JPH06264305A - Biodegradable fiber and its production - Google Patents

Abstract

PURPOSE:To obtain a biodegradable fiber for industrial materials having high tensile strength in good operability by melt-spinning a mixture containing a poly(beta-hydroxyalkanoate) and poly-epsilon-caprolactone in a specific ratio and drawing the resultant spun yarn. CONSTITUTION:A mixture of a poly(beta-hydroxyalkanoate) having about 750000 molecular weight and consisting of a copolymer of a poly-3-hydroxybutyrate and a poly-3-hydroxyvalerate in a molar ratio of 94/6 and poly-epsilon-caprolactane having about 80000 molecular weight containing these both components in a weight ratio of (95/5) to (55/45) is blended with a nucleating aid such as boron nitride and a plasticizer such as triacetin and the blend is melt-spun from a spinneret at 120-200 deg.C. The spun yarn is subjected to air cooling at 40-80 deg.C and then a lubricant is applied to the spun yarn and the yarn is successively drawn to >=2.0 times at one or two or more stages in a warm bath at 60 deg.C to provide the objective biodegradable fiber suitable for fibers, etc., for industrial materials used as fishing, agricultural and woodworking uses in good operability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable fiber obtained by melt spinning a mixture of poly (β-hydroxyalkanoate) and poly-ε-caprolactone and a method for producing the same.

[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 possible to use a material which is naturally degradable (biodegradable or biodegradable).

Conventionally, as naturally degradable polymers, polysaccharides such as cellulose and chitin, proteins and polypeptides (polyamino acids) such as cut gut (intestinal line) and regenerated collagen, poly (β-hydroxyalkanoate), polyglycolide. Poly (α-oxy acid) such as and polylactide
, And aliphatic polyesters such as poly-ε-caprolactone are well known.

However, when fibers are produced from these polymers, they must be produced by a wet spinning method like polysaccharides and polyamino acids, or poly (α-oxy acid) s are used.
As described above, since the cost of the material is extremely high, there are problems that the manufacturing cost becomes high and that high strength fiber cannot be obtained.

[0006] Among them, poly-ε-caprolactone is a relatively inexpensive, completely biodegradable synthetic polymer and can be melt-spun, but its use is partly due to its low melting point of 60 ° C. There was a problem of being limited.

As an inexpensive material which is naturally disintegratable, polyethylene is mixed with starch, and a film formed by blending linear low-density polyethylene with about 6% starch is used as a shopping bag. Some have been put to practical use.

[0008] However, even if fibers are produced from polyethylene mixed with such starch, not only are they not completely biodegraded, but mechanical properties such as strength are remarkably inferior, and industrial materials requiring high strength. It cannot be used as a service.

Poly (β-hydroxyalkanoate) produced by microorganisms in nature is well known as a thermoplastic polyester having a melting point of 130 to 180 ° C. Although it has been attempted to produce fibers from poly (β-hydroxyalkanoate), it was reported that a monofilament having a tensile strength of 3 g / d was obtained (Nikkan Kogyo Shimbun, January 17, 1992). However, there is no report that a multifilament having practically sufficient strength was obtained. The major reason is poly (β-hydroxyalkanoate)
Since the crystallization rate is extremely slower than that of nylon, polyethylene terephthalate, etc., it was difficult to unwind from the package due to fusion between filaments during melt spinning and winding. To prevent fusion,
Even if the spinning is performed under the condition that the crystallization is sufficiently promoted, the stretching becomes difficult, and only the yarn having low strength is obtained.

The present inventors have previously found that a polyfilament having a strength of 2.0 g / d or more can be obtained from poly (β-hydroxyalkanoate) by appropriately selecting spinning and drawing conditions. However, there was a problem in operational stability, and it was found that industrialization was difficult.

[0011]

DISCLOSURE OF THE INVENTION The present invention is poly (β-hydroxyalkanoate) (which is relatively inexpensive and has a certain heat resistance such that it can be put to practical use and is completely decomposed by microorganisms). (Including a copolymer, the same applies hereinafter) is intended to improve the operational stability during spinning and obtain a high-strength fiber.

