JPH03249217A - Light-weight sheath-core conjugate hollow polyester fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having soft touch and excellent heat- insulation and suitable as a material for autumn or winter clothes by using a polyester containing sporadically dispersed polyolefin as a core component and a polyester free from polyolefin as a sheath component and conjugating both components at a specific ratio. CONSTITUTION:The objective fiber having a void content of >=5% after the heat-treatment at 160 deg.C for 5min is produced by conjugating (A) a core component consisting of a polyester containing 4-20wt.% of a polyolefin having a density of <=1.1g/cm<3> (preferably polypropylene, etc.) and dispersed in the form of islands of 0.05-5.0mu in size and (B) a sheath component consisting of a polyester (preferably same as the polyester of the core component) free from polyolefin. The conjugation ratio of the core component is >=70wt.% and the hollowness of the fiber is >=5%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to lightweight fibers, and more particularly to core-sheath composite hollow polyester fibers that are lightweight by blending polyester with polyolefin.

[Prior Art] Polyester fibers have excellent functionality and are inexpensive to manufacture, so they are widely used for clothing, textile materials, and industrial applications. However, polyester, especially polyethylene terephthalate, has a high density of the polymer itself.
Furthermore, since it has a high degree of crystallinity, the fiber density and rigidity are high, so it is not suitable as a material for use in fields where light weight and soft texture are particularly required.

Many studies have been made to solve these problems. For example, it is a technique that lowers the apparent density of fibers by providing hollow portions in the fibers, as seen in Japanese Patent Application Laid-Open No. 52-77228. However, since the fibers produced using this technology only have one or a few hollow parts in the fiber axis direction, their bending rigidity is higher when compared to fibers of the same fineness that do not have hollow parts. Woven fabrics, knitted fabrics, and non-woven fabrics using this fiber have a strong rough hard layer, and if you try to achieve a lighter weight by increasing the hollowness ratio, the hollow part will collapse. However, it was not possible to achieve weight reduction and soft texture using technology.

In addition, as seen in JP-A No. 59-76971, a fiber is prepared by dispersing and compounding a substance in polyethylene terephthalate along the fiber direction, and then a portion of the substance is dispersed and compounded by a method such as alkali reduction processing. However, the fibers obtained by this method have long voids in the direction of the fiber axis, and the blended substances are dispersed in streaks, so the fibers can be fused with a little friction. The problem was that the surface was fibrillated.

Furthermore, JP-A-55-137208 discloses a fiber having micropores which is obtained by blending a polymer having a relatively low affinity with a substrate polymer. This fiber is lightweight because it has micropores, but although it can achieve the intended purpose in filter applications, etc., as stated in the publication, it is difficult to heat set and dye after fiber formation in clothing applications. Since various heat treatments are typically performed, the compounded polymer has the disadvantage of falling off. Further, the substrate polymer disclosed herein does not sufficiently withstand heat treatment at about 160° C. in clothing applications.

Furthermore, Japanese Patent Application Laid-Open No. 57-47912 proposes an invention in which polyester is blended with polyolefin for the purpose of improving the spinning productivity of polyester. However, the invention aims to produce ordinary polyester fibers with high productivity by blending incompatible polyolefins to provide a roller role, and the technical idea is to create voids to reduce weight. has not been disclosed at all.

Also, JP-A-55-137208, JP-A-57-
A common drawback of fibers made by blending polyester with polyolefin, as in Publication No. 47912, is that the polyolefin oozes out onto the fiber surface during the blended fiber manufacturing process or after product production, impairing process passability and significantly impairing the product's texture. That's true.

[Problems to be Solved by the Invention] The present invention was achieved as a result of intensive studies aimed at eliminating the above-mentioned drawbacks and achieving weight reduction.

[Means for Solving the Problems] The object of the present invention described above is to blend polyolefins having a density of 1.1 g/a+f or less in an amount of 4% by weight or more and 20% by weight or less, and in which there are no islands of polyolefins in a sea of polyester. A core-sheath composite hollow fiber comprising, as a core component, a polyester that is dispersed in the form of polyolefins and whose polyolefin islands have a size of 0.05 μm or more and 5.0 μm or less, and a sheath component that is a polyester that does not substantially contain polyolefin. The core-sheath composite hollow fiber has a hollowness ratio of 5% or more, the composite ratio of the fiber is such that the core component is 70% by weight or more, and 1
This is achieved by using a lightweight core-sheath composite hollow polyester fiber with a void content of 5% or more after heat treatment at 60° C. for 5 minutes.

