JPS639976B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a hollow packaging band made of thermoplastic resin. Conventional general-purpose packaging bands made of polypropylene are
The band is simply melted and extruded from a die with a rectangular cross section, then cooled, solidified, and stretched.The band is relatively hard and can dig into or damage objects such as cardboard boxes during packaging, and may even damage the product after packaging. During cargo handling work, there were cases where the hands holding the band were cut or injured. In order to solve the above problem, a foamed band is provided in which a foaming agent is added and the foaming agent is decomposed and foamed during melt extrusion, but this foamed band has numerous small intermittent bubbles in the band. exists in
For this reason, sufficient breaking strength cannot be obtained.
Further, most of the packaging bands are used in automatic packaging machines, and in this case, the bands are required to have rigidity in the longitudinal direction. If the band lacks rigidity in the longitudinal direction, it will have poor passage through the arch when feeding the band, leading to poor feeding.
Nowadays, packaging lines are becoming unmanned and faster, and mechanical suitability for automatic packaging machines is as important as the basic physical properties of the band. However, foamed bands have low bending rigidity in the longitudinal direction, and therefore have poor mechanical suitability for automatic packaging machines, resulting in problems in terms of the incidence of packaging defects. The present invention was made as a result of intensive research to solve the conventional drawbacks, and its purpose is to provide a hollow band for packaging that has high breaking strength, high rigidity, excellent suitability for automatic packaging machines, and is soft and pleasant to the touch. It is on offer. That is, according to the present invention, a thermoplastic resin band is formed by integrally extruding a thermoplastic resin from a die and then stretched and oriented in the longitudinal direction, and the bands are arranged parallel to each other and substantially It consists of a substantially rectangular outer periphery formed from upper and lower sides and left and right sides with the same wall thickness, and a partition leg that is connected between the upper and lower sides and partitions the outer periphery in parallel to the longitudinal direction, and the partition leg The band defines a number of adjacent hollow parts, and the cross-sectional area of the hollow parts is 20 to 80% of the total cross-sectional area of the outer periphery, and the thickness of the band is 0.3 to 0.7.
mm, and the strength per unit cross-sectional area of the resin portion consisting of the outer periphery and the partition leg is 40 kg/mm ² or more. In the hollow band of the present invention, both the outer peripheral part and the partition leg part are uniformly cooled during molding, so there is no uneven molecular orientation between them.
A band with excellent stretching orientation and high breaking strength can be easily obtained. On the other hand, general-purpose packaging bands are simply extruded from a die with a rectangular cross section in a molten state and cooled to solidify, so the cooling rate is different between the outer periphery and the center, so the crystalline state is different between the outer periphery and the center. It is thought that the stretching orientation is inferior compared to that of the above-mentioned materials, and that the breaking strength is not sufficient.
It should be noted that the foamed band has countless small bubbles intermittently present in the band, which become defects and cause the band to break, resulting in a lack of breaking strength. For the above reasons, the hollow band of the present invention has a breaking strength per unit cross-sectional area of the resin part that is 1.3 to 1.5 times higher than that of a general-purpose packaging band, and 1.5 to 2.0 times higher than that of a foamed band. Therefore, hollow bands can achieve the same breaking strength with 67 to 77% of the resin material of general-purpose packaging bands and 50 to 67% of foam bands.
The use of resin materials and costs are reduced, and the weight per unit length is reduced, making the band itself easier to handle. In addition, in the case of the hollow band of the present invention, there are many partition legs parallel to the length direction, and since the thickness can be increased relative to the cross-sectional area of the resin part, the bending rigidity in the length direction of the band is large. , has excellent mechanical suitability for automatic packaging machines. Furthermore, since the hollow band has an air intermediate layer, the band has low rigidity in the width direction and is soft overall, so it will not damage the items to be packed during packaging, and it will not hurt your hands even if you hold the band during cargo handling after packing. It won't cut or hurt your hands. On the other hand, in the case of foam bands, the foaming ratio is 1.5 times (the cross-sectional area ratio of the space is 1.5 times) due to the breaking strength and manufacturing issues.
