CN107629424A - A kind of micro- porous polylactic acid film - Google Patents

Abstract

The invention provides a kind of micro- porous polylactic acid film, internal holes with 1 3000nm scopes, one side surface possesses surface holes of the diameter in the range of 1 3000nm, another side surface does not possess surface holes, the average circularity of internal holes and surface holes is more than 2, containing the difference of the average circularity of the average circularity of near surface side internal holes and opposite side internal holes is more than 1 in a thickness direction in the range of internal holes, the ratio of the separate internal hole number of film and all internal hole numbers is more than 10%.The advantage of the invention is that micro- porous polylactic acid film with this kind of special hole pattern can be made, the film manufacturing process is simple, high speed, being capable of part even complete biodegradable.Micro- porous membrane can have been applied in fields such as packaging, hygiene care, water process, medical science.

Description

A kind of micro- porous polylactic acid film

Technical field

The invention belongs to polymeric material field, is related to a kind of polylactic acid film with microporous structure.

Background technology

Micro- porous membrane as moisture permeable waterproof film, battery diaphragm, seperation film, tissue engineering material, energy storage material etc., The multiple fields such as hygiene care, medical treatment, building, water process, agricultural, electronic product, decoration are widely used.Micro- porous membrane Preparation method, mainly have foaming, particle-filled-stretching, solvent etched, phase separation, self assembly etc., it is micro- made from various methods Porous membrane respectively has feature in structure.

PLA is a kind of Biodegradable polyester, and micro- porous membrane containing the polymer has been mentioned, and can be protected in health It is applied in the fields such as reason, medical treatment.

CN 201110414695.4 uses phase detachment technique, there is provided a kind of aperture PLA controllable between 5-400 μm Material, it can be used as the porous support of used in tissue engineering.But technology preparation technology is complicated, the aperture of prepared material compared with Greatly, it is not suitable for preparing the porous polylactic acid film with sub-micron or Nano grade hole.

CN 201510242996.1 prepares PLA microporous barrier using the method for particle-filled-etching, and preparation has sub-micro The PLA microporous barrier of meter level hole, moisture permeability is up to 6400g/m²·day.But because hole pattern is single so that film Intensity increases and rapid decrease with aperture, is unfavorable for its application on actual product.

CN201310504568.2 discloses a kind of micro- porous polylactic acid orientation film, has in the range of 10-1000nm Surface holes and such hole area sum accounts for more than the 20% of the film gross area.But prepared two surfaces of film all holes are simultaneously And the pattern and size of hole limit its application in selection absorbs without obvious difference.

CN 200310109726.0 discloses a kind of preparation method of Polyurethane Porous Membranes, with ethylene glycol or polyethylene glycol For pore-foaming agent, using water as coagulator, the Polyurethane Porous Membranes side surface apertures of preparation are between 5-20 μm, another side surface Aperture is between 30-80 μm, and rate of perviousness is in 900-1800g/m²Between day.Although resulting two tables of polyurethane film The pore size in face difference, but hole is circle, can cause mechanical property isotropism, influence performance.

CN201410642682.6 discloses a kind of film with surface channel, the film be by two layers of perforated membrane with it is micro- Perforated membrane-porous microsphere that hole ball is compounded to form-porous membrane composite film, the film have good choosing for bacterial virus Select strainability.Although prepared perforated membrane can control the pattern in both side surface hole, preparation technology is complex, compound During can device to hole pattern have a great impact.

