JPWO2017170330A1 - Polypropylene resin multilayer film and packaging body using the same - Google Patents

Abstract

An object of the present invention is to provide a polypropylene resin multilayer film that can be used in a wide range of packaging fields by having both good automatic packaging suitability due to having high heat seal strength and fusing sealability. Mainly composed of polypropylene-based resin, on one side of the base layer (A) and base layer (A), from the group consisting of propylene / ethylene / butene-1 copolymer, propylene / butene-1 copolymer, propylene / ethylene copolymer It has a surface layer (B) mainly composed of a polypropylene-based resin composition comprising at least one selected copolymer, and the opposite surface of the surface layer (B) has propylene / ethylene / butene-1 copolymer Polypropylene having a sealing layer (C) mainly composed of a polypropylene resin composition comprising at least one polymer selected from the group consisting of a polymer, a propylene / butene-1 copolymer and a propylene / ethylene copolymer Resin multilayer film.

Description

  The present invention relates to a polypropylene-based resin multilayer film and a package using the same, and in particular, a fresh product made of plants that require high freshness such as vegetables, fruits, and flowers by having heat sealability and anti-fogging effect. The present invention relates to a polypropylene resin multilayer film suitable for packaging (hereinafter referred to as fruits and vegetables in the present specification) and a package using the same.

  Conventionally, polypropylene resin films are widely used in the packaging field such as food packaging and fiber packaging because they are excellent in optical properties, mechanical properties, packaging suitability and the like. In particular, antifogging films are widely used for packaging vegetables and other fruits and vegetables.

  In fruit and vegetable packaging, labor saving is required for agricultural work due to the recent decline in the agricultural population, and the spread of automatic packaging devices is spreading. A so-called pillow packaging system is adopted as an automatic packaging apparatus for fruits and vegetables, and a bag making process by heat sealing and a filling process of contents can be performed simultaneously.

An outer layer composed of a biaxially stretched film mainly composed of crystalline polypropylene and an olefin polymer having a melting point lower by 10 to 90 ° C. than the melting point of the outer layer. A laminated film for packaging raw vegetables made of a film-like product is disclosed (for example, see Patent Document 1).
However, since the film disclosed in Patent Document 1 uses a propylene / ethylene / butene-1 copolymer in the heat seal layer, there is a problem in terms of both low-temperature sealability and seal strength.
Also, two or more layers having a base layer mainly composed of polypropylene resin and a heat seal layer mainly composed of polyolefin resin using propylene / butene-1 copolymer and propylene / ethylene / butene-1 copolymer A packaging film comprising a laminate of the above is disclosed (for example, see Patent Document 2).
However, there is a problem that the seal strength is not sufficient.

On the other hand, there are still many fruits and vegetables that are not automatically packaged, and there are also uses for carrying out bag making and filling separately. Many of the bag making processes in that case are carried out by a fusing seal method.
If it is possible to use both pillow packaging and fusing-sealed packaging as a fruit and vegetable packaging film, there is an advantage in terms of inventory management from the standpoint of farmers such as farmers and converters.
However, none of the conventional pillow wrappable films can be fused and sealed.

Japanese Patent No. 3104166 Japanese Patent No. 4385443

  To provide a polypropylene-based resin multilayer film that can be used in a wide range of packaging fields by combining low-temperature sealing properties and high heat-sealing strength with good automatic packaging suitability and fusing sealing properties. It is an issue.

