TWI707765B - Fresh-keeping film and wrap-around body - Google Patents

Abstract

The present invention provides a cling film, which has good adhesion when used, has a sense of tension and toughness, transparency, anti-longitudinal cracking effect and anti-rolling effect. It is not easy to crack even after being heated under high temperature (such as a microwave oven). The rate of cracking when rolled is low, and the oxygen and water barrier properties are excellent. The fresh-keeping film of the present invention has a tensile strength of 100 MPa or more perpendicular to the direction of travel (TD), a tensile elongation of 100% or less, a tensile modulus of 280 MPa or more, and a tensile strength of the direction of travel (MD) The modulus of elasticity is 380 MPa or more, preferably the long crystal period is 12.5 nm or less.

Description

Fresh-keeping film and wrap-around body

The invention relates to a cling film and a cling film roll body using the cling film.

Previously, cling film was used in more ordinary households because of its excellent properties such as its adhesion to each other or to the adherend, gas barrier properties to gases such as water vapor or oxygen, and cutting properties when placed in a packaging box. Used as plastic wrap for food etc. The household cling film is mainly used for the preservation of food in refrigerators or freezers, or the use of microwave ovens to heat food in containers.

Among the products currently on the market as the household cling film, the one that has received the best evaluation for ease of use is a film mainly composed of polyvinylidene chloride resin. On the other hand, in addition to this, there are also commercially available films with polyethylene resins, polypropylene resins, polyvinyl chloride resins, or poly-4-methylpentene-1 resins as the main component, and they are not as good as poly The adhesiveness of vinylidene chloride-based resin cling film is the poorer of the cling film, and the cling film made of vinylidene chloride is widely used.

For example, Patent Documents 1 and 2 disclose technologies related to the characteristic of easy cutting in the width direction in addition to the characteristic that the film is not easily broken in the longitudinal direction in the traveling direction.

In addition, Patent Document 3 discloses a technique for improving the adhesion or the oxygen and water vapor barrier properties when metal or metal oxide is vapor-deposited by the fibril structure of the surface. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5501792 [Patent Document 2] International Publication No. 2016/189987 Specification [Patent Document 3] Japanese Patent Laid-Open No. 11-077824

[The problem to be solved by the invention]

The suitability of cling film for household use requires a sense of tension and toughness along with transparency and cutting properties. In addition, it is also required to have the stability of melting perforation and large deformation or fusion to the container or less deterioration of itself during heating and cooking using a microwave oven, etc., and in order to prevent freshness from being peeled off the plastic wrap after heating and cooking When the film breaks and the fragments of the cling film are mixed into the food, the strength of the cling film after heating is also required. Furthermore, the adhesiveness of the cling film to each other and the container during wrapping is required. In addition, at the same time as the adhesiveness, consumers also strongly demand that the wound cling film in the packaging box is pulled out of the box as the opposite characteristic. Good pullability in time. Furthermore, the household cling film is supposed to be used by consumers, and is rolled from the original sheet state of more than 1000 m to a paper tube to a roll length of about tens of meters. In the rewinding (rewinding) step to a paper tube or the like, if the film strength is insufficient, the film may be broken and the film may not be transported, which may reduce production efficiency.

However, Patent Documents 1 to 3 are unable to achieve both the longitudinal crack suppression effect at the time of cutting, the rewinding suppression effect, the oxygen and water barrier properties, the crack suppression effect after heating to a high temperature, and the rewinding to the paper tube. A cling film with crack suppression effect, adhesion, tension and toughness, and transparency.

The present invention is a novel cling film with better adaptability, which is to provide a kind of good adhesion when used, with tension and toughness, transparency, anti-longitudinal cracking effect and anti-rolling effect, and it is heated at high temperature (such as microwave oven) It is not easy to rupture afterwards, the occurrence of rupture during rewinding is low, and the cling film has excellent oxygen and water barrier properties. [Technical means to solve the problem]

The inventors of the present invention have a strong sense of tension and toughness, transparency, anti-longitudinal cracking effect and anti-rolling effect. It is not easy to crack after heating at high temperature (such as microwave oven), and cracking occurs during rewinding. Diligent research was conducted on the viewpoint that the oxygen and water barrier properties are low and the oxygen and water barrier properties are excellent. As a result, it was found that the above problems can be solved by having a specific range of tensile strength, tensile elongation, and tensile modulus of elasticity. It maintains sufficient breaking strength during stretching in the TD direction and suppresses the effect of breaking during rewinding, thus completing the present invention. That is, the present invention relates to the following. (1) A kind of cling film whose tensile strength in the direction perpendicular to the direction of travel (TD) is more than 100 MPa, the tensile elongation is less than 100%, the tensile modulus of elasticity is more than 280 MPa, and the direction of travel ( MD) has a tensile modulus of 380 MPa or more. (2) The cling film mentioned in (1) above, the long period of crystallization is 12.5 nm or less. (3) As for the cling film (1) or (2) above, regarding the heat shrinkage rate at 120℃ measured in accordance with ASTM D-2732, the heat shrinkage rate in the direction of travel (MD) is 4-30%, the direction of travel The ratio (MD/TD) of the thermal shrinkage rate (MD) to the thermal shrinkage rate in the direction (TD) perpendicular to the direction of travel (MD/TD) is 2 or less. (4) The fresh-keeping film of any one of (1) to (3) above, which has a network structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the network of the network structure is composed of fibrils Structure, and in the above-mentioned network structure, the average width of the observed fibrils is 145 nm or less. (5) The cling film described in any one of (1) to (4) above has an oxygen permeability of 110 cm ³ /m ² ·day·atm (at 23°C) or less, and a water vapor permeability of 20 g/ m ² ·day (at 38°C, 90%RH) or less. (6) The cling film as in any one of (1) to (5) above, with a thickness of 5-15 μm. (7) The cling film as described in any one of (1) to (6) above, which contains a copolymer containing 85-97% by mass of vinylidene chloride monomer and 15-3% by mass of vinyl chloride monomer. (8) A method of manufacturing the cling film as described in any one of (1) to (7) above, which includes the step of extending the unstretched sheet in the traveling direction and the direction perpendicular to the traveling direction, The magnification is 4.0 or less, and the stretch magnification in the direction perpendicular to the traveling direction is 5.8 or more. (9) A wound body, which is formed by winding the cling film of any one of (1) to (7) above on a roll core. [Effects of Invention]

According to the present invention, it is possible to provide a cling film, which is a novel cling film with better applicability and good adhesion during use, has a sense of tension and toughness, transparency, anti-vertical cracking effect, and anti-rolling effect. It is suitable for use in microwave ovens. It is not easy to break even after heating, the rate of breakage during rewinding is low, and the oxygen and water barrier properties are excellent.

Hereinafter, a mode for implementing the present invention (hereinafter referred to as "this embodiment") will be described in detail. In addition, the present invention is not limited to the following embodiments, and can be implemented with various changes within the scope of the gist.

