JP2012031279A - Biodegradable mulch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid-based biodegradable mulch film, in particular, excellent in flexibility, impact resistance and bleeding-proofness, as to a biodegradable mulch film high in a soil-water holding property and excellent in growing performance of a crop.SOLUTION: This biodegradable mulch film comprises a composition having a glass transition temperature Tg within a range of 0°C or higher to 45°C or lower, and a thermal shrinkage rate Sm (winding longitudinal direction) when treated for 30 minutes at 65°C, and a thermal shrinkage rate St (width direction (direction perpendicular to the winding longitudinal direction)), satisfy respectively a condition of 3St≤Sm; 2≤Sm≤5 (%); and -1≤St≤2 (%), in the biodegradable mulch film.

Description

  The present invention relates to a biodegradable multi-film that has high soil water retention and excellent crop growth, is not easily torn even when exposed to wind and rain, and has excellent adhesion to straw, in particular, flexibility, impact resistance, The present invention relates to a polylactic acid-based biodegradable multi-film excellent in bleeding resistance.

  Currently, in the agricultural field, agricultural multi-films are widely used for the purpose of improving the growth and yield of crops. As a general usage method of the agricultural multi-film, a ridge having a mountain-shaped or trapezoidal cross-section and a long and straight soil is raised, covered with the ridge, and used to cover the soil surface. The crops are pierced with multi-films for planting, and seedlings are planted there. Multi-films are used, for example, for the purpose of water retention and warming of the soil until the seedlings have sufficiently rooted in the soil, suppression of weed propagation until the seedlings grow and the crops are harvested, and maintenance of the shape of the straw. ing.

  Many of these agricultural multi-films are made of polyolefins such as polyethylene. However, polyolefins do not biodegrade even if left in a natural environment, and must be recovered after use. In addition, a physically deteriorated and dirty multifilm after use is difficult to reuse, and in most cases, there is only a method of discarding it, but there is still a problem that processing costs as waste are high.

  In order to solve this problem, the period of use as an agricultural multi-film can be used in the same way as a conventional polyolefin multi, and after being used, it is immersed in the ground as it is and completely decomposed by microorganisms in the soil. Degradable agricultural multi-films are being studied. As these biodegradable multi-films, films using biodegradable resins such as aliphatic polyesters having a specific structure have been studied. However, compared to polyolefin, the biodegradable resin described above has the property of allowing water vapor to pass through. When a multi-film is used, the soil has poor water retention, and the soil is too dry, resulting in poor crop growth. there were.

  Patent Document 1 discloses a technique in which fatty acid amides or waxes are blended or applied as a water vapor barrier property-imparting agent, and talc is further used as a filler.

  Patent Document 2 discloses a biodegradable multifilm containing at least 20 parts by mass of an aromatic aliphatic polyester having a relatively low water vapor permeability among biodegradable resins and further containing 10 to 50 parts by mass of an inorganic filler. Has been.

  Conventionally, biodegradable multi-films have been developed around soft biodegradable resins produced from petroleum-derived raw materials. In recent years, the issue of global warming due to an increase in the concentration of carbon dioxide in the atmosphere has become a global problem. In the field of plastic products, plant-derived plastics originally derived from carbon sources (carbon dioxide) in the atmosphere are attracting attention. Has been. Of these, polylactic acid, which is excellent in transparency and relatively advantageous in terms of cost, has been studied for practical use as a biodegradable multifilm. When polylactic acid is applied to a flexible film application typified by polyolefin, it lacks flexibility and impact resistance. Therefore, various attempts have been made to improve these properties and put them into practical use.

For example, Patent Document 3 discloses a film made of a composition obtained by adding polylactic acid to a polyhydric alcohol ester or hydroxy polycarboxylic acid ester plasticizer, SiO ₂ as an anti-blocking agent, and a lubricant. Patent Document 4 discloses a film made of polylactic acid, an aliphatic polyester having a glass transition point of 0 ° C. or less, and a plasticizer. Patent Document 5 discloses a film made of a lactic acid resin and a plasticizer, which is mainly intended for use in stretch packaging. Patent Document 6 discloses a film obtained by further crystallizing a film composed of a plurality of types of polylactic acid having different D-form concentrations and a plasticizer. Patent Document 7 discloses a film made of polylactic acid, an aliphatic polyester, and a specific plasticizer. Patent Document 8 discloses a multifilm composed of polylactic acid, a biodegradable aliphatic aromatic copolymer polyester having a glass transition temperature of 0 ° C. or lower, an oxyester plasticizer, and an inorganic filler.

  Patent Document 9 discloses a polylactic acid-based film excellent in flexibility, impact resistance, and bleed resistance using polylactic acid and a plasticizer that is solid at room temperature.

JP 2004-352987 A JP-A-2005-192465 JP-A-8-34913 JP 2000-273207 A JP 2003-12934 A JP 2006-45290 A Japanese Patent No. 3753254 JP 2004-57016 A JP 2009-138085 A

  In the technique described in Patent Document 1, if the amount of fatty acid amides or waxes added is excessively increased, the resin viscosity will be greatly reduced, which will interfere with film formation by a general inflation method for multi-film applications. Is limited. In addition, when applying too much, it becomes easy to block if the amount of application is increased too much, and the amount of application is limited, such as being easy to slip and causing the winding shape to collapse before use. It was insufficient technology.

  In the technique described in Patent Document 2, the aromatic aliphatic polyester certainly has a relatively low water vapor transmission rate in the biodegradable resin, but the difference is still not small compared with the polyolefin, and addition of an inorganic filler is also possible. Since the effect of is also limited, the water retention capacity of the soil when it was made into a multifilm was an insufficient technique.

  Since all of the techniques of Patent Documents 3 to 8 use a plasticizer that is a liquid at room temperature, there was a certain effect in terms of imparting flexibility, impact resistance, etc. to polylactic acid. Inherently, it was not practical because it was easy to bleed and the performance was not stable over time and it was easy to block. In addition, when these films are made into multi-films, they have inferior soil water retention compared to polyolefins, and the soil is too dry, resulting in poor crop growth. There was no effective suggestion about the technology to compensate for the drawbacks on the left.

  The technique described in Patent Document 9 is similar to the techniques described in Patent Documents 3 to 8, and these films have a property of allowing water vapor to pass through compared to polyolefin. Inferior to the above, the soil was too dry and the crops were poorly grown. There was no effective suggestion about the technology to compensate for the drawbacks on the left.

  As described above, various biodegradable multifilms with high soil water retention and excellent crop viability, and various polylactic acid biodegradable multifilms with excellent flexibility, impact resistance, and bleed resistance. Although it has been studied, it has not yet been achieved.

  Therefore, in view of the background of such prior art, the present invention relates to a biodegradable multi-film having high soil water retention and excellent crop viability, and in particular, a polylactic acid system excellent in flexibility, impact resistance, and bleed resistance. It is intended to provide a biodegradable multifilm.

In order to solve the above problems, the present invention employs the following means. That is, the biodegradable multifilm of the present invention is
It is composed of a composition having a glass transition temperature Tg in the range of 0 ° C. or more and 45 ° C. or less, and has a heat shrinkage ratio Sm (winding length direction) and heat shrinkage rate St (width direction (winding length) when treated at 65 ° C. for 30 minutes. A biodegradable multifilm characterized in that the direction perpendicular to the vertical direction)) satisfies the following conditions.
3St ≦ Sm
2 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)
Moreover, the preferable aspect of the said biodegradable multifilm is (1) thickness is 18 micrometers or less, (2) the said composition is 30 to 95 mass% of polylactic acid-type resin, and 5 plasticizers. (3) The composition contains 5% by mass or more and 45% by mass or less of an aliphatic aromatic polyester, and (4) Adhesive peel force defined in the specification. As is characterized by being 15 g / 15 mm or less.

  The present invention relates to a biodegradable multifilm having high soil water retention and excellent crop growth, and in particular, a polylactic acid-based biodegradable multifilm excellent in flexibility, impact resistance, and bleed resistance is provided. Is done. The present invention is excellent in adhesiveness to cocoons that are not easily torn even when exposed to wind and rain, and can be preferably used as a biodegradable multifilm.

