JPS6049008B2 - Manufacturing method of high performance filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-performance filter, and particularly to a method for producing a high-performance filter material used in air purifiers, air conditioners, and the like.

In recent years, air pollution has become particularly prevalent in urban areas, and air purifiers and other devices are needed for environmental hygiene, to maintain the cleanliness of precision equipment rooms and medical rooms, and to maintain the quality of products at manufacturing plants. It has become desirable to improve the performance of the air filters used.

In general, in order to improve the filtration performance of air filters, that is, to reduce the critical diameter of fine particles that can be filtered from door to door and increase collection efficiency, felt or nonwoven fabrics made of fibers with very small fiber diameters are used. Filter media such as

Conventionally, glass wool has been mainly used as a material for high-performance air filters, and is composed of extremely thin short fiber glass wool with a fiber diameter of 0.5 to 3 microns, which are laminated randomly. Although it has high dust efficiency and excellent heat resistance, glass wool has poor bending resistance and has the disadvantage that broken glass fibers are scattered during ventilation. The cost is high in comparison. Filters made from organic fiber felt or nonwoven fabric obtained by conventional methods are inexpensive, but the fiber diameter is at most 10 microns, making them unsuitable for high-performance air filters. The high-performance air filter referred to here refers to one that can capture 50% or more of 0.3 micron dust in the atmosphere, and is a nonwoven fabric obtained from fibers with a fiber diameter of 5 microns or less, preferably 3 microns or less. It was discovered that it has high performance air filter characteristics. Therefore, as a method for manufacturing a fiber structure that is an organic fiber and has an ultrafine fiber diameter, for example, 2
After making a nonwoven fabric by three-dimensionally intertwining sea-island type composite fibers made of more than one type of polymeric substance, at least one type of polymeric substance is extracted with an organic solvent, leaving only the polymeric substance of the island component, and forming a nonwoven fabric. (Japanese Patent Publication No. 51-6261), or extruding a molten polymer of thermoplastic resin containing an inert gas or foaming substance from a die and rapidly cooling the extruded molten polymer. A method is known in which the fibers are divided into sheets by utilizing the bursting of air bubbles (Japanese Patent Publication No. 48-38349 and Japanese Patent Publication No. 49-18508). However, in the former method, aromatic solvents are generally used to dissolve the polymeric substances of the sea components using organic solvents, and not only does it take a long time to extract the sea components, but also the polymeric substances of the sea components are removed after extraction. This method requires two steps to wash the nonwoven fabric with methanol and then with water, and also requires treatment of the waste liquid containing the eluted polymeric substance, complicating the process and causing large losses. In the latter case, since an inert gas or a substance that generates an inert gas is kneaded into a molten polymer and extruded, it is difficult to control the spinning process and the operability is unstable. Another method is to dissolve an organic material with fiber-forming ability in an organic solvent and spray the solution through a nozzle to create a web of ultra-fine short fibers, which can then be used as a filter material! (Japanese Patent Publication No. 46-139m, Japanese Unexamined Patent Application Publication No. 1973)
0-108677) is publicly known. By this method, ultra-fine organic fibers are obtained, and the web produced from the obtained fibers has sufficient properties as a high-performance air filter. However, in order to reduce the diameter of the fibers obtained by this method, it is necessary to lower the concentration of the organic material, which does not increase productivity, and if a large amount of solvent is required, there is an economic loss. Moreover, there is also the risk of environmental pollution caused by organic solvents. Furthermore, a serious drawback of these known examples is that the nonwoven fabric made only of ultra-fine fibers lacks strength and cannot be used alone, and it is always necessary to incorporate a reinforcing material. On the other hand, the applicant has reported a method for producing a nonwoven fabric using ultrafine fibers that does not have the above-mentioned drawbacks.

(Japanese Unexamined Patent Publication No. 50-8967) In this method, two types of fiber-forming polymers with low mutual adhesion are bonded along the longitudinal direction, and one component A branches radially in the cross section.
A web is created using a split conjugate fiber consisting of a segment of component A and a segment of component B that complements the radial portion, and the conjugate fibers are bonded or intertwined. The nonwoven fabric obtained by this method is a highly strong and flexible nonwoven fabric, and at the same time, it has excellent performance as a filter because of the entanglement of ultrafine fiber bundles. As a performance air filter, it is an air filter made of ultra-fine glass wool. The current situation is that it is still not sufficient compared to the first. The present inventors re-needled the nonwoven fabric etc. to entangle the ultrafine fibers more closely, and made the A component polyamide and the B component polyester,
They discovered that by pressurizing polyamide at a temperature near its melting point, a nonwoven fabric filter with high strength and high permeability could be obtained, and after further research, they completed the present invention.