The fresh-keeping film of this embodiment has a tensile strength X ₁ (MPa) in the direction perpendicular to the traveling direction (hereinafter also referred to as the "TD direction") of 100 or more, preferably in the range of 100≦X ₁ ≦300. If the tensile strength in the TD direction is in the range of 100 MPa or more, the strength to break in the direction perpendicular to the TD direction during cutting is sufficient. In the case of wrapping plastic wrap for food packaging, it breaks longitudinally during cutting Defects are suppressed. When the tensile strength in the TD direction is within the range of 300 MPa, the breaking strength in the direction perpendicular to the TD direction during cutting is not too high. In the case of wrapping plastic wrap for food packaging, it may be difficult to cut The tendency of longitudinal cracking defects to be suppressed. In terms of practical use, it is more preferably 170≦X ₁ ≦300, and more preferably 190≦X ₁ ≦300.

Moreover, the tensile elongation X ₂ (%) of the TD direction of the cling film of this embodiment is 100 or less, preferably 15≦X ₂ ≦100. If the tensile elongation in the TD direction is within the range of 100% or less, the film will be easily cut during cutting. In the case of wrapping the cling film for food packaging, longitudinal cracks during cutting are suppressed. When the tensile elongation in the TD direction is within the range of 15% or less, the film is moderately stretched during cutting and becomes easy to cut. In the case of wrapping plastic wrap for food packaging, it may be longitudinal when cutting. The tendency of cracking defects to be suppressed. In terms of the feeling of use in actual use, it is more preferably 15≦X ₂ ≦60, and more preferably 15≦X ₂ ≦50.

Furthermore, the wrap film of this embodiment has a tensile modulus X ₃ (MPa) in the direction of travel (hereinafter also referred to as "MD direction") and a tensile modulus Y (MPa) in the TD direction, which are 380≦X _3. Preferably 380≦X ₃ ≦900, and 280≦Y, preferably 280≦Y≦880. If the tensile modulus of elasticity in the MD direction is in the range of 380 MPa or more, the tension and toughness of the film will improve and the handling becomes easier. In addition, if the tensile modulus of elasticity in the TD direction is in the range of 280 MPa or more, the tension and toughness of the film are improved, and handling becomes easier. When the tensile modulus of elasticity in the MD direction is in the range of 900 MPa or less, there is a tendency for the film to become moderately hard and easy to handle. In addition, when the tensile modulus of elasticity in the TD direction is in the range of 880 MPa or less, the film tends to become moderately hard and easy to handle. In terms of practical use, it is more preferably 540≦X ₃ ≦900, and still more preferably 620≦X ₃ ≦900. Similarly, in terms of actual use, it is more preferably 420≦Y≦880, and even more preferably 500≦Y≦880. The method of controlling the tensile strength, tensile elongation and tensile modulus of elasticity in the TD direction, and the tensile modulus of elasticity in the MD direction within the above-mentioned ranges is not particularly limited. For example, the stretching ratio may be controlled to Traveling direction: 4.0 or less (preferably 3.8 or less), the direction perpendicular to the traveling direction: 5.8 or more, or use a polymer with a lower glass transition temperature, or add a nucleating agent appropriately.

Furthermore, in this embodiment, the tensile strength, tensile elongation and tensile modulus of elasticity in the TD direction, and the tensile modulus of elasticity in the MD direction can be measured by the method described in the following examples.

The cling film of this embodiment has a thermal shrinkage rate at 120°C measured in accordance with ASTM D-2732. The thermal shrinkage rate in the traveling direction (MD) is 4~30%, and the thermal shrinkage rate in the traveling direction (MD) is perpendicular to The ratio (MD/TD) of thermal shrinkage in the direction of travel (TD) is 2 or less. By controlling the heat shrinkage rate in a specific range in this way, the cling film of the present embodiment can maintain sufficient strength especially after heating at high temperature, and can suppress cracking defects after heating to high temperature.

The heat shrinkage rate in the direction of travel (MD) at 120°C of the cling film of this embodiment is further preferably 4% to 25%, and more preferably 4% to 20% in terms of practical use.

Furthermore, in this embodiment, the thermal shrinkage rate of MD and TD at 120°C can be measured by the method described in the following examples.

[Components of plastic wrap] The cling film of this embodiment is preferably formed of a component containing a polymer.

In this embodiment, the so-called polymer refers to a polymer having film-forming ability. The polymer means a polymer that accounts for more than 50% by weight of the entire film.

Amorphous polymers will be described below, but since they cannot form a surface network structure that is effective for imparting adhesion, in this embodiment, it is preferable not to use a polymer that becomes the main body of the film.

However, even if it is an amorphous polymer, as long as it is an amount that the crystalline polymer can be partially crystallized, it may be blended and used. Furthermore, the crystalline polymer may also be a hydrogen-bonded polymer like cellulose or aromatic polyamide which does not have a clear crystal melting point. When the crystal melting point is higher than the decomposition temperature, try wet film formation. Steps such as solvent recovery are required, which becomes disadvantageous in terms of operation. From the viewpoint of operability, it is preferable to use a polymer with a crystal melting point of 350°C or less that can be melt-formed in the manufacturing step.

As the polymer forming the cling film of this embodiment, polyvinylidene chloride resin, polyolefin resin, polyester resin, and polyamide resin can be preferably used. For example, polyolefin resins include polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and copolymers based on these, and polyester resins include Polyethylene terephthalate, polytrimethylene terephthalate, poly-1,4-cyclohexamethylene terephthalate, polyethylene 2,6-naphthalate, polylactic acid, Polyhydroxyglycolic acid and the like. Examples of polyamide resins include nylon 6, nylon 7, nylon 66, nylon 610, nylon 612, nylon 46, and nylon 6T.

As the polymer forming the cling film of the present embodiment, it is more preferable to include a polyvinylidene chloride-based resin composition. The polyvinylidene chloride-based resin composition can be a homopolymer of vinylidene chloride monomer, or a copolymer of vinylidene chloride monomer and a monomer copolymerizable therewith. In this specification, the "polyvinylidene chloride-based resin cling film" refers to a cling film containing a polyvinylidene chloride-based resin composition. The polyvinylidene chloride resin composition may contain one type of polyvinylidene chloride resin, or may contain two or more types of polyvinylidene chloride resin.

The monomer copolymerizable with the vinylidene chloride monomer is not particularly limited, and examples include vinyl chloride, acrylates such as methyl acrylate and butyl acrylate, methyl methacrylate, butyl methacrylate, etc. Methacrylate, acrylonitrile, vinyl acetate, etc. Among these, from the viewpoint that the oxygen and water barrier properties and the extrusion processability are easily balanced, and the film adhesiveness is also excellent, vinyl chloride is preferred. These may be used individually by 1 type, and may use 2 or more types together.

