Disclosure of Invention
The invention aims to provide a multifunctional composite melt-blown non-woven fabric and a preparation method thereof. The method comprises the steps of compounding a conventional polypropylene non-woven fabric and a fluorine-containing graft modified polypropylene non-woven fabric through double-layer melt-blowing to obtain the gradient electret filter material. The electrostatic electret filter has the advantages of good electrostatic electret effect, high air filtering efficiency and low pressure resistance.
In order to achieve the purpose, the invention provides a multifunctional composite melt-blown non-woven fabric which comprises at least one layer of polypropylene melt-blown non-woven fabric and at least one layer of fluorine-containing graft modified polypropylene melt-blown non-woven fabric, wherein the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is obtained by melt polymerization of polypropylene and fluorine-containing olefin monomers under the action of an initiator.
As a further improvement of the invention, the mass ratio of the polypropylene chain segment to the fluorine-containing chain segment in the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is 100 (2-20).
As a further improvement of the invention, the fluorine-containing olefin monomer is a functional monomer containing double bonds and fluoacid ester groups.
As a further improvement of the invention, the fluorine-containing olefin monomer comprises but is not limited to one or more of trifluoroethyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, tridecafluorooctyl methacrylate and heptadecafluorodecyl methacrylate.
As a further improvement of the invention, the surface electrostatic potential of the polypropylene melt-blown non-woven fabric is 200-3000V, the surface electrostatic potential of the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is 1000-8000V, and the surface electrostatic potential of the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is greater than that of the polypropylene melt-blown non-woven fabric, so as to form a surface electrostatic potential gradient.
As a further improvement of the invention, the filtering efficiency of the multifunctional composite melt-blown non-woven fabric on PM2.5 is more than or equal to 99%, and the filtering pressure resistance is less than or equal to 20 Pa.
The preparation method of the multifunctional composite melt-blown non-woven fabric comprises the following steps:
s1, weighing polypropylene, an initiator and a fluorine-containing olefin monomer according to a mass ratio of 100 (0.5-10) to (2-20), uniformly mixing the polypropylene, the initiator and the fluorine-containing olefin monomer, and then carrying out melt blending modification in a double-screw extruder to obtain a fluorine-containing graft modified polypropylene melt-blown material;
s2, melting and mixing polypropylene in a double-screw extruder to obtain a polypropylene melt-blown material;
s3, carrying out double-layer melt-blowing on the fluorine-containing graft modified polypropylene melt-blown material obtained in the step S1 and the polypropylene melt-blown material obtained in the step S2 to obtain the multifunctional composite melt-blown non-woven fabric.
As a further improvement of the invention, in step S1, the melt index of the polypropylene is 1000-1800g/10 min; in step S2, the melt index of the polypropylene is 500-1800g/10 min.
As a further improvement of the invention, in the step S1, the temperature of the melt blending modification is 160-230 ℃.
As a further improvement of the invention, in step S2, the melt index of the polypropylene is 800-1800 g/10 min.
The invention has the beneficial effects that:
1. the multifunctional composite melt-blown non-woven fabric provided by the invention is formed by compounding a conventional polypropylene non-woven fabric and a fluorine-containing graft modified polypropylene non-woven fabric, and the gradient electret filter material can be obtained due to the excellent electrostatic electret effect of the fluorine-containing polypropylene melt-blown non-woven fabric. By utilizing the gradient of the electret charge, most harmful substances such as aerosol, particulate matters, PM2.5 and the like can be concentrated on the fluorine-containing graft modified polypropylene melt-blown non-woven fabric layer in the process of air filtration and use. The surface electrostatic potential gradient is utilized, so that directional filtration is realized, the filtration effect is improved, and charge attenuation can be effectively inhibited through the mutual influence of the two layers of surface electrostatic potential gradients. And the charge decay rate is obviously reduced, and the service life of the device is greatly prolonged.
2. The multifunctional composite melt-blown non-woven fabric provided by the invention adopts polypropylene with the molecular weight of 25000-60000, and the obtained non-woven fabric has a better electret effect after the fluorine-containing olefin monomer is grafted. And compounding the gradient electret filter material with a polypropylene non-woven fabric with the molecular weight of 100000-400000 to obtain the gradient electret filter material which has the advantages of good electrostatic electret effect, high air filtration efficiency, low pressure resistance and the like. The composite non-woven fabric electret charge gradient is regulated and controlled by regulating and controlling the chain segment composition of the fluorine-containing graft modified polypropylene, so that the electret effect and the charge stability are improved, and the charge storage capacity is also enhanced.
3. The multifunctional composite melt-blown non-woven fabric prepared by the method overcomes the defects of difficult functional modification and poor electrostatic electret effect of the traditional melt-blown non-woven fabric in the aspect of performance, and realizes the diversification of the performance of the melt-blown polypropylene non-woven fabric. Has great potential of industrialized production.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to specific embodiments.
It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the scheme of the present invention are shown in the specific embodiments, and other details not closely related to the present invention are omitted.
