JPH0444011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrafine fiber structure made of two types of fluororesins and having excellent hookability, abrasion resistance, tensile strength, etc., and excellent workability, and a method for producing the same. More specifically, we have an ultrafine fiber structure made of two types of fluorine-based resins with an average fineness of 0.0001 to 0.9 denier, and a sea-island structure fiber structure in which the fluorine-based resin is used as an island component and a specific polyolefin is used as a sea component. The present invention relates to a method for producing the ultrafine fiber structure, which comprises solvent treatment.

Some fluorocarbon resins have extremely excellent properties, such as good water repellency, oil repellency, and stain resistance, but the industrial use of fluorocarbon resin microfibers with these properties is limited. There are things that are immeasurable. However, one of the weaknesses of such resins is that they have low tensile strength. Such weaknesses pose a major problem in fully demonstrating the above-mentioned excellent properties industrially.
For example, when a cloth made of fluorocarbon resin that takes advantage of water repellency or stain resistance is put into practical use, the cloth cannot withstand long-term use due to hooking, pulling, or abrasion effects due to the low strength of the fibers. Sometimes.

The present inventors have conducted extensive research to solve these problems associated with fluorocarbon resin ultrafine fiber structures, and have found that it is necessary to increase the tensile strength of the first fluorocarbon resin fiber structure itself. By kneading and spinning a second fluorocarbon resin with high tensile strength at a certain ratio, microfiber structures such as nonwoven fabrics, etc. can be created without impairing the excellent properties of the first fluorocarbon resin. It has been found that the resistance of textiles, etc. to hooking, pulling or abrasion can be improved.

Therefore, the present invention provides a mixture of a fluororesin (A) having excellent surface properties and a fluororesin (B) having high mechanical strength, with an average fineness of 0.0001 to 0.9.
A denier fluorocarbon resin ultrafine fiber structure and a mixture of the fluorocarbon resins (A) and (B) are hot-melted and kneaded with a polyolefin having a melt index of 3 or less, and the resulting mixture is spun. and optionally entangled to obtain a sea-island fiber structure having fluororesin as an island component and polyolefin as a sea component, and then removing the polyolefin with a solvent, which is characterized by an average fineness of 0.0001 to 0.9. The present invention provides a method for producing a denier fluorine resin ultrafine fiber structure. Here, the fiber structure of the present invention includes those in the form of yarn, woven fabric, knitted fabric, web, nonwoven fabric, and the like.

Examples of the fluororesin (A) having excellent surface properties, such as excellent water repellency, oil repellency, stain resistance, and heat resistance used in the present invention, include copolymers containing tetrafluoroethylene as a main component. In particular, copolymers of perfluorofluorine monomers, such as copolymers of tetrafluoroethylene and hexafluoropropylene copolymers or copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers, and furthermore, copolymers of tetrafluoroethylene and perfluoroalkyl vinyl ethers are used. Examples include copolymers with perfluoroalkyl acrylates, and mixtures thereof. In addition, a third copolymer such as vinyl fluoride,
A small amount of vinylidene fluoride, ethylene trifluoride, ethylene chloride trifluoride, etc. may be used.

Examples of the fluororesin (B) having high mechanical strength used in the present invention include copolymers of tetrafluoroethylene and ethylene, copolymers of tetrafluoroethylene and trifluorochloroethylene, and the like. There is a mixture of All of these copolymers have heat resistance and are thermally stable even when kneaded and extruded with fluororesin (A), while their tensile strength alone is higher than that of fluororesin (A). It is significantly larger than .

Such fluororesin (A) and fluororesin
(B) is mixed, kneaded and melt extruded, but these resins must not be chemically mixed during the kneading and melt extrusion. At least the respective crystal systems must not change or become amorphous. If the fibers do not have at least each crystal structure independently, the strength of the ultrafine fiber structure obtained by kneading, extrusion spinning, and optionally entanglement followed by solvent treatment will be insufficient.

