JP4240076B2 - Polypropylene-based resin laminated film and method for producing the same - Google Patents

Description

  The present invention relates to a film for packaging, and in particular, has antifogging properties, and has good slipperiness, blocking resistance and transparency, and vegetables, root vegetables, fruits, flowers, flowering trees, mushrooms The present invention relates to a film suitable for packaging fresh products made of plants or animals that require high freshness such as fish and meat (hereinafter referred to as “fresh products”).

  Films made of polyolefin resins are widely used as packaging materials for various articles including food. In particular, polypropylene film has excellent mechanical properties, optical properties such as transparency, gloss, etc., gas barrier properties, food hygiene properties such as odorlessness, etc., so it is widely used mainly in the field of food packaging. It has been. However, polypropylene-based resin films have the disadvantage that they are poor in blocking resistance, and tend to cause a phenomenon that the films adhere to each other (so-called blocking phenomenon), and the workability of packaging and the like may be significantly reduced. ing.

  Therefore, as a method for preventing blocking of a polypropylene resin film, a method of blending organic fine particles such as inorganic fine powder represented by silicon dioxide or a crosslinked polymer as a so-called antiblocking agent in the film In addition, a method has been devised in which a slip agent such as fatty acid amide is combined.

  In addition, a method of laminating a sealing layer mainly composed of a polyolefin resin on the surface of a base layer mainly composed of a polypropylene resin is used when making a bag of a polypropylene resin film having high antifogging properties. Yes. In addition, when a sealing layer made of a polyolefin resin is laminated on a base layer made of a propylene resin, a low melting point polyolefin resin is used as the sealing layer so that the processed bag exhibits sufficient strength. It is often used as a forming resin, and the use of such a low-melting polyolefin resin has been a factor that further deteriorates the slipping and blocking properties of the film. As a method for solving such a problem, a method of adding organic polymer fine particles having a predetermined particle diameter and inert fine particles such as inorganic fine particles to a resin for forming a seal layer has been proposed (Patent Document). 1).

Japanese Patent Laid-Open No. 2003-237827

  Polypropylene resins, on the other hand, have been conventionally obtained by polymerizing propylene in the presence of a catalyst having a very low activity such as a titanium trichloride-organoaluminum compound using a so-called solvent method. As a result, several highly active catalysts have been developed. As a result, it has become possible to obtain a polypropylene resin more inexpensively and efficiently by using a so-called gas phase method. However, the polypropylene resin obtained by using the highly active catalyst by the above-described gas phase method has a large average particle size, a narrow particle size distribution, and a low fine powder content. When inorganic fine particles are added to a resin in order to produce such a polypropylene resin film, there is a problem that the dispersibility of the inorganic fine particles is deteriorated.

  Therefore, dispersibility of inorganic fine particles in polypropylene resin obtained by the vapor phase method is improved by utilizing inorganic fine particles having a predetermined particle size and apparent specific gravity in order to eliminate such problems. The technique to make it develop has been developed (Patent Document 2).

Japanese Patent Laid-Open No. 8-81591

  However, in the method of Patent Document 2, usable inorganic fine particles are limited to those having a relatively large particle diameter, a large apparent specific gravity, and a small pore volume. Therefore, a polypropylene-based resin film that is not necessarily excellent in blocking resistance cannot be obtained, and good slipperiness cannot be expressed, so that when the film is wound into a roll shape, wrinkles easily enter the film roll. . In addition, when a bag-making process or a printing process is performed using a film roll having such wrinkles, the defect rate is increased.

  The object of the present invention is to solve the problems in the above-described conventional polypropylene resin film, and is made of a polypropylene resin that is efficiently produced at low cost by a gas phase method, and has excellent blocking resistance and good slipperiness. It is an object of the present invention to provide a polypropylene-based resin film that is less likely to get wrinkled into a film roll when wound into a roll and has good processability during bag making processing and printing processing. Moreover, it is providing the manufacturing method which can manufacture such a polypropylene resin film cheaply and efficiently.

Among the present inventions, the invention described in claim 1 is such that a sealing layer mainly composed of a polyolefin resin is laminated on both front and back surfaces of a base layer mainly composed of a polypropylene resin, and is biaxially stretched. A polypropylene resin laminated film for packaging fresh products having a thickness of 10 μm or more and less than 70 μm and a haze value of 2.0% or more and 5.0% or less , and a polypropylene resin and a seal constituting the base layer A polyolefin-based resin constituting the layer is formed by a vapor phase method, and the laminated film contains all of the Al in an amount of 15 mg / kg or more and less than 150 mg / kg, and at least the inorganic fine particles in the seal layer Is added and the following formulas (1) to (6) are satisfied.
(1) An antifogging agent is blended in at least one of the resin forming the base layer and the resin forming the seal layer. (2) The base layer is formed of a propylene-ethylene copolymer, and the propylene-ethylene. The ethylene content in the copolymer is 0.5 wt% or more and less than 1.5 wt% (3) The seal layer is an ethylene / butene-1 copolymer, an ethylene / propylene / butene-1 copolymer, Ethylene / acrylic acid copolymer, ionomer cross-linked ethylene / acrylic acid copolymer with metal ion, polypropylene, polybutene-1, butene / ethylene copolymer, propylene / ethylene copolymer, propylene / butene-1 copolymer Polymers using one or more of propylene / ethylene / butene-1 copolymer and propylene / pentene copolymer (4) The coefficient of dynamic friction measured in an atmosphere of 40 ° C. is 0.61 or more and 1.1 or less (5) Time until air is completely removed from between the films when the pressure is reduced by stacking two films. The air escape index is 1.8 seconds or more and 9.0 seconds or less. (6) The container is left in an atmosphere of 5 ° C. for 30 minutes with the opening of a container containing hot water of 50 ° C. covered. The dew adherence area after taking it out from the room temperature atmosphere to 1/4 or less of the whole

  The structure of the invention described in claim 2 is that, in the invention described in claim 1, the air escape index is 7.8 seconds or less.

The structure of the invention described in claim 3 is that, in the invention described in claim 1, the ratio of the thickness of the seal layer to the whole layer of the laminated film is 1/60 to 1/3.

The structure of the invention described in claim 4 is that, in the invention described in claim 1, an antifogging agent is added to the base layer and the seal layer.

The structure of the invention described in claim 5 is the invention described in claim 1, in which the cutting edge temperature is 370 ° C. using a fusing sealing machine in which the cutting edge angle is adjusted to 60 degrees and the cutting edge set temperature is adjusted to 390 ° C. Thus, the defective rate when a fusing seal bag for a film is produced at a shot speed of 120 bags / min is 5% or less.

The structure of the invention described in claim 6 is the structure of the invention described in claim 1, after applying a pressure of 1 kg / cm ² at 140 ° C. for 1 second to heat-seal the seal layers, The strength when the heat-sealed part is peeled 180 degrees is that it is 1.5 N / 15 mm or more and 6.0 N / 15 mm or less.

The structure of the invention described in claim 7 is that, in the invention described in claim 1, the wetting tension of the surface of the seal layer is 35 mN / m or more and 45 mN / m or less.

The structure of the invention described in claim 8 is that, in the invention described in claim 1, the resin forming the sealing layer has the melt flow rate adjusted to 1.5 g / 10 min or more and 9.0 g / 10 min. The thing, or a mixture thereof.

The structure of the invention described in claim 9 is the invention described in claim 1, wherein the polyolefin resin layer forming the seal layer has an average particle diameter of 1.0 μm or more and less than 12.0 μm, and a pore volume. Is added with inorganic fine particles of 1.0 ml / g or more and less than 2.0 ml / g.

The structure of the invention described in claim 10 is that, in the invention described in claim 4 , the antifogging agent is a polyoxyethylene alkylamine type antifogging agent, a polyoxyethylene alkylamine fatty acid ester type antifogging agent, or a fatty acid. That is, it is a combination of at least two of glycerin ester type antifogging agents.

The structure of the invention described in claim 11 is that, in the invention described in claim 4 , the amount of the antifogging agent in the entire layer of the laminated film is 0.2% by weight or more and less than 1.5% by weight. .

