Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
  • B29C48/08—Flat, e.g. panels flexible, e.g. films
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
  • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
  • B32B2307/514—Oriented
  • B32B2307/518—Oriented bi-axially
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2323/00—Polyalkenes
  • B32B2323/10—Polypropylene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/10—Homopolymers or copolymers of propene
  • C08J2323/12—Polypropene

Definitions

• the present invention relates to a polypropylene film which is excellent in flatness and quality at high temperature in addition to high temperature heat shrinkability.
• Heat-shrinkable films are used for food packaging, label packaging for the purpose of imparting design characteristics and protecting contents, and heat-shrinkable base materials for coating functional layers for controlling the orientation of functional layers. Used for various purposes. Of these, polypropylene heat-shrinkable films are excellent in strength and releasability, and thus are preferably used in these applications. So far, high heat-shrinkable films using ⁇ -olefin-based copolymers (for example, Patent Documents 1, 2, and 3) and high-shrinkable films mainly composed of polypropylene resin with low crystallinity (for example, Patent Documents 4 and 5). Has been reported.
• Patent Documents 1 to 3 fish eyes are likely to occur due to thermal deterioration and poor dispersion, and it may be unsuitable for use as a label or as a release base material.
• a low melting point polyethylene resin or polypropylene resin is mainly used as in Patent Documents 4 and 5, the film shrinks during the film forming process or during storage after winding, causing wrinkles on the product roll. In some cases, the flatness of the film deteriorated at high temperatures.
• an object of the present invention is to solve the above problems. That is, it is to provide a polypropylene film which is excellent in flatness and quality at high temperature in addition to high temperature heat shrinkability.
• the polypropylene film of the present invention has a thermal shrinkage ratio of 4% or more and 30% or less after treatment at 130 ° C for 15 minutes in the main shrinking direction, and the differential scanning calorie
• the purpose of the present invention is to have a melting peak temperature of 155 ° C. or higher when the temperature is raised from 30 ° C. to 260 ° C. at 20 ° C./min in total DSC.
• the polypropylene film of the present invention is suitable for each application of the heat-shrinkable film because the flatness of the film at high temperature is good, despite having high heat-shrinkability in a specific direction in the film plane. Can be used.
• polypropylene film may be simply referred to as a film hereinafter.
• the polypropylene film means a film containing 80% by mass or more and 100% by mass or less of polypropylene with respect to 100% by mass of the total mass of the film.
• the content of polypropylene in the polypropylene film is preferably 90% by mass or more and 100% by mass or less, and more preferably 95% by mass or more and 100% by mass or less.
• the polypropylene film of the present invention is not a microporous film, but a film that does not have a large number of pores, and specifically a polypropylene film having a porosity of 0% or more and less than 20%.
• the porosity of the polypropylene film is more preferably 0% or more and less than 10%, further preferably 0% or more and less than 5%.
• the porosity of the film can be calculated from the following formula from the specific gravity ( ⁇ ) of the film and the specific gravity (d) of the sheet which was hot-pressed at 280 ° C. and 5 MPa and then quenched with water at 25 ° C.
• Porosity (%) [(d- ⁇ ) / d] ⁇ 100
• the polypropylene film of the present invention has a thermal shrinkage ratio of 4% or more and 30% or less after being treated at 130 ° C. for 15 minutes in the main shrinking direction.
• the heat shrinkage rate after treatment at 130 ° C. for 15 minutes is less than 4%, for example, the film of the present invention is laminated or coated with another product to shrink the film of the present invention, thereby aligning the product.
• the orientation of the product after shrinkage may be insufficient.
• the heat shrinkage rate after heat treatment at 130 ° C. for 15 minutes in the main shrinkage direction exceeds 30%, the shrinkage is too large and wrinkles occur, or the flatness deteriorates and the appearance becomes poor.
• the upper limit of the heat shrinkage rate in the main shrinkage direction after treatment at 130 ° C. for 15 minutes is more preferably 25% or less, further preferably 20% or less, and the lower limit is more preferably 6% or more, further preferably 8% or more. , And most preferably 10% or more.
• the heat shrinkage rate after treatment at 130 ° C. for 15 minutes in the main shrinkage direction is a value measured by the method described in the section of Examples. In order to set the heat shrinkage rate after treatment at 130 ° C.
• the composition of the raw materials and the laminated structure are set within the ranges described below, and the longitudinal stretching condition, the transverse stretching condition, It is preferable that the heat setting conditions and the relaxation conditions are within the ranges described below.
• the direction parallel to the film forming direction is called the film forming direction, the longitudinal direction or the MD direction, and the direction orthogonal to the film forming direction in the film plane is called the width direction or the TD direction.
