WO2018097161A1

WO2018097161A1 - Multilayer polypropylene film

Info

Publication number: WO2018097161A1
Application number: PCT/JP2017/041940
Authority: WO
Inventors: 岡田一馬; 久万琢也; 山中康平
Original assignee: 東レ株式会社
Priority date: 2016-11-25
Filing date: 2017-11-22
Publication date: 2018-05-31
Also published as: JPWO2018097161A1; CN110023086A; KR20190082798A; JP7070426B2; KR102405861B1

Abstract

The present invention addresses the problem of providing a multilayer polypropylene film which has excellent mold releasability, surface smoothness and transparency. A multilayer polypropylene film according to the present invention has a surface layer (I) on at least one surface of a base material layer (II) that is mainly composed of a polypropylene. The surface layer (I) has a surface free energy of 18-28 mN/m and a gloss value of 40% or more.

Description

Laminated polypropylene film

The present invention relates to a laminated polypropylene film that is excellent in releasability, surface smoothness, and transparency and can be suitably used as a release film.

Polypropylene films are excellent in transparency, mechanical properties, electrical properties, etc., and are therefore used in various applications such as packaging, mold release, tape, cable wrapping and electrical applications such as capacitors. In particular, since it has excellent surface releasability and mechanical properties, it is suitably used as a release film or process film for various members such as plastic products, building materials and optical members.

The required characteristics for the release film are appropriately set depending on the intended use, but in recent years, they may be used as a cover film for a resin layer having adhesiveness such as a photosensitive resin. When covering an adhesive resin layer, if the cover film is poorly releasable, it cannot be peeled cleanly when it is peeled off, and the shape of the resin layer that is the protective surface changes, or peeling marks remain on the protective surface Therefore, a film having a low surface free energy and good releasability is required. Moreover, when the surface smoothness of a cover film is bad, when it uses, for example as a release film of an optical member, the surface unevenness | corrugation of a film may transfer to an optical member and may affect the visibility of a product. Furthermore, if the cover film has poor transparency, it may interfere with a process inspection such as defect observation after bonding with the photosensitive resin. From the above, in order to use in a release film having high required characteristics such as an optical member, a film having mold release property, surface smoothness, and transparency may be required.

As a means for improving releasability, for example, in Patent Document 1, the releasability is improved by roughening the surface such as a method of forming β crystals on the film surface layer or adding particles to the inner layer of the film. Although examples have been described, the surface smoothness and transparency were insufficient. Patent Documents 2 and 3 describe examples in which the release property is improved by adding a polymethylpentene resin to the film surface layer, but the surface smoothness and transparency are insufficient. It was. Further, Patent Document 4 describes an example in which the surface free energy is reduced by surface irregularities, but the releasability is insufficient. Moreover, since the unevenness is formed by coating or the like in post-processing, the cost may increase.

WO2016 / 006578 JP 2014-30974 A WO2016 / 051897 publication JP 2000-117900 A

The object of the present invention is to solve the above-mentioned problems. That is, it is to provide a laminated polypropylene film excellent in releasability, surface smoothness, and transparency.

In order to solve the above-described problems and achieve the object, the laminated polypropylene film of the present invention is a laminated film having a surface layer (I) on at least one surface of a base material layer (II) mainly composed of polypropylene. The surface free energy of the surface layer (I) is 18 to 28 mN / m, and the gloss value is 40% or more.

The laminated polypropylene film of the present invention is excellent in releasability, surface smoothness, and transparency, and therefore can be suitably used as a release film.

The laminated polypropylene film of the present invention is a laminated film having a surface layer (I) on at least one surface of a base material layer (II) mainly composed of polypropylene, and the surface free energy of the surface layer (I) is 18 to 28 mN / m. The surface free energy is more preferably 18 to 27 mN / m, still more preferably 18 to 26 mN / m, and particularly preferably 18 to 25 mN / m. When the surface free energy exceeds 28 mN / m, when it is used as a release film for surface protection, if the adherend is strongly adhered, it cannot be peeled cleanly, and the surface shape of the adherend changes or adheres. Peeling marks may remain on the body surface. The lower the surface free energy, the better the releasability, but the lower limit is about 18 mN / m for the polypropylene film. In order to make the surface free energy in the above range, it is effective to set the raw material composition of the film in the range described later and the film forming conditions in the range described later, and particularly to add a resin having a low surface free energy to the film surface layer. is there.

The gloss value of the surface layer (I) is 40% or more. More preferably, it is 80% or more, More preferably, it is 100% or more, Most preferably, it is 120% or more. The gloss value is an index representing the glossiness, and has a high correlation with surface smoothness and transparency, and a higher value is preferable, but the upper limit is substantially about 155%. In order to set the gloss value in the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described later. In particular, the range in which the addition concentration of the low surface free energy added to the surface layer is described later By adjusting to, the compatibility between the resin with low surface free energy added to the surface layer and polypropylene resin is enhanced, the cooling conditions in casting are strengthened, and the formation of spherulites on the film surface is reduced as much as possible and the surface free energy It is effective to perform horizontal stretching and heat treatment at a temperature higher than the melting point of the low resin, to uniformly distribute the resin having a low surface free energy on the film surface layer, and to smooth the film surface.

Conventionally, there are many examples in which release properties have been improved by including a resin with low surface free energy such as polymethylpentene, fluorine-based resin, or silicon resin in the film surface layer, but these resins have compatibility with polypropylene resin. Since it was low, it was not uniformly dispersed in the polypropylene resin, and the surface smoothness and transparency were insufficient. By adjusting the composition of the raw material used for the surface layer to the range described later, the present invention improves the compatibility between the resin having a low surface free energy and the polypropylene resin, and further makes the film forming conditions described later to obtain polypropylene. The present invention provides a polypropylene film having excellent releasability, surface smoothness, and transparency that cannot be achieved by conventional polypropylene films by controlling the crystal state of the film and suppressing a decrease in transparency in the stretching process. Is.

