Biodegradable fibers

Abstract

The present invention provides a biodegradable fiber which does not become brittle in a moist heat environment, and which has excellent alkali resistance.　Disclosed is a biodegradable fiber which contains a blend polymer containing a polyethylene terephthalate, a polybutylene adipate terephthalate and a polylactic acid, wherein the content of the polyethylene terephthalate in the fiber is 80 mass% or more. It is preferable that the content of the polyethylene terephthalate in the fiber is at least 93 mass% or more, the content of the polybutylene adipate terephthalate in the fiber is 0.4 mass% to 2.4 mass%, the content of the polylactic acid in the fiber is 0.4 mass% to 2.4 mass%, and the ratio of the content of the polybutylene adipate terephthalate to the content of the polylactic acid is 40 / 60 to 60 / 40 in terms of the mass ratio.

Description

Technical Field

[0001] The present invention relates to biodegradable fibers mainly composed of polyethylene terephthalate.

Background Art

[0002] Polyethylene terephthalate fibers are preferably used in various applications due to their excellent mechanical and chemical properties.

[0003] On the other hand, in recent years, in view of environmental problems, biodegradable fibers have been attracting attention. A typical fiber is polylactic acid fiber.

[0004] Polylactic acid fibers have poor alkali resistance and cannot improve the texture by alkali weight reduction like polyethylene terephthalate, so they are not suitable for clothing applications. Also, since they hydrolyze and embrittle in a wet-heat environment, they are not suitable for vehicle interior materials used in a high-temperature environment, etc., and the applications where they are used have been limited.

[0005] As a biodegradable fiber excellent in alkali resistance, a core-sheath type composite fiber having polyethylene terephthalate in the sheath and polylactic acid in the core has been proposed (Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, although the fiber in Patent Document 1 has its surface covered with polyethylene terephthalate, the core becomes brittle under humid and hot conditions, and a decrease in fiber strength could not be prevented. In addition, polylactic acid in the core leaches out during alkali reduction. Furthermore, although the polylactic acid used in the core is biodegradable, the polyethylene terephthalate used in the sheath is not, so it was insufficient in terms of environmental impact.

[0008] As described above, conventionally, there were no biodegradable fibers that could be used in humid and hot environments and exhibited alkali resistance. Therefore, the objective is to provide a fiber that is primarily composed of polyethylene terephthalate but also exhibits excellent biodegradability. Furthermore, the objective is to provide biodegradable fibers that do not become brittle even in humid and hot environments and have excellent alkali resistance. [Means for solving the problem]

[0009] As a result of various studies, the inventors of the present invention have discovered that if a fiber is made of a blend polymer mainly composed of polyethylene terephthalate and containing specific amounts of polybutylene adipate terephthalate and polylactic acid, polyethylene terephthalate fibers, which normally exhibit almost no biodegradability, can be effectively biodegraded, and have completed the present invention. In other words, the object of the present invention is achieved by a biodegradable fiber comprising a blend polymer containing polyethylene terephthalate, polybutylene adipate terephthalate, and polylactic acid, wherein the polyethylene terephthalate content in the fiber is 80% by mass or more. Furthermore, the inventors have discovered that a fiber made of a blend polymer mainly composed of polyethylene terephthalate and containing polybutylene adipate terephthalate and polylactic acid in specific mixing ratios and amounts does not become brittle even in a humid and hot environment, has good alkali resistance to the extent that alkali weight reduction is possible, and moreover, a fiber can be obtained in which the entire fiber biodegrades in a manner exceeding the content of polybutylene adipate terephthalate and polylactic acid. In other words, the object of the present invention is achieved by a biodegradable fiber comprising a blend polymer containing polyethylene terephthalate, polybutylene adipate terephthalate, and polylactic acid, characterized in that the content of polyethylene terephthalate in the fiber is at least 93% by mass, the content of polybutylene adipate terephthalate in the fiber is 0.4 to 2.4% by mass, the content of polylactic acid in the fiber is 0.4 to 2.4% by mass, and the ratio of the content of polybutylene adipate terephthalate to polylactic acid is 40 / 60 to 60 / 40 by mass.

[0010] Furthermore, the above-mentioned biodegradable fiber preferably contains 98% by mass or more of polyethylene terephthalate, and the ratio of polybutylene adipate terephthalate to polylactic acid is preferably 50 / 50 to 60 / 40 by mass (polybutylene adipate terephthalate / polylactic acid). This makes it possible to produce a biodegradable fiber that combines higher resistance to humid and hot environments with biodegradability and alkali resistance. Furthermore, it is preferable that the biodegradability rate of the biodegradable fiber after 135 days in the ASTM D5511 test is 15% or more.

[0011] Furthermore, it is preferable that the rate of decrease in the breaking strength of the biodegradable fiber after the following humid heat environment test is 25% or less. (Humid heat environment test) A tubular knitted material is prepared, and a 120mm x 150mm test specimen is taken from the prepared tubular knitted material. After heat setting, the specimen is measured using a Shimadzu AG-IS Autograph (registered trademark) tensile testing machine under the conditions of a sample width of 50mm, a test length of 50mm, and a constant tensile speed of 100mm / min. The maximum value of the load on the load-elongation curve is defined as the breaking strength (cN). The specimen is measured twice in both the longitudinal and transverse directions, and the average value is defined as the breaking strength before the humid heat environment test. Using an ESPEC Corporation PR-3KP windless constant temperature and humidity testing machine, the specimen is left to stand in a humid heat environment at a temperature of 80°C and relative humidity of 95% for 400 hours. After 400 hours, the breaking strength is measured twice using the tensile test described above, in the same manner as before the humid heat environment test, and this is defined as the breaking strength after the humid heat environment test. Using these average values, the rate of decrease in breaking strength under humid heat conditions is calculated using the following formula. The percentage decrease in breaking strength under a humid heat environment is calculated as follows: (%) = {(Breaking strength before humid heat environment test - Breaking strength after humid heat environment test) / (Breaking strength before humid heat environment test)} × 100

[0012] Furthermore, it is preferable that the mass reduction rate of the biodegradable fiber after the alkali resistance test described below is 15% or less. (Alkali resistance test) A cylindrical knit is prepared, and a 100 mm x 100 mm test specimen is taken from the prepared cylindrical knit. The mass (W1) at the moisture equilibrium state is measured, and the specimen is immersed in a 4 mass% sodium hydroxide aqueous solution maintained at 98 ± 2°C for 30 minutes. After 30 minutes, the test specimen is removed, washed with water, dried, and brought back to the moisture equilibrium state, and its mass (W2) is measured. This measurement is performed twice, and the average value is used to calculate the mass reduction rate using the following formula. Mass reduction rate (%)={(W1-W2) / W1}×100 [Effects of the Invention]

[0013] According to the present invention, even polyethylene terephthalate, which does not inherently exhibit biodegradability, can be made to exhibit biodegradability and have good alkali resistance, so they do not dissolve immediately when reduced by alkali, and they are less prone to embrittlement even in humid and hot environments. Furthermore, the resulting biodegradable fibers have tensile strength and elongation at break equivalent to those of polyethylene terephthalate fibers. [Modes for carrying out the invention]

[0014] The biodegradable fiber of the present invention must contain polyethylene terephthalate (hereinafter referred to as PET) as the main component, and must also contain a blended polymer containing polybutylene adipate terephthalate (hereinafter referred to as PBAT) and polylactic acid. By blending PBAT and polylactic acid with PET, biodegradability is imparted to PET fibers that do not inherently exhibit biodegradability.

[0015] The biodegradable fibers of the present invention are biodegraded by a synergistic effect of two components: hydrolysis by polylactic acid, a hydrolyzable material, in the high-temperature, high-humidity environment of soil, which promotes biodegradation through the action of microorganisms, and direct biodegradation by PBAT, an enzymatic decomposition material, which is biodegraded by microorganisms.

[0016] The biodegradable fiber of the present invention preferably contains at least 93% by mass of PET. Furthermore, it is preferable that the PET content in the fiber is 95% by mass or more. If the PET content in the fiber is 93% by mass or more, it can be used in the same applications as PET fibers without impairing the high tensile strength and alkali resistance properties of fibers made solely of PET, and because its strength does not easily decrease in humid and hot environments.

[0017] In this invention, PET may be homo-PET, or copolymerized PET obtained by copolymerizing with an alkali metal sulfoisophthalate or the like.

[0018] In the present invention, PET may have modifiers such as light-resistant agents, heat-resistant agents, and matting agents added to it in order to improve various physical properties.

[0019] In the present invention, the content of PBAT is preferably 0.4 to 2.4% by mass. Further, it is preferably 0.6 to 2.2% by mass, and more preferably 0.8 to 2.0% by mass. If it is 0.4% by mass or more, biodegradability can be imparted to PET. Also, if it is 2.4% by mass or less, the alkali resistance is good, and the breaking strength and elongation at break are less likely to decrease.

[0020] In the present invention, the content of polylactic acid is preferably 0.4 to 2.4% by mass. Further, it is preferably 0.6 to 2.2% by mass, and more preferably 0.8 to 2.0% by mass. If it is 0.4% by mass or more, it is easily hydrolyzed in the soil, and biodegradability can be imparted to PET. If it is 2.4% by mass or less, it is less likely to embrittle even in a humid heat environment, the alkali resistance is good, and the breaking strength and elongation at break are less likely to decrease.

[0021] In the present invention, the ratio of the contents of PBAT and polylactic acid is preferably 40 / 60 to 60 / 40 by mass ratio. Further, it is preferably 45 / 55 to 55 / 45, and more preferably 48 / 52 to 52 / 48. When the ratio of the contents is in the range of 40 / 60 to 60 / 40, biodegradability can be imparted to PET due to the synergistic effect of PBAT and polylactic acid. Also, the strength is less likely to decrease even in a humid heat environment.

[0022] For the biodegradable fiber of the present invention, the biodegradation rate after 135 days in the ASTM D5511 test is preferably 15% or more. Further, it is more preferably 20% or more, and particularly preferably 25% or more. If the biodegradation rate after 135 days is 15% or more, sufficient biodegradability is exhibited. Also, for the biodegradable fiber of the present invention, the biodegradation rate after 360 days in the ASTM D5511 test is preferably 35% or more. Further, it is more preferably 40% or more, and particularly preferably 45% or more. Furthermore, the biodegradable fibers of the present invention preferably exhibit a biodegradation rate of 57% or higher after 675 days in the ASTM D5511 test. More preferably, it is 60% or higher, and particularly preferably 65% ​​or higher.

[0023] The biodegradable fibers of the present invention preferably exhibit a reduction in tensile strength of 25% or less after the humid heat environment test described later. More preferably, it is 15% or less, and particularly preferably 10% or less. If the reduction is 25% or less, it can be used in applications where humid heat environments may be present, similar to PET fibers.

[0024] The biodegradable fibers of the present invention preferably have a mass reduction rate of 15% or less after the alkali resistance test described later. If the rate is 15% or less, the texture can be moderately improved by alkali reduction, similar to PET fibers.

[0025] The total fineness of the biodegradable fibers of the present invention is not particularly limited and may be the same as that used for ordinary PET fibers. From the viewpoint of spinnability and mechanical strength, it is preferably 1 to 300 dtex. If it is 1 to 100 dtex, it will maintain a good texture when used mainly for clothing applications. If it is 30 to 300 dtex, it will maintain a good strength when used for vehicle applications.

[0026] The biodegradable fibers of the present invention preferably have a single filament fineness of 0.8 to 25 dtex. If the fineness is 0.8 dtex or higher, good strength is maintained when mainly used for clothing applications. If the fineness is 25 dtex or lower, the specific surface area of ​​the fiber is large and biodegradable.

[0027] The biodegradable fibers of the present invention preferably have a tensile strength of 2.0 cN / dtex or higher. More preferably, it is 2.5 cN / dtex or higher, and particularly preferably 3.0 cN / dtex or higher. If the tensile strength is 2.0 cN / dtex or higher, the spinning operation and process passability in the manufacturing and weaving processes are good, and it can be used in the same applications as PET fibers.

[0028] The biodegradable fibers of the present invention preferably have a break elongation of 20% or more. If it is 20% or more, the spinning operation and process passability in the manufacturing and weaving processes are good, and it can be used in the same applications as PET fibers.

[0029] The biodegradable fibers of the present invention may be circular in shape or have an irregular cross-section. For example, irregular cross-sections include multi-lobed, triangular, flattened, and elliptical shapes.

[0030] The biodegradable fibers of this invention can be used as long fibers, but can also be used in woven or knitted fabrics. Furthermore, they can be processed from long fibers into short fibers, which can be used as padding. They can also be used in nonwoven fabrics. [Examples]

[0031] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Furthermore, the physical property measurements and evaluations in the examples were carried out as follows.

[0032] (Tensile test) In accordance with JIS L 1013, measurements were taken using a Shimadzu AGS-1kNG Autograph® tensile testing machine under the conditions of a sample yarn length of 200 mm and a constant tensile speed of 200 mm / min. The breaking strength (cN / dtex) was defined as the value obtained by dividing the maximum load on the load-elongation curve by the fineness, and the elongation at that time was defined as the elongation at break (%). Three measurements were taken, and the average value was calculated.

[0033] (Biodegradability assessment) Anaerobic biodegradability tests were conducted at 52±2℃ in accordance with the ASTM D5511 standard.

[0034] (Humid heat environment test) Using a tubular knitting machine (NCR-EW) (manufactured by Eiko Sangyo Co., Ltd.), tubular knitting was performed with two-ply yarn to produce tubular knits with 30 wale threads / inch and 37 coarse threads / inch. A 120mm x 150mm test specimen was taken from the produced tubular knit, heat-set at 190°C for 1 minute, and then measured using a Shimadzu AG-IS Autograph® tensile testing machine under the conditions of a sample width of 50mm, a test length of 50mm, and a constant tensile speed of 100mm / min. The maximum value of the load on the load-elongation curve was defined as the breaking strength (cN). The breaking strength was measured twice in both the longitudinal and transverse directions of the test specimen, and the average value was taken as the breaking strength before the humid heat environment test. Using an ESPEC Corporation PR-3KP constant temperature and humidity tester, the specimen was left undisturbed in a humid heat environment at 80°C and 95% relative humidity for 400 hours. After that, the breaking strength was measured twice in both the longitudinal and transverse directions of the test specimen, and the average value was taken as the breaking strength after the humid heat environment test. The rate of decrease in breaking strength under humid heat conditions was calculated using the following formula. The percentage decrease in breaking strength under a humid heat environment is calculated as follows: (%) = {(Breaking strength before humid heat environment test - Breaking strength after humid heat environment test) / (Breaking strength before humid heat environment test)} × 100

[0035] (Alkali resistance test) Using a tubular knitting machine (NCR-EW) (manufactured by Eiko Sangyo Co., Ltd.), tubular knitting was performed with two-ply yarn to produce tubular knits with 30 wale threads / inch and 37 course threads / inch. A 100 mm x 100 mm test piece was taken from the produced tubular knit, and the mass (W1) at the moisture equilibrium state was measured. The test piece was then immersed in a 4 mass% sodium hydroxide aqueous solution maintained at 98 ± 2°C for 30 minutes. After the test piece was removed, washed with water, dried, and brought back to the moisture equilibrium state, and the mass (W2) at that time was measured. This measurement was performed twice, and the average value was used to calculate the mass loss rate using the following formula. The mass loss rate was used as an indicator of alkali resistance. Mass reduction rate (%)={(W1-W2) / W1}×100

[0036] (Example 1) A blended polymer was obtained by mixing PET (98% by mass), PBAT (1.0% by mass), and polylactic acid (1.0% by mass), with a mass ratio of 50 / 50 between PBAT and polylactic acid. This blended polymer was melt-extruded at 294°C and stretched 3.1 times at GR1 (circular speed 1350 m / min, temperature 90°C) and GR2 (circular speed 4200 m / min, temperature 140°C) to produce 84 dtex / 36f biodegradable fibers. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers.

[0037] (Example 2) Biodegradable fibers were prepared in the same manner as in Example 1, except that the PBAT content was set to 1.1% by mass, the polylactic acid content to 0.9% by mass, and the ratio of PBAT to polylactic acid content was 55 / 45 by mass. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1.

[0038] (Example 3) Biodegradable fibers were prepared in the same manner as in Example 1, except that the PBAT content was set to 0.9% by mass, the polylactic acid content to 1.1% by mass, and the ratio of PBAT to polylactic acid content was 45 / 55 by mass. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1.

[0039] (Example 4) Biodegradable fibers were prepared in the same manner as in Example 1, except that the PET content was 96% by mass, the PBAT content was 2.0% by mass, and the polylactic acid content was 2.0% by mass. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1.

[0040] (Example 5) Biodegradable fibers were prepared in the same manner as in Example 1, except that the PET content was set to 96% by mass, the PBAT content to 2.2% by mass, and the polylactic acid content to 1.8% by mass, with the ratio of PBAT to polylactic acid content being 55 / 45 by mass. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1.

[0041] (Comparative Example 1) Multifilaments were prepared in the same manner as in Example 1, except that melt spinning was performed using only PET. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained multifilaments in the same manner as in Example 1.

[0042] (Comparative Example 2) Using only polylactic acid, a multifilament of 84 dtex / 36 f was prepared by melt-extrusion at 230°C and melt-spinning using a conventional method. The obtained multifilament underwent tensile testing, biodegradability evaluation, and alkali resistance testing in the same manner as in Example 1. In addition, a moist heat environment test was performed in the same manner as in Example 1, except that the heat-setting temperature was set to 120°C.

[0043] (Comparative Example 3) Multifilaments were prepared in the same manner as in Example 1, except that the PBAT content was 2.0% by mass and polylactic acid was omitted. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1.

[0044] (Comparative Example 4) Multifilaments were prepared in the same manner as in Example 1, except that they did not contain PBAT and the polylactic acid content was 2.0% by mass. Tensile tests, biodegradability evaluations, humid heat environment tests, and alkali resistance tests were performed on the obtained biodegradable fibers in the same manner as in Example 1. These results are also shown in Table 1.

[0045] [Table 1]

[0046] As a result of the fiber property evaluation, it was found that PET fibers, which are normally almost biodegradable, exhibit excellent biodegradability over a long period of time when they contain both polylactic acid and PBAT (Examples and Comparative Examples 1, 3, 4). Furthermore, the results from each example and Comparative Examples 3 and 4 showed that the fibers of the examples could suppress the decrease in strength even when exposed to high temperature and high humidity environments. Furthermore, the results from Comparative Example 2 confirmed that the fibers of the examples, which mainly contain PET, are fibers with excellent alkali resistance, and that particularly excellent alkali resistance can be obtained by setting the PET content to 97% by mass or more (Examples 1, 2, and 3). In addition, it was confirmed that particularly excellent alkali resistance can be obtained by setting the PBAT / polylactic acid content ratio to 1 or more (Examples 2, 3, 4, and 5). Furthermore, in Examples 1 and 2, it was found that it is possible to produce fibers with excellent biodegradability while keeping the tensile strength after the humid heat environment test particularly low at 4% or less. As shown in Table 1, Examples 1-5 demonstrated sufficient biodegradability. Furthermore, they maintained sufficient strength even in humid and hot environments and exhibited excellent alkali resistance. Their breaking strength and elongation were comparable to PET without any decrease. The resulting biodegradable fibers were suitable for use in clothing and vehicle interior materials.

[0047] Comparative Example 1 showed no decrease in strength under humid and hot conditions and exhibited high alkali resistance, but did not show biodegradability. Comparative Example 2 had excellent biodegradability, but its strength decreased significantly under humid and hot conditions. It also had poor alkali resistance and completely dissolved after 10 minutes of immersion in a sodium hydroxide solution. Comparative Examples 3 and 4 had poor biodegradability, with a biodegradation rate of less than 15% after 135 days in the ASTM D5511 test. [Industrial applicability]

[0048] The biodegradable fibers of the present invention exhibit biodegradability through hydrolysis in soil, yet show little reduction in strength even when used in humid and hot environments. Therefore, they are suitable for use in, for example, vehicle interior materials used in high-temperature environments. Furthermore, they have excellent alkali resistance, and like PET fibers, their texture can be improved by alkali reduction, making them suitable for use in, for example, clothing. In addition, they can be suitably used in industrial materials, consumer goods, and other applications similar to those of ordinary PET fibers.

Claims

1. A fiber comprising a blend polymer containing polyethylene terephthalate, polybutylene adipate terephthalate, and polylactic acid, The polyethylene terephthalate content in the fibers is 93% by mass or more and 98% by mass or less. The content of the polybutylene adipate terephthalate in the fiber is greater than 0.9% by mass and less than 2.0% by mass. The polylactic acid content in the fiber is 0.4% by mass or more and less than 1.1% by mass, A biodegradable fiber in which the ratio of the content of polybutylene adipate terephthalate to the content of polylactic acid is 50 / 50 to 55 / 45 by mass.

2. The biodegradable fiber according to claim 1, characterized in that the biodegradation rate after 135 days in the ASTM D5511 test is 15% or more.

3. The biodegradable fiber according to claim 1, characterized in that the rate of decrease in tensile strength after a humid heat environment test is 4% or less.

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