JP6369342B2 - Biaxially stretched polypropylene film - Google Patents

Description

  The present invention relates to a biaxially stretched polypropylene film having high transparency and excellent smoothness.

  Biaxially stretched polypropylene films are widely used as packaging and industrial material films because of their excellent lightness, thermal stability, and mechanical properties. In particular, using the low surface energy of polypropylene film, it is widely used as a non-silicone protective material or mold release material in the manufacturing process of electronic components, electronic substrates, thermosetting resin members such as fiber reinforced plastics, etc. Has been. In recent years, in the electronic and photosensitive fields, further visibility and protective effects are required, and improvements in transparency and surface smoothness are required.

  Conventionally, crystallization nucleating agents have been used to improve the transparency of biaxially oriented polypropylene films. Patent Document 1 proposes a method for producing a stretched β-crystal polypropylene film in which a predetermined amount of amide compound having a specific structure is blended with polypropylene as a β-crystal nucleating agent. However, the film obtained by the method described in Patent Document 1 is a surface roughened film and is not a film having a smooth surface.

  Patent Document 2 proposes to use a specific amount of an amide compound having a specific structure as a compound having a nucleating action in a sheet or film forming polypropylene resin composition. However, when the film is manufactured, the amide compound contained in the film surface is dropped and bleed-out causes contamination of the manufacturing process, resulting in a decrease in film productivity. Moreover, since the unevenness | corrugation by a crystallization nucleating agent arises on the surface of a film, favorable smoothness is not acquired.

  Patent Document 3 has a strength of at least 400 MPa and is substantially composed of a central layer (B) and one or two other layers (A), and a nucleating agent is present in the central layer (B). AB type or ABA type uniaxially stretched polyolefin multilayer films have been proposed. However, since the polyolefin multilayer film is a uniaxially stretched film, it does not have a higher transparency than a biaxially stretched film.

  Patent Document 4 proposes a protective film obtained by laminating an adhesive layer on one side of a base film made of an α-olefin resin composition containing an amide compound having a specific structure as a nucleating agent. . However, since the base film is an unstretched film, the transparency is low. Moreover, since the said amide-type compound drops | omits in a film manufacturing process, and contamination of a film manufacturing process generate | occur | produces by bleeding out, productivity falls.

  Patent Document 5 proposes a laminated stretched film stretched at least uniaxially and comprising a crystalline polypropylene layer containing a crystal nucleating agent and a crystalline polypropylene layer containing an antiblocking agent. However, since a crystalline polypropylene layer containing an antiblocking agent is present on at least one surface, contamination of the process occurs due to the removal of the antiblocking agent in the film production process. Further, good smoothness of the film surface cannot be obtained due to the anti-blocking agent.

Japanese Patent Laid-Open No. 06-64038 JP 2007-63484 A JP 2010-517812 A JP 2012-17417 A JP-A-8-290536

  An object of the present invention is to provide a biaxially oriented polypropylene film that has high transparency and smoothness and does not contaminate the film production process.

  The inventors have at least one intermediate layer B between two surface layers A, and at least one of the surface layers A has a crystallization nucleating agent and an antiblocking agent content of 10 ppm or less. The at least one intermediate layer B contains a crystallization nucleating agent, and the surface roughness of at least one surface has a center line average roughness (Ra) of 0.03 to 0.10 μm and a maximum roughness ( The present inventors have found that the above problems can be solved by a biaxially stretched polypropylene film having a Rmax of 0.3 to 1.0 μm, and have completed the present invention.

That is, the present invention includes the following.
[1] A laminated film having at least one intermediate layer B between two surface layers A, wherein at least one of the surface layers A has a crystallization nucleating agent and an antiblocking agent content of 10 ppm or less. The at least one intermediate layer B contains a crystallization nucleating agent, and the surface roughness of at least one of the surfaces has a center line average roughness (Ra) of 0.03 to 0.10 μm and a maximum roughness A biaxially stretched polypropylene film having (Rmax) of 0.3 to 1.0 μm.
[2] The biaxially stretched polypropylene film according to [1], wherein the content of the crystallization nucleating agent contained in the at least one intermediate layer B is 10 to 1000 ppm.
[3] The minimum value of transparency measured in the MD direction (flow direction) and TD direction (width direction) of the film in accordance with ASTM D 1746 is 60% or more, according to [1] or [2] Biaxially stretched polypropylene film.
[4] The biaxially stretched polypropylene film according to any one of [1] to [3], wherein the MFR is 1.5 to 7.0 g / 10 minutes.
[5] The biaxially stretched polypropylene film according to any one of [1] to [4], wherein the ash content is 200 ppm or less.
[6] The biaxially stretched polypropylene film according to any one of [1] to [5], wherein the surface layer A is composed of a blend of a polypropylene resin and a polyolefin resin different from the polypropylene resin.
[7] The biaxially stretched polypropylene film according to any one of [1] to [6], wherein the crystallization nucleating agent contained in the intermediate layer B is an organic crystallization nucleating agent.

