JP2021075338A - Wrap film - Google Patents

Abstract

To provide a wrap film inhibited from tearing troubles, excellent in oxygen gas barrier property and touch feeling.SOLUTION: A wrap film 17 contains at least one compound selected from the group consisting of a vinylidene chloride resin containing 72 to 93 mol% of a vinylidene chloride repeating unit, citrate, dibasic acid ester, and acetylated fatty acid glyceride, and has a content of 0.5 mass% or more and less than 3 mass% of the compound based on a total amount of the wrap film 17, a tensile elasticity of 250 to 570 MPa in an MD direction, and a low-temperature crystallization initiation temperature of 40 to 60°C measured by a temperature modulation type differential scanning calorimeter.SELECTED DRAWING: Figure 2

Description

The present invention relates to a wrap film.

Wrap film formed from vinylidene chloride resin has excellent oxygen gas barrier property, water vapor barrier property (moisture proof property) and transparency, and can be heated in a microwave oven, so that fresh fish, raw meat, processed meat, fresh vegetables, etc. It is widely used for packaging prepared foods, etc. for the purpose of blocking oxygen and preventing moisture.

In particular, recently, oxygen gas barrier properties have been strongly required for wrap films from the viewpoints of preventing the oxidation of fats and oils, preserving active ingredients such as vitamins, and preventing putrefaction due to the growth of molds, fungi and yeasts (for example, cited documents). See 1.).

JP-A-2019-43677

By the way, in melt extrusion, if the vinylidene chloride resin stays in the extruder for a certain period of time, the vinylidene chloride resin may be decomposed and carbonized, and the carbide may become a foreign substance. Further, even if foreign matter is generated in melt extrusion, puncture may not occur during inflation film formation and a wrap film may be normally produced depending on the degree of foreign matter. However, in such a case, it is conceivable that a tear trouble may occur starting from a foreign substance.

Therefore, various additives are added to the vinylidene chloride resin from the viewpoints of film extrusion processability, crystallinity, transparency, softening temperature, etc., and in particular, plasticization from the viewpoint of film extrusion processability. Generally, an agent is added. However, it has been found that the oxygen gas barrier property is rather lowered and the feel of touch is lowered depending on the type and amount of the plasticizer used.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a wrap film which suppresses tearing troubles, has an excellent oxygen gas barrier property, and has an excellent feel.

The present inventors have diligently studied to solve the above problems. As a result, they have found that the above problems can be solved by adjusting the content of at least one compound selected from the group consisting of citric acid ester, dibasic acid ester, and acetylated fatty acid glyceride, and completed the present invention. I came to do it.

That is, the present invention is as follows.
[1]
A vinylidene chloride-based resin containing 72 to 93 mol% of vinylidene chloride repeating units,
Contains at least one compound selected from the group consisting of citrate esters, dibasic acid esters, and acetylated fatty acid glycerides.
The content of the compound is 0.5% by mass or more and less than 3% by mass with respect to the total amount of the wrap film.
The tensile elastic modulus in the MD direction is 250 to 570 MPa.
The low temperature crystallization start temperature measured by a temperature-modulated differential scanning calorimeter is 40 to 60 ° C.
Wrap film.
[2]
The tear strength in the TD direction is 2.0 to 6.0 cN.
The wrap film according to [1].
[3]
The thickness is 6-18 μm,
The wrap film according to [1] or [2].
[4]
Contains epoxidized vegetable oil,
The content of the epoxidized vegetable oil is 0.5 to 3% by mass with respect to the total amount of the wrap film.
The wrap film according to any one of [1] to [3].
[5]
Oxygen permeability at 23 ° C. is 110 cm ³ / m ² · day · atm or less.
The wrap film according to any one of [1] to [4].
[6]
The ratio of high motility components measured by pulse NMR is 4.5% or less.
The wrap film according to any one of [1] to [5].
[7]
The ratio of hypokinetic components measured by pulse NMR is 65.0% or less.
The wrap film according to any one of [1] to [6].

According to the present invention, it is possible to provide a wrap film in which tearing troubles are suppressed, oxygen gas barrier properties are excellent, and a feeling of touch is excellent.

It is the schematic of the apparatus used in the film forming process of this invention. This is an example of using the film of the present invention.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited thereto, and various modifications can be made without departing from the gist thereof. Is.

In the present embodiment, the "TD direction" refers to the width direction of the resin in the film forming line, and refers to the direction perpendicular to the direction in which the wrap film is pulled out from the wound body when the wrap film is formed. Further, the "MD direction" refers to the flow direction of the resin in the film forming line, and refers to the direction in which the wrap film is pulled out from the wound body when the wrap film is formed.

[Wrap film]
The wrap film of the present embodiment contains at least one compound selected from the group consisting of a vinylidene chloride resin containing 72 to 93 mol% of vinylidene chloride repeating units, a citric acid ester, a dibasic acid ester, and an acetylated fatty acid glyceride. The content of the compound is 0.5% by mass or more and less than 3% by mass with respect to the total amount of the wrap film, the tensile elasticity in the MD direction is 250 to 570 MPa, and the temperature-modulated differential scanning calorific value is The low temperature crystallization start temperature measured by the meter is 40 to 60 ° C.

In the present embodiment, the content of at least one compound selected from the group consisting of citric acid ester, dibasic acid ester, and acetylated fatty acid glyceride is 0.5% by mass in the wrap film having the above-mentioned predetermined constitution. When the content is less than 3% by mass, the effect of exhibiting a sufficient oxygen gas barrier property is obtained. In addition, the wrap film of the present embodiment has the effect of suppressing tearing troubles and providing an excellent feel.

The reason why the tear trouble is suppressed and the oxygen gas barrier property is further improved by adjusting the content of the above compound is not clear, but it is considered as follows. That is, during melt extrusion, the resin stays in the extruder for a certain period of time, but by adjusting the content of the above compound, the low-motility component of the vinylidene chloride resin increases, which further improves the oxygen gas barrier property. It is thought that. Further, by adjusting the content of the above compound, the feeling of touch becomes excellent. The above reason is an estimation and is not limited to this. Hereinafter, the present embodiment will be described in detail.

(Vinylidene chloride resin)
The vinylidene chloride-based resin is not particularly limited as long as it contains vinylidene chloride, and examples thereof include a vinylidene chloride copolymer containing a monomer polymerizable with vinylidene chloride.

The monomer copolymerizable with the vinylidene chloride monomer is not particularly limited, but for example, vinyl chloride; acrylic acid ester such as methyl acrylate and butyl acrylate; and methacrylic acid ester such as methyl methacrylate and butyl methacrylate. Acrylic acid, methacrylic acid; acrylonitrile; vinyl acetate and the like. These monomers may be used alone or in combination of two or more. Of these, vinyl chloride is more preferable.

