JP2022164221A - wrap film - Google Patents

Abstract

To provide a wrap film which prevents rice from adhering to the wrap film, for example, when a rice ball is cooked using the wrap film.SOLUTION: A wrap film contains a vinylidene chloride-based resin, wherein the vinylidene chloride-based resin contains 72 mol%-93 mol% of vinylidene chloride, with the contact angle of water to the surface of the wrap film being 70° or more and 120° or less.SELECTED DRAWING: None

Description

The present invention relates to wrap films.

Vinylidene chloride resins are excellent in properties such as transparency, water resistance and gas barrier properties, and are therefore used as food packaging materials such as wrap films. In recent years, food packaging materials are required to have not only the above properties, but also properties such as molding processability and thermal stability, and to have higher functionality. Examples of methods for making food packaging materials highly functional include a method of blending additives such as plasticizers and heat stabilizers. As such an additive, for example, an epoxidized vegetable oil is used to suppress color tone change of the wrap film (see, for example, Patent Documents 1 and 2).

WO2015/029594 JP 2014-15590 A

By the way, it is common practice to cook rice balls, such as rice balls and sushi, using wrap films. Specifically, for example, a cling film is spread, salt is sprinkled on it, rice and ingredients are placed on it, wrapped with cling film from all sides, and the cling film is gripped to cook rice balls. At this time, by using a wrap film, there is an advantage that it is sanitary because there is no direct contact with the rice ball. In addition, when a vinylidene chloride-based wrap film is used, it is hygienic because the heat resistance is high, and the polymer does not elute from the wrap film.

However, for example, when cooking rice, the sticky component of the rice oozes out to the outside, and when the sticky component dries, it tends to stick, and the moisture at the interface between the surface of the rice and the wrap film decreases. As a result, rice may stick to the cling film.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cling film that prevents cooked rice from sticking to the cling film when cooked rice is cooked using the cling film.

The present inventors have made intensive studies to solve the above problems. As a result, in the wrap film containing the vinylidene chloride resin, the amount of vinylidene chloride in the vinylidene chloride resin is set to a specific range, and the contact angle of water with respect to the surface of the wrap film is set to a specific range, thereby solving the above problems. I found that it can be done, and came to complete the present invention.

That is, the present invention is as follows.
[1]
Contains vinylidene chloride resin,
The vinylidene chloride-based resin contains 72 mol% to 93 mol% of vinylidene chloride,
The contact angle of water with respect to the surface of the wrap film is 70° or more and 120° or less.
wrap film.
[2]
The tensile modulus in the MD direction is 250 MPa to 600 MPa,
The wrap film according to [1].
[3]
The tear strength in the TD direction is 2 cN to 6 cN,
The wrap film according to [1] or [2].
[4]
The thickness is 6 μm to 18 μm,
The wrap film according to any one of [1] to [3].

According to the present invention, it is possible to provide a cling film that prevents cooked rice from sticking to the cling film when the cling film is used to cook rice balls.

It is a schematic diagram of an example of the manufacturing process of the wrap film of the present invention.

Hereinafter, an embodiment of the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to this, and various modifications are possible without departing from the gist thereof. is.

In this embodiment, the "TD direction" refers to the width direction of the resin in the film production line, and when used as a wrap film, refers to the direction perpendicular to the direction in which the wrap film is pulled out from the roll. The term "MD direction" refers to the direction in which the resin flows in the film production line, and refers to the direction in which the wrap film is pulled out from the roll when the wrap film is formed.

[wrap film]
The wrap film of the present embodiment contains a vinylidene chloride-based resin, the vinylidene chloride-based resin contains 72 mol % to 93 mol % of vinylidene chloride, and the contact angle of water with respect to the surface of the wrap film is 70° or more and 120° or less. is.

The wrap film of the present embodiment has a contact angle of water with respect to the surface of the wrap film of 70° or more and 120° or less. It has the effect of not sticking.
Although the mechanism by which this effect is produced is not clear, the present inventors presume as follows. The wrap film of the present embodiment has a contact angle of water with respect to the surface of the wrap film of 70° or more. It can be held in a thick hemispherical shape although it spreads to some extent, and the contact angle of the water is 120 ° or less, so that the held water approaches a spherical shape but remains in place. can be done. As a result, it is believed that the wrap film of the present embodiment prevents the cooked rice from sticking to the wrap film when, for example, rice balls are cooked using the wrap film.
From the same point of view, the wrap film of the present embodiment preferably has a contact angle of water with respect to the surface of the wrap film of 70° or more and 120° or less, more preferably 70° or more and 100° or less.
The method for adjusting the contact angle of water with respect to the surface of the wrap film to the above range is not particularly limited, but includes a method of appropriately adjusting the type and amount of additive to be contained in the wrap film.
In this embodiment, the contact angle of water with respect to the surface of the wrap film can be measured by the method described in Examples.

