WO1991000935A1

WO1991000935A1 - Porous fiber and production thereof

Info

Publication number: WO1991000935A1
Application number: PCT/JP1990/000890
Authority: WO
Inventors: Toshinobu Koshoji; Hironari Honda; Kiyonobu Okamura; Kunio Misoo
Original assignee: Mitsubishi Rayon Co., Ltd.
Priority date: 1989-07-13
Filing date: 1990-07-11
Publication date: 1991-01-24
Also published as: EP0438598A4; EP0438598A1

Abstract

A porous fiber having a pore structure comprising interconnected spaces enclosed with lamellae and a number of longitudinally arranged fibrils that connect the lamellae with each other all over the fiber, which is produced by blending a polyolefin with a hydrophilic copolymer mainly comprising monomer units represented by formula (I) and ethylene units, melt spinning the blend, and stretching the resulting fiber; wherein R?1 and R2¿ represent each independently hydrogen or methyl, and n is 1 to 9. The obtained fiber has permanent hydrophilicity and a large surface area, is very lightweight and soft to the touch, has a fair white color without transparence, and is endowed with excellent mechanical properties in spite of its high void fraction.

Description

Description Porous fiber and its manufacturing technology

The present invention relates to a porous polyolefin-based fiber. Background technology

In recent years, the diversification of textiles for clothing and industrial materials has progressed, and as part of the diversification, there has been an increasing demand for fibers that are lightweight, have a soft texture, and have appropriate strength. .

As a method for achieving a light weight and a soft hand, there is a method of making fibers porous.

As a method for making the fibers porous, for example, a method in which a blowing agent is blended into a thermoplastic polymer, melt-spun, and the foaming agent is decomposed at the spinning stage to cause foaming to make the fibers porous. After blending and spinning additives for pore formation (inorganic salts, organic low molecular weight compounds, etc.) that can be extracted into thermoplastic polymers, the additives are extracted with an appropriate solvent to make them porous. Etc.

However, in the method of blending the blowing agent, it is difficult to obtain a uniform and fine porous structure, and it is difficult to obtain a stable quality. That is, to increase the porosity In addition, there is a problem that fibers with high porosity are difficult to obtain and the process stability in the spinning process is low, because the yarn breaks frequently and the strength is greatly reduced.

In the extraction method, the process becomes complicated, and it is difficult to completely remove the additive from the fiber by the extraction, and this additive easily remains as an impurity in the product fiber. This also affects the texture, making it difficult to obtain a sufficiently good texture, and trying to increase the porosity causes a significant decrease in strength. Not in a situation. On the other hand, as one of the diversification of iron and steel, there is a strong demand for fibers having excellent water absorption and sweat absorption properties, and fibers with excellent properties of these properties are being actively studied.

These properties can be obtained by using fibers imparted with hydrophilicity.

Various materials are used as materials for hydrophilic fibers, but attention has been paid to the development of polyolefin steel fibers, which are superior in terms of strength and the like, to applications that require hydrophilicity.

Since polyrefin is a hydrophobic material, hydrophilization treatment is required to develop polyrefin fibers for applications requiring hydrophilicity. However, in the method of hydrophilization using a hydrophilizing agent such as a surfactant, the obtained hydrophilic fibers are not liable to fall off due to contact with water. Therefore, there is a problem of losing hydrophilicity. In addition, even if melt-spun a blend of a commonly used hydrophilic substance, good performance fibers cannot be obtained due to poor affinity between the hydrophilic substance and polyolefin. There's a problem. Disclosure of the invention

The inventors of the present invention have conducted intensive studies in view of the above-mentioned situation, and as a result, it has been found that excellent results are obtained by melt-spinning and drawing a blend of a hydrophilic copolymer having specific performance in a polyolefin. The present inventors have found that a porous fiber having a porous structure and permanent hydrophilicity and which can simultaneously satisfy various properties such as lightness, soft feel, and water absorption can be obtained. .

It is an object of the present invention to provide a porous fiber which is hydrophilic in nature, has a very light and soft feel and exhibits excellent mechanical properties despite its high porosity. And.