According to a twelfth aspect of the present invention, there is provided a manufacturing method for manufacturing the polypropylene-based resin laminated film according to the first aspect, wherein a polypropylene-based resin and a polyolefin-based resin are coextruded from a plurality of extruders. The film-forming process for forming an unstretched polypropylene-based resin laminate sheet by melt extrusion and the unstretched polypropylene-based resin laminate sheet obtained in the film-forming process are biaxially stretched in the longitudinal and transverse directions. An axial stretching step and satisfy the following requirements (a) to (d).
(A) The film forming step includes a propylene-ethylene copolymer granulated once by adding inorganic fine particles, a propylene-ethylene copolymer granulated twice by adding inorganic fine particles, and polypropylene To form a sealing layer with a resin
(B) The granulation in the film forming step is performed using a rotating body adjusted to a rotation speed of 100 rpm or more and 500 rpm or less, and the rotation speed of the rotating body in the first granulation is set to the second granulation. (C) The film forming step forms a base layer with a propylene-ethylene copolymer, and the ethylene content in the propylene-ethylene copolymer is increased. (D) the biaxial stretching step is heat-fixed after biaxial stretching in the longitudinal and transverse directions, and The heat setting temperature is adjusted to 160 ° C or higher and lower than 170 ° C

  Since the polypropylene resin laminated film of the present invention can be manufactured using a polypropylene resin obtained by a gas phase method, it can be manufactured inexpensively and efficiently. Moreover, it is excellent in blocking resistance, has good slipperiness, and it is difficult for wrinkles to enter the film roll when wound into a roll, and the processability during bag making and printing is good. Furthermore, since the added antifogging agent is easy to bleed out to the surface, it is excellent in antifogging property and also excellent in transparency. Therefore, the polypropylene-based resin laminated film of the present invention can be suitably used for packaging fresh products such as vegetables.

  On the other hand, according to the method for producing a polypropylene-based resin laminated film of the present invention, as described above, the polypropylene-based resin laminated film has excellent antifogging properties, high transparency, and good workability during bag making processing and printing processing. A film can be manufactured inexpensively and efficiently.

  In the polypropylene resin laminated film of the present invention, the polypropylene resin mainly used for forming the base layer includes a solid catalyst component, an organoaluminum compound component, and an electron donating compound component containing aluminum, magnesium, titanium and halogen as essential components. And a polypropylene-based resin obtained by vapor phase polymerization in the absence of a liquid medium using the catalyst.

  The polyolefin resin suitable for forming the seal layer (heat seal layer) of the polypropylene resin laminated film of the present invention is a polyolefin resin having a melting point lower than the melting point of the polypropylene resin forming the base layer. For example, an ethylene / butene-1 copolymer, an ethylene / propylene / butene-1 copolymer, an ethylene / acrylic acid copolymer, an ionomer obtained by crosslinking an ethylene / acrylic acid copolymer with a metal ion, polypropylene, polybutene- 1, one or more of butene / ethylene copolymer, propylene / ethylene copolymer, propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer, propylene / pentene copolymer, etc. Can be used. Among them, a random copolymer of propylene, ethylene, and an α-olefin having 4 or more carbon atoms, which is blended so as to have a melting point of 140 ° C. or lower, is preferably a polyester-based resin or a polyamide-based resin. Resins, polycarbonate resins and the like can also be used within a range that does not impair the characteristics of the film. Moreover, an ultraviolet absorber, antioxidant, antistatic agent, etc. can also be arbitrarily mix | blended. In addition, as a method for polymerizing the resin, a method by gas phase polymerization can be used in the same manner as the resin used for the base layer in consideration of economy.

  The polypropylene resin laminated film of the present invention requires that the surface of the seal layer has antifogging properties. That is, in the case of a film used for packaging, such as the polypropylene-based resin laminated film of the present invention, not only the fogging phenomenon on the inner surface of the package is prevented and the commercial value is increased, but also water droplets formed by the progress of fogging. Antifogging property is also an extremely important property in preventing water rot of the contents of the package due to the above. As a method for expressing the antifogging property on the surface of the seal layer as described above, a method of exposing (bleeding out) the antifogging agent to the surface of the seal layer on the side in contact with the fresh product during the storage period or the distribution period is suitably used. be able to. In addition, in order to bleed out the antifogging agent on the surface of the seal layer during the storage period and distribution period, a resin that forms the base layer and a seal layer are formed at the time of film production (at the time of melt extrusion of the raw material resin). A method of adding an antifogging agent to at least one of the resins to be used can be employed. If the method of blending the antifogging agent in the base layer forming resin or the sealing layer forming resin at the time of melt extrusion of the raw material resin is adopted, it involves a change in temperature of the temperature compared to the method of applying the antifogging agent to the surface of the film. It is preferable because the antifogging property can be stably and continuously exhibited during such a distribution period.

  In addition, when adopting a method of blending the antifogging agent in the base layer forming resin and the seal layer forming resin at the time of melt extrusion of the raw material resin, when adding the antifogging agent to both the base layer forming resin and the seal layer forming resin, The smooth bleed-out of the anti-fogging agent is preferable because it lasts for a long time. In addition, even when the antifogging agent is blended only in the base layer forming resin, the antifogging agent in the base layer forming resin sequentially bleeds out to the surface of the seal layer via the seal layer during the storage period or the distribution period. Gradually, the surface of the seal layer becomes antifogging. In addition, in order to connect excellent antifogging properties in the long run in the distribution process, even if the antifogging agent on the surface is washed away by preventing the fogging caused by the action of the contents of the package, It is necessary for the antifogging agent to bleed out to the surface of the seal layer one after another immediately and continuously, so that the surface of the seal layer has an antifogging property. Therefore, in setting the anti-fogging property in the present invention, it is preferable to consider re-expression after wiping off the surface anti-fogging agent.

  As the antifogging agent used in the present invention, it is preferable to use a polyoxyethylene alkylamine type, a polyoxyethylene alkylamine fatty acid ester type, and a fatty acid glycerin ester type together. As the polyoxyethylene alkylamine type, polyoxyethylene Examples include laurylamine, polyoxyethylene beef tallow amine, polyoxyethylene stearylamine, polyoxyethylene oleylamine, polyoxyethylene beef tallow propylene diamine, polyoxyethylene stearyl propylene diamine, polyoxyethylene N-cyclohexylamine, polyoxyethylene metaxylene diamine can do. Moreover, as a typical example of the polyoxyethylene alkylamine fatty acid ester type, there can be mentioned one in which the above-mentioned polyoxyethylene alkylamine type representative example and the following fatty acid are ester-bonded. Stearic acid, behenic acid, lauric acid, oleic acid, palmitic acid, coconut fatty acid, beef tallow fatty acid, rapeseed fatty acid, castor fatty acid, myristic acid. Furthermore, examples of the fatty acid glycerin ester type include myristic acid monoglyceride, monostearic acid monoglyceride, monoisostearic acid monoglyceride, monooleic acid monoglyceride, mono olive oil monoglyceride, dioleic acid monoglyceride, distearic acid monoglyceride, monoundecylenic acid monoglyceride and the like. .

  In addition to the above three types of antifogging agents, other antifogging agents may be added. Examples of such antifogging agents include monostearic acid diglyceride, monoisostearic acid diglyceride, monooleic acid diglyceride, and dioleic acid. Examples include polyglycerin fatty acid ester type typified by diglyceride, triisostearic acid diglyceride and the like.

  The preferred amount of antifogging agent for exhibiting antifogging properties in the present invention is that the antifogging agent is preferably present in the range of 0.2 to 1.5% by weight in combination with the inner and outer surfaces of the film, It is more preferably 0.3 to 1.2% by weight, and further preferably 0.5 to 1.0% by weight. If the amount of the anti-fogging agent is less than 0.2% by weight, the anti-fogging effect is not exerted sufficiently, which is not preferable. Conversely, if the amount of the anti-fogging agent exceeds 1.5% by weight, the anti-fogging agent Is not preferable because it becomes saturated and economically unfavorable, and a large amount of the antifogging agent migrates to the film surface, and the film surface is in a state where powder is sprayed and the appearance is deteriorated.

