JPH07324227A - Biodegradable composite fiber - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a biodegradable conjugate fiber having a certain heat resistance and a practically sufficient strength, and capable of easily obtaining fibers having different tenacity retention periods in a natural environment. [Structure] A polyhydroxyalkanoate having a melting point of 70 ° C. or higher or a copolymer thereof is used as a core component, and a polybutylene succinate, a polyethylene succinate or a copolymer thereof having a high degree of polymerization of 70 ° C. or higher is used as a sheath component. Biodegradable composite fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable conjugate fiber having practically sufficient strength and capable of easily obtaining biodegradable fibers having different tenacity retention periods in a natural environment. .

[0002]

2. Description of the Related Art Conventionally, fibers having excellent strength and weather resistance have been required as fibers for industrial materials used for fishing, agriculture and civil engineering, and mainly consist of polyamide, aromatic polyester, vinylon, polyolefin and the like. Things are being used. However, these fibers are not self-degradable, and there is a problem in that they cause various pollutions if left in the sea or mountains after use. This problem can be solved by incineration, landfilling, or recovery and recycling after use, but since such processing requires a great deal of money, it is actually left in the sea or mountains, which not only damages the landscape. In many cases, birds, marine life, and divers are entangled and killed, and entangled with the screw of a ship to cause a ship accident.

As a method for solving such a problem, it is considered to use biodegradable (biodegradable or naturally degradable) fibers, and biodegradable fibers made of aliphatic polyester have been attracting attention.

For example, JP-A-5-59611 and JP-A-5-59611.
No. 59612 discloses a high strength filament made of polycaprolactone. However, polycaprolactone has a problem that its melting point is as low as about 60 ° C., its biodegradation rate is high, and its use is limited.

Polyhydroxyalkanoates produced by microorganisms are well known as thermoplastic polyesters having a melting point of 100 ° C. to 180 ° C., and the Nikkan Kogyo Shimbun dated January 17, 1992 has a tensile strength of 3 g / It is reported that the monofilament of d was obtained. But this fiber
There was a problem that the strength was not practically sufficient and the biodegradation rate was too fast.

Further, Japanese Patent Laid-Open No. 5-93316 and 5
-93318 discloses a core-sheath type which is excellent in strength characteristics of poly-ε-caprolactone or poly-β-propiolactone and a poly-3-hydroxybutyrate / poly-3-hydroxyvalerate copolymer. A composite fiber is disclosed. However, there is a problem that this composite fiber loses its fiber shape when embedded in soil for 2 months, and cannot retain its strength for a medium to long term.

[0007]

DISCLOSURE OF THE INVENTION The present invention has constant heat resistance and excellent strength characteristics that can withstand practical use, retains sufficient strength for practical use in a natural environment for a certain period, and exceeds a certain period. And a biodegradable fiber that is decomposed by microorganisms, rapidly loses its strength, and is then completely decomposed. Another object of the present invention is to provide a biodegradable fiber from which fibers having different tenacity retention periods in a natural environment can be easily obtained.

[0008]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have made polyhydroxyalkanoate having a fast biodegradation rate a core component, and have a relatively slow biodegradation rate. The inventors have found that this object can be achieved by using a composite fiber having a sheath component of polybutylene succinate, polyethylene succinate or a copolymer thereof which gives a high strength fiber, and arrived at the present invention.

That is, according to the present invention, a polyhydroxyalkanoate having a melting point of 70 ° C. or higher or a copolymer thereof is used as a core component, and polybutylene succinate, polyethylene succinate or a copolymer thereof having a high polymerization degree of 70 ° C. or higher is used. The gist of the invention is a biodegradable conjugate fiber, which is characterized in that the coalescence is used as a sheath component.

The present invention will be described in detail below. In the present invention, a polyhydroxyalkanoate or a copolymer thereof having a melting point of 70 ° C. or higher is used as the core component, and specifically, a homopolymer or a copolymer having a repeating unit of the following formula and / or formula is used. Polymers are mentioned, which are usually obtained as microbial polyesters produced by microorganisms. The most preferred _{-O- (CH 2) n-CO-} (n = 2~4 integer) -O-CH (R) (the alkyl group of R = carbon number 1 to 11) -CH ₂ -CO- of these The compounds are copolymers of poly-3-hydroxybutyrate and poly-3-hydroxyvalerate, and poly-3-hydroxybutyrate and poly-4.
-Copolymer with hydroxybutyrate.

