JP2002201578A - Biodegradable string for automatically binding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biodegradable string having mechanical suitability for an automatically binding machine. SOLUTION: This biodegradable string comprises a polylactic acid and a polybutylene succinate or a polycaprolactone in the weight ratio of 5:95-30:70 and is drawn at 2.5-5.0 draw ratio in an uniaxial direction. The biodegradable string has excellent mechanical suitability for the automatically binding machine and is friendly to the environment due to its biodegradability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a string which has mechanical suitability for an automatic binding machine and has biodegradability.

[0002]

2. Description of the Related Art There are two types of binding cords, one for hand binding and one for automatic binding machines, both of which are manufactured by similar manufacturing methods. As a raw material, polypropylene (PP) and high-density polyethylene (HDPE) are used, but HDPE is generally used for an automatic binding machine. In a general manufacturing process of a tying cord, after mixing and melting by an extruder, a molten resin is extruded from a die, cooled to form a raw film, and while the raw film is heated, a uniaxial drawing is performed by a stretching machine. It is stretched in the direction and wound up. As a method of stretching,
There are an in-line method in which the stretching step is performed continuously from the film forming, and an off-line method in which the unstretched film is wound once, rewound and stretched again. In the past, the off-line method was adopted to prevent stretching breakage in the stretching machine.However, there is a problem in the slit section due to embrittlement due to cooling of the film and film distortion due to aging. Has been adopted. The binding strength and elongation properties are also required for the cord for hand binding, but the strings for automatic binding machines include, in addition to the binding strength and elongation properties,
Additional machine suitability is also required for automatic binding machines. Additional mechanical suitability includes tensile impact resistance when bundling the ties, unwinding ability when unwinding the string, and bundling suitability when forming a knot. Polyolefin resins such as PP and HDPE generally have good mechanical suitability for automatic binding machines.

[0003] However, recently, "environmentally friendly" has been shouted out loudly, and the occurrence of pollution and environmental destruction due to the incineration and landfill of used polyolefin products has become a problem. Most of the straps for automatic binding machines are also discarded as general garbage after finishing the binding function, so they cannot be free from pollution and environmental destruction. Therefore,
Just because it satisfies the machine suitability for automatic binding machines,
Rather than relying on polyolefin resins such as P and HDPE, immediate action is being sought. Considering the problem of pollution generation and environmental destruction, if a string that is biodegradable and satisfies the mechanical suitability for an automatic binding machine can be obtained, it is no exception.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a string which has mechanical suitability for an automatic binding machine and has biodegradability.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have determined that polylactic acid and polybutylene succinate or polycaprolactone are contained in a weight percentage of 5:95 to 30: It has been found that the problem can be solved by a string for a biodegradable automatic binding machine that is contained at a ratio of 70 and stretched in a uniaxial direction at a stretching ratio of 2.0 to 5.0 times. After the stretching step, the width of the single bundle tape is reduced to 1/4.
It has been found that the following double-stranded string for a biodegradable automatic tying machine is more preferable, and that a string for a biodegradable automatic tying apparatus annealed under specific conditions is more preferable.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a string for a biodegradable automatic binding machine according to the present invention will be described in detail.

As polylactic acid, Lacty (trade name) manufactured by Shimadzu Corporation, Lacia (trade name) manufactured by Mitsui Chemicals, Inc.
Ecoplay (trade name) manufactured by Cargill Japan Co., Ltd. and the like.

[0008] Examples of polybutylene succinate or polycaprolactone include Bionole (trade name) manufactured by Showa Polymer Co., Ltd. and Cell Green (trade name) manufactured by Daicel Chemical Co., Ltd.

In the string for a biodegradable automatic tying machine of the present invention, a mixing ratio of polylactic acid and polybutylene succinate or polycaprolactone of 5:95 to 30:70 is considered from the viewpoint of tying strength and tensile impact strength. It is preferable to mix them. If the proportion of polylactic acid is more than 30% by weight, the binding strength can be increased, but the tensile impact resistance decreases and the unrolling property deteriorates, which is not preferable. If the proportion of polylactic acid is less than 5% by weight, the binding strength is not increased, which is not preferable. 10% by weight of polylactic acid and polybutylene succinate or polycaprolactone:
Those containing at a ratio of 90 to 20:80 are particularly preferred.

