JP2018021148A - Polylactic acid film, heat-shrinkable film prepared with the film, molding or heat-shrinkable label prepared with the heat-shrinkable film, and container prepared with the molding or having the label attached thereto - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid film having excellent transparency and rigidity, and provide a heat-shrinkable film prepared with the polylactic acid film, having excellent shrinkable properties, and also high transparency and rigidity.SOLUTION: A polylactic acid film has at least one layer predominantly composed of a mixed resin composition of a polylactic acid resin (A) and a cellulose ester (B) with an acetyl group content of 10-25 mass% and a butyryl group content of 25-45 mass%. In the mixed resin composition, a mixture ratio between (A) and (B) is (A)/(B)=92/8-55/45 mass%, and an internal haze value in accordance with JIS K7136 is 15% or less.SELECTED DRAWING: None

Description

  The present invention relates to a polylactic acid film excellent in transparency and rigidity. The present invention also relates to a heat-shrinkable film having excellent shrinkage characteristics, transparency and rigidity.

  Polylactic acid-based resins are plant-derived materials that use lactic acid obtained by fermentation of starch as a raw material, and are attracting attention from the viewpoints of measures against global warming and substitution of petroleum resources that are expected to be depleted in the future. While this polylactic acid-based resin has features such as excellent transparency and rigidity, it has a limitation in that it has a low crystallization speed and is inferior in heat resistance for crystallization and use in a molded product or the like. Further, when used as a film, the glass transition temperature is relatively low, so there is a limit to use in heat resistant applications. Various technical studies have been made on the modification of such a polylactic acid resin.

  On the other hand, cellulose derivatives such as cellulose and cellulose ester are the most produced biomass materials on the earth, and are attracting attention from the same viewpoint as the polylactic acid resin. For example, a method of melt spinning by adding a water-soluble plasticizer such as polyethylene glycol to cellulose acetate is known, but the use of a hygroscopic plasticizer such as polyethylene glycol is limited. Therefore, a more versatile method was expected.

  By the way, many beverages such as tea, juice, and coffee are currently sold in a state of being filled in containers such as plastic bottles, and in recent years, plastic bottle sales of alcoholic beverages such as wine have been seen. . As such diversity increases, the importance of heat-shrinkable labels that are mounted to differentiate from other products and to improve the visibility of products is increasing. The heat-shrinkable label is used not only for beverages but also for foods, toiletries, medical products, chemicals, and industrial products.

  This heat-shrinkable label printing is usually applied on the back side of the film to prevent the printed material from slipping off due to rubbing or scratching between containers, and therefore the heat-shrinkable label original film requires high transparency. Is done. Therefore, polyvinyl chloride resin, polystyrene resin, aromatic polyester resin, and polylactic acid resin are used as the material of the film. Among them, the polylactic acid resin is used for the reasons described above. It is also attracting attention as a material for heat-shrinkable films.

  In addition, polylactic acid-based resins are attracting attention in terms of environmental considerations because they have high tensile modulus and tensile strength and can be made into thin films. Since the importance of environmentally friendly products will continue to increase, further improvement in the rigidity of polylactic acid is required.

  By the way, a method for improving the characteristics of each resin by a polymer blend of a polylactic acid resin and cellulose ester is known. For example, Patent Document 1 proposes a resin composition having flexibility and heat resistance by adding a natural product to a resin composition composed of a polymer component composed of polylactic acid and aliphatic polyester and a plasticizer. . Patent Document 2 proposes a method for improving moldability by mixing an aliphatic polyester such as polylactic acid with cellulose ester. Patent Documents 3 and 4 propose resin compositions having transparency, mechanical properties, and heat resistance by mixing a polylactic acid resin, cellulose ester, and a compatibilizing agent.

Japanese Patent Laid-Open No. 11-241008 JP 2003-82160 A WO 2004/087812 JP 2004-204217 A

However, the technology of Patent Document 1 includes starch, chitin, chitosan, and celluloses as natural products, and only acetyl cellulose is exemplified as the cellulose, and there is no specific example that is actually blended. Moreover, the technique of patent document 2 is only shown improving the moldability of a cellulose ester, and the technique which improves the characteristic of polylactic acid is not mentioned. Patent Documents 3 and 4 show that polylactic acid, cellulose ester and a compatibilizer improve heat resistance, but the polymer blend of polylactic acid and cellulose ester maintains rigidity while maintaining rigidity. There is no example showing the improvement of the above, and there is no mention of a technique having characteristics as a heat shrinkable label.
As described above, in the prior art, there has never been studied to improve the rigidity of the polylactic acid resin and obtain a highly transparent film and a heat-shrinkable film.

  This invention is made | formed in view of the said subject, ie, the subject of this invention is providing the polylactic acid-type film excellent in transparency and rigidity. In particular, an object of the present invention is to provide a polylactic acid heat-shrinkable film having excellent shrinkage characteristics, high rigidity and excellent transparency, and suitable for applications such as shrink wrapping, shrink tying wrapping and shrinkage labels.

