JP3200262B2 - Stretch wrapping film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film for stretch packaging and a method for producing the same. In particular, it is suitable for food tray packaging and notebook packaging, and has excellent suitability for packaging machines such as slipperiness, heat sealability, and adhesion, and also has excellent surface properties such as label adhesion, anti-fog properties, and optical properties. And a film using a well-balanced polyolefin-based resin as a raw material.

[0002]

2. Description of the Related Art Conventionally, for stretch packaging of foods,
Due to its price and film properties, especially excellent surface properties, vinyl chloride or other copolymers
Plasticization, for example, a PVC-based stretch film containing 30 to 50% by volume of a plasticizer has been used. However, as is well known, these films have been pointed out with environmental problems such as generation of hydrogen chloride gas during incineration and generation of harmful reaction products containing chlorine, and especially for food packaging. When used, there is also a hygienic problem that the contained plasticizer easily migrates to food.

As a means for solving the environmental and sanitary problems of such a PVC stretch film, a polyolefin stretch film has been developed and marketed. However, at present, the above-mentioned polyolefin-based stretch films have not yet been widely used as substitutes for PVC-based stretch films, despite their excellent environmental and hygienic properties.

[0004] The cause of this is that there is a problem in that it is generally expensive compared to a PVC stretch film, but as a technical problem, a polyolefin stretch film is a so-called “machine The performance problem of poor "relevance" has not yet been sufficiently solved.

[0005]

For stretch packaging using a PVC-based stretch film, a packaging machine specially developed for a PVC-based stretch film is used.
For example, most packaging machines currently operating in Japan for food packaging are PVC-based stretch film-specific packaging machines. Packaging machines for polyolefin-based stretch films have been developed, but the number of operating machines is still small. Therefore, in order to spread the polyolefin-based stretch film, it was necessary to be able to satisfactorily pack it even with a PVC-based stretch film-type packaging machine.

However, when a polyolefin-based stretch film is used in a PVC-based stretch film-type packaging machine, there are cases where it cannot be satisfactorily wrapped (hereinafter referred to as "poor machine-related"). For example, in order to perform packaging in a packaging machine, it is necessary to normally transport the film by a transport mechanism in the packaging machine. During the transfer,
The film must have good slipperiness with "parts that need to slide (such as film holding plate)" in the packaging machine, but on the other hand, "the parts that need to be in close contact with the film (film transport belt, film transport "Roll etc.") requires sufficient adhesion. PVC-based stretch films have a well-balanced combination of the apparently contradictory surface properties of slipperiness and adhesion, but in general, polyolefin-based stretch films have a different balance between slipperiness and adhesion than PVC-based stretch films. When used in a packaging machine developed for stretch films, there were cases where packaging could not be performed due to problems such as poor transport.

In particular, an example of a packaging machine of a part of a push-up type (elevator type) PVC stretch film specification will be described as an example, and a general film transport mechanism in the packaging machine will be described. The film is held by being brought into close contact with a rubber belt or the like for transporting the film, and the film is transported by moving the rubber belt with the power of a motor or the like. Move while rubbing.

At that time, the front end of the polyolefin stretch film is rubbed with the film pressing plate and rolled into a twisted shape (hereinafter simply referred to as a stretch).
Transport troubles were likely to occur, resulting in insufficient dimensions of the film and packaging problems. According to the investigations by the inventors, in general tray packaging, if the length of the film for which the size is insufficient is about 40 mm or more due to the generation of the tray, the packaging will be defective. It has been found that packaging can be carried out without any problem if it is 20 mm or less.

In the case of a polyolefin-based stretch film, the surface of the film which is rubbed with the film pressing plate during conveyance is apt to be scratched due to melting caused by frictional heat generated at that time. In addition, a hole was formed in the package, and the finished packaging, particularly the quality, was reduced. On the other hand, the PVC-based stretch film was free from such problems of stiffness and scratching, although it was very strong and flexible. Therefore, it was necessary to solve transport troubles and flaws such as twisting of a polyolefin-based stretch film.

[0010] The cause of this transport trouble is mainly due to the lack of slipperiness in the transport speed of the film on the film surface (the speed at which the film is rubbed). Therefore, as a preventive measure, calcium carbonate, silica, It has been considered that inorganic fine particles such as diatomaceous earth and solid lubricants such as spherical silicone resins are added to improve the slipperiness of the film. A report of an attempt to improve the slipperiness of a film by using a solid lubricant is disclosed in, for example, JP-A-60-12.
No. 7367, JP-A-1-129050 and JP-A-3-205440. But,
Even if those methods were tried, the mechanical engagement with the above-mentioned PVC stretch film specification packaging machine was not so much improved. In particular, since there is almost no effect of suppressing the occurrence of this, the adhesiveness (adhesion) of the film is too low,
At the time of stretch packaging, the film was unnecessarily easily removed from the film holder of the packaging machine, and the packaging property was sometimes reduced.