The content of the invention

Constantly expand with the application of micro- porous membrane, it has been found that in the prior art, micro- porous membrane hole is put down Equal circularity is smaller, causes mechanical property isotropism, and hole presence it is larger reduce the mechanical property of film in itself Can, which has limited application of micro- porous membrane in the field such as packaging, decoration, hygiene care.And hole is average circular at present Larger micro- porous membrane is spent because the hole average circularity of film surface and inside is close, although with larger average circle Degree hole film contrast the smaller film of average circularity mechanical property increase so that micro- porous membrane it is above-mentioned The field of limitation is applied, but due to film it is overall all containing hole and hole average circularity it is close, the film is existed The selection of specific morphology material is absorbed and the fixed application retained is restricted, so as to limit micro- porous membrane in sewage The application of processing, biomedicine etc..For existing micro- porous polylactic acid film, hole average circularity is close, and Both side surface all has hole, it may have the shortcomings of above-mentioned mechanical property that refers to is not high, without good absorbability, limits The application of film.

In order to solve the defects of prior art, the invention provides a kind of micro- porous membrane of PLA, it has special Hole pattern.

The present invention provides a kind of micro- porous polylactic acid film, and the film has inside of the diameter in the range of 1-3000nm Hole and thin film layer thickness containing internal holes accounts for more than the 5% of overall film thickness, the film is in the scope containing internal holes Inside the difference of the average circularity of near surface side internal holes and the average circularity of opposite side internal holes is big in a thickness direction In 1.

Described internal holes refer to completely by the hole of polymer and/or other maskaperture masks, can be by microscope in film Section on observe the pores.

The described film layer containing internal holes refers to, in the thickness range, the area of section of film internal holes accounts for this More than 10% film layer of thick layer area.

Described near surface internal holes, which refer to calculate inside from surface, draws one parallel to film surface on 2% thickness Line, all internal holes passed through by this line.Accordingly, the average pore size of near surface internal holes and average circularity are respectively by this The average pore size and average circularity for institute's hole that line passes through.

Described opposite side internal holes refer to that in the thick layer containing internal holes the other side corresponding with surface is past In calculate on 2% thickness one line parallel to film surface of picture, all internal holes passed through by this line.Accordingly, opposite side The average pore size and average circularity of internal holes are respectively the average pore size and average circularity of the institute's hole passed through by this line. Film average circularity and opposite side of near surface side internal holes in a thickness direction in the range of containing internal holes The difference of the average circularity of internal holes refers to calculate the average circle of hole that the line drawn on 2% thickness is passed through inward from both sides The difference of degree.

The area of section of the internal holes can count with the following method：Utilize the means such as diamond cutter or ion polishing, edge The longitudinal direction (MD) of film or laterally (TD) direction, after preparing MD- normal direction (ZD) section or TD-ZD sections, with microscope (electronics Microscope or AFM etc.) section is observed, image processing techniques is recycled, MD- of the hole in film layer can be counted Area sum on ZD sections or TD-ZD sections accounts for the percentage (area of section accounting) of the thickness thin film sectional layer area.

The circularity refers to the void shape and circular difference degree, is defined by the formula：

According to above formula, round circularity is 1.The cross sectional shape of hole gets over stray circle, then circularity is bigger.

The internal holes average circularity of micro- porous polylactic acid film possesses difference in a thickness direction, shows internal holes Pattern it is different in a thickness direction, the internal holes average circularity of near surface side is larger and the internal holes of opposite side are averagely round Shape degree is smaller, and this feature causes micro- porous polylactic acid film to have selection absorbability, the average circle of near surface side internal holes The difference of shape degree and the average circularity of opposite side internal holes is more than 1, and difference is bigger, and effect is more obvious.

The thin film layer thickness that micro- porous polylactic acid film contains internal holes accounts for more than the 5% of overall film thickness.Contain Internal holes thin film layer thickness is bigger, and the penetrability of film is better, and further, it is total that the thin film layer thickness containing internal holes accounts for film More than the 20% of thickness, in order that film has more preferable absorbent properties, prevent the material after absorbing from being oozed from the opposite side of film Go out, limit the thin film layer thickness containing internal holes accounts for overall film thickness less than 95%.

The moisture permeability refer to unit area film within the 24h times through vapor amount number, the value is bigger, table Bright moisture-inhibiting ability is stronger.

