JPS5915065A - Cloth for packing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low-temperature shrinkable packaging cloth suitable for shrink-wrapping items to be packaged.

In general, heat-shrinkable films made of polyvinyl chloride or long-chain branched polyethylene are commonly used for shrink packaging. However, Konera's heat-shrinkable film is inferior in mechanical strength such as tear strength, tensile strength, and abrasion resistance, and is also susceptible to notch propagation, so it is not suitable for packaging at corner or pointed edges of the packaged item. There were constant troubles during storage or transportation, such as film breakage. For this reason, the above-mentioned conventional heat-shrinkable films were hardly used in the field of heavy-duty packaging, and were mostly used in the field of light-duty packaging, where mechanical damage was relatively small.

In addition, the temperature at which the heat-shrinkable film can be compressed is high, and the directionality of shrinkage behavior is slight anisotropy in the M direction and T direction, but it is not large. However, it is completely inconceivable that the shrinkage behavior can be changed only in a part of the width. Therefore, although it is possible to shrink-wrap an object having a simple shape, the present situation is that if the shape of the object becomes even slightly complicated, the desired shrink-wrapping cannot be performed.

Furthermore, due to limitations in film-forming technology, the heat-shrinkable film has a width of 1000+n+n to 1500m at the current technology level.
This is the largest width that can be manufactured, and for this reason it has not been used in the heavy packaging field.

The present inventors have conducted various studies to solve the above-mentioned problems of heat-shrinkable films used for shrink wrapping.
25 to 90 parts by weight of linear polyethylene with short chain branches having a density of less than 0.935 g/crd and dense IJlt
O,9451Ard or higher polyethylene 010-75
A packaging cloth produced by weaving or knitting a thread-like material or a tape-like material obtained by melt-extruding a composition consisting of parts by weight and then drawing it at a temperature of less than 12&r= for either or both of the warp and weft. It was discovered that the above-mentioned problems could be solved by this method.

The linear polyethylene 8 having a short chain distribution used in the present invention is produced by converting ethyl 1/one, propylene, butene, etc. using a catalyst consisting of a transition metal compound and an organometallic compound.
It can be obtained by copolymerizing α-olefins such as 1, hexene-1,4-)f-lupentene-1, hexene-1, and octene-1, and there are no particular limitations on the polymerization method, such as a gas phase method, It can be produced using any method such as a slurry method or a solution method. However, it is necessary that the density of the obtained polymer be less than 0.935 g/c4 and above 0.905 g/crlJJ. The density of the polymer is 0.935 j! If it exceeds /cA, there will be no problem with the strength of the cloth, but the heat shrinkability will decrease, resulting in a decrease in shrinkage binding force, and as a result, shrink wrapping properties will become very poor. However, for example, if the density is 0
．． If it is less than 905 jjArd, there is a tendency in some cases that problems occur in the stretchability of the film and the strength becomes insufficient.

A linear polyethylene prisoner having a density within the above-mentioned range is
It is necessary that the branch is a short chain, and there is no particular limitation on the length of the branch chain, but it is desirable that the length of the branch chain is less than 10 carbons. It is not suitable because it has poor stretchability and tends to have insufficient heat shrinkage. Furthermore, there is no particular limitation on the melt flow rate (190°C, 2.16 Kf, hereinafter referred to as MFR) of the linear polyethylene (2), but from the viewpoint of strength and heat shrinkability, MFR is 2. It is preferable that Ojj/10m=or less.

From the viewpoint of formability and stretchability, MFR is 0.1g710
It is preferable that it is more than normal. ``Also, high load melt flow rate (19°℃, 2x,
6)/melt flow rate C or less HLMFR/MI
4? Similar to the melt flow rate described above, there is no particular limitation on the melt flow rate, but if the HLMI'R/MFR ratio is 40 or more, problems may occur in terms of stretchability and strength. Density 0.935 g with short chain branching
In the case of linear polyethylene with a molecular weight distribution of less than /crtl, it is preferable to use one with a HLMFR1MFR ratio of less than 40 and a narrow molecular weight distribution, since it is inferior in strength and stretchability compared to ordinary high-density polyethylene.

Polyethylene ■ with a density of 0.945 fj/c4jj is produced by homopolymerizing ethylene, propylene, butene-1, etc. using a catalyst consisting of chromium oxide and a carrier, a transition metal compound, and an organometallic compound. It can be obtained by copolymerization with an α-olefin, and there are no particular limitations on the polymerization method. For example, it can be produced using any method such as a solution method or a slurry method.

It is important that the density of this polyethylene is 0.945 gAr1 or more; if it is less than 100 g, the composition will lack stretchability and strength. Furthermore, due to the same circumstances as the linear polyethylene prison, the MFR is 2 to 0.1 g/l Om
rn, IIFMFR/MFR is preferably less than 40.