  On the other hand, in the polypropylene-based resin laminated film of the present invention, it is necessary to add inorganic fine particles to the resin forming the seal layer for the purpose of improving blocking resistance and improving slipperiness. The inorganic fine particles have an average particle size of 1.0 to 12.0 μm, preferably 1.3 to 4.0 μm, and a pore volume of 1.0 to 2.0 ml / g, preferably 1.25 to 1. 80 ml / g can be used. When either the average particle diameter or the pore volume is out of this range, good blocking resistance and slipperiness cannot be obtained. That is, when the average particle size is less than 1.0 μm, the film has insufficient blocking resistance, and it is difficult to adjust μH40 within the range of 0.2 or more and 1.1 or less. If it exceeds 0 μm, the appearance and transparency are deteriorated. Further, if the pore volume exceeds 2.0 ml / g, the dispersion during kneading with the resin deteriorates. If the pore volume is less than 1.0 ml / g, the scratch resistance deteriorates, and in addition, the amount per added weight This is not preferable because the number of particles is reduced, and it is necessary to increase the amount of addition when trying to add the same number of particles, resulting in poor transparency. As inorganic fine particles, silicon dioxide, magnesium silicate, aluminum silicate, calcium carbonate, magnesium oxide and the like can be suitably used. Among these inorganic fine particles, silicon dioxide having an average particle diameter of 1.5 to 4.0 μm and a pore volume of 1.0 to 2.0 ml / g can be preferably used. Moreover, it is preferable that the compounding quantity of the inorganic type microparticles | fine-particles with respect to resin which forms a base layer and a sealing layer shall be 0.05-0.60 weight part with respect to 100 weight part of resin. If it is less than 0.05 part by weight, the blocking resistance is insufficient, and if it exceeds 0.60 part by weight, the dispersibility is deteriorated and the appearance and transparency are deteriorated. The blending amount of the inorganic fine particles is more preferably 0.10 to 0.40 parts by weight from the viewpoint of blocking resistance and dispersibility. It is preferable to use silicon dioxide having an average particle diameter of 1.5 to 4.0 μm and a pore volume of 1.0 to 2.0 ml / g so as to have a blending amount of 0.10 to 0.40 parts by weight. Particularly preferred. The pore volume of the inorganic fine particles can be measured by a known method such as the method of JIS-K-1150 based on the BET method. Further, as a pore volume measuring device, an autosorb 1 manufactured by Cantachrome, a high-speed specific surface area / pore distribution measuring device Asap 2400 manufactured by Shimadzu Corporation, or the like can be suitably used.

  Furthermore, the polypropylene resin laminated film of the present invention needs to be adjusted so that the haze value is 0.4% or more and 5.0% or less so that the contents can be easily seen. If the haze value exceeds 5.0%, the transparency becomes insufficient when used for packaging fresh products, which is not preferable. Further, the lower limit of the haze value is preferably 0.8% or more, and particularly preferably 1.0% or more. Further, the upper limit of the haze value is preferably 4.0% or less, and particularly preferably 3.5% or less. In addition, although a haze value is so preferable that it is low, when it considers that addition of an antiblocking agent to resin is indispensable, it thinks that it is practically impossible to obtain a polypropylene resin film of less than 0.4%. It is done.

  Furthermore, the polypropylene-based resin laminated film of the present invention preferably contains 15 mg / kg or more and less than 150 mg / kg of Al in the entire laminated film. Generally, in the polymerization of polypropylene, an organoaluminum compound is used as a co-catalyst. In the conventional polymerization method such as a solvent method, the organoaluminum compound is removed in the catalyst removal step, whereas the present invention In the polypropylene raw material obtained by vapor phase polymerization used in No. 1, only deactivation of the catalyst is carried out, so Al is present in the raw material. That is, the presence of Al in the laminated film means that the laminated film is produced using a polypropylene raw material obtained by vapor phase polymerization. Compared to the polypropylene raw material obtained by the solvent method raw material, the polypropylene raw material obtained by vapor phase polymerization does not require a catalyst, atactic polypropylene removal step, and a solvent recovery step necessary for the removal, so energy consumption It can be said that this is an economical raw material, and a laminated film manufactured using the raw material can be said to be an environmentally friendly and economical film. Moreover, more preferable content of Al is 20 mg / kg or more and less than 80 mg / kg with respect to all the laminated film layers. The amount of Al contained in the entire layer of the laminated film can be determined by a method in which a predetermined amount (about 1.0 g) of a sample is dry-decomposed and treated with an acid and then measured by plasma emission analysis.

  In addition, in the polypropylene-based resin laminated film of the present invention, the resin forming the sealing layer is one having a melt flow rate adjusted to 1.5 g / 10 min or more and 9.0 g / 10 min, or a mixture thereof. preferable. By using the resin having the melt flow rate adjusted as described above or a mixture thereof as the resin for forming the seal layer, it is easy to adjust the dynamic friction coefficient (μH40) and AR of the film by granulation described later. It will be a thing.

  In addition, when the polypropylene resin film is continuously produced and wound up as a mill roll, it takes a very long time for the physical properties to stabilize (when it is aged in an ordinary atmosphere of about 40 ° C., 12 The state of unstable physical properties continues for about hours). Therefore, the film roll is likely to be wrinkled due to the occurrence of tightening due to the fact that the physical properties of the film after manufacture are not stable for a long time.

  From the above findings, the inventors of the present invention are not sufficient to control only the coefficient of friction as normally considered in order to prevent wrinkles from entering the film roll during aging, It is indispensable that the wound films (the front surface and the back surface of the film) slide appropriately and that air can escape from between the wound films at an appropriate speed. I guessed. Further, the degree of slippage between the wound films can be estimated by the dynamic friction coefficient at 40 ° C. (that is, μH40) of a film having stable physical properties (film after aging), and from between the wound films. It was presumed that the ease of air removal could be estimated by the AR (air escape index) value of the film having stable physical properties. And based on those inferences, as a result of intensive studies on the relationship between the degree of wrinkles during aging and the values of μH40 and AR of a film having stable physical properties, the values of μH40 and AR of a film having stable physical properties are When it was in the predetermined range, it was ascertained that no wrinkles occurred on the film roll during aging. However, in a film that requires a low haze value (that is, high transparency) such as the polypropylene resin laminated film of the present invention, the type and amount of lubricant to be added are greatly limited. By simply adjusting the amount, it was impossible to control the values of μH40 and AR within the desired ranges, and it was considered necessary to control the degree of dispersion of the lubricant in the resin. Therefore, as a result of trial and error by the inventors of the present invention considering the degree of dispersion of the lubricant in the resin, the method described later (see paragraphs 0053 to 0064) can be used without using a large amount of lubricant. The present inventors have found that a polypropylene resin film that simultaneously satisfies the haze value, desired μH40, and desired AR value can be obtained.

  That is, the polypropylene resin laminated film of the present invention needs to have a dynamic friction coefficient (that is, μH40) measured in an atmosphere of 40 ° C. of 0.2 or more and 1.1 or less. If μH40 is less than 0.2, the films are too slippery and unwinding after winding into a roll is undesirable. Conversely, if μH40 exceeds 1.1, the slipperiness is poor and the roll After the film is wound up, it is not preferable because wrinkles easily enter the film roll. The lower limit of μH40 is preferably 0.3 or more, and particularly preferably 0.35 or more. Further, the upper limit of μH40 is preferably 1.0 or less, and particularly preferably 0.95 or less.

  Furthermore, the polypropylene-based resin laminated film of the present invention has an air release index (that is, AR) of 1.8 seconds or more, which is the time taken for air to escape from between the films when two films are stacked and decompressed. It must be 0 seconds or less. When winding a polypropylene-based resin laminated film into a roll shape to form a film roll, it is preferable to wind it while entraining a certain amount of air. When the amount of entrainment is small, blocking becomes easy, and in the case of the polypropylene resin laminated film as in the present invention, since the glass transition point is a negative region, the dimensional change occurs even at room temperature, so the overlapping films Since they follow each other and cause a dimensional change, wrinkles are generated, which is not preferable. In particular, in a stretched film, wrinkles are likely to enter in the direction in which the stress during stretching remains. On the other hand, too much entrained air is not preferable because the overlapped films can be freely deformed individually, so that the film is stale and wrinkles are generated in the direction perpendicular to the film flow direction. And if the value of AR is less than 1.8 seconds, the entrained air will be lost immediately, so it is not preferable because the films are blocked or wrinkles occur in the product film roll due to residual stress during stretching. On the other hand, if the AR value exceeds 9.0 seconds, the entrained air is retained for a long time, so that the film may be damaged and the product film roll may have wrinkles in the direction perpendicular to the film flow direction. It is not preferable because it occurs. The lower limit of the AR value is preferably 2.0 seconds or more, and particularly preferably 2.5 seconds or more. The upper limit of the AR value is preferably 7.8 seconds or less, more preferably 7.5 seconds or less, and particularly preferably 7.0 seconds or less.

