JP5517276B2 - Polyester film - Google Patents

Description

  The present invention relates to a polyester film mainly composed of a polylactic acid resin, and relates to a film that is excellent in flexibility and transparency, and that changes in properties such as strength and elongation of the film over time are suppressed. Further, the present invention relates to a polyester film that is excellent in stretchability and film forming stability in an inflation film forming method and can be suitably used as a wrap film, stretch film, multifilm, bag body, and the like.

  Conventionally, as a method of disposing of a polymer resin molded product used for packaging materials or the like, a method of processing by a method such as incineration or landfill has been long. However, in recent years, waste disposal issues such as greenhouse gas emissions from incineration, deterioration of incinerators due to high combustion heat, environmental pollution due to landfill reduction and dumping have become a major issue. Under such circumstances, biodegradable plastics have attracted a great deal of attention as environmentally friendly materials that are degraded by enzymes and microorganisms. In particular, products related to molded articles using aliphatic polyesters, particularly polylactic acid, have been actively developed. In particular, a polyester film made of a polylactic acid resin has been developed in the industrial materials and packaging materials fields.

  Polylactic acid is a polymer obtained by producing lactic acid using starch obtained from cereals such as corn, and potatoes such as sweet potato, and further by chemical synthesis, and among aliphatic polyesters, it can be synthesized from plant-derived raw materials, In addition, because of its excellent mechanical properties, heat resistance, and transparency, research and development has been actively conducted for the purpose of developing various molded products such as films, sheets, tapes, fibers, ropes, nonwoven fabrics, and containers. . However, in applications such as wrapping film for packaging, for example, polylactic acid is not flexible enough as it is, and various softening techniques mainly by adding a plasticizer have been studied.

  For example, as a flexible polylactic acid composition, a technique using a plasticizer such as a phthalate ester that is frequently used by adding to polyvinyl chloride is disclosed (for example, see Patent Document 1). As a technique limited to packaging wrap film use, for example, a stretched film made of a composition containing a resin mainly composed of a lactic acid aliphatic polyester and a liquid additive is disclosed (for example, see Patent Document 2). . However, when a plasticizer or a liquid additive that is usually used such as a phthalate ester is added to soften the resin, the melt viscosity characteristic is lowered with the plasticization of the resin, and the extrusion film forming property is lowered. In particular, in the inflation film-forming method used in the manufacture of packaging films such as bags, it is difficult to maintain the shape during extrusion upward, the film formation tends to become unstable, and furthermore, high-strength stretch molding is difficult. there were. Further, in a molding method such as blow molding, there are cases where problems such as sagging occur when reheating a film or sheet, resulting in molding failure. Furthermore, the decomposition is accelerated by the polyester resin, the oligomer, the plasticizer, the hydroxyl group or the carboxyl group of the liquid additive, etc., and the physical properties of the film or the molded product greatly change over time, resulting in inferior practicality.

Moreover, the technique using the high molecular weight plasticizer which has a polylactic acid segment and a polyether segment in 1 molecule is disclosed (patent document 3). However, it is an insufficient technique for the melt viscosity characteristics in the inflation film forming method and blow molding, and degradation of physical properties over time such as decomposition occurs due to the influence of hydroxyl groups and carboxyl groups of plasticizers and oligomers. It wasn't enough.
Furthermore, a technique using a composition having a specific viscosity range using two or more aliphatic polyesters in order to improve flexibility and inflation suitability (Patent Document 4) is sufficiently compatible. However, there was a problem that transparency was insufficient and heat sealability was insufficient.
As described above, while attempts have been made to add flexibility by adding a plasticizer to polylactic acid resin, it has been given sufficient flexibility and transparency, and it is also possible to form inflation film and blow molding. It has not been achieved for a film having excellent properties, and has not been achieved for a film in which changes in physical properties over time due to decomposition are suppressed.
JP-A-4-335060 JP 2000-26623 A International Publication No. 2004/000939 Pamphlet JP-A-11-124430

  An object of the present invention is to eliminate the above-described problems. That is, not only is it excellent in flexibility and transparency required for wrap films, stretch films, multi-films, bags, etc., but it is also excellent in heat sealability, and stretchability, film forming stability and blow molding in the inflation film forming method. It is an object of the present invention to provide a polylactic acid film that is excellent in properties and in which changes in properties such as strength and elongation of the film over time are suppressed.

The above object can be achieved by the following means.
(1) In a total of 100% by mass of the polylactic acid resin, the plasticizer, and the polyfunctional compound, the polylactic acid resin is 50 to 95% by mass, the plasticizer is 4 to 49% by mass, and the polyfunctional compound is 0.1 to 5% by mass. A polyester film comprising:
And the tensile modulus is 0.1 to 1.5 GPa,
The polylactic acid resin, Ri aspect der to combination with the homo lactic acid and noncrystalline homo lactic acid having a crystallinity,
The plasticizer has one or more polylactic acid segments having a number average molecular weight of 1500 to 10,000 in one molecule and a polyether and / or polyester segment having a number average molecular weight of 1,000 to 20,000. And
The polyfunctional compound is characterized copolymer der Rukoto of methyl methacrylate and methacrylic acid glycidyl ester, a polyester film.

  The polyester film of the present invention is not only excellent in flexibility, transparency and heat sealability, but also excellent in stretchability, film forming stability and blow moldability in the inflation film forming method, and suitable for a wide range of film forming methods and forming methods. In addition, since excellent properties such as strength and elongation of the film can be maintained, it can be suitably used as a wrap film, a stretch film, a multifilm, a bag, and the like.

The polyester film of the present invention has a polylactic acid resin of 50 to 95 masses in a total of 100 mass% of a polylactic acid resin, a plasticizer, and a polyfunctional compound in order to impart unique flexibility typified by a wrap film and a stretch film. %, A plasticizer of 4 to 49% by mass and a polyfunctional compound of 0.1 to 5% by mass. From the viewpoint of handleability when used, such as the strength of the film, it is more preferably 57 to 80% by mass of a polylactic acid resin, 10 to 40% by mass of a plasticizer, and 0.3 to 3% by mass of a polyfunctional compound.
When the polylactic acid resin is less than 50% by mass, the films may be blocked or the shape may be difficult to maintain, resulting in poor process passability and slit processability during film production. In addition, problems such as being unable to stick to and peel off articles to be packaged may occur. On the other hand, when the content of the polylactic acid resin exceeds 95% by mass, it does not deform following the shape of the article or food to be packaged, and sufficient flexibility cannot be obtained. In addition, problems such as tearing of the film and damaging the packaged items occur during packaging.

  Here, the polylactic acid resin of the present invention is a polymer produced using L-lactic acid and / or D-lactic acid as a main starting material. And in the polyester film of this invention, it is preferable that 70 mass% or more of the polylactic acid resin structural component of this invention is a polylactic acid polymer which has the crystallinity which uses L- or D-lactic acid as a starting material.

  Polylactic acid includes poly-L-lactic acid composed of L-lactic acid, poly-D-lactic acid composed of D-lactic acid, and a racemic body thereof, but the polylactic acid resin of the present invention has crystallinity. It is preferable that the ratio of L-lactic acid of the lactic acid component comprised in the range to have is 99-70 mass%, and it is more preferable if it is 99-80 mass%. In addition, depending on the purpose of use, two or more types of homopolylactic acid having different optical purities may be used in combination for the purpose of imparting or improving necessary functions. For example, homopolylactic acid having crystallinity and amorphous These homopolylactic acids can also be used in combination.

