JPH0655968B2 - Foam synthetic fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention relates to a foam of a sheath / core type two-layer structure comprising a core portion having sponge-like pores and a sheath portion which can be clearly distinguished from the core portion. The present invention relates to a fiber, and provides a new and useful fiber that has the characteristics of conventional foamed fibers and reinforces its greatest drawback, strength, and newly adds animal hair-like appearance, texture, and color effects. To do. That is, its main purpose is to reduce the weight of products, use bulkiness, heat retention, heat insulation, and improve economy based on weight reduction, and the other purpose is to look and wind similar to animal hair. And to obtain fibers with a special color effect. Therefore, its application has a wide range of applications such as sheets, bedding, interior products, non-woven fabrics and napped products as well as various knitted fabrics.

"Prior art""Problems to be solved by the invention" In recent years, in addition to so-called essential fiber improvement and functionality improvement such as design of new fiber composition and addition of fiber characteristics by post-addition, three-dimensional fiber Various measures have been taken to improve the added value by elaborating on the physical structure. For example, it is possible to divide the sea-island type cross-section fibers found in synthetic leather, to make them ultra-fine, to make the cross-section shape irregular, and to modify the fine structure of the fiber surface. Foamed fibers belong to the latter category, with the aim of improving the weight, bulkiness, softness, elasticity, etc. by providing a cell portion in which the fibers are independent or communicating with each other in the fiber, or a structure in which these are mixed,
Many attempts have been made.

Examples of such representatives include Japanese Examined Patent Publication Nos. 43-4536 and 4
6-850 and Japanese Patent Laid-Open No. 58-36208, all of which are intended for partial use in synthetic grass, industrial materials, or in interior products, and are intended for so-called general fibers such as clothing. Not a thing. Further, due to its structure, it lacks mechanical properties that can withstand processing as a general fiber such as spinning, knitting and weaving, particularly strength and elongation, and more decisive things are coloring (undiluted solution coloring, dyeing, When printing, the gloss and transparency are reduced and the quality is remarkably impaired. On the other hand, Japanese Patent Publications 42-21300, 51-210 and 58.
-38527 and the like seems to have been exactly intended for this field, but its actual condition is that it has only a few pores per fiber cross section, and the characteristics of the foamed fiber are not exerted yet, and it is still unsatisfactory. I have to say that it is enough. Furthermore, JP-A-5
0-77616 discloses an example of a composite fiber, but (1) a sheath / core composed of the same composition cannot be obtained, (2) always two or more kinds of spinning dope, (3) a composite nozzle It is not economically advantageous to use the product because the product device is complicated, and (4) the performance is significantly different from the object of the present invention.

"Means for Solving Problems" The present invention has been completed in view of the above circumstances, and has the above-mentioned drawbacks that conventional foamed fibers have by forming a foamed structure into two layers of a sheath / core. It has been eliminated, and the texture and color effect have been further improved.

A core comprising fibers containing 25% by weight or more of acrylonitrile obtained by wet spinning using one kind of spinning dope, and having a fiber cross-section, which is arranged in a sponge shape by a large number of pores and wall surfaces partitioning the pores; The core portion and the sheath portion having a structure distinguishable from each other, the polymers constituting the sheath portion and the core portion are the same composition, and the area ratio of the core portion to the cross-sectional area is 5 to 90%. Animal hair foam synthetic fiber characterized by.

The large number of pores of the present invention and the core arranged in a sponge shape by the wall surface partitioning the pores are the portions that are included by the sheath that does not substantially include the pores described below, and are independent. Alternatively, air bubbles that are in communication with each other, or a large number of voids mixed therein are randomly dispersed in the substantially central part of the cross section of the fiber, or a form in which they are blocked with a film-like film or a yeast foam during baking. The structure means a sea-island structure. However, the positioning in the cross section of the fiber is not particularly limited as long as it is surrounded by the sheath portion and within the area.

