CN116121888A - Secondary drafting and bundling collection method for micro-nano fibers - Google Patents

Abstract

The invention relates to a method for secondary drawing and bundle collection of micro-nano fibers, comprising the following steps: the first step: spraying supercritical fluid spinning solution from the spinneret hole in the spinneret, and volatilizing the solvent into fiber; the second step: make the fiber pass through the heating area, fiber opening and secondary drafting area in sequence, and obtain the micro-nano fiber of fiber opening and secondary drafting; the third step: under the action of negative air pressure, the fiber opening and The second-drawn micro-nano fibers are collected on the collection net of the conveying device, then pass through the oven, hot pressing roller, guide roller, and finally wind up on the collection roller to obtain a nonwoven fabric. Compared with the prior art, the method of the invention can prepare the nonwoven fabric with high strength, good barrier performance and comfortable performance.

Description

A secondary drafting and bundle collection method for micro-nano fibers

technical field

The invention relates to the technical field of spinning, in particular to a method for secondary drafting and bundle collection of micro-nano fibers.

Background technique

Flash spinning technology was first discovered in 1957 by Herbeit Blade of DuPont in the study of polyolefin foaming. Flash spinning is a special case of dry spinning. The polymer rapidly forms fibers when the solvent flashes, also known as instant spinning. Flash spinning is a spinning method in which the polymer solution is above the boiling point of the solvent and extruded through the spinneret under high pressure to reach normal pressure. Due to the sudden drop in pressure during spinning, the solvent evaporates rapidly, and extremely fine fiber strands are ejected. Then the fiber tow is opened to form a fluffy fiber network structure, and then it is collected, conveyed and hot-rolled to form a non-woven fabric. Flash nonwovens have unique product characteristics, with excellent puncture resistance, tear resistance and waterproof and breathable properties, and can be widely used in various functional protective clothing. The protective clothing prepared by it is light and soft, has good barrier properties, and has air-permeable pores on the cloth surface, which is more comfortable than other protective clothing. In addition, flash nonwovens are also widely used in packaging, printing, construction, and agriculture.

The raw materials for flash spinning mainly include fiber-forming polymers, main solvents, secondary solvents and additives. In order to facilitate the dissolution of polymers, the polymers used in the flash spinning process are generally some linear polymers, such as polyethylene and polypropylene. The main solvent used in flash spinning generally has a low boiling point (less than 100°C), and its types mainly include aromatic hydrocarbons (such as benzene, toluene, etc.), halogenated hydrocarbons (such as methylene chloride, chloroform, carbon tetrachloride, ethyl chloride, etc.) alkane, trichlorofluoromethane, etc.), aliphatic hydrocarbons (such as butane, n-hexane, pentene, heptane, etc.) and alicyclic hydrocarbons (such as cyclohexane, unsaturated hydrocarbons, etc.), according to the fiber-forming polymer Different selections or combinations; the main function of the secondary solvent in the flash spinning process is to help dissolve, increase or decrease the cloud point pressure of the spinning solution, and reduce the surface tension of the polymer, etc., and its main types include alkanes, halogenated hydrocarbons, cyclic Alkanes, alcohols and some gases. A small amount of additives usually need to be added in the flash spinning process, the main function is to make the flash spinning process go smoothly or to endow the product with certain characteristics to meet the application of the product in certain fields. Commonly used additives mainly include nucleating agents, antioxidants, stabilizers, dyes, functional materials, etc.

At present, the strength of the nonwoven fabric produced by the domestic flash method is poor, and the fiber distribution in the nonwoven fabric is uneven. When the size of the void in the nonwoven fabric is small, it leads to poor comfort. When it is used, the comfort is improved, but the barrier performance is deteriorated, and it is difficult to meet the requirements for the use of non-woven fabrics in protective clothing. Therefore, the preparation of nonwoven fabrics with high strength, good barrier properties and comfortable properties is an urgent problem to be solved.

Contents of the invention

The purpose of the present invention is to provide a secondary drafting and bundle collection method of micro-nano fibers in order to overcome the above-mentioned defects in the prior art. The secondary draft and bundle collection method of micro-nano fibers of the present invention can produce high Non-woven fabrics with high barrier properties and good comfort properties.

The purpose of the present invention can be achieved through the following technical solutions:

The purpose of the present invention is to provide a secondary drafting and bundle collection method of micro-nano fibers, comprising the following steps:

The first step: the supercritical fluid spinning solution is sprayed from the spinneret hole in the spinneret, and the solvent is volatilized to form fibers;

The second step: make the fiber pass through the heating zone, fiber opening and secondary drafting zone in sequence to obtain the micro-nano fiber of fiber opening and secondary drafting;

Step 3: Under the action of negative air pressure, the micro-nano fibers that have been opened and drawn twice are collected on the collection net of the conveying device, and then pass through the oven, hot-pressing roller, guide roller, and finally wind up on the collection roller , and finally obtain a nonwoven fabric.