  The present invention relates to the above-described problem, that is, a biodegradable multifilm having high soil water retention and excellent crop growth, and further, a polylactic acid biodegradable multifilm excellent in flexibility, impact resistance, and bleed resistance. As a result of intensive studies, it has been found that the biodegradable multifilm having specific thermal properties and shrinkage properties significantly improves the adhesion to straw and consequently exhibits high soil water retention. In addition, it has been found for the first time that it has succeeded in solving such a problem because it has been found that it has excellent mechanical properties such as being hard to break even when exposed to wind and rain due to the adhesion effect to the ridge.

  Hereinafter, the biodegradable multifilm of the present invention will be described.

  The multifilm referred to in the present invention means a film for covering an object. For example, in an agricultural multifilm which is an embodiment of the multifilm, it is used to cover a soil surface where crops are present. It is a film.

  The biodegradability of the biodegradable multifilm of the present invention is defined as the degree of biodegradability obtained according to JIS K6953-2000 being 60% or more and 100% or less within 90 days. Since the use period of a general agricultural multi-film is usually about 3 months at the shortest, the biodegradation degree may be 60% or more and 100% or less within 90 days. is necessary.

  The inventors of the present invention, as a result of intensive studies on the disadvantages of the conventional biodegradable multifilm, poor water retention of soil, poor soil growth due to excessive soil drying, We have tackled this problem from a completely different perspective and found a way to remedy the above drawbacks. That is, it is composed of a composition having a glass transition temperature Tg in the range of 0 ° C. or higher and 45 ° C. or lower and has a heat shrinkage ratio Sm (winding length direction) and heat shrinkage ratio St (width direction) when treated at 65 ° C. for 30 minutes. When the film having Sm and St satisfying the specific condition for (the direction perpendicular to the winding length direction)) is coated with a straw such as Tabata using the film, the film is gradually and moderately It shrinks and adheres to the heel.

  Normally, the moisture in the soil contained in the cocoons covered with the multi-film is transpired through the multi-film directly from the inner surface (soil side) to the outer surface (external side) of the multi-film. In multi-films, so-called planting holes for planting crops are spaced at regular intervals and exist as openings, so the amount of water that evaporates from these planting holes is overwhelmingly large. Although this fixed planting hole depends on the crop, the diameter of the hole is normally about 5 cm or more even if it is small, and there are several holes at intervals of about 15 to 60 cm. Therefore, when there is a gap between the ridge and the multi-film, and the gap leads to the planting hole, the water evaporated from the soil passes through the gap and freely escapes from the planting hole to the outside of the multi-film, and the inside of the multi-film. The air near the soil is always in a relatively low humidity state. For this reason, the evaporation of moisture from the soil is further facilitated, and the transpiration of moisture proceeds at an accelerated rate.

  In the case of general polyethylene and other biodegradable multifilms, the Tg of the composition constituting them is 0 ° C. or less, and Sm and St are greatly different from the biodegradable multifilm of the present invention. In most cases, St is less than 2%. And these films hardly shrink even after stretching. Therefore, even if it is closely attached to the cocoon without any gap at the time of spreading, the soil settles with time and the cocoon gradually tightens after spreading / spreading, so the gap between the soil surface of the cocoon and the multi-film spreads. It will be one side. Then, the water evaporated from the soil passes through the gap and freely escapes from the fixed hole to the outside of the multi-film, and the transpiration of water proceeds at an accelerated speed as described above.

  On the other hand, the biodegradable multi-film of the present invention is in close contact with the cocoon by gradually and appropriately shrinking the film even when the soil settles down and the cocoon gradually tightens after erecting / stretching. It has a characteristic of always maintaining the state. Therefore, it is possible to effectively suppress the transpiration of moisture from the above-mentioned fixed planting hole and to keep soil moisture well for a long period of time. Furthermore, as a secondary effect that the multi-film is always in close contact with the straw, the multi-film is difficult to flutter and torn easily even when exposed to strong wind and rain, and the weeds generated in the multi-film are also pressed against the high-temperature soil, so the overgrowth is effective There are effects such as being able to suppress.

  The biodegradable multifilm of the present invention having the above-described effects is composed of a composition having a glass transition temperature Tg in the range of 0 ° C. or higher and 45 ° C. or lower. Here, the glass transition temperature Tg is a value of the composition constituting the film of the present invention, and is a value obtained by measuring the film of the present invention itself by a method described later. The composition having a Tg of 0 ° C. or more and 45 ° C. or less is not particularly limited, but may be, for example, a mixture of two or more polymers, or a mixture of a polymer and a plasticizer. In addition, a single polymer may be used. In addition, it is important that the glass transition temperature of the composition constituting the film is in the range of 0 ° C. or higher and 45 ° C. or lower. If the glass transition temperature exists even in this range, the glass transition temperature is outside this temperature range. Even if it exists, it does not become a problem in particular. In addition, from the viewpoint of effectively imparting the property of constantly maintaining the state in which the film is gradually and appropriately shrunk and is in close contact with the wrinkles, the glass transition temperature of the composition constituting the film is a temperature range exceeding 45 ° C. It is preferable that it does not exist.

  In an embodiment where the mixture is a mixture of two or more polymers and / or a mixture of a polymer and a plasticizer, and the polymers or the polymer and the plasticizer are compatible with each other, the Tg of the composition is a single temperature. For example, a case of a mixture of a polylactic acid resin and a plasticizer, which is a preferable example of the present application described later, will be described. When homopolylactic acid is used as the polylactic acid resin, the glass transition temperature of homopolylactic acid is 57 ° C. When a polyethylene glycol-based compound is used as the plasticizer, the plasticizer has a glass transition temperature of 0 ° C. or less, which is different from the value of homopolylactic acid. Furthermore, since homopolylactic acid and polyethylene glycol are compatible with each other, the composition as a mixture thereof has a single glass transition temperature different from that of homopolylactic acid and plasticizer, and the glass transition temperature Tg is 0 ° C. or more and 45 ° C. It becomes as follows.

  When the Tg of the composition is less than 0 ° C., it is too low compared to the use temperature as a multi-film, so the film has a strong shrinkage stress from the point of storage in a roll before use after film formation, and is wound by tightening. Appearance tends to get worse. In this case, wrinkles occur in the rolled state and the wrinkled part is caught when unwound, and the flatness of the unwound film may be poor and the mechanical characteristics may partially deteriorate, etc. In some cases, the film lacks practicality. When the Tg of the composition exceeds 45 ° C., it is too high compared to the use temperature as a multi-film, so that it does not shrink so much after stretching and the effect of adhering to the wrinkles becomes insufficient. Therefore, from the above viewpoint, the Tg of the composition constituting the film is preferably as close as possible to the multifilm use temperature, and the Tg of the composition constituting the film is preferably 30 ° C. or higher and 38 ° C. or lower.

  Examples of the composition having a glass transition temperature Tg of 0 ° C. or higher and 45 ° C. or lower include, for example, polyester copolymers composed of aliphatic diols such as polyethylene terephthalate / succinate and aromatic dicarboxylic acids / aliphatic dicarboxylic acids, glycolic acid and lactic acid And various random copolymer polymers such as a polyhydroxycarboxylic acid copolymer, or a plasticizer-added polymer such as a mixture of a polylactic acid resin and a plasticizer. In recent years, plant-derived raw material plastics originally derived from carbon sources (carbon dioxide) in the atmosphere have attracted attention, so the use of a mixture of polylactic acid resin and plasticizer that is plant-derived raw material and can be produced economically Is preferred.

  When a polylactic acid-based resin is used for the biodegradable multifilm of the present invention, L-lactic acid and / or D-lactic acid is the main component, and a component derived from lactic acid is preferably 70% by mass or more and 100% by mass or less. In particular, homopolylactic acid composed of L-lactic acid and / or D-lactic acid is preferably used.

  The polylactic acid resin used in the present invention preferably has crystallinity. The polylactic acid resin has crystallinity when the polylactic acid resin is sufficiently crystallized under heating and then subjected to differential scanning calorimetry (DSC) measurement in an appropriate temperature range. This means that the heat of crystal melting derived from is observed.

  When the polylactic acid resin used in the present invention has crystallinity, it is suitable for imparting blocking resistance when a composition containing the polylactic acid resin is used as a film. In general, homopolylactic acid has higher melting point and crystallinity as the optical purity is higher. The melting point and crystallinity of polylactic acid are affected by the molecular weight and the catalyst used during polymerization, but normally, homopolylactic acid having an optical purity of 98% or higher has a melting point of about 170 ° C. and a relatively high crystallinity. Further, as the optical purity is lowered, the melting point and crystallinity are lowered. For example, homopolylactic acid having an optical purity of 88% has a melting point of about 145 ° C., and homopolylactic acid having an optical purity of 75% has a melting point of about 120 ° C. It is. Homopolylactic acid with an optical purity lower than 70% does not show a clear melting point and is amorphous.

