JPH07278965A - Biodegradable conjugate monofilament and its production - Google Patents

Abstract

PURPOSE:To provide a biodegradable sheath-core conjugate monofilament having a certain heat-resistance satisfiable as a fishery material, agricultural material- and general industrial material and completely decomposable by microorganisms after use. CONSTITUTION:This biodegradable sheath-core conjugate monofilament is produced by using a polybutylene succinate as the core part and a copolymer of polybutylene succinate and polyethylene succinate at a molar ratio of 100/0 to 65/35 or 20/80 to 0/100 and having a melting point lower than that of the core polymer as the sheath part, melt-spinning the polymers through a spinneret having a circular sheath-core conjugate spinning nozzle, cooling the spun filament in a cooling water bath having a temperature lower than the crystallization temperature of the sheath polymer by 10-40 deg.C, subjecting the cooled filament immediately to multistage drawing in a hot water bath at a 1st-stage draw ratio of >=5 and <7 and a total draw ratio of >=7 and carrying out the relaxed heat-treatment of the drawn filament in an oven.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a certain heat resistance composed of a copolymer of polybutylene succinate and polyethylene succinate (including a homopolymer) and has excellent dimensional stability and biodegradability. The present invention relates to a composite monofilament and its manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as fibers for industrial materials used for fisheries, agriculture, and civil engineering, fibers having excellent yarn quality performance such as strength and weather resistance have been required, and mainly polyamide, aromatic polyester, vinylon. , Polyolefin, etc. are used. However, these fibers have no natural degradability, and if used and left in the sea or mountains, they cause various pollution. This problem,
After use, it can be solved by incineration, landfilling or recovery and recycling, but since such processing requires a large amount of money, it is actually left in the sea or mountains and damages the landscape, as well as birds and oceans. It often happens that entanglement with life creatures, divers, etc. and killing, or entanglement with the screw of a ship to cause a ship accident.

As a method for solving such a problem, it is conceivable to use a naturally degradable (hydrolyzable or biodegradable) material.

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. Well-known are poly (α-oxy acids) such as polylactide and aliphatic polyesters such as poly-ε-caprolactone.

However, when fibers are produced from these polymers, they must be produced by a wet spinning method like polysaccharides and polyamino acids, and poly (α-oxy acid)
As described above, there are problems in that the cost of the material is extremely high, and it is not possible to obtain high-strength fibers. In addition, poly-ε-caprolactone is a relatively inexpensive, completely biodegradable synthetic polymer and can be melt-spun, but its melting point is as low as 60 ° C, so its use is limited. It was

Poly (β-hydroxyalkanoate), which is naturally produced by microorganisms, is well known as a biodegradable thermoplastic polyester having a melting point of 130 to 180 ° C., and attempts have also been made to produce fibers. For example, there is a report that a monofilament having a tensile strength of 3 g / d was obtained (Nikkan Kogyo Shimbun, January 17, 1992), but there was a problem that this strength was not practically sufficient.

[0007] The present inventors have previously mentioned that polybutylene succinate, which is inexpensive and has a certain heat resistance that can be put to practical use, is completely decomposed by microorganisms in a natural environment. It was found that a high-strength biodegradable monofilament can be obtained from a copolymer with polyethylene succinate (Japanese Patent Application No. 5-300905). However, although this biodegradable monofilament showed better characteristics than conventional ones, improvement in knot strength and abrasion resistance was desired.

[0008]

DISCLOSURE OF THE INVENTION The present invention is inexpensive and has a certain degree of heat resistance that can be put to practical use, and is excellent in physical properties, particularly knot strength and abrasion resistance, and in a natural environment. The present invention aims to provide a biodegradable composite monofilament that is completely decomposed by microorganisms and a method for producing the same.

[0009]

In order to solve the above-mentioned problems, the inventors of the present invention have made earnest studies and, as a result, have found that polybutylene succinate (referred to as PBS) and polyethylene succinate (PES) having specific copolymerization molar ratios are used. The inventors have found that this object can be achieved by spinning a composite monofilament in which the sheath portion is a polymer having a melting point lower than that of the core portion using a copolymer of

That is, the gist of the present invention is as follows. (1) A core-sheath type composite monofilament comprising a copolymer of PBS and PES in a molar ratio range of 100/0 to 65/35 and 20/80 to 0/100, wherein the sheath portion is lower than the core portion. Biodegradable composite monofilament composed of melting point polymer. (2) Concentric core composed of a copolymer of PBS and PES in a molar ratio of 100/0 to 65/35 and 20/80 to 0/100, and a sheath portion of which is made of a polymer having a lower melting point than that of the core portion. Unspun yarn obtained by melt-spinning a sheath-core type composite monofilament and cooling the spun yarn in a cooling bath within a range of 10 ° C to 40 ° C lower than the crystallization temperature of the polymer of the sheath. The method for producing a biodegradable composite monofilament, which comprises multi-stage stretching such that the first stage draw ratio is 5 times or more and less than 7 times and the total draw ratio is 7 times or more.