• the main shrinkage direction in the present invention means 15 °, 30 °, 45 °, 60 °, 75 °, 90 ° with respect to the MD direction when the MD direction is 0 ° in the plane of the film. It is the direction in which the highest value is obtained when the heat shrinkage rate after treatment at 130 ° C. for 15 minutes is measured in each direction forming angles of 105 °, 120 °, 135 °, 150 °, and 165 °. If it is not possible to determine which direction is the MD direction from the appearance of the film, measure the heat shrinkage after processing for 15 minutes at 130 ° C in 15 ° increments from any direction, and determine the direction with the highest heat shrinkage.
• the contraction direction is not possible to determine which direction is the MD direction from the appearance of the film, measure the heat shrinkage
• the polypropylene film of the present invention has a melting peak at 155 ° C. or higher when the temperature is raised from 30 ° C. to 260 ° C. at 20 ° C./min by a differential scanning calorimeter DSC.
• the temperature of the melting peak when the temperature is raised at 20 ° C./minute from 30 ° C. to 260 ° C. with a differential scanning calorimeter DSC is more preferably 160 ° C. or higher, still more preferably 165 ° C. or higher, most preferably 170 ° C. or higher. Is.
• the melting peak temperature is less than 155 ° C., it becomes difficult to perform stretching and heat treatment at a high temperature, and thus the heat shrinkage rate after the treatment at 100 ° C.
• the upper limit of the melting peak temperature is not particularly limited, but the heat shrinkage rate after treatment at 130 ° C. for 15 minutes may be low, and is therefore set to 180 ° C.
• the raw material composition and the laminated structure are within the ranges described below, and the longitudinal stretching conditions, the transverse stretching conditions, the heat setting conditions, and the relaxation conditions are within the ranges described below.
• biaxial stretching in the longitudinal and width directions is important.
• the polypropylene film of the present invention preferably has a heat shrinkage ratio of 10% or less after treatment at 100 ° C. for 15 minutes in the main shrinkage direction.
• the heat shrinkage rate after treatment at 100 ° C. for 15 minutes in the main shrinkage direction is more preferably 8% or less, further preferably 7% or less, and particularly preferably 6% or less.
• the lower limit of the heat shrinkage rate after treatment at 100 ° C. for 15 minutes is preferably more than 1%, more preferably more than 2%.
• the heat shrinkage rate after treatment at 100 ° C. for 15 minutes in the main shrinkage direction is a value measured by the method described in the section of Examples. In order to set the heat shrinkage rate after treatment at 100 ° C.
• the composition of the raw materials and the laminated structure are set within the ranges described below, and the longitudinal stretching condition, the transverse stretching condition, the heat setting condition, and the relaxation are set. It is preferable to set the conditions within the range described below.
• the polypropylene film of the present invention preferably has a modulus of elasticity in the thickness direction at 23 ° C. of at least one surface measured by a nanoindentation method of 2.0 GPa or more.
• the elastic modulus in the thickness direction is more preferably 2.1 GPa or more, still more preferably 2.2 GPa or more.
• the elastic modulus in the thickness direction is not particularly limited as long as it is 2.0 GPa or more, but in order to increase the elastic modulus in the thickness direction, it is necessary to increase the crystallinity of the film, and from the viewpoint of being compatible with the film-forming property,
• the upper limit is substantially about 5.0 GPa.
• the raw material composition of the film and the laminated structure of the film should be within the ranges described below, and the conditions of casting during film formation (sheet forming process of melt extruded resin) It is preferable to set the longitudinal and transverse stretching conditions within the range described below.
• the elastic modulus in the thickness direction is preferably 2.0 GPa or more on at least one side, and more preferably 2.0 GPa on both sides.
• both the stress in the main shrinkage direction and the elongation at 2% in the direction orthogonal to the main shrinkage direction are 24 MPa or more.
• the F2 value in the main shrinkage direction and the direction orthogonal to the main shrinkage direction is more preferably 26 MPa or more, further preferably 28 MPa or more.
• the raw material composition and the laminated structure are set within the ranges described below, and the longitudinal stretching condition, the transverse stretching condition, the heat setting condition, It is preferable that the relaxation condition is within the range described below.
• the polypropylene film of the present invention preferably has a thickness variation in the main shrinkage direction of 2.0% or less, more preferably 1.5% or less, and further preferably 1.0% or less from the viewpoint of winding property. .
• the lower limit is not particularly limited, but it is substantially 0.1%.
• the polypropylene film of the present invention preferably has a heat shrinkage stress at 130 ° C. in the main shrinkage direction of 1.0 MPa or more. It is more preferably 1.5 MPa or more, still more preferably 2.0 MPa or more. The higher the heat shrinkage stress at 130 ° C., the more preferably it is used for the shrinkable base material, but the upper limit is 10 MPa in order to suppress natural shrinkage.