The content of the vinylidene chloride repeating unit is 72 to 93 mol%, preferably 80 to 93 mol%, and more preferably 82 to 93 mol% with respect to the total amount of the vinylidene chloride resin. When the content of the vinylidene chloride repeating unit is 72 mol% or more, the glass transition temperature of the vinylidene chloride resin is low, and the wrap film tends to be soft. Thereby, for example, tearing of the wrap film can be reduced even when used in a low temperature environment. On the other hand, when the content of the vinylidene chloride repeating unit is 93 mol% or less, a large increase in crystallinity is suppressed, and deterioration of moldability during film stretching tends to be suppressed.

The content of the vinylidene chloride repeating unit is not particularly limited, but can be measured using, for example, a highly decomposed proton nuclear magnetic resonance measuring device (400 MHz or more). More specifically, 0.5 g of wrap film is dissolved in 10 ml of tetrahydrofuran (THF), about 30 ml of methanol is added to precipitate a resin component, and then the precipitate is separated by centrifugation, vacuum dried, and made of vinylidene chloride. Obtain a sample for measuring the resin. Then, the obtained measurement sample is dissolved in deuterated tetrahydrofuran so as to be 5% by mass, and then this solution is subjected to 1 H-NMR measurement at a measurement atmosphere temperature of about 27 ° C. The content of vinylidene chloride repeating units is calculated using a unique chemical shift relative to tetramethylsilane in the resulting spectrum. For example, in the case of a copolymer of vinylidene chloride and vinyl chloride, the peaks of 3.50 to 4.20 ppm, 2.80 to 3.50 ppm, and 2.00 to 2.80 ppm are used for calculation.

The content of the repeating unit of the comonomer (vinyl chloride) of the vinylidene chloride-vinyl chloride copolymer is preferably 7 to 28 mol%, more preferably 10 to 19 mol%, based on the total amount of the copolymer. is there. When the comonomer content of the vinylidene chloride copolymer is within the above range, tearing of the wrap film is reduced, and deterioration of moldability during film stretching tends to be further suppressed.

The weight average molecular weight (Mw) of the vinylidene chloride copolymer is preferably 50,000 to 250,000, more preferably 60,000 to 230,000, still more preferably 80,000 to 200,000. is there. When the weight average molecular weight (Mw) is within the above range, the mechanical strength of the wrap film tends to be further improved. The vinylidene chloride-based resin having a weight average molecular weight within the above range can be obtained, for example, by controlling the charging ratio of the vinylidene chloride monomer and the vinyl chloride monomer, the amount of the polymerization initiator, or the polymerization temperature. In this embodiment, the weight average molecular weight (Mw) can be determined by gel permeation chromatography (GPC method) using a standard polystyrene calibration curve.

The content of the vinylidene chloride resin is preferably 88 to 98% by mass, more preferably 90 to 99% by mass, based on the total amount of the wrap film. When the content of the vinylidene chloride resin is within the above range, the plasticizing effect of the additive or the like increases the amount of hypokinetic components of the vinylidene chloride resin, which tends to further improve the oxygen gas barrier property. .. Further, when the content of the vinylidene chloride resin is within the above range, it is possible to suppress the film from being easily stretched, and the tearing trouble tends to be further suppressed. The method of measuring the content of each component from the wrap film differs depending on the analysis target. For example, the content of vinylidene chloride resin is measured by dissolving 0.5 g of a sample in 10 ml of tetrahydrofuran, adding about 30 ml of methanol to precipitate a resin component, and then separating the precipitate by centrifugation, drying, and weighing. Can be obtained.

(Additive)
The wrap film of the present embodiment contains at least one compound selected from the group consisting of citric acid ester, dibasic acid ester, and acetylated fatty acid glyceride. The citric acid ester is preferable from the viewpoint of handleability, and tributyl acetylcitrate is particularly preferable.

(Citric acid ester)
The citrate ester is not particularly limited, and examples thereof include triethyl citrate, tributyl citrate, triethyl acetyl citrate, tributyl acetyl citrate (ATBC), and tri-n- (2-ethylhexyl) acetyl citrate.

Of these, tributyl acetylcitrate is preferred. By using such a citric acid ester, the vinylidene chloride-based resin is plasticized, the molding processability is further improved, and the low-motility component of the vinylidene chloride-based resin is increased, thereby further improving the oxygen gas barrier property. In addition, the feel tends to be improved.

(Dibasic acid ester)
The dibasic acid ester is not particularly limited, and is, for example, an adipic acid ester such as dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, dioctyl adipate; , Adipic acid esters such as octyl azerate; sebacic acid esters such as dibutyl sebacate (DBS) and di-2-ethylhexyl sebacate; phthalates such as dimethyl phthalate, diethyl phthalate and dioctyl phthalate.

Among these, an aliphatic dibasic acid ester is preferable, and dibutyl sebacate is more preferable. By using such a dibasic acid ester, the vinylidene chloride-based resin is plasticized, the molding processability is further improved, and the low-motility component of the vinylidene chloride-based resin is increased, thereby further improving the oxygen gas barrier property. In addition, the feel tends to be improved.

(Acetylated fatty acid glyceride)
The acetylated fatty acid glyceride is not particularly limited, and is, for example, acetylated caprylic acid glyceride, acetylated capric acid glyceride, acetylated laurate glyceride, acetylated myristic acid glyceride, acetylated palm kernel oil glyceride, and acetylated coconut oil glyceride. , Acetylated castor oil glyceride, acetylated hardened castor oil glyceride.

The acetylated fatty acid glyceride may be any of acetylated monoglyceride of fatty acid, acetylated diglyceride of fatty acid, and acetylated triglyceride of fatty acid. For example, the acetylated lauric acid glyceride includes acetylated monoglyceride of lauric acid, acetylated diglyceride of lauric acid (DALG: diacetyllauroylglycerol), and acetylated triglyceride of lauric acid. Of these, acetylated lauric acid glyceride is preferable, and acetylated diglyceride of lauric acid is more preferable. By using such an acetylated fatty acid glyceride, the amount of hypokinetic components of the vinylidene chloride resin is increased, which tends to further improve the oxygen gas barrier property and the feel of touch.

The content of citric acid ester, dibasic acid ester, and acetylated fatty acid glyceride is determined by extracting the additive from the wrap film at a temperature 5 to 10 ° C. lower than the boiling point of the extraction solvent using an organic solvent such as acetone. It can be obtained by gas chromatography analysis.