  Amorphous homopolylactic acid is a polylactic acid resin that does not exhibit a melting point and has substantially no crystal structure when subjected to differential scanning calorimetry (DSC) at a temperature elevation rate of 20 ° C./min. The crystallinity of polylactic acid is controlled by the optical purity of polylactic acid, and in the case of polylactic acid mainly composed of L-lactic acid, the proportion of D-lactic acid, that is, the amount of copolymerization of D-lactic acid increases, The melting point decreases with the decrease in the properties, and the polylactic acid does not exhibit a melting point when the copolymerization amount is approximately 10% or more.

  The proportion of amorphous homopolylactic acid may be determined within a range that does not impair the effects of the present invention. However, the higher the amount of plasticizer added, the higher the proportion of amorphous homopolylactic acid may be. Is preferable for improving.

  The plasticizer cannot be present in a polylactic acid crystal having a dense structure, and is contained in a gap between molecules of an amorphous part. That is, the amount of the plasticizer that can be held in the resin is determined by the amount of the amorphous part in the resin.

  In addition, in the case of being composed only of amorphous polylactic acid, since it has substantially no crystals, sufficient heat resistance such as melting at a low temperature may not be obtained. Therefore, when using amorphous polylactic acid, it is preferable to use together with crystalline polylactic acid.

  In general, homopolylactic acid has a higher melting point as the optical purity is higher. For example, poly L-lactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C., but has a high heat resistance when formed into a polylactic acid-based molded product. When it is desired to impart the above, it is preferable that at least one of the polylactic acid polymers used contains polylactic acid having an optical purity of 95% or more.

In the method for producing polylactic acid, L-lactide, D-lactide, and DL-lactide (racemate), which are cyclic dimers, are produced from L-lactic acid and D-lactic acid as raw materials, and the lactide is subjected to ring-opening polymerization. Thus, there are a lactide method for obtaining a polymer and a direct polymerization method for obtaining a polymer by direct dehydration condensation of lactic acid in a solvent or the like.
In the present invention, polylactic acid obtained by either polymerization method can be used in the same manner. However, in the lactide method, lactide remains in the polylactic acid, and therefore, when a molded article such as a film is produced. Since precipitation of lactide occurs, the film forming process may be contaminated. Therefore, it is preferable that the residual lactide content in the polymer is 0.3% by mass or less.

  The polylactic acid resin of the present invention has a number average molecular weight of preferably from 20,000 to 250,000, more preferably from 40,000 to 150,000, more preferably from 50,000 to 110,000, from the viewpoint of overall film properties, particularly mechanical properties. It is particularly preferable if it is present.

  The polylactic acid resin of the present invention may be a copolymerized polylactic acid obtained by copolymerizing monomer residues other than L-lactic acid and D-lactic acid. As the monomer component to be copolymerized, glycolic acid, 3 Examples include hydroxycarboxylic acids such as -hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, and 6-hydroxycaproic acid, glycol compounds having an ester forming ability, dicarboxylic acid compounds, and ester derivatives thereof. Specifically, examples of the glycol compound include ethylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol and the like. Examples of the dicarboxylic acid compound include succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, and dimethyl ester derivatives thereof. it can. Among these, a copolymer component that does not particularly inhibit the biodegradability of polylactic acid can be preferably used. For example, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid And ethylene glycol, trimethylene glycol, tetramethylene glycol succinic acid, adipic acid, and sebacic acid.

  Moreover, you may blend a well-known biodegradable resin in the range which does not impair the effect of this invention. Examples of such biodegradable resins include polyethylene succinate, polybutylene succinate, polybutylene adipate, and copolymers thereof, but compatibility with polylactic acid and transparency of the film, From the viewpoint of heat sealability, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 5 parts by mass or less with respect to 100 parts by mass of the total of the polylactic acid resin, the plasticizer, and the polyfunctional compound. .

  Examples of the plasticizer contained in the polyester film of the present invention include phthalate esters such as diethyl phthalate, dioctyl phthalate and dicyclohexyl phthalate, di-1-butyl adipate, di-n-octyl adipate, and sebacine. Aliphatic dibasic acid esters such as di-n-butyl acid and di-2-ethylhexyl azelate, phosphoric acid esters such as diphenyl-2-ethylhexyl phosphate and diphenyloctyl phosphate, tributyl acetylcitrate, acetyl Hydroxypolycarboxylic acid esters such as tri-2-ethylhexyl acid and tributyl citrate, fatty acid esters such as methyl acetylricinoleate and amyl stearate, glycerin compounds such as glycerin, diglycerin and triglycerin, and these glycerins Acidification Polyhydric alcohol ester series, Epoxidized soybean oil, Epoxidized linseed fatty acid butyl ester, Epoxy plasticizer such as octyl epoxy stearate, Polyester plasticizer such as polypropylene glycol sebacate, Polyalkylene ether series, Ether Fats and oils such as ester oils, acrylate plasticizers, vegetable oils such as olive oil, castor oil, rapeseed oil, peanut oil, coconut oil, animal oils such as liver oil, lanolin, lard, beeswax, and mineral oils such as liquid paraffin and petroleum jelly Compounds such as fatty acids and fatty acid esters constituting these fats and oils can be mentioned. These are preferably safe without problems even when used for food packaging.

  It is more preferable to use a plasticizer having a polylactic acid segment from the viewpoint of bleed-out resistance. Here, the polylactic acid segment refers to a lactic acid block polymer composed of polylactic acid or oligolactic acid. The polylactic acid segment is compatible with a polylactic acid resin as a base material, and as a result, some of the plasticizer molecules are polylactic acid crystals. This is because the plasticizer bleed out from the film can be suppressed by the anchor effect.

  Furthermore, a plasticizer having a polylactic acid segment has a polylactic acid segment having one or more polylactic acid segments having a molecular weight of 1500 to 10,000 and a molecular weight of 1,000 to 20,000 in terms of anchoring effect and plasticizing effect. It is particularly preferable to use a polymer plasticizer having an ether and / or polyester segment.

  Furthermore, as the polyether segment in the plasticizer, a polyalkylene glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyhexamethylene glycol, or a segment made of a copolymer of these polyalkylene glycols is preferably used. Can do. Further, in terms of compatibility with the polylactic acid resin and film adhesion, a plasticizer containing a polyethylene glycol or polypropylene glycol component is preferable, and it is particularly preferable to use the plasticizer in combination according to various objective properties.

  In the case of using a plasticizer having a polylactic acid segment, in order to make the effect of suppressing bleed out more remarkable, the polylactic acid resin as a base material contains a polylactic acid resin having a crystallinity of 95% or more in optical purity. Preferably, it contains more than 10% by mass of polylactic acid resin having crystallinity in 100% by mass of polylactic acid resin to be used. More preferably, it is in the range of 10% by mass or more and less than 50% by mass from the viewpoint of compatibility with flexibility.

  Furthermore, the plasticizer of the present invention has a plasticizer viscosity of 1 to 5 Pa · s at the melting point of the plasticizer + 30 ° C. from the viewpoint of suppressing bleed out of the plasticizer and making the melt viscosity of the film a good range. Preferably there is. The viscosity of the plasticizer refers to an average value measured five times by the viscosity measuring method shown in JISK7117-1. When the viscosity of the plasticizer at the melting point of the plasticizer + 30 ° C. is less than 1 Pa · s, the bleed-out resistance becomes insufficient, or the melt viscosity of the film of the present invention when a large amount of the plasticizer is added. It may be difficult to make the value in a good range. Further, when the viscosity of the plasticizer at the melting point of the plasticizer + 30 ° C. exceeds 5 Pa · s, sufficient flexibility may not be obtained. Preferably, the viscosity of the plasticizer at the melting point of the plasticizer + 30 ° C. is 1.5 to 5 Pa · s, more preferably 2 to 5 Pa · s, and particularly preferably 3 to 5 Pa · s.

