WO2013031755A1 - Polylactic acid film - Google Patents

Abstract

A polylactic acid film comprising a composition containing a polylactic acid resin (A), having a non-continuous concave or convex section on at least one surface of the film, and having a moisture permeability of 500-3,000 g/(m²/day). Provided is a polylactic acid film having excellent moisture permeability, water resistance, flexibility, and workability, and also having a high degree of biomass.

Description

Polylactic acid film

The present invention relates to a polylactic acid-based film that is excellent in moisture permeability, waterproofness, flexibility and processability and has a high degree of biomass.

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 which satisfies both purposes and is relatively advantageous in terms of cost. However, when trying to apply polylactic acid to flexible film applications in which polyolefins such as polyethylene are used as typical materials, they lack flexibility and impact resistance, so various attempts have been made to improve these properties and put them to practical use. Has been made.

In the field of moisture permeable films, for example, Patent Document 1 discloses a porous sheet formed by stretching at least uniaxially a sheet containing a polylactic acid resin, a filler, and a general polyester plasticizer. Patent Document 2 discloses that a mixture containing a polylactic acid-based polymer, an aliphatic-aromatic copolymer polyester, a plasticizer, and a fine powder filler is melted to form a film, and longitudinally stretched and laterally stretched. A porous film having pores is disclosed.

JP 2007-112867 A JP 2004-149679 A

In the techniques described in Patent Document 1 and Patent Document 2 described above, a stretching process at the time of film production is essential. When the stretching process is necessary, the number of processes increases and the apparatus becomes large, which is disadvantageous in terms of manufacturing simplicity and manufacturing cost. Further, in the method using filler blending and stretching, moisture permeability is exhibited, but the elongation of the film is greatly lowered after stretching, and the processability of the film when used in each application is inferior.

In other words, a polylactic acid film having excellent moisture permeability and flexibility and high biomass has been studied so far, but it is disadvantageous in terms of manufacturing simplicity and manufacturing cost, and its processing performance is poor. It was enough.

In view of the background of such conventional technology, the present invention is intended to provide a polylactic acid film that is excellent in moisture permeability, waterproofness, flexibility, processability and has a high degree of biomass.

The polylactic acid film of the present invention has the following configuration in order to solve the above problems. That is,
A film containing a polylactic acid-based resin (A), which has a concave or convex discontinuous portion on at least one side of the film, and has a moisture permeability of 500 to 3,000 g / (m ² · day). A polylactic acid film.

The method for producing a polylactic acid film of the present invention has the following constitution (1) or (2) in order to solve the above problems. That is,
(1) A method for producing a polylactic acid film having an embossing step of passing a film between a roll having a convex portion and an elastic roll, or
(2) A method for producing a film having an embossing process in which a roll having a convex part and a roll having a concave part form a male and female, and the film is passed between them, the depth of the concave part being the height of the convex part 5 to 80% of the polylactic acid film production method.

In the polylactic acid film of the present invention, the height of the discontinuous portion is preferably 20 to 150 μm.

The polylactic acid-based film of the present invention contains a thermoplastic resin (B) other than the polylactic acid-based resin (A), and the total amount of the polylactic acid-based resin (A) and the thermoplastic resin (B) is 100% by mass. The lactic acid resin (A) is preferably 10 to 95% by mass, and the thermoplastic resin (B) is preferably 5 to 90% by mass.

The polylactic acid film of the present invention preferably contains 1 to 200 parts by mass of the filler (C) with respect to 100 parts by mass in total of the polylactic acid resin (A) and the thermoplastic resin (B).

The polylactic acid film of the present invention is a block copolymer in which the thermoplastic resin (B) has a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, and an aliphatic polyester system. It is preferably at least one resin selected from the group consisting of a resin and an aliphatic aromatic polyester resin.

The polylactic acid-based film of the present invention is selected from the group consisting of a block copolymer in which the thermoplastic resin (B) has 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 comprise a combination of at least one resin selected from the group consisting of an aliphatic polyester resin and an aliphatic aromatic polyester resin.

In the method (1) for producing a polylactic acid film of the present invention, the polylactic acid film contains a thermoplastic resin (B) other than the polylactic acid resin (A), and the polylactic acid resin (A) and the thermoplastic resin are used. In the total 100% by mass of (B), the polylactic acid resin (A) is 10 to 95% by mass, the thermoplastic resin (B) is 5 to 90% by mass, and the thermoplastic resin (B) is a polyether segment. At least one resin selected from the group consisting of a block copolymer having a polylactic acid segment and a block copolymer having a polyester segment and a polylactic acid segment, and an aliphatic polyester resin and an aliphatic aromatic polyester resin It is preferably composed of a combination with at least one resin selected.

In the method (2) for producing a polylactic acid film of the present invention, the depth of the concave portion is preferably 45 to 80% of the height of the convex portion.

In the method (2) for producing a polylactic acid film of the present invention, it is preferable that the material of the roll having the convex portion is a metal roll and the material of the roll having the concave portion is a paper roll.

According to the present invention, there is provided a polylactic acid-based film that is excellent in moisture permeability, waterproofness, flexibility, processability, and has a high degree of biomass. The polylactic acid film of the present invention can be preferably used for applications requiring moisture permeability, waterproofness, flexibility and processability. Specifically, medical and hygiene materials such as bed sheets, pillow covers, back sheets for absorbent articles such as sanitary napkins and paper diapers; clothing materials such as rainy clothing and gloves; garbage bags and compost bags, or vegetables and fruits It can preferably be used for packaging materials such as food bags such as bags for various industrial products.

It is sectional drawing of the uneven | corrugated | grooved part of the embossing roll surface. It is the figure which looked at the uneven | corrugated | grooved part of the embossing roll surface from the top. It is sectional drawing of the uneven | corrugated | grooved part of a film.

As a result of earnestly examining the above-mentioned problem, that is, a polylactic acid-based film that is excellent in moisture permeability, waterproofness, flexibility, processability, and high biomass, a recess or This is the first successful solution to this problem by having discontinuous portions of protrusions and keeping moisture permeability within a certain condition.

That is, the present invention is a film containing a polylactic acid-based resin (A), having a discontinuous portion of a concave portion or a convex portion on at least one side of the film, and having a moisture permeability of 500 to 3,000 g / (m ² -A polylactic acid film that is day).

Hereinafter, the polylactic acid film of the present invention will be described.
(Polylactic acid resin (A))
It is important that the polylactic acid film of the present invention contains a polylactic acid resin (A).

The polylactic acid resin (A) is a polymer mainly composed of monomer units selected from L-lactic acid units and D-lactic acid units. Here, the main constituent component means that the mass ratio of the lactic acid unit is the maximum in the constituent unit of the polymer. The mass ratio of the lactic acid unit in the polylactic acid resin (A) is preferably 70% by mass to 100% by mass in 100% by mass of the polymer.

As the polylactic acid resin, poly L-lactic acid, poly D-lactic acid and the like are preferably used. The term “poly L-lactic acid” as used in the present invention means that 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 polymer. On the other hand, poly-D-lactic acid as used 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 polymer.

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, when the content ratio of the D-lactic acid unit in the poly L-lactic acid is increased, the crystallinity of the poly L-lactic acid is lowered and approaches an amorphous state. Conversely, if the content ratio of D-lactic acid units in poly-L-lactic acid 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. That is, when the content ratio of the L-lactic acid unit in the poly-D-lactic acid is increased, the crystallinity of the poly-D-lactic acid is lowered and approaches an amorphous state. Conversely, if the content of L-lactic acid units in poly-D-lactic acid decreases, the crystallinity of poly-D-lactic acid increases.

