JP2009052056A - Roll-like article of polylactic acid-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roll-like article of a polylactic acid-based film which does not generate "sagging" or "node". <P>SOLUTION: Ten-point average of surface roughness Rz of the polylactic acid-based film is 2.0 or less. Surface hardness of the roll-like article which is made by winding the polylactic acid-based film is within a range of 86-95 degree when measured with a C type rubber hardness meter based on the Japanese Industrial Standard JIS K7312. Wherein, average thickness of the polylactic acid-based film is preferably within a range of 7-80 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a roll of a biodegradable film, and particularly relates to a roll of a polylactic acid film.

Many conventional plastic products, especially plastic packaging materials, are often disposable, and disposal after use and disposal has become a problem. Examples of general packaging plastic materials include polyethylene, polypropylene, polyethylene terephthalate, and the like, but these resins generate a large amount of heat during combustion, which may damage the combustion furnace during the combustion process. Even today, polyvinyl chloride, which is used in large quantities, cannot be burned due to its self-digestibility. Plastic products including materials that cannot be incinerated are often landfilled in the soil, but they remain stable in the natural environment over a long period of time, so that they hardly remain decomposed and accumulate. For this reason, if the landfill disposal site is shortened or disposed of in the natural environment, the natural landscape is damaged or the living environment such as marine life is destroyed.
Therefore, research and development of materials that have low combustion heat and decompose and disappear over time in a natural environment are being actively conducted. One of such materials that has attracted attention is polylactic acid. Polylactic acid has a calorific value of less than half that of polyethylene, and gradually disintegrates and decomposes in soil and water by hydrolysis and biodegradation. Become. Furthermore, since the starting material is derived from a plant, there is an advantage that it does not depend on a depleted petroleum resource.

Currently, it is required to obtain a film, a sheet, or a container such as a bottle using polylactic acid. Since polylactic acid is highly brittle, it is not suitable for a film that requires flexibility and toughness, but it is known that a film stretched uniaxially or biaxially has improved brittleness.
However, since polylactic acid is water-absorbing, the following may occur depending on the storage state of the film.
A film wound in a roll shape (normal film storage state) absorbs moisture in the air from the outermost surface of the roll shape and the end of the roll. Furthermore, when there is a gap in the roll-shaped film, air easily enters from the gap part at the end of the roll, so that the moisture can be more easily absorbed. The film that has absorbed moisture from the roll end portion has a longer end dimension than the center portion, so-called “sag” occurs. On the other hand, in order to prevent “sagging”, so-called “kumps” are likely to occur when wound in a tightly wound state. In particular, when the thickness of the film is not uniform, for example, when the thickness is uneven in the width direction, the hump is likely to occur.
Therefore, there has been a demand for a roll of a polylactic acid film wound in a good state without causing “sag” or “kump”.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a roll-like product of a polylactic acid film that does not cause sagging or galling.

The roll-like product of the polylactic acid film of the present invention has a ten-point average roughness Rz of the surface of the polylactic acid-based film of 2.0 or less, and the surface hardness of the roll-like product around which the polylactic acid-based film is wound, Based on Japanese Industrial Standard JIS K7312, the value measured with a C-type rubber hardness meter is in the range of 86 to 95 degrees.
Here, the average thickness of the polylactic acid film may be in the range of 7 to 80 μm.
The polylactic acid film may have a wet tension of at least one side of 400 μN / cm or more.

  ADVANTAGE OF THE INVENTION According to this invention, the roll-form thing of the polylactic acid-type film wound by the favorable state which does not generate | occur | produce "sagging" or "kump" can be provided. Further, it is possible to provide a polylactic acid-based film that does not absorb moisture even when stored for a long period of time, and that does not decrease the wetting tension of the polylactic acid-based film over time even when subjected to an antistatic treatment or the like.

BEST MODE FOR CARRYING OUT THE INVENTION

  The polylactic acid film roll-like product of the present invention is obtained by winding a polylactic acid film, and the surface hardness of the rolled state is a value measured using a rubber hardness meter based on Japanese Industrial Standard JIS K7312 ( Rubber hardness) needs to be in the range of 86 to 95 degrees, and preferably in the range of 88 to 93 degrees. When the surface hardness of the roll-shaped material is in the range of 86 to 95 degrees, the film can be wound well without causing “sag” or “kump” on the film. In other words, if the surface hardness of the roll-shaped material is less than 86 degrees, a gap is generated in the roll-shaped material, which causes a sag. Further, when the surface hardness exceeds 95 degrees, it becomes a tightly wound state, so that the bulge is likely to occur, and as a result, “sagging” occurs in the film wound on the bulge.

