JP2002284905A - Stretch packaging film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stretch packaging film composed of a chlorine-free resin, having excellent anticlouding property, heat-resistance, strength, cutting easiness and gloss and enabling easy stretch packaging with an automatic packaging machine. SOLUTION: The film for stretch packaging is composed of 100 pts.wt. of an ethylene-vinyl alcohol copolymer having an ethylene content of 5-40 mol% and 5-20 pts.wt. of a polyhydric alcohol and has a tensile elongation at break of 50-200% in longitudinal direction of the film.

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 used for general purposes or business use.

[0002]

2. Description of the Related Art Conventionally, films containing a plasticized polyvinyl chloride resin as a main component have been widely used as stretch wrapping films for general or business use in terms of cost and ease of use. Was. However, for example,
Tray packaging for food is one of the applications of stretch packaging film.However, when food is packaged in trays and sold over the counter, moisture is condensed on the film surface due to condensation of moisture inside the film due to display at low temperatures. However, there is a problem that the film may be fogged, and the visibility of the contents is impaired. The problem of fogging due to moisture condensation can be prevented by adding a surfactant called an antifogging agent. The anti-fog agent bleeds out to the surface of the film to turn the water droplets attached to the surface of the film into a thin water film, and transmits light linearly to improve visibility. Furthermore, the effect of bringing about so-called "slimming" on the surface and reducing the friction between the tray and the film when stretching the tray or the like using an automatic packaging machine can be obtained.

However, in recent years, the problem of environmental pollution has been emphasized, and the use of films containing chlorine tends to be refrained. Films containing no chlorine, which can be substituted for plasticized polyvinyl chloride resin films, have been developed. Requested.

For example, Japanese Patent Application Laid-Open No. 61-44635 discloses that a layer mainly composed of an ethylene-vinyl acetate copolymer is laminated and integrated on both sides of a layer mainly composed of a propylene-α-olefin copolymer. A stretch wrapping film is shown, and excellent antifogging properties can be imparted by adding an antifogging agent to the surface ethylene-vinyl acetate copolymer layer. However, although the stretch wrapping film has improved antifogging properties, the ethylene-vinyl acetate copolymer exposed on the surface has a low melting point, and thus tends to have insufficient heat resistance. For example, the film is used in a convenience store or the like. If the packed lunches are heated in a microwave oven in a state of being stacked in multiple stages, the films may fuse together,
There was a problem such as torn.

[0005] A stretch packaging film made of only a polyolefin-based resin such as a polyethylene-based resin or a polypropylene-based resin has been proposed. However, cuttability tends to be insufficient. There was a problem that it could not be cut as desired with a saw blade that was attached to the blade.

As a method for solving the above-mentioned problems of heat resistance and cutability, for example, Japanese Patent Application Laid-Open No. 58-47040 discloses a packaging film obtained by adding a specific polyethylene and a nucleating agent to polypropylene. However, there was a problem that the gloss of the packaging film was insufficient. In particular, a stretch wrapping film for business use has a problem in that display performance is reduced due to insufficient gloss.

Further, a film is formed from a hydrophilic resin such as a polyvinyl alcohol resin without blending an anti-fogging agent, and water adhering to the film surface is mixed with the resin to form a water film, thereby improving the anti-fogging property. There is also a way to make it happen.
However, general-purpose polyvinyl alcohol-based resins are not suitable for extrusion, and are generally formed by a casting method or the like, and when the film obtained by the method is used for stretch packaging, the film is stretched in the longitudinal direction. There was a problem that the elongation at the time of pulling was too large and the cut property was reduced. In addition, since the casting method requires a drying step, there is also a problem that the production efficiency is low.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an automatic packaging which is composed of a chlorine-free resin, has excellent anti-fogging properties, heat resistance, strength and cutability, has excellent gloss and An object of the present invention is to provide a stretch packaging film that can easily perform stretch packaging by a machine. Another object of the present invention is to provide a manufacturing method capable of easily obtaining the stretch packaging film with high production efficiency.

