JP2006327019A - Laminated polypropylene type film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene type film excellent in water resistance, moisture proofing and color development in printing, easy to remove after adhesion, and useful as a packaging film or an adhesive label. <P>SOLUTION: The film comprises, as a core layer, a foamed polypropylene type film containing any one of inorganic fine particles, inactive organic fine particles and an incompatible polymer and comprises on both surfaces of it, as surface layers, polypropylene type films which contain either of inorganic fine particles and inactive organic fine particles and which substantially are not foamed. The ratio of the thicknesses of both surface layers is 1:5-1:16, and, in the thickness of ≤50 μm of the laminated film, the all light transmittance of the film is 5-45%, the haze is 50-95% and the internal haze is ≥50% of the haze value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polypropylene film excellent in water resistance, moisture resistance, and color development of printing. More specifically, it is easy to re-peel after adhesion, and is suitable for use as a label, a seal, etc. The present invention relates to an excellent polypropylene film.

Conventionally, packaging bags and adhesive tapes made of polypropylene film as a base film have been used after evaluating the excellent properties such as transparency, toughness and water resistance of stretched polypropylene film. . While having these excellent characteristics, there is a drawback that the color of the printing ink appears thin when printing is performed on a transparent film.
On the other hand, a white film to which a white pigment is added is well known as a film having excellent color developability (see, for example, Patent Document 1). White films are widely used for various packaging materials, adhesive tapes, and labels because of their color-enhancing properties due to their excellent concealability.
However, the white film has a defect that the film strength is lowered because the white film has a cavity in the film.

  In addition, various problems have been pointed out in the method of use. For example, in applications such as labeling or sticking white film, the method of use, that is, repeated use of peeling off the sticker from the release paper However, it is regarded as a problem that the surface layer portion of the film is missing, and improvement in the strength in the thickness direction of the film is desired.

  In response to these indications, conventionally, as a white pigment of a polypropylene film, a method of adding particles that have a small particle size and do not generate voids, low crystallization of the entire film, low stretching ratio, etc. A method for improving the film strength is disclosed.

  However, as a white pigment of polypropylene film, the film obtained by adding particles that have a small particle size and do not generate cavities is poor in concealing property and poor in color of printing ink. The film obtained by increasing the amount of added has problems such as high cost of film products due to the high price of pigment particles. Further, in the method of reducing the orientation of the film, the voids around the pigment particles are insufficient, the hiding property is poor, and the color of the printing ink is poor. Further, there has been a problem that a film lack of waist occurs and a cost problem is caused by increasing the film thickness in order to compensate for the lack of waist.

  The present invention relates to a polypropylene film that solves the problems of the conventional polypropylene film and is excellent in water resistance, moisture resistance, and color development of printing, and more specifically, a label that can be easily peeled off after adhesion. An object of the present invention is to provide a polypropylene film suitable for use as a seal or the like and excellent in printability.

  In order to achieve the above object, the polypropylene film of the present invention has a foamed polypropylene film containing any one of inorganic fine particles, inert organic fine particles, and incompatible polymers as a core layer, and both surface layers are coated with inorganic fine particles and insoluble fine particles. A substantially non-foamed polypropylene film containing any of the active organic fine particles is used as a surface layer, the thickness ratio of both surface layers is 1: 5 to 1:16, and the total light beam of the film when the laminated film thickness is 50 μm or less. The transmittance is 5 to 45%, the haze is 50 to 95%, and the internal haze is 50% or more of the haze value.

When the light transmittance is high, the affixed surface and contents can be seen through from the opposite side of the print surface of the film, the print looks light, or the color of the print changes, resulting in poor color development.
In addition, the light transmittance decreases and the haze value increases. However, if the haze of the entire film increases, protrusions are formed on the film surface, resulting in poor film gloss, ink loss during printing, and color development. Is inferior.

  In the polypropylene-based film having the above-described constitution and excellent in the color developability of printing of the present invention, the film having the above characteristics is excellent in the strength in the thickness direction of the film, and is excellent in removability after adhesion.

  In this case, the total light transmittance of the polyolefin film can be 45% or less.

  When the total light transmittance of the polypropylene film is 45% or less, the film reflectivity is improved by the concealing property, and the color developability of the printing ink printed on the film is excellent.