Further, the fibers obtained in the first step are fiber bundles.

Further, the supercritical fluid spinning solution in the first step includes polyolefin, main solvent, and co-solvent; the number of pores of the polyolefin is selected from one of polyethylene, polypropylene, and polymethylpentene; The number of pores of the main solvent is selected from one of benzene, methylene chloride, butane, cyclohexane, and 1,2-dichloroethane; the number of pores of the cosolvent is selected from cyclopentane, chlorodifluoro One of methane, tetrafluoroethane, nitrogen, and carbon dioxide.

Further, the mass of the polyolefin accounts for 8-20% of the total mass of the polyolefin and the solvent; the mass ratio of the main solvent to the co-solvent is (9-3):1.

Further, the solvent refers to a mixed solvent of a main solvent and a co-solvent.

Further, the number of holes in the spinneret hole in the spinneret in the first step is selected from one of 1 hole, 2 holes, 3 holes, 4 holes, and 5 holes; the diameter of the spinneret hole is 0.5 ~1.5mm.

Further, the heating temperature in the heating area in the second step is 40-100°C, the purpose of heating is to further remove the incompletely volatilized solvent in the fiber and avoid the adhesion between fibers; the fiber opening and The secondary drafting area uses compressed air to disperse the fibers evenly and further refine them. The air velocity of the compressed air is 5000-12000m/min.

Further, the negative air pressure in the third step is realized by the suction device, the maximum pressure of the suction device is -1~-0.01MPa, the purpose of using the negative air pressure is: the speed of the micro-nano fiber under the action of compressed air It is very fast and easy to drift around, making it difficult to collect the micro-nano fibers. However, the use of negative air pressure for collection can make the micro-nano fibers evenly and stably collected on the collection net of the conveying device.

Further, the micro-nanofibers have a diameter of 0.1-1.5 μm.

Further, in the third step, the heating temperature of the oven is 150-300° C., and the heating time is 10-30 s, and the micro-nano fibers pass through the oven to conduct in-situ cross-linking among the fibers.

Further, the temperature of the hot pressing rollers in the third step is 60-120° C., the speed is 5-15 m/min, and the distance between the hot-pressing rollers is 0.05-1.5 mm. Rolling is carried out to make a non-woven fabric, and the thickness of the non-woven fabric is 0.1-1mm.

Further, the speed of the hot pressing roller in the third step is greater than the transmission speed of the conveying device, and the speed difference between the hot pressing roller and the conveying device is 0.05-0.3m/min, so that the crimped fibers can straighten.

Further, the winding speed of the collection roller in the third step is 5-20 cm/min, the speed of the hot pressing roller is consistent with the winding speed of the collecting roller, and the nonwoven fabric between the hot pressing roller and the collecting roller has no tension .

Further, the grammage of the nonwoven fabric is 30-100g/m ² , the length of the nonwoven fabric is 20-50m, and the width is about 80cm.

Mechanism of the present invention is introduced as follows:

First of all, after the supercritical fluid spinning solution passes from the high-pressure chamber to the low-pressure chamber, the solvent and the polymer undergo slight phase separation. When the spinning solution passes through the spinneret, the solvent changes from liquid to vapor, and expands rapidly at the spinneret hole. The polymer and the solvent are accelerated to form a supersonic flow due to expansion, and the polymer in the fluid exists in the form of beaded droplets; and the solvent undergoes a phase transition, and the solvent and the polymer undergo phase separation. At the same time as the phase heat conversion, the fluid relies on the velocity gradient to generate High-speed stretching. The whole process is completed in an instant, and the polymer rapidly crystallizes, thereby rapidly forming extremely fine fiber bundles. Then heat the fiber to remove the residual solvent in the fiber bundle, so that the fibers in the fiber bundle can avoid sticking; then use compressed air to open the fiber bundle and perform secondary drafting treatment to obtain micro-nano fibers; Under the action of the machine, the high-speed moving fibers are collected, so that the fibers are evenly deposited on the collection net. Then the fluffy fiber network structure is introduced into the oven to soften the fibers in the fluffy fiber network structure, and the softened non-woven fabric is calendered with a hot pressing roller, then the non-woven fabric passes through the guide roller, and finally is wound The equipment collects non-woven fabrics, and the winding equipment is equipped with multiple collection rollers to realize continuous collection of non-woven fabrics and improve production efficiency.

Compared with the prior art, the present invention has the following beneficial effects:

1) The secondary drafting and bundle collection method of micro-nano fibers provided by this technical solution further volatilizes the solvent by heating after the fiber bundles are sprayed out, avoiding the adhesion between fiber bundles, and making the fibers Bundle opening and secondary stretching, the prepared fibers have small diameter and narrow diameter distribution.