Further, the average circularity of micro- porous polylactic acid film internal holes of the present invention is all higher than 2.Average circle Degree is bigger, shows that the pattern in hole more deviates circle, anisotropic degree is higher, and perforated membrane possesses more preferable mechanical performance, makes It is wider to obtain the application of perforated membrane, on the other hand, it is more specific that bigger average circularity make it that film has for absorption Selectivity, the absorbability of micro-porous film can be controlled by adjusting circularity.Further, the average circularity of internal holes is more than 3, the average circularity of internal holes does not have the upper limit.

The ratio of the separate internal hole number of micro- porous polylactic acid film of the present invention and all internal hole numbers exists More than 10%, the film with separate internal hole possesses more preferable mechanical performance relative to the film with dependent internal holes, In addition, independent internal holes will not be such that absorbed material enters inside film, have influence on material further extraction or after Processing.Accounting of the separate internal hole in all internal holes is bigger, and above-mentioned performance is more obvious.

The separate internal hole refers to the internal holes being not communicated between adjacent hole on the section of film, by micro- Mirror can observe internal holes on the section of film, count the percentage that all separate internal hole numbers account for all internal hole numbers Than.

The side also surface of micro- porous further preferred film of polylactic acid film of the present invention possesses diameter in 1- Surface holes between 3000nm.The possessing of surface holes can make film have a more preferable absorbability, and surface within this range Aperture can then make film possess certain selection absorbability, and keep preferable mechanical performance.

Further, micro- porous polylactic acid film of the present invention is in the surface holes average circularity with surface holes side More than 2, further, the average circularity of the surface holes is preferably greater than 4, and the average circularity of the surface holes does not have the upper limit. The raising of average circularity makes micro- porous membrane possess the selection absorbability to special appearance material, and average circularity is bigger, Select the effect of absorption more obvious.Meanwhile the raising of surface holes average circularity also enhances the mechanical performance of film.

Another side surface of micro- porous polylactic acid film of the present invention does not possess surface holes.One side surface possesses surface holes And the structure that another side surface does not possess surface holes can improve the selective absorbability of micro- porous membrane and make making for film Apparatus is directional.After material enters perforated membrane from the side for having surface holes, because the opposite side of film does not have surface holes, So material will not ooze out from the opposite side of film, the composition of structure required for filtering out so can be very good；And work as material When contacting a side surface without surface holes, film can't absorbing material, can so film is avoided during use Interference, enhances the application in fields such as filtering, biomedicines.

Contain polylactic resin A in micro- porous polylactic acid film, content is preferably micro- more between 40-100 parts by weight Contain filler B in the film of hole, filler B content is between 0.1-60 parts by weight.

Described polylactic resin A can be any polylactic resin, can be that (poly- third hands over PLA further Ester) or lactic acid with the one or more in the copolymer of other chemical constitutions.

The molecular structure of preferable PLA is, by L lactic acid or the 80-100mol% and respective enantiomer 0- of D lactic acid The molecular structure that 20mol% is formed.Above-mentioned polylactic resin can be used as raw material from one or both of L lactic acid or D lactic acid, And obtained by dehydrating polycondensation.Preferably, ring-opening polymerisation can be passed through from the lactide of the cyclic dimer as lactic acid And obtain.There are cyclic dimer i.e. L lactides, cyclic dimer i.e. D lactides, the D lactic acid of D lactic acid of L lactic acid in lactide Study of Meso-Lactide and the racemic mixture of D lactides and L lactides obtained from carrying out cyclic dimer with L lactic acid That is DL lactides.Any lactide can be used in the present invention.But, the preferred D lactides of main material or L lactides.

It is random to refer to that lactic acid is formed with any chemical structural units with the copolymer of other chemical constitutions for described lactic acid One or more in copolymer, block copolymer or graft copolymer.Wherein, the chain length of lactic acid units is not special Limit, but consider from the angle of mechanical property for improving micro- porous membrane, preferably lactic acid chain length is that 1-20 ten thousand divides equally again Son amount.Described lactic acid is examined with the copolymer of other chemical constitutions from the angle for improving biological degradability and environment friendly Consider, preferably the same hydroxycarboxylic acid of lactic acid, binary or polyalcohols or the copolymer of binary or polybasic carboxylic acid class.

