JPH05131544A - Heat-shrinkable cylinder - Google Patents

Abstract

PURPOSE:To obtain a heat-shrinkable cylinder made of a film which covers a material to be packaged such as a bottle and is thermally shrunk to package it and good in heat sealing properties and free from generation of odor at a time of sealing and excellently adheres to the material to be packaged and is free from a strain in the printed pattern of the film and used for a packaged body having excellent appearance. CONSTITUTION:A film constituted of a terpolymer of propylene, ethylene and alpha-olefine (alpha-olefine has 4-10C, ethylene to the whole copolymerized component is 0.2-10wt.%, alpha-olefine is 1.5-25wt.% and melt index at 230 deg.C is 0.5-15) is used and formed into a cylindrical shape. In this film, the degree of thermal shrinkage (degree of dry heat shrinkage at 120 deg.C for 5min) in the lateral direction is regulated to two times or more for the degree of heat shrinkage in the longitudinal direction. The longitudinal direction is set in the axial direction of the cylinder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-shrinkable olefin film, which has a cylindrical shape and is suitable for packaging bottles, containers, rods and the like.

[0002]

2. Description of the Related Art Recently, outer packaging for improving the appearance of packaged goods, tight packaging for avoiding direct impact of contents, label packaging for protecting glass bottles or plastic containers and displaying products, and other transportation spaces. For the purpose of reducing the number of articles, bundling packaged articles, etc., the exterior of packaged articles, label seals of various molded articles, cap seals, etc. are widely used.
The plastic films used for these purposes include
It is required to have anisotropic heat shrinkability, heat sealability, printability, etc., and in order to achieve these purposes, conventionally, films made of polyvinyl chloride, electron beam irradiated polyethylene, etc. have been used. In addition, biaxially oriented polypropylene film is used as a light packaging material such as a container of instant cup ramen.

[0003]

However, while the above polyvinyl chloride film has good heat shrinkability, it has poor heat sealability and therefore requires the use of an adhesive, and the chlorine gas generated when incinerating waste is Unfavorable due to corrosion and environmental problems. Further, in the case of the polyethylene film, transparency and gloss are not sufficient, and it is difficult to obtain a film having different heat shrinkage rates in the longitudinal and transverse directions. Furthermore, since the biaxially stretched polypropylene film has a low heat shrinkage ratio at a low temperature, it needs to be heat shrunk at a high temperature, and at that time, the temperature of the packaged object also rises, which causes an obstacle such as alteration or coloring of the packaged object. Deformation of the exterior material or the container itself may occur. The present inventor has completed the present invention as a result of earnest research in order to solve the above problems and meet market demands.

[0004]

That is, the present invention is
The ethylene content is 0.2 to 10% by weight, the α-olefin having 4 to 10 carbon atoms is 1.5 to 25% by weight, and the melt index at 230 ° C is 0.5 to 15% with respect to all the copolymerization components.
Which is a propylene / ethylene / α-olefin terpolymer (α-olefin has 4 to 10 carbon atoms), and the film has a lateral heat shrinkage ratio (120 ° C., 5 ° C.).
Free heat shrinkage per minute) is 2 against the heat shrinkage in the longitudinal direction.
It is a heat-shrinkable cylinder characterized by forming a cylindrical shape by using a heat-shrinkable film that is double or more in the lengthwise direction in the axial direction.

The thickness of the film used in the present invention is 10 to
It is in the range of 500 microns. Usually, a film having a thickness of 10 to 250 μm is referred to as a film, and a film having a thickness of 250 to 500 μm is referred to as a sheet. In this specification, the above film and sheet are not distinguished and are collectively referred to as a film. .

The propylene / ethylene / α-olefin terpolymer which forms the film has an ethylene content of 0.2 to 10
% By weight, .alpha.-olefin having 4 to 10 carbon atoms is 1.5 to 25% by weight, preferably 3 to 20% by weight, and the balance is propylene. Within this composition range, the terpolymer may be a random copolymer, a block copolymer, or a block copolymer of copolymer units having different monomer ratios.