In the case of using a copolymer of vinylidene chloride monomer and the above-mentioned monomers, from the viewpoints of crystallinity, processability, and film properties, it is preferable to include 85-97% by mass of vinylidene chloride monomer, And 15~3% by mass copolymers of monomers copolymerizable with it. By setting the ratio of vinylidene chloride monomer to 85% by mass or more, the oxygen and water barrier properties or film cutting properties can be further improved. By setting the ratio of vinylidene chloride monomer to 97% by mass or less, it can be further improved. Improve processability. The monomer ratio is a value calculated from the integral ratio of the peak derived from each monomer component of the ¹ H-NMR spectrum measured by FX-270 (manufactured by JEOL Ltd.) using d-THF as a solvent.

The weight average molecular weight of the polyvinylidene chloride resin composition is not particularly limited, but is preferably 70,000 to 110,000, more preferably 80,000 to 100,000. By setting the weight average molecular weight of the polyvinylidene chloride-based resin composition to be equal to or higher than the above lower limit value, further favorable film strength can be obtained, and by setting the weight average molecular weight of the polyvinylidene chloride resin composition to be equal to or lower than the above upper limit value, processability can be further improved. Here, the weight average molecular weight is measured by gel-permeation chromatography (GPC) using tetrahydrofuran as a mobile phase, and calibrated and converted using polystyrene with a known molecular weight.

In the polyvinylidene chloride resin composition, well-known additives such as plasticizers and stabilizers can be formulated. The plasticizer is not particularly limited, and known ones can also be used. For example, acetyl tributyl citrate, acetylated monoglyceride, dibutyl sebacate, etc. are mentioned. The stabilizer is not particularly limited, and known ones can also be used. Examples include epoxidized vegetable oils such as epoxidized soybean oil and epoxidized linseed oil.

In addition to this, it is also possible to add well-known weather resistance improvers, antifogging agents, antibacterial agents, oligomers such as polyester, MBS (methyl Methyl acrylate-butadiene-styrene) and other polymers. The weather resistance improver is not particularly limited, and known ones can also be used. For example, ultraviolet absorbers such as 2-(2'-hydroxy-3'5'-di-tert-butylphenyl)-5-chlorobenzenetriazole and the like can be cited. The antifogging agent is not particularly limited, and known ones can also be used. For example, surfactants such as glycerol fatty acid esters, diglycerol fatty acid esters, and sorbitan fatty acid esters can be cited. The antibacterial agent is not particularly limited, and known ones can also be used. For example, natural antibacterial agents such as grapefruit seed extract and Mengzong bamboo extract can be cited.

The cling film of this embodiment does not necessarily have to be composed of a single layer. In the case of a multilayer structure, as long as the layer in contact with the container is mainly composed of crystalline polymer, it has a network structure that is observed by the phase image of AFM, and If the liquid component is included, the adhesiveness in actual use does not change, and it can also include a multilayer structure of two or more layers.

The cling film of this embodiment may also contain a liquid component.

The liquid component is preferably used according to the type of polymer. Furthermore, from the viewpoint of imparting flexibility to the film, if at least one type of polymer is, for example, an aliphatic hydrocarbon-based polymer, it is preferably used for those that have an alkyl group or a methylene chain moiety in the liquid component. In the case of ester-based polymers and amide-based polymers, it is preferable to use those containing functional groups having hydrogen bonding ability such as carbonyl groups, ether groups, and hydroxyl groups.

For example, examples of those having an alkyl group include mineral oil, liquid paraffin, and saturated hydrocarbon compounds. Examples of functional groups containing hydrogen bonding ability such as carbonyl groups, ether groups, and hydroxyl groups include: aliphatic alcohols, alicyclic alcohols, these polyhydric alcohols, and the aforementioned alcohol components and aliphatic or aromatic (polyhydric) carboxylic acids Acid esters, esters of aliphatic hydroxycarboxylic acids and alcohols and/or fatty acids, and modified products of these esters, and polyoxyethylene alkyl ethers and/or esters thereof. More specifically, for example, polyglycerols such as glycerin or diglycerin, triglycerin, tetraglycerin, etc.; and the raw materials for alcohol components, and fatty acids as acid components such as lauric acid, palmitic acid, and stearin Mono-, di-, and tri-esters of acids, oleic acid, linoleic acid, etc.; or esters of sorbitol anhydride and the above fatty acids; or ethylene glycol, propylene glycol, tetramethylene glycol, and condensation of these Or esters of citric acid, malic acid, tartaric acid, etc., as aliphatic hydroxy carboxylic acids, and lower alcohols with carbon number 10 or less; or as polycarboxylic acids, malonic acid, succinic acid, glutaric acid Esters of acids, adipic acid, etc. and aliphatic alcohols; or epoxidized soybean oil, epoxidized linseed oil, etc. as modified products of these esters. Especially when it is used as a cling film for food packaging, it is preferable to use a liquid component as a food additive prescribed by the Food Sanitation Law. Moreover, from the viewpoint of heat resistance, it is preferable to use a liquid component having a boiling point of 200°C or higher.

[Surface structure of cling film] The cling film of this embodiment preferably has a network structure on the surface of at least one layer, which is observed by the phase image of an atomic force microscope (hereinafter also referred to as "AFM").

In the cling film of this embodiment, the net-like structure is preferably such that the average width of the fibrils constituting the net observed by the phase image of AFM is 145 nm or less. When the average width of the fibrils is 145 nm or less, the film strength becomes moderate and the cutting performance is improved. In addition, as the cutting performance is improved, the rate of occurrence of rewinding is also reduced, and the rate of occurrence of breakage during rewinding is also reduced. Furthermore, a developed crystalline structure is formed after stretching, so the heat shrinkage rate in the direction of travel (MD) is reduced, and the ratio of the heat shrinkage rate in the direction of travel (MD) to the heat shrinkage rate in the direction perpendicular to the direction of travel (TD) ( MD/TD) also decreased.

In addition, when the average width of the fibrils is 1 nm or more, it becomes sufficient for the additives to maintain the surface of the network structure, the adhesion becomes moderate, and the drawability is improved, which is preferable. In terms of practical use, the average width of the fibrils is more preferably 10 nm~145 nm. More preferably, it is 45 nm to 145 nm.

Here, the so-called phase image of AFM is the one that visualizes the phase information of the stimulation of the cantilever of the AFM. In the cling film of this embodiment, the net-like structure is, for example, the fibril is the part where the phase delay of the cantilever stimulation is less, and the hole is the part where the phase delay is greater, as shown in Figure 1, the darker part It is a hole, and the bright part is a fibril. That is, when comparing the fibril with the hole, the hole part is more amorphous.

Furthermore, in this embodiment, the average width of fibrils can be measured by the method described in the following examples.

In addition, in the cling film of this embodiment, there are various methods for forming the surface network structure. For example, the network structure can be formed by aligning crystallization in the biaxial stretching process. In the cling film of this embodiment, in order to express a net-like structure, it is preferable to form the net-like structure by biaxial stretching. However, in the case of wet film formation, even if the active stretching is not performed, if there is a step of desolventizing under tension, the stretching is substantially due to the shrinkage stress, so if free shrinkage does not occur, it may not be performed Positive biaxial extension.

