JP4794187B2 - Film cutter and storage box with film cutter - Google Patents

Description

  In the present invention, a wrap film, aluminum foil or cooking sheets (hereinafter referred to as “wrap film etc.”) wound in a roll shape on a cylindrical core are stored and cut into a desired length as required. The present invention relates to a film cutter mounted on a storage box for taking out, and a storage box with a film cutter mounted with the film cutter.

  Wrap film etc. is stored in a storage box attached with a sawtooth film cutter attached to the edge of the front plate, bottom plate or lid plate of the box, pulling out the wrap film etc. to an arbitrary length when necessary, Cut and use with a serrated film cutter attached to the storage box. Sawtooth film cutters that cut wrap films, etc., are usually made of metal. However, metal cutters are easy to damage fingers during handling, and are always dangerous. However, there was a problem that it had to be removed from the storage box and processed.

In view of the above, recently, a cutter using paper as a material instead of a metal material has been proposed and put into practical use in part. These paper cutters can be broadly divided into so-called “resin-cured paper blades” made of paperboard, which are coated or impregnated with a thermosetting resin, and raw paper made of cellulose fibers. Using a vulcanized fiber obtained by dry-molding by extracting and removing zinc chloride after forming a uniform layer thickness by using a gluing action, a moisture-proof coating is formed on this and punched into a sawtooth shape. There are two types of cutters, so-called “VF blades”.
The paper cutter and the storage box are usually bonded by a method of applying an adhesive to the storage box or the cutter and bonding them by an ultrasonic fusion method (Patent Document 1: Japanese Patent Laid-Open No. 7-52255). Publication). Although these paper cutters solve the problems of the metal cutters pointed out above, it cannot be denied that the paper cutters are inferior in cutting performance and cutting durability compared to metal cutters. In particular, the problem is remarkable in a wrap film made of polyethylene or polyvinyl chloride having a relatively large film elongation. For example, it cannot be used for a long wrap film exceeding 50 m.

  As another material, a film cutter based on a polylactic acid polymer starting from a plant such as corn has been devised. (Patent Document 2: Japanese Patent No. 3573605) Since the starting material is derived from a plant, it has characteristics such as being able to escape from a depleted petroleum resource.

JP-A-7-52255 Japanese Patent No. 3573605

  By the way, although the film cutter mainly composed of the above-mentioned polylactic acid-based polymer has cutting properties and cutting durability almost the same as those of metal cutters, the film cutter is mounted on the storage box. The caulking method, which is the same as that for metals, is insufficient because the material is difficult to be plastically deformed, and the fusion strength is insufficient for the ultrasonic fusion method. Therefore, it is used in a bonding method in which an adhesive is applied, but in this method, the adhesive is expensive, and a process of applying the adhesive to a storage box or a film cutter is necessary, resulting in a low manufacturing cost. There was a problem of getting higher. Furthermore, even though corners, storage boxes (made of paper) and lap cutters use non-petroleum plant-based raw materials, the adhesives are still made from petroleum-based materials.

  Therefore, the object of the present invention is to provide a polylactic acid polymer that has the same cutting performance and durability as a metal film cutter, and can be bonded to a storage box by an ultrasonic fusion method without using an adhesive. It is providing the film cutter which has as a main component. Still another object of the present invention is to provide a film cutter that does not require time and effort for disposal, does not adversely affect the environment even when incinerated or landfilled, and can escape from exhausted petroleum resources. .

  As a result of intensive studies to solve the above-mentioned problems, the starting material is a polylactic acid-based polymer derived from a plant as a main component, and the sheet base material used for the film cutter has a specific composition and layer structure. The present invention has been completed by finding that no adhesive is used and strong adhesion is ensured, and the cutting performance and durability are the same as those of metal cutters, which does not adversely affect the environment and can be easily discarded. It came to do.