  According to the present invention, the content of the crystallization nucleating agent and the antiblocking agent in the surface layer is 10 ppm or less, and the crystallization nucleating agent is included in the intermediate layer, so that the biaxial stretching has excellent smoothness and high transparency. A polypropylene film can be obtained. Therefore, the biaxially stretched polypropylene film of the present invention can be suitably used as an electronic component, an electronic substrate, a protective film for a photosensitive film, a non-silicone type release film or release liner, and a separator film for a protective material. In addition, the biaxially stretched polypropylene film of the present invention can be produced without the crystallization nucleating agent and the antiblocking agent being removed or contaminated by bleeding.

FIG. 1 shows the result of microscopic observation of the surface of the biaxially stretched film of the present invention obtained in Example 1 with reflected light. FIG. 2 shows the result of microscopic observation of the surface of the biaxially stretched film of the present invention obtained in Example 2 with reflected light. FIG. 3 shows the result of microscopic observation by the reflected light of the surface of the biaxially stretched film not according to the present invention obtained in Comparative Example 1.

  The biaxially stretched polypropylene film of the present invention is a laminated polypropylene film composed of two surface layers A and at least one intermediate layer B containing a crystallization nucleating agent.

  The surface layer A and the intermediate layer B are made of polypropylene resin. As the polypropylene resin, a crystalline isotactic polypropylene resin which is a homopolymer of propylene is preferable. In the present invention, the crystalline isotactic polypropylene resin preferably has a mesopentad fraction ([mmmm]) of 93% or more, which is a stereoregularity obtained by high-temperature nuclear magnetic resonance (NMR) measurement, and more preferably Is 93% or more and 97% or less.

  When the mesopentad fraction [mmmm] is 93% or more, the crystallinity of the resin is improved by the high stereoregularity component, and high thermal stability and mechanical properties are exhibited. When the isotactic mesopentad fraction [mmmm] is less than 93%, the thermal stability and mechanical heat resistance tend to be inferior. On the other hand, if the mesopentad fraction [mmmm] is too high, the rate of solidification (crystallization) at the time of forming the cast raw sheet becomes too high, and peeling from the metal drum for forming the sheet tends to occur, and the stretchability May decrease.

The high temperature NMR apparatus for measuring the mesopentad fraction ([mmmm]) is not particularly limited, and is generally a commercially available high temperature nuclear magnetic resonance (NMR) apparatus capable of measuring the degree of stereoregularity of polyolefins. For example, a high temperature Fourier transform nuclear magnetic resonance apparatus (high temperature FT-NMR) manufactured by JEOL Ltd. and JNM-ECP500 can be used. The observation nucleus is ¹³ C (125 MHz), the measurement temperature is 135 ° C., and the solvent is ortho-dichlorobenzene (ODCB: ODCB and deuterated ODCB mixed solvent (mixing ratio = 4/1)). It is done. The method by high temperature NMR can be performed by a known method, for example, the method described in “Japan Analytical Chemistry / Polymer Analysis Research Roundtable, New Edition Polymer Analysis Handbook, Kinokuniya, 1995, p. 610”. .
The measurement mode is single pulse proton broadband decoupling, the pulse width is 9.1 μsec (45 ° pulse), the pulse interval is 5.5 sec, the number of integration is 4500 times, and the shift reference is CH ₃ (mmmm) = 21.7 ppm. The

  The pentad fraction representing the degree of stereoregularity is a combination of a pentad of a consensus “meso (m)” arranged in the same direction and a consensus “rasemo (r)” arranged in the same direction (mmmm or mrrm). Etc.) is calculated as a percentage from the integrated intensity value of each signal derived from. Regarding the attribution of each signal derived from mmmm, mrrm, etc., reference is made to the description of the spectrum such as “T. Hayashi et al., Polymer, 29, 138 (1988)”. The mesopentad fraction ([mmmm]) can be controlled by appropriately adjusting the polymerization conditions of polypropylene resin, the type of catalyst, the amount of catalyst, and the like.