  Furthermore, when using a polylactic acid-type resin for the biodegradable multifilm of the present invention, it is preferable to mix homopolylactic acid having crystallinity and amorphous homopolylactic acid. The proportion of the amorphous homopolylactic acid is preferably 50 parts by mass or more and 90 parts by mass or less, with the total amount of the polylactic acid resin used being 100 parts by mass. In this range, it is easy to make a multi-film having a moderate potential shrinkage stress even at room temperature, and when the multi-film is covered with vines such as fields, the film gradually and moderately shrinks and adheres well to the cocoons. Easy to get effect.

  The polylactic acid resin used in the present invention has a weight average molecular weight of usually at least 50,000, preferably 80,000 to 400,000, and more preferably 100,000 to 300,000. In addition, a weight average molecular weight here means the molecular weight which measured with the chloroform solvent by the gel permeation chromatography (GPC), and was computed by the polymethylmethacrylate conversion method.

  By setting the weight average molecular weight of the polylactic acid-based resin to at least 50,000, the mechanical properties can be excellent when a composition containing the polylactic acid-based resin is processed into a film.

  Further, when a polylactic acid resin is used in the biodegradable multifilm of the present invention, it is a copolymerized polylactic acid obtained by copolymerizing other monomer components having ester forming ability in addition to L-lactic acid and D-lactic acid. May be. Examples of copolymerizable monomer components include glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid, and other hydroxycarboxylic acids, as well as ethylene glycol, propylene glycol, and butane. Compounds containing a plurality of hydroxyl groups in the molecule such as diol, neopentyl glycol, polyethylene glycol, glycerin, pentaerythritol or their derivatives, succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2 , 6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, 5-tetrabutylphosphonium sulfoisophthalic acid and the like, or compounds containing a plurality of carboxylic acid groups in the molecule. In addition, it is preferable to select a biodegradable component among the above-described copolymer components.

  The production method of the polylactic acid-based resin will be described later in detail, but a known polymerization method can be used, and examples thereof include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

  When a polylactic acid resin is used for the biodegradable multifilm of the present invention, the glass transition temperature of homopolylactic acid is about 57 ° C., so that the Tg of the composition constituting the film of the present invention is 0 ° C. or more and 45 ° C. or less. In order to control, it is necessary to mix and use polylactic acid copolymerized by selecting a component that lowers the glass transition temperature or a plasticizer that lowers the glass transition temperature. In the former case, a relatively long polymerization time is required to obtain a copolymerized polylactic acid having a weight average molecular weight of 50,000 or more, which is economically disadvantageous, and homopolylactic acid and a plasticizer that can be produced at a relatively low cost. The latter used in combination is economically advantageous.

  When the composition constituting the film of the present invention is a mixture of a polylactic acid resin and a plasticizer, the polylactic acid resin is contained in an amount of 30% by mass to 95% by mass and the plasticizer is contained in an amount of 5% by mass to 30% by mass. It preferably consists of a composition. In this case, it is particularly suitable as a practical application technique for plant-derived raw materials, and it is also possible to impart practically sufficient flexibility when a biodegradable multifilm is formed.

  Moreover, when using a polylactic acid-type resin for the biodegradable multifilm of this invention, it is preferable to further contain aliphatic aromatic polyester other than a polylactic acid-type resin and a plasticizer so that it may mention later. From such a viewpoint, the composition constituting the biodegradable multifilm of the present invention contains 30% by mass or more and 90% by mass or less of the polylactic acid resin and 5% by mass or more and 25% by mass or less of the plasticizer. Is more preferable.

  As the plasticizer that can be used in the present invention, those that are liquid at room temperature or those that are solid at room temperature can be used. For example, phthalic acid such as diethyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, etc. Esters, aliphatic dibasic acid esters such as di-1-butyl adipate, di-n-octyl adipate, di-n-butyl sebacate, di-2-ethylhexyl azelate, diphenyl-2-phosphate Phosphoric acid esters such as ethylhexyl and diphenyloctyl phosphate, hydroxy polyvalent carboxylic acid esters such as tributyl acetylcitrate, tri-2-ethylhexyl citrate and tributyl acetylcitrate, methyl acetylricinoleate, amyl stearate, etc. Fatty acid ester series, glycerin triacetate , Polyhydric alcohol esters such as triethylene glycol dicaprylate, epoxidized soybean oil, epoxidized linseed oil fatty acid butyl ester, epoxy plasticizers such as octyl epoxy stearate, polyester plasticizers such as polypropylene glycol sebacate , Polyalkylene ether type, ether ester type, acrylate type and the like, and a mixture of plural kinds of plasticizers among these is also included.

  In agricultural applications, considering the possibility of residual undegraded products remaining in compost and farmland temporarily, plastics approved by the US Food Sanitation Agency (FDA), the Sanitation Council for Polyolefins (JHOSPA), etc. It is preferable that it is an agent. Examples of such plasticizers include triacetin, epoxidized soybean oil, epoxidized linseed oil, epoxidized linseed oil fatty acid butyl ester, adipic acid-based aliphatic polyester, acetyl citrate tributyl, acetyl ricinoleic acid ester, glycerin fatty acid ester, sucrose Examples thereof include fatty acid esters, sorbitan fatty acid esters, adipic acid dialkyl esters, bis (alkyldiglycol) adipates, and polyethylene glycols.

  When using a polylactic acid-based resin for the biodegradable multifilm of the present invention, from the viewpoint of durability during storage before use, including suppression of bleed out of the plasticizer and blocking of the film, dimensional stability, For example, polyethylene glycol having a number average molecular weight of 1,000 or more is preferably solid at room temperature. From the same viewpoint, it is a block copolymer having a polyether-based segment and / or a polyester-based segment and a polylactic acid segment having a number average molecular weight of 1,200 or more and 10,000 or less in one molecule. Further preferred.

  The block copolymer (hereinafter referred to as “block copolymer plasticizer”), which is a preferred embodiment of the plasticizer used in the present invention, will be described below.

  The mass ratio of the polylactic acid segment contained in the block copolymer plasticizer is preferably less than 50% by mass of the entire block copolymer plasticizer because a desired flexibility can be imparted with a smaller amount of addition. It is preferable from the viewpoint of bleed-out suppression that it is more than%. Further, the number average molecular weight of the polylactic acid segment in one molecule of the block copolymer plasticizer is preferably 1,200 or more and 10,000 or less. When the polylactic acid segment of the block copolymer plasticizer is 1,200 or more, sufficient affinity is produced between the block copolymer plasticizer and the polylactic acid resin, and a part of the segment Is incorporated into a crystal formed from a polylactic acid resin as a base material, thereby causing the plasticizer molecule to be anchored to the base material, and exerts a great effect on the bleed-out suppression of the block copolymer plasticizer. The number average molecular weight of the polylactic acid segment of the block copolymer plasticizer is preferably 2,000 or more and less than 6,000. The polylactic acid segment of the block copolymer plasticizer has an L-lactic acid-derived component of 95% by mass to 100% by mass, or a D-lactic acid-derived component of 95% by mass to 100% by mass. % Or less is preferable because bleeding out is particularly suppressed.

  In addition, the block copolymer plasticizer has a polyether segment and / or a polyester segment, but when it has a polyether segment, from the viewpoint that a desired flexibility can be imparted by adding a smaller amount, More preferably, the segment has a segment made of polyalkylene ether, and particularly preferably has a segment made of polyethylene glycol. When the block copolymer plasticizer has a polyalkylene ether such as polyethylene glycol, polypropylene glycol, or polyethylene glycol / polypropylene glycol copolymer, especially a polyether segment such as polyethylene glycol, it has an affinity for polylactic acid resin. Since it is high, it is excellent in reforming efficiency, and is particularly preferable because a desired flexibility can be imparted by adding a small amount of plasticizer.

  In addition, when the block copolymer plasticizer has a segment composed of a polyalkylene ether, the polyalkylene ether segment portion tends to be easily oxidized or thermally decomposed when heated at the time of molding or the like. It is preferable to use a hindered amine-based antioxidant or a phosphorus-based heat stabilizer in combination.