It is another object of the present invention to provide a porous fiber which does not have a problem of the solvent and the pore-forming additive remaining in the fiber made porous by the extraction method.

The porous fiber of the present invention that can achieve these objects has the following formula: One one

R ¹

-f C H 2 —C

C 0 0 (C H C H 0) H

R ²

(In the above formula, R ¹ and R ² independently represent a hydrogen or a methyl group, and n is 1 to 9.) A hydrophilic unit mainly composed of a monomer unit A and an ethylene unit B represented by Having a pore structure composed of a functional copolymer X and a polyolefin Y, wherein a space surrounded by lamellae and a number of longitudinally arranged fibrils connecting the lamellae communicates with each other. .

This porous fiber is obtained by melt-spinning a blend of a hydrophilic copolymer mainly composed of a monomer unit A and an ethylene unit B represented by the above formula, and a polyolefin Y, and is not drawn. The process of obtaining the fiber and heat-treating the undrawn fiber in a vacuum or an inert gas medium at a temperature lower than the melting point of polyolefin Y for at least one hour, and then drawing to make it porous. And a method comprising the steps of:

The porous polyolefin-based fiber of the present invention is entirely surrounded by lamellas and a number of longitudinally arranged fibrils connecting the lamellas from the fiber surface to the fiber center. The space has a communicating pore structure It has a large surface area, is very lightweight, has a soft feel, has a clear white appearance without a sense of transparency, and exhibits excellent mechanical properties despite its high porosity.

In addition, as described above, in the porous fiber obtained by the extraction method, an extraction solvent, an additive for forming pores, and the like often remain in the fiber. On the other hand, in the porous fiber of the present invention, since the undrawn fiber obtained by melt-spinning a blend having a specific composition is made porous, the porous fiber is extracted by the extraction method. It does not contain a solvent such as the obtained porous fiber or an additive for forming pores. Therefore, the porous fiber of the present invention is a sanitary material and has a permanent hydrophilic property, so that it is used as a material for clothing that directly touches the skin, such as underwear, which is required to have excellent sweat absorption properties. Or as a medical fabric material. Further, the porous fiber of the present invention can be used as a material for various industrial materials including wipers and adsorption materials by utilizing its large water content and water absorption in pores. is there. BEST MODE FOR CARRYING OUT THE INVENTION

The porous fiber of the present invention comprises a hydrophilic copolymer X having a monomer unit A and an ethylene unit B represented by the above-mentioned formula as main components, and a polyolefin Y, And a number of longitudinal arrangements connecting the lamellas. It has a pore structure in which the space surrounded by the fibrils communicates.

Examples of the polyolefin Y as one component of the porous fiber of the present invention include polyethylene, polypropylene, poly (3-methylbutene-11), poly (4-methylpentene-11) and the like. be able to.

As the polyolefin Y, it is preferable to use one having a high degree of crystallinity, and it is preferable to use a crystal of an undrawn fiber obtained by melt-spinning a blend obtained by blending a hydrophilic copolymer X described later with a blend. It is preferable to select a polymer having a degree of crystallinity of 40% or more, preferably 50% or more, and a crystal orientation degree of 50% or more, preferably 60% or more. Yes.

The value of n in the above formula representing the unit A represents the average degree of polymerization of the alkylene glycol units in the unit A (average of the number of oxyalkylene groups), and is in the range of 1 to 9.

When n exceeds 9, polyalkylene glycol (meta) acrylate as a component for introducing unit A becomes a viscous substance, and ethylene as a component for introducing unit B is obtained. This makes it difficult to make a homogeneous reaction between and, making it impossible to obtain hydrophilic copolymer X.

When n is 1 to 2, high reactivity is obtained in the reaction between the component for introducing unit A and the component for introducing unit B. Industrially, it is possible to industrially supply a hydrophilic copolymer X having a small variation in quality, and to provide a hydrophilic porous steel with a small amount of components eluted in water.

In the hydrophilic copolymer X, units A differing in the degree of polymerization of the alkylene glycol units of the unit A and the types of R ¹ and R ² may be mixed.For example, oxetylene and oxypropylene may be mixed. It may be mixed in the unit of work.

