阅读说明：本技术 一种熔喷驻极体聚合物非织造布的制备方法 (Preparation method of melt-blown electret polymer non-woven fabric ) 是由 陈钢进 张剑锋 于 2020-02-13 设计创作，主要内容包括：本发明涉及一种熔喷驻极体聚合物非织造布的制备方法,其包括以下步骤：(1)熔喷非织造布：采用熔喷法制备聚合物非织造布,在熔喷生产过程时,使熔喷聚合物非织造布形成相对不规整晶相结构；(2)驻极体制备：将非织造布进行电场极化制备驻极体,在非织造布极化时,维持极化电场条件下,通过加热或拉伸工艺,使得非织造布在不规整晶相结构向规整晶相结构转变过程中,电荷被注入体内,从而获得高电荷存储稳定性的熔喷驻极体聚合物非织造布。本发明利用转变过程更利于束缚电荷的形成、电荷不容易脱阱的特点,最终获得高电荷存储稳定性的熔喷驻极体聚合物非织造布。(The invention relates to a preparation method of melt-blown electret polymer non-woven fabric, which comprises the following steps: (1) melt-blown nonwoven fabric: the polymer non-woven fabric is prepared by adopting a melt-blown method, and the melt-blown polymer non-woven fabric forms a relatively irregular crystalline phase structure in the melt-blown production process; (2) preparing an electret: the electret is prepared by carrying out electric field polarization on the non-woven fabric, and when the non-woven fabric is polarized, the non-woven fabric is heated or stretched under the condition of maintaining a polarization electric field, so that electric charges are injected into a body in the process of converting an irregular crystalline phase structure into a regular crystalline phase structure, and the melt-blown electret polymer non-woven fabric with high charge storage stability is obtained. The melt-blown electret polymer non-woven fabric with high charge storage stability is finally obtained by utilizing the characteristics that the transformation process is more beneficial to formation of bound charges and the charges are not easy to be trapped.)

1. A method for preparing melt-blown electret polymer nonwoven fabric is characterized by comprising the following steps:

(1) Melt-blown nonwoven fabric: the polymer non-woven fabric is prepared by adopting a melt-blown method, and the melt-blown polymer non-woven fabric forms a relatively irregular crystalline phase structure in the melt-blown production process;

(2) Preparing an electret: the electret is prepared by carrying out electric field polarization on the non-woven fabric, and when the non-woven fabric is polarized, the non-woven fabric is heated or stretched under the condition of maintaining a polarization electric field, so that electric charges are injected into a body in the process of converting an irregular crystalline phase structure into a regular crystalline phase structure, and the melt-blown electret polymer non-woven fabric with high charge storage stability is obtained.

2. The method of making a melt blown electret polymer nonwoven fabric of claim 1 wherein the melt blown nonwoven fabric comprises the steps of:

(1.1) modification of Polymer chips: adding 0.1-0.5 Wt% of a modification auxiliary agent into the polymer slices, and controlling the melt index of the mixture to be 800-1600 to prepare modified polymer slices, wherein the modification auxiliary agent is any one or mixture of more than two of modified rosin, stearate and ethylene bis-stearamide;

(1.2) melt-blowing preparation of nonwoven:

(1.2.1) selecting a spinneret plate with the aperture diameter of 0.1-0.4 micron and the length-diameter ratio of 10-17, and feeding the modified polymer melt into the spinneret plate by using a metering pump in a molten state;

(1.2.2) controlling the temperature of an extruder at 200-260 ℃, the temperature of a spinneret plate at 230-290 ℃, the frequency of a metering pump at 20-30 Hz, and extruding the modified polymer melt from a spinneret hole;

(1.2.3) blowing the melt extruded out of the spinneret orifice into superfine fibers by using high-speed hot air, wherein the temperature of the high-speed hot air is 200-370 ℃, and the air speed is Mach number of 0.5-0.8;

(1.2.4) sucking and cooling the superfine fibers to the coagulating net curtain through a suction fan to form the non-woven fabric, wherein the suction temperature is 0-10 ℃, and the air speed is Mach number of 0.5-0.8.

3. The method for preparing the melt-blown electret polymer nonwoven fabric according to claim 1, wherein the polarized electric field is maintained by electrode discharge of a single power supply, unipolar, linear multi-cord planar corona discharge device, the voltage of the polarized electric field is-10 to-30 KV, the number of linear cord electrodes is 6 to 10, and the distance between each cord electrode is 3 to 8cm, and the filaments are arranged in the same plane.

4. The method for preparing the melt-blown electret polymer nonwoven fabric according to claim 1, wherein the heating process is carried out at the bottom of the nonwoven fabric at a temperature of 50-120 ℃.

5. The method of claim 2, wherein the modifying additive is a blend of modified rosin, stearate, ethylene bis-stearyl in an amount of 0.2 Wt%.

6. The method of making a melt-blown electret polymer nonwoven web of claim 2 wherein the high velocity hot air temperature is 300 ℃ and the air velocity is mach number 0.6; the air suction temperature is 5 ℃, and the air velocity is Mach number 0.7.