The melt index of the above terpolymer (measurement temperature 230 ° C., unit g / 10 minutes, hereinafter abbreviated as MI) is 0.5 to 15, preferably 1.0 to 10. MI is
When it is less than 0.5, the film forming speed for obtaining a transparent and smooth film is lowered, and the load power consumption is increased. Also,
When the MI exceeds 15, the heat shrinkability is lowered, the heat shrinkage rate is small especially in a low temperature range, and the transparency is also lowered.

The resin of the film used in the present invention is mixed with other polymers, additives such as an antistatic agent, a lubricant, an antiblocking agent, etc. within a range not departing from the object of the present invention, so that the automatic wrapping property and the wrapping property can be improved. The slipperiness of the object can be improved. Examples of the antistatic agent include ethylene oxide adducts of alkylamines, ethylene oxide adducts of alkylamides, betaine type antistatic agents, monoglycerides of other fatty acid esters, polyoxyethylene alkylphenyl ethers, and the like. Generally, fatty acid amide type, higher fatty acid ester type, wax type, metallic soap and the like are used. As the anti-blocking agent, silica, calcium carbonate, magnesium silicate, inorganic additives such as calcium phosphate, nonionic surfactant, anionic surfactant, incompatible organic polymer
(Eg, polyamide, polyester, polycarbonate, etc.) are used.

These additives are added to the resin component in an amount of 0.05
.About.5% by weight, preferably 0.1 to 3% by weight. In addition to the above additives, pigments, dyes, ultraviolet absorbers and the like can be added depending on the purpose.

One of the features of the film used in the present invention is that the heat shrinkage in the transverse direction (dry heat free shrinkage at 120 ° C. for 5 minutes) is at least twice the dry heat free shrinkage in the longitudinal direction. That is. Thereby, when the film is formed into a cylindrical shape and coated on an unwrapped product, and heat-shrinked to be brought into close contact with the object to be packaged, the cuttability becomes better than in the case where the heat shrinkage ratio in the longitudinal direction is large.

If the heat shrinkage in the transverse direction is less than twice the heat shrinkage in the longitudinal direction, that is, if the heat shrinkage in the longitudinal direction exceeds 0.5 times the heat shrinkage in the transverse direction, this film is used. When used to manufacture cylinders, they have a poor appearance when heat-shrinked. For example, heat sealing in the axial direction with the longitudinal direction of the film as the axial direction and the lateral direction as the circumferential direction, to create a film cylinder having the same length as the height of the packaged object, and coating this film cylinder on the packaged object. When it is made to heat-shrink, the film cylinder contracts laterally along the outer peripheral surface of the packaged object, but the length of the film cylinder also becomes shorter than the height of the packaged object due to longitudinal contraction. The upper and lower ends of the cylinder are retracted inwardly of the upper and lower ends of the packaged object, and the upper and lower edges of the cylinder become zigzag, resulting in poor appearance. In particular, when a cylinder of a printed film is used, the printed pattern is distorted at the upper and lower edges and the appearance is deteriorated.

As can be understood from the above description, the heat shrinkage in the longitudinal direction is preferably small, and the dry heat free shrinkage at 120 ° C. for 5 minutes is generally 15% or less. On the other hand, it is preferable that the heat shrinkage in the horizontal direction is large, but it is usually 3.5 to 4.0 times the heat shrinkage in the vertical direction.
It is preferably 80%. The larger the unevenness of the outer shape of the packaged object, the higher the heat shrinkage in the lateral direction is required.

The film used in the present invention is produced by the ordinary T-die method and the inflation method by stretching mainly in the transverse direction or by stretching and heat-setting under specific conditions. Further, using a separate extruder to co-extrude from one die, or to produce an unstretched film by further laminating one layer extruded one layer,
This unstretched film is stretched at least in the transverse direction, preferably in the longitudinal and transverse directions successively or simultaneously. In addition, one layer is extruded into a film, and after longitudinal stretching if necessary, at least one surface is extruded and laminated, and further stretched in the transverse direction, or after separately extruded into a film,
It is also possible to use a method in which both are laminated while being longitudinally stretched, and further stretched in the lateral direction. Then, when laminating the both, an adhesive may be used if necessary.