That is,
(1) The film cutter of the present invention is a laminate composed of at least two layers mainly composed of a polylactic acid-based polymer, and the thickness of all layers is 0.15 mm to 0.5 mm.
The content ratio Da (%) of D-lactic acid to the total of L-lactic acid and D-lactic acid of the polylactic acid polymer constituting one outermost layer (A layer),
The relationship between the ratio Db (%) of D-lactic acid to the total of L-lactic acid and D-lactic acid of the polylactic acid polymer constituting the other outermost layer (B layer) is as follows:
0.5 ≦ Da ≦ 5 and 16.5 ≧ Db-Da> 3
Further, the B layer has a thickness of 12.5 μm or more, the thickness ratio of the B layer in the entire laminate is 20 % or less, and is bonded to the storage box by an ultrasonic fusion method. It is a layer.
(2) Moreover, in this invention, it is preferable that the said laminated body is biaxially stretched.
(3) The storage box with a film cutter of the present invention is mounted with the film cutter according to the above (1) or (2) by ultrasonic fusion so that the layer B is disposed on the surface of the storage box. It is characterized by that.

In the present invention, by forming a polylactic acid polymer into a layer structure having a specific composition, it has the same cutting ability and cutting durability as a metal film cutter, and also uses ultrasonic fusion without using an adhesive. It is possible to provide a film cutter that can be adhered to the storage box by the attaching method.
In addition, it is possible to provide a film cutter that does not require time and effort for disposal, does not adversely affect the environment when incinerated or landfilled, and can escape from exhausted petroleum resources.

  Embodiments of the present invention will be described below.

(Polylactic acid polymer)
The film cutter according to the present invention is composed mainly of a polylactic acid polymer.
The polylactic acid polymer is a polymer formed by condensation polymerization of a monomer mainly composed of lactic acid. The lactic acid includes two kinds of optical isomers, L-lactic acid and D-lactic acid, and the crystallinity is different depending on the ratio of these two kinds of structural units. For example, a random copolymer having a ratio of L-lactic acid to D-lactic acid of approximately 80:20 to 20:80 has no crystallinity, and becomes a transparent, completely amorphous polymer that softens near a glass transition point of 60 ° C.

  On the other hand, a random copolymer having a ratio of L-lactic acid to D-lactic acid of approximately 100: 0 to 80:20 or 20:80 to 0: 100 has crystallinity. The crystallinity is determined by the ratio of L-lactic acid and D-lactic acid, but the glass transition point of this copolymer is a polymer of about 60 ° C. as described above. This polymer becomes an amorphous material with excellent transparency by being rapidly cooled after melt extrusion, and becomes a crystalline material by slowly cooling. For example, a homopolymer composed of only L-lactic acid or only D-lactic acid is a semicrystalline polymer having a melting point of 180 ° C. or higher.

  The polylactic acid polymer used in the present invention is a homopolymer whose structural unit is L-lactic acid or D-lactic acid, that is, poly (L-lactic acid) or poly (D-lactic acid), the structural unit is L-lactic acid and It is a copolymer that is both D-lactic acid, that is, poly (DL-lactic acid), and a mixture thereof. Further, it is a copolymer with other hydroxycarboxylic acid and diol / dicarboxylic acid as a copolymerization component. There may be. It may also contain a small amount of chain extender residues.

As the polymerization method, a known method such as a condensation polymerization method or a ring-opening polymerization method can be employed. For example, in the condensation polymerization method, polylactic acid having an arbitrary composition can be obtained by directly dehydrating condensation polymerization of L-lactic acid, D-lactic acid or a mixture thereof.
In the ring-opening polymerization method (lactide method), polylactic acid can be obtained by using a selected catalyst while using lactide, which is a cyclic dimer of lactic acid, with a polymerization regulator or the like as necessary. .

  Examples of the other hydroxycarboxylic acid units copolymerized with polylactic acid include optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, Such as 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid, etc. Examples thereof include lactones such as bifunctional aliphatic hydroxycarboxylic acid, caprolactone, butyrolactone, and valerolactone.