From the viewpoint of maintaining the mechanical strength of the film, the content ratio of the L-lactic acid unit in the poly L-lactic acid or the content ratio of the D-lactic acid unit in the poly D-lactic acid is 80 to 100 mol% is preferable, and more preferably 85 to 100 mol%.

The polylactic acid resin (A) used in the present invention may be copolymerized with a monomer unit other than the lactic acid unit. 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, 5-tetrabutylphosphonium isophthalic acid; hydroxycarboxylic acids such as glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid; caprolactone And lactones such as valerolactone, propiolactone, undecalactone, and 1,5-oxepan-2-one. The amount of copolymerization of other monomer units other than the lactic acid unit is preferably 30 mol% or less, more preferably 10 mol% or less, in 100 mol% of all monomer units in the polymer. . In addition, it is preferable to select the component which has biodegradability among the above-mentioned monomer units according to a use.

The polylactic acid resin (A) may be mixed with a small amount of poly D-lactic acid when the main component is poly L-lactic acid, or a small amount of poly L-lactic acid when the main component is poly D-lactic acid. preferable. This is because the stereocomplex crystal formed thereby has a higher melting point than a normal polylactic acid crystal (α crystal), so that the heat resistance of the film is improved.

The mass average molecular weight of the polylactic acid resin (A) 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.

As a method for producing the polylactic acid resin (A), details will be described later, but a known polymerization method can be used. Specific examples include a direct polymerization method from lactic acid and a ring-opening polymerization method via lactide.

The content of the polylactic acid resin (A) contained in the polylactic acid film of the present invention is not particularly limited as long as the polylactic acid resin (A) is contained in the film.

The polylactic acid film of the present invention preferably contains not only the polylactic acid resin (A) but also a thermoplastic resin (B) other than the polylactic acid resin (A) described later. In the polylactic acid film of the present invention, the polylactic acid resin (A) is 10 to 95% by mass in the total 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B). The plastic resin (B) is preferably 5 to 90% by mass.

The film of the present invention contains a thermoplastic resin (B) other than the polylactic acid resin (A), and in a total of 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B), By setting A) to 10% by mass or more, a film having excellent heat resistance and biomass properties is obtained, and by setting the polylactic acid resin (A) to 95% by mass or less, a film having excellent flexibility is obtained. The content of the polylactic acid resin (A) in the film is more preferably 20 to 90% by mass in a total of 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B). It is more preferably from ˜85% by mass, particularly preferably from 40 to 80% by mass.

The content of the polylactic acid resin (A) with respect to the entire polylactic acid film of the present invention is preferably 5 to 90% by mass, more preferably 10 to 85% by mass, and 15 to 80% by mass. % Is more preferable, and 20 to 75% by mass is particularly preferable.
(Embossing)
In the present invention, the method of providing the concave or convex discontinuous portions on at least one surface of the film is not particularly limited, but a method by embossing is preferable. In embossing, stretching at the time of film production is achieved by forming a large number of fine local pores in the film and / or forming a large number of thinned portions by local stretching of the embossed portion. Without depending on the process, moisture permeability, waterproofness, flexibility and workability can be imparted.

In view of the above, the polylactic acid film of the present invention is preferably a film in which a large number of fine pores are formed, that is, a porous film.

Hereinafter, an example of an embossing roll used in embossing will be described with reference to FIGS. 1 and 2.

The unevenness of the embossing roll surface used in the present invention is preferably 50 to 700 μm. The unevenness difference here is a length (corresponding to “a” in FIG. 1) corresponding to a difference between the lowest height portion and the highest height portion of the embossing roll surface. When the unevenness difference is 50 μm or more, the embossed film has a concave portion or a discontinuous portion due to the embossing, and is excellent in moisture permeability and flexibility. Moreover, since the uneven | corrugated difference is 700 μm or less, the embossed film can appropriately control the height of the concave or convex discontinuous portions by embossing, and is excellent in waterproofness and workability. It will be. The unevenness difference on the surface of the embossing roll is more preferably from 100 to 500 μm, and further preferably from 200 to 400 μm.

The pitch of the concave or convex portions on the surface of the embossing roll used in the present invention is preferably 0.5 to 2.0 mm. The pitch of the concave portion or the convex portion here is the shortest length (corresponding to b in FIG. 1) of the repeating length of the concave portion or the convex portion on the surface of the embossing roll. When the pitch of the concave portions or the convex portions is 0.5 mm or more, the embossed film has excellent waterproofness and workability. Moreover, since the pitch of the said recessed part or a convex part is 2.0 mm or less, the film after embossing becomes the thing excellent in moisture permeability and a softness | flexibility. The pitch of the concave or convex portions on the surface of the embossing roll is more preferably 0.5 to 1.5 mm, and further preferably 0.5 to 1.0 mm.

The embossing roll pattern used in the present invention is not particularly limited, and includes a square convex pattern, a lattice convex pattern, a turtle shell pattern, a diamond pattern, a quadrangular pyramid pattern, a truncated cone pattern, a vertical line pattern, a horizontal line pattern, and the like. Although it can be used, the crimping area is preferably 0.02 to 0.80 mm ² . The crimping area referred to here is the area of the embossing roll surface having a high height (the area of the plane corresponding to c × d in FIG. 2) per embossing roll pattern. That is, when a convex part exists in the embossing roll surface, it is the area of the surface of a convex part. On the other hand, when there is a recess on the surface of the embossing roll, the area other than the recess is the area of the embossing roll because the height of the embossing roll surface is high. The crimping area is more preferably 0.04 to 0.60 mm ² , further preferably 0.06 to 0.40 mm ² . The crimping area ratio is preferably 8 to 40%. The crimping area ratio here is the ratio of the area of the embossing roll surface having a high height (the area of the plane corresponding to c × d in FIG. 2) per unit area of the embossing roll. That is, when a convex part exists in the embossing roll surface, it is the area ratio of the surface of a convex part. On the other hand, when there is a recess on the surface of the embossing roll, the area ratio is the portion of the embossing roll whose surface is high except for the recess. The crimping area ratio is more preferably 12 to 30%, still more preferably 16 to 20%. The arrangement of the irregularities may be a regular arrangement in which the irregularities are arranged vertically and horizontally, or a staggered arrangement.

The embossing method in the present invention may be a combination of an embossing roll and an elastic roll such as a rubber roll, a paper roll, and a woolen paper roll, or a combination of an embossing roll and a female embossing roll corresponding to the uneven shape. The material of the embossing roll is not particularly limited, but is generally a metal roll. Specific examples of the material of the female embossing roll include an elastic roll such as a rubber roll, a paper roll, and a woolen paper roll in addition to the same metal roll as the embossing roll.