The stretching ratio in the machine direction in the production of the film is 1.0 to 2.0 times, preferably 1.0 to 1.5 times. That is, stretching in the machine direction may be omitted. The stretching temperature is 70 to 160 ° C., preferably 80 to 140 ° C. When the stretching temperature in the machine direction is less than 70 ° C., the transparency of the film is low, and when the stretching temperature exceeds 160 ° C., the film is Adheres to the stretching rolls, and when the intermediate stretching roll is not used, the neck-in variation becomes large, and the transverse stretching in the next step becomes unstable.

The stretching ratio in the transverse direction is 5.0 to 16 times, preferably 6.0 to 12 times, and 7.0 to 13 times is the preferable range when it is required that the heat shrinkability in the transverse direction is further increased. The stretching temperature is 80 to 160 ° C, preferably 90 to 140 ° C.
If the temperature is less than 80 ° C, the number of times the film breaks increases and the yield decreases, while if it exceeds 160 ° C,
Breakage occurs at the clip part of the tenter and at the center of the film due to thermal softening.

The film stretched as described above is maintained at the above stretched state by subsequently lowering the temperature to 120 ° C., preferably 80 ° C. or lower, or rapidly cooling to 0 ° C., preferably around 10 ° C., or While keeping the size change of ± 10%, let it stand for 2 to 10 seconds until it reaches room temperature. Cooling after this stretching is performed by air cooling, a cooling roll, a cooling belt, or a combination thereof.

The surface of the stretched film obtained as described above is subjected to surface activation treatment by corona discharge treatment, discharge treatment in various gas atmospheres, acid treatment, flame treatment, etc., and if necessary, printing, Metal deposition can be applied.

The film used in the present invention has not only heat shrinkability but also excellent high-speed ultrasonic sealing property as compared with general polyolefin films. Of course, it is needless to say that heat bonding by a thermal method such as a normal hot plate seal, multipoint seal, fusing seal, and bonding with an adhesive are possible.

The heat-shrinkable film used in the present invention is formed into a cylindrical shape having the longitudinal axis as an axis, and the film cylinder is coated on the object to be packaged and then heat-shrinked to form the outer surface of the object to be packaged. It is suitable as an exterior material to be closely adhered to. The conditions for heat shrinkage are 160 ~ for hot air.
200 ℃, 2 to 10 seconds, the film temperature at that time
70 to 150 ° C is preferable. The relationship between the heating temperature and the time is determined by the wind speed of the hot air, the blowing angle, and the like.

Examples of the articles to be packaged include glass or plastic bottles, paper, plastic, containers made of other materials, rod-like bodies such as legs of desks and chairs, or spherical bodies. Then, not only the object to be packaged but also the product name, advertisement, notice, etc. can be displayed by printing on the exterior material.

Embodiments of the present invention will be described below. Example 1 Propylene-ethylene-butene-1 terpolymer of MI 4.5 (ethylene content 4.5% by weight, butene-1 content 16
% By weight), 0.35 part by weight of glycerin ester of stearic acid, 0.8 part by weight of alkylamine type antistatic agent and 0.1 part by weight of erucic acid amide were added to prepare a composition.
The composition is melt extruded to obtain an unstretched film (thickness: 530μ)
And then stretched 1.1 times in the machine direction at 114 ° C and then 9.5 times in the transverse direction at 120 ° C.
It was cooled to 0 ° C. and then to room temperature for 4 seconds with a relaxation rate of 1.5%. Further, corona discharge treatment is applied to one side to a thickness of 50
A heat shrinkable film of μ was obtained.

Printing was performed on the discharge-treated surface of this heat-shrinkable film to form a cylindrical shape. This film cylinder has a diameter of 50
mm and a height of 150 mm were covered on the outside of a paper tubular body and a plastic tubular body and heated to 210 ° C. to evaluate the shrinkage state by the heat shrinkage time. For comparison, a similar test was conducted on a biaxially shrinkable polypropylene film (Comparative Example 1) and a uniaxially shrinkable polyvinyl chloride film (Comparative Example 2).