  As a homopolymer of propylene, a known method, for example, a method of polymerizing propylene in a hydrocarbon solvent using a Ziegler catalyst system composed of titanium and an aluminum compound, a method of polymerizing in liquid propylene (bulk polymerization), and a gas phase What was manufactured by the method of superposing | polymerizing etc. may be used and what is marketed may be used.

  For the surface layer A, a blend of a polypropylene resin and a polyolefin resin different from the polypropylene resin can be used in order to improve the peelability of the film. Examples of other polyolefin resins include polymers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexane. However, in the present invention, when a blend of a polypropylene resin and another polyolefin resin is used, it is preferable to use a polypropylene homopolymer from the viewpoint of the smoothness of the resulting film surface.

  In the present invention, the melt flow rate (MFR) at 230 ° C. and 2.16 kgf is preferably 1.0 g / 10 min to 7.0 g / 10 min, more preferably 1.5 g / 10 min to 6.0 g / 10. Minutes, more preferably, a polypropylene resin having a weight of 2.0 g / 10 min to 4.0 g / 10 min can be used. When a polypropylene resin having a melt flow rate lower than 1.0 g / 10 min is used, the resin fluidity is remarkably lowered, it becomes difficult to control the thickness of the cast raw sheet, and a stretched film must be accurately produced in the width direction. Is not practically preferable. Further, when the melt flow rate is higher than 7.0 g / 10 min, the extrusion moldability is excellent, but the stretchability is remarkably lowered with the decrease in the mechanical properties of the obtained sheet, and the biaxial stretch molding cannot be performed. This is not preferable because it causes difficulties. Further, in the surface layer A and the intermediate layer B, polypropylene resins having different melt flow rates can also be used.

  In the surface layer A, the content of the crystallization nucleating agent and the antiblocking agent is 10 ppm or less. When the content of the crystallization nucleating agent and the antiblocking agent exceeds 10 ppm, the biaxially stretched film manufacturing process may cause contamination and bleedout due to the dropping of the crystallization nucleating agent and the antiblocking agent. In some cases, a smooth surface cannot be obtained in a biaxially stretched film. The content of the crystallization nucleating agent and the antiblocking agent in the surface layer A is preferably 5.0 ppm or less, more preferably 0 ppm.

  The crystallization nucleating agent used for the intermediate layer B is not particularly limited as long as it is a conventionally known crystallization nucleating agent, such as an organic crystallization nucleating agent, an inorganic crystallization nucleating agent, and a polymer crystallization nucleating agent. These can be used alone or in combination of two or more.

  Examples of the organic crystallization nucleating agent include 1,2,3-propanetricarboxylic acid tricyclohexylamide, 1,2,3-propanetricarboxylic acid tri (2-methylcyclohexylamide), and 1,2,3-propanetricarboxylic acid. Amide crystallization nucleating agents such as tri (3-methylcyclohexylamide) and 1,2,3-propanetricarboxylic acid tri (4-methylcyclohexylamide); sorbitol crystallization nucleating agents such as dibenzylidene sorbitol and dimethylbenzylidene sorbitol Alkali metal salts of aromatic carboxylic acids such as sodium p-tert-butylbenzoate and aluminum dibenzoate; aluminum salts, sodium 2,2-methylenebis (4,6-di-tert-butylphenyl) phosphate, etc. Metal salts of aromatic phosphates, etc. Amide crystallization nucleating agents and sorbitol nucleating agent for crystallization Among al is preferred. As a typical commercial product of an amide-based crystallization nucleating agent, for example, Rikaclear PC-1 manufactured by Shin Nippon Chemical Co., Ltd. can be mentioned. As a typical commercial product of the sorbitol-based crystallization nucleating agent, for example, Clear Master manufactured by Dainichi Seika Kogyo Co., Ltd. may be mentioned.