As a result of intensive studies to solve the problems of the prior art, the present inventor has completed the following invention.
That is, an object of the present invention is to provide a mixed resin composition of a polylactic acid resin (A) and a cellulose ester (B) having an acetyl group content of 10 to 25% by mass and a butyryl group content of 25 to 45% by mass. And the mixing ratio of (A) and (B) in the mixed resin composition is (A) / (B) = 92/8 to 55/45% by mass. This is solved by a polylactic acid film having an internal haze value of 15% or less in accordance with JIS K7136.

  According to the present invention, a polylactic acid film having high transparency and rigidity can be obtained. In addition, a heat-shrinkable film having excellent shrinkage characteristics, high rigidity, and excellent transparency can be obtained. Since the heat-shrinkable film has excellent shrinkage characteristics and high rigidity and transparency, it can be suitably used for applications such as shrink wrapping, shrink-bound packaging, and shrink labels.

  Hereinafter, a film as an example of an embodiment of the present invention (hereinafter referred to as “the film of the present invention”), a heat shrinkable film of the present invention, a molded product of the present invention, a label of the present invention, and a container of the present invention will be described. To do. However, the scope of the present invention is not limited to the embodiments described below.

  In the present specification, “main component” is intended to allow other components to be included within a range that does not hinder the action and effect of the resin contained as the main component. Further, the term does not limit the specific content, but it is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and 100% by mass or less, based on the entire constituent components. It is a component that occupies the range.

<Film of the present invention>
The film of the present invention contains a polylactic acid resin (A) and a cellulose ester (B) as a resin composition.

<Polylactic acid resin (A)>
The polylactic acid-based resin (A) used in the present invention is a homopolymer of D-lactic acid or L-lactic acid, or a copolymer thereof, specifically, a poly ( D-lactic acid), poly (L-lactic acid) whose structural unit is L-lactic acid, and poly (DL-lactic acid) which is a copolymer of L-lactic acid and D-lactic acid. A mixed resin of a plurality of the above copolymers having different copolymerization ratios with L-lactic acid is also included.

The copolymer of L-lactic acid and D-lactic acid preferably has a copolymerization ratio of D-lactic acid and L-lactic acid (hereinafter abbreviated as “D / L ratio”), preferably “1/99” to "10/90" or "90/10" to "99/1", more preferably "1/99" to "9.5 / 90.5" or "90.5 / 9.5" to " 99/1 ”, more preferably“ 1/99 ”to“ 9/91 ”or“ 91/9 ”to“ 99/1 ”.
When the D / L ratio is higher than 99 or less than 1, high crystallinity is exhibited, the melting point is high, and the heat resistance and mechanical properties tend to be excellent. However, when used as a heat-shrinkable film, it usually involves printing and a bag-making process using a solvent, so that the crystallinity of the constituent material itself can be lowered appropriately in order to improve printability and solvent sealability. Necessary. Moreover, when crystallinity is too high, orientation crystallization advances at the time of extending | stretching, and there exists a tendency for the film shrinkage | contraction characteristic at the time of heating to fall. Furthermore, even as a film in which crystallization is suppressed by adjusting stretching conditions, crystallization proceeds before shrinkage due to heating during heat shrinkage, and as a result, there is a tendency to cause shrinkage unevenness and insufficient shrinkage. .

On the other hand, when the D / L ratio is less than 90 and higher than 10, the crystallinity is almost completely lost. As a result, when the labels collide with each other after heat shrinkage, they are fused by heat. Trouble may occur. Further, in the stretching process, the thickness tends not to be uniform in the width direction, the surface smoothness is hardly imparted, and the transparency tends to be hindered.
By adjusting the D / L ratio within the above range, it is possible to obtain a heat-shrinkable film that hardly causes such problems and has excellent shrinkage characteristics. In the film of the present invention, polylactic acid resins having different D / L ratios can be blended. It is preferable to blend polylactic acid resins having different D / L ratios because the D / L ratio of the polylactic acid resins can be adjusted relatively easily. In this case, what is necessary is just to make it the value which averaged D / L ratio of several lactic acid-type polymer in the said range. By blending two or more polylactic acid resins having different D / L ratios and adjusting the crystallinity according to the intended use, it is possible to balance heat resistance and heat shrinkage characteristics.

  The polylactic acid-based resin (A) is a non-aliphatic dicarboxylic acid other than lactic acid such as α-hydroxycarboxylic acid and terephthalic acid as a small amount of copolymerization component as long as the essential properties are not impaired. At least one selected from the group consisting of aliphatic dicarboxylic acids such as acids and succinic acids, non-aliphatic diols such as ethylene oxide adducts of bisphenol A, and aliphatic diols such as ethylene glycol can be used. For the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound, or an acid anhydride can be used.