• the polypropylene film of the present invention preferably has a heat shrinkage stress at 100 ° C. in the main shrinkage direction of 0.5 MPa or less. It is more preferably 0.3 MPa or less, still more preferably 0.1 MPa or less.
• the number of fish eyes having a long side of 50 ⁇ m or more is preferably 20 / m 2 or less.
• the long side refers to the long side of a rectangle circumscribing the fish eye when measuring the size of the fish eye.
• the number of fish eyes is more preferably 15 / m 2 or less, further preferably 10 / m 2 , and particularly preferably 5 / m 2 or less.
• the lower limit is not particularly limited, but it is substantially 0.001 pieces / m 2 or more because the cleanliness of the production equipment and the cost increase due to foreign matter management and the decrease in productivity become problems.
• the number of fish eyes to be 20 / m 2 or less can be achieved by setting the raw material composition and the melt extrusion conditions within the ranges described below, and suppressing the generation of foreign substances due to deterioration of the resin and poor dispersion.
• the number of fish eyes in the present invention refers to a value measured by the method described in the section of Examples.
• the polypropylene film of the present invention preferably has a dynamic friction coefficient ⁇ d of 0.4 or less measured by overlapping one surface of the film with the back surface thereof. It is more preferably 0.3 or less.
• the lower limit of the dynamic friction coefficient ⁇ d is substantially about 0.1, and if it is less than 0.1, roll misalignment may easily occur.
• the raw material composition of the film and the laminated structure of the film should be within the ranges described below, and the conditions for casting (sheet-forming process of melt-extruded resin) and vertical / It is preferable to set the transverse stretching conditions within the range described below.
• polypropylene raw material A For the polypropylene film of the present invention, it is preferable to use at least two types of polypropylene raw materials (for convenience, these two types of polypropylene raw materials are referred to as polypropylene raw material A and polypropylene raw material B, respectively).
• One of the polypropylene raw materials, polypropylene raw material A is preferably a polypropylene raw material having high crystallinity in order to improve the strength and slipperiness of the film surface.
• the polypropylene raw material B which is another polypropylene raw material is preferably a polypropylene raw material having a low crystallinity and a low melting point in order to improve the heat shrinkability of the film.
• the polypropylene raw material A preferably has a mesopentad fraction of 0.95 or more, more preferably 0.97 or more.
• the mesopentad fraction is an index showing the stereoregularity of the crystalline phase of polypropylene measured by the nuclear magnetic resonance method (NMR method), and 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 specified.
• the polypropylene raw material A preferably has a melt flow rate (MFR) of 0.5 to 20 g / 10 minutes (230 ° C., 21.18 N load), and more preferably a melt flow rate (MFR) of 1 to 10 g / 10. Minute (230 ° C., 21.18 N load), particularly preferably 2 to 5 g / 10 min (230 ° C., 21.18 N load), from the viewpoint of film formability and tensile rigidity of the film.
• MFR melt flow rate
• MFR melt flow rate
• the polypropylene preferably used as the polypropylene raw material A has a melting point of 150 ° C or higher, preferably 155 ° C or higher, and more preferably 160 ° C or higher. If the melting point is less than 150 ° C, the heat shrinkage rate after treatment at 100 ° C for 15 minutes becomes large, and the film may shrink during the film forming process, the coating process, or the storage after winding, which may reduce the flatness. is there. There is no particular upper limit to the melting point, but 170 ° C. is generally the upper limit.
• the polypropylene raw material B is preferably a polypropylene raw material having a low crystallinity and a low melting point in order to improve the heat shrinkability of the film.
• a polypropylene raw material B low stereoregular polypropylene, homopolypropylene such as syndiotactic polypropylene, polypropylene- ⁇ -olefin copolymer and the like can be used, but from the viewpoint of suppressing fish eyes, metallocene-based Polypropylene is preferable, and metallocene-based homopolypropylene is more preferable.
• examples of the ⁇ -olefin include ethylene, 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, etc. may be used. it can.
• the molar fraction of ⁇ -olefin contained in the copolymer is preferably 15% or less, more preferably 10% or less, still more preferably less than 5%.
• the quality may be deteriorated due to generation of fish eyes.
• the polypropylene preferably used as the polypropylene raw material B has a melting point of 135 ° C or lower, preferably 120 ° C or lower, more preferably 110 ° C or lower, and further preferably 90 ° C or lower. If the melting point is higher than 135 ° C, the shrinkability of the polypropylene film may be insufficient.