  Examples of the inorganic crystallization nucleating agent include talc, mica, nanoclay, metal whisker, carbon whisker, nanotube, zeolite, alumina, silica, and aluminosilicate material. Among these, talc is preferable.

  Examples of the polymer crystallization nucleating agent include cyclic olefin polymers such as polycyclohexene, polycyclopentene and polycyclobutene, branched cyclic polymers having a cyclic structure such as polyvinylcyclohexane in the side chain, and poly-3-methyl- 1-butene, poly-3-methyl-1-pentene, poly-3-ethyl-1-pentene, branched olefin polymers having 3 or more carbon atoms such as poly-4-methyl-1-pentene, and fluorine-containing compounds such as polytetrafluoroethylene A polymer etc. are mentioned.

  In the present invention, an organic crystallization nucleating agent and an inorganic crystallization nucleating agent are preferable because good smoothness and transparency are obtained in the obtained film, and it is difficult to deposit in a filter when a polymer filter is used. An organic crystallization nucleating agent is more preferable.

  The content of the crystallization nucleating agent in the intermediate layer B is preferably 10 to 1000 ppm. The organic crystallization nucleating agent can be used in the intermediate layer B at a content of 100 to 1000 ppm, and the inorganic crystallization nucleating agent at a content of 10 to 100 ppm. If the content of the crystallization nucleating agent in the intermediate layer B is within the above range, it is preferable because a biaxially stretched polypropylene film having high transparency can be obtained.

  The intermediate layer B is preferably composed of a polypropylene resin composition obtained by mixing a polypropylene resin and a crystallization nucleating agent. The mixing method is not particularly limited, but a method of dry blending a polypropylene resin polymer powder or pellet and a crystallization nucleating agent using a mixer or the like, and supplying a polypropylene resin and a crystallization nucleating agent to a kneader. However, there is a method of obtaining a blend resin by melt-kneading, but any method may be used. There are no particular restrictions on the mixer or kneader, and the kneader may be either a single screw type, a twin screw type or a multi-screw type higher than that. Any of the kneading types of the same direction rotation and the different direction rotation may be used.

  In the case of blending by melt kneading, as long as good kneading can be obtained, the kneading temperature is not particularly limited, but is generally in the range of 200 ° C to 300 ° C, preferably 230 ° C to 270 ° C. A too high kneading temperature is not preferable because it causes deterioration of the resin. In order to suppress deterioration during resin kneading and mixing, the kneader may be purged with an inert gas such as nitrogen. The melt-kneaded resin is generally pelletized to a suitable size using a known granulator, whereby a mixed polypropylene resin composition can be obtained.

  From the polypropylene resin and the polypropylene resin composition, the biaxially stretched polypropylene film of the present invention can be produced using a conventionally known method. For example, in the case of a layer structure of layer A / layer B / layer A, first, the polypropylene resin constituting the surface layer A and the polypropylene resin composition constituting the intermediate layer B are extruded at 230 to 270 ° C., respectively. The resin is melted in the machine, and a three-layer resin layer composed of layer A and layer B is formed using a resin confluence apparatus. Next, the laminated sheet composed of layer A / layer B / layer A is brought into close contact with an air knife on at least one metal drum controlled at 30 to 90 ° C., and formed into a sheet shape to obtain a cast raw sheet. . Then, the biaxially stretched polypropylene film of the present invention is obtained by biaxially stretching the cast raw sheet.

  Examples of the merging apparatus include a method of merging resins in a polymer pipe before the die, a feed block method of merging at a lamination unit provided in a resin introduction portion of the die, a manifold lamination method of laminating both resins after widening in the die, and the like Is exemplified, but not particularly limited. Although the manifold method is excellent in terms of the accuracy of the laminated thickness, it can be selected as appropriate in consideration of economy.

  There is no particular deadline in the layer structure in the case of a multi-layer, but when the layer structure is a layer A / layer B / layer A structure, there is no problem such as thermal curl of the film, and the film has excellent flatness. preferable. Further, the thickness of the surface layer A (layer A × 1/2) is preferably 2% to 20%, more preferably 2% to 10% with respect to the thickness of the intermediate layer B.

  Moreover, after melt-kneading a polypropylene resin and / or a polypropylene resin composition in an extruder, a fine foreign material etc. can be removed with the polymer filter installed between the extruder and the confluence | merging apparatus. Thereby, a fish eye (micro foreign material) can be reduced. As the polymer filter, a filter having high filtration accuracy is preferably used.