The total content of at least one compound selected from the group consisting of citrate ester, dibasic acid ester, and acetylated fatty acid glyceride is 0.5% by mass or more and less than 3% by mass with respect to the total amount of the wrap film. , It is preferably 0.5 to 2.5% by mass, and more preferably 0.7 to 2.5% by mass. When the total content of the above compounds is 0.5% by mass or more, the share of melt extrusion becomes appropriate, and the composition smoothly passes through the extruder, so that the thermal decomposition of the vinylidene chloride resin is suppressed. .. Further, when the total content of the above compounds is less than 3% by mass, the amount of the low-motility component of the vinylidene chloride-based resin is increased, which further improves the oxygen gas barrier property and the feel of touch.

(Epoxy vegetable oil)
The wrap film of the present embodiment may contain an epoxidized vegetable oil. The epoxidized vegetable oil can act as a stabilizer for extruding vinylidene chloride-based resins. The epoxidized vegetable oil is not particularly limited, but generally includes those produced by epoxidizing edible oils and fats. Specifically, examples of the epoxidized vegetable oil include epoxidized soybean oil (ESO) and epoxidized linseed oil. Of these, epoxidized soybean oil is preferred. By using such an epoxidized vegetable oil, the feel of the wrap film tends to be further improved, and the pullability of the film from the cosmetic box tends to be further improved.

The content of the epoxidized vegetable oil in the present embodiment is preferably 0.5 to 3% by mass, more preferably 1 to 2.5% by mass, still more preferably 1 to 1% by mass, based on the total amount of the wrap film. 2% by mass. When the content of the epoxidized vegetable oil is 0.5% by mass or more, the quality change of the wrap film tends to be further suppressed. Further, when the content of the epoxidized vegetable oil is 3% by mass or less, the color tone change of the wrap film is more suppressed, and the stickiness due to bleeding tends to be suppressed. The method of measuring the content of each component from the wrap film differs depending on the analysis target. For example, the content of the epoxidized vegetable oil can be obtained by analyzing the reprecipitation filtrate of the wrap film by NMR.

Specifically, 50 mg of the sample was weighed, dissolved in a deuterated solvent (solvent: deuterated tetrahydrofuran, internal standard: dimethyl terephthalate, volume: 0.7 ml), and measured by 400 MHz proton NMR (integration number: 512 times). It can be obtained by using the ratio of the integrated value of 2.23 to 2.33 ppm as the integrated value to the integrated value of 8.05 to 8.11 ppm and calculating the quantitative value by the absolute calibration curve method.
Integral ratio = Integral value (2.23 to 2.33 ppm) / Integral value (8.05 to 8.11 ppm)

(Other additives)
The wrap film of the present embodiment may contain additives other than the above. Such additives are not particularly limited, but are, for example, plasticizers other than the above, stabilizers other than the above, weather resistance improvers, colorants such as dyes or pigments, antifogging agents, antibacterial agents, lubricants, nuclei. Examples thereof include agents, oligomers such as polyester, and polymers such as methyl methacrylate-butadiene-styrene copolymer (MBS).

The plasticizer other than the citric acid ester, the dibasic acid ester, and the acetylated fatty acid glyceride is not particularly limited, and specific examples thereof include glycerin, glycerin ester, wax, liquid paraffin, and phosphoric acid ester. The plasticizer may be used alone or in combination of two or more.

The stabilizer other than the epoxidized vegetable oil is not particularly limited, but specifically, 2,5-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, 4,4'-thiobis-. (6-t-butylphenol), 2,2'-methylene-bis- (4-methyl-6-t-butylphenol), octadecyl-3- (3', 5'-di-t-butyl-4'-hydroxy Antioxidants such as phenyl) bropionate and 4,4'-thiobis- (6-t-butylphenol); laurate, myristate, palmitate, stearate, isostearate, oleate, ricinol Heat stabilizers such as acid salts, 2-ethyl-hexyl salts, isodecanoates, neodecanoates, and calcium benzoate can be mentioned. The stabilizer may be used alone or in combination of two or more.

The weather resistance improver is not particularly limited, but specifically, ethylene-2-cyano-3,3'-diphenylacrylate, 2- (2'-hydroxy-5'-methylphenyl) benzolithriazole, 2 -(2'-Hydroxy-3'-t-butyl-5'-methylphenyl) 5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone and the like. Be done. The weather resistance improver may be used alone or in combination of two or more.

The colorant such as a dye or a pigment is not particularly limited, and specific examples thereof include carbon black, phthalocyanine, quinacridone, indoline, an azo pigment, and red iron oxide. The colorant may be used alone or in combination of two or more.

The antifogging agent is not particularly limited, and specific examples thereof include glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene fatty acid alcohol ether, polyoxyethylene glycerin fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. The antifogging agent may be used alone or in combination of two or more.

The antibacterial agent is not particularly limited, and specific examples thereof include a silver-based inorganic antibacterial agent. The antibacterial agent may be used alone or in combination of two or more.

The lubricant is not particularly limited, but specifically, a fatty acid hydrocarbon-based lubricant such as ethylene bissteroamide, butyl stearate, polyethylene wax, paraffin wax, carnauba wax, myristyl myristate, and stearyl stearate, and a higher fatty acid lubricant. , Fatty acid amide-based lubricants, fatty acid ester lubricants and the like. The lubricant may be used alone or in combination of two or more.

The nucleating agent is not particularly limited, and specific examples thereof include a phosphoric acid ester metal salt and the like. The nucleating agent may be used alone or in combination of two or more.

The content of the other additives is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0.1% by mass, based on the total amount of the wrap film. It is as follows. The lower limit of the content of other additives is not particularly limited, but is 0% by mass or more with respect to the total amount of the wrap film.

(Thickness of wrap film)
The thickness of the wrap film of the present embodiment is preferably 6 to 18 μm, more preferably 9 to 12 μm. When the thickness of the wrap film is within the above range, the trouble of film breakage is suppressed, the cuttability is further improved, and the adhesion is further improved.

More specifically, when the thickness is 6 μm or more, the tear strength of the wrap film in the TD direction and the MD direction is further improved, and the film breakage during use tends to be further suppressed. Further, when the thickness is 6 μm or more, the tear strength tends to be less significantly reduced. Therefore, when pulling out the wrap film from the wound body and when picking out the end of the film rewound into the cosmetic box, the trouble of tearing the wrap film from the end cut by the cutting blade attached to the cosmetic box is more likely to occur. It is suppressed.

On the other hand, when the thickness is 18 μm or less, the force required to cut the wrap film with the cutting blade attached to the cosmetic box can be reduced, and the cutability tends to be further improved. Further, when the thickness is 18 μm or less, the wrap film easily fits the shape of the container, and the adhesion to the container tends to be further improved.

