is to provide a process for the preparation of electret materials which is simple, safe, efficient, low-cost, does not cause damage to the surface and structure of the material, is suitable for industrial mass production, and is able to overcome the above-mentioned problems or at least partially solve the above-mentioned technical problems.
A second object of the present invention is to provide a device for the preparation of electret materials which is simple, safe, efficient, low-cost, does not cause damages to the surface and structure of the material, is suitable for industrial mass production, and is able to overcome the above-mentioned problems or at least partially solve the above-mentioned technical problems.
The third purpose of the invention is to provide an electret material prepared by the preparation method of the electret material.
In order to achieve the purpose, the invention adopts the technical scheme that:
according to one aspect of the present invention, there is provided a method of making an electret material, comprising the steps of:
(a) providing a base material;
(b) spraying electret liquid on the surface of one side of the base material, and applying negative pressure on the surface of the other side of the base material for the first time, so that the electret liquid can be soaked in the thickness direction of the base material, and the electret liquid and the base material can generate relative friction;
(c) applying negative pressure to the base material obtained in the step (b) for the second time to enable the electret liquid to be drawn away along the direction vertical to the surface of the non-woven fabric, and enabling the electret liquid and the base material to generate relative friction again;
(d) and drying to obtain the electret material.
Further, the second application of negative pressure is to apply negative pressure to one side surface of the base material, or to apply negative pressure to the other side surface of the base material;
preferably, the steps (b) and (c) are performed one or more times.
Further, an electret liquid is ejected to one side surface of the base material by a liquid ejecting apparatus; applying negative pressure to the other side surface of the base material for the first time by using a first negative pressure device; applying negative pressure to the base material for the second time by using a second negative pressure device;
preferably, the liquid spraying device comprises a nozzle, and the distance between the nozzle and the base material is 5-20 cm, preferably 10-15 cm;
the spraying pressure of the liquid spraying device is 0.1-5 MPa, preferably 0.1-1 MPa;
the jet flow of the liquid spraying device is 0.1-10 m3Preferably 0.5 to 5 m/h3/h；
Preferably, the pressure applied by the first negative pressure device is in the range of 0.01-0.05 MPa, preferably 0.01-0.03 MPa;
preferably, the first negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm, preferably 20-40 mm;
preferably, the pressure applied by the second negative pressure device is in the range of 0.01-0.1 MPa, preferably 0.01-0.05 MPa;
preferably, the second negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm, preferably 1-10 mm.
Further, the drying temperature is less than or equal to 110 ℃, and preferably less than or equal to 100 ℃.
Further, the electret liquid comprises water;
preferably, the electret liquid further comprises an electrolyte, and the electrolyte is preferably a weakly acidic substance or a weakly alkaline substance;
preferably, the pH value of the electret liquid is 4-10, and the conductivity is 0.1-500 us/cm.
Further, the base material includes a nonwoven fabric or a composite material containing a nonwoven fabric;
preferably, the manufacturing process of the non-woven fabric comprises at least one of melt-blowing, spun-bonding, needle-punching or hydro-punching;
preferably, the non-woven fabric comprises at least one of Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), or polylactic acid (PLA);
preferably, the base material is preheated before step (b).
According to another aspect of the present invention, there is provided an apparatus for preparing an electret material, comprising a liquid electret unit and a drying unit, wherein the liquid electret unit comprises:
a liquid ejecting device for ejecting an electret liquid to a surface of a base material;
at least two negative pressure devices for applying negative pressure to the surface of the base material, respectively;
at least one of the negative pressure device and the liquid spray device is respectively arranged on two sides of the base material.
It is understood that the manufacturing apparatus is a manufacturing apparatus capable of implementing the above-described method of manufacturing electret materials, i.e., the manufacturing method and the manufacturing apparatus are corresponding.
Further, the negative pressure device comprises a first negative pressure device and a second negative pressure device, and the first negative pressure device and the liquid spraying device are respectively positioned on two sides of the base material;
preferably, the first negative pressure device is vertically opposite to the liquid spraying device;
preferably, the second negative pressure device and the first negative pressure device are positioned on the same side of the base material, or the second negative pressure device and the first negative pressure device are respectively positioned on two sides of the base material;
preferably, the cross section of the negative pressure device is funnel-shaped, the negative pressure device is provided with a slit, and the width range of the slit is 1-40 mm;
preferably, the liquid spraying device is provided with a plurality of parallel nozzles, and the distance between each nozzle and the base material is 5-20 cm.
