Flame-retardant melt-blown non-woven fabric and preparation method thereof

Abstract

The invention discloses a flame-retardant melt-blown non-woven fabric and a preparation method thereof.The preparation method comprises the following steps that a polypropylene melt-blown special material and polyphenylene sulfide slices are evenly mixed according to the mass ratio of 85-90: 10-15, and a mixture is prepared; respectively feeding the mixture and the electric electret master batch from a main feeding port and a secondary feeding port of a double-screw extruder, carrying out a melting reaction, and extruding to obtain a polymer melt; the extruded polymer melt is sprayed out from a spray head of a spinneret plate and drafted through hot air of a high-speed hot air flow to form nascent fibers, and the nascent fibers are bonded to a receiving web curtain through a negative pressure adsorption device by means of waste heat of the nascent fibers and collected into a web to form a primary melt-blown non-woven fabric; and carrying out high-pressure electret treatment on the primary melt-blown non-woven fabric, and rolling to obtain the flame-retardant melt-blown non-woven fabric. The flame-retardant melt-blown non-woven fabric prepared by the invention is excellent in flame retardance and stable in filtering efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of textile materials, and relates to a flame-retardant meltblown non-woven fabric and a preparation method thereof. Background Art

[0002] Meltblown non-woven fabric is a superfine fiber non-woven material formed by high polymers (such as polypropylene, polyester, etc.) through high-temperature melting and high-speed air flow drawing. It has the characteristics of high porosity, large specific surface area, excellent filtration performance, etc., and is widely used in the fields of medical and health (masks, surgical gowns), air / liquid filtration, protective materials, automotive interiors, aerospace, etc. In scenarios with high fire hazards (such as public facilities, transportation vehicles, fire protection supplies), strict requirements are put forward for the flame-retardant performance of meltblown non-woven fabrics.

[0003] The conventional process realizes flame retardancy by adding halogen-based or phosphorus-based flame retardants. It is difficult to achieve uniform dispersion of halogen-based or phosphorus-based flame retardants in fibers, which affects the stability of the flame-retardant effect; when the addition amount of halogen-based or phosphorus-based flame retardants is too high (such as >15%), it will cause fiber embrittlement, and the breaking strength will decrease by 30%-50%. For example, phosphorus-containing flame retardants may reduce the melt strength of polypropylene and affect the spinning stability; flame retardant particles (such as aluminum hydroxide) may block the fiber pores, increasing the filtration resistance by more than 50%, especially more obvious in high-gram-weight meltblown fabrics; the post-treatment flame-retardant process (such as the dipping method) has problems such as complex process and high cost.

[0004] The invention patent with publication number CN116815415A discloses a flame-retardant and antibacterial polypropylene meltblown non-woven fabric and a preparation method thereof. ZIF-8 is impregnated in an AgNO3 aqueous solution, stirred at a temperature of 20-30°C for 3-10h, centrifuged and washed with deionized water 3-5 times to remove surface adsorbed ions. The obtained solid product is calcined in a muffle furnace to obtain an Ag-ZnO composite; 1-8wt% of the Ag-ZnO composite, 1-8wt% of IFR and 90-98wt% of PP are melt-mixed under the working condition of a twin-screw extruder, then sent to a spinneret through a metering pump, and laid into a web after being blown out by a blower, and the Ag-ZnO / IFR / PP meltblown non-woven fabric is collected. The polypropylene meltblown non-woven fabric of the present invention has excellent flame-retardant performance and antibacterial performance, but the intumescent flame retardant added in this preparation method contains a phosphorus-based component, which will reduce the filtration efficiency and produce harmful substances during combustion. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a flame-retardant meltblown non-woven fabric and a preparation method thereof, which solve the problems that the existing traditional meltblown non-woven fabric is easy to melt and drip when encountering fire, and the addition of conventional flame retardants (such as halogen-based, phosphorus-based) may reduce the filtration efficiency and produce harmful substances during combustion.

[0006] The technical solution provided by the present invention is as follows:

[0007] The present invention provides a method for preparing a flame-retardant meltblown non-woven fabric, and the method includes the following steps: Mix polypropylene meltblown special material and polyphenylene sulfide chips evenly according to a mass ratio of 85-90:10-15 to obtain a mixed material; Feed the above-mentioned mixed material and the electret masterbatch into the main feeding port and the secondary feeding port of a twin-screw extruder respectively, carry out a melting reaction, and obtain a polymer melt after extrusion; Spray the extruded polymer melt from the nozzles of a spinneret plate, and after hot air stretching by a high-speed hot air stream, form primary fibers, and then collect and form a web on a receiving wire mesh by means of a negative pressure adsorption device and using the self-residual heat of the primary fibers to obtain a primary meltblown non-woven fabric; Carry out high-voltage electret treatment and winding on the obtained primary meltblown non-woven fabric to obtain the flame-retardant meltblown non-woven fabric.