[0012]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have formulated poly (β-hydroxyalkanoate) with an appropriate amount of poly-ε-caprolactone, and The inventors have found that this object can be achieved by spinning under the spinning and drawing conditions, and have reached the present invention.

That is, the gist of the present invention is as follows. (1) Poly (β-hydroxyalkanoate) and poly-ε
Fibers obtained by melt-spinning a mixture with caprolactone in a weight ratio of 95/5 to 55/45 and having a tensile strength of 2.0 g / d.
The above is a microbial degradable fiber characterized by the above. (2) Poly (β-hydroxyalkanoate) and poly-ε
-Mixing with caprolactone in a weight ratio of 95/5 to 55/45
A method for producing a biodegradable fiber, which comprises melt-spinning at 120 to 200 ° C, air-cooling a spun yarn at 40 to 80 ° C, and subsequently stretching at 2.0 times or more in one or more steps. .

The present invention will be described in detail below. Examples of the poly (β-hydroxyalkanoate) used in the present invention include poly-3-hydroxypropionate, poly-3-hydroxybutyrate, poly-3-hydroxycaprolate, and poly-3-hydroxyheptanoate. , Poly-3-hydroxyoctanoate and copolymers of these with poly-3-hydroxyvalerate and poly-4-hydroxybutyrate, etc., and these are usually obtained as microbial polyesters produced by microorganisms. Among these, the most preferable ones are copolymers of poly-3-hydroxybutyrate and poly-3-hydroxyvalerate, and poly-3-hydroxybutyrate and poly-.
It is a copolymer with 4-hydroxybutyrate.

Poly (β-hydroxyalkanoate)
Having a molecular weight of about 30,000 to 1,000,000 are preferable from the viewpoints of spinnability and properties of the obtained fiber.

On the other hand, the poly-ε-caprolactone having a molecular weight of about 3,000 to 100,000 is preferable from the viewpoints of spinnability and properties of the obtained fiber.

The mixing ratio of poly (β-hydroxyalkanoate) and poly-ε-caprolactone is 95 by weight.
It is necessary to set / 5 to 55/45. If the proportion of poly-ε-caprolactone is less than 5% by weight, the effect of improving the spinning stability is insufficient, and if it exceeds 45% by weight, the heat resistance of the obtained fiber is lowered, which is not preferable.

Poly (β-hydroxyalkanoate) and poly-ε-caprolactone are prepared by mixing the two components beforehand.
After melting and kneading with a shaft extruder etc. to make chips,
It may be subjected to melt spinning, or chips of both components may be supplied to an extruder type melt spinning machine and kneaded to perform melt spinning.

A crystal nucleating agent such as boron nitride or titanium dioxide is contained in an amount of 0.1 to 5.0% by weight, preferably 0.5 to 2.0% by weight. Further, it is also preferable to contain a plasticizer such as triacetin in an amount of 1 to 20% by weight.

The fibers of the present invention are poly (β-
It can be produced by melt spinning a mixture of hydroxyalkanoate and poly-ε-caprolactone under the optimum conditions described below and stretching.

The melt spinning temperature depends on the molecular weight of the poly (β-hydroxyalkanoate) used and the mixing ratio of poly-ε-caprolactone, but it is necessary to set the temperature to 120 to 200 ° C. If the spinning temperature is lower than 120 ° C, melt extrusion is difficult, and if it exceeds 200 ° C, the polymer is remarkably decomposed to deteriorate the yarn-forming operability, and it becomes difficult to stably obtain high-strength fibers.

The melt-spun yarn is air-cooled at 40 to 80 ° C., and a normal spinning oil for synthetic fibers is applied thereto, and subsequently, one or more stages of cold or hot drawing between rollers. Be used for. The total draw ratio depends on the required performance of the target fiber, but the spinning speed is 10 to 500 m / min.
To maintain the tensile strength of 2.0 g / d or more, it is necessary to set the draw ratio to 2.0 or more.

