JP6302060B2 - Microporous polylactic acid oriented film and its application - Google Patents

Description

  The present invention belongs to the technical field of polymer materials and relates to a polylactic acid film having a microporous structure.

  Microporous films are widely used in many fields such as healthcare, medical, construction, water treatment, agriculture, electrical products, and ornaments as moisture permeable waterproof films, battery separators, separation films, tissue engineering materials, and energy storage materials. It is used. The production method of microporous film mainly includes foaming, particle filling-stretching, solvent etching, phase separation, self-organization, etc. Microporous film produced by various methods has its own structure depending on its structure. Has characteristics.

  Polylactic acid is a biodegradable polyester, and a microporous film containing the polymer has already been proposed and can be used in fields such as healthcare and medicine.

In CN201310185870.6, the surface pore area in the range of 0.2-7μm diameter occupies 0.5% -15% of the total surface area by particle filling-stretching method, the water resistance is over 800mm, and the moisture permeability is A microporous oriented film containing 1000 g / m ² · day, a bending resistance of less than 40 mm, and containing a biodegradable polymer such as polylactic acid is provided. The film can be used in the healthcare field as a moisture permeable waterproof film.

  In CN201110414695.4, a phase separation technique provides a polylactic acid material that can be used as a porous stent for tissue engineering and has a pore diameter of 5 to 400 μm.

  In CN201080052568.8, a powder obtained by pulverizing a polylactic acid foam, which can be used as a water-absorbing material, is bonded to each other by fusion bonding to obtain a continuous porous structure having a pore size of 100 to 2000 μm.

  In the various techniques described above, although the pore diameter of the produced microporous film is different, it is difficult to produce a microporous polylactic acid film having micropores of submicron / nano level and uniform pore diameter.

  In addition, when used as a semipermeable membrane such as a moisture permeable waterproof film, there may be a special requirement for temperature sensitivity.

  For example, the amount of transmission may need to change with temperature. For example, the humidity of the contents can be adjusted by the moisture permeability of the polylactic acid microporous film. When trying to lower the humidity of the contents at a low temperature, the film is required to have high moisture permeability. On the other hand, when the humidity of the content is increased at a high temperature or the content is not further lost, the film is required to have low moisture permeability. For example, the volatilization rate of the content of a volatile fragrance | flavor component can be adjusted with the moisture permeability of a polylactic acid microporous film. At low temperatures, volatile aroma components need to permeate the film quickly, whereas at high temperatures, volatile aroma components need to permeate the film slowly.

  Also, for example, the transparency may need to change with temperature. For example, the transparency of the film is poor at low temperatures, and the transparency of the film is good at high temperatures.

  On the other hand, in the prior art, no technical proposal has been submitted for achieving the above-mentioned uniform polylactic acid microporous film having submicron / nano level pores and having a pore diameter and pore area that are temperature sensitive.

  With the expansion of the application range of microporous film, in the prior art, microporous polylactic acid film has a drawback that it has a large pore size and non-uniform pore size distribution, etc., resulting in healthcare, medical care, construction, water treatment, agriculture, electronics, We found that application in fields such as packaging and decoration is limited. In addition, temperature responsiveness may be required.

  In order to solve the drawbacks of the prior art, the present invention provides a microporous polylactic acid oriented film.

  An oriented film is a term well known to those skilled in the art, and is obtained by uniaxially stretching or biaxially stretching an unstretched film produced by a method such as casting, inflation, casting, press molding, etc. It is a film obtained by orienting chains and / or crystals. In general, orientation formation provides beneficial performance and properties such as improved strength, toughness, and transparency to the film, but it is also possible to impart heat shrinkability to the film depending on post-treatment conditions. The orientation of the film may be performed by a unidirectional or bi-directional stretching machine, or may be performed by an improved inflation method such as a tubular method. A method for measuring whether or not the film has orientation is a known technique, and as usual means, there are an X-ray diffraction method, a birefringence method, a Raman spectroscopy method, an infrared method, an ultrasonic method and the like.

  The present invention has surface pores having a diameter in the range of 10 to 1000 nm when the film is below the glass transition temperature of the polylactic acid component in the film, and the total area of such pores is the total surface area of the film. A microporous polylactic acid oriented film occupying 20% or more is provided. An oriented polylactic acid film has better strength and storage stability than an unoriented polylactic acid film.

  Surface pores as used herein refer to pores that are exposed to the outside and are not completely obstructed by the polymer and / or other pores, and such pores are observed on the surface of the film by a microscope.

  The area of the holes refers to the projected area of the holes in the horizontal plane when the film is placed horizontally. The total area of the film refers to the projected area of the film in a horizontal plane when the film is placed horizontally.

  Submicron nano-level pore diameters in the range of 10 to 1000 nm can effectively inhibit the passage of liquid water on the premise that the penetration of water vapor is not inhibited.

  The vitrification transition temperature means the temperature at which the amorphous phase of the polymer transforms from the glassy state to the rubbery state, or from the latter to the former, and is the lowest temperature at which the amorphous polymer segment can move freely. Show. The Tg of polylactic acid is usually about 55 ° C. and may be affected by one or more factors among crystallinity, orientation, cross-linking, additive type or content. The presence of factors such as crystals, orientation, or cross-linking has the effect of limiting the motion of the amorphous polymer segment, which can increase the Tg. Due to the presence of additives such as plasticizers or copolymerizable monomers, the Tg of polylactic acid may drop to about 15 ° C or lower, and the specific effect depends on the type or content. .