  The polylactic acid film wound in a roll shape is a film formed using a polylactic acid polymer, and the ten-point average roughness Rz of the film surface is 2.0 or less. When the ten-point average roughness Rz is larger than 2.0, when the film is wound in a roll shape, a gap is generated and “sag” is generated in the film. In addition, when transparency is required for the film, it is harmful if Rz is larger than 2.0.

  A film is a thin flat product whose thickness is extremely small compared to the length and width and whose maximum thickness is arbitrarily limited as defined by JIS, and is usually supplied in the form of a roll. Say. By the way, a sheet is a thin product that is generally thin and has a small thickness instead of length and width. (JIS K 6900). Since the boundary between the film and the sheet is not clear and is difficult to distinguish clearly, in this application, the term “film” includes “sheet”, and the term “sheet” includes “film”.

  In the present invention, since the polylactic acid film wound in a roll shape has a roll surface hardness of 86 to 95 degrees, the average thickness thereof is in the range of 7 to 80 μm, preferably 10 to 70 μm, more preferably. Is selected within the range of 15-60 μm. If the thickness of the polylactic acid film is too thick, the rigidity becomes so high that “deflection” due to the film gap is less likely to occur, but the surface hardness of 86 to 95 degrees may not be achieved. Further, if the film is too thin, the film may be broken during winding in a roll shape. Therefore, if the winding hardness is reduced, a predetermined surface hardness may not be achieved.

The polylactic acid film wound in a roll shape preferably has a wetting tension of at least one surface of 400 μN / cm or more. The polylactic acid film is often printed on the surface or laminated with paper or other plastic film or metal foil via an adhesive. However, since the polylactic acid-based film has low surface wetting tension, the formed printing layer and adhesive layer were easily peeled off. Therefore, it is preferable to improve the wetting tension by treating the film. When the surface wetting tension is 400 μN / cm or more, the formed printed layer or adhesive layer does not peel off. In the present invention, “wetting tension” is a value measured based on JIS K6768.
As a method for improving the wetting tension of the film, there are chemical treatment, flame treatment, plasma treatment, corona treatment and the like. The corona treatment is preferably used because the corona treatment can be easily performed on the film by arranging a corona treatment apparatus in a conventional film production line.
The chemical treatment, flame treatment, plasma treatment, corona treatment and the like can be performed based on conventionally known methods.

  The polylactic acid film in the present invention comprises a resin composition containing a polylactic acid polymer as a main component. Examples of the polylactic acid polymer used in the present invention include poly (L-lactic acid) having a structural unit of L-lactic acid, poly (D-lactic acid) having a unit structure of D-lactic acid, a structural unit of L-lactic acid, and A copolymer that is both D-lactic acid, that is, poly (DL-lactic acid) and a mixture thereof can be mentioned.

As a polymerization method of the polylactic acid-based polymer, 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, a polylactic acid polymer 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), lactide, which is a cyclic dimer of lactic acid, is converted into polylactic acid using an appropriate catalyst such as tin octylate while using a polymerization regulator as necessary. A polymer can be obtained. Lactide includes L-lactide, which is a dimer of L-lactic acid, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid. Accordingly, by mixing and polymerizing, a polylactic acid polymer having an arbitrary composition and crystallinity can be obtained.

  The polylactic acid polymer used in the present invention preferably has a weight average molecular weight of 60,000 to 700,000, more preferably 80,000 to 600,000, and particularly preferably 100,000 to 300,000. When the weight average molecular weight of the polylactic acid polymer is too small, practical physical properties such as mechanical properties and heat resistance are hardly expressed, and when it is too large, the melt viscosity is too high and the molding processability may be poor.