In the case where the crystallization speed of the polymer is relatively fast although it is the time point of extension, the polymer can also be extruded by melting and cooled in air to extend while crystallizing. In the case where crystallization takes time At this time, the extension in the molten state may not follow the crystallization, the oriented crystallization does not occur effectively, and the network structure is not exhibited. Therefore, it is preferable to temporarily adjust to a solid state and then extend above the glass transition temperature. In addition, in order to increase the crystallization rate, a nucleating agent may be appropriately added.

[Long crystallization cycle of plastic wrap] In addition, the long period of crystallization of the cling film of this embodiment is preferably 12.5 nm or less, and more preferably 8.2 nm to 12.5 nm. In the case of the above-mentioned long crystal period of 8.2 nm or more, the film has sufficient strength when cut, and when the food packaging wraps the cling film, the longitudinal cracking defect is reduced when cut. In addition, the film has sufficient strength, thereby reducing the incidence of breakage during rewinding. Furthermore, a developed crystalline structure is formed after stretching, so the heat shrinkage rate in the direction of travel (MD) is reduced, and the ratio of the heat shrinkage rate in the direction of travel (MD) to the heat shrinkage rate in the direction perpendicular to the direction of travel (TD) ( MD/TD) also decreased.

On the other hand, if the above-mentioned crystal long period is 12.5 nm or less, the film becomes easy to cut. In the case of a wrapper for food packaging, longitudinal cracking defects are reduced in the case of cutting. In addition, since the film becomes easy to cut, the rate of occurrence of breakage during rewinding is also reduced. Furthermore, a developed crystalline structure is formed after stretching, so the heat shrinkage rate in the direction of travel (MD) is reduced, and the ratio of the heat shrinkage rate in the direction of travel (MD) to the heat shrinkage rate in the direction perpendicular to the direction of travel (TD) ( MD/TD) also decreased. In terms of practical use, the above-mentioned long crystal period is more preferably 9.0 nm to 12.5 nm.

Furthermore, in this embodiment, the long crystal cycle can be measured by the method described in the following examples.

[Evaluation of oxygen and water barrier properties] Generally, in order to maintain freshness, the cling film is required to have oxygen barrier properties and water barrier properties.

The oxygen permeability of the cling film of this embodiment is preferably 110 cm ³ /m ² ·day·atm (at 23°C) or less, and the water vapor permeability is preferably 20 g/m ² ·day (at 38°C, 90 %RH) or less.

In addition, the oxygen permeability X (cm ³ /m ² ·day·atm (at 23° C.)) of the cling film of this embodiment is more preferably in the range of 1≦X≦110. If the oxygen permeability is in the range of 1≦X≦110, the oxygen barrier property is sufficient, and the freshness of the food is sufficiently maintained. When X<1, it may be difficult to exhibit sufficient freshness retention performance, and when X>110, it tends to be difficult to exhibit sufficient barrier properties. In terms of the feeling of use in actual use, 1≦X≦77 is more preferable, and 1≦X≦50 is still more preferable. In addition, the water vapor transmission rate Y (g/m ² ·day (at 38° C., 90% RH)) of the cling film of this embodiment is more preferably in the range of 1≦Y≦20. If the water vapor permeability is in the range of 1≦Y≦20, the water vapor barrier property is sufficient, and the freshness of the food is sufficiently maintained. When Y<1, it may be difficult to express sufficient freshness retention performance, and when Y>20, it may be difficult to express sufficient barrier properties. In terms of the feeling of use in actual use, 1≦Y≦18 is more preferable, and 1≦Y≦10 is still more preferable.

The method of controlling the oxygen permeability and water vapor permeability within the above-mentioned ranges is not particularly limited. For example, it is possible to include: controlling the stretch magnification to the direction of travel: 4.0 or less (preferably 3.8 or less), perpendicular to the direction of travel Direction: Above 5.8, or use polymer with lower glass transition temperature, or add nucleating agent appropriately.

In addition, in this embodiment, the oxygen permeability and water vapor permeability can be measured by the method described in the following examples.

[Manufacturing method of cling film] Next, an example of the manufacturing method of the cling film of this embodiment is demonstrated. Various methods can be used for manufacturing the cling film containing the polyvinylidene chloride resin composition, and the expansion film method is usually used. That is, according to this embodiment, a cling film obtained by inflation molding can be produced. More preferably, the cling film of this embodiment is a polyvinylidene chloride-based resin cling film obtained by stretching the polyvinylidene chloride-based resin composition at least in the MD direction and performing inflation molding. In the expansion film forming method, for example, after the polyvinylidene chloride resin composition is melt-extruded from a circular die in a tube shape, the outer side of the tube resin is filled with cold water in a storage tank called a cold water tank, etc. Refrigerant contact. At this time, in a state where a refrigerant is injected and accumulated in a tubular (tube-shaped) resin clamped by the pinch roller through the die opening, the inside is brought into contact with a refrigerant such as mineral oil to solidify and form For the membrane. In this specification, the portion (extrudate) of the cylindrical resin sandwiched between the die opening and the pinch roller is called "long tube". The refrigerant (liquid) injected into the long tube is called "long tube liquid". In addition, the long tube is folded by the above-mentioned pinch rolls and the like to form a tubular double-layer film, which is called a "parison".

The expansion film forming method will be described in more detail below. Fig. 4 is a conceptual diagram of an example of the method of manufacturing the cling film of this embodiment.

First, in the extrusion step, the molten polyvinylidene chloride resin composition is extruded in a tubular shape from the die mouth (3) of the circular die (2) by the extruder (1) to form a long tube (Tube-shaped polyvinylidene chloride resin composition) (4).

Next, in the cooling and solidification step, the outer side of the long tube (4) as the extrudate is brought into contact with cold water in the cold water tank (6), and the long tube liquid (5) is injected into the long tube (4) by conventional methods. ) And accumulate, thereby cooling the long tube (4) from inside and outside to solidify it. At this time, the long tube (4) is in a state where the long tube liquid (5) is coated on its inner side. The solidified long tube (4) is folded by the first pinch roller (7) to form a parison (8) as a double-layer sheet. The coating amount of the long tube liquid is controlled by the pinch pressure of the first pinch roller (7).

For the long tube liquid, water, mineral oil, alcohols, polyhydric alcohols such as propylene glycol or glycerin, cellulose or polyvinyl alcohol aqueous solutions, etc. can be used. These can be used alone or in combination of two or more. In addition, in the long tube liquid, the above-mentioned weather resistance improver, anti-fogging agent, antibacterial agent, etc., used for food packaging materials may be added within a range that does not hinder the effects of this embodiment.

The coating amount of the long tube liquid is not particularly limited. From the viewpoint of the openness of the parison and the adhesion of the film, it is preferably 50 to 20000 ppm, more preferably 100 to 15000 ppm, and even more preferably 150 to 10000 ppm. Here, the coating amount (ppm) refers to the mass of the long tube liquid applied to the long tube in mass ppm relative to the total mass of the long tube.