  The plasticizer having such a viscosity range is not particularly limited, but a higher molecular weight plasticizer is preferable from the viewpoint that the temperature dependency of the viscosity equal to or higher than the melting point of the plasticizer is small. The average molecular weight is preferably 500 or more, more preferably 1000 or more, still more preferably 3000 or more, and particularly preferably 5000 or more.

  The plasticizer contained in the polyester film of the present invention preferably has reactivity with a resin or a polyfunctional compound from the viewpoint of bleed-out resistance. The reactive plasticizer is a plasticizer having a hydroxyl group or a carboxyl group at the end of the plasticizer or the main chain or side chain of the plasticizer, a plasticizer having a carbodiimide group, a glycidyl group, an oxazoline group or an isocyanate group. By reacting with a resin or a polyfunctional compound, the molecular chain is copolymerized to increase the molecular weight, and exudation and extraction of the plasticizer are suppressed, and the bleed-out resistance is improved.

  The polyester film of the present invention needs to contain 4 to 49% by mass of a plasticizer in a total of 100% by mass of the polylactic acid resin, the plasticizer and the polyfunctional compound, from the viewpoint of obtaining sufficient flexibility and handleability. is there. If it is less than 4% by mass, sufficient flexibility may not be obtained, and if it exceeds 49% by mass, problems such as deterioration in handleability as a composition or film occur, and problems such as film blocking. May occur. The plasticizer content is more preferably 10 to 40% by mass, and further preferably 15 to 40% by mass.

  In addition, when a plasticizer that does not have a polylactic acid segment is used as the plasticizer, the plasticizer exudes and is extracted (bleeded out), so that the flexibility is lowered, the physical properties change over time, the film surface is whitened and packaged. Problems such as contamination of articles may occur.

  As a method for producing a plasticizer contained in the polyester film of the present invention, for example, a plasticizer having one or more polylactic acid segments in one molecule and having a polyether and / or polyester-based segment is as follows. Can be manufactured. A commercially available polyethylene glycol having a predetermined molecular weight having hydroxyl groups at both ends and lactide which is a cyclic dimer of lactic acid are mixed at a predetermined ratio, and for example, tin octylate is added as a polymerization catalyst, and both hydroxyl groups of polyethylene glycol are added. Lactide is subjected to ring-opening addition polymerization from the terminal to obtain an ABA type triblock copolymer covalently bonded to a polylactic acid segment-polyethylene glycol segment-polylactic acid segment. The molecular weight of the polylactic acid segment can be controlled by controlling the addition amount of polyethylene glycol and lactide and the polymerization catalyst and the conditions of the ring-opening addition polymerization, whereby a desired polymer plasticizer can be obtained. .

  The polyester film of the present invention has many polylactic acid resins and plasticizers from the viewpoint of suppressing degradation of the polylactic acid resin or plasticizer and maintaining mechanical properties over time, and improving the film forming property and blow moldability. It is preferable to contain a polyfunctional compound in the range of 0.1 to 5% by mass in a total of 100% by mass of the functional compound.

Examples of the polyfunctional compound of the polymer type, a copolymer of main methacrylic acid with methyl methacrylate glycidyl ester is particularly preferably used from the viewpoint of compatibility with the polylactic acid can be obtained good and transparent film Can do. Furthermore, these polyfunctional compounds may be used alone or in combination of two or more. As described above, the polyester film of the present invention preferably contains a polyfunctional compound in the range of 0.1 to 5% by mass. Although it can adjust with the reactivity of a polyfunctional compound and the number of functional groups, More preferably, it is 0.3-3 mass%, More preferably, it is 0.5-2 mass%, Most preferably, it is 0.5-1 mass%. is there.

  If the content of the polyfunctional compound is less than 0.1% by mass, the degradation of the polylactic acid resin or the plasticizer cannot be suppressed, the mechanical properties such as elongation are deteriorated, and the film is broken in the use environment. In some cases, sufficient film-forming properties and moldability may not be obtained. On the other hand, when the content exceeds 5% by mass, the dispersion state of the polyfunctional compound is deteriorated and the film is whitened or the transparency is insufficient, or the reaction between the polyfunctional compounds proceeds to form foreign matters. The resin or film may be cured and the flexibility may be impaired.

  Formation of foreign substances by reaction between such polyfunctional compounds is easy to form due to the number of functional groups and high acidity of the resin composition containing the polyfunctional compound, and the number of functional groups per molecule is 3 or more. When the polyfunctional compound is added in an amount of 1% by mass or more, for example, the acid value of these compositions is preferably 60 equivalents / ton or less, more preferably 30 equivalents / ton or less, and still more preferably 20 equivalents / ton. Tons or less.

  The melt viscosity at 170 ° C. of the polyester film of the present invention is preferably 400 to 3000 Pa · s. When the melt viscosity is less than 400 Pa · s, it is difficult to maintain the shape during upward extrusion, and the stability during inflation film formation becomes insufficient. Furthermore, tearing is likely to occur during high-magnification stretch molding, which may be difficult. Further, in a molding method such as blow molding, problems such as sagging may occur when reheating a film or sheet, resulting in molding failure. Further, when the melt viscosity exceeds 3000 Pa · s, the amount of deformation at the time of stretching is small, and it becomes difficult to stretch at a high magnification, or in blow molding or the like, it becomes difficult to mold to a desired shape. There is a case. Furthermore, the flexibility of the film may be insufficient. The melt viscosity at 170 ° C. of the polyester film is more preferably 500 to 2500 Pa · s, still more preferably 600 to 2000 Pa · s, and particularly preferably 700 to 1500 Pa · s.

  In order to set the melt viscosity of the polyester film at 170 ° C. to a specific range, the molecular weight of polylactic acid resin and plasticizer to be used, the amount of addition, the method of controlling the amount of addition of polyfunctional compound, and further by decomposition in an extruder Examples thereof include a method for suppressing a decrease in viscosity. For example, a polylactic acid resin having a higher molecular weight or a higher melting point can be used, a melt viscosity at 170 ° C. can be increased by increasing the addition amount of the polylactic acid resin, a plasticizer having a higher molecular weight and higher viscosity can be used, Although the melt viscosity can be increased by reducing the amount added, it is preferable to control the amount of polyfunctional compound added from the viewpoint of making the film properties such as flexibility good, and to lower the viscosity by decomposition. It is a method of suppressing the above.

  In order to suppress decomposition in the polyester of the present invention, it is preferable to suppress thermal decomposition of a polylactic acid resin or a plasticizer. In particular, it is possible to suppress hydrolysis in which the decomposition rate increases due to the amount of water or the amount of carboxyl group end groups in the polyester. Most effective. As a method for reducing the amount of water in the polyester, for example, a method of previously drying a polylactic acid resin or a plasticizer to be used is used. The polylactic acid resin to be used or a polylactic acid resin and a plasticizer and a polyfunctional compound are used. The moisture content of the polyester is preferably 1000 ppm or less, more preferably 500 ppm or less, and still more preferably 300 ppm or less. Furthermore, it is preferable to form a film using a vacuum vent type twin screw extruder while removing moisture in the melt extrusion process. Examples of the method for reducing the amount of the carboxyl group terminal group of the polyester include a method of esterifying the terminal with an aliphatic alcohol or the like, and a method of blocking the terminal with a polyfunctional compound or bonding the terminals to each other.