  When the block copolymer plasticizer has a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate · 3-hydroxyvalerate), polycaprolactone, or ethylene glycol, Polyesters composed of aliphatic diols such as 1,4-butanediol and aliphatic dicarboxylic acids such as succinic acid and adipic acid are preferably used as the polyester-based segment. In addition, for reasons such as productivity and cost of the plasticizer, when it is used as either one of the polyether-based segment and the polyester-based segment, from the viewpoint that desired flexibility can be imparted by adding a smaller amount of the plasticizer. It is preferable to use a polyether-based segment.

  Furthermore, the number average molecular weight of the polyether segment and / or the polyester segment in one molecule of the block copolymer plasticizer is preferably 7,000 or more and less than 20,000. By setting the above range, the composition constituting the biodegradable multi-film has sufficient flexibility, and the melt viscosity of the composition is set to an appropriate level, and the film forming process such as the inflation film forming method is performed. Sex can be stabilized.

The biodegradable multifilm of the present invention has a heat shrinkage ratio Sm (winding length direction) and a heat shrinkage ratio St (width direction (direction perpendicular to the winding length direction)) when treated at 65 ° C. for 30 minutes. The following conditions are met.
3St ≦ Sm
2 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)
In the case of Sm> 5 (%) and / or St> 2 (%), the film after winding is gradually contracted over time while being stored in a roll state, and is wound by so-called winding tightening. Appearance deteriorates. Furthermore, the winding hardness becomes too high, blocking occurs and unwinding becomes unstable. In addition, when Sm <2 (%), it is difficult to obtain a film having an appropriate potential shrinkage stress at room temperature, and when it is stretched on a straw such as Tabata, the film is hardly shrunk and has an adhesion effect on the straw. Is insufficient. Further, in the case of St <-1 (%), the winding shape of the film end portion is deteriorated, the flatness is lost, and the unwinding becomes unstable. Here, when Sm and St are negative values less than 0, it means that the film is stretched.

  In addition, in the case of 3St> Sm, it means that the shrinkage rate in the winding direction of the film is smaller than 3 times the shrinkage rate in the width direction. Too much. As a result, the multi-film is likely to be locally broken, especially when the film adheres to the reed with hard protrusions on the soil surface of the reed and the weeds that push up the multi-film excessively. .

  Further, from the above viewpoint, Sm and St are preferably in the ranges of 3.5 ≦ Sm ≦ 5 (%) and 0 ≦ St ≦ 1 (%), respectively.

  The biodegradable multifilm of the present invention preferably has an adhesion peel strength As specified in the specification of 10 g / 15 mm or less. The biodegradable multifilm of the present invention comprises a composition having a glass transition temperature Tg in the range of 0 ° C. or more and 45 ° C. or less, and is a film having a moderate potential shrinkage stress even at room temperature. It tends to be relatively easier to block than the multi-film. However, when the adhesion peel strength is 10 g / 15 mm or less, there is no problem such as blocking even when the film is used after storage for a certain period of time after film formation, and good unwinding property can be maintained. In order to set the adhesion peel strength to 10 g / 15 mm or less, for example, when the main component is a blend of a polymer and a plasticizer, select a plasticizer with excellent bleed resistance such as a solid plasticizer at room temperature. Further, there is a method of adding an effective amount of an organic lubricant, but it is particularly effective to add organic particles and inorganic particles described later to make the ten-point average roughness Rz of the film surface 3 μm or more. Further, the lower the adhesion peel strength is, the better, but the lower limit is 0 g / 15 mm.

  The biodegradable multifilm of the present invention is usually a film having a thickness of 10 μm or more and 50 μm or less, depending on the application, and is often used at 25 μm or less. If the thickness is within the range of 10 μm or more and 50 μm or less as an agricultural multi-film, the film has good handleability, and roll roll form and unwindability are also practically sufficient. The thickness is preferably 18 μm or less from the viewpoint of always maintaining the state in which the film is gradually and appropriately shrunk and is in close contact with the wrinkles, which is an effect of the present invention, even after erection / stretching. From the standpoint of sustaining, the thickness is more preferably 16 μm or less, and particularly preferably 14 μm or less.

  When a polylactic acid resin is used for the biodegradable multifilm of the present invention, the impact resistance and biodegradability are improved, and the melt viscosity is improved to form a stable bubble, particularly in the inflation film forming method. The composition constituting the film preferably contains 5% by mass or more and 45% by mass or less of an aliphatic aromatic polyester in addition to the polylactic acid resin and the plasticizer. If the content of the aliphatic aromatic polyester is 5% by mass or more, the improvement effect is easily obtained mainly from the viewpoint of impact resistance. If the content is 45% by mass or less, biodegradation is mainly used in agricultural applications. Appropriate biodegradability can be imparted in the field where the property is required.

  Examples of the aliphatic aromatic polyester that can be used in the biodegradable multifilm of the present invention include poly (butylene succinate / terephthalate), poly (butylene adipate / terephthalate), and the like. Among them, poly (butylene adipate terephthalate) is preferably used as one having a large improvement effect in both impact resistance and biodegradability.

  In the composition which comprises the biodegradable multifilm of this invention, you may contain components other than having mentioned above in the range which does not impair the effect of this invention. For example, known antioxidants, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, antioxidants, ion exchange agents, crystal nucleating agents, coloring pigments, etc. Alternatively, inorganic fine particles, organic particles, and organic lubricants may be added as necessary as a lubricant.

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.

  Moreover, when adding particles for the purpose of improving slipperiness and blocking resistance, for example, inorganic particles include silicon oxide such as silica, various carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate, Various sulfates such as calcium sulfate and barium sulfate, various composite oxides such as kaolin and talc, various phosphates such as lithium phosphate, calcium phosphate and magnesium phosphate, various oxides such as aluminum oxide, titanium oxide and zirconium oxide Fine particles made of various salts such as lithium fluoride can be used.

  As the organic particles, fine particles made of calcium oxalate, terephthalate such as calcium, barium, zinc, manganese, magnesium, or the like are used. Examples of the crosslinked polymer particles include fine particles made of a vinyl monomer such as divinylbenzene, styrene, acrylic acid or methacrylic acid, or a copolymer. In addition, organic fine particles such as polytetrafluoroethylene, benzoguanamine resin, thermosetting epoxy resin, unsaturated polyester resin, thermosetting urea resin, and thermosetting phenol resin are also preferably used.

  The average particle diameter of both inorganic particles and organic particles is not particularly limited, but is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 1 to 4 μm. The addition amount of both the inorganic particles and the organic particles is not particularly limited, but is preferably 0.1% by mass or more and 5% by mass or less of the biodegradable multifilm of the present invention, and the ten-point average roughness Rz of the film surface described above. In order to set the thickness to 3 μm or more, the content is particularly preferably 2.5% by mass to 5% by mass.

  Examples of organic lubricants include liquid paraffins, natural paraffins, synthetic paraffins, aliphatic hydrocarbons such as polyethylene, stearic acid, lauric acid, hydroxystearic acid, fatty castors such as hard castor oil, stearic acid amide, oleic acid amide, Fatty acid amides such as erucic acid amide, lauric acid amide, ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis lauric acid amide, fatty acid metal salts such as aluminum stearate, lead stearate, calcium stearate, magnesium stearate , Fatty acid (partial) esters of polyhydric alcohols such as glycerin fatty acid esters and rubitan fatty acid esters, long chain fatty acid esters such as long chain ester waxes such as butyl stearate and montan wax And the like. When using a polylactic acid-based resin for the biodegradable multifilm of the present invention, stearic acid amide or ethylenebisstearic acid amide, which is easy to obtain an effect in a small amount, is preferable from the viewpoint of appropriate compatibility with polylactic acid.

  Next, the method for producing the biodegradable multifilm of the present invention will be specifically described in the case of using a polylactic acid resin as a preferred example.

  The polylactic acid resin in the present invention can be obtained, for example, by the following method. As a raw material, a lactic acid component of L-lactic acid or D-lactic acid is mainly used, and a hydroxycarboxylic acid other than the lactic acid component described above can be used in combination. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, lactide, glycolide, etc. can be used as a raw material. Furthermore, dicarboxylic acids and glycols can also be used.