In the present invention, a non-aliphatic diol such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A is used as a small amount of a copolymer component in order to improve heat resistance. be able to. 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.
The polylactic acid-based polymer used in the present invention may be a copolymer with other hydroxycarboxylic acid units such as lactic acid and / or α-hydroxycarboxylic acid other than lactic acid. It may be a copolymer with a group dicarboxylic acid.
However, the polylactic acid polymer component is included in an amount of 50% by mass or more.

As other hydroxycarboxylic acid units, optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid), glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid 2-functional aliphatic hydroxycarboxylic acids such as 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, 2-hydroxycaproic acid and caprolactone And lactones such as 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.

  By adjusting the copolymer composition and molecular weight of the polylactic acid polymer, the polylactic acid polymer equivalent heat of fusion can be set within a specific range, for example, 20 J / g to 60 J / g.

  In the present invention, the polylactic acid polymer can contain another aliphatic polyester as a softening agent. Here, the aliphatic polyester is mainly composed of a polymer obtained by condensation polymerization of an aliphatic (including alicyclic group, the same applies hereinafter) dicarboxylic acid component and an aliphatic diol component.

  The aliphatic polyester can be obtained by a known method such as a direct method or an indirect method. Here, the direct method is to remove moisture generated during polymerization of each component of the aliphatic dicarboxylic acid component and the aliphatic diol component while removing the moisture contained in each component. However, it is a method of obtaining a high molecular weight product by direct polymerization. The indirect method is an indirect production method in which an aliphatic dicarboxylic acid component and an aliphatic diol component are polymerized to an oligomer level, and then a high molecular weight product is obtained using a small amount of a chain extender.

  Examples of the aliphatic dicarboxylic acid component include aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, and dodecanedioic acid, and anhydrides and derivatives thereof, and two or more types can be used in combination. . Examples of the aliphatic diol include aliphatic diols such as ethylene glycol, butanediol, hexanediol, octanediol, cyclopentanediol, cyclohexanediol, and cyclohexanedimethanol, or derivatives thereof. it can. Each of the aliphatic dicarboxylic acid unit and the aliphatic diol unit is preferably mainly composed of a bifunctional compound having an alkylene group or a cycloalkylene group having 2 to 10 carbon atoms.

  As said aliphatic polyester, the aliphatic polyester which has a structure of following General formula (1) is mentioned as a preferable thing. However, the weight average molecular weight of the aliphatic polyester is preferably 20,000 to 300,000, and more preferably 150,000 to 250,000. If the weight average molecular weight of the aliphatic polyester is in the range of 20,000 to 300,000, the properties as a polymer will not be inferior or bleed out over time, and heat sealability may be improved. it can. Furthermore, if the weight average molecular weight of the aliphatic polyester is in the range of 20,000 to 300,000, the melt viscosity will not be too high and the mixing property with polylactic acid will not be lowered, and the extrusion moldability will not be lowered. .

式中、Ｒ^１およびＲ^２は、炭素数２〜１０のアルキレン基またはシクロアルキレン基である。ｎは、重量平均分子量が２万〜３０万となるのに必要な重合度である。ｎ個のＲ^１またはＲ^２は、それぞれ同一でも異なっていてもよい。また、式（１）で表される脂肪族ポリエステルは、エステル結合残基に代えて、ウレタン結合残基及び／又はカーボネート結合残基を重量平均分子量の５％まで含有することができる。

In the formula, R ¹ and R ² are an alkylene group or a cycloalkylene group having 2 to 10 carbon atoms. n is the degree of polymerization necessary for the weight average molecular weight to be 20,000 to 300,000. n pieces of R ¹ or R ² may be the same or different from each other. Moreover, the aliphatic polyester represented by Formula (1) can contain a urethane bond residue and / or a carbonate bond residue up to 5% of the weight average molecular weight in place of the ester bond residue.

From the viewpoint of impact resistance and cold resistance, the glass transition temperature (Tg) is preferably 0 ° C. or lower.
Particularly preferably used aliphatic polyesters include, for example, polyethylene suberate, polyethylene sebacate, polyethylene decanedicarboxylate, polybutylene succinate, polybutylene adipate, polybutylene sebacate, polybutylene succinate adipate and their co-polymers. Coalescence is mentioned.