Moreover, the polypropylene resin laminated film of the present invention applied a pressure of 1 kg / m ² at 140 ° C. for 1 second to heat-seal the seal layers, and then peeled off those heat-sealed portions by 180 degrees. Strength (so-called seal strength) is preferably 1.5 N / 15 mm or more and less than 6.0 N / 15 mm. When the seal strength is less than 1.5 N / 15 mm, it is not preferable because the bag easily opens too much when used for packaging. On the contrary, when the seal strength is 6.0 N / 15 mm or more, packaging is performed. This is not preferable because the bag is difficult to open when used for applications. The lower limit of the seal strength is preferably 2.0 N / 15 mm or more, and particularly preferably 3.0 N / 15 mm or more. Further, the upper limit of the seal strength is preferably less than 5.0 N / 15 mm, and particularly preferably less than 4.0 N / 15 mm.

  On the other hand, in the polypropylene-based resin laminated film of the present invention, the wet tension of the surface of the seal layer is adjusted to 35 mN / m or more and 45 mN / m or less from the viewpoint of printability and expression of the antifogging effect by the antifogging agent. It is necessary. Further, the lower limit of the wetting tension on the surface of the seal layer is preferably 37 mN / m or more, and on the contrary, the upper limit of the wetting tension on the surface of the seal layer is more preferably 43 mN / m or less. When the wetting tension is less than 35 mN / m, it is not preferable because the antifogging effect on the film surface becomes poor. On the other hand, when the wetting tension exceeds 45 mN / m, blocking and wall breakage are likely to occur. .

Next, the preferable manufacturing method of the polypropylene resin laminated film of this invention is demonstrated. The unstretched film was formed by supplying a base layer forming resin mainly composed of crystalline polypropylene and a seal layer forming resin mainly composed of polyolefin to separate extruders, heating and melting, and passing through a filtration filter. After laminating the base layer-forming resin and the sealing layer-forming resin in a T-die at a temperature of 220 to 320 ° C., continuous extrusion is performed by melting and extruding from a slit-shaped T-die outlet and cooling and solidifying. It is preferable to form a stretched film. At this time, if the resin is dropped onto a drum-shaped take-up machine (chill roll) and air is blown from the surface opposite to the surface in contact with the chill roll with an air knife, the adhesion between the unstretched sheet and the chill roll increases. It is preferable because an unstretched sheet having a smooth surface and a uniform thickness can be obtained. The wind pressure of the air knife at this time is preferably in the range of 700 to 2200 mmH ₂ O. A low wind pressure is not preferable because the non-stretched sheet and the chill roll are not evenly adhered to each other. On the other hand, a high wind pressure is not preferable because the non-stretched sheet is unevenly contacted with the chill roll. Further, the resin temperature at the time of melt extrusion as described above is a temperature range in which resin degradation does not occur, and is preferably a temperature range of about 230 to 290 ° C, and more preferably a temperature range of about 270 to 280 ° C. preferable.

  In addition, the resin temperature of the base layer forming resin mainly composed of crystalline polypropylene and the sealing layer forming resin mainly composed of polyolefin at the time of melt extrusion is the melting point of each resin when there is a clear melting point. The temperature is preferably 60 ° C. or higher, and more preferably 70 ° C. or higher and does not cause thermal degradation. If the resin temperature is within such a temperature range, the influence of the relaxation time distribution of the melt deformation depending on the molecular weight distribution of the polyolefin resin during melt extrusion can be reduced, so the thickness unevenness of the unstretched film is reduced. can do. The chill roll temperature is preferably adjusted to a temperature of 30 ° C. or lower, and more preferably adjusted to 20 ° C. or lower. If the resin temperature at the time of melt extrusion is low and the chill roll temperature is high, the crystallization of the resin tends to proceed, the film surface becomes rough, and thickness unevenness tends to occur, which is not preferable.

  After the unstretched film is formed as described above, the unstretched film is biaxially stretched to be biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. As the sequential biaxial stretching method, the unstretched film is heated to a temperature of 90 to 140 ° C., stretched 3 to 7 times in the longitudinal direction, cooled, and then led to a tenter type stretching machine. After heating to a temperature and stretching 7 to 12 times in the width direction, heat setting (heat treatment) at a predetermined temperature to relax by 2 to 15%, preferably 4 to 10% in the width direction, cooling and winding up The method can be adopted. By heat-fixing while relaxing after stretching, the distortion of melt deformation depending on the molecular weight distribution of the polyolefin resin is eliminated, so the physical properties such as heat shrinkability of the laminated film are stabilized over the entire width of the film. As a result, the shrinkage and dimensional change of the seal part at the time of heat sealing are reduced, and as a result, it is possible to obtain a good-looking package without deformation of the seal part. A preferred heat setting method will be described later.

  The ratio of the thickness of the seal layer laminated on the base layer is not particularly limited, but is usually 1/60 to 1/3 (both sides of the base layer) with respect to all layers (base layer and seal layer) of the laminated film. The total thickness is preferably 1/50 to 1/5, and more preferably 1/30 to 1/10. When the thickness ratio of the seal layer is smaller than 1/60, the seal strength when the bag is processed becomes insufficient, and the reliability as a package is not preferable. Further, if the thickness ratio of the sealing layer is larger than 1/3, the so-called “waist” disappears in the entire laminated film due to the small proportion of the base layer portion, and the shape of the package after filling the contents is This is not preferable because it is unstable and lacks commercial value. Moreover, the thickness of the laminated film is not particularly limited, but can be appropriately determined within a range of about 10 to 70 μm suitable as a packaging film having high antifogging properties. In addition, the range of the more preferable thickness of a laminated film is 15-60 micrometers.

  Moreover, since the polypropylene resin laminated film of the present invention is mainly used for packaging fresh food products such as vegetables, it preferably has good fusing and sealing properties. Specifically, using a fusing sealing machine in which the blade edge angle is adjusted to 60 degrees and the blade edge setting temperature is adjusted to 390 ° C., the film temperature is 370 ° C. and the shot speed is 120 bags / minute at 370 ° C. When the fusing seal bag is prepared, it is preferable that the defect rate (the ratio of defects in the welded state and the cut state) per 1000 pieces of fusing seal bags to be formed is 5% or less. Further, the defect rate is more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and particularly preferably 4% or less.

  Furthermore, the polypropylene resin laminated film of the present invention can be subjected to surface treatment such as corona discharge treatment or flame treatment on one or both surfaces. A preferable method of corona discharge treatment will be described later.

Moreover, in order to obtain the polypropylene resin laminated film of the present invention, it is necessary to take the following means during production. By taking such means, it becomes possible to obtain a film having good antifogging properties, transparency, blocking resistance, and slipperiness, and which is difficult to cause wrinkles when rolled up.
(1) Adjustment of dispersion condition of inorganic fine particles in sealing layer forming resin (2) Adjustment of ethylene content in base layer forming resin (3) Adjustment of heat setting condition after transverse stretching (4) Adjustment of corona discharge treatment condition Hereinafter, each of the above-described means will be described sequentially.

(1) Adjustment of dispersion condition of inorganic fine particles in seal layer forming resin In the production of the polypropylene resin laminated film of the present invention, when inorganic fine particles are added to the polyolefin resin forming the seal layer, the powder Rather than adding the inorganic fine particles in the extruder and kneading, a masterbatch polymer chip in which high-concentration inorganic fine particles are added to the polyolefin resin is prepared in advance, and the master chips are then mixed with the inorganic fine particles. It is necessary to employ a method of diluting with a polyolefin resin not included.

  The master chip for forming the seal layer is prepared by adding inorganic fine particles to the polyolefin resin and stirring it with a mixer or blender. Then, the mixture is put into an extruder, kneaded, melt extruded, and pelletized. It is necessary to mix with a polyolefin resin chip that does not contain inorganic fine particles and then use the mixture (hereinafter, as described above, the inorganic fine particles are added to the resin and stirred, and then placed in an extruder. The process of kneading and melt-extrusion to form a pellet is called a granulation process).

