JP2892964B2 - Biodegradable fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to biodegradable fibers, and more particularly to biodegradable fibers used in natural environments such as fishing materials such as fishing lines and fishing nets, civil engineering materials such as nets for buried soil, agricultural materials such as seeding tapes, and the like. It relates to degradable fibers.

[0002]

2. Description of the Related Art Fishing lines, fishing nets, nets for soils, and the like are connected and knitted by bundling, so that the knot strength is more important than the tensile strength. In order to achieve such an object, there has been proposed a method of realizing a hard elastic fiber structure in which the inner layer portion of the nylon is highly blended and the surface layer portion has elasticity. Specifically, a steam treatment method (JP-B-47-43768, JP-B-60-7721) and a surface treatment method (JP-A-51-38597) are known.

Similarly, for polyvinylidene fluoride, a relaxation heat treatment method (JP-A-60-181314) and a high-temperature strain heat treatment method (JP-A-60-231815) are known.

[0004] These methods are basically a method in which a thermal relaxation treatment is performed or a surface is chemically and physically changed during or after multi-stage drawing. The inner layer of the fiber cross section is highly oriented, and the surface layer is formed. Fibers having a low orientation and elastic structure can be obtained.

As a method for producing hydroxyalkanoate fibers, Japanese Patent Publication No. 2-63055 and Japanese Patent Publication No.
63056 is known. Figure 1
63055 discloses an apparatus.

Reference numeral 1 in the figure denotes a die for feeding the extrudate 2 into water in a water tank 3. The extrudate 2 is water-cooled while moving in water along the guides 4 and 5, and is conveyed to the pins 8 and the heater plate 9 side via the first take-off roller 7 as monofilaments 6. After the monofilament 6 is drawn in the area on the heater plate 9, the second take-up roller 10 is drawn.
Is wound up by the take-up roller 11. By molding in such a manner, a fiber containing a lot of crystals whose c-axis direction is oriented parallel to the fiber axis is obtained.

[0007]

In order to obtain a fiber having a high tensile strength and a high knot strength, a structure in which the orientation of the surface layer is lower than that of the inner layer and the molecular chain orientation of the amorphous portion in addition to the crystalline portion is high. Are suitable.

Japanese Patent Application Laid-Open No. 58-82723 and Japanese Patent Publication No.
As shown in Japanese Patent No. 63055, the preformed product of hydroxyalkanoates is brittle even when the temperature is raised, and breaks before being plastically deformed and oriented even when it is stretched by an ordinary method. When the crystallinity of the preform is low, the preform is rubbery and sticky, and the crystallization speed from the amorphous state is low, so that it is difficult to achieve the orientation and to handle. Therefore, it is difficult to separately control the structure of the inner layer and the surface of the fiber by the conventional heat treatment such as relaxation heat treatment or heating only the surface layer to the melting point or higher.

Further, treating the surface layer with an organic solvent or another resin has an undesired effect as a fiber material used in a natural environment, such as environmental destruction due to residual solvent and degradation of degradability due to coating of different materials.

The present invention has been made in view of the above circumstances, and by controlling the fiber structure of a hydroxyalkanoate resin, the surface layer is more flexible than the inner layer and the molecular chain of the amorphous portion is highly enhanced. Provide biodegradable fiber with high oriented tensile strength and high knot strength, which can reduce the load on nature without being decomposed by microorganisms and accumulated in the environment even if fishing nets used in the field are washed away or left The purpose is to do.

[0011]

According to the present invention, there are provided preheating conditions (temperature, time) and stretching conditions (temperature, time) in a stretching step.
By changing the heat treatment conditions (temperature, time) and controlling the proportion of crystals having different crystal styles, the degree of crystallinity, the degree of orientation including amorphous, etc. between the inner layer and the surface layer of the fiber cross section Is a biodegradable fiber having high tensile strength and high knot strength.

The following description will be made mainly on the case where the stretching temperature is fixed at 60 ° C. and the heat treatment temperature is changed.

Hydroxyalkanoates, which are thermoplastic resins produced by microorganisms, are homo- or copolymers composed of many monomers having different molecular structures. Representative monomers include 3-hydroxypropionate,
3-hydroxybutyrate, 4-hydroxybutyrate, 3-hydroxyvalerate, 5-hydroxyvalerate, 3-hydroxycaprolate, 3-hydroxyheptanoate, 3-hydroxyoctanoate. However, it is not limited to the components listed here, but includes other components.