Furthermore, these fluororesins (A) and (B) need to be sufficiently oriented during spinning by selecting the polyolefin used as the sea component in order to shape the sea-island fiber structure. This is because the mechanical strength of the fluororesin (B) is significantly different, especially when it is sufficiently oriented and when it is not. For example, the tensile strength of non-oriented and highly oriented polytetrafluoroethylene-ethylene copolymer, which is one of the fluororesins (B), is 4.
Kg/mm ² and 10 Kg/mm ² , and even more highly oriented ones can reach 30 Kg/mm ² or more. On the other hand, the tensile strength of the fluororesin (A) is usually 2 to 3 kg/mm ² .

These fluororesins (A) and (B) have a temperature of 1 at 320°C.
×10 ³ to 8 × 10 ⁴ poise, more preferably 5 × 10 ³
It has a melt viscosity of ~5×10 ⁴ poise and a high melting point. Therefore, the processing temperature for these resins is usually 280°C or higher. In order to obtain sufficient spinnability, a processing temperature of 300°C or higher is preferred.

It is preferable that the melt viscosities of the fluororesins (A) and (B) be as close as possible. This is possible if the viscosity ratio of the fluororesin (A) and (B) is within the range of 0.2 to 5.
If the difference is greater than this, the fluororesin having a lower viscosity will not be sufficiently oriented and the fibers will not be sufficiently thin.

Furthermore, the weight mixing ratio of fluororesin (A) to (B) is 20:
It is preferably within the range of 80 to 80:20, more preferably within the range of 35:65 to 65:35. This is because if the weight ratio of fluorocarbon resin (A) is less than 20, it will not exhibit the same properties as perfluorophore resin in terms of water repellency, oil repellency, chemical resistance, etc., whereas if the weight ratio is more than 80, such properties will not be exhibited. This is because there is no industrial advantage in terms of hooking, tensile or frictional strength of structures made using fibers.

In order to sufficiently orient each of these resins in the ultrafine fiber structure made of these fluorocarbon resins (A) and (B), it is necessary to create a sea-island structure that is obtained intermediately during the production of the ultrafine fiber structure. The sea component resin of the fiber structure has a melt viscosity comparable to that of these fluorocarbon resins, and although it is not compatible with these fluorocarbon resins, it has an affinity to the extent that they can be micromixed during melting. In addition to satisfying the conditions of the presence of a solvent that can be dissolved and removed, it must also have sufficient spinnability during extrusion spinning.

As a result of studying a large number of thermoplastic resins, the present inventors found that a polyolefin having a melt index of 3 or less could satisfy these requirements, and completed the present invention.

Known resins such as polyethylene, polypropylene, ethylene-based copolymers, propylene-based copolymers, polyisoprene, polybutylene, and mixtures thereof are used as such polyolefins. ,
Polyethylene and polypropylene are preferably used from the viewpoint of economy.

The polyolefin used in the present invention is thermally stable enough to be hot-melted and kneaded with the fluororesins (A) and (B), and has a weight loss rate of 0.05%/min under a nitrogen atmosphere at 350°C. It is preferable that it is below. Polystyrene, polymethyl methacrylate, etc., which are used as sea components in general sea-island manufactured fibers, have a high weight loss rate when heated and are thermally unstable, so they cannot be used from the standpoint of thermal stability. Can not.

Melt index is 3 or less, preferably 1.5~
0.01 polyolefin has a high melt viscosity and can be micromixed with fluorine fibers (A) and (B) by hot melt kneading, extrusion spinning, and optionally entangling to form a sea-island fiber structure. can be formed. Polyolefins with a melt index greater than 3 have a low crystalline melting point and are extremely fluid polymers above that melting point, so the melt viscosity during coextrusion is too low and there is no stringiness, resulting in an unsatisfactory sea-island fiber structure. Even if it were possible, the fluororesins (A) and (B) could not be made into sufficiently thin fibers during spinning. Furthermore, it is impossible to highly orient the fluororesins (A) and (B), and only fibers with poor properties can be obtained. Note that the melt index was measured based on JIS K-760. By using polyolefin with a melt index of 3 or less in this way, fluorocarbon resins (A) and (B)
When hot melt-kneaded and extrusion-spun, it exhibits sufficient spinnability and forms fibers with a sea-island structure. It is possible to obtain a fluorine-based resin mixed fiber with a high degree of strength.

