JP2010163203A - Wrapping film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wrapping film that is excellently adherent, flexible, cuttable, is extremely less in bleed out of plasticizer and a change in dimensional change or suchlike with time, furthermore, is extremely less in physical change due to hydrolysis of polylactic resin, and is suitably used for wrapping food, etc. <P>SOLUTION: In the wrapping film having one or two or more film layers and a cut energy of 50 mJ or less, at least one of the film layers is a film layer (a) extended at least in one direction, which contains (A) polylactic acid resin, (B) plasticizer composed of dicarboxylic acid ester, which includes at least one benzene ring in a molecular structure and a molecular weight of 200 to 3,000, and (C) carbodiimide compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wrap film.

  Wrapping films for food packaging are used for purposes such as wrapping food or a dish or container containing food, preserving food in a refrigerator or freezer, heating in a microwave oven, or the like. In addition, when food is temporarily placed on a table or the like, it is also used for dust prevention.

  Thermoplastic resins are generally used for wrapping films for food packaging. Main examples include polyvinylidene chloride, polyvinyl chloride, polyethylene, and polypropylene. Among these, polyvinylidene chloride wrap has multiple properties required for wrapping, such as adhesion, flexibility, and cutability, and further changes in physical properties over time, bleed out, and film width. Because there is almost no shrinkage, it is often used as a food packaging film.

  On the other hand, in recent years, the carbon dioxide concentration in the atmosphere has increased due to the emission of carbon dioxide generated when incinerating used plastics and the like, and the associated global warming problem has been regarded as important.

  Then, the wrap film which made the plant-derived resin which is carbon neutral the main raw material is proposed.

  One of the widely used plant-derived resins is polylactic acid resin. The polylactic acid resin is a resin obtained by polymerizing lactic acid produced by fermenting starch such as corn, but itself has a high rigidity and is a hard and brittle resin. Therefore, in order to make this a film that requires adhesiveness and flexibility, such as a wrap film, the composition of the wrap film is designed by adding several plasticizers and additives, and the cut property that is a feature of the wrap film is also included. Need to give. Therefore, it is very difficult to suppress changes over time such as bleed out and shrinkage of the film width while maintaining the adhesiveness, flexibility and cutability necessary for wrapping. Furthermore, when using a polylactic acid resin as a wrap film, it is also necessary to control changes in physical properties associated with hydrolysis over time derived from the resin.

  As a wrap film mainly using a polylactic acid resin, for example, Patent Documents 1 to 5 disclose wrap films containing a polylactic acid resin and a plasticizer.

JP 2006-321913 A JP 2006-27113 A JP 2006-16605 A JP 2006-69146 A JP 2006-131687 A

  However, in the wrap film mainly using the conventional polylactic acid resin, the plasticizer molecules escape from between the polymer chains of the polylactic acid resin constituting the wrap film, and as a result, the plasticizer bleeds out. Deterioration of the feeling of wrap touch, dimensional change of the film, etc. may be caused.

  In addition, the unstretched wrap film may not have sufficient cutting properties or tensile strength of the film. In the case of a wrap film to which no hydrolysis inhibitor has been added, the wrap film is pulled by hydrolysis of the polylactic acid resin. In some cases, mechanical properties such as strength and tensile elongation were inferior.

  Therefore, the present invention is not only excellent in adhesion, flexibility and cutability, but also has very little change over time such as bleed-out of plasticizer and dimensional change, and furthermore, there is very little change in physical properties due to hydrolysis of polylactic acid resin. An object of the present invention is to provide a wrap film that can be suitably used for food packaging and the like.

As a result of intensive studies to solve the above problems, the present inventors have completed the present invention. That is, the present invention is as follows.
(1) A wrap film having one or more film layers and a cut energy of 50 mJ or less, wherein at least one of the film layers is a polylactic acid resin (A) and at least one benzene ring in the molecular structure A film layer (a) containing a plasticizer (B) and a carbodiimide compound (C) made of a dicarboxylic acid ester having a molecular weight of 200 to 3000 and stretched in at least one direction. Wrapped film.
(2) The film layer (a) is composed of 2 to 35 parts by mass of the plasticizer (B) and 0.1 to 5 parts by mass of the carbodiimide compound with respect to 100 parts by mass of the polylactic acid resin (A). The wrap film according to (1), which is a film layer containing (C) and stretched 3 to 10 times in at least one direction.
(3) The wrap film according to (1) or (2), wherein the plasticizer (B) is an adipic acid ester.
(4) The wrap film according to any one of (1) to (3), wherein at least one of the film layers is a film layer containing a wax.
(5) The wrap film according to any one of (1) to (4), wherein at least one of the film layers is a film layer containing a plate-like filler.
(6) The wrap film according to any one of (1) to (4), wherein the film layer (a) is a film layer containing a wax and / or a plate-like filler.
(7) A wrap film roll formed by winding the wrap film according to any one of (1) to (6) around a core.

  According to the present invention, it has excellent adhesion, flexibility and cutability, changes with time such as bleed-out and dimensional changes and changes in physical properties due to hydrolysis, can be produced from plant-derived resins, and is used for food packaging. A suitable wrap film can be provided.

It is the schematic which looked at the winding state by the winder for paper tube winding from the side.

  Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The wrap film according to the present embodiment is a wrap film having one or two or more film layers and a cut energy of 50 mJ or less, and at least one of the film layers is a polylactic acid resin (A) in a molecular structure. A film layer (a) containing a plasticizer (B) and a carbodiimide compound (C) composed of a dicarboxylic acid ester having at least one benzene ring and a molecular weight of 200 to 3000, and stretched in at least one direction It is a wrap film characterized by being.

  The polylactic acid-based resin (A) represents a resin containing 80% by mass or more of lactic acid as a monomer unit. For example, polylactic acid, a block copolymer of polylactic acid and polyester other than polylactic acid, lactic acid, diol, and dicarboxylic acid Examples thereof include a copolymer and a copolymer of lactic acid and a hydroxycarboxylic acid other than lactic acid.

  The polylactic acid is a polymer of L-lactic acid, a polymer of D-lactic acid, or a copolymer of L-lactic acid and D-lactic acid. When the polylactic acid is a copolymer of L-lactic acid and D-lactic acid, the content of the unit structure derived from L-lactic acid is 90% by mass or more or 10% by mass or less with respect to the total amount of polylactic acid. Preferably there is. When the proportion of the unit structure derived from L-lactic acid is 90% by mass or more and 10% by mass or less, the crystallinity of polylactic acid is improved, and the heat resistance and dimensional stability of the wrap film tend to be improved.

  Examples of the polylactic acid include “Natureworks 4042D (registered trademark, the same applies hereinafter)”, “Natureworks 4032D (registered trademark, the same applies hereinafter)” of Natureworks, and the like.

  When the polylactic acid resin (A) is polylactic acid, the wrap film according to this embodiment may further contain a polyester other than polylactic acid. At this time, it is preferable that content of polylactic acid in a wrap film is 80 mass% or more with respect to the total mass of polyester other than polylactic acid and polylactic acid. Examples of polyesters other than polylactic acid include “Ecoflex (registered trademark, the same applies hereinafter)” manufactured by BASF.

  Examples of the polyester other than polylactic acid include a copolymer of diol and dicarboxylic acid, and a polymer of hydroxycarboxylic acid other than lactic acid. The diol is not particularly limited, and examples thereof include saturated aliphatic diols having 2 to 20 carbon atoms such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. Can be mentioned. These diols can be used alone or in combination. Further, the dicarboxylic acid is not particularly limited, but examples thereof include saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms such as malonic acid, succinic acid, glutanic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. And aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. These dicarboxylic acids can be used alone or in combination. Examples of hydroxycarboxylic acids other than lactic acid include glycolic acid, 2-hydroxycaproic acid, 2-hydroxy-n-butyric acid, and 2-hydroxyisocaproic acid. These hydroxycarboxylic acids can be used alone or in combination.

  Examples of the block copolymer of polylactic acid and polyester other than polylactic acid include “Plamate (registered trademark, the same applies hereinafter)” manufactured by DIC Corporation. As the “polyester other than polylactic acid” that forms a block copolymer with polylactic acid, the above-described “polyester other than polylactic acid” can be used.

  In the copolymer of lactic acid, diol, and dicarboxylic acid, the diol is not particularly limited. For example, carbon such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, and 1,5-pentanediol. A saturated aliphatic diol having a number of 2 to 20 can be used. These diols can be used alone or in combination. Further, the dicarboxylic acid is not particularly limited, but examples thereof include saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms such as malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid. And aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid. These dicarboxylic acids can be used alone or in combination.