In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention provides a multifunctional composite melt-blown non-woven fabric which comprises at least one layer of polypropylene melt-blown non-woven fabric and at least one layer of fluorine-containing graft modified polypropylene melt-blown non-woven fabric, wherein the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is obtained by melt polymerization of polypropylene and fluorine-containing olefin monomers under the action of an initiator. The gradient electret filter material can be obtained by compounding the conventional polypropylene non-woven fabric and the fluorine-containing graft modified polypropylene non-woven fabric. By utilizing the gradient of the electret charge, most harmful substances such as aerosol, particulate matters, PM2.5 and the like can be concentrated on the fluorine-containing graft modified polypropylene melt-blown non-woven fabric layer in the process of air filtration, so that the directional filtration is realized, and the filtration effect is improved. And the charge decay rate is significantly reduced. The non-woven fabric prepared by the invention has the advantages of good electrostatic electret effect, high air filtration efficiency, low pressure resistance and the like.
The mass ratio of the polypropylene chain segment to the fluorine-containing chain segment in the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is 100 (2-20). The composite non-woven fabric electret charge gradient is regulated and controlled by regulating and controlling the chain segment composition of the fluorine-containing graft modified polypropylene, so that the electret effect and the charge stability are improved, and the charge storage capacity is also enhanced.
The fluorine-containing olefin monomer is a functional monomer containing double bonds and fluoate ester groups. Preferably, the fluorine-containing olefin monomer comprises but is not limited to one or more of trifluoroethyl methacrylate, octafluoropentyl methacrylate, dodecafluoroheptyl methacrylate, tridecafluorooctyl methacrylate and heptadecafluorodecyl methacrylate.
The surface electrostatic potential of the polypropylene melt-blown non-woven fabric is 200-3000V, the surface electrostatic potential of the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is 1000-8000V, and the surface electrostatic potential of the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is larger than that of the polypropylene melt-blown non-woven fabric, so that a surface electrostatic potential gradient is formed. In actual use, charge can be injected by charging the electret. The composite nonwoven fabric is charged, for example, by corona discharge at a voltage of about 14000V. The quantity of the charges stored in the double-layer non-woven fabric is controlled through different voltage electrode charging time, so that the purpose of electret charge gradient is achieved. The surface electrostatic potential gradient is utilized, so that directional filtration is realized, the filtration effect is improved, and charge attenuation can be effectively inhibited through the mutual influence of the two layers of surface electrostatic potential gradients.
The filtering efficiency of the multifunctional composite melt-blown non-woven fabric on PM2.5 is more than or equal to 99%, and the filtering pressure resistance is less than or equal to 20 Pa.
The preparation method of the multifunctional composite melt-blown non-woven fabric comprises the following steps:
s1, weighing polypropylene, an initiator and a fluorine-containing olefin monomer according to a mass ratio of 100 (0.5-10) to (2-20), uniformly mixing the polypropylene, the initiator and the fluorine-containing olefin monomer, and then carrying out melt blending modification in a double-screw extruder to obtain a fluorine-containing graft modified polypropylene melt-blown material; the initiator is one of dicumyl peroxide, benzoyl peroxide and di-tert-butyl peroxide;
s2, melting and mixing polypropylene in a double-screw extruder to obtain a polypropylene melt-blown material;
s3, carrying out double-layer melt-blowing on the fluorine-containing graft modified polypropylene melt-blown material obtained in the step S1 and the polypropylene melt-blown material obtained in the step S2 to obtain the multifunctional composite melt-blown non-woven fabric.
In the invention, polypropylene is selected as a base material, and a functional monomer containing double bonds and two characteristic functional groups of a fluoacid ester structure is selected as a graft modifier. Under the action of high temperature and oxidation, the preparation process mainly comprises two reactions, one is to form polypropylene macromolecular chain free radicals, and fluorine-containing olefin monomers and the free radicals undergo a grafting reaction; the other is the beta-chain scission reaction of polypropylene, namely, the chain scission reaction of polypropylene molecules can occur when the polypropylene is added with a peroxide initiator, and a byproduct is generated. The fluorine-containing olefin monomer has higher reactivity with the polypropylene molecular chain, so that PP free radicals can quickly react with the fluorine-containing olefin monomer and inhibit potential beta-scission reaction to a certain extent.
Due to the existence of double bond functional groups, the antibacterial monomer is grafted to the main chain of the polypropylene. And then, due to the existence of the nitrogen-containing functional group, an antibacterial structure with halamine can be formed on the molecular chain of the successfully grafted polypropylene melt-blown material through the action of amine halogenation, so that the polypropylene melt-blown material is endowed with excellent antibacterial performance.
In step S1, the melt index of the polypropylene is 1000-1800g/10 min; in step S2, the melt index of the polypropylene is 500-1800g/10 min. In step S1, the melt index of the polypropylene is preferably 1200-1600g/10min, more preferably 1300-1500 g/10min, and even more preferably 1400g/10 min. In step S2, the melt index of the polypropylene is preferably 800 to 1500g/10min, more preferably 1000 to 1300g/10min, and still more preferably 1100 to 1200g/10 min. The conditions for determining the melt index were: temperature: 230 ℃, load: 2160g, pressure to which the sample is subjected: 0.2982 MPa.
