JPS648747B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing an antistatic polyurethane elastic fiber nonwoven fabric. Conventional Technology A wide variety of nonwoven fabrics have been proposed and used in many fields, but most of these nonwoven fabrics are composed of inelastic polymers such as polyamide, polyester, and polyolefin. Antistatic nonwoven fabrics made of highly elastic fibers such as polyurethane elastomer have not been put to practical use. Several proposals have been made so far regarding nonwoven fabrics made of polyurethane elastic fibers. For example, Japanese Patent Publication No. 43-26578 proposes treating a web made of short fibers of polyurethane elastic fibers with aldehyde. Furthermore, Japanese Patent Publication No. 43-26592 proposes subjecting a web made of short fibers of polyurethane elastic fibers to heat and pressure treatment. Furthermore, Japanese Patent Publication No. 52-81177 proposes a method in which a polyurethane elastomer is dry-spun to form a web containing a solvent, and then the solvent is removed. However, in any of the methods, the resulting nonwoven fabric tends to have weak bonds between fibers and to be coarse and rigid, making it impossible to obtain a high-quality product. Furthermore, the manufacturing process becomes complicated, which is extremely disadvantageous economically. Furthermore, no efforts have been made to impart antistatic properties. At present, there is currently no known method for manufacturing an antistatic polyurethane elastic fiber nonwoven fabric in an industrially advantageous manner. Problems to be Solved by the Invention Under the current circumstances, the present inventors have conducted intensive research and examination on the production of antistatic polyurethane elastic fiber nonwoven fabrics, and have completed the present invention.
That is, an object of the present invention is to provide an antistatic polyurethane elastic fiber nonwoven fabric. Another object is to provide an industrially advantageous method for manufacturing such nonwoven fabrics. Means for Solving the Problem In the method of the present invention, after adding and kneading a polyisocyanate compound to a molten polyurethane elastic body, when manufacturing a nonwoven fabric by a melt blowing method, conductive fibers are entrained in a high-speed air stream together with the polyurethane elastic fibers. It is characterized in that it is deposited and collected in a sheet form and contains 0.05 to 5% by weight of the dielectric fiber. As the polyurethane elastomer applied to the present invention, known segmented polyurethanes can be used, but melt-spuntable thermoplastic polyurethane elastomers are particularly suitable. Such a polyurethane elastomer is made of a low melting point polyol with a molecular weight of 500 to 6000, such as dihydroxy polyether, dihydroxy polyester, dihydroxy polycarbonate, dihydroxy polyester amide, etc.
The following organic diisocyanates, such as P, P'-
diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate,
Polymers obtained by reacting hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, 2,6-diisocyanate methyl caproate, hexamethylene diisocyanate, etc. with a chain extender having a molecular weight of 500 or less, such as glycol, amino alcohol, or triol. It is. Among these polymers, particularly good are polyurethanes using polytetramethylene glycol, polyε-caprolactone, or polybutylene adipate as the polyol. When polyethylene glycol is used as a polyol, it improves hydrophilicity and is therefore used for special purposes. In addition, as an organic diisocyanate,
P,P-diphenylmethane diisocyanate is preferred. Furthermore, P,P'-bishydroxyethoxybenzene and 1,4-butanediol are suitable as chain extenders. The polyisocyanate compound used in the present invention is preferably a compound having at least two isocyanate groups and having an average molecular weight of 400 or more,
For example, it can be synthesized by reacting a polyol with a molecular weight of 500 to 6,000 used in the synthesis of polyurethane elastomer with twice the molar amount of an organic diisocyanate with a molecular weight of 500 or less. At this time, a compound having three or more hydroxyl groups may be used as the polyol. Also used are organic diisocyanate duplexes. Suitable polyisocyanate compounds include polytetramethylene glycol having a molecular weight of 500 to 2000 and having hydroxyl groups at both ends, polycaprolactone, or polybutylene adipate containing P,P'-
A compound to which double mole of diphenyl diisocyanate is added can be mentioned. The amount of the polyisocyanate compound added is preferably 5 to 30% by weight, particularly preferably 10 to 20% by weight. The amount added varies depending on the type of polyisocyanate compound used, but if the amount added is small, the intended physical performance of the polyurethane nonwoven fabric will be insufficient and the effect of improving spinning operability will be small.