  The glass transition temperature of a polymer can be measured by detecting changes in volume, thermodynamic properties, mechanical properties, and electromagnetic properties. Commonly used means are differential scanning calorimetry (DSC) or dynamic thermomechanical performance analysis (DMA). Although there is a difference in the vitrification temperature measured by different methods, the vitrification temperature in the present invention is measured by a measurement method in the following specific implementation methods.

  When the film is below the glass transition temperature of the polylactic acid component in the film, the pore diameter of the submicron / nano-level surface pores having a diameter in the range of 10 to 1000 nm is based on the premise that the penetration of water vapor is not inhibited. The passage of liquid water can be effectively inhibited.

  Increasing the total pore area of the surface holes having a diameter in the range of 10 to 1000 nm is advantageous in improving moisture permeability. In the present invention, the total area of such holes preferably occupies 20% or more of the total surface area of the microporous polylactic acid oriented film. From the viewpoint of further increasing the water vapor transmission rate, in the present invention, the total pore area of the surface pores having a diameter in the range of 10 to 1000 nm preferably occupies 35% or more of the total surface area of the film, 45 More preferably, it occupies% or more. The upper limit of the surface hole area is not particularly limited, but may be, for example, 70% or less.

  A uniform pore size is advantageous for improving the mechanical properties and moisture permeability uniformity of the film. In the present invention, the surface pores having a diameter in the range of 10 to 1000 nm have a uniform pore size, and the pore size distribution is preferably less than 2.0, more preferably less than 1.5, and even more preferably less than 1.3. The lower limit of the pore size distribution is not particularly limited, but may be, for example, 1.05 or more.

  Furthermore, in the microporous polylactic acid oriented film, the film further has internal pores having a diameter in the range of 10 to 1000 nm when the temperature is equal to or lower than the glass transition temperature of the polylactic acid component in the film. The presence of the internal holes is advantageous for further improving the moisture permeability of the film.

  An internal hole as referred to in the present invention refers to a hole that is completely blocked by polymer and / or other holes, and this type of hole is observed by a microscope in the cross section of the film.

  For the internal hole, the amount of this type of hole can be determined by the ratio of the cross-sectional area. Create a MD-thickness (ZD) or TD-ZD section along the longitudinal direction (MD) or transverse direction (TD) of the film by means such as diamond knife or ion milling, and then use a microscope (such as an electron microscope or This section is observed using an atomic force microscope, etc., and the percentage of the area of this kind of hole in the MD-ZD section of the film or in the TD-ZD section of the film is accounted for by image processing technology. The (cross-sectional area occupancy) can be calculated statistically. According to statistical calculation, the cross-sectional area is set to 100%, and the cross-sectional area occupancy ratio of the internal holes having the diameter in the range of 10 to 1000 nm in the present invention is preferably 20% or more. From the viewpoint of further improving the moisture permeability, in the present invention, the internal pores having a diameter in the range of 10 to 1000 nm is more preferably 35% or more, and further preferably 45% or more. The upper limit of the cross-sectional area occupation ratio of the internal hole is not particularly limited, but may be, for example, 70% or less. From the viewpoint of improving the uniformity of the film, in the present invention, the pore diameter of the internal pores in the range of 10 to 1000 nm is uniform, and the pore diameter distribution is preferably less than 2.0, more preferably less than 1.5, and less than 1.3. Is more preferable. The lower limit of the pore size distribution is not particularly limited, but may be, for example, 1.1 or more.

  About the microporous polylactic acid oriented film of this invention, temperature sensitivity can be provided by the change of prescription or a manufacturing process. After the film is placed at a temperature 30 ° C. or more higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, the total pore area of the surface pores whose diameter is in the range of 10 to 1000 nm is reduced by 50% or more. To do. The decrease in pore area is due to the reduction in pore diameter.

  Furthermore, after the film is placed at a temperature 30 ° C. or higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, the total pore area of the internal pores whose diameter is in the range of 10 to 1000 nm is 50% Decrease more. This degree of area reduction is controlled by adjusting the formulation and drawing process parameters described below to meet actual requirements.

  For the microporous polylactic acid oriented film having temperature sensitivity, when the film is placed at a temperature 30 ° C. higher than the glass transition temperature of the polylactic acid component in the film, or higher for 1 hour, the diameter is 10 to Due to the reduction in pore size and total area of internal and / or surface pores in the 1000 nm range, the film may tend to increase light transmission and decrease haze. In one technical solution, after the film is placed at a temperature 30 ° C. higher than or higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, the light transmittance exceeds 90% and the haze is 10%. Less than films can be obtained. Internal and / or surface pores with a diameter in the range of 10 to 1000 nm after the film has been placed at a temperature 30 ° C. above or higher than the glass transition temperature of the polylactic acid component in the film for 1 hour Due to the decrease in the pore size and the total area of the film, the film may tend to have a reduced moisture permeability. In one technical solution, after the film is placed at a temperature 30 ° C higher than or higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, a film whose moisture permeability is reduced by 40% or more is obtained. Can do. The film can be used as a packaging film or a decorative film due to changes in transparency and moisture permeability.