• the polypropylene preferably used as the polypropylene raw material B has a melting point of preferably 50 ° C. or higher, more preferably 60 ° C. or higher, and further preferably 65 ° C. or higher. When the melting point is less than 50 ° C, the resulting polypropylene film may have poor strength.
• the polypropylene preferably used as the polypropylene raw material B has a weight average molecular weight (Mw) of preferably 500,000 or less, more preferably 400,000 or less, and further preferably 300,000 or less. When the weight average molecular weight exceeds 500,000, increase in melt viscosity may be a problem. On the other hand, the polypropylene preferably used as the polypropylene raw material B has a weight average molecular weight of preferably 10,000 or more, more preferably 30,000 or more, still more preferably 50,000 or more.
• the resulting film may be inferior in shrinkability
• the Z + 1 average molecular weight (Mz + 1) is preferably 2.5 million or less, more preferably 2.2 million or less, and 1.5 million or less. Is more preferable.
• the lower limit of Mz + 1 is preferably 100,000 or more, more preferably 150,000 or more, and further preferably 200,000 or more.
• polypropylene raw material examples include “WELNEX” and “WINTEC” of metallocene-based propylene-ethylene copolymer manufactured by Nippon Polypro Co., Ltd. and Idemitsu Kosan Co., Ltd. of metallocene-based homopolypropylene.
• a commercially available product such as “Elmodu” (registered trademark) manufactured by the present invention can be appropriately selected and used.
• the polypropylene raw material used in the present invention includes various additives such as an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, an antiblocking agent, a filler, and a viscosity modifier within a range that does not impair the object of the present invention. It is also possible to add a coloring preventing agent and the like.
• the type and amount of antioxidant is important from the viewpoint of long-term stability.
• an antioxidant a phenolic one having steric hindrance is preferable, and when a plurality of kinds of antioxidants are used in combination, at least one kind is preferably a high molecular weight type having a molecular weight of 500 or more.
• BHT 2,6-di-t-butyl-p-cresol
• 1,3,5-trimethyl-2,4,6- Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene for example, Irganox (registered trademark) 1330 manufactured by BASF: molecular weight 775.2
• tetrakis [methylene-3 (3,5-di-t- Butyl-4-hydroxyphenyl) propionate] methane eg, Irganox (registered trademark) 1010: molecular weight 1177.7 manufactured by BASF
• Irganox registered trademark 1010: molecular weight 1177.7 manufactured by BASF
• the total content of these antioxidants is preferably in the range of 0.03 to 1.0 mass% with respect to the total amount of polypropylene. If the amount of the antioxidant is too small, the polymer may deteriorate in the extrusion process and the film may be colored, or the long-term heat resistance may be poor. If the amount of the antioxidant is too large, the transparency may decrease due to the bleed-out of these antioxidants.
• a more preferable content is 0.1 to 0.9% by mass, and a particularly preferable content is 0.2 to 0.8% by mass.
• Crystal nucleating agent can be added to the polypropylene raw material used in the present invention within a range not deviating from the object of the present invention.
• Crystal nucleating agents include ⁇ crystal nucleating agents (dibenzylidene sorbitols, sodium benzoate, etc.), ⁇ crystal nucleating agents (potassium 1,2-hydroxystearate, magnesium benzoate, N, N′-dicyclohexyl-2,6-) Examples thereof include amide compounds such as naphthalene dicarboxamide and quinacridone compounds).
• the addition amount is usually 0.5% by mass or less, preferably 0.1% by mass.
• the polypropylene film of the present invention preferably has a film thickness of 30 ⁇ m or more and 100 ⁇ m or less.
• the lower limit is more preferably 40 ⁇ m or more, further preferably 50 ⁇ m or more. If the film thickness is less than 30 ⁇ m, wrinkles may occur, or the flatness may be deteriorated, resulting in poor appearance.
• the upper limit of the thickness is more preferably 90 ⁇ m or less, further preferably 80 ⁇ m or less. If the film thickness exceeds 100 ⁇ m, the amount of resin used may increase and the productivity may decrease, or the film may be difficult to bend and the processability may deteriorate.
• the polypropylene film of the present invention is composed of at least two layers having different properties, the A layer containing the polypropylene raw material A described above as a preferred propylene raw material as a main component, and the polypropylene raw material described above as a preferred propylene raw material. It is preferable to include two layers of B layer containing A and the polypropylene raw material B described above as a preferable propylene raw material.
• the main component described here means the one having the highest mass% (the one having a large content) among the components constituting each layer of the film.
• the layer A constituting the polypropylene film of the present invention is mainly composed of a polypropylene raw material A composed of a propylene homopolymer, but other unsaturated hydrocarbon copolymer components such as polypropylene- It may contain an ⁇ -olefin copolymer and the like.
