JPH0548173B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a laminated shrink wrapping material with improved tear strength and notch propagation resistance of the shrink wrapping film. (Prior art) Once a tear occurs in packaging materials such as paper or plastic film during transportation, the tear propagates and becomes a large tear that not only damages the packaging form but also damages the contents. The disadvantage is low strength and notch propagation resistance. Therefore, in order to increase this tear strength and notch propagation resistance,
In general film-like packaging materials, there are examples in which a thread-like material or tape-like material is attached as a reinforcing material. (Problems to be Solved by the Invention) Films for shrink wrapping also share the drawbacks of low tear strength and notch propagation resistance, so lamination of reinforcing materials as described above may be considered. However, in the case of shrink wrapping materials, a good packaging finish is required after shrink wrapping, and the presence of thread-like or tape-like materials as the reinforcing material impairs the packaging finish. (Means for Solving the Problems) The present invention was arrived at as a result of various studies to solve the above ^- mentioned circumstances. A woven or knitted fabric using a linear polyethylene thread or tape having a heat shrinkage rate of 0.7 of the woven or knitted fabric at 80 to 110°C.
It is a packaging material made by laminating films that are ~1.3 times as large. In the present invention, the linear polyethylene having short chain branches having a density of less than 0.945 g/cm ³ may be blended with polyethylene or polypropylene having a higher density, if necessary. Density 0.945 with heat shrinkability in the present invention
A thread-like or tape-like product made of linear polyethylene having short chain branching of less than g/cm ³ can be obtained, for example, as follows. A linear polyethylene having short chain branches having a density of less than 0.945 g/cm ³ is extruded into a film, and after cooling, it is slit and stretched at 50 to 120°C and 4 to 9 times. In addition, in order to improve stretchability and strength by blending polyethylene with a higher density into the linear polyethylene, it was previously possible to slit the polyethylene at 70 to 120°C.
Stretch 4 to 9 times. Furthermore, in order to improve the shrinkage stress retention rate at room temperature by blending a polypropylene homopolymer with the linear polyethylene, it is slit in the same manner as before and stretched at 70 to 120°C and 2 to 8 times. In addition, outside of these stretching conditions, strength and heat shrinkage may decrease at low and high temperatures.
On the low magnification side, the heat shrinkage rate will decrease, and on the high magnification side, there is a concern that the stretching will break. Furthermore, the die slits used in carrying out the present invention include T-shaped dies, circular dies,
Conventionally used nozzles, such as filament-shaped nozzles and band-shaped rectangular nozzles, can be used. Cooling after extrusion can be carried out, for example, by water cooling,
Either air cooling, contact with a chill roll, etc. can be used. Furthermore, stretching is oven stretching,
Any stretching method such as roll stretching, wet stretching, or hot plate stretching may be used, but since there is a large difference between the melting point and the optimal stretching temperature, it is preferable to use hot plate stretching, which is relatively inexpensive and easy to control heat. . According to the present invention, the highly shrinkable and high-strength filament or tape-like material obtained by the above method can be used as a part or all of the warp, a part or all of the weft,
Alternatively, the desired shrink wrapping material can be obtained by weaving or knitting using a part or all of both the warp and the weft. Weaving and knitting can be carried out using conventionally commonly used loom and knitting machine techniques. The specs of the yarn to be used are selected and determined as appropriate depending on the shape of the item to be packaged. for example,
If you need a shrink wrapping material that shrinks only in the MD direction (but not in the TD direction), use the above-mentioned thread-like material or tape-like material for the warp, and use a normal thread-like material with a low heat shrinkage rate for the weft. Good, and vice versa
If a shrink wrapping material that shrinks only in the TD direction but not in the MD direction is required, the above-mentioned weaving spec in which the warp and weft are reversed may be used. Also,
If a shrink wrapping material that shrinks in both the MD and TD directions is required, the thread-like material or tape-like material may be used for both the warp and the weft. A film whose heat shrinkage rate at 80 to 110°C is 0.7 to 1.3 times that of the woven or knitted fabric is:
The thermal shrinkage rates of both are in the range of 0.7 to 1.3 times that of the other at a predetermined temperature of 80 to 110°C, and it is preferable that they be as close to each other as possible. Such a film can be obtained by using low-density polyethylene, polypropylene, polyvinyl chloride, etc., and adjusting the heat shrinkage rate by appropriately changing the density, melt flow rate, stretching temperature, stretching ratio, etc. In the lamination method, a heat-shrinkable film may be laminated on a woven or knitted fabric using an ordinary laminator, and resins of the same type can easily adhere to each other, but an anchor treatment may be performed to improve adhesion. In addition, it may be made of not only two layers of woven or knitted fabric and film, but also a multilayer of three or more layers. According to the packaging material of the present invention, the presence of a woven or knitted fabric using a thread-like or tape-like material made of linear polyethylene having short chain branches with a density of less than 0.945 g/cm ³ makes it possible to use conventional shrink wrapping. The film's shortcomings of low tear strength and notch propagation resistance and low shrinkage rate are overcome, and the packaging finish is also good. The present invention will be explained in more detail by giving Examples and Comparative Examples below. Examples Using the raw resin shown in Table 1, a raw film was formed by an air-cooled inflation method using a 65 mmφ extruder and a 250 mmφ spiral die, and after slitting, a hot plate stretching machine was used to form the raw film at the temperatures shown in Table 1.
A tape having a width of 7 mm and a denier of 1000 was obtained by stretching at a magnification. The tensile strength and heat shrinkage rate of this tape were measured and the results are also shown in Table 1. Use this tape for each warp and weft, 10 pieces
A plain weave fabric was woven using a 2700 mm width sluzer loom with 10 strands/inch, and the density was 0.919 on a 50 μ thick shrink film of commercially available low density polyethylene with long chain branches.
g/cm ³ , MFR 0.8 g/10 min low density polyethylene was melt extruded and laminated under pressure with a roller to form an adhesive layer 25 μ thick. The shrinkage rate and other physical properties of this packaging material are as shown in Table 2, and the tear strength of the packaging material of the present invention is significantly superior to that of a shrink film. Also bicycle rim 10
When a book was shrink-wrapped using this packaging material, the packaging had a good finish. Comparative Example 1 The woven fabric in Example was shrink-wrapped, but the wrapping was poor. Comparative Example 2 A shrink wrapping test was conducted using only the shrink film in Example 2, and as shown in Table 2, the tensile strength,
The dart impact value was low and the dynamic load impact resistance was poor. Comparative Example 3 A woven fabric was made in the same manner as in the example using high-density polyethylene with a density of 0.950 g/cm ³ and an MFR of 0.9 g/10 min as the raw resin, and the same shrink film as used in the example was used. Laminated. As shown in Tables 1 and 2, the thermal shrinkage rate was low, and therefore good packaging could not be achieved even if the temperature of the shrink tunnel was raised to the point where the laminated packaging material was on the verge of melting. Comparative example 4 Density is 0.950 instead of linear polyethylene
A laminated packaging material was manufactured in the same manner as in the example except that high-density polyethylene with a density of 0.9 g/cm ³ and an MFR of 0.9 g/10 min was used. As shown in Tables 1 and 2, the thermal shrinkage rate was low, and good packaging could not be achieved even if the temperature of the shrink tunnel was raised to the point where the laminated packaging material was on the verge of melting.