Then, air is injected into the inside of the parison (8), whereby the parison (8) opens again to become a tube. The parison (8) is reheated with warm water (not shown) to a temperature suitable for stretching. The warm water adhering to the outer side of the parison (8) is squeezed by the second pinch roll (9). Then, in the expansion step, air is injected into the tubular parison (8) heated to a suitable temperature, and the bubble (10) is formed by expansion and extension, thereby obtaining a stretched film.

The long period of crystallization of the cling film can be controlled by the stretching ratio and the crystallinity of the polymer constituting the cling film. The greater the stretching ratio in the TD direction and the stretching ratio in the MD direction, the longer the crystal cycle will become The greater the tendency, the higher the crystallinity of the polymer, the greater the long-term crystal cycle.

In the method of manufacturing the cling film of this embodiment, it is preferable to include the step of stretching the unstretched sheet in the traveling direction and the direction perpendicular to the traveling direction. In this case, the stretching ratio in the TD direction is preferably It is 5.8 times or more, and the stretching ratio in the MD direction is 4.0 times or less. From the viewpoint of film forming properties, the stretching ratio in the MD direction is more than 3.4 times and 3.8 times or less. The upper limit of the stretch magnification in the TD direction is not particularly limited, and is, for example, 8.5 times or less.

The method of controlling the stretching ratio is not particularly limited, and a known method can be adopted. For example, a method of controlling the elongation temperature by changing the temperature of warm water for reheating can be cited. In order to reduce the stretching ratio, the lower the stretching temperature, the lower the stretching ratio. In this state, the expanded bubble is stable, so it is preferable. At this time, from the viewpoint of the stability of the expanded foam, it is preferably higher than the stretched room temperature. The extension temperature is more preferably 34°C or less, and still more preferably 25°C to 34°C. In addition, the stretching temperature is the temperature at the midpoint of the distance between the point where the stretching ends in the MD direction and the TD direction and the MD direction from the point where the winding starts.

After that, the stretched film is folded by the third pinch roller (11) to become a double-layer film (12). The double-layer film (12) is wound by a winding roller (13). Furthermore, this film is cut, and it peels so that it may become a single film (single-layer peeling). Finally, the film is wound on a roll core such as a paper tube to obtain a wrap of cling film wound on the paper tube.

The long crystallization cycle is not only affected by the stretching ratio, but also by the thermal history. If the cling film is subjected to thermal history, the long period of crystallization will decrease and the tear strength will decrease. Therefore, it is preferable that the cling film is not subjected to excessive heat history. For example, it is preferable not only in the case of aging treatment, but also in the case of conveying the cling film in summer, or in the case of placing the cling film near a heat source such as a stove when used at home, etc. The film does not suffer from a high thermal history, thereby preventing the long period of crystallization from becoming too low and preventing the film from becoming easily broken.

The above description is an example of the method of manufacturing the cling film of the present embodiment, and can be performed by various device configurations or conditions other than the above, and for example, other known methods can also be used.

[Winding body] The cling film of this embodiment can be used in various forms, for example, it can be made into a roll-shaped polyvinylidene chloride resin cling film. In the case of making roll-shaped cling film, it can have a core or no core.

When it is set to be wound around the core, for example, it can be made into a wrap with a cylindrical core and the wrap of the polyvinylidene chloride resin wrap of the present embodiment wound on the core. Around the body. The wound body refers to the shape of a reel by winding the cling film on a core or the like.

The rewinding defect that occurs during the use of roll-shaped cling film etc. can be effectively suppressed for the cling film of this embodiment. The material or size of the core is not particularly limited, and known cores such as paper tubes can be used. Furthermore, if the cling film is in a roll shape, it may have a core or not. The wrapper of the wrap film of this embodiment can be stored in a packaging box with a cutter for cutting wrap for use.

[Thickness of cling film] The thickness of the cling film of the present embodiment is not particularly limited, but from the viewpoint of usability and optical properties, it is preferably 5 to 30 μm, more preferably 5 to 15 μm.

[Evaluation of Adhesiveness] Next, the adhesive work amount X (mJ/25 cm ² ) of the cling film of this embodiment is in the range of 1≦X≦2.5. If 1≦X, the cling film tends to exhibit sufficient adhesion. In addition, if X≦2.5, the peeling of the cling film becomes easy, and the so-called excessive adhesion can be suppressed. When the cling film is wound for food packaging, it tends to be easily pulled out. In terms of practical use, it is more preferably 1.5≦X≦2.4, and more preferably 1.8≦X≦2.3.

[Evaluation of the difficulty of rupture after heating] The cling film manufactured under the above points is extended in the direction perpendicular to the direction of travel (TD) compared with the direction of travel (MD). It is stretched at a high magnification and is within the range of ensuring film stability. The direction perpendicular to the direction of travel (TD) and the direction of travel (MD) extend. Therefore, at 120℃, the thermal shrinkage rate of the travel direction (MD) can be controlled to 4%~30%, and the travel direction (MD) The ratio of the thermal shrinkage rate of) and the thermal shrinkage rate (MD/TD) in the direction perpendicular to the direction of travel (TD) is controlled to be 2 or less. Since the cling film has such heat-shrinking properties, after putting the contents such as oily food into the container, covering the container with the cling film and sealing it, heat it with a microwave oven, etc., exposing the cling film to high temperature, and then peel it off to keep it fresh When filming, it can prevent the fresh-keeping film from breaking and the fragments from being mixed into the food. In terms of the feeling of use in actual use, the MD heat shrinkage rate at 120°C of the cling film of this embodiment is further preferably 4%-25%, more preferably 4%-20%. [Example]

Examples and comparative examples are listed below to further explain the present invention in detail. In addition, the observation of the network structure on the surface of the cling film by AFM, the long period of crystallization of the cling film, the tear strength, the longitudinal fracture defect rate, the adhesion, the tensile strength, the tensile elongation, the tensile modulus of elasticity, The evaluation of tension and toughness, transparency, rewinding rate, oxygen permeability, water vapor permeability, heat shrinkage rate, cracking difficulty after heating, and cracking rate during rewinding, use the following measuring methods.

(1) AFM measurement Attach the film to the Si wafer and use the Dimension Icon made by Bruker to observe the phase image on the surface in tapping mode. In the measurement, a Si single crystal cantilever (spring constant catalog value 40 N/m) is used, and the scan rate is 0.5-2 Hz, the scan size is 1 μm×1 μm, and the number of sampling points is 512× Implemented under the condition of 256 or 512×512. The contact pressure of the cantilever is controlled by the membrane, and the set point is 240-320 mV when the target amplitude is 400 mV, and the set point is 800 mV when the target amplitude is 800 mV ( Set Point) is in the range of 450-500 mV. When measuring the width of the fibril (fibril diameter), one image is divided into four for each phase image, and 5 parts of the fibril considered to be typical for each area are selected. In particular, a total of 5 fibril diameters are compared. The average value of the large part is adopted as the average width of the fibril.