The laminated polypropylene film of the present invention preferably has a haze value of 50% or less. More preferably, it is 30% or less, more preferably 10% or less, and particularly preferably 3% or less. When the haze value exceeds 50%, since the transparency of the laminated film is low, it may be an obstacle when performing process inspection such as defect observation after bonding with the photosensitive resin. The lower limit of the haze value is not particularly limited, but the lower limit is substantially about 0.1%. In order to set the haze value in the above range, the raw material composition of the film is set in the range described below, and the film forming conditions are set in the range described below. In particular, the compatibility between the resin having low surface free energy added to the surface layer and the polypropylene resin is set. It is effective to enhance the cooling conditions in the casting and casting, and to reduce the formation of spherulites on the film surface as much as possible.

The laminated polypropylene film of the present invention preferably has a heat shrinkage of 2.5% or less at 120 ° C. for 15 minutes in the longitudinal direction. More preferably, it is 2.2% or less, More preferably, it is 1.8% or less. In the present application, a direction parallel to the film forming direction is referred to as a film forming direction, a longitudinal direction, or an MD direction, and a direction perpendicular to the film forming direction in the film plane is referred to as a width direction or a TD direction. If the thermal shrinkage in the longitudinal direction at 120 ° C for 15 minutes exceeds 2.5%, the film will deform and peel off, for example, when passing through a drying process where heat is applied after bonding with other materials. Or wrinkles. The lower limit of the heat shrinkage rate is not particularly limited, but the film may swell, and the lower limit is substantially about −2.0%. In order to set the heat shrinkage ratio in the above range, the raw material composition of the film is set in the range described later, and the film forming conditions are set in the range described below, and in particular, the heat fixing and relaxation conditions after biaxial stretching are set in the range described below. Is effective.

In the laminated polypropylene film of the present invention, the sum of the tear strength in the film longitudinal direction and the width direction is preferably 2.5 N / mm or more. More preferably, it is 3.0 N / mm or more, More preferably, it is 3.5 N / mm or more. The tear strength correlates with the interlayer adhesion (adhesion between the surface layer (I) and the base material layer (II)) of the laminated film, and the higher the value, the better the interlayer adhesion. When the sum of the tear strength in the film longitudinal direction and the width direction is less than 2.5 N / mm, the interlayer adhesion is low, and when the film is transported or peeled from the photosensitive resin, the interlayer peeling occurs at the laminated film interface. May occur. Although the upper limit of the sum of the tear strengths is not particularly limited, the upper limit is substantially 10 N / mm. In order to make the sum of the tear strengths in the above range, the raw material composition of the film is in the range described later, and the film forming conditions are in the range described later. In particular, the compatibility between the resin having a low surface free energy added to the surface layer and the polypropylene resin. It is effective to increase the orientation of the film, for example, to increase the stretching ratio or to increase the draw ratio.

The thickness of the laminated polypropylene film of the present invention is appropriately adjusted depending on the application and is not particularly limited, but is preferably 0.5 μm or more and 100 μm or less. When the thickness is less than 0.5 μm, handling may be difficult, and when it exceeds 100 μm, the amount of resin may increase and productivity may decrease. Since the laminated polypropylene film of the present invention is excellent in tear strength even when the thickness is reduced, the handling property can be maintained. In order to make use of such characteristics, the thickness is more preferably 1 μm or more and 40 μm or less, further preferably 1 μm or more and 30 μm or less, and particularly preferably 1 μm or more and 15 μm or less. The thickness can be adjusted by the screw speed of the extruder, the width of the unstretched sheet, the film forming speed, the stretch ratio, and the like within a range not deteriorating other physical properties.

The surface layer (I) of the laminated polypropylene film of the present invention preferably comprises an olefin resin as a main component. More preferably, it is 90 mass% or more, More preferably, it is 95 mass% or more, Most preferably, it is 99 mass% or more. Here, in the present invention, the “main component” means that the proportion of the specific component in all the components is 50% by mass or more. Addition of non-olefin resins such as fluorine resin and silicon resin can be expected to improve releasability, but non-olefin resins are particularly low in compatibility with olefin resins such as polypropylene. In some cases, it is not uniformly dispersed in the resin and the surface smoothness and transparency may be impaired. From the above viewpoint, the surface layer (I) of the laminated polypropylene film of the present invention preferably comprises an olefin resin, and more preferably comprises an olefin resin as a main component.

The surface layer (I) of the laminated polypropylene film of the present invention is preferably an olefin resin in which a part of the olefin resin is a 4-methylpentene-1 unit, and 4-methyl-1- A pentene / α-olefin copolymer is more preferable. Resin containing 4-methylpentene-1 unit has the effect of lowering the surface free energy, and has higher affinity with polypropylene resin than non-olefin resin, so that dispersibility in polypropylene resin can be improved. it can. Examples of the olefin resin, a part of which is 4-methylpentene-1 unit, include TPX (registered trademark) DX310, TPX (registered trademark) DX231, and TPX (registered trademark) MX004 manufactured by Mitsui Chemicals, Inc. It can be illustrated. Further, 4-methyl-1-pentene / α-olefin copolymer is particularly preferably used because of its high compatibility with polypropylene resin. The α-olefin is preferably a linear or branched α-olefin having 2 to 20 carbon atoms, more preferably 2 to 10 carbon atoms, and still more preferably 2 to 5 carbon atoms. For example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and the like can be mentioned, but not limited thereto. For example, a 4-methyl-1-pentene / α-olefin copolymer as disclosed in JP 2013-194132 A is preferably used.

In the laminated polypropylene film of the present invention, it is preferable that the surface layer (I) contains an olefin resin containing 4-methylpentene-1 unit and having a melting point of 160 ° C. or less, and the melting point is 150 ° C. or less. More preferred. An olefinic resin comprising 4-methylpentene-1 unit and a polypropylene resin have high affinity but are not compatible with each other, and thus form a domain like a sea-island structure. Due to the presence of this sea-island structure, unevenness in releasability may occur or transparent smoothness may be impaired. When the melting point of the olefin resin containing 4-methylpentene-1 unit is 160 ° C. or higher, voids are stretched at the domain interface of the sea-island structure by the olefin resin containing 4-methylpentene-1 unit and the polypropylene resin. May occur, and smoothness and transparency may be deteriorated.

