JPH10310166A - Long material for binding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long material for binding which can be widely used and which is biodegradable because the refuse problem has been taken into consideration, by drawing biodegradable polylactic acid resin after it has been formed. SOLUTION: Polylactic acid resin having the average molecular weight as much as 20000 is extruded at 230 deg.C by a molding machine to form a band-form raw material. Thereafter, it is uniaxially stretched in the longitudinal direction at 140 deg.C to form the three times raw material. A pattern is formed on the surface by finally passing it through rollers to form a binding band (15 mm wide and 1 mm thick). A binding band made of polylactic acid itself shows sufficient physical properties by uniaxially stretching it. Any problems do not arise in particular even when a corrugated cardboard case in which an outdoor instrument (40 kg) of an air conditioner is packed, is continually swayed forward and backward and also sideways at an amplitude of 5 mm and at a frequency of 5-50 Hz at every 5 min cycle for one hour. It is buried in a depth of 10 cm for one year and thereafter, the appearance is evaluated. It is confirmed that the binding band is gradually decomposed by the enzyme in the ground.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biodegradable long binding body.

[0002]

2. Description of the Related Art Conventionally, bands and cords formed by stretching a crystalline synthetic resin such as polypropylene, nylon, polyethylene terephthalate or the like for packing and packing are excellent in durability and mechanical strength. , Has been used in large numbers in various fields.

However, these are not decomposed when used and disposed of in landfills, and are deposited semi-permanently in their original form. In addition, incineration garbage may not be recognized due to concerns about damaging the incinerator due to its large heat value per unit. Furthermore, in recent years, the enactment of the Containers and Packaging Recycling Law is obliging manufacturers to collect even binding bands.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
According to Japanese Patent No. 10262, a resin composed of a biodegradable resin (polycaprolactone) and a crystalline synthetic resin is proposed.

[0005]

However, polycaprolactone, which is an aliphatic polyester, has a low melting point of about 60 ° C., so that it has been difficult to use it alone as a band for binding. For this reason, it is compounded with a crystalline synthetic resin such as polypropylene, but the applications that can still be used are limited.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a long binding body that can be developed for a wide range of uses and has biodegradability in consideration of the dust problem.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a long binding body formed by molding a biodegradable polylactic acid resin and then stretching it. The biodegradable polylactic acid resin itself as a binding band, a string, or the like, or by containing it, is gradually degraded to the molecular level in soil when it is landfilled after use. Further, even when the biodegradable resin is turned into incineration garbage, since the heat generated per unit of the biodegradable resin is smaller than that of polypropylene or the like, it is possible to reduce the load on the incinerator. In addition, no harmful gas is generated. Furthermore, polylactic acid has excellent physical properties such as heat resistance and mechanical strength among biodegradable resins.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 for solving the above-mentioned problem is a long binding body formed by molding a biodegradable polylactic acid resin and then stretching it.

A second aspect of the present invention is an elongate body for binding obtained by molding a resin composed of biodegradable polylactic acid and 50 wt% or less of polypropylene and then stretching the resin.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 A polylactic acid resin having an average molecular weight of 20,000 was extruded at 230 ° C. by a molding machine to produce a band-shaped material, and then uniaxially stretched three times in the length direction at 140 ° C. A binding band A (width 15 mm, thickness 1) whose surface is embossed by passing between rollers
mm).

(Example 2) A polylactic acid resin having an average molecular weight of 20,000 was extruded at 230 ° C by a molding machine to prepare a band-shaped material, and then biaxially stretched four times at 140 ° C. By passing through, a binding band B (width 15 mm, thickness 1 mm) whose surface was embossed was obtained.

(Comparative Example 1) Polypropylene was extruded at 230 ° C by a molding machine to produce a band-shaped material,
The film was uniaxially stretched seven times in the length direction at 7 ° C., and finally passed between rollers to obtain a binding band C (width 15 mm, thickness 1 mm) whose surface was subjected to graining.

The results of evaluating the physical properties of the samples A to C are shown in Table 1.

[0015]

[Table 1]

From the above results, it was clarified that the binding band composed of polylactic acid itself exhibited sufficient physical properties by uniaxially or biaxially stretching. In addition, in comparison between the uniaxial and the biaxial, the biaxial was superior. The polylactic acid used in the examples is an aliphatic polyester, and is a crystalline thermoplastic polymer represented by the chemical formula (1).

[0017]

Embedded image

Although its glass transition temperature is about 60 ° C.,
The temperature was shifted to the high temperature side by stretching the molded body. Further, the melting point is 175 ° C., which is high among biodegradable resins.

As a practical evaluation, a cardboard box in which an outdoor unit of an air conditioner (weight 40 kg) was packed was tested with the samples A and B. The conditions were as follows: the amplitude was 5 mm, the width was 5 mm, the width was 5 Hz, and the sweep was 5 minutes as one cycle. As a result, there was no particular problem.