On the other hand, as the sheath component, polybutylene succinate, polyethylene succinate or a copolymer thereof, the melting point is 70 ° C. or higher and the copolymerization molar ratio is 100/0 to 65/35.
And those in the range of 20/80 to 0/100 are used, and particularly, the copolymerization molar ratio of 100/0 to 80/20 and 10 /
Those in the range of 90 to 0/100 are preferably used. Further, polybutylene succinate, polyethylene succinate or copolymers thereof, it is necessary to use those having a high degree of polymerization, in terms of spinnability and strength characteristics of the obtained fiber, the number average molecular weight is about 30,000. The above is preferably used.

Both the core component and the sheath component may contain a small amount of other thermoplastic biodegradable component within the range that the respective basic characteristics are not impaired.

In the conjugate fiber of the present invention, the degree of biodegradation varies depending on the environment in which it is used, the thickness, etc., but by changing the ratio of the core component and the sheath component, a strong holding period in a natural environment is obtained. Can be changed. That is, if the ratio of the sheath component having a slow biodegradation rate is increased, the strong holding period can be lengthened, and if this ratio is decreased, the strong holding period can be shortened.

The strength holding period can be changed by using the thickness of the sheath component of the composite fiber as a guide, for example, 2 to 15 μm for about 6 months, 10 to 30 μm for about 1 year, and 20 μm for 2 years or more. The above is appropriate. The thickness of the single yarn is determined in consideration of the required thickness of the sheath component, the initial strength and the spinnability, but it is desirable that the thickness is 5 μm or more, and when the tenacity holding period is one year or more. , 25 μm or more, and particularly preferably 100 μm or more. The core-sheath weight ratio is appropriately 1/5 to 5/1, preferably 1/3 to 3/1.

The composite fiber of the present invention has a polyhydroxyalkanoate or a copolymer thereof as a core component, and a polybutylene succinate, polyethylene succinate or a copolymer thereof having a high degree of polymerization as a sheath component, and is prepared by a conventional method. It can be produced by melt spinning, drawing.
The temperature of melt spinning varies depending on the composition of both core and sheath components and the degree of polymerization, but is preferably 130 to 220 ° C. Spinning temperature 13
If it is less than 0 ° C, melt extrusion is difficult, and if it exceeds 220 ° C, thermal decomposition becomes remarkable, and it becomes difficult to obtain high-strength fiber.

The melt-spun yarn is air-cooled or water-cooled, and then continuously or once wound up in the spinning process, and then subjected to one or more cold-drawing or hot-drawing. The total draw ratio depends on the spinning speed, the shape of the target fiber, and the required performance. For example, in the case of a monofilament, it is necessary to draw 5.0 times or more to obtain a tensile strength of 4.0 g / d or more. is necessary. In the case of multifilament, in order to have a tensile strength of 3.0 g / d or more,
It is necessary to stretch the film 2.5 times or more.

The form of the fiber may be any of multifilament, monofilament and staple, and is appropriately selected according to the purpose of use.

The conjugate fiber of the present invention has a certain heat resistance and excellent strength characteristics for practical use, and the strength retention period in a natural environment can be changed by changing the composite ratio of the core-sheath. It is a degradable fiber. Therefore, the composite fiber of the present invention is a fishing net material such as a fishing net or fishing line, an insect repellent, an agricultural material such as a bird net or a vegetation net, a living material such as a compost bag, a thread for attaching a transmitter for wildlife ecological research. It is suitable as a fiber used in a natural environment such as a biological material.

[0019]

The composite fiber of the present invention has a relatively slow biodegradation rate for the sheath component and uses a polymer that gives high-strength fiber, and uses a high biodegradation rate polymer for the core component. At that time, it retains practically sufficient strength for a certain period of time, and then the sheath component biodegrades, and if a part of the core component is exposed, biodegradation of the core component also starts rapidly and the strength of the fiber decreases rapidly. Then, by changing the thickness, thickness, etc. of the sheath component, the strong holding period can be changed under the natural environment.