(Tear strength)
The tear strength of the wrap film of the present embodiment in the TD direction is preferably 2.0 to 6.0 cN, more preferably 2.0 to 4.0 cN, and further preferably 2.2 to 3.0 cN. is there. When the tear strength in the TD direction is 2.0 cN or more, it is possible to reduce the tear when the wrap film is pulled out from the wound body, and it is possible to suppress an unintended tear trouble when the wrap film is used. On the other hand, when the tear strength in the TD direction is 6.0 cN or less, the film is easily torn when the film is cut in the TD direction with the cutting blade attached to the cosmetic box, and the cutability is improved.

The tear strength of the wrap film of the present embodiment in the TD direction can be adjusted by adjusting the composition of the vinylidene chloride resin, the additive composition, the stretch ratio of the film, the stretch rate, the thickness of the film, and the like. Although not particularly limited, for example, the tear strength in the TD direction tends to be improved by lowering the draw ratio in the TD direction or thickening the wrap film, increasing the draw ratio in the TD direction, or using a wrap film. By making it thinner, it tends to decrease. The tear strength is measured by the method described in Examples.

(Tensile modulus)
The tensile elastic modulus of the wrap film of the present embodiment in the MD direction is 250 to 570 MPa, preferably 300 to 500 MPa, and more preferably 350 to 500 MPa. When the tensile elastic modulus in the MD direction is 250 MPa or more, when a force is applied to cut the film with the cutting blade, the film can be suppressed from extending in the MD direction, the cutting blade can easily bite into the film, and the cut property can be obtained. Is improved. On the other hand, when the tensile elastic modulus in the MD direction is 570 MPa or less, the film is soft, the film can be cut neatly along the shape of the cutting blade, and the occurrence of a large number of crevices on the cut end face tends to be suppressed. As a result, when the film is pulled out from the wound body and when the end portion of the film rewound into the cosmetic box is picked out, it tends to be possible to suppress the trouble of tearing the film from the cut end face.

The tensile elastic modulus in the MD direction of the wrap film of the present embodiment can be adjusted by adjusting the composition of the vinylidene chloride resin, the additive composition, the stretching ratio of the film, the stretching speed, and the like. Although not particularly limited, for example, the tensile elastic modulus in the MD direction tends to be improved by increasing the draw ratio or reducing the amount of the additive, and lowers the draw ratio or increases the amount of the additive. As a result, it tends to decrease. The tensile elastic modulus is measured by the method described in Examples.

(Low temperature crystallization start temperature)
In the wrap film of the present embodiment, the wrap film is physically deteriorated due to the heat history received during the distribution process and storage, and the tear trouble caused by the physical deterioration can be estimated from the low temperature crystallization start temperature. The low-temperature crystallization start temperature is an index showing the thermal stability of microcrystals formed and grown by being exposed to high temperatures during distribution and storage in a warehouse after wrap film production, and the molecular chain is regenerated by the low-temperature crystallization start temperature. It is possible to evaluate the degree of alignment, that is, the susceptibility to tear trouble due to physical deterioration of the wrap film.

From the above viewpoint, the low temperature crystallization start temperature measured by the temperature-modulated differential scanning calorimeter (hereinafter, also referred to as “temperature-modulated DSC”) of the wrap film of the present embodiment is preferably 40 to 60 ° C. , More preferably 40 to 55 ° C, still more preferably 40 to 50 ° C. When the low-temperature crystallization start temperature is within the above range, tearing troubles can be suppressed while maintaining the cutability of the wrap film, and the feel of the wrap film tends to be further improved. The details will be described below.

The low temperature crystallization start temperature of the conventional wrap film was over 60 ° C. On the other hand, the low temperature crystallization start temperature of the wrap film of the present embodiment is 60 ° C. or lower, which is set to a lower temperature. When the low temperature crystallization start temperature is within the above range, the rearrangement of the molecular chains is suppressed, and the trouble of tearing the wrap film is further suppressed.

More specifically, the wrap film of the present embodiment and the conventional wrap film behave differently when exposed to heat due to the difference in the low temperature crystallization start temperature. For example, in the conventional wrap film, when it is exposed to an atmosphere of 20 ° C. or higher for a long time during distribution and storage in a warehouse, it is considered that the molecular chains of the vinylidene chloride resin are rearranged and the formation and growth of microcrystals occur. Be done. It is presumed that such rearrangement of the molecular chains occurs because the orientation of the molecular chains of the produced wrap film and the stress of the film are not sufficiently relaxed. It is considered that the more the wrap film is exposed to a high temperature, the more easily the molecular chain rearrangement occurs, so that the film is physically deteriorated and the tear trouble is easily induced.

On the other hand, in the wrap film of the present embodiment, the low temperature crystallization start temperature is set to 60 ° C. or lower by sufficiently relaxing the orientation of the molecular chains of the vinylidene chloride resin and the stress of the film at the time of production. As a result, in the wrap film of the present embodiment, even if it is exposed to 20 ° C. or higher for a long time during distribution and storage in a warehouse, the molecular chains are less likely to be rearranged, and deterioration of the film and further tearing trouble are suppressed. As a result, it is possible to simultaneously achieve the contradictory task of suppressing tearing troubles while maintaining the cuttability.

On the other hand, as a result of examination by the present inventors, the low temperature crystallization start temperature was 40 ° C. when the wrap film was stored at −30 ° C., which is lower than the glass transition temperature after production. That is, when it can be considered that the wrap film has not received any heat after production, the low temperature crystallization start temperature was 40 ° C. Since it is considered that the closer the low temperature crystallization start temperature is to this temperature, the rearrangement of the molecular chains and the tearing trouble can be suppressed, the lower limit of the temperature range of the low temperature crystallization start temperature is set to 40 ° C.

The method of adjusting the low-temperature crystallization start temperature within the above range is not particularly limited, and examples thereof include a method of sufficiently relaxing the orientation of the molecular chains of the vinylidene chloride resin and the stress of the film. Specifically, by adjusting the product of the stretching ratio in the MD direction and the stretching ratio in the TD direction (MD stretching ratio × TD stretching ratio) and the temperature during stretching, the stress applied in the stretching process is adjusted, and the oriented crystal It is possible to set the degree of crystallization as appropriate. Further, a method of storing the wrap film at a low temperature for a predetermined time can be mentioned.

Here, the "low temperature crystallization start temperature" is the extrapolation start temperature (temperature rise) of the exothermic peak caused by the low temperature crystallization in the temperature-heat flow curve of the irreversible component obtained by the temperature rise measurement by the temperature modulation type DSC. The temperature at the intersection of the line extending the baseline on the low temperature side to the high temperature side and the tangent line drawn at the point where the gradient is maximized on the curve on the low temperature side of the crystallization peak in the measurement).