  In the copolymer of lactic acid and a hydroxycarboxylic acid other than lactic acid, examples of the hydroxycarboxylic acid other than lactic acid include glycolic acid, 2-hydroxycaproic acid, 2-hydroxy-n-butyric acid, and 2-hydroxyisocaproic acid. Etc. can be used. These hydroxycarboxylic acids can be used alone or in combination.

  The weight average molecular weight (Mw) of the polylactic acid resin (A) is preferably 80,000 to 400,000, more preferably 100,000 to 300,000, and further preferably 150,000 to 250,000. . When the weight average molecular weight of the polylactic acid-based resin (A) is 80,000 or more, there is a tendency that sufficient mechanical strength can be obtained for practical use. When the weight average molecular weight is 400,000 or less, an appropriate melt viscosity ( 3,000 to 30000 poise, resin temperature: 195 ° C., share rate: 1.00E-02). Here, the weight average molecular weight (Mw) indicates a value measured by gel permeation chromatography (hereinafter sometimes referred to as “GPC”), specifically, measured by the method described in the examples. can do.

  The plasticizer (B) is composed of a dicarboxylic acid ester having at least one benzene ring in the molecular structure, and the molecular weight of the dicarboxylic acid ester is 200 to 3000. The dicarboxylic acid ester has a structure in which a dicarboxylic acid and an alcohol are ester-bonded. In the dicarboxylic acid ester, the benzene ring may be included in the molecular structure derived from dicarboxylic acid, or may be included in the molecular structure derived from alcohol. The molecular weight is a relative molecular mass and is a value representing the relative mass of a molecule. That is, this is a numerical value representing the mass of a molecule in units based on the mass of one atom of carbon 12 being exactly 12.

  When a plasticizer (B) has the said structure, a wrap film which suppresses bleed-out and is excellent in dimensional stability can be obtained. Moreover, it becomes possible to keep the touch feeling of a wrap film favorable. The reason for this effect is that the polarity of the benzene ring in the plasticizer (B) strongly interacts with the polymer chain of the polylactic acid resin (A), and the plasticizer (B) is polylactic acid. This is considered to be difficult to escape from between the polymer chains of the resin (A).

  When the molecular weight of the dicarboxylic acid ester is 200 or more, it becomes difficult for the plasticizer molecule to escape from the polymer chain of the polylactic acid resin (A), and bleeding out is further suppressed. Moreover, since it is 3000 or less, a plasticizer molecule | numerator is easy to penetrate | invade between the polymer chains of a polylactic acid-type resin (A), and when a plasticizer (B) and a polylactic acid-type resin (A) are knead | mixed, a plasticizer ( Separation of B) and the polylactic acid resin (A) hardly occurs.

  Further, the plasticizer (B) has high plasticization efficiency, and the total amount of plasticizer added can be reduced as compared with the case where only the plasticizer having no benzene ring in the molecular structure is used. For this reason, the cut property of a wrap film can be maintained suitably.

  The plasticizer (B) is preferably an ester of a saturated aliphatic dicarboxylic acid and an alcohol having at least one benzene ring in the molecular structure. The wrap film containing such a plasticizer (B) tends to exhibit the above-described effects more remarkably. This is because when the benzene ring is located in the molecular structure derived from alcohol, other polar groups in the plasticizer molecule interact with the polymer chain of the polylactic acid resin (A). This is thought to be because it is less likely to cause steric hindrance.

  Examples of the saturated aliphatic dicarboxylic acid include saturated aliphatic dicarboxylic acids having 3 to 20 carbon atoms such as malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. . Examples of the alcohol having at least one benzene ring in the molecular structure include benzyl alcohol, phenethyl alcohol, and hydrocinnamyl alcohol.

  As the plasticizer (B), an adipic acid ester having at least one benzene ring in the molecular structure and a molecular weight of 200 to 3000 from the viewpoint of obtaining a wrap film that suppresses bleed out and has excellent dimensional stability. More preferred. As such an adipic acid ester, for example, “DAIFATTY-101 (registered trademark, the same applies hereinafter)” manufactured by Daihachi Chemical Industry Co., Ltd. can be mentioned.

  In addition to the plasticizer (B), the wrap film according to the present embodiment may further contain a known plasticizer (hereinafter sometimes referred to as a plasticizer (D)). At this time, it is preferable that content of the plasticizer (B) in a wrap film is 40 mass% or more with respect to the plasticizer whole quantity.

  The plasticizer (D) added to the wrap film according to this embodiment preferably has a molecular weight of 200 to 3000. When the molecular weight is 200 or more, the plasticizer molecule is difficult to escape from the polymer chain of the polylactic acid resin (A), and bleed out is further suppressed. Moreover, when it is 3000 or less, the plasticizer molecule easily enters between the polymer chains of the polylactic acid resin (A), and when the plasticizer (D) and the polylactic acid resin (A) are kneaded, the plasticizer (D ) And the polylactic acid resin (A) are less likely to separate. The molecular weight is a relative molecular mass and is a value representing the relative mass of a molecule. This is a numerical value representing the mass of a molecule in units based on the mass of one atom of carbon 12 being exactly 12.

The SP value of the plasticizer (D) added to the wrap film according to this embodiment is preferably 6 to 13. The plasticizer (D) having an SP value in the range of 6 to 13 is well mixed with the polylactic acid-based resin (A) because it has a value approximate to the SP value (10.2) of polylactic acid. Tend to fit. The SP value can be calculated by the following formula (I) (see J. Appl. Chem., 3, 71 (1953)).
SP value = dΣG / M (I)
[D indicates density, G indicates molar traction force constant, and M indicates molecular weight. ]

  As such a plasticizer (D), for example, “Rikemar PL019” (molecular weight: about 360, SP value: 9.8) manufactured by Riken Vitamin Co., Ltd., “New Sizer 510R” manufactured by NOF Corporation. (Molecular weight: about 1000, SP value: 8.1).

  Further, when the plasticizer (D) has a polar group containing an oxygen atom or a nitrogen atom in the molecular structure, the plasticizer molecule strongly interacts with the polymer chain of the polylactic acid resin (A), and the plasticizer molecule Is difficult to escape from between the polymer chains of the polylactic acid resin (A), and as a result, bleeding out of the plasticizer (D) tends to be suppressed.

  Examples of the plasticizer (D) include glycerin fatty acid ester, citrate ester, aliphatic adipic acid ester, epoxidized vegetable oil, and the like. These may be used alone or in combination of two or more. When the wrap film which concerns on this embodiment contains plasticizers (D) other than a plasticizer (B), content of the plasticizer (D) in a wrap film is 60 mass% or less with respect to the plasticizer whole quantity. It is preferable that

  It is preferable that content of a plasticizer (B) is 5-35 mass parts with respect to 100 mass parts of polylactic acid-type resin (A), and it is more preferable that it is 10-30 mass parts. When the content of the plasticizer (B) is 5 parts by mass or more, the polylactic acid resin (A) can be sufficiently plasticized, and a wrap film excellent in flexibility can be obtained. Moreover, when content of a plasticizer (B) is 35 mass parts or less, while a possibility that a plasticizer will bleed out from a wrap film will become low, a polylactic acid-type resin (A) and a plasticizer (B) will be a film. Since it mixes well at the time of extrusion, film formation can be performed stably.

  In the present embodiment, the carbodiimide compound (C) is blocked by reacting with the terminal carboxyl group of the polylactic acid resin (A), and the carboxyl group is prevented from promoting hydrolysis of the ester bond as an acid catalyst. As hydrolysis of the ester bond proceeds, the polymer chain of the polylactic acid resin (A) has a low molecular weight, and as a result, the wrap film becomes brittle and physical properties such as tensile strength and tensile elongation may be impaired. Moreover, when pulling out a wrap film from the wrap film roll which concerns on this embodiment, a fracture | rupture occurs and it may become difficult to pull out stably.

  Examples of the carbodiimide compound (C) include those having a basic structure represented by the following general formula (II).

  In the above formula, n represents an integer of 1 or more, and R represents a divalent organic group. n is preferably between 1 and 50, and examples of R include an aliphatic divalent organic group, an alicyclic divalent organic group, and an aromatic divalent organic group.