Further, the sheath portion having a structure distinguishable from the core portion refers to a portion having a denseness equivalent to that of a normal fiber that does not have a foamed structure, but does not necessarily mean that it does not necessarily include void portions. That is, it is sufficient if the structure has such a denseness that it can be differentiated from the core. However, it goes without saying that the effect of the two-layer structure, which is an important point of the present invention, must be kept to the extent that the effect is not impaired. The purpose of the above structure is different from that of a completely hollow structure such as a normal hollow fiber, and in such a structure, the cross section is easily deformed by thermal or mechanical external force, and the effect of the present invention is not obtained. I can't get it. Furthermore, the core has only a few pores per cross section of the fiber such as conventional fibers, the core is dispersed throughout the cross section and the boundary with the sheath is not clear, or the fiber surface part The one in which the core portion protrudes up to the above is not the object of the present invention. Sixth
The figure shows the typical cross-sectional shape of these conventional products. Fig. 6 (A) is an example of foamed fiber by a chemical foaming agent, and Fig. 6 (B) is an example of a phase separation method by blending incompatible polymers. Further, the same (C) is a foamed fiber having a hollow structure obtained by using a low boiling point material.

The two-layer structure of the present invention can be obtained by using the cross-sectional structure of natural animal hair shown as an example in FIGS. 4 and 5 as one evaluation criterion, and it can be expressed by the area ratio of the core to the cross-sectional area. .
At this time, the area ratio of the core portion / cross section is calculated by a method described later by a cross-sectional photograph, but the range of 5 to 90% is preferable.
If it is less than 5%, the effect as a foamed fiber cannot be sufficiently exerted, and if it exceeds 90%, it cannot be put to practical use particularly in terms of mechanical properties. More preferably, when it is 10 to 60%, the object of the present invention is most effectively achieved. In addition, by measuring the physical properties of various fibers as with ordinary fibers and adding characteristics such as thickness in coloring, especially in dark and light colors, subtle luster and transparency, color tone, etc. Become.

Next, a method for producing the fiber of the present invention will be described. First, the following method can be applied as a basic means for obtaining such a structure. (1) Heat-foaming with a low boiling point compound,
(2) Utilization of gas generated by decomposition by chemical foaming agent, (3) Encapsulation of inert gas or air, (4) Blend of foamable resin, (5) Incompatible liquid or solid dispersed in polymer Extraction by treatment, (6) phase separation by blending a resin which is not compatible with the polymer but is miscible, (7) densification of the sheath portion by post-treatment, (8) combination of two or more of these.

Hereinafter, as an example, description will be made based on the method (1).

First, it is necessary that the polymer constituting the fiber of the present invention contains 25% by weight or more of acrylonitrile, more preferably 35 to 85% by weight of acrylonitrile, and further preferably 40 to 60% by weight of acrylonitrile. If the content of acrylonitrile is less than 25% by weight, it is difficult to obtain animal hair-like appearance, texture and color effect. Of course, these can be used as a homopolymer, a copolymer, or a polymer blend. Furthermore,
Additives that are commonly used, that is, stabilizers, organic and inorganic pigments and dyes, matting agents, various texture modifiers, flame retardants, whitening agents, etc. If so, there is no problem. In addition, in order to enhance the foaming efficiency, a commonly used nucleating agent selected from the group consisting of alkali metal or alkaline earth metal carbonates, silicates, metal oxides, cellulose derivatives and the like will be described later. It is also effective to use it together with a foaming agent.

Next, the basic shape of the fiber is normal circle, horseshoe shape, cocoon shape,
The shape is not limited to potatoes, triangles, stars, and other irregular shapes. However, a hollow or triangular shape is not preferable because it is easily deformed or broken by a mechanical external force. Also in the case of a composite fiber, it is not preferable for the above reason.

The second is the spinning method. First, the basic concept of using a low boiling point compound will be described. Usually, in order to obtain a foamed fiber with a low boiling point compound, a liquid low boiling point compound (hereinafter referred to as a foaming agent) is added under normal pressure before the solvent solution of the thermoplastic polymer is supplied to the spinning nozzle. Mix to make a spinning dope. After spinning, the foaming agent contained in the fiber yarn is vaporized by heating to a temperature above its boiling point in the process of fiber formation, and the structure is obtained by the generated gas expansion force. After the drawing and heat treatment, there is no difference from what is done with ordinary fibers. The following description follows the order of this basic method.

