WO2013021772A1

WO2013021772A1 - Biodegradable film

Info

Publication number: WO2013021772A1
Application number: PCT/JP2012/067650
Authority: WO
Inventors: 山村剛平; 坂本純; 廣田真之
Original assignee: 東レ株式会社
Priority date: 2011-08-08
Filing date: 2012-07-11
Publication date: 2013-02-14
Also published as: CN103732657A; CN103732657B; KR20140048298A; JP5867406B2; KR101970847B1; JPWO2013021772A1

Abstract

This biodegradable film contains a lactic acid resin (A) and a biodegradable resin (B) other than the lactic acid resin (A). The biodegradable film has a structure wherein, in a cross section along the length direction and the thickness direction of the film, a disperse phase comprising the lactic acid resin (A) is dispersed in a continuous phase comprising the biodegradable resin (B), the disperse phase being dispersed in the form of ellipses elongated in the length direction of the film or in the form of layers elongated in the length direction of the film. The biodegradable film satisfies the formula W_A/W_B ≤ 2.0P_A/P_B, wherein P_A is the content (mass%) of the lactic acid resin (A) and P_B is the content (mass%) of the biodegradable resin (B) in a total of 100 mass% of the lactic acid resin (A) and the biodegradable resin (B), W_A is the thickness (nm) of the disperse phase, and W_B is the thickness (nm) of the continuous phase. The present invention provides a biodegradable film that has excellent flexibility, tear resistance, transparency, and biomass characteristics, and that achieves excellent effects particularly in inflation film-forming methods.

Description

Biodegradable film

The present invention relates to a biodegradable film that is excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, and particularly exhibits a good effect by an inflation film-forming method.

In recent years, with increasing environmental awareness, attention has been focused on soil pollution problems caused by the disposal of plastic products and global warming problems caused by increased carbon dioxide caused by incineration. As a measure against the former, various biodegradable resins, and as a measure against the latter, a resin made of biomass (plant-derived raw material) that does not give a new carbon dioxide load to the atmosphere even if it is incinerated has been extensively researched and developed. ing. Attention has been focused on polylactic acid that satisfies both requirements and is relatively advantageous in terms of cost. When polylactic acid is applied to soft film applications typified by polyolefins such as polyethylene, 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 1 discloses a resin comprising polylactic acid, a copolymer of a biodegradable aliphatic polyester having a glass transition temperature of 0 ° C. or lower and an aromatic copolymer polyester, a plasticizer, and an inorganic filler as constituent components. A film comprising the composition is disclosed. Patent Document 2 discloses a film comprising a composition containing a polylactic acid-based resin and a plasticizer and defining elongation, thickness, and heat shrinkage rate. Furthermore, Patent Document 3 discloses a biodegradable resin composition and film in which diisocyanate is added to a mixture of a polyester composed of adipic acid, terephthalic acid and butanediol and polylactic acid.
JP 2002-327107 A JP 2009-138085 A Japanese Patent No. 3411289

Although the above-mentioned Patent Document 1 describes the improvement of the flexibility and impact resistance of the film, it does not disclose any technique for improving tear resistance and transparency. The tear resistance and transparency were insufficient.

In addition, although the above-mentioned Patent Document 2 describes the improvement of the flexibility and impact resistance of the film, it does not disclose any technique for improving the tear resistance. The tearability was insufficient.

Furthermore, although it is described in Patent Document 3 that it is possible to optimize both biodegradability and mechanical properties according to the application, the disclosed technique is not transparent. The tearability was insufficient.

As described above, various studies have been made on technologies related to biodegradable films that are excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, and in particular, that exhibit good effects in the inflation film forming method. However, it has not been achieved yet.

Therefore, in view of the background of such conventional technology, the present invention provides a biodegradable film that is excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, and that exhibits particularly good effects by the inflation film-forming method. The task is to do.

In order to solve the above problems, the biodegradable film of the present invention has the following configuration. That is,
A biodegradable film comprising a lactic acid resin (A) and a biodegradable resin (B) other than the lactic acid resin (A) (hereinafter simply referred to as “biodegradable resin (B)”), In the cross section in the length direction and the thickness direction, the continuous phase composed of the biodegradable resin (B) has an elliptical shape in which the dispersed phase composed of the lactic acid resin (A) is long in the length direction of the film or the length of the film. It has a dispersed structure in long layered directionally, in total 100 wt% of the lactic acid resin (a) and biodegradable resin (B), the content of the lactic acid resin (a) (mass%) P _a When the content (mass%) of the biodegradable resin (B) is P _B , the thickness (nm) of the dispersed phase is W _A , and the thickness (nm) of the continuous phase is W _B , A biodegradable film that meets the requirements.

W _A / W _B ≦ 2.0 × P _A / P _B
Biodegradable film of the present invention preferably has a thickness W _A of the disperse phase is 5 ~ 100 nm.

The biodegradable film of the present invention preferably has a tear strength of the film by the trouser tear method defined in JIS K7128-1 (1998) of 5 N / mm or more in both the length direction and the width direction.

The biodegradable film of the present invention preferably has P _A : P _B = 5: 95 to 60:40.

Biodegradable film of the present invention, the temperature 200 ° C., a melt viscosity eta _A, temperature 200 ° C. of the lactic acid resin (A) at a shear rate of 100 sec ^-1, biodegradable resin at a shear rate 100 sec ^-1 of (B) When the melt viscosity is η _B , it is preferable to satisfy the following formula.

0.3 ≦ η _A / η _B ≦ 1.1
The biodegradable film of the present invention preferably contains a compatibilizer.

In the biodegradable film of the present invention, the lactic acid resin (A) is composed of a block copolymer having a polyether segment and a polylactic acid segment, and a block copolymer having a polyester segment and a polylactic acid segment. It is preferable to consist of at least one selected from homopolylactic acid.

In the biodegradable film of the present invention, the biodegradable resin (B) is at least one selected from the group consisting of polybutylene succinate, polybutylene succinate adipate, and polybutylene adipate terephthalate. preferable.

According to the present invention, there is provided a biodegradable film that is excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, and particularly exhibits a good effect by an inflation film-forming method. The biodegradable film of the present invention is mainly required for flexibility, tear resistance, transparency in addition to biodegradability and biomass. Agricultural multi-film, sheet for pine fumigation, compost bag, etc. It can be preferably used for agricultural and forestry applications, food packaging applications such as vegetables and fruits, individual packaging for clothing, handbags for shopping, garbage bags, bags for various industrial products, and the like.

It is an example of the cross-sectional photograph (magnification: 50,000 times) of the biodegradable film of this invention.

The present invention, as a result of diligent research on a biodegradable film that is excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, in particular, exhibits a good effect by the inflation film formation method. For the first time to solve such a problem by containing biodegradable resins other than lactic acid resins and biodegradable resins other than lactic acid resins, and by keeping the relationship between the content ratio of these resins and the dispersion state within certain conditions Is. That is, the present invention is a biodegradable film containing a lactic acid-based resin (A) and a biodegradable resin (B), wherein the biodegradable resin (B ) In a continuous phase composed of a lactic acid resin (A) dispersed in an elliptical shape long in the length direction of the film or in a layer shape long in the length direction of the film. ) And the biodegradable resin (B) in a total of 100% by mass, the content (% by mass) of the lactic acid resin (A) is P _A and the content (% by mass) of the biodegradable resin (B) is P _B. the thickness of the dispersion phase (nm) W _a, when the thickness of the continuous phase (nm) was W _B, a biodegradable film which satisfies the following equation.

W _A / W _B ≦ 2.0 × P _A / P _B
Hereinafter, the biodegradable film of the present invention will be described.
(Lactic acid resin (A))
It is important that the biodegradable film of the present invention contains a lactic acid resin (A). The lactic acid-based resin (A) as used in the present invention refers to those having 5 to 100% by mass of a lactic acid unit component based on 100% by mass of the whole polymer. Here, the component composed of lactic acid units is biomass (plant-derived raw material).