[0009]

The stretch packaging film of the present invention comprises 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 40 mol% and 5 to 20 parts by weight of a polyhydric alcohol, and The tensile elongation at break in the longitudinal direction of the film is 50 to 200%.

[0010] When the ethylene content of the ethylene-vinyl alcohol copolymer used in the present invention is reduced, the water resistance of the obtained film for stretch packaging is reduced, and the strength is reduced due to moisture, or the water is dissolved in water. Therefore, it becomes impossible to package food containing water and the like, and furthermore, it becomes difficult to melt-extrude. Since the tensile elongation at break in the direction exceeds the range described below, the cutability is reduced and the stretch packaging becomes difficult, and the anti-fogging property is reduced. Therefore, it is limited to 5 to 40 mol%, and preferably 20 to 3 mol%.
5 mol%.

The lower the degree of polymerization of the ethylene-vinyl alcohol copolymer, the lower the water resistance of the obtained film for stretch packaging, and the lower the strength due to moisture. 500 or more is preferable because food and the like cannot be packaged. The polymerization degree is a value measured according to JIS K 6726.

When the degree of saponification of the ethylene-vinyl alcohol copolymer becomes small, the water resistance of the obtained stretch packaging film decreases, and the strength decreases due to moisture. It becomes impossible to package foods, etc.
When the ethylene content of the ethylene-vinyl alcohol copolymer is small, melt extrusion may be difficult, and it is difficult to obtain a film for stretch packaging having a tensile elongation at break in the range described later. , More preferably 95 to 99%. The saponification degree is J
It is a value measured according to IS K 6726.

The melt flow rate (hereinafter referred to as "MFR") of the ethylene-vinyl alcohol copolymer is as follows:
When it becomes smaller, melt extrusion becomes difficult, and it is difficult to obtain a stretch packaging film having a tensile elongation at break in the range described later.Also, even if melt extrusion is possible, high-speed film formation is difficult, and production efficiency decreases. Therefore, it is preferably 1 g / 10 min or more, more preferably 2 to 20 g / 10 min, and the MFR of the resin component after adding a polyhydric alcohol described below.
Is preferably 7 g / 10 min or more, and more preferably 9 to 2 minutes.
It is preferable to adjust so as to be 0 g / 10 minutes. The MFR is based on JIS K 7210, and the temperature is 230
It is a value measured at a load of 21.18N in ° C.

The polyhydric alcohol used in the present invention includes, for example, glycerin, diglycerin, ethylene glycol, diethylene glycol, polyethylene glycol and the like. These may be used alone or in combination of two or more. . Among them, glycerin or diglycerin is preferable because it has good compatibility with the above-mentioned ethylene-vinyl alcohol copolymer, and further, when the above-mentioned ethylene-vinyl alcohol copolymer is melt-extruded, the amount of smoke is small and the moldability is excellent.

When the molecular weight of the polyhydric alcohol is small, the amount of smoke generated during the process of forming into a film, particularly when melt-extrusion is large, the moldability is reduced. When the molecular weight is large, the molecular weight of the ethylene-vinyl alcohol copolymer is reduced. Is less than 80 to 650, and more preferably 85 to 250, since the compatibility of the resulting stretch-wrapping film decreases and the flexibility of the obtained stretch packaging film decreases. The above molecular weight is based on JIS K
It is a value measured according to 6726.

If the amount of the polyhydric alcohol is too small, the flexibility of the obtained stretch packaging film becomes insufficient, the suitability of an automatic wrapping machine used for stretch packaging is reduced, and the obtained stretch packaging film has When the anti-fogging property is reduced, and the stretch packaging film is wound after being manufactured and then re-deployed at the time of use, static electricity is likely to be generated. The strength of the film for use decreases, and it becomes easy to break when touching projections, etc.In addition, the amount of polyhydric alcohol that bleeds out on the surface of the obtained stretch packaging film increases. , The flavor may be impaired, so that the content of the ethylene-vinyl alcohol copolymer is 5 to 5 parts by weight. 0 is limited to parts by weight, preferably 6
１５15 parts by weight.