Next, the foaming agent is preferably one that easily evaporates and vaporizes within the processing temperature in the usual spinning process, and has a boiling point of 120 ° C. or lower,
It is preferably in the range of 10 to 100 ° C. from the standpoints of adjustment of the spinning dope, foaming efficiency and heat energy consumption. Examples of such a foaming agent include lower aliphatic hydrocarbons such as pentane, hexane, heptane and petroleum ether, lower alicyclic hydrocarbons such as cyclopentane and cyclohexane, alcohols such as methanol and ethanol, ethyl bromide and iodide. Halogenated hydrocarbons such as methyl and methylene chloride, ethers such as diethyl ether, 1,1,2-trichloro-
Examples thereof include chlorofluorocarbons such as 1,2,2-trifluoroethane and trichloromonofluoromethane, as well as ketones, aldehydes and esters. These foaming agents are added to a solvent solution of the polymer to form a spinning solution for the fibers, and particularly when a solvent is used, it is necessary to carefully select the solvent together with the kind of the foaming agent as described later. This is exactly what has reached the present invention, and the behavior of the two in the solidification process is important. That is, in the conventional method, for example, when quoting the patent of acrylic foamed fiber, the foaming agent is a non-solvent for the polymer in relation to the solvent used, and a solvent solution of the polymer, and It is a necessary condition that the polymer is insoluble or hardly soluble in a coagulation liquid (hereinafter referred to as a coagulation liquid). As an example of this, Japanese Patent Publication Sho 5
1-210, inorganic solvents such as nitric acid and sodium thiocyanate found in Examples of JP-B-58-38527, dimethylformamide (DMF) and dimethylsulfoxide (DMF) found in JP-B-41-6297 and JP-B-42-21300. Examples are polar organic solvents such as DMSO) and dimethylacetamide (DMA). But according to this method,
All the foaming agents are simply dispersed in the solution,
Such a state may cause serious effects such as agglomeration of the foaming agent during the transfer of the spinning dope, clogging of the spinneret, a decrease in foaming efficiency, and a decrease in the strength of the resulting expanded fiber. Moreover, the structure does not serve as the object of the present invention for the reason described below. That is, the foaming agent in the present invention is a non-solvent for the polymer, and soluble in the solvent and solvent solution of the polymer, and insoluble in the coagulating liquid of the polymer, water, or sparingly soluble Must. The reason why the polymer must be a non-solvent here is that the structure is formed by the expansive force of the generated gas due to the vaporization of the foaming agent, and therefore the existence of an interface with the polymer is required. It is because the solubility of the polymer in the solvent and the solvent solution is an essential point for preventing the influence of the above-mentioned dispersed matter and for obtaining the structure of the present invention described below. . In addition, the coagulation liquid in the wet spinning and the insolubility or poor solubility in water are for preventing elution of the foaming agent from the outside of the system and for making it function as effectively as possible.