  The aliphatic polyester may be a tri- or higher functional carboxylic acid or alcohol, or hydroxycarboxylic acid for the purpose of providing a branch in the polymer in order to improve the melt viscosity. Specifically, polyfunctional components such as malic acid, tartaric acid, citric acid, trimellitic acid, pyromellitic acid, pentaerythritol and trimethylolpropane can be used. However, when these polyfunctional components are used in a large amount, the resulting polymer has a crosslinked structure, resulting in loss of thermoplasticity or generation of a microgel having a partially highly crosslinked structure even if thermoplastic. When formed into a film, fish eyes may be formed. Accordingly, the amount of these polyfunctional components used is preferably very small, and is limited to an amount that does not greatly affect the chemical properties, physical properties, etc. of the polymer.

  In the present invention, together with the aliphatic polyester or in place of the aliphatic polyester, a block copolymer of a polylactic acid polymer and an aliphatic polyester (a product obtained by transesterifying a part thereof or a small amount of chain). Including products containing extender residues). This block copolymer can be prepared by any method. For example, a block copolymer can be obtained by polymerizing a monomer as the other component in the presence of either a polylactic acid polymer or an aliphatic polyester. Usually, a block copolymer of polylactic acid and aliphatic polyester is obtained by polymerizing lactide in the presence of an aliphatic polyester prepared in advance. Basically, polymerization can be carried out in the same manner as in the case of preparing a polylactic acid resin by the lactide method, except that an aliphatic polyester is allowed to coexist. At this time, lactide polymerization proceeds, and at the same time, an appropriate transesterification reaction occurs between the polylactic acid and the aliphatic polyester, and a copolymer having relatively high randomness is obtained. When an aliphatic polyester urethane having a urethane bond is used as a starting material, ester-amide exchange is also generated.

  In the present invention, the blending ratio of the polylactic acid polymer and the aliphatic polyester is preferably in the range of 97: 3 to 40:60, more preferably 90:10 to 50:50, by weight. Is within the range.

In the present invention, a plasticizer can be used alone or in combination with the aliphatic polyester as a softening agent. Examples of the plasticizer used in the present invention include di-n-octyl phthalate, di-2-ethylhexyl phthalate, dibenzyl phthalate, diisodecyl phthalate, ditridecyl phthalate, diundecyl phthalate and other phthalic acid derivatives, dioctyl isophthalate and other isophthalates. Acid derivatives, adipic acid derivatives such as di-n-butyl adipate, dioctyl adipate, maleic acid derivatives such as di-n-butyl maleate, citric acid derivatives such as tri-n-butyl citrate, monobutyl itaconate, etc. Low molecular weight compounds such as itaconic acid derivatives, oleic acid derivatives such as butyl oleate, ricinoleic acid derivatives such as glycerin monoricinoleate, phosphate esters such as tricresyl phosphate and trixylenyl phosphate, polyethylene adipate, poly Polymeric plasticizers such as acrylate and the like.
Of these plasticizers, triacetin (glycerin triacetate) and lactic acid oligomers having a polymerization degree of about 2 to 10 are preferably used.

  The blending ratio of the plasticizer is preferably 5 to 40% by mass and more preferably 10 to 30% by mass with respect to 100% by mass of the polylactic acid polymer. When the blending ratio of the plasticizer is less than 5% by mass, the rigidity of the polylactic acid film may not be sufficiently reduced. When the blending ratio of the plasticizer exceeds 40% by mass, the glass transition temperature of the polylactic acid-based film becomes considerably lower than room temperature, which may cause difficulty in handling during film formation. Even if handling is not difficult, the plasticizer may migrate to the film surface (so-called bleed out), the film surface may become sticky, and slipperiness may be reduced. Moreover, if the blending ratio of the plasticizer is 40% by mass or less, even when the object is packaged with the polylactic acid film of the present invention, the plasticizer does not migrate to the packaged object.