The stretch packaging film of the present invention is composed of the above-mentioned ethylene-vinyl alcohol copolymer and polyhydric alcohol, but may further contain various additives such as an anti-fogging agent as required.

As the antifogging agent, any conventionally known antifogging agent can be used, for example, aliphatic alcohol fatty acid esters, higher fatty acid esters and the like. These may be used alone or in combination of two or more. You may use together. Anti-fog agent,
It is preferably added when a more excellent antifogging property is required, such as a commercial stretch packaging film that is displayed at a low temperature. It becomes difficult to generate static electricity when the film is rolled up and unfolded again during use, and the secondary handling property such as packing in a box is further improved. The amount of the anti-fogging agent added, the amount of the anti-fogging agent that bleeds out to the surface of the stretch packaging film obtained when the amount increases increases, so that the transfer to the packaged object easily occurs, for example, when packaging food. So, there is a risk that it will be transferred to food and spoil the flavor,
The amount is preferably 2 parts by weight or less based on 100 parts by weight of the ethylene-vinyl alcohol copolymer.

In the stretch packaging film of the present invention, when the tensile elongation at break in the longitudinal direction is small, the film tends to be easily cut, and the handleability is reduced. Since the suitability of the automatic wrapping machine used for stretch wrapping is reduced,
It is limited to 0 to 200%, preferably 50 to 120%. The tensile elongation at break is a value measured according to JIS K 7127.

The thickness of the stretch packaging film is as follows:
When thinner, the strength decreases, when it comes into contact with protrusions, etc., it becomes easier to break, and when it becomes thicker, cutability decreases, making stretch packaging difficult. Is preferably 6 to 20 μm, more preferably 8 to 18 μm.

It is preferable that a water-resistant layer made of a polyvinyl alcohol resin is integrally laminated on one surface of the stretch packaging film. In addition, in the stretch packaging film in which the water-resistant layer is laminated and integrated, the water-resistant layer is set to the outside during the stretch packaging.

Examples of the polyvinyl alcohol-based resin constituting the water-resistant layer include polyvinyl alcohol.

The lower the degree of polymerization of the polyvinyl alcohol resin, the lower the water resistance of the obtained stretch packaging film, and when exposed to moisture, the water resistant layer swells and the low molecular weight component of the polyvinyl alcohol resin elutes. Therefore, the number is limited to 1100 or more, and preferably 1150 or more.

The saponification degree of the polyvinyl alcohol-based resin is limited to 97% or more because the water resistance of the obtained stretch packaging film decreases as the water resistance decreases, and the water resistant layer easily swells when exposed to moisture. Preferably 98%
That is all.

When the thickness of the water-resistant layer is small, the effect of improving the water resistance of the stretch packaging film obtained is small, and when the thickness is large, the cut property of the obtained stretch packaging film is reduced and the stretch packaging is difficult to perform. Also,
The suitability of the automatic packaging machine used for stretch packaging is reduced,
Since the cost is higher and the cost is disadvantageous,
〜3 μm is preferred.

As a method for obtaining the above-mentioned film for stretch packaging, a casting method which is usually applied to a polyvinyl alcohol-based resin such as an ethylene-vinyl alcohol copolymer, since the tensile elongation at break of the obtained film hardly falls within the above range. Extrusion molding is preferred. That is, the ethylene-vinyl alcohol copolymer and the polyhydric alcohol are melt-kneaded, introduced into an extruder, extruded from a die attached to the extruder tip into a film, and the film is pulled by a roll or the like to apply tension. The winding method is preferable. When the water-resistant layer is laminated and integrated on one surface of the stretch packaging film, the ethylene-vinyl alcohol copolymer and the polyhydric alcohol are melt-kneaded, introduced into an extruder, and attached to the extruder tip. It is preferable to extrude the film from a die, pull the film with a roll or the like, apply tension to the film, apply the polyvinyl alcohol resin to one surface of the film, and wind the film.