Moreover, if the amount added is too large, non-uniform mixing, deterioration of yarn quality, etc. tend to occur, and the spinning operation becomes unstable, which is not preferable. The molecular weight of the polyisocyanate compound used in the present invention is usually 400 or more, preferably 800 to 3,000. The molecular weight of the polyisocyanate compound applied to the present invention is the apparent molecular weight calculated from the isocyanate group weight measured by amine titration. The conductive fiber used in the present invention has a length of 1
It is preferable that the electric resistance of a single yarn per cm (measured by applying about 100 V/cm of DC) is 10 ¹⁰ Ω/cm or less. Such conductive fibers include thin metal wires (e.g., silver, copper, aluminum, stainless steel, etc.), organic fibers plated with metals or conductive metal compounds (e.g., indium oxide, etc.), and organic fibers coated on the surface or inside of organic fibers. Conductive metal compounds (e.g. copper iodide,
(copper sulfide, indium oxide, etc.) formed by chemical means, organic fibers with a conductive resin film containing conductive particles such as carbon black, and conductive polymers containing conductive particles such as carbon black. Examples include those in which a conductive layer (conductive layer) and a non-conductive polymer are combined during spinning. Conductive particles other than carbon black include metal particles, metal compound (semiconductor) particles such as zinc oxide, tin oxide, and copper sulfide, and inorganic particles such as titanium oxide particles that contain zinc oxide, tin oxide, and indium oxide on the surface. Examples include those in which conductive metal oxides such as these form a metal film. All of the above-mentioned conductive fibers can be used for the purpose of the present invention, but fine metal wires are more difficult to handle than organic fibers, and fibers with a conductive film on their surface tend to have the film peeled off due to friction. Therefore, conductive composite fibers in which a conductive component and a non-conductive component are combined during spinning are most preferable. Conductive fibers account for 0.05% to 5% by weight of the total weight of the nonwoven fabric.
It is preferable to contain it, more preferably 0.1% to 3
Weight%. The content varies depending on the type of conductive fiber used, but if the content is small, it will be difficult to obtain the desired antistatic performance. If the content is too large, the antistatic performance will improve, but this is the greatest feature of the polyurethane elastic fiber nonwoven fabric. It is not preferable because flexibility and elasticity are impaired. The meaning of adding and kneading a polyisocyanate compound to the polyurethane elastomer of the present invention is that the added and kneaded polyisocyanate compound reacts to form crosslinks after fiber formation. Its properties are completely different from that of the body, and it is insoluble in solvents such as dimethylformamide or tetrahydrofuran at room temperature. Therefore, the nonwoven fabric of the present invention has high strength and excellent stretch recovery properties, and exhibits performance that has not been available in the past. The polyisocyanate compound used in the method of the present invention not only improves the physical properties of the resulting nonwoven fabric, but also has the effect of lowering the melt viscosity of the polyurethane elastomer during the spinning process, making it possible to lower the spinning temperature. It becomes easy to avoid thermal decomposition of the polyurethane elastomer, and spinning operability is improved. In addition, since the polyurethane elastic fibers deposited as a nonwoven fabric have high adhesiveness, the bond with the conductive fibers becomes strong, and a nonwoven fabric can be easily obtained by pressing or the like without using an adhesive. The production of the nonwoven fabric of the present invention involves a part for melt extruding the thermoplastic polyurethane elastomer, a part for adding and mixing the polyisocyanate compound, a spinning device equipped with a spinning head for the nonwoven fabric, and a part for supplying the conductive fibers with a high-speed air stream. Preferably, it is carried out by a device. As such a spinning device, a known device used for adding a modifier during spinning can be used. As a spinning head for nonwoven fabrics, any known shape can be used, but a spinning head equipped with a nozzle for discharging molten polymer and slits on both sides of the nozzle for discharging heated inert gas is particularly suitable. Such a spinning head is described, for example, in Japanese Patent Publication No. 41-7883. Although it is possible to use a kneading device having a rotating part in the part where the polyisocyanate compound is added to and mixed with the molten polyurethane, it is more preferable to use a mixing device having a stationary kneading element. . As the mixing device having a static kneading element, a known one can be used. The shape and number of elements of the static kneading element will vary depending on the conditions of use, but should be selected so that sufficient mixing of the polyurethane elastomer and polyisocyanate compound is completed before they are discharged from the spinneret. is essential. In addition, a known air suction car can be used as a device for supplying conductive fibers, but