  Specific examples of the carbodiimide compound (C) include poly (4,4′-dicyclohexylmethanecarbodiimide), bis (dipropylphenyl) carbodiimide, poly (4,4′-diphenylmethanecarbodiimide), and poly (p-phenylenecarbodiimide). ), Poly (m-phenylene carbodiimide), poly (tolyl carbodiimide), poly (diisopropyl phenylene carbodiimide), poly (methyl-diisopropyl phenylene carbodiimide), poly (triisopropyl phenylene carbodiimide), and the like. It is done. These carbodiimide compounds may be used alone or in combination of two or more.

  As the carbodiimide compound (C), a polycarbodiimide compound is preferable. When the carbodiimide compound (C) is a polycarbodiimide compound, the heat resistance of the wrap film is improved due to the thermal stability of the polycarbodiimide compound. Moreover, the polycarbodiimide compound has a plurality of carbodiimide groups in one molecule, and this carbodiimide group reacts with the carboxylic acid of the polylactic acid resin (A) to perform blocking. That is, when the carbodiimide compound (C) is a polycarbodiimide compound, the polymer chain of the polylactic acid-based resin (A) is connected via the polycarbodiimide compound, so that the chain length of the polymer chain is extended. By extending the polymer chain, the lowering of the molecular weight of the polymer chain can be delayed, and the tensile strength and tensile elongation of the wrap film can be maintained in a suitable range over a long period of time.

  The polycarbodiimide compound can react with an active polar group in addition to the carboxyl group of polylactic acid. Therefore, when the plasticizer contains a polar group, it reacts with the polar group of the plasticizer, ties the polymer chain of the polylactic acid resin (A) and the plasticizer, and suppresses the bleedout of the plasticizer. it can. When the plasticizer is held in the wrap film due to suppression of bleed out, the flexibility in the wrap film can be maintained for a long time. That is, the polycarbodiimide compound also functions as an additive for keeping the wrap film flexible.

  Examples of such polycarbodiimide compounds include “Carbodilite LA-1 (registered trademark, the same applies hereinafter)” manufactured by Nisshinbo Co., Ltd.

  The content of the carbodiimide compound (C) is preferably 0.1 to 5 parts by mass and more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the polylactic acid resin (A). More preferably, it is 0.5 to 2 parts by mass. When the content of the carbodiimide compound (C) is 0.1 parts by mass or more, when extruding the film, it reacts efficiently with the terminal carboxyl group of the polylactic acid resin (A) and suppresses the promotion of the hydrolysis rate. can do. A film can be shape | molded by moderate melt viscosity (3000-30000 poise, the resin temperature: 195 degreeC, share rate: 1.00E-02) as it is 5 mass parts or less.

  In the present embodiment, the tensile elastic modulus is an index indicating the softness and firmness when the wrap film is handled. Polylactic acid itself has a high rigidity, is a hard and brittle resin, and does not function as a wrap film. Therefore, it is necessary to soften polylactic acid by adding a plasticizer to polylactic acid, that is, to lower the tensile elastic modulus of polylactic acid. The tensile modulus also affects the adhesion required for the wrap film. When the tensile elastic modulus is lowered, the shape followability of the wrap film to the package body is improved, the contact area between the wrap film and the package body is increased, and as a result, the adhesion is increased.

  The tensile elastic modulus of the wrap film is not particularly limited, but is preferably 300 to 1500 MPa, and more preferably 400 to 1000 MPa, from the viewpoint of appropriate adhesion and ease of use. When the tensile elastic modulus is 300 MPa or more, after the wrap film is pulled out from the wrap film roll and cut, the wrap films stick to each other, become crumpled, and it becomes difficult to wrap foods, When the tube-wrapped wrap film is cut with the saw blade attached to the storage box, the wrap film stretches, the saw blade does not bite, and it is difficult for the cutting property to be impaired. In addition, when the tensile elastic modulus is 1500 MPa or less, the wrap film becomes too hard, the shape following property to the packaged body is deteriorated, and the adhesiveness is not easily lost. Here, the tensile elastic modulus of the wrap film indicates an average of the tensile elastic modulus in the MD direction and the tensile elastic modulus in the TD direction. The MD direction is a flow direction during film formation, and the TD direction is a direction orthogonal to the MD direction.

  In the present embodiment, the tensile strength is an index indicating the firmness and stiffness when the wrap film is handled and the durability until it breaks. If the polylactic acid film is unstretched, the tensile strength is not sufficient and the durability to function as a wrap film is poor. The composition constituting the film is extruded into a film shape, cooled to below the crystallization temperature, and heated and stretched again, whereby the polymer chains in the film are oriented and crystallized, and the tensile strength can be increased. .

  The tensile strength of the wrap film is not particularly limited, but is preferably 50 to 200 MPa, and more preferably 80 to 150 MPa. If the tensile strength is 50 MPa or more, after the wrap film is pulled out from the wrap film roll and cut, the wrap films will stick together and become crumpled, and it will be difficult to wrap food, etc. When pulled, it is difficult for breakage to occur outside the portion in contact with the saw blade. In addition, when the pressure is 200 MPa or less, the wrap film becomes too hard, the shape following property to the package body is deteriorated, and the adhesiveness is hardly deteriorated. In addition, the tensile strength of a wrap film shows the average of the tensile strength in MD direction and the tensile strength in TD direction here. The MD direction is a flow direction during film formation, and the TD direction is a direction orthogonal to the MD direction.

  In this embodiment, the adhesion work is an index indicating the adhesion of the wrap film to the package. Adhesion is important for the wrap film because it does not peel off after wrapping the food, and also covers and sticks the container / dish to seal the food contained in the container / dish. Polylactic acid has high rigidity, and the polymer chain of polylactic acid does not have many polar groups, so that it itself has poor adhesion. In this embodiment, the polylactic acid is softened, the shape followability to the packaged body is increased, and the adhesiveness is increased by adding a component having many polar groups between the polymer chains of polylactic acid. In order to increase the adhesion, the adhesion work can be adjusted by adding a plasticizer (B), a plasticizer (D), or other additives having a polar group to polylactic acid. The method for measuring the work of adhesion is described in detail later, but is the energy required when the lap film surfaces are brought into contact with each other and peeled off.

  Since the plasticizer (B) has an excellent effect as a plasticizer for softening polylactic acid and has many polar groups in its molecular structure, it is held between the polymer chains of polylactic acid and covered. It interacts with the polar group on the surface of the package to produce adhesion. That is, the plasticizer (B) is an additive having an effect of imparting adhesiveness in addition to plasticity.

  The adhesion work of the wrap film is not particularly limited, but is preferably 0.5 to 2.5 mJ, and more preferably 0.7 to 2.0 mJ. If the work of close contact is 0.5 mJ or more, the wrap film will stick firmly when food, containers, dishes, etc. are wrapped, so the wrap film may be peeled off from the food and the food may be exposed or peeled off from the container, dish, etc. Such problems are less likely to occur. Also, if the work of adhesion is 2.5 mJ or less, it will be difficult to pull out the wrap film from the wrap film roll, and after the wrap film is pulled out from the wrap film roll and cut, the wrap films will stick together and crumpled. Therefore, problems such as wrinkles are less likely to occur.

  In the present embodiment, the pulling power is an index indicating the force required to pull out the wrap film from the wrap film roll when the wrap film is wound around a core such as a paper tube to form a wrap film roll. Since the pulling power is greatly related to the force with which the wrap films stick to each other, the work of contact is an important factor. Moreover, blocking is mentioned as a factor which increases pulling power. Blocking is considered to occur when two films are stacked, the molecular chain of the amorphous part of the film moves across the interface between the two films, and a part of the interface between the films disappears. That is, in order to control the pulling output, it is possible to adjust the adhesion work and not to cause blocking. In the present embodiment, the plasticizer (B) hardly bleeds out, and the plasticizer molecules are less likely to move in the film surface direction within the film. Therefore, the plasticizer concentration near the film surface does not increase and the molecular chain does not easily move. That is, the occurrence of blocking can be suppressed as compared with the case where a conventional plasticizer is used.

  In the present embodiment, it is preferable that the work of adhesion is appropriately adjusted by selecting the type and amount of the plasticizer and additive. Further, as a method for suppressing blocking, there is a method in which orientation crystallization is promoted by performing a heat treatment after stretching to reduce and suppress the amorphous portion.