A combination of solvent and blowing agent selected according to the above definition, for example 1,1,2-trichloro-to DMF.
When 1,2,2-trifluoroethane or 1,1,2-trichloro-1,2,2-trifluoroethane for acetone, pentane, hexane, etc. are used, why can the structure of the present invention be obtained? Regarding the above, the present inventors consider as follows. That is, the spinning dope is extruded from the spinning nozzle into the coagulation liquid, and the solvent is first diffused from the surface portion to the outside of the fiber system. In the case of the wet method, the coagulation liquid is mainly used. Drop, release of polymer,
A series of fiber forming processes called precipitation and so-called coagulation start. This coagulation process gradually progresses toward the center of the fiber while repeating the mutual diffusion of the diffusion of the solvent from the surface portion of the fiber to the outside of the system and the infiltration of the coagulation liquid to form a so-called uncoagulated elastic yarn. At this time, a sheath portion referred to in the present invention, a sheath-like shell generally called a skin layer, is formed on the fiber surface portion closest to the solidification phase, and this skin layer inhibits rapid solidification inside the fiber. In addition, it has a function of preventing elution of the foaming agent out of the system. Therefore, when the concentration of the solvent with respect to the polymer at this point is viewed in the radial direction from the outer peripheral portion of the fiber cross section to the center, the concentration distribution will show as the solvent concentration increases toward the center. . On the other hand, since the foaming agent is originally a non-solvent for the polymer, it is in a state of being dissolved with the solvent in the spinning dope, and accordingly, in the coagulation process, the diffusion behavior is similar to that of the solvent. However, since it is insoluble or sparingly soluble in the coagulation liquid or water, it is not eluted outside the fiber system, or a small amount remains even if it is eluted. In other words, in the area close to the fiber surface, the solvent diffuses out of the fiber system, so that the mixed solution of the solvent and the foaming agent (hereinafter referred to as the mixed solution) loses its ability to dissolve in the polymer, and It is in a dispersed form, but is in a dissolved state with the polymer in other portions. When this point is compared with the conventional method, the solvent and the foaming agent show completely different behaviors due to the properties of the conventional method. In particular, the foaming agent, which was originally in a dispersed state in the spinning dope, is more repelled from the polymer and the solvent when coagulation is disclosed, and is isolated randomly throughout the fiber or is isolated from each other. And exhibit clear phase separation, which is essentially different from the state of the invention.

Subsequently, this uncoagulated elastic yarn is heated to a temperature above the boiling point of the foaming agent contained therein with a heat medium such as hot water or heating steam in the washing step, and vaporized, but external heating at this time is performed. As a result, the coagulation is further promoted, the skin layer becomes stronger, and the release of the polymer and the mixed solution also progresses as the solvent in the central portion diffuses out of the fiber system. However, at the same time, the residual solvent itself is heated to generate a dissolving power for the polymer again, and the mixed solution having a dispersed state in the portion close to the fiber surface has a higher solvent concentration than that of the sheath portion. The transition to the fiber central portion with less mechanical interference and the phenomenon occur rapidly at the portion corresponding to the core portion in the present invention. These interactions are combined with the expansion force of the foaming agent which is separated from the solvent by heating above the boiling point temperature and is vaporized, and the plasticizing effect of the polymer by heating is combined to form a core having sponge-like voids. Along with the transition of the foaming agent (mixed liquid) to the fiber central portion, on the other hand, in the portion close to the fiber surface, a densified sheath portion is formed as compared with the core portion, and here, for the first time, the basic structure of the present invention, That is, the sheath / core bilayer structure is invented. In the conventional method, that is, when a foaming agent insoluble in a solvent is used, the behavior of the above-mentioned solvent and the foaming agent is essentially irrelevant to migration of the solvent containing the foaming agent. Therefore, the structure of the resulting fiber is also a random foam of a foaming agent which is simply in a dispersed state, or only the so-called small number of huge pores where only the foaming agent is separated and aggregated with the polymer in the fiber and locally foamed. I have nothing to own. It is no exaggeration to say that the properties and distribution of these foaming agents and solvents inside the fiber and the behavior during heating determine the foamed structure of the final fiber.

Next, the fiber which has undergone the steps of coagulation and heating (foaming) undergoes a predetermined treatment, that is, primary drawing, washing with water, drying, secondary drawing, heat treatment, crimping, etc., to become the final fiber. You can go almost the same way. The heating (foaming) treatment may be performed at the same time as solidification, primary stretching, washing with water or the like. In addition, spinnability, antistatic, water repellent, oil repellent,
The adhesion of various oil agents for the purpose of antifouling, texture improvement, etc. does not affect the performance of the present invention at all, and can be carried out as necessary. Furthermore, the same applies to post-processing such as dyeing, printing, coating, laminating and patterning.