  Moreover, the microporous polylactic acid oriented film of this invention does not have temperature sensitivity or can make temperature sensitivity weak by the change of prescription or a manufacturing process. That is, after the film is placed at a temperature 30 ° C. higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, the total pore area of the surface holes whose diameter is in the range of 10 to 1000 nm is 50%. Decrease below (excluding 50%).

  Furthermore, after the film is placed at a temperature 30 ° C. or more higher than the glass transition temperature of the polylactic acid component in the film for 1 hour, the sum of the hole cross-sectional areas of the internal holes whose diameter is in the range of 10 to 1000 nm is Reduce by 50% or less (excluding 50%).

  From the viewpoint of further improving the moisture permeability of the film, in the present invention, the microporous polylactic acid oriented film can have internal pores having a diameter of more than 1 μm and less than 100 μm. Statistics can be made by the method described above. After statistical calculation, the cross-sectional area is set to 100%, and the cross-sectional area occupation ratio of the internal holes in the present invention in which the diameter is in the range exceeding 1 μm and less than 100 μm is preferably 10% or more. The lower limit of the cross-sectional area occupancy is not particularly limited, but may be, for example, 30% or less.

The microporous polylactic acid oriented film comprises the following parts by weight of polylactic acid resin A: 40 to 99.9 parts by weight, preferably 40 to 99 parts by weight, hydrophilic organic compound B: 0.1 to 60 parts by weight , preferably 1 to 60 parts by weight ; the hydrophilic organic compound B is one or several kinds selected from organic compounds that can be dissolved or swollen in water.

  From the viewpoint of structure, the polylactic acid resin A may be any polylactic acid resin, and further, polylactic acid (polylactide), or one or several kinds of copolymers of lactic acid and other chemical structures. There may be.

  The molecular structure of polylactic acid is preferably a molecular structure composed of L-lactic acid or D-lactic acid of 80 to 100 mol% and each enantiomer of 0 to 20 mol%. The above-mentioned polylactic acid resin is obtained by dehydration polycondensation using one or two of L-lactic acid or D-lactic acid as a raw material. Preferably, it is obtained by ring-opening polymerization of lactide, which is a cyclic dimer of lactic acid. Lactide was obtained by cyclic dimerization of L-lactide, a cyclic dimer of L-lactic acid, D-lactide, a cyclic dimer of D-lactic acid, and D-lactide and L-lactide. There is meso-lactide and DL-lactide, which is a racemic mixture of D-lactide and L-lactide. Any lactide may be used in the present invention. However, as the main raw material, D-lactide or L-lactide is preferable.

  The copolymer of lactic acid and other chemical structures refers to one or several kinds of random copolymers, block copolymers, or graft copolymers composed of lactic acid and arbitrary chemical structural units. Among them, the chain length of the lactic acid unit is not particularly limited, but from the viewpoint of improving the mechanical performance of the microporous film, the chain length of lactic acid is preferably 1 to 200,000 weight average molecular weight. As a copolymer of lactic acid and other chemical structure, from the viewpoint of improving biodegradability and environmentally friendly, a copolymer of lactic acid and hydroxycarboxylic acids, glycol or polyols, dicarboxylic acid or polyvalent carboxylic acids is preferable.

  From the viewpoint of crystallization characteristics, the polylactic acid resin A may be a crystalline polylactic acid resin, an amorphous polylactic acid resin, or a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin. From the viewpoint of improving moldability, an amorphous polylactic acid resin or a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin is preferred. With respect to the mixture of the crystalline polylactic acid resin and the amorphous polylactic acid resin, from the viewpoint of improving moldability, the amorphous polylactic acid resin preferably accounts for 30% or more of the total amount of the mixture, and more preferably 50% or more.

  There are various methods for determining the ratio of the crystalline polylactic acid resin and the amorphous polylactic acid resin in the film. One method is differential scanning calorimetry (DSC). After separating the components of the film sample and separating the polylactic acid component, the ratio of crystalline polylactic acid resin to amorphous polylactic acid resin can be determined by performing DSC measurement and calculating the melting enthalpy .

  The molecular weight of the polylactic acid resin A is not particularly limited, but from the viewpoint of improving moldability and mechanical performance, the weight average molecular weight is preferably 50,000 to 500,000, more preferably 80,000 to 300,000. preferable.

  The above-mentioned organic compound that can be dissolved in water means that the organic compound can be dissolved in 1 g or more in 100 g of water at a certain temperature in 4 to 100 ° C.

  An organic compound that can swell in water means that 1 g of the organic compound can swell by 10% or more in 100 g of water at a temperature of 4 to 100 ° C.

  The hydrophilic organic compound B may be a low molecular weight organic compound, a high molecular weight organic compound, and / or a polymer.

  Specifically, the hydrophilic organic compound B is an alcohol small molecule compound such as ethylene glycol, diethylene glycol, glycerol or propylene glycol, a carboxylic acid small molecule compound such as succinic acid or lactic acid, lactide, caprolactone, lactate ester, Ester-based small molecule compounds such as citrate ester, glycerol ester or isosorbide, polyether polymer such as polyethylene glycol, polyethylene oxide, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, or polyether-polyolefin copolymer, polyether- Polyester copolymer, polyether polyurethane, polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, polyacrylic One or several types selected from amide, polymaleic acid, quaternary ammonium salt of diallylamine polymer, polyaspartic acid, polyepoxysuccinic acid, carboxymethylinulin, starch or derivatives thereof, cellulose ether, chitin, xanthan gum, or vegetable gum It may be.