The properties of the films of Example 1 and Comparative Examples 1 and 2 and the results of shrinkage evaluation are shown in Table 1 below.

[0024]

[Table 1]

As can be seen from Table 1 above, the transparency of the film of Example 1 is slightly inferior to that of the Comparative Example, but it has practical transparency, and the film of Example 1 is Excellent heat-sealing strength, low surface resistivity, and excellent antistatic properties. Also, the film of Example 1 has a good appearance after packaging, like the conventional polyvinyl chloride film, and has heat sealability as compared with the polyvinyl chloride film, and the generation of odor during heat sealing. There is no.

The transparency and haze in Table 1 above are
It is a value measured by a haze tester manufactured by Toyo Seiki Co., Ltd. according to JIS-K6714. Heat seal strength is 1 kg / cm ² , 0.5 with a gradient heat sealer manufactured by Toyo Seiki Co., Ltd.
After heat-sealing for 2 seconds, set the peel strength to 2
It is a value measured at a speed of 00 mm / min. Surface resistivity is
It is a value measured by using a static onest meter manufactured by Shishido Shokai after allowing the film to stand in an atmosphere of 23 ° C. and 65% RH for 24 hours. In the heat shrinkage ratio of 5 minutes, M indicates the vertical direction, T indicates the horizontal direction, and the heat shrinkage is evaluated as follows: ◎ is the highest, ◯ is good, △ is the practical limit, × is bad, and the plastic tube is deformed. Indicates that it has been deformed.

Example 2 A heat-shrinkable film having a total thickness of 60 μ was obtained by using various copolymers having different monomer contents in Example 1 above.
A printing ink for polypropylene (trade name PP-ST, manufactured by Toyo Ink Co., Ltd.) was used to print on one surface of this film that had been subjected to corona discharge treatment. Table 2 shows the results of evaluation of heat resistance when these films were formed into a cylinder with the longitudinal direction as the axial direction, generation of wrinkles in the heat-sealed portion, and appearance of the heat-sealed portion after heat shrinkage.

Polymer type Name MIA Isotactic polypropylene 2.5 B Propylene / ethylene copolymer (ethylene content 0.4% by weight) 4.0 C Propylene / ethylene copolymer (ethylene content 3.0% by weight) 2.5 D propylene -Ethylene / butene-1 terpolymer (ethylene content 3.0% by weight, butene-1 content 2.0% by weight) 7.0 E propylene / ethylene / butene-1 terpolymer (ethylene content 3.0% by weight, Butene-1 content 20% by weight) 7.0 F propylene / ethylene / butene-1 terpolymer (ethylene content 20% by weight, butene-1 content 15% by weight) 4.0

[0029]

[Table 2]

Regarding the tube loading property in Table 2 above, the film was made into a cylindrical shape with a circumference of 162 mm, and this cylindrical film was
Covering the outer surface of a container having a different diameter part in which a cylindrical body having a diameter of 50 mm and an annular recess of 44 mm in diameter is formed in a part thereof, and tapping the film lightly indicates the difficulty of loading the container into the container. Tube loadability is a criterion for whether or not it can be continuously loaded at high speed by an automatic packaging machine. This tube loading property is the film's waist, antistatic property, bending fixing property,
Lubricity with respect to the container is an important factor, and is not simply determined by the resin that easily undergoes heat shrinkage and its stretching conditions. Good tube loadability ○,
A somewhat good one is indicated by Δ, and a poor one is indicated by x.

With respect to the appearance after heat shrinkage, hot air at 210 ° C. was blown on the heat seal portion for 5 seconds to cause heat shrinkage, and then the appearance (wrinkles, sagging, etc.) of the heat seal portion was visually evaluated. If the heat sealing is incomplete or insufficient, heat shrinkage may cause peeling or floating.

