JP5276984B2 - Porous film and substrate for printing - Google Patents

Description

  The present invention relates to a film comprising a polylactic acid-based resin, a polyolefin and a compatibilizing agent, and more specifically, a porous film having a surface structure having biodegradability and excellent printability, and a printing substrate using the same Regarding materials.

  Conventionally, it is known to mold a polyolefin-based composition into a film shape having a porous structure. This is a film in which a porous structure is imparted by stretching a film obtained by forming a raw resin composition (see, for example, Patent Document 1). In recent years, attention has been focused on improving the compatibility between the polyolefin and the polyester in the composition, and a compatibilizer has been added as an additive to improve the physical properties of the composition itself (for example, Patent Document 2). reference).

Furthermore, by using a biodegradable polyester as the main component of the raw material composition, biodegradability has been imparted using, for example, a polylactic acid resin. Examples of such a film include a pore-containing film used for a shrinkable label covering a beverage plastic bottle (see, for example, Patent Document 3).
However, some films made of polylactic acid resin and polyolefin made porous can be printed, but there is a problem in printability compared to cellulosic substrates, that is, paper, and further improvement in printability is required. It was.

Japanese Patent Publication No. 50-38665 JP 2005-307157 A JP 2006-45296 A

  The present invention relates to a porous film excellent in printability, having an appropriate surface smoothness and excellent in concealment, and the porous film, as compared with a film made of a conventional porous polylactic acid resin and polyolefin. It aims at providing the base material for printing which consists of a quality film.

  The inventors of the present invention have made extensive studies in order to develop a porous film composed of a polylactic acid-based resin, a polyolefin, and a compatibilizing agent having the above-mentioned preferable properties. As a result, a polylactic acid-based resin, a polyolefin having a specific physical property value, preferably a polypropylene-based resin, and a resin composition containing those compatibilizers are blended at an appropriate ratio to form a film, and then stretched to obtain a porous material. It was found that the object can be achieved by forming a structure, and the present invention was completed based on this finding.

That is, the present invention
(1) With respect to 100 parts by mass of (A) polylactic acid-based resin, (B) the melt flow rate is 0.5 to 3.0 g / 10 minutes, and the storage elastic modulus at 100 ° C. is 200 to 500 MPa. A surface obtained by stretching a resin composition containing 0.2 to 10 parts by mass of a compatibilizer (C) with respect to 40 to 100 parts by mass of a polyolefin resin and 100 parts by mass of a total of (A) and (B) components. A porous film having micropores,
(2) The porous film according to the above (1), wherein the tensile elastic modulus of the component (B) is 1.2 to 2.0 GPa,
(3) The porous film according to (1), wherein the heat shrinkage rate in the extrusion direction when the porous film is immersed in hot water at 80 ° C. for 10 seconds is 20% or less,
(4) The porous film according to any one of the above (1) to (3), wherein the component (B) is a highly crystalline propylene homopolymer, a highly crystalline ethylene / propylene copolymer, or a mixture thereof,
(5) The porous film according to any one of the above (1) to (3), wherein the component (C) is a styrene-ethylene / butylene-styrene block copolymer,
(6) The resin composition comprising the (A) component, the (B) component, and the (C) component that forms a sea-island structure, wherein the (B) component is an island layer (domain). the film,
(7) The porous film according to the above (1), which has fine pores on the surface and has voids parallel to the front and back surfaces inside the film,
(8) The porous film is composed of thin films to be laminated, micropores are opened in the thin film, the micropores form micropores on the front and back surfaces of the film, and the gaps between the thin films are connected to the front and back of the film. The porous film according to (7),
(9) The porous film according to (1), wherein the apparent specific gravity is 0.30 to 0.90,
(10) A printing substrate comprising the porous film according to any one of (1) to (9) above,
It is.

  The porous film of the present invention is a film having a multilayer structure of porous thin films and a moderately smooth surface, which can absorb printing ink quickly and has excellent printability as well as concealment. It can be set as the outstanding printing base material which exhibits the paper shape as a whole.

2 is a surface electron micrograph of the film obtained in Example 1. 6 is a surface electron micrograph of the film obtained in Example 5. 6 is a surface electron micrograph of the film obtained in Example 7. 2 is a cross-sectional electron micrograph of the film obtained in Example 7. 6 is a surface electron micrograph of the film obtained in Comparative Example 4. 6 is a cross-sectional electron micrograph of the film obtained in Comparative Example 4. 6 is a surface electron micrograph of the film obtained in Comparative Example 7. 6 is a cross-sectional electron micrograph of the film obtained in Comparative Example 7. 6 is a surface electron micrograph of the film obtained in Comparative Example 8. 10 is a cross-sectional electron micrograph of the film obtained in Comparative Example 8.

Hereinafter, the present invention will be described in more detail.
The film according to the present invention is a porous film having a porous structure on the surface, a polylactic acid resin, a melt flow rate of 0.5 to 3.0 g / 10 min, and a storage elastic modulus at 100 ° C. 200 to 500 MPa, preferably, obtained by stretching and porous a polyolefin resin having a tensile modulus of 1.2 to 2.0 GPa, preferably a polypropylene resin and a compatibilizer. is there.