  From the viewpoint of easy availability of raw materials, the hydrophilic organic compound B is ethylene glycol, glycerol, succinic acid, lactic acid, lactide, lactic acid ester, tributyl citrate, triethyl citrate, acetyl triethyl citrate, acetyl tributyl citrate, Glyceryl triacetate, isosorbide, polyethylene glycol, polyethylene oxide, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyethylene glycol-polylactic acid copolymer, polypropylene glycol-polylactic acid copolymer, polyethylene glycol-polypropylene glycol-polylactic acid copolymer , Polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone, starch, polymaleic acid, or polyaspartic acid May be one or several are.

  From the viewpoint of improving the amount of surface pores and / or internal pores having a diameter in the range of 10 to 1000 nm and improving pore size uniformity, a hydrophilic organic compound B having good compatibility with polylactic acid A is more preferred. Specifically, ethylene glycol, glycerol, succinic acid, lactic acid, lactide, lactic acid ester, tributyl citrate, triethyl citrate, triethyl citrate, acetyl tributyl citrate, glyceryl triacetate, isosorbide, polyethylene glycol, polyethylene oxide, polypropylene It may be one or several of glycol, polyethylene glycol-polypropylene glycol copolymer, polyethylene glycol-polylactic acid copolymer, polypropylene glycol-polylactic acid copolymer, or polyethylene glycol-polypropylene glycol-polylactic acid copolymer.

  In the present invention, there is no special requirement for the molecular weight of the hydrophilic organic compound B, and from the viewpoint of the mechanical performance of the film, the number average molecular weight is preferably less than 100,000, and the number average molecular weight is 50,000. More preferably, it is less than. The lower limit of the number average molecular weight is not particularly limited, but may be 55 or more, for example.

  When the film further has an internal hole whose diameter is in the range of more than 1 μm and less than 100 μm, the moisture permeability of the film can be further improved. When the inventor further calculates the polylactic acid resin A and the hydrophilic organic compound B in 100 parts by weight based on the microporous polylactic acid oriented film, the incompatible hydrophobic component C is contained within 400 parts by weight. It has been found that the film can be formed with internal pores having a diameter in the range of more than 1 μm and less than 100 μm. The incompatible hydrophobic component C is one or several types selected from substances that can form a multiphase structure with polylactic acid at 40 to 100 ° C. excluding the hydrophilic organic compound B. The phrase “a polyphase structure can be formed with polylactic acid at 40 to 100 ° C.” means that a polyphase structure can be formed with polylactic acid at an arbitrary temperature within a temperature range of 40 to 100 ° C.

  A multiphase structure is a term commonly used in the field of polymer, and there is a two-phase or multiphase system between a polymer and a polymer, a polymer and a small molecule compound, or a polymer and an inorganic substance at a certain temperature. Say that. The multiphase structure can be judged directly by a microscopic observation method such as an optical microscope, an electron microscope, an atomic force microscope, or an indirect method such as a differential scanning calorimeter or a dynamic mechanical property analyzer. You can also

  The incompatible hydrophobic component C may be organic, inorganic, or a mixture of organic and inorganic. Specifically, the incompatible hydrophobic component C is a small molecule compound such as alkane, alkene, aromatic, etc. having less than 100 carbon atoms excluding the hydrophilic organic compound B, polyolefin, polyurethane, polylactic acid. Polyester, polyamide, polyimide, polycarbonate, polythioether, polyether, fluorine-containing polymer, unsaturated resin, epoxy resin, acrylic resin, or polystyrene, wood flour, cellulose, sisal fiber, bamboo fiber, etc. Plant fiber, animal fiber such as wool fiber, organic synthetic fiber such as aromatic polyamide fiber, aromatic polyester fiber, glass fiber, asbestos fiber, carbon fiber, graphite fiber, metal fiber, potassium titanate whisker, aluminum borate whisker , Magnesium whisker, silicon Whisker, wollastonite, sepiolite, asbestos, slag fiber, zonotlite, silicon apatite, gypsum fiber, silica fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber or boron fiber, glass flake, non-swelling mica Swellable mica, graphite, metal foil, ceramic beads, talc, clay, mica, sericite, zeolite, bentonite, vermiculite, montmorillonite, dolomite, kaolin, fine silicic acid, feldspar powder, potassium titanate, fine hollow glass sphere, One kind or several kinds are selected from substances such as calcium carbonate, magnesium carbonate, calcium sulfate, titanium dioxide, boehmite alumina, silica, gypsum, novaculite, dawsonite or clay.

  The incompatible hydrophobic component C may be subjected to arbitrary interfacial modification and interfacial compatibilization in order to improve interfacial adhesion with the polylactic acid resin.

  From the viewpoint of maintaining and improving the biodegradability of the material, the incompatible hydrophobic component C is preferably a biodegradable polymer or an inorganic filler.

  The incompatible hydrophobic component C includes polyhydroxybutyrate, poly (hydroxybutyrate-co-hydroxyvalerate), hydroxybutyrate-cohydroxyhexanoate polymer, polybutylene succinate, polybutylene succinate adipate In polycaprolactone, polybutylene adipate terephthalate, polypropylene adipate terephthalate, polybutylene succinate terephthalate, polyethylene carbonate, polypropylene carbonate, polycyclohexene carbonate, calcium carbonate, talc, mica, zeolite, vermiculite, titanium dioxide, silica, calcium sulfate or montmorillonite More preferably, it is one kind or several kinds.