• examples of the ⁇ -olefin include ethylene, 1-butene, 1-pentene, 3-methylpentene-1,3-methylbutene-1,1-hexene, and 4-methylpentene.
• Examples thereof include 1,5-ethylhexene-1,1-octene, 1-decene, 1-dodecene, vinylcyclohexene, styrene, allylbenzene, cyclopentene, norbornene and 5-methyl-2-norbornene.
• the mole fraction of ⁇ -olefin in the copolymer is preferably 5% or less from the viewpoint of suppressing the fish eye by controlling the heat shrinkage rate after the treatment at 130 ° C. for 15 minutes and the melting peak temperature of the film within a preferable range. , And more preferably less than 3%.
• the A layer constituting the polypropylene film of the present invention preferably contains 90% by mass or more of the polypropylene raw material A when the mass of the A layer is 100% by mass from the viewpoint of control of heat shrinkability and slipperiness.
• the content of the polypropylene raw material A in the A layer is more preferably 95% by mass or more, further preferably 97% by mass or more, and most preferably 99% by mass or more.
• the content of the polypropylene raw material A in the layer A is less than 90% by mass, the dimensional stability at 100 ° C. for 15 minutes described above may be deteriorated or the slipperiness at high temperature may be decreased.
• the weight average molecular weight (Mw) of the raw material of the layer A constituting the polypropylene film of the present invention is preferably 800,000 or less, more preferably 600,000 or less, and further preferably 400,000 or less. When the weight average molecular weight exceeds 800,000, increase in melt viscosity may be a problem. On the other hand, the lower limit of Mw is preferably 100,000 or more, more preferably 150,000 or more, and further preferably 200,000 or more. When the weight average molecular weight is less than 100,000, the resulting film may have poor shrinkability.
• the polypropylene raw material for the layer A preferably has a Z + 1 average molecular weight (Mz + 1) of 2.5 million or less, more preferably 2 million or less, and even more preferably 1.7 million or less.
• the lower limit of Mz + 1 is preferably 1 million or more, more preferably 1.2 million or more, still more preferably 1.4 million or more.
• the B layer constituting the polypropylene film of the present invention preferably contains the polypropylene raw material A in an amount of 20% by mass or more, more preferably 30% by mass or more, further preferably 40% by mass, when the mass of the B layer is 100% by mass. % Or more.
• the polypropylene raw material A is less than 20% by mass, the dimensional stability at 100 ° C. for 15 minutes may be deteriorated, and the layer A and the layer may be disturbed.
• the proportion of the polypropylene raw material A in the B layer is preferably 95% by mass or less, more preferably 90% by mass. % Or less, more preferably 80% by mass or less.
• the layer B constituting the polypropylene film of the present invention preferably contains the polypropylene raw material B in an amount of 10% by mass or more, more preferably 15% by mass or more, further preferably 25% by mass, when the mass of the B layer is 100% by mass. % Or more.
• the content of the polypropylene raw material B is less than 10% by mass, sufficient heat shrinkability after treatment at 130 ° C. for 15 minutes may not be obtained in some cases.
• the proportion of the polypropylene raw material B in the B layer is preferably 95% by mass or less, more preferably 90% by mass or less, More preferably, it is 80 mass% or less.
• the weight average molecular weight (Mw) of the raw material of the layer B constituting the polypropylene film of the present invention is preferably 500,000 or less, more preferably 400,000 or less, and further preferably 300,000 or less. When the weight average molecular weight exceeds 500,000, increase in melt viscosity may be a problem. On the other hand, the lower limit of Mw is preferably 100,000 or more, more preferably 150,000 or more, and further preferably 200,000 or more. When the weight average molecular weight is less than 100,000, the resulting film may have poor shrinkability.
• the polypropylene raw material for the B layer preferably has a Z + 1 average molecular weight (Mz + 1) of 2,000,000 or less, more preferably 1.7,000,000 or less, and further preferably 1.4,000,000 or less.
• the lower limit of Mz + 1 is preferably 500,000 or more, more preferably 600,000 or more, still more preferably 800,000 or more.
• the ratio (Mw (A) / Mw (B)) of the weight average molecular weight of layer A and the weight average molecular weight of layer B in the polypropylene film of the present invention is preferably 0.2 to 3.0. It is more preferably 0.4 to 2.5, still more preferably 0.6 to 2.0.
• the ratio of the Z + 1 average molecular weight of the A layer and the Z + 1 average molecular weight of the B layer (Mz + 1 (A) / Mz + 1 (B)) in the polypropylene film of the present invention is preferably 0.2 to 5.0. It is more preferably 0.4 to 4.5, still more preferably 0.5 to 4.0.
