A melt-blown polypropylene composite material and its preparation method and application

Abstract

The present invention discloses a melt-blown polypropylene composite material and its preparation method and application, and relates to the technical field of polymer materials. The present invention provides a melt-blown polypropylene composite material, comprising the following components in parts by weight: 80-93 parts of polypropylene melt-blown material, 3-12 parts of aliphatic polyamide, 1-5 parts of zirconium phosphate, and 3-5 parts of electret masterbatch. The present invention introduces aliphatic polyamide and zirconium phosphate into the polypropylene melt-blown material, and improves the crystallization ability of the material through the action of hydrogen bonds in the aliphatic polyamide, thereby improving the electrostatic electret performance of the material. Zirconium phosphate has a layered structure and can absorb nitroxyl radicals generated by the redox reaction of hindered amines in the system, thereby slowing down the reaction of nitroxyl radicals with phenolic antioxidants, and effectively reducing the red-yellow discoloration of the material.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, in particular to a melt-blown polypropylene composite material and a preparation method and application thereof. Background Art

[0002] At present, conventional polypropylene meltblown materials often contain phenolic antioxidants to improve the aging performance of polypropylene materials. Hindered amine electrets (HALS) are used as electrets together with polypropylene meltblown materials to significantly improve the filtration performance of the fiber. The existing water electret technology is to add hindered amine electrets (HALS) to the polypropylene meltblown material, and then use ultrapure water to rub the electret at high speed to make the fiber deeply electret. Compared with conventional corona electret technology (abbreviated as electric electret), this technology has higher filtration efficiency and lower resistance. However, during the polymer processing, hindered amine electrets will undergo redox cycles with hydrogen peroxides under hot oxygen conditions, and one of the intermediate products is a stable nitroxyl radical. There is evidence that these free radicals can oxidize phenolic antioxidants to diphenyl quinone, causing the material to turn red and yellow.

[0003] Meltblown materials that produce red and yellow discoloration seriously affect the product's appearance, gradually deteriorate in aging resistance and charge decay resistance, and significantly reduce the product's lifespan. These shortcomings limit their application in the air filtration field. Therefore, there is an urgent need to develop a high-performance meltblown material with high efficiency, low resistance, resistance to charge decay, and resistance to red and yellow discoloration. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a melt-blown polypropylene composite material and its preparation method and application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a melt-blown polypropylene composite material, comprising the following components in parts by weight: 80-93 parts of polypropylene melt-blown material, 3-12 parts of aliphatic polyamide, 1-5 parts of zirconium phosphate, and 3-5 parts of electret masterbatch.

[0006] The inventors discovered that introducing aliphatic polyamide and zirconium phosphate into polypropylene meltblown material improves the material's crystallization ability through the hydrogen bonding of the aliphatic polyamide, allowing more charge to accumulate at the interface between the crystalline and amorphous regions, thereby improving the material's filtration performance and strength. Zirconium phosphate has a layered structure that can absorb nitroxyl radicals produced by the redox reaction of hindered amines in the system, effectively reducing the material's red-yellow discoloration. Furthermore, zirconium phosphate has a large specific surface area, which helps form more "traps" for storing charge. The charge stored in these "traps" is less likely to migrate and escape due to hydrogen bonding, significantly improving the material's resistance to charge decay.

[0007] Preferably, the weight proportions of the aliphatic polyamide can be selected from 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, and 12 parts; and the zirconium phosphate can be selected from 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, and 5 parts.

[0008] Preferably, the melt index of the polypropylene meltblown material is 1200-1500 g / 10 min, and the melt index of the polypropylene meltblown material is measured according to ASTM D1238 using a weight of 2.16 kg and a temperature of 190° C.

[0009] Preferably, the melt-blown polypropylene composite material comprises the following components in parts by weight: 85-89 parts of polypropylene melt-blown material, 5-8 parts of aliphatic polyamide, 3-4 parts of zirconium phosphate, and 3-5 parts of electret masterbatch.

[0010] The inventors found that when the polypropylene meltblown material, aliphatic polyamide, and zirconium phosphate are selected in the above-mentioned weight proportions, the prepared meltblown polypropylene composite material has better resistance to charge decay and red and yellow discoloration after forming a meltblown nonwoven material, and has higher strength.

