JP2003192011A - Band for tying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a band for tying which has appropriate flexibility and elastic recovery rate suitable for packing and tying fragile articles such as plastic products or the like and has good tensile break strength and heat resistance, and is applicable for an automatic baler. <P>SOLUTION: The band for tying 1 is manufactured by extruding a blended polymer composed of 40 to 60 wt.% of PP and 40 to 60 wt.% of an olefinic thermoplastic elastomer (TPO) and stretching it monoaxially by draw ratio of 3 to 7. It is preferable that the TPO is composed of 30 to 60 wt.% of polypropylene hard segment and 40 to 70 wt.% of ethylene-propylene rubber and it is a polymerization type and it has the so-called island-sea structure where fine particles of olefin rubber as a soft segment having 3 μm or less in size are dispersed evenly in the matrix as the hard segment. It is also preferable that the tensile break strength in the stretched direction of the band for tying 1 is 40 MPa or more at 20 to 40% elongation and the elastic recovery is 80% or more at 5% elongation and heat shrinkage ratio is 3% or less. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bundling string used for packing and bundling articles, and more particularly to a bundling string suitable for bundling and bundling vulnerable articles.

[0002]

2. Description of the Related Art Conventionally, polypropylene tying cords such as uniaxially oriented tape made of polypropylene have been widely used for packing and tying various articles. However, when the tiles, bricks, steel pipes, plastic products, and the like are bundled with a normal polypropylene tying cord, the polypropylene tying cord is rigid, so that there is an inconvenience that the packaged item is damaged or damaged. For this reason, ethylene-vinyl acetate copolymer (EVA) tying cords have been used for packaging such fragile articles.

The EVA tying cord is suitable for packaging and tying vulnerable articles because it has appropriate flexibility and excellent elastic recovery rate. However, since this EVA tying string has a tensile breaking strength of only about one-third that of a normal polypropylene tying string, packaging of heavy objects,
It cannot be used for bundling, it cannot be applied to general-purpose or general-purpose automatic packing machines due to its poor rigidity, it has low heat resistance and has a large heat shrinkage rate, so it is easily deformed, so it is widely used. It has not been done.

[0004]

Therefore, the object of the present invention is to provide a suitable tensile rupture strength, which has suitable flexibility and elastic recovery rate suitable for packing and binding vulnerable articles such as plastic products. The object is to obtain a binding string that has heat resistance, can be used for packing heavy objects, and can be applied to an automatic packing machine.

[0005]

In order to solve such a problem, the invention according to claim 1 provides polypropylenes 40 to 6
A binding cord obtained by extruding a blend polymer composed of 0 wt% and 40 to 60 wt% of an olefinic thermoplastic elastomer containing 40 to 70 wt% of soft segment ethylene / propylene rubber, and uniaxially stretching at a draw ratio of 3 to 7 times. is there.

According to a second aspect of the present invention, in the olefinic thermoplastic elastomer, fine particles of 3 μm or less of the soft segment ethylene-propylene rubber are uniformly dispersed in the hard segment matrix. It is a binding string.

The invention according to claim 3 is characterized in that the tensile breaking strength in the stretching direction is 140 MPa or more at 20 to 40% elongation, and the elastic recovery rate at 5% elongation in the stretching direction is 80% or more. It is the cord for bundling described in 2. The invention according to claim 4 is the bundling cord according to claim 1, 2 or 3, wherein the heat shrinkage in the stretching direction when immersed in boiling water for 3 minutes is 3% or less.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
The binding cord of the present invention is made of a blend polymer of polypropylene and an olefinic thermoplastic elastomer. As the polypropylene used here, a polypropylene homopolymer and, in addition thereto, a block copolymer or a random copolymer obtained by copolymerizing a comonomer consisting of an α-olefin such as ethylene or 1-butene in an amount of 5 wt% or less are used. This polypropylene melt flow rate (temperature: 230 ° C., load: 2.16 kg, time: 10
Min) is 0.5 to 5 and the weight average molecular weight is 2
Those of 10,000 to 40,000 are preferable.

Further, as the olefinic thermoplastic elastomer, one in which the hard segment is made of polypropylene and the soft segment is made of ethylene / propylene rubber is essentially used. The polypropylene that constitutes the hard segment can be the above-mentioned polypropylene. The hard segment is of course not limited to this, polyethylene, polystyrene,
It may be nylon or the like. Further, in this olefin-based thermoplastic elastomer, polypropylene of the hard segment serves as a matrix, and fine particles having a particle diameter of 3 μm or less, preferably 1 to 2 μm, of the ethylene / propylene rubber which is the soft segment are uniformly dispersed in the matrix. What takes the form of a so-called sea-island structure is preferable.