  The melt viscosity at 170 ° C. of the polyester film of the present invention refers to the melt viscosity determined by a known melt viscosity measurement method. Specifically, for example, in a flow tester manufactured by Shimadzu Corporation, at a cylinder temperature of 170 ° C. and a load of 10 kg. A test is conducted to measure the shear rate and the melt viscosity, the average value is obtained at the time of three measurements, and further measured under a total of five load conditions, and a shear rate of 100 sec-1 obtained from the melt viscosity curve with respect to the shear rate. The melt viscosity of

  The polyester film of the present invention has other plasticizers and antioxidants that do not have a polylactic acid segment as long as the effects of the present invention are not impaired, UV stabilizers, anti-coloring agents, matting agents, and deodorants. Inorganic fine particles, organic particles, and organic compounds may be added as necessary as flame retardants, weathering agents, antistatic agents, mold release agents, antioxidants, waxes, ion exchange agents, or coloring pigments.

Examples of the antioxidant include hindered phenols and hindered amines.
Color pigments include inorganic pigments such as carbon black, titanium oxide, zinc oxide, iron oxide, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, and quinocridone. Organic pigments such as thioindigo can be used.

  For the purpose of improving the slipperiness and blocking resistance of the film, when adding inorganic fine particles or organic particles, for example, silica, colloidal silica, alumina, alumina sol, kaolin, talc, mica, calcium carbonate, polystyrene Particles such as polymethyl methacrylate and silicone can be used.

  Moreover, from the point which makes transparency favorable, the particle | grains which have a refractive index close | similar to polyester used as a base material are preferable, and particles, such as a silica, colloidal silica, a polymethylmethacrylate, are more preferable at such a point.

  Moreover, as particles used for the polyester film of the present invention, it is preferable to select naturally occurring inorganic particles or biodegradable particles. In particular, it is preferable to use particles that are not substantially deformed at the extrusion temperature of the resin composition used in the present invention because the shear effect is increased and the polyfunctional compound and other additives can be uniformly dispersed. Furthermore, it is preferable that the particle surface has a hydroxyl group or a carboxyl group because the dispersibility of the polyfunctional compound and the formation of foreign matter due to self-reaction can be suppressed.

The average particle size of the particles used in the present invention is not particularly limited, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm, and most preferably 0.08 in terms of making the transparency good. ~ 2 μm.
The addition amount of the particles is preferably adjusted as appropriate according to requirements such as transparency, tube-like film obtained by an inflation film-forming method, bag-like film opening property, film handling property, process passability, etc. Although not particularly limited, 0.01 to 10 parts by mass is preferable with respect to a total of 100 parts by mass of the polylactic acid resin, the plasticizer, and the polyfunctional compound, and more preferably 0.05 to 5 parts by mass. More preferably, it is 0.05-3 mass parts. In particular, it is preferable to use in the range of 0.05 to 1 part by mass in combination with the organic lubricant described later.

  Furthermore, an organic lubricant is added for the purpose of improving the slipperiness of the polyester film of the present invention, the opening of tube-like and bag-like films in the inflation film-forming method, and the opening of bag-like products such as garbage bags. It is preferable. Preferred organic lubricants include oleic acid amide, stearic acid amide, erucic acid amide, behenic acid amide, N-oleyl palmitoamide, N-stearyl erucamide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis lauryl. Amide organic lubricants such as acid amides, methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl erucate, methyl behenate, butyl laurate, butyl stearate, myristic Isopropyl acid, isopropyl palmitate, octyl palmitate, octyl palm fatty acid ester, octyl stearate, lauryl laurate, stearyl long stearate, long chain fatty acid higher alcohol ester, behenine behenate, Monoester organic lubricants such as cetyl stannate, as well as zinc stearate, calcium stearate, magnesium stearate, aluminum stearate, barium stearate, lithium stearate, lead stearate, sodium oleate, barium laurate, lauric acid Examples include fatty acid salts such as zinc, silicon compounds, carnauba wax, and candelilla wax. Of these, amide-based lubricants can be suitably used from the viewpoints of excellent slipperiness and bleed-out resistance. From the viewpoint of dispersibility in the polylactic acid resin, stearic acid amide, ethylene bis stearic acid amide, and ethylene bis lauric acid amide are preferable, and stearic acid amide is more preferable.

  The preferred amount of organic lubricant added to the film is in the range of 0.1 to 1.5 parts by mass, more preferably 0, per 100 parts by mass in total of the polylactic acid resin, the plasticizer and the polyfunctional compound. .3 to 1.0 part by mass, more preferably 0.3 to 0.8 part by mass, particularly preferably 0.32 to 0.6 part by mass. If the amount is less than 0.1 parts by mass, sufficient effects cannot be obtained in terms of slipperiness and openness, and if it exceeds 1.5 parts by mass, the transparency of the film may be impaired or the surface may bleed out. In some cases, the process and the articles to be packed may be contaminated.

  The polyester film of the present invention preferably has a tensile elastic modulus of 0.1 to 1.5 GPa obtained by a tensile test at 23 ° C. When the tensile elastic modulus of the film is less than 0.1 GPa, elongation and slackening may occur in film formation and processing steps, and handling properties, process passability, and slit processability may be poor. Further, when used as a wrap film, there may be a problem that the film is deformed and cannot be efficiently packaged before wrapping an article such as a container or food. Moreover, when it exceeds 1.5 GPa, it does not deform following the shape of the article or food to be packaged, and sufficient adhesion may not be obtained. Further, excessive force is required for packaging, and problems such as damage to the package may occur.

  A more preferable range of the tensile modulus is 0.1 to 1.3 GPa, more preferably 0.15 to 1.2 GPa, and particularly preferably 0.2 to 1.0 GPa.

  In the present invention, the term “tensile test” means a test performed under a tensile speed of 300 mm / min using a Tensilon universal testing machine in accordance with JIS K7161 and JIS K7127 in an atmosphere of 23 ° C. In the present invention, the tensile elastic modulus means the difference in stress between two points on the straight line by using the first linear portion of the stress-strain curve obtained in the above tensile test. This is the value obtained by dividing.

  When the polyester film of the present invention is used as a packaging film such as a wrap film, the haze is preferably 10% or less because the contents can be easily distinguished. It is preferably 7% or less, more preferably 5% or less, and particularly preferably 3% or less.

  Further, the haze is preferably as low as possible, but in practice it is difficult to make it less than 0.1%. However, 0.1% or more and 10% or less is sufficient from the viewpoint of distinguishing the contents.

As a method for setting the haze range of the film, it is important to control the addition amount and combination of additives such as particles to be added, as well as the compatibility of the polylactic acid resin and the plasticizer constituting the film. .
As a method for setting the haze of the film to 10% or less, for example, a method of reducing the addition amount of other resins and particles having low compatibility and additives, and other resins excluding polylactic acid resins and plasticizers are preferable. It is particularly preferable that the configuration is not included.

  In applications where a certain degree of concealment is required, such as garbage bags or agricultural multi-films, or where light transmittance is low or absorption such as sunlight is preferred, carbon black or oxidation may be used as necessary. A color pigment typified by titanium may be added.

  Although the manufacturing method of the polyester film of this invention is illustrated concretely below, the manufacturing method of the film of this invention is not limited to this. First, as a method for producing a polylactic acid resin, for example, polymerization of poly-L-lactic acid can be performed as follows.

  0.02 parts by mass of tin octylate is added to 100 parts by mass of commercially available L-lactide and polymerized at 190 ° C. for 15 minutes in a nitrogen atmosphere to obtain a precursor poly-L-lactic acid. After making this precursor poly L-lactic acid into chips, poly L-lactic acid suitable for film production can be obtained by solid-phase polymerization at 140 ° C. for 3 hours in a nitrogen atmosphere.