[0011] Preferably, in the melt-blown polypropylene composite material, the number of methylene monomers in the aliphatic polyamide is n, where n is an even number and n≠0.

[0012] The aliphatic polyamide described herein has a molecular chain composed of methylene groups and amide groups, with the molecular chain forming a linear structure consisting of -CN- chains. It can be one or more of p-type polyamide or mp-type polyamide. In p-type polyamide, amide groups are distributed along the molecular chain, with p-1 consecutive methylene groups between every two polyamide groups. In mp-type polyamide, m consecutive methylene groups are located between two imino groups, and p-2 methylene groups are located between two carboxyl groups. The p-type or mp-type polyamides described herein vary in the number of carbon atoms contained in their monomers, resulting in different ratios of hydrogen bonds formed between the molecular chains and the density of hydrogen bonds along the molecular chains. A greater proportion of these hydrogen bonds results in a stronger crystallization ability and greater strength. The more interfaces formed during crystallization, the more charge traps are formed on these interfaces when fabricated into fibrous electret materials. This increases the charge density of the fibrous material, resulting in a better electrostatic effect and manifested as higher filtration efficiency and resistance to charge decay. Polyamides whose monomers all contain an even number of methylene groups are preferred; in such polyamides, 100% of the amide groups on the molecular chain can form hydrogen bonds. However, if all or one of the monomers contains an odd number of methylene groups, only 50% of the amide groups on the polyamide molecular chain can form hydrogen bonds.

[0013] The inventors found that when the number of methylene monomers in the aliphatic polyamide is n, n is an even number and n≠0, the prepared melt-blown polypropylene composite material has better resistance to charge decay and red and yellowing after forming a melt-blown non-woven material, and has higher strength.

[0014] Preferably, the number of methylene monomers in the aliphatic polyamide is 10 to 18. More preferably, the number of methylene monomers in the aliphatic polyamide is 10 to 16. Most preferably, the aliphatic polyamide is at least one of PA11 and PA612.

[0015] The inventors have found that when the number of methylene monomers in the aliphatic polyamide is 10-16, the prepared melt-blown polypropylene composite material has better resistance to charge decay and red-yellow discoloration after forming a melt-blown nonwoven material.

[0016] In addition, the present invention provides a method for preparing the melt-blown polypropylene composite material, comprising the following steps:

[0017] (1) Weigh various components according to the ratio;

[0018] (2) mixing the components in step (1) to obtain a mixture A;

[0019] (3) The mixture A obtained in step (2) is conveyed to a screw extruder for extrusion granulation to obtain the melt-blown polypropylene composite material.

[0020] Furthermore, the present invention provides application of the meltblown polypropylene composite material in the field of air filtration.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) by introducing aliphatic polyamide and zirconium phosphate into polypropylene meltblown material, the crystallization ability of the material is improved through the action of hydrogen bonds in the aliphatic polyamide, thereby improving the electrostatic electret properties of the fiber material; (2) zirconium phosphate has a large specific surface area, which helps to form more "traps" for storing charges. The charges stored in the "traps" migrate less and escape less under the action of hydrogen bonds, thereby significantly improving the material's resistance to charge decay; (3) zirconium phosphate can absorb nitroxyl radicals generated by the redox reaction of hindered amines in the system, thereby slowing down the reaction of nitroxyl radicals with phenolic antioxidants, and ultimately effectively reducing the red-yellow discoloration of the material. DETAILED DESCRIPTION

[0022] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0023] In the examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0024] The raw materials used in the examples and comparative examples are described below, but are not limited to these materials:

[0025] Polypropylene meltblown material 1: PP-91500NC001, Kingfa Science & Technology, melt mass flow rate 1500 g / 10 min at 190°C / 2.16 kg;

[0026] Polypropylene meltblown material 2: Metocene MF650Y, Basel, melt mass flow rate 1200 g / 10 min at 190 °C / 2.16 kg;

[0027] Electret masterbatch 1: YBL-EW032 NC001, Kingfa Technology; the electret masterbatch contains polypropylene meltblown material, hindered amine, stearate, antioxidant and other ingredients;

[0028] Electret masterbatch 2: RCE20, Yancheng Ruize Masterbatch Co., Ltd.