[0008] Furthermore, the addition amount of the electret masterbatch is 1-3% of the mass of the polypropylene meltblown special material.

[0009] Furthermore, the twin-screw extruder has five zones with different temperatures, and the rotation speed of the screw of the twin-screw extruder is 50-60 r / min.

[0010] Furthermore, the five temperature zones of the twin-screw extruder are respectively: the temperature of the first screw zone is 280-285 °C, the temperature of the second screw zone is 285-300 °C, the temperature of the third screw zone is 285-290 °C, the temperature of the fourth screw zone is 280-290 °C, and the temperature of the fifth screw zone is 280-285 °C.

[0011] Furthermore, during the high-temperature air stream high-speed stretching process, the temperature of the hot air is 280-320 °C, the flow rate of the hot air is 200-250 m / s, and the air pressure of the hot air is 0.4-0.5 MPa.

[0012] Furthermore, the diameter of the primary fibers obtained after hot air stretching by a high-speed hot air stream is 1-5 μm.

[0013] Furthermore, the aperture of the spinneret plate is 0.15-0.25 mm, the distance between the nozzles of the spinneret plate and the receiving wire mesh is 10-30 cm, and the receiving speed is 5-8 cm / s.

[0014] Furthermore, during the high-voltage electret treatment process, place the primary meltblown non-woven fabric in a high-voltage discharge device and carry out electret treatment at a voltage of 50-80 kV for 1-2 s.

[0015] Further, the special polypropylene meltblown material and polyphenylene sulfide chips are placed in a mixer for mixing. The rotation speed of the mixer is 40 - 80 r / min, the mixing time is 8 - 10 min, and the mixing temperature is 30 - 50 °C.

[0016] Further, the rotation speed of the screw of the twin-screw extruder is 50 - 60 r / min.

[0017] The present invention also provides a flame-retardant meltblown non-woven fabric, which is prepared according to the above-mentioned preparation method.

[0018] Beneficial effects

[0019] In the preparation method of the present invention, polyphenylene sulfide chips are used as raw materials. Since polyphenylene sulfide chips themselves have excellent flame-retardant properties, high-standard flame-retardant requirements of the flame-retardant DIN53438 standard can be easily achieved without adding any additional fillers or auxiliaries. Moreover, polyphenylene sulfide chips also exhibit high thermal stability and can maintain their original excellent properties and quality in a wide temperature range.

[0020] In the preparation method of the present invention, intrinsic flame retardancy is achieved through the selection of high heat-resistant materials and process optimization, avoiding the addition of traditional halogen-based or phosphorus-based flame retardants, ensuring environmental protection, stable fiber structure, and the flame-retardant performance is not affected by long-term use of light. The specific advantages are as follows:

[0021] (1) Halogen-based or phosphorus-based flame retardants are not added to the raw materials, avoiding potential hazards of chemical substances to the environment and human body during production and use, and being more in line with the trend of green production;

[0022] (2) Halogen-based or phosphorus-based flame retardants are not added to the raw materials, and the fiber structure is not damaged. The material is softer, more breathable, suitable for products in direct contact with the skin, and has a more comfortable hand feeling;

[0023] (3) Traditional flame-retardant non-woven fabrics need to mix halogen-based or phosphorus-based flame retardants and adjust the process, while this material directly achieves flame retardancy in the spinning or web-forming stage, with a shorter production process and lower cost;

[0024] (4) Chemical flame retardants may absorb moisture, causing the material to harden or fail, while this material has more stable flame-retardant performance and is not prone to problems such as mildew and discoloration during long-term storage;

[0025] (5) The flame retardancy achieved through the structure of the material itself has very little efficiency attenuation and stable performance, and is suitable for products that need to be used for a long time. Brief description of the drawings

[0026] Figure 1 It is a schematic diagram of the combustion test of the flame-retardant meltblown non-woven fabric in the embodiment of the present invention.

[0027] Figure 2It is a schematic diagram of the combustion test of the flame-retardant melt-blown nonwoven fabric of the comparative example of the present invention. DETAILED DESCRIPTION

[0028] In order to make the application clearer and more complete, the technical solutions of the present invention will be further explained below through specific examples. However, the following examples are only examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims. The present application will be described in detail below with reference to specific embodiments.