The core component of the fiber of the present invention will be described in detail below.

In order to reduce the weight of polyester, it is advantageous that the density of the blended polymer is lower, and it is preferable that the blending of the polymer with the base polymer polyester is lower because weight reduction can be achieved due to the generation of voids during stretching. The density of the polyolefin blended into the core component must be 1.18/cmf or less. Preferably 1.0g/a/or less,
Particularly preferably, it is 0.9g10+f or less.

A polyolefin is required as a material that satisfies these requirements. Examples of polyolefins include polyethylene, polypropylene, polystyrene, and polymethylpentene, among which polypropylene and polymethylpentene are preferred because of their poor compatibility with polyethylene terephthalate, relatively high melting point, and low density. When polyester is used for clothing, it is generally heat treated at about 160° C., so it is important that the voids generated by this heat treatment do not decrease significantly. The melting point of the polyolefin is preferably 200°C or higher, more preferably 220°C or higher. In particular, polymethylpentene is preferred because it has a low affinity with polyester and a high melting point.

In order to reduce the weight of the fibers, it is necessary to have a low density of the polyolefin blended and at the same time to contain as many voids as possible in the fibers. The void content after heat treatment needs to be 5% or more based on the core-sheath composite fiber, preferably 10% or more, more preferably 20% or more, particularly preferably 30% or more. In order to reduce the weight, it is preferable that the void content after heat treatment is high, but in terms of spinnability and physical properties of the fibers, fibers containing 50% or more of voids after heat treatment are not preferred.

Moreover, it is not a problem even if substances other than polyolefin are mixed together with polyolefin as long as it does not impede weight reduction. Rather, it is preferable to use them in combination as long as they promote weight reduction. For example, it is preferable to use calcium carbonate, which is a substance with poor compatibility with polyester, especially polyethylene terephthalate, because it helps to form voids in the fibers. However, if the amount is too large, the spinning properties will be poor, so it is preferable that the amount of other components than the polyolefin be 10% by weight or less.

The amount of polyolefin to be blended varies depending on the target degree of weight reduction of the fiber, but it is required to be 4% by weight or more in order to impart a sufficiently lightweight feel. Preferably it is 8% by weight or more, particularly preferably 11% by weight or more. On the other hand, if the amount of polyolefin blended is too large, the spinning properties will deteriorate.
Since the original functionality of polyethylene terephthalate is lost, the content should be 20% by weight or less.

Preferably it is 15% by weight or less.

In order to reduce the weight of the fiber, it is preferable to blend polyolefin into the entire fiber, but in this case, the processability may deteriorate due to bleeding of the polyolefin during the processing process,
The texture of the product will deteriorate. The fiber of the present invention is an excellent fiber that achieves weight reduction, does not impede processability, and does not impair the feel of the product.

The composite ratio of the core components is required to be 70% by weight or more in order to achieve weight reduction, which is the objective of the present invention. However, if the composite ratio of the core component is too high, the sheath component becomes thin, and the polyolefin blended with the core component polyester oozes out during the subsequent high-order processing steps, including the silk-spinning process, resulting in poor process passability. It will make it significantly worse. The composite ratio of the core components is preferably 80% by weight or more, particularly preferably 90% by weight or more and 95% by weight or less.

In order not to lose the original characteristics of polyester, it is necessary that the polyolefin in the fiber cross section of the core component is dispersed in the form of islands in a sea of polyester.

Here, the sea is a state that exists continuously extending throughout the entire fiber when an arbitrary cross section is observed, and the island is a state that exists almost independently in the sea of polyester. When the islands are continuous, the boundary area between the two becomes small, which reduces the occurrence of voids, which is not preferable.