Here, the film manufacturing method of the present invention is a film manufacturing method including an embossing process in which a roll having a convex portion and a roll having a concave portion form a male and female and the film is passed between them. Is preferably 5 to 80% of the height of the convex portion. In that case, it is preferable that the material of the roll which has a convex part is a metal roll, and the material of the roll which has a recessed part is a paper roll. Further, the depth of the concave portion is more preferably 25 to 80% of the height of the convex portion, and further preferably 45 to 80%. When the depth of the concave portion is 5% or more of the height of the convex portion, a film having excellent moisture permeability can be obtained. When the depth of the concave portion is 80% or less of the height of the convex portion, a film having excellent waterproofness and workability can be obtained.
(Film shape)
It is important that the polylactic acid-based film of the present invention has a concave or convex discontinuous portion on at least one surface of the film. In addition, it is a preferable aspect that the discontinuous part of a recessed part or a convex part is formed by embossing. Here, having a discontinuous part of a concave part or a convex part means that at least one side of the film is not a continuous form in which the entire surface of at least one side of the film is on the same plane (the same height when viewed from the cross-sectional direction). This means that the entire surface is not on the same plane due to the presence of a concave or convex portion.

Hereinafter, the shape of the polylactic acid film of the present invention will be described with reference to FIG.

The height of the discontinuous portion of the polylactic acid film of the present invention is preferably 20 to 150 μm. The height of the discontinuous portion here is a length corresponding to the difference between the lowest and highest portions of the film surface when a cross section including the discontinuous portion is observed (corresponding to e in FIG. 3). ). When the height of the discontinuous portion is 20 μm or more, the film has excellent moisture permeability and flexibility. Moreover, it becomes a film excellent in waterproofness and workability because the height of the said discontinuous part is 150 micrometers or less. The height of the discontinuous portion is more preferably 50 to 145 μm, and further preferably 100 to 140 μm. The method for setting the height of the discontinuous portion in the range of 20 to 150 μm is, for example, by using an embossing roll having the above-mentioned preferable shape and embossing at a preferable roll temperature, linear pressure, and roll speed described later. is there.

The pitch of the discontinuous portions of the polylactic acid film of the present invention is preferably 0.5 to 2.0 mm. The pitch of a discontinuous part here is the shortest length (equivalent to f of FIG. 3) of the repetition length of the recessed part or convex part of a film. When the pitch of the discontinuous portions is 0.5 μm or more, the film is excellent in waterproofness and workability. Moreover, it becomes a film excellent in moisture permeability and a softness | flexibility because the height of the said discontinuous part is 2.0 mm or less. The pitch of the discontinuous portions is more preferably 0.7 to 1.5 mm, and further preferably 0.9 to 1.2 mm. A method for setting the pitch of the discontinuous portion within the above range is, for example, embossing with an embossing roll having the above-described preferable concave or convex pitch.

The thickness of the discontinuous portion of the polylactic acid film of the present invention is preferably 5 to 50 μm. The thickness of the discontinuous portion of the film as used in the present invention refers to the thickness of the thinnest portion among the discontinuous portions (recesses and protrusions) (for example, portions corresponding to g and h in FIG. 3). . When the thickness of the discontinuous portion is 5 μm or more, the film is excellent in waterproofness and workability. Moreover, it becomes a film excellent in moisture permeability and a softness | flexibility because the thickness of the said discontinuous part is 50 micrometers or less. The thickness of the discontinuous portion is more preferably 8 to 30 μm, and further preferably 10 to 20 μm. The method for setting the thickness of the discontinuous portion within the above range is, for example, using an embossing roll having the above-described preferable shape, using a roll of a preferable material and combination, and preferable roll temperature, linear pressure, and roll described later. Embossing at speed.
(Moisture permeability)
It is important that the polylactic acid film of the present invention has a moisture permeability of 500 to 3,000 g / (m ² · day). The method for measuring moisture permeability in the present invention is as described in the section of “Moisture permeability” in the Examples. In the present invention, for the film containing the polylactic acid-based resin (A), for example, an embossing roll having a preferable shape described above is used, and a preferable material and a combination of rolls are used. The water vapor transmission rate can be within the above range by embossing at a roll speed. When the moisture permeability is in this range, it can be preferably used for applications requiring moisture permeability.

Moisture permeability, 000 preferably ~ is ^{3,000g / (m 2 · day)} , more preferably ^{1,500 ~ 3,000g / (m 2 ·} day), 2,000 ~ 3 000 g / (m ² · day) is particularly preferable.
(Thermoplastic resin other than polylactic acid resin (B))
In order to improve the flexibility, moisture permeability, waterproofness, and processability, the polylactic acid film of the present invention is a thermoplastic resin other than the polylactic acid resin (A) (in the present invention, the thermoplastic resin (B) and Preferably). Examples of the thermoplastic resin (B) include polyacetal, polyethylene, polypropylene, polyamide, poly (meth) acrylate, polyphenylene sulfide, polyether ether ketone, polyester, polyurethane, polyisoprene, polysulfone, polyphenylene oxide, polyimide, polyetherimide, An ethylene / glycidyl methacrylate copolymer, a polyester elastomer, a polyamide elastomer, an ethylene / propylene terpolymer, an ethylene / butene-1 copolymer, a polymer containing starch, a resin plasticizer, and the like can be used.

Specific examples of polyesters include aromatic polyester resins such as polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate; poly (ethylene succinate terephthalate), poly (butylene succinate terephthalate), poly (butylene adipate terephthalate), etc. Aliphatic aromatic polyester resins: polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), polycaprolactone, polybutylene succinate, poly (butylene succinate) Aliphatic polyester resins such as adipate) can be used. Among these, from the viewpoint of maintaining biodegradability, aliphatic aromatic polyester resins or aliphatic polyester resins are preferable.

Furthermore, as the aliphatic aromatic polyester resin and aliphatic polyester resin used as the thermoplastic resin (B), poly (butylene adipate) having relatively high flexibility from the viewpoint of improving flexibility, moisture permeability, and waterproofness. (Terephthalate), polybutylene succinate, poly (butylene succinate adipate), poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-3hydroxyvalerate), and polycaprolactone are preferred. When the thermoplastic resin (B) contains these relatively flexible polyesters, the polylactic acid-based resin (A) and the thermoplastic resin (B) are reduced in the thickness direction of the film by forming an inflation film. A layered alloy structure is formed which also overlaps the layers. It has been found in the present invention that this layered alloy structure greatly contributes to the development of the waterproof property of the embossed film.

As a specific example of the polymer containing starch suitable as the thermoplastic resin (B), Novamont's biodegradable resin “Matterby” (registered trademark) can be used.

Specific examples of resin plasticizers suitable as the thermoplastic resin (B) include polyester plasticizers such as polypropylene glycol sebacate, polyalkylene ether plasticizers, ether ester plasticizers, acrylate plasticizers, and the like. Can be used. Among such plasticizers, from the viewpoint of maintaining the biodegradability of the entire film, the resin-based plasticizer preferably has biodegradability. Further, from the viewpoint of the bleed-out resistance of the plasticizer and the heat resistance and blocking resistance of the film, the resin-based plasticizer is, for example, a normal temperature (20 ° C. ± 15 ° C.) such as polyethylene glycol having a number average molecular weight of 1,000 or more. ) In a solid state, that is, a melting point exceeding 35 ° C. Moreover, it is preferable that melting | fusing point is 150 degrees C or less at the point which matches melt processing temperature with a polylactic acid-type resin (A).

From the same viewpoint, a resin-based plasticizer suitable as the thermoplastic resin (B) is a block copolymer having a polyether segment and a polylactic acid segment, or a block copolymer having a polyester segment and a polylactic acid segment. More preferably, it is a coalescence. Here, the plasticizing component is a polyether segment and a polyester segment. Here, the polyester segment means a segment made of polyester other than polylactic acid. Hereinafter, 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 are collectively referred to as a “block copolymer plasticizer”. These block copolymer plasticizers will be described below.