From crystal property, described polylactic resin can be crystalline polylactic acid resin or amorphism Polylactic resin, or can be the mixture of crystalline polylactic acid resin and amorphism polylactic resin.From raising mouldability It can consider, preferably amorphism polylactic resin or the mixture of crystalline polylactic acid resin and amorphism polylactic resin.It is right In crystalline polylactic acid resin and the mixture of amorphism polylactic resin, consider from processability is improved, it is preferably noncrystalline Property polylactic resin accounts for more than the 30% of total weight of the mixture, further preferred more than 50%.

On the molecular weight of polylactic resin, there is no particular limitation, but from improving molding processibility and mechanical property Consider in angle, preferable weight-average molecular weight 50,000~500,000, further preferred 80,000-30 ten thousand.

Described filler B can be inorganic matter or small molecular organic compounds or macromolecular organic compound And/or polymer.

Specifically, it is small can be selected from the alcohols such as inorganic salts, diglycol, glycerine, propane diols by described filler B The carboxylic acids such as molecular compound, succinic acid, lactic acid micromolecular compound, lactide, caprolactone, lactate, citrate, glycerine The esters such as ester or Coronex micromolecular compound, polyethylene glycol, polyethylene glycol oxide, polypropylene glycol, polyethylene glycol third It is the polyether-based polymers such as diol copolymer or polyethers-polyolefin copolymer, polyether-polyester copolymer, EU, poly- It is vinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, polyacrylamide, poly, diallyl quaternary ammonium polymer, poly- Aspartic acid, poly-epoxy succinic acid, Carboxymethylinulin, starch or derivatives thereof, cellulose ether, chitin, xanthans or plant One or more in glue.

The present invention do not required particularly for described filler B molecular weight, but from the mechanical property of film, Preferred number average molecular weight is less than 100,000, and further preferred number-average molecular weight is less than 50,000.The lower limit of number-average molecular weight does not limit especially It is fixed.

The present invention do not require particularly for the physical state of the filler B, can be liquid, colloid, solid particle, Solid powder either mixture.Do not required particularly for filler B pattern, can be it is spherical, can be it is aspherical, It can be spherical and aspherical mixture.Size and dimensional homogeneity for filler B also do not require particularly, Filler B size can with close, can also difference it is larger.

Described micro- porous polylactic acid film is prepared present invention preferably uses following methods.It should be clear that with lower section Method is to prepare several, the micro- porous polylactic acid film of the present invention having in the special micro- porous membrane methods of hole pattern PLA Preparation method be not limited to following several, other preparation methods can also be selected to realize the effect that is reached of the present invention.

Method one

Polylactic resin A and filler B are prepared into blend by extrusion, blend is initial thin by extruding curtain coating preparation Film, taken out after initial film is soaked in the liquid C of heat, it is empty using heat in the side of film after drying at different temperatures Gas is heated, and either cooled or be utilized respectively in the both sides of film in the side of film hot air and cold using cold air Air cooling-down, simple tension, biaxial tension are carried out while air-treatment or is not stretched, preparation has special hole pattern The micro- porous membranes of PLA.Described liquid C is selected from water or water content is more than 10 parts by weight in terms of the parts by weight of mixing liquid 100 Mixing liquid.Described mixing liquid including but not limited to：One or more of liquid in water, ethanol, ethylene glycol or glycerine The mixed liquor of body (water content is more than 10%).From price and green concept, preferably water.For the clean of water quality or water Net degree does not have particular/special requirement, from the point of view of product cleaning, is preferred with more pure water.Such as running water, deionization Water or distilled water.For the time of liquid infiltration, without special requirement, if fluid temperature is relatively low, can select longer Dip time, if fluid temperature is higher, in order to prevent the hydrolysis of PLA, shorter dip time can be selected, generally 4s-10h.The temperature of the liquid C is 40-100 DEG C.Consider from the angle for improving processing stability, preferred liquid C temperature is 60-90℃。