The device further comprises an unreeling unit and a reeling unit, wherein the unreeling unit, the liquid electret unit, the drying unit and the reeling unit are sequentially and continuously arranged;
preferably, the device further comprises a liquid collecting device, wherein the liquid collecting device is used for collecting the redundant electret liquid, and the liquid collecting device is preferably a water tank.
According to another aspect of the present invention, there is provided an electret material produced by the method for producing an electret material as described above.
Compared with the prior art, the technical scheme provided by the invention can achieve the following beneficial effects:
the preparation method and the preparation device of the electret material provided by the invention adopt a cooperative matching mode of spraying the electret liquid and applying negative pressure, namely, under the cooperative matching action of the liquid spraying device and the negative pressure device, the base material can be quickly and fully infiltrated, the base material can be fully infiltrated in the thickness direction, and the base material and the electret liquid can generate at least two times of relative friction to generate better electret effect.
The electret material preparation method and the electret material preparation device can ensure uniformity and stability of the electret in all directions under the condition of not damaging the surface appearance and the internal structure of the base material, thereby improving the production efficiency and the product quality, realizing the effects of low cost, simplicity, safety and high efficiency, uniformly and stably charging, being suitable for liquid electret of base materials with different gram weights and thicknesses, and being easy to realize industrialized large-scale production.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic flow chart illustrating the production of an electret material according to an exemplary embodiment of the invention;
FIG. 2 is a schematic structural diagram of a liquid electret unit according to an exemplary embodiment of the invention;
fig. 3 is a schematic structural diagram of a liquid electret unit according to another exemplary embodiment of the invention.
Icon: i, an unwinding unit; II, a liquid electret unit; III-a drying unit; IV-a winding unit;
1-an unwinding device; 2-a matrix material; 3-a guide roller; 4-a liquid spraying device; 5-a first negative pressure device; 6-a second negative pressure device; 7-a water tank; 8-baking oven; 9-a winding device.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
It should be noted that:
unless otherwise defined, technical and scientific terms used herein have the same meaning as is familiar to those skilled in the art.
All the technical features mentioned herein, as well as preferred features, may be combined with each other to form new solutions, if not mentioned specifically.
In the present invention, unless otherwise specified, the individual operation steps may be performed sequentially or may be performed out of order. For example, other steps may be included between the various steps of the operation, and the order may be reversed between the steps of the operation. Preferably, the preparation process herein is carried out sequentially.
In order to overcome the defects of the prior art and meet the requirements of the prior market, the invention provides a simple, safe, efficient and low-cost electret material preparation method and device, which can not damage the surface and the internal structure of the material, does not need to carry out corona on non-woven fabrics, has uniform and stable charging, and can be suitable for base materials (particularly non-woven fabric materials) with different gram weights, thicknesses and materials.
In a first aspect, in at least one embodiment, there is provided a method of making an electret material, comprising the steps of:
(a) providing a base material;
(b) spraying electret liquid on the surface of one side of the base material, and applying negative pressure on the surface of the other side of the base material for the first time, so that the electret liquid can be soaked in the thickness direction of the base material, and the electret liquid and the base material can generate relative friction;
(c) applying negative pressure to the base material obtained in the step (b) for the second time to enable the electret liquid to be drawn away along the direction vertical to the surface of the non-woven fabric, and enabling the electret liquid and the base material to generate relative friction again;
(d) and drying to obtain the electret material.
The invention is characterized in that the electret liquid is sprayed on one side surface of the base material, negative pressure is applied on one side surface of the base material and/or the other side surface of the base material, and the electret liquid can fully infiltrate the base material and generate relative friction with the base material at least twice.
The synergistic cooperation mode of spraying the electret liquid and applying negative pressure is adopted, so that the problems that the penetrating force of the existing spray charging method in the thickness direction is not enough, and the electret effect is difficult to be ideal for a base material with high gram weight and thickness can be avoided, the corona charging is not needed, the defect of the corona charging can be avoided, a closed controlled vacuum environment is not needed, the operation is relatively simple, and the required environment is suitable for industrial large-scale production.