Specific examples of α-hydroxycarboxylic acids other than lactic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy- Examples include bifunctional aliphatic hydroxycarboxylic acids such as 3-methylbutyric acid, 2-methyllactic acid, and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone, and valerolactone.
Specific examples of the dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like. Examples of the diol include ethylene glycol, 1,4-butanediol, 1, 4-cyclohexane dimethanol etc. are mentioned.

  Copolymerization ratio [lactic acid / (α-hydroxycarboxylic acid other than lactic acid, diol, or dicarboxylic acid)] of a copolymer of lactic acid and α-hydroxycarboxylic acid, diol, or dicarboxylic acid other than lactic acid is particularly limited. Although not, the mass ratio is preferably “100/0” to “50/50”, more preferably “100/0” to “60/40”, and even more preferably “100/0” to “70/30”. It is. If the copolymerization ratio is within the above range, a film having a good balance of physical properties such as rigidity, transparency and impact resistance can be obtained. Moreover, as a structure of these copolymers, a random copolymer, a block copolymer, and a graft copolymer are mentioned, Any structure may be sufficient. However, a block copolymer or a graft copolymer is preferable from the viewpoint of impact resistance and transparency of the film.

  The polylactic acid resin (A) has a weight average molecular weight of 20,000 or more, preferably 40,000 or more, more preferably 60,000 or more, and considering the upper limit value, preferably 400,000 or less, preferably 350,000 or less, more preferably 300,000 or less. When the weight average molecular weight is 20,000 or more, an appropriate resin cohesive force can be obtained, and the film can be prevented from being insufficiently stretched or embrittled. On the other hand, if the weight average molecular weight is 400,000 or less, the melt viscosity can be lowered, which is preferable from the viewpoint of production and productivity improvement. The weight average molecular weight can be measured by gel permeation chromatography (hereinafter referred to as “GPC”).

  As a polymerization method of the polylactic acid-based resin (A), a known method such as a condensation polymerization method or a ring-opening polymerization method can be employed. For example, in the case of a condensation polymerization method, a polylactic acid resin having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of D-lactic acid, L-lactic acid, or a mixture thereof. Further, in the ring-opening polymerization method, a lactide which is a cyclic dimer of lactic acid is subjected to ring-opening polymerization in the presence of a predetermined catalyst while using a polymerization regulator or the like, if necessary. A lactic acid resin can be obtained. The lactide includes DL-lactide, which is a dimer of L-lactic acid. By mixing and polymerizing these as necessary, a polylactic acid resin having an arbitrary composition and crystallinity can be obtained. it can.

  As a typical example of the polylactic acid resin (A), “Nature Works” manufactured by Nature Works LLC and the like are commercially available. Moreover, as a specific example of the random copolymer of polylactic acid-type resin, diol, and dicarboxylic acid, "GS-Pla" (made by Mitsubishi Chemical Corporation) is mentioned, for example.

<Cellulose ester (B)>
Generally, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose diacetate, cellulose triacetate, cellulose acetate phthalate, etc. are known as cellulose esters. In the present invention, cellulose acetate butyrate is used. Thus, it was found that good results were obtained in terms of compatibility with the polylactic acid resin, improvement of transparency and rigidity of the film, and balance of shrinkage characteristics of the heat shrinkable film.

  It is important that the cellulose ester (B) has an acetyl group content of 10 to 25% by mass. The acetyl group content is preferably 12 to 20% by mass, and more preferably 13.5 to 17.5% by mass. When the acetyl group content is within the above range, the compatibility with the polylactic acid resin is excellent, and the resulting film has excellent balance of transparency and rigidity, moldability, and the like.

  Moreover, it is important that the butyryl group content of the cellulose ester (B) is 25 to 45% by mass. The butyryl group content is preferably 30 to 40% by mass. When the butyryl group content is within the above range, the compatibility with the polylactic acid resin is excellent, and the resulting film has excellent balance between transparency and rigidity, moldability, and the like.

  The cellulose ester (B) preferably has a hydroxyl group content of 0.5 to 5.0%. In order to obtain good compatibility with polylactic acid, the content is more preferably 1.0 to 4.5%, and further preferably 1.0 to 3.5%.

  The number average molecular weight of the cellulose ester (B) is not particularly limited, but the lower limit is preferably 8,000 or more, more preferably 10,000 or more, and further preferably 12,000 or more. Moreover, as an upper limit, 100,000 or less are preferable, 90,000 or less are more preferable, and it is further more preferable that it is 80,000 or less.

  As a commercial item of cellulose ester (B), for example, [CA] “CAB” “CAP” series manufactured by Eastman Chemical Co. can be mentioned, and these are commercially available. These cellulose esters (B) may be used singly or in combination of two or more types having different compositions.

