JP2005178217A - Polypropylene multilayered sealant film and laminated film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene multilayered sealant film for a retort containing no air bubbles at the laminating interface with a heat-resistant film, excellent in laminate appearance and capable of easily taking out content after retort processing and capable of performing heat sealing at a relatively low temperature. <P>SOLUTION: The polypropylene multilayered sealant film has a heat sealing surface (A) for performing heat sealing and a laminate surface (B) for laminating a heat-resistant film. The surface roughnesses of the heat sealing surface (A) and the laminate surface (B), that is, three-dimensional center surface average roughness, three-dimensional maximum height, three-dimensional ten-score average roughness and the ridge density of the surface above a center surface by 0.1 μm are respectively adjusted so as to become predetermined ranges. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polypropylene-based multilayer sealant film, and more particularly to a polypropylene-based multilayer sealant film for retort used for retort processing in a state of being bonded to a heat resistant film.

  Processed retort products, especially retort processed foods, range from foods such as cooked curry to foods that do not have surplus moisture such as hamburgers and sausages. Among these, when the food which does not have surplus moisture is retort processed, since there is no liquid flowing around the food, the sealant films are in direct contact with each other without any liquid. Therefore, a phenomenon (retort blocking) in which the sealant films are fused may occur.

  As a countermeasure against the problem of retort blocking, a method of adding an anti-blocking agent during the production of a sealant film as in Patent Document 1 and a method of making a difference between the surface roughness of the sealing surface and the surface roughness of the bonded surface is known. It has been. According to this method, the problem of retort blocking can be solved without leaving bubbles on the laminate surface.

Special Table 2002-542207

  When retorting is performed using a sealant film, in addition to the above-described retort blocking phenomenon, there may be a phenomenon that the opening of the bag is difficult to expand when the contents are taken out after retorting (open mouth failure). However, such a method of making a difference in the surface roughness between the sealing surface and the bonding surface as described above cannot solve such a mouth opening defect phenomenon.

  The object of the present invention is to solve the problems of the above-mentioned conventional polypropylene film for retort, does not contain air bubbles at the bonding interface with the heat resistant film, has an excellent laminate appearance, and has contents after retorting. An object of the present invention is to provide a polypropylene-based multilayer sealant film for retort that can be easily taken out, and a laminate film in which such a sealant film and a heat-resistant film are bonded together.

Among the present inventions, the configuration of the invention described in claim 1 is that a film formed of a polypropylene-based synthetic resin is laminated in at least two layers, and a heat sealing surface (A ) And a laminate surface (B) for laminating with a heat resistant film, the heat seal surface (A) and the surface roughness of the laminate surface (B), It exists in the following range.
(A) Surface roughness:
Three-dimensional center plane average roughness 0.040-0.200 μm
3D maximum height 2.0-10.0μm
Three-dimensional ten-point average roughness 1.5-6.0 μm
Surface density of 1000 density / mm ² or more (B) on the surface 0.1 μm above the center surface:
Three-dimensional center plane average roughness 0.015 to 0.250 μm
3D maximum height 0.2-1.9μm
Three-dimensional ten-point average roughness 0.2-1.4 μm

  The structure of the invention described in claim 2 is that, in the invention described in claim 1, the melting point of the resin forming the heat seal surface is 130 to 150 ° C.

  The structure of the invention described in claim 3 is that the polypropylene-based multilayer sealant film according to claim 1 or 2 and the heat-resistant film are bonded together.

  “Three-dimensional center plane average roughness”, “three-dimensional maximum height”, “three-dimensional ten-point average roughness”, and “mountains on a plane 0.1 μm above the center plane” are the surface roughness of the film in the present invention. “Density” (hereinafter, simply referred to as “0.1 mountain density”) is measured by the following method.