In the hydrophilic copolymer X, the composition ratio of both A and B units is not particularly limited, but the ratio of the unit A is 80 to 10% by weight (unit A / unit B = 800 ~ 10 Z90, weight ratio). That is, when the content of the unit A is less than 10% by weight, the porous fiber does not show sufficient hydrophilicity, whereas when the content exceeds 80% by weight, the hydrophilic copolymer is generally excessively high. The hydrophilic copolymer X tends to contain a large amount of a low molecular weight substance, and the hydrophilic copolymer X is easily eluted from the porous fiber blended with the low molecular weight substance and the polyolefin Y.

In order for the porous fiber to exhibit sufficient hydrophilicity, the ratio of the unit A is more preferably 70 to 15% by weight, and more preferably 70 to 40% by weight. Especially preferred

In addition, the molecular weight of the hydrophilic copolymer X is not particularly limited, but it is necessary for the porous fiber to exhibit permanent hydrophilicity. Is preferably a high molecular weight substance, and the intrinsic viscosity [7?] In xylene at 75 ° C. is preferably about 0.07 to 0.40 d £ / g. If [?] Is smaller than this range, the hydrophilic copolymer tends to bleed out during use, while if [ry] is larger than this range, Since the flowability of the hydrophilic copolymer is low, the proportion of the hydrophilic copolymer on the surface of the porous steel including the pore surface tends to be low.

The hydrophilic copolymer X basically consists of units A and B, but other units other than these units may be contained as long as the hydrophilic properties of the porous fiber are not impaired. Good.

As such a third unit, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated monomer, an ethylenically unsaturated monomer unit which can be introduced with an ethylenically unsaturated carboxylic acid, or the like. C can be mentioned. The unit C can be contained in an amount of about 1 to 40 parts by weight, preferably about 1 to 10 parts by weight, based on 100 parts by weight of the total amount of the units A and B.

The content of the hydrophilic copolymer X and the polyolefin Y in the porous fiber of the present invention is not particularly limited, and may be arbitrarily selected depending on the required degree of hydrophilicity and ease of production. good. Generally, the unit A in the hydrophilic copolymer is The ratio of X and Y can be determined according to the content of unit B and the like. In general, when the content of the unit A as a hydrophilic component in the hydrophilic copolymer X is large, the porous fiber shows sufficient hydrophilicity even if the content of X in the porous fiber is small. However, when the content of the unit A is small, it is necessary to increase the content of X in the porous fiber in order for the porous fiber to exhibit sufficient hydrophilicity.

When this porous fiber is obtained by a melt spinning or drawing method, if a large amount of the hydrophilic copolymer X containing a large amount of the unit A is blended in the raw material polymer, the unstretched fiber spun out Inversely, the growth of lamellar crystals is hindered.On the contrary, if the hydrophilic copolymer X has a small content of unit A, it is not stretched even if the amount of X in the raw polymer is increased. The blend amounts of X and Y can be determined in consideration of the fact that the growth of lamellar crystals in the fiber is not easily inhibited.

In the porous fiber of the present invention, the content of the polyolefin Y is preferably about 95 to 50% by weight (No .- / Z. 50, weight ratio). If the content of the polyrefin is less than this range, it is difficult to grow lamellar crystals sufficiently in the undrawn fiber, and it tends to be difficult to obtain a fiber having an excellent porous structure. .

The porous fiber of the present invention preferably has a porosity of 30 to 80% and a tensile strength of 0.5 to 8 gZ. d. The tensile elongation is preferably 1 to 300%. If the porosity is less than the above lower limit, the lightness and texture tend to be insufficient, and if the porosity exceeds the upper limit, the strength tends to be insufficient. The strength and elongation are preferably in the above ranges in consideration of clothing use.

Hereinafter, the method for producing the porous fiber of the present invention will be described.

First, the above-mentioned hydrophilic copolymer X and polyolefin Y are sufficiently uniformly blended. Examples of the blending method include a method of blending these polymers with a blender such as a V-type blender, a method of blending them in a melt extruder and then pelletizing them. No.