The lactic acid-based resin (A) in the present invention is composed of a polylactic acid-based resin in which the constituent component consisting of lactic acid units is 60% by mass or more and 100% by mass or less, and the constituent component consisting of lactic acid units is 5% by mass to 60% by mass. % Other lactic acid-based resin (in the lactic acid-based resin (A), a polymer having a lactic acid unit component content of 5 mass% or more and less than 60 mass% is simply referred to as “other lactic acid resin” hereinafter. Classified). The film of the present invention is not particularly limited as long as it contains the lactic acid-based resin (A), and it contains any of the polylactic acid-based resin or other lactic acid-based resins. The film preferably contains both a polylactic acid resin and another lactic acid resin as the lactic acid resin (A).

Hereinafter, first, a polylactic acid resin in which a constituent component composed of a lactic acid unit is 60% by mass or more and 100% by mass or less will be described.

The poly-L-lactic acid referred to in the present invention refers to those in which the content of L-lactic acid units is more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the lactic acid resin (A). On the other hand, the poly-D-lactic acid referred to in the present invention refers to those having a D-lactic acid unit content of more than 50 mol% and not more than 100 mol% in 100 mol% of all lactic acid units in the lactic acid resin (A).

Poly L-lactic acid changes in the crystallinity of the resin itself depending on the content ratio of the D-lactic acid unit. That is, if the content ratio of D-lactic acid units in poly-L-lactic acid increases, the crystallinity of poly-L-lactic acid decreases and approaches amorphous, and conversely the content ratio of D-lactic acid units in poly-L-lactic acid. As the amount decreases, the crystallinity of poly-L-lactic acid increases. Similarly, the crystallinity of the resin itself of poly D-lactic acid varies depending on the content ratio of L-lactic acid units. In other words, if the content ratio of L-lactic acid units in poly-D-lactic acid increases, the crystallinity of poly-D-lactic acid decreases and approaches amorphous, and conversely, the content ratio of L-lactic acid units in poly-D-lactic acid. As the amount decreases, the crystallinity of poly-D-lactic acid increases.

The content ratio of the L-lactic acid unit in the poly L-lactic acid used in the present invention, or the content ratio of the D-lactic acid unit in the poly D-lactic acid used in the present invention is a viewpoint for maintaining the mechanical strength of the composition. From 100 to 100 mol% of all lactic acid units, 80 to 100 mol% is preferable, and 85 to 100 mol% is more preferable.

The crystalline polylactic acid resin referred to in the present invention is a case where the polylactic acid resin is sufficiently crystallized under heating and then measured with a differential scanning calorimeter (DSC) in an appropriate temperature range. This refers to a polylactic acid resin in which the heat of crystal melting derived from the polylactic acid component is observed.

On the other hand, the amorphous polylactic acid resin referred to in the present invention refers to a polylactic acid resin that does not exhibit a clear melting point when measured in the same manner.

Also, when the main component of the lactic acid resin (A) used in the present invention is poly L-lactic acid, poly D-lactic acid is used. When the main component of the lactic acid resin (A) is poly D-lactic acid, poly D-lactic acid is used. It is also preferable to mix a small amount of L-lactic acid. This is because a stereocomplex crystal formed from poly L-lactic acid and poly D-lactic acid has a higher melting point than normal crystals and improves heat resistance. At this time, the mass average molecular weight Mw of the polylactic acid to be mixed in a small amount is smaller than the mass average molecular weight Mw of the main component polylactic acid, from the viewpoint of maintaining the mechanical strength of the film, and from the viewpoint of efficiently forming a stereocomplex crystal. Is preferable. The mass average molecular weight Mw of the polylactic acid mixed in a small amount is preferably 0.5 to 50%, more preferably 1 to 40%, more preferably 2 to 30% of the mass average molecular weight Mw of the main component polylactic acid. More preferably.

Further, the lactic acid resin (A) used in the present invention is a polylactic acid block copolymer composed of a segment composed of L-lactic acid units and a segment composed of D-lactic acid units. Is preferable. In this case, since the polylactic acid block copolymer forms a stereocomplex crystal in the molecule, the melting point is higher than that of a normal crystal. For efficient stereocomplex crystal formation, the segment length satisfying Mw _Y <Mw _X / 2 for the mass average molecular weight Mw _X of the polylactic acid block copolymer and the maximum mass average molecular weight Mw _Y of one unit of segment. It is preferable that

The polylactic acid resin used in the present invention may be either a homopolylactic acid composed only of lactic acid units or a polylactic acid resin copolymerized with other monomer units other than lactic acid. Other monomers include ethylene glycol, propylene glycol, butanediol, heptanediol, hexanediol, octanediol, nonanediol, decanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, glycerin, pentane Glycol compounds such as erythritol, bisphenol A, polyethylene glycol, polypropylene glycol and polytetramethylene glycol, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, malonic acid, glutaric acid, cyclohexanedicarboxylic acid , Terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4'-diphenyl ether dica Dicarboxylic acids such as boronic acid, 5-sodium sulfoisophthalic acid and 5-tetrabutylphosphonium isophthalic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid and other hydroxycarboxylic acids, caprolactone And lactones such as valerolactone, propiolactone, undecalactone, and 1,5-oxepan-2-one. The copolymerization amount of the other monomer units is preferably 0 to 30 mol%, preferably 0 to 10 mol%, based on 100 mol% of the whole monomer units in the polymer of the polylactic acid resin. Is more preferable. In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

The mass average molecular weight Mw of the polylactic acid resin used in the present invention is preferably 50,000 to 500,000, more preferably 80,000 to 400,000 in order to satisfy practical mechanical properties. More preferably, it is 10,000 to 300,000.

Next, another lactic acid resin in which the constituent component composed of lactic acid units is 5% by mass or more and less than 60% by mass will be described.

The biodegradable film of the present invention preferably uses a polylactic acid resin and another lactic acid resin simultaneously as the lactic acid resin (A) in order to exhibit flexibility, tear resistance, and transparency. Here, homopolylactic acid is more preferably used as the polylactic acid resin. The other lactic acid resin is particularly preferably a block copolymer having a polyether segment and a polylactic acid segment and / or a block copolymer having a polyester segment and a polylactic acid segment ( These block copolymers are hereinafter referred to as “block copolymer plasticizers”). Here, the plasticizing component is a polyether segment or a polyester segment. That is, the lactic acid resin (A) is more preferably used in combination with homopolylactic acid and a block copolymer plasticizer. Hereinafter, the “block copolymer plasticizer” will be described.

The block copolymer plasticizer develops flexibility by plasticizing the polylactic acid resin, plays a role as a compatibilizer between the polylactic acid resin and the biodegradable resin (B), and melts the polylactic acid resin. Tear resistance and transparency are exhibited by the role of forming a dispersion structure to be described later by adjusting the viscosity.

The mass ratio of the polylactic acid segment in the block copolymer plasticizer is preferably 50% by mass or less based on the total of the block copolymer plasticizer, since a desired flexibility can be imparted with a smaller amount of addition, preferably 5 mass. % Or more is preferable from the viewpoint of suppressing bleed-out. The number average molecular weight Mn of the polylactic acid segment in one molecule of the block copolymer plasticizer is preferably 1,200 to 10,000. When the number average molecular weight Mn of the polylactic acid segment in the block copolymer plasticizer is 1,200 or more, sufficient affinity is produced between the block copolymer plasticizer and the polylactic acid resin, A part of the segment is incorporated into a crystal formed from a polylactic acid-based resin and forms a so-called eutectic, thereby causing the block copolymer plasticizer to bind to the polylactic acid-based resin. Great effect in suppressing bleed-out of plasticizer. The number average molecular weight Mn of the polylactic acid segment in the block copolymer plasticizer is more preferably 1,500 to 6,000, and further preferably 2,000 to 5,000. The polylactic acid segment in the block copolymer plasticizer is such that L-lactic acid is 95 to 100% by mass or D-lactic acid is 95 to 100% by mass. Therefore, it is preferable.