Further, since these methods are basically methods for improving the slipperiness by increasing the roughness of the film surface due to the presence of fine particles, the transparency of the film deteriorates due to the presence of the particles, or In particular, in the case of a thin film, holes may be formed in the film due to inorganic particles projecting from the film. The problem that holes are formed in the film causes a problem of a decrease in productivity when a thin film is stretched and manufactured, and particularly causes a bubble puncture in an inflation method. Furthermore, when obtaining a normally stretched thin film, a fine filter at the outlet of the extruder, generally a screen pack of about 250 mesh is often used, in which case inorganic fine particles and the like are added. When a resin is used, there is also a problem that the productivity is reduced due to clogging of the filter.

It is also conceivable to mix a lubricant with a resin, extrude the film, form a film, and then bleed the lubricant from inside the film to improve the slipperiness of the film.
In this case, the lubricant bleeds during the extrusion process and the raw resin pellets slide with the screw, which often causes a decrease in extrusion stability. In particular, the more effective the lubricant is in improving the slipperiness of the film, the more likely it is to slip with the screw and less likely to be kneaded.

Examples of using lubricants having poor antifogging properties such as general silicone oils as lubricants are described in JP-A-2-45366, JP-A-5-39375,
JP-A-5-170958 and the like are available. In the methods disclosed in these publications, when the amount of silicone oil present on the film surface is too large, not only the adhesion is reduced, but also the antifogging property is reduced even if a sufficient amount of the antifogging agent is added to the film. I also had the problem. Although the cause of the decrease in antifogging properties is not strictly clear, poor antifogging is caused by the fact that the amount of silicone oil is too large and a silicone oil film is present on the outer surface of the antifogging agent present on the film surface. It is considered that the spot appears on the film surface.

As described above, there has been no polyolefin-based stretch film which has simultaneously solved the mechanical properties and the anti-fogging property of a PVC-based stretch film packaging machine. The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a polyolefin-based stretch film which has a good balance between slipperiness and adhesion, good mechanical engagement, and is excellent in antifogging property, heat sealability, label adhesiveness, and optical properties in stretch packaging. .

[0015]

Means for Solving the Problems As a result of the research, the inventors have found that
When a predetermined amount of antifogging agent is mixed with a resin material in advance, and a film formed by heating and melting with an extruder and a predetermined amount of silicone oil is used for the film, a machine for a PVC-specific stretch packaging machine is used. It has been found that both the properties and the antifogging property can be satisfied, and the above-mentioned problems can be solved, and the present invention has been accomplished.

That is, the present invention is as follows. 1) The total of the 200% elongation load in the vertical and horizontal directions is 150
0 g / cm width or less, at least one surface of the film is a layer made of a polyolefin resin, and 0.3 to 50 mg / cm
m ² of silicone oil are applied, 0.5-5
A stretch film for a push-up type packaging machine, wherein 0 mg / m ^{2 of} an antifogging agent is present inside the film. 2) After applying a silicone emulsion to one side of a film raw material containing a resin material therein, which is formed by heating and melting the resin raw material with an extruder, the film raw material is stretched in at least one axis direction, and The silicone emulsion is transferred to the coated surface by bringing the coated surface of the stretched film into contact with the coated surface,
The method for producing a stretch film for a push-up type packaging machine according to 1), wherein a silicone emulsion is provided on both sides of the film.

Hereinafter, the present invention will be described in detail. First, the polyolefin resin will be described. At least one surface of the film used in the present invention is a layer made of a polyolefin-based resin, but the kind of the resin is not particularly limited, and for example, the following resin group is preferably used.

That is, a monomer selected from polyethylene (hereinafter referred to as PE), polypropylene (hereinafter referred to as PP), or a vinyl ester monomer, an aliphatic unsaturated monocarboxylic acid, or an aliphatic unsaturated monocarboxylic acid alkyl ester, and ethylene Copolymers or their derivatives, copolymers of different α-olefins (other than ethylene), ethylene-α
Olefin copolymers (especially α-olefins have 3 to
12 are preferable, for example, butene-1, hexene-1, heptene-1, 4-methyl-1-pentene, octene-1 and the like, butyl rubber-based elastomer, styrene-butadiene-based elastomer (particularly thermoplastic block copolymer). Unified), crystalline polypropylene, crystalline polybutene
1 (hereinafter referred to as PB-1).