• the thickness ratio of each of the A layer and the B layer to the total thickness of the polypropylene film of the present invention is preferably 10% or more, more preferably 15% or more, still more preferably 20% or more.
• the surface layer (outermost layer) is preferably the layer A described above from the viewpoint of slipperiness.
• the slipperiness may be reduced due to blocking or the like.
• the polypropylene film of the present invention may include particles on at least one surface layer for the purpose of imparting slipperiness.
• Such particles are not particularly limited as long as they do not impair the effects of the present invention, and for example, inorganic particles or organic particles can be used.
• inorganic particles silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, zeolite particles and the like
• organic particles acrylic resin particles, styrene resin particles, polyester resin particles, polyurethane resin particles , Polycarbonate-based resin particles, polyamide-based resin particles, silicone-based resin particles, fluorine-based resin particles, or copolymer resin particles of two or more kinds of monomers used in the synthesis of the above resins.
• the average particle size of the particles added to the surface layer is preferably 0.1 ⁇ m or more and less than 1.0 ⁇ m. If the average particle size is less than 0.1 ⁇ m, the particles may aggregate to form coarse particles, and the shape may be transferred to the bonded base material. When the average particle diameter is 1.0 ⁇ m or more, voids are easily generated at the particle interface during stretching, and the shape may be transferred to the coated functional layer. In addition, particles added to the surface layer may fall off during film formation, resulting in increased surface roughness.
• the average particle diameter is more preferably 0.15 ⁇ m or more and less than 0.9 ⁇ m, and even more preferably 0.15 ⁇ m or more and less than 0.8 ⁇ m.
• the method for producing the polypropylene film of the present invention will be described with reference to specific examples, but the present invention should not be construed as being limited thereto.
• the raw material for layer A is supplied to the single-screw extruder for layer A
• the raw material for layer B is supplied to the single-screw extruder for layer B
• melt extrusion is performed at 200 to 260 ° C.
• the laminated unstretched sheet having a layer structure of A layer / B layer / A layer is obtained by laminating so as to have a laminated thickness ratio of / 1 and discharging onto a cast drum.
• the surface temperature of the cast drum is preferably 10 to 130 ° C, more preferably 20 to 100 ° C.
• any of an electrostatic application method, an adhering method utilizing surface tension of water, an air knife method, a press roll method, an underwater casting method, etc. may be used, but the flatness is An air knife method that is good and capable of controlling the surface roughness is preferable.
• the cast sheet obtained as described above is biaxially stretched to obtain a film having desired strength and heat shrinkability.
• the biaxial stretching method, inflation simultaneous biaxial stretching method, stenter simultaneous biaxial stretching method, such as a stenter sequential biaxial stretching method can be selected any method, film-forming stability, thickness uniformity, film heat From the viewpoint of shrinkage control, it is preferable to adopt the stenter sequential biaxial stretching method, and it is particularly preferable from the viewpoint of heat shrinkage control to perform stretching in the MD direction and then stretching in the TD direction.
• the temperature of the unstretched cast sheet is controlled so that it can be stretched.
• the temperature control method a method using a temperature-controlled rotating roll, a method using a hot air oven, or the like can be adopted.
• the stretching temperature in the longitudinal direction is 100 to 150 ° C., more preferably 110 to 140 ° C., and most preferably 130 to 140 ° C. from the viewpoint of film characteristics and its uniformity.
• the stretching temperature is less than 100 ° C, uneven stretching or film breakage may occur, or the heat shrinkage rate after treatment at 100 ° C for 15 minutes may increase, which may occur during the film forming process, coating process, or storage after winding.
• the film may shrink and the flatness may deteriorate.
• the stretching temperature is higher than 150 ° C, the orientation of the film is weak and the heat shrinkability at high temperature may decrease.
• the stretching ratio in the longitudinal direction is preferably 2 to 7 times, more preferably 2.5 to 6.5 times, and further preferably 3 to 6 times. If the draw ratio is less than 2 times, the orientation of the film will be weakened, and the heat shrinkability and tensile rigidity may decrease. On the other hand, if it exceeds 7 times, film breakage may occur.
• the uniaxially stretched film obtained by stretching in the longitudinal direction is stretched in the width direction.
• the biaxially stretched film is obtained by guiding the uniaxially stretched film to a tenter type stretching machine, gripping the ends of the film with clips, and stretching the film in the width direction.
• the stretching temperature in the width direction is preferably 125 to 175 ° C, more preferably 135 ° C to 170 ° C, still more preferably 145 ° C to 165 ° C.
