JPH07310231A - Porous and light-weight polyethylene terephthalate fiber - Google Patents

Abstract

PURPOSE:To obtain a porous polyethylene terephthalate fiber having light weight and excellent heat-retaining property and mechanical strength and excellent in the screening of ultraviolet and visible rays. CONSTITUTION:This porous and light weight fiber comprises a polyethylene terephthalate. The periphery of the fiber consists of a dense and nonporous layer. Fine pores are present in the core part of the fiber in a state connected with each other in the direction of the fiber axis. The average diameter (D) of the fine pores is 0.1-10mum. The fiber contains a porous part having an L/D ratio of >100 (L is the length in the direction of the fiber axis) and the density of the fiber is <=1.30g/cm<3>.

Description

Detailed Description of the Invention

[0001]

[Industrial application] The present invention can be applied to the field of clothing such as synthetic cotton, non-woven fabric and woven fabric, as well as construction materials and composite materials, and has excellent heat retention and mechanical strength, and excellent ultraviolet / visible light shielding properties. Porous lightweight fiber.

[0002]

2. Description of the Related Art Conventionally, several methods have been proposed as means for reducing the weight of porous polyethylene terephthalate. For example, JP-A-47-14418 discloses a method of molding a porous fibrous material by mixing an inorganic material with a polymer mixture, melt-molding and stretching. In this method, additives are indispensable in addition to the polymer, the additives may fall off from the fibrous material after molding, and the strength may decrease due to the additives, so it is difficult to say that it is a good fiber. .

Further, Japanese Patent Laid-Open Nos. 52-15627 and 57-84702 disclose methods for obtaining porous fibers by utilizing the hard elastic property. Does not have a sufficiently large volume, and since it is a hole penetrating to the outside of the fiber, sufficient lightness and heat retention cannot be obtained. There is also a method of making it porous by a post-treatment as seen in the weight reduction processing method (for example, alkali treatment). However, even with such a method, it is not possible to obtain sufficient heat retention because the pores penetrate to the outside of the fiber. It has the drawback that the melt remains attached to the fibers.

There is also a method of spinning into a hollow shape using a hollow spinneret, but in order to increase the hollow ratio, it is necessary to use a special polymer having a high viscosity and perform spinning under special conditions. Even if the fiber is spun under such conditions, a sufficient hollow ratio (density) cannot be obtained, and only fibers having inferior lightness and heat retention can be obtained. Further, in Japanese Patent Laid-Open No. 64-20312, the melting point of the thermoplastic polymer is rapidly cooled after melt molding, and
A method of making porous by stretching at an ambient temperature of 0 ° C. or lower is disclosed. However, it does not necessarily become porous under the range of the manufacturing conditions disclosed herein, and it is difficult to manufacture on an industrial level. Moreover, since the L / D of the pores is small, it is difficult to reduce the density, and the strength is likely to decrease because the pores are non-uniform in the fiber axis direction.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polyethylene terephthalate fiber which is excellent in lightness, heat retention, mechanical strength, and ultraviolet / visible light shielding property.

[0006]

For this reason, the present inventor has arrived at the present invention as a result of extensive studies to improve the drawbacks of the prior art. That is, the present invention is a fiber made of polyethylene terephthalate, which has a dense non-porous layer at the outer peripheral portion of the fiber, has fine pores connected in the fiber axial direction inside the fiber, and has an average diameter (D ) Is 0.
1 to 10 μm, including a porous portion having a ratio (L / D) to the length (L) in the fiber axis direction of more than 100, and having a fiber density of 1.30 g / cm ³ or less And porous light weight fiber.

The porous lightweight fiber of the present invention is a fiber made of polyethylene terephthalate, which is composed of a dense non-porous layer at the outer peripheral portion of the fiber and has fine pores connected in the fiber axial direction inside the fiber. The average diameter (D) of the micropores is 0.
It is a fiber having a porous portion having a ratio (L / D) of 1 to 10 μm and a length (L) in the fiber axis direction of more than 100, and a fiber density of 1.30 g / cm ³ or less. .