The size of the polyolefin islands is important because it affects the amount of micropores that occur at the polyester-polyolefin interface. If the size of the islands is too small, the specific surface area will increase, but the amount of voids will decrease, which is not preferable. On the other hand, if it is too large, it is not preferable because not only the spinning properties become poor, but also various kinds of irregularities such as dyeing irregularities occur. The size of polyolefin islands is 0.05 μm or more, 5.0
It is necessary that the thickness be less than μm. Preferably 2.0μ
m or less and 0.1 μm or more.

In order to maintain the desired size of the polyolefin islands, the melt viscosity of the polyolefin is preferably higher than the melt viscosity of the polyester, particularly preferably at least twice the melt viscosity of the polyester.

The fibers of the present invention are mainly suitable for clothing, but in clothing applications, they are generally heat treated at 200°C or less for the purpose of imparting dimensional stability, and the fibers can withstand temperatures of at least 160°C. It is necessary. Preferably, it is a fiber that can withstand temperatures of 200°C or higher. For this purpose, the melting point of the fiber is preferably 240°C or higher, more preferably 250°C or higher.

In the present invention, the melting point refers to PERKIN-ELMAR D
This is a value measured using SC-4 at a heating rate of 16°C/min. Here, when there are multiple melting peaks, it refers to the peak temperature with a large amount of heat of fusion.

In this sense, the polyester of the present invention is preferably polyethylene terephthalate, but it may also contain commonly used copolymer compositions or blends within the range that satisfies the above melting point, and the amount thereof is determined between the base polymer and the polyolefin. It may be contained as long as it is 10% by weight or less based on the total amount.

Since the fiber of the present invention is used for clothing and texture is also important, the fineness is 0. The range is preferably 5 denier or more and 5 denier or less. Since the fibers of the present invention contain voids, they are lighter than ordinary polyethylene terephthalate fibers with the same cross-sectional area, have low bending rigidity, and have a soft texture.

The sheath component of the fiber of the present invention is not particularly limited as long as it is polyester. That is, it may be substantially polyethylene terephthalate, or it may be a copolymerized polyester obtained by copolymerizing dicarboxylic acid, diol, etc., which are used for boat fishing.

Further, a matting agent or the like may be added. It is preferable that the composition of the sheath component and the polyester composition of the core component are substantially the same in terms of uniformity of dyeability and approximation of shrinkage characteristics. However, if the sheath component contains a polyolefin, it is not possible to sufficiently prevent poor process passability and deterioration of the product's texture due to bleeding of the polyolefin, which is the objective of the present invention. The polyolefin content of the sheath component is preferably 0.1% by weight or less.

By forming the fiber of the present invention into a hollow cross-sectional shape, it is possible to further improve the lightness, which is the object of the present invention. That is, it is not enough to simply have voids in the fibers to reduce weight; it is also necessary to have one or more hollow portions penetrating in the fiber axis direction in addition to the voids. The hollowness ratio necessary for weight reduction is 5% or more. If the hollowness ratio is less than 5%, the effect of having a hollow portion is not sufficient. Preferably it is 10% or more, more preferably 20% or more. However, when the hollowness ratio exceeds 50%, the bending rigidity increases, resulting in a rough and hard texture.
In addition, the hollow portion is crushed and the practical effect is not sufficient, which is not preferable.

The fiber of the present invention can be produced, for example, as follows.

As a core component, molten polymethylpentene is added to molten polyethylene terephthalate in an amount of 12% by weight based on the total of polyethylene terephthalate and polymethylpentene.
After blending and thorough stirring, this blended polymer is formed into granules.

This blended polymer is dried under reduced pressure at 160°C and then melted. On the other hand, as the sheath component, polyethylene terephthalate is melted and discharged from a concentric core-sheath composite hollow mouthpiece consisting of a plurality of slits.

The shear stress when discharging from the mouth hole is 10 x 106dy.
It is preferable to set the particle size to ne/- or less in order to avoid unnecessarily dispersing the particle size of polymethylpentene. Further, for the same reason, the deformation ratio after discharge (the value obtained by dividing the undrawn yarn take-off speed by the flow speed in the die hole) is more preferably 200 or less, preferably 80 or less.

The obtained undrawn yarn is drawn at a low drawing temperature to create voids, and then heat treated to improve dimensional stability.

[Example] The present invention will be explained in more detail with reference to Examples below.

The measurement method used in the examples is as follows.