In the laminated polypropylene film of the present invention, the content of the olefin resin comprising 4-methylpentene-1 unit in the resin composition of the surface layer (I) is 0.1 to 15% by mass, or 85 to 100%. % By mass is preferable, and 0.1 to 10% by mass, or 90 to 100% by mass is more preferable. When the content of the olefin resin comprising 4-methylpentene-1 unit is higher than 15 mass% and lower than 85 mass%, the transparency and smoothness of the film may be impaired. The reason is estimated below. Transparency and smoothness are high when a polypropylene resin and an olefin-based resin containing 4-methylpentene-1 units are not blended and formed into films independently. However, as described above, an olefin resin and a polypropylene resin containing 4-methylpentene-1 unit have high affinity but are not compatible with each other, and thus form a domain like a sea-island structure. Moreover, since both resin also differs in refractive index, it can be estimated that transparency and smoothness of a laminated film are impaired.

From the above, in order to improve transparency and smoothness, it is necessary to reduce the domains as much as possible by increasing the compatibility of both resins. In order to reduce the domain, it is important to lower the concentration of one of the resins. The olefin resin containing 4-methylpentene-1 unit should be 15% by mass or less, or conversely 85% by mass. This is achieved by the above. Hereinafter, each case will be described.

When the amount of the olefin resin containing 4-methylpentene-1 unit is reduced to 15% by mass or less, there is a concern that the releasability is insufficient. Therefore, it is preferable to use a technique for improving the releasability. For example, it is preferable to set the thickness of the surface layer (I) to be thin so that an olefin-based resin containing many 4-methylpentene-1 units appears on the surface of the film of the surface layer (I). Further, by adding an olefin resin containing 4-methylpentene-1 unit having a melting point of 160 ° C. or less to the surface layer (I), and performing transverse stretching and heat treatment at a temperature equal to or higher than the melting point, the matrix polypropylene resin As a result of the stretching deformation, the domain of the olefin resin comprising 4-methylpentene-1 unit is deformed flatly and distributed uniformly, so that no voids are formed at the interface. It becomes possible to improve releasability. In addition, a technique in which an olefin resin containing 4-methylpentene-1 unit is kneaded with a polypropylene resin in advance to form a chip is also preferably used from the viewpoint of improving dispersibility.

When the olefin-based resin containing 4-methylpentene-1 unit is 85% by mass or more, there is a concern that interfacial delamination may occur at the interface between the inner layer and the surface layer. It is preferable to use a technique for improving the above. For example, in order to enhance the compatibility with the polypropylene resin used in the base material layer (II), a 4-methyl-1-pentene / α-olefin copolymer is used, or a butene polymer is used as the third component. The method to add is mentioned. Since the butene polymer has a high affinity for both polypropylene and 4-methylpentene-1 polymer, it is possible to improve the adhesive strength at the interface between the inner layer and the surface layer. In addition, since the stretching stress is reduced by the addition, voids are less likely to occur at the interface between the olefin resin matrix containing 4-methylpentene-1 units and the domain of the polypropylene resin, and the transparency, smoothness, and releasability are reduced. It becomes possible to improve. In addition, the surface layer (I) contains an olefin resin containing 4-methylpentene-1 unit having a melting point of 160 ° C. or less, and is subjected to transverse stretching at a temperature equal to or higher than the melting point to be melted by heat treatment. At the interface between the olefinic resin matrix containing methylpentene-1 units and the domain of the polypropylene resin, voids hardly occur during stretching, and it becomes possible to improve transparency, smoothness and releasability. In addition, a technique in which a polypropylene resin is preliminarily kneaded with an olefin resin containing 4-methylpentene-1 unit to form a chip is also preferably used from the viewpoint of improving dispersibility.

In addition, in order to improve the transparent smoothness of the film regardless of the addition concentration of the olefin resin containing 4-methylpentene-1 unit, there is also a method of rapidly cooling the cast drum temperature after extrusion to 30 ° C. or less. Preferably used.

The raw materials used for the polypropylene laminated film of the present invention include antioxidants, heat stabilizers, antistatic agents, lubricants composed of inorganic or organic particles, and further anti-blocking agents and fillers as long as the effects of the present invention are not impaired. Various additives such as an incompatible polymer may be contained. In particular, it is preferable to contain an antioxidant for the purpose of suppressing oxidative deterioration of polypropylene or a resin having a low surface free energy. It is preferable that antioxidant content shall be 2 mass parts or less with respect to 100 mass parts of polypropylene compositions, More preferably, it is 1 mass part or less, More preferably, it is 0.5 mass part or less.

Next, the polypropylene raw material preferably used for the base material layer (II) of the present invention will be described. There is no problem even if the raw material contained in the surface layer (I) is contained in the base material layer (II).

The polypropylene raw material is preferably polypropylene having a cold xylene soluble part (hereinafter CXS) of 4% by mass or less and a mesopentad fraction of 0.95 or more. If these conditions are not satisfied, the film-forming stability may decrease, and the tear strength of the film may decrease.

Here, the cold xylene soluble part (CXS) refers to a polypropylene component dissolved in xylene when the film is completely dissolved in xylene and then deposited at room temperature, and has low stereoregularity. It is considered that the component which is difficult to crystallize due to a low molecular weight is applicable. If many such components are contained in the resin, the tear strength of the film may be reduced. Therefore, CXS is preferably 4% by mass or less, more preferably 3% by mass or less, and particularly preferably 2% by mass or less. CXS is preferably as low as possible, but about 0.1% by mass is the lower limit. In order to bring the CXS of the polypropylene resin within the above range, a method of increasing the catalytic activity in obtaining the resin, a method of washing the obtained resin with a solvent or propylene monomer itself, and the like can be used.

From the same viewpoint, the mesopentad fraction of the polypropylene raw material is preferably 0.95 or more, more preferably 0.97 or more. The mesopentad fraction is an index indicating the stereoregularity of the crystal phase of polypropylene measured by a nuclear magnetic resonance method (NMR method). The higher the numerical value, the higher the crystallinity, the higher the melting point, and the higher the temperature. It is preferable because it is suitable for use. The upper limit of the mesopentad fraction is not particularly specified. In order to obtain a resin having such a high stereoregularity, there are a method of washing resin powder obtained with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or a promoter, and a composition. Preferably employed.

The polypropylene raw material is more preferably a melt flow rate (MFR) of 1 to 10 g / 10 minutes (230 ° C., 21.18 N load), particularly preferably 2 to 5 g / 10 minutes (230 ° C., 21.18 N load). ) Is preferable from the viewpoints of film forming properties and film tear strength. In order to set the MFR to the above value, a method of controlling the average molecular weight or the molecular weight distribution is employed.