Further, the method sprays the electret liquid to one side surface of the base material, and applies negative pressure to one side surface of the base material and/or the other side surface of the base material, so that the penetration of surface layer liquid into the base material can be accelerated, the base material can be quickly and fully infiltrated, the base material can be fully infiltrated in the thickness direction, and the base material and the electret liquid can generate at least two times of relative friction to generate a better electret effect. Meanwhile, the method can ensure the uniformity and stability of the electret in all directions under the condition of not damaging the surface appearance and the internal structure of the base material, thereby improving the production efficiency and the product quality, ensuring uniform and stable charging, being suitable for liquid electrets of base materials with different gram weights and thicknesses, providing a low-cost, simple, safe and efficient electret method for the liquid electrets of the materials, and being easy to realize industrialized large-scale production.
It is noted that, herein, "and/or" is used to indicate that one or both of the illustrated cases may occur, e.g., a and/or B includes (a and B) and (a or B).
The above-mentioned application of negative pressure to one surface of the base material and/or the other surface of the base material means that negative pressure may be applied only to one surface of the base material, only to the other surface of the base material, or both negative pressure and negative pressure may be applied to one surface of the base material and the other surface of the base material.
The above-mentioned "one side surface of the base material" and "the other side surface of the base material" are two surfaces opposed to each other in the thickness direction of the base material; that is, from one side surface of the base material to the other side surface in the thickness direction. One surface of the base material may be referred to as a front surface of the base material, and the other surface of the base material may be referred to as a back surface of the base material.
The above-mentioned "relative friction occurs at least twice", which means that the base material may have relative friction with the electret liquid several times, for example, two or more relative frictions occur.
Further, it is understood that, according to the method of the present invention, it is possible to eject an electret liquid to one side surface of a base material and apply a negative pressure to the other side surface of the base material; or spraying electret liquid to one side surface of the base material, and then applying negative pressure to one side surface of the base material; the electret liquid can be sprayed on one side surface of the base material, negative pressure is applied to the other side surface of the base material, and then negative pressure is applied to any side surface of the base material.
Preferably, in the method, the electret liquid is sprayed on one side surface of the base material, the negative pressure is applied to the other side surface of the base material, and then the negative pressure is applied to any side surface of the base material, so that a better electret effect can be obtained.
The preparation method will be described in further detail below with reference to preferred embodiments, in particular, examples according to the present invention, as shown in fig. 1 to 3. Therefore, according to the method provided by the embodiment of the invention, the obtained electret material contains a large amount of static charges, the performance is excellent, the whole preparation process is simple to operate, the manufacturing is convenient, the manufacturing cost is low, the safety is realized, and the efficiency is high.
Step (a): providing a base material;
in this step, the substrate material is transported from the unwinding device to the liquid electret unit.
According to an embodiment of the present invention, step (a) comprises: the base material such as non-woven fabric material is conveyed to the liquid electret unit from the unreeling device under the action of the guide roller.
It should be noted that the present invention is not limited to the substrate material, and may be selected from the types commonly used in the art for preparing electret materials, including but not limited to nonwoven fabrics, composite materials including nonwoven fabrics, and the like. The following specific examples are described in further detail mainly with reference to non-woven fabrics as an example, but it should be understood that the type of the base material is not limited thereto.
Further, the manufacturing process of the non-woven fabric includes, but is not limited to, one of melt-blowing, spun-bonding, needle-punching and water-punching, and the material of the non-woven fabric includes, but is not limited to, one or more of Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET) and polylactic acid (PLA). That is, the electret nonwoven material may be one of nonwoven fabrics manufactured using various molding apparatuses, including those manufactured by melt-blowing, spun-bonding, needle-punching, water-punching, or the like, or a nonwoven composite material. The base material of the non-woven fabric is one or a combination of PP, PET, PE and PLA.
Preferably, the base material is preheated before step (b).
Preferably, the temperature of the preheating treatment is 80-120 ℃; in the pretreatment temperature range, the storage stability and the durability of the later charge are further facilitated.
The matrix material such as non-woven fabric material is first pre-heat treated before electret treatment, so that the resin may be re-crystallized to make the later charge storage stable and lasting.
Step (b): spraying electret liquid and applying negative pressure reversely.