Subsequently, the blend polymer is melt-spun with a normal spinning machine and wound as an undrawn fiber. The spinning temperature is preferably 20 "Ό higher than the melting point of polyolefin Y (hereinafter referred to as Tm) and 80 ° C higher than the melting point. If the fiber is spun at a temperature lower than the lower limit of the temperature range, the obtained undrawn fiber is highly oriented, but the maximum drawing amount when the drawing is made porous in a subsequent drawing step can be increased. On the other hand, spinning at a temperature higher than the upper limit of the above temperature range is not preferable because it is difficult to obtain a material having a sufficiently high porosity. In order to perform stable spinning and increase the crystallinity of the spun undrawn fiber, a slow cooling section with a length of about 1 to 3 m and an ambient temperature of about 50 to 100 ° C is provided immediately below the spinneret. This is preferred.

If the length of the slow cooling section is less than 1 m or the ambient temperature is less than 50 ° C, thread breakage immediately below the spinneret frequently occurs, and the process stability tends to decrease, which is not preferable. Conversely, if the length of the slow cooling section is longer than 3 m or the ambient temperature is higher than 100 ° C, the cooling of the yarn will be insufficient and substantial draft will occur. However, this is not preferable from the viewpoint of the crystal orientation of the obtained undrawn fiber.

Also, the spinning draft employs slightly lower conditions compared to the case of the polyolefin alone system, but is preferably about 50 to 2000, more preferably about 100 to 2000. It is about 1000.

The undrawn fiber obtained in this way is heated at a temperature of Tm or less, preferably (Tm−10 ° C) to (Tm−30 ° C), in order to increase its crystallinity. Heat treatment (anneal treatment) for one hour or more in a fixed or relaxed state. The longer the processing time, the better, but considering the economy, it is set to about 48 hours or less, and more preferably about 3 to 48 hours.

When such a long heat treatment is performed in air, In the meantime, since the hydrophilic copolymer X deteriorates, a method of performing heat treatment in an inert gas or in a vacuum is employed in the present invention.

The heat-treated product is made porous by stretching, but a stretching method combining cold stretching and hot stretching is usually employed. That is, first, approximately (Tm−220 ° C) to (Tm−80 ° C), or more preferably (Tm−160 ° C) to (Tm−90 ° C). )) And then hot stretched at a temperature in the range of approximately (Tm-60 ° C) to (Tm-5.C).

These cold stretching and hot stretching may be multi-stage stretching of two or more stages.

Cold drawing is an important step in producing the fiber of the present invention. In this step, microcracks are generated in the amorphous portion between the lamellar crystals of the highly oriented crystalline undrawn fiber. It is expanded by the subsequent thermoplastic stretching in the hot stretching step, and the above-mentioned specific porous structure is obtained. The stretching amount in the cold stretching is preferably 5 to 100%, and the hot stretching amount is set so that the total stretching amount of the cold stretching and the hot stretching is 100 to 700%. It is preferable to set If the heat stretching temperature is higher than Tm-5 ° C, the fiber becomes transparent and the desired porous structure cannot be obtained. If the hot stretching temperature is lower than the above lower limit, the lower the temperature, the lower the porosity, which is not preferable. No. On the other hand, if the total drawing amount exceeds 700%, yarn breakage frequently occurs during drawing, which is not preferable. Although the morphological stability of the porous fiber obtained in this way is almost assured by hot drawing, it can be reduced to (Tm-60 ° C) if necessary.

At a temperature of (T m-5 ° C), one or more stages of heat or wet heat treatment may be heat set in a tensioned or relaxed state. Further, in order to further increase the hydrophilicity of the fiber, the fiber may be treated with heated water or steam at about 50 to 120 ° C as necessary.

(Example)

Hereinafter, the present invention will be further described with reference to Examples. In the Examples, the crystallinity of the blend polymer was obtained by integrating the omnidirectional diffraction intensities using a wide-angle X-ray diffractometer. I asked for it.

Crystallinity Xc = (Integrated value of total diffraction intensity-Integral value of diffraction intensity of amorphous portion) Integral value of total diffraction intensity The degree of crystal orientation was determined using a wide-angle X-ray diffractometer (110). ) The half-width of the distribution of the diffraction intensity of the surface in the fiber axis direction was calculated, and calculated by the following formula.