(vinylidene chloride resin)
The vinylidene chloride-based resin used in the present embodiment is not particularly limited as long as it contains 72 mol % to 93 mol % of vinylidene chloride, and examples thereof include vinylidene chloride copolymers containing vinylidene chloride and a polymerizable monomer. .

The monomer copolymerizable with vinylidene chloride is not particularly limited, but examples include vinyl chloride; acrylic acid esters such as methyl acrylate and butyl acrylate; methacrylic acid esters such as methyl methacrylate and butyl methacrylate; , methacrylic acid; acrylonitrile; vinyl acetate; These monomers may be used singly or in combination of two or more. Among these, vinyl chloride is more preferable.

The content of vinylidene chloride is 72 mol % to 93 mol %, preferably 75 mol % to 87 mol %, more preferably 79 mol % to 85 mol %, relative to the total amount of the vinylidene chloride resin. When the content of vinylidene chloride is 72 mol % or more, the glass transition temperature of the vinylidene chloride resin tends to be low and the wrap film tends to be soft. As a result, tearing of the wrap film can be reduced even when used in a low-temperature environment such as in winter. On the other hand, when the vinylidene chloride content is 93 mol % or less, a significant increase in crystallinity is suppressed, and there is a tendency to suppress deterioration of moldability during film stretching.

The method for measuring the content of vinylidene chloride is not particularly limited, but for example, it can be measured using a high-resolution proton nuclear magnetic resonance spectrometer (400 MHz or higher). More specifically, 0.5 g of the wrap film is dissolved in 10 mL of THF (tetrahydrofuran), about 30 mL of methanol is added to precipitate the resin content, and then the precipitate is separated by centrifugation, vacuum dried, and vinylidene chloride-based Obtain a sample of the resin for measurement. Then, after dissolving the obtained sample for measurement in deuterated tetrahydrofuran so as to have a concentration of 5% by mass, this solution is subjected to H-NMR measurement at a measurement ambient temperature of about 27°C. The vinylidene chloride content is calculated using the characteristic chemical shift relative to tetramethylsilane in the resulting spectrum. For example, for a copolymer of vinylidene chloride and vinyl chloride, peaks at 3.50 to 4.20 ppm, 2.80 to 3.50 ppm and 2.00 to 2.80 ppm are used for calculation.

In the vinylidene chloride-based resin, the content of monomers polymerizable with vinylidene chloride is preferably 7 to 28 mol%, more preferably 13 to 25 mol%, and still more preferably 15 to 21 mol%. . By keeping the content of the vinylidene chloride and polymerizable monomer within the above range, tearing of the wrap film is reduced even when used in a low temperature environment, and the deterioration of moldability during film stretching is further suppressed. tend to be

The weight average molecular weight (Mw) of the vinylidene chloride resin is preferably 50,000 to 250,000, more preferably 60,000 to 230,000, still more preferably 80,000 to 200,000. . When the weight average molecular weight (Mw) of the vinylidene chloride resin is within the above range, the mechanical strength of the wrap film tends to be further improved. A vinylidene chloride resin having a weight average molecular weight within the above range can be obtained, for example, by controlling the charging ratio of vinylidene chloride monomer and vinyl chloride monomer, the amount of polymerization initiator, or the polymerization temperature. In the present 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 79% by mass to 96% by mass with respect to the total amount of the wrap film. When the content of the vinylidene chloride-based resin is within the above range, the plasticizing effect of the additive or the like reduces the share of melt extrusion, so that the generation of foreign matter tends to be further suppressed. In addition, when the content of the vinylidene chloride resin is within the above range, it is possible to suppress the film from becoming easily stretched, and the cuttability of the film tends to be further improved. The method for measuring the content of each component from the wrap film differs depending on the object to be analyzed. For example, the content of the vinylidene chloride resin is obtained by dissolving 0.5 g of a sample in 10 mL of THF (tetrahydrofuran), adding about 30 mL of methanol to precipitate the resin content, and then centrifuging to separate and dry the precipitate. It can be obtained by weight measurement.

(Additive)
The wrap film of the present embodiment may contain various additives in addition to the vinylidene chloride resin described above. As described above, for example, by appropriately adjusting various additives, the contact angle of water on the surface of the wrap film can be 70 ° or more and 120 ° or less, or the vinylidene chloride resin is plasticized and molded. The processability is further improved, and the feeling of touch is further improved.
Various additives will be described in detail below.