  Furthermore, as a master chip for forming the seal layer, a combination of a kneading process performed once (one time granulation chip) and a kneading process repeated twice (twice granulation chip) are used in combination. There is a need to. Moreover, when using the 1st granulation chip and the 2nd granulation chip in combination, the mixing ratio of the 1st granulation chip and the 2nd granulation chip is in the range of 1: 9 to 9: 1. It is preferable to adjust inward. Furthermore, when using a once-granulated chip and a twice-granulated chip together, the particle size of the inorganic fine particles added when forming the once-granulated chip and the inorganic added when forming the twice-granulated chip It is preferable to make the particle diameter of the system fine particles as close as possible. That is, when the once-granulated chip and the twice-granulated chip are used in combination, the particle diameter of the inorganic fine particles added when forming the once-granulated chip and the inorganic added when forming the twice-granulated chip The difference from the particle size of the system fine particles is preferably less than 2.0 μm.

  When only a double granulation chip to which inorganic fine particles having a small particle size of less than 1.5 μm were added was used at the time of forming the seal layer, μH40 increased, the slipperiness deteriorated, and the film was wound into a roll. Sometimes film rolls are easily wrinkled, which is not preferable. In addition, when wrinkles occur in such a film roll, the film roll is tightened during storage, and air that is trapped between the films is reduced, which makes it difficult for the antifogging agent to bleed out and prevent the film from being fogged. Sex worsens. Moreover, when wrinkles occur in the film roll, when the bag is melted and bag-making (lamination), the bag cannot be made cleanly, and the appearance of the formed bag deteriorates. In addition, when only a single granulation chip to which inorganic fine particles having a large particle size of 1.5 μm or more are added is used, the AR value becomes extremely small, and the air trapped between the films is reduced as described above. For this reason, it is not preferable because the film roll is likely to be wrinkled because the overlapping films follow and deform when the film roll is stored. Moreover, the antifogging agent becomes difficult to bleed out as described above, and the antifogging property of the film is deteriorated. Furthermore, if only a single granulation chip to which inorganic fine particles having a small particle size of less than 1.5 μm are added is used, fish eyes are formed on the film due to insufficient dispersibility of the inorganic fine particles, resulting in poor appearance. It is not preferable. In addition, as the master chip for forming the sealing layer, in addition to the once-granulated chip and the twice-granulated chip to which inorganic particles have been added, an organic fine particle is added within a range that does not deteriorate the fusing seal strength. It is also possible to use grain chips in combination.

  When kneading as described above, the rotational speed of a rotating body such as a screw of an extruder is preferably adjusted to 100 rpm to 500 rpm, more preferably 250 rpm to 450 rpm, and more preferably 270 rpm to 430 rpm. It is particularly preferable to adjust to. In addition, when granulating twice as described above, it is preferable that the rotational speed of the rotating body in the first granulation is higher than the rotational speed of the rotating body in the second granulation.

(2) Adjustment of ethylene content in base layer forming resin In the production of the polypropylene resin laminated film of the present invention, as described above, as the polypropylene resin forming the base layer, various polypropylene resins mainly composed of polypropylene. Among them, it is preferable to use a copolymer of polypropylene and ethylene or a modified product thereof. Among such copolymers and modified products, it is preferable to use a resin having an ethylene content of 0.5 wt% or more and less than 1.5 wt%. By using such a resin, the antifogging agent added to the base layer is likely to bleed out, and the antifogging property (initial antifogging property and antifogging durability described later) of the polypropylene resin film is remarkably improved.

  When the content of ethylene in the copolymer constituting the base layer is 1.5% by weight or more, the film is softened and becomes difficult to slip, and μH40 increases. Moreover, the value of AR increases, it becomes difficult for air to escape from between the wound films, and wrinkles are easily generated on the film roll. Furthermore, the film is likely to lose heat, the haze value is increased, and the transparency is lowered. On the other hand, when the ethylene content is less than 0.5% by weight, the antifogging agent is difficult to bleed out, and good antifogging properties cannot be obtained. This is not preferable because the shape of the material may be deformed and good sealing strength cannot be obtained, or the fusing and sealing properties at the time of bag-making process are deteriorated.

(3) Adjustment of heat setting conditions after transverse stretching In addition, as described above, the polypropylene-based resin laminated film of the present invention is an unstretched film formed by laminating a seal layer on a base layer by a coextrusion method. Manufactured by heat-fixing after stretching in the vertical and horizontal biaxial directions. In the production of such a biaxially stretched film, in the case of production of a normal polypropylene resin film, it is usually heat-set at a temperature of 155 ° C. or more and less than 160, which is slightly below the melting point, but the film of the present invention. In order to obtain the above, it is necessary to perform the heat setting treatment at an extremely higher temperature than usual, ie, 160 ° C. or more and less than 170 ° C. By performing the heat setting treatment at such a high temperature, the shrinkage stress of the film is removed, the change with time after being wound into a roll is suppressed, and the generation of wrinkles is reduced to a very low level. Therefore, bleed-out failure of the antifogging agent due to generation of wrinkles does not occur, and the situation of deterioration of the antifogging property of the film does not occur. Moreover, the situation of the workability deterioration in the bag making process or the printing process due to the occurrence of wrinkles does not occur.

  When the temperature of the heat setting process exceeds 170 ° C., the film surface melts, heat is lost, rough skin occurs, μH40 is lowered and slippery, and air between the films is easy to escape (AR becomes small). It is not preferable because the transparency and appearance of the film are poor and the film cannot be used. On the other hand, when the temperature of the heat setting treatment is below 160 ° C., it is likely to be gradually cooled, and spherulites grow during surface recrystallization, resulting in poor transparency, and the shrinkage stress of the film increases and the change with time increases. This is not preferable because wrinkles easily enter the film roll during storage.

(4) Adjustment of corona discharge treatment conditions In the production of the polypropylene resin laminated film of the present invention, it is necessary to subject the surface of the film to corona discharge treatment under predetermined conditions. That is, the corona discharge treatment can employ various known methods, but is applied to the surface of the film after biaxial stretching by an electrode such as an aluminum bar type suspended in the width direction of the film. It is preferable to carry out with a processing power of 15 to 45 W / m ² / min after adjusting the distance between the film and the electrode to 1 to 3 mm. And it is necessary to adjust the wetting characteristic of the film surface after corona discharge to the range of 35 mN / m or more and 45 mN / m.

  When the degree of corona discharge treatment is weak, additives such as internal lubricants are difficult to bleed out to the outside, the slipperiness is deteriorated (μH40 increases), and air is difficult to escape (the AR value increases). ). Further, during bag making, slipping between the two folded films may be worsened, or friction between the bag making machine and the film may increase, making it impossible to produce a good-looking fusing sealed bag. In addition, since the internal antifogging agent is also difficult to bleed out to the outside, it is difficult to develop good antifogging properties. Further, when the degree of corona discharge treatment is increased, the film surface is roughened (surface irregularities resulting from the corona discharge treatment are formed), and the above-described problems are eliminated, and the slipperiness is improved ( μH40 is reduced) and air is easily removed (AR value is decreased). However, when the degree of corona discharge treatment becomes extremely strong, the so-called “skin roughness” of the film surface becomes severe, which is caused by the “skin roughness”. The transparency becomes low (haze increases) and the bleed-out speed of the added antifogging agent becomes extremely fast, and the transparency deteriorates over time due to the presence of a large amount of antifogging agent. May be invited. In addition, since the additives and resins on the film surface deteriorate and become a low molecular weight substance, it becomes easy to stick and block easily. At this time, the antifogging property may be lowered by peeling off the antifogging agent on one side when peeling the bonded films. Therefore, in order to control the μH40 and AR values within a desired range while exhibiting sufficient antifogging properties and transparency, and exhibiting good fusing and sealing properties, corona discharge treatment is performed with an appropriate strength. For this purpose, it is effective to perform the corona discharge treatment according to the above-described embodiment.

  Below, the measuring method of the characteristic value used in this specification is shown.