【table】

【table】

[Table] In Table 1, 1 is a copolymer of ethylene and butene-1,
It has short chain branches. 2 JIS K6760 (polyethylene) JIS K6758 (polypropylene) 3 JIS L1073 Chuck distance 300mm Take-up speed 300mm 4 After immersion in a glycerin bath for 1 minute each In Table 2 1 After immersion in a glycerin bath for 1 minute at each temperature 2 Dirt: 38mmφ hemisphere Body, 1m height 3 Wrap the car wheel disk with a 15% margin in length, heat seal the edges, and the lowest temperature that can be wrapped tightly inside the Sylink tunnel in 20 seconds. 4 Minimum transit time that allows for tight packaging at 185℃ through heat sealing in the same manner as in the previous section. 5 ◎...Very good, 〇...Good, ×...Poor6 Number of times when perforation was observed. 7 The temperature of the shrink tunnel was raised to the point where the laminated packaging material was on the verge of melting, but good packaging could not be achieved.

Claims (1)

[Claims] 1 Woven or knitted fabric made of linear polyethylene thread or tape having short chain branching with a density of less than 0.945 g/cm ³ and having heat shrinkability, and
A packaging material formed by laminating films having a heat shrinkage rate at ~110°C that is 0.7 to 1.3 times that of the woven or knitted fabric.