The olefinic thermoplastic elastomer is preferably one having a hard segment of 30 to 60 wt% and a soft segment of 40 to 70 wt%, and further a polymerized one produced in the reactor. Good quality stability and uniform physical properties. Further, the melt flow rate of this thermoplastic elastomer is 0.
About 2 to 5 is preferable. As a specific example of such a thermoplastic elastomer, "Zelas 501" manufactured by Mitsubishi Chemical Corporation
3 ”,“ Zelas 5053 ”and the like.

The mixing ratio of polypropylene and thermoplastic elastomer is such that polypropylene is 40 to 60 wt% and thermoplastic elastomer is 40 to 60 wt%. If polypropylene is less than 40 wt%, the tensile rupture strength and rigidity of the binding cord are lowered. However, if the polypropylene content exceeds 60 wt%, the binding string becomes rigid and the packaged item is easily damaged. If necessary, the blend polymer of this polypropylene and the thermoplastic elastomer contains calcium carbonate,
Inorganic fillers such as talc, antistatic agents, colorants and the like can be added as appropriate.

The binding string of the present invention can be produced from the blended polymer having such a composition by a known method using a known extrusion apparatus and stretching apparatus. For example, the blended polymer is heated to 190 to 250 ° C. by an extruder with a T-die.
After melt-kneading at a temperature of 1, the material is extruded with a wide die or slit die and the extruded wide sheet or strip is brought into close contact with a cooling roll, or is cooled and solidified by using an air knife method or a dipping method in a water tank. To do.

The cooled strip-shaped material is left as it is, the cooled sheet-shaped material is slit into a predetermined width, and then heated in a hot-air heating furnace, hot water tank, heating roll, hot plate, far-infrared heating furnace, etc. to rotate. Between two or more sets of nip rolls having different speeds, a multi-stage drawing of one stage or two stages or more is performed in the length direction.

The degree of this stretching determines the degree of crystal orientation of the binding string, and the strength of the binding string is almost determined. The stretching conditions are such that the stretching ratio is 2 to 8 times, preferably 3 to 7 times. Subsequent to this stretching treatment, embossing may be applied to make the surface textured, or an annealing treatment may be performed to remove the strain.

FIG. 1 shows an example of the binding cord 1 of the present invention thus obtained. This example has a width of 6 to 18 mm and a thickness of 0.3 to 0.6 mm. And the basis weight is 2.0 to 7.0 g / m, and a plurality of vertical creases 2, 2, ...
Are formed on both surfaces of the binding string along the longitudinal direction thereof. By forming such a large number of vertical crevices 2, 2, ... While maintaining the tensile rupture strength of the string, it is possible to reduce its weight, straightness (the string itself is less bendable and difficult to bend), and There are advantages of improving the suitability for packaging, straightness (feedability in a packing machine), and the like.

The binding cord of the present invention is 20 to 40%, preferably 25 to 40% in the stretching direction (longitudinal direction) thereof.
% Tensile elongation at break is 140 MPa or more, preferably 140 to 240 MPa, more preferably 18
It is required to be 0 to 220 MPa. If the tensile strength at break is less than 140 MPa, the tensile strength of the cord for binding is insufficient, and it becomes difficult to pack and bind heavy objects. Further, if the elongation is smaller than the above range, it is rigid,
It does not match the gist of the present invention.

Furthermore, it is desirable that the binding cord of the present invention has an elastic recovery rate of 80% or more at 5% elongation in the stretching direction, preferably 85 to 95%, more preferably 95 to 100%. If this value is less than 80%, loosening or slackening occurs after bundling, which becomes a cause of impairing the tight binding property and the fitting property to the object to be packed. The elastic recovery rate in the present invention means 6.1 of JIS L 1096 (general woven fabric test method).
It is the same as the elongation modulus measured by the test method described in Section 3.1.

Further, it is important that the binding cord of the present invention has a heat shrinkage rate of 3% or less in the stretching direction. The heat shrinkage here means a value measured by immersing the bundling cord in boiling water for 3 minutes, taking it out, and naturally cooling it. If this heat shrinkage ratio exceeds 3%, the straightness of the cord is impaired by post-contraction after the cord is manufactured, and the cord is bent.