[Dynamic friction coefficient at 40 ° C. (μH40)]
A film cut into a predetermined size (moving film) is wrapped around a 1500 g flat rectangular parallelepiped mounting jig whose bottom surface is flat so that the seal layer is on the outside, and the bottom surface of the mounting jig (vertical × The side = 7 cm × 5 cm) is covered with a moving film. On the other hand, another film (fixed film) cut sufficiently large compared to the mounting jig has a sealing layer on a horizontal base part of which is heated to 40 ° C. (part extending over a length of 20 cm). Paste it so that it faces upward. After that, the mounting jig to which the moving film is attached is placed on the fixed film, the sealing layer of the moving film and the sealing layer of the fixed film are joined, and in this state, the mounting jig is used by using the driving device. Is pulled at a speed of 2.5 m / min and passed over the heated part of the base. Then, the dynamic friction coefficient when passing through the heated portion is calculated as μH40. The film for measurement is aged for 12 hours or more in an atmosphere of 23 ° C. and 65 RH%, and the measurement itself is performed in an atmosphere of 23 ° C. and 65 RH%. The measurement is repeated 5 times with the sample changed, and the average value is calculated as μH40.

[Air leakage index (Air leakage: AR)]
The air escape rate of the film is measured using the apparatus shown in FIG. That is, after the film 4 is placed on the ring-shaped base 1, the ring-shaped film presser 2 is placed on the base 1 from the top of the film 4, and the film 4 is fixed in a state where tension is applied. Next, another film 5 is placed on the film retainer 2, another ring-shaped film retainer 8 is placed on the film 5, and the film retainers 8, 2 and the base 1 are fixed using the screws 3. Here, the film presser 2 has a circular slot 2a on the upper surface, a hole 2c in which a part of the slot 2a and the outer part of the film presser 2 communicate with each other, and a part of the slot 2a and the inner side of the film presser 2 It has a pore 2d communicating with the portion. Note that the two films 4 and 5 are both installed such that the outer surface when wound in a roll is on the upper side.

  After the film is set as described above, by operating the vacuum pump 6 connected to the pore 2c via the pipe 7, the film 5 is sucked into the slot 2a and tension is applied. It becomes. Further, since the film overlap portion X where the film 4 and the film 5 overlap is also decompressed through the pores 2d in the film retainer 2, the film 4 and the film 5 are separated from the outer peripheral portion between the overlapped portions X. Start to stick. The close contact state can be grasped by observing interference fringes from the upper part of the film overlap portion X. Then, after the interference fringes are generated on the outer periphery of the film overlapping portion X, the time (seconds) until the interference fringes spread on the entire surface of the film overlapping portion X and the movement of the interference fringes stops is measured. Let it be the “air escape index”. The measurement is repeated 5 times by replacing two film samples, and the average value is calculated as the AR value.

[Haze value]
The obtained biaxially oriented film is cut into a predetermined size, and measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., 300A) according to JIS K7136. The measurement is repeated 5 times with the sample changed, and the average value is obtained.

[Initial anti-fogging property]
The antifogging property of the film is measured in the following order.
(1) Put 300 mL of hot water at 50 ° C. into a 500 mL upper opening container.
(2) The container opening is sealed with the film with the antifogging measurement surface of the film facing inside.
(3) After being left in a cold room at 5 ° C., it is taken out at room temperature (about 23 ° C.), and the dew adhesion state on the film measurement surface is evaluated in the following 6 levels. The measurement is repeated 5 times with the film sample replaced, and the average grade is defined as the initial antifogging property (for example, when each grade is 6, 6, 5, 4, 4 when measured 5 times) Is grade 5.)
Grade 6: No dew on the entire surface (attachment area = 0)
Evaluation grade 5: Slight dew adhesion (up to 1/5 of adhesion area)
Evaluation grade 4: Some dew adhesion (up to 1/4 adhesion area)
Evaluation grade 3: Dew adhesion of about 1/2 (up to 2/4 of adhesion area)
Evaluation grade 2: almost dew adhesion (up to 3/4 adhesion area)
Evaluation grade 1: Dew adhesion on the entire surface (adhesion area 3/4 or more)

[Anti-fog durability]
The antifogging property of the film is measured in the following order.
(1) Put 300 mL of hot water at 50 ° C. into a 500 mL upper opening container.
(2) The container opening is sealed with the film with the antifogging measurement surface of the film facing inside.
(3) Leave in a cold room at 5 ° C.
(4) After leaving in a 5 ° C. cold room for 12 hours, move to a 30 ° C. environment and leave for 12 hours.
(5) After the operation of (4) is repeated for 2 days, the dew adhesion state of the film measurement surface is evaluated in the following 6 stages. The measurement is repeated 5 times with the sample changed, and the average grade is assumed to be anti-fogging sustainability (for example, when each grade is 6, 6, 5, 4, 4 when measured 5 times). Is grade 5.)
Grade 6: No dew on the entire surface (attachment area = 0)
Evaluation grade 5: Slight dew adhesion (up to 1/5 of adhesion area)
Evaluation grade 4: Some dew adhesion (up to 1/4 adhesion area)
Evaluation grade 3: Dew adhesion of about 1/2 (up to 2/4 of adhesion area)
Evaluation grade 2: almost dew adhesion (up to 3/4 adhesion area)
Evaluation grade 1: Dew adhesion on the entire surface (adhesion area 3/4 or more)

[Fusing sealability]
Using a fusing seal machine (manufactured by Kyoei Printing Machinery Co., Ltd .: PP500 type side welder), a fusing seal bag (200 mm × 300 mm) of the film is produced under the following conditions. And the defect rate per 1000 pieces of produced fusing seal bags is calculated | required as fusing sealing property.
Conditions: fusing blade; cutting edge angle 60 degrees, cutting edge set temperature 390 ° C, cutting edge actual temperature: 370 ° C
Number of shots: 120 bags / min

[Heat seal strength]
Sample of product removal width x length direction 500mm is sampled, and this is divided into three equal parts in width direction. From each center part, sample of size of width direction 50mm x length direction 250mm is sampled. Is folded in half so that the sealing surfaces are aligned, and hot plate sealing is performed under the conditions of a heat sealing temperature of 140 ° C., a pressure of 1 kg / cm ² , and a heat sealing time of 1 second to produce a 15 mm wide test piece. The 180 degree peel strength of this test piece is measured and set as a heat seal strength (N / 15 mm). The measurement is repeated 5 times with the biaxially stretched film sample replaced, and the average value is calculated.

[Wet tension]
Measured in an atmosphere of 23 ° C. and 65% RH in accordance with JIS-K-6768 method. The measurement is repeated 5 times with the biaxially stretched film sample replaced, and the average value is calculated.

[Melt flow rate (MFR)]
Measured by the method of Condition-14 according to JIS K7210. The measurement is repeated 5 times by replacing the raw resin sample, and the average value is calculated.

[Ethylene content]
The ethylene content in the propylene-ethylene copolymer is determined by the 13C-NMR spectrum method according to the method described on pages 615 to 617 of the Polymer Analysis Handbook (published by Kinokuniya Shoten in 1995). In addition, it can also be determined by the IR spectrum method according to the method described in the section “(i) Random copolymer” on page 256 of the same document.

[Average particle size of inorganic fine particles]
The weight distribution is measured with a Coulter counter multisizer, and the average particle diameter is indicated by 50% diameter. In addition, it is also possible to obtain an average particle size from a biaxially stretched film by image processing, or to obtain an average particle size from a residue after the obtained film is treated with an acid or the like.

[Pore volume of inorganic fine particles]
It measured by the method of JIS-K-1150 based on a BET system.

[Product film roll trap]
After aging the polypropylene-based resin film wound up in a roll shape for 12 hours in an atmosphere of 40 ° C., the film roll is visually observed, and the presence or absence of wrinkles is determined according to the following criteria.
○ ・ ・ No wrinkle △ ・ ・ There are no wrinkles, but the product yield is poor.

  Hereinafter, the present invention will be described in detail by way of examples. However, the present invention is not limited to the embodiments of the examples, and can be appropriately changed without departing from the spirit of the present invention. . Tables 1 and 2 show properties, compositions, granulation conditions, composition of seal layers in Examples and Comparative Examples, and the like of raw material chips A to G used in Examples and Comparative Examples.