That is, an object of the present invention is to correct the above-mentioned drawbacks, and to provide a high-performance filter with excellent strength and extremely high permeability, and an industrially advantageous manufacturing method thereof.
This object is made of a splittable composite fiber with a single fiber fineness of 3 denier or less and a cross section that can be divided into 5 or more segments, in which polyamide and polyester are joined at a joining ratio of 1:5 to 5:1 along the longitudinal direction. The web is treated with a solvent that swells the polyamide but does not swell the polyester, and the composite fibers constituting the web are divided into segments, subjected to needling, and pressure treated at a temperature of 200 to 250°C to remove the polyamide component. This is achieved by fusion bonding, and the obtained nonwoven fabric filter has polyamide fibers partially fused to form a skeleton, and the ultrafine polyester fibers are entwined with each other as if they were wrapped around the polyamide fibers. Because of this, it has a high level of perforation performance. The polyamide used in the present invention is one whose main component is so-called nylon-6 obtained by ring-opening polymerization of ε-caprolactam, and nylon-6 is 9. Polyamides obtained from lactams such as γ-butyrolactam, δ-valerolactam, heptolactam, and laurinlactam, or polycondensation of diamines such as nylon-66 and dicarboxylic acid salts. Polyamide may be mixed therein, and flame retardants such as phosphorus-containing nitrogen compounds, thiourea resin powder, heat resistant agents, pigments, etc. may also be included.

Further, the polyester used in the present invention contains 85% by weight or more of polyethylene terephthalate, may contain polybutylene terephthalate, poly 1,4-cyclohexane dimethylene terephthalate, etc., and may also be a copolymer. Furthermore, the above-mentioned flame retardant, heat resistant agent, pigment, etc. may be included. The cross section of the splittable conjugate fiber according to the present invention that can be divided into five or more segments is as shown in FIGS.

In particular, A, b, and d are representative ones whose cross sections are composed of segments of a polyamide component that branches radially and segments of a polyester component that complement the radial portion, and c is
A typical example consisting of a polyamide component segment whose cross section branches radially, a polyester component segment that complements the radial portion and has a model recess facing toward the center, and a wedge-shaped polyamide component segment that complements the recess. be. The splittable composite fiber only needs to be split into a total of 5 or more segments, and the polyamide and polyester may each be split equally or at a ratio close to that, but at least one of the split polyamide segments is 0.
．． It is more preferable if it has a denier of 4 or more.

It is also desirable that the polyester component be divided into more segments and that the polyester segments can form ultrafine fibers of 0.05 to 0.3 denier. As described below, this is achieved by partially heat-sealing polyamide segments near the melting point of polyamide, allowing the partially fused polyamide segments to play the role of a steel frame in a building, maintaining the strength of the nonwoven fabric, and using ultra-fine polyester fibers. This is because the polyamide skeleton is to be randomly entangled with the polyamide skeleton. In this sense, it is necessary that the bonding ratio of polyamide and polyester be 1:5 to 5:1, and that the denier of the single yarn be 3 or less. Further, it is preferable that the joining ratio is 1:3 to 3:1 and the denier of the single yarn is 2 or less. That is, if the ratio of the polyamide component is low, the strength of the resulting nonwoven fabric will not be sufficient even if the divided polyamide segments are heat-sealed. Moreover, if the ratio of the polyamide component is too high, the polyamide skeleton will be too large, and the permeability effect of the ultra-fine polyester segments will not be fully exhibited. In other words, splittable composite fibers,
Consisting of segments of a polyamide component that branch radially in its cross section and segments of a polyester component that complement the radial portion, or complement segments of a polyamide component that branch radially in its cross section and the radial portion. However, in the case of a composite fiber consisting of a segment of a polyester component having a model concave portion facing toward the center and a segment of a wedge-shaped polyamide component that complements the concave portion,
The above idea can be more than satisfied. Next, a conventional method may be used to manufacture a web from the resulting splittable conjugate fibers.