[Three-dimensional center plane average roughness]
In accordance with JIS-0601, a three-dimensional contact surface roughness meter is used to determine the concavo-convex curve of the film surface along the longitudinal direction of the film, and the operation is repeated a predetermined number of times at intervals of 2 μm in the width direction of the film roll. To obtain a “cross-section curved surface” of a predetermined range (hereinafter referred to as “reference surface”) on the film surface. Further, a “roughness curved surface” obtained by removing shape accuracy and surface waviness component from the “cross-sectional curved surface” by a cutoff filter is obtained. Further, as the “center plane”, a plane in which the volume surrounded by the plane and the “roughness curved surface” is equal and minimum on the upper side and the lower side of the plane is obtained. Then, when the orthogonal coordinate axes X and Y axes are placed on the obtained “center plane” and the axis orthogonal to the “center plane” is the Z axis, the value calculated by the following formula I (expressed in μm) "Three-dimensional center plane average roughness" (hereinafter also referred to as SRa). In the following formula I, f (x, y) is a “roughness curved surface”, and Lx and Ly are the sizes of the reference surface.

[Three-dimensional maximum height]
As the “average surface”, a plane in which the sum of squares of the deviation between the plane and the “cross-section curved surface” is equal and minimum on the upper side and the lower side of the plane is obtained. The distance (expressed in μm) between the two planes when the “cross-section curve” is sandwiched between two planes parallel to the “average plane” is referred to as “three-dimensional maximum height” (hereinafter also referred to as SRmax). ).

[Three-dimensional ten-point average roughness]
The difference (expressed in μm) between the average height of the top from the highest to the fifth and the average depth of the bottom from the deepest to the fifth from the “average surface” is expressed as “three-dimensional ten-point average roughness” ( Hereinafter, it is also referred to as SRz).

[0.1 mountain density]
In a plane parallel to the “center plane” and 0.1 μm higher than the “center plane”, the number of peaks (projections) is measured and converted to 1 mm ² to represent “0.1 peak density” And

  The polypropylene-based multilayer sealant film of the present invention (hereinafter simply referred to as a sealant film) does not cause roll blocking when it is wound alone or when it is laminated with a heat resistant film. In addition, when bag forming and retorting are performed by bonding to a heat resistant film, retort blocking does not occur and the mouth opening is excellent, so that the contents can be easily taken out. Furthermore, when the sealant film of the present invention is bonded to a heat resistant film, no air bubbles are formed at the bonding interface, so that the laminate appearance is excellent. Moreover, the laminate film of the present invention can easily take out the contents after retorting and can heat-seal the laminate surfaces at a low temperature.

  In the sealant film of the present invention, each layer may be formed with a polypropylene polymer having the same composition as a main component, or may be formed with a polypropylene polymer having a different composition as a main component. As the polypropylene polymer forming each layer of the sealant film, a polypropylene homopolymer, a polypropylene random copolymer, a polypropylene block copolymer, and the like can be used. However, the resin of the heat seal surface is preferably a polypropylene random copolymer.

  The polypropylene random copolymer that can be used in the present invention is a random copolymer (polypropylene-α olefin) of a large amount (about 85 wt% or more) of propylene and a small amount (about 15 wt% or less) of α-olefin. Random copolymer). As the α-olefin monomer for obtaining such a polypropylene random copolymer, ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and the like can be used. It is particularly preferable to use ethylene and butene-1 from the viewpoint of properties. Moreover, the alpha-olefin used for copolymerization should just be at least 1 or more types, and can mix and use 2 or more types as needed.

  Moreover, when using a polypropylene random copolymer, the polypropylene random copolymer must have a melt flow rate at 230 ° C. (hereinafter referred to as MFR) in the range of 1 to 10 g / 10 min. It is preferable in the range of 2 to 6 g / 10 min from the viewpoint of film formability and productivity. In addition, when using this polypropylene random copolymer for a heat seal layer, it is necessary that the melting | fusing point exists in the range of 130-150 degreeC. If the melting point is lower than 130 ° C, retort blocking is likely to occur.