<Mixing ratio>
It is important that the mixing ratio of the polylactic acid resin (A) and the cellulose ester (B) is (A) / (B) = 92/8 to 55/45% by mass.
The lower limit of the mixing ratio of the cellulose ester (B) is preferably 10% by mass or more, and the upper limit is preferably 40% by mass or less. Moreover, the lower limit of the mixing ratio of the polylactic acid resin (A) is preferably 60% by mass or more, and the upper limit is preferably 90% by mass or less.
When the lower limit of the mixing ratio of the cellulose ester (B) is in the above range, the rigidity when used as a film is sufficient. Moreover, if the upper limit of the mixing ratio of the cellulose ester (B) is within the above range, transparency can be satisfied.

<Other ingredients>
The mixed resin composition of the present invention may contain a resin other than the polylactic acid resin (A) and the cellulose ester (B) as long as the effects of the present invention are not impaired.
Specific examples of other resins include (meth) acrylic acid ester resins, (meth) acrylic acid resins, polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, chlorinated polyethylene resins. Resins, polyester resins other than polylactic acid resins, polycarbonate resins, polyamide resins, polyacetal resins, ethylene vinyl acetate copolymers, polymethylpentene resins, polyvinyl alcohol resins, cyclic olefin resins, polybutylene sushi Nate resin, polyacrylonitrile resin, polyethylene oxide resin, cellulose resin, polyimide resin, rigid polyurethane resin, polyphenylene sulfide resin, polyphenylene ether resin, polyvinyl acetal resin, polybutadiene resin Fat, polybutene resin, polyamideimide resin, polyamide bismaleimide resin, polyarylate resin, polyetherimide resin, polyetheretherketone resin, polyetherketone resin, polyethersulfone resin, polyketone resin , Polysulfone resins, aramid resins, silicone resins, and the like, and copolymers containing these resins as main components, core-shell multilayer polymers, and modified products thereof.
Among these, (meth) acrylic ester resin, ethylene vinyl acetate copolymer, polybutylene succinate resin, polyethylene oxide resin, and polyvinyl acetal resin are excellent in compatibility with polylactic acid resin, Blending with a polylactic acid-based resin is effective for adjusting the glass transition temperature that affects shrinkage characteristics, and for imparting further fracture resistance by being finely dispersed in the polylactic acid-based resin.

  Furthermore, to the mixed resin composition of the present invention, in addition to the above-mentioned other components, additives generally blended in the resin composition can be appropriately added within a range that does not significantly impair the effects of the present invention. Examples of the additive include recycled resin generated from trimming loss of ears and the like, silica, talc, kaolin, carbonic acid, which are added for the purpose of improving / adjusting moldability, productivity and various physical properties of the porous film. Inorganic particles such as calcium, pigments such as titanium oxide and carbon black, flame retardants, weathering stabilizers, heat stabilizers, antistatic agents, melt viscosity improvers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents , Antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, antifogging agents, antiblocking agents, slip agents, colorants and the like.

<Transparency: Internal haze value>
It is important that the film of the present invention has an internal haze value measured in accordance with JIS K7136 of 15% or less. The internal haze value is more preferably 10% or less, and further preferably 8% or less. If the internal haze value is 15% or less, the transparency of the film is sufficient, and sufficient visibility of the covering and the back surface printing when mounted as a label or the like can be obtained.
The internal haze value can be adjusted by adopting the above-mentioned ones as the type, composition, and blending amount of the polylactic acid resin (A) and cellulose ester (B) in the mixed resin composition of the present invention. it can.

<The heat-shrinkable film of the present invention>
The heat-shrinkable film of the present invention is obtained by stretching the film of the present invention in at least one direction.

<Heat shrinkage>
The heat shrinkable film of the present invention preferably has a heat shrinkage rate in the main shrinkage direction of 20% or more and 80% or less when immersed in warm water at 80 ° C. for 10 seconds, and the lower limit is 30% or more. More preferably, the upper limit is 70% or less.
In order to set the heat shrinkage rate within the above range, the stretching speed, stretching temperature, stretching ratio, and temperature and time in heat treatment and relaxation treatment in the stretching step in the method for producing a heat shrinkable film of the present invention described later are described. It can be adjusted by stretching conditions such as relaxation rate.

  The “heat shrinkage rate” in the present invention is the percentage of shrinkage with respect to the original size before shrinkage in% in the longitudinal direction or the transverse direction, as will be described later. Further, the “main shrinkage direction” means the larger one of the longitudinal direction and the transverse direction in the stretching direction, and is a direction corresponding to the outer circumferential direction when the bottle is attached to a bottle, for example.