• the stretching temperature in the width direction is preferably higher than the melting point of the polypropylene raw material B, more preferably 30 ° C. or higher, further preferably 50 ° C. or higher than the melting point. When the stretching temperature is less than 125 ° C.
• the film may shrink during the film forming process, the coating process, or the storage after winding, and the flatness may be deteriorated.
• the temperature exceeds 175 ° C, the orientation of the film may be weak and the tensile rigidity may be lowered, or the film may be broken due to resin melting.
• the draw ratio in the width direction is preferably 1.5 to 15 times, more preferably 2.5 to 12 times, and further preferably 6 to 10 times. If the draw ratio is less than 1.5 times, the tensile rigidity may decrease and the productivity may deteriorate. On the other hand, if the draw ratio exceeds 15 times, the film may be easily broken.
• Relaxation and heat-fixing treatments are performed by holding clips in the width direction with tension while giving a relaxation rate of 0-8% in the width direction, and heat-setting at a temperature of 100 ° C or more and less than 160 ° C, and then 80- After the cooling process at 100 ° C., the film is led to the outside of the tenter and the clip at the end of the film is released.
• the heat treatment temperature is more preferably 110 ° C. or higher and lower than 155 ° C., further preferably 120 ° C. or higher and lower than 150 ° C.
• the heat treatment temperature is preferably higher than the melting point of the polypropylene raw material B, more preferably higher than the melting point by 30 ° C. or higher, still more preferably higher than 50 ° C. or higher.
• the relaxation rate is more preferably 0 to 6%, further preferably 0 to 4%. If the relaxation rate exceeds 6%, the heat shrinkability after treatment at 130 ° C for 15 minutes may be insufficient. If the temperature at which relaxation is applied is 160 ° C. or higher, the heat shrinkability after treatment at 130 ° C. for 15 minutes may be insufficient. On the other hand, if it is less than 100 ° C, the dimensional stability of the film at a temperature of 100 ° C or less may be insufficient.
• the polypropylene film of the present invention obtained as described above is excellent in heat shrinkability at high temperature (130 ° C.) and at the same time has good flatness at high temperature (100 ° C.). It can be preferably used for label packaging for the purpose of imparting or protecting the contents, or for use as a release base material that requires heat shrinkability after forming a functional layer. In particular, it can be suitably used as a release film.
• Thermal contraction rate ⁇ (l 0 ⁇ l 1 ) / l 0 ⁇ ⁇ 100 (%) The measurement is carried out in the plane of the film, when the MD direction is 0 °, with respect to the MD direction, 15 °, 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 °, 135 °.
• the heat shrinkage was measured in each direction, and the direction showing the highest value was defined as the main shrinkage direction, and the results are shown in the table.
• the heat shrinkage rate is measured in 15 ° increments from any direction, and the highest direction is taken as the main shrinkage direction.
• the main shrinkage direction in the examples coincided with the width direction in all examples.
• the values in the longitudinal direction are also shown in the table.
• Thermomechanical analyzer TMA / SS6000 manufactured by Seiko Instruments Inc.
• Test mode L control mode
• Test length 20mm
• Temperature range 23 ⁇ 200 °C
• Temperature rising rate 10 ° C./min
• SS program 0.1 ⁇ m / min
• Measurement atmosphere In nitrogen Measurement thickness: The film thickness of (1) above was used.
• Elastic modulus in the thickness direction (EIT) measured by the nanoindentation method For the measurement, a nano indenter “ENT-2100” manufactured by Elionix Co., Ltd. was used according to the method defined in ISO 14577 (2002). A drop of "Aron Alpha” (registered trademark) professional impact resistance manufactured by Toagosei Co., Ltd. is applied to a polypropylene film, and the biaxially oriented polypropylene film is fixed to a dedicated sample fixing base via an instant adhesive. The measurement was performed with the surface layer side as the measurement surface. A triangular pyramid diamond indenter (Berkovich indenter) having an interridge angle of 115 ° was used for the measurement.
• the measurement data was processed by a dedicated analysis software (version 6.18) of "ENT-2100" to measure the indentation elastic modulus EIT (GPa).
• Measurement mode Load-unload test Maximum load: 0.5mN Holding time when the maximum load is reached: 1 second Loading speed, unloading speed: 0.05mN / sec
• a tensile test was performed on each measurement sample in a direction orthogonal to the main shrinkage direction.
• the test was performed 5 times each in the main contraction direction and the direction orthogonal to the main contraction direction, and the F2 value was calculated by obtaining the arithmetic mean value in each direction.
• the flow rate of the eluting solvent was 1.0 ml / min, and the refractive index detector was used for detection.
• Mw weight average molecular weight
• Z + 1 average molecular weight (Mz + 1) of each of the A layer and the B layer are described.