  Further, the propylene block copolymer that can be used in the present invention is a random copolymer of a large amount (about 85% by weight or more) of propylene and a small amount (about 15% by weight or less) of α-olefin, and a large amount. This is a block copolymer of a copolymer of (about 50% by weight or more) α-olefin and a small amount (about 50% by weight or less) of propylene. As the α-olefin monomer for obtaining such a propylene block copolymer, ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, and the like can be used. From the viewpoint of the cold shock resistance, it is particularly preferable to use ethylene and butene-1. Moreover, the alpha-olefin used for copolymerization should just be at least 1 or more types, and can mix and use 2 or more types as needed. Furthermore, the amount of α-olefin in the propylene block copolymer is not particularly limited, but is preferably 2 to 20% from the viewpoint of transparency of the film and resistance to cold shock.

  When a propylene block copolymer is used, the propylene block copolymer must have an MFR in the range of 1 to 10 g / 10 min at 230 ° C., and transparency and cold shock resistance of the film. It is preferable that it is in the range of 2 to 6 g / 10 minutes from the surface. In addition, when using this propylene block copolymer for a heat seal layer, it is necessary for the melting | fusing point to exist in the range of 130-150 degreeC. If the melting point is lower than 130 ° C, retort blocking is likely to occur.

  In addition, a thermoplastic elastomer can be added to the sealant film of the present invention for the purpose of improving impact resistance at a low temperature. The thermoplastic elastomer is at least one selected from ethylene / propylene rubber (EPR), ethylene / butene rubber (EBR), ethylene / vinyl acetate copolymer (EVA), hydrogenated block copolymer, etc. Can be used. The amount of the thermoplastic elastomer added varies depending on the type of polypropylene resin as a base, but is 20% or less with respect to the weight of all components constituting the layer, and with respect to the weight of all components constituting the entire film. It is preferable that it is 10% or less. If the amount of the thermoplastic elastomer exceeds the range, it is not preferable because it is likely to be extracted with a solvent or the like and may cause a problem in food hygiene.

In order to control the surface roughness of the sealant film of the present invention, a method of adjusting the addition amount of an inert antiblocking agent can be used. Examples of the anti-blocking agent include known silica, zeolite, aluminum borate, etc. In order to set the “0.1 crest density” of the heat seal surface to 1000 pieces / 1 mm ² or more, the average particle diameter A method of adding a predetermined amount of an anti-blocking agent of 0.1 to 1.0 μm to the heat seal layer can be suitably used. Further, instead of adding the anti-blocking agent having a predetermined particle size as described above, it is possible to adopt a method in which a high density polyethylene resin is dispersed to form fine protrusions on the surface. By adding an anti-blocking agent with a predetermined particle size or dispersing a high-density polyethylene resin, the film during retorting is adjusted by adjusting the three-dimensional surface roughness of the heat seal surface to a predetermined range. It is possible to improve the openability by finely dispersing the contact portions between each other.

The sealant film of the present invention has a heat seal surface “SRa” in the range of 0.040 to 0.200 μm, “SRmax” in the range of 2.0 to 10.0 μm, and “SRz” of 1. In the range of .5 to 6.0 μm, “0.1 crest density” is 1000 pieces / mm ² or more, and “SRa” of the laminate surface is in the range of 0.015 to 0.250 μm. It is necessary that “SRmax” is in the range of 0.2 to 1.9 μm and “SRz” is in the range of 0.2 to 1.4 μm. If the “0.1 crest density” of the heat seal surface is smaller than the above range, the effect of preventing the opening failure phenomenon is reduced, which is not preferable. Further, if “SRa”, “SRmax”, and “SRz” of the heat seal surface and the laminate surface are smaller than the above ranges, not only the opening failure phenomenon but also the laminate blocking phenomenon is likely to occur, which is not preferable. On the other hand, if “SRa”, “SRmax”, and “SRz” of the heat seal surface and the laminate surface are larger than the above ranges, bubbles remain at the laminate interface and the appearance of the laminate deteriorates, which is not preferable.