(Long-chain alkyl ester of stearic acid)
The wrap film of the present embodiment may contain stearic acid long-chain alkyl ester as an additive. Since the wrap film of the present embodiment contains a stearic acid long-chain alkyl ester as an additive, the contact angle of water with respect to the surface of the wrap film tends to be 70° or more and 120° or less. Although the reason for this is not clear, it is believed that the carbonyl group of the stearic acid long-chain alkyl ester exhibits moderate compatibility with water and the long-chain alkyl moiety has a water-repellent effect.

Although the stearic acid long-chain alkyl ester is not particularly limited, saturated alkyl groups or unsaturated alkyl groups having 4 or more alkyl groups are preferable. Pentyl stearate, hexyl stearate, octyl stearate and the like.

The content of the stearic acid long-chain alkyl ester is preferably more than 1% by mass and 10% by mass or less with respect to the total amount of the wrap film. When the content of the stearic acid long-chain alkyl ester is within the above range, the desired contact angle of water can be obtained by bleeding and spreading on the surface of the wrap film. In addition, the vinylidene chloride resin is plasticized, which tends to further improve moldability and feel to the touch.

(Oleic acid long-chain alkyl ester)
The wrap film of the present embodiment may contain an oleic acid long-chain alkyl ester as an additive. Since the wrap film of the present embodiment contains an oleic acid long-chain alkyl ester as an additive, the contact angle of water with respect to the surface of the wrap film tends to be 70° or more and 120° or less. Although the reason for this is not clear, it is believed that the carbonyl group of the oleic acid long-chain alkyl ester exhibits moderate compatibility with water and the long-chain alkyl moiety has a water-repellent effect.

Although the long-chain alkyl ester of oleic acid is not particularly limited, saturated alkyl groups or unsaturated alkyl groups having 4 or more alkyl groups are preferable. pentyl, hexyl oleate, octyl oleate and the like.

The content of the oleic acid long-chain alkyl ester is preferably more than 1% by mass and 10% by mass or less with respect to the total amount of the wrap film. When the content of the oleic acid long-chain alkyl ester is within the above range, the desired contact angle of water can be obtained by bleeding and spreading on the surface of the wrap film. In addition, the vinylidene chloride resin is plasticized, which tends to further improve moldability and feel to the touch.

(monoacetylated fatty acid ester)
The wrap film of the present embodiment may contain a monoacetylated fatty acid ester as an additive. Since the wrap film of the present embodiment contains a monoacetylated fatty acid ester as an additive, the contact angle of water with respect to the surface of the wrap film tends to be 70° or more and 120° or less. Although the reason for this is not clear, it is believed that the two carbonyl groups of the monoacetylated fatty acid ester exhibit moderate compatibility with water, and the long-chain alkyl portion of the fatty acid has a water-repellent effect.

Although the monoacetylated fatty acid ester is not particularly limited, O-acetylhydroxy fatty acid ester is preferred. Examples of O-acetylhydroxy fatty acid esters include, but are not limited to, ethyl acetyllactate, butyl acetyllactate, ethyl acetylhydroxybutyrate, methyl acetylricinoleate, and butyl acetylricinoleate.

The content of the monoacetylated fatty acid ester is preferably more than 1% by mass and 10% by mass or less with respect to the total amount of the wrap film. When the content of the monoacetylated fatty acid ester is within the above range, the desired contact angle of water can be obtained by bleeding and spreading on the surface of the wrap film. In addition, the vinylidene chloride resin is plasticized, which tends to further improve moldability and feel to the touch.

(Hydrogenated rosin derivative)
The wrap film of the present embodiment may contain a monoacetylated fatty acid ester as an additive. Since the wrap film of the present embodiment contains a hydrogenated rosin derivative as an additive, the contact angle of water with respect to the surface of the wrap film tends to be 70° or more and 120° or less. Although the reason for this is not clear, it is believed that the carbonyl group of the hydrogenated rosin derivative exhibits moderate compatibility with water, and the six-membered ring structure portion of the rosin has a water-repellent effect.

Examples of hydrogenated rosin derivatives include, but are not limited to, hydrogenated rosin, hydrogenated glyceryl rosinate, hydrogenated pentaerythrityl rosinate, hydrogenated methyl rosinate, (hydrogenated rosin/diisostearate)glyceryl, and trihydrogen. Added glyceryl rosinate, (hydroxystearic acid/stearic acid/rosin acid) pentaerythrityl, and partially hydrogenated methyl rosinate. Among these, hydrogenated methyl rosinate is preferred.