In this case, the void content of the polypropylene film may be 8 to 28 cc / 100 g.

  When the above-mentioned polyolefin film has a void content of 8 to 28 cc / 100 g, it can be developed on various labels due to its paper-like texture, lightness, cushioning, and the like, and has high delamination strength. Since it becomes excellent, it is particularly useful for applications such as adhesive labels.

Furthermore, in this case, an ink layer can be formed on the surface layer of the thinner side of the polyolefin film.

  According to the polypropylene film of the present invention, particularly when used as a label or a seal, it is a film excellent in peelability and printing color development.

  Hereinafter, embodiments of the polyolefin film excellent in printability of the present invention will be described.

  The polypropylene film excellent in color developability and re-peeling after adhesion of the present invention can be obtained as follows.

  In the present invention, the polypropylene-based resin forming the polypropylene-based film may be polypropylene, polypropylene such as α-olefin copolymer polypropylene, copolymers thereof, or mixtures thereof. It is recommended to use a polypropylene-based resin whose main component is a copolymerized polypropylene of 1% or less of ethylene from the viewpoint of stability and economic efficiency. The polypropylene film in the present invention is a film formed using such a polypropylene resin, and an unstretched film, a uniaxially stretched film, or a biaxially stretched film can be obtained by a known method.

  A more preferable polypropylene-based resin for achieving the object of the present invention has an intrinsic viscosity of preferably 1.5 to 2.5, and more preferably 1.8 to 2.2. When the intrinsic viscosity is less than 1.5, the film becomes brittle, and troubles such as cutting occur at the time of processing such as printing, which is difficult to handle. Moreover, when larger than 2.5, when melt-extrusion at the time of shaping | molding, a load is high and productivity will be inferior.

  A more preferable polypropylene film for achieving the object of the present invention is a polypropylene film containing a cavity as the core layer (A). As a method for forming a cavity in a polypropylene film, an incompatible resin or inorganic or organic fine particles are blended with the polypropylene resin forming the film, and after forming the film, the film is stretched to be incompatible with the polyolefin resin. There are widely known methods for forming fine cavities at the interface with resin and fine particles, and methods for forming bubbles in the film by adding a foaming agent to polyolefin resin and generating reaction gas by heat in the extruder. Yes. The polyolefin film used in the present invention is not limited to the type of cavity formation method, but due to ease of control of the size and amount of cavity formation, fine particles are blended and interfacial peeling occurs in the polyolefin resin by stretching. The method of obtaining a cavity is recommended.

  Examples of the inorganic fine particles used here include calcium carbonate, silicon dioxide, barium sulfate, magnesium oxide, alumina, and zeolite. Examples of the fine organic particles include polycarbonate, polybutylene terephthalate, cross-linked polyurethane and the like, and those having various coatings on the surface of these fine particles can form cavities in the film. If it is, it can be used arbitrarily.

  The preferred size of these fine particles varies depending on the thickness of the film, but the average particle size is about 0.1 to 10 μm. More preferably, the one in the range of 1.0 to 4.0 μm is used in consideration of foaming efficiency and printing omission due to coarse particles.

  The shape of these fine particles may be spherical, cubic, cylindrical, conical, disk-shaped, or irregular, and even if the particles are porous, interfacial peeling occurs in the film due to stretching. However, what is necessary is just to form a cavity.

  The surface layers (B) and (C) are polypropylene films that do not substantially contain cavities. However, slipping and blocking resistance are improved by adding a small amount of inert organic particles to improve the handling of the film.

  A more preferred embodiment is that the total light transmittance of the polypropylene film is 45% or less, more preferably 30% or less. The void content of the polypropylene film is preferably in the range of 8 to 28 cc / 100 g.

  Further, in order to improve the light reflectivity of the film and improve the color developability of the printing ink, the total light transmittance is preferably 45% or less. However, this is easily achieved by incorporating cavities in the film. be able to. In this case, the characteristics of the raw materials such as the type of polyolefin resin forming the film, melt viscosity, molecular weight, and the amount, type, shape, particle size, and particle size of the fine particles to be blended into the film are to be expressed in the film manufacturing process. The total light transmittance also changes because the size and amount of the cavities differ depending on the stretching conditions such as the temperature and magnification, but concealing the light beam when the total light transmittance exceeds 40% simply by developing the cavities in the film. The total light transmittance can also be adjusted by adding inorganic fine particles capable of imparting properties.