  Examples of the aliphatic diol copolymerized with the polylactic acid polymer include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid. If necessary, a non-aliphatic diol such as a non-aliphatic dicarboxylic acid such as terephthalic acid and / or an ethylene oxide adduct of bisphenol A may be used as a small amount copolymerization component.

  The preferred range of the weight average molecular weight of the polylactic acid polymer used in the present invention is 60,000 to 700,000, more preferably 80,000 to 400,000, and particularly preferably 100,000 to 300,000. If the molecular weight is too small, practical physical properties such as mechanical properties and heat resistance are hardly expressed, and if it is too large, the melt viscosity is too high and the molding processability is poor.

(Other biodegradable aliphatic polyester)
In addition, in the film cutter of the present invention, biodegradable aliphatic polyesters other than polylactic acid resins are impaired in terms of their practical properties in order to improve a certain degree of flexibility and various processability. You may add in the range which is not.
Examples of the biodegradable aliphatic polyester include polyhydroxycarboxylic acid, aliphatic diol and aliphatic dicarboxylic acid, or aliphatic polyester obtained by condensing aliphatic diol, aliphatic dicarboxylic acid and aromatic dicarboxylic acid, or Aliphatic aromatic polyester, aliphatic polyester copolymer obtained from aliphatic diol and aliphatic dicarboxylic acid, and hydroxycarboxylic acid, aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, synthetic aliphatic polyester, Examples include aliphatic polyesters that are biosynthesized.

  Examples of the polyhydroxycarboxylic acid include 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, Examples thereof include homopolymers and copolymers of hydroxycarboxylic acids such as 2-hydroxycaproic acid.

  Examples of the aliphatic diol include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like. Examples of the aromatic dicarboxylic acid include terephthalic acid and isophthalic acid. Aliphatic polyesters obtained by condensing these aliphatic diols and aliphatic dicarboxylic acids, and aliphatic aromatic polyesters obtained by condensing aliphatic diols, aliphatic dicarboxylic acids and aromatic dicarboxylic acids, One or more compounds can be selected from each of the compounds and subjected to condensation polymerization, and further, if necessary, jumped up with an isocyanate compound or the like to obtain a desired polymer.

Examples of the aliphatic diol and aliphatic carboxylic acid used in the aliphatic polyester copolymer obtained from the aliphatic diol, the aliphatic dicarboxylic acid, and the hydroxycarboxylic acid are the same as those described above. L-lactic acid, D lactic acid, DL lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2 -Methyl lactic acid, 2-hydroxycaproic acid and the like, for example, polybutylene succinate lactic acid, polybutylene succinate adipate lactic acid and the like.
However, the composition ratio in this case is mainly an aliphatic diol and an aliphatic dicarboxylic acid, and the mol% is aliphatic diol: 35 to 49.99 mol%, aliphatic dicarboxylic acid: 35 to 49.99 mol%. Hydroxycarboxylic acid: 0.02 to 30 mol%.

  The aliphatic polyester obtained by ring-opening polymerization of the above cyclic lactones can be obtained by polymerizing one or more of ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like as a cyclic monomer.

  Examples of the synthetic aliphatic polyester include copolymers of cyclic acid anhydrides and oxiranes such as succinic anhydride and ethylene oxide, propylene oxide.

  Examples of the aliphatic polyester biosynthesized in the microbial cells include aliphatic polyesters biosynthesized by acetyl coenteam A (acetyl CoA) in the microbial cells including Alkali geneus eutrophus. The aliphatic polyester biosynthesized in the cells is mainly poly-β-hydroxybutyric acid (poly-3HB), but is copolymerized with hydroxyvaleric acid (HV) to improve the practical properties of plastics. It is industrially advantageous to make a copolymer of poly (3HB-CO-3HV). The HV copolymerization ratio is generally preferably 0 to 40 mol%. Furthermore, long-chain hydroxyalkanoates such as 3-hydroxyhexanoate, 3-hydroxyoctanoate and 3-hydroxyoctadecanoate may be copolymerized in place of hydroxyvaleric acid.