(2) Long-period measurement of crystals The long-period of crystals is determined by the measurement of Small Angle X-ray Scattering (SAXS) using the following equipment and conditions. The device is manufactured by Rigaku Co., Ltd. NANOPIX X-ray incident direction film normal direction X-ray wavelength 0.154 nm Optical system point collimation (first: 0.55 mmΦ, second: open, protection: 0.35 mmΦ) Detector HyPix-6000 (two-dimensional Detector) Camera length SAXS: 1113 mm Exposure time comparative examples 5~8, 10, 12: 10 minutes/1 sample Examples 1-9, comparative examples 1-4, 9, 11: 1 hour/1 test In this way, the X-ray scattering pattern obtained from HyPix-6000 is subjected to the background correction of the detector and the empty cell scattering correction. After that, circle averaging is performed to obtain SAXS distribution I(q). Further, the distribution of SAXS the I (q) for multiplying the q-Lorentz (Lorentz) ² of the correction. Calculate the Bragg angle θ based on (Equation 1) and substitute it into Bragg’s equation (Equation 2) to calculate the crystalline long period d by calculating the magnitude of the scattering vector from the peak of the SAXS distribution after Lorentz's correction.

q=4π sinθ/λ Equation (1) θ: Bragg angle q: size of scattering vector λ: X-ray wavelength

2d sinθ=λ Equation (2) d: Long period of crystallization θ: Bragg angle λ: X-ray wavelength

(3) Tear strength It is measured according to ASTM-D-1992. The measurement is performed in an atmosphere of 23°C and 50%RH. Use a light load tear tester (manufactured by Toyo Seiki) to measure the tear strength (unit: cN) in the MD and TD directions.

(4) Longitudinal fracture defect rate A commercially available plastic wrap packaging box (manufactured by Asahi Kasei Home Products, trade name Saran Wrap packaging box, 30 cm×20 m) was used for the cut test. The test is conducted in an atmosphere of 23°C and 50%RH. Fixing the opening of the packaging box at 30° and cutting the film, it is calculated as the probability (%) of the longitudinal cracking of the film when the cut film is pulled out. The N number system is performed 500 times (unit: %).

(5) Adhesiveness It is assumed that the cling film is used in the home, and the adhesion between the cling film is evaluated. The measurement is performed in an atmosphere of 23°C and 50%RH. First, prepare two aluminum jigs with a base area of 25 cm ² , a height of 55 mm, and a weight of 400 g, and attach filter paper with the same area as the base area to the bottom surfaces of the two jigs. Cover the cling film on the bottom surface of the two jigs with filter paper attached to it without wrinkles, and fix it with a rubber band. The two jigs are overlapped with the bottom surface of the side covering the cling film, and pressed together with a load of 500 g for 1 minute. Secondly, using a tensile and compression testing machine (manufactured by Shimadzu Corporation), the amount of work (unit: mJ/25 cm ² ) necessary to peel the two cling film surfaces perpendicular to each other at a speed of 5 mm/min was measured.

(6) Tensile strength, tensile elongation Measure according to ASTM-D-882. The measurement is performed in an atmosphere of 23°C and 50%RH. Using a tensile and compression testing machine (manufactured by Shimadzu Corporation), at a speed of 300 mm/min, stretch the cling film with a width of 1 cm and a distance of 10 cm between the chucks up and down to determine the strength at break (unit: MPa) ), and elongation (unit: %).

(7) Tensile modulus of elasticity Measure according to ASTM-D-882. Cut the film in the MD direction of the film and the direction parallel to the TD direction with a length of 12 cm and a width of 1 cm to prepare a measurement sample. The measurement is performed in an atmosphere of 23°C and 50%RH. Using a tensile and compression testing machine (manufactured by Shimadzu Corporation), stretch the cling film set to 10 cm between the chucks at a speed of 5 mm/min, and set the strength at the point of 2% displacement (stroke 2 mm) It is 50 times, converted into 100% displacement, and measured by this (unit: MPa).

(8) Evaluation of tension and toughness Prepare 20 skilled sensory inspectors. Use plastic wrap of 30 cm in length and width on a glass container with a diameter of 15 cm at the opening. The feeling of use when covering the container is evaluated according to the following points.

Evaluation mark content A: Excellent tension and toughness, and easy operation. B: It is excellent in tension and toughness, and no problem is felt in handling. C: The sense of tension and toughness is poor, but no problem is felt in operation. D: The tension and toughness are poor, and it is not easy to use.

(9) Haze It is measured according to JIS-K-7136. The measurement is performed in an atmosphere of 23°C and 50%RH. The haze (unit: %) was measured using a turbidity meter (manufactured by Nippon Denshoku Corporation).

(10) Evaluation of the incidence of rupture during rewinding After cutting the double-layer film and peeling it into a single film, use a commercially available plastic wrap paper tube (manufactured by Asahi Kasei Home Products, trade name Saran Wrap paper tube, 30 cm×20 m) Reel in paper tube. The film conveying speed during winding is 300 m/min, and the roll length is 20 m. In the winding operation, the probability (%) that the film is broken and the film cannot be conveyed is calculated. The N number system is performed 3000 times (unit: %). Evaluate according to the following points.

Evaluation mark content A: The rate of rupture during rewinding is 0.03% or less (the number of ruptures is less than 1/3000). B: The rate of rupture during rewinding is higher than 0.03% and less than 0.07% (the number of ruptures is more than 1 and less than 2/3000). C: The rate of rupture during rewinding is higher than 0.07% and less than 0.10% (the number of ruptures is more than 2 and less than 3/3000). D: The rate of rupture during rewinding is higher than 0.10% (the number of ruptures is more than 3/3000).

(11) Heat shrinkage rate Measure according to ASTM D-2732. The measurement is performed in a constant temperature bath adjusted to a set temperature (120°C), and the sample of the cling film is allowed to stand for 1 minute. After 1 minute, take out the cling film from the constant temperature bath, and within 30 minutes in an atmosphere of 23°C and 50% RH, mark the initial marks in the direction of travel (MD) and the direction perpendicular to the direction of travel (TD). The length is measured. At this time, calculate the reduction value from the original length of 10 cm as a percentage to the original length of 10 cm. The calculated percentage becomes the thermal shrinkage rate.

(12) Evaluation of the difficulty of rupture after heating at 120℃ Imagine using cling film in a microwave oven to evaluate the difficulty of breaking the cling film when heated. The cling film wound on the paper tube is rolled out, and the film is cut in the MD direction and the direction parallel to the TD direction with a length of 10 cm and a width of 10 cm to prepare an evaluation sample. Cut into the incision on the end face of the cut sample parallel to the TD direction and the end face of the unwinding side (the side close to the surface layer). The notch is when the evaluator looks at the cling film rolled in the paper tube from the front, and places the wound body in such a way that the end surface of the unwinding side is rolled out from the upper direction. At this time, when viewed by the self-evaluator, it becomes the direction on the left. Starting from the position where the center moves 1/√2 cm, cut into the incision at an angle of 45° with the end face parallel to the TD direction, with a length of 1 cm. The sample cut into the cling film with the cuts in the above sequence is allowed to stand for 1 minute in a constant temperature bath adjusted to a set temperature (120°C). After 1 minute, the cling film was taken out from the constant temperature bath, and the cracking difficulty was evaluated in an atmosphere of 23°C and 50% RH. The evaluation of the difficulty of rupture is to cut into the end surface of the cut-out cling film in the above order, and hang a plumb from the center of the cut end surface to measure the load resistance. The plumb system starts from the 10 g plumb, and hangs 20 g, 30 g, 40 g, 50 g, 60 g, 70 g in order from the lighter one. The maximum load when the cling film ruptures is measured. The heavier the maximum load when the cling film is ruptured, the less likely it is to break after heating the cling film at high temperatures. The N number system is performed 500 times, and the average value of 500 times is calculated, and the difficulty of breaking the cling film after heating at high temperature is judged according to the following points.