  The above-mentioned fine particles used for concealing light rays are of any type as long as they have a size and properties that do not substantially generate cavities in the film even when the film is stretched. Good titanium dioxide is recommended. The crystal structure may be a rutile type or anatase type, and the surface thereof may be subjected to various surface treatments for light resistance and color tone adjustment. However, the particle diameter is preferably a number average particle diameter of 0.2 to 0.3 μm from the viewpoint of concealing effect and substantially no foaming.

  In the above polypropylene film, other additives for improving quality such as slipperiness and antistatic property, for example, wax, metal soap for improving productivity, in the range not impairing the object of the present invention. A known heat stabilizer, an antioxidant, an antistatic agent, an ultraviolet absorber, and the like which are usually added to a polypropylene film can be appropriately blended.

  In order to produce a polypropylene film, a method of blending polypropylene resin, inorganic or organic fine particles, various additives, etc. is not particularly limited, but a V-type blender, a screw-type blender, a drive blender, a ribbon blender, In general, the mixture is uniformly mixed using a mixer such as a Henschel mixer, and then kneaded and pelletized.

A film can be manufactured by the method illustrated below using the pellet obtained in this way.
a: Using two extruders, these pellets were melt-extruded at a temperature higher than the melting point of the polyolefin resin, for example, at a temperature of 180 to 300 ° C., and the polyolefin film of the core layer (A) from one extruder The resin composition for forming the resin is melt-extruded and the resin composition constituting the surface layers (B) and (C) is melt-extruded from the other extruder, and they are laminated in or out of the die. And then stretching.
b: Sheets constituting a single layer of a polyolefin-based film that has been extruded and formed in advance into a sheet shape, or uniaxially stretched, on both surfaces, a polyolefin-based resin layer that forms the surface is melt-extruded and laminated, How to stretch.

  The thickness of the polyolefin-based film excellent in printability of the present invention varies depending on the application and the method of use, but the thickness is usually preferably 10 to 250 μm.

  The film-forming conditions of the polyolefin film used in the present invention can be extruded and stretched at a temperature and a magnification at which desired film properties and void content can be achieved. For example, it is not different from the film forming conditions in the case of a general polyolefin resin, and it is a sheet obtained by solidifying a resin composition melt-extruded at an extrusion temperature of 180 to 300 ° C. with a cooling roll of 10 to 100 ° C. It can be obtained by performing the following stretching.

  In the stretching step, the film can be stretched at an area magnification of about 8 to 50 times, preferably about 10 to 40 times. Further, the stretching method is not limited to uniaxial stretching or biaxial stretching. In the case of biaxial stretching, it can be carried out by simultaneous biaxial stretching method, sequential biaxial stretching method, inflation method or the like. Axial stretching is common.

  As conditions for carrying out sequential biaxial stretching, first, stretching is performed about 3 to 8 times between rolls having a circumferential speed difference heated to 100 to 150 ° C. in the longitudinal direction, and then using a tenter stretching machine in the width direction. The film is stretched about 4 to 10 times at a temperature of about 140 to 170 ° C. After that, it is obtained by winding after performing a heat setting treatment at a temperature of about 150 to 170 ° C.

  Further, the film of the present invention is subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, flame treatment, etc. to improve the adhesiveness without any trouble with respect to the present invention. May be performed by a so-called in-line process performed in the film manufacturing process, or by a so-called off-line process in which the manufactured film is processed as a subsequent process.

Furthermore, this polypropylene film is subjected to corona discharge treatment or plasma treatment in a substantially oxygen-free atmosphere in the presence of nitrogen gas after being biaxially stretched, and an imino type or a surface layer portion having a depth of 10 nm from the surface. / And a method of introducing an amino nitrogen atom is preferred. As a typical surface treatment method, for example, an apparatus as shown in Japanese Patent Publication No. 5-9459 can be used, and it can be obtained by performing corona discharge treatment essentially under a nitrogen gas atmosphere. At this time, the processing conditions are related to various factors such as the film speed, the distance between the electrodes, the roll temperature before the processing, the atmospheric temperature, and the processing power. For example, the processing power is in the range of 5000 to 12000 J / m ² . There is practical. There is also a method of chemically modifying the film surface by putting various gases in a plasma state.