The mass ratio of the polylactic acid segment contained in the block copolymer plasticizer is preferably 50% by mass or less of the entire block copolymer plasticizer, because a desired flexibility can be imparted with a smaller amount of addition, preferably 5 It is preferable from the point of bleed-out suppression that it is more than mass%. Preferably, in 100% by mass of the block copolymer plasticizer, the mass ratio of the lactic acid unit is 5% by mass to 45% by mass, and the mass ratio of the polyether segment or the polyester segment is 55% by mass to 95% by mass. .

In addition, the number average molecular weight 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 of the polylactic acid segment of the block copolymer plasticizer is 1,200 or more, the block copolymer plasticizer that is the thermoplastic resin (B) and the polylactic acid resin that is the resin (A) A sufficient affinity arises between In addition, a part of the polylactic acid segment is taken into the crystal formed from the resin (A) to form a so-called eutectic so that the block copolymer plasticizer, which is the thermoplastic resin (B), is added to the resin. It produces an effect of stopping in (A) and exerts a great effect on the bleed-out suppression of the block copolymer plasticizer. As a result, the blocking resistance of the film is also excellent. In addition, this block copolymer plasticizer is greatly superior in moisture permeability as compared with a plasticizer that is liquid at normal temperature and a plasticizer that does not form a eutectic even when it is solid at normal temperature. This is because the eutectic formed improves the hole formation efficiency by embossing described later. The number average molecular weight 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. In the polylactic acid segment of the block copolymer plasticizer, the L-lactic acid unit is 95 to 100% by mass, or the D-lactic acid unit is 95 to 100% by mass. Therefore, it is preferable.

When the block copolymer plasticizer has a polyether segment, it is more preferable to have a segment made of polyalkylene ether as the polyether segment. Specific examples of the polyether segment include segments made of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyethylene glycol / polypropylene glycol copolymer, and the like. In particular, a segment made of polyethylene glycol is preferable because it has high affinity with the polylactic acid-based resin (A) and is excellent in modification efficiency, and can impart desired flexibility with a small amount of addition.

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

When the block copolymer plasticizer has a polyester segment, polyglycolic acid, poly (3-hydroxybutyrate), poly (3-hydroxybutyrate, 3-hydroxyvalerate), polycaprolactone, ethylene glycol, propane Polyesters composed of aliphatic diols such as diol 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 components of the polyether segment and the polyester segment in one molecule, or may contain only one of the components. For reasons of plasticizer productivity, cost, etc., when either component is used, it is preferable to use a polyether 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 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 the above range, the composition constituting the polylactic acid film has sufficient flexibility, and when the composition containing the polylactic acid resin (A) is used, the melt viscosity is set to an appropriate level, 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 polyether segment and / or the polyester segment and the polylactic acid segment, but at least one block of polylactic acid segment is a block common from the viewpoint of more effectively suppressing bleed out. It is preferably at the end of the polymer plasticizer molecule. Most preferably, the block of polylactic acid segment is at both ends of the block copolymer plasticizer molecule.

This block copolymer plasticizer contributes to the development of the flexibility of the whole film and the moisture permeability and waterproofness of the film by softening the polylactic acid resin (A).

Next, a block copolymer plasticizer that employs polyethylene glycol having a hydroxyl terminal at both ends as a polyether segment (hereinafter, polyethylene glycol is referred to as PEG) will be described in detail.

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 _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 -PEG-PLA type 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 of one polylactic acid segment of this block copolymer plasticizer can be determined as (1/2) × (w _L / w _E ) × M _PEG . The mass percentage of the total block copolymer plasticizer of the polylactic acid segment component can be substantially determined as _{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 determined to be substantially 100 × w _E / (w _L + w _E )%.

In addition, when isolate | separating a block copolymer plasticizer from a film and evaluating the number average molecular weight of each segment in a block copolymer plasticizer, it can carry out as follows. As a method for separating the block copolymer plasticizer from the film, for example, the 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. The block copolymer plasticizer is obtained by removing the precipitate by filtration and evaporating the solvent of the filtrate. The block copolymer plasticizer thus separated is measured for number average molecular weight (hereinafter referred to as M) using gel permeation chromatography (GPC). In addition, a polylactic acid segment, a polyether-based segment and / or a polyester-based segment are identified by ¹ H-NMR measurement. The molecular weight of one polylactic acid segment contained in the block copolymer is M × {1 / (number of polylactic acid segments in one molecule)} × (I _PLA × 72) / [(I _PE × UM _PE / N _PE ) + (I _PLA × 72)]. Here, I _PLA is the signal integrated intensity in ¹ H-NMR measurement derived from hydrogen of the methine group of the PLA main chain, and I _PE is ¹ H-NMR derived from the polyether segment and / or the polyester segment. Indicates the signal integration intensity in the measurement. UM _PE is the molecular weight of the monomer unit of the polyether segment and / or polyester segment, and N _PE is the ¹ H-NMR measurement corresponding to I _PE of the polyether segment and / or polyester segment. The number of chemically equivalent protons that give a signal. The number average molecular weight of the polyether segment and / or the polyester segment can be calculated by M− (number average molecular weight of polylactic acid segment) × (number of polylactic acid segments in one molecule).

Note that the film to be embossed usually does not contain a plasticizer. This is because the plasticizer tends to bleed out by pressure bonding during embossing, and the physical properties of the film change, and the bleed out plasticizer stains the embossing roll. In the present invention, the above-mentioned problems can be solved by using a resin plasticizer as the plasticizer. Further, among resin plasticizers, it has been found that it is preferable to use a block copolymer having a polyether segment and a polylactic acid segment, or a block copolymer having a polyester segment and a polylactic acid segment. .

Effects other than flexibility and moisture permeability due to the inclusion of the thermoplastic resin (B) depend on the type of resin, for example, bubble formation in the inflation film-forming method by improving melt viscosity and melt tension. Stabilization can be mentioned. Moreover, when poly (meth) acrylate is contained as the thermoplastic resin (B), the high-temperature rigidity of the polylactic acid-based film is improved. When the polyester is contained, the impact resistance and toughness of the polylactic acid-based film are improved. When the containing polymer is contained, the biodegradability promotion of the polylactic acid-based film can be mentioned.

The content of the thermoplastic resin (B) contained in the polylactic acid film of the present invention is 5 to 90% by mass in a total of 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B). It is preferable. By setting it as 5 mass% or more, it becomes a film excellent in flexibility. By setting it to 90 mass% or less, it becomes a film excellent in heat resistance. The content of the thermoplastic resin (B) is preferably 10 to 80% by mass, more preferably 15 to 70% by mass, in a total of 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B). More preferably, it is particularly preferably 20 to 60% by mass.
(Combination of thermoplastic resin (B))
The polylactic acid film of the present invention may contain only one kind of the above-mentioned thermoplastic resin (B), or may contain two or more kinds in combination. There is no restriction | limiting in particular in resin to combine, Resin chosen from thermoplastic resin groups other than the polylactic acid-type resin mentioned above as a thermoplastic resin (B) can be combined, respectively. Among them, a combination of a resin-based plasticizer and a thermoplastic resin other than the resin-based plasticizer is preferable from the viewpoint of achieving both flexibility and moisture permeability. In particular, it has been found that when the resin-based plasticizer and a thermoplastic resin other than the resin-based plasticizer are combined as the thermoplastic resin (B), the moisture permeability and the waterproof property are dramatically improved.