Further, the block copolymer plasticizer has at least one selected from the group consisting of polyether-based segments and polyester-based segments, but a smaller amount is a block copolymer of a polyether-based segment and a polylactic acid segment. From the viewpoint of adding desired flexibility, it is preferable. Furthermore, in the block copolymer of a polyether segment and a polylactic acid segment, the polyether segment is more preferably a segment composed of a polyalkylene ether from the viewpoint of imparting desired flexibility with a smaller amount of addition. . Specifically, examples of the polyether-based segment include a segment made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, etc., and in particular, a segment made of polyethylene glycol is a polylactic acid-based segment. Since the affinity with the resin is high, the reforming efficiency is excellent, and a desired flexibility can be imparted with a small amount of addition, which is preferable.

In addition, when the block copolymer plasticizer has a segment made of polyalkylene ether, the polyalkylene ether segment tends to be oxidized and easily decomposed when heated at the time of molding or the like. It is preferable to use an antioxidant such as a hindered amine or a heat stabilizer such as a phosphorus.

When the block copolymer plasticizer has a polyester-based segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), polycaprolactone, or ethylene glycol, Polyesters composed of aliphatic diols such as propanediol and butanediol and aliphatic dicarboxylic acids such as succinic acid, sebacic acid and adipic acid are preferably used as the polyester segment.

The block copolymer plasticizer may contain both the polyether segment and the polyester segment in one molecule, or may be either one of the components. From the viewpoint of plasticizer productivity, cost, and the like, when using any one component, it is preferable to use a polyether-based segment from the viewpoint that desired flexibility can be imparted by adding a smaller amount of the plasticizer. That is, a preferred embodiment as a block copolymer plasticizer is a block copolymer of a polyether segment and a polylactic acid segment.

Furthermore, the number average molecular weight Mn of the polyether segment or the polyester segment in one molecule of the block copolymer plasticizer is preferably 7,000 to 20,000. By setting it as the said range, the composition which comprises the biodegradable film of this invention has sufficient softness | flexibility, and also the composition containing lactic acid-type resin (A) and biodegradable resin (B), In this case, the melt viscosity can be adjusted to an appropriate level, and the film forming processability such as the inflation film forming method can be stabilized.

There is no particular limitation on the order configuration of each segment block of the polylactic acid segment and at least one selected from the group consisting of the polyether segment and the polyester segment, but from the viewpoint of more effectively suppressing bleed out, at least 1 It is preferred that the polylactic acid segment of the block is at the end of the block copolymer plasticizer molecule.

Next, the case where polyethylene glycol having a hydroxyl terminal at both ends (hereinafter referred to as PEG) is employed as the polyether segment will be specifically described.

The number average molecular weight of PEG having hydroxyl groups at both ends (hereinafter, the number average molecular weight of _PEG is Mn _PEG ) 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 _L parts by mass are added to w _E parts by mass of PEG having hydroxyl groups at both ends, lactide is subjected to ring-opening addition polymerization at both hydroxyl groups of PEG and sufficiently reacted, so that PLA is substantially obtained. A block copolymer of the type -PEG-PLA can be obtained (where PLA stands for polylactic acid). This reaction is performed in the presence of a catalyst such as tin octylate as necessary. The number average molecular weight Mn of one polylactic acid segment of this block copolymer plasticizer can be determined by (1/2) × (w _L / w _E ) × Mn _PEG . The mass percentage of the total block copolymer plasticizer of the polylactic acid segment component can be determined by _{_{100 × w L / (w L}} + w E). Furthermore, the mass ratio of the plasticizer component excluding the polylactic acid segment component to the entire block copolymer plasticizer can be obtained by 100 × w _E / (w _L + w _E ).

In order to evaluate the number average molecular weight Mn of the polyether segment, the polyester segment, and the polylactic acid segment in the block copolymer plasticizer from the biodegradable film in the present invention, a block copolymer plasticizer is used. As a separation method, for example, a biodegradable film is uniformly dissolved in an appropriate good solvent such as chloroform and then dropped into an appropriate poor solvent such as water or a water / methanol mixed solution, followed by filtration to obtain a polylactic acid resin, Examples include a reprecipitation method in which a precipitate mainly containing the degradable resin (B) is removed, and a solvent of the filtrate is volatilized to obtain a block copolymer plasticizer. For the block copolymer plasticizer thus separated, the number average molecular weight Mn is measured using gel permeation chromatography (GPC), and the polylactic acid segment, the polyether-based segment and / or the polyester are measured by ¹ H-NMR measurement. Identify system segments. And the molecular weight of one polylactic acid segment which the block copolymer has is Mn × {1 / (number of polylactic acid segments)} × (I _PLA × 72) / {(I _PE × UM _PE / N _PE ) + (I _PLA × 72)} is calculated. However, I _PLA is the signal integral intensity in ¹ H-NMR measurement derived from hydrogen of the methine group in the PLA main chain, and I _PE is ¹ H-NMR measurement derived from the polyether-based segment and / or the polyester-based segment. UM _PE is the molecular weight of the monomer unit of the polyether-based segment and / or the polyester-based segment, and N _PE is a chemical that gives the signal integrated strength of the polyether-based segment and / or the polyester-based segment. The number of equivalent protons. The number average molecular weight of the polyether segment and / or polyester segment can be calculated by Mn− (number average molecular weight of polylactic acid segment) × (number of polylactic acid segments). Here, Mn represents the number average molecular weight of the block copolymer plasticizer measured by GPC.

The block copolymer plasticizer contained in the composition constituting the biodegradable film of the present invention is preferably 1 to 30% by mass in 100% by mass of the lactic acid resin (A). By setting the content to 1% by mass or more, the functions as the plasticizer, compatibilizing agent and melt viscosity modifier described above can be sufficiently expressed. , Strength, durability, and bleed-out resistance of the plasticizer are increased. The content of the block copolymer plasticizer is preferably 5 to 25% by mass, more preferably 10 to 20% by mass in 100% by mass of the lactic acid resin (A).

The content of the block copolymer plasticizer in 100% by mass of the lactic acid resin (A) is preferably 1 to 30% by mass, but the remaining 70 to 99% by mass is a polylactic acid resin. It is preferable.

The production method of the lactic acid-based resin (A) will be described in detail later, 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.

The biodegradable film of the present invention preferably contains 5 to 60% by mass of the lactic acid resin (A) in 100% by mass of the entire composition constituting the biodegradable film. By setting the lactic acid resin (A) to 5% by mass or more in 100% by mass of the entire composition constituting the biodegradable film, the lactic acid resin (A) becomes 60%. By setting it as the mass% or less, it becomes what was excellent in the softness | flexibility and tear resistance. In 100% by mass of the entire composition constituting the biodegradable film, the lactic acid resin (A) is more preferably 20 to 55% by mass, and further preferably 35 to 50% by mass.
(Biodegradable resin (B))
In order for the biodegradable film of the present invention to exhibit flexibility and tear resistance, it is important to contain a biodegradable resin (B) other than the lactic acid resin (A). The biodegradable resin (B) also plays a role of adjusting the biodegradation rate and adjusting the melt viscosity of the entire composition constituting the biodegradable film to form stable bubbles, particularly in the inflation film forming method.

Specific examples of the biodegradable resin (B) include, for example, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), polycaprolactone, polyethylene succinate, Aliphatic polyesters such as polybutylene succinate, polybutylene succinate and adipate, aliphatic polyesters represented by polyethylene succinate and terephthalate, polybutylene succinate and terephthalate, polybutylene adipate and terephthalate, etc. Plastic starch, a resin composed of starch and aliphatic (aromatic) polyester, cellulose ester and the like are preferably used. Moreover, it is preferable to use a plant-derived raw material for some or all of these structural components from the viewpoint of enhancing the biomass properties.

Among them, the biodegradable resin (B) is selected from the group consisting of polybutylene succinate, polybutylene succinate adipate and polybutylene adipate terephthalate because it has a great effect of improving flexibility and tear resistance. More preferably, at least one of these is used. Polybutylene adipate terephthalate has the highest effect of improving flexibility and tear resistance.