35%) or more, it is difficult to increase the ratio above 35%, but hollow bands have excellent breaking strength and manufacturing stability, so the ratio of the space can be varied widely depending on the application. This feature becomes even more useful when used for manual packaging. Most packing bands are used in automatic packing machines, but they are also often used for manual packing. For example, packaging using a manual tightening machine with a heat welding mechanism,
Metal fittings seal packaging using manual tightening machine and sealing machine,
There are many methods for speed stopper and buckle packing, as well as hand-tied and manual packing. In any of these cases, the band is wrapped around the packaged item by hand and pulled.
The band is even softer than that for automatic packaging machines.
A good feel is required. Therefore, a hollow band that has high breaking strength, allows the proportion of the space to be changed widely, and is bulky, soft, and comfortable to the touch is far more suitable for manual packaging than conventional bands. Further, due to the unique cross-sectional shape of the hollow band, it has excellent metal sealing strength, speed stopper strength, buckle strength, and knot strength when tied. This is because the metal fitting seal, speed stopper, buckle, and knot seals of conventional bands slip, making them less strong, whereas hollow bands collapse under local concentrated stress, so no slipping occurs. This results in high seal strength. In summary, hollow bands have the following characteristics compared to general-purpose packing bands and foam bands. Excellent strength per unit resin section cross-sectional area. It has rigidity in the length direction and has excellent mechanical suitability for automatic packaging machines. The rigidity in the width direction is small, and the band is soft and feels good to the touch. The ratio of the space can be changed widely and arbitrarily. Excellent metal seal strength, speed stopper strength, and knot strength. Here, the cross-sectional shape of the hollow band of the present invention will be explained. There are various cross-sectional shapes of the hollow band as shown in FIGS. 2 and 3, but regardless of the cross-sectional shape, they are arranged parallel to each other and have upper and lower sides 1 and 1 of substantially the same thickness. A large number of hollow parts 2 are defined within the generally rectangular outer periphery formed by the left and right sides 1', 1' by partition legs 3 running in the longitudinal direction, and the hollow parts have a total cross-sectional area of 20 ~80%, and the thickness between the top and bottom sides 1 and 1 is
0.3 to 0.7 m/m, and the strength per unit cross-sectional area of the resin part consisting of the outer periphery and the partition legs 3 must be 40 Kg/mm ² or more. In other words, if the hollow part is less than 20% of the total cross-sectional area, sufficient breaking strength per unit cross-sectional area of the resin part will not be obtained, and the softness will not be sufficient, causing damage to the packaged items during packaging or making it difficult for hands to handle during cargo handling. It can cut you or hurt your hand. On the other hand, if the hollow portion exceeds 80%, the band will be easily crushed and will be crushed when pressed by the feed roller and tightening roller of the automatic packaging machine, reducing the rigidity in the longitudinal direction of the band and causing problems with poor feeding. more likely to occur. On the other hand, even if the total thickness is less than 0.3m/m,
The bending rigidity in the longitudinal direction is reduced, and mechanical suitability for automatic packaging machines is reduced due to the occurrence of feeding errors. On the other hand, if the thickness exceeds 0.7 m/m, the band tends to bend in the length direction and is likely to break. That is, although the band is supplied wrapped around a paper tube, the curl tends to remain when it is wound around the paper tube, and when it is packed with an automatic packing machine, the band is held in the chamber, but it is likely to break at that time. This causes poor feeding and poor tightening, resulting in decreased mechanical suitability. If the cross-sectional area of the resin part is different on the top and bottom, it will warp in the width direction with the side with the larger cross-sectional area inward, and if it is different on the left and right, it will meander in the length direction with the side with the larger cross-sectional area inward. In both cases, band feeding and tightening defects are likely to occur, and the suitability of the machine for automatic packaging machines is reduced. In addition, the band cross-sectional area, resin part cross-sectional area, space part cross-sectional area ratio, breaking strength (unit resin part cross-sectional area strength, the same shall apply hereinafter), longitudinal rigidity, resistance to breakage, fully automatic packaging machine as described in the specification of this application. The suitability, width direction rigidity, metal seal