In the production of the polylactic acid film according to the present invention, a heat stabilizer, a light stabilizer, a light absorber, a lubricant, an inorganic filler, a colorant, a pigment, etc. may be added for the purpose of adjusting various physical properties. it can.
Moreover, in this invention, it is preferable to provide the slipperiness and antiblocking property of a film by mix | blending inorganic particles etc. and roughening the film surface. Examples of such inorganic particles include inert silicon oxide (silica), titanium oxide, calcium carbonate, magnesium carbonate, talc, kaolin, alumina and the like, and preferably silicon dioxide such as silica, calcium carbonate, carbonate Magnesium, talc, titanium dioxide, kaolin and the like can be mentioned, and silicon dioxide such as silica is particularly preferable. Only 1 type may be used for the said inorganic particle, and 2 or more types may be mixed and used for it.
The blending amount of the inorganic particles is appropriately determined in consideration of various physical properties and the like. However, when transparency is required for the film, for example, it is preferably mixed within a range of 0.01 to 1 part by mass. . Further, if considering the roll-up property of the film, it is better that the surface roughness is high. However, if the ten-point average roughness Rz exceeds 2.0, the winding gap becomes large, so that “sag” as described above. When the transparency is required, those having Rz exceeding 2.0 are inappropriate.

  Mixing of a polylactic acid polymer and a softening agent (aliphatic polyester and / or plasticizer) is performed by charging respective raw materials into the same extruder. After mixing each material, directly extrude from the die to produce a film directly, or extrude into a strand shape to produce pellets, and then put the obtained pellets again into an extruder to produce a film A polylactic acid polymer film is obtained. However, in any method, reduction in molecular weight due to decomposition must be taken into consideration. Therefore, it is necessary to appropriately select the melt extrusion temperature in consideration of the melting point change due to the composition ratio of the L-lactic acid structure and the D-lactic acid structure of the polylactic acid polymer, the melting point of the aliphatic polyester, the mixing ratio, and the like. . In practice, a temperature range of 100 to 250 ° C. is usually selected.

  As a method for producing a polylactic acid polymer film according to the present invention, a method for obtaining a substantially unstretched film by a T-die casting method, an inflation method, etc., and a stretched film by a tenter method, a roll stretching method, a tubular method, etc. There are two types of methods to obtain. Here, the method for producing a stretched film, particularly the method for producing a stretched film by a tenter method, will be mentioned, but it is not limited thereto.

  In the production of stretched films, especially biaxially stretched films, the film is held by a process in which the film is brought into contact with a heating roll and subjected to longitudinal stretching due to the peripheral speed difference between the rolls, and a clip operating on the rail. There is a sequential biaxial stretching method having a step of guiding and stretching and heat treatment, and a simultaneous biaxial stretching method in which the film holding the film is accelerated in the longitudinal direction and spreads in the lateral direction, and the film is stretched simultaneously in the longitudinal and lateral directions. . In any of the methods in the present invention, it is preferable that the film is once heated in a heating furnace and stretched, followed by heat treatment. As for the heat treatment conditions, the temperature is preferably 70 ° C. to 160 ° C., more preferably 90 ° C. to 140 ° C., particularly preferably 100 to 140 ° C., and the treatment time is within a range of 1 second to 5 minutes. Is preferred. If the temperature is less than 70 ° C., it is difficult to obtain the heat treatment effect, and if it is higher than 160 ° C., the sheet tends to be drawn down. If the treatment time is less than 5 seconds, it is difficult to obtain the heat treatment effect, and if it exceeds 5 minutes, the heat treatment equipment becomes long and the economic efficiency is lowered.

  In the present invention, if necessary, the polylactic acid film can be subjected to antistatic treatment, antifogging treatment and the like. For example, an antistatic agent or an antifogging agent is kneaded inside the polylactic acid film, or a coating solution containing an antistatic agent or an antifogging agent is applied to at least one surface of the polylactic acid film. Is done by. Examples of the antistatic agent and the antifogging agent include those containing a surfactant as a main component, but are not particularly limited thereto. As the antistatic agent and the surfactant, for example, an anionic or cationic surfactant, or a hydrophilic compound having a high SP value even if it is a nonionic surfactant can be used. Antistatic agents are mainly those that suppress static electricity by adsorbing moisture in the air, and antifogging agents evaporate from foods such as vegetables and fish meat that are packaged in films. It suppresses the formation of water droplets by finely dispersing moisture on the film surface to form a continuous layer. Therefore, in order to exhibit the antistatic effect and the antifogging effect, the moisture content of the film is preferably 0.1% or more, more preferably 0.15% or more. However, if the moisture content of the film exceeds 0.5%, the film surface may become sticky, or the wetting tension of the film surface may be reduced, so the moisture content of the film should be 0.5% or less. Is preferred.