Above all, when it is used as a film for stretch packaging, it is used because the 200% elongation load in the vertical and horizontal directions when the film is formed on the film must be adjusted within the range described in the claims of the present invention. In many cases, a soft resin is also used as the polyolefin resin. These soft resins are PE, vinyl ester monomer, aliphatic unsaturated monocarboxylic acid, at least one monomer selected from aliphatic unsaturated monocarboxylic acid alkyl ester and a copolymer of ethylene, or a copolymer thereof. Derivatives, copolymers of olefins (other than ethylene), ethylene-α-olefin copolymer elastomers (linear VLDPE, ULDPE
Butyl rubber-based elastomer, styrene-butadiene-based elastomer, and the like.

These resins may be used alone, but may be a copolymer, a mixed composition, or a required amount of a plasticizer,
It may contain an antiblocking agent, an antioxidant, an antistatic agent and the like. If necessary, a resin other than the above-mentioned polyolefin-based resin may be mixed, but even in such a case, the above-mentioned polyolefin-based resin is contained in the surface layer at 70% by weight or more. Is preferred.

The film may be a single layer of a polyolefin-based resin or a multilayer film in which one or more other resin layers are laminated. In the case of a multilayer, at least one surface of the film needs to be a layer of the polyolefin resin. Next, the silicone oil will be described.
The function of the silicone oil in the present invention does not hinder the surface properties such as anti-fog properties required for the stretch film, and the above-mentioned portion required to slip in the packaging machine and the improvement in the slipperiness of the film as described above allow the stretchability to be improved. It is to eliminate the problem of sawing and film damage in the packaging machine.

The type of the silicone oil to be used is not particularly limited, and may be properly used depending on the use and the like. For example, dimethyl silicone oil, methylphenyl silicone oil and the like, polyether-modified silicone oil,
A simple substance such as an alkyl-modified silicone oil and an amino-modified silicone oil may be used, or a mixture containing at least one or more of these oils is preferably used. The viscosity of the oil is not particularly limited, but an oil having an appropriate viscosity may be selected from, for example, ease of application by an application method. Especially when used for food packaging, 100-100
It is preferably in the range of 0000 cs (centistokes).

When applying silicone oil to a film in the production method of the present invention, it is preferable to use a silicone emulsion. Silicone emulsion, said silicone oil, water, alcohols,
Macroemulsions, miniemulsions, microemulsions and the like with ethers and the like (hereinafter, the three are collectively referred to as emulsions), including those containing an emulsifier such as a surfactant for stabilizing the emulsion.

Among the above-mentioned emulsions, a preferred emulsion is a system mainly composed of silicone oil and water. In this case, it is preferable that the emulsion is an O / W type in which oil particles are dispersed in an aqueous phase. The macroemulsion referred to here generally has an average oil particle diameter of 0.4 μm or more, the miniemulsion has an oil diameter of about 0.1 to 0.4 μm, and the microemulsion generally has an oil particle diameter of about 0.01 to 0.1 μm. Means a dispersion system. Since macroemulsions and miniemulsions are generally thermodynamically unstable, they are generally milky white containing a nonionic, anionic or cationic surfactant as a third component, if necessary, for stabilization. Liquid. On the other hand, microemulsions are generally thermodynamically more stable than macroemulsions and miniemulsions, and are generally transparent because oil particles have a wavelength equal to or less than the wavelength of visible light, and are preferred depending on film production methods and applications.

The emulsion is preferably stable. For this purpose, a nonionic or anionic or cationic surfactant may be additionally used. Further, in particular, an additional antifogging agent for assisting the antifogging property of the antifogging agent contained inside the film, an inorganic lubricant such as silica fine particles or metal fine particles for further improving the sliding property, or an organic lubricant such as fine particle silicone resin. It may be one to which an appropriate amount of a third component such as a lubricant is added. However, when the third component or the like is added, the amount of addition is within a range that does not cause concentration unevenness or dispersion unevenness that causes coating unevenness, and is particularly within a range that does not cause instability such as demulsification and the like. It is necessary to be within a range that does not hinder the production of

The oil concentration in the emulsion, the amount of oil to be finally adhered to the film is not limited particularly if Re Ah within the scope of the present invention. However, although it depends on the film forming method and coating method,
It is preferable to use an emulsion having an oil concentration of 0.1 to 50% by weight, more preferably 1 to 40% by weight, from the viewpoint of the stability of the emulsion and the ease of adjusting the coating amount.
If an emulsion with an excessively high concentration is used, the viscosity is so high that coating unevenness tends to occur.On the other hand, if an emulsion with an excessively low concentration is used, the amount of the applied emulsion must be increased in order to adhere a required amount of oil to the film. Therefore, this also causes uneven coating, which is not preferable.