An example of a method for measuring the low temperature crystallization start temperature will be described. First, a differential scanning calorimetry device (DSC) (input-compensated double furnace DSC 8500) manufactured by PerkinElmer Co., Ltd. is used, and a temperature-heat flow curve of an irreversible component is obtained by a step scan measurement mode. The conditions for the step scan measurement at this time are that the measurement temperature is 0 to 180 ° C., the temperature rise rate is 10 ° C./min, the temperature rise step width is 4 ° C., and the isothermal time is 1 min. In the obtained temperature-heat flow curve, the external start temperature of the exothermic peak caused by low temperature crystallization is defined as the low temperature crystallization start temperature.

In the temperature rise measurement of the differential scanning calorimeter, crystallization and crystal melting compete with each other. Therefore, in the conventional DSC measurement method, the heat flow derived from the formation / growth and melting of microcrystals is canceled out, and it is difficult to examine the thermal behavior of the microcrystals. Therefore, the conventional wrap film and the wrap film of the present embodiment are used. It was difficult to distinguish. On the other hand, when the step scan measurement of the temperature-modulated DSC is used, it is possible to separate the heat flow of irreversible components such as crystallization and reversible components such as crystal melting and glass transition, and evaluate the thermal behavior of microcrystals. Is possible. Therefore, in the measurement of the low temperature crystallization start temperature of the present embodiment, the step scan measurement of the temperature-modulated DSC is used.

<Pulse NMR>
In the wrap film of the present embodiment, the ratio of high motility components measured by pulse NMR is preferably 4.5% or less, more preferably 4.0% or less, still more preferably 3.5%. It is as follows. The ratio of low motility components is preferably 65.0% or less, more preferably 63.0% or less, and preferably 61.0% or more. When the ratio of high motility components is in the above range, the frequency of occurrence of cuts tends to decrease. Further, when the hypokinetic component is in the above range, the tearing trouble is further suppressed.

Unlike high-resolution NMR, which is widely used in determining the structure of organic compounds, pulse NMR can measure each relaxation time of 1H nuclei related to molecular motility in the system, and its high quantification. This is an analytical method that can determine the abundance ratio of each motor component in the system by using.

In the present embodiment, 1H spin-spin relaxation is used to determine Cs: the mole fraction of the low motility component, Cm: the mole fraction of the intermediate component, and Cl: the mole fraction of the high motility component in the wrap film. Time T2 is used.

Specifically, the fitting is performed using the linear least squares method so that the free induction decay (FID) signal obtained in the measurement of the spin-spin relaxation time T2 of 1H fits approximately the following equation. Is preferable.

here,
C _s : Mole fraction of low motility component C _m : Mole fraction of intermediate component C _l : Mole fraction of high motility component T _s : Relaxation time of low motility component T _m : Relaxation time of intermediate component T _l : Relaxation time of high motility component.

[Oxygen gas barrier property]
Generally, the wrap film is required to have an oxygen gas barrier property in order to maintain its freshness. The oxygen permeability of the wrap film of the present embodiment at 23 ° C. is preferably 1 to 110 cm ³ / m ² · day · atm, more preferably 1 to 77 cm ³ / m ² · day · atm, and even more preferably 1 to 77 cm 3 / m 2 · day · atm. Is 1 to 50 cm ³ / m ² · day · atm. When the oxygen permeability is within the above range, the oxygen gas barrier property is further improved, and the freshness of the food tends to be sufficiently maintained.

The oxygen permeability of the wrap film at 23 ° C. can be measured by the method described in Examples. The method of controlling the oxygen permeability of the wrap film at 23 ° C. in the above range is not particularly limited, but for example, the draw ratio in the MD direction is set to 4.0 or less, preferably 3.8 or less, or the TD direction. Examples include a method of setting the stretching ratio of 5.8 or more, a method of using a polymer having a low glass transition temperature, and a method of adding a nucleating agent as appropriate.

[Manufacturing method of wrap film]
The method for producing the wrap film of the present embodiment is not particularly limited, and is, for example, from a vinylidene chloride resin containing 72 to 93 mol% of vinylidene chloride repeating units, a citric acid ester, a dibasic acid ester, and an acetylated fatty acid glyceride. Examples thereof include a method of melt-extruding a composition containing at least one compound selected from the above group to form a film, and a step of stretching the obtained film in the MD direction and the TD direction. The details will be described below.

(Mixing process)
FIG. 1 shows a schematic view of an example of a wrap film manufacturing process. First, a vinylidene chloride resin, at least one compound selected from the group consisting of citric acid ester, dibasic acid ester, and acetylated fatty acid glyceride, and epoxidized vegetable oil, if necessary, are mixed by a mixer. To obtain the composition. At this time, various additives may be mixed as needed. The mixer is not particularly limited, but for example, a ribbon blender, a Henschel mixer, or the like can be used. The obtained composition is preferably aged for about 1 to 30 hours and used in the next step.

(Melting extrusion process)
Next, the obtained composition is melted by an extruder 1 and a tubular film is extruded from the die mouth 3 of the die 2 to form a sock 4 (also referred to as a pile).

(Cooling process)
The sock liquid 5 is injected into the inside of the sock 4, and the outside of the sock 4 is brought into contact with the cold water of the cold water tank 6. As a result, the sock 4 is cooled from both the inside and the outside, and the film constituting the sock 4 is solidified. The solidified sock 4 is folded by the first pinch roll 7 to form the parison 8.

(Stretching process)
Subsequently, air is injected into the inside of the parison 8 to open the parison 8 and form an annular film. At this time, the sock liquid 5 applied to the portion corresponding to the inner surface of the sock 4 exerts an effect as an opening agent for the parison 8. The parison 8 is then reheated with warm water to a temperature suitable for stretching in the open state. The hot water adhering to the outside of the parison 8 is squeezed by the second pinch roll 9.

Air is injected into the inside of the parison 8 heated to an appropriate temperature as described above to form the bubble 10. When this air spreads the parison from the inside, the film is stretched and a stretched film is obtained. The film in the TD direction is mainly stretched by the amount of air, and the film in the MD direction is stretched by applying tension in the flow direction of the film using a second pinch roll 9 and a third pinch roll 11 or the like. Will be done.

The process from the first pinch roll 7 to the third pinch roll 11 is called a stretching step. Since the stretchability of the parison 8 is improved when the stretching speed is slowed down, in the conventional method for producing a wrap film, the stretching speed in the MD direction is adjusted to 0.08 times / s or less, and the stretching speed in the TD direction is set to 3. It was adjusted to 0 times / s or less. On the other hand, in the method for producing a wrap film of the present embodiment in which the crystallization start temperature is controlled to 40 to 60 ° C., the stretching ratio in the MD direction and the TD direction and the stretching speed in the MD direction and the TD direction are predetermined. It is preferable to adjust to the range.