Among resin-based plasticizers, from the viewpoint of heat resistance, moisture permeability, blocking resistance, and bleed-out resistance, the block copolymer plasticizer described above, that is, a block copolymer having a polyether segment and a polylactic acid segment. A polymer or a block copolymer having a polyester segment and a polylactic acid segment is preferred. More preferably, it is a block copolymer having a polyether segment and a polylactic acid segment.

Among the thermoplastic resins other than the resin-based plasticizer, the above-described aliphatic polyester resins and aliphatic aromatic polyester resins are preferable from the viewpoint of biodegradability. Among them, from the viewpoints of flexibility and waterproofness, poly (butylene adipate terephthalate), polybutylene succinate, poly (butylene succinate adipate), poly (3-hydroxybutyrate), poly (3-hydroxy More preferred are resins selected from butyrate-3-hydroxyvalerate) and polycaprolactone.

That is, the thermoplastic resin (B) includes a block copolymer having a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, an aliphatic polyester resin, and an aliphatic aromatic. At least one resin selected from the group consisting of polyester resins is preferred. And at least one resin (resin-based plasticizer) selected from the group consisting 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 more preferable from a viewpoint of moisture permeability improvement to consist of a combination with at least 1 resin (thermoplastic resin other than resin-based plasticizer) selected from aliphatic polyester-based resins and aliphatic aromatic polyester-based resins.

In the present invention, a polylactic acid resin (A) softened with a block copolymer when a film having the above composition is provided with a discontinuous portion of a concave or convex portion on at least one side of the film by embossing or the like. It has been found that both the moisture permeability and the waterproof property can be achieved at a very high level by the synergistic effect of the moisture permeability and waterproof property development effect and the waterproof effect of the layered alloy structure.

When the thermoplastic resin (B) is a combination of a resin-based plasticizer and a thermoplastic resin other than the resin-based plasticizer, the blending mass ratio is (resin-based plasticizer / resin-based plasticizer Other than thermoplastic resin) = (5/95) to (95/5), more preferably (10/90) to (80/20), and (20/80) to (60 / 40) is more preferable.
(Mixing of crystalline polylactic acid resin and amorphous polylactic acid resin)
The polylactic acid resin (A) contained in the polylactic acid film of the present invention is preferably a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. This is because, by using a mixture, the advantages of both crystalline and amorphous polylactic acid resins can be achieved.

The crystalline polylactic acid-based resin is polylactic acid when the polylactic acid-based 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 a melting point derived from a component is observed. On the other hand, an amorphous polylactic acid-based resin refers to a polylactic acid-based resin that does not exhibit a clear melting point when the same measurement is performed.

The inclusion of the crystalline polylactic acid resin is suitable for improving the heat resistance and blocking resistance of the film. In addition, when the above-mentioned block copolymer plasticizer is used as the resin (B), the crystalline polylactic acid-based resin forms a eutectic with the polylactic acid segment of the block copolymer plasticizer, thereby preventing bleeding out. It has a great effect.

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 is because the amorphous portion is provided by containing the amorphous polylactic acid resin in the film, and the plasticizer is easily dispersed therein.

From the viewpoint of improving heat resistance and blocking resistance, the crystalline polylactic acid-based resin has a total content of L-lactic acid units in poly-L-lactic acid or a content of D-lactic acid units in poly-D-lactic acid. In 100 mol% of lactic acid units, 96 to 100 mol% is preferable, and 98 to 100 mol% is more preferable.

When a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin is used, when the total of the crystalline polylactic acid resin and the amorphous polylactic acid resin is 100% by mass, the crystalline polylactic acid resin The content of is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 20 to 40% by mass.
(Filler (C))
The polylactic acid film of the present invention preferably contains a filler (C) in order to improve moisture permeability. As the filler (C), an inorganic filler and / or an organic filler can be used.

Filler refers to a substance added as a base material for improving various properties, or an inert substance added for the purpose of increasing the volume, increasing the volume, or reducing the cost of the product.

Examples of inorganic fillers include carbonates such as calcium carbonate, magnesium carbonate, and barium carbonate; sulfates such as magnesium sulfate, barium sulfate, and calcium sulfate; zinc oxide, silicon oxide (silica), zirconium oxide, magnesium oxide, and oxide. Metal oxides such as calcium, titanium oxide, magnesium oxide, iron oxide, and alumina; hydroxides such as aluminum hydroxide; complex oxides such as silicate minerals, hydroxyapatite, mica, talc, kaolin, clay, montmorillonite, and zeolite A phosphate such as lithium phosphate, calcium phosphate or magnesium phosphate; a metal salt such as lithium chloride or lithium fluoride can be used.

Among these, from the viewpoints of improving the moisture permeability of the film, maintaining mechanical properties such as strength and elongation, and reducing costs, calcium carbonate, barium carbonate, barium sulfate, calcium sulfate, silicon oxide (silica), titanium oxide, Mica, talc, kaolin, clay and montmorillonite are preferred.

The average particle diameter of the filler (C) is not particularly limited, but is preferably 0.01 to 10 μm. When the average particle diameter is 0.01 μm or more, high filling in the film is possible, and as a result, the film has a high potential for making the film porous and improving moisture permeability. When the average particle size is 10 μm or less, the embossability of the film, that is, local stretchability is improved, and as a result, the film has a high potential for increasing the porosity and moisture permeability of the film. The average particle size is more preferably 0.1 to 8 μm, further preferably 0.5 to 5 μm, and most preferably 1 to 3 μm. Here, the average particle diameter is a 50% cumulative distribution average particle diameter measured by a laser diffraction scattering method.

The filler (C) can be surface-treated as necessary. Surface treatment agents for surface treatment include phosphate ester compounds, fatty acids, surfactants, fats and oils, waxes, carboxylic acid coupling agents, silane coupling agents, titanate coupling agents, and polymer surface treatments. An agent or the like can be used. Among these, at least one compound selected from a phosphate ester compound, a fatty acid, a polymer surface treatment agent, a surfactant, a silane coupling agent, and a titanate coupling agent is preferable. A compound selected from phosphoric ester compounds and fatty acids is more preferred. By performing the surface treatment, the affinity with the matrix resin is improved, which is effective in suppressing the aggregation of the filler and improving the dispersibility, and can be uniformly dispersed in the resin composition. As a result, it becomes possible to obtain a film excellent in processability such as stretching for expressing good moisture permeability.

Further, in order to improve the dispersibility of the filler (C) in the resin composition, it is preferable to further add a dispersant.

The content of the filler (C) in the film is preferably 1 to 200 parts by mass with respect to 100 parts by mass in total of the polylactic acid resin (A) and the thermoplastic resin (B). A film excellent in moisture permeability by adjusting the content of the filler (C) in the film to 1 part by mass or more with respect to 100 parts by mass in total of the polylactic acid resin (A) and the thermoplastic resin (B). It becomes. Moreover, the tensile strength of a film is made by making content of the filler (C) in a film into 200 mass parts or less with respect to a total of 100 mass parts of a polylactic acid-type resin (A) and a thermoplastic resin (B). In addition, the film has excellent workability while maintaining the tensile elongation, and has good melt processability, embossability, that is, local stretchability when the film is produced. The blending amount of the filler (C) is more preferably 3 to 150 parts by mass and further preferably 5 to 100 parts by mass with respect to 100 parts by mass in total of the resin (A) and the resin (B). The amount is preferably 25 to 70 parts by mass.