Method two

Polylactic resin A and filler B is prepared into blend by extrusion, blend prepares initial film by being blow molded, past One surface of initial film applies one layer of hot liquid, after naturally dry, then is stretched in 75 DEG C of hot-airs, obtains having spy The micro- porous membranes of PLA of different hole pattern.The amount of liquid coated in two surfaces can be with identical, can also be different；Coating Liquid can be with identical, can also be different.Selected from water or in terms of the parts by weight of mixing liquid 100, water content is more than 10 to described liquid The mixing liquid of parts by weight.Described mixing liquid including but not limited to：One kind in water, ethanol, ethylene glycol or glycerine or more The mixed liquor of plurality of liquid (water content is more than 10%).From price and green concept, preferably water.For water quality or The clean level of water does not have particular/special requirement, from the point of view of product cleaning, is preferred with more pure water.Such as running water, Deionized water or distilled water.The temperature of the liquid is 40-100 DEG C.Consider from the angle for improving processing stability, preferably Fluid temperature is 60-90 DEG C.

Method three

Polylactic resin A and filler B are prepared into blend A by extrusion, it is thin that by blowing prepared by blend A into blend Film A；Polylactic resin A is prepared into polylactic acid film B by blowing, blend thin filmses A and polylactic acid film B is answered by hot pressing The method of conjunction obtains initial film C.Taken out after initial film C is soaked into different time in the liquid C of heat, naturally dry is laggard Row simple tension, biaxial tension do not stretch, and obtain the micro- porous membranes of PLA with special hole pattern.The compound temperature of hot pressing Generally 40-150 DEG C of degree, pressure is generally 0.1-10MPa, and hot pressing time is generally 10s-1h.Described liquid C is selected from water Or water content is more than the mixing liquid of 10 parts by weight in terms of the parts by weight of mixing liquid 100.Described mixing liquid includes but unlimited In：The mixed liquor of one or more of liquid in water, ethanol, ethylene glycol or glycerine (water content is more than 10%).From price and Green concept is set out, preferably water.There is no particular/special requirement for the clean level of water quality or water, the angle clean from product Consider, be preferred with more pure water.Such as running water, deionized water or distilled water.For the time of liquid infiltration, do not have Special requirement, if fluid temperature is relatively low, longer dip time can be selected, if fluid temperature is higher, in order to prevent The hydrolysis of PLA, shorter dip time, generally 4s-10h can be selected.The temperature of the liquid C is 40-100 DEG C.From Improve and consider in the angle of processing stability, preferred liquid C temperature is 60-90 DEG C.

Micro- porous polylactic acid film of the present invention possesses surface due to the side surface with special hole pattern, film Hole, another side surface do not possess surface holes, and this can cause the film to have good application in the absorption of material, such as in water In terms of processing, the side of film can absorb the material of given shape and can be retained in film, will not be from the another of film Side is oozed out, meanwhile, the separate internal hole of certain content will not make absorbed material enter film depths, beneficial to carrying for material Take and post-processing.For another example the side of film can absorb specific material and opposite side will not absorb, and this can cause this Film has been applied in layering absorption etc..

Brief description of the drawings

Fig. 1 is that the A surfaces SEM of embodiment 10 schemes.

Fig. 2 is that the B surface SEM of embodiment 10 schemes.

Fig. 3 is the larger multiplication factor SEM figures of section of embodiment 10.

Fig. 4 is the smaller multiplication factor SEM figures of section of embodiment 10.

Embodiment

The present invention is described in more detail by following examples, but the embodiment does not form the limit to the present invention System.