strength, speed stopper strength, knot strength, crush resistance, longitudinal bending tendency, and longitudinal meandering were measured as follows. - The cross-sectional area of the band was determined by dividing the weight of a certain length of band by the apparent specific gravity of the band determined using a density gradient tube (however, hollow bands were determined by actual measurements from enlarged photographs). The cross-sectional area of the resin part is determined by dividing the weight of a band of a certain length by the true specific gravity determined by melting and defoaming the band using a hot press.The cross-sectional area ratio of the space part is the difference between the cross-sectional area of the band and the cross-sectional area of the resin part. I asked for it from・Measurement of breaking strength was performed using a sample with a chuck distance of 200 mm.
It was stretched at a tensile speed of 200 mm/min, the strength at break was determined, and this was divided by the cross-sectional area of the resin portion to determine the strength at break.・Longitudinal rigidity and resistance to bending are determined by placing a sample with a length of 80 mm between two fulcrums with a distance of 47 mm, placing the third fulcrum in the center, and placing the third fulcrum at a distance of 100 mm.
The maximum stress when lowering at a speed of mm/min was taken as the stiffness in the length direction, and the strain at that time was taken as the resistance to breakage. That is, the greater the maximum stress, the greater the rigidity in the longitudinal direction, and the greater the strain at that time, the more difficult the band is to break. In addition, from the viewpoint of suitability for automatic packaging machines, each must be at least 110g and at least 5.5mm.・ Suitability for fully automatic packing machine is arch size 1000W x
Using 800Hmm fully automatic packing machine from Company D, 300W×
A 250H x 500L wooden box was packed 2000 times, and the number of defects that occurred during that time was investigated. As a fully automatic packaging band, it is required that the number of failures occur is 0. - For the stiffness in the width direction, the stiffness in the width direction was defined as the maximum stress when a sample with a length of 30 mm was stood perpendicular to the width direction, compressed at a speed of 10 mm/min, and bent. The smaller the rigidity of the band in the width direction, the less it will dig into or damage the item to be packaged, and the more the band will feel soft when gripped.・ Strong metal seal is 0.4 mm thick and 27.5 mm long.
The breaking strength was measured using the same method as the breaking strength of a sample sealed with a general-purpose open seal using a binding loom, and the speed stopper strength was measured using a sample with both ends of the band fixed with a speed stopper, and the knot strength was measured using a hand-tied sample. It was measured using the same method as strength. - The compression recovery rate was measured to determine the resistance to crushing when compressed by the feed roller or tightening roller of an automatic packaging machine, and the recovery after release. In other words, the maximum compression load is 20Kg with a cylinder with a radius of 5mm across the entire width of the band, and the compression and recovery speed is 0.5mm/
The compression hysteresis curve in minutes was determined, and the resistance to crushing was determined from the strain and recovery rate at this time. In addition, from the suitability of automatic packing machines, the distortion and recovery rate are
0.55mm or less and 50% or more are required. - The bending tendency in the length direction was determined by hanging a 2m band wrapped around a 200mm diameter paper tube and leaving it for one week from a height of 2m and measuring the distance from the floor to the end of the band. In order to be suitable for automatic packaging machines, it must be 300mm or less. - The meandering in the length direction was determined by measuring the maximum amount of meandering when a 2m band was placed closely on a horizontal table. 50mm or less is desirable for suitability for automatic packaging machines. <Example 1> A hollow band of the present invention with the cross-sectional shape shown in FIG. 2 made from PP (polypropylene) with an MI (melt index) of 3 (Example 1) and general-purpose PP from Company A
A comparison study of the band, the foamed PP band of company B, and the foamed PP band of company C revealed that the various properties are as shown in Table 1. 67% of PP band,
Although the breaking strength is 71% and 56% of that of the foamed PP band, the breaking strength is the same as that of a general-purpose PP band and is larger than that of the foamed PP band. In addition, since it has greater rigidity in the longitudinal direction, it has better mechanical suitability for automatic packaging machines than foamed PP bands. Furthermore, the lateral rigidity is much lower than general-purpose PP bands and smaller than foamed PP bands, so it is soft and does not dig into the packaged items, making it highly suitable for cargo handling work.