  In the microporous polylactic acid oriented film of the present invention, a plasticizer, a compatibilizing agent, a terminal sealant, a flame retardant, a nucleating agent, an antioxidant, a lubricant, and an antistatic agent are used as long as the object of the present invention is not impaired. One or several kinds of additives such as an agent, an antifogging agent, a light stabilizer, an ultraviolet absorber, a pigment, an antifungal agent, an antibacterial agent and a foaming agent can be added. Some of the hydrophilic organic compound B and the incompatible hydrophobic component C can also be used as additives such as plasticizers, nucleating agents, fillers, lubricants, pigments or dyes.

  The microporous polylactic acid oriented film has good hydrophilicity, and when immersed in water at 25 ° C. for 10 minutes, the water content of the film becomes 1 to 50% of the total mass of the film.

  In the microporous polylactic acid oriented film, the polylactic acid resin has a weight average molecular weight of 50,000 to 500,000, preferably 80,000 to 400,000 in order to satisfy practical mechanical properties, More preferably.

  The present invention utilizes the hydrophilicity of the hydrophilic organic compound, and preferably produces the microporous polylactic acid oriented film by the following method.

  First step: Each raw material is extruded and mixed by a method such as closed type or open type roller type mixing.

  Second step: An unoriented film is obtained from the mixture obtained in the first step by casting, inflation, rolling, press molding, extrusion, and casting.

  Third step: An oriented film is produced by any of the following methods:

Method 1 The oriented film is produced by uniaxially or biaxially stretching an unoriented film with water vapor at the same time.

Method 2 The oriented film is produced by uniaxially or biaxially stretching simultaneously with heating the unoriented film with a liquid. The liquid is selected from water or a mixed liquid having a water content greater than 10 parts by weight when the mixed liquid is calculated by 100 parts by weight. Examples of the liquid mixture include, but are not limited to, one or more liquid mixtures (water content greater than 10%) in water, ethanol, ethylene glycol, or glycerol. Water is preferable from the viewpoint of cost, greening and environmental friendliness. Although there is no special requirement for water quality and cleanliness, relatively pure water such as tap water, deionized water, or distilled water is preferable from the viewpoint of product quality.

Method 3 An oriented film is produced by immersing an unoriented film after immersing it in a liquid, heating it with hot air, and simultaneously uniaxially or biaxially stretching it. The liquid is selected from water or a mixed liquid having a water content greater than 10 parts by weight when the mixed liquid is calculated by 100 parts by weight. Examples of the mixed liquid include, but are not limited to, one or several mixed liquids (water content is greater than 10%) in water, ethanol, ethylene glycol, or glycerol. Water is preferable from the viewpoint of cost, greening and environmental friendliness. Although there is no special requirement for water quality or cleanliness, relatively pure water such as tap water, deionized water, or distilled water is preferable from the viewpoint of product quality. There is no special requirement for immersion time, but if the temperature of the liquid is low, a relatively long immersion time can be selected, and if the temperature of the liquid is high, a relatively short immersion to prevent hydrolysis of polylactic acid Time can be selected, usually 4s-10h.

  In the above three methods, the unstretched film has no special requirement for water content before it is stretched. On the other hand, experiments have shown that when the water content is 0.1-30% of the total mass, it is advantageous for the uniformity of the microporous structure.

  In the above-mentioned three methods, the stretching temperature is 40 to 100 ° C. From the viewpoint of improving processing stability, the stretching temperature is preferably 60 to 97 ° C.

  By adjusting drawing process parameters such as formulation and draw ratio, the hole diameter of the surface (and internal) holes can be controlled, and the number average value of the hole diameters of the holes in the range of 10 to 1000 nm is: Usually 100 to 800 nm (with an accuracy of 10 nm unit). The larger the draw ratio, the larger the pore size.

  In addition to the above method, the microporous polylactic acid oriented film can be produced by adding a general-purpose film forming process such as heat setting.

  Furthermore, by adding the fourth step, a microporous polylactic acid oriented film having no temperature sensitivity or low temperature sensitivity can be produced.

  Fourth step: Post-treatment is performed on the oriented film, and the post-treatment may be any one or several of the following methods, but is not limited thereto.

  Method 1: The oriented film is immersed in a liquid, and the liquid used is selected from water or a mixed liquid having a water content greater than 10 parts by weight when the mixed liquid is calculated in 100 parts by weight. It is selected from 40 to 99 ° C, preferably 60 to 90 ° C, and the post-treatment time is 1 s to 180 min, and preferably 2 s to 120 min.

Method 2: A highly heat-resistant material is applied to the surface of the film, and a solution, suspension, or dispersed heat-resistant material is applied to the surface of the film holes.
The coating material is one kind or several kinds of epoxy resin, urethane resin, and acrylic resin.
The application method is any one type or several types during dipping, roll coating, and spray coating.