  The pulling force of the wrap film is not particularly limited, but is preferably 5 to 100 cN, and more preferably 5 to 60 cN. Although details of the method for measuring the pulling power will be described later, the force required for pulling out the wrap film by fixing the end of the wrap film and pulling it while rotating the paper tube portion of the paper tube-wrapped wrap film is used. If the pulling power is 5 cN or more, the force at the time of pulling out is too light, and it becomes difficult to cause a problem that an excessive amount of wrapping film is pulled out by the force applied to pull out the wrapping film. Further, if the strength is less than 100 cN, the force for pulling out the wrap film is too great, and the wrap film breaks during the pull-out, or when the paper tube-wrapped wrap film is stored in a storage box or the like, It is difficult for the tube-wrapped film to jump out of the storage box due to excessive force.

  In the present embodiment, the cut energy is an index indicating the cutability of the wrap film, that is, the ease of cutting. If the cutting property is poor, the wrap film will not cut along the saw blade attached to the storage box, it will be cut at an unintended place, the cutting edge will be lost, and excessive force will be required to cut the wrap film. It may be difficult to cut the film.

  The cut property is greatly related to the orientation of the polymer chain constituting the wrap film and the oriented crystal. In other words, the composition of the wrap film and the stretching conditions at the time of making the wrap film are important for the cut property of the wrap film, the crystallinity of the composition, the magnification during stretching, the temperature, the stress relaxation rate after stretching, the temperature of the heat treatment step. The time can be adjusted as appropriate. In addition to the orientation of polymer chains and oriented crystals, the wrap film's cut property is also related to physical properties such as the tensile elastic modulus, tensile strength, and tensile elongation of the wrap film. It is also necessary.

  The cut energy of the wrap film is not particularly limited, but is preferably 5 to 50 mJ, and more preferably 10 to 30 mJ. The details of the measurement method of cut energy will be described later, but the energy required for cutting along the saw blade attached to the storage box using the paper tube wrapped wrap film as the wrap film is cut energy. And When the cut energy is 5 mJ or more, the film is difficult to break except at the portion where the film is in contact with the saw blade, and the break propagates starting from the cut at the saw blade, so that the wrap film is difficult to tear diagonally. Also, if it is 50 mJ or less, the wrap film will stretch and the saw blade will not bite, and it will be difficult for the cutting performance to be poor, and the film cut surface may be in the form of tearing without following the shape of the saw blade. Less likely to occur.

  In this embodiment, bleeding out means that a plasticizer, a low molecular weight component of a polylactic acid resin, or the like exudes from the surface of the wrap film. When the bleed-out occurs, the touch feeling of the film is deteriorated, and when the bleed-out is severe, the bleed material may adhere to the packaged object. As a method for suppressing bleed out, a plasticizer having a polar group having a high affinity with the polymer chain of the polylactic acid resin (A) in the molecular structure is selected, or hydrolysis of polylactic acid is suppressed. For example, the generation of low molecular weight components can be suppressed.

  The carbodiimide compound (C) has an effect of suppressing the generation of low molecular weight components by inhibiting hydrolysis. In addition, the polymer chain of the polylactic acid resin (A) and a plasticizer having a polar group are connected to each other, and the effect of suppressing bleeding out of the plasticizer having a polar group is obtained.

  The amount of bleed out is pasted on a glass plate of 1000 mm × 1000 mm so that there is no gap, so that there is no gap, no air, etc., and placed in an atmosphere of temperature 23 ° C. and humidity 50% for 24 hours, Thereafter, when the wrap film is peeled off, the weight of the bleed material remaining on the glass plate is evaluated. The bleed-out amount of the wrap film according to the present embodiment is not particularly limited, but is preferably 100 mg or less, and more preferably 70 mg or less. When the bleed-out amount is 100 mg or less, the touch feeling of the film is kept good, and the bleed material is difficult to adhere to the package.

  In this embodiment, the width of the wrap film is reduced after placing the wrap film in a paper tube wound state in an atmosphere of a temperature of 40 ° C. and a humidity of 90% for 24 hours, compared to before placing it in the atmosphere. Show the percentage. When the width contraction occurs, there are problems such that bleeding out is likely to occur, and the end portions of the paper tube winding film are uneven and the appearance is poor.

  The width shrinkage of the wrap film is not particularly limited, but is preferably 3% or less, and more preferably 1% or less. When the width shrinkage is 3% or less, bleed-out hardly occurs, and the end portions of the wrap film are almost uniform, so that the dimensions can be stably maintained.

  In the present embodiment, the thickness of the wrap film is not particularly limited, but is preferably 5 to 15 μm, and more preferably 7 to 13 μm. The thickness of the wrap film is greatly related to the flexibility, adhesion, cut property, touch feeling, etc. of the wrap film. When the thickness of the wrap film is 5 μm or more, the strength of the wrap film is too weak and breaks, or after the wrap film is drawn out from the paper tube-wrapped wrap film and cut, the wrap films stick together, become crumpled, wrinkles, etc. This makes it difficult to wrap foods that are contained. In addition, when the thickness is 15 μm or less, problems such as a decrease in flexibility due to a thick wrap film, a deterioration in shape followability to a package, a decrease in adhesion, and a poor cutting property are less likely to occur. .

  The wrap film includes one or more film layers and has a cut energy of 50 mJ or less, and at least one of the film layers is a polylactic acid resin (A) and at least one benzene in the molecular structure. It is a film layer (a) containing a plasticizer (B) and a carbodiimide compound (C) made of a dicarboxylic acid ester having a ring and a molecular weight of 200 to 3000, and stretched in at least one direction. It is a wrap film.

  The wrap film may be a single layer film composed of a film layer (a), or a multilayer film including one or two or more film layers (a), that is, one or two or more layers between two opposing surface layers. It may be a multilayer film provided with a core layer. When the wrap film is a multilayer film, it is preferable that the surface layer of the multilayer film is the film layer (a) from the viewpoints of adhesion and suppression of bleeding out of the plasticizer. Bleed-out can be efficiently suppressed by coating the layer having a high possibility that the plasticizer bleeds out with the film layer (a).

  The plasticizer (B) has a benzene ring in the molecular structure. Since this benzene ring interacts strongly with the polymer chain of the polylactic acid resin (A), it is considered that the plasticizer (B) is difficult to bleed out. Therefore, the higher the ratio of the plasticizer (B) to the total amount of plasticizer contained in the film layer (a), the more difficult it is to bleed out. For example, the bleed-out can be more efficiently suppressed by coating a layer having a high possibility of bleed-out of the plasticizer with the film layer (a) having a high content of the plasticizer (B).

  The multilayer film may include a plurality of film layers (a), and all of the layers constituting the multilayer film may be the film layer (a). At this time, each of the plurality of film layers (a) is a polylactic acid resin (A), a plasticizer comprising a dicarboxylic acid ester having at least one benzene ring in the molecular structure and a molecular weight of 200 to 3000 ( The content ratio of B) and the carbodiimide compound (C) may be different.

  The multilayer film may have a symmetric or asymmetric layer structure.

  In the multilayer film, the thickness of the film layer (a) is preferably 10% or more with respect to the thickness of the entire multilayer film.

  As a film layer other than the film layer (a) contained in the multilayer film, a layer made of a single polylactic acid resin, a layer made of a composition in which (B) or a known additive is blended with an aliphatic polyester resin, etc. Although various forms are mentioned, from a viewpoint of maintaining the biodegradability of a film, the layer which consists of a resin composition which has aliphatic polyester resin as a main component is preferable.

  In the wrap film, one or more of the film layers constituting the wrap film may contain a wax and / or a plate-like filler. When wax or a plate-like filler is contained in the film layer, the water vapor permeability of the wrap film is lowered. When the wax or the plate-like filler is finely dispersed in the layer, it is considered that water molecules are prevented from passing through the layer, and as a result, the water vapor permeability of the wrap film is lowered.

The water vapor permeability of the wrap film is not particularly limited, but is preferably 500 g / m ² / day or less, and 300 g / m ² / day or less in an atmosphere of a temperature of 40 ° C. and a humidity of 90%. It is more preferable. The water | moisture content of a to-be-packaged body (for example, foodstuff) can be hold | maintained for a long period as water vapor permeability is 500 g / m < ² > / day or less.

  The wax is not particularly limited, but is generally a naturally occurring wax such as montan wax, carnauba wax, cotton wax, beeswax, wood wax, wool wax, and mineral or synthetic waxes. Are used alone or in combination of two or more. In addition, other components can be added to the film layer containing the wax in order to adjust properties such as mechanical properties, water vapor permeability, and decomposability.