  Moreover, the synthesis | combination of the polymeric plasticizer which has the polylactic acid segment which can be preferably used by this invention can be performed as follows. By mixing 71 parts by mass of a commercially available polyethylene glycol having a number average molecular weight of 10,000, 29 parts by mass of L-lactide and 0.02 parts by mass of tin octylate and polymerizing at 160 ° C. for 2 hours in a nitrogen atmosphere, both ends of polyethylene glycol In addition, an ABA type triblock copolymer having a poly L-lactic acid unit having a number average molecular weight of 2,000 can be obtained.

  Furthermore, for the purpose of removing low molecular weight substances such as catalyst deactivation and unreacted substances, for example, a method of adding phosphoric acid or phosphate ester according to the amount of catalyst, a method of drying under reduced pressure, A method of mixing and stirring with water to remove catalyst deactivation and a low molecular weight substance, or a combination of these can be employed. From the viewpoint of uniformly dispersing the multi-possible compound, a method of reducing the acid content of the plasticizer or the composition is preferable, and care should be taken when using phosphoric acid or phosphate ester.

  The film of the present invention can be produced using the polylactic acid resin and plasticizer obtained as described above. In any case, in order to suppress degradation of the polylactic acid resin and plasticizer used and generation of decomposition products, vacuum drying is performed at 90 ° C. to 110 ° C., the degree of vacuum is set to a high vacuum of 10 Torr or less, and the drying time is 6 It is preferable to set the time or longer.

  In the production of a stretched film, for example, the above-mentioned polyester dried under vacuum can be melt-extruded into a tube shape or a sheet shape from an annular die or slit-shaped base by a known method. From the viewpoint of suppressing an increase in low molecular weight substances such as the above, it is preferable that the extrusion temperature is lower, and that the residence time is shorter. Specifically, the temperature of the extruder, polymer piping, die, etc. is preferably 200 ° C. or lower, more preferably 190 ° C. or lower, and more preferably 180 ° C. or lower. The residence time from when the polylactic acid resin composition is melted in the extruder until it is discharged from the die is preferably 20 minutes or less, more preferably 10 minutes or less, and more preferably 5 minutes or less. Is more preferable.

  When a plasticizer is added to a polylactic acid resin, for example, a blend chip obtained by mixing a polylactic acid resin master chip and a polylactic acid resin homochip containing a high concentration of plasticizer is supplied to an extrusion system of a film forming machine such as an extruder. However, in order to reduce the lactide content while minimizing the thermal degradation of the composition, the raw material is dried under vacuum and extruded using a twin-screw extruder. A method of continuously adding a plasticizer in a liquid state by heating it to the polylactic acid polymer melted in the machine as necessary, and melt-kneading it is preferable. Further, a method is preferred in which a vent port is provided in the middle of the twin screw extruder, the vent port is decompressed, and melt kneading while removing low molecular weight components such as moisture and oligomers generated during melting. The unstretched film obtained by such a method can be obtained by continuously stretching in at least one direction. As a method for producing a stretched film, a method such as an inflation method, a tubular method, a stenter-type sequential biaxial stretching method, a simultaneous biaxial stretching method, or the like can be used. The polymer is extruded into a tube shape from the cylindrical annular die formed, air is sealed in the tube, the bubble is expanded by being bubbled with the pressure, and the stretched film is cooled by a medium such as air or water. To get.

  When using the stenter-type sequential biaxial stretching method, for example, the extruded sheet-like melt is brought into close contact with a casting drum and cooled and solidified to obtain an unstretched film. The unstretched film is stretched in the longitudinal direction by roll stretching utilizing the peripheral speed difference of the heated roll, and then stretched in the direction perpendicular to the first-stage stretching direction in a tenter having a continuous clip. A heat treatment can be applied internally and / or after winding.

  The film of the present invention can be applied to any manufacturing method, and is not particularly limited. However, the film is easy to produce in a bag shape, and has little loss at the film edge during manufacturing. The method can be suitably used.

  The stretching conditions of the film can be appropriately adjusted according to the desired heat shrinkage characteristics, dimensional stability, strength, elongation, elastic modulus, etc., and can be performed by any method, but at least 1.1 times in the uniaxial direction. It is preferable to be stretched as described above. Stretching and crystallizing the base polylactic acid polymer by stretching, and at the same time promoting the incorporation of the polylactic acid segment of the polymer plasticizer into the crystal, volatilization, leaching and extraction of the plasticizer (Bleed-out) can be further suppressed, which is preferable. In addition, crystallization can be promoted while maintaining transparency, and strength physical properties are improved by orientation crystallization, so that a film having both flexibility and strength can be obtained.

  For example, in the case of the inflation method, stretching is performed in the cooling process of the resin extruded in a molten state, and the stretching ratio is controlled by the amount of air enclosed in the tube and the film take-up speed. In this case, the draw ratio in the longitudinal direction is the speed ratio between the speed of the resin extruded from the lip portion of the annular die and the speed of taking the film, and the draw ratio in the width direction is the circumferential length of the lip of the annular die and after stretching. Is the ratio of the circumference of the film. The draw ratio can be arbitrarily set in the range of 1.1 to 20 times in the longitudinal direction and the width direction, respectively, and either the longitudinal direction or the width direction may be increased or the same. The draw ratio of the film may be adjusted as appropriate according to the desired thickness, flexibility, handleability, and productivity, but in the case of inflation film formation, the film formation stability and the difference in physical properties in the longitudinal and width directions It is preferable to set the draw ratio in the longitudinal direction higher than the draw ratio in the width direction from the point of reducing, and the draw ratio in the longitudinal direction is preferably 2 times or more of the draw ratio in the width direction, more preferably 3 to 3. 15 times. A preferable range of the draw ratio in each direction is 2 to 20 times in the longitudinal direction and 1 to 10 times in the width direction. From the viewpoint of promoting the incorporation of the polylactic acid segment of the plasticizer into the crystal and the transparency, it is preferably 2 to 8 times, more preferably 2.5 to 8 times in at least one direction.

  Although not particularly limited, when the sequential biaxial stretching method is used, if the stretching ratio in one direction exceeds 10, the stretchability in the second direction is lowered, and the film breaks during film formation. It may be easy to adjust or the transparency of the film may be deteriorated. In the sequential biaxial stretching method, the stretching ratio in each direction is 1.1 to 10 times, preferably 1.5 to 5 times in the longitudinal direction when the first stretching is in the longitudinal direction, and is 1. in the width direction. 1 to 10 times, preferably 1.5 to 6 times. The area magnification, which is the area ratio of the film before and after stretching, is preferably 4 to 60 times, more preferably 6 to 50 times, and even more preferably 6 to 40 times. From the viewpoint of the strength and productivity of the film, it is preferable to set a higher draw ratio.

  In the case of using an inflation film, the stretching temperature is preferably within the range of the melting point of the polyester used or less and the glass transition temperature or more, and the air temperature or ambient temperature of the cooling ring can be controlled according to the intended strength and the like. preferable. In the case of using the sequential biaxial stretching method, the stretching temperature is preferably not less than the glass transition temperature of the polyester to be used and not more than the crystallization temperature from the viewpoint of biaxial stretching property and film transparency.