Method 3: The film is coated on the surface of the film.
The coating material is gold, platinum, aluminum, silver, nickel, molybdenum, copper, tin, niobium, zinc, tungsten, titanium, chromium, zirconium, silicon, graphite, aluminum oxide, indium oxide, titanium oxide, magnesium oxide, oxidation Calcium, antimony trioxide, bismuth oxide, gadolinium oxide, tungsten oxide, titania, silica, ceria, yttria, niobium pentoxide, scandium oxide, zirconium dioxide, tantalum pentoxide, zinc oxide, silicon dioxide, tungsten fluoride, barium fluoride , Lead fluoride, cerium fluoride, lanthanum fluoride, aluminum nitride, titanium nitride, or silicon nitride.

  The coating method may be one or several types during vacuum sputtering, vacuum ion plating, ion beam deposition, ion beam assisted deposition, optical coating, chemical vapor deposition, and vacuum deposition.

Method 4: A cross-linking agent is added in the film production step, and cross-linking is performed in this step.
The crosslinking agent is one of polyfunctional polyester acrylate, triallyl isocyanurate, epoxy-acrylate, polyether acrylate, polyfunctional alcohol or ethylene glycol acrylate, urethane acrylate, epoxy-cation, benzophenone, aziridine, amines, thioxanthone Or several types.

  There are one or several types of crosslinking methods in gamma ray irradiation crosslinking, electron beam irradiation crosslinking, microwave radiation crosslinking, and ultraviolet crosslinking.

  Advantages of the present invention are that a microporous oriented film having nano-level micropores having dense and homogeneous characteristics such as temperature responsiveness can be manufactured, and the processing method is simple, rapid, and toxic. In addition, there is no need to use harmful solvents, and it is green and environmentally friendly. The microporous oriented film can be applied to various fields such as healthcare, medical care, architecture, water treatment, agriculture, electronics, packaging and decoration.

Specific embodiments

  The present invention will be described in more detail by the following examples, but the present invention is not limited to the examples.

The test methods used in the examples and comparative examples are as follows, and all tests are tested at 25 ° C. unless there is a clear description of the test temperature;
Thickness: Measured with a Sanyo 7050 film thickness meter and the average of nine data.
Weight average molecular weight and number average molecular weight: Measured by gel permeation chromatography, using tetrahydrofuran as the mobile phase, measured three times, and averaged.
Glass transition temperature (Tg) of polylactic acid component: It can be obtained from the first heating curve of the film using a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min.

Moisture permeability: JIS Z0208: conforms to 1976, humidity is 90%. Measure three times and take the average value.
Transparency: Light transmittance and haze are measured using a photoelectric haze meter according to GB / T2410-2008.
Moisture content: After the sample was 24h vacuum dried at 25 ° C., weighed m _1, and 10min immersed in water, after taking out, wipe the surface water, weighed m _2, containing according to equation (1) Calculate the amount of water.

<Surface structure measurement>
The surface structure is observed at 25 ° C.
Hole diameter d: Observe the surface of the film with a scanning electron microscope (SEM), take five photos at different positions at a magnification of 10,000 times, draw the outline of the hole with a pen, and then use the image processing software ImageJ1 .46r is used to calculate the area S of each surface hole, and further according to equation (2), the hole diameter d of each hole (ie, the diameter of a circle having an area equal to the area of the hole).

Average pore diameter (nano-level pore) d _n : The average pore diameter of pores having a diameter in the range of 10 to 1000 nm is calculated according to the formula (3).

Here, Σd is the sum of the hole diameters d of holes having a diameter in the range of 10 to 1000 nm, and n is the number of holes having a calculated diameter in the range of 10 to 1000 nm.
Pore size distribution (nano-level pores) SD: First, the volume average pore size d _v is calculated according to equation (4-1), and then the pore size distribution SD is calculated according to equation (4-2).

Here, Σd ⁴ is the sum of the fourth power of the hole diameter d of a hole having a hole diameter in the range of 10 to 1000 nm, and Σd ³ is the sum of the third power of the hole diameter d of a hole having a hole diameter in the range of 10 to 1000 nm. It is.
Area ratio (nano-level pores) S%: Percentage of the total surface area by the area of surface pores with a diameter in the range of 10-1000 nm. Calculate according to equation (5).

Here, ΣS _m is the sum of SEM observation areas.

<Internal structure measurement>
The internal structure is observed at 25 ° C.
Create a flat MD-ZD cross section by means of diamond knife or ion milling, and observe the cross section with SEM.
Hole diameter d: The hole diameter of the inner hole is calculated by the above-mentioned surface hole diameter statistics and calculation method.
Average pore diameter (nano-level pore) d _n : The average pore diameter of pores having a diameter in the range of 10 to 1000 nm is calculated according to the formula (3). Here, Σd is the sum of the hole diameters d of the holes having a hole diameter in the range of 10 to 1000 nm.
Pore size distribution (nano-level pores) SD: First, the volume average pore size d _v is calculated according to equation (4-1), and then the pore size distribution SD is calculated according to equation (4-2).

Area ratio (nano-level pores) S%: Percentage of the total surface area by the area of surface pores with a diameter in the range of 10-1000 nm. Calculate according to equation (5).
Average pore diameter (micron level hole) d ′ _m : Shows the average diameter of pores having a diameter in the range of 1 to 100 μm, and is calculated according to equation (6).

  Here, Σd ′ is the sum of the hole diameters d of holes having a hole diameter in the range of 1 to 100 μm, and m is the number of holes having a calculated diameter in the range of 1 to 100 μm.