[Create anti-blocking agent master batch]
RW140EG (manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 4.0% by weight, melt flow rate: 5.0 g / 10 min), Irganox 1010 (manufactured by Ciba Specialty Chemicals), a propylene-ethylene copolymer powder 0.15 parts by weight, Irgafos 168 (manufactured by Ciba Specialty Chemicals) 0.15 parts by weight, Sirisia 350 (manufactured by Fuji Silysia Chemical Co., silicon dioxide powder) as inorganic fine particles; average particle diameter 1.8 μm, pores 2.0 parts by weight of a volume of 1.60 ml / g) was blended to make a total weight of 20 kg, and mixed for 5 minutes with a 115 L super mixer at a peripheral speed of 20 m / sec.

  Next, the mixed raw material was adjusted under the conditions in which the screw rotation speed and feeder rotation speed were adjusted to 300 rpm and 20 rpm, respectively, using a 45 mmφ twin screw extruder (screw diameter 43 mmφ L / D; 19.5). Pellet A was obtained by granulating only once. Also, after granulating the same mixed raw material under the same conditions as pellet A (first granulation), using the same twin-screw extruder, the screw rotation speed and feeder rotation speed were set to 220 rpm and 20 rpm, respectively. Under the adjusted conditions, granulation (second granulation) was performed again to obtain pellet B. On the other hand, pellets C were obtained by granulating the same mixed raw material only once using the same twin-screw extruder and adjusting the screw rotation speed and the feeder rotation speed to 220 rpm and 20 rpm, respectively. . Furthermore, after granulating the same mixed raw material under the same conditions as the pellet C (first granulation), the same raw material is granulated under the same conditions as the first granulation using the same twin-screw extruder (second time granulation). Pellets D were obtained. At the time of adjusting the mixed raw materials, the inorganic fine particles were converted into silicia 310P (manufactured by Fuji Silysia Chemical Co., silicon dioxide powder; average particle diameter 1.4 μm) and silicia 420 (manufactured by Fuji Silysia Chemical Co., silicon dioxide powder; The average particle size was changed to 1.9 μm pore volume of 1.25 ml / g), and pellets E and F were obtained by granulating only once under the same conditions as pellet A. In addition, organic fine particles (Sumitomo Chemical Co., Ltd., CS18; polymer beads with an average particle size of 1.8 μm) are added instead of inorganic fine particles, and granulation is performed only once under the same conditions as pellet A when adjusting the mixed raw materials. The pellet G was obtained by doing. In the granulation of the pellets A to G, the filter mesh configuration is 50 mesh / 100 mesh / 50 mesh, and the temperatures of the first to fourth cylinders, the adapter, and the die are 200 ° C. and 210 ° C., respectively. 220 ° C., 220 ° C., 220 ° C., and 220 ° C. (see Table 1).

[Example 1]
<Creation of seal layer>
As an antiblocking agent master batch, 2.5% by weight of pellet A, 12.3% by weight of pellet B, and FSX66E8 as a base material (a polypropylene resin manufactured by Sumitomo Chemical Co., produced by a vapor phase method, ethylene content 2 0.5 wt%, butene-1 content 7.0 wt%, melt flow rate 3.5 g / 10 min) 68.7 wt%, BH180EL-2 (manufactured by Sumitomo Chemical Co., Ltd., produced by the vapor phase method) Resin, butene-1 content 25.0 wt%, melt flow rate 3.0 g / 10 min) 16.0 wt%, monostearic acid monoglyceride 0.4 wt%, erucic acid amide 0.1 wt% % Was melt-mixed in a 115 mmφ extruder (L / D; 29) to form a heat seal layer.

<Creation of base layer>
FS2011DG3 (manufactured by Sumitomo Chemical Co., Ltd. produced by a vapor phase method, ethylene content 0.9 wt%, melt flow rate 2.5 g / 10 min) 97.89 wt%, S131 (gas phase method) Manufactured polypropylene resin manufactured by Sumitomo Chemical Co., Ltd., ethylene content 5.0 wt%, melt flow rate 1.7 g / 10 min) 1.26 wt%, monostearic acid monoglyceride 0.10 wt%, poly 0.60% by weight of oxyethylene (2) stearylamine monostearate and 0.15% by weight of polyoxyethylene (2) stearylamine are tandem extruders (first stage 175 mmφ, L / D; 17, second The base layer was melt-mixed in a step 220 mmφ, L / D; 20).

<Creating a film>
A three-layer T die (multi-manifold type) at 260 ° C. with a base layer discharge rate of 1980 kg / H and a seal layer discharge rate of 126 kg / H while the base layer and the seal layer are melted in each extruder. , Lip width 900 mm, lip gap 2.4 mm), and then extruded onto a 20 ° C. casting roll with an air knife at a wind speed of 1050 mmAq, taken up at a speed of 58.8 m / min, cooled and solidified to form a sheet. Obtained. The obtained sheets were continuously superheated with rolls sequentially heated from 108 ° C. to 130 ° C., respectively, and then the respective roll speeds were 65.44 m / min and 242. By adjusting the speed to 12 m / min and adding a speed difference, the film was stretched by 3.7 times and then relaxed with a roll heated to 130 ° C. The longitudinally stretched sheet was subsequently preheated in an oven at 167.5 ° C. at a speed of 241.4 m / min, and then 10.7 times at a deformation speed of 1.39 m / sec at 155 ° C. The film is further stretched in a transverse direction to 165 ° C., relaxed by 8% in 4.5 seconds while being heat-set in an environment of 165 ° C., and cooled in an environment of 40 ° C. for 1.5 seconds, whereby a sealing layer of 0.8 μm and a base layer of 18. A two-type three-layer film having a total thickness of 20 μm laminated in the order of 4 μm and a seal layer of 0.8 μm was continuously produced. Thereafter, the surface of the film thus continuously produced is subjected to corona discharge treatment so that the wetting tension of the film surface becomes 39 mN / m, and the film after the corona discharge treatment is subjected to an absolute humidity of 8 g / kg DryAir or more. Under a controlled environment, the film was wound at a winding speed of 241.4 m / min to obtain a winding film roll having a width direction of 6240 mm and a flow direction of 29000 m. Further, the wound film roll was stored in an environment of 40 ° C. for 12 hours and naturally relaxed, and then slit into a size of 600 mm in the width direction and 4000 m in the flow direction to obtain 70 product film rolls. The obtained product film roll was free from wrinkles and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the above-mentioned method. The evaluation results are shown in Table 3. In addition, a predetermined amount (about 1.0 g) of a film sample was cut out from the obtained film roll, the film sample was dry-decomposed and treated with acid, and then the Al content was measured by plasma emission analysis. The content was 34 mg / kg.

[Example 2]
In Example 1, when producing a sealing layer, the product film roll was obtained like Example 1 except having used the pellet C instead of the pellet A. FIG. The obtained product film roll was free from wrinkles as in Example 1 and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Example 3]
In Example 1, when creating the sealing layer, the pellet G was used instead of the pellet A, and a part of the pellet B was replaced with the pellet F. Other than that was carried out similarly to Example 1, and obtained the product film roll. The obtained product film roll was free from wrinkles as in Example 1 and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Example 4]
In Example 1, the thickness of the seal layer of the two-kind / three-layer film after biaxial stretching was adjusted to 0.00 by adjusting the discharge amount of the extruder for forming the base layer and the discharge amount of the extruder for forming the seal layer, respectively. The thickness of the base layer was changed to 18.8 μm (ie, 0.6 μm sealing layer, 18.8 μm base layer, and 0.6 μm sealing layer were sequentially laminated in two types and three layers of 6 μm) Film). Other than that was carried out similarly to Example 1, and obtained the product film roll. The obtained product film roll was free from wrinkles as in Example 1 and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Example 5]
When forming the heat-seal layer, the anti-blocking agent master batch is 5.0% by weight of pellet A, 10.0% by weight of pellet B, 68.5% by weight of FSX66E8 as the base material, and 16 of BH180EL-2. 0.0 wt%, monoglyceride monostearic acid 0.4 wt%, and erucic acid amide 0.1 wt% were melt-mixed in the same 115 mmφ extruder as in Example 1. Other than that was carried out similarly to Example 1, and obtained the product film roll. The obtained product film roll was free from wrinkles as in Example 1 and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Example 6]
When forming the heat seal layer, 1.2 wt% of pellet A, 17.5 wt% of pellet B as an antiblocking agent master batch, 64.8 wt% of FSX66E8 as base materials, and 16 BH180EL-2 0.0 wt%, monoglyceride monostearic acid 0.4 wt%, and erucic acid amide 0.1 wt% were melt-mixed in the same 115 mmφ extruder as in Example 1. Other than that was carried out similarly to Example 1, and obtained the product film roll. The obtained product film roll was free from wrinkles as in Example 1 and could be favorably subjected to processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Comparative Example 1]
In Example 1, when creating the sealing layer, the pellet B was used in place of the pellet A, and the total amount of the pellet B was 14.8% by weight. Other than that was carried out similarly to Example 1, and obtained the product film roll. The obtained product film roll was wrinkled and had problems in processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Comparative Example 2]
In Example 1, when creating the seal layer, the product film roll was prepared in the same manner as in Example 1 except that the pellet A was used instead of the pellet B, and the total amount of the pellet A was 14.8% by weight. Obtained. The obtained product film roll was wrinkled and had problems in processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Comparative Example 3]
In Example 1, when producing a seal layer, production of a film roll was attempted in the same manner as in Example 1 except that pellet E was used instead of pellet B. However, since a large number of foreign matters were generated due to poor dispersion of inorganic fine particles, a film sample worthy of evaluation could not be obtained.