The present invention will be described in detail below. The copolymer of PBS and PES used in the present invention is required to have a molar ratio of 100/0 to 65/35 and 20/80 to 0/100, particularly a molar ratio of 100/0.
Those in the range of -80/20 and 10 / 90-0 / 100 are preferred. The melting point of the copolymer of PBS and PES changes as shown in FIG. 1 depending on the copolymerization molar ratio. The polymers having the above copolymerization molar ratio have a melting point of 70 ° C. or higher and have a certain heat resistance, but the polymers outside the above range have a melting point of less than 70 ° C. and are inferior in heat resistance, which is not preferable. Also, PBS and PE
It is preferable that the copolymer with S has a number average molecular weight of about 30,000 or more from the viewpoints of spinnability and characteristics of the obtained monofilament.

In the present invention, a composite monofilament using a low melting point polymer in the sheath and a high melting point polymer in the core is used, and it is desirable that the difference in melting point is 5 ° C. or more, preferably 10 ° C. or more. In a copolymer of PBS and PES, a lower melting point copolymer has a lower Young's modulus and becomes more flexible, and thus a knot strength and abrasion resistance of a monofilament obtained by using a low melting point copolymer in the sheath portion Is improved.

Further, PBS and PE are used as the core polymer.
The copolymerization molar ratio with S is 100/0 to 80/20 or 5/95 to 0.
It is preferable to use the one of / 100. PBS and PE
If the proportion of the larger component of S is less than the above range, the polymer is flexible and has a low crystallinity, and the linear strength and knot strength of the obtained composite monofilament are inferior.

The weight ratio of the core portion to the sheath portion is 2/1 to
5/1 is preferred. If the proportion of the core portion is too small, the linear strength and knot strength of the monofilament will be low, and conversely if it is too large, the effect of the sheath component will be small and no improvement in knot strength will be seen.

In order to produce the monofilament of the present invention, first, the molar ratio is 100/0 to 65/35 and 20/80 to 0/10.
A concentric sheath-core type composite monofilament composed of a copolymer of PBS and PES in the range of 0 and having a sheath portion made of a polymer having a lower melting point than the core portion is melt-spun.

The spinning temperature varies depending on the copolymerization molar ratio of the polymer used, but is preferably 150 to 220 ° C. If the spinning temperature is less than 150 ° C, melt extrusion is difficult, and if it exceeds 220 ° C, the polymer is significantly decomposed.
It becomes difficult to obtain a high-strength monofilament.

The spun yarn is cooled in a cooling bath in the range of 10 ° C. to 40 ° C. below the crystallization temperature of the polymer in the sheath. Cooling is performed through a coolant bath of water, ethylene glycol or the like. If the cooling temperature is too high, deformation may occur on the yarn path changing rollers or guides in the refrigerant bath due to insufficient cooling. Further, since this type of polymer has a slow crystallization rate, if the cooling temperature is too low, crystallization does not proceed, and when a plurality of monofilaments are spun from the same die, the monofilaments may adhere to each other.

The cooled undrawn yarn is drawn once or continuously without being wound. Stretching
It needs to be done in multiple stages. The first-stage stretching is performed at room temperature or in a heated gas or in a heated liquid such as hot water, glycerin, ethylene glycol, or silicone oil at a temperature not higher than the melting point of the sheath polymer, at least 5 times and less than 7 times. At a draw ratio of. If the draw ratio of the first stage is less than 5 times, uneven stretch occurs, while if it is 7 times or more, cutting frequently occurs, which is not preferable. The stretching from the second stage onward is usually performed in a heating atmosphere in the vicinity of the melting point of the sheath polymer, preferably in the range of 15 ° C. lower to 30 ° C. higher than the melting point, although it depends on the heating time.

The composite monofilament of the present invention thus obtained is inexpensive, has a certain heat resistance that can be practically used, excellent physical properties and biodegradability as described above.

[0020]

The reason why the composite monofilament of the present invention exhibits excellent linear strength and knot strength is not clear, but the linear strength is maintained by the rigid layer of the core, and the flexible layer of the sheath relaxes the stress applied to the knot. It seems to do. Further, it is considered that the abrasion resistance is improved by the soft layer of the sheath portion.