The amount of the silicone oil applied to the film is 0.3 to 50 mg / m ² per coated surface of the film.
, Preferably 1 to 25 mg / m ² , more preferably ² to 15 mg / m ² . 0.3
If the amount is less than mg / m ² , the film will have insufficient slipperiness, for example, the film will be rounded in a packaging machine, resulting in poor conveyance. On the other hand, if it is 50 mg / m ² or more, the anti-fogging effect of the anti-fogging agent coexisting on the film surface is hindered, and the anti-fogging property is lowered, and the film is required to be in close contact with a film conveying belt or film conveying roll. In many cases, the adhesion becomes insufficient and the film cannot be transported.

The amount of coating may be adjusted by adjusting the concentration of silicone oil in the silicone emulsion, or, in the case of film formation by the inflation method, in the course of film production,
What is necessary is just to perform by a well-known method, such as adjustment of the pinch roll pressure which conveys a stretched film. The antifogging agent will be described. In the present invention, it is necessary to add an antifogging agent in order to give the film antifogging properties. Non-ionic surfactants such as polyhydric alcohol fatty acid esters and polyoxyethylene alkyl ethers and other effective substances may be used as the antifogging agent. They include, for example, diglycerin monoglyceride of oleic acid or lauric acid, sorbitan monolaurate, polyoxyethylene nonyl phenyl ether, glyceride monooleate, alkyl alkylolamide, polyoxyethylene monooleate and the like. Particularly preferred examples of the components are diglycerin monooleate, diglycerin oleate such as diglycerin-diolate, or diglycerin monolaurate, diglycerin laurate such as diglycerin dilaurate, and also diglycerin laurate. Examples include diglycerin stearate such as monostearate and diglycerin distearate, glycerin-monooleate, and glycerin-diolate. Depending on the application or the like, an appropriate substance may be selected from these and used singly or as a mixture.

The surface amount of the above antifogging agent must be 0.5 to 50 mg / m ² , preferably 1 to 35 mg / m ² , more preferably 3 to 25 mg / m ² per coated surface of the film. ² 0.5 mg / m ² surface weight
If it is less than 50%, the antifogging property is not sufficiently exhibited, and 50 mg
/ M ² or more is not preferable because not only does the silicone oil inhibit the slipperiness of the film, but it also gives the film a sticky feeling.

The ratio between the amount of the silicone oil applied and the surface amount of the antifogging agent is preferably silicone oil / antifogging agent =
Within the range of 10/1 to 1/20, more preferably 5/1
A value within the range of １／1/10 facilitates the balance between the slipperiness and the anti-fog property, and is better. It is not particularly necessary to dispose the above antifogging agent or silicone oil on the entire surface of the film.For example, when coating with a coater or the like after forming a film, the antifogging agent is disposed only on the portion where the antifogging property is required, The silicone oil may be provided only in a portion requiring a slipperiness. In this case, the amount of silicone oil applied and the amount of antifogging agent surface indicate the amount of adhesion of only the coating portion where the silicone oil and antifogging agent are required.

A method for producing a film will be described. The method of producing the film is, for example, a method of stretching a tubular film raw material extruded by a circular die by an inflation method, a method of uniaxially stretching a film raw material extruded by a general T-die, or a method of sequentially or simultaneously biaxially stretching the film. Is taken. Extrusion may be performed by one extruder, or may be co-extruded by a plurality of extruders to form a multilayer film.

In the production of the film of the present invention, it is necessary to heat and melt the resin raw material with an extruder to form a film raw material containing an antifogging agent. In this case, since the antifogging agent added after the film formation gradually bleeds on the film surface, it is easy to make the thickness of the antifogging agent film uniform.
Therefore, the antifogging property is exhibited at an excellent level, and the film tends to be uniform over the entire surface. As an example of a method of including an antifogging agent in the film raw material, the antifogging agent may be kneaded into the resin raw material by inline injection during the extrusion process,
It is also possible to prepare resin pellets in the form of a masterbatch in which an antifogging agent has been kneaded in advance, and extrude the resin pellets into a film raw material.

The silicone oil is preferably applied using the above-mentioned silicone emulsion. For example, in the case of extrusion using a circular die, when the tubular raw material of the molten film immediately after extrusion is water-cooled in a cooling water tank or the like. The silicone emulsion preferably adjusted by the above method is put in a tube, and sealed with a nip roll (hereinafter, the liquid sealed in the tube of the tubular film between the nip rolls and the like is referred to as a sock liquid).
By doing so, it is applied to the inner surface of the raw tubular film. It is preferable to control the coating amount by adjusting the nip pressure of the nip roll and the oil concentration in the emulsion, and then to stretch the film by an inflation method, since it is possible to easily and continuously coat a thin and uniform silicone emulsion. .