  Further, the sealant film of the present invention contains known additives (for example, a heat stabilizer, a neutralizing agent, an antistatic agent, an antifogging agent, etc.) as necessary as long as the effects of the present invention are not impaired. It is also possible to make it.

  On the other hand, the layer structure of the sealant film of the present invention includes a two-layer structure of a heat seal layer (layer on the heat seal surface side) and a laminate layer (layer on the laminate surface side), or a gap between these two layers. A layer structure of three or more layers provided with one or more intermediate layers can be employed. Moreover, although the thickness of a sealant film can be arbitrarily set by the specific use, it is 10-200 micrometers normally, Preferably it is 25-120 micrometers. In addition, the proportion of each layer in the total thickness of the sealant film is preferably 80 to 40% of the heat seal layer and 20 to 60% of the laminate layer in the case of a two-layer structure. In the case of three or more layers, the heat seal layer preferably has a thickness of 50 to 15%, the intermediate layer has a thickness of 20 to 70%, and the laminate layer has a thickness of 10 to 50%.

  An example of the sealant film and laminate film of the present invention is shown in FIGS. FIG. 1 shows a cross section of a sealant film having a two-layer structure (conceptual diagram). The sealant film 1 is formed by laminating a laminate layer 1b on a heat seal layer 1a. FIG. 2 shows a cross-section of a three-layer sealant film (conceptual diagram). The sealant film 2 is formed by laminating an intermediate layer 2c and a laminate layer 2b on a heat seal layer 2a. Yes. On the other hand, FIG. 3 shows a cross section of a laminated film for retort (conceptual diagram). The laminated film 3 for retort is formed by laminating a heat resistant film 4 on a laminated layer 1b of a two-layer sealant film. Is formed. In FIG. 1 and FIG. 2, three types of protrusions of large, medium and small sizes are mixed, but the large and medium size protrusions indicate protrusions due to the anti-blocking agent having a large particle diameter. The small-sized protrusions are protrusions formed by high-density polyethylene or an anti-blocking agent having a small particle diameter.

  Next, the manufacturing method of the sealant film of this invention is demonstrated. As a method for forming a film constituting each layer of the sealant film, an additive such as an antiblocking agent or an organic lubricant is added in a necessary amount to the polymer that is a raw material of the film constituting each layer, and the film is about 160 to 300 ° C. It is possible to use a method in which a film is obtained by melt-extruding at a temperature, passing through a filtration filter, discharging from a die, and solidifying by cooling. In addition, as a method of discharging from the die and cooling and solidifying, a method of discharging from a T die in a sheet shape and winding it around a metal drum whose temperature is adjusted to about 20 to 80 ° C. and cooling and solidifying, or a tube shape from a cylindrical die It is possible to employ a method in which air is blown into a bubble to form bubbles and cooled and solidified. Moreover, the obtained film (unstretched film) can be uniaxially or biaxially stretched as necessary within a range not impairing the heat sealability.

  Moreover, in order to improve the adhesiveness of the laminate surface, it is preferable to perform a physical or chemical surface treatment. Examples of such surface treatment methods include electrical methods such as corona discharge treatment and plasma treatment, chemical treatments such as acid / alkali treatment, and physical methods such as flame treatment. These treatment methods can be carried out singly or in combination.

  Furthermore, the sealant film of the present invention includes a biaxially stretched polyethylene terephthalate film, a biaxially stretched nylon 6 film, a biaxially stretched nylon 6,6 film, a biaxially stretched polybutylene terephthalate film, a polyimide film, a polyarylate film, and the like. An adhesive film can be attached. As a method of bonding, a method of dry laminating through an adhesive, a method of extruding through a melted resin such as polyethylene and sand laminating, and applying heat to the laminating side of the sealant film of the present invention to crimp in a molten state Methods and the like.