[0023]

According to the method of the present invention, a multifilament having high strength and no fusion can be produced with good yarn-making operation. Although the reason for this is not clear, it is possible to lower the spinning temperature by about 20 ° C. by mixing poly (β-hydroxyalkanoate) with poly-ε-caprolactone. It is considered to act as a plasticizer and accelerate crystallization in the cooling process.

Since the fiber of the present invention is composed of biodegradable poly (β-hydroxyalkanoate) and biodegradable poly-ε-caprolactone, it has good biodegradability and It has excellent heat resistance and strength characteristics due to the heat resistance of (β-hydroxyalkanoate) and the improvement of the spinnability by blending poly-ε-caprolactone.

[0025]

EXAMPLES Next, the present invention will be specifically described by way of examples. The methods for measuring and evaluating characteristic values and the like are as follows. (a) Spinnability In continuous spinning for 1 hour, the case where there was no yarn breakage was regarded as good. (b) Tensile strength Measured according to JIS L 1013. (c) Heat resistance When using a differential scanning calorimeter DSC-7 type manufactured by Perkin Elmer Co., Ltd., when heat melting behavior was measured at a heating rate of 20 ° C./min,
The case where the main peak (endotherm) was 90 ° C or higher was regarded as good. (d) Biodegradability Samples were buried in soil for 2 months and taken out, and the case where the multifilament lost its shape or the tensile strength retention rate was 50% or less was regarded as good.

Examples 1 to 4 and Comparative Examples 1 to 2 The molecular weight is about 750,000 and the molar ratio of poly-3-hydroxybutyrate to poly-3-hydroxyvalerate is 94/6.
0.3 mm of a copolymer of poly-ε-caprolactone (PCL) having a molecular weight of about 80,000, a crystal nucleating agent (boron nitride) and a plasticizer (triacetin) in an amount of 0.3 mm.
Approximately 160 ℃ melt spinning from the spinneret of φ × 36 holes,
After cooling with air at 60 ° C and applying oil, continue to 60
In a warm water bath at ℃, draw at the draw ratio shown in Table 1, and
A multi-filament of / 36f was obtained. Table 1 shows the results of evaluation of the spinnability, the tensile strength, the heat resistance and the biodegradability of the obtained multifilament.

[0027]

[Table 1]

[0028]

Industrial Applicability According to the present invention, there is provided a microbial-decomposable fiber having a certain level of heat resistance and strength characteristics that can be practically used. The fiber of the present invention is suitable as a fishery material, an agricultural material, a civil engineering material, a sanitary material, a waste treatment material, etc., and is constant if left in an environment (underground or underwater) where microorganisms are present after use. As it is completely biodegraded after the period,
It does not require special waste treatment and is useful for pollution prevention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Takahashi 23 Uji Kozakura, Uji City, Kyoto Prefecture Central Research Institute of the Unitika Corporation (72) Inventor Naoki Kanemoto 23 Uji Kozakura, Uji City, Kyoto Unitika Corporation Central (72) Inventor Yoshinobu Muta 1-24-15 Higashino, Urayasu City, Chiba Prefecture

Claims (3)

[Claims] 1. Poly (β-hydroxyalkanoate)
Of poly-ε-caprolactone 95/5 to 55/45
Which is a fiber obtained by melt spinning a mixture of
A biodegradable fiber, which is 2.0 g / d or more. 2. Poly (β-hydroxyalkanoate)
Of poly-ε-caprolactone 95/5 to 55/45
Melt-spin the mixture at 120-200 ℃,
After air-cooling at 80 ℃, continue to 2.0 in 1st or 2nd or more
A method for producing a microbially degradable fiber, which comprises stretching the fiber more than twice. 3. The method according to claim 2, wherein the mixture used for spinning contains a crystal nucleating agent.