In this case, a silicone emulsion may be applied to the outer surface of the raw tubular film before stretching by a coater or the like, but contamination of rolls and the like by silicone oil during the production process is a problem. In such a case, it may be necessary to take measures such as lowering the oil concentration of the emulsion applied to the outer surface than the emulsion of the sock liquid, or applying the emulsion only to a necessary portion.

In order to dispose the silicone emulsion on both sides of the film and to impart lubricity to both sides, it is necessary to use a method of transferring the silicone emulsion on the film-coated side to the non-coated side after stretching. The method of transfer is to peel off the double film in the form of a tube that has been folded after stretching into a single piece (one sheet), and then roll the single film into contact with the non-coated side by, for example, winding it into a roll. It is preferable to carry out. In practice, it is particularly complicated when the film is peeled into a single film, and the film is rolled and transferred using a normal slitting process of dividing the film into appropriate widths for actual packaging. Since a process is not required, it is simple and more preferable.

The following effects can be obtained by employing a transfer method for disposing the silicone emulsion on both sides of the film. In other words, immediately after stretching, the antifogging agent present on the coating surface of the film bleeding on the film surface is not so large yet, and a very small amount forms a layer on the film surface, and the sock liquid The silicone emulsion applied as a layer forms a layer. In this state, the film is stretched, and the film is wound into a roll using the single slit process. When the non-coated surface is brought into contact with the emulsion layer on the coated surface, only the silicone emulsion is easily transferred evenly. The surface abundance of the silicone emulsion tends to be uniform on both the surface and the non-coated surface. This method is particularly effective when the coating layer is to be made as thin as possible or when a very small amount of coating is desired, since the amount of silicone emulsion applied per area on the final film is reduced by stretching after coating. .

The stretching conditions for stretching after coating are preferably such that the morphology of the oil particles in the emulsion is not destroyed as much as possible (stretching temperature), preferably 80 ° C. or lower, more preferably 60 ° C. or lower. It is good to stretch. In this case, it is easy to maintain a state in which the silicone oil is dispersed in the aqueous phase in the form of particles in the applied silicone emulsion immediately after stretching. Then, after the transfer by the slit, the antifogging agent bleeds between the oil particles on the film and eventually covers the particles, so that it is thought that more effective antifogging property is exhibited. With respect to the slipperiness, there is no problem even if the oil surface is covered with the anti-fog agent as long as the amount of silicone oil applied is within the range of the present invention.

When the direct inflation method of directly blowing up from a die is used, a coating method similar to the above method may be used. In this case, if a sock solution is used, it is preferable to use any nip rolls before the ear portion slitting step in the tubular film before the ear portion is slit. In the case of the T-die method, as in the case of the circular die method, it is preferable to apply silicone oil in any step from immediately after extrusion to stretching.

A silicone oil is applied on one side of a flat film formed by a T-die method or a film cut into single pieces after being formed by an inflation method and then cut off, and then, for example, wound up in a roll form on the non-coated side. It may be transferred. However, among the above-mentioned methods, it is preferable to apply silicone oil to the tubular raw material before stretching and then stretch it, since a trace amount of coating can be performed.

When the antifogging property and the sliding property are not particularly required on the entire surface of the film, for example, a silicone oil or a silicone emulsion is directly applied to only a portion of the film to which the sliding property is to be imparted, using a coater or the like. Any method may be used, and there is no particular need for transfer. The formed film may be heat-treated before or after the stretching step in order to improve dimensional stability. Also, to improve the surface properties of the film by applying a corona treatment on the silicone oil-coated surface, the non-coated surface or both surfaces to improve the wettability of the film to the antifogging agent or silicone oil, or to improve the heat resistance. Electron beam irradiation or the like may be performed as needed.

The thickness of the obtained film is preferably 2 to 50 μm, more preferably 5 to 25 μm when used for packaging. The film formed as described above needs to have a total of 200% elongation load in the longitudinal and transverse directions of the film of 1500 g / cm width or less, and more preferably, for imparting stretchability suitable for stretch packaging. Is preferably in the range of 200 to 1200 g / cm width. The total value of 200% vertical and horizontal elongation load is 150
If the width exceeds 0 g / cm, the film becomes difficult to stretch and the stretchability is reduced. When the film is wrapped in a tray with a packaging machine, wrinkles are likely to remain on the surface of the film without a heat tunnel, and the appearance tends to be very poor. .