Specifically, the stretching ratios in the MD direction and the TD direction in the stretching step of the present embodiment are independently, preferably 1.5 to 3.5 times, and more preferably 1.7 to 3.0 times. Is. The area magnification in the stretching step of the present embodiment is preferably 4.0 to 7.0 times, more preferably 5.0 to 6.0 times. Here, the stretching ratio in the MD direction refers to the stretching ratio of the parison 8 stretched in the MD direction. For example, in FIG. 1, the ratio of the rotation speed of the third pinch roll 11 to the rotation speed of the first pinch roll 7 is used. Can be calculated. The stretching ratio in the TD direction refers to the stretching ratio of the parison 8 stretched in the TD direction. For example, in FIG. 1, it is calculated by the ratio of the width length of the double ply film 12 to the width length of the parison 8. Can be done. The stretching ratio in the MD direction can be adjusted by, for example, the rotation speed ratio of the first pinch roll 7 and the third pinch roll 11, and the stretching ratio in the TD direction is, for example, the stretching temperature of the parison 8 or the size of the bubble 10. Can be adjusted with.

The stretching speed in the MD direction in the stretching step of the present embodiment is preferably 0.09 to 0.12 times / s. The average stretching speed in the MD direction refers to the stretching ratio in the MD direction with respect to the time it takes for the parison to pass between the first pinch roll 7 and the third pinch roll 11. For example, in FIG. 1, the first pinch roll 7 It can be calculated by the rotation speed, the rotation speed of the third pinch roll 11, and the time required for the parison 8 to pass between the first pinch roll 7 and the third pinch roll 11. The stretching speed in the MD direction can be adjusted by, for example, the rotation speed of the first pinch roll 7 or the third pinch roll 11 or the distance between the first pinch roll 7 and the third pinch roll 11.

Further, the stretching speed in the TD direction in the stretching step of the present embodiment is preferably 3.1 to 4.0 times / s. The average stretching speed in the TD direction refers to the stretching ratio in the TD direction with respect to the time required for the parison 8 to expand to the bubble 10. For example, in FIG. 1, it was measured using still images of the parison 8 and the bubble 10. It can be calculated from the time required for stretching in the TD direction calculated from the stretching length and the rotation speed of the third pinch roll 11, and the stretching ratio in the TD direction. The stretching speed in the TD direction can be adjusted by, for example, the rotation speed of the third pinch roll 11.

The stretching temperature is not particularly limited, but is preferably 30 to 45 ° C.

After the stretching step, the stretched film is folded by the third pinch roll 11 to become a double ply film 12. The double ply film 12 is wound by the winding roll 13.

(Mitigation process)
In the method for producing a wrap film of the present embodiment, it is preferable to have a relaxation step for relaxing the wrap film immediately after stretching. A relatively common relaxation method in the method for producing a wrap film is to relax the film by using heat from an infrared heater or the like after stretching. However, in the present embodiment, instead of this relaxation step, it is preferable to use a method of relaxing the stretched film by making the rotation speed of the take-up roll 13 slower than that of the third pinch roll 11. This is because, in the present embodiment, when the conventional relaxation method using heat is used, the heat causes the formation and growth of microcrystals that cause the film to tear, and the crystallization start temperature may exceed 60 ° C. Because there is.

The relaxation ratio in the relaxation step using the third pinch roll 11 and the take-up roll 13 is preferably 7 to 15%, more preferably 9 to 13%. When the relaxation ratio is 15% or less, the occurrence of slack in the film between the third pinch roll 11 and the take-up roll 13 tends to further suppress the occurrence of wrinkles. Further, when the relaxation ratio is 7% or more, the wrap film can be sufficiently relaxed, and even when exposed to a high temperature, the rearrangement of the molecular chains is suppressed and the low temperature crystals are suppressed. The crystallization start temperature can be 60 ° C. or lower. Further, this tends to reduce tearing troubles. Here, the "relaxation ratio" refers to the ratio of the double-ply film 12 contracted between the third pinch roll 11 and the take-up roll 13. For example, in the case of FIG. 1, the winding with respect to the rotation speed of the third pinch roll 11 It can be calculated using the ratio of the take roll 13.

The ambient temperature of the relaxation step using the third pinch roll 11 and the take-up roll 13 is preferably 25 to 32 ° C. When the ambient temperature is within the above range, the formation and growth of microcrystals tends to be suppressed.

(Slit process)
The wrap film wound as described above is slit and wound while being peeled off to form a single wrap film, and is temporarily stored in the original state for 1 to 3 days. Finally, the raw fabric is wound back into a paper tube and packed in a cosmetic box to obtain a wrap film wound body stored in the cosmetic box.

(Storage process)
In the method for producing a wrap film of the present embodiment, after slitting the wrap film, a storage step of storing the wrap film in the original state may be performed. The storage temperature is preferably 19 ° C. or lower, more preferably 5 to 19 ° C., and even more preferably 5 to 15 ° C. The storage time is preferably 20 to 50 hours, more preferably 24 to 40 hours.

The atmospheric temperature during storage can suppress the formation and growth of microcrystals that induce an increase in film tearing troubles. In general, the storage place of the raw material is often at a relatively high temperature because it is not adjacent to the manufacturing process of the wrap film or is not temperature-controlled.

On the other hand, in the method for producing a wrap film of the present embodiment, the physical deterioration of the film due to the rearrangement of the molecular chains tends to be suppressed by setting the atmospheric temperature at the time of storing the slit raw fabric to 19 ° C. or lower. .. This makes it easier for the wrap film to tear from the end cut with the cutting blade attached to the cosmetic box when pulling out the wrap film from the winding body or when picking out the end of the film that has been rewound into the cosmetic box. Tends to be suppressed.

In addition, since the atmospheric temperature during storage of the slit raw fabric is 5 ° C or higher, the wrap film is sufficiently relaxed, and when it is exposed to 20 ° C or higher during subsequent distribution and storage, the molecular chains are less likely to be rearranged. It tends to be.

Therefore, it is preferable to store the original slit fabric under the above-mentioned storage conditions, whereby a film in which the molecular chains in the amorphous portion are relaxed while suppressing the formation and growth of microcrystals can be obtained. In this way, by relaxing the orientation of the molecular chains during storage of the raw fabric, it becomes difficult for microcrystals to form and grow even when the film is exposed to high temperatures during distribution and storage, and tearing troubles can be suppressed.