The biodegradable resin (B) contained in the biodegradable film of the present invention is preferably 40 to 95% by mass in 100% by mass of the entire composition constituting the biodegradable film. When it is 40% by mass or more, an effect of improving flexibility and tear resistance is easily obtained, and when it is 95% by mass or less, transparency and appropriate biodegradability can be imparted. In 100% by mass of the entire composition constituting the biodegradable film, the biodegradable resin (B) is more preferably 45 to 80% by mass, and further preferably 50 to 65% by mass.
(Plasticizer)
The biodegradable film of the present invention may contain a plasticizer as long as it does not hinder biodegradability, mainly to impart flexibility.

Examples of the plasticizer include phthalate esters such as diethyl phthalate, dioctyl phthalate and dicyclohexyl phthalate, di-1-butyl adipate, di-n-octyl adipate, di-n-butyl sebacate, and azelain. Aliphatic dibasic acid esters such as di-2-ethylhexyl acid, phosphoric acid ester systems such as diphenyl-2-ethylhexyl phosphate, diphenyloctyl phosphate, tributyl acetylcitrate, tri-2-ethylhexyl acetylcitrate, acetyl Hydroxy polyvalent carboxylic acid esters such as tributyl citrate, fatty acid esters such as methyl acetylricinoleate and amyl stearate, polyhydric alcohol esters such as glycerol triacetate and triethylene glycol dicaprylate, epoxidized soybean oil, Examples include epoxy-based plasticizers such as oxypropylated linseed oil butyl ester and octyl epoxy stearate, polyester-based plasticizers such as polypropylene glycol sebacate, polyalkylene ethers such as polyethylene glycol, ether esters, and acrylates. . And it is also possible to use a mixture of two or more of these as a plasticizer.

Furthermore, from the viewpoint of the bleed-out resistance of the plasticizer and the blocking resistance of the film, for example, polyethylene glycol having a number average molecular weight Mn of 1,000 or more, it is solid at ordinary temperature (20 ° C. ± 15 ° C.), that is, the melting point is 35 ° C. Is preferably exceeded.
(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
The polylactic acid resin which is one of the lactic acid resins (A) contained in the composition constituting the biodegradable film of the present invention is a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. There may be. By using a mixture, the advantages of both crystalline and amorphous polylactic acid resins can be achieved.

As described above, the crystalline polylactic acid resin was measured with a differential scanning calorimeter (DSC) in an appropriate temperature range after the polylactic acid resin was sufficiently crystallized under heating. In this case, it refers to a polylactic acid resin in which a melting point derived from a polylactic acid component is observed.

On the other hand, the amorphous polylactic acid resin refers to a polylactic acid resin that does not exhibit a clear melting point when the same measurement is performed.

That is, the inclusion of the crystalline polylactic acid resin is suitable for improving the tear resistance, heat resistance, and blocking resistance of the film. When the block copolymer plasticizer is used, the crystalline polylactic acid resin has a great effect on bleed-out resistance by forming a eutectic with the polylactic acid segment of the block copolymer plasticizer. To do.

On the other hand, the inclusion of an amorphous polylactic acid resin is suitable for improving the flexibility and bleed-out resistance of the film. This has an effect of providing an amorphous part in which the plasticizer can be dispersed.

The crystalline polylactic acid-based resin used in the biodegradable film of the present invention is obtained from the viewpoint of improving tear resistance, heat resistance, and blocking resistance, the content of L-lactic acid units in poly L-lactic acid, or poly The content ratio of D-lactic acid units in D-lactic acid is preferably 94 to 100 mol%, more preferably 96 to 100 mol%, and still more preferably 98 to 100 mol% in 100 mol% of all lactic acid units.

When the amount of the polylactic acid resin in the composition constituting the biodegradable film of the present invention is 100% by mass, the ratio of the crystalline polylactic acid resin is preferably 5 to 80% by mass. The amount is more preferably 60% by mass, and further preferably 20 to 40% by mass.
(Compatibilizer)
In the biodegradable film of the present invention, it is preferable to contain a compatibilizing agent for polylactic acid resin and biodegradable resin (B) for the purpose of improving tear resistance and transparency.

Although the kind of compatibilizer is not particularly limited, it is mainly classified into the following three types. The first is the structure of the polylactic acid resin itself, a structure similar to the polylactic acid resin, at least one structure selected from structures having good compatibility with the polylactic acid resin, and the biodegradable resin (B). It has a structure having at least one structure selected from the structure itself, a structure similar to the biodegradable resin (B), and a structure compatible with the biodegradable resin (B). Second, it can be chemically bonded to the terminal group (carboxyl group or hydroxyl group) of either or both of the lactic acid resin (A) and the biodegradable resin (B) by addition reaction or condensation reaction. It has a functional group. The third one has a catalytic ability for a condensation reaction or a transesterification reaction between the lactic acid resin (A) and the biodegradable resin (B).

As specific examples of the first class, polylactic acid has good compatibility with acrylic resins, and examples thereof include polyolefin / acrylic resin copolymers, polyester / acrylic resin copolymers, and the like. It is done.

As specific examples of the second class, the functional group contains at least one functional group selected from a glycidyl group, an acid anhydride group, a carbodiimide group, an isocyanate group, an oxazoline group, and an amino group. Compounds.

Examples of the compound containing a glycidyl group include glycidyl ether compounds, glycidyl ester compounds, glycidyl amine compounds, glycidyl imide compounds, glycidyl (meth) acrylate compounds, and alicyclic epoxy compounds. Commercially available products include a copolymer of ethylene, acrylate ester and glycidyl (meth) acrylate, DuPont's “BIOMAX” (registered trademark) Strong series, Arkema ’s “LOTADER” (registered trademark) series, BASF's “JONCRYL” (registered trademark) series of glycidyl group-containing acrylic / styrene copolymers, “Reseda” (registered trademark) series of Toagosei Co., Ltd., glycidyl group-containing acrylic resins, Alfon "(registered trademark) series.

Examples of the compound containing an acid anhydride group include compounds containing succinic anhydride, maleic anhydride, phthalic anhydride, and the like. Commercially available products include the “BONDINE” ® (registered trademark) series of Arkema, which is a copolymer of ethylene and acrylic acid ester and maleic anhydride, and “OREVAC” ® (registered) of Arkema, a maleic anhydride graft polymer. Trademark) series, DuPont's “Bynel” series, Sanyo Chemical Industries' “Umex” (registered trademark) series, Kraton made by copolymerizing maleic anhydride with styrene-ethylene-butylene-styrene copolymer (SEBS) The company “KRATON” (registered trademark) series and the like.

A compound having a carbodiimide group is a compound having at least one carbodiimide group represented by (—N═C═N—) in the molecule, and those commercially available are those manufactured by Nisshinbo Industries, Ltd. Examples include “Carbodilite” (registered trademark) series and “STABAXOL” (registered trademark) series of Rhein Chemie.

Examples of the compound containing an isocyanate group include hexamethylene diisocyanate.

Specific examples of those classified in the third category include organometallic compounds and sulfur acid compounds. Examples of the organometallic compound include carboxylic acid metal salt compounds such as zinc stearate, zinc acetate, magnesium acetate and manganese acetate, organotitanium compounds such as titanium tetraisopropoxide, and organoaluminum compounds. Examples of the sulfur acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, sodium p-toluenesulfonate, sodium dodecylbenzenesulfonate, and the like.