In the step, the electret liquid is sprayed to one side surface of the base material, negative pressure is applied to the other side surface of the base material for the first time, the electret liquid can be soaked in the thickness direction of the base material, and the electret liquid and the base material can generate relative friction.
According to an embodiment of the present invention, step (b) comprises: in liquid electret unit, liquid jet equipment sprays electret liquid toward one side surface of non-woven fabrics for the non-woven fabrics top layer is fully soaked, simultaneously, exerts reverse negative pressure through first negative pressure device on the opposite side surface of non-woven fabrics, and top layer liquid pierces through the non-woven fabrics with higher speed, makes the non-woven fabrics obtain fully soaking in the thickness direction, and liquid takes place relative friction with the non-woven fabrics when soaking the non-woven fabrics, produces preliminary electret effect.
In this step, to the non-woven fabrics of different grammes per square metre and thickness, accessible control hydrojet device's jet distance, injection pressure and jet flow control liquid are to the velocity of flow and the dynamics of non-woven fabrics, make the liquid that erupts be the atomizing form, and the liquid that adjacent nozzle erupted overlaps alternately each other, makes liquid spray on the non-woven fabrics surface evenly in non-woven fabrics width direction, does not destroy the structure of non-woven fabrics simultaneously.
Preferably, the liquid spraying device comprises a nozzle, and the distance between the nozzle and the base material is 5-20 cm, preferably 10-15 cm;
the spraying pressure of the liquid spraying device is 0.1-5 MPa, preferably 0.1-1 MPa;
the jet flow of the liquid spraying device is 0.1-10 m3Preferably 0.5 to 5 m/h3/h。
It is to be understood that the recitation of a range of values herein is intended to be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, injection pressures of 0.1 to 5MPa are understood to include not only the explicitly recited 0.1MPa and 5MPa, but also individual values within the indicated range, such as 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.8MPa, 1MPa, 2MPa, 3MPa, 4MPa, 5MPa, and the like.
Preferably, the first negative pressure device is provided with a slit, and the width adjustable range of the slit is 1-40 mm, preferably 20-40 mm. It is understood that the surface of the first negative pressure device is provided with a slit, and the width of the slit can be shown by referring to fig. 2. If the width of the slit is too narrow, the liquid ejected from the nozzle cannot thoroughly wet the nonwoven fabric. The adjustable range of the reverse pressure applied by the first negative pressure device is 0.01-0.05 MPa, and preferably 0.01-0.03 MPa. Through the slit width and the pressure of adjusting first negative pressure device, the speed and the dynamics that the steerable top layer liquid pierces through the non-woven fabrics to do not destroy the structure of non-woven fabrics when making the non-woven fabrics top layer fully soak.
The liquid content of the cloth surface of the fully soaked non-woven fabric is over 600 percent.
(c) Negative pressure is again applied.
In the step, negative pressure is applied to the base material obtained in the step (b) for the second time, so that the electret liquid is drawn away along the direction vertical to the surface of the non-woven fabric, and the electret liquid and the base material can generate relative friction again.
According to an embodiment of the present invention, step (c) comprises: and (c) sucking the non-woven fabric material obtained in the step (b) after infiltration under the action of a second negative pressure device, so that liquid contained in the non-woven fabric is sucked away along the direction vertical to the surface of the non-woven fabric, and the non-woven fabric and the liquid are subjected to relative friction again to generate a good electret effect.
In the step, the second negative pressure device is provided with a slit, and the width of the slit can be adjusted within the range of 1-40 mm, preferably 1-10 mm. It will be appreciated that the surface of the second underpressure means is provided with slits, the width of which can be seen with reference to fig. 2. If the width of the slit of the second negative pressure device is too wide, the negative pressure applied during suction needs to be increased, which increases energy consumption and is not beneficial to electret effect. The adjustable range of the reverse pressure applied by the second negative pressure device is 0.01-0.1 MPa, preferably 0.01-0.05 MPa. Through adjusting second negative pressure device's slit width and pressure, take out the inside liquid of non-woven fabrics away, make and produce abundant friction between non-woven fabrics and the liquid, improve the electret effect, do not cause the destruction to non-woven fabrics structure simultaneously.
Preferably, the extracted liquid can be stored in a liquid collecting device such as a water tank, and the electret liquid can be recycled, so that the cost is saved, and the device is safe and environment-friendly.