Fluorine resin (A) obtained by such a method
It can be seen that the degrees of orientation π of and (B) both show values of 0.6 or more, indicating sufficient orientation.

The mixing ratio of polyolefin and all-fluorinated resin is such that the all-fluorinated resin can form an island structure, and the remaining fluorinated resin can be recovered as ultrafine fibers when the polyolefin is dissolved and removed. used. In terms of weight ratio, the ratio of all fluorine resin to polyolefin is preferably 1:0.01 to 2.5, particularly preferably 1:0.3 to 2.0. If there is too much polyolefin, the length of the ultrafine fibers of the fluorocarbon resin will be shortened, and the efficiency will be poor. If there is too little polyolefin, the fluorocarbon resin fibers will become too thick or will stick together, making it difficult to form uniform ultrafine fibers. I can't get it.

The fluororesin (A), the fluororesin (B), and the polyolefin may be in powder form or may be mixed as pellets, but by mixing the three, hot-melting, kneading, and extrusion spinning, sea islands can be formed. Structural fibers can be formed. The hot melt kneading may be carried out by any method as long as the three components are melted and kneaded sufficiently, but it is usually carried out by kneading the mixture in a hot extruder and then extruding it into pellets. The temperature of the die part of the extruder is usually preferably 280 to 360°C. It is desirable to repeat this pelletizing process two or more times to ensure sufficient kneading. It is preferable that the resin mixture sufficiently kneaded in this way is spun using a general spinning machine to form fibers having a fineness of about 30 to 300 deniers. At this time, the extruded yarn is spun by winding it up at high speed. The draft ratio is preferably in the range of 50 to 1000, and the fibers thus obtained can be sufficiently drawn to obtain long fibers with a sea-island structure. If the draft rate is not sufficient, the fluorocarbon resin will not be stretched and orientation will not be achieved. Therefore, the fiber shape does not become thin, the fibers do not have the desired fiber length, and because the degree of orientation is low, only low strength can be obtained.

Incidentally, the sea-island structure fiber thus obtained can also be further cold-stretched. Next, the sea-island structure fiber is treated with a solvent to remove the polyolefin to obtain a mixed ultrafine fiber of fluorocarbon resin (A) and fluorocarbon resin (B), and from this fiber, for example, a nonwoven fabric is made and an ultrafine fiber structure is obtained. can be obtained. However, if the fibers are made into ultra-fine fibers, the fibers are so thin that it is often difficult to obtain a cloth-like product through post-processing. Therefore, the sea-island structure fibers can be pre-entangled to form a fiber entangled body (woven fabric, knitted fabric, non-woven fabric, etc.) and then subjected to solvent treatment to obtain an ultrafine fiber structure. The term "entanglement" here refers not only to making the material into a widely entangled state, for example, making it into a non-woven fabric, but also includes knitting and weaving using known methods. Since the sea-island structure fiber has a certain yarn diameter, it has the advantage that a fiber entangled body with a large area can be easily obtained. In addition, since such sea-island structure fiber entangled bodies are essentially made by knitting and interweaving fibers, they often have irregularities and gaps in the thickness of the fibers, and are more difficult to form than those made of mixed fluororesin fibers. When it is desired to obtain a membrane having uniform micropores, it is desirable to make the entangled body as dense as possible at this stage. In order to obtain this dense structure, it is preferable to heat-treat woven fabrics, knitted fabrics, non-woven fabrics, etc. at temperatures above the melting point of polyolefin and below the melting points of fluorocarbon resins (A) and (B). Coalescence is obtained, and finally a uniform fine porous membrane (non-woven fabric-like material) can be obtained. Furthermore, by heat-treating the entangled body under pressure, a dense structure can be obtained, which is a desirable method.

When the polyolefin, which is a sea component, is completely removed from the thus obtained sea-island structure fibers and the entangled body using a solvent, a filamentous or porous membrane-like fiber structure made of ultrafine fluorine resin fibers is obtained.