For example, the splittable composite fiber extruded from the spinneret hole is stretched to have a monolithic denier of 3 deniers or less, and then cut into short fibers, and preferably after being crimped at this time, the fibers are cut into short fibers. Then, after forming the composite fibers into a web using a random webber, the composite fibers are needle punched to make them three-dimensional, or the spun composite fibers are directly accumulated on a belt to form a web, so-called spunbond. (This includes the so-called sprayed fiber method, which produces nonwoven fabrics made of short fibers, and the so-called spunbonded method, which produces nonwoven fabrics made of long fibers.). In addition, the aforementioned short fibers are 25 to 10 T, especially 30 to 80 T! A material cut to a length of Rm can be suitably used. The splittable conjugate fibers constituting the nonwoven fabric thus obtained are divided into 5 or more segments and subjected to a 70% treatment using a solvent that swells polyamide or does not swell polyester.

The solvent used for this may be any solvent as long as it does not swell the polyester, such as pencil alcohol and its derivatives, phenol, formic acid, acetic acid, etc., and an aqueous solution of 1 to 99%, preferably 5 to 30% of these. Or it is made into a water-based emulsion. Further, the treatment temperature is preferably 40 to 90°C. The nonwoven fabric is immersed in the aqueous solution or aqueous emulsion for 2 minutes or more, squeezed with a mangle, and then washed with water. The longer the soaking time, the more uniform the division.
If the immersion is too long, the polyamide will expand too much and become brittle, so it is desirable to immerse the polyamide for 5 to 6 times. After washing with water, the nonwoven fabric has entangled composite fibers that are completely divided into five or more segments, as shown in FIG. After drying the nonwoven fabric, it is needle punched again. As a result, the entangled ultrafine fiber bundles are further loosened and densified.
However, since the fibers are ultra-fine, the threads are slightly cut due to needle penetration, resulting in a decrease in strength, but this does not pose a particular problem in the present invention. That is, the re-needled nonwoven fabric is then subjected to pressure heat treatment at a temperature of 200 to 250°C, preferably 210 to 230°C, using a metal flat plate hydraulic press machine having hot plates on the upper and lower surfaces. At temperatures below 200°C, the polyamide will not fuse at all, and at temperatures above 250°C, the melting of the polyamide will be too intense and the film-like layer of polyamide will feel too strong, and even the polyester will be heat-fused. Sometimes.

The time required for heating and pressing may be within a range in which the ultrafine polyamide in the nonwoven fabric is thermoplasticized or semi-melted and the polyamide ultrafine fibers are partially fused, and the temperature is 240 to 250°C.
Within this range, it is better to do it in the shortest possible time. In the nonwoven fabric produced by the above method, as shown in FIG. Ultra-fine polyester fibers held together are intertwined with each other.

Therefore, the nonwoven fabric obtained by the method of the present invention has high strength, has a large surface area per unit volume because the ultrafine fibers are tightly intertwined, and can be used as a single unit as a high-performance filter with extremely high filtering efficiency. It becomes.
8. Next, the method of the present invention will be specifically explained using examples. Incidentally, "1%" in Examples means 1% by weight unless otherwise specified. Example 1 Nylon-6 and polyethylene terephthalate were each melted using an extruder and extruded from a composite spinning nozzle, and the bonding ratios of nylon-6 and polyethylene terephthalate were 1:8, 1:5, 1:3, 1:1, 3: 1,5:1
, 8:1, seven types of split composite filaments having cross sections as shown in FIG. After winding at a speed of /Min, it is stretched at a stretching ratio of 3.2 with a roller heater at 85°C and a plate heater at 150°C to form a 45d
/28f composite filament was obtained.

In the filament, A in FIG. 1b was a nylon-6 component and B was a polyethylene terephthalate component. This composite filament is 51w! Cut into n short fibers, use a random webber to make a web, and heat the web at 200X
．． The nonwoven fabric obtained by needle punching was immersed in an aqueous emulsion of 15% benzyl alcohol at 50°C for 5 minutes, then squeezed with a mangle, washed in a 30°C water bath, and placed in a hot air dryer at 100°C. and dried. A portion of the nonwoven fabric was cut out and observed under an electron microscope, and the result was as shown in FIG. The obtained nonwoven fabric was again treated with 10CyX. /d After needle punching, the hot plates on the upper and lower surfaces were pressurized at 10 k9/d for 1 minute using a metal flat plate hydraulic press machine that was kept at 215°C. The shape of the obtained nonwoven fabric filter was observed again using an electron microscope and was found to be as shown in FIG. The filter performance of the nonwoven fabric in each step is shown in Table 1, and the strength of the finally obtained nonwoven fabric filter is shown in Table 2. From the above two tables, the bonding ratio is 1:5 to nylon 6:polyethylene terephthalate.
It is clear that 5:1 has high filtration efficiency and high strength.