That is, the present invention has the following configuration.
1. Mainly composed of polypropylene-based resin, on one side of the base layer (A) and base layer (A), from the group consisting of propylene / ethylene / butene-1 copolymer, propylene / butene-1 copolymer, propylene / ethylene copolymer It has a surface layer (B) mainly composed of a polypropylene-based resin composition comprising at least one selected copolymer, and the opposite surface of the surface layer (B) has propylene / ethylene / butene-1 copolymer Polypropylene having a sealing layer (C) mainly composed of a polypropylene resin composition comprising at least one copolymer selected from the group consisting of a polymer, a propylene / butene-1 copolymer and a propylene / ethylene copolymer Polypropylene resin multilayer film, characterized by satisfying the following a) to c).
a) The heat seal rising temperature of the seal layer (C) is 115 ° C. or more and 125 ° C. or less, and the heat seal arrival strength is 3.0 N / 15 mm or more.
b) The thickness of the sealing layer (C) has a range of 1.5% or more and 5% or less with respect to the entire film layer. c) An antifogging agent is included in at least the sealing layer (C).
2. The temperature of the melting point of the resin having the lowest melting point among the copolymers constituting the sealing layer (C) is in the range of 120 to 130 ° C., and the content thereof is 50 wt% or more and 85 wt% or less. The polypropylene resin multilayer film according to item 1.
3. The copolymer having the highest melting point among the copolymers constituting the sealing layer (C) has a melting point of 130 ° C. or more and 140 ° C. or less, and the content thereof is 15% by weight or more and 50% by weight or less. The polypropylene-based resin multilayer film according to Item.
4). The temperature of the melting point of the copolymer constituting the sealing layer (C) is in the range of 120 to 140 ° C., the content of the copolymer at 120 to 130 ° C. is 50% by weight to 85% by weight, and 130 2. The polypropylene-based resin multilayer film as described in 1 above, wherein the content of the copolymer at ˜140 ° C. is 15 wt% or more and 50 wt% or less.
5. The base layer (A) is selected from the group consisting of isotactic polypropylene, propylene / ethylene copolymer, propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer and propylene / pentene copolymer. 2. The polypropylene resin multilayer film according to 1 above, which is mainly composed of a polypropylene resin comprising at least one copolymer and contains an antifogging agent.
6). The package using the polypropylene resin multilayer film in any one of said 1-5.

  By optimizing the seal thickness and composition, the polypropylene resin multilayer film of the present invention can be provided with a good pillow packaging property at a lower cost than before, and can also have a fusing seal property. .

1. Characteristics of the polypropylene resin multilayer film of the present invention 1-1. Base layer (A)
In the present invention, the base layer (A) is composed of isotactic polypropylene, propylene / ethylene copolymer, propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer and propylene / pentene copolymer. The main component is a polypropylene resin composition comprising at least one polymer selected from the group. The melting point of the entire base layer is preferably 145 ° C. or higher, more preferably 150 ° C. or higher. If it is less than 145 ° C., the heat resistance of the film as a whole is poor, and the appearance of the package may be impaired when it is automatically packaged. Further, the melt flow rate (MFR) can be 0.1 to 100 g / 10 min, preferably 0.5 to 20 g / 10 min, and more preferably 1.0 to 10 g / 10 min.

It is necessary to add an antifogging agent to the resin forming the base layer (A). When an antifogging agent is not added, the inside becomes cloudy when packaging fruits and vegetables, and it becomes easy to rot, so the commercial value is lowered.
As a mechanism of the antifogging expression of the polypropylene resin multilayer film of the present invention, an antifogging agent is added to the resin forming the base layer (A), so that the antifogging agent is produced during film production and during storage after film formation. The agent sequentially moves to the surface layer (B) and the seal layer (C), and the film surface is in a state having antifogging properties. The effect can be exerted when packaging fruits and vegetables that are characterized by sustaining physiological action even after harvesting.
And in order to maintain excellent anti-fogging properties in the long term in the distribution process, the package should be stored in a room temperature atmosphere rather than frozen storage, considering the temperature change during storage and distribution. It is preferable to select an antifogging agent that exhibits antifogging properties continuously during the course of repeating temperature changes between 5 and 30 ° C.

  Examples of the antifogging agent added to the resin forming the base layer (A) of the polypropylene-based resin multilayer film of the present invention include polyhydric alcohol fatty acid esters, higher fatty acid amines, and higher fatty acid amides. Typical examples include higher fatty acid amines and amide ethylene oxide adducts. The amount of the antifogging agent present in the film is preferably 0.1 to 10% by weight, particularly preferably 0.2 to 5% by weight in terms of all layers.