Evaluation mark content A: The average maximum load at the time of rupture is heavier than 60 g. B: The average maximum load at the time of rupture is heavier than 50 g and less than 60 g. C: The maximum load average value at the time of rupture is more than 40 g and less than 50 g. D: The average value of the maximum load when rupture occurs is 40 g or less.

(13) Oxygen permeability OX TRAN 2/21MH <trade name> manufactured by MOCON company was used, and the measurement method was based on ASTM D3985 to determine the oxygen permeability. Install the sample on the device and use the value after 4 hours. The measurement was performed at 23°C. The lower the oxygen permeability, the higher the oxygen barrier.

(14) Water vapor permeability Using PERMATRAN W-398 <trade name> manufactured by MOCON company, the measurement method is based on ASTM F1249, and the water vapor transmission rate is measured. Install the sample on the device and use the value after 3 hours. The measurement was performed under the conditions of 38°C and 90%RH. The lower the water vapor permeability, the higher the water barrier.

(15) Rewind rate A commercially available plastic wrap packaging box (manufactured by Asahi Kasei Home Products, trade name Saran Wrap packaging box, 30 cm×20 m) was used for the cut test. The test is conducted in an atmosphere of 23°C and 50%RH. Fixing the opening of the packaging box at 30° and cutting the film, it is calculated as the probability (%) of film rewinding when the cut film is pulled out. The N number system is performed 500 times (unit: %).

[Example 1] The polyvinylidene chloride resin composition with a weight average molecular weight of 90,000 vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at a temperature of 170°C and used for melting The extruder performs melt extrusion, and expands and stretches the obtained parison to form a cylindrical film. The weight average molecular weight is measured by gel permeation chromatography (GPC) using tetrahydrofuran as a mobile phase, and calibrated and converted using polystyrene with a known molecular weight. At this time, the stretch magnification in the MD direction was 3.8 times, and the stretch magnification in the TD direction was 5.8 times. In addition, the elongation temperature was set to 26°C. After folding and winding the cylindrical film, it is cut into a width of 300 mm, and one side is peeled off as a single film, and the other side is wound on a paper tube with an outer diameter of 36.6 mm and a length of 305 mm for 20 m to produce a thickness of approximately A 10 μm plastic wrap wrapped in a paper tube. AFM measurement, SAXS measurement, tear strength, tensile elongation, tensile modulus of elasticity, heat shrinkage rate, difficulty of breaking after heating at 120°C, incidence of breakage during rewinding, and rewinding of the obtained film Table 1 shows the results of the evaluation of the rate, oxygen permeability, moisture permeability, adhesion, and transparency.

[Example 2] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction was 3.6 times, and the stretch magnification in the TD direction was 6.0 times. In addition, the stretching temperature was set to 25°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 3] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. Set the stretch magnification in the MD direction to 3.5 times, and set the stretch magnification in the TD direction to 6.1 times. In addition, the stretching temperature was set to 25°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 4] The liquid components (15 parts by weight of glycerol diacetate monolaurate) are mixed and melted at a temperature of 220°C to become the main crystalline polymer (85 parts by weight of polylactic acid), and melted by a melt extruder Extrusion, the obtained parison is expanded and stretched to form a cylindrical film. The stretch magnification in the MD direction is set to 3.8 times, and the stretch magnification in the TD direction is set to 8.0 times. In addition, the elongation temperature was set to 33°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 5] Mix and melt the liquid ingredients (15 parts by weight of triacetin) or other additives (3 parts by weight of epoxidized linseed oil, 2 parts by weight of mineral oil) at a temperature of 280°C to become the main crystalline polymer ( Nylon 66 (80 parts by weight), and melt extruded with a melt extruder, and the obtained parison is expanded and stretched to form a cylindrical film. The stretch magnification in the MD direction is set to 3.4 times, and the stretch magnification in the TD direction is set to 8.5 times. In addition, the stretching temperature was set to 25°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 6] Mix and melt liquid ingredients (10 parts by weight of mineral oil) or other additives (5 parts by weight of Marukarez (registered trademark)®, 5 parts by weight of Tuftec (registered trademark)®) at a temperature of 200°C to become the main body with high crystallinity The molecule (80 parts by weight of polypropylene) is melt-extruded by a melt extruder, and the obtained parison is expanded and stretched to form a cylindrical film. The stretch magnification in the MD direction is set to 3.8 times, and the stretch magnification in the TD direction is set to 7.2 times. In addition, the elongation temperature was set to 26°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 7] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction is set to 3.7 times, and the stretch magnification in the TD direction is set to 5.8 times. In addition, the stretching temperature was set to 25°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 8] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction is 3.6 times, and the stretch magnification in the TD direction is 6.1 times. In addition, the elongation temperature was set to 34°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Example 9] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction is 3.5 times, and the stretch magnification in the TD direction is 6.2 times. In addition, the elongation temperature was set to 31°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 1 shows the evaluation results of the obtained film.