In the string for a biodegradable automatic tying machine of the present invention, an inflation method, a T-die method or the like can be applied as an extrusion molding method. The unstretched raw film obtained by extrusion molding is slit into a required width to form a single bundle tape.

In the cord for a biodegradable automatic tying machine according to the present invention, as a stretching method, a roll stretching method, a hot plate stretching method or the like can be applied. Further, any of an in-line system in which a stretching step is continuously performed after film forming and an off-line system in which an unstretched film is wound once, rewound and stretched again can be applied.

A sufficient binding strength can be obtained by stretching a mixture of polylactic acid and polybutylene succinate or polycaprolactone at the above mixing ratio to a stretching ratio of 2.0 to 5.0 in the uniaxial direction. Brought. If the stretching ratio is less than 2.0, the uniaxial orientation of the molecular chains is weak, and sufficient binding strength cannot be obtained. On the other hand, when the stretching ratio is more than 5.0 times, stretching breakage occurs at a considerable frequency, which hinders the production of a string for a biodegradable automatic tying machine. The stretching ratio is a value obtained by dividing the take-up speed of the pinch roll after stretching by the withdrawal speed of the pinch roll before stretching.

If desired, stabilizers, lubricants, plasticizers, fillers, coloring agents and the like can be added to the resin composition used in the present invention.

In the present invention, in order to reduce the width of the single-bundled tape to 1/4 or less after the stretching step, for example, it is squeezed with a finger or passed through a narrow groove.

In the present invention, the annealing of the string for a biodegradable automatic binding machine is performed by a differential scanning calorimetry (DSC), and a melting curve (1st-heat melting curve) obtained by heating a molded article at a constant rate as it is. And a melting curve (2nd-heat melting curve) obtained by raising the temperature of the molded article once to melt it, and then gradually raising the temperature of the slowly cooled product again at a constant rate. 70-100
This is performed so that a peak generated by annealing can be confirmed in the range of ° C. FIG. 1 shows a melting curve in differential scanning calorimetry (DSC). The horizontal axis represents temperature (° C.), and the vertical axis represents energy change per unit mass (W / g). 1st
A peak generated by annealing at 91 ° C. can be confirmed in the -heat melting curve. The internal stress is removed by annealing the single-bundle tape having a width of 1/4 or less as a double-bundle string after the stretching step under conditions such that a peak caused by annealing can be confirmed within the above range. In addition, since the double bundled string shape can be maintained, the feeding property and the automatic binding property are remarkably improved.

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Example 1 15% by weight of polylactic acid (Lacty 9400, manufactured by Shimadzu Corporation) and 85% by weight of polybutylene succinate (Bionore # 1001, manufactured by Showa Polymer Co., Ltd.) were mixed with a tumble mixer. Equipped with an extruder having an L / D of 28 and a diameter of 55 mm
After melt-kneading at 90 ° C., an unstretched raw film was obtained by inflation molding. The stretching process was performed in an in-line system, and the film was stretched 2.7 times at a hot plate temperature of 90 ° C. At this time, the width of the single bundle tape was 30 mm. This was re-wound while squeezing by hand to form a double-bundle string.
At this time, the width of the double bundled string was 5 mm. The rewound string was annealed to obtain a string for a biodegradable automatic binding machine of the present invention. 1st-heat melting curve of DSC and 2nd
The heat melting curve is shown in FIG. The melting curve is JIS
Heating rate 10 ° C / min, cooling rate 1 according to K7121
Obtained at 0 ° C./min. Table 1 shows the evaluation results.

Example 2 Example 1 was repeated except that a mixture of 30% by weight of polylactic acid (Lacty 9400, manufactured by Shimadzu Corporation) and 70% by weight of polybutylene succinate (Bionore # 1001, manufactured by Showa Polymer Co., Ltd.) was used. Similarly, a string for a biodegradable automatic binding machine of the present invention was obtained. Table 1 shows the evaluation results.

Example 3 The same procedure as in Example 1 was carried out except that a mixture of 15% by weight of polylactic acid (Lacti 9400 manufactured by Shimadzu Corporation) and 85% by weight of polycaprolactone (Cell Green PHB02 manufactured by Daicel Chemical Industries, Ltd.) was used. Thus, a string for a biodegradable automatic binding machine of the present invention was obtained. Table 1 shows the evaluation results.