  In addition, various additives for improving quality such as slipperiness and antistatic properties, for example, lubricants such as wax and metal soap for improving productivity, plasticity, as long as the effects of the present invention are not impaired. It is also possible to add known heat stabilizers, antioxidants, antistatic agents, ultraviolet absorbers and the like that are usually added to additives, processing aids, and polypropylene films.

1-2. Surface layer (B)
In the present invention, the surface layer (B) is at least one copolymer selected from the group consisting of a propylene / ethylene / butene-1 copolymer, a propylene / butene-1 copolymer and a propylene / ethylene copolymer. It is preferable that the main component is a polypropylene resin composed of a coalescence, and the heat seal rising temperature is 130 ° C. or higher and 140 ° C. or lower. In order to set the heat seal rising temperature of the surface layer (B) to 130 to 140 ° C., it is preferable to select a copolymer so as to include a propylene / ethylene / butene-1 copolymer.
The heat seal rising temperature of the surface layer (B) is the heat seal when the surfaces of the surface layer (B) of the film of the present invention face each other and the heat seal pressure is 1 kg / cm 2 and the time is 1 second. It is the temperature at which the strength is 1 N / 15 mm. When the heat seal rising temperature of the surface layer (B) is 130 ° C. or higher, the surface layer (B) is not easily fused to the seal bar at the time of heat sealing of the pillow packaging, and bag making is easy. When the temperature is 140 ° C. or lower, the back-pasted part is easy to fuse with the package exterior part at the time of pillow packaging, and the appearance is good, and when the package is stacked, the back-pasted part is not caught and the seal is not peeled off.

  The thickness of the surface layer (B) is preferably in the range of 1 to 10% with respect to the entire film layer. When it is 10% or less, the fused resin portion called a poly pool at the time of fusing sealing does not become too large, and the fusing seal strength is further improved. When it is 1% or more, the function as a surface layer is easily exhibited.

  The surface of the surface layer (B) preferably has antifogging properties. When packaging fruits and vegetables and displaying them at supermarkets, it will look better if the surface becomes cloudy due to condensation.

  In addition, various additives for improving quality such as slipperiness and antistatic properties, for example, lubricants such as wax and metal soap for improving productivity, plasticity, as long as the effects of the present invention are not impaired. It is also possible to add known heat stabilizers, antioxidants, antistatic agents, ultraviolet absorbers and the like that are usually added to additives, processing aids, and polypropylene films. It is also possible to blend inorganic or organic fine particles to ensure the blocking resistance and slipperiness of the film.

  Examples of inorganic fine particles include silicon dioxide, calcium carbonate, titanium dioxide, talc, kaolin, mica, zeolite, etc., and these shapes are not limited to spherical, elliptical, conical, indeterminate, and types, The desired particle size can be used and blended depending on the purpose and usage of the film. Moreover, as organic fine particles, cross-linked particles such as acrylic, methyl acrylate, and styrene-butadiene can be used, and various shapes and sizes can be used in the same manner as inorganic fine particles. Is possible. In addition, various surface treatments can be applied to the surface of these inorganic or organic fine particles, and these can be used alone or in combination of two or more. The above also applies to the seal layer (C) described later.