Crystallinity (%) =

H (no / (1 8 0-H (no) X 1 0 0

[H ₍₁₁₀₎ : Half-width at (1 1 0) plane]

Further, the content of the units A and B in the hydrophilic polymer X was determined by measuring the oxygen atoms in the hydrophilic polymer X with an elemental analyzer. It was calculated by quantification.

The average degree of polymerization (n) of the alkylene glycol units in the unit A was calculated from the degree of polymerization of the alkylene glycol units in the unit A measured by gel permeation chromatography (GPC). . Example 1

Consists of 60% by weight of hydroxyxetyl monomethacrylate unit as unit A and 40% by weight of ethylene unit as unit B. Intrinsic viscosity in xylene at 75 ° C

[7?] Is a hydrophilic copolymer X with 0.19 d £ g and high density polyethylene with a density of 0.965 g Z cm ³

(Tm = 133.C, manufactured by Mitsubishi Yuka Co., Ltd., Mitsubishi Polytec JX120) at a ratio of 15:85 (weight ratio) and melt-kneaded in a melt extruder. Pelletized and dried further.

Next, this pellet was supplied to a spinning machine, and a spinning temperature of 15.5 was established with a spinning cylinder having a length of 2 m immediately below the spinneret, a hole diameter of 1.0 mmΦ, and a number of holes of 4 mm. It was spun from a spinneret of No. 0 and wound on a pobin at a spinning draft of 314 at a spinning speed of 250 m / min.

The undrawn fiber thus obtained was heat-treated at 115 ° C under a nitrogen atmosphere for 24 hours under a constant length. This unextended The crystallinity of the drawn fiber was 62% and the degree of crystal orientation was 75%.

Next, the undrawn fiber is subjected to cold drawing at 25% by 80%, and then, in a 2 m long heating box heated to 115 ° C, the total drawing amount becomes 5200%. Heat stretching was carried out until this time. Furthermore, a relaxation heat set was performed in a 2 m long heating box heated to the same temperature so that the total elongation was 400%.

The obtained porous fiber is a slit-shaped space surrounded by lamellas and a number of longitudinally arranged fibrils connecting the lamellas, from the fiber surface to the center. Have a very soft touch, a porosity of 62.3%, a tensile strength of 3.38 g / d, and a tensile elongation of 50%. It was 5%. Next, this porous fiber lg was immersed in 200 cc of ion-exchanged water for 1 hour, dehydrated with a centrifugal separator at 1000 rpm for 5 minutes, and the weight gain was measured. The water content was determined to be 135%. Examples 2 and 3

Consisting of 50% by weight of hydroxyxethyl monomethacrylate unit as unit A and 50% by weight of ethylene unit as unit B, the intrinsic viscosity in xylene at 75 ° C [ 7?] Is 0.19 d £ g and the hydrophilic copolymer X used in Example 1 is Mitsubishi Polyjet JX—20, which is 15:85 (weight ratio, 2) or 2 0: 8 0 (Weight ratio, Example 3) was blended, and a porous fiber was obtained in the same manner as in Example 1.

These porous fibers had slit-like pores similar to those of Example 1, and had the performance shown in Table 1.

Examples 4 and 5

Hydroxylethyl monomethacrylate unit as unit A 48 parts by weight, ethylene unit as unit B 52 parts by weight, and vinyl acetate as unit C 2 parts by weight Thus, a hydrophilic copolymer X having an intrinsic viscosity [7?] In xylene of 75 ° C. of 0.19 d £ g and the Mitsubishi PolyJC JX— 2 0 and 1 5: 8 5

(Weight ratio, Example 4) or 20:80 (weight ratio, Example 5) was blended, and a porous fiber was obtained in the same manner as in Example 1.

These porous fibers had the same thread and soot pores as those of Example 1, and had the performance shown in Table 1.

Example 6

The average degree of polymerization (n) of polyethylene glycol is 45 wt% of poly (ethylene glycol) monomethacrylate units of 6 and 55 wt% of ethylene units. ?] Is 0.15 dZg and the Mitsubishi copolymer used in Example 1 JX-20 was blended at a ratio of 20:80 (weight ratio), and a porous fiber was obtained in the same manner as in Example 1.