[0008] The density of fibers is 1.30 g / cm ³ or less, preferably 1.20 g / cm ³ or less, more preferably 1.10 g / cm
Must be ³ or less. If the density exceeds 1.30 g / cm ³ , sufficient heat retention and lightweight properties are not exhibited. The term “fiber density” as used herein refers to a value obtained by measuring a fiber having a total single fiber length of 10 cm or more by using a density gradient tube method. At this time, in the fiber of the present invention, since the dense non-porous layer exists in the outer peripheral portion of the fiber, the density gradient liquid does not enter the pores existing inside the fiber.

The fibers of the present invention have an apparent density of 1.3.
It is 0 g / cm ³ or less, and the porous portion and the portion without pores may exist independently in the fiber axis direction,
When the ratio of the length of the portion where no holes are present is preferably 50% or less, more preferably 30% or less, the heat retaining property, the lightweight property, and the ultraviolet and visible light shielding properties are excellent.

In the present invention, it is important that the non-porous layer has a structure in which the non-porous layer is present on the outer peripheral portion of the fiber in the porous portion. With such a structure, the fine pores become pores that are not connected to the outside of the fiber, and the heat retention is improved. The average diameter of the micropores in the porous part is 0.1-10 μm
Must be It is difficult to confirm fine pores of less than 0.1 μm using a scanning electron microscope (SEM) or the like. On the other hand, if it is 10 μm or more, the fibers are likely to be crushed when they are handled, and there is a possibility that sufficient heat retaining property and lightweight property may not be exhibited.

The ratio (L / D) of the average diameter (D) of the fine pores to the length (L) of the fine pores in the axial direction of the fiber exceeds 100, which means that the light weight of the porous lightweight fiber of the present invention is high. It is important for excellent mechanical strength. When L / D is 100 or less, when stress such as tension is applied to the fiber, the stress is concentrated on the polymer portion between the pores, which easily breaks and mechanical strength is lowered, It may be difficult to densify. When manufactured at an industrial level,
It is very difficult to produce fibers with L / D of 100 or less.

The shape of the fibers is not limited to the circular shape, and may have various modified cross-sections if necessary. Further, the thickness of the fiber is not particularly limited, and any size can be selected depending on the application. The polymer used for the porous lightweight fiber of the present invention is preferably polyethylene terephthalate (hereinafter abbreviated as PET) consisting only of ethylene terephthalate units, but other than that, conventionally known dicarboxylic acid components, dioxy components, oxycarboxylic acid components. It is also possible to use copolymerized polyethylene terephthalate obtained by copolymerizing the above, or a mixed polyester obtained by melt-mixing polyethylene terephthalate or copolymerized polyethylene terephthalate with another homopolyester or a copolymerized polyester.

It is also possible to use a copolymer having a amide bond, an ether bond, a carbonate bond or the like in the copolymerized polyethylene terephthalate, or a fiber-forming polyester or polyester ether other than polyethylene terephthalate. Of course, for this polymer, conventionally known catalysts, anti-coloring agents, heat-resistant agents,
The weather resistance improver may contain inert fine particles and the like.

The degree of polymerization of the polymer is not particularly limited, but the solution viscosity (ηsp / c) measured using o-chlorophenol is preferably in the range of 0.3 to 3, more preferably 0.5. It is better to be in the range of 1.2. ηsp / c
Is less than 0.3, the strength of the spun fiber tends to be weak. If ηsp / c exceeds 3, the fluidity during melt molding is poor and spinning is difficult, and the degree of orientation of the fibers during spinning tends to be high, such being undesirable.