The content of the hydrogenated rosin derivative is preferably more than 1% by mass and 10% by mass or less with respect to the total amount of the wrap film. When the content of the hydrogenated rosin derivative is within the above range, the desired contact angle of water can be obtained by bleeding and spreading on the surface of the wrap film. In addition, the vinylidene chloride resin is plasticized, which tends to further improve moldability and feel to the touch.

(fatty acid diester of triethylene glycol)
The wrap film of the present embodiment may contain a monoacetylated fatty acid ester as an additive. Since the wrap film of the present embodiment contains the fatty acid diester of triethylene glycol as an additive, the contact angle of water with respect to the surface of the wrap film tends to be 70° or more and 120° or less. Although the reason is not clear, it is considered that the triethylene glycol portion of the fatty acid diester of triethylene glycol exhibits compatibility with water, and the long-chain alkyl portion of the fatty acid ester has a water-repellent effect.

Fatty acid diesters of triethylene glycol include, but are not particularly limited to, triethylene glycol dicaprylate, triethylene dicaprate, triethylene glycol distearate, and the like. Among these, triethylene glycol dicaprylate and triethylene dicaprate are preferred.

The content of the fatty acid diester of triethylene glycol is preferably more than 1% by mass and 10% by mass or less with respect to the total amount of the wrap film. When the content of the fatty acid diester of triethylene glycol is within the above range, the desired contact angle of water can be obtained by bleeding and spreading on the surface of the wrap film. In addition, the vinylidene chloride resin is plasticized, which tends to further improve moldability and feel to the touch.

(Other additives)
The wrap film of the present embodiment can contain at least one compound selected from the group consisting of citric acid esters, dibasic acid esters, and acetylated fatty acid glycerides. Citric acid esters are preferred from the standpoint of handleability, and acetyl tributyl citrate is particularly preferred.

(Citrate ester)
Citric acid esters include, but are not limited to, triethyl citrate, tributyl citrate, acetyl triethyl citrate, acetyl tributyl citrate (ATBC), and acetyl tri-n-(2-ethylhexyl) citrate.

Among these, acetyl tributyl citrate is preferred. By using such a citric acid ester, the vinylidene chloride resin is plasticized, the moldability is further improved, and by imparting flexibility to the wrap film, adhesion is improved, and the feeling of touch is improved. tend to improve.

(dibasic acid ester)
The dibasic acid ester is not particularly limited, but examples thereof include dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, and dioctyl adipate; di-2-ethylhexyl azelate; , azelate such as octyl azelate; sebacate such as dibutyl sebacate (DBS) and di-2-ethylhexyl sebacate; phthalate such as dimethyl phthalate, diethyl phthalate and dioctyl phthalate.

Among these, aliphatic dibasic acid esters are preferred, and dibutyl sebacate is more preferred. By using such a dibasic acid ester, the vinylidene chloride resin is plasticized, the moldability is further improved, and by imparting flexibility to the wrap film, the adhesion is improved, and the touch feeling is improved. tend to improve.

(acetylated fatty acid glyceride)
Acetylated fatty acid glycerides include, but are not limited to, acetylated caprylic glyceride, acetylated capric glyceride, acetylated lauric glyceride, acetylated myristate glyceride, acetylated palm kernel oil glyceride, and acetylated coconut oil glyceride. , acetylated castor oil glycerides, and acetylated hydrogenated castor oil glycerides.

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. Among these, acetylated lauric acid glyceride is preferable, and acetylated diglyceride of lauric acid is more preferable. By using such an acetylated fatty acid glyceride, flexibility is imparted to the wrap film, which tends to improve adhesion and further improve touch feeling.

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

The total content of at least one compound selected from the group consisting of citric acid esters, dibasic acid esters, and acetylated fatty acid glycerides imparts superior molding processability to the total amount of the wrap film, and additives From the viewpoint of preventing excessive adhesion of the wrap film when the content is high, it is preferably 3% by mass to 8% by mass, more preferably 3.5% by mass to 7% by mass. In particular, when the vinylidene chloride resin wrap film contains 3% by mass or more of citric acid ester or dibasic acid ester, the mobility of the molecular chains of the vinylidene chloride resin becomes high, so that the formation and growth of microcrystals occur. Rearrangement is likely to occur, physical deterioration is likely to occur when exposed to high temperatures, and the film tends to stretch, making it difficult for the cutting blade to bite into the film, which tends to reduce cuttability. The effect of the configuration is remarkable.