  The polylactic acid resin can be obtained by a method of directly dehydrating and condensing the raw materials or a method of ring-opening polymerization of the cyclic ester intermediate. For example, in the case of producing by direct dehydration condensation, lactic acid or lactic acid and hydroxycarboxylic acid are preferably subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly a phenyl ether solvent, and particularly preferably a solvent distilled by azeotropic distillation. A polymer having a high molecular weight can be obtained by polymerizing by a method in which water is removed from the solvent and the solvent is brought into a substantially anhydrous state and returned to the reaction system.

  It is also known that a high molecular weight polymer can be obtained by subjecting a cyclic ester intermediate such as lactide to ring-opening polymerization under reduced pressure using a catalyst such as tin octylate. At this time, a method for adjusting the conditions for removing moisture and low molecular weight compounds during heating and refluxing in an organic solvent, a method for suppressing the depolymerization reaction by deactivating the catalyst after completion of the polymerization reaction, and a method for heat-treating the produced polymer Can be used to obtain a polymer with a small amount of lactide.

  Next, in one of the preferred embodiments of the present invention, a polylactic acid segment having a number average number molecular weight of 1,200 or more and 10,000 or less is used in one molecule, and a polyether segment and / or a polyester segment. A more specific example of the block copolymer plasticizer having the following will be described.

A polyethylene glycol having a hydroxyl group at both ends (hereinafter, polyethylene glycol is referred to as PEG) is prepared. The number average molecular weight of PEG having hydroxyl ends at both ends (hereinafter, the number average molecular weight of _PEG is referred to as _MPEG ) is usually calculated from the hydroxyl value determined by a neutralization method or the like in the case of a commercially available product. In a system in which lactide w _A parts by mass are added to w _B parts by mass of PEG having hydroxyl groups at both ends, lactide undergoes ring-opening addition polymerization at both hydroxyl groups of PEG and is sufficiently reacted. A block copolymer of type (A) -PEG (B) -PLA (A) can be obtained (PLA here indicates polylactic acid). This reaction is performed in the presence of a catalyst such as tin octylate as necessary. The number average molecular weight of one polylactic acid segment of the plasticizer made of this block copolymer can be substantially determined as (1/2) × (w _A / w _B ) × M _PEG . The mass percentage of the total block copolymer plasticizer of the polylactic acid segment component can be substantially determined as _{100 × w A / (w A} + w B)%. Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire block copolymer plasticizer can be determined to be substantially 100 × w _B / (w _A + w _B )%.

  Block copolymer plasticizer contains a large amount of unreacted PEG, reactants with PEG whose terminal polylactic acid segment number average molecular weight is less than 1,200, by-products such as lactide oligomers, impurities, etc. If included, it is preferable to remove them, for example, by the following purification method. The synthesized block copolymer plasticizer is uniformly dissolved in an appropriate good solvent such as chloroform, and then an appropriate poor solvent such as a water / methanol mixed solution or diethyl ether is added dropwise. Alternatively, precipitation is performed by adding a good solvent solution in a large excess of poor solvent, and the solvent is evaporated after separating the precipitate by centrifugation or filtration. After immersing the block copolymer plasticizer in water, the mixture is heated to 50 to 90 ° C. and stirred as necessary, and then the organic phase containing the block copolymer plasticizer is extracted and dried to remove water. The purification method is not limited to the above, and the above operation may be repeated a plurality of times as necessary. Removal of by-products such as lactide oligomers can prevent a decrease in viscosity when a polylactic acid resin composition is obtained, and the melt viscosity of the composition is set to an appropriate level to stabilize processing. It is also preferable because it can be performed.

When a plasticizer of a PLA (A) -PEG (B) -PLA (A) type block copolymer is prepared by the method described above, the molecular weight of one polylactic acid segment of the prepared plasticizer is as follows: It can be determined by the method. That is, based on a chart obtained by ¹ H-NMR measurement using a deuterated chloroform solution of a block copolymer plasticizer, {I _PLA × (molecular weight of polylactic acid monomer unit) / (number of polylactic acid segments) } / {I _PEG × (molecular weight of PEG monomer unit) / (number of chemically equivalent protons)} × M _PEG . That is, when a PLA (A) -PEG (B) -PLA (A) type block copolymer plasticizer is prepared, {I _PLA × 72/2} / {I _PEG × 44/4} × M _PEG . However, I _PEG is the signal integral intensity derived from the hydrogen of the methylene group of the PEG main chain part, and I _PLA is the signal integral intensity derived from the hydrogen of the methine group of the PLA main chain part. When the reaction rate of lactide during the synthesis of block copolymer plasticizer is sufficiently high and almost all lactides are synthesized under the condition of ring-opening addition to the PEG end, it is often obtained by ¹ H-NMR measurement. The molecular weight of one polylactic acid segment of the plasticizer is preferably determined by the above method based on the chart obtained.

  In obtaining the composition (composition which comprises the biodegradable multifilm of this invention) containing a polylactic acid-type resin and a plasticizer, an aliphatic aromatic polyester, or another component in this invention, each component is It is possible to produce a composition by uniformly mixing a solution dissolved in a solvent, and then removing the solvent. However, steps such as dissolution of the raw material in the solvent and removal of the solvent are unnecessary, and this is a practical production method. It is preferable to employ a melt-kneading method for producing a composition by melt-kneading each component. The melt kneading method is not particularly limited, and a commonly used known mixer such as a kneader, roll mill, Banbury mixer, single-screw or twin-screw extruder can be used. Among these, from the viewpoint of productivity, it is preferable to use a single screw or twin screw extruder.

  The mixing order is not particularly limited, for example, after dry blending a polylactic acid-based resin and a plasticizer, a method of using a melt kneader, or after preparing a master batch in which a polylactic acid-based resin and a plasticizer are previously melt-kneaded, Examples thereof include a method of melt-kneading the master batch with a polylactic acid resin and the other components described above. Further, if necessary, a method of melt-kneading other components at the same time, or preparing a master batch in which a polylactic acid-based resin and other additives are melt-kneaded in advance, the master batch, the polylactic acid-based resin, and a plasticizer component You may use the method of melt-kneading. Moreover, when adding components, such as a plasticizer liquid at normal temperature, it can also add from the raw material supply hole vent hole of an extruder using a metering pump separately from a solid component at normal temperature.

  The temperature at the time of melt kneading is preferably in the range of 150 ° C. to 240 ° C., and more preferably in the range of 200 ° C. to 220 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

  The biodegradable multi-film of the present invention is a production of an existing film such as a known inflation method, T-die casting method, and biaxial stretching method after T-die casting using the composition obtained by the above-described method. It can be obtained by law.

  In producing the biodegradable multi-film of the present invention, for example, when the composition obtained by the above-described method is once chipped, and melt-kneaded again to perform extrusion / film formation, the chip is heated to 60 to 110 ° C. It is preferable that the moisture content of the composition is 1200 ppm or less by drying for 6 hours or more. Furthermore, it is preferable to reduce the lactide content in the composition by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. By reducing the moisture content of the composition to 1200 ppm or less and reducing the lactide content, hydrolysis during melt-kneading can be prevented, thereby preventing molecular weight reduction, the melt viscosity is set to an appropriate level, and the film-forming process is stabilized. It is also preferable because it can be made. From the same point of view, when chipping or melt extrusion / film formation is performed once, melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances using a twin-screw extruder with a vent hole. It is preferable.

  As a method for forming the biodegradable multifilm of the present invention, an inflation method is preferred. In the case of forming a film by the inflation method, it is easy to suppress the molecular orientation, and to easily give the elongation necessary for practicality of the multifilm, that is, the so-called elongation. In addition, since it is easy to suppress orientation crystallization, it is easy to obtain a film having an appropriate potential shrinkage stress even at room temperature, which is a feature of the biodegradable multifilm of the present invention. When manufacturing by the inflation method, for example, the composition prepared by the method as described above is melt-extruded with a twin-screw extruder with a vent hole and led to an annular die, and extruded from the annular die and supplied with dry air inside. Then, it is formed into a balloon shape (bubble), air-cooled and solidified uniformly with an air ring, taken up at a specified take-up speed while being folded flat with a nip roll, and then cut at both ends or one end as necessary. Take it.

  In this case, depending on the discharge amount from the annular die, the take-up speed of the nip roll, and the bubble blow ratio, the thickness may be adjusted so that the thickness is usually 10 μm or more and 50 μm or less.To increase the thickness accuracy and uniformity, The annular die is preferably a spiral type.