[0029] The reagent materials used in the embodiments of the present invention can be purchased routinely. The purchaser of polyphenylene sulfide slice (PPS) is Dongguan Suguang Plastic Raw Materials Co., Ltd., with a grade of 1140L4; the purchaser of polypropylene meltblown special material (PP) is Sinopec Qingdao Refining and Chemical Co., Ltd., with a grade of PPH-Y35; the purchaser of electric electret masterbatch is Shandong Dawn Polymer Materials Co., Ltd., with a grade of GM01-G.

[0030] The embodiment of the present invention provides a method for preparing a flame retardant melt-blown nonwoven fabric, which specifically comprises the following steps:

[0031] S1: Raw material blending modification:

[0032] Polyphenylene sulfide chips (PPS) and polypropylene melt-blown special materials (PP) are placed in a mixer in proportion, the speed of the mixer is set to 40-80r / min, the mixing time is 8-10min, the mixing temperature is 30-50°C, and a mixture is obtained after mixing. In the mixture, PP accounts for 85%-90%, and PPS accounts for 10%-15%. The mixture is then fed through the main feeding port of a twin-screw extruder, and the electret masterbatch is fed through the secondary feeding port of the twin-screw extruder for melting reaction. The addition amount of the electret masterbatch is 1%-3% of the mass of PP. The addition of the electret masterbatch improves the filtration efficiency of the melt-blown non-woven fabric.

[0033] S2: Melting and spinning

[0034] By adjusting the meltblowing process parameters, a dense fiber structure is formed to reduce flammability:

[0035] (1) In order to ensure that PPS flows fully, the melting temperature needs to be controlled at 280-300℃. To avoid thermal degradation of PP, the melting temperature needs to be controlled not to exceed 300℃. To ensure that the electret masterbatch and PP are evenly mixed, the melting temperature needs to be controlled not to exceed 300℃. Therefore, for the five different temperature zones of the twin-screw extruder, the temperature of screw zone 1 is set to 280~285℃, the temperature of screw zone 2 is set to 285~300℃, the temperature of screw zone 3 is set to 285~290℃, the temperature of screw zone 4 is set to 280~290℃, and the temperature of screw zone 5 is set to 280~285℃.

[0036] (2) The polymer melt extruded by the twin-screw extruder is ejected from the nozzle of the spinneret and stretched by high-speed hot air flow to form nascent fibers. The hot air temperature is 280-320°C, the hot air flow rate is 200-250 m / s, and the hot air pressure is 0.4-0.5 MPa. The diameter of the nascent fibers obtained after high-speed hot air flow stretching is 1-5 μm, which increases the surface area and density and delays combustion.

[0037] S3: Fiber web

[0038] The primary fibers are bonded to the mesh curtain using the residual heat of the primary fibers through a negative pressure adsorption device, and collected into a mesh, forming a primary melt-blown non-woven fabric with a multi-layer staggered structure, which reduces the porosity, reduces oxygen permeability, and optimizes the fiber stacking density; wherein, the aperture of the spinneret is 0.15~0.25mm, the distance between the nozzle and the receiving mesh curtain is 10~30cm, and the receiving speed is 5~8cm / s.

[0039] S4: Electret treatment

[0040] Use high-voltage discharge device with a discharge voltage of 50~80 kV and a time of 1~2 seconds to enhance filtration efficiency.

[0041] The following is a detailed description of a method for preparing a flame-retardant melt-blown nonwoven fabric of the present application through Examples 1 to 9:

[0042] Example 1

[0043] A method for preparing a flame-retardant melt-blown nonwoven fabric comprises the following steps: placing polypropylene melt-blown special material (PP) and polyphenylene sulfide chips (PPS) in a mass ratio of 90:10 into a mixer for a mixing time of 10 minutes, a mixing speed of 60 r / min, a mixing temperature of 50°C, and obtaining a mixture after sufficient and uniform mixing; feeding the mixture into a twin-screw extruder through a main feeding port, and then adding an electret masterbatch into the twin-screw extruder through a secondary feeding port, the screw speed being 50 r / min, the amount of the electret masterbatch added being 3% of the mass of the polypropylene melt-blown special material (PP), and setting five heating sections on the screw, with a specific temperature of The settings are: screw zone 1: 285°C; screw zone 2: 300°C; screw zone 3: 288°C; screw zone 4: 285°C; screw zone 5: 280°C; after being heated and melted by the screw, it is extruded and sprayed out from a nozzle of a spinneret with an aperture of 0.20 mm. The fiber diameter is 3~5μm when the high-speed hot air flow with a hot air temperature of 300°C, a hot air flow rate of 250m / s and a hot air pressure of 0.5MPa is stretched. The distance between the nozzle and the receiving mesh curtain is adjusted to 10cm, the receiving speed is controlled at 5cm / s, and the fibers are collected into a web on the receiving mesh curtain. A high-voltage discharge device is used with a discharge voltage of 80 kV for 2 seconds, and finally the fiber is rolled up to prepare a flame-retardant melt-blown non-woven fabric.