• Example 1 Highly crystalline PP (manufactured by Prime Polymer Co., Ltd., MFR: 2.9 g / 10 min, melting point 164 ° C.) was supplied to the A layer as a polypropylene raw material A to a uniaxial melt extruder for the A layer, and B In the layer, 65 parts by mass of the polypropylene raw material A and low stereoregular PP as polypropylene raw material B (manufactured by Idemitsu Kosan Co., Ltd., "Elmodu" (registered trademark) S901, MFR: 50 g / 10 minutes, melting point: 80 ° C.) ) 35 parts by mass of dry blended material is fed to a uniaxial melt extruder for layer B, melt-extruded at 240 ° C., and foreign matter is removed by a 60 ⁇ m-cut sintering filter.
• a composite T die having a three-layer structure of layer / B layer / A layer was laminated at a thickness ratio of 3/4/3, and was discharged onto a cast drum whose surface temperature was controlled at 30 ° C. to obtain a cast sheet. . Then, preheated to 130 ° C. by using a plurality of ceramic rolls, and stretched 4.5 times in the longitudinal direction of the film at 130 ° C., introduced into the tenter type stretching machine with the end portions held by clips, and at 160 ° C. After preheating for 3 seconds, the film was stretched 8.0 times in the width direction of the film at 150 ° C. In the subsequent heat treatment step, heat treatment is performed at 130 ° C.
• Example 2 A polypropylene film was obtained in the same manner as in Example 1 except that the lamination thickness ratio was 1/8/1, the width-direction preheating temperature was 170 ° C., the stretching temperature was 160 ° C., and the film thickness was 30 ⁇ m. .
• Example 3 In the A layer, 80 parts by mass of highly crystalline PP (manufactured by Prime Polymer Co., Ltd., MFR: 2.9 g / 10 min, melting point: 164 ° C.) as a polypropylene raw material A, and low stereoregular PP (Idemitsu) as a polypropylene raw material B. Kosan Co., Ltd. "Elmodu" (registered trademark) S901, MFR: 50 g / 10 minutes, melting point: 80 ° C) 20 parts by mass of dry blend was used as a raw material for the layer A, and the layer thickness ratio was 2 /.
• highly crystalline PP manufactured by Prime Polymer Co., Ltd., MFR: 2.9 g / 10 min, melting point: 164 ° C.
• low stereoregular PP Idemitsu
• the stretching temperature in the longitudinal direction was 125 ° C.
• the preheating temperature in the width direction was 170 ° C.
• the stretching temperature was 160 ° C.
• the heat treatment temperature was 120 ° C.
• the film thickness was 15 ⁇ m.
• a polypropylene film was obtained in the same manner.
• Example 4 "WELNEX” RFG4VM (MFR: 6.0 g / 10 min, melting point: 130 ° C.) manufactured by Japan Polypro Co., Ltd. was used as the polypropylene raw material B, the lamination thickness ratio was 2/6/2, and the film thickness was 40 ⁇ m.
• a polypropylene film was obtained in the same manner as in Example 1 except that.
• Example 5 A polypropylene film was obtained in the same manner as in Example 1 except that the mixing ratios of the polypropylene raw material A and the polypropylene raw material B for the B layer were 55 parts by mass and 45 parts by mass, respectively, and the film thickness was 12 ⁇ m. It was
• Example 6 In the layer A, 90 parts by mass of highly crystalline PP (manufactured by Prime Polymer Co., Ltd., MFR: 2.9 g / 10 minutes, melting point: 164 ° C.) as a polypropylene raw material A, polypropylene ethylene random copolymer as a polypropylene raw material B (Sumitomo Chemical Co., Ltd.) Noblene S131 (Mfg. Co., Ltd., MFR: 1.5 g / 10 min, melting point: 132 ° C.) 10 parts by mass of dry blend was supplied to a single-screw melt extruder for the A layer, and the above for the B layer.
• highly crystalline PP manufactured by Prime Polymer Co., Ltd., MFR: 2.9 g / 10 minutes, melting point: 164 ° C.
• B Suditomo Chemical Co., Ltd.
• Noblene S131 Mfg. Co., Ltd., MFR: 1.5 g / 10 min, melting
• polypropylene raw material A and 40 parts by mass of polypropylene raw material B having low stereoregularity PP manufactured by Idemitsu Kosan Co., Ltd., "ELMODU” (registered trademark) S901, MFR: 50 g / 10 minutes, melting point: 80 ° C.)
• polypropylene ethylene random copolymer manufactured by Sumitomo Chemical Co., Ltd., Nobrene S131, MFR: 1.5 g / 10 minutes, melting point: 1

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