(epoxidized vegetable oil)
The wrap film of this embodiment may contain epoxidized vegetable oil. Epoxidized vegetable oils can act as stabilizers for vinylidene chloride-based resin extrusion processing. Epoxidized vegetable oils are not particularly limited, but generally include those produced by epoxidizing edible fats and oils. Specifically, epoxidized vegetable oils include, for example, epoxidized soybean oil (ESO) and epoxidized linseed oil. Among 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 case tends to be further improved.

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

Specifically, 50 mg of a sample is weighed, dissolved in a deuterated solvent (solvent: deuterated tetrahydrofuran, internal standard: dimethyl terephthalate, volume: 0.7 mL), and measured by 400 MHz proton NMR (number of integrations: 512 times), The ratio of the integral value of 2.23 to 2.33 ppm to the integral value of 8.05 to 8.11 ppm is defined as the integral ratio, and the quantitative value is calculated by the absolute calibration curve method.
Integral ratio = integral value (2.23 to 2.33 ppm) / integral value (8.05 to 8.11 ppm)

The wrap film of the present embodiment may contain additives other than those described above. Examples of such additives include, but are not limited to, 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 agents, oligomers such as polyester, and polymers such as methyl methacrylate-butadiene-styrene copolymer (MBS).

Stabilizers other than epoxidized vegetable oils are not particularly limited, but specific examples include 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) propionate and 4,4′-thiobis-(6-t-butylphenol); laurate, myristate, palmitate, stearate, isostearate, oleate, ricinol 2-ethyl-hexylate, isodecanoate, neodecanoate, and calcium benzoate. A stabilizer may be used individually by 1 type, and may be used in combination of 2 or more types.

The weather resistance improver is not particularly limited, but specific examples include ethylene-2-cyano-3,3'-diphenyl acrylate, 2-(2'-hydroxy-5'-methylphenyl)benzolitriazole, 2 -(2'-Hydroxy-3'-t-butyl-5'-methylphenyl)5-chlorobenzotriazole, 2-hydroxy-4-methoxybenzophenone, and 2,2'-dihydroxy-4-methoxybenzophenone, and the like. be done. The weather resistance improvers may be used singly or in combination of two or more.

Colorants such as dyes or pigments are not particularly limited, but specific examples include carbon black, phthalocyanine, quinacridone, indoline, azo pigments, and red iron oxide. Colorants may be used singly or in combination of two or more.

Antifog agents are not particularly limited, but specific examples include glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene fatty acid alcohol ethers, polyoxyethylene glycerin fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. The antifogging agents may be used singly or in combination of two or more.

The antibacterial agent is not particularly limited, but specific examples thereof include silver-based inorganic antibacterial agents and the like. The antibacterial agents may be used singly or in combination of two or more.

Lubricants are not particularly limited, but specific examples include fatty acid hydrocarbon lubricants such as ethylene bissteramide, butyl stearate, polyethylene wax, paraffin wax, carnauba wax, myristyl myristate and stearyl stearate, and higher fatty acid lubricants. , fatty acid amide lubricants, and fatty acid ester lubricants. Lubricants may be used singly or in combination of two or more.

The nucleating agent is not particularly limited, but specific examples thereof include phosphate ester metal salts and the like. Nucleating agents may be used singly or in combination of two or more.

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

More specifically, when the thickness of the wrap film is 6 μm or more, the tear strength of the wrap film in the TD and MD directions is further improved, and the film tends to be more suppressed during use. Further, when the thickness of the wrap film is 6 μm or more, there is a tendency that the tear strength is less likely to decrease significantly. Therefore, when pulling out the wrap film from the roll and when picking up the end of the film rewound in the cosmetic box, the trouble of tearing the wrap film at the edge cut by the cutting blade attached to the cosmetic box is more likely. Suppressed.

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

(Tear strength)
The tear strength in the TD direction of the wrap film of the present embodiment is preferably 2.0 cN to 6.0 cN, more preferably 2.0 cN to 4.0 cN, still more preferably 2.2 cN to 3.0 cN. be. When the tear strength in the TD direction is 2.0 cN or more, tearing when pulling out the wrap film from the roll can be reduced, and unintended tear troubles when using the wrap film can be suppressed. On the other hand, when the tear strength in the TD direction is 6.0 cN or less, the film is easily torn when cut in the TD direction with a cutting blade attached to the cosmetic box, and the cutability is improved.

The tear strength in the TD direction of the wrap film of the present embodiment can be adjusted by the composition of the vinylidene chloride resin, the composition of the additive, the draw ratio of the film, the draw speed, 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. By making it thinner, it tends to decrease. The tear strength is measured by the method described in Examples.