[0044] Examples 2 - 3:

[0045] The difference from Example 1 lies in that the distance between the nozzle and the receiving mesh curtain is different. As shown in Table 1, the others are the same as in Example 1.

[0046] Examples 4 - 5:

[0047] The difference from Example 1 lies in that the discharge voltage parameters are different. As shown in Table 1, the others are the same as in Example 1.

[0048] Examples 6 - 7:

[0049] The difference from Example 1 lies in that the proportion of each raw material in the preparation process is different. As shown in Table 1, the others are the same as in Example 1.

[0050] Examples 8 - 9:

[0051] The difference from Example 1 lies in that the addition ratio of the electret masterbatch in the preparation process is different. As shown in Table 1, the others are the same as in Example 1.

[0052] Comparative Example 1

[0053] The difference from Example 1 is that polyphenylene sulfide chips were not added in step S1.

[0054] The test data of the relevant parameters of the examples are shown in Table 1, and the performance data of Example 1 before and after air blowing are shown in Table 2.

[0055] Table 1 Parameter settings and performance test results of Examples 1 - 9

[0056]

[0057] Combined with Table 1, the analysis is as follows:

[0058] 1) Comparing Examples 1, 6, and 7, it can be seen that the mass ratio of the special polypropylene melt - blown material to the polyphenylene sulfide chips has a significant impact on the flame - retardant performance of the flame - retardant melt - blown non - woven fabric. The higher the proportion of polyphenylene sulfide chips, the better the flame - retardant performance of the melt - blown non - woven fabric. However, too high a proportion will affect the filtration efficiency and resistance of the melt - blown non - woven fabric, thus affecting the product performance;

[0059] 2) Comparing Examples 1, 2, and 3, it can be seen that the distance between the nozzle and the receiving mesh curtain will affect the packing density of the ultrafine fibers, thereby affecting the porosity of the material, and further affecting the filtration efficiency and resistance of the melt - blown non - woven fabric;

[0060] 3) By comparing Examples 1, 4, and 5, it can be seen that electrostatic electret is to charge the fiber surface through high-voltage corona discharge. When the electret voltage is too low, the charge density on the fiber surface is insufficient, and the electrostatic adsorption capacity for particulate matter (especially fine particles below 0.3 μm) is weak, resulting in low filtration efficiency. Excessive voltage will cause the fiber surface charge to be oversaturated, and may even damage the fiber structure (such as fiber fusing and surface damage), which will instead lead to uneven charge distribution in some areas and a decrease in local filtration efficiency;

[0061] 4) By comparing Examples 1, 8, and 9, it can be seen that the addition amount of the electroelectret masterbatch directly affects the efficiency of the flame-retardant meltblown nonwoven fabric. The lack of polar components (such as silica, carbon black, ionic polymers) that provide charge capture sites in the masterbatch results in a low charge density on the surface of the meltblown fibers, weak electrostatic adsorption capacity for submicron particles (such as aerosols below 0.3 μm), and low efficiency. Excessive polar fillers may agglomerate during the meltblown process, forming local impurities or particles, destroying the fiber uniformity, and causing abnormal porosity (too large or too small) in some areas, which will instead reduce the stability of the filtration efficiency.

[0062] Table 2: Performance comparison data of the material before and after air blowing in Example 1

[0063]

[0064] Judging from Table 2, for a flame-retardant meltblown nonwoven fabric provided by the present invention, after 14 days of air blowing, there is basically no difference in efficiency, resistance compared with before air blowing, indicating that the filtration performance of this material is stable and can ensure long-term use.

[0065] Figure 1 For the comparison chart before and after combustion in Example 6, according to the German DIN53438 standard test method, a flame-retardant meltblown nonwoven fabric provided by the present invention can reach the highest flame-retardant standard required by this standard: surface: F1, edge: K1, indicating that the material has good flame resistance in an open flame, is not easy to continue burning or spread, and has excellent flame-retardant performance; it is suitable for scenarios with high fire protection requirements (such as furniture, vehicle interiors, building materials, etc.); DIN 53438 is a commonly used standard in Europe, and products meeting this standard are competitive in the EU market. Comparing the flame-retardant meltblown nonwoven fabric prepared in Example 6, the flame-retardant performance of Comparative Example 1 is significantly worse, and the material continues to burn and produces drips ( Figure 2 ) According to the German DIN53438 standard test method, the flame-retardant performance: surface: F3, edge: K3.