As shown in fig. 2 and 3, the second application of negative pressure may be performed by applying negative pressure to one side surface of the base material or applying negative pressure to the other side surface of the base material. That is, the first negative pressure device and the second negative pressure device may be located on the same side of the base material, or may be located on two opposite sides of the base material.
Preferably, said steps (b) and (c) are carried out one or more times; that is, steps (b) and (c) may be repeated.
And (c) repeatedly arranging the step (b) and the step (c) according to the thickness of the base material and the electret requirement, so that a better electret effect is achieved.
(d) And (5) drying.
In this step, the base material obtained in step (c) is dried to obtain an electret material.
According to an embodiment of the present invention, step (d) comprises: and (3) drying the electret non-woven fabric material in a drying unit to obtain the dry high-efficiency non-woven fabric filter material containing a large amount of static charges.
Preferably, the drying temperature in the drying unit is 110 ℃ or less, preferably 100 ℃ or less;
according to the invention, a suitable drying temperature can be selected depending on the properties of the matrix material, for example a drying temperature of 110 ℃ or less, preferably 100 ℃ or less. After the drying is sufficient, the electrode needs to be taken out quickly, and the electric charge after the electrode is placed is prevented from being heated and attenuated.
The lower limit of the drying temperature is not particularly limited, and since the specifications of the respective products are different and the electret speeds are different, the drying temperature can be adjusted appropriately according to the actual conditions, and generally, the drying temperature is not lower than 70 ℃.
In order to protect the cloth surface from being damaged, the net curtain can be used as a supporting layer in the processes of electret and drying.
Preferably, the electret liquid comprises water;
preferably, the electret liquid further comprises an electrolyte, and the electrolyte is preferably a weakly acidic substance or a weakly alkaline substance;
preferably, the pH value of the electret liquid is 4-10, and the conductivity is 0.1-500 us/cm.
According to the invention, the electret liquid of the electret material is water, preferably distilled water or purified water, and a certain amount of electrolyte can be added, so that the electret liquid has a pH value of 4-10 and an electric conductivity of 0.1-500 us/cm. It should be noted that the electrolyte is not particularly limited, and may be selected from those commonly used in the art for preparing electret materials, including but not limited to weakly acidic materials, weakly basic materials, and the like. Typically but not limitatively, the electrolyte added is natural weak acidic substances such as malic acid, acetic acid, citric acid, etc., or weak alkaline substances such as sodium acetate, sodium carbonate, etc., and the content is below 1000 ppm. Weak acid or weak alkaline solution is used for electret of the non-woven fabric material, so that the electret effect and the stability of charge storage can be improved.
In a second aspect, there is provided in at least one embodiment a device for producing an electret material, comprising a liquid electret unit and a drying unit, wherein the liquid electret unit comprises:
a liquid ejecting device for ejecting an electret liquid to a surface of a base material;
at least two negative pressure devices for applying negative pressure to the surface of the base material, respectively;
at least one of the negative pressure device and the liquid spraying device is respectively positioned on two sides of the base material.
The preparation device is a device for realizing the preparation method of the electret material, and the preparation device and the preparation method of the electret material are based on the same inventive concept, so that the preparation device at least has the same advantages as the preparation method of the electret material, and the details are not repeated.
In some preferred embodiments, the liquid electret unit comprises at least two negative pressure devices, and the liquid ejecting device and the negative pressure device are respectively located on both sides of the base material. It is to be understood that the liquid ejecting apparatus and at least one of the negative pressure apparatuses are respectively located on both sides of the base material, and the location of the other negative pressure apparatuses is not particularly limited.
Further, the negative pressure device comprises a first negative pressure device and a second negative pressure device, and the first negative pressure device and the liquid spraying device are respectively positioned on two sides of the base material;
the first negative pressure device is vertically opposite to the liquid spraying device;
preferably, the second negative pressure device and the first negative pressure device are located on the same side of the base material, or the second negative pressure device and the first negative pressure device are located on two sides of the base material respectively.
In some preferred embodiments, the preparation apparatus further includes an unwinding unit and a winding unit, and the unwinding unit, the liquid electret unit, the drying unit and the winding unit are sequentially and continuously arranged.
Preferably, a liquid collecting device is further included for collecting excess liquid, preferably a sink.