  Moreover, although the extrusion temperature of the composition containing polylactic acid-type resin etc. is the range of 150-240 degreeC normally, thickness accuracy and a uniformity are improved and also a favorable roll winding form and unwinding property are provided. For this purpose, the temperature of the annular die is important, and the temperature of the annular die is in the range of 150 to 190 ° C, preferably 150 to 170 ° C. If the temperature of the annular die is less than 150 ° C., the temperature at which the composition is extruded is too low, the molding behavior at the time of blow-up immediately after discharge becomes uneven, the thickness accuracy deteriorates, and the winding shape becomes poor. When a film is formed because the stress at the time of up is too high, the heat shrinkage rate is high, and the winding shape is further deteriorated by so-called winding tightening over time. On the other hand, when the temperature of the annular die exceeds 190 ° C., the viscosity of the composition is too low, the thickness accuracy is deteriorated and the winding shape is poor, and the bubble formation itself tends to be unstable. From the same viewpoint, the temperature of the annular die is more preferably 160 to 170 ° C.

  The bubble blow ratio depends on the relationship between the discharge rate and the take-up speed of the nip roll, but the film may be too anisotropic if it is too low or too high. Tends to be unstable, and is usually in the range of 2.0 to 4.0.

Moreover, in order to provide an appropriate heat shrinkage rate and to control so that 3St ≦ Sm, 2 ≦ Sm ≦ 5 (%), and −1 ≦ St ≦ 2 (%), basically, Sm and St The absolute amount and the balance of the value are controlled. For example, there are the following methods for increasing the absolute amount of both Sm and St.
(1) The additive viscosity and the component amount are selected to increase the melt viscosity of the composition forming the biodegradable multifilm.
(2) Lower the temperature of the annular die.
(3) Reduce the thickness.
Further, for example, the following method can be used to increase the absolute amount of Sm without changing St much, that is, to control the balance.
(4) Increase the take-up speed by a nip roll after forming from a circular die to form a balloon.
(5) Lower the blow ratio.
For example, in order to increase the absolute amount of only St without changing Sm so much, the method opposite to the above (4) and (5) may be adopted.

  Furthermore, after forming into a film, various surface treatments may be applied for the purpose of improving printability, laminate suitability, coating suitability, and the like. Examples of the surface treatment include corona discharge treatment, plasma treatment, flame treatment, acid treatment, etc., and any method can be used, but continuous treatment is possible, and equipment for existing film forming equipment is used. Corona discharge treatment can be exemplified as the most preferable because of its easy installation and simple processing.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited thereto.
[Measurement and evaluation method]
Measurements and evaluations shown in the examples were performed under the following conditions.
(1) Glass transition temperature of the composition: Tg (° C.)
About 5 mg of the film sample was weighed and packed in a sample pan to obtain a measurement sample. Based on JIS K7121-1987, the differential scanning calorimeter (DSC) measurement was performed to 100 degreeC by the temperature increase rate of 20 degree-C / min after hold | maintaining at -50 degreeC for 5 minutes. From the observed DSC curve, Tg was determined as the midpoint glass transition temperature.
(2) Average thickness in the width direction: Ta (μm)
Along the width direction of the film sample, thicknesses at 20 positions were measured at equal intervals from one end to the other end. The measurement was performed with a micrometer according to JIS K7130-1999 (Method A), and the average thickness of each measurement value: Ta (μm) was determined.
(3) Thermal contraction rate: Sm, St (%)
Cut out the test direction as a longitudinal direction into 140 mm × 10 mm, put a rating line between 100 mm in the longitudinal direction, hold the inside at 65 ° C. and treat it in a dry heat oven for 30 minutes, then measure the dimension between the rating lines, The shrinkage was calculated according to the following formula. The measurement was performed five times for each level, and the heat shrinkage rate Sm in the winding length direction was determined from the average value of the five measurements.

Shrinkage rate (%) = {(dimension before shrinkage) − (dimension after shrinkage)} / (dimension before shrinkage) × 100
The heat shrinkage rate St in the width direction was obtained by the same method.
(4) Ten-point average roughness: Rz (μm)
Using universal surface shape measuring instrument SE-3FA (manufactured by Kosaka Laboratory Ltd.), stylus tip radius: 2 μm, measuring direction: winding length direction, measuring length: 1 mm, X pitch: 1.0 μm, Y pitch: 5 μm, The ten-point average roughness Rz (μm) was measured under three-dimensional measurement conditions of X feeding speed: 0.1 mm / second and low-frequency cut: 0.25 mm.
(5) Adhesive peel strength: As (g / 15 mm)
Two strip-shaped test pieces having a width of 15 mm and a length of 150 mm were cut out from the film sample so that the long side was in the film winding direction. The two test pieces were superposed on both the long side and the short side without any deviation, and a load of 10 g / cm ² was applied only to a portion of 100 mm from one end in the length direction for 1 hour in an atmosphere at 80 ° C. A sample was prepared for measurement of adhesion peel strength.

Tensilon universal testing machine UTC-100 type (manufactured by Orientec Co., Ltd.) was used for the measurement of adhesion peel force. The above-mentioned measurement sample is set to the upper and lower chucks using the unloaded portion as the gripping portion, and the tensile test is performed to the chuck position where all the 100mm-adhered portions are peeled off at a pulling speed of 200mm / min. It was. At this time, an automatic table that can always maintain a state in which the portion to which the load was applied and in close contact with the tension direction was at an angle of 90 ° was used in combination, and the tensile test was performed by placing the portion in close contact with the table. The maximum stress in a single tensile test was measured. The measurement was performed 5 times per level, and the average value of 5 tests was obtained and used as the adhesion peel strength.
(6) Impact strength (kN · m / mm)
Using a film impact tester (manufactured by Toyo Seiki Co., Ltd.), impact strength was measured in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH using a hemispherical impact head having a diameter of 1/2 inch. The measurement was performed 5 times for each level, and the average value of the 5 measurements was obtained. Furthermore, the average thickness was determined by dividing by Ta × 10 ⁻³ (mm) and obtained as a value per unit thickness.
(7) Roll roll appearance and appearance After storing the roll sample for 3 days in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH, a tape measure is used at the position where the roll diameter is the maximum and the minimum position in the width direction of the roll sample. The circumference of the roll was measured.

From the measured circumference, the maximum value and the minimum value of the winding diameter were calculated using the formula of (winding diameter) = perimeter / 3.14. The ratio of the difference between the maximum value and the minimum value of the winding diameter with respect to the minimum value: D (%) was determined and judged according to the following criteria.
A: D ≦ 1%
○: 1% <D ≦ 1.5%
Δ: 1.5% <D ≦ 3%
×: 3% <D
(8) Unwinding property After the roll sample is stored for 3 days in an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH, an iron shaft having a diameter smaller than the inner diameter of the paper tube is passed through the paper tube of the roll sample, and both ends of the iron shaft are passed. The roll is placed in a state where the roll can be rotated horizontally and freely, and the state of unwinding when the film is unwound at a speed of 10 m / min is visually observed. It was judged.
(Double-circle): It can unwind smoothly without a problem.
○: Discontinuous unwinding from time to time due to slight wrinkles and blocking.
Δ: Discontinuous unwinding due to wrinkles and blocking.
X: Due to wrinkles and blocking, the film is pulled and deformed or broken during unwinding.
(9) Adhesion to cocoons A multi-film expansion test was conducted in the middle of March in a field in Ibaraki Prefecture. A tractor with a multier was used to simultaneously stretch the cocoon, and the shape of the cocoon was a cocoon having a cocoon width of 60 cm and a cocoon height of 35 cm. In addition, the length was 50 m for each level, and the stretching speed and the like were performed under the same conditions for each level. The field where the extension test was conducted was somewhat clayey and contained many relatively hard soil blocks with a diameter of 3 cm or more.

  Two weeks after the expansion, a special cone-shaped jig was pierced from the top of the multi-film, and holes of about 12 to 15 cm in diameter and about 12 to 15 cm in depth were formed in a row at the top of each ridge, Tobacco seedlings were placed in each hole and transplanted.

  At the beginning of May, one month after the transplantation, “adhesion to the heel” was judged according to the following criteria.