7. The method of claim 3, wherein the voltage of the polarizing electric field is-20 KV, the number of the wire-like string electrodes is 8, and the distance between each string electrode is 5 cm.

8. The method of claim 4, wherein the polypropylene nonwoven is heated at 100 ℃ and the polylactic acid nonwoven is heated at 60 ℃.

9. the method of claim 1, wherein the polymer is polypropylene, the irregular crystalline phase structure is a pseudo-hexagonal crystal, and the regular crystalline phase structure is α crystal.

10. the method of claim 1, wherein the polymer is polylactic acid, the irregular crystalline phase structure is a mixed crystal comprising an intermediate phase, α' crystal form and an alpha crystal form, and the regular crystalline phase structure is the alpha crystal form.

Technical Field

The invention belongs to the technical field of purification engineering and air filtration, and particularly relates to a preparation method of melt-blown electret polymer non-woven fabric.

Background

The melt blowing method is developed in the 50 th 20 th century, and is a method for obtaining superfine polymer non-woven fiber material by blowing polymer melt through high-speed and high-temperature air flow to rapidly stretch the polymer melt. The polymer slice is heated and pressurized to be in a molten state, the melt is distributed to flow to a spinneret orifice at the front end of a nozzle, and is extruded and stretched by high-speed and high-temperature airflow to form superfine polymer fiber, and the superfine polymer fiber is cooled, solidified and deposited on a collecting screen to form the melt-blown non-woven fabric.

The melt-blown non-woven fabric has the characteristics of fine fiber diameter, large specific surface area, small pores, high porosity and the like, and is widely applied to a filtering material for solid-gas separation. In particular, the melt-blown non-woven fabric is made into an electret material which can have an electrostatic field for a long time through a special electret forming technology, and a high-efficiency air filter material with almost zero resistance can be obtained. The melt-blown electret polymer non-woven fabric air filter material can filter PM2.5 and smaller harmful particles such as dust, bacteria and the like, is widely applied to labor insurance, medical masks, gas masks, air purifiers and dust collectors, and becomes a leading material for air purification in clean rooms, air filtration in automobiles and engine air filtration.

The existing melt-blown electret air filter material is generally formed by applying a high-voltage electric field (such as corona discharge) or by friction, hydrothermal evaporation and other methods on a prepared melt-blown nonwoven fabric to charge the material to form an electrostatic field. The charges carried by the material are mainly shallow trapped charges, exist on the surface of the fiber and the shallow surface, are easy to attenuate when in use, have poor stability of filtering performance, greatly shorten the service life of the material and influence the reliability of filtering facilities.

Chinese patent CN101905101A discloses a preparation method of melt-blown polypropylene electret filter material, which comprises the following steps: 1) and polypropylene modification: melting raw material polypropylene, and mixing with an additive to prepare modified polypropylene; 2) melt-blowing to prepare non-woven fabric: a) feeding the modified polypropylene melt into a spinneret plate by using a metering pump in a molten state; b) and extruding the modified polypropylene melt from a spinneret orifice. c) Blowing the melt extruded out of the spinneret orifice into superfine fibers by high-speed hot air, and enabling the superfine fibers to fly to a condensing screen curtain to be cooled and bonded to form a fiber web; 3) and preparing the electret: and (3) enabling the fiber web obtained in the step (2) to pass through an electrode of a corona discharge device, and enabling the fiber web to be electret through electrode discharge to obtain the electret.

The polymer generally has a structure in which a crystalline phase and an amorphous phase coexist, and the conductivity of the amorphous phase structure is large while the conductivity of the crystalline phase structure is small. Under the action of an electric field, when current passes through the material body, charges are accumulated on the interface between a crystalline phase and an amorphous phase, each microcrystalline particle is equivalent to a dipole (called quasi-dipole) and can be used as a charge trap source, the size of a trap energy level of the microcrystalline particle is related to the regularity of a microcrystalline structure, and the regularity is better and the trap energy level is higher. Generally, polymers have a plurality of crystal phase structures, and some polymers form quasi-crystal or smectic structures, which have different crystal phase stability. The more stable the crystalline phase, the better the regularity, the more stable the quasi-dipole formed and the higher the trap level.

The polypropylene in the patent has various crystalline phase structures in the melt-blowing process, and the crystalline phase structures are not regulated, so that the performance stability of the manufactured filter material is poor, and the use reliability of the filter equipment is seriously influenced.

Disclosure of Invention

Based on the problems existing in the background art, the invention aims to provide a preparation method of melt-blown electret polymer non-woven fabric, which can enable the material to form deep trapped charges and greatly improve the charge storage stability of the material.