[Table] <Examples 2 and 3> The cross-sectional shape shown in FIG. 2 of the present invention made from a PP-PE block copolymer with an MI of 1 and containing 7% PE, and the thickness and cross-sectional area A comparative study of hollow bands with different ratios (Examples 2 and 3), a band with the same shape as a conventional band prototyped from the same raw material (Comparative Example 1), a general-purpose PP band from Company A, and a foamed PP band from Company A. The results are shown in Table 2. As a result,
In the hollow bands of Examples 2 and 3, the cross-sectional area of the resin part, that is, the weight per unit length, was 69% of that of the general-purpose PP band.
Although it is 60% of the foamed PP band, it is versatile.
Superior metal sealing strength, speed stopper strength, and knot strength compared to PP bands and foamed PP bands.

【table】

[Table] Also, in terms of manual packing workability, hollow bands are superior to other bands because they are soft and have a good feel. Note that the difference depending on the resin is small, and the difference depending on the cross-sectional shape is much larger. <Examples 4 and 5> Two types of hollow bands of the present invention (Examples 4 and 5), which are made of a raw material in which 3% calcium carbonate fine powder is added to PP with an MI of 3, and have different spatial cross-sectional area ratios, Comparing the cross-sectional area ratios of 18% (Comparative Example 2) and 82% (Comparative Example 3), the unit resin cross-sectional area strength of Comparative Example 2 with a space cross-sectional area ratio of 18% was 33 Kg/mm ² . It is not sufficient and the softness is also insufficient. On the other hand, the cross-sectional area ratio
In Comparative Example 3 with 82%, the compressive strain was large and the recovery rate was poor, so the mechanical suitability for automatic packaging machines was not good.
On the other hand, Examples 4 and 5 with 25% and 75% had no practical problems.

【table】

[Table] <Example 6, 7> Add 3% calcium carbonate fine powder to PP with MI of 3
Two types of hollow bands of the present invention (Examples 6 and 7) whose thickness was changed depending on the added raw material, and a band whose thickness was 0.25 m/m
Comparing the hollow bands of Comparative Example 4 and Comparative Example 5 of 0.75 m/m, the apparent thickness was 0.25 m/m.
In Example 4, the bending rigidity in the longitudinal direction was small and feed defects occurred, so the suitability for automatic packaging machines was not good. On the other hand, Comparative Example 5 of 0.75 m/m tended to bend in the length direction and easily broke, resulting in poor feeding. Example 6 with 0.3 m/m and 0.70 mm on the other hand,
7 had no problems at all.

【table】

[Table] <Examples 8 and 9> A hollow band (Comparative Example 6) and a left band using a PP-PE random copolymer having an MI of 3 and containing 3% PE as a raw material and having different cross-sectional areas of the resin part at the top and bottom of the band (Comparative Example 6) and the left A hollow band with different sides (Comparative Example 7) and a hollow band of the present invention with the same top and bottom and left and right sides (Examples 8 and 9) were manufactured and compared. In Comparative Example 6, where the cross-sectional area was different at the top and bottom, it warped in the width direction, and in Comparative Example 8, where the cross-sectional area was different at the left and right sides, it meandered in the length direction, resulting in poor feeding and was extremely unsuitable for automatic packaging machines. On the other hand, in Examples 8 and 9 in which the top and bottom and left and right sides were the same, there was no problem at all.

【table】

[Table] The warpage in the width direction was measured as the distance between the center of the line connecting both ends of the band and the center of the band surface. In addition, the longitudinal meandering was measured by measuring the degree of arcuate curvature within the 2 m length of the band as the distance between the center of the chord of the arc and the longitudinal center of the curved side surface of the band.

[Brief explanation of the drawing]

The drawings show a typical example of the hollow band according to the present invention, and FIG. 1 is a perspective view thereof, FIG. 2 is a sectional view thereof, and FIG. 3 is an example of another modified cross section. Note that the symbols in the figure are as follows. 1...Top, bottom side, 2...Band hollow part, 3...
Band partition legs.

Claims (1)

[Claims] 1. A thermoplastic resin band formed by integrally extruding a thermoplastic resin from a die and then stretched and oriented in the longitudinal direction, wherein the band is arranged parallel to each other and has upper and lower layers of substantially the same thickness. a substantially rectangular outer periphery formed from sides and left and right sides, and partition legs that are connected between the upper and lower sides and partition the outer periphery in parallel to the longitudinal direction, and a large number of hollow spaces that are adjacent to each other by the partition legs. The cross-sectional area of this hollow part is 20 to 80% of the total cross-sectional area of the outer periphery, the thickness of the band is 0.3 to 0.7 mm, and the unit cross-sectional area of the resin part consisting of the outer periphery and the partition leg. The strength per unit is 40Kg/
A hollow band for packaging made of thermoplastic resin, characterized in that it has a diameter of mm ² or more.