The polypropylene raw material may contain other unsaturated hydrocarbon copolymerization components or the like as long as the object of the present invention is not impaired, or may be blended with a polymer that is not propylene alone. Examples of such a copolymer component and a monomer component constituting the blend include ethylene, propylene (in the case of a copolymer blend), 1-butene, 1-pentene, 3-methylpentene-1, 3- Methylbutene-1,1-hexene, 4-methylpentene-1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene, 5-methyl-2 -Norbornene and the like. From the viewpoint of tear strength and heat resistance, the copolymerization amount or blend amount is preferably less than 1 mol% in terms of copolymerization amount and less than 10 mass% in terms of blend amount.

The laminated polypropylene film of the present invention has a laminated structure having a surface layer (I) on at least one surface of a base material layer (II) containing polypropylene as a main component. At this time, the thickness of the _{T 1} of the surface layer (I), when the base layer a thickness of (II) was _{T _2,} it is preferable the value of T 1 / _{T 2} is 0.3 or less. More preferably, it is 0.2 or less, More preferably, it is 0.12 or less. When the value of T ₁ / T ₂ exceeds 0.3, interfacial peeling at the laminated interface between the inner layer and the surface layer may occur or the transparent smoothness may be impaired. In order to make a lamination | stacking thickness ratio into the said range, it can adjust with the screw rotation speed of each extruder used for surface layer (I) and base material layer (II). Here, in the case of a laminated polypropylene film having a three-layer configuration of A layer / B layer / A layer, the total thickness of the front and back surfaces (A layer) is defined as the thickness T ₁ of the front layer (I). Further, in the case of a laminated polypropylene film having three different layers of A layer / B layer / C layer, the thickness T ₁ of the surface layer (I) is determined by measuring the surface free energy of each film surface of the A layer and the C layer, the thickness of the surface layer (a layer or C layer) of the lower layer to T _1.

Next, the method for producing the laminated polypropylene film of the present invention will be described, but the present invention is not necessarily limited thereto.

First, raw materials for the surface layer (I) and the base material layer (II) are supplied to each single-screw extruder, and melt extrusion is performed at 200 to 260 ° C. Then, after removing foreign substances and modified polymer with a filter installed in the middle of the polymer tube, a multi-manifold type A layer / B layer / A layer composite T die has a lamination thickness ratio of 1/15/1, for example. And discharged onto a cast drum to obtain a laminated unstretched sheet having a layer configuration of A layer / B layer / A layer. At this time, the cast drum preferably has a surface temperature of 15 to 50 ° C. As an adhesion method to the casting drum, any method among an electrostatic application method, an adhesion method using the surface tension of water, an air knife method, a press roll method, an underwater casting method, etc. may be used. From the viewpoint, the air knife method is preferable. The air temperature of the air knife is preferably 20 to 50 ° C., and the blowing air speed is preferably 130 to 150 m / s, and a double tube structure is preferable in order to improve the uniformity in the width direction. Further, it is preferable to appropriately adjust the position of the air knife so that air flows downstream of the film formation so as not to cause vibration of the film.

The obtained unstretched sheet is allowed to cool in the air and then introduced into the longitudinal stretching step. In the longitudinal stretching step, an unstretched sheet is first brought into contact with a plurality of metal rolls maintained at 100 ° C. or more and less than 150 ° C., preheated to the stretching temperature, stretched 3 to 8 times in the longitudinal direction, and then cooled to room temperature. If the stretching temperature is 150 ° C. or more, stretching unevenness may occur or the film may break. On the other hand, if the draw ratio is less than 3 times, stretch unevenness may occur, the orientation of the film becomes weak, and the tear strength may decrease.

Next, the longitudinally uniaxially stretched film is guided to a tenter, the end of the film is held with a clip, and the transverse stretching is stretched 7 to 13 times in the width direction at a temperature of 120 to 180 ° C, preferably 120 to 170 ° C. If the stretching temperature is low, the film may break, and it is preferable to stretch at a temperature equal to or higher than the melting point of the olefin resin containing 4-methyl-1-unit contained in the surface layer (I). Melting | fusing point +10 degreeC or more is more preferable, and melting | fusing point +20 degreeC or more is still more preferable. However, if the stretching temperature is too high, the rigidity of the film may decrease. In addition, when the magnification is high, the film may be broken, and when the magnification is low, the orientation of the film is weak and the tear strength may be lowered. Therefore, the upper limit is about 180 ° C.

In the subsequent heat treatment and relaxation treatment steps, the clip is heat-set at a temperature of 100 ° C. or more and less than 160 ° C. while being relaxed at a relaxation rate of 2 to 20% in the width direction while holding the clip in the width direction. The film is guided to the outside of the tenter through a cooling process at 100 ° C., the clip at the film end is released, the film edge is slit in the winder process, and the film product roll is wound up. Control of the conditions of the heat treatment and relaxation process is very important in adjusting the heat shrinkage rate. The relaxation rate is more preferably 5 to 18%, still more preferably 8 to 15%. The heat setting temperature is more preferably 120 ° C. or more and less than 160 ° C., and further preferably 140 ° C. or more and less than 160 ° C. At this time, heat treatment is preferably performed at a temperature equal to or higher than the melting point of the olefin resin including 4-methyl-1-unit included in the surface layer (I), more preferably melting point + 10 ° C. or higher, and melting point + 20 ° C. or higher. Further preferred.

The laminated polypropylene film of the present invention obtained as described above can be used in various applications such as packaging films, release films, process films, sanitary products, agricultural products, building products, medical products, In particular, since it is excellent in releasability, it can be preferably used as a release film and a process film. Since it is excellent in especially transparent smoothness, it is preferably used as release films, such as a cover film of an adhesive resin layer.

Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.

(1) Film thickness Five points were measured using a micro thickness gauge (manufactured by Anritsu), and an average value was obtained.

(2) Surface free energy Four types of liquids, water, ethylene glycol, formamide, and methylene iodide, were used as measurement solutions, and the contact angle meter CA-D type manufactured by Kyowa Interface Chemical Co., Ltd. was used. The static contact angle with respect to the film surface was determined. The static contact angle was measured 30 seconds after each liquid was dropped on the film surface. The components of the contact angle and the surface tension of the measurement solution obtained for each liquid were substituted into the following equations, and the simultaneous equations consisting of the following equations were solved for γSd, γSp, and γSh.