The tensile breaking strength of the binding cord of the present invention is 140
In order to set the pressure to MPa or more, the elastic recovery rate to 80% or more, and the heat shrinkage rate to 3% or less, the types of raw materials polypropylene and olefinic thermoplastic elastomer, the mixing ratio of the blended polymer, and the draw ratio during drawing It is possible by selecting the stretching conditions such as the stretching temperature and the stretching speed.

In such a binding cord, the physical properties such as tensile breaking strength, rigidity, elastic recovery rate and heat shrinkage ratio are intermediate between those of the conventional polypropylene binding cord and EVA binding cord. Indicates a value. Therefore, even if vulnerable articles such as tiles, bricks, steel pipes, and plastic products are bound and packaged, they are not damaged or damaged. Further, since it can pack heavy objects, has high rigidity and good weldability, it can be applied to an automatic packing machine. Furthermore, since it has good heat resistance and low heat shrinkability, the binding string does not stretch or bend after binding.

A specific example will be shown below. Polypropylene (manufactured by Idemitsu Petrochemical Co., Ltd., trade name "E-200GP") 50
A blend polymer of 50 wt% and 50 wt% of an olefinic thermoplastic elastomer (trade name "Zelas 5013" manufactured by Mitsubishi Chemical Co., Ltd.) is extruded and stretched to have a longitudinal grain 2 as shown in FIG. A binding string 1 having a thickness of 0.6 mm was produced. The draw ratio was 6 times. In addition, "Zelas 5013" is a polypropylene (homo) matrix containing 50 parts of ethylene / propylene rubber as a high molecular weight rubber.
It is said to be a polymerization-type olefin-based thermoplastic elastomer having a sea-island structure in which particles having an average particle size of 1 to 2 μm are uniformly finely dispersed at a ratio of about 60 wt%.

Table 1 shows the physical properties of the binding cord. Table 1
For comparison, a conventional polypropylene tying string and E
The physical properties of the VA binding string (vinyl acetate content 5 wt%) are also shown. Table 2 shows the elastic recovery rates (according to the JIS method) of these three types of binding strings.

[0023]

[Table 1]

[0024]

[Table 2]

Another specific example will be shown. Width 1 as above
A product of the present invention having a thickness of 5 mm and a thickness of 0.6 mm was produced, and for comparison, a tying string of a comparative example was similarly produced using an olefin-based thermoplastic elastomer of another company. This olefinic thermoplastic elastomer contains polypropylene,
It consists of about 90 wt% ethylene-propylene rubber. Tables 3 and 4 show the physical property values of these binding strings.

[0026]

[Table 3]

[0027]

[Table 4]

The tying cord of this comparative example is generally easy to stretch and somewhat poor in straightness, but the strength conforms to the criteria of the present invention, and the elastic recovery rate after stretching is not inferior.
However, the heat shrinkage ratio was 2.4 times larger than that of the product of the present invention, which caused bending and could not be put to practical use.

[0029]

As described above, in the binding cord of the present invention, the tensile breaking strength, rigidity, elastic recovery rate,
The heat shrinkage shows an intermediate value between the conventional polypropylene tying cord and EVA tying cord. Therefore, even if vulnerable articles such as tiles, bricks, steel pipes, and plastic products are bound and packaged, they are not damaged or damaged. Also, it can pack and bind heavy objects, has high rigidity and good weldability, so it can be applied to an automatic packing machine and can also be used for hand binding. Furthermore, since it has good heat resistance and low heat shrinkability, the binding string does not stretch or bend after binding. In addition, the tying cord of the present invention has a manufacturing cost substantially equal to that of the conventional EVA tying cord, and can be provided at a relatively low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a binding cord of the present invention.

[Explanation of symbols]

1 ... Bundling string, 2 ... Vertical grain.

Claims (4)

[Claims] 1. Polypropylene 40 to 60 wt% and soft segment ethylene / propylene rubber 40 to 70 w
Olefinic thermoplastic elastomer containing t% 40-6
A binding cord obtained by extruding a blend polymer of 0 wt% and uniaxially stretching at a stretch ratio of 3 to 7 times. 2. The binding cord according to claim 1, wherein the olefinic thermoplastic elastomer is one in which fine particles of ethylene / propylene rubber of a soft segment of 3 μm or less are uniformly dispersed in a matrix of a hard segment. 3. The binding cord according to claim 1, wherein the tensile breaking strength in the stretching direction is 140 MPa or more at 20 to 40% elongation and the elastic recovery rate at 5% elongation in the stretching direction is 80% or more. . 4. The binding cord according to claim 1, 2 or 3, which has a heat shrinkage in the stretching direction of 3% or less when immersed in boiling water for 3 minutes.