  The heat shrinkage rate in the main shrinkage direction serves as an index for determining adaptability to a shrinkage process in a relatively short time (several seconds to about several tens of seconds) such as for use as a shrinkage label for a PET bottle. At present, the shrinkage processing machine most commonly used industrially for labeling of PET bottles is generally called a steam shrinker that uses steam as a heating medium for shrinking. Furthermore, the heat-shrinkable film needs to be sufficiently heat-shrinked at a temperature as low as possible from the viewpoint of the influence of heat on the object to be coated. However, in the case of a film with high temperature dependence and extremely different shrinkage ratios depending on the temperature, parts with different shrinkage behavior tend to occur with respect to the temperature spots in the steam shrinker, so shrinkage spots, wrinkles, avatars, etc. occur. However, the shrink-finished appearance tends to deteriorate. From the viewpoint of including these industrial productivity, if the thermal shrinkage rate in the main shrinkage direction of the film when immersed in warm water at 80 ° C. for 10 seconds is 20% or more, the film is sufficiently adhered to the coated object within the shrinkage processing time. It is preferable because it can produce a good shrinkage appearance without spots, wrinkles and avatars, and the upper limit of the heat shrinkage rate in the main shrinkage direction of the film when immersed in warm water at 80 ° C. for 10 seconds is In order to suppress rapid shrinkage of the film, it is preferably 80% or less.

  When the heat-shrinkable film of the present invention is used as a heat-shrinkable label, the heat shrinkage rate in the direction orthogonal to the main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds is −10% or more and 10 % Or less (minus shrinkage indicates that the film has expanded after immersion in hot water, and in the case of a uniaxially stretched film, it may be observed in the measurement of the heat shrinkage in the direction perpendicular to the main shrinkage direction. ), Preferably -8% or more and 8% or less, and more preferably -6% or more and 6% or less. If the film has a thermal shrinkage rate of -10% or more and 10% or less in the direction perpendicular to the main shrinkage direction, the dimensional change in the direction perpendicular to the main shrinkage direction after shrinkage is small, and the printed pattern and characters after shrinkage are distorted. In addition, it is preferable because the vertical pulling phenomenon is less likely to occur when mounted on a container.

<Tensile modulus>
The heat-shrinkable film of the present invention has a tensile modulus in the machine direction and the transverse direction of 4000 MPa or more as measured in accordance with JIS K7127 under the conditions of an atmospheric temperature of 23 ° C. and a tensile speed of 5 mm / min. It is preferable. The tensile elastic modulus is more preferably 4200 MPa or more, and further preferably 4500 MPa or more. If the tensile elastic modulus is 4000 MPa or more, the stiffness of the entire film can be increased, and problems such as the film meandering during processes such as printing and bag making of heat-shrinkable labels are less likely to occur. In addition, even when the film thickness is thin, when covering the film made in a container such as a plastic bottle with a labeling machine, etc., it is easy to cover the film diagonally or the yield is likely to decrease due to the film being folded back. It is preferable because dots hardly occur. The upper limit is not particularly limited, but the higher the tensile elastic modulus, the thinner the label thickness tends to be.

<Storage elastic modulus difference (ΔE ')>
The heat-shrinkable film of the present invention preferably has a storage elastic modulus difference (ΔE ′) of 2.0 Pa or less. The difference in storage modulus is more preferably 1.8 or less, and still more preferably 1.5 or less. The storage elastic modulus difference in the present invention is a test piece having a width of 4 mm × a length of 60 mm, using a viscoelastic spectrometer DVA-200 (manufactured by IT Measurement Co., Ltd.), with a vibration frequency of 10 Hz, a strain of 0.1%, Storage elastic modulus at 90 ° C. when dynamic viscoelasticity was measured in the transverse direction under the conditions of a heating rate of 3 ° C./min and a chucking distance of 2.5 cm and a measurement temperature in the range of −100 ° C. to 150 ° C. E _'90 and the storage modulus at 60 ° C. E' ₆₀ difference ΔE of '= log E' is a representation in _{90 -logE '60.} When the difference in storage elastic modulus is 2.0 Pa or less, the change in film rigidity from the glass transition temperature (Tg) to the shrinkage temperature becomes gradual, and the shrinkage unevenness of the film can be suppressed and the occurrence of wrinkles is reduced. This is preferable because it is possible. The lower limit is not particularly limited, but if the film maintains a sufficient heat shrinkage rate, the smaller the value, the better the shrink finish.

<Layer structure>
The film of this invention should just have at least 1 layer which has the mixed resin composition of this invention as a main component, and may be a single | mono layer structure, or a laminated structure.
The laminated structure may be formed by laminating a plurality of layers (1) having the composition of the present invention as a main component, or may be a laminated structure with a layer (2) having other resins as a main component. Specific examples include (1) / (1), (1) / (1) / (1), (1) / (2), (1) / (2) / (1), (2) / ( 1) / (2), (1) / (2) / (1) / (2) / (1), etc., in addition to the above, depending on the required film quality, Even combinations can be employed.
In addition, when the layer which has the mixed resin composition of this invention as a main component in a laminated structure is used as a front and back layer, since the transparency and rigidity improvement effect can be anticipated most in various layer structures, it is preferable. Moreover, it is preferable also when it uses for an intermediate | middle layer since the same effect can be anticipated.

  Examples of a method for forming the laminated structure include a co-extrusion method, a method of forming a film of each layer, and then superposing and heat-sealing, a method of bonding with an adhesive, and the like.