Such a fiber cannot be produced by a usual method, and can be produced only by drawing an undrawn yarn having a special structure under special conditions as shown below. The porous lightweight fiber of the present invention can be obtained by first forming a fibrous material having a low degree of orientation by a melt molding method, and then performing neck stretching. The degree of orientation of the fibrous material after melt molding is determined by the birefringence (Δ
n), 0.02 or less, preferably 0.
It is desirable that it is 015 or less, more preferably 0.01 or less. If Δn exceeds 0.02, the generation of voids due to stretching becomes insufficient, the density exceeds 1.30 g / cm ³ , and there is a possibility that the heat retaining property and the lightness are impaired. Δ
It was possible to obtain the porous lightweight fiber of the present invention from a fibrous material having a measurement limit of n of 0.001. Δn is 0.02
Fibers that have been melt-molded once may be subjected to treatments such as hot drawing as long as they are as follows.

The spinning nozzle used for spinning is not limited to a circular shape. A modified cross section may be used if necessary. In order to obtain a low orientation fibrous material, it is desirable to set the spinning temperature in the range of 20 to 150 ° C. higher than the melting point of the polymer. When spinning is carried out in a temperature range lower than this temperature range, the polymer is incompletely melted and melt fracture easily occurs, resulting in a decrease in stability in the stretching step. On the contrary, when spinning is carried out in a temperature range higher than this temperature range, decomposition and modification of the polymer are likely to occur, resulting in reduction in strength and elongation.

The polymer discharged at an appropriate spinning temperature needs to be wound to obtain a low orientation fibrous material. For this purpose, it is desirable to lower the spinning draft so as to make it difficult to orient, rapidly cool and solidify using cold air or the like, and wind at a low spinning speed. The porous lightweight fiber is obtained by keeping the low-orientation fibrous material obtained as described above at a temperature below the softening point of the fibrous material before stretching and at a relatively low temperature of about 150 ° C. or less and a high-magnification neck. It can be obtained by stretching. Neck drawing is a drawing in which a drawing point is fixed and a necking point in which the fiber diameter is rapidly changed occurs. It is desirable that the draw ratio is a high ratio that allows a sharp neck point and that the fiber can be stably drawn without breaking.

The neck-stretched and porous fiber may be heat-set, heat-stretched, and heat-relaxed at a temperature not higher than the melting point, if necessary.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. The measuring method was as follows. (1) Average Diameter of Micropores, Length in Fiber Axis Direction The average diameter of the micropores was measured on the cross section of the fiber using a scanning electron microscope (SEM) and an image analyzer. The length in the fiber axis direction was measured by using a SEM on the longitudinal section of the fiber.

(2) Density If the density is 1.05 g / cm ³ or more, the total single yarn length is 10 c.
Fibers of m or more were measured by the density gradient tube method. As the density gradient liquid, a mixed liquid of carbon tetrachloride and toluene was used. 1.
When it was less than 05 g / cm ³ , it was confirmed by floating in a density gradient tube, and then calculated using the cross-sectional area of the fiber, the weight, and the length ratio of the porous portion.

(3) Birefringence (Δn) The measurement was carried out with a polarizing microscope using a sodium lamp as a light source and olive oil as the immersion liquid. (4) Breaking ratio and mechanical properties Using Tensilon at room temperature, yarn length 5 cm, test speed 5 c
It was measured and determined under the condition of m / min.

The fiber was drawn by using two drawing rolls and a plate heater installed between them. The stretching temperature is indicated by the surface temperature of this plate heater. The draw ratio was determined from the fiber fineness (weight per unit length) before and after drawing.

[0023]

Example 1 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 18 and a spinning speed of 315 m / min. This fiber had a Δn of 0.004 and a breaking draw ratio of 6.0 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 5.9.