Examples of the polylactic acid resin in the present invention include polymers of oxyacids such as lactic acid, malic acid and glycolic acid, or copolymers thereof, specifically, polylactic acid, poly (α-malic acid), polyglycolic acid. , Glycolic acid-lactic acid copolymer, and the like. Among them, polylactic acid is particularly preferable.
These polylactic acid resins may be used singly or in combination of two or more.

  The polylactic acid resin in the present invention includes a resin generally called a so-called biodegradable plastic, that is, an aliphatic polyester such as polycaprolactone aliphatic polyester, microorganism-produced aliphatic polyester, polybutylene succinate, and polyethylene succinate. Can also be mixed.

The polycaprolactone-based aliphatic polyester can be obtained by ring-opening polymerization of ε-caprolactone and is decomposed by many bacteria while being a water-insoluble polymer, and has a general formula: — (O (CH ₂ ) ₅ CO) - an aliphatic polyester having a repeating unit represented by. Examples of such commercially available products of polycaprolactone-based aliphatic polyester include “Tone” (trade name) sold by Nihon Unicar Co., Ltd., PH series of “Cell Green” (trade name) sold by Daicel Chemical Industries, Ltd., There are CBS series.

  The microorganism-produced aliphatic polyester is a thermoplastic polymer having a melting point derived from a living body. Specific examples include polyhydroxybutyrate (PHB), poly (hydroxybutyric acid-hydroxypropionic acid) copolymer, poly (hydroxybutyric acid-hydroxyvaleric acid) copolymer, and the like.

  The polyolefin resin in the present invention has a melt flow rate of 0.5 to 3.0 g / 10 minutes, preferably 0.5 to 2.5 g / 10 minutes, and a storage elastic modulus at 100 ° C. of 200 to 500 MPa, preferably Is a polyolefin resin having a tensile modulus of 1.2 to 2.0 GPa, preferably a polypropylene resin. When the melt flow rate is 0.5 to 3.0 g / 10 min and the storage elastic modulus at 100 ° C. is 200 to 500 MPa, a resin composition composed of a polylactic acid resin, a polyolefin resin, and a compatibilizer is appropriate. It becomes a mixed state and can be made porous by stretching it. Furthermore, when the tensile elastic modulus of the polyolefin resin is 1.2 GPa or more, the obtained porous film can have a sufficient elastic modulus to be used as a printing substrate, and is 2.0 GPa or less. And the selection range of a draw ratio can be expanded in the extending process which creates a porous film.

  Here, the melt flow rate is a value measured in accordance with JIS K 7210 “Testing method for melt mass flow rate and melt volume flow rate of plastic-thermoplastic plastic”. The storage elastic modulus at 100 ° C. is a stress generated when a vibration load or strain is applied to the sample at 100 ° C. in accordance with JIS K 7244-4 “Plastics—Test method for dynamic mechanical properties”. The tensile elastic modulus is a value obtained from a tensile stress-strain curve calculated by a method defined in JIS K 7113 “Plastic test method”.

More specifically, the polyolefin resin in the present invention has a polypropylene resin, a high density polyethylene, a medium density polyethylene, a low density polyethylene, an extremely low density, and the melt flow rate and the storage elastic modulus at 100 ° C. are in the specific range. Mention may be made of polyethylene, linear low-density polyethylene, chlorinated polyethylene, polybutylene, polybutadiene, polybutene, polymethylpentene, polystyrene, and mixtures and copolymers thereof.
The copolymer may have a polyolefin skeleton, for example, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-vinyl chloride copolymer, ethylene-vinyl chloride copolymer, ethylene-propylene copolymer, Propylene-vinyl chloride copolymer, ethylene-vinyl alcohol copolymer, ethylene-α-olefin copolymer, methyl acrylate-ethylene copolymer, ethyl acrylate-ethylene copolymer, maleic anhydride-ethylene copolymer, Mention may be made of maleic anhydride-methyl acrylate-ethylene copolymer, glycidyl methacrylate-ethylene copolymer, glycidyl methacrylate-methyl acrylate-ethylene copolymer, glycidyl methacrylate-vinyl acetate-ethylene copolymer, and mixtures thereof. it can.

Specific examples of the polypropylene resin include a propylene homopolymer, a copolymer of propylene and an α-olefin, or a mixture thereof. The α-olefin is an α-olefin having 2 to 20 carbon atoms excluding propylene, ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1 -Pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-pentene and the like can be mentioned. The copolymer of propylene and α-olefin may be a block copolymer or a random copolymer, and may be a copolymer of a plurality of α-olefins.
As the α-olefin, ethylene is most preferable.

  Among the polypropylene resins, a highly crystalline propylene homopolymer, a highly crystalline ethylene / propylene copolymer or a mixture thereof, a highly crystalline polypropylene resin or a propylene homopolymer, a propylene homopolymer and a highly crystalline ethylene A mixture with a propylene copolymer is particularly preferred. Furthermore, a highly crystalline propylene homopolymer has higher crystallinity than a graft type or block type polymer, has an appropriate elastic modulus, and is easy to stretch because it is a single component. More preferable.