(Layer structure)
The film cutter according to the present invention is a laminate composed of at least two layers mainly composed of polylactic acid polymers having different crystallinity. Here, the polylactic acid polymer constituting one outermost layer (A layer) is preferably crystalline. Moreover, the polylactic acid-type polymer which comprises the other outermost layer (B layer) uses a thing with crystallinity lower than the polylactic acid-type polymer which comprises A layer.
Moreover, when mounting the film cutter of this invention to a storage box, it is preferable that B layer is arrange | positioned by the storage box surface.

The D-lactic acid content ratio Da (%) of the polylactic acid polymer constituting the A layer and the D-lactic acid content ratio Db (%) of the polylactic acid polymer constituting the B layer are:
Da ≦ 7 and Db-Da> 3
It is important to have a relationship of

(A layer)
That is, since the A layer serves as a support layer for bonding the film cutter and the storage box, the ratio Da of D-lactic acid in the polylactic acid polymer constituting the A layer is preferably 7% or less, and preferably 5%. The following is more preferable. If it is 7% or less, the degree of crystallinity as the support layer is sufficient, and shrinkage deformation does not occur when heated in terms of heat resistance.

(B layer)
Since the B layer becomes an adhesive layer by ultrasonic fusion with the storage box, the ratio Db of D-lactic acid in the polylactic acid polymer constituting the B layer may be higher than Da by more than 3%. preferable. If this difference is greater than 3%, both the crystallinity and the melting point are sufficiently different from the polylactic acid polymer constituting the A layer, and a high temperature that affects the A layer as a support layer. It is not necessary to bond under excessive conditions such as. That is, in high-temperature bonding, the support layer is also heated to cause heat shrinkage, which causes problems such as waviness and wrinkles in the product.
Therefore, in order to lower the crystallinity and the melting point as compared with the support layer, it is preferable to set the above range.

  The polylactic acid polymer constituting the A layer and the polylactic acid polymer constituting the B layer may be two or more different polylactic acid polymers. In this case, the D-lactic acid content ratios Da and Db are average values calculated from the blending ratio of D-lactic acid constituting two or more types of polylactic acid-based polymers.

The A layer and the B layer constitute one outermost layer of the laminate.
Therefore, the laminate may have a two-layer configuration of A layer / B layer or a three-layer configuration of A layer / A layer / B layer. Furthermore, a multilayer structure of A layer / B layer / A layer... / B layer or A layer / B layer / B layer / A layer.
Furthermore, one or more recycled resin layers or another third layer may be laminated as an intermediate layer between the A layer / B layer as long as the effects of the present invention are not impaired.

(B layer thickness ratio)
The thickness of the B layer constituting the outermost layer of these final laminates is 2 μm or more, preferably 5 μm or more, and the thickness ratio in the laminate is 80% or less, preferably 60% or less. . If the thickness is less than 2 μm, the desired adhesiveness may not be obtained. If the thickness ratio exceeds 80%, when the film cutter is heated and melted with an ultrasonic fusing device, there are too many melted parts, resulting in a product. Problems such as undulations and wrinkles may occur.

(Thickness of film cutter)
The thickness of the film cutter of the present invention is about 0.15 mm to 0.5 mm, preferably about 0.2 mm to 0.35 mm. If it is less than 0.15 mm, there is no rigidity, and there may be problems such as deformation when the film cutter cuts a wrap film or the like. On the other hand, when the thickness is 0.5 mm or more, problems such as poor cutting performance may occur.

(Inorganic filler)
The film cutter of the present invention can contain an inorganic filler in order to improve strength, durability, etc. or improve workability. Inorganic fillers include calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, zinc oxide, magnesium oxide, calcium oxide, titanium oxide, alumina, aluminum hydroxide, hydroxyapatite, silica, mica, talc , Kaolin, clay, glass powder, asbestos powder, zeolite, silicate clay and the like.