  A film having such surface characteristics has good printability and can be printed with any printing ink, but it is preferable to print with an ultraviolet curable ink and cure to form an ultraviolet curable printing ink layer. It is.

  The ultraviolet curable printing ink layer referred to in the present invention is a printing layer obtained by three-dimensional crosslinking and curing by irradiating ultraviolet rays in a wavelength region of, for example, 200 to 400 nm to a printing part printed with an ultraviolet curable printing ink. I mean. Further, the ultraviolet curable printing ink refers to a printing ink that can form a printing layer by three-dimensional crosslinking and curing in a short time by irradiation with ultraviolet rays. There are acrylate, thiol, epoxy, silicon and the like. As basic components, unsaturated polyester-based, polyurethane-based, epoxy-based, silicon-based, reactive oligomers typified by silicon-based acrylate, photopolymerizable monomer, photopolymerization initiator, pigment, polymerization inhibitor, wax, etc. Consists of.

The film of the present invention may further be added or coated with additives such as an antistatic agent, a weathering agent, an antifogging agent, and a slipping agent depending on the purpose. In addition, the film of the present invention can be used after embossing, printing, extrusion lamination processing, laminating with other resin films, paper, cloth and the like according to the purpose.

  Next, specific examples of contents and effects of the present invention will be described by way of examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the measuring method of the characteristic value in this specification is as follows.

(1) Total light transmittance and haze: The total light transmittance and haze were determined according to JIS-K-7105 using 1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

(2) Internal haze: Zedel oil was applied to both sides of the film, sandwiched between two glass plates, and measured according to JIS-K-7105, using 1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

(3) Particle size measurement: 50% weight average was measured by a Coulter counter method with Coulter Multisider II (Coulter).

(4) Intrinsic viscosity; measured according to JIS-K-7367-3.

(5) Peelability: Evaluation is made using a cellophane adhesive tape (manufactured by Sekisui Chemical Co., Ltd .: 12 mm width, hereinafter abbreviated as adhesive tape). The adhesive side of the adhesive tape is firmly adhered to the thicker surface layer (C) of the polypropylene film with a finger length of 3 cm. Next, the film edge is fixed with a finger, the adhesive tape is peeled from one direction at a speed of 2 cm / sec at an angle of 90 ° C., and the amount of the surface layer (C) peeled off from the laminated film is adhered to the adhesive tape side. Evaluate by
◎: Surface layer (C) does not migrate at all to the adhesive tape side ○: A part of the surface layer (C) peels thinly in the layer thickness direction on the adhesive tape side and adheres to the cello tape (registered trademark) side , Transferred state △: the entire surface layer (C) peeled thinly in the layer thickness direction on the adhesive tape side, adhered to the cello tape (registered trademark) side, transferred state ×: surface layer on the adhesive tape side The entire surface of (C) is peeled off in the layer thickness direction, adhered to the cello tape (registered trademark) side, and transferred.

(6) Cavity content It is calculated from the following equation using the cavity volume present in 100 g of the polyolefin film.

(7) Printing ink printability: An ultraviolet curable printing ink (manufactured by TOKA / trade name: Best Cure, 161 ink, T & K) is applied on the obtained film to an RI tester (manufactured by Meisei Co., Ltd./RI-2). Type) was printed so that the amount of printing ink was 2.0 g / m ^2, and irradiated with 500 mJ / cm ² of ultraviolet rays with an ultraviolet irradiator and cured, and the following color development was evaluated.