  Hereinafter, the sealant film and the laminate film of the present invention will be specifically described by way of examples. However, the embodiments of the present invention are not limited only to the embodiments.

[Example 1]
The following propylene polymer (a) to which the following additives (d, e, f) have been added in advance is melted by an extruder and supplied to a T die, and the following additives (d) are added in advance. By melting the propylene polymer (a, c) with a separate extruder, supplying it to a T-die, discharging it into a sheet, winding it around a metal drum adjusted to 40 ° C., cooling and winding it up A film having a thickness of 60 μm having a two-layer structure of a heat seal layer and a laminate layer (contact side with a metal drum) was produced. Further, in the production of the film of Example 1, the blending ratio of the additive to the propylene polymer and the composition of the propylene polymer of the heat seal layer and the laminate layer were adjusted as shown in Table 1, respectively. did. Furthermore, in the manufacture of the film of Example 1, the thickness of the heat seal layer and the thickness of the laminate layer were adjusted to be substantially the same.
(A) Propylene / ethylene random copolymer having an ethylene content of 4.5% by weight and an MFR at 230 ° C. of about 3.6 g / 10 min and a melting point of about 138 ° C. (c) An ethylene content of 60% by weight at 230 ° C. Ethylene / propylene rubber (d) with a MFR of about 4.0 g / 10 min (d) single particle size type and spherical silica (e) single shape type with an average particle size of about 4.0 μm and an average particle size of about 8.0 μm Amorphous silica with an aluminum borate (f) aggregate shape type and an average particle diameter of about 0.8 μm The average particle diameter of the antiblocking agent is the weight average diameter calculated from the particle size distribution obtained by a Coulter counter. It was. Moreover, MFR and melting | fusing point of resin were measured with the following method.

[MFR]
According to JIS-K-6758 (polypropylene test method), an extrusion plastometer equipped with a cylinder, piston and die is held at 230 ° C. for at least 15 minutes, and the sample is placed in the cylinder, 21.18 N (2.16 kgf) It was pushed out of the die by a piston with a load of. Thereafter, the extrudate is cut off after 6 minutes of preheating, and the extrudate (extruded product without bubbles) extruded thereafter has a predetermined sampling time (for example, the extrusion amount is 1.0 to 3.5 g / 10 min). In this case, a sample for mass measurement was collected by cutting when the amount reached 60 seconds, and 30 seconds when the extrusion amount was 3.5 to 10 g / 10 minutes. Then, after cooling, the mass of the sample was accurately measured to the unit of 1 mg, and using the following formula II, the mass (g) of the sample extruded per 10 minutes was calculated as MFR.
MFR = 600 × m / t (II)
In Formula II, m is the average value (g) of the mass of the cut sample, and t is the sampling time (second) of the sample for mass measurement.

[Melting point]
Using a differential scanning calorimeter (DSC), an endothermic chart was obtained under the condition of a heating rate of 10 ° C./min, and the peak temperature of the maximum peak at the time of crystal melting in the endothermic chart was calculated as the melting point.

Also, using the obtained film of Example 1, three-dimensional surface roughness (“SRa”, “SRmax”, “SRz”, “0.1 crest density”), laminate appearance, laminate blocking strength, opening strength The properties such as haze (transparency) were evaluated. Further, the film of Example 1 was dry-laminated with a biaxially stretched nylon 6 film having a thickness of 15 μm (dry laminate with a biaxially stretched nylon 6 film coated with an ester adhesive so as to have a solid content of 3 g / m ² ). The properties of the laminate film were evaluated. Table 2 shows the evaluation results of the film and laminate film of Example 1. In addition, the characteristic of the evaluated film is based on the following measuring method.