The present invention will be described below mainly using a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate. FIG. 4 shows the crystal structure of the 3-hydroxybutyrate polymer among the hydroxyalkanoates. The c-axis of each axis of the crystal is parallel to the molecular chain, and the molecular chain has a helical form.

When the heat treatment temperature is changed in the present invention,
FIG. 5 shows the birefringence of the entire fiber determined by a polarizing microscope.
The intrinsic birefringence of 3-hydroxybutyrate calculated using the atomic coordinates in the crystal is a negative value at −0.0755. Therefore, the larger the negative absolute value is, the more oriented the molecular chain is in the fiber axis direction.

FIG. 6 shows a schematic diagram of a polarizing microscope of a cross section of the fiber. According to FIG. 6, a unique distribution of petals was observed inside the fiber, and a region of an orientation pattern different from that of the inner layer was observed on the surface layer.

FIG. 7 shows a schematic diagram of an interference microscope on the side surface of the fiber. In the fiber having a uniform internal structure, the interference fringes draw a smooth arc that is convex to the right, but in FIG. 7, a shallow arc that is convex at the center is drawn to the left. Therefore, it can be confirmed that there is a structural distribution in the fiber cross section.

FIG. 8 shows a birefringence distribution in a cross section obtained from observation with an interference microscope. In the entire fiber, the birefringence decreases and the orientation in the fiber axis direction increases as the heat treatment temperature increases.
Looking at the distribution in the cross section of the fiber, when the heat treatment temperature is 100 ° C or lower, the orientation of the fiber inner layer is higher than that of the surface layer, and is substantially uniform at 120 ° C, and when it exceeds 120 ° C, the fiber surface layer is more oriented than the inner layer. Will be higher.

When the heat treatment temperature is changed in the present invention,
FIG. 9 shows the crystallinity of the entire fiber and the ratio of the two types of crystals determined from the wide-angle X-ray diffraction pattern. In FIG. 9, Xc,
c indicates a crystal in which the c axis is oriented in the fiber direction, and Xc, n indicates c
The crystal has an axis oriented perpendicular to the fiber axis.

As the heat treatment temperature increases, the degree of crystallinity increases, and in particular, the proportion of crystals whose c-axis is oriented in the fiber axis direction increases.

The carbonyl group was determined by infrared spectroscopy.
FIG. 10 shows the infrared dichroic ratio orientation coefficient of the fiber. Similar to the birefringence of FIG. 5, the orientation increases as the heat treatment temperature increases.

The carbonyl group was determined by infrared spectroscopy.
FIG. 11 shows the infrared dichroic ratio orientation coefficient of the surface layer and the inner layer of the fiber. When the heat treatment temperature is low, the inner layer is highly oriented, but when the heat treatment temperature is high, the orientation of the surface layer is increased, which is the same as the result of birefringence.

In the case where the crystal molecular chains are arranged in the fiber axis direction, the case where the crystal molecular chains are perpendicular, and the case where the amorphous molecular chains are not oriented, the infrared dichroic ratio orientation coefficient obtained from the atomic coordinates is -0.5. , 0.25, 0. In addition, the intrinsic birefringence becomes -0.0755, 0.0383, and 0, respectively. Since it is 0 in the case of non-orientation, ignoring it, the values of the two types of orientation in the crystal are almost the same, so that the infrared dichroic orientation coefficient and birefringence should show the same tendency.
However, in spite of the birefringence results in FIG. 5, the fiber subjected to the heat treatment at a low temperature shows a positive value, but the infrared dichroic ratio orientation coefficient in FIG. 10 shows a negative value.

The molecular chain of the 3-hydroxybutyrate polymer usually takes a helical form. However, when it is considered that the molecular chain is stretched by applying a high stress in the molecular chain direction and takes a planar zigzag structure, it is considered to have a infrared zigzag structure. The color ratio orientation coefficient and the intrinsic birefringence are -0.5 and -0.01, respectively. Therefore,
Considering this planar zigzag structure, the infrared dichroic ratio orientation coefficient contributes negatively and the birefringence contributes positively, so that the above-described difference in the tendency can be explained. Therefore, portions in the amorphous portion molecular chains are highly oriented in the part and the fiber axis direction of the non-oriented (paracrystalline: quasicrystals) and are present, 1 draft highly oriented molecular chain structure It is possible to consider a planar zigzag structure that is stretched by applying a high stress.

In the present invention, a wide-angle X-ray diffraction pattern in the equator direction of the drawn yarn produced by changing the heat treatment temperature is shown in FIG.
There are three peaks around 13.5 °, 17 ° and 20 ° shown in FIG. The first two of them are the (020) plane of the crystal and the (11) plane.
The third is a peak caused by a highly oriented molecular chain in the amorphous part.