  The polylactic acid film has a property of absorbing moisture when left in a normal environment. Furthermore, when an antistatic treatment or an antifogging treatment is performed on the polylactic acid film, the film absorbs more water. Then, even if the treatment for improving the wetting tension is performed on the film surface, the wetting tension decreases with time, so that a problem arises that the printed layer or the like formed on the film surface is easily peeled off. Usually, the time-lapse decrease with respect to the wetting tension immediately after the corona treatment is about 10 μN / cm under dry conditions, but becomes larger under high humidity conditions. For example, the wetting tension set to 450 μN / cm or more is 400 μm / cm. Can even go down. The same can be said when an inorganic filler is mixed in the film. A polylactic acid film wound in a roll absorbs moisture in the air from the outermost surface of the roll and from the end of the roll, but if there is a gap in the roll film, air enters from there. Moisture is absorbed. Therefore, the roll film needs to be wound in a good state so that there is no gap.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to these examples. In addition, the various measured values and evaluation method used in the Example were measured by the method shown below, and it evaluated and calculated | required.

(1) Average thickness of film Using a dial gauge thickness meter, ten points were randomly selected on the film and measured, and the average value was obtained.

(2) Ten-point average roughness The measurement was performed based on the method described in Japanese Industrial Standard JIS B0601. Ten-point average roughness (Rz) was determined using a surface roughness measuring instrument “SE-3F” manufactured by Kosaka Laboratory. However, the stylus tip radius of the measuring instrument was 2 μm, the load was 30 mg, the measurement length was 8 mm, and the cutoff value was 0.08 mm.

(3) Surface hardness of film roll-shaped material After slitting the film, it was rolled up and the surface hardness of the film was measured. The surface hardness is based on JIS K 7312, using a C-type rubber hardness tester, giving a constant load of 1.6 kg, and the upper surface of the film roll from the one end to the other end of the roll Was measured at intervals of 50 mm. The average value of the measured value was calculated and used as the surface hardness. For example, for a film having a width of 800 mm, 15 points are measured. As a rubber hardness meter, Model Asker C manufactured by Kobunshi Keiki Co., Ltd. was used. The shape of the push needle is round, height 2.54, diameter 5.08 hemisphere, and the spring load is 539 mN at 0 degree and 8379 mN at 100 degree.

(4) Change in wetting tension over time Wetting tension immediately after corona treatment is applied to the film, and wetting of the film after being wound into a roll and left for 2 months at a temperature of 23 ° C and a humidity of 50% The tension was measured based on JIS K6768.

(5) Comprehensive evaluation When good evaluation was obtained in all of the evaluation items, it was indicated by “◯”, and when even one evaluation was poor, it was indicated by “x”.

(Example 1)
Polylactic acid (manufactured by Cargill Dow, “4031D”) and 1 part by mass of silica having an average particle size of 3.5 μm (trade name: Silicia 440, manufactured by Fuji Silysia Chemical Co., Ltd.) as an antiblocking agent were dried. Thereafter, it was put into a 40 mmφ same-direction twin screw extruder. The mixture was melt-mixed at about 210 ° C. in a twin-screw extruder, extruded as a strand, and cut into pellets while cooling. This pellet was used as a master batch, dried, mixed with the dried polylactic acid polymer and silica, and charged again into a 40 mmφ co-directional twin screw extruder. However, they are mixed so that the amount of silica is 0.1 parts by mass. In a twin-screw extruder, melt extrusion was performed at a set temperature of 210 ° C., and contacted with a rotating 45 ° C. cooling drum was rapidly cooled and solidified to produce a substantially amorphous polylactic acid film. Subsequently, the prepared film is heated while continuously contacting with a hot water circulation roll (however, an infrared heater is used in combination), and stretched 3.0 times at 73 ° C. in the longitudinal direction between the peripheral speed difference rolls, and then The sheet stretched in the machine direction was guided to a tenter while being held with a clip, and stretched 3.5 times at 75 ° C. in the vertical direction (MD) of the film flow. Thereafter, a heat treatment was performed at 140 ° C. for about 15 seconds to produce a polylactic acid film having a thickness of 40 μm. Next, the produced polylactic acid film was subjected to corona treatment, and immediately wound up on a winder. However, the corona treatment was performed so that the wetting tension of the film was 460 μN / cm. The obtained polylactic acid film was designated as film No. Set to 1. Film No. 1 had an average thickness of 40 μm and a ten-point average roughness of 1.6 μm.