[3D surface roughness]
In accordance with JIS-0601, a three-dimensional contact type surface roughness meter (manufactured by Kosaka Manufacturing Co., Ltd .: Model ET-30K) was used to obtain the uneven surface curve of the film surface along the longitudinal direction of the film, and the operation of the film roll By repeating 150 times at intervals of 2.0 μm in the width direction, a “cross-section curved surface” of a predetermined range (length 1.0 mm × width 0.2 mm) on the film surface was obtained. Further, using a data analysis device (manufactured by Kosaka Seisakusho: model AT-30K), a “roughness curved surface” and a “center plane” were obtained from the “cross section curved surface”. And the axis along the longitudinal direction of the film on the “center plane” is the X axis, the axis along the width direction of the film is the Y axis, and the axis perpendicular to the “center plane” is the Z axis. “SRa” was calculated by I. In addition, using the data analysis apparatus, an “average surface” was obtained, and “SRmax” and “SRz” were calculated based on the “average surface”. Further, using the data analysis apparatus, a plane at a position 0.1 μm higher than the “center plane” was obtained, and “0.1 mountain density” was calculated on the plane.

[Laminate appearance]
A sample film dry-laminated with a biaxially stretched nylon 6 film was aged at 40 ° C. for 2 days, and then the number of bubbles present in the laminated portion was measured with the naked eye. And it evaluated in three steps according to the generated number of bubbles generated. The evaluation criteria are as follows.
○: 0 to 5 pieces / 1000 cm ²
Δ: 6-20 pieces / 1000 cm ²
×: 21 or more / 1000 cm ²

[Laminate blocking strength]
Using two films dry-laminated in the same manner as in the evaluation of the laminate appearance, the surface on the biaxially stretched nylon 6 film side of one film and the surface on the sample film side of the other film were overlapped. After pre-heat treatment at 30 ° C. for 30 minutes, a load of 14.1 MPa (MN / m ² ) was applied to a 7 cm × 7 cm portion with a hot press and pressurized at 50 ° C. for 15 minutes, followed by the method of ASTM-D-1893 The peel strength was measured. And it evaluated in three steps according to the measured peeling strength. The evaluation criteria are as follows.
○: 0 to 150 mN / 70 mm
Δ: Over 150 mN and less than 300 mN / 70 mm
X: 300 mN or more / 70 mm
In addition, if the laminate blocking strength is in the range of 0 to 150 mN / 70 mm, the sealant film can be used as it is without spraying the powder.

[Opening strength]
Sample film surfaces of two films that were dry-laminated in the same manner as in the evaluation of the laminate appearance and laminate blocking strength were overlapped, sampled at 8 cm x 13 cm, applied with a 1 kg load, and retort at 125 ° C for 30 minutes. The tube was treated with hot water. Next, the film was resampled to 7 cm × 11 cm, and the peel strength was measured by the method of ASTM-D1893. And it evaluated in three steps according to the measured peeling strength.
○: 0 to 40 mN / 70 mm
Δ: Over 40 mN and less than 250 mN / 70 mm
X: 250 mN or more / 70 mm
If the opening strength is in the range of 0 to 40 mN / 70 mm, it can be opened with almost no resistance, but if it exceeds 40 mN and less than 250 mN / 70 mm, there is a slight resistance when opening, and 250 mN or more / 70 mm. If it becomes, it will be hard to open if there is no trigger of the impact etc. to an opening part.

[Haze (Transparency)]
In accordance with JIS-K-7105 (plastic optical property test method), the diffuse transmittance and total light transmittance of a sample film (sealant film and the above laminate film) of 5 cm square by an integrating sphere type light transmittance measuring device. Then, the ratio of the diffuse transmittance and the total light transmittance was calculated as haze by the following formula II.
H = Td / Tt × 100 (II)
In Formula II, H is haze (%), Td is diffuse transmittance (%), and Tt is total light transmittance (%).