2) The secondary drafting and bundle collection method of micro-nano fibers provided by this technical solution uses negative pressure to uniformly collect the fibers, then heats the fibers, and uses hot pressing rollers for rolling, so that the fibers are formed Bonding points, a nonwoven fabric with high strength, good barrier performance and comfortable performance is prepared.

Description of drawings

FIG. 1 is a SEM image of micro-nanofibers in Example 1 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. Features such as component models, material names, connection structures, and control methods that are not clearly stated in this technical solution are regarded as common technical features disclosed in the prior art.

A method for secondary drafting and bundle collection of micro-nano fibers, comprising the following steps:

The first step: the supercritical fluid spinning solution is sprayed from the spinneret hole in the spinneret, and the solvent is volatilized to form fibers;

The second step: the fiber passes through the heating zone, fiber opening and secondary drafting zone in sequence to obtain the micro-nano fiber of fiber opening and secondary drafting;

Step 3: Under the action of negative air pressure, the micro-nano fibers that have been opened and drawn twice are collected on the collection net of the conveying device, then pass through the oven, hot pressing roller, guide roller, and finally wind up on the collection roller. Finally, a nonwoven fabric is obtained.

Example 1

This embodiment provides a method for secondary drafting and bundle collection of micro-nano fibers, which includes the following steps:

First, 20 g of polyethylene, 180 g of methylene chloride, and 20 g of cyclopentane were dissolved under high temperature and high pressure to obtain a supercritical fluid spinning solution. The supercritical fluid spinning solution enters the low-pressure chamber from the high-pressure chamber, and is sprayed out from the spinneret with a single spinneret hole. The diameter of the spinneret hole is 1.2mm. The solvent evaporates quickly to form fiber bundles, and then passes through the heating area, In the fiber opening and secondary drawing area, the temperature in the heating area is 80°C, the air velocity in the fiber opening and secondary drawing area is 9000m/min, and then under the action of a negative air pressure of 0.05MPa, the fiber opening and secondary drawing The stretched micro-nano fibers are collected on the collection net of the conveying device, and then pass through the oven at 180°C, the hot pressing roller, the guide roller, and finally wind up on the collection roller. The time for the micro-nano fibers to pass through the oven is 30s, the temperature of the hot pressing rollers is 80°C, the speed is 6m/min, the distance between the hot pressing rollers is 1mm; the speed of the collecting rollers is 5.95cm/min. The thickness of the finally obtained nonwoven fabric is 0.8mm, the length is 30m, the width is about 80cm, the grammage is 50g/m ² , the air permeability of the nonwoven fabric is 32mm/s, and the maximum tensile breaking strength is 243N/5cm .

As shown in Figure 1, the SEM image of a bundle of micro-nano fibers prepared by the flash evaporation method shows that the fibers have a good surface morphology.

Example 2

This embodiment provides a method for secondary drafting and bundle collection of micro-nano fibers, the specific steps are as follows:

The method of secondary drawing and bundle collection of micro-nano fibers is as follows: firstly, 30 g of polypropylene, 170 g of methylene chloride, and 30 g of cyclopentane are dissolved under high temperature and high pressure to obtain a supercritical fluid spinning solution. The supercritical fluid spinning solution enters the low-pressure chamber from the high-pressure chamber, and is sprayed out from the spinneret with three spinneret holes. The diameter of the spinneret holes is 0.8mm. The solvent evaporates quickly to form fiber bundles, and then passes through the heating area in turn. , fiber opening and secondary drafting area, the temperature in the heating area is 90°C, the air velocity in the fiber opening and secondary drafting area is 10000m/min, and then under the action of negative air pressure of 0.07MPa, the fiber opening and secondary drafting The stretched micro-nano fibers are collected on the collection net of the conveying device, then pass through an oven at 260°C, hot pressing rollers, guide rollers, and finally wind up on the collection rollers. The time for the micro-nano fibers to pass through the oven is 15s, the temperature of the hot pressing rollers is 100°C, the speed is 12m/min, the distance between the hot pressing rollers is 1.2mm; the speed of the collecting rollers is 11.8cm/min. The thickness of the finally obtained nonwoven fabric is 1.1mm, the length is 36m, the width is about 80cm, the grammage is 90g/m ² , the air permeability of the nonwoven fabric is 27mm/s, and the maximum tensile breaking strength is 273N/5cm .