Embodiment and the method for testing used in comparative example are as follows, for all tests, if not clearly stating test Temperature, then tested at 25 DEG C：

Thickness：Determined using the type thickness gauge of instrument company of Sanyo 7050, take the average value of 9 data.

Rate of perviousness：Based on JIS Z0208:1976, humidity 90%.Measure 3 times, averages.

Tensile strength：Film is cut into 10mm × 150mm sample sizes, according to standard GB/T 1040.3:2006 tests, Measure three times, is averaged.

Water absorption：One layer of deionization moisture film is applied in film surface, water film thickness is observed under the microscope and counts flat Average；Water film thickness and assembly average are observed again after 1h is placed at 25 DEG C.Calculate thickness difference twice and judge film Water absorption.

Water permeability：By film slitting into 50mm × 50mm sample sizes, four angles of film are fixed on support, thin The upper 10g deionized waters of film upper surface drop, place 1h at 25 DEG C, observe and confirm that there is anhydrous ooze out lower surface.

<Surface topography determines>

Surface topography observation is carried out at 25 DEG C.

Aperture d：Film surface is observed with SEM (SEM), random shooting diverse location times magnification The photo 5 that 10000 times of rate is opened, and after ticking hole profile with pen, each surface holes are calculated with image processing software ImageJ 1.46r Area S, the girth C of each surface holes, then by formula calculate each hole aperture d (a kind of diameter of equal value, i.e., it is equal with hole area Diameter of a circle)：

Average pore size d_n：By the aperture averaging value in hole of the formula calculated diameter in the range of 1-3000nm,

Wherein, ∑ d is adding and the 1- that n calculates for participation for the aperture d in hole of the aperture in the range of 10-3000nm The number in the hole in the range of 3000nm, the number in the hole typically counted is about at 3500 or so.

Circularity e is calculated by formula：

When e is 1, figure is circle；E is bigger, and figure and the gap of circle are bigger.

Average circularity e_sCalculated by formula：

<Internal morphology determines>

Surface topography observation is carried out at 25 DEG C.

The means such as diamond cutter or ion polishing prepare smooth MD-ZD sections, and the section is observed with SEM,

Aperture d：By the statistics and computational methods in aforementioned surfaces aperture, the aperture of internal holes is calculated.

Average pore size d_n：By the aperture averaging value in hole of the formula calculated diameter in the range of 1-3000nm.Wherein, ∑ d is hole The aperture d in hole of the footpath in the range of 1-3000nm plus and.

Overall film thickness ratio is accounted for containing internal holes thin film layer thickness：Measured by MD-ZD sections containing internal holes film The thickness of layer, while film layer gross thickness is measured, calculate both ratio s.

Separate internal hole number accounts for the ratio of all internal hole numbers：All separate internals on MD-ZD sections are counted respectively The quantity of the quantity in hole and all internal holes, calculate both ratio c.

Embodiment and the raw material used in comparative example are as follows：

＜ polylactic resin ＞ (A)

A-1：PLA, 4032D, Natureworks companies of the U.S..Weight average molecular weight 200,000.

A-2：PLA, 4060D, Natureworks companies of the U.S..Weight average molecular weight 230,000.

＜ fillers ＞ (B)

B-1：Polyethylene glycol, number-average molecular weight 1000, Chinese Chinese medicines group.

B-2：PLA-PEG-PLA triblock copolymer, according to CN200810018621.7 embodiment 1 Manufactured.Number-average molecular weight 20,000.

The film surface hole for providing side is A surface holes, and the near surface internal holes from the surface 2% thickness distance inward are A internal holes；Accordingly, the internal holes that the other side corresponding with surface calculates 2% thickness distance inward are B internal holes, separately Side surface holes are B surface hole.