The research of the invention shows that the electret effect of the non-woven fabric obtained by grafting the fluorine-containing olefin monomer with the polypropylene with the melt index of 1000-1800g/10min is better. The gradient electret filter material obtained by compounding the polypropylene non-woven fabrics with the remelting index of 500-1800g/10min has the advantages of good electrostatic electret effect, high air filtration efficiency, low pressure resistance and the like.
In step S1, the temperature of the melt blending modification is 160-230 ℃.
Example 1
A multifunctional composite melt-blown non-woven fabric is prepared by the following steps:
s1, weighing polypropylene, benzoyl peroxide and trifluoroethyl methacrylate with a melt index of 1400g/10min according to a mass ratio of 100:2:10, uniformly mixing, and then carrying out melt blending modification (at a processing temperature of 180 ℃) in a double-screw extruder to obtain a fluorine-containing graft modified polypropylene melt-blown material;
s2, melting and mixing polypropylene with a melt index of 1150g/10min in a twin-screw extruder to obtain a polypropylene melt-blown material (the melt index of the polypropylene melt-blown material is 1000g/10 min);
s3, carrying out double-layer MM melt-blowing on the fluorine-containing graft modified polypropylene melt-blown material obtained in the step S1 and the polypropylene melt-blown material obtained in the step S2 to obtain the multifunctional composite melt-blown non-woven fabric.
And carrying out electret charging on the prepared multifunctional composite melt-blown non-woven fabric to ensure that the surface electrostatic potential of the polypropylene melt-blown non-woven fabric is 2000V, and the surface electrostatic potential of the fluorine-containing graft modified polypropylene melt-blown non-woven fabric is 5000V so as to form a surface electrostatic potential gradient.
The single fluorine-containing graft modified polypropylene non-woven fabric obtained by melt-blowing in the step S1 has a PM2.5 filtration efficiency of 99.90-99.99%, a filtration pressure resistance of 5-20 Pa, and a charge decay rate of 0.2-1% after one month.
And the PM2.5 filtering efficiency of the single polypropylene non-woven fabric obtained by adopting the melt-blown material of the step S2 is 94.00% -98.95%, the filtering pressure resistance is 20-50 Pa, and the charge attenuation rate is 10-35% after one month.
The single fluorine-containing graft modified polypropylene non-woven fabric obtained by melt-blowing in the step S1 has a PM2.5 filtration efficiency of 94.00% -98.95%, a filtration pressure resistance of 10-50 Pa, and a charge decay rate of 10-30% after one month.
Examples 2 to 5
A multifunctional composite meltblown nonwoven fabric, which is different from example 1 in that the mass ratios of polypropylene, benzoyl peroxide and trifluoroethyl methacrylate are shown in table 1 at step S1. The rest is substantially the same as that of embodiment 1, and will not be described herein.
TABLE 1 preparation conditions and filtration Properties of examples 2 to 5
As can be seen from table 1, in examples 2 and 3, under the same initiator content, as the content of trifluoroethyl methacrylate increases, the higher the polypropylene surface electrostatic potential is, the better the filtering effect of PM2.5 is, and the lower the filtering pressure resistance is, the smaller the charge decay rate is. In examples 4 and 5, under the condition of the same content of functional monomer trifluoroethyl methacrylate, with the increase of the content of initiator DCP, the higher the surface electrostatic potential of the composite melt-blown nonwoven fabric is, the higher the PM2.5 filtration efficiency is, the smaller the filtration pressure resistance is, and the lower the charge decay rate is.
Examples 6 to 9
A multifunctional composite melt-blown nonwoven fabric, compared with example 1, is different in that the molecular weights of polypropylene in step S1 and step S2 are shown in Table 2. The rest is substantially the same as that of embodiment 1, and will not be described herein.
TABLE 2 preparation conditions and filtration Properties of examples 6 to 9
As can be seen from table 2, in examples 6 and 7, when polypropylene having the same melt index is used in the S2 step, the melt index of the polypropylene used in S1 or S2 is too high or too low, and the filtration performance of the prepared composite meltblown fabric is deteriorated, i.e., the surface electrostatic potential is decreased, the PM2.5 filtration efficiency is deteriorated, the filtration pressure resistance is increased, the charge decay rate is also increased, and the mechanical properties thereof are affected to a certain extent.
In conclusion, the multifunctional composite melt-blown non-woven fabric provided by the invention is formed by compounding the conventional polypropylene non-woven fabric and the fluorine-containing graft modified polypropylene non-woven fabric, and the gradient electret filter material can be obtained due to the excellent electrostatic electret effect of the fluorine-containing polypropylene melt-blown non-woven fabric. By utilizing the gradient of the electret charge, most harmful substances such as aerosol, particulate matters, PM2.5 and the like can be concentrated on the fluorine-containing graft modified polypropylene melt-blown non-woven fabric layer in the process of air filtration and use. The surface electrostatic potential gradient is utilized, so that directional filtration is realized, the filtration effect is improved, and charge attenuation can be effectively inhibited through the mutual influence of the two layers of surface electrostatic potential gradients. And the charge decay rate is obviously reduced, and the service life of the device is greatly prolonged.
Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.