(Other additives)
Furthermore, the film cutter of the present invention can be modified in various ways by adding secondary additives. Examples of secondary additives include stabilizers, antioxidants, UV absorbers, pigments, electrostatic agents, conductive agents, mold release agents, plasticizers, fragrances, antibacterial agents, nucleating agents, and other similar ones. Can be mentioned.

(Lamination method)
The method for laminating the laminate constituting the film cutter of the present invention is not particularly limited as long as the object of the present invention is not impaired. For example, (1) using two or three or more extruders, multi-manifold or feed Co-extrusion method that is laminated with a block type die and extruded as a molten sheet, (2) A method of coating the other resin on one of the unrolled layers, (3) Roll or press each layer at an appropriate temperature The method of using and thermocompression bonding, or the method of (4) bonding using an adhesive agent etc. are mentioned.

  In addition, as a method for imparting heat resistance to the polylactic acid polymer constituting the layer A of the laminate, (1) a method of slowly cooling the melted laminate, (2) a method of annealing the laminate, 3) A method in which the laminate is biaxially stretched and then heat-treated can be mentioned. The method (3), which can be expected to improve physical properties such as impact resistance by molecular orientation, provides a more practical laminate. It is preferable.

(Production method)
As a method for producing a biaxially stretched laminate comprising a polylactic acid-based polymer as a main component, a sheet-like product or a cylindrical product extruded from a T-die, I-die, round die, etc. is cooled by a cast roll, water, compressed air, etc. Examples include a method of rapidly cooling and solidifying in a state close to an amorphous state and then stretching biaxially by a roll method, a tenter method, a tubular method, or the like.
Usually, in the production of a biaxially stretched laminate, a sequential biaxial stretching method in which longitudinal stretching is performed by a roll method and a lateral stretching is performed by a tenter method, and a simultaneous biaxial stretching method in which stretching is performed by a tenter simultaneously in the vertical and horizontal directions are generally used.
As stretching conditions, a stretching temperature of 55 to 90 ° C., preferably 65 to 80 ° C., a longitudinal stretching ratio of 1.5 times, preferably 2 to 4 times, a transverse stretching ratio of 1.5 to 5 times, preferably 2 to 4 times. The stretching speed is 10 to 100000% / min, preferably 100 to 10000% / min. However, these suitable ranges vary depending on the composition of the polymer and the thermal history of the unstretched sheet, and therefore can be appropriately determined in consideration of the strength and elongation of the laminate.
When the stretching ratio and the stretching temperature are not within the above ranges, the thickness accuracy of the obtained laminate is significantly reduced, and this tendency is particularly remarkable in a laminate that is heat-treated after stretching. Such thickness fluctuation is a factor that causes the appearance of products such as wrinkles and undulations in the secondary processing.

  Examples are shown below, but the present invention is not limited by these. In addition, the physical-property value in an Example and a comparative example was measured and evaluated with the following method.

(1) Stretch ratio Longitudinal stretch ratio = Flow rate of laminate after longitudinal stretching / Flow rate of original sheet before longitudinal stretching

Transverse stretch ratio = {(Laminated body width after stretching) − (Width held by clip)} / {(Original sheet width before stretching) − (Width held by clip)}

The draw ratio in the transverse direction is the value obtained by subtracting the width of the portion gripped by the clip of the tenter from the width of the original sheet before longitudinal stretching, and the length obtained by subtracting the width of the portion held by the clip from the width obtained after transverse stretching. This is the value assigned.

(2) Ultrasonic welding Using an ultrasonic welding device having an ultrasonic oscillator, an ultrasonic vibrator, and a welding horn, a paperboard having a weight of 400 g / m ² and a thickness of 0.8 mm on a set table. Then, a film cutter was placed thereon, and the horn was lowered from above to a pressure-bonding amount of 0.2 mm, and was ultrasonically bonded for a predetermined time.
Crimping amount = (film cutter thickness + paperboard thickness)-(distance from tip of fusion horn to set stand)

(3) Ultrasonic fusion strength The film cutter and the paperboard were peeled off by hand, and the paperboard was broken by ○, and the one peeled off at the interface regardless of the resistance when peeled was marked by x.