These porous fibers had the same slit-like pores as those of Example 1 and had the performance shown in Table 1.

Example 7 and Example 8

It consists of 35 parts by weight of ethylene glycol monomer having an average degree of polymerization (n) of polyethylene glycol of 6 and 65 parts by weight of ethylene unit. The hydrophilic copolymer X having an intrinsic viscosity [77] of 0.15 d ノ g and the Mitsubishi Polytech JX—20 used in Example 1 were mixed in a ratio of 20:80 (weight The blend was blended at a ratio of Example 7) or 25:75 (weight ratio, Example 8), and a porous fiber was obtained in the same manner as in Example 1.

Comparative Example 1

A porous polyethylene fiber was produced in the same manner as in Example 1 using only Mitsubishi Polyethylene JX-20, which is a high-density polyethylene, as a polymer, and the water content was measured to be 6%. Was. Table 1 Porosity Tensile strength Tensile elongation Water content No ^U No No No Example 1 3 38 50 5 135 Non 2 3 24 53 6 11 q Non 3 58 5 3 4 48 3 151 Nog 4 • 61 8 3.33 50 5 108 Nono 5 58. 0 3.36 46.7 139 Noso 6 59.8 3.18 48.5 5 115 Nono 7 61.5 3.05 50.2 76 Nono 8 56.5 3.33 46.8 125

Claims

1. The following formula:

R

-(C Η 2 — C-

C 0 0 (CHCH 0) H Mouth R ²

(In the above formula, R ¹ and R ² independently represent hydrogen or a methyl group, and n is 1 to 9.) The monomer unit A and the carboethylene unit B represented by Hydrophilic copolymer X and polyolefin Y

A porous fiber having a pore structure in which a space surrounded by lamellas and a number of longitudinally arranged fibrils connecting the lamellas communicates with each other.

2. The porous material according to claim 1, wherein the weight composition ratio (X / Y) of the hydrophilic copolymer X and the polyolefin Y is in the range of 5Z95 to 50/50. Quality fiber.

3. The method according to claim 1, wherein the weight composition ratio (A / B) of the unit A and the unit B in the hydrophilic copolymer X is in the range of 80Z20 to 100/90. Porous fiber.

4. The porous fiber according to claim 3, wherein the intrinsic viscosity [77] of the hydrophilic copolymer X in xylene at 75 ° C is in the range of 0.07 to 0.40 d £ g. .

5. The polyolefin Y is polyethylene. 5. The porous fiber according to any one of items 1 to 4.

6. The porosity according to any one of claims 1 to 5, wherein the porosity is in the range of 30 to 80%, the tensile strength is in the range of 0.5 to 8 g / d, and the tensile elongation is in the range of 1 to 300%. Porous fiber.

7. Monomer unit A and ethylene unit represented by the following formula

A process of melt-spinning a blend of a hydrophilic copolymer X mainly containing B and a polyrefin Y to obtain an undrawn iron fiber; Or a heat treatment at a temperature not higher than the melting point of polyolefin Y in an inert gas medium for at least one hour, followed by a drawing process to make the fibers porous.

R ¹

I

-C H 2 —C

C 0 0 (CH 2 ♦ CH 0) _n H

I

R ²

(In the above formula, R ¹ and R ² independently represent a hydrogen or a methyl group, and n is 1 to 9.)

8. The method for producing a porous fiber according to claim 7, wherein the weight composition ratio (X / Y) of the hydrophilic copolymer X and the polyolefin Y is in the range of 5Z95 to 50Z50. .

9. The porous material according to claim 7 or 8, wherein the weight composition ratio (AB) of the unit A and the unit B in the hydrophilic copolymer X is in the range of 80/20 to 1/90. Fiber manufacturing method.

10. The porous fiber according to claim 9, wherein the intrinsic viscosity [77] of the hydrophilic copolymer X in xylene at 75 is in the range of 0.07 to 0.4 djG / g. Recipe.

11. The method for producing a porous fiber according to any one of claims 7 to 10, wherein the polyolefin '' is polyethylene.