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

The invention relates to a preparation method of melt-blown electret polymer non-woven fabric, which comprises the following steps: (1) melt-blown nonwoven fabric: the polymer non-woven fabric is prepared by adopting a melt-blown method, and the melt-blown polymer non-woven fabric forms a relatively irregular crystalline phase structure in the melt-blown production process;

(2) Preparing an electret: the electret is prepared by carrying out electric field polarization on the non-woven fabric, and when the non-woven fabric is polarized, the non-woven fabric is heated or stretched under the condition of maintaining a polarization electric field, so that electric charges are injected into a body in the process of converting an irregular crystalline phase structure into a regular crystalline phase structure, and the melt-blown electret polymer non-woven fabric with high charge storage stability is obtained.

Preferably, the melt-blown nonwoven fabric comprises the following steps:

(1.1) modification of Polymer chips: adding 0.1-0.5 Wt% of a modification auxiliary agent into the polymer slices, and controlling the melt index of the mixture to be 800-1600 to prepare modified polymer slices, wherein the modification auxiliary agent is any one or mixture of more than two of modified rosin, stearate and ethylene bis-stearamide;

(1.2) melt-blowing preparation of nonwoven:

(1.2.1) selecting a spinneret plate with the aperture diameter of 0.1-0.4 micron and the length-diameter ratio of 10-17, and feeding the modified polymer melt into the spinneret plate by using a metering pump in a molten state;

(1.2.2) controlling the temperature of an extruder at 200-260 ℃, the temperature of a spinneret plate at 230-290 ℃, the frequency of a metering pump at 20-30 Hz, and extruding the modified polymer melt from a spinneret hole;

(1.2.3) blowing the melt extruded out of the spinneret orifice into superfine fibers by using high-speed hot air, wherein the temperature of the high-speed hot air is 200-370 ℃, and the air speed is Mach number of 0.5-0.8;

(1.2.4) sucking and cooling the superfine fibers to the coagulating net curtain through a suction fan to form the non-woven fabric, wherein the suction temperature is 0-10 ℃, and the air speed is Mach number of 0.5-0.8.

Preferably, the polarized electric field is maintained by electrode discharge of a single-power supply, single-polarity linear multi-string wire planar corona discharge device, the voltage of the polarized electric field is-10 to-30 KV, the number of linear string wire electrodes is 6 to 10, and the distance between every two string wire electrodes is 3 to 8cm and is placed in the same plane.

Preferably, the heating process is carried out at the bottom of the non-woven fabric, and the heating temperature is 50-120 ℃.

Preferably, the modified auxiliary agent is a mixture of modified rosin, stearate and ethylene bis-stearyl, and the dosage of the modified auxiliary agent is 0.2 Wt%.

Preferably, the temperature of the high-speed hot air is 300 ℃, and the air speed is Mach number 0.6; the air suction temperature is 5 ℃, and the air velocity is Mach number 0.7.

Preferably, the electret voltage is-20 KV, the number of the linear string wire electrodes is 8, and the distance between each string wire electrode is 5 cm.

Preferably, the heating temperature of the polypropylene nonwoven fabric is 100 ℃ and the heating temperature of the polylactic acid nonwoven fabric is 60 ℃.

preferably, the polymer is polypropylene, the irregular crystalline phase structure of the polymer is a quasi-hexagonal crystal form, and the regular crystalline phase structure of the polymer is an alpha crystal form.

preferably, the polymer is polylactic acid, the irregular crystalline phase structure of the polylactic acid is mixed crystal comprising a middle phase, an α' crystal form and an α crystal form, and the regular crystalline phase structure of the polylactic acid is the α crystal form.

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:

1. In the melt-blown process, the crystal phase structure of the polymer is controlled to form a quasi-crystal and smectic structure with relatively irregular crystals, so that the obtained non-woven fabric is easier to accumulate charges in the subsequent electric field polarization;

2. When the electric field is polarized, along with the process of converting the irregular crystalline phase structure into the regular crystalline phase structure, electric charges are injected into the fibrous body to form deep trap electric charges. The melt-blown electret polymer non-woven fabric with high charge storage stability is finally obtained by utilizing the characteristics that the transformation process is more beneficial to formation of bound charges and the charges are not easy to be trapped.

Drawings

FIG. 1 is a schematic thermal stimulated discharge spectrum of a melt-blown polypropylene electret nonwoven fabric of example 1;

FIG. 2 is a schematic diagram showing the change in filtration efficiency of a melt-blown polypropylene electret nonwoven fabric sample during high temperature processing;

FIG. 3 is a schematic diagram of a thermal stimulated discharge spectrum of a meltblown polylactic acid electret nonwoven fabric comparative example 3;

FIG. 4 is a schematic thermal stimulated discharge spectrum of a meltblown polylactic acid electret nonwoven fabric of example 2;

FIG. 5 is a schematic diagram showing the change in filtration efficiency of a melt-blown polylactic acid electret nonwoven fabric sample during high temperature treatment;

FIG. 6 is a schematic view showing the transition of crystal phases of the polymer of the present invention upon heat treatment.

Detailed Description

For further understanding of the present invention, the present invention will be described in detail with reference to examples, which are provided for illustration of the present invention but are not intended to limit the scope of the present invention.