γS, γSd, γSp, and γSh are the surface free energy, dispersion force component, polar force component, and hydrogen bond component of the film surface, respectively, and γL, γLd, γLp, and γLh are the surface free energy and dispersion force of the measurement solution used, respectively. It represents a component, a polar force component, and a hydrogen bond component. Here, as the surface tension of each liquid used, the value proposed by Panzer (J. Panzer, J. Colloid Interface Sci., 44, 142 (1973)) was used.

(3) Gross value According to JIS K-7105 (1981), 5 points of data measured under the conditions of an incident angle of 60 ° and a light receiving angle of 60 ° using a digital variable gloss meter UGV-5D manufactured by Suga Test Instruments Co., Ltd. The average value was defined as the gloss value of the film.

(4) Haze value Three (three) square film samples each having a side of 5 cm are prepared. The sample is then allowed to stand for 40 hours in a normal state (23 ° C., relative humidity 50%). Each sample is carried out by using a turbidimeter “NDH5000” manufactured by Nippon Denshoku Industries Co., Ltd., in accordance with JIS “How to Determine Haze of Transparent Material” (K7136 2000 version). The three haze values (three) of each were averaged to obtain the haze value of the film.

(5) Thermal shrinkage (120 ° C)
Cut out five specimens with a width of 10 mm and a length of 200 mm (measurement direction) in the width direction of the film, mark them as marks at 25 mm from both ends, and measure the distance between the marks with a universal projector. Let it be a length (l ₀ ). Next, the test piece is sandwiched between papers and taken out after heating for 15 minutes in an oven kept at 120 ° C. with zero load. After cooling at room temperature, the dimension (l ₁ ) is measured with a universal projector and measured as follows. formula,
Thermal contraction rate = {(l ₀ −l ₁ ) / l ₀ } × 100 (%)
The average value of the five samples was taken as the heat shrinkage rate.

(6) Tear Strength The tear strength (N / mm) in the longitudinal direction and width direction of the film was measured using a digital light load tear tester manufactured by Toyo Seiki Seisakusho. The sample size is 63 mm in the tear direction, 50 mm in the direction perpendicular to the tear direction, 13 mm incision is made in the tear direction, the tear strength (mN) when the remaining 50 mm is torn is read, and the tear is calculated using the following formula The strength (N / mm) was calculated.
Tear strength (N / mm) = Tear strength (mN) / Sample thickness (μm)
The measurement was performed 5 times, and the average value was taken as the tear strength.

(7) Releasability of adhesive tape Polyester adhesive tape NO.
31B was pasted with a roller, and it was cut into a width of 19 mm to prepare a sample. The sample was peeled off at a speed of 500 mm / min using a tensile tester and evaluated according to the following criteria.
A: No delamination occurs between the surface layer (I) and the base material layer (II),
Peeling is possible at a constant speed.
B: Although delamination does not occur between the surface layer (I) and the base material layer (II),
Peel resistance is slightly strong, and the speed increases and decreases during peeling.
C: delamination occurs between the surface layer (I) and the base material layer (II),
Alternatively, peeling is very heavy, and peeling marks remain on the adherend surface.

(8) Suitability for defect inspection Acrylic adhesive (SK Dyne (registered trademark) 1310, manufactured by Soken Chemical Co., Ltd.) is diluted with ethyl acetate, toluene, and MEK on one side of the laminated polypropylene film, and the solid content of the adhesive is 100. The coating material in which 2.0 parts by mass of a curing agent (Coronate D-90, manufactured by Nippon Polyurethane Industry Co., Ltd.) is mixed with the part by mass is hand-coated, dried in an oven at 80 ° C. for 30 seconds, and the adhesive layer thickness Produced a 1000 nm adhesive film. On this adhesive film, a 40 μm thick “Zeonor Film” (registered trademark) manufactured by Nippon Zeon Co., Ltd. is sampled into a square with a width of 100 mm and a length of 100 mm, and the back surface of the adhesive film and the “Zeonor film” are placed in contact with each other. Then, it was sandwiched between two acrylic plates having a thickness of 5 mm, applied with a load of 2 kgf, and allowed to stand in an atmosphere at 23 ° C. for 24 hours. After 24 hours, the surface of the “ZEONOR film” (the surface on which the adhesive film was in contact) was visually observed and evaluated according to the following criteria.
A: It is clean and is the same as before weighting.
B: Weak unevenness is confirmed.
C: Strong unevenness is confirmed.

(9) Melting point A 5 mg sample was taken in an aluminum pan and measured using a differential scanning calorimeter (RDC220 manufactured by Seiko Denshi Kogyo). First, the temperature is raised from room temperature to 260 ° C. at a rate of 10 ° C./min (first run) in a nitrogen atmosphere, held for 10 minutes, and then cooled to 20 ° C. at 10 ° C./min. After maintaining for 5 minutes, the melting peak temperature observed when the temperature was raised again (second run) at 10 ° C./min was taken as the melting point.

Example 1
4 parts by mass of homopolypropylene (Prime Polymer Co., Ltd., TF850H, MFR: 2.9 g / 10 min) and 96 parts by mass of 4-methyl-1-pentene / propylene copolymer (melting point: 130 ° C.) The raw material is supplied from the weighing hopper to the twin screw extruder so that it is mixed at a ratio, melt kneaded at 260 ° C, discharged from the die in a strand shape, cooled and solidified in a 25 ° C water bath, and cut into chips. Thus, a polypropylene raw material (A) for the surface layer (I) was obtained. The 4-methyl-1-pentene / propylene copolymer had a copolymerization ratio of 73 mol% for 4-methyl-1-pentene and 27 mol% for propylene.