  The filtration accuracy should be as small as 10 μm (98% cut size) or less, preferably 5 μm or less. If the accuracy is too high (the size is too small) (for example, 1 μm or less), the removal rate of fish eyes (fine foreign matter) will be high, but the resin differential pressure in and out of the polymer filter will become too high, and extrusion molding (casting) Production (resin discharge) during the production of the original fabric is likely to be unstable, which is not practically preferable. On the other hand, if the filtration accuracy is larger than 10 μm (decrease accuracy), the filter eyes become larger, so the removal rate of fish eyes (fine foreign matter) becomes worse, and the fish eye (fine foreign matter) targeted by the present invention is deteriorated. ) Cannot be reduced, which is not preferable.

  As a filter medium used for the polymer filter, generally known filter media can be used without limitation. Examples of such a filter medium include a sintered metal nonwoven fabric (fiber sintered body), a laminated sintered wire mesh, and a powder sintered body. Moreover, as a filter type, a leaf disk filter, a candle filter, a pack filter, or the like can be used without limitation. Above all, for molding polypropylene resin with reduced fish eyes (fine foreign matter) according to the present invention, a leaf disk type filter using a sintered metal nonwoven fabric (fiber sintered body) has a large differential pressure (pressure loss). In addition, since stable discharge is obtained and the service life is long, it can be preferably employed.

  The biaxial stretching method for obtaining the film of the present invention is preferably a tenter method having good thickness unevenness and flatness. The tenter method also includes a simultaneous biaxial stretching method and a sequential biaxial stretching method, and either method may be used. Hereinafter, although the method of obtaining this invention film by the sequential biaxial stretching method is demonstrated, it is not limited to this.

  As a sequential biaxial stretching method, first, the cast raw fabric sheet is maintained at a temperature of 100 to 160 ° C., and is stretched 4 to 5 times in the MD direction (flow direction) through a roll provided with a speed difference. Subsequently, the stretched film is guided to a tenter and stretched 8 to 10 times in the TD direction (width direction) at a temperature of 160 ° C. or higher, and then relaxed and heat-set, and wound. The wound film can be cut to a desired product width after being subjected to an aging treatment in an atmosphere of about 20 to 45 ° C. By such a stretching process, a stretched film having excellent mechanical strength and rigidity is obtained.

  In addition, a heat stabilizer and an antioxidant may be added to the biaxially stretched polypropylene film of the present invention for the purpose of imparting chemical stability to the polypropylene resin and the polypropylene resin composition. Specific examples include phenol-based, hindered amine-based, phosphite-based, lactone-based, and tocopherol-based thermal stabilizers and antioxidants. More specifically, dibutylhydroxytoluene, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (Ciba Specialty Chemicals Co., Ltd .: “Irganox®) 1010 "), 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4hydroxy) benzene (Ciba Specialty Chemicals Co., Ltd .:" Irganox®) 1330 "), tris (2,4-di-t-butylphenyl) phosphite (Ciba Specialty Chemicals Co., Ltd .:" Irgafos (registered trademark) 168 "). Among these, at least one selected from phenolic antioxidants or a combination thereof, a combination of phenolic and phosphite, and phenolic and lactone, phenolic and phosphite and lactone Is preferable from the viewpoint of imparting chemical stability of the polypropylene resin.

  Furthermore, the biaxially stretched polypropylene film of the present invention may contain an organic and / or inorganic slip agent, a chlorine scavenger, and an antistatic agent as long as the object of the present invention is not adversely affected. Examples of the slip agent include aliphatic amides such as stearic acid amide and erucic acid amide, lauric acid diethanolamide, alkyldiethanolamine, aliphatic monoglyceride, aliphatic diglyceride, silica, alumina, and silicone cross-linked polymer. Examples of the chlorine scavenger include calcium stearate and hydrotalcite. Examples of the antistatic agent include alkyl methyl dibetaine, alkyl amine diethanol and / or alkyl amine ethanol ester and / or alkyl amine diethanol diester.