[Example 2]
The propylene polymer (a) forming the heat seal layer is changed to the following propylene polymer (b), and the propylene polymer (a, c) forming the laminate layer is changed to the propylene polymer (c). The same as in Example 1 except that the propylene polymer (b) was changed to the following and the blending ratio of the propylene polymer (b) to the propylene polymer (c) was adjusted as shown in Table 1. Thus, a film of Example 2 was obtained. Moreover, while evaluating the characteristic of the film of obtained Example 2 by the method similar to Example 1, the film of Example 2 was laminated by the method similar to Example 1, and the characteristic of the laminated film was evaluated. . Table 2 shows the evaluation results of the film of Example 2 and the evaluation results of the laminate film.
(B) Propylene / ethylene block copolymer having an ethylene content of 10% by weight and an MFR at 230 ° C. of about 2.0 g / 10 min and a melting point of about 135 ° C.

[Example 3]
The following high density polyethylene (g) is added to the propylene polymer (a) forming the heat seal layer, and the blending ratio of the high density polyethylene (g) and the propylene polymer (a) is adjusted as shown in Table 1. A film of Example 3 was obtained in the same manner as Example 1 except that. Moreover, while evaluating the characteristic of the film of obtained Example 3 by the method similar to Example 1, the film of Example 3 was laminated by the method similar to Example 1, and the characteristic of the laminated film was evaluated. . Table 2 shows the evaluation results of the film of Example 3 and the evaluation results of the laminate film.
(G) High density polyethylene having an MFR at 190 ° C. of about 1.0 g / 10 min, a density of about 0.954 g / cm ³ and a melting point of 132 ° C.

[Comparative Example 1]
While changing the additive (d, e, f) previously added to the propylene polymer (a) forming the heat seal layer only to the additive (d, e), the propylene polymer ( A film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the blending ratio of a) to the additives (d, e) was adjusted as shown in Table 1. In addition, the conceptual diagram of the cross section of the film of the comparative example 1 is shown in FIG. Moreover, while evaluating the characteristic of the film of the obtained comparative example 1 by the method similar to Example 1, the film of the comparative example 1 was laminated by the same method as Example 1, and the characteristic of the laminated film was evaluated. . Table 2 shows the evaluation results of the film of Comparative Example 1 and the evaluation results of the laminate film.

[Comparative Example 2]
While changing the additive (d, e, f) previously added to the propylene polymer (a) forming the heat seal layer to only the additive (d, f), the propylene polymer ( A film of Comparative Example 2 was obtained in the same manner as in Example 1 except that the blending ratio of a) to the additive (d, f) was adjusted as shown in Table 1. Moreover, while evaluating the characteristic of the film of the obtained comparative example 2 by the same method as Example 1, the film of the comparative example 2 was laminated by the same method as Example 1, and the characteristic of the laminated film was evaluated. . Table 2 shows the evaluation results of the film of Comparative Example 2 and the evaluation results of the laminate film.

[Comparative Example 3]
The following propylene polymer (a, c) to which the following additives (d, e, f) have been added in advance is melted by an extruder, supplied to a T die, discharged into a sheet, and heated to 40 ° C. A 60 μm-thick film having a single-layer structure was produced by winding on a temperature-controlled metal drum, cooling and winding. Moreover, in manufacture of the film of the comparative example 3, it adjusted so that the compounding ratio of the additive to a propylene polymer and the composition of a propylene polymer might become as Table 1, respectively. Furthermore, in the production of the film of Comparative Example 3, as in the production of the film of Example 1, the thickness of the heat seal layer and the thickness of the laminate layer were adjusted to be substantially the same.
(A) Propylene / ethylene random copolymer having an ethylene content of 4.5% by weight and an MFR at 230 ° C. of about 3.6 g / 10 min and a melting point of about 138 ° C. (c) An ethylene content of 60% by weight at 230 ° C. Ethylene / propylene rubber (d) with a MFR of about 4.0 g / 10 min (d) single particle size type and spherical silica (e) single shape type with an average particle size of about 4.0 μm and an average particle size of about 8.0 μm Amorphous silica with an aluminum borate (f) aggregate shape type and an average particle size of about 0.8 μm

  The characteristics of the obtained film of Comparative Example 3 were evaluated by the same method as in Example 1, the film of Comparative Example 3 was laminated by the same method as in Example 1, and the characteristics of the laminated film were evaluated. Table 2 shows the evaluation results of the film of Comparative Example 3 and the evaluation results of the laminate film.