Embodiment 1~11, comparative example 1~4

Raw material is pressed into certain proportioning double screw extruder extruding pelletization, 175-200 DEG C of extrusion temperature.Then, pass through Single screw extrusion machine is cast, 180-200 DEG C of casting temperature, prepares the initial film that thickness is 100 μm.And then by initial film 15min is soaked in 75 DEG C of hot water, after drying at different temperatures, according to the logical of the listed heating air of table 1 and cooling air Whether enter and whether stretch and prepare micro- porous membrane with different stretch mode, obtain embodiment 1~11 and comparative example 1~2, Comparative example 3~4 is the micro- porous membranes of existing PLA.At 25 DEG C, the structure and performance of each film are determined, is listed in table 1.

Embodiment 12~16, comparative example 5~6

Raw material is pressed into certain proportioning double screw extruder extruding pelletization, 175-200 DEG C of extrusion temperature.Then, pass through Single screw extrusion machine is blow molded, and prepares the initial film that thickness is 100 μm.180-200 DEG C of blow temperatures.And then according to listed by table 2 Processing mode toward 85 DEG C of hot water of surface coating constant weight, after naturally dry, stretch, obtain in 75 DEG C of hot-airs Embodiment 12~16, comparative example 5~6.At 25 DEG C, the structure and performance of each film are determined, is listed in table 2.

Embodiment 17~20, comparative example 8~9

Raw material is pressed into certain proportioning double screw extruder extruding pelletization, 175-200 DEG C of extrusion temperature.Then, pass through Single screw extrusion machine is blow molded, and prepares blend thin filmses A and polylactic acid film B that thickness is 100 μm, 180-200 DEG C of blow temperatures. Blend thin filmses A and polylactic acid film B progress hot pressing is compound, and temperature is 90-120 DEG C, prepares initial film C.And then according to Initial film C is soaked different time, naturally dry after taking-up by processing mode listed by table 3 in 85 DEG C of hot water, and is used not Same stretching mode prepares film, obtains embodiment 17~20, comparative example 8~9.At 25 DEG C, the knot of each film is determined Structure and performance, it is listed in table 3.

Table 1

(note 1：Water absorbability：++++represent water absorbability is good, +++ it is preferable to represent water absorbability, ++ representative has certain water Absorbability ,+representative can absorb water, and × representative does not absorb water.

Note 2：Water permeability：× represent it is waterproof.)

The (Continued) of table 1

Table 2

Table 3

That is mentioned in this specification is " a variety of " comprising being more than a kind of all situations, i.e. " one or more " including one kind, Two kinds, three kinds ... etc..When recording upper and lower bound respectively for certain number range in this specification, or with the upper limit and When the mode of lower values records certain number range, each upper limit and each lower limit described in it can be combined as new numerical value model Enclose, this should be considered to be identical with the record form of the number range combined is directly expressly recited.Without departing from this hair In the case of bright purport, those skilled in the art can be changed and improve to the present invention, and these are also included within the model of the present invention In enclosing.

Claims (6)

1. A kind of 1. micro- porous polylactic acid film, it is characterised in that：The film has inside of the diameter in the range of 1-3000nm Hole and thin film layer thickness containing internal holes accounts for more than the 5% of overall film thickness, the film is in the scope containing internal holes Inside the difference of the average circularity of near surface side internal holes and the average circularity of opposite side internal holes is big in a thickness direction In 1.
2. 2. micro- porous polylactic acid film according to claim 1, it is characterised in that：The average circle of the film internal holes Degree is all higher than 2.
3. 3. micro- porous polylactic acid film according to claim 2, it is characterised in that：The separate internal hole number of the film Ratio with all internal hole numbers is more than 10%.
4. 4. micro- porous polylactic acid film according to claim 1, it is characterised in that：One side surface of the film is also equipped with Surface holes of the diameter between 1-3000nm.
5. 5. micro- porous polylactic acid film according to claim 4, it is characterised in that：The film is possessing surface holes side Surface holes average circularity be more than 2.
6. 6. micro- porous polylactic acid film according to claim 4 or 5, it is characterised in that：Another side surface of the film Do not possess surface holes.