(A) Color developability; The color developability of the printed part subjected to the above printing was visually evaluated as follows.
◎: Sufficient color development ○: Can be used without practical problems ×: Thin color development, practical problems

Example 1
Polypropylene resin having a melting point of 159 ° C. as core layer: FS2011DG3 (ethylene component 0.6 wt%, MI = 2.5 g / 10 min, limiting viscosity = 2.07 dl / g) 95.0 wt% made by Sumitomo Chemical, PMMA particles : Polypropylene resin layer (A) mixed with 3.0% by weight of Nippon Shokubai Eposta MA1004 (average particle size 4.0 μm) and titanium dioxide particle-containing polypropylene: 2.0% of PPM7862 made by Dainichi Seika Co., Ltd. As the surface layer, a polypropylene resin layer (B) containing polypropylene resin FS2011DG3 and 1.0% by weight of PMMA particles: Nippon Catalyst Epester MA1002 (average particle size 2.0 μm) melt-mixed, and polypropylene as the thicker surface layer -Based resin FS2011DG3 and PMMA particles: Nippon Shokubai Eposta MA1002 ( The particle-containing polypropylene resin layer (C) in which 1.0% by weight of an average particle size of 2.0 μm was melt-mixed was melted by a separate extruder at a temperature of 260 ° C., and the melt was joined by a composite adapter. Later, it was extruded from a T-die and quenched with a cooling drum to obtain a three-layer unstretched laminated film having a (B / A / C) structure.

  The unstretched laminated film is first stretched 5 times at 130 ° C. in the machine direction and then 8.5 times at 155 ° C. in the transverse direction and then heat treated at a temperature of 160 ° C. while relaxing 3% (B) The corona treatment was performed on both sides of the layer (C), and the film was obtained by winding with a film winder. The final film thickness was 40 μm. The thickness ratio of each B / A / C layer of this film was 1/24/15.

(Example 2)
A 40 μm film was obtained in which only the thickness ratio of each B / A / C layer was changed to 1/31/8 by the same raw materials and method as in Example 1.

(Comparative Example 1)
A 40 μm film was obtained in which only the thickness ratio of each layer of B / A / C was changed to 1/35/4 by the same raw materials and method as in Example 1.

(Comparative Example 2)
A 40 μm film was obtained in which only the thickness ratio of each B / A / C layer was changed to 15/10/15 by the same raw materials and method as in Example 1.

  These characteristic values are shown in Table 1. Although the film obtained in Example 1 has good peelability and color developability, the film of Comparative Example 1 has good color developability but has poor peelability and is not practical.

The film of Comparative Example 2 has good peelability but poor color development and does not endure practical use.
.

Industrial application fields

  The present invention is a polypropylene-based film that is excellent in water resistance, moisture resistance, and color development of printing, and can be easily peeled off after adhesion, and is suitable for use as a label, a seal, and the like.

Claims (3)

It consists of a film containing a large number of fine cavities containing at least 50% by weight of polypropylene resin and inorganic particles having an average particle diameter of 0.1 to 10.0 μm and / or inert organic particles having an average particle diameter of 1.0 to 10.0 μm. The core layer (A) contains a substantially fine cavity containing 2% by weight or less of a crystalline polypropylene resin having an intrinsic viscosity of 1.5 to 2.5 and an inert organic particle having an average particle size of 1.0 to 4.0 μm. Film (B) (C) is laminated on both surface layers, the thickness ratio of both surface layers (B) and (C) is 1: 5 to 1:16, and the total light transmission of the film is obtained when the laminated film thickness is 50 μm or less. A polypropylene film having a rate of 5 to 45%, a haze of 50 to 95%, and an internal haze of 50% or more of the haze value. It consists of a film containing 50% by weight or more of polypropylene resin and inorganic particles having an average particle diameter of 0.1 to 10.0 μm and / or inert organic particles having an average particle diameter of 1.0 to 10.0 μm, and 25% of the total thickness. 2% by weight of a crystalline polypropylene resin having an intrinsic viscosity of 1.5 to 2.5 and inert organic particles having an average particle diameter of 1.0 to 4.0 μm on the core layer (A) having a thickness of not less than 75% and not more than 75% 2. The laminated polypropylene film according to claim 1, wherein the unstretched laminated film in which the surface layers (B) and (C) containing at most% are laminated on both sides is at least uniaxially stretched. The polypropylene resin layer (A) and the polypropylene resin layer (B) (C) are laminated polypropylene films laminated in a (B) / (A) / (C) configuration, and are thinner than the (C) layer (B) A pressure-sensitive adhesive label, wherein the layer is printed, and the pressure-sensitive adhesive layer is applied to the layer (C) which is thinner than the layer (B).