It is preferable to have a thread speed meter so that the feed rate can be controlled. The installation method or number of air suction cars is as follows:
The conductive fibers differ depending on the dispersion state or content of the polyurethane elastic fibers on the non-woven fabric surface, but for example, one method is to shake the head from side to side with one air sukkah and incorporate the conductive fibers in a V-shape on the non-woven fabric surface, or Depending on the purpose of use of the product, methods and numbers can be used, such as a method in which several fixed air suction wheels are used to contain the liquid in a straight line, or a method in which several air suction cars are oscillated to be applied over the entire surface. It is important to select it appropriately. Regarding the installation location of the air sukkah, for example, a method of installing the air sukkah such that the conductive fibers are also deposited on the same line where the polyurethane elastic fibers are sprayed and deposited on the net;
Alternatively, the polyurethane elastic fiber nonwoven fabric may be attached in any location before it is wound up as a product, but the bond between the polyurethane elastic fiber and the conductive fiber tends to be strong. It is more preferred to install an air sucker so that the fibers are deposited on the net at the same time. An example of an embodiment of the present invention will be described below. Pellets of thermoplastic polyurethane elastomer are fed from a hopper and heated and melted by an extruder. The melting temperature is preferably in the range of 190 to 230°C. On the other hand, the polyisocyanate compound is
It is melted at a temperature below ℃ and degassed in advance. If the melting temperature is too high, the quality of the polyisocyanate compound is likely to change, so it is preferable that the melting temperature is as low as possible within the melting range, and a temperature between room temperature and 100° C. is appropriately used. The molten polyisocyanate compound is measured by a metering pump, filtered by a filter if necessary, and added to the molten polyurethane at a meeting point provided at the tip of the extruder. The polyisocyanate compound and polyurethane are kneaded using a kneading device having static kneading elements. This mixture is calculated by a calculation pump and introduced into the spinning head.
As the spinning head, a conventional nonwoven fabric spinning device may be used, but it is preferable to design the spinning head in a shape that minimizes the retention area of the mixture as much as possible. After removing foreign matter using a filter layer such as a wire mesh or glass beads, if necessary, the mixture is discharged from a nozzle arranged in a row, and is heated by a heated high-speed air stream ejected from a slit. It is deposited and collected on the finer and moving nets. On the other hand, the conductive fibers pass through a nip roller whose speed is set so as to have a predetermined content, are sucked and ejected by an air sucker, and are deposited on the net at the same time as the polyurethane elastic fibers. The web collected on the net is immediately pressed with rollers, if necessary, and taken off as a nonwoven fabric. As above,
By the method of the present invention, it becomes possible to industrially advantageously produce an antistatic polyurethane elastic fiber nonwoven fabric. Effects of the Invention In addition, the nonwoven fabric obtained by the method of the present invention has an elongation at break of 300% or more, a recovery rate at 100% elongation of 85% or more, and has excellent elasticity, flexibility, breathability,
It is used alone for various purposes due to its antistatic properties, but it can be made into even more diverse products by combining it with other materials. Such materials include inelastic polymers, such as synthetic fibers such as polyester, nylon, polyolefin, and acrylic, or knitted fabrics made of natural fibers such as cellulose and wool;
Examples include net fabrics, non-woven fabrics, and webs. Further, films such as polyurethane, foam sheets, etc. can also be used. Such products and uses include materials for various clothing such as sportswear and foundations that require elasticity, as well as interlining, batting, reinforcing agents, stretch tapes, bands, etc. In addition, it has the ability to fit into various shapes, cushion, and mold, so it can be used for packing, cushioning materials, fillers, etc.