In the present invention, the highly crystalline polypropylene resin includes a wide range of polypropylene resins known to have the same degree of crystallinity as or higher than ordinary polypropylene resins, and has a differential thermal scanning calorific value. The thing of the temperature of the melting heat peak calculated | required by a meter can be 130 to 170 degreeC.
These polyolefin resins may be used individually by 1 type, and may be used in combination of 2 or more type.

The compatibilizing agent in the present invention is not limited to a block copolymer, a random copolymer, and a graft copolymer, but can be essentially dissolved in a polyolefin or a part having affinity in a molecule and can be essentially dissolved in a polylactic acid resin. Or a polymer having a portion having an affinity. Specifically, for example, styrene-ethylene-butylene block copolymer, styrene-ethylene-butylene-styrene block copolymer, ethylene-ethylene-butylene-ethylene block copolymer, styrene-ethylene-butadiene-styrene copolymer Examples thereof include hydrogenated styrene-isopropylene-styrene copolymer, ethylene-propylene-diene random copolymer, and the like.
Among these, a styrene-ethylene / butylene-styrene block copolymer is preferable because it improves the compatibility between polylactic acid and a polypropylene resin.

The blending ratio of the polylactic acid resin, the polyolefin resin, and the compatibilizer is 40 to 100 parts by mass, preferably 65 to 100 parts by mass of the polyolefin resin with respect to 100 parts by mass of the polylactic acid resin. Moreover, a compatibilizing agent is 0.2-10 mass parts with respect to 100 mass parts of mixture of polylactic acid-type resin and polyolefin resin, Preferably it is 0.5-6 mass parts.
These resin compositions form a sea-island structure, and the polyolefin resin as the component (B) becomes an island layer (domain).

When the blending ratio of the polyolefin resin is 40 parts by mass or more with respect to 100 parts by mass of the polylactic acid resin, the resin composition composed of the polylactic acid resin, the polyolefin resin, and the compatibilizer is stretched to make the film porous. When forming, holes can be opened both on the surface and inside of the film. When the amount is 100 parts by mass or less, a homogeneous porous film can be obtained by stretching a resin composition comprising a polylactic acid resin, a polyolefin resin, and a compatibilizing agent without unevenness. Even if the blending ratio of the polylactic acid resin and the polyolefin resin is within the above range, if there is no compatibilizing agent, a film-like product cannot be obtained by stretching, or even if obtained, for printing using the film The substrate is inferior in water-based ink absorbability and print setability. From these things, in the resin composition before extending | stretching, the suitable magnitude | size for expressing the structure of the porous film of this invention exists in the diameter of the island layer (domain) of the sea island structure derived from a compounding component. Presumed to exist. In other words, the characteristic structure of the porous film of the present invention can be expressed by blending as described above.
Further, if the blending ratio of the compatibilizer is less than 0.2 parts by mass with respect to 100 parts by mass of the mixture of the polylactic acid resin and the polyolefin resin, the polylactic acid resin and the polyolefin resin cannot be mixed uniformly. If it exceeds 10 parts by mass, the compatibilizer itself may be agglomerated in the mixture of the polylactic acid resin and the polyolefin resin.

  Other components may be added to the resin composition comprising a polylactic acid resin, a polyolefin resin, and a compatibilizer as long as the production of the porous film of the present invention is not hindered. Examples of other components include a colorant, a light resistance agent, a heat resistance agent, a moisture resistance agent, a fluorescent agent, an antistatic agent, and the like depending on the use of the resin composition. Furthermore, inorganic particles for improving the writing property or for enhancing the tactile sensation and texture can be mentioned as necessary. Examples of inorganic particles include calcium carbonate, aluminum oxide, titanium dioxide, silicon dioxide, barium sulfate, talc, and kaolin.

  There is no particular limitation on the apparatus and method for blending the polylactic acid resin, the polyolefin resin, and the compatibilizer. Using a general apparatus used for polymer blending, for example, a predetermined amount of polylactic acid resin, polyolefin resin and compatibilizer chips are mixed with a ribbon blender, tumbler, Henschel mixer (trade name), then a Banbury mixer, What is necessary is just to knead | mix using a uniaxial or biaxial extruder, and to extrude from a T die and to obtain a film-form composition. The kneading temperature is preferably 200 to 300 ° C, for example, and more preferably 230 to 250 ° C. When the temperature is 200 ° C. or higher, the polylactic acid resin and the polyolefin resin can be sufficiently melt-kneaded to create a uniform kneaded body. When the temperature is 300 ° C. or lower, the film-like composition can be obtained without thermally decomposing the resin. Can be obtained.