  Moreover, you may heat-process the film after extending | stretching as needed for the purpose of making the dimensional stability and intensity | strength of a film favorable. The heat treatment is preferably performed at a higher temperature in the range of the glass transition temperature to the melting point of the polyester from the viewpoint of film strength and dimensional stability, specifically 40 to 120 ° C. Further, the stretching speed can be appropriately adjusted within a range of 100 to 50000% / min. Further, it is more preferable to perform heat treatment at 100 ° C. or higher for 10 seconds or longer for the purpose of stabilizing the structure of crystals and plasticizer in the film and reducing low molecular weight components such as oligomer components in the film. Further, the heat treatment may be performed by relaxing in the film longitudinal direction and the width direction. When a specific elongation such as a stretch film is required, the draw ratio and heat treatment temperature are preferably adjusted as appropriate. The draw ratio is 1 to 10 times the area magnification, and the heat treatment temperature is 120 ° C. or less and 20 seconds or less. A short heat treatment is preferable.

  Moreover, it is preferable that the film thickness of the polyester film of this invention is 5-100 micrometers from a viewpoint used as a film for packaging, and it is more preferable if it is 7-60 micrometers. It is preferable that it is 7-15 micrometers from the point which makes the shape followability at the time of wrapping articles | goods especially at the point used as a wrap film.

  The polyester film of the present invention is preferably subjected to surface treatment such as corona discharge treatment or plasma treatment from the viewpoint of enhancing the functionality of the film surface. Further, a different adhesive resin or the like may be coated in the film production in-line or offline, or a metal compound may be deposited and used.

  The polyester film of the present invention not only has excellent flexibility, transparency, and heat sealability, but also has excellent stretchability, film formation stability, and blow moldability in the inflation film forming method, and the strength and elongation of the film over time. It is possible to maintain excellent characteristics by suppressing characteristic changes in the film, and it can be suitably used as a wrap film, stretch film, multi-film, bag body, and the like.

Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.
(1) Identification of constituent components of film ¹ H-NMR (nuclear magnetic resonance apparatus) measurement and ¹³ C-NMR measurement of a film sample were performed to identify constituent components. If necessary, the film was hydrolyzed, the derivatization of the decomposition product, and the GC / MS measurement of the derivative product were performed, and the resin and additives that were constituted were specified.

In the case of a laminated film, using a transmission electron microscope (H-7100FA type manufactured by Hitachi), the sheet cross section is obtained by an ultrathin section method (stained with RuO _{4 as} necessary) at an acceleration voltage of 100 kV and a magnification of 10,000. Observation was performed at a magnification of 100,000 times, the interface was grasped, the laminated structure was confirmed, and the analysis was cut out for each layer. If necessary, microscopic IR analysis of the cross section of the film was performed by the film surface or frozen ultrathin section method.
(2) Number average molecular weight [Mn] of film constituents
The sample was dissolved in a THF (tetrahydrofuran) solution so as to be 1 mg / cc, and measured in terms of polystyrene using GPC (gel permeation chromatography). The instrument is LC-10A series manufactured by Shimadzu Corporation, the solvent is THF (for high performance liquid chromatography), the detector is RI detector (RID-10A), the column is Shodex (trademark) KF-806L and KF- manufactured by Showa Denko KK 804L (each 300 mm × 8 mmφ) was used in series. The column temperature is 30 ° C., and the flow rate is 1.0 ml / min (on-line deaeration system with He). The polystyrene used as a standard is a polystyrene standard manufactured by Shodex (trademark). No. Used S-6850, S-1190, S-205, S-52.4, S-13.9, and S-1.31. These were measured by drawing a calibration curve by cubic approximation.
(3) Melting point of polylactic acid resin and plasticizer [° C]
It measured using the differential scanning calorimeter (Seiko Denshi Kogyo make, RDC220). 5 mg of a polylactic acid resin sample was heated from 20 ° C. to 200 ° C. at a heating rate of 20 ° C./min under a nitrogen atmosphere, held for 5 minutes, rapidly cooled, held at 0 ° C. for 5 minutes, and then heated at 20 ° C./min. The temperature at the minimum point of the endothermic curve was determined from the DSC curve when measured at the speed, and was taken as the melting point. Further, the temperature at the maximum point of the exothermic curve was determined and used as the crystallization temperature.

The melting point of the plasticizer was defined as the minimum point of the endothermic curve when 5 mg of a sample was held at −50 ° C. for 5 minutes in a nitrogen atmosphere and then measured at a rate of temperature increase of 20 ° C./min.
(4) Flexibility: Tensile modulus of elasticity of film [GPa]
A film sample was cut into a longitudinal direction of 150 mm and a width direction of 10 mm, and conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH in advance. This sample was subjected to a tensile test under the conditions of an initial length of 50 mm and a tensile speed of 300 mm / min using a Tensilon universal tester UTC-100 (Orientec Co., Ltd.) in an atmosphere of 23 ° C. according to JIS K7161 and JIS K7127. It was.
Next, using the first linear part of the stress-strain curve obtained in the tensile test, the difference in stress between two points on the straight line is divided by the difference in strain between the same two points, and a total of five tests are performed. Then, an average value was obtained, and this was taken as the tensile modulus and evaluated according to the following criteria.

  (Double-circle): The range whose tensile elastic modulus is 0.1 or more and less than 1.0 GPa.

  ◯: Range where the tensile modulus is 1.0 or more and less than 1.3 GPa.

  (Triangle | delta): The range whose tensile elasticity modulus is 1.3-1.5GPa.

X: The value whose tensile elastic modulus is less than 0.1 or more than 1.5.
(5) Stability over time: tensile elongation [%], elongation retention [%]
The film sample was subjected to a tensile test by the above-described method, and the tensile elongation was determined as a ratio to the test length from the length at which the film was broken, and was defined as the tensile elongation before treatment.

  Separately, the film sample was taken out in a constant temperature and humidity chamber at a temperature of 40 ° C. and a humidity of 60% for 1 week, taken out for 24 hours in an environment of a temperature of 23 ° C. and a humidity of 60%, and then subjected to a tensile test by the above method. The tensile elongation after storage was determined. The rate of change when the tensile elongation before storage was set to 100 was calculated, the elongation retention was determined, and evaluated according to the following criteria.

  A: The elongation retention is 95% or more.

  ○: Elongation retention is in the range of 85% or more and less than 95%.

  Δ: Elongation retention is in the range of 80% or more and less than 85%.

X: Elongation retention is less than 80%.
(6) Melt viscosity (Pa · s)
The film sample was dried under reduced pressure under a vacuum of 1 torr at 80 ° C. for 5 hours, and then a flow tester CFT-500A (die diameter 1 mm, die length 10 mm, plunger cross-sectional area 1 cm ² ) manufactured by Shimadzu Corporation at a cylinder temperature of 170 ° C. The test was conducted under a load of 10 kg, the shear rate and the melt viscosity were measured, and the average value at the time of three measurements was obtained. Furthermore, each measurement was performed under a total of five load conditions, and the melt viscosity at a shear rate of 100 sec ^{−1 was} defined as the melt viscosity at 170 ° C. from the melt viscosity curve with respect to the shear rate.
(7) Viscosity of plasticizer (Pa · s)
Using a B-type viscometer B-8L manufactured by Tokyo Keiki Co., Ltd., the viscosity (Pa · s) of each plasticizer was measured under a temperature condition of melting point + 30 ° C. In the measurement, the n number is 5, and the average value is obtained as the viscosity (Pa · s).
(8) Transparency: film haze value [%]
A film sample was cut into a longitudinal direction of 40 mm and a width direction of 30 mm, and conditioned for 24 hours in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH. This sample was subjected to haze measurement using a haze meter (HGM-2GP manufactured by Suga Test Instruments Co., Ltd.) in an atmosphere of 23 ° C. based on JIS K 7105 (1985). The measurement was performed at three arbitrary locations, the average value was adopted, and evaluation was performed according to the following criteria.

  The film haze value is obtained by the above measuring instrument, and is a value obtained by dividing the scattered light transmittance by the total light transmittance and multiplying by 100.