[0066] In summary, in the present invention, polyphenylene sulfide chips (PPS) are first blended with a conventional polypropylene meltblown special material (PP) in a certain proportion, and then an electret masterbatch is added. The flame retardancy of the substrate is improved by adjusting the blending ratio, and then it is melt-extruded through a screw, and the fibers are stretched to a fineness of 1-5 μm by a high-temperature and high-speed air flow to form an ultrafine fiber layer. Then, the meltblown fibers are bonded to a forming screen by using the residual heat of the meltblown fibers themselves to collect the web, forming a multi-layer staggered structure. Then, an electret treatment is carried out by using a high-voltage discharge device to enhance the filtration efficiency, and finally, it is wound up. The flame-retardant meltblown non-woven fabric prepared by the present invention has excellent flame retardancy and stable filtration efficiency.

Claims

1. A preparation method of a flame-retardant meltblown non-woven fabric, characterized in that, The method comprises the following steps: Mix polypropylene meltblown special material and polyphenylene sulfide chips evenly in a mass ratio of 85 - 90:10 - 15 to obtain a mixed material; Feed the above-mentioned mixed material and the electret masterbatch into the main feeding port and the secondary feeding port of a twin-screw extruder respectively, conduct a melting reaction, and obtain a polymer melt after extrusion; Eject the extruded polymer melt from the nozzles of a spinneret plate, and after hot air stretching by a high-speed hot air flow, form primary fibers, and then collect and form a web on a receiving wire mesh by means of a negative pressure adsorption device and using the residual heat of the primary fibers themselves to obtain a primary meltblown nonwoven fabric; Conduct high-voltage electret treatment and winding on the obtained primary meltblown nonwoven fabric to obtain the flame-retardant meltblown nonwoven fabric.

2. The preparation method of the flame-retardant meltblown non-woven fabric according to claim 1, wherein, The addition amount of the electret masterbatch is 1 - 3% of the mass of the polypropylene meltblown special material.

3. The preparation method of the flame-retardant meltblown nonwoven fabric according to claim 1, characterized in that, The twin-screw extruder has five zones with different temperatures, and the rotation speed of the screw of the twin-screw extruder is 50 - 60 r / min.

4. The preparation method of the flame-retardant meltblown nonwoven fabric according to claim 3, wherein, The five temperature zones of the twin-screw extruder are respectively: the temperature of the first screw zone is 280 - 285 °C, the temperature of the second screw zone is 285 - 300 °C, the temperature of the third screw zone is 285 - 290 °C, the temperature of the fourth screw zone is 280 - 290 °C, and the temperature of the fifth screw zone is 280 - 285 °C.

5. The preparation method of the flame-retardant meltblown nonwoven fabric according to claim 1, wherein During the high-temperature air flow high-speed stretching process, the temperature of the hot air is 280 - 320 °C, the flow rate of the hot air is 200 - 250 m / s, and the air pressure of the hot air is 0.4 - 0.5 MPa.

6. The preparation method of the flame-retardant meltblown non-woven fabric according to claim 1, wherein, The diameter of the primary fibers obtained after hot air stretching by a high-speed hot air flow is 1 - 5 μm.

7. The preparation method of the flame-retardant meltblown nonwoven fabric according to claim 1, characterized in that, The pore diameter of the spinneret plate is 0.15 - 0.25 mm, the distance between the nozzles of the spinneret plate and the receiving wire mesh is 10 - 30 cm, and the receiving speed is 5 - 8 cm / s.

8. The preparation method of the flame-retardant meltblown nonwoven fabric according to claim 1, wherein During the high-voltage electret treatment process, place the primary meltblown nonwoven fabric in a high-voltage discharge device and conduct electret treatment at a voltage of 50 - 80 kV for 1 - 2 s.

9. The preparation method of the flame-retardant meltblown non-woven fabric according to claim 1, wherein Place the polypropylene meltblown special material and the polyphenylene sulfide chips in a mixer for mixing. The rotation speed of the mixer is 40 - 80 r / min, the mixing time is 8 - 10 min, and the mixing temperature is 30 - 50 °C.

10. A flame-retardant meltblown non-woven fabric, characterized in that, Prepared according to the preparation method described in any one of claims 1 - 9.

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