As the polypropylene raw material for the surface layer (I), the above-mentioned polypropylene raw material (A) is supplied to a uniaxial melt extruder for the surface layer (I), and the above-mentioned homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The laminate was laminated at a thickness ratio of 1/25/1 with a B / A composite T die, discharged onto a casting drum whose surface temperature was controlled at 18 ° C., and closely adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 125 ° C. using a ceramic roll, and stretched 4.5 times in the longitudinal direction of the film between 125 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter type stretching machine, preheated at 165 ° C. for 3 seconds, stretched 7.8 times in the width direction at 155 ° C., and given 13% relaxation in the width direction. A heat treatment is performed at 158 ° C., followed by a cooling process at 100 ° C., and then led to the outside of the tenter, the film end clip is released, the film is wound around the core, and a laminated polypropylene film having a thickness of 11 μm (surface layer 0.4 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Example 2)
94 parts by mass of the homopolypropylene (TF850H) and 6 parts by mass of the 4-methyl-1-pentene / propylene copolymer (melting point: 130 ° C.) were fed to a twin screw extruder and melt kneaded at 260 ° C. Then, it was discharged from the die in a strand shape, cooled and solidified in a 25 ° C. water bath, and cut into a chip shape to obtain a polypropylene raw material (B) for the surface layer (I).

As the polypropylene raw material for the surface layer (I), the polypropylene raw material (B) is supplied to a uniaxial melt extruder for the surface layer (I), and the polypropylene raw material for the base layer (II) is used as the homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The B / A composite T-die was laminated at a thickness ratio of 1/13/1, discharged onto a casting drum whose surface temperature was controlled at 23 ° C., and closely adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 130 ° C. using a ceramic roll, and stretched 4.7 times in the longitudinal direction of the film between 130 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter type stretching machine, preheated at 170 ° C. for 3 seconds, and then stretched 8.0 times in the width direction at 160 ° C., giving a relaxation of 12% in the width direction. A heat treatment is performed at 155 ° C., and then a cooling process at 100 ° C. is conducted to the outside of the tenter, the film end clip is released, the film is wound around the core, and a laminated polypropylene film having a thickness of 13 μm (surface layer: 1.0 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Example 3)
88 parts by mass of the homopolypropylene (TF850H) and 12 parts by mass of 4-methyl-1-pentene resin (manufactured by Mitsui Chemicals, DX310, melting point 232 ° C.) are fed to a twin screw extruder and melted at 260 ° C. Kneading was carried out, the strand was discharged from the die, solidified by cooling in a water bath at 25 ° C., and cut into chips to obtain a polypropylene raw material (C) for the surface layer (I).

The polypropylene raw material (C) is supplied as a polypropylene raw material for the surface layer (I) to a uniaxial melt extruder for the surface layer (I), and the polypropylene raw material for the base layer (II) is the homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The layers were laminated at a thickness ratio of 1/25/1 by a B / A composite T die, discharged onto a casting drum whose surface temperature was controlled at 33 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 138 ° C. using a ceramic roll, and stretched 4.8 times in the longitudinal direction of the film between 138 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter-type stretching machine, preheated at 171 ° C. for 3 seconds, stretched 8.0 times in the width direction at 166 ° C., and given 10% relaxation in the width direction. A heat treatment is performed at 143 ° C., and then a cooling process at 100 ° C. is conducted to the outside of the tenter, the clip at the end of the film is released, the film is wound around the core, and a laminated polypropylene film having a thickness of 12 μm (surface layer 0.6 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

Example 4
5 parts by mass of the homopolypropylene (TF850H), 90 parts by mass of 4-methyl-1-pentene resin (manufactured by Mitsui Chemicals, MX004, melting point 228 ° C.), polybutene-1 resin (manufactured by Mitsui Chemicals, P5050N) ) 5 parts by mass of raw material is fed to a twin screw extruder, melt kneaded at 260 ° C., discharged from a die in a strand shape, cooled and solidified in a 25 ° C. water tank, cut into a chip shape, and surface layer (I Polypropylene raw material (D) was obtained.

The polypropylene raw material (D) is supplied as a polypropylene raw material for the surface layer (I) to a uniaxial melt extruder for the surface layer (I), and the polypropylene raw material for the base layer (II) is the homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / They were laminated with a B / A composite T die at a thickness ratio of 1/14/1, discharged onto a casting drum whose surface temperature was controlled at 23 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 135 ° C. using a ceramic roll, and stretched 5.2 times in the longitudinal direction of the film between 135 ° C. rolls provided with a difference in peripheral speed. Next, the end part is introduced into a tenter type stretching machine by holding a clip, preheated at 168 ° C. for 3 seconds, and then stretched 8.0 times in the width direction at 163 ° C., giving a relaxation of 6% in the width direction. A heat treatment is performed at 138 ° C., and then a cooling process at 100 ° C. is conducted to the outside of the tenter. A clip at the end of the film is released, the film is wound around a core, and a laminated polypropylene film having a thickness of 18 μm (surface layer: 1.3 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Example 5)
9 parts by mass of the homopolypropylene (TF850H), 86 parts by mass of 4-methyl-1-pentene resin (Mitsui Chemicals, MX004, melting point 228 ° C.), polybutene-1 resin (Mitsui Chemicals, P5050N) ) 5 parts by mass of raw material is fed to a twin screw extruder, melt kneaded at 260 ° C., discharged from a die in a strand shape, cooled and solidified in a 25 ° C. water tank, cut into a chip shape, and surface layer (I ) Polypropylene raw material (E) was obtained.

The polypropylene raw material (E) is supplied as a polypropylene raw material for the surface layer (I) to a uniaxial melt extruder for the surface layer (I), and the polypropylene raw material for the base layer (II) is the homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / A B / A composite T die was laminated at a thickness ratio of 1/6/1, discharged onto a casting drum whose surface temperature was controlled at 52 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 140 ° C. using a ceramic roll, and the film was stretched 4.6 times in the longitudinal direction of the film between 140 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter type stretching machine, preheated at 171 ° C. for 3 seconds, stretched 7.6 times in the width direction at 166 ° C., and given 15% relaxation in the width direction. A heat treatment is performed at 156 ° C., and then a cooling process at 100 ° C. is conducted to the outside of the tenter. The clip at the end of the film is released, the film is wound around the core, and a laminated polypropylene film having a thickness of 22 μm (surface layer 3.7 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Example 6)
10 parts by mass of homopolypropylene (Prime Polymer Co., Ltd., TF850H, MFR: 2.9 g / 10 min) and 90 parts by mass of 4-methyl-1-pentene / propylene copolymer (melting point: 130 ° C.) The raw material is supplied from the weighing hopper to the twin screw extruder so that it is mixed at a ratio, melt kneaded at 260 ° C, discharged from the die in a strand shape, cooled and solidified in a 25 ° C water bath, and cut into chips. Thus, a polypropylene raw material (A) for the surface layer (I) was obtained. The 4-methyl-1-pentene / propylene copolymer had a copolymerization ratio of 73 mol% for 4-methyl-1-pentene and 27 mol% for propylene.