The 200% elongation load is the ratio of length / width:
Preferably in the range of 1 to 10, more preferably 1 to 5
In many cases, the package finish is better when the value is within the range. In order to adjust the 200% elongation load within the above range, for example, when a mixed resin is used, softer ones are increased, stretching conditions such as stretching temperature and stretching ratio are adjusted, or heat treatment before and after film formation is performed. What is necessary is just to perform by a well-known method, such as adjustment of heat processing conditions, such as temperature and heat processing time.

[0043]

As described above, the film of the present invention is
(A) applying a silicone emulsion to one side of a film raw material previously containing an anti-fog agent and then stretching the film; and (b) applying a silicone emulsion-coated surface of the stretched film to the stretched film not coated with the silicone emulsion. By contacting the other surface with a method such as winding in a roll form and transferring the film, the amount of silicone oil applied to the film surface can be extremely reduced to 0.3 to 50 mg / m ^2. Thus, an effect that uniform coating without unevenness can be obtained.

Therefore, the film of the present invention has an advantage that the silicone oil gives the film an appropriate sliding property.
The problem of transporting the film, such as a scratch, in the packaging machine is significantly improved as compared with the conventional polyolefin-based stretch film, and the mechanical engagement is greatly improved. Further, in the present invention, the antifogging property is also good, and it is maintained for a long time. Although the mechanism of the development of anti-fogging properties is not exactly clear, especially when the O / W emulsion is attached to the film, the oil particles are dispersed on the film surface immediately after the film is formed. An antifogging agent film is formed on the portion where no antifogging agent exists. Although the oil itself does not have anti-fog properties, the oil exists in very fine particles (usually 0.01 μm to 1.0 μm in diameter), which is the size of water droplets that is problematic for anti-fog properties. (Usually 0.1 mm to 30 mm in diameter), so that the oil portion does not hinder the anti-fogging property of the film as a whole, or the coating of the anti-fogging agent wraps the oil particles and forms the uppermost film. This is probably because a layer of an antifogging agent is formed on the outer surface. According to the latter idea, even after some time has passed since the film formation, the oil particles cannot maintain the particle state on the film, and even if the oil particles are disintegrated to some extent and become close to a film shape, the antifogging agent film already has a considerable portion of the oil particles. It is considered that the antifogging property is not hindered because the antifogging property is formed so as to wrap around.

[0045]

EXAMPLES The present invention will be described below in more detail with reference to Examples, which do not limit the present invention in any way. The method of measuring the evaluation items in the examples will be described below. (1) [Left length] A measuring device that simulates the transport mechanism of a general stretch wrapping machine is created, and when the film is transported, the deviation length due to the fact that the film is rounded from the regular stop position at the front end of the film is stretched. Measured as length. The normal stop position is the position where the front end of the film should stop after transporting the film for a certain distance, assuming that the film is completely in contact with the film feed rubber belt, and is unique to the apparatus. is there.

At the time of transport, the film is held in close contact with a rubber belt for transporting the film, and the belt is transported by moving the belt with a motor. In this case, the film is transported while rubbing a film feed plate fixed to the apparatus. The film holding plate is a plate made of high-density polyethylene, and the film feed belt has a width of 20 mm and a length of 10 mm on the surface holding the film.
It is a polyurethane rubber having protrusions of 2 mm in the length direction, 20 mm in the width direction, and 0.5 mm in height for each mm.

For the measurement, a film is sandwiched between the above-mentioned film pressing plate and the rubber belt, a load is applied by a spring so that the weight of the rubber protrusion becomes 1.0 kg / cm ^2, and the belt and the film are brought into close contact with each other, and a certain distance ( 400 mm), the belt is suddenly started at a relative speed of 60 cm / min, and the length of the belt when the belt is suddenly stopped is measured. Specifically, a commercially available packaging machine (Teraoka Seiko Co., Ltd., AW2600jr (PVC specification)) or the like is preferable as the model machine. Further, a measuring device made by modeling the film transport portion (friction portion) of these packaging machines may be used. From this, a length of 20 mm or less was regarded as a pass.

(2) [Anti-fogging property] A plastic container containing 200 cc of tap water at 20 ° C. was wrapped with a film to be measured, and the container was stored in a refrigerator at 5 ° C. for 30 minutes, and the state of the film was observed. Judgment was made based on the following criteria, and 4 or more antifogging properties were judged as acceptable. Anti-fogging property 1 point: fog-like fogging occurs on the entire surface of the film, and the inside of the film is not visible. Anti-fogging property 2 points: Transparent water droplets of 2 to 5 mm adhere to almost the entire surface. The inside is tentatively visible. Anti-fogging property 3 points: Water droplets of 10 to 20 mm occupy almost the entire surface. Anti-fogging property 4 points: Middle of 3 to 5 points. A partially continuous water film is seen, but the inside is clearly visible. Anti-fogging 5 points: A continuous mirror-like water film is seen on the entire surface and the inside is clearly visible. (3) [Cellotape adhesion (g / 20 mm width) )] A cellophane tape is stuck to a film to form a strip sample having a width of 20 mm, and the peel strength between the cellophane tape and the film of the strip sample is measured by a tensile tester.