  The content of the wax in the composition constituting the film layer is not particularly limited, but is preferably 2 to 60% by mass based on the total amount of the composition constituting the film layer, and 5 to 30 More preferably, it is mass%. When the content is 2% by mass or more, the water vapor permeability can be sufficiently lowered. When it is 60% by mass or less, the water vapor permeability can be lowered while maintaining good film-forming properties and transparency of the film layer.

  The plate-like filler is not particularly limited, and organic or inorganic fillers and pigments are used. For example, natural or synthetic minerals, ceramics, metals, resins, or composites thereof are used. Examples of the inorganic plate-like filler include natural or synthetic mica (mica), talc, silica and the like.

  Although content of the said plate-shaped filler in the composition which comprises a film layer is not specifically limited, It is preferable that it is 0.01-50 mass% on the basis of the composition whole quantity which comprises a film layer. . If it is 0.01% by mass or more, the water vapor permeability can be sufficiently lowered. Moreover, water vapor permeability can be lowered | hung while maintaining film forming property and transparency of a wrap film as it is 50 mass% or less.

  You may add a compatibilizing agent suitably to the composition which comprises a film layer. Examples of the compatibilizer include styrene-based thermoplastics such as maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, and aliphatic carboxylic acid-modified products of the wax used in the present invention, and styrene-ethylene-butylene block copolymers. An elastomer etc. are mentioned. Although content of a compatibilizing agent is not specifically limited, It is preferable that it is 0.01-50 mass% on the basis of the composition whole quantity which comprises a film layer. When the content is 0.01% by mass or more, a sufficient compatibilizing effect can be obtained, and when it is 50% by mass or less, a sufficient compatibilizing effect can be obtained while maintaining the film forming property of the wrap film. Can do.

  The wrap film may add an adhesion-imparting agent to the film layer in order to impart adhesion. When the wrap film is a multilayer, an adhesion-imparting agent can be added to all layers, but a sufficient effect can be obtained only by adding it to the surface layer.

  Examples of the adhesion-imparting agent include, but are not limited to, natural product-based adhesion imparting agents, petroleum-derived resins, styrene resins, phenolic resins, xylene resins, and the like. It is a natural rubber resin that is an adhesion promoter.

  It is preferable that the usage-amount of the said adhesion imparting agent is 1-15 mass% with respect to the whole film layer to add. When the amount is 1% by mass or more, the necessary adhesion work can be imparted to the wrap film, and when the amount is 15% by mass or less, excessive increase in the adhesion work is suppressed and the drawability of the wrap film is maintained. it can.

[Wrap film manufacturing method]
Hereinafter, the manufacturing method of the wrap film which concerns on this embodiment is demonstrated in detail. In addition, the manufacturing method of the wrap film which concerns on this embodiment is not limited to the following description.

  As a method for forming a wrap film, it is preferable to select specific production conditions in combination with a specific composition in order to realize suitable ranges of flexibility, adhesion, and cutability. The specific conditions mainly relate to the range of setting conditions and the operation method in the extrusion molding process, the stretching process, and the heat treatment process. As an outline, for example, a single layer or multilayer molten sheet is cooled and solidified by a cooling roll by a T-die molding method, and then a film is obtained by sequential biaxial stretching or simultaneous biaxial stretching, or a tube by an annular slit die. A film-like extrusion film is extruded, and after cooling and solidifying by, for example, air cooling or water cooling, a film forming method by a stretching method such as a tubular stretching method in which bubbles are formed to obtain a film by multiaxial stretching may be selected. preferable. Here, in order to obtain a film, a film forming method that does not include a stretching step, for example, a method of forming a thin unstretched film while taking a melt extruded from a T-die as it is with a casting roll, is because it is unsuitable for stretching orientation, It is difficult to obtain the wrap film required in this embodiment because the cutting ability of the saw blade attached to the storage box tends to be poor.

  The wrap film is, for example, a resin composition obtained by melt-kneading a polylactic acid resin (A), a plasticizer (B), a carbodiimide compound (C), and other components (hereinafter abbreviated as “resin composition”). After being extruded and then cooled and solidified, and then reheated and then subjected to a process of stretching in at least one direction. Moreover, it is preferable to heat-fix in order to adjust temporal changes, such as a bleed out of a wrap film obtained, and a dimensional change.

  In this embodiment, as the melt-kneading method for obtaining the resin composition, a same-direction rotating twin-screw extruder, a different-direction rotating twin-screw extruder, a single-screw extruder, and the like can be used. From this point, it is preferable to use a twin-screw extruder rotating in the same direction. Here, it is important that the resin composition is well kneaded and mixed uniformly. If the kneading is not uniform, there may be variations in physical properties such as adhesion work and pulling force when a wrap film is obtained. . In addition, the twin-screw extruder is excellent in conveying the raw material in the screw as compared with the single-screw extruder, and is excellent in kneadability, so that it is suitable for uniformly mixing the resin composition.

  In addition, there is a method in which the polylactic acid resin (A), the plasticizer (B), and the carbodiimide compound (C) are pelletized with another extruder in advance, and this is supplied to the extruder, but the carbodiimide compound (C In some cases, the effect of extending the chain length) may occur excessively, and the screw torque and resin viscosity may become unstable and extrusion may not be performed. Therefore, when the polylactic acid resin (A) is melted in the extruder, necessary materials such as a plasticizer (B), a carbodiimide compound (C), an additive, a wax, a plate-like filler are added, and the die is used as it is. A continuous method of forming and proceeding to the next step is preferable.

  When the wrap film has a multilayer structure, it is preferable to use at least one layer made of the resin composition as a surface layer. At this time, for melt extrusion of other layers, for example, an extruder corresponding to each layer and a merging part for each layer are supplied to a die or the like within a known range, or a die having a layered merging portion It may be coextruded in the inside.

  Co-extrusion is a laminating method in which the resin composition obtained by melt-kneading is superposed into a film in a molten state by a feed block method, a multi-manifold method, or a combination of these, and then cooled and solidified. is there.

  In the production of a wrap film, the resin composition is extruded into a predetermined shape by a T die or an annular slit die at the tip of an extruder, and then immersed in cold water or brought into contact with a cooled casting roll or the like. It is preferable to rapidly cool to a temperature at which crystals do not grow, that is, below the crystallization temperature of the composition. For example, 20 parts by mass of adipic acid ester containing at least one benzene ring in the molecular structure was added to 100 parts by mass of a polylactic acid resin (L-D copolymer having a D-form content of 4% by mass). In the system, the temperature of the casting roll or the like for the rapid cooling is preferably 45 ° C. or less. This temperature is determined so as to prevent crystal growth as described above with reference to the glass transition temperature of the resin composition. Here, when the cooling temperature is high, a crystal grows, and therefore, in the subsequent stretching step, it tends to cause tearing or tearing and tend to be difficult to stretch.

  In this embodiment, stretching refers to re-heating the film layer obtained by coextrusion or the like to a temperature equal to or higher than the glass transition temperature of the compound in the resin composition constituting the film layer, thereby stretching the molecules. This is the step of aligning.

  If the wrap film is a flat film, a flat stretching method can be employed in which the film is stretched using a roll or restraint. If the film is a tube, the cooled and solidified tube is sandwiched between rolls, and then air is used. A tubular stretching method in which the film is stretched by inflating with pressure can be employed.

  When the film is stretched, the polymer chains of the film are oriented and oriented and crystallized to improve the cut property of the wrap film, but the flexibility may be impaired and the plasticizer may bleed out. Therefore, in order to achieve the maintenance of flexibility and the suppression of bleed-out while improving the cutability, the film layer has a function as a plasticizer (B) and a bleed-out inhibitor that are difficult to bleed out and have a high plasticizing effect. It is necessary to add a carbodiimide compound (C) having Examples of such a plasticizer (B) include adipic acid esters containing at least one benzene ring in the molecular structure.

  As a heating method at the time of stretching, roll heating, hot air heating, infrared heating or the like can be suitably used.

  Stretching is preferably performed in the film flow direction (MD direction) and / or in the direction orthogonal to the film direction (TD direction). The stretching step is performed by a method such as a longitudinal uniaxial stretching method, a tubular stretching method, or a sequential biaxial stretching method.