  A: Haze is less than 1%.

  ○: Haze is 1% or more and less than 5%.

  Δ: Haze in the range of 5% or more and 10% or less.

X: Numerical value of haze exceeding 10%.
(9) Bleed-out resistance: Weight change rate after hot water treatment [%]
A film sample that has been conditioned for 1 day or more in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH is measured before the treatment, and after being treated in distilled water at 90 ° C. for 30 minutes, again under the same conditions as before the treatment. After adjusting the humidity, the weight was measured. The weight change rate was calculated as a ratio of the weight change (decrease) before and after the treatment to the weight before the treatment, and was evaluated according to the following criteria.

  A: Weight change rate is less than 3%.

  ○: The weight change rate is in the range of 3% or more and less than 5%.

  (Triangle | delta): The range whose weight change rate is 5% or more and less than 7%.

X: The rate of weight change is 7% or more.
(10) Heat seal property: heat seal strength [N]
Two film samples were overlapped, and only the upper metal flat plate was heated to 120 ° C. using a heat seal tester (TP-01 manufactured by Tester Sangyo), and heat sealed with a gauge pressure of 0.2 MPa and a pressurization time of 0.5 seconds. . After sealing, the sample was allowed to cool to room temperature, and then cut into a strip shape having a width of 15 mm in the MD direction to obtain a test piece. Each film edge of the test piece was pulled in the opposite direction by a Tensilon universal testing machine UTC-100 (Orientec Co., Ltd.) at a test speed of 200 mm / min, and the maximum peel strength was defined as heat seal strength. evaluated.

  A: Heat seal strength is 20 N or more.

  ○: Heat seal strength is in a range of 15N or more and less than 20N.

  (Triangle | delta): The range whose heat seal strength is 10N or more and less than 15N.

X: Heat seal strength is less than 10N.
(Manufacture of raw material resin)
The polylactic acid resin, plasticizer, and polyfunctional compound used for film formation were prepared as follows.
(Polylactic acid P1)
0.01 parts by mass of tin octylate is added to 100 parts by mass of L-lactide and polymerized at 185 ° C. for 30 minutes in a nitrogen atmosphere to obtain a precursor poly-L-lactic acid. After this precursor poly-L-lactic acid was chipped, solid phase polymerization was performed at 140 ° C. for 3 hours under a nitrogen atmosphere to obtain polylactic acid P1 having a number average molecular weight of 90,000. When the polylactic acid P1 was subjected to DSC measurement, the polylactic acid A had crystallinity, the crystallization temperature was 130 ° C., and the melting point was 171 ° C.
(Polylactic acid P2)
By adding 0.02 parts by mass of octylic acid to 35 parts by mass of DL-lactide to 65 parts by mass of L-lactide, polymerizing at 185 ° C. for 60 minutes in a nitrogen atmosphere, and then discharging onto strands to form chips. Polylactic acid B having an average molecular weight of 75,000 was obtained. When DSC measurement was performed on polylactic acid P2, polylactic acid P2 did not exhibit crystallinity, and crystallization temperature and melting point were not observed.
(Plasticizer S1)
After mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 8000, 38 parts by mass of L-lactide and 0.025 parts by mass of tin octylate, the mixture was polymerized at 150 ° C. for 3 hours in a nitrogen atmosphere, and then discharged and cooled to obtain a composite. It was. Next, 400 parts by mass of water was added to 100 parts by mass of the composite, and the mixture was stirred at 60 ° C. for 2 hours, followed by dehydration by filtration, and further drying at 80 ° C. under reduced pressure of 5 torr. A plasticizer S1 having a polylactic acid segment having a number average molecular weight of 2500 was obtained.
The melting point of the plasticizer S1 was 140 ° C., and the viscosity at the melting point + 30 ° C. was 1.6 Pa · s.
(Plasticizer S2)
With respect to 62 parts by mass of a polypropylene glycol / ethylene glycol block copolymer having a number average molecular weight of 10,000 and 38 parts by mass of L-lactide prepared by addition reaction of ethylene oxide at both ends of polypropylene glycol having a number average molecular weight of 3000, Polylactic acid having a number average molecular weight of 3000 is the same as plasticizer S1 except that 0.015 parts by mass of tin octylate is mixed and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 2.5 hours in a nitrogen atmosphere. A block copolymer of polypropylene glycol / ethylene glycol having a segment at both ends and polylactic acid, plasticizer S2, was obtained.
The melting point of the plasticizer S2 was 145 ° C., and the viscosity at the melting point + 30 ° C. was 3.1 Pa · s.
(Plasticizer S3)
0.015 parts by mass of tin octylate is mixed with 50 parts by mass of polyethylene glycol having a number average molecular weight of 10,000 and 50 parts by mass of L-lactide, and in a reaction vessel equipped with a stirrer at 160 ° C. in a nitrogen atmosphere. A plasticizer S3 having a polylactic acid segment having a number average molecular weight of 5000 was obtained in the same manner as the plasticizer S1 except that the polymerization was performed for 5 hours.
The melting point of the plasticizer S3 was 154 ° C., and the viscosity at the melting point + 30 ° C. was 3.5 Pa · s.
(Plasticizer S4)
Epoxidized linseed oil butyl ester plasticizer Adekasizer (registered trademark) “D-178” manufactured by Asahi Denka Kogyo Co., Ltd. was used as the plasticizer S4.
This plasticizer had a melting point of about 2 ° C. and a viscosity at 32 ° C. of 0.023 Pa · s.
(Plasticizer S5)
After mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 8000, 38 parts by mass of L-lactide and 0.025 parts by mass of tin octylate and polymerizing at 150 ° C. for 3 hours in a nitrogen atmosphere, 0.1 part by mass of phosphoric acid was added. After the addition, the mixture was stirred for 5 minutes, stirred for 20 minutes under reduced pressure of 10 torr, discharged, cooled, and a plasticizer S5 having polylactic acid segments having a number average molecular weight of 2500 at both ends of polyethylene glycol was obtained.
The melting point of the plasticizer S5 was 140 ° C., and the viscosity at the melting point + 30 ° C. was 1.8 Pa · s.
(Polyfunctional compound C1)
Carbodiimide-modified isocyanate manufactured by Nisshinbo Co., Ltd. Carbodilite (registered trademark) “LA-1” was used as the multifunctional compound C1.
(Polyfunctional compound C2)
Kaneka's methyl methacrylate-glycidyl methacrylate-acrylic acid ester copolymer, Kaneace (registered trademark) “MP-20” was used as the multifunctional compound C2.
(Polyfunctional compound C3)
Takemoto Yushi Co., Ltd. Bisoxazoline compound “BOX-210” was used as multifunctional compound C3.
(Polyfunctional compound C4)
Trisglycidyl isocyanurate, Tepic (registered trademark) “TEPIC-S” manufactured by Nissan Chemical Industries, Ltd. was used as the multifunctional compound C4.
(Example)
Examples of the present invention and comparative examples are shown below.
( Reference Example 1)
A mixture of 15 parts by mass of polylactic acid resin (P1), 54 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S1) and 1 part by mass of polyfunctional compound (C1) is vacuum vented at a cylinder temperature of 190 ° C. The mixture was melt-kneaded and homogenized while being reduced in pressure from a vacuum vent hole and maintained at a vacuum degree of 1 torr using a twin-screw kneading extruder to obtain a chipped composition. The resulting composition was transparent.