The method of melt-kneading is not particularly limited, and any conventionally known method may be employed. Examples thereof include a method using a kneader mixer, a roll, and the like, and a method of melt-kneading in an extruder. You may.

The clearance of the above-mentioned die may be appropriately adjusted depending on the desired thickness of the obtained stretch packaging film. However, whether it is narrow or wide, the tensile elongation at break in the longitudinal direction of the obtained stretch packaging film is within the above range. Is preferably 1 to 2.5 mm. As the above die,
The use of a T-die is preferred because the tensile elongation at break in the longitudinal direction of the obtained stretch packaging film tends to be in the above range. In addition, an inflation method or the like can be adopted. In the case of extrusion molding, the longitudinal direction of the stretch packaging film is the extrusion direction (MD).

Even if the molding temperature at the time of extrusion from the die to the film after melt-kneading, that is, the die temperature is low or high, the tensile breaking elongation in the longitudinal direction of the obtained stretch packaging film hardly falls within the above range. So, 190-23
0 ° C. is preferred.

The tension applied to the extruded film may be appropriately adjusted. However, when the tension is small, the tensile elongation at break in the longitudinal direction of the obtained stretch packaging film is difficult to fall within the above range. It is preferable that the speed of the take-up roll is 105 to 120% of the extrusion speed, since the winding speed or breakage occurs.

The method for applying the polyvinyl alcohol-based resin is not particularly limited, and any conventionally known method may be employed. For example, a direct gravure coater, an offset gravure coater, a comma coater or the like is used. Method.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 An ethylene-vinyl alcohol copolymer having an ethylene content of 26 mol% (degree of polymerization 550,
Saponification degree 98%, MFR 4 g / 10 min) 100 parts by weight,
9 parts by weight of diglycerin (molecular weight: 166.17) are melt-kneaded by a kneader mixer to obtain a resin composition (MFR12).
g / 10 minutes), and introducing the resin composition into an extruder,
T-die (clearance 1.
2mm), extruded into a film at a die temperature of 220 ° C,
The film immediately after extrusion was pulled with tension by a take-up roll at a speed of 115% of the extrusion speed to have a thickness of 12 μm.
m, and the stretch packaging film was wound up.

Example 2 As an ethylene-vinyl alcohol copolymer, an ethylene-vinyl alcohol copolymer having an ethylene content of 6 mol% was used.
Vinyl alcohol copolymer (degree of polymerization 550, degree of saponification 9
Example 1 except that 8%, MFR 7 g / 10 min) was used.
In the same manner as in Example 1 to obtain a resin composition (MFR 21 g / 10 min).
m, and the stretch packaging film was wound up.

Example 3 The procedure was carried out except that an ethylene-vinyl alcohol copolymer having an ethylene content of 32 mol% (polymerization degree: 550, saponification degree: 98%, MFR: 2 g / 10 minutes) was used as the ethylene-vinyl alcohol copolymer. A resin composition (MFR 10 g / 10 min) was obtained in the same manner as in Example 1, and a thickness of 12 μm was obtained from the resin composition in the same manner as in Example 1.
m, and the stretch packaging film was wound up.

Example 4 An ethylene-vinyl alcohol copolymer having an ethylene content of 26 mol% (degree of polymerization 550,
Saponification degree 98%, MFR 4 g / 10 min) 100 parts by weight,
9 parts by weight of diglycerin (molecular weight: 166.17) are melt-kneaded by a kneader mixer to obtain a resin composition (MFR12).
g / 10 minutes), and introducing the resin composition into an extruder,
T-die (clearance 1.
2mm), extruded into a film at a die temperature of 220 ° C,
The film immediately after extrusion is tensioned by a take-up roll at a speed of 115% of the extrusion speed and pulled. Further, one surface of the film is coated with polyvinyl alcohol (degree of polymerization of 120).
0, a saponification degree of 98%) by a direct gravure coater to a thickness of 2 μm to obtain a stretch packaging film having a thickness of 14 μm, and to stretch the stretch packaging film so that the polyvinyl alcohol layer is on the core side. Wound up.