[Comparative Example 4]
In Example 1, when producing a sealing layer, the product film roll was obtained like Example 1 except having used the pellet C instead of the pellet A and using the pellet D instead of the pellet B. FIG. The obtained product film roll was wrinkled and had problems in processing such as printing and bag making. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Comparative Example 5]
Product film in the same manner as in Example 1 except that the heat setting conditions after transverse stretching of the film in Example 1 were changed to those in which 8% relaxation was performed for 4.5 seconds in an environment of 171 ° C. Got a roll. And the characteristic of the film which comprises the obtained product film roll was evaluated by the method similar to Example 1. FIG. The evaluation results are shown in Table 3.

[Effects of Example Film]
From Table 3, since the film of an Example has (micro | micron | mu) H40, AR, and a haze value satisfy | fill the conditions of this invention, antifogging property and transparency are favorable, a wrinkle does not generate | occur | produce in a film roll, and a fusing sealing property Is found to be good. On the other hand, the film of Comparative Example 1 has a large μH40, does not satisfy the conditions of the present invention, the film roll is wrinkled, and the fusing and sealing properties are extremely poor. Has a small AR value, does not satisfy the conditions of the present invention, the film roll is wrinkled, the fusing and sealing properties are poor, and the film of Comparative Example 5 has poor transparency and the haze value is The conditions of the invention were not satisfied, and the contents were not clearly visible during packaging.

  Since the polypropylene-based resin laminated film of the present invention has excellent characteristics as described above, it can be suitably used for packaging fresh products.

It is explanatory drawing which shows the cross section of the apparatus which measures the air escape speed of a film.

Explanation of symbols

  1 .. Base plate, 2, 8 .... Film holder, 2a ... Slot, 2c ... Hole, 2d ... Hole, 3. Screw, 4, 5 .... Film, 6. Vacuum pump, 7 ..Pipe, X..Film overlap.

Claims (12)

A sealing layer mainly composed of a polyolefin resin is laminated on both front and back surfaces of a base layer mainly composed of a polypropylene resin, is biaxially stretched, has a thickness of 10 μm or more and less than 70 μm, and has a haze value of 2 A polypropylene-based resin laminated film for packaging fresh products that is not less than 0.0% and not more than 5.0% ,
The polypropylene resin constituting the base layer and the polyolefin resin constituting the seal layer are formed by the vapor phase method, and the entire layer of the laminated film contains 15 mg / kg or more and less than 150 mg / kg Al. A polypropylene-based resin laminated film for packaging fresh products, wherein inorganic fine particles are added to at least the seal layer and satisfy the following formulas (1) to (6).
(1) An antifogging agent is blended in at least one of the resin forming the base layer and the resin forming the seal layer. (2) The base layer is formed of a propylene-ethylene copolymer, and the propylene-ethylene. The ethylene content in the copolymer is 0.5 wt% or more and less than 1.5 wt% (3) The seal layer is an ethylene / butene-1 copolymer, an ethylene / propylene / butene-1 copolymer, Ethylene / acrylic acid copolymer, ionomer cross-linked ethylene / acrylic acid copolymer with metal ion, polypropylene, polybutene-1, butene / ethylene copolymer, propylene / ethylene copolymer, propylene / butene-1 copolymer Polymers using one or more of propylene / ethylene / butene-1 copolymer and propylene / pentene copolymer (4) The coefficient of dynamic friction measured in an atmosphere of 40 ° C. is 0.61 or more and 1.1 or less (5) Time until air is completely removed from between the films when the pressure is reduced by stacking two films. The air escape index is 1.8 seconds or more and 9.0 seconds or less. (6) The container is left in an atmosphere of 5 ° C. for 30 minutes with the opening of a container containing hot water of 50 ° C. covered. The dew adherence area after taking it out in a room temperature atmosphere is 1/4 or less of the whole   2. The polypropylene-based resin laminated film according to claim 1, wherein an air escape index is 7.8 seconds or less.   The ratio of the thickness of the sealing layer with respect to all the layers of a laminated film is 1/60-1/3, The polypropylene resin laminated film of Claim 1 characterized by the above-mentioned.   2. The polypropylene-based resin laminated film according to claim 1, wherein an antifogging agent is added to the base layer and the seal layer.   Defect rate when creating a fusing seal bag for a film at a shot speed of 120 bags / min at a cutting edge temperature of 370 ° C. using a fusing sealing machine with the cutting edge angle adjusted to 60 degrees and the cutting edge set temperature adjusted to 390 ° C. The polypropylene-based resin laminated film according to claim 1, wherein the content is 5% or less. After applying a pressure of 1 kg / cm ² at 140 ° C. for 1 second to heat-seal the seal layers, the strength when the heat-sealed portions are peeled 180 degrees is 1.5 N / 15 mm 6 or more 6 It is 0.0 N / 15mm or less, The polypropylene-type resin laminated film of Claim 1 characterized by the above-mentioned.   2. The polypropylene-based resin laminated film according to claim 1, wherein the wetting tension on the surface of the seal layer is 35 mN / m or more and 45 mN / m or less.   2. The polypropylene resin according to claim 1, wherein the resin forming the sealing layer is one having a melt flow rate adjusted to 1.5 g / 10 min or more and 9.0 g / 10 min, or a mixture thereof. Laminated film.   Inorganic-based fine particles having an average particle diameter of 1.0 μm or more and less than 12.0 μm and a pore volume of 1.0 ml / g or more and less than 2.0 ml / g are added to the polyolefin resin layer forming the seal layer. The polypropylene-based resin laminated film according to claim 1.   The antifogging agent is a combination of at least two or more of a polyoxyethylene alkylamine type antifogging agent, a polyoxyethylene alkylamine fatty acid ester type antifogging agent, and a fatty acid glycerin ester type antifogging agent. The polypropylene resin laminated film according to claim 4.   5. The polypropylene resin laminated film according to claim 4, wherein the amount of the antifogging agent in the entire laminated film is 0.2 wt% or more and less than 1.5 wt%. A production method for producing the polypropylene-based resin laminated film according to claim 1,
A film forming step of forming an unstretched polypropylene resin laminate sheet by melt extrusion of a polypropylene resin and a polyolefin resin by a coextrusion method from a plurality of extruders,
A biaxial stretching step of biaxially stretching the unstretched polypropylene-based resin laminate sheet obtained in the film-forming step in the longitudinal direction and the transverse direction,
The manufacturing method of the polypropylene resin film characterized by satisfying the following requirements (a) to (d).
(A) The film forming step includes a propylene-ethylene copolymer granulated once by adding inorganic fine particles, a propylene-ethylene copolymer granulated twice by adding inorganic fine particles, and polypropylene (B) The granulation in the film forming step is performed using a rotating body adjusted to a rotation speed of 100 rpm or more and 500 rpm or less. (C) The film forming step forms a base layer with a propylene-ethylene copolymer, and the rotational speed of the rotating body in the granule is higher than that of the rotating body in the second granulation. The ethylene content in the propylene-ethylene copolymer is adjusted to 0.5 wt% or more and less than 1.5 wt% (d) It biaxial stretching process, the longitudinal and transverse direction together and performs heat after biaxial stretching is obtained by adjusting the temperature of the heat fixing below 160 ° C. or higher 170 ° C.

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