[0020]

EXAMPLES Next, the present invention will be specifically described by way of examples. The tensile strength and elongation properties were measured according to JIS L 1013. The thickness of the sheath component was measured by taking a cross-sectional photograph with a microscope. Further, the biodegradability was evaluated by immersing the sample in seawater, taking out the sample every predetermined period, and measuring the tensile strength.

EXAMPLE 1 Poly-3-hydroxybutyrate / poly-3-hydroxyvalerate copolymer having a melting point of 156 ° C. and a number average molecular weight of about 200,000 (molar ratio of about 88/12) was used as a core component, and the melting point was 114 ° C. ,
Using polybutylene succinate having a number average molecular weight of about 45,000 as a sheath component, a monofilament having a core-sheath weight ratio of 1/1 was produced as follows. Both components were supplied to an extruder type melt spinning machine, melted at a temperature of 160 ° C, spun out from a spinneret having two spinning holes with a diameter of 2.1 mm, and cooled in a hot water bath at 50 ° C, then 10 m / min. Picked up at a speed of 65
The first stage drawing was carried out in a warm water bath at ℃ at a draw ratio of 5.5, followed by the second step drawing at a draw ratio of 1.8 in an oven at 110 ° C., and further relaxation heat treatment in an oven at 100 ° C. and winding. The obtained monofilament has a sheath component thickness of 41.
The diameter was 284 μm.

Example 2 A monofilament was obtained in the same manner as in Example 1 except that the weight ratio of the core-sheath was changed to 3/1. The obtained monofilament had a sheath component thickness of 19 μm and a fiber diameter of 283 μm.

Comparative Example 1 The same poly-3-hydroxybutyrate / poly-3-hydrovalerate copolymer used in Example 1 alone,
The monofilament was spun under the optimal conditions for spinning.

Comparative Example 2 The same polybutylene succinate used in Example 1 was used alone to spin a monofilament under optimal conditions for spinning.

Example 3 The same copolymer as in Example 1 was used as the core component, and the melting point was 109 as the sheath component.
℃, polybutylene succinate / polyethylene succinate copolymer with a number average molecular weight of about 44,000 (molar ratio 90/10)
Was used to produce a multifilament having a core-sheath weight ratio of 3/2 as follows. Both components are supplied to an extruder type melt spinning machine, melted at a temperature of 160 ° C, spun from a spinneret having 24 spinning holes of 0.3 mm in diameter, blown with cooling air of 13 ° C, and then spun at 40 ° C. After cooling through a cylinder, applying an oil agent, the undrawn yarn was once wound at a speed of 1200 m / min, and then drawn at a draw ratio of 3.7 with a hot roller at 60 ° C. The obtained multifilament was 75d / 24f, and the thickness of the sheath component of the single yarn was 2 μm and the fiber diameter of the single yarn was 19 μm.

The tensile strength and elongation and the biodegradation rate of the fibers obtained in the above Examples and Comparative Examples are shown in Table 1 and the tenacity retention rate is shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

In Examples 1, 2 and 3, the tensile strength sharply decreased after 18, 9 and 3 months, respectively. On the other hand, in Comparative Example 1, the tensile strength sharply decreased after 1 month, and in Comparative Example 2, the tensile strength decreased only after 30 months.

[0031]

EFFECTS OF THE INVENTION According to the present invention, it has a certain heat resistance and excellent strength characteristics capable of withstanding practical use, retains sufficient strength for a certain period of time in a natural environment, and after a certain period of time, A biodegradable fiber is provided which is decomposed by microorganisms, rapidly loses its strength, and is then completely decomposed. Also,
According to the present invention, by changing the ratio of the core component and the sheath component, it is possible to obtain biodegradable fibers having different tenacity retention periods in a natural environment.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shigemitsu Murase 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. A polyhydroxyalkanoate or a copolymer thereof having a melting point of 70 ° C. or higher as a core component, and a polybutylene succinate, a polyethylene succinate or a copolymer thereof having a high degree of polymerization of 70 ° C. or higher as a sheath component. A biodegradable composite fiber characterized by the following.