(Comparative Example 1) An ethylene-vinyl alcohol copolymer was used except that an ethylene-vinyl alcohol copolymer having an ethylene content of 45 mol% (polymerization degree: 550, saponification degree: 98%, MFR: 6 g / 10 min) was used. A resin composition (MFR 20 g / 10 min) was obtained in the same manner as in Example 1, and a thickness of 12 μm was obtained from the resin composition in the same manner as in Example 1.
m, and the stretch packaging film was wound up.

Comparative Example 2 Instead of the ethylene-vinyl alcohol copolymer, polyvinyl alcohol (polymerization degree 5
(00, saponification degree 98%, MFR 10 g / 10 min) except that a resin composition was obtained in the same manner as in Example 1 and extruded from the T-die from the resin composition in the same manner as in Example 1; Was not obtained.

Comparative Example 3 A resin composition (M) was prepared in the same manner as in Example 1 except that the amount of diglycerin was changed to 3 parts by weight.
FR 7 g / 10 min.), And a 12-μm-thick film for stretch packaging was obtained from the resin composition in the same manner as in Example 1, and the stretch-wrapping film was wound up.

Comparative Example 4 The amount of diglycerin added was 25
A resin composition (MFR 36 g / 10 min) was obtained in the same manner as in Example 1 except that the amount was changed to parts by weight, and a 12-μm-thick stretch packaging film was obtained from the resin composition in the same manner as in Example 1. The film for stretch packaging was wound up.

The stretch packaging films obtained in Examples and Comparative Examples all had excellent gloss. In addition, for each stretch packaging film, tensile elongation at break, anti-fogging property, heat resistance, tensile strength at break, cutability and suitability for an automatic packaging machine were evaluated as follows, and the results are shown in Table 1.
In addition, about the film for stretch packaging obtained in Example 4, when performing stretch packaging, the polyvinyl alcohol layer was made to be outside.

(Tensile Elongation at Break) The tensile elongation at break in the longitudinal direction (MD) and the width direction (TD) perpendicular to the longitudinal direction of the stretch packaging film was measured in accordance with JIS K7127. In addition, the test piece used the No. 3 type test piece, and performed the test speed at 500 mm / min.

(Anti-fogging property) Absorbent cotton impregnated with 100 g of water was placed in a rectangular plastic tray measuring 120 mm in length and 200 mm in width, and stretch-wrapped with a stretch-wrapping film to form a single package. After leaving the package at a temperature of 0 ° C. for 30 minutes, the package was visually observed and evaluated as follows. ：: Water droplets did not adhere to the surface of the stretch packaging film, and the contents of the package were visible. Δ: Water droplets adhered to the surface of the stretch packaging film, but the contents of the package were visible. ×: Water droplets adhered to the surface of the stretch packaging film, and the contents of the package were not visible.

(Heat resistance) A rectangular plastic heat-resistant tray measuring 120 mm long x 200 mm wide is placed on a 80 mm long heat-resistant tray.
× A rectangular weight of 300 g with a width of 150 mm was placed thereon, and stretch-wrapped with a stretch packaging film to form a single package. Three packages were prepared, the three were stacked in three stages, placed in a 500 W microwave oven, and heated for 2 minutes. The operation of taking out the packages was repeated, and the temperature at which the stretch packaging film began to be thermally fused was measured.

(Tensile breaking strength) The tensile breaking strength of the stretch packaging film in the longitudinal direction (MD) and the width direction (TD) perpendicular to the longitudinal direction was measured according to JIS K7127. In addition, the test piece used the No. 3 type test piece, and performed the test speed at 500 mm / min.