[0021]

EXAMPLES Next, the present invention will be specifically described by way of examples. The measurement and evaluation methods are as follows. (a) Linear strength and knot strength Measured according to JIS L 1013. (b) Biodegradability (weight reduction rate) A monofilament with a sample length of 10 m was formed into a ridge shape, and from September 12
It was buried in soil for 3 months of the month and then taken out, and the weight reduction rate was obtained and evaluated. (c) Abrasion resistance A load of 0.2 g / d is applied to a monofilament with a sample length of 20 cm, a hexagon wrench with a diameter of 4.0 mm is used for the friction element, and the number of strokes is 36 times / min, the stroke length is 72 mm, and the friction angle is 90 degrees. A friction test was conducted on and the number of times until the monofilament was cut was measured and evaluated.

Example 1 PBS and PE having a number average molecular weight of about 40,000 and a molar ratio of 80/20.
PB with a copolymer of S as a sheath and a number average molecular weight of about 40,000
S is used as a core part and is separately supplied to an extruder type melt spinning machine, melted at a temperature of 160 ° C, and a spinneret having two 2.1 mm diameter spinning holes so that the weight ratio of the sheath core is 1/3. After spinning in a water bath with a temperature of 16 ° C. and a length of 2 m, it was taken out at a speed of 10 m / min and immediately drawn with a draw ratio (DR ₁ ) of 5.2 times in a warm water bath of 65 ° C. Stretching in the second step is performed, then in the oven with a heating length of 3 m and a temperature of 120 ° C., the second stretching step is performed so that the total draw ratio (DR _T ) is 7.9 times. 0.95 times relaxed heat treatment in an oven at 125 ℃
A 0.286 mm composite monofilament was obtained.

Examples 2 to 5 When a composite monofilament was obtained by the same method as in Example 1, yarn was made under the conditions shown in Table 1.

Comparative Examples 1 to 7 When a composite monofilament and a single-component monofilament were obtained by the method according to Example 1, spinning was performed under the conditions shown in Table 1.

Table 1 shows the yarn forming conditions and the like of the above Examples and Comparative Examples, and Table 2 shows the characteristic values and the like of the obtained monofilaments.

[0026]

[Table 1]

[0027]

[Table 2]

As is clear from Table 2, in Examples 1 to 5 of the present invention, monofilaments having a high linear strength and a high knot strength and good abrasion resistance were obtained. However, in Comparative Examples 1 to 4 as single-component monofilaments, Comparative Example 5 in which the difference in melting point of the sheath core is reversed, and Comparative Example 6 in which the total draw ratio is less than 7 times, only monofilaments having inferior characteristics are obtained. I couldn't do it. Further, in Comparative Example 7 in which it was attempted to draw 7 times or more in one stage, the yarn breakage was remarkable, and the yarn making was impossible.

[0029]

Industrial Applicability According to the present invention, a biodegradable composite monofilament having a certain level of heat resistance and high strength, which can be put to practical use as a general industrial material, is provided. The biodegradable monofilament of the present invention is suitable for fishing materials such as fishing nets and fishing lines, insect repellents, agricultural materials such as bird-prevention nets and vegetation nets, living materials such as compost bags, and other general industrial materials. After use, since it is completely decomposed after a certain period of time if left in an environment where microorganisms are present, using the composite monofilament of the present invention does not require special waste treatment,
It becomes possible to prevent pollution.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a copolymerization molar ratio and a melting point in a copolymer of PBS and PES.

Claims (2)

[Claims] 1. A molar ratio of 100/0 to 65/35 and 20/80 to 0.
A core-sheath type composite monofilament comprising a copolymer of polybutylene succinate and polyethylene succinate in the range of 100/100, characterized in that the sheath part is composed of a polymer having a lower melting point than the core part. Biodegradable composite monofilament. 2. A molar ratio of 100/0 to 65/35 and 20/80 to 0.
/ 100 range polybutylene succinate and polyethylene succinate copolymer, the sheath is composed of a polymer having a lower melting point than the core, concentric sheath core type composite monofilament is melt spun, spun yarn The strip is cooled in a cooling bath within a temperature range of 10 ° C to 40 ° C lower than the crystallization temperature of the polymer of the sheath, and the undrawn yarn obtained has a first stage draw ratio of 5 times or more, 7 A method for producing a biodegradable composite monofilament, which comprises multi-stage stretching so that the total stretching ratio is 7 times or more at less than twice.