<Adhesion to heel>
◎: The multi-film is in close contact with the soil surface of the straw without any gaps, and even if the surface of the multi-film is about 2 cm square, it is difficult to pinch by hand. It is in close contact with the soil surface by the tension of the film.
○: The multi-film is in close contact with the soil surface of the straw without any gaps. Even if the surface of the multi-film is 2cm square by hand, the film is lifted about 1cm from the soil surface and released. Re-adhere so that it sticks to the soil surface with tension.
Δ: The multi-film is in close contact with the soil surface of the cocoon without any gaps in most parts, and even if the surface of the multi-film has a surface area of about 2 cm by hand and is lifted about 1 cm from the soil surface and released, the film It adheres again so that it sticks to the soil surface with the tension of, but there is a part with a gap in part such as the periphery of the planting hole and the edge of the ridge.
×: There is a uniform gap between the soil surface of the multi-film and the straw, and it is possible to pick up the multi-film from the soil surface by about 1 cm or more, and when the hand is released, the wrinkles remain on the film in that part. .
(10) Water retention The moisture content of the soil was measured simultaneously with the evaluation of the adhesion to the straw. As the soil for measurement, about 1 kg of soil having a depth of about 15 cm from the surface was collected so that the soil at each depth had the same ratio at the middle position between adjacent planting holes. After measuring the mass of the soil in advance, spread it thinly on a vat and dry it in a hot air oven at 100 ° C. for 24 hours or more and measure the mass in a completely dry state. Asked.

(Soil moisture content) = ((Soil mass before drying) − (Soil mass after drying)) / (Soil mass before drying) × 100 (%)
From the moisture content determined by the above method, “water retention” was judged according to the following criteria.

<Water retention>
○: 20% ≦ (soil moisture content)
Δ: 10% ≦ (soil moisture content) <20%
×: (Soil moisture content) <10%
(11) Durability after stretching At the beginning of July 3 months after transplantation, the presence or absence of tearing of the multi-film was visually observed, and “durability after stretching” was judged according to the following criteria.
<Durability after extension>
○: Holes and tears of a size that can pass a sphere with a diameter of 2 cm are 2 or less in 50 m of heel length Δ: Holes or tears of a size that can pass a sphere of 2 cm in diameter are 3 or more places in a 50 m of heel length 10 or less x: Holes or tears that are large enough to pass a sphere with a diameter of 2 cm, but 11 or more in a 50m length
[Polylactic acid resin used]
(Polylactic acid PL1)
Weight average molecular weight = 200,000, D-form content = 12.0%, melting point = none, moisture content = 490 ppm,
(Polylactic acid PL2)
Weight average molecular weight = 220,000, D-form content = 1.4%, melting point = 166 ° C., moisture content = 360 ppm,
(Polylactic acid PL3)
Weight average molecular weight = 220,000, D-form content = 5.0%, melting point = 150 ° C., moisture content = 360 ppm,
(Polylactic acid PEG copolymer PL4)
10 parts by mass of polyethylene glycol (PEG) having a number average molecular weight of 10,000, 81 parts by mass of L-lactide, 9 parts by mass of meso lactide and 0.1 part by mass of tin octylate are mixed and polymerized at 160 ° C. for 3 hours or more in a nitrogen atmosphere. As a result, PL4 made of a polylactic acid-polyethylene glycol block copolymer was obtained. Immediately after obtaining PL4, moisture-proof packaging was performed and stored.

Weight average molecular weight = 160,000, D-form content = 4.5%, melting point = 145 ° C., moisture content = 660 ppm,
The weight average molecular weights of PL1 to PL4 were measured by using Waters 2690 manufactured by Japan Waters Co., Ltd., using polymethyl methacrylate as a standard, a column temperature of 40 ° C., and a chloroform solvent.
[Plasticizer used]
(Plasticizer PS1)
Acetyltributyl citrate (Morimura Corporation, trade name “Citroflex A-4”)
(Plasticizer PS2)
Polyethylene glycol (manufactured by Sanyo Chemical Industries, trade name “PEG-10000”)
(Plasticizer PS3)
By mixing 62 parts by mass of polyethylene glycol having a number average molecular weight of 8,000, 38 parts by mass of L-lactide and 0.1 part by mass of tin octylate and polymerizing at 160 ° C. for 3 hours in a nitrogen atmosphere, both ends of polyethylene glycol are obtained. A plasticizer S1 having a polylactic acid segment having a number average molecular weight of 2,500 was obtained. Immediately after obtaining the plasticizer S1, moisture-proof packaging was performed and stored. When the water content was measured, it was 1650 ppm.
[Used aliphatic polyester resin, aliphatic aromatic polyester resin]
(Polyester PA1)
Polybutylene succinate and adipate resin (made by Showa Polymer Co., Ltd., trade name “Bionore” # 3001)
(Polyester PA2)
Polybutylene succinate resin (Mitsubishi Chemical Corporation, trade name “GSPla” AZ91T)
(Polyester PA3)
Polybutylene adipate terephthalate resin (BASF, trade name "Ecoflex")
[Used organic lubricant]
(Lubricant SL1)
Stearic acid amide (Nippon Yushi Co., Ltd., trade name "Alflow S-10")
[Used particles]
(Inorganic particles PT1)
Talc (Nippon Talc Co., Ltd., trade name “SG-95”), average particle size = 2.5 μm
(Inorganic particles PT2)
Calcium carbonate (manufactured by Maruo Calcium Co., Ltd., trade name “Caltex®”), average particle size = 2.8 μm
The average particle diameter is the cumulative median diameter (Median diameter), that is, the particle at which the cumulative curve becomes 50% when the cumulative curve is obtained by setting the total volume of the powder aggregate to 100%. It was a diameter (50% diameter [μm]), and was determined by a Microtrac FRA laser type particle size distribution analyzer.
[Preparation of polylactic acid resin film]
Example 1
A mixture of 58.6% by mass of polylactic acid PL1, 15.7% by mass of polylactic acid PL2, 24.3% by mass of plasticizer PS3, and 1.4% by mass of inorganic particles PT2 is a screw diameter of 44 mm at a cylinder temperature of 190 ° C. The composition 1 was obtained by subjecting to a twin-screw extruder equipped with a vacuum vent, and melt-kneading and homogenizing the vacuum vent while degassing and then chipping the composition 1.

After drying this composition for 10 hours with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C., the composition 1 is 70% by mass and polyester PA 3 is 30% by mass. Supplied to a uniaxial extruder with a screw diameter of 65 mm with a cylinder temperature of 190 ° C and a spiral-shaped annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C. And then cooled with a cooling ring, taken up at 30 m / min while being folded with a nip roll above the die, cut at both ends with an edge cutter, and cut into two pieces, each wound with a winder of 1350 mm in width. . A film having a final thickness of 20 μm was prepared by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Example 2)
A film was obtained in the same manner as in Example 1 except that the final thickness was adjusted to 18 μm by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Example 3)
A film was obtained in the same manner as in Example 1 except that the final thickness was adjusted to 15 μm by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
Example 4
A mixture of 57.1% by mass of polylactic acid PL1, 14.3% by mass of polylactic acid PL2, 24.3% by mass of plasticizer PS3, 4.3% by mass of inorganic particles PT2 is a screw diameter of 44 mm at a cylinder temperature of 190 ° C. Were subjected to a melt-kneading and homogenization while degassing the vacuum vent part, to obtain a composition 2 that was chipped.

The composition 2 was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and finally the composition shown in Table 1 as a mixture of 70% by mass of composition 2 and 30% by mass of polyester PA3. To a single screw extruder with a screw diameter of 65 mm at an extruder cylinder temperature of 190 ° C., and from a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C., in a blow ratio of 3.4. Extruded upward, air-cooled with cooling ring, folded at 20m / min while folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two sheets, each wound with a 1350mm width film with a winder It was. A film having a final thickness of 15 μm was prepared by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Example 5)
A film was obtained in the same manner as in Example 1 except that the final thickness was 13 μm by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Example 6)
A mixture of 98.8% by mass of polylactic acid PEG copolymer PL4 and 1.2% by mass of lubricant SL1 was supplied to a twin screw extruder with a vacuum diameter of 44 mm and a cylinder temperature of 190 ° C., and the vacuum vent was degassed. Then, composition 3 was obtained which was melt-kneaded and homogenized to form chips.