(Cutability) The wound stretch packaging film is cut into a roll having a width of 300 mm, placed in a commercially available household wrap box with a simple saw blade, and the stretch packaging film is pulled out of the box by 200 mm. Then, cutting was performed with a simple saw blade. Repeat this 10 times,
The number of cut errors in which the stretch packaging film was not cut along the saw blade was counted, and evaluated as follows. ：: 1 or less cut error △: 2 to 5 cut errors ×: 6 or more cut errors

(Suitability for Automatic Packaging Machine) The wound stretch packaging film was cut into a roll having a width of 500 mm and set in a push-up automatic packaging machine. Then, 120mm in length
× 100 plastic trays 200 mm wide were stretch-wrapped continuously, the number of packages that could be beautifully packed was counted, and the packing success rate was calculated by the following formula. Packaging success rate (%) = 個数 number of beautiful packages (pieces) / 100
(Pcs) x 100

[0048]

[Table 1]

[0049]

The film for stretch packaging of the present invention comprises:
Since it is composed of a specific ethylene-vinyl alcohol copolymer and a polyhydric alcohol, and has a tensile elongation at break in a specific range in a specific range, it has suitable flexibility and strength as a film for stretch packaging, It is excellent in suitability for automatic packaging machines used for packaging, hardly breaks suddenly due to projections or external forces on the packaged object, and is excellent in secondary handling. In addition, it has both excellent antifogging property and water resistance. Even when foods are displayed at a low temperature after packaging, moisture inside the film does not condense and form water droplets, and excellent visibility is secured. It can be used for packaging foods and the like that do not decrease in strength or dissolve in water and contain water. Further, it has excellent heat resistance, and the films are not fused or broken even when heated in a microwave oven or the like. Furthermore, it has excellent cutting properties, and can be easily cut as desired even with a saw blade that is easily attached to a box such as a household wrap. In addition to the above, since it is made of a chlorine-free resin, the influence on the environment is small even when incinerated. According to the method for producing a film for stretch packaging of the present invention, the film for stretch packaging can be easily obtained with high production efficiency.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 65/40 BSG B65D 65/40 BSGF 4J002 BSN BSNF BSQ BSSQF C08J 7/04 C08J 7/04 Z C08K 5 / 053 C08K 5/053 C08L 29/04 C08L 29/04 S // B29K 23:00 B29K 23:00 29:00 29:00 B29L 7:00 B29L 7:00 F term (reference) 3E086 AA01 AB01 AC22 AD17 BA04 BA15 BA33 BB66 BB71 BB85 BB87 BB90 4D075 BB07X CA03 CA18 CA22 CA38 CA39 CB04 DA04 DB36 DB40 DC36 EB19 EB52 EB55 4F006 AA19 AA56 AB20 BA05 CA07 4F071 AA15X AA29 AA29X AA80 AA04 AF01 AF13 AF01 AF01 AF13 AF01 AF05 AG03 AH81 KA01 KA17 KL84 KW26 KW41 4J002 BE031 CH022 EC046 EC056 ED036

Claims (5)

[Claims] 1. A film comprising 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 40 mol% and 5 to 20 parts by weight of a polyhydric alcohol, and having a tensile elongation at break in the longitudinal direction of the film of 50 to 200%. There is a film for stretch packaging. 2. The stretch packaging film according to claim 1, wherein the polyhydric alcohol is glycerin or diglycerin. 3. A water-resistant layer made of a polyvinyl alcohol-based resin having a degree of polymerization of 1100 or more and a degree of saponification of 97% or more is integrally laminated on one surface of the stretch packaging film according to claim 1 or 2. Stretch packaging film. 4. Melting and kneading 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 40 mol% and 5 to 20 parts by weight of a polyhydric alcohol, extruding the film, and applying tension to the film. The method for producing a stretch packaging film according to claim 1, wherein the method is characterized in that: 5. Melt-kneading 100 parts by weight of an ethylene-vinyl alcohol copolymer having an ethylene content of 5 to 40 mol% and 5 to 20 parts by weight of a polyhydric alcohol, extruding the film, applying tension to the film, The method for producing a stretch packaging film according to claim 3, wherein a polyvinyl alcohol resin having a degree of polymerization of 1100 or more and a degree of saponification of 98% or more is coated on one surface of the film.