The blending amount of the compatibilizing agent in the biodegradable film of the present invention is 100 in total for the lactic acid-based resin (A) and the biodegradable resin (B) for the first and second classifications. The amount is preferably 0.01 to 30 parts by mass, more preferably 0.05 to 20 parts by mass, still more preferably 0.1 to 10 parts by mass, and particularly preferably 0.5 to 3 parts by mass with respect to parts by mass. By making the compounding amount of the compatibilizing agent 0.01 parts by mass or more, there is a tendency that the effect of improving the transparency and tear resistance can be sufficiently expressed. A decrease in fluidity can be suppressed. In addition, the above-mentioned third classification is preferably 0.01 to 3 parts by mass with respect to 100 parts by mass in total of the lactic acid resin (A) and the biodegradable resin (B), and 0.05 ˜2 parts by mass is more preferable, and 0.1 to 1 part by mass is more preferable. By making the compounding amount of the compatibilizing agent 0.01 parts by mass or more, there is a tendency that the effect of improving transparency and tear resistance can be sufficiently expressed, and by making it 3 parts by mass or less, the melt viscosity is lowered. Can be suppressed.
(Distributed structure)
The biodegradable film of the present invention has a dispersed phase composed of a lactic acid resin (A) in a continuous phase composed of a biodegradable resin (B) other than a lactic acid resin, in a cross section in the length direction and the thickness direction of the film. Lactic acid in a total of 100% by mass of the lactic acid-based resin (A) and the biodegradable resin (B) having a structure in which the film is dispersed in an elliptical shape that is long in the length direction of the film or a layer that is long in the length direction of the film The content (% by mass) of the resin (A) is P _A , the content (% by mass) of the biodegradable resin (B) is P _B , the thickness (nm) of the dispersed phase is W _A , and the continuous phase the thickness (nm) of when the W _B, it is important to satisfy the following equation.

W _A / W _B ≦ 2.0 × P _A / P _B
Here, the continuous phase and the disperse phase are a so-called sea-island structure sea and a discontinuous phase.

In the case of the biodegradable film of the present invention, since the dispersed phase is long in the length direction of the film, it may be difficult to determine either the continuous phase or the dispersed phase. In that case, when confirming the dispersion structure with a transmission electron microscope (TEM), which will be described later, the observation range is shifted in the length direction of the film, and it is determined that the tip of the island structure is the dispersed phase. To do.

The inventors have made the biodegradable film flexible and tear resistant by the lactic acid resin (A) and the biodegradable resin (B) constituting the biodegradable film having the above-described dispersion structure. It was found that transparency and biomass can be imparted. In other words, polylactic acid-based resin is a resin that has both biomass and biodegradability, but among the biodegradable resins, the tear resistance is low, so the following three factors (i) to (iii) are adjusted. I found out that the problem was solved.

(i) Since the lactic acid resin (A) is a dispersed phase and the biodegradable resin (B) is a continuous phase, the flexibility and tear resistance of the film can be improved. Methods for such a phase structure is of (a) or to the preferred range described later the ratio of P _A and P _B, (b) lactic acid resin (A) and biodegradable resin (B) It is mentioned to make the relationship of melt viscosity into a preferable range described later.

Here, the dispersed phase of the lactic acid-based resin (A) means that the lactic acid-based resin (A) is the largest component in mass among all the components in the dispersed phase. Therefore, the dispersed phase comprising the lactic acid resin (A) includes components other than the lactic acid resin (A), for example, various additives, organic lubricants, particles, and other components other than the lactic acid resin (A). But you can.

Similarly, the continuous phase of the biodegradable resin (B) means that the biodegradable resin (B) is the largest component in mass in all the components in the continuous phase. Therefore, the dispersed phase made of the biodegradable resin (B) may contain components other than the biodegradable resin (B).

(ii) A structure in which the disperse phase composed of the lactic acid-based resin (A) is dispersed in an elliptical shape that is long in the length direction of the film or a layer that is long in the length direction of the film in the cross section in the length direction and the thickness direction of the film By taking the above, the influence of the lactic acid resin (A) on the tear resistance of the film can be reduced. As a result, the tear resistance of the film can be improved, and further, the transparency can be improved. Here, “elliptical” and “layered” refer to the ends on both sides in the length direction when observed with a transmission electron microscope, which will be described later, at a magnification at which the entire thickness direction of the film can be seen. The case where it is formed is “elliptical”, and the case where at least one end in the length direction is not observed is “layered”. Examples of the method for obtaining such a dispersion structure include the above-described method (b) and (c) when the film is formed by inflation, the blow ratio and the draw ratio are set in the preferred ranges described later.

(iii) By satisfying W _A / W _B ≦ 2.0 × P _A / P _B , the influence of the lactic acid resin (A) on the tear resistance of the film can be reduced. Tearability can be improved. This condition indicates that the ratio of the thickness of the dispersed phase to the continuous phase (W _A / W _B ) in a film produced at a certain blending ratio (P _A / P _B ) is below a certain value, Examples of the method for satisfying this condition include the method (b) and the method (c). This condition is preferably _{_{_{W A / W B ≦ 1.5P A}}} / P B, and more preferably _{_{_{W A / W B ≦ 1.2P A}}} / P B.

Biodegradable film of the present invention, a high transparency, for expressing a high tear resistance, it is preferable that the thickness W _A of the disperse phase is 5 ~ 100 nm. More preferably, it is 10 to 60 nm, further preferably 20 to 50 nm, and particularly preferably 20 to 40 nm. For the same purpose, the thickness _{W B} of the dispersed phase is preferably 10 ~ 100 nm. The thickness is more preferably 30 to 80 nm, further preferably 30 to 70 nm, and particularly preferably 30 to 60 nm. The thickness _{W A} of the dispersed phase to the 5 ~ 100 nm, there can be mentioned the method of the method and said (b) (c).

This is because, in the cross section of the film, the lactic acid resin (A), which is relatively weak in tear resistance, is finely dispersed to express the tear resistance of the entire film. Also, the lactic acid resin (A), This is because the thickness of both phases of the biodegradable resin (B) is made smaller than the wavelength of visible light so as to exhibit transparency.
(A content of _{P A} lactic acid-based resin (A), the content of _P B of the biodegradable resin (B))
The biodegradable film of the present invention has the above-described dispersion structure and exhibits high biomass properties in addition to high flexibility, transparency, and tear resistance, so that P _A : P _B = 5: 95-60: 40 is preferred. More preferably, P _A : P _B = 20: 80 to 55:45, and still more preferably P _A : P _B = 35: 65 to 50:50. Here, the unit of _{P A} and _{P B} are by weight.
(Relationship between melt viscosity of lactic acid resin (A) and biodegradable resin (B))
Since the biodegradable film of the present invention satisfies the above-mentioned conditions for the dispersion structure, the melt viscosity of the lactic acid resin (A) at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ is η _A , a temperature of 200 ° C., and a shear rate of 100 sec ^{−. When} the melt viscosity of the biodegradable resin (B) in ¹ is η _B , it is preferable that 0.3 ≦ η _A / η _B ≦ 1.1 is satisfied. 0.5 ≦ η _A / η _B ≦ 0.9 is more preferable, and 0.5 ≦ η _A / η _B ≦ 0.6 is more preferable.

Here, the melt viscosity η _A of the lactic acid-based resin (A) is measured as a resin obtained by melt-kneading both when the lactic acid-based resin (A) is composed of a polylactic acid-based resin and another lactic acid-based resin.

The preferred range of the melt viscosity η _A of the lactic acid resin (A) is 400 to 1,300 Pa · s, more preferably 400 to 1,000 Pa · s, and still more preferably 700 to 1,000 Pa · s. s.

The preferable range of the melt viscosity η _B of the biodegradable resin (B) is 700 to 1,300 Pa · s, more preferably 1,100 to 1,300 Pa · s, and still more preferably 1,100 to 1 250 Pa · s, particularly preferably 1,200 to 1,250 Pa · s.
(Tear strength)
The biodegradable film of the present invention preferably has a tear strength of 5 N / mm or more in the length direction and width direction of the film by the trouser tear method defined in JIS K7128-1 (1998). . More preferably, it is 11 N / mm or more, More preferably, it is 19 N / mm or more. The higher the tear strength, the better. However, the upper limit is considered to be about 200 N / mm as a practically achievable numerical value. If the tear strength in the length direction and width direction of the film is 5 N / mm or more, it is used for agricultural multi-film for agriculture, sheet for fumigation of pine worms, compost bags, food packaging for vegetables and fruits, clothing When used for individual packaging, shopping handbags, garbage bags, or other industrial products, sufficient tear resistance can be obtained, and it is difficult to break, improving practicality.