The composition 3 was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and finally the composition shown in Table 1 as a mixture of 85% by mass of composition 3 and 15% by mass of polyester PA1. A film having a final thickness of 20 μm was obtained in the same manner as in Example 1 except that the film was used. The evaluation results of the obtained film are shown in Table 1.
(Example 7)
A mixture of 64.7% by mass of polylactic acid PL3, 10.6% by mass of plasticizer PS1, 20% by mass of plasticizer PS3 and 4.7% by mass of inorganic particles PT2 is vacuum with a cylinder temperature of 190 ° C. and a screw diameter of 44 mm. It used for the twin-screw extruder with a vent, and the composition 4 made into chip | tip was obtained after melt-kneading and homogenizing, degassing a vacuum vent part.

The composition 4 was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and finally the composition shown in Table 1 as a mixture of 70% by mass of composition 2 and 15% by mass of polyester PA2 To a single screw extruder with a screw diameter of 65 mm at an extruder cylinder temperature of 190 ° C., and from a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 155 ° C., in a blow ratio of 3.4. Extruded upward, air-cooled with cooling ring, folded at 20m / min while folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two pieces, each wound with a 1350mm width film with a winder It was. A film having a final thickness of 20 μm was prepared by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Example 8)
A mixture of 58.6% by mass of polylactic acid PL1, 15.7% by mass of polylactic acid PL2, 24.3% by mass of plasticizer PS3, and 1.4% by mass of lubricant SL1 has a cylinder temperature of 190 ° C. and a screw diameter of 44 mm. It was used for the twin-screw extruder with a vacuum vent, and it melt-kneaded and homogenized, deaerating a vacuum vent part, and obtained the chip | tip composition 5 obtained.

  The composition 5 was dried with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, and finally the composition shown in Table 1 as a mixture of 70% by mass of composition 5 and 30% by mass of polyester PA3. To a single screw extruder with a screw diameter of 65 mm at an extruder cylinder temperature of 190 ° C., and from a spiral annular die with a diameter of 200 mm, a lip clearance of 1.3 mm, and a temperature of 180 ° C., in a blow ratio of 4.3 Extruded upward, cooled by air with a cooling ring, taken up at 35 m / min while folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two pieces, each wound with a 1350 mm wide film with a winder It was. A film having a final thickness of 20 μm was prepared by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.

(Comparative Example 1)
A mixture of 60% by mass of polylactic acid PL1, 17.6% by mass of polylactic acid PL2, 21.4% by mass of plasticizer PS3 and 1.0% by mass of lubricant SL1 is a vacuum vent having a cylinder temperature of 190 ° C. and a screw diameter of 44 mm. It was used in a twin screw extruder, melted and kneaded while degassing the vacuum vent portion, and then homogenized to obtain a composition 1 that was chipped.

After drying this composition with dehumidified hot air at a temperature of 100 ° C. and a dew point of −25 ° C. for 10 hours, a composition shown in Table 1 as a mixture of 70% by mass of composition 1 and 30% by mass of polyester PA1 was finally obtained. Supplied to a single-screw extruder with a screw diameter of 65 mm with a cylinder temperature of 190 ° C and a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C. Then, the sheet was cooled with a cooling ring, taken up at 20 m / min while being folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two sheets, and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 2)
A film having a final thickness of 20 μm was obtained in the same manner as in Example 2 except that the plasticizer PS1 was used instead of the plasticizer PS2. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 3)
A mixture of 75% by mass of polylactic acid PL1, 22% by mass of polylactic acid PL2, and 3% by mass of plasticizer PS3 was subjected to a twin screw extruder with a vacuum diameter of 44 mm and a cylinder temperature of 190 ° C., and the vacuum vent part was removed. After melt-kneading and homogenizing with air, we continue to measure with a gear pump. From a spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C., the bubble ratio is upward at a bubble ratio of 3.4 Then, the sheet was cooled with a cooling ring, taken up at 20 m / min while being folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two sheets, and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 4)
A mixture of 99% by mass of polyester PA3 and 1.0% by mass of lubricant SL1 is supplied to a twin screw extruder with a vacuum vent with a cylinder diameter of 160 ° C. and a screw diameter of 44 mm, and melted and kneaded while degassing the vacuum vent. After that, it was measured with a gear pump, extruded from a spiral type annular die having a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 165 ° C. in a bubble ratio of 3.4 and then air-cooled by a cooling ring. The sheet was taken up at 20 m / min while being folded with a nip roll above the die, and both ends were cut with an edge cutter and cut into two sheets, and each film was wound with a winder. A film having a final thickness of 20 μm was obtained by adjusting the discharge amount. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 5)
In the same manner as in Comparative Example 1, a film having a final thickness of 8 μm was obtained by further adjusting the discharge rate. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 6)
As in Comparative Example 1, except that the screw diameter is 65 mm, the cylinder temperature is 200 ° C., supplied to a single screw extruder, extruded from a spiral annular die with a temperature of 200 ° C., the nip roll take-up speed is 35 m / min, and the discharge amount is adjusted. As a result, a film having a final thickness of 20 μm was obtained. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 7)
In the same manner as in Comparative Example 1, except that a spiral annular die having a diameter of 200 mm was used, the tube was extruded upward at a blow ratio of 4.3, and the discharge rate was adjusted by adjusting the discharge rate of the nip roll to 15 m / min. A film having a thickness of 20 μm was obtained. The evaluation results of the obtained film are shown in Table 1.
(Comparative Example 8)
The film having a final thickness of 20 μm was obtained in the same manner as in Comparative Example 1 except that the film was extruded from a spiral annular die having a temperature of 145 ° C. to adjust the discharge amount. The evaluation results of the obtained film are shown in Table 1.

  Each of the biodegradable multifilms of Examples 1 to 8 is composed of a composition having a glass transition temperature Tg in the range of 0 ° C. or higher and 45 ° C. or lower, and has a heat shrinkage ratio Sm (30 m when treated at 65 ° C. for 30 minutes). Winding length direction), heat shrinkage rate St (width direction (direction perpendicular to winding length direction)) satisfies the conditions specified in the present specification, and quality such as roll appearance, appearance, unwinding property, It was a multi-film excellent in practicality such as adhesion to ridges, water retention and durability.

  On the other hand, in the comparative example, the heat shrinkage ratio Sm (winding length direction) was less than 2%, the adhesion to the heel was insufficient, and the water retention was also insufficient (Comparative Examples 1-4). ).

  Even if the heat shrinkage ratio Sm (winding length direction) is 2% or more, if the heat shrinkage ratio St (width direction) exceeds 2%, there are projections such as hard soil blocks on the soil surface of the straw. As it was, the film was in close contact with the wrinkles, and the portion was locally broken, resulting in insufficient durability (Comparative Examples 5 and 7).

  Further, when the heat shrinkage ratio Sm (winding length direction) exceeded 5%, the winding shape deteriorated due to winding tightening (Comparative Examples 6 and 8).

The present invention relates to a biodegradable multifilm having high soil water retention and excellent crop growth, and further is a polylactic acid-based biodegradable multifilm excellent in flexibility, impact resistance, and bleed resistance. The biodegradable multi-film of the present invention has a particular thermal property and shrinkage property, thereby significantly improving the adhesion to the cocoon, resulting in high soil water retention. Due to the adhesion effect, it has characteristics that are excellent in other mechanical properties such as being hardly broken even when exposed to wind and rain, and can be preferably used as an agricultural multi-film having biodegradability. is there.

Claims (5)

It is composed of a composition having a glass transition temperature Tg in the range of 0 ° C. or more and 45 ° C. or less, and has a heat shrinkage ratio Sm (winding length direction) and heat shrinkage rate St (width direction (winding length) when treated at 65 ° C. for 30 minutes. A biodegradable multifilm characterized in that the direction perpendicular to the vertical direction)) satisfies the following conditions.
3St ≦ Sm
2 ≦ Sm ≦ 5 (%)
-1 ≦ St ≦ 2 (%)   The biodegradable multifilm according to claim 1, wherein the thickness is 18 µm or less.   The biodegradable multifilm according to claim 1 or 2, wherein the composition contains a polylactic acid resin in an amount of 30% by mass to 95% by mass and a plasticizer in an amount of 5% by mass to 30% by mass.   The biodegradable multifilm according to any one of claims 1 to 3, wherein the composition contains 5% by mass or more and 45% by mass or less of an aliphatic aromatic polyester.   The biodegradable multifilm according to any one of claims 1 to 4, wherein the adhesion peeling force As is 10 g / 15 mm or less.