"Function""Effect of the Invention" The foamed fiber thus obtained not only has the same characteristics as ordinary fibers, but also has various excellent properties based on its structure. That is, it is lightweight, bulky, heat-retaining, and heat-insulating. In particular, the greatest feature of the two-layer structure is that the strength of the foam, which has not been achieved in the past, is maintained, and that it can sufficiently withstand higher-order processing of general fibers such as dyeing, spinning, knitting and weaving. Even more surprising is that the present invention has a gloss, texture and color effect similar to natural animal hair, which will be described in detail below.

The characteristic of natural animal hair becomes remarkable when it is colored with a pigment or dye originally possessed. That is, when observing natural animal hair well, especially what is called stab hair or guard hair in the industry, even though they have almost the same fineness, the difference in light color and dark color makes them thick and glossy. Looks completely different. In other words, when light colors such as beige and gray look thick and matte, when they become dark colors such as brown and black, the partial baldness looks extremely thin and has a transparent luster. Furthermore, since the dark and light tones are continuously changed in one hair, the appearance is very delicate and tasty. The present inventors have hypothesized that this is due to the optical characteristics of the so-called bone marrow portion of the animal hair cross section, and as a result of further studies, obtained the following conclusions. That is, although the detailed reason has not been clarified yet, the present inventors presume that there is multiple reflection and light scattering of incident light with respect to the boundary between the sheath and the core and the sponge structure of the core. That is, in the light color, since the absolute amount of the colorant is small and the transparency of the fiber is high, the incident light is almost linearly transmitted through the sheath portion and reaches the sheath / core boundary. But,
Here, some diffuse reflection occurs, and most of the rest is multiple-reflected in the sponge layer, and the same matte effect as that when an apparent inorganic substance is added is exhibited. On the other hand, in the case of a dark color, the incident amount itself is absorbed by the large amount of colorant, and these phenomena at the boundary surface have almost no effect on appearance. In addition, since the sheath portion is originally dense, the gloss of the fiber surface gives a subtle glossy feeling to the viewer, in combination with the so-called mirror surface effect created by the sheath / core boundary. It is considered that the feeling of thickness is due to the change in sensation of apparent expansion and contraction based on the difference in gloss and gloss (strength). In addition, if the sponge part itself is viewed as a multi-layered layer, it may have the same pearly luster as when the scale pigment is added, contributing to the "subtle luster". It is also possible that Further, regarding the texture, it is considered that it is due to this two-layer structure that is strong in thickness and mechanical external force and rich in resilience.

"Examples" Hereinafter, the present invention will be described more specifically with reference to Examples.
These are merely examples, and the present invention is not limited to the description of these examples.

The area ratios and apparent specific gravities described in the text and Examples were measured by the following methods: (a) Area ratio calculation method: Using scanning electron microscope (Hitachi S-510 type), single fiber A photograph was taken from a vertical upper part of the cross section at a constant magnification and at a constant distance, and after confirming the sheath / core structure, the total cross-sectional area was obtained. Next, the total cross-sectional area of a non-foamed fiber (blank) having the same composition and fineness as that of the fiber is obtained by the same method, and the area ratio of the core portion to the total cross-sectional area is calculated by the following formula. The average value was calculated.

Area ratio (%) = (Ss−Sb) / Ss × 100 where Ss: total cross-sectional area of expanded fiber Sb: total cross-sectional area of non-expanded fiber (b) Calculation method of apparent specific gravity; sample (sliver) about 0.5 g And after precise weighing in air,
It was dipped in an upper and lower water tank of an automatic hydrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.) based on the underwater substitution method so as not to become faster than the wetting rate of the fiber itself, and calculated by the detected amount of water substitution.
At this time, bubbles tend to adhere to the surface of the sample in water,
A small amount of fluorine-based surfactant was added as a bubble removing agent.