The biaxially stretched polypropylene film of the present invention thus obtained has a surface roughness of at least one surface of 0.03 to 0.10 μm in the center line average roughness (Ra), and the maximum roughness ( Rmax) is 0.3 to 1.0 μm. When Ra or Rmax is within the above range, the surface of the biaxially stretched polypropylene film becomes smooth, and when bonded as a protective film or a release film, irregularities are not easily formed between the protective body and voids and air voids are generated. Can be suppressed satisfactorily. In addition, wrinkles and lateral shifts are less likely to occur during lamination and winding, and releasability is also obtained.
In the biaxially stretched polypropylene film of the present invention, the surface roughness of at least one surface is preferably 0.03 to 0.09 μm in the center line average roughness (Ra) and 0.3 to 0.0 in the maximum roughness (Rmax). 0.9 μm, more preferably 0.03 to 0.08 μm in the center line average roughness (Ra), and 0.3 to 0.8 μm in the maximum roughness (Rmax).

  For example, Ra and Rmax are measured by a method defined in JIS-B0601, etc., using a stylus type or non-contact type surface roughness meter that is generally widely used. There are no restrictions on the manufacturer or model of equipment that can be used. In the examination in the present invention, Ra and Rmax were obtained in accordance with the method defined in JIS-B0601 (1982) using a surface roughness / contour shape measuring device Surfcom 1400D manufactured by Tokyo Seimitsu Co., Ltd. Either the contact method (stylus type using a diamond needle or the like) or the non-contact method (non-contact detection using a laser beam or the like) can be used, but in the study in the present invention, the measurement was performed with a measurement load of 750 μN.

In the biaxially stretched polypropylene film of the present invention, the minimum value of transparency measured in the MD direction (flow direction) and TD direction (width direction) of the film is preferably 60% or more, more preferably 65% or more, and still more preferably. 70% or more. A transparency of 60% or more is preferable because the state of being attached to the adherend can be visually recognized.
In the present invention, the transparency is a value measured according to ASTM D 1746, and can be measured using, for example, a transparency measuring instrument (clarity meter) TM-1D manufactured by Murakami Color Research Laboratory Co., Ltd. it can.

  The biaxially oriented polypropylene film of the present invention preferably has a melt flow rate (MFR) at 230 ° C. and 2.16 kgf of 1.5 g / 10 min to 7.0 g / 10 min, more preferably 2.0 g / 10 min. It is -6.0g / 10min, More preferably, it is 2.5g / 10min-5.0g / 10min. When the melt flow rate is lower than 1.5 g / 10 minutes, the resin fluidity is remarkably lowered, the control of the thickness of the cast raw sheet becomes difficult, and the stretched film cannot be accurately produced in the width direction. It is not preferable for practical use. Further, when the melt flow rate is higher than 7.0 g / 10 min, the extrusion moldability is excellent, but the stretchability is remarkably lowered with the decrease in the mechanical properties of the obtained sheet, and the biaxial stretch molding cannot be performed. This is not preferable because it causes difficulties.

In the biaxially stretched polypropylene film of the present invention, from the viewpoint of reducing fish eyes (fine foreign matter), it is preferable that the ash content due to the polymerization catalyst residue or the like is small, preferably 200 ppm or less, and 100 ppm or less. By setting the ash content to 200 ppm or less, fine foreign matters are remarkably reduced, and contamination when used for electronic parts can be reduced, which is preferable.
In the present invention, the fish eye (fine foreign matter) is a film product that contains a foreign material, an unmelted product, an oxidatively deteriorated product, etc. in the material when the material resin is melted by heat, extruded and stretched to produce a film. It is the thing taken in. If the number of fish eyes is large, it may cause contamination of foreign matter, voids, and air voids when bonded as protective films used in the manufacturing process of electronic parts, electronic substrates, and photosensitive materials. I can say that.

  The thickness of the film of the present invention is preferably 5 μm or more and 60 μm or less, more preferably 10 to 50 μm, and still more preferably 20 to 50 μm. If the thickness of the film is less than 5 μm, it is not preferable because it is not suitable for uses such as a protective film and a release material. On the other hand, when the thickness of the film exceeds 60 μm, the film cannot be stretched uniformly and may not be practically used.