When the heat treatment temperature is in the range of 80 ° C. to 120 ° C., the peak intensity due to the highly oriented molecular chains in the amorphous part is relatively strong, and the peak strength is lower on the lower and higher temperature sides.

FIG. 13 shows a wide-angle X-ray diffraction pattern of the fiber according to the conventional method. While the two peaks due to the crystals are large, the peaks due to the highly oriented molecular chains in the amorphous part at 20 ° are quite small. 55% crystallinity
The crystal in which the c-axis of the crystals is oriented in the fiber axis direction is 7
5%, and the crystal orientation is very high. Although the orientation of the whole fiber is high due to the orientation of the crystal in this way,
Since the orientation of the molecular chain is low in the amorphous part, the fiber has low tensile strength.

The orientation of the amorphous molecular chain can be estimated from the tensile strength and elongation. The fiber according to the present invention has a low modulus, a high tensile strength, a low elongation and a low crystallinity as compared with the fiber according to the conventional method. Although the crystallinity is low and the crystal orientation is low, the elongation is less than half because the orientation of the amorphous molecular chains is high.

In the present invention, a fiber having high tensile strength and equivalent knot strength can be obtained under low-temperature heat treatment conditions. This is because not only the crystal part, but also the amorphous part contains many parts consisting of molecular chains highly oriented in the fiber axis direction, so the tensile strength is high, and the knot strength is low because the molecular orientation of the surface layer is lower than that of the inner layer. Get higher.

When the heat treatment is performed at a high temperature, the fibers are highly oriented as a whole, and fibers having a high elastic modulus can be obtained. However, since there are few portions composed of highly oriented molecular chains, the amorphous portion is weak, and the tensile strength is low as a whole. Further, since the molecular orientation of the surface layer is higher than that of the inner layer, the knot strength is lower than the tensile strength.

In the present invention, it is preferable that spinning and drawing are not performed continuously but performed in discrete steps.

The above temperature ranges vary depending on the types of hydroxyalkanoates and the copolymer composition. Accordingly, it is necessary to determine the melting start temperature, melting peak temperature (melting point), melting end temperature, crystallization start temperature, crystallization peak temperature (crystallization point), and crystallization end temperature of each resin after measurement.

[0033]

According to the present invention, a fiber having flexibility, high tensile strength and high knot strength is obtained by having a structure in which the orientation of the surface layer is lower than that of the amorphous portion and the inner layer in which the molecular chains are highly oriented in the fiber axis direction. Is obtained.

[0034]

Hereinafter, embodiments of the present invention will be described together with comparative examples.

FIG. 2 is a schematic explanatory view showing a part of an apparatus used in the method for producing a biodegradable fiber of the present invention. Reference numeral 21 in the figure denotes an extruder that supplies the extrudate 22 into warm water in a water tank 23. Reference numerals 24, 25, and 26 are guides for guiding the extruded product 22, reference numeral 27 is a take-up roller, and reference numeral 28 is a take-up roller.
La

FIG. 3 is a schematic explanatory view of an apparatus for drawing a fiber wound by a winding roll of the apparatus of FIG. Reference numeral 31 in the figure denotes a delivery roller for feeding the melt spun fiber 32 to the heating furnace 33. Reference numerals 34 and 35 in the figure are heating rollers,
Reference numerals 36 and 37 indicate a heating plate, reference numeral 38 indicates a take-up roller, and reference numeral 39 indicates a take-up roller.

In this embodiment, a fiber is manufactured using such an apparatus as follows.

First, a copolymer of hydroxybutyrate and hydroxyvalerate (PHB / HV = 92/8) was
Extruded into hot water in a water tank 23 at 160 ° C. by an extruder 21,
Melt spin. Here, the temperature of the hot water in the water tank 23 is 50 ° C.
To be kept. The fiber sent into the warm water is cooled and solidified, and is wound up by a winding roller 28 via a guide 26 and a take-up roller 27 (see FIG. 2).

Next, as shown in FIG. 3, in a process separate from spinning, the present fiber is preheated at 150 ° C., stretched 7 times at 60 ° C., and further heat-treated at 1.1 ° C. at 100 ° C. Manufacture fiber.

Comparative Example 1 A fiber spun by the same method as in the above example was subjected to a drawing heat treatment at 150 ° C., 60 ° C., and 60 ° C. under drawing conditions to produce a fiber.