[Comparative Example 1] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=91/9 (mass ratio) is melted at 170°C, and melt extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction is set to 3.7 times, and the stretch magnification in the TD direction is set to 4.3 times. In addition, the stretching temperature was set to 40°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 2] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is melted at 170°C, and melted and extruded by a melt extruder , Expand and extend the obtained parison to form a cylindrical film. The stretch magnification in the MD direction is 5.0 times, and the stretch magnification in the TD direction is 6.0 times. In addition, the stretching temperature was set to 35°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 3] The polyethylene is melted at a temperature of 170° C., and melt-extruded using a melt extruder, and the obtained parison is expanded and stretched to form a cylindrical film. The stretch magnification in the MD direction is 5.0 times, and the stretch magnification in the TD direction is 5.0 times. In addition, the elongation temperature was set to 39°C. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 4] Mix and melt liquid ingredients (10 parts by weight of mineral oil) or other additives (5 parts by weight of Marukarez (registered trademark)®, 5 parts by weight of Tuftec (registered trademark)®) at a temperature of 200°C to become the main body with high crystallinity The molecule (80 parts by weight of polypropylene) is extruded from an extruder equipped with a T-die with a slit width of 20 mm×0.5 mm, and is rapidly cooled with water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 140°C, the stretcher is used to implement sequential biaxial stretching to 2.0×2.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 5] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 140°C, the stretcher is used to implement sequential biaxial stretching to 1.0×8.6 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 6] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 38°C, the stretcher is used to implement successive biaxial stretching to 4.3×1.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 7] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 39°C, the stretcher is used to implement sequential biaxial stretching to 5.3×1.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 8] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 40°C, the stretcher is used to implement sequential biaxial stretching to 6.3×1.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 9] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 42°C, the stretcher is used to implement sequential biaxial stretching to 8.0×1.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 10] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 49°C, the stretcher is used to implement sequential biaxial stretching to 3.5×10.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 11] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 49°C, the stretcher is used to implement sequential biaxial stretching to 5.0×7.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Comparative Example 12] The polyvinylidene chloride resin composition with vinylidene chloride (VDC)/vinyl chloride (VC)=88/12 (mass ratio) is mixed and melted at a temperature of 170°C, and the slit width is 20 mm since the installation The extruder is extruded with a T-die of ×0.5 mm and rapidly cooled by water to form a sheet on the film. Then, while the original sheet is passed through a heating zone set at 53°C, the stretcher is used to implement sequential biaxial stretching to 5.0×10.0 times and take it up. In addition, the cling film rolled in a paper tube with a thickness of about 10 μm was manufactured using the operation according to Example 1. Table 2 shows the evaluation results of the obtained film.

[Table 1]

[Table 2]

Figure 2 shows the AFM phase image of the film surface obtained in Example 1. A uniform network structure is observed. In Examples 2, 3, 4, 5, 6, 7, 8, 9, and Comparative Examples 4, 9, 10, 11, and 12, a network structure was also observed. In the examples, since the tensile strength, tensile elongation, and tensile modulus of elasticity are in a specific range, as shown in the evaluation in Table 1, the desired effects are obtained. However, in Comparative Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12, since the tensile strength, tensile elongation and tensile modulus of elasticity are not specific ranges, Therefore, as shown in the evaluation in Table 2, the desired effect was not obtained. The AFM phase image of the film surface of Comparative Example 1 is shown in FIG. 3. [Industrial availability]

The cling film of the present invention has good adhesion when used, has a sense of tension and toughness, transparency, anti-longitudinal cracking effect and anti-rolling effect. It is not easy to crack after being heated to a high temperature (for example, 120°C). A cling film with a low incidence of cracking and excellent oxygen and water barrier properties, so it can be preferably used as a cling film for various packaging mainly for food packaging.

1‧‧‧Extruder 2‧‧‧Round mold 3‧‧‧Mold mouth 4‧‧‧Tubular vinylidene chloride resin composition (long tube) 5‧‧‧Long tube liquid 6‧‧‧Cold water tank 7‧‧‧The first pinch roller 8‧‧‧Parison 9‧‧‧The second pinch roller 10‧‧‧Bubble 11‧‧‧The third pinch roller 12‧‧‧Double film 13‧‧‧Reel roll 14‧‧‧Hole 15‧‧‧Fiber

Figure 1 is a schematic diagram of the network structure observed with the phase image of the atomic force microscope (AFM). Figure 2 is an atomic force microscope (AFM) phase image of the surface of the cling film of Example 1 of this case. Figure 3 is the phase image of the atomic force microscope (AFM) on the surface of the cling film of Comparative Example 1 of this case. Fig. 4 is a conceptual diagram of an example of the method of manufacturing the cling film of this embodiment.

Claims (21)

A kind of cling film whose tensile strength in the direction perpendicular to the direction of travel (TD) is more than 100MPa, the tensile elongation is less than 100%, and the modulus of tensile elasticity is more than 280MPa; the tensile elasticity in the direction of travel (MD) The modulus is above 380MPa; the long crystal period is below 12.5nm; and the oxygen permeability is 110cm ³ /m ² . day. Below atm (at 23℃), the water vapor transmission rate is 20g/m ² . day (at 38°C, 90%RH) or less. Such as the cling film of claim 1, the long period of crystallization is 8.2nm or more. Such as the cling film of claim 1, the long period of crystallization is 9.0nm or more. Such as the cling film of any one of claims 1 to 3, in which the heat shrinkage rate at 120°C measured according to ASTM D-2732, the heat shrinkage rate in the direction of travel (MD) is 4~30%, and the direction of travel (MD) The ratio (MD/TD) of the thermal shrinkage rate in the direction perpendicular to the direction of travel (TD) (MD/TD) is 2 or less. The cling film according to any one of claims 1 to 3, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the structure, the average width of the observed fibrils is less than 145nm. The fresh-keeping film of claim 4, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the net structure, the observation The average width of the obtained fibrils is less than 145nm. The cling film according to any one of claims 1 to 3, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the structure, the average width of the observed fibrils is 1 nm to 145 nm. The fresh-keeping film of claim 4, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the net structure, the observation The average width of the obtained fibrils is 1 nm to 145 nm. The cling film according to any one of claims 1 to 3, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the structure, the average width of the observed fibrils is 10nm or more and 145nm or less. The fresh-keeping film of claim 4, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the net structure, the observation The average width of the obtained fibrils is 10nm to 145nm. Such as the fresh-keeping film of any one of claims 1 to 3, which has a utilization principle on the surface of at least one layer The network structure observed in the phase image of the sub-force microscope. The network of the network structure is composed of fibrils. In the network structure, the average width of the fibrils observed is 45nm to 145nm. The fresh-keeping film of claim 4, which has a net structure on the surface of at least one layer as observed by the phase image of an atomic force microscope, and the net of the net structure is composed of fibrils. In the net structure, the observation The average width of the obtained fibrils is 45nm to 145nm. For example, the fresh-keeping film of any one of claims 1 to 3, 6, 8, 10, and 12 has a thickness of 5 to 15 μm. Such as the fresh-keeping film of claim 4, its thickness is 5~15μm. For example, the fresh-keeping film of claim 5 has a thickness of 5-15μm. Such as the cling film of any one of claims 1 to 3, 6, 8, 10, 12, which contains a copolymer containing vinylidene chloride monomer 85-97% by mass and vinyl chloride monomer 15-3% by mass . Such as the cling film of claim 4, which contains a copolymer containing 85-97% by mass of vinylidene chloride monomer and 15-3% by mass of vinyl chloride monomer. For example, the cling film of claim 5, which contains a copolymer containing 85-97% by mass of vinylidene chloride monomer and 15-3% by mass of vinyl chloride monomer. For example, the cling film of claim 13, which contains a copolymer containing 85-97% by mass of vinylidene chloride monomer and 15-3% by mass of vinyl chloride monomer. A method for manufacturing a cling film according to any one of claims 1 to 19, which comprises the step of stretching an unstretched sheet in a traveling direction and a direction perpendicular to the traveling direction, the stretching ratio in the traveling direction is 4.0 or less, and The stretch magnification in the direction perpendicular to the direction of travel is above 5.8. A winding body, which is formed by winding the cling film according to any one of claims 1 to 19 on a roll core.

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