[0029] Aliphatic polyamide 1: PA11, BMNO P20, Arkema, France, the number of methylene monomers is 10;

[0030] Aliphatic polyamide 2: PA612, 151L NC010, DuPont, USA, contains 6 consecutive methylene groups between the two imino groups and 10 methylene groups between the two carboxyl groups;

[0031] Aliphatic polyamide 3: PA1010, 200NN, Arkema, France, contains 10 consecutive methylene groups between the two imino groups and 8 methylene groups between the two carboxyl groups;

[0032] Aliphatic polyamide 4: PA6, B3EG6–NC, BASF, the number of methylene monomers is 5;

[0033] Aliphatic polyamide 5: PA12, L20G, Swiss EMS, the number of methylene monomers is 11;

[0034] Zirconium phosphate 1: Hubei Wei's Chemical Reagent, needle-shaped zirconium phosphate;

[0035] Zirconium phosphate 2: Shanghai Runhe Nanotechnology, layered zirconium phosphate;

[0036] Zirconium phosphate 3: Jinda Nanotechnology, cubic zirconium phosphate;

[0037] Montmorillonite: XFI44, Nanjing Xianfeng Nanotechnology Co., Ltd., purity greater than 98%;

[0038] Examples and Comparative Examples

[0039] The components and weight proportions of the melt-blown polypropylene composite materials of the embodiments and comparative examples of the present invention are shown in Tables 1 and 2. The preparation methods of the melt-blown polypropylene composite materials of the embodiments and comparative examples comprise the following steps:

[0040] (1) Weigh various components according to the ratio;

[0041] (2) uniformly mixing the components in step (1) to obtain a mixture A;

[0042] (3) conveying the mixture A obtained in step (2) to a twin-screw extruder for extrusion granulation to obtain the melt-blown polypropylene composite material; wherein the twin-screw extrusion temperature is 180-200-210-220-220-220-220-210°C, and the die head is 220-230°C.

[0043] Table 1

[0044]

[0045]

[0046] Table 2

[0047]

[0048] Performance Testing

[0049] The melt-blown polypropylene composite materials prepared in the examples of the present invention and the comparative examples were prepared into melt-blown nonwoven materials using conventional methods. The method used to prepare the melt-blown nonwoven materials during the test of the present invention is as follows:

[0050] S1: The melt-blown polypropylene composite material is uniformly metered and fed into a single-screw extruder through a metering scale; the temperature of each temperature zone of the single-screw extrusion granulation is 160-180-220-240-240-240°C, the temperature of the screen changer and metering pump is 230-240°C, and the mesh size of the screen changer is 30+500+300+80 mesh; the temperature of the melt pipe is 245-245-245°C;

[0051] S2: Spinning and refinement: After plasticization and homogenization, the fibers enter the spinning assembly. The spinning assembly consists of a die and a spinneret. The die temperature is set at 260°C and fine-tuned according to the weight of each zone.

[0052] S3: Collect and form a web; the fibers stretched by hot air are sprayed onto a mesh curtain or a roller metal mesh to form a fiber web;

[0053] S4: High-speed friction electret: use ultrapure water to rub the fiber at high speed, and then dry it;

[0054] S5: Slitting and winding.

[0055] 1. Electrostatic electret performance test: The filtration efficiency (PFE) of meltblown fabrics with the same resistance and the same weight is evaluated. The test conditions are TSI 8130A, flow rate 32L / min, aerosol type NaCl, 0.3um, and test area 100cm. 2 The meltblown fabric weighs 25gsm. (The default resistance tolerance is ±1.0pa, which is equivalent to resistance, and the filtration performance PFE tolerance is ±0.2% which is equivalent to efficiency.)

[0056] 2. Aging performance test: Perform material aging treatment according to the following steps to evaluate the PFE attenuation amplitude and anti-red and yellowing performance.

[0057] (1) Place at (38±2.5)℃ and (85±5)% relative humidity for (24±1)h;

[0058] (2) Place in a dry environment at (80±3)℃ for 20 days;

[0059] (3) Place at (-30±3)℃ for (24±1)h.