The temperature for dissolving and removing polyolefin with a melt index of 3 or less, which is a sea component, from a fiber structure with a sea-island structure is preferably in the range of room temperature to 200°C. Examples include aromatic hydrocarbons, halogenated aliphatics, halogenated cyclized resins, halogenated aromatic hydrocarbons, aliphatic esters having a total carbon number of 8 or more, ketones, and diacyl ethers. Specifically, tetrachlorethylene, etc. at 40℃ or higher, paraxylene, ortho-xylene, metaxylene, etc. at 60℃ or higher, n-butyl acetate, etc. at 100℃ or higher, diphenyl ether, tripalmitin, etc. at 110℃ or higher. Tetralin, diphenyl oxide, diphenyl, n-hexane, 1-dodecanol, n-decanol, anisole, nonylphenol, octylphenol, n-octanol, benzyl phenyl ether, p-tertiary amyl alcohol, nitrobenzene, dibutyl phthalate, etc. 150 Squalene, glycoldipalmitate and the like at temperatures above 0.degree. C. are preferably used. The dissolution time can be appropriately selected depending on the type of solvent and temperature.

When the polyolefin is completely dissolved, an ultrafine mixed fiber structure of fluorocarbon resins (A) and (B) remains, which can be washed with acetone, benzene, etc. to obtain a mixed fiber structure. The mixed fiber structure obtained in this way has each degree of orientation (π) of 0.6
It is composed of ultrafine fibers with a fineness of 0.001 to 0.9 denier, and has excellent water repellency, oil repellency, and mechanical strength. Therefore, for example, in the case of a nonwoven fabric, the fabric is extremely flexible and has the property of repelling water and oil. When such cloth is used to make sportswear, for example, the clothing has excellent breathability and water vapor permeability, does not allow water droplets to pass through, and is extremely resistant to stains caused by sweat. On the other hand, when such a nonwoven fabric is also used for carpets, etc., it becomes extremely stain resistant compared to conventional carpets, and even if it does become somewhat soiled, it can be easily removed.

Furthermore, non-woven fabrics made of such thin fibers can be used as filters to remove small particles from the air, but even when used in such filters, there is extremely little deterioration due to long-term use, and there is no adhesion. It is easy to remove dirt and reuse.

Furthermore, by making such ultrafine fibers into a mat shape, it can be made into an industrial filter cloth.
Since this material is resistant to most chemicals, it can be used in a wide range of industrial and medical applications.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but these Examples are not intended to limit the present invention.

Example 1 Melt viscosity at 320℃ as fluororesin (A) 2×10 ⁴
Poise, 0.5 kg of tetrafluoroethylene-hexafluoropropylene copolymer (Teflon FEP110 manufactured by DuPont) with a contact angle of 108 degrees with water at 25℃, and fluorocarbon resin
(B) Dissolution viscosity at 320℃ 1.2 × 10 ⁴ poise, 25
Tetrafluoroethylene-ethylene copolymer with a contact angle of 94 degrees with water at ℃ (Akron COP C- manufactured by Asahi Glass Co., Ltd.)
55A) as polyolefin, melt index 0.5, melt viscosity at 320℃ 0.8×
10 ⁴ , the rate of weight loss under nitrogen atmosphere at 350℃ is
0.008% by weight/min of polyethylene (Shorex S6006M, manufactured by Showa Denko KK) was blended in the form of 1 kg pellets, which were then extruded into pellets using an extruder.

The temperature conditions during extrusion were 250°C, 270°C, 300°C, and 320°C from the hopper side to the die side, and the temperature at the die part was 320°C. The pellets thus obtained were extruded and pelletized again using the same machine under the same temperature conditions to improve the kneading effect.

The obtained pellets are heated at 320℃ through a nozzle with a diameter of 1 mm.
It was spun with The draft rate at that time was 200.
The sea-island structure fiber thus obtained was 58 denier. Next, the obtained fibers were treated with paraxylene, a solvent for polyethylene, at 120°C for 2 hours. The fibers were taken out of the solvent and treated again with fresh paraxylene at 120°C for 1 hour, then taken out and immersed in benzene. Further, it was immersed in acetone, taken out and dried.