  There is no particular limitation on the method of stretching the film-like composition thus obtained. For example, as the biaxial stretching method, a method of stretching in the machine direction (extrusion direction in the film-like composition) by roll stretching and then stretching in the width direction with a tenter, or a method of biaxial stretching with a tenter at the same time can be mentioned. In these stretching operations, the film-like composition is stretched at around 60 to 140 ° C., preferably 75 to 100 ° C. in the vicinity of its glass transition point, for example, when polylactic acid and an ethylene-propylene copolymer are used. . At this time, when increasing the blending amount of polylactic acid, it is preferable to select a lower temperature in this temperature range. The stretching ratio is 1.5 to 5 times (area magnification: 2.25 to 25 times), preferably 2.5 to 3.5 times (area magnification: 6.25 to 12.25 times) in both length and width. . The longitudinal and lateral stretching ratios may be different. Further, the stretched film may be cooled by a conventional method to adjust the shrinkage stress.

  By biaxially stretching the film-like composition as described above, the porous film of the present invention having a thickness of 50 to 300 μm and having a characteristic porous structure can be obtained. This porous film has fine pores on the surface and has voids parallel to the front and back surfaces inside. For example, FIGS. 3 and 4 show typical surface and cross-sectional states of the porous film of the present invention. The porous film of the present invention has a pie-skin shape in which thin films of about 1 μm are laminated in the thickness direction in the cross section, and the thin films are not adhered to each other, and there are several between the thin films or on the thin film on the surface. The resin particles of μm to several tens μm are stuck or fused. The thin film has many substantially circular holes having a diameter of about 20 to 60 μm.

  The front and back surfaces of the porous film of the present invention are also composed of the above-described thin film with holes opened. When the structure in the thickness direction of the film of the holes opened on the front and back surfaces of this porous film is further characteristic, It can be seen that it has a simple structure. That is, since many thin films having similar holes opened are laminated in the film thickness direction with the positions of the holes being irregular, the holes opened on the front and back surfaces of the porous film of the present invention are in the film thickness direction. The film is blocked by the thin film laminated inside the film without penetrating the film. As described above, the porous film of the present invention is considered to be able to express an appropriate concealing property because it has a structure in which a large number of thin films with holes opened are laminated.

The porous film of the present invention preferably has a heat shrinkage rate of 20% or less in the extrusion direction of the film-like composition from which the porous film was immersed for 10 seconds in hot water at 80 ° C. .

  The porous film of the present invention has an apparent specific gravity in the range of 0.30 to 0.90, preferably 0.30 to 0.70, and has an opacity of 65 measured in accordance with JIS P 8149. As described above, the total light transmittance is preferably 45% or less.

As described above, the porous film of the present invention has a cross-sectional structure in which the surface is easy to carry ink, so that it has excellent printing characteristics, and further has a cross-sectional structure in which a large number of thin films with holes are laminated. It is also useful as a printing substrate having excellent concealability.
The printing of the printing substrate in the present invention includes not only printing by a printing machine such as offset printing using a physical printing plate, gravure printing, silk screen printing, but also printing by a printer such as an ink jet printer or a thermal transfer printer. included. In particular, when the substrate is strongly required to absorb ink, such as printing with an oxidation polymerization type ink, printing with an ink jet printer, etc., and when the substrate is required to have concealability, the micropores on the surface of the present invention Internal voids work very effectively.
The porous film of the present invention can be directly printed, and can be used as a substrate for printing without special processing for printing. In addition, the porous film of the present invention is subjected to surface treatment such as antistatic treatment, corona treatment, easy adhesion treatment, adhesive processing, and bonding of other materials as necessary while taking advantage of its characteristics. It is good also as a base material for printing by giving a process.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.
The physical properties of the polyolefin resin used and the obtained porous film were measured as follows.
(1) Melt flow rate Based on JIS K7210, it measured on condition of measurement temperature: 230 degreeC and load: 21.18N using the melt indexer (120SAS-2000 by Yasuda Seiki Seisakusho).
(2) Storage elastic modulus at 100 ° C. Based on JIS K 7244-4, using a dynamic viscoelasticity measuring device (EXTRA6000 manufactured by SII Co., Ltd.), vibration frequency 1 Hz, temperature rising rate: 5 ° C./min. The storage elastic modulus at 100 ° C. was determined.
(3) Water-based ink absorptivity test The ink absorptivity was evaluated using a water-based dye ink (manufactured by Shachihata Kogyo Co., Ltd., Shachihata stamp ink S-1 black) and a letter size. The ink absorptivity was judged according to the following criteria by rubbing the imprinted part with a soft cloth 30 seconds after the imprinting.
A: Less ink fading B: Ink fading but characters are readable C: Ink disappears and unreadable D: Composition does not form a film (a porous film cannot be produced) 4) Printing set property test RI-2 type tester (manufactured by Ishikawajima Industrial Machinery Co., Ltd.), and Dainippon Ink Chemical Co., Ltd., trade name “FUSION G” Using “N Indigo”, solid printing was performed under the condition of an ink loss of 0.2 g, and the ink set-off was evaluated. The evaluation of the set-off was evaluated according to the following criteria by applying paper to the printing part, pressurizing, and transferring the ink after 120 minutes from printing.
a: Little transfer and excellent setability.
b: Many transfers and inferior setability.
c: The composition does not become a film (a porous film cannot be produced) and the print set test cannot be performed.