Size of islands (dispersion): This value is the average diameter of polyolefin islands scattered in a sea of polyester when a fiber cross section is observed with a transmission electron microscope.

Void content after heat treatment: After the fibers were heat treated at 160°C for 5 minutes at normal pressure, 20 arbitrary cross sections of the fibers were observed using a transmission electron microscope, and the ratio of the void area to the entire fiber area was calculated. Expressed as an average.

Note that samples that were not subjected to normal pressure treatment at 160° C. for 5 minutes were simply treated as void content. However, the area of the so-called hollow part, which is a virtually infinite continuous void in the fiber axis direction, is the area of the entire fiber,
and voids.

Hollowness ratio: Determined from the area of the hollow portion of the total area determined from the outer shape in any cross section of the fiber, and expressed as a percentage.

Example 1 86% by weight polyester consisting essentially of polyethylene terephthalate as a core component with a density of 0.89 g/cm
14% by weight of polymethylpentene (f) was melt-blended to obtain a dispersed polymer having an average dispersion diameter of 35 μm. The melt viscosity of the polyolefin at this time was about three times that of polyethylene terephthalate. On the other hand, the same material as the core component polyethylene terephthalate was used for the sheath component. These polymers are transferred from the concentric core/sheath composite hollow base to the core/
An undrawn yarn was obtained by discharging the yarn so that the sheath ratio was 90/10, and then drawing was performed. The stretching temperature at this time was 30°C,
Following the stretching, heat treatment at 125°C was performed. When the cross section of this fiber was observed with an electron microscope, it was found that the polymethylpentene islands were dispersed in an island shape with a size of 0.6 μm in the sea of polyester, and the void content was 23.9%. Also, the denier and number of filaments are 75 denier and 2, respectively.
There were 4 filaments. The residual elongation was 23%. The fabric made of these fibers is soft, and its softness is 160 degrees Celsius.
There was almost no change even after heat treatment for 5 minutes. Note that the hollowness ratio after heat treatment was 21.3%. The void content after heat treatment was 20.6%.

Example 2 86% by weight polyester consisting essentially of polyethylene terephthalate as a core component with a density of 0.89 g/cm
14% by weight of polypropylene f was melt-blended to give an average dispersion diameter of 20 μm. On the other hand, the sheath component polymer was the same as in Example 1. These polymers were discharged from a concentric core-sheath composite hollow nozzle consisting of a circular slit having a notch (core/sheath = 90/10) to form undrawn yarns, which were then drawn. The stretching temperature at this time was 30°C,
The residual elongation was 23%.

When the cross section of the fiber was observed using an electron microscope, it was found that polypropylene was dispersed in the form of islands with an island size of 0.5 μm in a sea of polyester, and the void content was 20.5%. The softness of the fabric made of the fibers was inferior to that of Example 1.

The softness of the fabric was the same as in Example 1 before heat treatment at 160°C, but the softness decreased due to heat treatment. The hollow ratio of this fiber after heat treatment was 20.9%, and the void ratio after heat treatment was 10.7%.

Example 3 82% by weight polyester consisting of 98% by mole of repeating units polyethylene terephthalate with a density of 0.89g
10 (18% by weight of polymethylpentene) was melt-blended to give an average dispersion diameter of 35 μm. This polymer was used as the core component, and a polymer made of the same polyester as the polyethylene terephthalate used as the core component was used as the sheath component. A core-sheath composite (core/sheath = 75/25) undrawn yarn was made using a spinneret hole with a smaller slit diameter than in Example 1, and then stretched.The stretching temperature at this time was 30°C, and the residual The elongation was 26%. During the production of this fiber, there was no breakage at all during spinning and drawing, and the spinning performance was extremely good. As a result of observing the cross section of the fiber with an electron microscope, The size of the island is 0.6 in the sea of polyester.
Island-shaped polymethylpentene of μm size is dispersed,
The void content was 16.6%. The hollowness ratio of this fiber was 15°4%. The fabric made of these fibers was soft, and the void content after heat treatment was 15.8%, which showed little change due to heat treatment, but the lightweight feel of the fabric was slightly inferior to that of Example 1.