  The raw materials used in the examples and comparative examples are as follows:

<Polylactic acid resin> (A)
A-1: Polylactic acid, 4032D, manufactured by NatureWorks, USA. The weight average molecular weight is 230,000.
A-2: Polylactic acid, 4060D, manufactured by NatureWorks, USA. The weight average molecular weight is 230,000.

<Hydrophilic organic compound> (B)
B-1: Polyethylene glycol, number average molecular weight 600, manufactured by China Pharmaceutical Group.
B-2: Polylactic acid-polyethylene glycol-polylactic acid triblock copolymer, produced according to Example 1 of CN200810018621.7. The number average molecular weight is 20,000.

<Incompatible hydrophobic component> (C)
C-1: Polybutylene succinate, Bionolle 1020, manufactured by Nippon Showa Polymer Co., Ltd.
C-2: Polybutylene adipate terephthalate, Ecoflex C1200, manufactured by BASF.
C-3: Calcium carbonate has a particle size of 1.2 to 3.5 μm and is manufactured by Sankyo Seiko Co., Ltd.

Examples 1-7
The raw material is extruded by a twin screw extruder at a constant blending ratio and pelletized, and the extrusion temperature is 175 to 200 ° C. Subsequently, it is blown by a single screw extruder to produce an unoriented film having a thickness of 100 μm, and the inflation temperature is 180 to 200 ° C. Further, the unoriented film was simultaneously biaxially stretched at a magnification of 3 × 3 in 85 ° C. water vapor to obtain an oriented film. Table 1 shows the composition of the film. The performance of each film was measured at 25 ° C. and shown in Table 1.

Comparative Examples 1-3
The raw material is extruded by a twin screw extruder at a constant blending ratio and pelletized, and the extrusion temperature is 175 to 200 ° C. Subsequently, it is blown by a single screw extruder to produce an unoriented film having a thickness of 100 μm, and the inflation temperature is 180 to 200 ° C. Further, the unoriented film was simultaneously biaxially stretched at a magnification of 3 × 3 in 85 ° C. water vapor to obtain an oriented film. Table 1 shows the composition of the film. The performance of each film was measured at 25 ° C. and shown in Table 1.

Examples 8-14, Comparative Example 4
The raw material is extruded by a twin screw extruder at a constant blending ratio and pelletized, and the extrusion temperature is 175 to 200 ° C. Next, the film was cast by a single screw extruder to produce an unoriented film having a casting temperature of 180 to 200 ° C. and a thickness of 120 μm. Further, the unoriented film was drawn in 80 ° C. water by the drawing method shown in Table 2 to obtain an oriented film. Table 2 shows the composition of the film. The performance of each film was measured at 25 ° C. and is shown in Table 2.

Examples 15-18
The raw material is extruded by a twin screw extruder at a constant blending ratio and pelletized, and the extrusion temperature is 175 to 200 ° C. Next, the film was cast by a single screw extruder to produce an unoriented film having a casting temperature of 180 to 200 ° C. and a thickness of 120 μm. Further, it was immersed in water at 80 ° C. for 30 minutes. Next, the unoriented film was drawn with 90 ° C. air by the drawing method shown in Table 3 to obtain an oriented film. Table 3 shows the composition of the film. The performance of each film was measured at 25 ° C. and shown in Table 3.

Examples 19-25
Each of the oriented films described in Examples 8 to 14 is allowed to stand under a temperature condition 30 ° C. higher than the glass transition temperature of the polylactic acid component in the film, and each performance is measured after 1 hour. The results are shown in Table 4.

Examples 26-32
Each of the oriented films described in Examples 8 to 14 is subjected to the following treatment.

Heat treatment method:
Soaking the oriented films described in Examples 8 and 9 in 80 ° C. water for 0.5 h;
Soaking the oriented films described in Examples 10 and 11 in water at 80 ° C. for 2 h;
Aluminum oxide is deposited on the surface of the oriented film described in Example 12 and has a thickness of 40 nm;
Silica is deposited on the surface of the oriented film described in Example 13 and has a thickness of 40 nm;
An epoxy resin having a thickness of 20 nm is applied to the surface of the oriented film described in Example 14;
Next, each film is left under a temperature condition 30 ° C. higher than the glass transition temperature of the polylactic acid component in the film, and each performance is measured after 1 hour. The results are shown in Table 5.
In the above-mentioned Example, GPC measurement is performed, and as a result, the weight average molecular weight of a polylactic acid component is 1-100,000.

All patent documents and non-patent documents referred to in this specification are incorporated herein by reference. "Several" as used herein includes all cases of more than one type, i.e., "one kind or several kinds" includes one kind, two kinds, the etc. three kinds such. In this specification, when an upper limit and a lower limit are respectively described for a certain numerical range, or when a numerical range that is a combination of the upper limit and the lower limit is described, each upper limit and each lower limit described is a new numerical range. Can be arbitrarily combined, and this should be regarded as the same as the description method in which the combined numerical range is clearly described. Unless it deviates from the meaning of this invention, those skilled in the art can change and improve this invention, and these are also contained in the scope of the present invention.