(5) Tensile modulus In accordance with JIS K 7113 “Plastic testing method”, a dumbbell-shaped test piece of polypropylene resin was prepared, and the width: 5 mm was used using Toyo Seiki Seisakusho's Strograph V1-D. The distance between chucks was 70 mm, and the tensile speed was 50 mm / min.

(6) Opacity A specimen of a porous film obtained in accordance with JIS P 8149 “Paper and paperboard—Opacity test method (backing of paper) —Diffusion illumination method” was prepared, and SPECTROTOPOMETER CM- manufactured by MINOLTA The opacity was measured using 3630.
(7) Thermal shrinkage (%)
The thermal shrinkage rate in the extrusion direction when a porous film having a length (extrusion direction) of 10 cm and a width of 10 cm was immersed in hot water at 80 ° C. for 10 seconds was measured.
(L ₀ −L ₁ ) / L ₀ × 100
L ₀ : length of the film in the extrusion direction before immersion in hot water, L ₁ : length of the film in the extrusion direction when immersed in hot water for 10 seconds.
(8) Apparent specific gravity Mass M (g) and thickness D (μm) of a porous film having a length of 10 cm and a width of 10 cm were measured, and an apparent specific gravity was determined from the following formula.
Apparent specific gravity = M / D × 10 ²
(9) Total light transmittance (%)
In accordance with JIS K 7105, the total incident light amount T ₁ and the total transmitted light amount T ₂ were measured using a direct reading Haze meter (manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the total light transmittance was determined from the following formula.
Total light transmittance = T ₂ / T ₁ × 100 (%)
(10) Haze degree In accordance with JIS K 7105, using a direct reading haze meter (manufactured by Toyo Seiki Seisakusho), total incident light amount T ₁ , total transmitted light amount T ₂ , diffused light amount T ₃ by measuring device, measuring device And the amount of diffused light T ₄ by the sample was measured, and the haze value was determined from the following formula.
Degree of haze = (T ₄ / T ₂ −T ₃ / T ₁ ) × 100 (%)

Example 1
100 parts by mass of polylactic acid pellets (“Lacia H-400” manufactured by Mitsui Chemicals, Inc.) as a polylactic acid-based resin, and homopolypropylene pellets (melt flow rate (MFR) 2.5 g / 10 min, 100 ° C.) as polyolefins The storage elastic modulus is 200 MPa, the tensile elastic modulus is 1.50 GPa, “FY6” manufactured by Nippon Polypro Co., Ltd.), 67 parts by mass, and a styrene-ethylene-butylene-styrene block copolymer (manufactured by JSR Co., Ltd.) 1.7 parts by mass of Dynalon 8630P ") were mixed with a Henschel mixer (trade name) and extruded at 230 ° C using a twin screw extruder to obtain composition pellets. The composition pellets were extruded from a T die at 230 ° C. using an extruder to obtain a film-like composition having a thickness of 500 μm. Next, this film-like composition was stretched up to 3.2 times in both longitudinal and lateral directions in an 85 ° C. atmosphere using a biaxial stretching apparatus (FILMSTRetching Tester X6H-S, manufactured by Toyo Seiki Seisakusho Co., Ltd.) (Magnification 10.24 times) A porous film was obtained.
When the surface of the obtained porous film was observed with an electron microscope (SEM), a large number of pores were opened, the surface had a moderately smooth porous structure, and a porous film having a paper shape as a whole. I found out. An SEM photograph of the surface of the porous film is shown in FIG. Moreover, the thermal contraction rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity, and the thickness of the obtained porous film were measured and evaluated by an aqueous ink absorptivity test and a print set property test as print suitability. The results are shown in Table 1.

Example 2
In Example 1, homopolypropylene pellets having an MFR of 0.5 g / 10 min, a storage elastic modulus at 100 ° C. of 370 MPa, and a tensile elastic modulus of 1.60 GPa (“EA9” manufactured by Nippon Polypro Co., Ltd.) A porous film was obtained in the same manner as in Example 1 except that.
When the surface of the obtained porous film was observed with an electron microscope, it was a porous film having a large number of pores, a moderately smooth porous structure, and a paper-like shape as a whole. all right. Further, in the same manner as in Example 1, the heat shrinkage rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity, the thickness measurement and the printability were evaluated. The results are shown in Table 1.

Example 3
In Example 1, homopolypropylene pellets having an MFR of 1.9 g / 10 min, a storage elastic modulus at 100 ° C. of 350 MPa, and a tensile elastic modulus of 1.80 GPa (“FY6H” manufactured by Nippon Polypro Co., Ltd.) A porous film was obtained in the same manner as in Example 1 except that.
When the surface of the obtained porous film was observed with an SEM, it was found that the porous film had a porous structure in which a large number of holes were opened, the surface was moderately smooth, and exhibited a paper shape as a whole. It was. Further, in the same manner as in Example 1, the heat shrinkage rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity, the thickness measurement and the printability were evaluated. The results are shown in Table 1.