As the polypropylene raw material for the surface layer (I), the above-mentioned polypropylene raw material (A) is supplied to a uniaxial melt extruder for the surface layer (I), and the above-mentioned homopolypropylene ( TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The layers were laminated at a thickness ratio of 1/22/1 with a B / A composite T die, discharged onto a casting drum whose surface temperature was controlled at 24 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 130 ° C. using a ceramic roll, and stretched 4.4 times in the longitudinal direction of the film between 130 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter type stretching machine, preheated at 138 ° C. for 3 seconds, stretched 7.7 times in the width direction at 138 ° C., and given 7% relaxation in the width direction. A heat treatment is performed at 139 ° C., and then a cooling process at 100 ° C. is conducted to the outside of the tenter, the clip at the end of the film is released, the film is wound around the core, and a laminated polypropylene film having a thickness of 15 μm (surface layer 0.7 μm) is obtained. Obtained. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Comparative Example 1)
Homopolypropylene resin (manufactured by Prime Polymer Co., Ltd., RF1342B, MFR = 3 g / 10 min, [mmmm] = 94%) 70 parts by mass, 4-methyl-1-pentene resin (manufactured by Mitsui Chemicals, Inc., TPX (registered trademark) ) MX0020, melting point 224 ° C.) 30 parts by mass was dry blended to obtain a polypropylene raw material (F) for the surface layer (I).

As the polypropylene raw material for the surface layer (I), the above-mentioned polypropylene raw material (F) is supplied to a uniaxial melt extruder for the surface layer (I), and the above-mentioned homopolypropylene ( RF1342B) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 230 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The layers were laminated with a B / A composite T die at a thickness ratio of 1/10/1, discharged onto a casting drum whose surface temperature was controlled at 30 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, sequential biaxial stretching was performed using a batch type biaxial stretching machine KARO IV manufactured by Bruckner. The stretching conditions were a preheating temperature of 165 ° C., a preheating time of 1 minute, a stretching temperature of 165 ° C., a stretching speed of 100% / sec, and a heat setting condition of 165 ° C. and 30 sec. The laminated polypropylene film having a thickness of 12 μm (surface layer: 1.2 μm) was obtained by stretching 4.5 times and a stretching ratio in the width direction of 9 times. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Comparative Example 2)
69 parts by mass of homopolypropylene resin (manufactured by Prime Polymer Co., Ltd., RF1342B, MFR = 3 g / 10 min, [mmmm] = 94%), 4-methyl-1-pentene resin (manufactured by Mitsui Chemicals, Inc., TPX) ) EP0518, melting point 180 ° C. 30 parts by mass, 1-butene polymer resin (manufactured by Mitsui Chemicals, Tuffmer (registered trademark) BL3450) is dry blended, and the polypropylene raw material (G) for the surface layer (I) is Obtained. As the polypropylene raw material for the surface layer (I), the above-mentioned polypropylene raw material (G) is supplied to a uniaxial melt extruder for the surface layer (I), and as the polypropylene raw material for the base layer (II), the above-mentioned homopolypropylene ( RF1342B) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 230 ° C., foreign matter is removed with a 60 μm cut sintered filter, and feed block type A / The layers were laminated at a thickness ratio of 1/23/1 with a B / A composite T die, discharged onto a casting drum whose surface temperature was controlled at 30 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 30 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, sequential biaxial stretching was performed using a batch type biaxial stretching machine KARO IV manufactured by Bruckner. Stretching conditions are a preheating temperature of 162 ° C, a preheating time of 2 minutes, a stretching temperature of 162 ° C, a stretching speed of 100% / sec, and a heat setting condition of 162 ° C and 30 sec. The biaxially stretched polypropylene film having a thickness of 20 μm (surface layer: 0.9 μm) was obtained by stretching 5 times and a stretching ratio in the width direction of 9 times. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Comparative Example 3)
99.7 parts by mass of homopolypropylene resin (manufactured by Sumitomo Chemical Co., Ltd., FLX80E4, MFR = 7.5 g / 10 min), β-crystal nucleating agent N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide (new) Nippon Rika Co., Ltd. (NU-100) 0.3 parts by mass, and antioxidants Ciba Specialty Chemicals IRGANOX1010 and IRGAFOS168 each 0.1 parts by mass are fed to the twin-screw extruder. The mixture was melt-kneaded at 300 ° C., discharged from a die in a strand shape, cooled and solidified in a water bath at 25 ° C., and cut into chips to obtain a polypropylene raw material (H) for the surface layer (I).

The polypropylene raw material (H) is supplied to the uniaxial melt extruder for the surface layer (I) as the polypropylene raw material for the surface layer (I), and homopolypropylene (TF850H is used as the polypropylene raw material for the base layer (II). ) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 240 ° C., foreign matter is removed with a 60 μm cut sintered filter, and then a feed block type A / B A cast sheet was obtained by laminating with a composite T die at a thickness ratio of 8/1 and discharging onto a cast drum whose surface temperature was controlled at 90 ° C. Next, the film was preheated to 125 ° C. using a plurality of ceramic rolls and stretched 4.6 times in the longitudinal direction of the film. Next, the end portion was introduced into a tenter-type stretching machine by holding it with a clip, preheated at 165 ° C. for 3 seconds, and then stretched 8.0 times at 160 ° C. In the subsequent heat treatment process, heat treatment is performed at 160 ° C while giving 10% relaxation in the width direction, and then the cooling process is performed at 130 ° C, leading to the outside of the tenter, releasing the clip at the end of the film, and winding the film around the core A laminated polypropylene film having a thickness of 15 μm (surface layer 1.7 μm) was obtained.

(Comparative Example 4)
Homo polypropylene resin (manufactured by Prime Polymer Co., Ltd., TF850H, MFR = 2.9 g / 10 min) 93.3 parts by mass, master material compounded with 80% by mass of calcium carbonate and 20% by mass of polypropylene (manufactured by Sankyo Seimitsu Co., Ltd.) 2480K, calcium carbonate particles: 6 μm) and 6.7 parts by mass were dry blended to obtain a polypropylene raw material (J) for the base layer (II).