Example 4 A drawn yarn was obtained by spinning yarn in the same manner as in Example 3, except that the amount of polymethylpentene as a core component was changed to 8% by weight. The cross section of the fiber was observed using an electron microscope, and polymethylpentene was dispersed in the form of islands with an island size of 0.6 μm in a sea of polyester, and the void content after heat treatment was 9.8.
%, and the hollowness ratio was 16.3%. Furthermore, the fabric obtained from the fibers was soft and lightweight, but was slightly inferior to that of Example 1.

Example 5 The polymer used as the core component was the same as in Example 1, but a static kneader was used immediately before compounding to change the size of the polymethylpentene islands in the fiber. The conditions other than this were the same as in Example 1. As a result of observing the cross section of this fiber with an electron microscope, it was found that the size of islands in the polymethylpentene fiber was 0.1 μm and was dispersed in an island shape, but the void content was 11.3%. The fineness and number of filaments were 75 denier and 24 filaments, respectively, and the residual elongation was 25%. Although the fabric made of this fiber was soft, it was inferior to that of Example 1. In addition,
The hollow ratio of this fiber was 20.1%, and the void content after heat treatment was 9.8%.

Example 6 In order to increase the size of polymethylpentene islands in the fiber, the same procedure as in Example 1 was carried out except that the filter layer immediately before the die was removed and the stretching ratio was slightly lowered. When spinning this polymer, thread breakage was occasionally observed during spinning. As a result of observing the cross section of this fiber with an electron microscope, it was found that the polymethylpentene islands had a size of 4.2 μm and were dispersed in an island shape, and the void content was 26.4%. The fineness and number of filaments were 79 denier and 24 filaments, respectively, and the residual elongation was 34%.

The fabric made of this fiber is soft and has a hollowness ratio of 19.
3%, and the void content after heat treatment was 24.9%.

Example 7 The same procedure as Example 1 was carried out except that the final discharge hole shape of the polymer was changed to reduce the hollowness ratio.

The fineness and number of filaments of this fiber were 75 denier and 24 filaments, respectively, and the residual elongation was 25% and the void content was 22.5%. The fabric made of this fiber was soft, and its softness remained almost unchanged even after heat treatment at 160°C. Note that the void content after heat treatment was 19.8%, and the hollow ratio was 7.4%.

Comparative Example 1 An experiment was conducted in the same manner as in Example 3 except that the composite ratio of core component/sheath component was changed to 30/70.

The dispersion of polymethylpentene was good as it was dispersed in the form of islands with an island size of 0.6 μm, but the void content after heat treatment was as low as 4.7%, and the fabric did not feel lightweight. I could not satisfy my purpose. Hollowness ratio is 14.2
%Met.

Comparative Example 2 A non-composite solid circular cross-section fiber consisting only of the blend polymer used as the core component in Example 1 was spun. After stretching, stretching and heat treatment were performed in the same manner as in Example 1. The size of the islands after the heat treatment was 0.6 μm, which was the same as in Example 3, but dropping of polymethylpentene onto the roller was observed during the stretching, and breakage of single fibers occurred. In addition, the texture of the fabric was soft and lightweight, but it felt a little sticky.

[Effect of the invention] The lightweight fiber according to the invention has a void content of 5% after heat treatment.
Since the polyethylene terephthalate described above is lightweight and has micropores, it has a texture suitable for use in general clothing. Furthermore, because it has an immovable air layer, heat retention is improved, especially,
Not only does it become a soft clothing material suitable for fall and winter use, but it also eliminates any polyolefin oozing during the yarn spinning process, high-order processing, and even after the product is made into clothing.

Claims (1)

[Claims] It is composed of 4% by weight or more and 20% by weight or less of polyolefin with a density of 1.1 g/cm^3 or less, and the polyolefin is dispersed in the form of islands in the sea of polyester, and the size of the polyolefin islands is Polyester having a diameter of 0.05 μm or more and 5.0 μm or less as a core component,
On the other hand, it is a core-sheath composite hollow fiber whose sheath component is polyester that does not substantially contain polyolefin, the hollowness ratio of the core-sheath composite hollow fiber is 5% or more, and the composite ratio of the fiber is such that the core component is 70% by weight or more. A lightweight core-sheath composite hollow polyester fiber having a void content of 5% or more after heat treatment at 160°C for 5 minutes.