1-3. Seal layer (C)
In the present invention, the seal layer (C) is at least one copolymer selected from the group consisting of a propylene / ethylene / butene-1 copolymer, a propylene / butene-1 copolymer and a propylene / ethylene copolymer. The heat seal rising temperature of the sealing layer (C) must be 115 ° C. or higher and 125 ° C. or lower, mainly composed of a polypropylene resin composed of coalescence. The heat seal rising temperature of the surface layer (C) is the heat seal when the surfaces of the surface layer (C) of the film of the present invention face each other and heat seal pressure is 1 kg / cm 2 and the time is 1 second. It is the temperature at which the strength is 1 N / 15 mm.
When the heat seal rising temperature of the seal layer (C) is 125 ° C. or less, even if the heat seal temperature is low, sufficient strength can be maintained and heat seal can be performed. In addition, the sealing part is excellent in sealing performance, and therefore, the freshness of the fresh product is maintained in combination with the anti-fogging property, the appearance of the contents is good, and the handling property of the package is excellent.
When the heat seal rising temperature of the sealing layer (C) exceeds 125 ° C., the melting point difference from the base layer (A) mainly composed of polypropylene resin is reduced, and the operation speed of automatic packaging cannot be sufficiently increased. Further, if the set temperature is increased in order to increase the heat seal strength, the entire laminated film contracts during heat sealing, which in turn causes wrinkles in the heat seal portion and causes poor sealing of the heat seal portion.
When the heat seal rising temperature of the sealing layer (C) is less than 115 ° C, the melting point difference from the base layer (A) becomes too large, resulting in delamination, and sufficient sealing strength cannot be secured for automatic packaging. It also leads to a decrease in fusing seal strength. In order to set the heat seal rising temperature of the heat seal layer (C) to 115 to 125 ° C., a combination of propylene / ethylene / butene-1 copolymer and propylene / butene-1 copolymer is preferable.

The heat seal arrival strength of the sealing layer (C) needs to be 3.0 N / 15 mm or more. If it is less than 3.0N / 15mm, it is inadequate to prevent the contents from falling off as an automatic package.

The melting point of the resin having the lowest melting point among the propylene / ethylene / butene-1 copolymer, propylene / butene-1 copolymer and propylene / ethylene copolymer constituting the sealing layer (C) is 120 to It is preferable that the resin having the lowest melting point in the range of 130 ° C. is added in the range of 50% by weight to 85% by weight.
When the amount is 85% by weight or less, the interlayer strength with the base layer (A) increases, so that the seal strength is sufficient. When the amount is 50% by weight or more, the seal strength at a low temperature is sufficient.
In the prior art, a propylene-butene copolymer having a low melting point is added to the seal layer resin in order to develop a low-temperature seal strength. However, since the propylene-butene copolymer contains a large amount of butene and ethylene components, The compatibility with the homopolypropylene resin is poor, and interfacial peeling occurs. Further, since the thickness of the seal layer is increased, the tendency is increased, and the seal strength of the original resin cannot be expressed.

The melting point of the resin having the highest melting point among the propylene / ethylene / butene-1 copolymer, propylene / butene-1 copolymer and propylene / ethylene copolymer constituting the seal layer (C) is preferably 130 ° C. As mentioned above, it is 140 degrees C or less, and it is preferable that the content is 15 to 50 weight%. More preferably, it is 130 degreeC or more and 135 degreeC or less. When the temperature is 140 ° C. or lower, the heat seal strength at a low temperature is sufficient, and the reliability as a package is increased. When the temperature is 125 ° C. or higher, the interlayer strength with the base layer (A) is increased and the seal strength is sufficient.
At this time, the temperature of the melting point of the copolymer constituting the seal layer (C) is in the range of 120 to 140 ° C., and the content of the copolymer at 120 to 130 ° C. is 50 wt% or more and 85 wt% or less. More preferably, the content of the copolymer at 130 to 140 ° C. is 15% by weight or more and 50% by weight or less.
At this time, the temperature of the melting point of the copolymer constituting the seal layer (C) is in the range of 120 to 140 ° C., and the content of the copolymer at 120 to 130 ° C. is 60 wt% or more and 85 wt% or less. More preferably, the content of the copolymer at 130 to 140 ° C. is 15% by weight or more and 40% by weight or less.

  The thickness of the sealing layer (C) needs to be in the range of 1.5 to 5% with respect to the entire film layer. If it is less than 1.5%, the heat seal strength is insufficient, and if it is thicker than 5%, the fusing seal strength is insufficient.

  The surface of the sealing layer (C) needs to have antifogging properties. As described above, this is to prevent the inside from being clouded by the physiological action of the contents when packaging fruits and vegetables and displaying or distributing them at supermarkets.

1-4. Film thickness Although the film thickness of the polypropylene resin multilayer film of the present invention varies depending on its use and usage, a polypropylene film as a packaging film is generally about 10 to 100 μm, and has mechanical strength and transparency. More preferably, it is about 15-50 micrometers.