Claims (21)

  A microporous polylactic acid oriented film having a surface pore with a diameter in the range of 10 to 1000 nm when the temperature is equal to or lower than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film, and the pore area of the surface pore The microporous polylactic acid oriented film occupies 20% or more of the total surface area of the microporous polylactic acid oriented film.   2. The microporous polylactic acid oriented film according to claim 1, wherein the pore size distribution of the surface pores having a diameter in the range of 10 to 1000 nm is less than 2.0.   2. The microporous oriented polylactic acid film according to claim 1, wherein the pore size distribution of the surface pores having a diameter in the range of 10 to 1000 nm is less than 1.5.   2. The microporous polylactic acid oriented film according to claim 1, having an internal pore having a diameter in a range of 10 to 1000 nm.   5. The microporous polylactic acid oriented film according to claim 4, wherein the pore size distribution of the internal pores having a diameter in the range of 10 to 1000 nm is less than 2.0.   5. The microporous polylactic acid oriented film according to claim 4, wherein the pore size distribution of the internal pores having a diameter in the range of 10 to 1000 nm is less than 1.5.   5. The microporous polylactic acid oriented film according to claim 4, wherein the cross-sectional area ratio of the internal pores having a diameter in the range of 10 to 1000 nm is 20% or more.   After being placed at a temperature 30 ° C. or more higher than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film for 1 hour, the sum of the pore areas of the surface holes whose diameter is in the range of 10 to 1000 nm is 2. The microporous polylactic acid oriented film according to claim 1, which is reduced by 50% or more. After being placed at a temperature 30 ° C. or higher than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film for 1 hour, the sum of the cross-sectional areas of the internal holes whose diameter is in the range of 10 to 1000 nm is The microporous polylactic acid oriented film according to any one of claims 4 to 7, which is reduced by 50% or more.   After being placed at a temperature 30 ° C. higher than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film for 1 hour, the sum of the pore areas of the surface holes whose diameter is in the range of 10 to 1000 nm is 50 2. The microporous polylactic acid oriented film according to claim 1, wherein the film is a reduction of% or less (excluding 50%). After being placed at a temperature 30 ° C. higher than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film for 1 hour, the sum of the cross-sectional areas of the internal pores having the diameter in the range of 10 to 1000 nm is 50 The microporous polylactic acid oriented film according to any one of claims 4 to 7, wherein the orientation is a reduction of not more than% (excluding 50%).   2. The microporous polylactic acid oriented film according to claim 1, having an internal pore having a diameter larger than 1 μm and in a range smaller than 100 μm. The microporous polylactic acid oriented film is
Polylactic acid resin A: 40 to 99.9 parts by weight and hydrophilic organic compound B: 0.1 to 60 parts by weight,
2. The microporous polylactic acid oriented film according to claim 1, wherein the hydrophilic organic compound B is selected from one or several organic compounds that can be dissolved or swelled in water.   14. The microporous polylactic acid oriented film according to claim 13, wherein the polylactic acid resin A is an amorphous polylactic acid resin or a mixture of a crystalline polylactic acid resin and an amorphous polylactic acid resin.   The hydrophilic organic compound B includes ethylene glycol, glycerol, succinic acid, lactic acid, lactide, lactic acid ester, tributyl citrate, triethyl citrate, acetyl triethyl citrate, tributyl acetyl citrate, glyceryl triacetate, isosorbide, polyethylene glycol, poly Ethylene oxide, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyethylene glycol-polylactic acid copolymer, polypropylene glycol-polylactic acid copolymer, polyethylene glycol-polypropylene glycol-polylactic acid copolymer, polyvinyl alcohol, polyethyleneimine, polyvinylpyrrolidone , Starch, polymaleic acid, polyaspartic acid, one or several types are selected. Microporous polylactic oriented film of claim 13.   When the polylactic acid resin A and the hydrophilic organic compound B are calculated in 100 parts by weight, they further include an incompatible hydrophobic component C within 400 parts by weight; the incompatible hydrophobic component C is the hydrophilic organic compound B 14. The microporous oriented polylactic acid film according to claim 13, wherein one or several kinds other than the compound B are selected from substances capable of forming a polyphase structure with polylactic acid at 40 to 100 ° C.   The incompatible hydrophobic component C includes polyhydroxybutyrate, poly (hydroxybutyrate-co-hydroxyvalerate), hydroxybutyrate-cohydroxyhexanoate polymer, polybutylene succinate, polybutylene succinate adipate , Polycaprolactone, polybutylene adipate terephthalate, polypropylene adipate terephthalate, polybutylene succinate terephthalate, polyethylene carbonate, polypropylene carbonate, polycyclohexene carbonate, talc (talcum powder), mica, zeolite, vermiculite, calcium carbonate, titanium dioxide, silica, sulfuric acid 17. The microporous polylactic acid oriented film according to claim 16, wherein one or several kinds are selected from calcium or montmorillonite.   2. The microporous polylactic acid oriented film according to claim 1, wherein the water content of the microporous polylactic acid oriented film is 1 to 50% of the total mass of the film when immersed in water at 25 ° C. for 10 minutes. .   2. The microporous polylactic acid oriented film according to claim 1, wherein in the microporous polylactic acid oriented film, the polylactic acid resin has a weight average molecular weight of 50,000 to 500,000.   It is characterized by having a light transmittance of over 90% and a haze of less than 10% after being placed at a temperature 30 ° C or higher than the glass transition temperature of the polylactic acid component in the microporous polylactic acid oriented film for 1 hour. The microporous polylactic acid oriented film according to claim 8 or 9.   Application of the microporous polylactic acid oriented film according to any one of claims 1 to 20 in the fields of health care, medical treatment, construction, water treatment, agriculture, electronics, packaging and decoration.