Film No. After cutting 1 using a slitter, the paper tube having an inner diameter of 76 mm and a wall thickness of 10 mm is adjusted so that the corona-treated surface becomes the inner surface, and the surface hardness of the roll is adjusted to 87 degrees. Turned to form a roll of polylactic acid film. However, the wound polylactic acid film had a width of 800 mm and a length of 500 m.
The obtained polylactic acid film roll was visually observed to determine whether there was any sag derived from winding deviation, sagging, or hump, and the change in wetting tension over time was evaluated. The results are shown in Table 1.

(Example 2)
In Example 1, film No. A roll of polylactic acid film was formed in the same manner as in Example 1 except that the polylactic acid film of No. 1 was adjusted and wound so that the surface hardness was 94 degrees. The obtained polylactic acid film roll was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Example 3)
A mixture of the synthesized polylactic acid polymer and polybutylene succinate / adipate (manufactured by Showa High Polymer Co., Ltd., trade name: Bionore # 3003) as an aliphatic polyester in a mass ratio of 87:13. Then, 1 part by mass of silica (Fuji Silysia Chemical Co., Ltd., trade name: Silicia 440) having an average particle size of 3.5 μm was added as an antiblocking agent and dried, and then charged into a 40 mmφ co-directional twin screw extruder. The mixture was melt-mixed at about 210 ° C. in a twin-screw extruder, extruded as a strand, and cut into pellets while cooling. This pellet was used as a master batch, dried, mixed with the dried polylactic acid polymer and silica, and charged again into a 40 mmφ co-directional twin screw extruder. However, they are mixed so that the amount of silica is 0.1 parts by mass. In a twin-screw extruder, melt extrusion was performed at a set temperature of 210 ° C., and contacted with a rotating 45 ° C. cooling drum was rapidly cooled and solidified to produce a substantially amorphous polylactic acid film. Subsequently, the prepared film was heated while continuously contacting with the hot water circulation roll (however, an infrared heater was used in combination), and stretched 2.8 times in the longitudinal direction at 73 ° C. between the peripheral speed difference rolls, The sheet stretched in the machine direction was guided to a tenter while being held with a clip, and stretched 3.5 times at 75 ° C. in the vertical direction (MD) of the film flow. Thereafter, a heat treatment was performed at 140 ° C. for about 20 seconds to produce a polylactic acid film having a thickness of 25 μm. Next, the produced polylactic acid film was subjected to corona treatment, and immediately wound up on a winder. However, the corona treatment was performed so that the wetting tension of the film was 460 μN / cm. The obtained polylactic acid film was designated as film No. 2. Film No. 2 had an average thickness of 25 μm and a ten-point average roughness of 1.8 μm.

Film No. After cutting 2 using a slitter, it was wound around a paper tube having an inner diameter of 76 mm and a wall thickness of 10 mm in a roll shape so that the corona-treated surface became the inner surface. Next, a polylactic acid film wound in a roll shape is unwound, and a surface-coated cationic antistatic agent (trade name: Anstex C-200X, manufactured by Toho Chemical Industry Co., Ltd.) is applied to the corona-treated surface. A 3% by mass aqueous solution was applied using a reverse coater type coating apparatus so that the film thickness after drying was 1 μm. However, the drying temperature was set to 80 ° C. After that, the surface coated with the antistatic agent aqueous solution is made the inner surface, and the surface opposite to the coated surface is subjected to corona treatment, adjusted to have a surface hardness of 90 degrees, and again in a roll shape. Rolled up to form a roll of polylactic acid film. However, the wound polylactic acid film had a width of 800 mm and a length of 500 m.
About the roll-like thing of the obtained polylactic acid-type film, it carried out similarly to Example 1, and evaluated about the time-dependent change of winding shift | offset | difference, sagging, sagging derived from a hump, and wet tension. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, film No. A roll of polylactic acid film was formed in the same manner as in Example 1 except that the polylactic acid film of No. 1 was wound so as to have a surface hardness of 97 degrees. The obtained polylactic acid film roll was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
In Example 1, film No. A roll of polylactic acid film was formed in the same manner as in Example 1 except that the polylactic acid film of No. 1 was adjusted and wound so that the surface hardness was 84 degrees. The obtained polylactic acid film roll was evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
In Example 3, film no. A roll of polylactic acid film was formed in the same manner as in Example 1 except that the polylactic acid film 2 was adjusted and wound so that the surface hardness was 84 degrees. The same evaluation as in Example 3 was performed on the obtained polylactic acid film roll. The results are shown in Table 1.