[Comparative Example 4]
The additive (d, e, f) added in advance to the propylene polymer (a) forming the sealant film is changed to only the additive (d, f), and the propylene polymer (a) and the additive (d , F) A film of Comparative Example 4 was obtained in the same manner as Comparative Example 3 except that the blending ratio with f) was adjusted as shown in Table 1. Moreover, while evaluating the characteristic of the film of the obtained comparative example 4 by the method similar to Example 1, the film of the comparative example 4 was laminated by the same method as Example 1, and the characteristic of the laminated film was evaluated. . Table 2 shows the evaluation results of the film of Comparative Example 4 and the evaluation results of the laminate film.

[Effects of Example Film]
As apparent from Table 1, the films of Examples 1 to 3 in which the surface roughness of the heat seal surface and the surface roughness of the laminate surface are included within the scope of the claims have good laminate appearance. The laminate blocking strength and open mouth strength were low, and it had the necessary characteristics as a sealant film for retort.

  On the other hand, the film of Comparative Example 1 having a small “0.1 crest density” on the heat-sealed surface had a good laminate appearance and low laminate blocking strength, but had a slightly large opening strength. Further, the films of Comparative Examples 2 and 4 having small “SRa”, “SRmax”, and “SRz” on the heat-sealed surface had good laminate appearance, but had high laminate blocking strength and open mouth strength. On the other hand, the film of Comparative Example 3 having large “SRa”, “SRmax”, and “SRz” on the laminate surface had a poor laminate appearance, although the laminate blocking strength and the opening strength were small.

  Since the polypropylene-based multilayer sealant film and laminate film of the present invention have excellent performance as described above, they can be suitably used for retorting of various kinds of articles, particularly for food.

It is explanatory drawing which expands and shows the cross section of a polypropylene type 2 layer sealant film. It is explanatory drawing which expands and shows the cross section of a polypropylene type 3 layer sealant film. It is explanatory drawing which expands and shows the cross section of the laminated film which laminated | stacked the heat resistant film on the polypropylene type 2 layer sealant film. It is explanatory drawing which expands and shows the cross section of the film of the comparative example 1.

Explanation of symbols

  1 .... sealant film, 1a ... heat seal layer, 1b ... laminate layer, 2 .... sealant film, 2a ... heat seal layer, 2b ... laminate layer, 2c ... intermediate layer, ... laminate film ( Laminated film for retort), 4. Heat resistant film.

Claims (3)

A film formed of a polypropylene-based synthetic resin is laminated in at least two layers, and includes a heat seal surface (A) for heat sealing and a laminate surface (B) for bonding to a heat resistant film. A polypropylene-based multilayer sealant film having
The polypropylene-based multilayer sealant film, wherein the heat seal surface (A) and the laminate surface (B) each have a surface roughness in the following range.
(A) Surface roughness:
Three-dimensional center plane average roughness 0.040-0.200 μm
3D maximum height 2.0-10.0μm
Three-dimensional ten-point average roughness 1.5-6.0 μm
Surface density of 1000 density / mm ² or more (B) on the surface 0.1 μm above the center surface:
Three-dimensional center plane average roughness 0.015 to 0.250 μm
3D maximum height 0.2-1.9μm
Three-dimensional ten-point average roughness 0.2-1.4 μm   The polypropylene-based multilayer sealant film according to claim 1, wherein the melting point of the resin forming the heat seal surface is 130 to 150 ° C.   A laminate film comprising the polypropylene-based multilayer sealant film according to claim 1 and a heat-resistant film bonded together.

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