Useful as a molding material. Furthermore, applications that take advantage of the friction coefficient and wear resistance unique to polyurethane elastic materials include various anti-slip applications such as shoe lining materials. Furthermore, this nonwoven fabric is extremely useful in fields where antistatic performance is required, as it exhibits particularly excellent effects. The present invention will be explained below with reference to Examples. Example 5550 parts of dehydrated polytetramethylene glycol with a hydroxyl value of 102 (all parts below mean parts by weight) and 1,4-bis(β-hydroxyethoxy)
500 parts of benzene and 1960 parts of P,P'-diphenylmethane diisocyanate are mixed in a kneader,
Powdered polyurethane was obtained by heating to 85°C. This was molded into pellets using an extruder. The relative viscosity at a concentration of 1 g/100 c.c. at 25° C. in dimethylformamide was 2.01. On the other hand, 1000 parts of polytetramethylene glycol having a hydroxyl value of 112 and 500 parts of P,P-diphenylmethane diisocyanate were reacted at 80°C for 30 minutes to obtain a viscous polyisocyanate compound. The isocyanate group content of this product was 5.60%. On the other hand, nylon 6 containing 35% carbon black (by weight) is placed in the center, and titanium oxide 2 is placed on both sides.
A three-layer conductive composite fiber with a circular cross section obtained by melt-spinning (volume composite ratio 1/10), stretching and crimping nylon 6 containing 50% of nylon in the form of a sandwich sandwich (see Figure 1 of JP-A No. 54-30919). A 9 denier/3 filament was obtained. The electrical resistance per cm of this material is 7.8×10 ⁷
It was Ω/cm. Using the polyurethane elastomer pellets and polyisocyanate compound thus obtained as raw materials, an extruder equipped with a kneading section consisting of a polyisocyanate compound supply device and a static kneading element, and both sides of nozzles with 0.5φ150 holes arranged in a row. Using a melt blow spinning device with a slit for injecting heated gas, the polymer was discharged at a rate of 0.3 g/min per nozzle, and the air heated to 220°C was heated to 4.5 kg/cm ^{2 .}
2000N/min was injected from the slit at a pressure of 2000N/min. On the other hand, the conductive fibers were also passed through a nip roller set at a predetermined speed, sucked into the air sucker into which the heated air had been introduced, and jetted out while shaking the head from side to side. The fine polyurethane elastic fibers and the conductive fibers ejected from the air sucker were collected simultaneously on a conveyor consisting of a 50-mesh wire mesh installed 25 cm below the nozzle, and then sandwiched between rollers to obtain a nonwoven fabric. The fabric weight of the nonwoven fabric was fixed at 80 g/ ^m2 , and the amount of polyisocyanate compound added was varied.
Furthermore, the properties of the samples with varying amounts of conductive fibers and those with varying amounts of conductive fibers were as shown in Table 1. If a polyisocyanate compound is not added, it is necessary to raise the spinning temperature, and the resulting product also has low strength and elongation, and the 100% elongation recovery rate is also poor. In addition, the amount added is 35
%, thread breakage occurred. In addition, the antistatic performance effect begins to appear when the content of conductive fiber is 0.05%. However, when the content was 7%, although the antistatic effect was very good, the flexibility and stretchability, which are the most important features of polyurethane elastic fiber nonwoven fabrics, were lost, resulting in low product value. In addition, the frictional charging voltage is calculated by rubbing against wool cloth 10 times (20℃,
40%RH) Measured value after 1 second. 【table】

Claims (1)

[Scope of Claims] 1. After adding and kneading a polyisocyanate compound to a molten polyurethane elastic body, when manufacturing a nonwoven fabric by a melt blowing method, conductive fibers are entrained in a high-speed air stream and deposited in a sheet shape together with polyurethane elastic fibers, Collect the conductive fibers at 0.05
A method for producing an antistatic polyurethane elastic fiber nonwoven fabric, characterized in that the content is 5% by weight. 2. The method according to claim 1, wherein 0.1 to 3% by weight of the total weight of the nonwoven fabric is comprised of conductive fibers. 3. The method according to claim 1, wherein the conductive fiber is a metal fiber or a fiber having a conductive layer containing conductive particles selected from metals, metal compounds, and carbon black. 4. The method according to claim 1, wherein the conductive fiber is a composite fiber in which a fiber-forming polymer is bonded to a conductive layer containing metal particles, conductive metal compound particles, or conductive carbon black particles.