2. Method for Forming Polypropylene Resin Multilayer Film of the Present Invention The polypropylene resin multilayer film of the present invention can be produced by the following method, but is not limited thereto.
For example, after melt lamination by T-die method or inflation method using an extruder suitable for the number of layers, it is cooled by a cooling roll method, water cooling method or air cooling method to form a laminated film, sequentially biaxial stretching method, simultaneous biaxial Examples of the stretching method include a stretching method and a tube stretching method.
Here, if the conditions at the time of manufacturing by a sequential biaxial stretching method are illustrated, the resin melt-extruded from the T-shaped die is cooled and solidified by a casting machine to produce a raw sheet.
The temperature at the time of melt lamination is preferably set in the range of 240 ° C. to 300 ° C. with reference to the melting point of the raw material resin used for each layer. The casting roll temperature is preferably set between 15 ° C. and 40 ° C. for the purpose of suppressing crystallization of the resin and improving transparency.
Next, after heating the raw sheet to a temperature suitable for stretching, the sheet is stretched in the flow direction of the sheet using the difference in speed between the stretching rolls. Considering this, it is preferable to set between 3 and 6 times. The stretching temperature is also preferably set between 100 ° C. and 150 ° C. in view of stable production without unevenness of stretching.
Next, both ears of the longitudinally stretched sheet are gripped by a tenter clip, and stretched while being sequentially expanded in a direction perpendicular to the flow of the sheet while being heated to a temperature suitable for stretching with hot air. In this case, the transverse draw ratio is preferably set between 7 times and 10 times in consideration of thickness variation and productivity. The stretching temperature is also preferably set between 130 ° C. and 180 ° C. in view of stable production without unevenness of stretching.
Finally, it is preferable to perform the heat setting treatment in the range of 150 ° C to 200 ° C.

  The polypropylene resin multilayer film of the present invention can be subjected to a surface treatment in order to improve printability, laminating properties and the like. Examples of the surface treatment method include corona discharge treatment, plasma treatment, flame treatment, and acid treatment, and are not particularly limited. It is preferable to perform a corona discharge treatment, a plasma treatment, and a flame treatment that can be carried out continuously and can be easily carried out before the winding step of the film production process.

  Hereinafter, specific examples of the present invention will be further described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof. In addition, the characteristic in this specification evaluated by the following method.

(1) Layer thickness A polypropylene resin multilayer film capable of automatic packaging was cut into a size of 1 cm × 1 cm, embedded in a UV curable resin, and solidified by irradiation with UV for 5 minutes. Thereafter, a cross-sectional sample was prepared with a microtome and observed with a differential interference microscope, and the thicknesses of the surface layer (B) and the seal layer (C) were measured. Samples were measured at five points, and the average value was calculated.

(2) Heat seal rise temperature Heat seal layers of polypropylene resin multilayer film capable of automatic packaging are stacked face to face, and heat seal pressure 1 kg / cm ² , time using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) Refers to the temperature at which the heat seal strength is 1 N / 15 mm when heat sealed in 1 second, the heat seal layer surfaces of the 5 cm × 20 cm film face each other, and the temperature is set at a pitch of 5 ° C. (seal surface 1cm x 3cm) heat seal at the same time, cut the center part to a width of 15mm, attach to the upper and lower chucks of the tensile tester, measure each strength when pulled at a pulling speed of 200mm / min, The heat seal strength was calculated (unit: N / 15 mm). A linear graph with temperature on the horizontal axis and heat seal strength on the vertical axis was drawn, and the temperature at which the heat seal strength exceeded 1 N / 15 mm was defined as the heat seal rising temperature.