Example 4
In Example 1, homopolypropylene pellets were obtained by homopolypropylene pellets having an MFR of 3.0 g / 10 min, a storage elastic modulus at 100 ° C. of 200 MPa, and a tensile elastic modulus of 2.90 GPa (“FL6H” manufactured by Nippon Polypro Co., Ltd.). A porous film was obtained in the same manner as in Example 1 except that.
When the surface of the obtained porous film was observed with an SEM, it was found that the porous film had a porous structure in which a large number of holes were opened, the surface was moderately smooth, and exhibited a paper shape as a whole. It was. Further, in the same manner as in Example 1, the heat shrinkage rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity, the thickness measurement and the printability were evaluated. The results are shown in Table 1.

Example 5
A porous film was obtained in the same manner as in Example 1, except that 100 parts by mass of polylactic acid pellets, 100 parts by mass of polypropylene pellets, and 2 parts by mass of styrene-ethylene-butylene-styrene block copolymer were used. It was.
When the surface of the obtained porous film was observed with an electron microscope, it was a porous film having a large number of pores, a moderately smooth porous structure, and a paper-like shape as a whole. all right. An electron micrograph of the surface of the porous film is shown in FIG. Further, in the same manner as in Example 1, the heat shrinkage rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity, the thickness measurement and the printability were evaluated. The results are shown in Table 1.

Example 6
In Example 5, a porous film was obtained in the same manner as in Example 5 except that the amount of the styrene-ethylene / butylene-styrene block copolymer was changed to 8 parts by mass.
When the surface of the obtained porous film was observed with an electron microscope, it was found that the porous film had a paper structure as a whole with a large number of pores and a moderately smooth porous structure. . Further, in the same manner as in Example 5, the thermal shrinkage rate, opacity, total light transmittance, haze degree, apparent specific gravity, thickness measurement and printability were evaluated. The results are shown in Table 1.

Comparative Example 1
In Example 1, the polypropylene pellet was a homopolypropylene pellet (“FB3HAT” manufactured by Nippon Polypro Co., Ltd.) having an MFR: 7.5 g / 10 min, a storage elastic modulus at 100 ° C .: 260 MPa, and a tensile elastic modulus of 1.70 GPa. Except for this, the composition was the same as in Example 1, but the composition did not form a film and a porous film could not be produced.

Comparative Example 2
In Example 1, polypropylene pellets were used except that the polypropylene pellets were MFR: 10 g / 10 min, storage elastic modulus at 100 ° C .: 610 MPa, and tensile elastic modulus was 2.05 GPa (“MA3H” manufactured by Nippon Polypro Co., Ltd.). Although it carried out similarly to Example 1, a composition did not become a film form and the porous film was not able to be produced.

Comparative Example 3
In Example 1, 100 parts by mass of polylactic acid pellets (“Lacia H-400” manufactured by Mitsui Chemicals, Inc.), homopolypropylene pellets (MFR: 1.9 g / 10 min, storage elastic modulus at 100 ° C., 350 MPa, tensile elastic modulus 11 parts by mass of 1.80 GPa “FY6H” manufactured by Nippon Polypro Co., Ltd., and 1.1 parts of styrene-ethylene-butylene-styrene block copolymer (“Dynalon 8630P” manufactured by JSR Corporation) as a compatibilizer. A film was obtained in the same manner as in Example 1 except for changing to parts by mass. In the same manner as in Example 1, the thermal shrinkage rate, opacity, total light transmittance, haze degree, apparent specific gravity, thickness measurement and printability were evaluated. The results are shown in Table 1.

  As Table 1 shows, polyolefin resin is 40-100 mass parts with respect to 100 mass parts of polylactic acid-type resin, MFR of the said polyolefin resin is 0.5-3.0 g / 10min, and 100 degreeC When the storage elastic modulus in is 200 to 500 MPa, it can be seen that the porous film of the present invention comprising a polylactic acid resin, a polyolefin resin, and a compatibilizing agent is a film excellent in printability.

Example 7
100 parts by mass of polylactic acid pellets (“Lacia H-400” manufactured by Mitsui Chemicals, Inc.) as a polylactic acid resin, and ethylene-propylene copolymer pellets (MFR: 2.5 g / 10 min, 100 ° C.) as a polypropylene resin Storage elastic modulus: 450 MPa, tensile elastic modulus: 1.65 GPa, “BC6C” manufactured by Nippon Polypro Co., Ltd.) 67 parts by mass, styrene-ethylene-butylene-styrene block copolymer (manufactured by JSR Co., Ltd.) 6.7 parts by weight of Dynalon 8630P ") were mixed with a Henschel mixer (trade name) and extruded at 240 ° C using a twin screw extruder to obtain composition pellets.
The composition pellets were extruded from a T die at 240 ° C. using an extruder to obtain a film-like composition having a thickness of 500 μm. Next, this film-like composition was stretched up to 3.2 times in both longitudinal and lateral directions in an atmosphere of 85 ° C. using a biaxial stretching apparatus (FILMSTRetching Tester X6H-S, manufactured by Toyo Seiki Seisakusho Co., Ltd.) (Area magnification: 10.24 times) A porous film was obtained.
When the surface and cross section of the obtained porous film were observed with an SEM, the porous film had a pie skin shape in which a thin film having a thickness of about 1 μm was laminated in the thickness direction. A large number of substantially circular holes of 20 to 60 μm are opened, and the surface has a structure made of a thin film with the same holes opened, and the open holes of the thin film on the surface of the porous film are laminated in the film thickness direction. It was found that the film was blocked by the open thin film. 3 and 4 show SEM photographs of the surface and cross section of the porous film. Moreover, the thermal contraction rate, the opacity, the total light transmittance, the haze degree, the apparent specific gravity and the thickness of the obtained porous film were measured, and the printability was evaluated by an aqueous ink absorptivity test and a print set property test. The results are shown in Table 2.