Further, according to an embodiment of the present invention, in the above-mentioned manufacturing apparatus, in the liquid electret unit, there are included one liquid ejecting device and at least two negative pressure devices, which may be labeled as a first negative pressure device and a second negative pressure device in this order, and the liquid ejecting device and the negative pressure device are respectively located on both sides of the nonwoven fabric. The liquid electret unit also comprises a device for receiving the surplus liquid, such as a water tank.
The liquid spraying device is located on one side of the surface of the non-woven fabric and is 5-20 cm away from the non-woven fabric, preferably 10-15 cm away from the non-woven fabric, a plurality of parallel nozzles are arranged below the non-woven fabric in width, sprayed atomized liquid is overlapped and crossed mutually, and the liquid can be uniformly sprayed on the surface of the non-woven fabric in the whole width direction, so that the surface layer of the non-woven fabric is fully soaked.
The first negative pressure device is positioned on the other side of the non-woven fabric and vertically opposite to the liquid spraying device, and under the action of negative pressure, liquid sprayed onto the non-woven fabric by the nozzle can quickly penetrate through the non-woven fabric, so that the non-woven fabric is quickly soaked in the thickness direction and reaches a saturated state.
The second negative pressure device is positioned behind the first negative pressure device, and can pump the liquid contained in the non-woven fabric away along the direction vertical to the surface of the non-woven fabric, so that friction is generated between the non-woven fabric and the liquid, and a good electret effect is generated.
The section of the negative pressure device is funnel-shaped, a slit channel is arranged inside the negative pressure device, and the width of the slit can be adjusted within the range of 1-40 mm; the width range of the slit of the first negative pressure device is preferably 20-40 mm; the width range of the slit of the second negative pressure device is preferably 1-10 mm.
The drying unit comprises a drying device, can accurately control the drying temperature and the drying speed, and meets the drying requirement of the electret non-woven fabric.
The winding unit comprises a winding device, and the winding speed, tension and pressure can be accurately controlled.
As can be seen from the above, the base material such as the nonwoven fabric material can be rapidly and fully infiltrated under the action of the liquid spraying device and the first negative pressure device, and can generate the preliminary electret effect; under the action of the second negative pressure device, liquid in the non-woven fabric is pumped out and electret again to obtain a good electret effect; according to the gram weight of the non-woven fabric, the steps of soaking and electret can be repeated, and the electret requirements of the non-woven fabrics with different gram weights are met.
The electret device and the electret method ensure the uniformity and stability of the electret in all directions under the condition of not damaging the surface appearance and the internal structure of the base material, thereby improving the production efficiency and the product quality, simultaneously, the redundant liquid can be repeatedly utilized, the liquid electret has the advantages of low cost, simplicity, safety and high efficiency, uniform and stable charging, and is suitable for non-woven fabric materials with different gram weights and thicknesses.
In a third aspect, there is provided in at least one embodiment an electret material produced by the method of making an electret material as described above.
The electret material obtained by the method has excellent performance, contains a large amount of static charges, has good electret effect and strong stability of charge storage, and is suitable for being used as a filter material in the fields of air filtering devices, air conditioners and the like.
It will be appreciated by those skilled in the art that the product according to the third aspect of the present invention is based on the same inventive concept as the above-described method for producing an electret material, and that the features and advantages described above with respect to the method for producing an electret material are equally applicable to the electret material, and will not be described in detail herein.
For the convenience of understanding, the present invention will be further described with reference to the drawings, specific examples and comparative examples, but the scope of the present invention is not limited thereto.
As shown in fig. 1-3, a device for preparing an electret material is formed by continuously arranging an unreeling unit i, a liquid electret unit ii, a drying unit iii and a reeling unit iv.
The liquid electret unit II comprises a
As shown in fig. 2, the
Fig. 3 shows another installation of the
The drying device of the drying unit III is an oven 8.
A method of making an electret material, comprising the steps of:
(a) the non-woven fabric 2 is conveyed to a liquid electret unit II by an unreeling device 1 under the action of a guide roller 3;
(b) in the liquid electret unit II, the
(c) the soaked non-woven fabric 2 is sucked under the action of the second
(d) and (3) drying the electret non-woven fabric 2 in an oven 8 to obtain a dry high-efficiency non-woven fabric filter material containing a large amount of static charges, and finally rolling the dry high-efficiency non-woven fabric filter material by a rolling device 9.
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