(3) overlaid facing heat seal layers to each other in reaching heat seal strength automatic wrappable polypropylene resin multilayer film, using heat gradient tester (manufactured by Toyo Seiki Co.), the heat sealing pressure 1 kg / cm ^2, time Was heat-sealed in 1 second, the central part was cut to a width of 15 mm, attached to the upper and lower chucks of a tensile tester, and calculated from the heat-seal strength when pulled at a tensile speed of 200 mm / min (unit: N / 15 mm) ).
The upper limit of the seal temperature was set to 150 ° C., and the numerical value at which the maximum strength was reached was defined as the ultimate heat seal strength.

(4) Anti-fogging property 1. Put 300 cc of warm water at 50 ° C. into a 500 cc top open container.
2. The container opening is sealed with the film with the antifogging measurement surface of the film on the inside.
Leave in a cold room at 3.5 ° C.
4). The state of dew adhesion on the film surface was evaluated in five stages with the hot water in the container completely cooled to the ambient temperature.
Evaluation grade 1: No dew on the entire surface (attachment area 0)
Evaluation grade 2: Slight 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 4: almost dew adhesion (up to 3/4 adhesion area)
Evaluation grade 5: Dew adhesion on the entire surface (adhesion area 3/4 or more)

(5) Suitability for automatic packaging Heat seal layers of polypropylene resin multilayer films that can be automatically packaged are stacked facing each other, and heat seal pressure is 1 kg / cm ² using a thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.). Heat-sealed in 1 second.
Evaluation was made according to the following criteria from the presence / absence of fusion of the surface layer (B) to the seal bar and the heat seal rising temperature.
○: No fusion to the seal bar • Rise temperature 115 ° C. or more and 125 ° C. or less Δ: No fusion to the seal bar • Rise temperature less than 115 ° C. or higher than 125 ° C. ×: Fusion to the seal bar

(6) Fusing Seal Strength Using a fusing sealing machine (manufactured by Kyoei Printing Machinery Co., Ltd .: PP500 type), a fusing seal bag of a polypropylene resin multilayer film capable of automatic packaging was created.
Condition: Fusing blade; Cutting edge angle 60 °
Sealing temperature: 370 ° C
Number of shots: 120 bags / min The fusing seal portion of the fusing seal bag is cut to a width of 15 mm, and both ends are grasped by the grasping portion of the tensile tester (gripping interval: 200 mm) with a tensile speed of 200 mm. Fusing seal strength (N / 15 mm) was calculated from the strength at the time when the seal portion was broken. The measurement was performed 5 times and averaged. It was judged that the fusing seal suitability was good at 20 N / 15 mm or more.

Example 1
(1) Resin used The resin which comprises each layer used by the following manufacture example is as follows.
[PP-1]: Propylene homopolymer: “FS2011DG3” manufactured by Sumitomo Chemical Co., Ltd., MFR: 2.5 g / 10 min, melting point: 158 ° C.
[PP-2]: Propylene / ethylene / butene-1 random copolymer: “FSX66E8” manufactured by Sumitomo Chemical Co., Ltd., ethylene content: 2.5 mol%, butene content: 7 mol%, MFR: 3 .1 g / 10 min, melting point: 133 ° C.
[PP-3]: Propylene / butene-1 copolymer: “SPX38F4” manufactured by Sumitomo Chemical Co., Ltd., butene content: 25 mol%, MFR: 8.5 g / 10 min, melting point: 128 ° C.

(2) Base layer (A) Resin composition [PP-1] is 0.16% by weight of glycerin monostearate (Matsumoto Yushi Seiyaku Co., Ltd., TB-123) as an antifogging agent, polyoxyethylene (2) stearyl 0.2% by weight of amine (Matsumoto Yushi Seiyaku Co., Ltd., TB-12) and 0.6% by weight of polyoxyethylene (2) stearylamine monostearate (Matsumoto Yushi Seiyaku Co., Ltd., Elex 334) were added. This was used as [PP-4] and 100% by weight was used as the base layer (A) forming resin.

(3) Surface layer (B) Resin composition [PP-2], organic polymer fine particles (CS30: Sumitomo Chemical Co., Ltd .: particle diameter 3.5 μm) 1.5 wt%, glycerin monostearate as an antifogging agent (Matsumoto Yushi Seiyaku Co., Ltd., TB-123) was melt-mixed at 0.45% by weight so that the resin temperature was 240 ° C., and pelletized.
This raw material was used as [PP-5] and 100% by weight was used as the resin for forming the surface layer (B).