In the composition consisting of the aforementioned linear polyethylene (2) having a density of less than 0.935 g/cA and polyethylene 0 having a density of 0.945 g/cA or more, the weight ratio is 25 to 25.
90710 to 75, and if the former is large or the latter is small outside this range, the stretchability and strength will be insufficient, while if the latter is large or the former is small, the heat shrinkability will decrease, and therefore the shrinkage binding force will decrease. As a result, shrink wrapping properties become very poor. Furthermore, the stress relaxation rate and creep resistance deteriorate, and the shrinkage stress is relaxed over time during shrink-wrapping and storage, causing the problem that the shrinkage binding force becomes loose.

This composition has a density of 0 in terms of stretchability and strength.
．． 920 g/ca or more, density less than 0.945 g/ca in terms of heat shrinkability, creep resistance, and heat sealability, M F RO, 1,9/10 tone or more in terms of formability and stretchability, strength In terms of MF R2g/lo = below, further in terms of formability) (LMFR/MFR is 1 (1, above), HI in terms of stretchability and strength, and MFR/MFR is preferably 40 or less.

According to the present invention, the composition described above is molded into a filament or a tape, and this molding can be carried out using a conventionally commonly used method, such as an inflation extruder. For molding, the composition is extruded into a film in the molten state through a slit in a die, and after cooling the film, it is slit and heated at a temperature below 120°C, preferably from 70 to 110°C. It is stretched at a magnification of, for example, 4 to 9 times, and formed into a desired thread-like product or tape-like product.

- When the stretching temperature is set to 120°C or higher in the forming mentioned above, not only does the stretching property deteriorate, but also slippage occurs between the molecular chains, so that the stretching operation does not effectively control the orientation, and therefore the desired strength and This is not preferable because the heat shrinkage rate cannot be obtained. In carrying out the present invention, there are no particular problems if the stretching temperature is less than 120°C, but if it is less than 70°C, there is a tendency for whitening to occur, various physical properties to decrease, or stretchability to decrease. Therefore, it is preferable to stretch at a temperature range of 70 to 110°C. Particularly preferred stretching temperature is 85~
The temperature is 105°C. In this temperature range, excellent stretchability and the most balanced physical properties can be obtained.

The stretching ratio during stretching in the present invention depends on the desired strength, heat shrinkability, etc., but is preferably 4 to 9 times. If the stretching ratio is less than 4 times, problems may occur in the strength and heat shrinkage rate of the obtained filament or tape.
Exceeding this may cause problems in stretchability. Furthermore,
In order to reduce natural shrinkage after stretching and to prevent collapse of the rolled straight pipe, heat treatment may be performed immediately after stretching while the dimensions are fixed, or it may be desirable to perform such treatment. .

According to the present invention, the highly contractible and high strength thread-like material or tape-like material obtained by the above method is applied to a part or all of the warp threads, a part or all of the weft threads, or a part or both of the warp threads and the weft threads. The desired shrink wrapping cloth can be obtained by weaving or knitting it in one or all parts. Weaving and knitting can be carried out using conventionally commonly used loom and knitting machine techniques. The specs of the raw yarn used are determined by selecting them as appropriate depending on the shape of the item to be packaged. For example, M
1) If a shrink cloth that shrinks only in the direction (does not shrink in the TD force direction) is required, use the thread-like material made of the above-mentioned linear polyethylene for the warp, and use a thread-like material with a normal low heat shrinkage rate for the weft. On the other hand, if a shrink cloth that shrinks in the TD force direction and does not shrink in the MD force direction is required, the above-mentioned weaving specifications in which the warp and weft are reversed may be used. Furthermore, if a shrink cloth that shrinks in both the MD and rD directions is required, a thread-like material made of the above-mentioned composition may be used for both the warp and the weft. Also,
For example, when shrink-wrapping an unusually shaped packaged item such as a foil disk for an automobile, thread-like materials made of the above-mentioned compositions with different heat shrinkage rates are used as weft threads according to the mold, and the warp threads are For this purpose, a filament having a certain heat shrinkage rate may be used, or the opposite method may be used.

The heat shrinkage rate of the filamentous material can be adjusted by appropriately changing the density, melt flow rate, stretching temperature, stretching ratio, etc. of both polyethylenes used.

In addition, conventionally used dies such as T-shaped dies, zergular dies, filament-shaped nozzles, and band-shaped rectangular nozzles can be used to carry out the present invention. For cooling, for example, water cooling, air cooling, contact with a chill roll, etc. can be used. Furthermore, for stretching, any stretching method such as oven stretching, roll stretching, wet stretching, or hot plate stretching may be used, but since there is a large difference between the melting point and the optimum stretching point, it is relatively inexpensive. It is preferable to use hot plate stretching because it is easy to control heat.