(4) Ultrasonic fusion appearance The appearance of the film cutter fused by the method described in the above item is visually observed, and there is no waviness, wrinkles, etc. Was marked and marked as x for practical problems.

(5) Cutting property A paperboard equipped with a film cutter having a shape as shown in FIG. 1 is made into a box, and a wrapping film for food packaging (Mitsubishi Resin Co., Ltd .: Trade name: Diawrap, polyvinyl chloride resin) Manufactured, thickness: 13 μm, width: 30 cm). The wrap film was set at an angle of 45 ° with respect to the film cutter, and the stress when it was pulled at a speed of 1000 mm / min was measured.

(6) Cutting durability The cutting test described in the previous section was repeated, and the stress when cutting was completed 500 times was measured.

(7) Comprehensive evaluation The above ultrasonic fusion strength and appearance are all ◯, and the cutability (initial) is a load equal to or less than that of the paper film cutter of Comparative Example 5 described later, and the cut durability. Samples with a value of (500 times) of 1.5 times or less of the initial load are marked with ◯, and there is at least one x in the ultrasonic fusion strength and appearance, or the values of cutability and cut durability However, a sample that does not satisfy the above was marked as x.

(Structure of the resin of the laminate)
As resin which comprises a laminated body, the 1st component independent shown in Table 1 or the mixture of the 1st component and the 2nd component was used. The D-lactic acid ratio in the case of the mixture was calculated as an average value from the mass fraction of both.

[Example 1]
A polylactic acid polymer (resin 1 in Table 1) having a structural unit of L-lactic acid: D-lactic acid = 99.5: 0.5 (Da = 0.5%) and having a glass transition point (Tg) of 58 ° C. In addition, 0.1 parts by mass of dried granular silica having an average particle diameter of 1.4 μm and 9 parts by mass of anatase-type titanium oxide were mixed, and the surface layer (from the two-layer multi-manifold die using a 40 mmφ single screw extruder ( Extruded at 220 ° C. as layer A).
Further, it has a structural unit of L-lactic acid: D-lactic acid = 80: 20, has a structural unit of L-lactic acid: D-lactic acid = 95: 5, 80% by mass of polylactic acid having a glass transition point (Tg) of 52 ° C. In addition, 20% by mass of polylactic acid having a glass transition point (Tg) of 56 ° C. was mixed and dried to a total of 100 parts by mass of polylactic acid (Db = 17%, resin 5 in Table 1) with an average particle size of 1.4 μm Silica: 0.1 parts by mass and 9 parts by mass of anatase-type titanium oxide were mixed and extruded at 210 ° C. as a back layer (B layer) from the same die with a 25 mmφ unidirectional twin screw extruder.
The discharge amount of the molten resin was adjusted so that the thickness ratio of the surface layer (A layer) and the back layer (B layer) was 9: 1. This coextruded sheet was quenched with a casting roll at about 43 ° C. to obtain an unstretched sheet. Subsequently, the film was stretched 2.6 times at 76 ° C. in the longitudinal direction, and then stretched 3.2 times at a temperature of 72 ° C. with a tenter in the width direction. The temperature of the heat treatment zone in the tenter was 140 ° C., and a heat treated laminate was produced. The amount of molten resin discharged from the extruder and the line speed were adjusted so that the thickness of the laminate was approximately 250 μm on average.

[Examples 2-5, 7, 10]
As shown in Table 2, a polylactic acid-based polymer (corresponding to each resin described in Table 1) having different L-lactic acid and D-lactic acid was used in the same manner as in Example 1 for the surface layer (A layer) and the back surface. A layer (B layer) was extruded to have a predetermined thickness ratio, biaxially stretched and then heat treated to obtain a laminate.