The fibers thus obtained all had a porous structure in the length direction and had a density of 0.64 g / cm ³ . S
When the fibers were observed by EM, the fibers had a diameter of 66.5μ.
A porous layer having a circular shape of m and having a large number of pores of about 0.35 to 2.0 μm in the cross section, and fine pores having a thickness of about 7.5 μm from the outer periphery of the fiber toward the inside. A porous layer was observed. When the pore diameter of this cross section was examined in more detail using an image analyzer, the average diameter of the pores was 0.9 μm. Also, when the longitudinal section of the fiber was observed, it was found that the fine pores were continuous beyond 100 μm, and L / D
Was confirmed to be over 100. The mechanical properties of this fiber are: strength 6.2 g / d, elongation 14%, elastic modulus 15
It was extremely excellent at 5 g / d.

The results are shown in Table 1.

[0026]

Example 2 The fiber spun and stretched in the same manner as in Example 1 was further stretched 1.4 times at 230 ° C. The obtained fibers all have a porous structure in the length direction,
The density was 1.00 g / cm ³ . When the cross section of the fiber was observed by SEM, the fiber had a circular shape with a diameter of 48.5 μm and a porous layer having a large number of pores with an average diameter of about 0.5 μm, and the thickness of the fiber from the outer periphery to the inside. Is about 7.5
A non-porous layer without micrometer pores was observed. Also, when observing the longitudinal cross section of the fiber, it was found that
It was confirmed that it was continuous over the above and L / D exceeded 100. The mechanical properties of this fiber are strength 8.
The fiber had a very high strength of 9 g / d, an elongation of 8% and an elastic modulus of 144 g / d.

The results are shown in Table 1.

[0028]

Example 3 The fiber spun and stretched in the same manner as in Example 1 was further subjected to 0.8 times relaxation heat treatment at 230 ° C.
The obtained fibers all had a porous structure in the length direction and had a density of 0.95 g / cm ³ . When the cross section of the fiber was observed by SEM, the fiber had a circular shape with a diameter of 63.3 μm and a porous layer having a large number of pores with an average diameter of about 0.7 μm, and the thickness from the outer peripheral portion of the fiber toward the inside. However, a non-porous layer having no fine pores of about 7.5 μm was observed. When the longitudinal section of the fiber was observed, it was found that the fine pores were 10
It was confirmed that the diameter was continuous over 0 μm and the L / D was over 100. The mechanical properties of this fiber were high, with a strength of 4.6 g / d, an elongation of 52% and an elastic modulus of 68 g / d.

The results are shown in Table 1.

[0030]

Example 4 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 18 and a spinning speed of 315 m / min. This fiber had a Δn of 0.004 and a breaking draw ratio of 6.0 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 4.2 times.

The obtained fiber has a porous structure in which a portion having a porous structure and a portion having no porous structure are alternately present in the lengthwise direction, and has a porous structure. The length ratio in the fiber axis direction of the part is 50%, and the density is 1.19 g /
It was cm ³ . When the cross section of the portion having a porous structure was observed by SEM, the fibers were circular with a diameter of 66.5 μm, and a porous layer having a large number of pores with an average diameter of about 0.7 μm From the outer periphery to the inside, a non-porous layer having a thickness of about 8.0 μm and having no fine pores was observed. When the longitudinal section of the fiber was observed, it was found that the fine pores were 10
It was confirmed that the diameter was continuous over 0 μm and the L / D was over 100. The mechanical properties of this fiber were excellent, with a strength of 5.2 g / d, an elongation of 21% and an elastic modulus of 86 g / d.

The results are shown in Table 1.

[0033]

Example 5 Polyethylene terephthalate (ηsp / c =
0.73) chips were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 57 and a spinning speed of 1000 m / min. This fiber had a Δn of 0.008 and a breaking draw ratio of 4.6 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 4.4.

The fibers thus obtained all had a porous structure in the length direction and had a density of 1.07 g / cm ³ . S
When the cross section of the fiber was observed by EM, the fiber had a diameter of 3
A porous layer having a circular shape of 2.7 μm and having a large number of pores having an average diameter of about 0.6 μm, and a non-porous layer having a thickness of about 9.0 μm from the outer peripheral portion of the fiber toward the inside and having no fine pores. Was recognized. Also, when the longitudinal section of the fiber was observed, the micropores were continuous over 100 μm and the L / D was 10
It was confirmed that it exceeded 0. The mechanical properties of this fiber are as follows: strength 6.0 g / d, elongation 16%, elastic modulus 122 g / d
It was very excellent as d.