Examples of the method for setting the tear strength in the length direction and the width direction of the film to 5 N / mm or more include the method (a), the method (b), and the method (c).
(Elongation)
The biodegradable film of the present invention preferably has an elongation in the length direction and width direction (direction perpendicular to the length direction) of 200% or more and 700% or less. When the elongation is 200% or more, the tear resistance becomes high, and in addition, various uses such as agricultural / forestry use, food packaging use, individual packaging for clothing, handbags for shopping, garbage bags, and bags for various industrial products. It is difficult to break when used for applications such as, and the practicality improves. Further, when the elongation is 700% or less, tarmi and wrinkles are less likely to occur during roll-to-roll running and during winding, and the roll winding shape and unwinding property are improved. The elongation in the length direction and the width direction is more preferably from 250% to 600%, and even more preferably from 300% to 500%.

As a method for adjusting the elongation in the length direction and the width direction to 200 to 700%, the blending amounts of the lactic acid resin (A) and the biodegradable resin (B) are within the above-mentioned preferred ranges, respectively. A method is mentioned.
(Tensile modulus)
The biodegradable film of the present invention preferably has a tensile modulus in the length direction and the width direction of 100 to 1,500 MPa in order to impart sufficient flexibility. The tensile modulus is more preferably 200 to 1,200 MPa, and further preferably 300 to 1,000 MPa.

As a method for setting the tensile modulus in the length direction and the width direction to 100 to 1,500 MPa, the blending amounts of the lactic acid resin (A) and the biodegradable resin (B) are set to the preferred ranges described above, respectively. The method of doing is mentioned.
(Thickness)
The biodegradable film of the present invention preferably has a film thickness of 5 to 200 μm. By setting the film thickness to 5 μm or more, the firmness of the film becomes strong, the handleability is excellent, and the roll winding shape and unwinding property are good. Flexibility is improved by setting the film thickness to 200 μm or less. Applications such as agriculture and forestry, food packaging, individual packaging for clothing, handbags for shopping, garbage bags, and bags for various industrial products In this case, in the inflation film-forming method, bubbles do not become unstable due to their own weight. The film thickness is more preferably 7 to 150 μm, further preferably 10 to 100 μm, and particularly preferably 12 to 50 μm.
(Organic lubricant)
The composition constituting the biodegradable film of the present invention preferably contains 0.1 to 5% by mass of an organic lubricant in 100% by mass of the whole composition. In this case, blocking after winding can be favorably suppressed. In addition, problems such as a decrease in melt viscosity and deterioration of workability due to excessive addition of an organic lubricant, or poor appearance such as bleed out and haze up when formed into a film are less likely to occur.

The organic lubricant is not particularly limited, and various materials can be used. For example, fatty acid amide organic lubricants can be used. Among them, an organic lubricant having a relatively high melting point, such as ethylene bis stearic acid amide, ethylene bis oleic acid amide, and ethylene bis lauric acid amide, is preferable from the viewpoint of expressing better blocking resistance.
(Haze)
The biodegradable film of the present invention preferably has a haze of 50% or less, more preferably 40% or less, still more preferably 30% or less, and particularly preferably 20% or less. If the haze is 50% or less, the contents may be formed when processed into food packaging applications, individual packaging for clothing, handbags for shopping, garbage bags, or bags for various industrial products. In many cases, it is preferable due to its high design properties such as easy confirmation and good appearance as a product. Since the haze of the biodegradable film is difficult to be less than 1% from the general characteristics of the lactic acid resin (A) and the biodegradable resin (B), the lower limit is about 1%. is there.
(Additive)
The composition constituting the biodegradable film of the present invention may contain additives other than those described above as long as the effects of the present invention are not impaired. For example, known crystal nucleating agents, antioxidants, UV stabilizers, anti-coloring agents, matting agents, deodorants, flame retardants, weathering agents, antistatic agents, antioxidants, ion exchange agents, and tackifying Agents, antifoaming agents, color pigments, dyes, end-capping agents and the like can be contained.

As a crystal nucleating agent, an organic crystal nucleating agent is a melamine compound, phenylphosphonic acid metal salt, benzenecarboxamide derivative, aliphatic carboxylic acid hydrazide, aromatic carboxylic acid hydrazide, sorbitol compound, amino acid, polypeptide, metal Phthalocyanine and the like can be preferably used. As the inorganic crystal nucleating agent, silicate minerals such as talc, clay, mica and kaolinite, carbon black and the like can be preferably used.

As the antioxidant, hindered phenols, hindered amines and the like can be preferably used.

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 preferably used.

Examples of the end capping agent include addition reaction type compounds such as carbodiimide compounds, epoxy compounds, and oxazoline compounds. End-capping the lactic acid-based resin (A) and the biodegradable resin (B) is preferable from the viewpoint of reducing strength reduction due to hydrolysis and imparting good durability by lowering the carboxyl group terminal concentration.
(particle)
Particles may be added to the composition constituting the biodegradable film of the present invention for the purpose of improving the slipperiness and blocking resistance of the processed product.

Such particles are not particularly limited, whether they are inorganic particles or organic particles. Examples thereof include silicon oxide such as silica, various carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate, calcium sulfate, and barium sulfate. Various sulfates such as Wollastonite, Potassium titanate, Aluminum boride, Sepiolite, etc. Various phosphates such as Lithium phosphate, Calcium phosphate, Magnesium phosphate, Aluminum oxide, Titanium oxide, Zirconium oxide In addition, particles composed of various oxides such as zinc oxide, hydroxides such as aluminum hydroxide and magnesium hydroxide, various salts such as lithium fluoride, and the like can be used.
(Production method)
Next, the method for producing the biodegradable film of the present invention will be specifically described, but the present invention is not limited thereto.

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.

In obtaining the composition constituting the biodegradable film of the present invention, that is, the composition containing the lactic acid resin (A), the biodegradable resin (B), or other components, each component is used as a solvent. It is possible to produce a composition by removing the solvent after uniformly mixing the dissolved solution, but steps such as dissolution of the raw material in the solvent, removal of the solvent, etc. are unnecessary, and each is a practical production method. It is preferable to employ a melt-kneading method for producing a composition by melt-kneading the components. 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 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 180 ° C. to 210 ° C. from the viewpoint of preventing deterioration of the lactic acid resin (A).

The biodegradable film of the present invention can be obtained, for example, by a known film production method such as a known inflation method, a tubular method, or a T-die cast method, using the composition obtained by the above-described method. In order to obtain the dispersion structure of the biodegradable film of the present invention, the inflation method is preferred.

In producing the biodegradable film of the present invention, for example, when the composition obtained by the above-described method is once pelletized, melt-kneaded again and extruded and formed into a film, the pellet is heated at 60 to 100 ° C. It is preferable to use a composition containing a polylactic acid resin or the like having a moisture content of 1,200 ppm or less, preferably 500 ppm or less, more preferably 200 ppm or less by drying for 6 hours or more. Furthermore, it is preferable to reduce the lactide content in the composition containing a polylactic acid resin or the like by vacuum drying under a high vacuum with a degree of vacuum of 10 Torr or less. The water content of the composition containing a polylactic acid resin or the like is 1,200 ppm or less, and further, by reducing the lactide content, hydrolysis during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. It is also preferable because the melt viscosity at the time of preparing a composition containing a polylactic acid resin or the like can be set to an appropriate level and the film forming process can be stabilized. From the same point of view, when pelletizing or melt-extrusion / film formation, a twin-screw extruder with a vent hole is used and melt extrusion is performed while removing volatiles such as moisture and low molecular weight substances. It is preferable.