(Comparative Example 4)
Film No. 1 in Example 1 In the production of 1, a master batch was prepared by changing to an silica having an average particle size of 5.2 μm as an antiblocking agent (manufactured by Fuji Silysia Chemical Co., Ltd., trade name: Silicia 450), and this master batch was used. A polylactic acid film was prepared in the same manner as in Example 1 except for the above. Next, the produced polylactic acid film was subjected to corona treatment, and immediately wound up on a winder. However, the corona treatment was performed so that the wetting tension of the film was 450 μN / cm. The obtained polylactic acid film was designated as film No. 3. Film No. 3 had an average thickness of 40 μm and a 10-point average roughness of 2.3.
Film No. After cutting 3 with a slitter, the paper tube having an inner diameter of 76 mm and a wall thickness of 10 mm is adjusted so that the corona-treated surface becomes the inner surface, and the roll-like product is adjusted so that the surface hardness is 88 degrees. Turned to form a roll of polylactic acid film. However, the wound polylactic acid film had a width of 800 mm and a length of 500 m.
The obtained polylactic acid film roll was evaluated in the same manner as in Example 1. The results are shown in Table 1.

As is clear from Table 1, in Examples 1 to 3, no winding deviation, sagging, or sagging derived from a winding hump was observed. Further, in Examples 1 to 3, the wetting tension hardly decreased with time, and even in Example 3 subjected to the antistatic treatment, almost no decrease in wetting tension was observed, and good results were obtained as a comprehensive evaluation. Obtained.
On the other hand, in Comparative Example 1, since the surface hardness of the roll-like product was higher than 95, a roll was formed, and thereby sagging occurred in the longitudinal direction. In Comparative Examples 2 and 3, since the surface hardness of the roll-shaped material was less than 86, winding deviation and sagging occurred, and the wetting tension decreased greatly with time. In particular, in Comparative Example 3 subjected to the antistatic treatment, wetting tension was deteriorated with time, and the following was confirmed in comparison with Example 3. That is, when the film is subjected to an antistatic treatment or the like, moisture in the air is easily absorbed, so that the film surface is sticky or the wetting tension is likely to be reduced. Even when antistatic treatment is applied to the film, the wetting tension does not decrease over time. In Comparative Example 4, since the ten-point average roughness of the film surface was larger than 2.0, a gap was formed, and as a result, sagging occurred in the roll. Moreover, in the comparative example 4, the time-dependent fall of the wetting tension was large.

  As described above in detail, according to the present invention, it is possible to provide a roll of a polylactic acid film wound in a good state without causing “sag” or “kump”. Further, it is possible to provide a polylactic acid-based film that does not absorb moisture even when stored for a long period of time, and that does not decrease the wetting tension of the polylactic acid-based film over time even when subjected to an antistatic treatment or the like.

  In the present invention, it is possible to realize a roll-shaped product that does not generate sagging and knots, which is suitable for a case where it is necessary to wind and store the biodegradable film in a roll shape.

Claims (3)

The ten-point average roughness Rz of the surface of the polylactic acid-based film is 2.0 or less, and the surface hardness of the roll-shaped product wound with the polylactic acid-based film is C-type rubber based on Japanese Industrial Standard JIS K7312 Ri range der value of 86 to 95 degrees when measured in hardness meter, and poly water content of the polylactic acid-based film is characterized in that 0.1% or more, 0.5% or less Roll of lactic acid film.   The roll-like product of a polylactic acid film according to claim 1, wherein an average thickness of the polylactic acid film is in a range of 7 to 80 µm.   The roll of polylactic acid film according to claim 1 or 2, wherein the polylactic acid film has a wet tension of at least one side of 400 µN / cm or more.