[Example 6]
In the back layer (B layer), biodegradable aliphatic polyester (Bionole 3003, Showa High Polymer melting point: 95 ° C., glass transition point: −40 ° C.) is polylactic acid / biodegradable aliphatic polyester = 90/10% by mass A laminate was obtained in the same manner as in Example 1 except that mixing was performed.

[Example 8]
A polylactic acid polymer (resin 1 in Table 1) having a structural unit of L-lactic acid: D-lactic acid = 99.5: 0.5 (Da = 0.5%) and having a glass transition point (Tg) of 58 ° C. Then, dry granular silica having an average particle size of 1.4 μm: 0.1 part by mass and 9 parts by mass of anatase-type titanium oxide were mixed, and the surface layer (from the three-layer multi-manifold die using a 40 mmφ single screw extruder ( A layer), and extruded at 220 ° C. as an intermediate layer.
Further, it has a structural unit of L-lactic acid: D-lactic acid = 80: 20, has a structural unit of L-lactic acid: D-lactic acid = 95: 5, 80% by mass of polylactic acid having a glass transition point (Tg) of 52 ° C. In addition, 20% by mass of polylactic acid having a glass transition point (Tg) of 56 ° C. was mixed and dried to a total of 100 parts by mass of polylactic acid (Db = 17%, resin 5 in Table 1) with an average particle size of 1.4 μm Silica: 0.1 parts by mass and 9 parts by mass of anatase-type titanium oxide were mixed and extruded at 210 ° C. as a back layer (B layer) from the same die with a 25 mmφ unidirectional twin screw extruder.
The amount of molten resin discharged was adjusted so that the thickness ratio of the surface layer (A layer), the intermediate layer, and the back layer (B layer) was 8: 1: 1. This coextruded sheet was quenched with a casting roll at about 44 ° C. to obtain an unstretched sheet. Subsequently, the film was stretched 2.6 times at 76 ° C. in the longitudinal direction, and then stretched 3.2 times at a temperature of 72 ° C. with a tenter in the width direction. The temperature of the heat treatment zone in the tenter was 140 ° C., and a heat treated laminate was produced. The amount of molten resin discharged from the extruder and the line speed were adjusted so that the thickness of the laminate was approximately 250 μm on average.

[Example 9]
A polylactic acid polymer (resin 1 in Table 1) having a structural unit of L-lactic acid: D-lactic acid = 99.5: 0.5 (Da = 0.5%) and having a glass transition point (Tg) of 58 ° C. Then, dry granular silica having an average particle size of 1.4 μm: 0.1 part by mass and 9 parts by mass of anatase-type titanium oxide were mixed, and the surface layer (from the three-layer multi-manifold die using a 40 mmφ single screw extruder ( Extruded at 220 ° C as layer A).
Further, it has a structural unit of L-lactic acid: D-lactic acid = 80: 20, has a structural unit of L-lactic acid: D-lactic acid = 95: 5, 80% by mass of polylactic acid having a glass transition point (Tg) of 52 ° C. In addition, 20% by mass of polylactic acid having a glass transition point (Tg) of 56 ° C. was mixed and dried to a total of 100 parts by mass of polylactic acid (Db = 17%, resin 5 in Table 1) with an average particle size of 1.4 μm Silica: 0.1 parts by mass and 9 parts by mass of anatase-type titanium oxide were mixed and extruded at 210 ° C as an intermediate layer and a back layer (B layer) from the same die in a 25 mmφ co-directional twin-screw extruder. did.
The amount of molten resin discharged was adjusted so that the thickness ratio of the surface layer (A layer), the intermediate layer, and the back layer (B layer) was 8: 1: 1. This coextruded sheet was quenched with a casting roll at about 44 ° C. to obtain an unstretched sheet. Subsequently, the film was stretched 2.6 times at 76 ° C. in the longitudinal direction, and then stretched 3.2 times at a temperature of 72 ° C. with a tenter in the width direction. The temperature of the heat treatment zone in the tenter was 140 ° C., and a heat treated laminate was produced. The amount of molten resin discharged from the extruder and the line speed were adjusted so that the thickness of the laminate was approximately 250 μm on average.