Next, an underground burial test was conducted. In the test method, samples A to C were buried at a depth of 10 cm for one year, and then evaluated by the weight change rate and appearance. The results are shown in (Table 2).

[0021]

[Table 2]

However, the weight change rate is based on the following (Equation 1).

[0023]

(Equation 1)

As is clear from Table 2, it was confirmed that the binding band made of the biodegradable resin was gradually degraded by enzymes in the soil. Further, the conventional one has no change in weight at all and keeps its shape as it is.

As is clear from the above results, the binding band made of polylactic acid resin exhibited excellent physical properties and also had biodegradability. However, there is a practical problem in terms of cost. When the conventional polypropylene band was changed to a polylactic acid band, there was a gap of several times.
Therefore, a study was made to suppress cost increase and maintain biodegradability by compounding polylactic acid and polypropylene. In addition, since the rigidity is high when stretched with 100% polylactic acid resin, the stretch must be performed at a relatively high temperature. Therefore, there is a case where drawing is inconvenient unless the management of the working conditions is strict. The addition of polypropylene improved the flowability during resin stretching.

(Example 3) A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of 10 wt% of polypropylene, and the mixture was molded at 230 ° C using a molding machine.
And then uniaxially stretched three times at 140 ° C. and finally passed between rollers to form a binding band D (width 15 m
m, thickness 1 mm).

Example 4 A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of 20 wt% of polypropylene, and the mixture was molded at 230 ° C. using a molding machine.
And then uniaxially stretched three times at 130 ° C. and finally passed between rollers to form a binding band E (15 m in width) having a grained surface.
m, thickness 1 mm).

(Example 5) A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of 30 wt% of polypropylene, and the mixture was molded at 230 ° C using a molding machine.
And then uniaxially stretched three times at 130 ° C. and finally passed between rollers to form a binding band F (width 15 m
m, thickness 1 mm).

(Example 6) A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of polypropylene of 40 wt%, and the molding machine was used at 230 ° C.
After being extruded to form a band-shaped material, it is uniaxially stretched four times at 120 ° C. and finally passed between rollers to form a binding band G (15 m in width) whose surface is embossed.
m, thickness 1 mm).

(Example 7) A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of 50 wt% of polypropylene, and the mixture was molded at 230 ° C using a molding machine.
And then uniaxially stretched 4 times at 120 ° C. and finally passed between rollers to form a binding band H (width 15 m
m, thickness 1 mm).

(Comparative Example 2) A resin obtained by mixing a polylactic acid resin having an average molecular weight of 20,000 and polypropylene was prepared at a mixing ratio of 60 wt% of polypropylene.
And then uniaxially stretched 4 times at 110 ° C., and finally passed between rollers to form a binding band I (15 m in width) whose surface was embossed.
m, thickness 1 mm).

In obtaining the samples D to I, the temperature and the magnification at the time of each stretching were selected in consideration of the physical properties.

Using the samples D to I, an underground burial test was performed. In the test method, the sample was buried at a depth of 10 cm for one year, and thereafter, the weight change rate and the appearance were evaluated. The results are shown in (Table 3).

[0034]

[Table 3]

As is clear from the above results, it was confirmed that when emphasis is placed on biodegradability in soil, which is the object of the present invention, the amount of polypropylene that can be mixed into polylactic acid is 50 wt% or less. In the case of Examples 4 to 7, biodegradable polylactic acid is decomposed to the molecular level, but polypropylene is essentially not decomposed at all. However, since the shape is not retained in its original form, it may be distinguished by the term biodegradability, but is included in the category of biodegradability in a broad sense. Biodegradable binding bands are also effective enough to reduce the volume of garbage.

In addition, even when it is incinerated garbage, the calorific value per unit is smaller than that of conventional polypropylene or the like, which is effective in reducing the load on the incinerator.

[0037]

As is clear from the above embodiment, according to the first aspect of the present invention, a biodegradable polylactic acid resin is molded and then stretched for binding. Because of its heat resistance and mechanical strength, it can be widely applied and developed as a band for binding and a string. Also, when used,
It is degraded to the molecular level by exhibiting its natural biodegradable properties. Furthermore, no harmful gas was generated as incineration waste, and the load on the furnace was reduced.

According to the second aspect of the present invention, a resin composed of biodegradable polylactic acid and 50% by weight or less of polypropylene is molded and then stretched to form a long binding body, which is useful for practical use. It was possible to provide a binding band, a string, and the like having specific physical properties and biodegradability at low cost. Further, the addition of polypropylene improved the fluidity during resin stretching.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Muneo Kameda 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] An elongated body for bundling, which is formed by molding a biodegradable polylactic acid resin and then stretching it. 2. The binding elongate body according to claim 1, wherein a resin comprising biodegradable polylactic acid and 50% by weight or less of polypropylene is molded and then stretched.