In particular, in the present invention, when the filler (C) is included in the composition capable of forming the layered alloy structure described above, the filler (C) becomes a starting point during embossing to induce interfacial peeling of the layered alloy, It has been found that the wettability can be greatly improved.
(Tensile elongation)
The polylactic acid-based film of the present invention preferably has a tensile elongation in the length direction and width direction (direction perpendicular to the length direction) of 50 to 300%. The tensile elongation is an index relating to workability when the polylactic acid film of the present invention is applied to various uses. The higher the tensile elongation, the better the workability. When the tensile elongation is 300% or less, tarmi and wrinkles are less likely to occur during production between rolls and during winding, and roll roll form and unwinding properties are improved. The tensile elongation in the length direction and the width direction is more preferably from 100 to 290%, further preferably from 150 to 280%. Examples of a method for adjusting the tensile elongation in the length direction and the width direction to 50 to 300% include, for example, a film made of a resin composition in which each of the above-mentioned preferred types and contents are blended. Using an embossing roll having a preferred shape, embossing at the above-described preferred roll temperature and linear pressure can be mentioned.
(Tensile modulus)
The polylactic acid film of the present invention preferably has a tensile modulus in the length direction and the width direction of 200 to 1,500 MPa in order to impart sufficient flexibility. The tensile modulus is an index relating to flexibility, and the smaller the tensile modulus, the better the flexibility. When the tensile elastic modulus is 200 MPa or more, tarmi and wrinkles are less likely to occur during production between rolls and during winding, and the roll winding shape and unwinding property are improved. The tensile elastic modulus is more preferably 250 to 1,200 MPa, further preferably 280 to 1,000 MPa, and particularly preferably 300 to 900 MPa. As a method for setting the tensile modulus in the length direction and the width direction to 200 to 1,500 MPa, for example, a film made of a resin composition in which each of the above-mentioned preferred types and contents are blended is described above. Using an embossing roll having a preferred shape, embossing at the above-described preferred roll temperature and linear pressure can be mentioned.
(Thickness)
The polylactic acid 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 handling property is excellent, and the roll winding shape and unwinding property are good. When the film thickness is 200 μm or less, the film is excellent in flexibility and moisture permeability. In particular, 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 still more preferably 12 to 50 μm.
(Additive)
In the composition which comprises the polylactic acid-type film of this invention, you may contain additives other than having mentioned above in the range which does not impair the effect of this invention. For example, known plasticizers, antioxidants, crystal nucleating agents, organic lubricants, UV stabilizers, endblockers, anti-coloring agents, matting agents, antibacterial agents, deodorants, flame retardants, weathering agents, antistatic Agents, antioxidants, ion exchange agents, tackifiers, antifoaming agents, color pigments, dyes and the like can be used.

As the organic lubricant, fatty acid amide compounds can be preferably used.

As the antioxidant, a hindered phenol-based antioxidant, a hindered amine-based antioxidant, and the like can be preferably used.

As the terminal blocking agent, addition reaction type compounds such as carbodiimide compounds, epoxy compounds, isocyanate compounds, oxazoline compounds can be preferably used.
(Lactic acid oligomer component amount)
In the polylactic acid film of the present invention, the amount of lactic acid oligomer component contained in the film is preferably 0.3% by mass or less. More preferably, it is 0.2 mass% or less, More preferably, it is 0.1 mass% or less. By controlling the amount of the lactic acid oligomer component contained in the film to 0.3% by mass or less, the deterioration of the handling property due to precipitation of the lactic acid oligomer component remaining in the film as a powder or liquid is suppressed, The progress of hydrolysis of the polylactic acid resin can be suppressed to prevent deterioration of the film over time, and furthermore, the odor peculiar to polylactic acid can be suppressed. The term “lactic acid oligomer component” as used herein refers to a cyclic dimer (lactide) of lactic acid that is most representative in quantity among lactic acid and linear oligomers and cyclic oligomers of lactic acid present in the film, that is, LL-lactide. , DD-lactide, and DL (meso) -lactide. A method for setting the amount of the lactic acid oligomer component to 0.3% by mass or less will be described later.
(Production method)
Next, the method for producing the polylactic acid film of the present invention will be specifically described, but the present invention is not limited thereto.

The polylactic acid resin (A) in the present invention can be obtained, for example, by the following method. As a raw material, L-lactic acid or D-lactic acid is used. Hydroxycarboxylic acids other than the lactic acid described above can also 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 subjected to azeotropic dehydration condensation in the presence of an organic solvent, particularly preferably a phenyl ether solvent, and water is removed from the solvent distilled by azeotropic distillation. A high molecular weight polymer can be obtained by polymerizing by a method in which the solvent which has been removed in a substantially anhydrous state is 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 of adjusting the conditions for removing moisture and low molecular weight compounds during heating and reflux in an organic solvent, a method of suppressing the depolymerization reaction by adding a phosphorus compound after the polymerization reaction and deactivating the catalyst, By using a method of heat-treating the produced polymer, a polymer having a small amount of lactide can be obtained.

A composition constituting the polylactic acid film of the present invention, that is, a composition containing a polylactic acid resin (A) and, if necessary, a thermoplastic resin (B), a filler (C) and other components. In obtaining the composition, it is possible to produce a composition by uniformly mixing a solution in which each component is dissolved in a solvent, and then removing the solvent. The method is preferable because steps such as dissolution of the raw material in the solvent and removal of the solvent are unnecessary. The melt kneading method is not particularly limited, and a 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 190 ° C. to 210 ° C. from the viewpoint of preventing the deterioration of the polylactic acid resin.

The polylactic acid-based film of the present invention uses, for example, a composition obtained by the above-described method, and combines an existing film forming method such as a known inflation method, a tubular method, or a T-die casting method with embossing. Can be obtained.

In forming the polylactic acid-based film of the present invention, for example, when the composition containing the polylactic acid-based resin obtained by the above-described method is once pelletized, melt-kneaded again, and extruded / film-formed, It is preferable to use a composition having a moisture content of 500 ppm (mass basis) or less by drying the pellets at 60 to 100 ° C. 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 water content of the composition to 500 ppm (mass basis) or less and reducing the lactide content, hydrolysis of the polylactic acid-based resin during melt-kneading can be prevented, thereby preventing a decrease in molecular weight. This is preferable because the melt viscosity of the product can be set to an appropriate level and the film forming process can be stabilized. From the same point of view, when the composition is once pelletized or melt-extruded / formed into a film, a biaxial extruder with a vent hole is used to remove volatiles such as moisture and low molecular weight substances. Melt extrusion is preferred.

The method for forming the polylactic acid film of the present invention by the inflation method is exemplified below.

The composition produced by the method as described above is melt-extruded with a twin screw extruder with a vacuum vent hole, led to an annular die, extruded from the annular die, and supplied with dry air to form a balloon. To do. Furthermore, it is air-cooled and solidified uniformly with an air ring, and after it is folded flat with a nip roll and taken at a predetermined take-up speed, both ends or one end is cut open as necessary to obtain a film before embossing. be able to. In order to develop good moisture permeability, the temperature of the annular die is important, and the temperature of the annular die is preferably in the range of 150 to 190 ° C, more preferably in the range of 155 to 185 ° C. As the annular die, it is preferable to use a rotary type and a spiral type from the viewpoint of thickness accuracy and uniformity of the obtained film. In addition, after forming into a film, surface treatment such as corona discharge treatment, plasma treatment, flame treatment, and acid treatment may be performed for the purpose of improving printability, laminate suitability, coating suitability, etc. The method is illustrated below.