[Comparative Examples 1 and 2]
As shown in Table 3, a polylactic acid-based polymer (corresponding to each resin described in Table 1) having different L-lactic acid and D-lactic acid was coated on the surface layer (A layer) and the back surface in the same manner as in Example 1. A layer (B layer) was extruded to have a predetermined thickness ratio, biaxially stretched and then heat treated to obtain a laminate.

[Comparative Example 3]
A polylactic acid polymer (resin 1 in Table 1) having a structural unit of L-lactic acid: D-lactic acid = 99.5: 0.5 (Da = 0.5%) and having a glass transition point (Tg) of 58 ° C. Dry particulate silica with an average particle size of 1.4 μm: 0.1 parts by mass and 9 parts by mass of anatase-type titanium oxide were mixed and extruded at 210 ° C. from a single-layer die using a 40 mmφ co-directional twin-screw extruder. did. This extruded sheet was quenched with a casting roll at about 42 ° C. to obtain an unstretched sheet. Subsequently, the film was stretched 2.6 times at 76 ° C. in the longitudinal direction, and then stretched 3.2 times at a temperature of 74 ° C. with a tenter in the width direction. The temperature of the heat treatment zone in the tenter was 140 ° C. to produce a heat treated sheet. The amount of molten resin discharged from the extruder and the line speed were adjusted so that the sheet thickness was approximately 250 μm on average.

[Comparative Example 4]
As shown in Table 3, L-lactic acid and D-lactic acid different polylactic acid polymers (corresponding to the resins shown in Table 1) are each made to have a predetermined thickness by the same method as in Comparative Example 1. Extrusion, biaxial stretching, and heat treatment were performed to obtain a laminate.

[Comparative Example 5]
A sample was made of a paper film cutter made of Dynic having a thickness of 0.3 mm in which paper was impregnated with resin.

[result]
As shown in Table 4, in Examples 1 to 10, it was a film cutter with no problem in ultrasonic fusion strength and ultrasonic fusion appearance. Further, the cutting ability and the cutting durability were lower than those of the paper film cutter, and good results were obtained.
On the other hand, in Comparative Examples 1 and 4, it was not possible to obtain a sample having no problem with the fusion strength and the appearance, and it was not possible to evaluate the cutting ability. In Comparative Example 2, there was a problem in the appearance of fusion, and in Comparative Example 3, sufficient fusion strength could not be obtained, and none of them reached evaluation of cutting performance.

FIG. 1 is a diagram showing an example of the film cutter of the present invention.

Explanation of symbols

1 film cutter 2 blades

Claims (3)

A laminate composed of at least two layers composed mainly of polylactic acid polymer, the total
The thickness of the layer is 0.15 mm to 0.5 mm, and the content ratio Da of D-lactic acid to the total of L-lactic acid and D-lactic acid of the polylactic acid polymer constituting one outermost layer (A layer) ( %) And D relative to the total of L-lactic acid and D-lactic acid of the polylactic acid polymer constituting the other outermost layer (B layer)
-The relationship with the ratio Db (%) of lactic acid is
0.5 ≦ Da ≦ 5 and 16.5 ≧ Db-Da> 3
Further, the B layer has a thickness of 12.5 μm or more, the thickness ratio of the B layer in the entire laminate is 20 % or less, and is bonded to the storage box by an ultrasonic fusion method. A film cutter characterized by being a layer.

The film cutter according to claim 1, wherein the laminate is biaxially stretched. A storage box with a film cutter, wherein the film cutter according to claim 1 or 2 is mounted by ultrasonic fusion so that the B layer is disposed on the surface of the storage box.

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