  When the stretching is uniaxial, stretching in the MD direction or TD direction is preferably performed at a magnification of 3 to 10 times, and more preferably at a magnification of 4 to 7 times. By stretching at a magnification of 3 times or more in the uniaxial direction, sufficient heat resistance by orientation crystallization can be obtained. Further, by setting the draw ratio in the uniaxial direction to 10 times or less, the film is not easily broken due to excessive crystallization.

  When biaxially stretched, it is preferably stretched at a magnification of 2 times or more and 5 times or less in each of the MD direction and the TD direction, and may be stretched at a magnification of 2.5 times or more and 4.5 times or less. More preferred. By stretching at a magnification of 2 times or more in each of the biaxial directions, sufficient heat resistance by orientation crystallization can be obtained. Further, by setting the draw ratio in each direction of the biaxial to 5 times or less, the film is not easily broken due to excessive crystallization.

  The draw ratio can be adjusted by the rotation speed of the roll and the width of the film restraint in the tenter. In the tubular drawing, the blow-up ratio by pressure air and the film take-up speed before and after the drawing process can be changed. Can be adjusted.

  The stretching temperature is preferably 35 to 90 ° C, and more preferably 40 to 80 ° C. When it is 35 ° C. or higher, stretching can be easily performed, and orientational crystallization of crystalline polylactic acid in the resin composition easily occurs. Further, when the temperature is 90 ° C. or lower, the film is less likely to sag or tear during preheating or stretching, and can be stretched satisfactorily.

  When stretching using a tubular stretching method, it is necessary to sandwich the film with a pinch roll after cooling and solidification in order to separate the process of cooling and solidifying the film and the process of stretching with pressurized air. At this time, in order to prevent defects such as wrinkling and tearing of the film, the temperature of the cooling water is preferably Tg-10 ° C. to Tg + 10 ° C. when the glass transition temperature of the resin composition is Tg. More preferably, it is set to −5 ° C. to Tg + 5 ° C. By setting the temperature of the cooling water to Tg-10 ° C. or higher, generation of wrinkles and tears due to vitrification of the film can be suppressed. Moreover, by setting it as Tg + 10 degrees C or less, it can shape | mold into a tube shape, without solidifying a film.

  When it is stretched by blowing in air under pressure after cooling and solidification, there is a feature that it has a layer made of an adhesive resin composition on the surface. In some cases, it may not be possible to enter the space, and stable stretching may not be possible. In order to prevent this, when the cooled and solidified film is sandwiched between rolls, it is effective to apply an anti-adhesive agent on the film by enclosing and retaining the film inside the film sandwiched between the rolls. More specifically, it is possible to extrude a film vertically downward from a cylindrical die, guide the film into water, solidify by cooling, and introduce an anti-sticking agent from above through a cavity provided in the center of the die.

  The anti-sticking agent is not particularly limited, but preferably has a surface tension of 15 to 40 mN / m so that the film surface can be wetted and spread well. When the surface tension is 15 mN / m or more, when the cooled and solidified tube-like film is sandwiched between rolls, the problem that the anti-adhesive agent is squeezed out by the rolls and the opening property of the film becomes poor is unlikely to occur. Moreover, if it is 40 mN / m or less, the anti-sticking agent will spread well on the film surface.

  Moreover, as the above-mentioned anti-sticking agent, one having a viscosity at 25 ° C. of 5 to 20000 mPa · s is preferable because wettability greatly affects the viscosity. When the viscosity is 5 mPa · s or more, when the cooled and solidified tubular film is sandwiched between rolls, the problem that the anti-sticking agent is squeezed out by the rolls and the film has poor opening properties is unlikely to occur. Moreover, if it is 16000 mPa * s or less, an anti-sticking agent will move fluidly and it can apply | coat to the film surface uniformly.

  Examples of the anti-sticking agent include, for example, polyhydric alcohols such as glycerin, polyglycerin, ethylene glycol, propylene glycol, and dipropylene glycol, esters with fatty acids, liquid paraffin, petrolatum, ceresin, microcrystalline wax, and squalane. Oils such as hydrogen, soybean oil, linseed oil, tung oil, castor oil, avocado oil and olive oil, epoxidized products thereof, acetylated tributyl citrate, dibutyl sebacate, dioctyl adipate, isobutyl stearate, diisononyl adipate, poly (Propylene glycol / adipic acid, lauric acid) ester and epoxidized stearic acid (2-ethylhexyl) ester of aliphatic alcohol and aliphatic carboxylic acid and / or aliphatic dicarboxylic acid. Carboxymethyl compound and the like. These anti-sticking agents may be used alone or in combination.

  In the present embodiment, the anti-sticking agent is used as a processing aid. Therefore, it is preferable that the application amount of the anti-adhesive agent on the film surface is such an amount that the film does not adhere and does not impair the adhesion of the surface. In order to control the coating amount on the film surface, if it is a water-soluble compound, a method using a diluted concentration as an aqueous solution is used. A method of floating as an oil film or an oil layer on the upper portion, a method of using it by emulsification, or the like can be preferably used. By controlling the coating amount by such a method, the coating amount of the anti-sticking agent can be controlled, and the anti-sticking agent can be removed from the film surface layer by immersion into the film and / or volatilization by heat treatment.

  The amount of the anti-sticking agent applied is preferably 100 to 5000 ppm with respect to the total mass of the film, more preferably 300 to 3000 ppm, and more preferably 500 to 1500 ppm. More preferably, it is applied. By applying at a rate of 100 ppm or more, the film is sufficiently prevented from sticking. By applying at a rate of 5000 ppm or less, it is easy to remove the anti-sticking agent from the surface due to transfer into the film, volatilization by hot air treatment, etc. It becomes difficult to inhibit the adhesion.

  In the present embodiment, the heat treatment step heats the film to a predetermined temperature or higher using a heating roll, hot air, infrared rays, etc., and promotes and promotes the stretch orientation crystallization generated in the stretch step to some extent or by stretching. This is a process of removing excessive tension of the generated molecular chain. By suppressing this crystallization promotion and excessive tension, it suppresses the change with time and gives cutability and blocking resistance.

  The method for heating the film is not particularly limited, but preferably exceeds the glass transition temperature of the resin composition constituting the surface layer and is lower than the melting point. For example, the resin composition constituting the surface layer is polylactic acid (PLA) / aromatic adipic acid (DAF-101) / epoxidized soybean oil (ESO) / carbodiimide compound (LA-1) = 77/20/2/1. In the case of (mass%), the glass transition temperature is 17 ° C. Details of the resin composition are shown in the Examples.

  As heating conditions, it is preferable that it is 70-140 degreeC, and it is more preferable that it is 80-130 degreeC. When the heating condition is 70 ° C. or higher, excessive tension of molecular chains can be removed, and when it is 140 ° C. or lower, fusing of the film during the heat treatment process can be prevented. The heat setting time under the above heating conditions is preferably 1 to 30 seconds, and more preferably 2 to 20 seconds.

  If there is insufficient heating due to a low temperature, a short heating time, or the like, sufficient physical properties cannot be fixed, and physical properties are likely to change even after production. This is thought to be because the increase in crystallinity proceeds very slowly after the heat treatment step. Due to the change in physical properties after the production, tightening particularly after winding the paper tube is induced, the drawability is deteriorated, and it may be difficult to draw out the wrap film by blocking hard. If the drawability deteriorates, that is, the pulling power is very large, it will be forcibly removed while destroying the fixed part of the blocking-like films, and the surface of the wrap film will be rough, As a result, the value of the work of adhesion is also reduced.

  If there is excessive heating due to reasons such as a high temperature or a long heating time, the film is torn or torn, making it difficult to produce a wrap film having excellent stability.

  In the heat treatment step, the stress relaxation operation is not particularly limited in the range corresponding to the shrinkage stress of the film in the vertical and horizontal directions during heating. This stress relaxation operation actually fixes the film width slightly narrower than the film width immediately after stretching (for example, fixing both ends of the film to a width narrower than the film width after stretching in the heat treatment heating zone of the tenter device). Is good. A preferable range of the relaxation rate is 3 to 15%. When it is 3% or more, excessive tension of molecular chains generated during stretching can be relieved, and when the wrap film is cut with a saw blade attached to the storage box, cutting along the saw blade becomes possible. If it is 15% or less, the film shrinks without exceeding the range of shrinkage stress of the film, and unevenness in thickness, variation in physical properties, etc. hardly occur.