  Since the biaxially stretched polypropylene film of the present invention has high transparency and excellent smoothness, the protective film for electronic parts, electronic substrates, photosensitive films, non-silicone type release films and release liners, and separator films for protective materials And so on.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

[Transparency]
The transparency of the biaxially stretched polypropylene film was measured using a transparency measuring instrument (clarity meter) TM-1D manufactured by Murakami Color Research Laboratory. The measurement method was performed in accordance with ASTM D 1746 in a state where the sample was cut into 5 cm × 5 cm, attached to the sample holder, and the sample holder was rotated. The measurement direction was measured three times for each of the MD direction (flow direction) and the TD direction (width direction), and the minimum value was used for evaluation.

[Surface roughness (smoothness)]
The center line average roughness (Ra) and maximum roughness (Rmax) of the biaxially stretched polypropylene film were measured using a surface roughness / contour measuring instrument Surfcom 1400D type manufactured by Tokyo Seimitsu Co., Ltd. JIS-B0601 (1982). Determined according to the method to follow. The measurement was performed 5 times, and the average value was used for evaluation. In the present invention, measurement was performed at a load of 750 μN by the contact method.

[Surface condition]
The surface state of the biaxially stretched polypropylene film was observed using a digital microscope VHX-2000 type manufactured by Keyence Corporation. Observation was performed at 100 times with reflected light.

[Film thickness]
The thickness of the biaxially stretched polypropylene film was measured according to JIS-P8118 using a micro thickness meter MEI-11 (JIS-B7502) manufactured by Citizen Precision.

[productivity]
The cast sheet was passed through a metal roll group extending in the flow direction, and after 2 hours at a predetermined draw ratio, the metal roll group was examined for soiling and used as an index of productivity.
○: No contamination and continuous production is possible.
X: Dirty and cannot be produced continuously.

[Ash content]
The ash content of the biaxially stretched polypropylene film was measured according to JIS-K 7250-1 (2006).

[MFR]
The MFR of the biaxially stretched polypropylene film was measured according to JIS-K 7210 (1999). The measurement conditions were 230 ° C. and 2.16 kgf. The measurement was performed three times, and the average value was used for evaluation.
[Example 1]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. Polypropylene resin composition obtained by adding 1.5% by mass of polypropylene resin B (MFR = 7.5 g / 10 min, talc 1000 ppm blended as a crystallization nucleating agent) to the resin pellets and performing dry blending The product was used as a raw material for the intermediate layer. For the surface layer, only the above-mentioned Primer Polypropylene resin A was used.

  The intermediate layer raw material was charged into the single-screw extruder I from the hopper for the intermediate layer.

  For the surface layer, the polypropylene resin A was put into the extruder II from the hopper.

  The resin of all layers passed through a polymer filter and was extruded from a multi-manifold die at 230 ° C. as a sheet of two types and three layers (configuration of layer A / layer B / layer A), and then the surface temperature was adjusted to 60 ° C. The material was cooled and solidified while being pressed onto the cooling drum by air pressure with an air knife to obtain a cast original sheet.

  Subsequently, the cast sheet was heated to 140 ° C. while being in contact with a metal roll, and then stretched about 4.5 times in the flow direction between rolls having a difference in peripheral speed. Next, the obtained uniaxially stretched film was introduced into a hot air oven while being sandwiched between clips, preheated to 180 ° C., stretched about 9 times in the width direction, and subsequently 170 ° C. while being relaxed by 5% in the width direction. The biaxially stretched polypropylene film having a thickness of about 30 μm was continuously obtained. The obtained biaxially stretched polypropylene film was wound up after trimming the end.

  The surface roughness, transparency, thickness, melt flow rate, and ash content of the obtained biaxially stretched polypropylene film were evaluated. The film and evaluation results are shown in Table 1.

[Example 2]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. To the above resin pellets, 0.8% by mass of a polypropylene masterbatch containing 2.5% of a crystallization nucleating agent (Rikaclear PC-1; amide-based crystallization nucleating agent manufactured by Nippon Nippon Chemical Co., Ltd.) is added and dry blended. The raw material for the intermediate layer was used.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as in Example 1 except for the intermediate layer material. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

Example 3
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. 1.0% by mass of a polypropylene masterbatch containing 10% of a crystallization nucleating agent (Daiichi Seika's clear master; sorbitol crystallization nucleating agent) is added to the above resin pellets, dry blending is performed, and the intermediate layer is used. Used as raw material.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as in Example 1 except for the intermediate layer material. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