The fact that hot plate stretching can be used for stretching is because the difference between the melting point and the maximum stretching temperature is small, which makes it possible to stretch the conventional high-density polyethylene, which is difficult to stretch at high speeds without using the roll stretching method, which increases cost. This can be said to be extremely advantageous economically compared to other cases. In addition, the low stretching temperature
Energy saving can also be achieved.

The composition used in the present invention may contain an antioxidant, an ultraviolet deterioration inhibitor, a lubricant, a pigment, and even a different resin.

Furthermore, depending on the intended use, the packaging cloth of the present invention may be laminated with a thermoplastic resin according to a conventional method. Lamination may also be carried out by a method such as Sandermany lamination using two or more sheets of the packaging cloth of the invention.

Hereinafter, the present invention will be explained in more detail according to Reference Examples, Examples, and Comparative Examples, but it goes without saying that the scope of the present invention is not limited to these.

Reference Examples 1 to 7, a - d A copolymer of ethylene and butene-1 having the physical properties shown in Table 1, consisting of a linear polyethylene matrix having short chain branches and polyethylene 0, shown in Table 1. For each composition having the M# ratio and physical properties, a 50μ thick film was b'y shaped by the inflation method, and after slitting, the first
A tape was obtained by stretching at the magnification and temperature shown in the table. The tensile strength and heat shrinkage rate of these tapes were measured and the results are also shown in Table 1.

Reference Examples 1 to 7, which correspond to tapes in the present invention, exhibit good tensile strength and heat shrinkage, but Reference Examples a to d, which do not correspond to tapes in the present invention, exhibit linear polyethylene If the density is high, the heat shrinkage rate is poor, and if the amount of Poly-Q (13) is small, as in Reference Example (1)), the elongation and tensile strength are poor; If the amount added to the chain polyethylene is small, the heat shrinkage rate will be poor, and if the stretching temperature is high as in Reference Example (d), the stretchability and heat shrinkage rate will be poor.

In Table 1, 1) JIS K6760 2) Stretching breakage condition after 15 hours ■: Very frequent, continuous operation impossible 2: Many, continuous operator Obstruction layer 3: present, 〃 Slightly impaired 4... Yes,
〃 Interfering heat 5...No, 〃 〃 3) JIS Li073 Chuck distance 300m Tensile speed 300 mm/m'' 4) Example 1 after immersion in a glycerin bath for 1 minute at each temperature
3 Using the tape in Reference Example 1 for the warp and weft, 10 pieces
A plain woven fabric was woven using a 2700 lJ Suliser loom at Io strands/inch (Example 1).

In addition, the density of the woven fabric in Example 1 was 0.9199%.
F R0,8g/l 0-# low density polyethylene 2
A 5μ thick film was laminated on one side (Example 2), and a plain woven fabric was woven and laminated on one side in the same manner as in Example 2 except that the tape in Reference Example 3 was used (Example 3).

Various physical properties were measured for these packaging cloths, but the second
Good results were obtained as shown in the table.

Comparative Examples 1 to 4 Plain weave fabric was woven and laminated on one side in the same manner as in Example 2 except that the tape in Reference Example a% C was used (Comparative Example 1.2).

For comparison, a commercially available 150μ thick Shrink film made of low density polyethylene with long chain branches (Comparative Example 3) and a commercially available 110μ thick Shrink film made of polyvinyl chloride (Comparative Example 4) were obtained.

Various physical properties were measured for these, as shown in Table 2.
When the density of the linear polyethylene G) is high as in Comparative Example 1, the heat shrinkage rate is low and the shrink wrapping property is also poor;
As shown in Comparative Example 3, even if the amount of linear polyethylene is small, the heat shrinkage rate is low and the shrink wrapping property is also poor. It has low tensile strength, tear strength, dirt impact, and dynamic load impact properties, and as shown in Comparative Example 4, even polyvinyl chloride Nyulink film has low tensile strength, tear strength,
Dirt impact, dynamic load impact resistance is low.

In table 2 l) After immersion in a glycerin bath for 1 minute at each temperature.

2) Dirt; 38WXn, m hemisphere, Lm height, 3) Wrap it around the car wheel disc with a 15% margin in length, heat seal the ends, and tighten the inside of the Nyulink tunnel in 20 seconds. The lowest temperature at which it can be packaged.

4) Minimum transit time that allows for tight packaging at 185°C in a shrink tunnel by heat sealing as in the previous section.

5) ◎...Very good, ○...Good, ×...Poor 6
) Number of times when perforation was observed.

Claims (1)

[Claims] 25-90 parts by weight of linear polyethylene (5) with short chain branching with a density of less than 0.935 gArk and a density of 0.94
5 g/cyA JJ, polyethylene (8110
120° C. after melt extrusion of a composition consisting of ~75 parts by weight
A packaging cloth produced by weaving or shrinking a thread-like material or a tape-like material stretched at a temperature of less than 100 ml for either or both of the warp and the weft.