  In this embodiment, the film after the heat treatment step is wound into a roll shape so as not to cause wrinkles or the like with a winder or the like. Here, since the crystallization of the film is advanced in the heat treatment step, if the film is wound while the crystallization is in progress, the films may be blocked and become fixed. In order to prevent this, it is preferable to cool the film before winding. This cooling is usually performed by exposing to an air flow near room temperature. Preferably, the film is sufficiently cooled by blowing cool air below the glass transition temperature, and then continuously wound. If it does in this way, it will become possible to prevent the adhering state of the wound roll-shaped film.

  The obtained wrap film is slit to a desired width, and a desired length is wound around a core such as a paper tube to obtain a wrap film roll. These can be stored and used in a storage box.

  The wrap film after slitting can be wound into a paper tube winding shape so as not to cause wrinkles or the like with a paper tube winding winder shown in FIG. At this time, the tension applied to the film is 2 of the tension from A which is the feeding point to B which is the point pressed by the pinch roller and the tension from B to C which is the point wound by the winding roller. There is one. Although it does not specifically limit as tension | tensile_strength concerning each, It is preferable that it is 0.5-5 kg from A to B and from B to C. When the weight is 0.5 kg or more, the wrap film can be wound around the paper tube without hesitation, and when the weight is 5 kg or less, the wrap film is hardly broken during winding.

  Hereinafter, the present embodiment will be specifically described with reference to examples and comparative examples, but the present embodiment is not limited to only these examples. The evaluation method and measurement method used in this embodiment are as follows.

(1) Work of adhesion Work of adhesion was measured by the following method. First, ^two cylindrical measuring jigs having a bottom area of 25 cm ² with filter paper attached to the entire bottom surface are prepared. A wrap film was placed on the bottom face so that no wrinkles could enter, and was fixed in a tension state. Next, the cylindrical measuring jig was placed up and down so that the lap film surfaces contacted each other, and a weight of 500 g was placed on the upper jig, and a load was applied to the lap film contacting surface for 1 minute. Thereafter, the weight was gently removed, and the energy required for peeling the wrap film in a direction perpendicular to the contact surface with a tensile tester at a tensile speed of 5 mm / min was defined as the work of adhesion. The measurement was performed under a constant temperature and humidity of a temperature of 23 ° C. and a humidity of 50%, and an average value of five measurements was taken as a measurement value.

(2) Pull output Pull output was measured by the following method. First, a wrap film prepared to have a width of 300 mm was wound around a paper tube having an outer diameter of 37 mm and an inner diameter of 34 mm, and an acrylic cylinder having an outer diameter of 32 mm / inner diameter of 24 mm and a steel rod having a diameter of 12 mm were connected via a bearing. The steel rod was fixed to a tensile tester by fitting it into a rotatable fixture, and the acrylic cylinder and paper tube-wrapped wrap film were allowed to rotate freely. The end of the wrap film was fixed to a plate having a width of 330 mm directly connected to the load cell of the tensile tester, and the load generated when the wrap film was pulled out at a speed of 1000 mm / min was used as the pulling force. The measurement was performed under a constant temperature and humidity of a temperature of 23 ° C. and a humidity of 50%, and an average value of five measurements was taken as a measurement value.

(3) Tensile modulus The tensile modulus was measured by a method based on ASTM-D882. The dimension of the wrap film piece was cut into a width of 10 mm and a length of 100 mm along the MD and TD directions, respectively, to obtain a test piece, and the measurement was performed at a tensile speed of 5 mm / min. A tangent line was drawn on the obtained stress-strain graph, and a value obtained by converting the stress value at 2% elongation into the thickness of the sample film was calculated, and the average value of the five measurements was taken as the measured value. The trade name “AUTOGRAPH AG-IS” (manufactured by Shimadzu Corporation) was used for the measurement.

(4) Tensile strength Tensile strength was measured by a method based on ASTM-D882. The dimensions of the wrap film pieces are cut out to a width of 10 mm and a length of 100 mm respectively along the MD and TD directions to make test pieces, and measured at a tensile speed of 300 mm / min, and an average value of five measurements is measured. Value. The trade name “AUTOGRAPH AG-IS” (manufactured by Shimadzu Corporation) was used for the measurement.

(5) Cut energy Cut energy was measured by the following method. First, a wrap film prepared to a width of 300 mm is wound on a paper tube having an outer diameter of 37 mm, an inner diameter of 34 mm, and a length of 307 mm, and placed in a storage box having a height of 44 mm, a depth of 44 mm, and a length of 317 mm. Fixed to the machine. At this time, the angle between the wrap film and the attached saw blade of the storage box is 90 ° so that the width direction of the storage box is inclined by 25 ° with respect to the pulling direction of the wrap film (the lid of the storage box is closed) And so on). The leading end of the drawn wrap film is fixed to a plate with a width of 330 mm that is directly connected to the load cell of the tensile tester via a double-sided tape with a width of 5 mm, and operates at a speed of 500 mm / min. The required energy was defined as cut energy. The trade name “AUTOGRAPH AG-IS” (manufactured by Shimadzu Corporation) was used for the measurement. The measurement was performed under a constant temperature and humidity of a temperature of 23 ° C. and a humidity of 50%, and an average value of five measurements was taken as a measurement value.

(6) Bleed-out The wrap film was stuck on a 1000 mm × 1000 mm glass plate without any gaps and placed in an atmosphere of a temperature of 23 ° C. and a humidity of 50% for 24 hours. Thereafter, the wrap film was peeled off from the glass plate, and the weight of the bleed material remaining on the glass plate was evaluated.

(7) Width shrinkage rate A wrap film prepared to have a width of 300 mm and a length of 20 m was wound around a paper tube, and the flap film width at that time was measured. Thereafter, the film was left for 24 hours in an atmosphere of a temperature of 40 ° C. and a humidity of 90%, the wrap film width was measured again, and the ratio of the film width that was shrunk compared to the wrap film width before being left was measured.

(8) Weight average molecular weight A wrap film prepared to have a width of 300 mm and a length of 20 m is wound around a paper tube, and the wrap film is stored in an atmosphere of a temperature of 60 ° C. and a humidity of 80% for 15 days. The weight average molecular weight of the resin component was measured. If this weight average molecular weight is 80,000 or more, the performance of the target product can be sufficiently expressed. The weight average molecular weight is a value measured by gel permeation chromatography (hereinafter referred to as GPC). 20 mg of the finely cut film is dissolved in 10 ml of chloroform, and the resulting solution is filtered through a 0.45 μm film made of PVDF to prepare a sample. The weight average molecular weight is measured using GPC (apparatus: alliance 2695, detector: RI waters 2414, analytical column: LF-804 × 1, LF-G × 1). At this time, as measurement conditions, the temperature is 40 ° C., the flow rate is 1 ml / min, and the standard sample is polystyrene.

  The components used in Examples and Comparative Examples are as shown in Table 1 and Table 2 below. In Tables 1 and 2, PLA represents polylactic acid (D-form content 4% by mass, manufactured by Natureworks, trade name “Natureworks”), and PD150 represents a lactic acid-sebacic acid-1,2 propanediol copolymer ( DIC Corporation, trade name “Puramate 150”), NF500 is maleic acid-modified polyethylene (trade name “Admer NF500”, manufactured by Mitsui Chemicals, Inc.), and DAF101 is aromatic-aliphatic- Adipic acid ester (made by Daihachi Chemical Industry Co., Ltd., trade name “DAIFATTY-101”, molecular weight 338) is shown, and PX-884 is aliphatic adipic acid ester (made by Asahi Denka Co., Ltd., trade name “PX”). -884 ", molecular weight 650), LA-1 represents a carbodiimide compound (Nisshinbo Co., Ltd., trade name" Carbodilite LA-1 ") , SBX represents a carbodiimide compound (Rhein Chemie, trade name “Stavaxol P”), ESO represents epoxidized soybean oil (manufactured by NOF Corporation, trade name “New Sizer 510R”, molecular weight 946), DACG Indicates acetylated monoglyceride (Riken Vitamin Co., Ltd., trade name “Riquemar PL019”, molecular weight 330), and WAX155 indicates paraffin wax (Nippon Seiki Co., Ltd., trade name “paraffin wax 155”). , MAE represents a synthetic swelling filler (manufactured by Coop Chemical Co., Ltd., trade name “Somasif MAE”). Moreover, a numerical value shows the content rate (mass%) in a composition in a table | surface.