[Comparative Example 1]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. The resin pellet was used as an intermediate layer raw material without adding a crystallization nucleating agent.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as in Example 1 except for the intermediate layer material. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

[Comparative Example 2]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. Resin composition obtained by adding 1.5% by mass of polypropylene resin B (MFR = 7.5 g / 10 min, blended with 1000 ppm of talc as a crystallization nucleating agent) to the above resin pellets and performing dry blending The product was used as an intermediate layer raw material and a surface layer raw material.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as Example 1 except for the raw materials. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

[Comparative Example 3]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. 0.8% by mass of a polypropylene masterbatch containing 2.5% of a crystallization nucleating agent (Rikaclear PC-1 manufactured by Shin Nippon Rika Co., Ltd .; amide-based crystallization nucleating agent) is added to the resin pellets, and dry blending is performed. The resin composition obtained by the above was used as a raw material for an intermediate layer and a surface layer.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as in Example 1 except for the raw materials. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

[Comparative Example 4]
As polypropylene resin, pellets of polypropylene resin A (MFR = 2.8 g / 10 min) manufactured by Prime Polymer Co., Ltd. were prepared. It was obtained by adding 1.0% by mass of a polypropylene masterbatch containing 10% of a crystallization nucleating agent (Clear Master manufactured by Dainichi Seika; a sorbitol crystallization nucleating agent) to the resin pellets and performing dry blending. The resin composition was used as a raw material for the intermediate layer and the surface layer.

  A biaxially stretched polypropylene film having a thickness of 30 μm was obtained in the same manner as in Example 1 except for the raw materials. Table 1 shows the evaluation results of the obtained biaxially stretched polypropylene film.

  As shown in Table 1, the biaxially stretched polypropylene films according to the present invention in Examples 1 to 3 contain a crystallization nucleating agent only in the intermediate layer, so that excellent transparency and smoothness are obtained without impairing productivity. It was what had.

  However, when the crystallization nucleating agent was not added, the transparency and surface properties could not be reduced (Comparative Example 1), which was not practical. Further, as is apparent from the results of Comparative Examples 2 to 4, when the crystallization nucleating agent is contained not only in the intermediate layer but also in the surface layer, dirt attached to the metal roll group to be stretched can be visually confirmed, Scratches and foreign matter due to dirt adhering to the metal roll group could be confirmed on the produced film, and it was not practical.

  1 to 3, the surface of the biaxially stretched polypropylene film according to the present invention (FIGS. 1 and 2) is smoother than the surface of the biaxially stretched polypropylene film not according to the present invention (FIG. 3). It can be seen that is improved.

  Thus, the biaxially stretched polypropylene film of the present invention is extremely suitable as a separator film for electronic parts, electronic substrates, photosensitive film protective films, non-silicone type release films and release liners, and protective materials. Is understood.

Claims (6)

A laminated film having at least one intermediate layer B between two surface layers A, wherein at least one of the surface layers A has a content of a crystallization nucleating agent and an antiblocking agent of 10 ppm or less, At least one intermediate layer B contains a crystallization nucleating agent, and the crystallization nucleating agent contained in the intermediate layer B is at least one selected from the group consisting of an amide crystallization nucleating agent and a sorbitol crystallization nucleating agent. And the surface roughness of at least one surface of the laminated film has a center line average roughness (Ra) of 0.03 to 0.10 μm and a maximum roughness (Rmax) of 0.3 to 1.0 μm. A biaxially oriented polypropylene film.   The biaxially stretched polypropylene film according to claim 1, wherein the content of the crystallization nucleating agent contained in the at least one intermediate layer B is 10 to 1000 ppm.   The biaxially oriented polypropylene film according to claim 1 or 2, wherein the minimum value of transparency measured in the MD direction (flow direction) and the TD direction (width direction) of the film in accordance with ASTM D 1746 is 60% or more. .   The biaxially stretched polypropylene film according to any one of claims 1 to 3, wherein the MFR is 1.5 to 7.0 g / 10 min.   The biaxially stretched polypropylene film according to any one of claims 1 to 4, wherein the ash content is 200 ppm or less.   The biaxially stretched polypropylene film according to any one of claims 1 to 5, wherein the surface layer A is composed of a blend of a polypropylene resin and a polyolefin resin different from the polypropylene resin.