This composition was dried under reduced pressure under a vacuum of 5 torr at 80 ° C. for 24 hours, and then supplied to a single screw extruder having a screw diameter of 30 mm, and an upward annular die having an extruder cylinder temperature of 190 ° C., a lip portion diameter of 70 mm, and a lip gap of 1 mm. It was extruded into a tube shape at a die temperature of 170 ° C. Next, after sandwiching the tubular sheet with the upper nip roll, air is fed into the tube, the longitudinal stretch ratio, which is the ratio of the extrusion speed and the take-off speed, is adjusted to 10 times, and the stretch ratio in the width direction is further increased. A stretched film having a thickness of 30 μm was prepared by adjusting the amount of air in the tube to 3.5 times. During stretching, the temperature of the cooling ring air was 20 ° C.
The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 1)
A film was formed in the same manner as in Reference Example 1 except that the amount of the polyfunctional compound (C1) added was 0.05 parts by mass.

The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 2)
Reference Example 1 except that a mixture of 20 parts by mass of polylactic acid resin (P1), 61 parts by mass of polylactic acid resin (P2), 7 parts by mass of plasticizer (S1), and 12 parts by mass of polyfunctional compound (C1) is used. A film was prepared in the same manner.

The evaluation results of the obtained film are shown in Table 1.
(Example 1 )
Reference Example 1 except that 15 parts by mass of polylactic acid resin (P1), 54 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S1), and 1 part by mass of polyfunctional compound (C2) are used. A film was prepared in the same manner.

The evaluation results of the obtained film are shown in Table 1.
(Example 2 )
Reference Example 1 except that 15 parts by mass of polylactic acid resin (P1), 54 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S3), and 1 part by mass of polyfunctional compound (C2) are used. A film was prepared in the same manner.

The evaluation results of the obtained film are shown in Table 1.
(Example 3 )
Except for making a mixture of 15 parts by mass of polylactic acid resin (P1) and 54.7 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S3), and 0.3 parts by mass of polyfunctional compound (C2), A film was prepared in the same manner as in Reference Example 1.

The evaluation results of the obtained film are shown in Table 1.
(Example 4 )
11 parts by mass of polylactic acid resin (P1), 53 parts by mass of polylactic acid resin (P2), 35 parts by mass of plasticizer (S1), 1 part by mass of polyfunctional compound (C2), and polylactic acid resin, plasticizer and polyfunctional A film was prepared in the same manner as in Reference Example 1, except that 0.5 parts by mass of stearamide as a lubricant was added to 100 parts by mass of the active compound. During stretching, the temperature of the cooling ring air was 15 ° C.

The evaluation results of the obtained film are shown in Table 1.
( Reference Example 2 )
Except for making a mixture of 10.5 parts by mass of polylactic acid resin (P1) and 55 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S2), and 4.5 parts by mass of polyfunctional compound (C3), A film was prepared in the same manner as in Reference Example 1.

The evaluation results of the obtained film are shown in Table 1.
( Reference Example 3 )
Reference Example 1 except that a mixture of 20 parts by mass of polylactic acid resin (P1), 60 parts by mass of polylactic acid resin (P2), 20 parts by mass of plasticizer (S4), and 1 part by mass of polyfunctional compound (C2) is used. A film was prepared in the same manner.

The evaluation results of the obtained film are shown in Table 1.
(Example 5 )
10 parts by mass of polylactic acid resin (P1), 53.5 parts by mass of polylactic acid resin (P2), 35 parts by mass of plasticizer (S5), 1.5 parts by mass of polyfunctional compound (C2), and further plastic with polylactic acid resin Reference Example 1 except that 0.5 parts by mass of stearamide as a lubricant and 0.5 parts by mass of 0.8 μm calcium carbonate particles were added to 100 parts by mass of the total of the agent and the multifunctional compound. A film was prepared in the same manner. During stretching, the temperature of the cooling ring air was 15 ° C.

The evaluation results of the obtained film are shown in Table 1.
( Reference Example 4 )
Reference Example 1 except that the mixture is 15 parts by mass of polylactic acid resin (P1), 54 parts by mass of polylactic acid resin (P2), 30 parts by mass of plasticizer (S3), and 1 part by mass of polyfunctional compound (C5). A film was prepared in the same manner.
The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 3)
Bionore (registered trademark) # 3001 (polybutylene succinate adipate) manufactured by Showa Polymer Co., Ltd. with respect to 21 parts by mass of polylactic acid resin (P1), 79 parts by mass of polylactic acid resin (P2), and 100 parts by mass of polylactic acid resin A film was prepared in the same manner as in Reference Example 1 except that 30 parts by mass of the mixture was used.

  The evaluation results of the obtained film are shown in Table 1.

The symbols in Table 1 have the following meanings.
P1: Polylactic acid P1
P2: Polylactic acid P2
S1: Plasticizer S1
S2: Plasticizer S2
S3: Plasticizer S3
S4: Plasticizer S4
S5: Plasticizer S5
C1: polyfunctional compound C1
C2: polyfunctional compound C2
C3: polyfunctional compound C3
C4: polyfunctional compound C4
SA: stearamide amide char: calcium carbonate particles PBSA: polybutylene succinate adipate From Table 1, the examples were extremely excellent in flexibility, transparency, bleed out resistance, stability over time, and heat sealability.

On the other hand, in Comparative Example 1, the amount of the polyfunctional compound was small, so that the viscosity was insufficient, and the film formation stability to the upper side at a high magnification was somewhat poorer than that of Reference Example 1. Also, the temporal stability was somewhat inferior to that of Reference Example 1.

  In Comparative Example 2, since the polyfunctional compound exceeded a specific upper limit, the transparency was poor.

  In Comparative Example 3, the compatibility between polylactic acid and polybutylene succinate was not sufficient, the transparency was poor, and the heat seal portion was peeled off and the heat seal strength was low. In the case of the heat seal strength as in Comparative Example 3, for example, when used as a garbage bag, there arises a problem that the bag is broken due to the weight of an object to be put therein and the dust is scattered.

In addition, the film of Example 4 or 5 has particularly excellent flexibility and has an opening property equivalent to a commercially available plastic bag by containing an organic lubricant and / or particles. It was a characteristic.

  The present invention relates to a polyester film mainly composed of a polylactic acid resin, not only excellent in flexibility and transparency, but also excellent in heat sealability, and excellent in stretchability, film forming stability and blow moldability in an inflation film forming method. It is suitable for a wide range of film forming methods and molding methods, and can retain excellent properties such as strength and elongation of the film, so that it can be suitably used as a wrap film, stretch film, multifilm, bag and the like.

Claims (5)

Polyester comprising 50 to 95% by weight of polylactic acid resin, 4 to 49% by weight of plasticizer, and 0.1 to 5% by weight of multifunctional compound in a total of 100% by weight of the polylactic acid resin, the plasticizer and the multifunctional compound. A film,
And the tensile modulus is 0.1 to 1.5 GPa,
The polylactic acid resin, Ri aspect der to combination with the homo lactic acid and noncrystalline homo lactic acid having a crystallinity,
The plasticizer has one or more polylactic acid segments having a number average molecular weight of 1500 to 10,000 in one molecule and a polyether and / or polyester segment having a number average molecular weight of 1,000 to 20,000. And
The polyfunctional compound is characterized copolymer der Rukoto of methyl methacrylate and methacrylic acid glycidyl ester, a polyester film. The polyester film according to claim 1, wherein the haze value of the film is 10% or less. The polyester film according to claim 1 or 2 , wherein a melt viscosity at 170 ° C is 400 to 3000 Pa · s. The polyester film according to any one of claims 1 to 3 , wherein the plasticizer has a viscosity of 1 to 5 Pa · s at a melting point of the plasticizer + 30 ° C. The polyester film according to any one of claims 1 to 4 , wherein the tensile elongation at 23 ° C is 150 to 600%.