The obtained ultrafine fibers are eyelash white cotton-like, and as a result of observation under a microscope, these fibers have a diameter of 0.1μ to 1μ.
It was confirmed that it was an aggregate of fibers of about (0.00015 to 0.015 denier).

On the other hand, the obtained sea-island structure fiber (average fineness: 58
As a result of X-ray diffraction photograph measurements of
It was an aggregate of highly oriented ultrafine fibers with a diameter of 0.86. This X-ray photograph is shown in Figure 1.

The degree of orientation (π) was determined by calculating the half-width by determining the half-width from a photograph taken by the diffraction X-ray method of the sea-island structure fibers before entanglement. In other words, from the wide-angle X-ray diffraction photograph, we focus on the diffraction arcs that indicate the reflection of the crystals of fluororesins (A) and (B), find the half-width Δθ of the intensity distribution in the circumferential direction of the diffraction arcs, and calculate this value. The degree of orientation was calculated from π=180−Δθ/180.

Here, the fluororesin (A) is a tetrafluoroethylene-hexafluoropropylene copolymer, and the fluororesin (B) is a tetrafluoroethylene-ethylene copolymer. In FIG. 1, A1 is the diffraction arc of the fluororesin (A), and B1 is the diffraction arc of the fluororesin (B) crystal.

Example 2 The 58 denier sea-island fiber was cut into short fibers of 3 cm, and the sea-island fiber was dispersed in water, disintegrated, and papered on a wire mesh to obtain a mat with a uniform thickness of 1 cm. After drying this pine in air at 70℃, heat press (~
100℃) and densified. This material was treated with hot paraxylene to dissolve and remove the polyethylene, and then washed with benzene and acetone to obtain a nonwoven mat. The nonwoven pine thus obtained was a supple nonwoven pine, and water formed into droplets on the nonwoven pine and fell off when it was tilted, showing complete water repellency. In addition, the air permeability was measured using JISP-8117B type and was less than 1 (sec/100c.c.).

This non-woven mat was cut to a width of 5 cm, and the tensile strength was measured using a tensile tester with a sample length of 2 cm.
It showed a breaking strength of 520Kg/ ^cm2 .

[Brief explanation of drawings]

Figure 1 shows the X of the ultrafine fiber structure obtained in Example 1.
This is a line diffraction photograph.

Claims (1)

[Scope of Claims] 1. A fluorine-based resin having an average fineness of 0.0001 to 0.9 denier, which is made of a mixture of a fluorine-based resin (A) having excellent surface properties and a fluorine-based resin (B) having high mechanical strength. Resin microfiber structure. 2 Comprising a fluororesin (A) with a water contact angle of 100° or more at 25°C and a fluororesin (B) with a tensile strength of 5 kg/mm ² or more, the resin (A) and (B) ) The fluororesin ultrafine fiber structure 3 according to claim 1, wherein the weight mixing ratio of fluororesin (A) or (B) is 20:80 to 80:20. The fluorine-based resin microfiber structure according to claim 1, wherein each of the fluorocarbon resin microfiber structures has a degree (π) of 0.6 or more. 4 A mixture of a fluororesin (A) having excellent surface properties and a fluororesin (B) having high mechanical strength is hot-melted and kneaded with a polyolefin having a melt index of 3 or less. The resulting mixture is spun and optionally entangled to obtain a sea-island structure fiber structure having fluororesin as an island component and polyolefin as a sea component, and then the polyolefin is removed with a solvent. A method for producing a fluorocarbon resin ultrafine fiber structure with an average fineness of 0.0001 to 0.9 deniers. 5 The fluororesin (A) has a water contact angle of 100° or more at 25°C, the fluororesin (B) has a tensile strength of 5 Kg/mm ² or more, and the resin (A) The weight mixing ratio of B) is
20:80 to 80:20, the method for producing a fluorocarbon resin ultrafine fiber structure according to claim 4. 6 Claim 4, wherein the weight mixing ratio of polyolefin and fully fluorine resin is 1:0.01 to 2.5.
5. A method for producing a fluororesin ultrafine fiber structure according to item 5.