When the biodegradable film of the present invention is produced by the inflation method, for example, the composition prepared by the method as described above is melt-extruded by a twin-screw extruder with a vent hole, led to an annular die, and extruded from the annular die. Then, dry air is supplied inside and formed into a balloon shape (bubble), further air-cooled and solidified uniformly by an air ring, and taken up at a predetermined take-up speed while being folded flat with a nip roll, then both ends as necessary. Alternatively, one end may be cut open and wound.

When the biodegradable film of the present invention is formed into an inflation film, it is important to adjust the blow ratio and the draw ratio during the inflation film formation. Here, the blow ratio is the stretch ratio in the width direction of the film, (the length in the width direction of the film when one end is cut open and wound) / (the length of the circumference of the annular die) Ask for. The draw ratio is the draw ratio in the length direction of the film and is expressed by (winding speed) / (discharge speed from the annular die). ) / {(Film thickness after film formation) × (blow ratio)}. In the biodegradable film of the present invention, the blow ratio is preferably 1.6 to 4.0 and the draw ratio is preferably 10 to 50 in order to form the dispersion structure described above. The blow ratio is more preferably 2.2 to 3.4, still more preferably 2.8 to 3.4. The draw ratio is more preferably 15 to 45, still more preferably 20 to 35.

The lip gap of the annular die may be adjusted so as to have a desired film thickness when the film is formed with the above-mentioned preferable blow ratio and draw ratio, but is usually 0.6 to 1.8, preferably 1.2 to 1.6. The annular die is preferably a spiral type from the viewpoint of thickness accuracy and uniformity, and from the same viewpoint, the annular die is preferably a rotary type.

In addition, the extrusion temperature when the biodegradable film of the present invention is formed into a film is usually in the range of 150 to 240 ° C., preferably 180 to 210 ° C., and the temperature of the annular die is usually in the range of 150 to 190 ° C. 155 to 170 ° C is preferable.

After being formed into a film, heat treatment may be performed in a heating roll or an oven in order to suppress thermal shrinkage of the 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) Dispersion structure The film is dyed with ruthenic acid, embedded in an epoxy resin, and then cut in a direction parallel to the length direction of the film and perpendicular to the film surface using an ultramicrotome. Produced. Using a transmission electron microscope (H-7100, manufactured by Hitachi High-Technology Co., Ltd.), the cut surface was first observed at a magnification at which the entire thickness direction of the film could be seen under the condition of an acceleration voltage of 100 kV. When it was divided into three equal parts in the vertical direction, a photograph was taken at a magnification of 50,000 times for the central part in the thickness direction for each of the three divided areas.

Cut the photographed photo into a 15cm x 15cm square with the length direction of the film vertical, and draw a line across the center of the vertical length (ie draw a line that divides the square vertically into equal areas) . With reference to the intersection of the line and the boundary portion of the phase dispersed in the shape of an ellipse that is long in the length direction of the film or a layer that is long in the length direction of the film, the phase structure at the left and right ends is omitted, and all the remaining dispersed phases are omitted. The thickness of the continuous phase was measured in units of 0.1 mm. Similarly, for the remaining two regions, the thickness of the dispersed phase and the continuous phase is measured, and after calculating the average value of all of the dispersed phase and the continuous phase, 1 mm of actual measurement is converted to 20 nm, and W _A and W _B (Nm) (the first decimal place was rounded off).

In addition, when it is difficult to determine either the continuous phase or the dispersed phase because the dispersed phase is long in the length direction of the film, the length of the film is confirmed in the confirmation of the dispersed structure with a transmission electron microscope (TEM). The observation range is shifted in the direction, and it is determined that the tip of the island structure is the dispersed phase.

FIG. 1 shows an example of a cross-sectional photograph of the film (magnification: 50,000 times).
(2) Tensile modulus (MPa)
A sample was cut into a strip shape having a length of 150 mm in the measurement direction and a width of 10 mm, and stress-strain measurement was performed as follows in an atmosphere at a temperature of 23 ° C. and a humidity of 65% RH. Using Tensilon UCT-100 manufactured by Orientec Co., Ltd., a tensile test was performed at an initial length between chucks of 50 mm and a tensile speed of 300 mm / min. Using the first linear part of the stress-strain curve, the distance between two points on the straight line The tensile modulus was calculated by dividing the difference in stress by the difference in strain between the same two points. The measurement was performed 10 times in total, and the average value (rounded to the first decimal place) was adopted. This was calculated for each of the length direction and the width direction.
(3) Tear strength (N / mm)
In an atmosphere of a temperature of 23 ° C. and a humidity of 65% RH, tear strength measurement by a trouser tear method was performed as follows according to JIS K 7128-1 (1998). Using Tensilon UCT-100 manufactured by Orientec Co., Ltd., the measurement was performed 10 times in total at a test speed of 200 mm / min, and the average value (rounded to the first decimal place) was adopted. This was calculated for each of the length direction and the width direction.
(4) Haze (%)
Using a haze meter HGM-2DP manufactured by Suga Test Instruments Co., Ltd., the haze value was measured according to the method specified in JIS K 7136 (2000). The measurement was performed 5 times by changing the measurement location for each sample, and the average value (rounded to the first decimal place) was adopted.
(5) Melt viscosity (Pa · s)
Using a flow tester CFT-500A manufactured by Shimadzu Corporation (die diameter 1 mm, die length 10 mm, plunger cross-sectional area 1 cm ² ), measured at a temperature of 200 ° C. with a preheating of 3 minutes, a melt viscosity value at a shear rate of 100 sec ⁻¹ (Pa · s) (rounded to the first decimal place) was adopted.
(6) Biomass degree (%)
The resin composition ratio (mass%) derived from biomass when the entire resin composition constituting the film was 100 mass% (rounded to the first decimal place) was evaluated according to the following criteria.