(4) [Heat Sealing Property] The sample packed in the tray was sealed at the bottom with a commercially available heat sealer, and evaluated in a temperature range where the sealing state was good.
The higher the upper limit of the temperature range and the lower the lower limit, the better. (5) [200% elongation load (g / cm width)] A strip sampled to a film width of 10 mm and a length of 100 mm was set on a tensile tester so as to have a chuck-to-chuck length of 50 mm, and pulled at a pulling speed of 200 mm / min. The load value when the elongation reaches 200% is read and measured. However, when the film breaks at less than 200%, a tangent is drawn at the point of elongation 20% before the point of breaking in the graph of elongation vs. elongation load,
The value obtained by elongating to the point of% elongation is used as a measured value. Thus, the total value measured in the longitudinal and transverse directions of the film is defined as a 200% elongation load. in this case,
The vertical direction is the direction of film flow during film formation, and the horizontal direction is the direction perpendicular to the vertical direction.

(6) [Actual packaging test] Teraoka Seiko Co., Ltd. PVC packaging machine A as a stretch packaging machine
The sheets were tray-packed using W2600jr (PVC), the appearance of sawing during transportation and the packaging finish were evaluated as follows, and only those films that received an A rating were accepted. A: This is 20 mm or less, and there is no film wrinkle on the tray surface after packaging. B: This is 20 mm or less, but film wrinkles appear on the tray surface after packaging. C: This is 20 mm or more, but film wrinkles on the tray surface after packaging. None D: The stiffness is 20 mm or more, and film wrinkles appear on the tray surface after packaging. (7) [Optical properties] The haze value was determined according to JIS K6714.

(8) [Amount of anti-fogging agent] The surface of the film was carefully rubbed with KBr powder to adhere the entire amount of the surface anti-fogging agent to the KBr powder. Sheet-shaped. This sheet was measured with an infrared spectrometer, and the surface amount was determined from the size of the peak of the wavelength unique to the antifogging agent added on the chart.

(9) [Silicone Oil Application Amount] After the amount of Si element on the film is quantified by a fluorescent X-ray method, the amount of the oil is determined by converting the amount of dimethylpolysiloxane molecules forming the silicone oil into weight. (By molecular weight conversion)

[0053]

Example 1 Layer A (surface layer) was 100% by weight of ethylene-vinyl acetate copolymer (hereinafter, EVA, vinyl acetate content 15% by weight, melt index (MI) = 2.0), and layer B ( The intermediate layer is composed of 61% by weight of EVA and an ethylene-propylene copolymer thermoplastic elastomer (hereinafter referred to as E).
PP, propylene content 15 mol%, MI = 0.4
5): 22% by weight of crystalline polypropylene (hereinafter referred to as P
P, MI = 7): a mixed composition of 17% by weight, and the A layer and the B layer where the C layer (core layer) is composed of 100% by weight of PP.
Layer and the C layer are laminated in the order of A / B / C / B / A, and a five-layer film having a thickness ratio of each layer of 15/30/10/30/15 is coextruded using an extruder and a circular die. The unstretched film raw material on the formed cylinder is once folded, quenched in a water bath, subsequently reheated to 50 ° C., stretched three times vertically and three times horizontally by the inflation method, and the tubular film is folded. After that, a single slit was formed to obtain a film having a thickness of 15 μm.

Diglycerin monolaurate as an antifogging agent was injected in-line into the A layer and the B layer by an extruder, and the surface amount of the antifogging agent was adjusted by the injection amount. O / W emulsion (oil particle diameter 0.4 μm) using dimethylpolysiloxane (viscosity 400 centistokes) as silicone oil and anionic surfactant as emulsifier was used for applying silicone oil. The amount of coating on the film was adjusted by diluting the emulsion with ion-exchanged water and adjusting the oil concentration.

When applying the silicone emulsion, a sock solution is used, and when the extruded tubular unstretched film is folded in a water bath, it is poured as a sock solution into the inner surface of the tube.
After adjusting the nip roll pressure and controlling the coating amount uniformly, apply a predetermined amount to the inner surface of the raw material, and then wind the single film slit into a roll using the single slit process after stretching. As a result, the silicone emulsion was transferred to the outer surface which was not coated.