After storage, the original slit fabric is, for example, rewound into a paper tube or the like, and is stored as a winding body 16 in a cosmetic box 1 provided with a film cutting blade 15 as shown in FIG. As illustrated in FIG. 2, the wrap film 17 is pulled out and used at the time of use.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

[Content of vinylidene chloride repeating unit]
The vinylidene chloride repeating unit of the wrap film was measured using a highly decomposed proton nuclear magnetic resonance measuring device. The reprecipitated filtrate of the wrap film was vacuum dried, and the solution dissolved in deuterated tetrahydrofuran so as to be 5% by mass was subjected to 1 H-NMR measurement at a measurement atmosphere temperature of about 27 ° C. For example, regarding the copolymer of vinylidene chloride and vinyl chloride, the peaks of the copolymer based on tetramethylsilane are 3.50 to 4.20 ppm, 2.80 to 3.50 ppm, and 2.00 to 2.80 ppm. Was used to calculate the content of repeating units of vinylidene chloride. For other copolymers, the content can be calculated using the peak of each monomer.

[Film thickness]
The thickness of the wrap film was measured using a dial gauge (manufactured by Teclock Co., Ltd.) in an atmosphere of 23 ° C. and 50% RH.

[Tear strength]
Assuming distribution of the wrap film after shipment and storage at home, the wrap film after production was stored in a constant temperature bath set at 28 ° C. for 1 month, and then the tear strength was measured.
A light load tear tester D type (manufactured by Toyo Seiki Co., Ltd.) was used to measure the tear strength of the wrap film, and the tear strength was measured in an atmosphere of 23 ° C. and 50% RH. The tear strength of the wrap film was measured with only one wrap film. At this time, the measurement range was appropriately selected so as to be 20 to 80% of the full scale. The sample length in the tear direction was 63.5 mm, and the sample width was 50.0 mm. At the time of measurement, after lifting and stopping the pendulum, the test piece was carefully attached to the knob, and the clamp was firmly tightened so that the position where the slit was inserted was in the center of the film width. The film was then slit with a knife attached to the device. At this time, the blade position of the knife was adjusted so that the cut length of the film was 12.7 mm ± 0.5 mm. After slitting, the pendulum was carefully released and the value of the force required to tear the test piece was read. Tests in which the tear line deviated by 10 mm or more from the extension line of the slit were excluded, and an additional test piece was tested instead. However, in this case, this does not apply if the tear is along the line of the embossed pattern. In addition, the measurement result was rounded off to the second decimal place.

[Tension modulus]
Assuming distribution of the wrap film after shipment and storage at home, the wrap film after production was stored in a constant temperature bath set at 28 ° C. for 1 month, and then the tensile elastic modulus was measured.
The tensile elastic modulus of the wrap film was measured using Autograph AG-IS (manufactured by Shimadzu Corporation) at 23 ° C. and in an atmosphere of 50% RH. The load at 2% elongation was measured under the conditions of a tensile speed of 5 mm / min, a distance between chucks of 100 mm, and a film width of 10 mm, and after dividing by the cross-sectional area of the measurement sample, the tensile elastic modulus was measured by multiplying by 50. At the time of measurement, the test piece was attached to the grip so that the MD direction of the test piece coincided with the axis of the tester. The test piece was evenly and firmly tightened with a grip to prevent slippage and to prevent the grip from slipping during the test. In addition, the pressure between the gripping tools must not cause cracking or rolling of the test piece. In addition, the measurement results were rounded off to the third digit with two significant figures.

[Low temperature crystallization start temperature]
As the measurement sample, assuming distribution after shipment of the wrap film and storage at home, the wrap film after production was stored in a constant temperature bath set at 28 ° C. for one month. For the measurement, a differential scanning calorimetry device (DSC) (input compensation type double furnace DSC 8500) manufactured by PerkinElmer Co., Ltd. is used, and a step scan measurement mode (sample weight: 6 mg, sample pan material: aluminum, measurement temperature: 0). ~ 180 ° C., heating rate: 10 ° C./min, temperature rising step width: 4 ° C., isothermal time: 1 min). An empty aluminum sample pan was also measured under the same temperature conditions and used as a blank. In the irreversible component of the temperature-heat flow curve, the temperature at which heat generation due to low temperature crystallization starts was defined as the low temperature crystallization start temperature.

[Pulse NMR]
Assuming distribution of the wrap film after shipment and storage at home, the wrap film after production was stored in a constant temperature bath set at 28 ° C. for 1 month, and then pulse NMR of the wrap film was measured. 1 g of a wrap film cut into a substantially square shape was folded into a cylindrical shape, packed in an NMR tube having a diameter of 10 mm, and measured by pulse NMR under the following conditions.
[conditions]
Equipment: Bruker Biоspin Мinispec МQ20
Nuclide: 1H
Measurement: T2
Measurement method: Solid echo method Measurement temperature: 40 ° C (measured 5 minutes after reaching the set temperature)
Accumulation number: 256 times Repeat time: 1.0 sec
Sample amount: Approximately 1 g

The obtained free induction decay (FID) curve was separated into three components using the following equation, and the component ratio and relaxation time of each component were determined.
The component represented by the function combining the Gaussian function and the sink function of the first term of the following equation is the hypomotility component, the component represented by the Lorentz function of the second term of the following equation is the intermediate component, and the Lorentz of the third term of the following equation The component represented by the function was defined as the high motility component.

C _s : Mole fraction of low motility component C _m : Mole fraction of intermediate component C _l : Mole fraction of high motility component T _s : Relaxation time of low motility component T _m : Relaxation time of intermediate component T _l : Relaxation time of high motility component

[Oxygen permeability]
OX TRAN 2/21 MH manufactured by MOCON was used, and ASTM D3985 was used as a reference for the measurement method. Oxygen permeability was measured under conditions of a temperature of 23 ° C. and a relative humidity of 50% RH. At this time, the sample was set in the device so that the measurement area was 50 cm ^2, and the value after 4 hours was adopted. The smaller the oxygen permeability value, the higher the oxygen barrier property.

[Effect of suppressing tearing trouble]
Assuming distribution of the wrap film after shipment and storage at home, the wrap film wound body immediately after production was stored for one month in a constant temperature bath set at 28 ° C. After that, in order to reproduce the vibration during distribution, a vibration tester (manufactured by IDEX Co., Ltd., product number "BF-50UT") is used to vibrate the wrap film winding body housed in the container (decorative box). I let you. The vibration test was performed as follows.

First, the films prepared in Examples and Comparative Examples are wound 20 m in width 220 mm in a paper tube having a length of 230 mm and an outer diameter of 36 mm in one rectangular parallelepiped container (inner dimensions of a cosmetic box; 42 mm × 42 mm × about 233 mm). Sixty winding body accommodating bodies containing one attached winding body were produced. It was housed in a corrugated cardboard box (inner dimensions 28 cm × 46 cm × 24 cm) so that there was no gap, and was fixed to the shaking table with a belt so that the longitudinal direction of the winding body was perpendicular to the shaking table. A vibration test was performed in an atmosphere of 23 ° C. and a relative humidity of 50% RH. The vibration test was carried out in the transport packaging mode for 20 minutes in a cycle in which the frequencies were changed in the order of 5 Hz, 30 Hz, and 5 Hz for 30 seconds. At that time, the amplitude was set so that the acceleration at 30 Hz was 3 G.