The results are shown in Table 1.

[0036]

Example 6 Polyethylene terephthalate (ηsp / c =
0.48) chips were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 34 and a spinning speed of 400 m / min. This fiber had a Δn of 0.002 and a breaking draw ratio of 6.5 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 6.3 times.

The fibers thus obtained all had a porous structure in the length direction and had a density of 0.54 g / cm ³ . S
When the cross section of the fiber was observed by EM, the fiber had a diameter of 8
A 4.5 μm circular porous layer having a large number of pores having an average diameter of about 1.3 μm, and a non-porous layer having a thickness of about 2.5 μm from the outer peripheral portion of the fiber toward the interior Was recognized. Observation of the longitudinal section of the fiber revealed that the micropores were continuous over 130 μm and the L / D was 10
It was confirmed that it exceeded 0. The mechanical properties of this fiber are: strength 4.9 g / d, elongation 8%, elastic modulus 108 g / d.
And was very good.

The results are shown in Table 1.

[0039]

Example 7 Polyethylene terephthalate (ηsp / c =
0.88) chips were dried by a known method and then melted at 320 ° C. to produce fibers at a draft ratio of 32 and a spinning speed of 350 m / min. The Δn of this fiber was 0.006, and the breaking draw ratio was 6.6. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 6.0.

The fibers thus obtained all had a porous structure in the length direction and had a density of 0.98 g / cm ³ . S
When the cross section of the fiber was observed by EM, the fiber had a diameter of 3
A porous layer having a circular shape of 3.8 μm and having a large number of pores having an average diameter of about 0.3 μm, and a non-porous layer having a thickness of about 5.0 μm from the outer peripheral portion of the fiber toward the inside thereof Was recognized. Also, when the longitudinal section of the fiber was observed, the micropores were continuous over 100 μm and the L / D was 10
It was confirmed that it exceeded 0. The mechanical properties of this fiber are strength 6.4 g / d, elongation 21%, elastic modulus 98 g / d.
And was very good.

The results are shown in Table 1.

[0042]

Example 8 Polyethylene terephthalate (ηsp / c =
0.73) chips were dried by a known method and then melted at 320 ° C. to produce fibers at a draft ratio of 1.6 and a spinning speed of 150 m / min. This fiber had a Δn of 0.002 and a breaking draw ratio of 6.8. The wound undrawn yarn was neck-drawn at a drawing temperature of 85 ° C. and a draw ratio of 6.6.

The fibers thus obtained all had a porous structure in the length direction and had a density of 0.92 g / cm ³ . S
When the cross section of the fiber was observed by EM, the fiber had a diameter of 2
A porous layer having a circular shape of 4.8 μm and having a large number of pores having an average diameter of about 0.4 μm, and a non-porous layer having a thickness of about 4.0 μm from the outer peripheral portion of the fiber toward the inside and having no fine pore Was recognized. Also, when the longitudinal section of the fiber was observed, the micropores were continuous over 100 μm and the L / D was 10
It was confirmed that it exceeded 0. The mechanical properties of this fiber are strength 6.8 g / d, elongation 12%, elastic modulus 102 g / d.
It was very excellent as d.

The results are shown in Table 1.

[0045]

Example 9 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 18 and a spinning speed of 315 m / min. This fiber had a Δn of 0.004 and a breaking draw ratio of 6.0 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 150 ° C. and a draw ratio of 5.9.