Example 2 Nylon 6 and polyethylene terephthalate were each melted using an extruder and extruded from a composite spinning nozzle to form a split composite filament having a cross section as shown in FIG. After winding at a speed of /Mln, the filament was drawn 3.2 times to obtain a composite filament of 50C1/28f.

In this filament, A in Figure 1 C is nylon 6.
Component B was a polyethylene terephthalate component.
The filament was cut into short fibers of 51 wn and made into a web using a random webber. The web was needle punched at 20 pots/d. The obtained nonwoven fabric was immersed in an aqueous emulsion of 15% benzyl alcohol, and 80° The temperature was raised to C and treated for a few minutes, followed by washing with water and drying. The nonwoven fabric is 1
00 pieces/d After needle punching, a metal flat plate hydraulic press machine that changes the temperature of the hot plate on the top and bottom surfaces punches 10k9/d ~
Pressure was applied for 1 minute. Table 3 shows the performance of the obtained nonwoven fabric filter. From the above, if the temperature is less than 200°C, the tensile strength and tensile efficiency are insufficient, and if the temperature is less than 250°C.
It can be seen that when the temperature is higher than that, the ventilation becomes poor. Example 3 Nylon 6 and polyethylene terephthalate were each melted using an extruder and extruded from a composite spinning nozzle, and the bonding ratio of nylon 6 and polyethylene terephthalate was 1:
3. After winding a split composite filament having a cross section as shown in FIG. 1b of 1 at a speed of 7007TL/Mln.
It was stretched 5 times to obtain a composite filament of 75d/48f.

In this filament, A in Figure 1b is nylon 6.
Component B was a polyethylene terephthalate component.
After the filament was crimped, it was cut into a length of 75 wurL to obtain short fibers. Next, a random web was used to form a web, and the web was needle punched at 10 discharges/d. The obtained nonwoven fabric was immersed in a 10% aqueous benzyl alcohol emulsion at 500C, wrung out with a mangle, washed with water, and dried. After drying, 100 needles/d were punched again, and then 2 needles were punched at 20k9/d using a metal flat plate hydraulic press machine.
Pressing was carried out at 10° C. for 1 minute. The density of the obtained nonwoven fabric filter is 0.075y/C! 11 thickness is 5.1Tr0n, tensile strength is 11.5k9/α, overload efficiency is 89%, and 0
．． For ventilation of 17TL,/Sec, the pressure loss is 10.
2? It was H2O.

[Brief explanation of drawings]

FIGS. 1a to 1e are cross-sectional views of examples of splittable composite fibers used in the present invention. In the figure, A indicates a segment of the polyamide component, and B indicates a segment of the polyester component.

Claims (1)

[Scope of Claims] 1. A split-type composite in which polyamide and polyester are bonded in a longitudinal direction at a bonding ratio of 1:5 to 5:1 and have a cross section that can be divided into 5 or more segments and have a single fiber fineness of 3 denier or less. A web made of fibers is treated with a solvent that swells polyamide but not polyester, and the composite fibers constituting the web are divided into segments, then needled, and pressure treated at a temperature of 200 to 250°C to form polyamide. A method for producing a high-performance filter characterized by fusing components. 2. The splittable conjugate fiber consists of a segment of a polyamide component that branches radially in its cross section and a segment of a polyester component that complements the radial portion, or a segment of a polyamide component that branches radially in its cross section. Claim 1, which is a composite fiber comprising: a segment of a polyester component having a wedge-shaped concave portion that complements the radial portion and faces toward the center; and a segment of a wedge-shaped polyamide component that complements the concave portion. the method of. 3. The method according to claim 1, wherein the web is formed using splittable conjugate fibers in the form of short fibers. 4. The method according to claim 3, wherein the splittable composite fiber is crimped and then cut into short fibers. 5. The method according to claim 1, wherein the solvent is benzyl alcohol.