Example 4 Example 1 was repeated except that the width of the double bundled string was 10 mm.
Using the same composition and method as above, a string for a biodegradable automatic tying machine was obtained. Table 1 shows the evaluation results.

Example 5 A string for a biodegradable automatic tying machine was obtained by the same composition and method as in Example 1 except that annealing was not performed. Table 1 shows the evaluation results.

Comparative Example 1 The procedure of Example 1 was repeated except that a mixture of 50% by weight of polylactic acid (Lacty 9400, manufactured by Shimadzu Corporation) and 50% by weight of polybutylene succinate (Bionore # 1001, manufactured by Showa Kogaku KK) was used. A string for a biodegradable automatic tying machine was obtained in the same manner. Table 1 shows the evaluation results.

Comparative Example 2 A string for a biodegradable automatic binding machine was obtained by the same composition and method as in Example 1 except that the stretching was performed at a draw ratio of 1.5. Table 1 shows the evaluation results.

The biodegradable automatic tying cords of Examples 1 to 5 and Comparative Examples 1 and 2 were evaluated for machine suitability with respect to the automatic tying machine using a Y80 type automatic tying machine manufactured by Yamada Kikai Kogyo.

Tensile impact resistance: A bundling test was performed for each of the examples and comparative examples, and the tensile impact resistance was evaluated based on the presence or absence of cutting at the stage of winding the string. The evaluation criteria are as follows. ○: No cutting ×: With cutting

Dispensing properties: A binding test was performed for each of the examples and comparative examples, and dispensing properties were evaluated based on the arm return position of the binding machine at the end of binding. The evaluation criteria are as follows. ：: Completely returned to the original position. Δ: Almost completely returned to the original position. ×: Does not return to the original position.

Automatic Binding Property: A binding test was performed for each of the examples and comparative examples, and the automatic binding property was evaluated based on the finished state of the knot at the end of the binding. The evaluation criteria are as follows. ◎: The finish of the knot is particularly beautiful, and the cut end is also particularly beautiful. ：: The finish of the knot is beautiful and the cut end is also beautiful. Δ: The knot is formed, but the finish is dirty. The cut is also dirty. X: No knot was formed and no unity was formed.

Comprehensive evaluation: Comprehensive evaluation of the mechanical suitability for an automatic binding machine was made based on the evaluation of tensile impact resistance, feeding property, and automatic binding property. The evaluation criteria are as follows. ：: The mechanical suitability for the automatic binding machine is good. Δ: The mechanical suitability for the automatic binding machine is insufficient. ×: Almost no mechanical suitability for the automatic binding machine.

[0029]

[Table 1]

[0030]

Industrial Applicability The string for a biodegradable automatic binding machine of the present invention has excellent mechanical suitability for an automatic binding machine and is environmentally friendly due to its biodegradability.

[Brief description of the drawings]

FIG. 1 is a melting curve in differential scanning calorimetry (DSC).

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasushi Okamoto 1-3-Sakaemachi, Sano-shi, Tochigi Pref.

Claims (4)

[Claims] 1. A polylactic acid and a polybutylene succinate or a polycaprolactone in a weight percentage of 5:95 to 30: 7.
0, and the stretching ratio in the uniaxial direction is 2.0 to 5.0.
A string for a biodegradable automatic tying machine, which is stretched twice. 2. Polylactic acid and polybutylene succinate or polycaprolactone in a weight percentage of 10:90 to 20:
2. The string for a biodegradable automatic tying machine according to claim 1, which is contained at a ratio of 80. 3. After the stretching step, the width of the single bundle tape is reduced to 1 /
4. A string of four or less double bundles.
Or the string for biodegradable automatic binding machines according to 2. 4. In a differential scanning calorimetry (DSC), a melting curve (1 s) obtained by raising the temperature of a molded article at a constant rate as it is.
When comparing a t-heat melting curve) with a melting curve (2nd-heat melting curve) obtained by raising the temperature of a molded article once and then gradually cooling the molded article at a constant rate. 2. The method according to claim 1, wherein the annealing is performed so that a peak generated by the annealing can be confirmed in the range of 70 to 100 ° C. in the first-heat melting curve.
The string for a biodegradable automatic tying machine according to any one of claims 1 to 3.