The shrinkability of the heat-sealed portion is sufficient in the next heat-shrinking step because the adhesive portion undergoes a thermal history when the two films are heat-sealed together by palm-sealing or overlapping. It is evaluated whether or not the heat shrinkage occurs, or wrinkles and cavities occur, or the heat shrinkage becomes insufficient.

The ultrasonic sealing property indicates whether or not a high-speed sealing is possible when a tubular film is produced from the film. ◯ mark is completely bonded, △
The mark indicates that the seal is adhered, but the seal strength is weak due to fluctuations in the thickness of the seal line, or there is an insufficient seal part.The mark x indicates that the seal is insufficient and the seal part peels off during the heat shrinking process. Shows what is going on. This ultrasonic sealing property has great significance in industrial production, and the high-speed ultrasonic sealing property means that it can be sufficiently sealed with low energy and that it retains sufficient shrinkage in the heat shrinking process. There is.

Example 3 In the above Example 1, the stretching ratio in the transverse direction was changed to 1
We manufacture films with different horizontal / vertical ratios of heat shrinkage at 20 ° C, form this film into a cylindrical shape with the longitudinal direction as the axial direction, and cover it on the outside of a paper cylinder with a diameter of 50 mm and a height of 150 mm. Then, hot air at 210 ° C. was blown for 10 seconds to cause heat shrinkage. Table 3 shows the measurement results of the floating distance from the lower end of the paper cylinder to the lower end of the film and the range of fluctuation of the floating distance on the peripheral surface of the cylinder at this time.

[0035]

[Table 3]

As can be seen from Table 3, when the horizontal heat shrinkage is more than twice the vertical heat shrinkage, the film hardly rises even if heat shrinks.

Example 4 In Example 1 above, the melt index MI of the propylene / ethylene / butene-1 terpolymer was changed to
A heat-shrinkable film having a thickness of 50μ was manufactured. This film was formed into a cylindrical shape in the same manner as in Example 3, covered with a paper cylinder and heat-shrinked. Table 4 shows film manufacturability, heat shrinkage ratio, and appearance of this film after heat shrinkage.

[0038]

[Table 4]

As can be seen in Table 4, MI is 1.0, 4.
5 and 12 have good manufacturability, film appearance, and appearance after shrink-wrapping, while MI of 0.3 has a large load power during extrusion and poor productivity, and The appearance is inferior. Further, those having MI of 20 have a low heat shrinkage rate at low temperature, and thus have poor appearance after shrink-wrapping.

[0038]

As described above, the heat-shrinkable cylinder of the present invention is made of a film composed of a propylene / ethylene / α-olefin terpolymer, and the heat shrinkage ratio of the film in the transverse direction is Since it is more than doubled and this vertical direction is used in the axial direction of the cylinder, it is easy to form the cylindrical shape, and it is covered with a packaged object such as a bottle, a container, or a rod-shaped body and blown with hot air. By heat-shrinking, the film can be brought into close contact with the surface of the article to be packaged for packaging. And the above film is propylene
Since it is composed of ethylene / α-olefin terpolymer, it has good sealing properties such as ultrasonic sealing properties, does not generate odor, and has excellent sealing strength and antistatic properties, and packaging It is easy, and there is no lifting or distortion of the film after packaging, excellent transparency and gloss, and good appearance. In addition, since the melt index of the above terpolymer is 0.5 to 15, it is also excellent in productivity.

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display area B29L 7:00 4F C08L 23:00

Claims (1)

[Claims] 1. The ethylene content based on all copolymerization components
0.2-10% by weight, C4-10-olefin content
A film made of a propylene / ethylene / α-olefin terpolymer (α-olefin has 4 to 10 carbon atoms) having a melt index of 1.5 to 25% by weight and a melt index at 230 ° C. of 0.5 to 15 is prepared. A heat-shrinkable film having a heat shrinkage in the transverse direction (120 ° C., free heat shrinkage for 5 minutes) twice or more the heat shrinkage in the longitudinal direction is used with the longitudinal direction set in the axial direction. A heat-shrinkable cylinder characterized by being formed into a cylindrical shape.