  The total thickness of the film of the present invention is not particularly limited, whether it is a single layer or a laminate, but it is preferably thinner from the viewpoint of transparency, shrinkage workability, raw material cost, and the like. Specifically, the total thickness of the stretched film is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less. Further, the lower limit of the total thickness of the film is not particularly limited, but is preferably about 10 μm in consideration of the handleability of the film.

<The manufacturing method of the film of this invention>
The manufacturing method of the film of this invention is not specifically limited, It can manufacture by a conventionally well-known method. Specifically, for example, a film can be obtained by an inflation method, a tubular method, a T-die method, or the like. The film of the present invention can be uniaxially or biaxially stretched. The stretching method is not particularly limited, and a conventionally known method such as a roll method, a tenter method, or a tubular method can be employed. Furthermore, the film of the present invention may be subjected to surface treatment for the purpose of imparting various functions. Specific examples of the surface treatment include corona treatment, plasma treatment, acid treatment, coating treatment, and the like, and can be appropriately selected and performed as necessary.

<The manufacturing method of the heat-shrinkable film of this invention>
The production method when the film of the present invention is a heat-shrinkable film is not particularly limited, and can be produced by a known method. Specifically, the resin is melted using an extruder, extruded from a T-die, cooled and solidified with a cooling roll, and roll-stretched in the longitudinal direction (film flow direction) or in the transverse direction (with respect to the film flow direction). Thus, the film is stretched in at least one direction by tenter stretching in the vertical direction). Moreover, you may extend | stretch simultaneously in the vertical direction and a horizontal direction with a simultaneous biaxial stretching machine. Furthermore, a tubular film may be radially stretched by an internal pressure by a tubular method, and a method of cutting a tubular material stretched by a tubular method into a planar shape is also included. The form of the film may be either a flat form or a tube form, but the flat form is preferred from the viewpoint of productivity (a few products can be taken in the width direction of the original film) and easy printing.

  The stretching ratio in the stretching is such that the longitudinal direction is 2 to 10 times, the transverse direction is 2 to 10 times, and preferably 3 to 6 times in the longitudinal direction, for applications such as overlapping and shrinking in two directions. Hereinafter, the horizontal direction is about 3 to 6 times. On the other hand, in applications such as heat-shrinkable labels that shrink mainly in one direction, the direction corresponding to the main shrinkage direction is 2 to 10 times, preferably 3 to 8 times, more preferably 3 to 7 times. The direction perpendicular to the main shrinkage direction is 1 to 2 times (1 time indicates a case where the film is not stretched), preferably 1.01 to 1.50 times. For this, it is desirable to select a magnification ratio in the category of uniaxial stretching. A film stretched at a draw ratio within the above range does not have an excessively large thermal shrinkage rate in the direction perpendicular to the main shrinkage direction. For example, when the film is attached to a container as a shrink label, the film is also formed in the height direction of the container. This is preferable because the so-called vertical shrinkage phenomenon that heat shrinks can be suppressed.

  The stretching temperature needs to be adjusted depending on the glass transition temperature of the resin used and the properties required for the heat-shrinkable film, but is generally 60 ° C. or higher, preferably 70 ° C. or higher, and the upper limit is 100 ° C. or lower, preferably 90 It is controlled in the range of ℃ or less.

  Next, the stretched film is subjected to a heat treatment or relaxation treatment at a temperature of about 50 ° C. or more and 100 ° C. or less for the purpose of reducing the natural shrinkage rate or improving the heat shrink property, if necessary. It cools rapidly within the time not to relax, and becomes a heat-shrinkable film.

  The heat-shrinkable film of the present invention is subjected to surface treatment and surface treatment such as corona treatment, printing, coating, and vapor deposition, as well as bag making and perforation treatment with various solvents and heat sealing, if necessary. Can do.

  The heat-shrinkable film of the present invention can be processed from a flat shape to a cylindrical shape or the like according to an article to be packaged and used for packaging. When printing is required in a cylindrical container such as a plastic bottle, first print the required image on one side of a wide flat film wound up on a roll, and then cut it to the required width while the print side is inside. The center seal (the shape of the seal portion is a so-called envelope) may be folded into a cylindrical shape. As the center sealing method, an organic solvent bonding method, a heat sealing method, an adhesive method, and an impulse sealer method can be considered. Among these, from the viewpoint of productivity and appearance, an adhesion method using an organic solvent is preferably used.

<The molded product of the present invention, the label of the present invention, and the container of the present invention>
The use of the heat-shrinkable film of the present invention is not particularly limited, but by using this as a base material, a printing layer, a vapor deposition layer, and other functional layers are laminated as necessary to form a bottle. (Blow bottle), tray, lunch box, prepared food container, dairy product container, and other various molded products.

  Moreover, the heat-shrinkable film of the present invention can be used as a base material for heat-shrinkable labels for food containers (for example, soft drinks or food PET bottles, glass bottles, preferably PET bottles). In this case, even a complicated shape (for example, a cylinder with a narrow center, a square column with a corner, a pentagonal column, a hexagonal column, etc.) can be closely attached to the shape and is mounted beautifully without wrinkles or avatars. Label. And the food container which installed the label can be used as a container. In addition, the said molded article and container can be produced by using a normal shaping | molding method.