The film formed by the method as described above is embossed between an embossing roll and a rubber roll or a paper roll to obtain a target polylactic acid film. At this time, the roll temperature is preferably 20 to 80 ° C., the nip pressure (linear pressure) is preferably 20 to 100 kg / cm, and the roll rotation speed is preferably 0.5 to 30 m / min. Embossing is normally performed only once, but may be performed twice or more as necessary.

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) Tensile modulus (MPa)
Tensile modulus was measured in an atmosphere of room temperature 23 ° C. and relative humidity 65% using “TENSILON” (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. Specifically, a sample was cut into a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and the distance between the initial tensile chucks was 50 mm and the tensile speed was 200 mm / min, according to the method defined in JIS K 7127 (1999). Ten measurements were made for each of the length and width directions, and the average value was taken as the tensile modulus.
(2) Tensile elongation (%)
Tensile elongation was measured in an atmosphere of room temperature 23 ° C. and relative humidity 65% using “TENSILON” (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. Specifically, a sample was cut into a strip shape having a length of 150 mm and a width of 10 mm in the measurement direction, and the distance between the initial tensile chucks was 50 mm and the tensile speed was 200 mm / min, according to the method defined in JIS K 7127 (1999). Ten measurements were made for each of the length direction and width direction, and the average value was taken as the tensile elongation.
(3) Moisture permeability Measurement of moisture permeability (g / (m ² · day)) three times according to the method specified in JIS Z 0208 (1976) using a constant temperature and humidity device set at 25 ° C and 90% RH. The average value was used and evaluated according to the following criteria.

^{AA: 2,000g / (m 2 ·} day) or more ^{A: 1,500g / (m 2 ·} day) or more 2,000g / ^{(m 2} · day) under ^{B: 1,000g / (m 2 ·} day) or more Less than 1,500 g / (m ² · day) C: 500 g / (m ² · day) or more and less than 1,000 g / (m ² · day) D: Less than 500 g / (m ² · day).
(4) Water resistance A water resistance test (hydrostatic pressure method; method A (low water pressure method)) was performed according to the method specified in JIS L 1092 (2009). At this time, the water level rising speed of the level device was 600 mm / min ± 30 mm / min. This water resistance (mm) was measured three times, and the average value was used for evaluation according to the following criteria.

A: 400 mm or more A: 300 mm or more and less than 400 mm B: 200 mm or more and less than 300 mm C: 100 mm or more and less than 200 mm D: less than 100 mm (5) Mass average molecular weight, number average molecular weight Standard polymethyl measured by gel permeation chromatography (GPC) It is a value in terms of methacrylate. 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. Measurement conditions were such that the flow rate was 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.
(6) Height of discontinuous portion Using an ultramicrotome, the film sample is −100 ° C. so that the cross section passing through the center of gravity of the concave or convex shape becomes the observation surface when the film surface is viewed from directly above. Ultrathin sections were collected at Using a scanning electron microscope, take a cross-sectional photograph of the thin film section of this film cross section at a magnification (for example, 200 times) that can confirm the length corresponding to the difference between the lowest part of the film surface and the highest part. Then, the height of the discontinuous portion was measured. This was performed at five locations by changing the observed concave or convex portions, and the average value obtained was defined as the height (μm) of the discontinuous portions in the present invention.

Below, the material used in the Example is demonstrated.
[Polylactic acid resin (A)]
(A1)
Crystalline poly L-lactic acid resin, mass average molecular weight = 200,000, D-form content = 1.4%, melting point = 166 ° C.
(A2)
Crystalline poly L-lactic acid resin, mass average molecular weight = 200,000, D-form content = 5.0%, melting point = 150 ° C.
(A3)
Amorphous poly L-lactic acid resin, mass average molecular weight = 200,000, D-form content = 12.0%, melting point = none The above melting point was obtained by heating the polylactic acid resin in a hot air oven at 100 ° C. for 24 hours. After that, using a differential scanning calorimeter RDC220 manufactured by Seiko Instruments Inc., a sample 5 mg was set on an aluminum pan, and the peak of the crystal melting peak when the temperature was raised from 25 ° C. to 250 ° C. at a heating rate of 20 ° C./min. Calculated as temperature.
[Thermoplastic resin (B) other than polylactic acid resin (A)]
(B1)
Polybutylene adipate terephthalate resin (trade name “Ecoflex” (registered trademark) FBX7011 manufactured by BASF)
(B2)
Polybutylene succinate resin (Mitsubishi Chemical Corporation, trade name “GSPla” (registered trademark) AZ91T)
(B3)
Polybutylene succinate / adipate resin (manufactured by Showa Polymer Co., Ltd., trade name “Bionore” (registered trademark) # 3001)
(B4)
62 parts by mass of polyethylene glycol having a number average molecular weight of 8,000, 38 parts by mass of L-lactide and 0.05 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. As a result, a block copolymer plasticizer B4 having a poly L-lactic acid segment having a number average molecular weight of 2,500 at both ends of polyethylene glycol having a number average molecular weight of 8,000 was obtained.
[Plasticizer (P)]
(P1)
Tributyl acetyl citrate, manufactured by Pfizer Inc., trade name “Citroflex” (registered trademark) A-4).
[Filler (C)]
(C1)
Calcium carbonate (manufactured by Sankyo Seimitsu Co., Ltd., trade name “Top Flow” (registered trademark) H200, average particle size: 1.7 μm)
[Metal embossing roll]
(I) Pattern: regular square pyramid trapezoidal pattern, regular arrangement, unevenness difference: 0.1 mm, pitch: 1.0 mm, crimping area: 0.16 mm ² , crimping area ratio: 16%, unevenness section angle θ: 18 °
(II) Pattern: regular square pyramid trapezoidal pattern, regular arrangement, unevenness difference: 0.3 mm, pitch: 1.0 mm, crimping area: 0.09 mm ² , crimping area ratio: 9%, irregularity section angle θ: 18 °
(III) Pattern: regular quadrangular pyramid trapezoidal pattern, regular arrangement, unevenness difference: 0.5 mm, pitch: 1.0 mm, crimping area: 0.04 mm ² , crimping area ratio: 4%, uneven section angle θ: 18 °
(IV) Pattern: regular square pyramid trapezoidal pattern, regular arrangement, unevenness difference: 0.3 mm, pitch: 1.0 mm, crimping area: 0.16 mm ² , crimping area ratio: 16%, uneven section angle θ: 18 °
(V) Pattern: regular square pyramid trapezoidal pattern, regular arrangement, unevenness difference: 0.3 mm, pitch: 0.5 mm, pressure bonding area: 0.04 mm ² , pressure bonding area ratio: 16%, unevenness cross section angle θ: 18 °
[Production of polylactic acid film]
(Comparative Example 1)
A mixture of 20 parts by mass of the polylactic acid resin (A1), 50 parts by mass of the polylactic acid resin (A3), and 30 parts by mass of the plasticizer (P1) was subjected to a twin screw extruder with a vacuum vent with a cylinder diameter of 190 ° C. and a screw diameter of 44 mm, The composition was obtained by melt-kneading while degassing the vacuum vent, homogenizing and then 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.