Example 3

This embodiment provides a method for secondary drafting and bundle collection of micro-nano fibers, the specific steps are as follows:

The secondary drawing and bundle collection method of micro-nano fibers, specifically: first, 25g of polyethylene, 170g of 1,2-dichloroethane, and 30g of tetrafluoroethane are dissolved under high temperature and high pressure to obtain supercritical Fluid spinning solution. The supercritical fluid spinning liquid enters the low-pressure chamber from the high-pressure chamber, and is sprayed out from the spinneret with a single spinneret hole. The diameter of the spinneret hole is 1mm. The solvent evaporates quickly to form fiber bundles, and then passes through the heating area, the In the fiber and secondary drawing area, the temperature in the heating area is 60°C, the air velocity in the fiber opening and secondary drawing area is 12000m/min, and then under the action of negative air pressure of 0.08MPa, the fiber opening and secondary drawing The micro-nano fibers are collected on the collection net of the conveying device, and then pass through a 200°C oven, hot pressing roller, guide roller, and finally wind up on the collection roller. The time for the micro-nano fibers to pass through the oven is 18s, the temperature of the hot-pressing rollers is 100°C, the speed is 10m/min, the distance between the hot-pressing rollers is 0.8mm; the speed of the collecting rollers is 9.97cm/min. The thickness of the finally obtained nonwoven fabric is 0.75mm, the length is 28m, the width is about 80cm, the grammage is 80g/m ² , the air permeability of the nonwoven fabric is 30mm/s, and the maximum tensile breaking strength is 263N/5cm .

The above descriptions of the embodiments are for those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative effort. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (10)

1. A secondary drafting and bundle collection method of micro-nano fibers, characterized in that, comprising the following steps: The first step: spray the supercritical fluid spinning liquid from the spinneret hole in the spinneret to make the solvent volatilize into fibers; The second step: make the fiber pass through the heating zone, fiber opening and secondary drafting zone in sequence to obtain the micro-nano fiber of fiber opening and secondary drafting; Step 3: Under the action of negative air pressure, the micro-nano fibers that have been opened and drawn twice are collected on the collection net of the conveying device, and then pass through the oven, hot-pressing roller, guide roller, and finally wind up on the collection roller , and finally obtain a nonwoven fabric. 2. according to claim 1, the secondary drafting and bundle collection method of a kind of micro-nano fiber is characterized in that, the supercritical fluid spinning solution described in the first step comprises polyolefin, main solvent, co-solvent; The polyolefin is selected from one of polyethylene, polypropylene, and polymethylpentene; The main solvent is selected from one of benzene, methylene chloride, butane, cyclohexane, and 1,2-dichloroethane; The cosolvent is selected from one of cyclopentane, chlorodifluoromethane, tetrafluoroethane, nitrogen, and carbon dioxide; The mass of the polyolefin accounts for 8-20% of the total mass of the polyolefin and the solvent; The mass ratio of the main solvent to the co-solvent is (9-3):1. 3. according to claim 1, the secondary drafting and bundle collection method of a kind of micro-nano fiber is characterized in that, the number of holes of the spinneret hole in the spinneret described in the first step is selected from 1 hole, 2 One of holes, 3 holes, 4 holes, 5 holes; The diameter of the spinneret hole is 0.5-1.5mm. 4. A method for secondary drawing and bundle collection of micro-nano fibers according to claim 1, characterized in that the heating temperature of the heating zone in the second step is 40-100°C; In the second step, the fiber opening and secondary drafting areas use compressed air to uniformly disperse and further refine the fibers, and the air velocity of the compressed air is 5000-12000m/min. 5. according to claim 1, the secondary drafting and bundle collection method of a kind of micro-nano fiber is characterized in that, in the third step, the negative air pressure is realized by a suction device, and the highest pressure of the suction device is- 1～-0.01MPa. 6. A method for secondary drawing and bundle collection of micro-nano fibers according to claim 1, characterized in that the diameter of the micro-nano fibers is 0.1-1.5 μm. 7. A method for secondary drawing and bundle collection of micro-nano fibers according to claim 1, characterized in that in the third step, the heating temperature of the oven is 150-300°C, and the heating time is 10-30s. 8. A method for secondary drafting and bundle collection of micro-nano fibers according to claim 1, characterized in that the temperature of the hot pressing roller in the third step is 60-120°C, and the speed is 5-15m/ min, the distance between the hot-pressing rollers is 0.05-1.5mm, and the hot-pressing rollers roll the cross-linked micro-nano fibers to make a non-woven fabric, and the thickness of the non-woven fabric is 0.1-1mm; In the third step, the speed of the heat-pressing roller is greater than the transmission speed of the conveying device, and the speed difference between the heat-pressing roller and the conveying device is 0.05-0.3 m/min. 9. according to claim 1, a kind of secondary drafting and bundle collection method of micro-nano fiber is characterized in that, the winding speed of the collecting roller in the third step is 5～20cm/min, and the heating and pressing roller The rotation speed is consistent with the winding speed of the collection roller. 10. A method for secondary drafting and bundle collection of micro-nano fibers according to claim 1, characterized in that the grammage of the non-woven fabric is 30-100 g/m ² , and the length of the non-woven fabric is 20 ~50m, the width is 80cm.

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