  The heat-shrinkable film of the present invention is extremely different from the heat-shrinkable film of the present invention in terms of the coefficient of thermal expansion and water absorption in addition to the heat-shrinkable label material used for plastic molded products that are deformed when heated to a high temperature. Different materials, such as polyolefin resin such as metal, porcelain, glass, paper, polyethylene, polypropylene, polybutene, polymethacrylate resin, polycarbonate resin, polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyamide resin, etc. It can also be suitably used as a heat-shrinkable label material for a package (container) using at least one selected as a constituent material.

  As a material constituting the plastic package, in addition to the above resins, polystyrene, rubber-modified high impact polystyrene (HIPS), styrene-butyl acrylate copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer Polymer, acrylonitrile-butadiene-styrene copolymer (ABS), (meth) acrylic acid-butadiene-styrene copolymer (MBS), polyvinyl chloride resin, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated Examples thereof include a polyester resin and a silicone resin. These plastic packages may be a mixture of two or more resins or a laminate.

  As mentioned above, the use of the composition of the present invention has been described using a heat-shrinkable film as a representative example, but the use of the film of the present invention is not limited to a heat-shrinkable film. It is also useful to be used as a base material for various parts, various injection-molded articles, medical materials, building materials, members for electric / electronic equipment, information recording films, sheet materials, labels, adhesive tapes, and the like.

  Examples are shown below, but the present invention is not limited by these examples.

<Evaluation method>
Measurement and evaluation shown in the examples were performed as follows. In the examples, the film take-up (flow) direction is described as the “longitudinal” direction (or “MD”), and the perpendicular direction thereof is described as the “transverse” direction (or “TD”).

(1) Thermal contraction rate The obtained film was cut into a size of 10 mm in length and 200 mm in width, and immersed in a hot water bath at 80 ° C. for 10 seconds, and the shrinkage was measured. The thermal shrinkage rate was expressed as a percentage of the shrinkage amount relative to the original size before shrinkage.

(2) Tensile elasticity modulus of the obtained film according to JIS K7127, temperature 1 of No. 1 test piece (total length 200 mm, width 10 mm to 25 mm strip, distance between marked lines 100 mm, distance between grips 150 mm) The tensile modulus was measured in the direction (MD) perpendicular to the main shrinkage direction at ° C.
○: When the tensile fracture modulus is 4000 MPa or more ×: When the tensile elongation at break is less than 4000 MPa

(4) Internal haze value About the obtained film, internal haze value was measured based on JISK7136, and it judged on the following reference | standard.
○: When the internal haze value is 15% or less ×: When the internal haze value exceeds 15%

(5) Storage elastic modulus difference About the obtained film, using a viscoelastic spectrometer DVA-200 (made by IT Measurement Co., Ltd.), a test piece of width 4 mm × length 60 mm, vibration frequency 10 Hz, strain 0.1 %, Temperature rising rate 3 ° C./min, and chuck distance 2.5 cm, storage temperature at 90 ° C. when dynamic viscoelasticity is measured in the transverse direction at a measurement temperature in the range of −100 ° C. to 150 ° C. It calculates a difference _{ΔE '= logE' 90 -logE '} 60 ₆₀ elastic modulus E' the storage modulus E at ₉₀ and 60 ° C. ', was judged by the following criteria.
○: When ΔE ′ is 2.0% or less ×: When ΔE ′ exceeds 2.0%

<Materials used>
(Polylactic acid resin (A))
-Product made from Nature Works LLC, a brand name: NatureWorks4060D, D body / L body weight = 12/88, It abbreviates as "A-1."
-Product made from Nature Works LLC, a brand name: NatureWorks4043D, D body / L body weight = 4/96, It abbreviates as "A-2."

(Cellulose ester (B))
-Product name: CAB381-0.1, acetyl group content 13.5%, butyryl group content 38%, hydroxyl group content 1.3%, number average molecular weight 20,000, abbreviation "B-1", manufactured by Eastman Chemical Co. To do.
-Product name: CAB321-0.1, acetyl group content 17.5%, butyryl group content 17.5%, hydroxyl group content 1.3%, number average molecular weight 12,000, "B-2", manufactured by Eastman Chemical Co. Abbreviated.
-Product name: CAB171-15, acetyl group content 29.5%, butyryl group content 17%, hydroxyl group content 1.1%, number average molecular weight 65,000, “B-3”, manufactured by Eastman Chemical Co.
-Product name: CAB551-0.2, acetyl group content 2.0%, butyryl group content 52%, hydroxyl group content 1.8%, number average molecular weight 30,000, abbreviation "B-4", manufactured by Eastman Chemical Co. To do.