excellent: 38% or more good: 25% or more, less than 38% fair: 5% or more, less than 25% bad: less than 5% (7) Mass average molecular weight Mw, number average molecular weight Mn
It is a value in terms of standard polymethyl methacrylate measured by gel permeation chromatography (GPC). GPC measurement uses a WATERS differential refractometer WATERS410 as a detector, WATERS MODEL510 high performance liquid chromatography as a pump, and Shodex GPC HFIP-806M and Shodex GPC HFIP-LG connected in series as a column. I went. The measurement conditions were a flow rate of 0.5 mL / min, hexafluoroisopropanol was used as the solvent, and 0.1 mL of a solution having a sample concentration of 1 mg / mL was injected.
[Lactic acid resin (A)]
(A1)
Poly L-lactic acid, mass average molecular weight Mw 200,000, D-form content 1.4 mol%, melting point 166 ° C., temperature 200 ° C., melt viscosity 1,400 Pa · s at a shear rate of 100 sec ⁻¹ , biomass degree 100%.
(A2)
Poly L-lactic acid, mass average molecular weight Mw 200,000, D-form content 12.0 mol%, no melting point, temperature 200 ° C., melt viscosity 1,250 Pa · s at a shear rate of 100 sec ⁻¹ , biomass degree 100%.
(A3)
62 parts by mass of polyethylene glycol having a number average molecular weight Mn of 8,000, 38 parts by mass of L-lactide and 0.05 parts by mass of tin octylate are mixed and polymerized in a reaction vessel equipped with a stirrer at 160 ° C. for 3 hours in a nitrogen atmosphere. Thus, a polylactic acid resin A3 having polylactic acid segments having a number average molecular weight Mn of 2,500 at both ends of polyethylene glycol having a number average molecular weight Mn of 8,000 was obtained. The biomass degree was 39%.
(A4)
A mixture of 30 parts by weight of the above (A1) and 70 parts by weight of the above (A2) was subjected to a twin screw extruder with a vacuum vent with a cylinder diameter of 200 ° C. and a screw diameter of 44 mm, and melted and kneaded while degassing the vacuum vent. And then pelletized to obtain a polylactic acid resin A4. The melt viscosity at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ was 1,300 Pa · s. The degree of biomass was 100%.
(A5)
A mixture of 27 parts by mass of (A1), 63 parts by mass of (A2) and 10 parts by mass of (A3) was subjected to a twin screw extruder equipped with a vacuum vent with a cylinder diameter of 200 ° C. and a screw diameter of 44 mm, and the vacuum vent part was removed. It melt-kneaded with air, homogenized, and then pelletized to obtain polylactic acid resin A5. The melt viscosity at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ was 1,000 Pa · s. The degree of biomass was 94%.
(A6)
A mixture of 24 parts by mass of (A1), 56 parts by mass of (A2) and 20 parts by mass of (A3) is subjected to a twin screw extruder with a vacuum diameter of 44 mm and a cylinder temperature of 200 ° C., and the vacuum vent is removed. The mixture was melt-kneaded with air, homogenized, and pelletized to obtain a polylactic acid resin A6. The melt viscosity at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ was 700 Pa · s. The degree of biomass was 88%.
(A7)
A mixture of 21 parts by mass of (A1), 49 parts by mass of (A2) and 30 parts by mass of (A3) was supplied to a twin screw extruder with a vacuum vent with a cylinder diameter of 200 ° C. and a screw diameter of 44 mm, and the vacuum vent part was removed. It melt-kneaded with air, homogenized, and then pelletized to obtain polylactic acid resin A7. The melt viscosity at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ was 400 Pa · s. The degree of biomass was 82%.
(A8)
Poly L-lactic acid, mass average molecular weight Mw 200,000, D-form content 5.0 mol%, melting point 150 ° C., temperature 200 ° C., melt viscosity 1,400 Pa · s at a shear rate of 100 sec ⁻¹ , biomass degree 100%.
[Biodegradable resin (B)]
(B1)
Polybutylene adipate terephthalate resin (trade name “Ecoflex” FBX7011 manufactured by BASF), melt viscosity of 1,200 Pa · s at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ .
(B2)
Polybutylene succinate resin (trade name “GS Pla” (registered trademark) AZ91T, manufactured by Mitsubishi Chemical Corporation), melt viscosity of 1,050 Pa · s at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ .
(B3)
Polybutylene succinate-adipate resin (manufactured by Showa Polymer Co., Ltd., trade name “Bionore” (registered trademark) # 3001), melt viscosity at a temperature of 200 ° C. and a shear rate of 100 sec ^−1, 1,250 Pa · s.
(B4)
Polybutylene adipate terephthalate resin (trade name “Ecoflex” FBX7020, manufactured by BASF), melt viscosity 650 Pa · s at a temperature of 200 ° C. and a shear rate of 100 sec ⁻¹ .
[Compatibilizer (C)]
(C1)
Ethylene / acrylic acid ester / glycidyl acrylate copolymer (“BIOMAX” (registered trademark) Strong 120 manufactured by DuPont).
(C2)
Ethylene / acrylic acid ester / glycidyl methacrylate copolymer ("LOTADER" (registered trademark) AX8900 manufactured by Arkema).
(C3)
Epoxy group-containing styrene / acrylic acid ester copolymer (“JONCRYL” (registered trademark) ADR-4368 manufactured by BASF).
(C4)
Epoxy group-containing acrylic graft resin (“Reseda” (registered trademark) GP-301, manufactured by Toagosei Co., Ltd.).
(C5)
Ethylene / acrylic acid ester / maleic anhydride copolymer (“BONDINE” (registered trademark) TX8030 manufactured by Arkema).
(C6)
Maleic anhydride modified styrene / ethylene / butylene / styrene copolymer (“KRATON” (registered trademark) FG1924 manufactured by Kraton).
(C7)
Polycarbodiimide (“Carbodilite” (registered trademark) LA-1 manufactured by Nisshinbo Industries, Inc.).
(C8)
Magnesium acetate (anhydrous).
(C9)
Titanium tetraisopropoxide.
(C10)
p-Toluenesulfonic acid.
(C11)
Hexamethylene diisocyanate.
[Production of biodegradable film]
(Comparative Example 1)
A mixture of 45 parts by mass of polylactic acid-based resin (A1) and 55 parts by mass of biodegradable resin (B1) was subjected to a twin screw extruder with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 45 mm and L / D = 32. The composition was obtained by melt-kneading while degassing the vacuum vent part, homogenizing, and pelletizing.

The pellets of this composition were vacuum-dried at a temperature of 60 ° C. for 12 hours using a rotary drum type vacuum dryer.

Pellets of this composition were supplied to a single screw extruder with a screw diameter of 65 mm at an extruder cylinder temperature of 190 ° C., and a blow ratio of 2.8 from a spiral annular die with a diameter of 250 mm, a lip clearance of 1.4 mm, and a temperature of 160 ° C. Then, it was extruded upward in a bubble shape, air-cooled with a cooling ring, taken up while being folded with a nip roll above the die, cut at both ends with an edge cutter and cut into two pieces, and each film was wound with a winder. By adjusting the discharge amount and the take-off speed, a film having a draw ratio of 25 and a final thickness of 20 μm was obtained. Table 1 shows the physical properties of the obtained film.

In Examples 1 to 26 and Comparative Examples 2 to 5, the final thickness was 20 μm in the same manner as in Comparative Example 1, except that the film raw materials and film forming conditions were changed as shown in Tables 1, 2 and 3. A film was obtained. The physical properties of the obtained film are shown in Table 1, Table 2, Table 3, and Table 4.

The biodegradable film of the present invention is a biodegradable film that is excellent in flexibility, tear resistance, transparency, and excellent in biomass properties, and in particular, exhibits a good effect by an inflation film forming method. Agricultural and forestry applications such as agricultural multi-films, pine worm fumigation sheets, compost bags, food packaging applications such as vegetables and fruits, which mainly require flexibility, tear resistance and transparency It can be preferably used for individual uses such as individual packaging for clothing, handbags for shopping, garbage bags, bags for various industrial products, and the like.

A: Dispersed phase B: Continuous phase

Claims

A biodegradable film containing a lactic acid-based resin (A) and a biodegradable resin (B) other than the lactic acid-based resin (A), wherein the biodegradable film is cross-sectional in the length direction and the thickness direction of the film. The continuous phase composed of the resin (B) has a structure in which the dispersed phase composed of the lactic acid-based resin (A) is dispersed in an ellipse that is long in the length direction of the film or a layer that is long in the length direction of the film. The content (mass%) of the lactic acid resin (A) in the total 100 mass% of the resin (A) and the biodegradable resin (B) is P A , and the content (mass%) of the biodegradable resin (B). the P B, the thickness of the dispersion phase (nm) W a, the thickness of the continuous phase (nm) is taken as W B, biodegradable film satisfies the following equation.
W A / W B ≦ 2.0 × P A / P B
The biodegradable film of claim 1 thickness W A of the disperse phase is 5 ~ 100 nm.
The biodegradable film according to claim 1 or 2, wherein the tear strength of the film by the trouser tear method defined in JIS K7128-1 (1998) is 5 N / mm or more in both the length direction and the width direction.
The biodegradable film according to any one of claims 1 to 3, wherein P A : P B = 5: 95 to 60:40.
Temperature 200 ° C., a melt viscosity eta A, temperature 200 ° C. of the lactic acid resin (A) at a shear rate of 100 sec -1, when the melt viscosity of the biodegradable resin at a shear rate of 100 sec -1 (B) was eta B, The biodegradable film according to any one of claims 1 to 4, which satisfies the following formula.
0.3 ≦ η A / η B ≦ 1.1
The biodegradable film according to any one of claims 1 to 5, comprising a compatibilizer.
Lactic acid-based resin (A) is at least one selected from the group consisting of a block copolymer having a polyether-based segment and a polylactic acid segment, and a block copolymer having a polyester-based segment and a polylactic acid segment, and homopolylactic acid, The biodegradable film according to any one of claims 1 to 6, comprising:
The biodegradable resin according to any one of claims 1 to 7, wherein the biodegradable resin (B) is at least one selected from the group consisting of polybutylene succinate, polybutylene succinate adipate and polybutylene adipate terephthalate. Sex film.