The polypropylene raw material (J) is supplied to the uniaxial melt extruder for the base material layer (II) as the polypropylene raw material for the base material layer (II), and homopolypropylene is used as the polypropylene raw material for the surface layer (I). (TF850H) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 240 ° C., and foreign matter is removed by a 60 μm cut sintered filter. / B composite T-die was laminated at a thickness ratio of 8/1, and discharged onto a cast drum whose surface temperature was controlled at 30 ° C. to obtain a cast sheet. At this time, it was set as the surface where the polypropylene raw material C of the base material layer contacts the cast drum. Next, the film was preheated to 125 ° C. using a plurality of ceramic rolls and stretched 4.6 times in the longitudinal direction of the film. Next, the end portion was introduced into a tenter-type stretching machine by holding it with a clip, preheated at 165 ° C. for 3 seconds, and then stretched 8.0 times at 160 ° C. In the subsequent heat treatment process, heat treatment is performed at 160 ° C while giving 10% relaxation in the width direction, and then the cooling process is performed at 130 ° C, leading to the outside of the tenter, releasing the clip at the end of the film, and winding the film around the core A laminated polypropylene film having a thickness of 19 μm (surface layer 2.1 μm) was obtained.

(Comparative Example 5)
100 parts by mass of homopolypropylene resin (manufactured by Prime Polymer Co., Ltd., TF850H, MFR = 2.9 g / 10 min) is supplied to a uniaxial melt extruder, melt extruded at 260 ° C., and a 60 μm cut sintered filter After removing the foreign matter, it was discharged onto a casting drum whose surface temperature was controlled at 30 ° C., and brought into close contact with the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 140 ° C. using a ceramic roll, and the film was stretched 4.6 times in the longitudinal direction of the film between 140 ° C. rolls provided with a peripheral speed difference. Next, the end is held by a clip and introduced into a tenter type stretching machine, preheated at 165 ° C. for 3 seconds, stretched 8 times in the width direction at 160 ° C., and 155 ° C. while giving 10% relaxation in the width direction. The film was then subjected to a heat treatment and then led to the outside of the tenter through a cooling process at 100 ° C., the clip at the end of the film was released, and the film was wound around a core to obtain a laminated polypropylene film having a thickness of 19 μm. Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

(Comparative Example 6)
95 parts by mass of homopolypropylene (Nippon Polypro Co., Ltd., Novatec PP FL1105C, MFR: 3.5 g / 10 min), poly-4-methyl-1-pentene (manufactured by Mitsui Chemicals, TPX RT18, melting point: 232 ° C) 5 parts by mass are fed to the twin-screw extruder from the weighing hopper so as to be mixed at this ratio, melt kneaded at 240 ° C, discharged from the die in a strand shape, and placed in a 25 ° C water tank After cooling and solidifying, it was cut into chips to obtain a polypropylene raw material (A) for the surface layer (I).

As the polypropylene raw material for the surface layer (I), the above-mentioned polypropylene raw material (A) is supplied to a uniaxial melt extruder for the surface layer (I), and the above-mentioned homopolypropylene ( (FL1105C) 100 parts by mass is supplied to a uniaxial melt extruder for the base material layer (II), melt extruded at 260 ° C., and foreign matter is removed by a 60 μm cut sintered filter. The layers were laminated with a B / A composite T die at a thickness ratio of 1/10/1, discharged onto a casting drum whose surface temperature was controlled at 25 ° C., and adhered to the casting drum with an air knife. Thereafter, the uncooled drum surface of the sheet on the casting drum was cooled by injecting compressed air at a temperature of 25 ° C. and a pressure of 0.3 MPa to obtain an unstretched sheet. Subsequently, the sheet was preheated to 140 ° C. using a ceramic roll, and stretched 4.8 times in the longitudinal direction of the film between 140 ° C. rolls provided with a peripheral speed difference. Next, the end of the tenter type stretching machine is introduced by gripping with a clip, preheated at 160 ° C. for 3 seconds, and then stretched 9.0 times in the width direction at 160 ° C., giving 5% relaxation in the width direction. Heat treatment was performed at 160 ° C., and the film was wound around a core to obtain a laminated polypropylene film having a thickness of 50 μm (surface layer: 5 μm). Table 1 shows the physical properties and evaluation results of the laminated polypropylene film.

As described above, the laminated polypropylene film of the present invention can be used in various applications such as a packaging film, a release film, a process film, a sanitary product, an agricultural product, a building product, and a medical product. In particular, since it is excellent in transparent smoothness, it can be preferably used as a release film and process film for applications requiring surface smoothness of products, and since it is excellent in releasability, it also covers an adhesive resin layer. It is preferably used as a release film such as a film.

Claims

A laminated film having a surface layer (I) on at least one surface of a base material layer (II) mainly composed of polypropylene, the surface free energy of the surface layer (I) is 18 to 28 mN / m, and the gloss value is Laminated polypropylene film that is 40% or more.
The laminated polypropylene film according to claim 1, wherein the surface layer (I) comprises an olefin resin as a main component.
The laminated polypropylene film according to claim 1 or 2, wherein the surface layer (I) comprises an olefin resin, a part of which is 4-methylpentene-1 unit.
The laminated polypropylene film according to claim 3, wherein the surface layer (I) contains an olefin resin containing 4-methylpentene-1 unit and having a melting point of 160 ° C or lower.
The value of T 1 / T 2 is 0.3 or less, where T 1 is the thickness of the surface layer (I) and T 2 is the thickness of the substrate layer (II). The laminated polypropylene film described.
The laminated polypropylene film according to any one of claims 1 to 5, wherein the film has a haze value of 50% or less.
The laminated polypropylene film according to any one of claims 1 to 6, wherein the thermal shrinkage in the longitudinal direction at 120 ° C for 15 minutes is 2.5% or less.
The laminated polypropylene film according to any one of claims 1 to 7, wherein the sum of the tear strengths in the film longitudinal direction and the width direction is 2.5 N / mm or more.
A release film using the laminated polypropylene film according to any one of claims 1 to 8.