(4) Seal Layer (C) Resin Composition A mixture of 20% by weight of [PP-2] and 80% by weight of [PP-3] was used as the resin for forming the seal layer (C).

Using three melt extruders, the base layer (A) is melt-extruded from the first extruder at a resin temperature of 280 ° C., and the surface layer (B) forming resin is heated to a resin temperature of 250 ° C. by the second extruder. Then, the sealing layer (C) forming resin is melt-extruded from the third extruder at a resin temperature of 250 ° C., and the surface layer (B) / base layer (A) / sealing layer (C) from the chill roll contact surface. Are laminated in a T die so that the thickness ratio is surface layer (B) / base layer (A) / seal layer (C) = 0.6 / 18.7 / 0.7, and extruded. The sheet was cooled and solidified with a cooling roll at 0 ° C. to obtain an unstretched sheet.
Subsequently, the metal roll heated to 130 ° C. was stretched 4.5 times in the longitudinal direction using the peripheral speed difference, and further introduced into a tenter stretching machine, and stretched 9.5 times in the transverse direction. . The preheating part temperature of the tenter stretching machine was 168 ° C., and the stretching part temperature was 155 ° C.

Furthermore, in the latter half of the tenter stretching machine, after heat setting was performed at 163 ° C., the surface layer (B) was subjected to corona discharge treatment using a corona discharge treatment machine manufactured by Kasuga Electric Co., and then the seal layer (C In the same manner, a corona discharge treatment was carried out, and a polypropylene resin multilayer film capable of being automatically packaged by winding with a film winder was obtained. The final film thickness was 20 μm.
The obtained multilayer film satisfies the requirements of the present invention, has sufficient heat seal strength and ultimate strength at low temperatures, and achieves both automatic packaging suitability and fusing seal suitability. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 2)
Example 1 except that by increasing the thickness of the base layer (A), the film thickness was 30 μm, the thickness ratio of the sealing layer (C) was 2.3%, and the thickness ratio of the surface layer was 2.0%. A laminated film was obtained in the same manner. The resulting laminated film had both automatic packaging suitability and fusing seal suitability as in Example 1. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 3)
Example 1 except that by increasing the thickness of the base layer (A), the film thickness was 40 μm, the thickness ratio of the sealing layer (C) was 1.8%, and the thickness ratio of the surface layer was 1.5%. A laminated film was obtained in the same manner. The resulting laminated film had both automatic packaging suitability and fusing seal suitability as in Example 1. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

Example 4
A laminated film was obtained in the same manner as in Example 3 except that the thickness ratio of the sealing layer (C) was 3.0% and the thickness ratio of the surface layer was 1.5%. The resulting laminated film had both automatic packaging suitability and fusing seal suitability as in Example 1. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 5)
A laminated film was obtained in the same manner as in Example 1 except that the amount of [PP-3] added to the sealing layer (C) was 70% by weight. The resulting laminated film had both automatic packaging suitability and fusing seal suitability as in Example 1. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Example 6)
A laminated film was obtained in the same manner as in Example 1 except that the amount of [PP-3] added to the sealing layer (C) was 50% by weight. The resulting laminated film had both automatic packaging suitability and fusing seal suitability as in Example 1. In addition, the anti-fogging property was at a level with no problem in the packaging of fruits and vegetables. Table 1 shows the film composition and physical property results.

(Comparative Example 1)
A laminated film was obtained in the same manner as in Example 1 except that the thickness ratio of the sealing layer (C) was 10%. The obtained laminated film was inferior to the fusing and sealing properties.
Table 2 shows the film composition and physical property results.

(Comparative Example 2)
By increasing the thickness of the base layer (A), the film thickness was 40 μm, the thickness ratio of the sealing layer (C) was 1%, and the thickness ratio of the surface layer was 1.5%. To obtain a laminated film. The obtained laminated film had a high seal rising temperature and was poor in automatic packaging suitability. Table 2 shows the film composition and physical property results.