(tensile modulus)
The MD tensile modulus of the wrap film of the present embodiment is preferably 250 MPa to 600 MPa, more preferably 300 MPa to 500 MPa, and still more preferably 350 MPa to 500 MPa. When the tensile modulus in the MD direction is 250 MPa or more, when a force is applied to cut the film with a cutting blade, the film can be prevented from stretching in the MD direction, and the cutting blade can easily bite into the film, resulting in cutability. improves. On the other hand, when the tensile modulus in the MD direction is 600 MPa or less, the film tends to be soft, the film can be cut cleanly along the shape of the cutting blade, and the occurrence of many cracks on the cut end surface can be suppressed. As a result, when pulling out the film from the roll and picking up the end of the film rewound in the cosmetic case, it tends to be possible to prevent the film from tearing from the cut end surface.

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

[Method for producing wrap film]
The method for producing the wrap film of the present embodiment is not particularly limited. and stretching the resulting film in the MD and TD directions. A detailed description will be given below.

(Mixing process)
FIG. 1 shows a schematic diagram of an example of the manufacturing process of the wrap film. First, a mixer is used to mix a vinylidene chloride resin and various additives to obtain a composition. At this time, various additives may be mixed as necessary. Although the mixer is not particularly limited, for example, a ribbon blender, a Henschel mixer, or the like can be used. The resulting composition is preferably aged for about 1 to 30 hours before use in the next step.

(Melt extrusion process)
The resulting composition is then melted by extruder 1 and a tubular film is extruded from die mouth 3 of die 2 to form sock 4 (also called pile).

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

(Stretching process)
Subsequently, by injecting air into the inside of the parison 8, the parison 8 is opened and an annular film is formed. At this time, the sock liquid 5 applied to the inner surface of the sock 4 works as an opening agent for the parison 8 . The parison 8 is then reheated with hot water to a temperature suitable for stretching while it is open. Hot water adhering to the outside of the parison 8 is squeezed out by the second pinch rolls 9 .

Air is injected into the inside of the parison 8 heated to the appropriate temperature as described above to form the bubble 10 . The air spreads the parison from the inside, stretching the film and obtaining a stretched film. The stretching of the film in the TD direction is mainly performed by the amount of air, and the stretching of the film in the MD direction is performed by applying tension in the film flow direction using the second pinch roll 9 and the third pinch roll 11, etc. done.

The process from the first pinch roll 7 to the third pinch roll 11 is called a stretching process. Since the stretchability of the parison 8 is improved when the stretching speed is slowed down, in the conventional wrap film manufacturing method, the stretching speed in the MD direction is adjusted to 0.08 times/second or less, and the stretching speed in the TD direction is adjusted to 3.0 times/second. It was adjusted to 0 times/second or less. In contrast, in the method for producing a wrap film of the present embodiment, it is preferable to adjust the draw ratio in the MD direction and the TD direction and the drawing speed in the MD direction and the TD direction within a predetermined range.

Specifically, the draw ratios in the MD direction and the TD direction in the drawing step used in the present embodiment are each independently preferably 4 times to 6 times, more preferably 4.1 times to 5.6 times. is. Here, the stretch ratio in the MD direction refers to the stretch ratio in which the parison 8 is stretched in the MD direction. For example, in FIG. can be calculated. The draw ratio in the TD direction refers to the draw ratio of the parison 8 stretched in the TD direction. For example, in FIG. can be done. The draw ratio in the MD direction can be adjusted, for example, by the rotation speed ratio of the first pinch roll 7 and the third pinch roll 11, and the draw ratio in the TD direction can be adjusted, for example, by the drawing temperature of the parison 8 and the size of the bubble 10. can be adjusted by

Further, the stretching speed in the MD direction in the stretching step of the present embodiment is preferably 0.09 times/second to 0.12 times/second. The average stretching speed in the MD direction refers to the stretching ratio in the MD direction with respect to the time the parison passes between the first pinch roll 7 and the third pinch roll 11. For example, in FIG. 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, for example, by 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 .

Furthermore, the drawing speed in the TD direction in the drawing step of the present embodiment is preferably 3.1 times/second to 4.0 times/second. 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. It can be calculated from the time required for stretching in the TD calculated from the stretching length and the rotational speed of the third pinch roll 11 and the stretching ratio in the TD. The stretching speed in the TD direction can be adjusted, for example, by the rotation speed of the third pinch rolls 11 .

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

After the stretching process, the stretched film is folded by the third pinch rolls 11 to form a double-ply film 12 . The double-ply film 12 is taken up by the take-up roll 13 .