(Comparative Example 2) A fiber spun in the same manner as in the above example was subjected to a drawing heat treatment at drawing conditions of 150 ° C, 60 ° C, and 140 ° C to produce a fiber.

Comparative Example 3 In Comparative Example 3, the same resin as in the above example was extruded at 160 ° C. into hot water in a water tank 3 (bath temperature 60 ° C.) by the extruder 1 using the apparatus shown in FIG. .
Next, it is continuously stretched 8 times by a heater plate 9 at 60 ° C. through a hot pin 8 at 120 ° C.
Wind up at 11.

Table 1 below shows the above-mentioned Examples, Comparative Examples 1, 2 and
The fiber draw ratio (times), heat treatment ratio (times),
Breaking strength (MPa), breaking elongation (%), knot strength (MP
a) and the knot / break ratio. Here, the breaking strength and elongation and the knot strength were obtained from a tensile test.

[0044]

[Table 1]

Thus, according to the above embodiment, the copolymer of hydroxybutyrate and hydroxyvalerate (PH
B / HV = 92/8) as a raw material, having a crystallinity and a distribution of crystal structure in a fiber cross-section, and having an amorphous portion in which molecular chains are highly oriented in the fiber axis direction. Therefore, the surface layer is more flexible than the inner layer, and a biodegradable fiber having high tensile strength and high knot strength can be obtained. Thus, even if a fishing net or the like used outdoors is washed away or left, the load on the natural world can be reduced without being decomposed by microorganisms and deposited in the environment.

[0046]

As described above in detail, according to the present invention, by controlling the fiber structure of the hydroxyalkanoate resin, the surface layer is more flexible than the inner layer, and the molecular chain of the amorphous portion is highly enhanced. A biodegradable fiber that is oriented with high tensile strength and high knot strength, and can reduce the load on the natural world without being decomposed by microorganisms and deposited in the environment even if fishing nets used outdoors are washed away or left. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a fiber spinning and stretching apparatus according to a conventional technique.

FIG. 2 is a schematic explanatory view of a fiber spinning apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic explanatory view of an apparatus for drawing the fiber spun in FIG. 2;

FIG. 4 is a conceptual diagram showing the arrangement of crystal axes and molecular chains of hydroxyalkanoates.

FIG. 5 is a characteristic diagram showing heat treatment temperature dependence of birefringence of a fiber according to the present invention.

FIG. 6 is a schematic diagram of a cross-sectional polarization microscope image of the fiber according to the present invention.

FIG. 7 is a schematic diagram of an interference micrograph of a fiber according to the present invention.

FIG. 8 is a birefringent cross-sectional distribution pattern diagram of the fiber according to the present invention.

FIG. 9 is a characteristic diagram showing the heat treatment temperature dependence of the crystallinity of the fiber according to the present invention.

FIG. 10 is a characteristic diagram showing an infrared dichroic ratio orientation coefficient at each heat treatment temperature of the fiber according to the present invention.

FIG. 11 is a characteristic diagram showing the infrared dichroic ratio orientation coefficient of the inner surface layer at each heat treatment temperature of the fiber according to the present invention.

FIG. 12 is a characteristic diagram showing the wide-angle X-ray diffraction intensity at each heat treatment temperature of the fiber according to the present invention.

FIG. 13 is a characteristic diagram showing a wide-angle X-ray diffraction intensity of a fiber according to a conventional method.

[Explanation of symbols]

21 ... Extruder, 22 ... Extrudate,
23 ... water tank, 27, 38 ... take-up roller, 28, 39 ... take-up roller
La, 32 ... fiber, 33 ... heating furnace.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Maekawa 3-136 Watanabe-dori, Chuo-ku, Fukuoka City, Fukuoka Prefecture Inside Chuko Kasei Kogyo Co., Ltd. Address Chukoh Kasei Kogyo Co., Ltd. (56) References JP-A-5-321025 (JP, A) JP 2-63055 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) D01F 6/62 305 D01F 6/00 D01F 6/84 303

Claims (2)

(57) [Claims] 1. A fiber made from a thermoplastic resin comprising a homopolymer or a copolymer of hydroxyalkanoates as a raw material.
Crystal part where the inner layer in the fiber cross section is highly oriented and the surface layer is low oriented
A biodegradable fiber having a crystal structure distribution of: and having an amorphous portion in which molecular chains are highly oriented in a fiber axis direction. 2. The method according to claim 2, wherein the hydroxyalkanoates are 3-
The biodegradable fiber according to claim 1, which is a copolymer of hydroxybutyrate and 3-hydroxyvalerate.