Example 8
In Example 7, ethylene-propylene copolymer pellets as a polypropylene resin (MFR: 2.5 g / 10 min, storage elastic modulus at 100 ° C .: 450 MPa, tensile elastic modulus: 1.65 GPa, manufactured by Nippon Polypro Co., Ltd. 43 parts by mass of “BC6C”), 5.7 parts by mass of a styrene-ethylene-butylene-styrene block copolymer (“Dynalon 8630P” manufactured by JSR Corporation) as a compatibilizing agent, and a film-like composition A porous film was obtained in the same manner as in Example 7 except that the atmosphere during stretching was 80 ° C.
When the surface and cross section of the obtained porous film were observed by SEM, it was found that the porous film had the same porous structure as in Example 7. Further, in the same manner as in Example 7, the thermal shrinkage rate, opacity, total light transmittance, haze degree, apparent specific gravity, and thickness were measured, and the printability was evaluated by an aqueous ink absorptivity test and a print set property test. The results are shown in Table 2.

Example 9
In Example 7, 10 parts by mass of a styrene-ethylene-butylene-styrene block copolymer (“Dynalon 8630P” manufactured by JSR Corporation) as a compatibilizing agent was used, and the atmosphere when stretching the film-like composition was A porous film was obtained in the same manner as in Example 7 except that the temperature was 80 ° C.
When the surface and cross section of the obtained porous film were observed by SEM, it was found that the porous film had the same porous structure as in Example 7. Further, in the same manner as in Example 7, the thermal shrinkage rate, opacity, total light transmittance, haze degree, apparent specific gravity, and thickness were measured, and the printability was evaluated by an aqueous ink absorptivity test and a print set property test. The results are shown in Table 2.

Example 10
In Example 7, a porous film was prepared in the same manner as in Example 7 except that 17 parts by mass of styrene-ethylene-butylene-styrene block copolymer (“Dynalon 8630P” manufactured by JSR Corporation) as a compatibilizing agent was used. Got.
When the surface and cross section of the obtained porous film were observed by SEM, it was found that the porous film had the same porous structure as in Example 7. Further, in the same manner as in Example 7, the thermal shrinkage rate, opacity, total light transmittance, haze degree, apparent specific gravity, and thickness were measured, and the printability was evaluated by an aqueous ink absorptivity test and a print set property test. The results are shown in Table 2.

Comparative Example 4
In Example 7, 33 parts by mass of ethylene-propylene copolymer pellets (“BC6C” manufactured by Nippon Polypro Co., Ltd.), a styrene-ethylene-butylene-styrene block copolymer (manufactured by JSR Co., Ltd.) as a compatibilizing agent A porous film was obtained in the same manner as in Example 7, except that 5.3 parts by mass of “Dynalon 8630P”) was used, and the atmosphere when stretching the film-like composition was 80 ° C.
When the surface and cross section of the obtained porous film were observed with an SEM, the cross section had a pie skin shape in which thin films of about 1 μm were laminated in the thickness direction, but the film surface had almost no holes. It was. The SEM photograph of the surface and cross section of a film is shown in FIG. 5, FIG. Further, in the same manner as in Example 7, the thermal shrinkage rate, Beck smoothness, opacity, total light transmittance, haze degree, apparent specific gravity, and thickness were measured, and the printability was evaluated by an aqueous ink absorptivity test and a print set property test. did. The results are shown in Table 2.

Comparative Example 5
In Example 7, 110 parts by mass of ethylene-propylene copolymer pellets (“BC6C” manufactured by Nippon Polypro Co., Ltd.) and a styrene-ethylene-butylene-styrene block copolymer (manufactured by JSR Co., Ltd.) as a compatibilizing agent. A film-like composition was obtained in the same manner as in Example 7 except that “Dynalon 8630P”) was changed to 8.4 parts by mass. Next, this film-like composition was stretched in the same manner as in Example 7. However, the film-like composition was not stretched uniformly, and a porous film could be obtained by partially tearing during stretching. There wasn't.