(relaxation process)
In the method for producing a wrap film of the present embodiment, it is preferable to include a relaxation step of relaxing the wrap film immediately after being stretched. A relatively common relaxation method used in the production of wrap films is to relax the film using heat from an infrared heater or the like after stretching. However, in this embodiment, 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 instead of the relaxation step. This is because, in the present embodiment, when the conventional relaxation method using heat is used, the heat causes the formation and growth of crystallites that cause film tearing.

The relaxation ratio in the relaxation step using the third pinch roll 11 and 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 wrinkles due to the slackness of the film between the third pinch roll 11 and the take-up roll 13 tends to be more suppressed. Further, when the relaxation ratio is 7% or more, the wrap film can be sufficiently relaxed, and rearrangement of molecular chains can occur even when exposed to high temperatures. Moreover, this tends to reduce tear troubles. Here, the “relaxation ratio” refers to the ratio of shrinkage of the double-ply film 12 between the third pinch roll 11 and the take-up roll 13. For example, in the case of FIG. It can be calculated using the ratio of the take-up roll 13 .

Also, the ambient temperature in the relaxation step using the third pinch roll 11 and the take-up roll 13 is preferably 25°C 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 up as described above is slit, rolled up while being peeled off so as to form one wrap film, and temporarily stored in the state of the original film for 1 to 3 days. Finally, the raw film is rewound on a paper tube and packed in a cosmetic box to obtain a wrap film roll housed in the cosmetic box.

(Storage process)
In the method of manufacturing the wrap film of the present embodiment, after slitting the wrap film, a storage step of storing the original sheet may be performed. The storage temperature is preferably 19°C or less, more preferably 5°C to 19°C, still more preferably 5°C to 15°C. The storage time is preferably 20 hours to 50 hours, more preferably 24 hours to 40 hours.

Hereinafter, the present invention will be described more specifically using examples and comparative examples. The present invention is by no means limited by the following examples.

[Content of vinylidene chloride]
The content (ratio) of vinylidene chloride in the polyvinylidene chloride resin in the wrap film was obtained from the content of vinylidene chloride repeating units measured using a high-resolution proton nuclear magnetic resonance spectrometer. Dissolve 0.5 g of wrap film in 10 mL of THF (tetrahydrofuran), add about 30 mL of methanol to precipitate the resin content, separate the precipitate by centrifugation, vacuum dry, and prepare a sample for measurement of vinylidene chloride resin. Obtained. Then, H-NMR measurement was performed on a solution obtained by dissolving the obtained sample for measurement in deuterated tetrahydrofuran so as to have a concentration of 5% by mass at a measurement ambient temperature of about 27°C. For example, for copolymers of vinylidene chloride (VDC) and vinyl chloride (VC), 3.50 to 4.20 ppm, 2.80 to 3.50 ppm, 2.80 to 3.50 ppm of the copolymer based on tetramethylsilane. Using the peak of 00 to 2.80 ppm, the content of repeating units of vinylidene chloride was calculated, and the calculated value was defined as the content of vinylidene chloride. For other copolymers as well, the content of repeating units can be calculated using the peak for each monomer.

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

[Tear strength]
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 measurement of the wrap film was performed using only one wrap film. The sample length in the tear direction was 63.5 mm and the sample width was 50.0 mm. During the measurement, the pendulum was lifted and stopped, then the test piece was carefully attached to the gripper, and the clamp was tightly tightened so that the slit was placed in the center of the film width. The film was then slit with a knife attached to the apparatus. 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 making the slit, the pendulum was carefully released and the value of the force required to tear the specimen was read. The read value was taken as the tear strength in the TD direction. Tests in which the tear line deviated more than 10 mm from the extension of the slit were excluded, and additional specimens were tested instead. In addition, the measurement results were rounded off to the second decimal place. The sample was changed and measured 5 times in total, and the average value of 5 times was used as the measured value.

[Tensile modulus]
Autograph AG-IS (manufactured by Shimadzu Corporation) was used to measure the tensile modulus of the wrap film, and evaluation was performed in an atmosphere of 23° C. and 50% RH. Measure the load at 2% elongation 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. It was measured. At the time of measurement, the gripper was attached so that the MD direction of the test piece coincided with the axis of the testing machine. The specimen was evenly clamped with grips to prevent slippage and to keep the grips from shifting during the test. Also, the pressure between the grips should not cause cracking or rolling of the specimen. In addition, the measurement results were rounded off to the third digit with two significant digits.