Then, a tear trouble evaluation was performed in an atmosphere of 23 ° C. and a relative humidity of 50% RH. As evaluators, 100 people who use wrap film for food packaging on a daily basis were selected. The evaluator carried out a series of operations of pulling out 50 cm of the film from the winding body having a width of about 23 cm housed in the container and then cutting the film with a tin film cutting blade attached to the dressing box 10 times each. That is, the occurrence rate of film tear trouble was derived from the number of times that the film was not pulled out smoothly due to tearing when the film was pulled out from the wound body out of 1000 times in total of 10 times by 100 people.

(Evaluation criteria for the effect of suppressing tearing trouble)
A: 0% or more and less than 10%: Very easy to use with almost no tearing trouble.
B: 10% or more and less than 15%: There are few tearing troubles and it is easy to use.
C: 15% or more: There are many tearing troubles and it is not easy to use.

[Maintaining the freshness of the contents]
After sealing the handle of one Ecuadorian banana with plastic wrap so that it would not come into contact with the outside air, the entire banana was wrapped in a single layer of plastic wrap to prevent it from coming into contact with the outside air. The packaged banana was placed in a constant temperature and humidity chamber having a temperature of 5 ° C. and a humidity of 50%, and the number of days until discoloration was evaluated.
(Evaluation criteria for maintaining freshness)
A: Discoloration over 10 days B: Discoloration in 7 to 10 days C: Discoloration in less than 7 days

[Feeling to the touch (smoothness)]
The texture (smoothness) of the wrap film was evaluated. As evaluators, 100 people who use wrap films for food packaging on a daily basis were selected and evaluated by the sensory evaluation of the evaluators. 10 points were given to each evaluator, 0 points were given to those who felt sticky, and 10 points were given to those who felt smooth, and the average score of 100 evaluators was calculated. This average score was used for evaluation. The evaluation environment was an atmosphere of 23 ° C. and a relative humidity of 50% RH.
[Evaluation criteria for texture (smoothness)]
A: 8 points or more: Very good level with no stickiness.
B: 3 points or more and less than 8 points: Good level with almost no stickiness.
C: Less than 3 points: Slightly sticky and slightly unpleasant level.

[Example 1]
Vinylidene chloride resin with a weight average molecular weight of 90,000 (vinylidene chloride repeating unit is 82 mol%, vinyl chloride repeating unit is 18 mol%) 96.0 parts by mass, tributyl acetylcitrate (Taoka Chemical Industry Co., Ltd.) 2.9 mass Parts, 1.1 parts by mass of epoxidized soybean oil (Newsizer 510R, Nippon Oil & Fats Co., Ltd.) were mixed with a Henshell mixer for 5 minutes. After mixing, it was aged for 24 hours or more to obtain a composition.

The obtained composition was supplied to a melt extruder to be melted, and melt-extruded from an annular die attached to the tip of the extruder to form a sock. At this time, the heating conditions of the extruder were adjusted so that the temperature of the molten resin at the slit outlet of the annular die was 170 ° C., and the mixture was extruded cyclically at an extrusion rate of 10 kg / hr.

After cooling this with a sock solution and a cold water tank, a parison was opened to form a bubble, and inflation stretching was performed. At this time, the MD direction was stretched 2.7 times and the TD direction was stretched 2.0 times to form a tubular film (bubble). The stretching temperature was 25 ° C.

After niping the obtained tubular film and folding it flat, the film is relaxed in the MD direction by controlling the speed ratio of the pinch roll and the take-up roll, and a double-ply film with a width of 280 mm is formed into two layers. I rolled it up. This film was slit to a width of 220 mm and rewound into a paper tube having an outer diameter of 92 mm while being peeled off into a single film. Then, a wound body of a wrap film was obtained by winding 20 m on a paper tube having an outer diameter of 36 mm and a length of 230 mm. Each evaluation was performed using the wound body of the obtained wrap film.

[Examples 2 to 4, Comparative Examples 1 to 3]
Wrapped bodies of the wrap films of Examples 2 to 4 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1 except that the conditions shown in Table 1 were changed. Each evaluation was performed using the wound body of the obtained wrap film.

※ ＡＴＢＣ：アセチルクエン酸トリブチル
ＤＡＬＧ：ジアセチルラウロイルグリセロール
ＥＳＯ ：エポキシ化大豆油

* ATBC: Tributyl acetyl citrate DALG: Diacetyl lauroyl glycerol ESO: Epoxy soybean oil

The wrap film of the present invention has industrial applicability as a wrap film used for food packaging, cooking, and the like.

1 ... Extruder, 2 ... Die, 3 ... Die mouth, 4 ... Sock (tubular composition), 5 ... Sock liquid (release agent for inflation molding), 6 ... Cold water tank, 7 ... 1st pinch roll, 8 ... Parison, 9 ... 2nd pinch roll, 10 ... Bubble, 11 ... 3rd pinch roll, 12 ... Double ply film, 13 ... Winding roll, 14 ... Cosmetic box, 15 ... Film cutting blade, 16 ... Winder, 17 … Wrap film

Claims (7)

A vinylidene chloride-based resin containing 72 to 93 mol% of vinylidene chloride repeating units,
Contains at least one compound selected from the group consisting of citrate esters, dibasic acid esters, and acetylated fatty acid glycerides.
The content of the compound is 0.5% by mass or more and less than 3% by mass with respect to the total amount of the wrap film.
The tensile elastic modulus in the MD direction is 250 to 570 MPa.
The low temperature crystallization start temperature measured by a temperature-modulated differential scanning calorimeter is 40 to 60 ° C.
Wrap film. The tear strength in the TD direction is 2.0 to 6.0 cN.
The wrap film according to claim 1. The thickness is 6-18 μm,
The wrap film according to claim 1 or 2. Contains epoxidized vegetable oil,
The content of the epoxidized vegetable oil is 0.5 to 3% by mass with respect to the total amount of the wrap film.
The wrap film according to any one of claims 1 to 3. Oxygen permeability at 23 ° C. is 110 cm ³ / m ² · day · atm or less.
The wrap film according to any one of claims 1 to 4. The ratio of high motility components measured by pulse NMR is 4.5% or less.
The wrap film according to any one of claims 1 to 5. The ratio of hypokinetic components measured by pulse NMR is 65.0% or less.
The wrap film according to any one of claims 1 to 6.

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