Example 1
A polylactic acid resin (A-1) is blended at a ratio of 45 mass%, a polylactic acid resin (A-2) at 45 mass%, and a cellulose ester (B-1) at a ratio of 10 mass%. Screw diameter 25mmφ), melt-kneaded at a set temperature of 200 ° C, shaped into a sheet with a T-die, cooled and solidified with a cast roll set at 50 ° C, and an unstretched sheet with a thickness of 200 µm Obtained. Next, this unstretched sheet was stretched 5 times in the width direction of the unstretched sheet using a film tenter (manufactured by Kyoto Kikai Co., Ltd.) set to a preheating temperature of 82 ° C., a stretching temperature of 82 ° C., and a heat treatment temperature of 82 ° C. A 40 μm heat-shrinkable film was obtained. The evaluation results of the obtained film are shown in Table 1.

(Example 2)
A heat-shrinkable film was obtained by the same method as in Example 1 except that the blending ratio of the polylactic acid resin and the cellulose ester was changed. The evaluation results of the obtained film are shown in Table 1.

(Example 3)
A heat-shrinkable film was obtained in the same manner as in Example 1 except that the cellulose ester was changed to (B-2). The evaluation results of the obtained film are shown in Table 1.

Example 4
A heat-shrinkable film was obtained in the same manner as in Example 3 except that the blending ratio of the polylactic acid resin and cellulose ester (B-2) was changed. The evaluation results of the obtained film are shown in Table 1.

(Example 5)
A heat-shrinkable film was obtained in the same manner as in Example 3 except that the blending ratio of the polylactic acid resin and cellulose ester (B-2) was changed. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 1)
A polylactic acid-based resin (A-1) is blended in a proportion of 50% by mass and a polylactic acid-based resin (A-2) is blended in a proportion of 50% by mass. A heat-shrinkable film having a thickness of 40 μm is formed in the same manner as in Example 1. Obtained. The evaluation results of the obtained film are shown in Table 2.

(Comparative Example 2)
A heat-shrinkable film was obtained by the same method as in Example 1 except that the blending ratio of the polylactic acid resin and the cellulose ester was changed. The evaluation results of the obtained film are shown in Table 2.

(Comparative Example 3)
Film collection was attempted by the same method as in Comparative Example 1 except that the blending ratio of the polylactic acid resin and the cellulose ester was changed. Sheeting was possible, but the film was broken in the process of stretching the sheet 5 times, and film collection was difficult.

(Comparative Example 4)
45% by mass of the polylactic acid resin (A-1), 45% by mass of the polylactic acid resin (A-2), and 10% by mass of the cellulose ester (B-3) are blended in the same manner as in Example 1. I tried to make a sheet by the method of. There was a difference in the melting temperature between the polylactic acid resin and the cellulose ester (B-3), making it difficult to form a sheet.

(Comparative Example 5)
45% by mass of the polylactic acid resin (A-1), 45% by mass of the polylactic acid resin (A-2), and 10% by mass of the cellulose ester (B-4) are blended in the same manner as in Example 1. By this method, a heat-shrinkable film having a thickness of 40 μm was obtained. The evaluation results of the obtained film are shown in Table 2.

As the results shown in Table 1, when the film of the present invention is a heat-shrinkable film, it can be made into a film having excellent shrinkage properties, excellent rigidity at normal temperature, and excellent transparency.
On the other hand, as shown in Table 2, when cellulose ester is not blended (Comparative Example 1), or is outside the scope of the present invention (Comparative Examples 2 to 5), film formation is difficult or rigidity is low. The film was not improved or was inferior in shrinkage properties.

  The polylactic acid-based film of the present invention is excellent in transparency and rigidity, and can be suitably used for films for packaging applications and industrial applications. Although the field of use of the film of the present invention is diverse, it can be suitably used particularly for heat-shrinkable films, heat-shrinkable labels and the like.

Claims (7)

  A layer mainly composed of a mixed resin composition of a polylactic acid resin (A) and a cellulose ester (B) having an acetyl group content of 10 to 25% by mass and a butyryl group content of 25 to 45% by mass. It has at least one layer, and the mixing ratio of (A) and (B) in the mixed resin composition is (A) / (B) = 92/8 to 55/45% by mass, and is in accordance with JIS K7136. A polylactic acid film having a haze value of 15% or less.   The film according to claim 1 is stretched in at least one direction and has a heat shrinkage ratio of 20 to 80% in a main shrinkage direction when immersed in warm water at 80 ° C. for 10 seconds. the film.   The heat-shrinkable film according to claim 2, wherein the tensile elastic modulus in the machine direction and the transverse direction, both measured in accordance with JIS K7127, is 4000 MPa or more.   The heat-shrinkable film according to claim 2 or 3, wherein a difference in storage elastic modulus is 2.0 Pa or less.   A molded article using the heat-shrinkable film according to claim 2 as a base material.   The heat-shrinkable label using the heat-shrinkable film in any one of Claim 2 to 4 as a base material.   A container equipped with the molded article according to claim 5 or the heat-shrinkable label according to claim 6.