[Contact angle]
A droplet of 2.0 μL of pure water is dropped on the surface of the test film attached to the preparation, and one second after the droplet is applied, the straight line connecting the left and right end points and the apex of the dropped droplet is contacted from the angle with respect to the test film surface. The contact angle of water on the surface of the wrap film was determined using a method of measuring according to the θ/2 method for calculating the angle. A contact angle meter DM 701 manufactured by Kyowa Interface Science Co., Ltd. was used as a measuring device for the contact angle of water, and evaluation was performed in an atmosphere of 23° C. and 50% RH. The sample was changed and measured 5 times in total, and the average value of 5 times was used as the measured value.

[Touch feeling (smooth feeling)]
An evaluation of the feeling of touch (smoothness) of the wrap film was carried out. As evaluators, 100 people who use wrap films for food packaging on a daily basis were selected, and evaluation was performed by sensory evaluation by the evaluators. 10 points were given to each evaluator, and 0 points were given for feeling sticky and 10 points were given for feeling 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 touch feeling (smooth feeling)]
⊚: 8 points or more: A very good level of smoothness without stickiness at all.
○: 3 points or more and less than 8 points: Good level with almost no stickiness.
x: Less than 3 points: Slightly sticky and somewhat unpleasant level.

[Amount of rice adhered]
Take out the freshly cooked rice in a tray, and when the heat is removed, weigh 100 g on a wrap film about 22 cm wide and 30 cm long. . After leaving the finished rice ball in a room at 23° C. for 3 hours, the cling film was opened and the state of adhesion of rice grains was evaluated according to the following criteria.
[Rice adhesion evaluation criteria]
⊚: Rice grains are not adhered at all.
○: The number of attached rice grains is 10 grains or less.
x: More than 10 rice grains adhered.

[Example 1]
A vinylidene chloride resin having a weight average molecular weight of 90,000 (82 mol% of vinylidene chloride repeating units and 18 mol% of vinyl chloride repeating units) was added with 5.5% by mass of acetyl tributyl citrate (Taoka Chemical Co., Ltd.) and epoxidized. 1.1% by mass of soybean oil (Newsizer 510R, NOF Corporation) and 1.0% by mass of n-butyl stearate (Excepar BS, manufactured by Kao Corporation) were mixed for 5 minutes in a Henschel mixer. After mixing, the mixture was aged for 24 hours or more to obtain a composition.

The resulting composition was fed to a melt extruder, melted, and melt extruded through 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 resin was annularly extruded at an extrusion speed of 10 kg/hour.

After cooling this with a sock liquid and a cold water bath, the parison was opened to form bubbles and subjected to inflation stretching under the stretching conditions shown in Table 1. At this time, the film was stretched 4.1 times in the MD direction and 5.6 times in the TD direction to form a tubular film (bubble). The stretching temperature was 35°C.

After the obtained tubular film is nipped and folded flat, the film is relaxed in the MD direction (relaxation ratio 10%) by controlling the speed ratio between the pinch roll and the take-up roll, and the double-ply film has a width of 280 mm. A two-ply film was wound up. This film was slit to a width of 220 mm, peeled off into one film, and rewound on a paper tube having an outer diameter of 92 mm. After that, by winding 20 m around a paper tube having an outer diameter of 36 mm and a length of 230 mm, a wound body of wrap film (thickness: 11 μm) was obtained. The wrap film roll thus obtained was stored at 15° C. for 30 hours, and was evaluated by the methods described above. Table 2 shows the evaluation results.

[Examples 2 to 8 and Comparative Examples 1 to 3]
A wrap film roll was prepared in the same manner as in Example 1 except that the type and amount of the additive was changed as shown in Table 1, and each evaluation was performed by the above methods. Table 2 shows the evaluation results.

INDUSTRIAL APPLICABILITY The wrap film of the present invention can be effectively used for food packaging and the like because the wrapped rice does not stick to the wrap film when cooked rice is cooked using the wrap film.

Reference Signs List 1 extruder 2 die 3 die mouth 4 tubular vinylidene chloride copolymer composition 5 sock liquid (releasing agent for inflation molding)
6 cold water tank 7 first pinch roll 8 parison 9 second pinch roll 10 bubble 11 third pinch roll 12 double ply film 13 winding roll

Claims (4)

Contains vinylidene chloride resin,
The vinylidene chloride-based resin contains 72 mol% to 93 mol% of vinylidene chloride,
The contact angle of water with respect to the surface of the wrap film is 70° or more and 120° or less.
wrap film. The tensile modulus in the MD direction is 250 MPa to 600 MPa,
The wrap film according to claim 1. The tear strength in the TD direction is 2 cN to 6 cN,
The wrap film according to claim 1 or 2. The thickness is 6 μm to 18 μm,
The wrap film according to any one of claims 1 to 3.

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