(Comparative Example 3)
A laminated film was obtained in the same manner as in Example 1 except that the amount of [PP-3] added to the sealing layer (C) was 40% by weight. The obtained laminated film had a high seal rising temperature and was poor in automatic packaging suitability. Table 2 shows the film composition and physical property results.

(Comparative Example 4)
A laminated film was obtained in the same manner as in Example 1 except that the amount of [PP-3] added to the sealing layer (C) was 100% by weight. The obtained laminated film was inferior to the fusing sealability. Table 2 shows the film composition and physical property results.

(Comparative Example 5)
A laminated film was obtained in the same manner as in Example 1 except that the addition of [PP-2] in the sealing layer (C) was changed to [PP-4]. The obtained laminated film had a high seal rising temperature and was poor in automatic packaging suitability. Table 2 shows the film composition and physical property results.

(Comparative Example 6)
A laminated film was obtained in the same manner as in Example 1 except that the thickness ratio of the seal layer (C) was changed to 6.0% and the thickness ratio of the surface layer was changed to 3.0%. The obtained laminated film had a low seal arrival strength, a high rise temperature, and was inferior in automatic packaging. Furthermore, it became inferior also to the fusing sealing property. Table 2 shows the film composition and physical property results.

  The polypropylene-based multilayer resin film that can be automatically packaged according to the present invention can provide a good pillow packaging property at a lower cost than before by optimizing the seal thickness and composition, and also has a fusing seal property. It has become possible. Moreover, since it has anti-fogging property, it is particularly suitable for packaging of fruits and vegetables.

Claims (6)

Mainly composed of polypropylene-based resin, on one side of the base layer (A) and base layer (A), from the group consisting of propylene / ethylene / butene-1 copolymer, propylene / butene-1 copolymer, propylene / ethylene copolymer It has a surface layer (B) mainly composed of a polypropylene-based resin composition comprising at least one selected copolymer, and the opposite surface of the surface layer (B) has propylene / ethylene / butene-1 copolymer Polypropylene having a sealing layer (C) mainly composed of a polypropylene resin composition comprising at least one polymer selected from the group consisting of a polymer, a propylene / butene-1 copolymer and a propylene / ethylene copolymer A polypropylene-based resin multilayer film which is a resin multilayer film and satisfies the following a) to c). a) The heat seal rising temperature of the seal layer (C) is 115 ° C. or more and 125 ° C. or less, and the heat seal arrival strength is 3.0 N / 15 mm or more.
b) The thickness of the sealing layer (C) has a range of 1.5% or more and 5% or less with respect to the entire film layer. c) An antifogging agent is included in at least the sealing layer (C).   The temperature of the melting point of the resin having the lowest melting point among the copolymers constituting the sealing layer (C) is in the range of 120 to 130 ° C., and the content thereof is in the range of 50 wt% to 85 wt%. The polypropylene resin multilayer film according to claim 1.   The polypropylene resin according to claim 1, wherein the resin having the highest melting point constituting the sealing layer (C) has a melting point of 130 ° C or higher and 140 ° C or lower and a content thereof in the range of 15 to 50% by weight. Multilayer film.   The temperature of the melting point of the copolymer constituting the sealing layer (C) is in the range of 120 to 140 ° C., the content of the copolymer at 120 to 130 ° C. is 50% by weight to 85% by weight, and 130 The polypropylene resin multilayer film according to claim 1, wherein the content of the copolymer at ˜140 ° C. is 15 wt% or more and 50 wt% or less.   The base layer (A) is selected from the group consisting of isotactic polypropylene, propylene / ethylene copolymer, propylene / butene-1 copolymer, propylene / ethylene / butene-1 copolymer and propylene / pentene copolymer. The polypropylene resin multilayer film according to claim 1, comprising a polypropylene resin mainly composed of at least one copolymer and containing an antifogging agent.   The package using the polypropylene resin multilayer film in any one of Claims 1-5.