[Example 1]
The composition shown in Table 1 was sufficiently melt-kneaded with a twin-screw extruder in the same direction at a resin temperature of the extruder kneading portion of about 200 ° C. A die plasticity 101 which is a liquid plasticizer was injected from a liquid injection portion provided in a cylinder of an extruder using a fixed liquid feed pump. The kneaded composition was extruded into a sheet form as a resin composition from a T die provided at the tip of the extruder. Next, an extruded sheet is guided to a cast roll having a smooth surface with a mirror finish and a surface temperature of 30 ° C. so that the roll surface is located within 3 mm from the die lip of the T die. This was rapidly cooled by contacting with. Next, the sufficiently cooled extruded sheet was introduced into a roll type longitudinal stretching machine. The roll surface temperature in the stretching zone was 50 ° C., and the film was stretched 3 times by the difference in the rotational speed between the upstream and downstream rolls of the roll disposed in the stretching zone. The stretched film after the longitudinal stretching was immediately introduced into a roll having a surface temperature of 120 ° C. to promote orientation crystallization, and a heat treatment step was performed. Next, the heat-treated wrap film was promptly guided to a cooling roll having a surface temperature of 30 ° C. and cooled. The sufficiently cooled wrap film was slit to a desired width and wound around a paper tube to form a paper tube-wrapped wrap film, which was stored in a storage box.
The wrap film thus obtained was measured for adhesion work, pulling force, tensile elastic modulus, cut energy, bleed out amount, width shrinkage rate, and weight average molecular weight. These results are shown in Table 3.

[Example 2]
The composition shown in Table 1 was sufficiently melt-kneaded with a twin-screw extruder in the same direction at a resin temperature of the extruder kneading portion of about 200 ° C. The die plasticity 101 and ESO which are liquid plasticizers were inject | poured using the fixed amount liquid pump from the liquid injection | pouring part provided in the cylinder of the extruder. The kneaded composition was extruded in a vertically downward direction as a cylindrical film from a cylindrical die having a cavity in the center. The obtained film was introduced into 25 ° C. cooling water, rapidly cooled and solidified, and sandwiched between two pinch rolls with a folding width of 130 mm. Here, in order to prevent adhesion between films, 300 cc of distilled water is introduced into a cylindrical film sandwiched by pinch rolls from a hollow portion provided at the center of a cylindrical die, and further, as a sticking prevention agent, 50 cc of paraffin (manufactured by Matsumura Oil Co., Ltd., trade name “Smoyl p70”) was introduced. The folding film coated with the anti-sticking agent on the surface was led to a differential roll capable of adjusting the take-up speed, and after passing through a step of heating to 60 ° C. with warm water, air was injected to stretch the tube. By adjusting the take-up speed after heating, the film is stretched 3 times in the flow direction of the film, that is, in the MD direction, and the diameter of the tube, that is, the stretching ratio in the TD direction is adjusted to 4 times by the air pressure. Got. Next, two stretched films are formed by slitting both ends of the cylindrical stretched film, each end is restrained by a restraining tool and guided to a heating furnace, and heat treatment is performed by blowing hot air at 100 ° C. for 5 seconds, A film was obtained. The relaxation during the heat treatment was adjusted to a relaxation rate of 10%. The obtained wrap film was slit to a desired width and wound around a paper tube to obtain a paper tube-wrapped wrap film, which was stored in a storage box. The lap film thus obtained was measured in the same manner as in Example 1. These results are shown in Table 3.

[Example 3]
Except that the composition shown in Table 1 was used and that ESO was injected from the liquid injection portion provided in the cylinder of the extruder, the same procedure as in Example 1 was performed until the longitudinal stretching step. The film after longitudinal stretching was immediately led to a cooling roll having a surface temperature of 30 ° C., and quickly cooled below the glass transition temperature. Thereafter, the stretched film is introduced into a tenter-type transverse stretching machine, stretched four times in the transverse direction, that is, in the TD direction at a stretching temperature of 55 ° C., and subsequently heat-treated by continuously blowing 125 ° C. hot air for 5 seconds. And a film was obtained. The relaxation during the heat treatment was adjusted to a relaxation rate of 5%. The obtained wrap film was slit to a desired width and wound around a paper tube to obtain a paper tube-wrapped wrap film, which was stored in a storage box. The lap film thus obtained was measured in the same manner as in Example 1. These results are shown in Table 3.

[Example 4]
The composition of the surface layer and the core layer shown in Table 1 was melt-kneaded at a resin temperature of 200 ° C. by the same-direction twin screw extruder. A die plasticity 101 which is a liquid plasticizer was injected from a liquid injection portion provided in a cylinder of an extruder using a fixed liquid feed pump. The kneaded composition was led to a feed block, laminated, and extruded from a T-die in the form of a surface layer / core layer / surface layer. Next, an extruded sheet is guided to a cast roll having a smooth surface with a mirror finish and a surface temperature of 30 ° C. so that the roll surface is located within 3 mm from the die lip of the T die. This was rapidly cooled by contacting with.
After the longitudinal stretching step, the same procedure as in Example 3 was performed. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 3.

[Example 5]
A wrap film was obtained in the same manner as in Example 4 except that the composition of the surface layer and the core layer shown in Table 1 was used. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 3.

[Example 6]
A wrap film was obtained in the same manner as in Example 4 except that the composition of the surface layer and core layer shown in Table 1 was used, and that DACG was injected from the liquid injection portion provided in the cylinder of the extruder. . About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 3.

[Examples 7 to 9]
A wrap film was obtained in the same manner as in Example 4 except that the surface layer and core layer compositions shown in Table 1 or Table 2 were used. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 3 or Table 4.

[Comparative Example 1]
A wrap film was obtained in the same manner as in Example 4 except that the surface layer and core layer compositions shown in Table 2 were used. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 4.

[Comparative Example 2]
A wrap film was obtained in the same manner as in Example 4 except that the surface layer and core layer compositions shown in Table 2 were used. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 4.

[Comparative Example 3]
A wrap film was obtained in the same manner as in Example 4 except that the surface layer and core layer compositions shown in Table 2 were used. About the obtained wrap film, the same measurement as Example 1 was performed. These results are shown in Table 4.

[Comparative Example 4]
The composition of the surface layer and the core layer shown in Table 2 was melt-kneaded at a resin temperature of 200 ° C. by the same-direction twin screw extruder. A die plasticity 101 which is a liquid plasticizer was injected from a liquid injection portion provided in a cylinder of an extruder using a fixed liquid feed pump. The kneaded composition was led to a feed block, laminated, and extruded from a T die with a surface layer / core layer / surface layer structure. Next, an extruded film is guided onto a cast roll having a smooth surface with a mirror finish and a surface temperature of 30 ° C. so that the roll surface is located within 3 mm from the die lip of the T die. This was rapidly cooled by contacting with a film to obtain a film. The obtained wrap film was slit to a desired width and wound around a paper tube to obtain a paper tube-wrapped wrap film, which was stored in a storage box. The lap film thus obtained was measured in the same manner as in Example 1. These results are shown in Table 4.

  The wrap film of the present invention is used as a wrap film for wrapping goods such as food, or food and food dishes stored in a refrigerator, freezer, etc., or heated in a microwave oven, etc. Useful.

DESCRIPTION OF SYMBOLS 1 ... Wrap film original fabric, 2 ... Roller, 3 ... Pinch roller, 4 ... Winding roller, 5 ... Paper tube.

Claims (7)

A wrap film having one or more film layers and a cut energy of 50 mJ or less,
At least one of the film layers is
A polylactic acid-based resin (A), containing a plasticizer (B) and a carbodiimide compound (C) comprising a dicarboxylic acid ester having a molecular weight of 200 to 3000 and having at least one benzene ring in the molecular structure; A wrap film, which is a film layer (a) stretched in a direction. The film layer (a)
2 to 35 parts by mass of the plasticizer (B) and 0.1 to 5 parts by mass of the carbodiimide compound (C) with respect to 100 parts by mass of the polylactic acid resin (A),
The wrap film according to claim 1, wherein the wrap film is a film layer stretched 3 to 10 times in at least one direction.   The wrap film according to claim 1, wherein the plasticizer (B) is an adipic acid ester.   The wrap film according to any one of claims 1 to 3, wherein at least one of the film layers is a film layer containing a wax.   The wrap film according to any one of claims 1 to 4, wherein at least one of the film layers is a film layer containing a plate-like filler.   The wrap film according to any one of claims 1 to 4, wherein the film layer (a) is a film layer containing a wax and / or a plate-like filler.   A wrap film roll formed by winding the wrap film according to any one of claims 1 to 6 on a core.

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