The dried composition pellets were supplied to a single screw extruder with a cylinder temperature of 180 ° C., and a blow spiral ratio of 2.4 mm from a rotary spiral annular die with a diameter of 250 mm, a lip clearance of 1.3 mm, and a temperature of 160 ° C. Extruded upward in the form of bubbles, air-cooled with a cooling ring, folded while being folded with a nip roll above the die, cut at both ends with an edge cutter, cut into two pieces, each wound with a winder, and a film with a final thickness of 20 μm Got. At this time, the draw ratio was 27. Table 1 shows the physical properties of the obtained film.
(Example 1)
A film having a thickness of 20 μm was obtained in the same manner as in Comparative Example 1 except that the composition of the film was changed as shown in Table 1.

Next, between the embossing roll (II) (upper stage) and the super-hard rubber roll (lower stage) having a hardness of D-90, in which the above film was set in an electric heating type embossing machine HTEM-300 manufactured by Yuri Roll Co., Ltd. Embossing was performed by passing under conditions of a roll temperature of 50 ° C. (both upper and lower stages), a nip pressure (linear pressure) of 50 kg / cm, and a roll rotation speed of 1.0 m / min. The physical properties of the film are shown in Table 1.
(Examples 2 to 24, Comparative Examples 2 to 3)
A film was obtained in the same manner as in Example 1 except that the composition of the film and the embossing conditions were changed as shown in Tables 1 to 4. The physical properties of the obtained film are shown in Tables 1 to 4.
(Comparative Example 4)
A film was obtained in the same manner as in Comparative Example 1 except that the composition of the film was changed as shown in Table 3. Table 3 shows the physical properties of the obtained film.
(Example 25)
A film having a thickness of 20 μm was obtained in the same manner as in Comparative Example 1 except that the composition of the film was changed as shown in Table 4.

Next, the film was set in an electric heating type embossing machine HTEM-300 manufactured by Yuri Roll Co., Ltd., having an embossing roll (V) (upper stage), an embossing roll (V), and a recess for forming a male and female, Between the paper rolls (lower stage) where the depth of the concave part is 25% of the height of the convex part of the embossing roll (V), the roll temperature is 50 ° C (both upper and lower stages), and the nip pressure (linear pressure) is 50kg. It was embossed by passing under the conditions of / cm and roll rotation speed of 1.0 m / min. The physical properties of the film are shown in Table 4.
(Example 26)
A film was obtained in the same manner as in Example 25 except that the depth of the concave portion of the paper roll (lower stage) was changed to 45% of the height of the convex portion of the embossing roll (V). Table 4 shows the physical properties of the obtained film.
(Example 27)
A film was obtained in the same manner as in Example 25 except that the depth of the concave portion of the paper roll (lower stage) was changed to 80% of the height of the convex portion of the embossing roll (V). Table 4 shows the physical properties of the obtained film.
(Comparative Example 5)
A film was obtained in the same manner as in Example 25 except that the depth of the concave portion of the paper roll (lower stage) was changed to 100% of the height of the convex portion of the embossing roll (V). Table 4 shows the physical properties of the obtained film.
(Examples 28 to 30, Comparative Example 6)
A film was obtained in the same manner as in Example 27 except that the composition of the film and the embossing conditions were changed as shown in Table 4. Table 4 shows the physical properties of the obtained film.

In Examples 1 and 2, bleed out of the plasticizer was observed from the obtained film, and the bleed out plasticizer was adhered to the embossed roll after processing.

In the other examples, the above problems did not occur.

Moreover, when cross-sectional observation was performed by the method as described in said (6) item about Examples other than Example 1, Example 12, Comparative Example 1, and Comparative Example 4, and a comparative example, many fine voids were formed. Film, that is, a porous film.

The polylactic acid-based film of the present invention is a polylactic acid-based film that is excellent in moisture permeability, waterproofness, flexibility, processability, and has a high degree of biomass. The polylactic acid-based film of the present invention comprises medical and hygiene materials such as bed sheets, pillow covers, and back sheets of absorbent articles such as sanitary napkins and paper diapers; clothing materials such as rainy clothes and gloves; garbage bags and compost bags, Or it can use for packaging materials, such as a bag for foodstuffs, such as vegetables and fruits, and a bag of various industrial products.

a ... unevenness on the surface of the embossing roll b ... pitch of the concave or convex surface on the surface of the embossing roll c ... one side for calculating the crimping area d ... one side for calculating the crimping area e ... height of the discontinuous part of the film f ... Pitch of discontinuous part of film g ... Thickness candidate of convex part h ... Thickness candidate of convex part θ ... Angle of uneven section

Claims (11)

1. A film containing a polylactic acid-based resin (A), which has a concave or convex discontinuous portion on at least one side of the film, and has a moisture permeability of 500 to 3,000 g / (m ² · day). Polylactic acid film.
2. The polylactic acid film according to claim 1, wherein the height of the discontinuous portion is 20 to 150 µm.
3. A thermoplastic resin (B) other than the polylactic acid resin (A) is contained, and the polylactic acid resin (A) is 10 to 10% in a total of 100% by mass of the polylactic acid resin (A) and the thermoplastic resin (B). The polylactic acid-based film according to claim 1 or 2, comprising 95% by mass and 5 to 90% by mass of the thermoplastic resin (B).
4. The polylactic acid type according to any one of claims 1 to 3, which contains 1 to 200 parts by mass of a filler (C) with respect to a total of 100 parts by mass of the polylactic acid type resin (A) and the thermoplastic resin (B). the film.
5. A block copolymer in which the thermoplastic resin (B) has a polyether segment and a polylactic acid segment, a block copolymer having a polyester segment and a polylactic acid segment, an aliphatic polyester resin, and an aliphatic aromatic polyester system The polylactic acid film according to claim 3 or 4, which is at least one resin selected from the group consisting of resins.
6. The thermoplastic resin (B) is at least one resin selected from the group consisting 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, and an aliphatic group 6. The polylactic acid film according to claim 3, comprising a combination with at least one resin selected from a polyester resin and an aliphatic aromatic polyester resin.
7. The manufacturing method of the polylactic acid-type film which has the embossing process which lets a film pass between the roll which has a convex part, and an elastic roll.
8. The polylactic acid-based film contains a thermoplastic resin (B) other than the polylactic acid-based resin (A), and in a total of 100% by mass of the polylactic acid-based resin (A) and the thermoplastic resin (B), the polylactic acid-based resin ( A) is 10 to 95% by mass, the thermoplastic resin (B) is 5 to 90% by mass, and the thermoplastic resin (B) is a block copolymer having a polyether segment and a polylactic acid segment, and a polyester segment. 8. A combination of at least one resin selected from the group consisting of a block copolymer having a polylactic acid segment and at least one resin selected from an aliphatic polyester-based resin and an aliphatic aromatic polyester-based resin. The manufacturing method of the polylactic acid-type film of description.
9. A roll manufacturing method in which a roll having a convex part and a roll having a concave part form a male and female and having an embossing process in which the film is passed between them, the depth of the concave part being 5 to 5 times the height of the convex part. A method for producing a polylactic acid film which is 80%.
10. The method for producing a polylactic acid film according to claim 9, wherein the depth of the concave portion is 45 to 80% of the height of the convex portion.
11. The manufacturing method of the polylactic acid-type film of Claim 9 or 10 whose material of the roll which has the said convex part is a metal roll, and the material of the roll which has the said recessed part is a paper roll.

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