Table 1 shows the physical properties and packaging characteristics of the stretch film thus formed. As shown in Table 1, this film has a 200% elongation load, an antifogging agent surface amount,
Silicone oil coating amount is within the scope of the present invention,
The antifogging property, the anti-strain property, and the evaluation by actual packaging were also good.

[0057]

Comparative Example 1 The layer B of the film was EVA: 48% by weight,
A film was formed in the same manner as in Example 1 except that PP: 13% by weight and PP: 39% by weight. 200% due to the use of relatively hard resin as a film material
This is an example when the elongation load becomes too large.

[0058]

Examples 2 to 4 and Comparative Examples 2 to 4 Films were formed in the same manner as in Example 1 except that the surface amount of the antifogging agent and the amount of silicone oil applied were changed. I got
However, Comparative Example 2 is an example where the amount of the antifogging agent surface is too small, and Comparative Examples 3 and 4 are an example where the amount of silicone oil applied is too small and an excessive amount.

[0059]

Example 5 The layer B of the film was EVA: 61% by weight, E
A film was formed in the same manner as in Example 1 except that the PP was 17% by weight and the PP was 22% by weight.

[0060]

Example 6 A film was formed in the same manner as in Example 1 except that the silicone-based lubricant was applied using a coater only to the end of the film after a single slit for film formation, instead of using a sock liquid. I got As described above, the first embodiment
6 and Comparative Examples 1 to 4, the film formability was good without any particular problem.

[0061]

REFERENCE EXAMPLE 1 A commercially available polyvinyl chloride film is given as an example.

[0062]

[Table 1]

Table 1 shows the physical properties and packaging characteristics of the film formed as described above. In all of Examples 1 to 6, both the mechanical engagement property and the antifogging property were good. In particular, in a packaging test using an actual stretch packaging machine using a film after a single slit, the surface of the film on the tray surface in both cases, whether the surface in contact with the tray is coated with silicone oil or the transfer surface, is used. There was no problem of wrinkles, there was no problem of poor transport due to "strain" generated by friction with the film pressing plate, and the scratches due to rubbing of the film were greatly improved. These improvement effects were maintained satisfactorily immediately after the single slit and after the film was stored at room temperature for 30 days.

In addition, Teraoka Seiko Co., Ltd. AW
Stretch wrapping machines other than 2600jr (PVC) (Automatic A18X manufactured by Fujipack and Ishida Co., Ltd.)
A packaging test was also performed with Wmini Mark II U), but all were successfully packaged. Stretch wrapping machine (Teraoka Seiko Co., Ltd. AW2)
600 jr (PE)), there was no problem in the suitability for packaging.

In addition, there was no decrease in optical properties, heat sealing properties, and adhesive properties of cellophane tape, which were concerns about the application of silicone oil, and the balance of properties required as a stretch film was very good overall. On the other hand, in Comparative Example 1, since the 200% elongation load of the film was too large as a stretch film, film wrinkles on the tray surface were not removed even after packaging, and the packaging finish was poor. In Comparative Examples 2 to 4, both the anti-fogging effect and the anti-fogging property could not be exhibited at the same time because the surface amount of the anti-fogging agent or the amount of silicone oil applied was inappropriate.

[0066]

As described above, the present invention not only has excellent wrapping properties in a stretch wrapping machine of a polyolefin film specification, but also has good wrapping and scratches in a stretch wrapping machine of a PVC film specification. The present invention provides an extremely practical and highly useful polyolefin-based stretch film film which can be satisfactorily packaged because the problems at the time of transportation have been greatly improved and the anti-fogging property and other surface properties are also good.

Claims (2)

(57) [Claims] 1. Total of 200% elongation load in longitudinal and transverse directions
Is 1500g / cm width or less,At least one of the films
One surface is a layer made of polyolefin resin,
0.3 to 5 on one surface of at least a part of the film.
0mg / m^TwoSilicone oilIs applied,
0.5-50mg / m^TwoAnti-fog agentExists inside the film
DoCharacterized byStretcher for push-up packaging machine
Film. 2. A silicone emulsion is applied to one surface of a film raw material containing a resin material and heated and melted by an extruder and containing an antifogging agent therein, and then the film raw material is stretched in at least one direction. 2. The method according to claim 1, wherein the silicone emulsion is transferred to the surface to be coated by further contacting the surface of the stretched film with the surface to be coated with the silicone emulsion, and the silicone emulsion is disposed on both surfaces of the film. Push-up packaging
Method of manufacturing stretch film for machine .