Comparative Example 6
In Example 7, the propylene homopolymer pellets were MFR: 7.5 g / 10 min, storage modulus at 100 ° C .: 260 MPa, tensile modulus: 1.7 GPa polypropylene (“FB3HAT” manufactured by Nippon Polypro Co., Ltd.) Except for the above, the film was stretched in the same manner as in Example 7. However, the film-like composition was not stretched uniformly, and it was partially torn during the stretching, so that a porous film could not be obtained.

Comparative Example 7
Homopolypropylene pellets (MFR: 1.9 g / 10 min, storage elastic modulus 350 MPa at 100 ° C., tensile elastic modulus 1 with respect to 100 parts by mass of polylactic acid pellets (“Lacia H-400” manufactured by Mitsui Chemicals, Inc.) .80 GPa “FY6H” manufactured by Nippon Polypro Co., Ltd.) was mixed with a Henschel mixer <trade name>, and the mixture was extruded from a T-die at 230 ° C. using an extruder to form a film having a thickness of 500 μm. A composition was obtained. Next, this film-like composition was stretched up to 3.2 times in both the longitudinal and lateral directions in an atmosphere of 80 ° C. using a biaxial stretching apparatus (FILMSTRetching Tester X6H-S, manufactured by Toyo Seiki Seisakusho Co., Ltd.) (Magnification 10.24 times) A porous film was obtained.
The obtained porous film was measured for heat shrinkage, opacity, total light transmittance, haze, apparent specific gravity, and thickness, and evaluated by an aqueous ink absorptivity test and a print set property test as printability. The results are shown in Table 2.

Comparative Example 8
In Comparative Example 7, a film-like composition was obtained in the same manner as Comparative Example 7 except that 43 parts by mass of homopolypropylene pellets (“FY6H” manufactured by Nippon Polypro Co., Ltd.) was used.
The obtained porous film was measured for heat shrinkage, opacity, total light transmittance, haze, apparent specific gravity, and thickness, and evaluated by an aqueous ink absorptivity test and a print set property test as printability. The results are shown in Table 2.

As shown in the examples of Table 2, the compounding amount of the polypropylene resin is 40 to 100 parts by mass with respect to 100 parts by mass of the polylactic acid resin, and the MFR of the polypropylene resin is 1.5 to 2.5 g. / 10 minutes, and when the storage elastic modulus at 100 ° C. is 350 to 500 MPa, the porous film of the present invention comprising a polylactic acid resin, a polypropylene resin and a compatibilizing agent has a thin film laminated in the thickness direction in the cross section. The film has a pie skin shape, and the film has a porous structure in which a number of substantially circular holes are opened in the thin film. This porous film was excellent in printability and excellent in hiding because of its high opacity.
As shown in FIGS. 5 and 6, the film of Comparative Example 4 had almost no holes on the surface, and the thin films to be laminated adhered to each other.
As shown in FIGS. 7 to 10, the films of Comparative Examples 7 and 8 to which no compatibilizer is added are inferior in water-based ink absorbability and print setability because the surface layer has few micropores and there are also few internal cavities. I understand that.

  The present invention relates to a porous film excellent in printability, having an appropriate surface smoothness and excellent in concealment, as compared with a conventional film made of a porous polylactic acid resin and polyolefin. A printing substrate made of a film can be provided.

Claims (9)

(A) A polyolefin resin having a melt flow rate of 0.5 to 3.0 g / 10 min and a storage elastic modulus at 100 ° C. of 200 to 500 MPa with respect to 100 parts by mass of the polylactic acid resin . Including 40 to 100 parts by mass, and with respect to a total of 100 parts by mass of component (A) and component (B) , styrene-ethylene / butylene block copolymer, styrene-ethylene / butylene-styrene block copolymer, ethylene Phase (C) selected from ethylene / butylene / ethylene block copolymer, styrene / ethylene / butadiene / styrene copolymer, hydrogenated styrene / isopropylene / styrene copolymer and ethylene / propylene / diene random copolymer the solubilizing agent formed by stretching a resin composition comprising 0.2 to 10 parts by weight, the porous having fine pores on the surface Fi Rum.   The porous film according to claim 1, wherein the component (B) has a tensile modulus of 1.2 to 2.0 GPa.   2. The porous film according to claim 1, wherein when the porous film is immersed in hot water at 80 ° C. for 10 seconds, the heat shrinkage rate in the extrusion direction is 20% or less.   The porous film according to any one of claims 1 to 3, wherein the component (B) is a highly crystalline propylene homopolymer, a highly crystalline ethylene / propylene copolymer, or a mixture thereof.   2. The porous film according to claim 1, wherein the resin composition comprising the (A) component, the (B) component, and the (C) component forming the sea-island structure has an island layer (domain) as the (B) component.   The porous film according to claim 1, wherein the porous film has fine holes on the surface and has voids parallel to the front and back surfaces inside the film. Porous film, made of a thin film to be laminated, said thin film opening micropores, fine pores to form a film front and rear surfaces of the micropores, claim is made to conduct the air gap between the thin film on the film front and back 6 The porous film according to 1.   The porous film according to claim 1, which has an apparent specific gravity of 0.30 to 0.90. Printing substrate made of a porous film according to any one of claims 1-8.

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