[0060] (4) The sample was placed at room temperature for 4 hours before testing.

[0061] 3. Red-Yellow Discoloration Performance Test: Four layers of meltblown fabric were overlapped and tested using a colorimeter. The LAB values were compared before and after aging, along with the A and B values and the total color difference ΔE. (Tests have shown that when Δa ≤ 0.5 and Δb ≤ 1.5, the overall color change is acceptable to the naked eye; values exceeding these values are considered significant.) Performance test data are shown in Tables 3 and 4.

[0062] Table 3 Example test items and data

[0063]

[0064]

[0065] Table 4 Comparative Example Test Items and Data

[0066]

[0067] It is found from Examples 1-4 and Comparative Examples 3-7 that when zirconium phosphate and aliphatic polyamide are added simultaneously, the two produce a synergistic effect. Under the condition of equivalent resistance, the electret effect of the fiber is better and the retention rate of PFE after aging is higher.

[0068] As can be seen from Examples 1-4 and Comparative Examples 1-2, as the content of zirconium phosphate and polyamide increases, the performance first increases and then decreases. This may be because when the amount of zirconium phosphate and polyamide is too high, the PA and zirconium phosphate have stronger intermolecular forces, making fiber drafting more difficult, resulting in a coarser fiber diameter under the same process conditions. This leads to slightly poorer filtration effect. The data shows that when the resistance is equivalent, the PFE is low, and the anti-red and yellowing effect is poor. This is mainly because the excess zirconium phosphate agglomerates and affects the dispersion effect. In addition, the excess polyamide changes the characteristics of the system and cannot bring out the good electrostatic electret properties of polypropylene. When the amount of zirconium phosphate and polyamide is too low, the synergistic effect on the electret effect is weak. The data shows that when the resistance is equivalent, the PFE is low, and the anti-red and yellowing effect is poor. Examples 2, 6, 7, 8, and 9 found that the PFE retention rate after aging is higher in polyamide with an even number of methylene groups than in polyamide with an odd number of methylene groups; and the smaller the Δa and Δb values, the lower the degree of red and yellowing of the material.

[0069] It was found in Examples 2, 5 and 2, 12 that zirconium phosphate and aliphatic polyamide, meltblown materials with different melt indices and different electret masterbatches all had synergistic effects.

[0070] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A meltblown polypropylene composite material, characterized in that: The invention comprises the following components in parts by weight: 80-93 parts of polypropylene melt-blown material, 3-12 parts of aliphatic polyamide, 1-5 parts of zirconium phosphate, and 3-5 parts of electret masterbatch; the electret masterbatch contains hindered amine.

2. The meltblown polypropylene composite material according to claim 1, wherein The invention comprises the following components in parts by weight: 85-89 parts of polypropylene melt-blown material, 5-8 parts of aliphatic polyamide, 3-4 parts of zirconium phosphate and 3-5 parts of electret masterbatch.

3. The meltblown polypropylene composite material according to claim 1 or 2, wherein: The melt index of the polypropylene melt-blown material is 1200-1500 g / 10 min, and the melt index of the polypropylene melt-blown material is measured according to ASTM D1238 using a weight of 2.16 kg and a temperature of 190° C.

4. The meltblown polypropylene composite material according to claim 1, wherein The number of methylene monomers in the aliphatic polyamide is n, where n is an even number and n≠0.

5. The meltblown polypropylene composite material according to claim 1, wherein The number of methylene monomers in the aliphatic polyamide is 10-16.

6. The meltblown polypropylene composite material according to claim 5, wherein The aliphatic polyamide is at least one of PA11 and PA612.

7. The method for preparing the meltblown polypropylene composite material according to any one of claims 1 to 6, wherein: The following steps are involved: (1) Weigh various components according to the ratio; (2) mixing the components in step (1) to obtain a mixture A; (3) The mixture A obtained in step (2) is conveyed to a screw extruder for extrusion granulation to obtain the melt-blown polypropylene composite material.

8. Use of the melt-blown polypropylene composite material according to any one of claims 1 to 6 in the field of air filtration.

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