The obtained fiber has a porous structure in which a portion having a porous structure and a portion having no porous structure are alternately present in the longitudinal direction, and thus the fiber has a porous structure. The length ratio in the fiber axis direction of the part is 70%, and the density is 1.15 g /
It was cm ³ . When the cross section of the portion having a porous structure was observed by SEM, the fibers were circular with a diameter of 71.1 μm, and a porous layer having a large number of pores with an average diameter of about 0.6 μm From the outer peripheral portion to the inner portion, a non-porous layer having a thickness of about 7.0 μm and having no fine pores was observed. When the longitudinal section of the fiber was observed, it was found that the fine pores were 10
It was confirmed that the diameter was continuous over 0 μm and the L / D was over 100. The mechanical properties of this fiber were excellent, with a strength of 7.3 g / d, an elongation of 15% and an elastic modulus of 156 g / d.

The results are shown in Table 1.

[0048]

Comparative Example 1 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 200 and a spinning speed of 2000 m / min. This fiber had a Δn of 0.021 and a breaking draw ratio of 3.8 times. The wound undrawn yarn was neck-drawn at a drawing temperature of 80 ° C. and a draw ratio of 3.7 times.

Although the obtained fiber has a porous structure, the length ratio in the axial direction of the fiber is low and the density is 1.31.
It was g / cm ³ . When the cross section of the fiber was observed by SEM, the fiber was circular with a diameter of 37.5 μm, only a few porous layers were observed, and the diameter of the micropores was about 0.1 μm. The results are shown in Table 1.

[0050]

Comparative Example 2 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 18 and a spinning speed of 315 m / min. This fiber had a Δn of 0.004 and a breaking draw ratio of 6.0 times. The wound undrawn yarn was drawn at a drawing temperature of 80 ° C. and a draw ratio of 3.9 times. The neck point was not clear in this stretch.

The obtained fiber did not have a porous structure and had a density of 1.36 g / cm ³ . When the cross section of the fiber was observed by SEM, the fiber had a circular shape with a diameter of 31.5 μm and no fine pores were observed. These results are shown in Table 1.
Shown in.

[0052]

Comparative Example 3 Spinning and drawing were performed in the same manner as in Example 1 except that fibers having a low degree of orientation were preheated to 75 ° C. and drawn. The fibers obtained in this case had no porous structure and had a density of 1.36 g / cm ³ . When the cross section of the fiber was observed by SEM, the fiber was circular with a diameter of 33.5 μm, and no fine pores were observed.

The results are shown in Table 1.

[0054]

Comparative Example 4 Polyethylene terephthalate (ηsp / c =
The chips of 0.73) were dried by a known method and then melted at 315 ° C. to produce fibers at a draft ratio of 18 and a spinning speed of 315 m / min. This fiber had a Δn of 0.004 and a breaking draw ratio of 6.0 times. The wound undrawn yarn was drawn at a drawing temperature of 180 ° C. and a draw ratio of 5.9. The fiber obtained does not have a porous structure and has a density of 1.39 g /
It was cm ³ . When the cross section of the fiber was observed by SEM, the fiber was circular with a diameter of 29.5 μm, and no fine pores were observed.

The results are shown in Table 1.

[0056]

[Table 1]

[0057]

INDUSTRIAL APPLICABILITY The porous lightweight fiber of the present invention is lightweight and excellent in heat retention and mechanical strength, and also has excellent ultraviolet and visible light shielding properties. It can also be applied to clothing fields, building materials, and composite materials. Further, since no impurities are mixed in and no special post-processing is required, there is no increase in cost and no deterioration in fiber physical properties, and it is an extremely excellent fiber.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area D04H 3/00 K F

Claims (1)

[Claims] 1. A fiber made of polyethylene terephthalate, the outer peripheral portion of which is a dense non-porous layer,
The fibers have fine pores connected in the axial direction of the fiber, the average diameter (D) of the fine pores is 0.1 to 10 μm, and the ratio (L / D) to the length (L) in the axial direction of the fiber. Contains more than 100 porous parts and has a fiber density of 1.30 g / cm ³
A porous lightweight fiber characterized by being: