JP7707103B2 - Biodegradable Fibers - Google Patents

Description

The present invention relates to a biodegradable fiber whose main component is polyethylene terephthalate.

Polyethylene terephthalate fibers are popular for a variety of applications due to their excellent mechanical and chemical properties.

On the other hand, in recent years, biodegradable fibers have been attracting attention in light of environmental issues. A typical example of such a fiber is polylactic acid fiber.

Polylactic acid fibers have poor alkali resistance and cannot improve their texture through alkali reduction like polyethylene terephthalate, making them unsuitable for clothing applications. In addition, they undergo hydrolysis and become brittle in hot and humid environments, making them unsuitable for use as interior materials for vehicles, which are used in high-temperature environments, and so their applications have been limited.

As a biodegradable fiber with excellent alkali resistance, a core-sheath type composite fiber with a polyethylene terephthalate sheath and a polylactic acid core has been proposed (Patent Document 1).

JP 2008-208482 A

However, although the surface of the fiber in Patent Document 1 is covered with polyethylene terephthalate, the core becomes brittle in a hot and humid environment, and it is not possible to prevent a decrease in the strength of the fiber. In addition, when the fiber is reduced in weight with alkali, the polylactic acid in the core dissolves. Furthermore, while the polylactic acid used in the core is biodegradable, the polyethylene terephthalate used in the sheath is not biodegradable, so the fiber is insufficient in terms of environmental impact.

As described above, there has been no biodegradable fiber available up to now that can be used in a hot and humid environment and exhibits alkali resistance.
Therefore, an object of the present invention is to provide a biodegradable fiber which does not become embrittled even in a hot and humid environment and has excellent alkali resistance.

As a result of extensive investigations, the present inventors have found that a fiber made of a blend polymer containing polyethylene terephthalate as a main component and specific amounts of polybutylene adipate terephthalate and polylactic acid in a specific mixing ratio can be obtained that does not become embrittled even in a moist and hot environment, has good alkali resistance to the extent that it can be reduced in weight by alkali, and further, is biodegradable as a whole fiber to an extent greater than the content of polybutylene adipate terephthalate and polylactic acid, and have completed the present invention.
That is, 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 content ratio of polybutylene adipate terephthalate and polylactic acid is 40/60 to 60/40 by mass.

It is also preferable that the biodegradable fiber has a biodegradation rate of 15% or more after 135 days in the ASTM D5511 test.

It is also preferable that the biodegradable fiber has a reduction rate of breaking strength of 25% or less after the following wet heat environment test.
(Heat and humidity environment test)
A cylindrical knit is prepared, and a test piece of 120 mm x 150 mm is taken from the prepared cylindrical knit, and after heat setting, it is measured using an AG-IS autograph tensile tester manufactured by Shimadzu Corporation under the conditions of a sample width of 50 mm, a test length of 50 mm, and a constant tensile speed of 100 mm/min. The maximum load in the load-elongation curve is taken as the breaking strength (cN). The test piece is measured twice in the vertical and horizontal directions, and the average value is taken as the breaking strength before the humid heat environment test. After 400 hours have passed, the test piece is left in a humid heat environment at a temperature of 80°C and a relative humidity of 95% using a windless constant temperature and humidity tester PR-3KP manufactured by Espec Corporation, and the breaking strength is measured twice in the same manner as before the humid heat environment test using the above tensile test, and the breaking strength after the humid heat environment test is taken as the breaking strength after the humid heat environment test. The average value is used to calculate the reduction rate of breaking strength in a humid heat environment using the following formula.
Reduction rate of breaking strength under moist heat environment (%)={(breaking strength before moist heat environment test−breaking strength after moist heat environment test)/(breaking strength before moist heat environment test)}×100

In addition, it is preferable that the mass loss rate of the biodegradable fiber after the alkali resistance test described below is 15% or less.
(Alkaline resistance test)
A cylindrical knit is produced, a 100 mm x 100 mm test piece is taken from the produced cylindrical knit, the mass (W1) in the moisture equilibrium state is measured, and then the test piece is immersed in a 4% by mass aqueous sodium hydroxide solution kept at 98±2°C, and after 30 minutes, the test piece is taken out, washed with water, dried, and then brought to moisture equilibrium again, and the mass (W2) at that time is measured. This measurement is carried out twice, and the mass reduction rate is calculated using the average value according to the following formula.
Mass reduction rate (%) = {(W1-W2)/W1}×100

According to the present invention, it is possible to obtain a biodegradable fiber that exhibits biodegradability even from polyethylene terephthalate, which is not inherently biodegradable, has good alkali resistance, does not dissolve immediately when reduced in alkali, and is not easily embrittled even in a moist and hot environment. Furthermore, the breaking strength and breaking elongation of the obtained biodegradable fiber are equivalent to those of polyethylene terephthalate fiber.

The biodegradable fiber of the present invention must contain a blend polymer that is mainly composed of polyethylene terephthalate (hereinafter referred to as PET) and contains polybutylene adipate terephthalate (hereinafter referred to as PBAT) and polylactic acid. By blending PET with PBAT and polylactic acid, biodegradability is imparted to the PET fiber, which is not inherently biodegradable.

The biodegradable fiber of the present invention is hydrolyzed in a high temperature and high humidity environment in soil by the hydrolyzable material polylactic acid, and is biodegraded by the synergistic effect of two components: the effect of promoting biodegradation by the action of microorganisms, and the effect of direct biodegradation by the action of microorganisms due to the enzymatically degradable material PBAT.

The biodegradable fiber of the present invention must be at least 93% by mass or more of PET. It is also 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, the high breaking strength, alkali resistance, and other properties of a fiber made only of PET are not lost, and the strength is less likely to decrease in a moist and hot environment, making it possible to use the fiber in the same applications as PET fiber.

The PET in the present invention may be not only homo-PET, but also copolymerized PET copolymerized with an alkali metal salt of sulfoisophthalic acid, etc.

The PET in the present invention may contain modifiers such as light resistance agents, heat resistance agents, and matting agents to improve various physical properties.

The PBAT content in the present invention must be 0.4 to 2.4% by mass. It is also preferable that it is 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 possible to impart biodegradability to PET. If it is 2.4% by mass or less, it has good alkali resistance and is less likely to decrease in breaking strength and breaking elongation.

The content of polylactic acid in the present invention must be 0.4 to 2.4% by mass. It is also preferable that it is 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 soil, and biodegradability can be imparted to the PET. If it is 2.4% by mass or less, it is less likely to become embrittled even in a humid and hot environment, has good alkali resistance, and is less likely to decrease in breaking strength and breaking elongation.

The content ratio of PBAT and polylactic acid in the present invention must be 40/60 to 60/40 by mass. It is also preferable that it is 45/55 to 55/45, and more preferably 48/52 to 52/48. When the content ratio is in the range of 40/60 to 60/40, the synergistic effect of PBAT and polylactic acid can impart biodegradability to PET. In addition, the strength is less likely to decrease even in a humid and hot environment.

The biodegradable fiber of the present invention preferably has a biodegradation rate of 15% or more after 135 days in the ASTM D5511 test. It is more preferable that the rate is 20% or more, and particularly preferably 25% or more. If the biodegradation rate is 15% or more after 135 days, the fiber exhibits sufficient biodegradability.

The biodegradable fiber of the present invention preferably has a reduction in breaking strength of 25% or less after the moist heat environment test described below. It is more preferable that the reduction is 15% or less, and particularly preferable that the reduction is 10% or less. If the reduction is 25% or less, the fiber can be used in applications where there is a possibility of a moist heat environment, similar to PET fibers.

The biodegradable fiber of the present invention preferably has a mass loss rate of 15% or less after the alkali resistance test described below. If it is 15% or less, the texture can be appropriately improved by alkali weight loss, similar to PET fiber.

The total fineness of the biodegradable fiber of the present invention is not particularly limited and may be the same as that used for ordinary PET fibers, and is preferably 1 to 300 dtex in terms of spinning operability and mechanical strength. If it is 1 to 100 dtex, it will maintain a good texture when used mainly for clothing applications. Also, if it is 30 to 300 dtex, it will maintain good strength when used for vehicle applications.

The biodegradable fiber of the present invention preferably has a single filament fineness of 0.8 to 25 dtex. If it is 0.8 dtex or more, it will maintain good strength when used mainly for clothing applications. If it is 25 dtex or less, the specific surface area of the fiber will be large and it will be easily biodegradable.

The biodegradable fiber of the present invention preferably has a breaking strength of 2.0 cN/dtex or more. It is more preferable that the breaking strength is 2.5 cN/dtex or more, and particularly preferable that the breaking strength is 3.0 cN/dtex or more. If the breaking strength is 2.0 cN/dtex or more, the spinning operability and the processability in the knitting and weaving process are good, and the fiber can be used in the same applications as PET fibers.

The biodegradable fiber of the present invention preferably has a breaking elongation of 20% or more. If it is 20% or more, the spinning operability and the processability in the knitting and weaving process are good, and it can be used in the same applications as PET fibers.

The biodegradable fibers of the present invention may be circular or have a modified cross section. For example, modified cross sections may be multi-lobed, triangular, flat, elliptical, etc.

The biodegradable fibers of the present invention can be used as long fibers, but can also be used as woven or knitted fabrics. They can also be processed from the long fibers to produce short fibers, and can also be used as batting. They can also be used as nonwoven fabrics.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples. In addition, the physical properties in the examples were measured and evaluated as follows.

(Tensile test)
Measurements were performed using a Shimadzu AGS-1kNG autograph tensile tester under conditions of a sample yarn length of 200 mm and a constant tensile speed of 200 mm/min in accordance with JIS L 1013. The maximum load in the load-elongation curve was divided by the fineness to determine the breaking strength (cN/dtex), and the elongation at that time was determined as the breaking elongation (%). Measurements were performed three times, and the average value was calculated.

(Biodegradability evaluation)
Anaerobic biodegradability tests were carried out at 52±2° C. according to ASTM D5511 standard.

(Heat and humidity environment test)
A cylindrical knitting machine (NCR-EW) (manufactured by Eiko Sangyo Co., Ltd.) was used to perform circular knitting using two combined yarns, producing a cylindrical knitting with 30 wales/inch and 37 courses/inch. A test piece of 120 mm x 150 mm was taken from the produced cylindrical knitting, and after heat setting at 190°C for 1 minute, it was measured using an AG-IS autograph tensile tester manufactured by Shimadzu Corporation under the conditions of a sample width of 50 mm, a test length of 50 mm, and a constant tensile speed of 100 mm/min. The load The maximum load in the elongation curve was taken as the breaking strength (cN), and the test piece was measured twice in each of the longitudinal and transverse directions, with the average value being taken as the breaking strength before the humid heat environment test. Using a windless constant temperature and humidity tester PR-3KP manufactured by Espec Corporation, the test piece was left in a humid heat environment of 80°C and 95% relative humidity for 400 hours, after which the breaking strength of the test piece was measured twice in each of the longitudinal and transverse directions, with the average value being taken as the breaking strength after the humid heat environment test. The rate of decrease in breaking strength in a humid heat environment was calculated using the following formula.
Reduction rate of breaking strength under moist heat environment (%)={(breaking strength before moist heat environment test−breaking strength after moist heat environment test)/(breaking strength before moist heat environment test)}×100

(Alkaline resistance test)
A cylindrical knitting machine (NCR-EW) (manufactured by Eiko Sangyo Co., Ltd.) was used to perform circular knitting with two combined yarns, producing a cylindrical knit with 30 wales/inch and 37 courses/inch. A test piece of 100 mm x 100 mm was taken from the produced cylindrical knit, and the mass (W1) in the moisture equilibrium state was measured. The test piece was then immersed in a 4% by mass aqueous sodium hydroxide solution maintained at 98±2°C. After 30 minutes, the test piece was removed, washed with water, dried, and then returned to a moisture equilibrium state, and the mass (W2) at that time was measured. This measurement was performed twice, and the mass loss rate was calculated using the average value according to the following formula. The mass loss rate was used as an index of alkali resistance.
Mass reduction rate (%) = {(W1-W2)/W1}×100

Example 1
A blend polymer was obtained by mixing 98% by mass of PET, 1.0% by mass of PBAT, and 1.0% by mass of polylactic acid, with the PBAT/polylactic acid content ratio being 50/50 by mass, and melt extruded at 294° C. and stretched 3.1 times with GR1 at a peripheral speed of 1350 m/min and a temperature of 90° C., and with GR2 at a peripheral speed of 4200 m/min and a temperature of 140° C. to produce a biodegradable fiber of 84 dtex/36f. The obtained biodegradable fiber was used to carry out a tensile test, a biodegradability evaluation, a moist heat environment test, and an alkali resistance test.

Example 2
A biodegradable fiber was produced in the same manner as in Example 1, except that the PBAT content was 1.1% by mass, the polylactic acid content was 0.9% by mass, and the PBAT and polylactic acid content ratio was 55/45 by mass. Using the obtained biodegradable fiber, a tensile test, biodegradability evaluation, moist heat environment test, and alkali resistance test were carried out in the same manner as in Example 1.

Example 3
A biodegradable fiber was produced in the same manner as in Example 1, except that the PBAT content was 0.9% by mass, the polylactic acid content was 1.1% by mass, and the PBAT and polylactic acid contents were mixed in a mass ratio of 45/55. Using the obtained biodegradable fiber, a tensile test, biodegradability evaluation, moist heat environment test, and alkali resistance test were carried out in the same manner as in Example 1.

Example 4
Except for changing the content of PET to 96% by mass, the content of PBAT to 2.0% by mass, and the content of polylactic acid to 2.0% by mass, a biodegradable fiber was produced in the same manner as in Example 1. Using the obtained biodegradable fiber, a tensile test, a biodegradability evaluation, a moist heat environment test, and an alkali resistance test were carried out in the same manner as in Example 1.

Example 5
A biodegradable fiber was produced in the same manner as in Example 1, except that the PET content was 96% by mass, the PBAT content was 2.2% by mass, the polylactic acid content was 1.8% by mass, and the PBAT and polylactic acid contents were mixed in a mass ratio of 55/45. Using the obtained biodegradable fiber, a tensile test, biodegradability evaluation, moist heat environment test, and alkali resistance test were carried out in the same manner as in Example 1.

(Comparative Example 1)
Except for melt spinning using only PET, a multifilament was produced in the same manner as in Example 1. Using the obtained multifilament, a tensile test, a biodegradability evaluation, a moist heat environment test, and an alkali resistance test were carried out in the same manner as in Example 1.

(Comparative Example 2)
Polylactic acid alone was melt extruded at 230°C and melt spun in a conventional manner to produce a multifilament of 84 dtex/36f. The multifilament obtained was subjected to a tensile test, a biodegradability evaluation, and an alkali resistance test 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.

(Comparative Example 3)
Except for the fact that the PBAT content was 2.0% by mass and that no polylactic acid was contained, a multifilament was produced in the same manner as in Example 1. Using the obtained biodegradable fiber, a tensile test, a biodegradability evaluation, a moist heat environment test, and an alkali resistance test were carried out in the same manner as in Example 1.

(Comparative Example 4)
A multifilament was produced in the same manner as in Example 1, except that no PBAT was contained and the content of polylactic acid was 2.0% by mass. Using the obtained biodegradable fiber, a tensile test, a biodegradability evaluation, a moist heat environment test, and an alkali resistance test were carried out in the same manner as in Example 1. These results are also shown in Table 1.

Examples 1 to 5 showed sufficient biodegradability. They also maintained sufficient strength even in a hot and humid environment and had excellent alkali resistance. Furthermore, the breaking strength and breaking elongation were not reduced and were equivalent to those of PET. The obtained biodegradable fibers were suitable for use as clothing fibers and fibers for vehicle interior materials.

Comparative Example 1 showed no loss of strength in a humid and hot environment, and high alkali resistance, but no biodegradability. Comparative Example 2 had excellent biodegradability, but showed a significant loss of strength in a humid and hot environment. It also had poor alkali resistance, completely dissolving after 10 minutes of immersion in an aqueous 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.

Although the biodegradable fiber of the present invention is biodegradable in soil after undergoing hydrolysis, it does not lose much strength even when used in a moist and hot environment, and therefore can be suitably used, for example, in vehicle interior materials used in high temperature environments. In addition, since it has excellent alkali resistance, it can be reduced in weight by alkali in the same way as PET fibers, improving the texture, and therefore can be suitably used, for example, in clothing applications. It can also be suitably used in the same applications as ordinary PET fibers, such as industrial materials and daily living materials.

Claims (4)

A fiber comprising a blend polymer comprising polyethylene terephthalate, polybutylene adipate terephthalate and polylactic acid,
A biodegradable fiber 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 content ratio of polybutylene adipate terephthalate to polylactic acid is 40/60 to 60/40 by mass. 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, wherein the rate of decrease in breaking strength after the following wet heat environment test is 25% or less.
(Heat and humidity environment test)
A cylindrical knit is prepared, and a test piece of 120 mm x 150 mm is taken from the prepared cylindrical knit, and after heat setting, it is measured using an AG-IS autograph tensile tester manufactured by Shimadzu Corporation under the conditions of a sample width of 50 mm, a test length of 50 mm, and a constant tensile speed of 100 mm/min. The maximum load in the load-elongation curve is taken as the breaking strength (cN). The test piece is measured twice in the vertical and horizontal directions, and the average value is taken as the breaking strength before the humid heat environment test. After 400 hours, the test piece is left in a humid heat environment at a temperature of 80°C and a relative humidity of 95% using a windless constant temperature and humidity tester PR-3KP manufactured by Espec Corporation, and the breaking strength in the vertical and horizontal directions is measured twice, and the average value is taken as the breaking strength after the humid heat environment test. Using these average values, the rate of decrease in breaking strength in a humid heat environment is calculated using the following formula.
Reduction rate of breaking strength under moist heat environment (%)={(breaking strength before moist heat environment test−breaking strength after moist heat environment test)/(breaking strength before moist heat environment test)}×100 The biodegradable fiber according to any one of claims 1 to 3, characterized in that the mass loss rate after the following alkali resistance test is 15% or less.
(Alkaline resistance test)
A cylindrical knit is produced, a 100 mm x 100 mm test piece is taken from the produced cylindrical knit, the mass (W1) in the moisture equilibrium state is measured, and then the test piece is immersed in a 4% by mass aqueous sodium hydroxide solution kept at 98±2°C, and after 30 minutes, the test piece is taken out, washed with water, dried, and then brought to moisture equilibrium again, and the mass (W2) at that time is measured. This measurement is carried out twice, and the mass reduction rate is calculated using the average value according to the following formula.
Mass reduction rate (%) = {(W1-W2)/W1}×100