Example 1 Acrylonitrile 50% by weight, vinyl chloride 49% by weight,
And a polymer obtained by copolymerizing 1% by weight of sodium styrenesulfonate with acetone were dissolved in acetone, and 40% by weight of the polymer was 1,1,2-trichloro-1,2,2-trifluoroethane and titanium dioxide 0.2. % Was added to adjust the final polymer concentration to 25% by weight, and then the mixture was stirred for 30 minutes in a closed container while maintaining it at 40 ° C. to obtain a spinning dope. Using a 200-hole spinneret with a hole diameter of 0.18 mm and 2
Discharge into a 21% acetone aqueous solution at 5 ° C and wind speed
It was immersed at 4.5 m / min for 9 seconds. Then, immerse for 6 seconds in a bath of the same composition and at the same temperature while stretching 1.8 times, and then at 75 ° C.
It was introduced into the hot water washing bath under tension and the foaming was completed by staying for about 1 minute. The water-washed yarn thus obtained was made to have a water content of 1% or less in an airflow dryer at 120 ° C., and subsequently subjected to a secondary drawing of 2.72 times and a tension heat treatment at 145 ° C. for 5 minutes to give a fineness of 15
A foamed fiber having a denier, an area ratio of 43% and an apparent specific gravity of 0.86 was obtained. When this product was subjected to normal finishing treatment to a high pile, it was not found in conventional pseudo animal hair napped products. It was light and had a high-quality hue, luster, and texture. A scanning electron micrograph of the obtained fiber cross section is shown in FIG.

Example 2 Except that a spinneret having a hole diameter of 0.1 mm and a number of holes of 1000 holes was used, the same apparatus as in Example 1 was used, the spinning was performed under the same conditions, and the final fineness was 3 denier, the area ratio was 28%, and the apparent specific gravity was 1.05. A foamed fiber was obtained. When a jersey was made with this product, it had a quality luster, texture, and sharpness, and was also lightweight and excellent in heat retention. A scanning electron micrograph of the obtained fiber cross section is shown in FIG.

Example 3 A polymer having the same composition as in Example 1 was dissolved in acetone, and 20% of n-pentane and 2% of calcium carbonate powder based on the weight of the polymer were added thereto to give a final polymer concentration of 25.
% In the closed container kept at 33 ℃ after adjusting to 30%
After stirring for a minute, a spinning dope was obtained. Using the same spinneret as in Example 1, the stock solution was discharged into a 50% aqueous acetone solution at 10 ° C. and immersed for 9 seconds at a winding speed of 4.5 m / min. Then, after dipping for 18 seconds in a 40% acetone aqueous solution at 30 ° C. while stretching by 3.06 times, primary foaming was continuously carried out for 12 seconds in a warm water bath at 50 ° C. 1 in hot water of 70 ℃
Allowed to stay for 3 seconds to complete foaming. The water-washed yarn thus obtained was set to have a water content of 1% or less in an airflow dryer at 120 ° C., and subsequently subjected to a secondary stretching of 2.65 times and a tension heat treatment at 145 ° C. for 5 minutes to obtain a fineness of 15 deniers and an area ratio. A foamed fiber having 16% and an apparent specific gravity of 0.95 was obtained. When I made a Wilton carpet using this one, it was bulky and had a waist,
Moreover, the color tone of the fiber cross section and the lateral direction slightly change. A characteristic one was obtained. FIG. 3 shows a scanning electron micrograph of the obtained fiber cross section.

[Brief description of drawings]

FIG. 1 shows the shape of the fiber obtained in Example 1 of the present invention, FIG. 2 as well as Example 2 and FIG. 3, and FIG. 3 is a scanning electron micrograph of the cross section of the fiber. 4 and 5 are cross-sectional photographs showing the shape of the fiber of natural animal hair cited as a reference example in the text, and FIG. 6 is a schematic view of a cross section of a conventional foamed fiber.

Claims (1)

[Claims] 1. A fiber comprising a fiber containing 25% by weight or more of acrylonitrile obtained by wet spinning using one kind of spinning dope, and having a fiber cross section arranged like a sponge by a large number of pores and wall surfaces partitioning the pores. A core portion and a sheath portion having a structure distinguishable from the core portion, and the polymers constituting the sheath portion and the core portion are the same composition, and the area ratio of the core portion to the cross-sectional area is 5 to 5. Animal hair foam synthetic fiber characterized by being 90%.