JPH10250011A - Polyethylene multilayer film for air-containing heat sterilized package - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyethylene multilayer film for an air-containing heat sterilized package which enables omission of a laminating process and enables execution of heat sterilization after unprocessed noodles or the like are hermetically packaged with air and which is excellent in sufficiency of a heat seal temperature range, a heat seal strength, heat resistance, water resistance, a water break property, fitness for packaging, mechanical fitness for a packaging machine, etc., and balanced well. SOLUTION: This film is composed of a layer wherein particles of 0.2 to 1.0 pts.wt. of which the average particle size is 5 to 15μm are contained in an ethylene.α olefin copolymer of 100 pts.wt. of which the Vicat softening point is 100 to 110 deg.C (layer A) and of a layer wherein particles of 0.05 to 0.5 pts.wt. of which the average particle size is 2 to 8μm are contained in an ethylene.αolefin copolymer of 100 pts.wt. of which the Vicat softening point is 120 to 128 deg.C (layer B).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a packaging film. More specifically, a laminating process such as dry lamination can be omitted, and after the raw noodles and the like are air-sealed and packaged, it is possible to perform heat sterilization, and a sufficient heat seal temperature range, heat seal strength, The present invention relates to a well-balanced polyethylene-based multilayer film for aeration and heat sterilization packaging, which has excellent heat resistance, water resistance, drainability, suitability for bag making, machine suitability with a packaging machine, and the like.

[0002]

2. Description of the Related Art Aerial heat sterilization is an area in which great demand is expected by accurately grasping recent market needs such as freshness, genuineness and gourmet, as typified by raw type packaged noodles. In order to enable long-term storage of wet noodles and the like at room temperature, selection of packaging materials is indispensable. Such an aerated heat sterilizing packaging film has various functions such as a sufficient heat seal temperature range, heat seal strength, heat sterilization suitability, heat resistance, water resistance, drainage, bag making suitability, and machine suitability with a packaging machine. Is required.

[0003] For example, a general bag-making process of a packaging material in a raw noodle packaging, a filling and packaging process of a raw noodle, and a sterilization process are as follows. First, in the bag making process, a single film film or a dry-laminated film is half-folded, and only a vertical seal of 10 to 20 mm is provided every several rows, usually at a width of 100 to 200 mm. Further, the middle of the vertical seal portion is slit, and a cylindrical film is formed and wound. In the next filling and packaging step, the lower portion of the film is sealed while being transported in the vertical direction, and then the film is cut in the horizontal direction to form a three-side sealed bag. After sandwiching both ends of the bag with a chuck, opening the bag and filling it with fresh noodles, the bag is pressed with a sponge and the upper seal is performed in a state where air remains to some extent inside. As a result, a four-side seal bag in which all sides are sealed is obtained. Since this method does not have a half-fold seal portion, there is no leakage from the seal portion, and the reliability is considered to be extremely high.
In the sterilization step, which is the final step, sterilization is usually performed by heating at 90 to 100 ° C. for several tens of minutes. Thereafter, the bag is cooled and dried, and the outer surface of the bag is dried.

[0004] Pneumatic packaging refers to packaging hermetically with some air remaining. This method has the feature that the unraveling of the raw noodles after opening is better than the packaging method containing almost no air, but on the other hand, the air contained in the packaging bag thermally expands during heat sterilization, and Due to the vaporization of the water content of the raw noodles, excessive pressure is applied to the seal portion. As a result, if the seal strength or the like is weak, the bag will break. The air-containing packaging bag needs to be configured to withstand the pressure at this time. As a method of reducing the pressure of the seal portion, it is only necessary to reduce the amount of air to be contained. However, it is not preferable because the phenomenon that the noodles of the raw noodles adhere to each other and the loosening of the noodles is remarkably impaired.

[0005] As another method of forming a packaging bag, there is molding from a blown film. In this method, it is not necessary to perform vertical sealing because it is already cylindrical, but there are cases where half-folded parts cannot be completely sealed during horizontal sealing,
As a result, there is a disadvantage that the contents come into contact with the outside air and the contents are spoiled, which is not preferable. Similarly, in a vertical pillow bag widely used for snacks and the like, an intersection of a vertical seal and a horizontal seal portion also easily causes seal leakage.

[0006] By the way, as a packaging material of such a pneumatically heated and sterilized packaging, a laminated product of a biaxially stretched nylon film and a non-stretched polypropylene film or an ethylene copolymer film composed of ethylene and α-olefin is used.
In particular, ethylene / α-olefin copolymer films are widely used because of their sealing strength, hot tack properties, impact resistance at low temperatures, and the like. These meet the required properties such as mechanical properties, heat resistance, and water resistance, but since the biaxially stretched nylon film is expensive, and because it is a laminate of different kinds of films, the upper seal and the seal after heat sterilization are particularly important. The lower seal portion has a disadvantage that the surplus seal easily curls inward, water easily accumulates in this portion, and the drainage of the accumulated water is poor.

As a method of eliminating water drainage, a laminate of ethylene / α-olefin copolymer films having different densities is known. Since this is a laminate of the same type of film, curling hardly occurs.
However, a laminating process of two types of films is required, and the process is complicated and increases the cost.

To solve these problems, for example, a multilayer film in which different kinds of resins are laminated has been reported. However, there is a drawback that the transparency is impaired upon recovery, and the strength is inferior due to poor interfacial adhesion between the resins, and it is desirable to use the same type of resin.

On the other hand, a multilayer film using only an ethylene / α-olefin copolymer is disclosed in JP-B-6-102375.
JP-A-6-75955, JP-A-2-1727
No. 37, 2-194159, 5-261
871, JP-A-61-120745, and 58
JP-A-160147 and JP-A-58-18260 disclose that these can be used as a kind of packaging film. However, when these are used as air-containing heat sterilization packaging, for example,
One or more of the following: the melting point of the seal layer is low, resulting in lack of heat resistance, causing breakage of the bag, and sufficient heat resistance but high seal start temperature, poor seal strength, and poor impact resistance. However, it was not possible to satisfy the required properties as a film for aerated and heat sterilized packaging.

[0010]

According to the present invention, a laminating step such as dry lamination can be omitted, and heat sterilization can be performed after air-tight packaging of raw noodles and the like. To provide a well-balanced polyethylene-based multi-layer film for aerated and heat sterilized packaging that has excellent heat sealing temperature range, heat sealing strength, heat resistance, water resistance, drainability, suitability for bag making, mechanical suitability with a packaging machine, and the like. As an issue.

[0011]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that specific ethylene α
The present inventors have found that a combination of an olefin copolymer and fine particles is most suitable for an aerated and heat sterilized packaging film such as fresh noodles, and have completed the present invention. That is, the present invention
(A layer) 0.2 parts by weight or more of fine particles having an average particle diameter of 5 μm or more and less than 15 μm with respect to 100 parts by weight of an ethylene / α-olefin copolymer (a) having a Vicat softening point of 100 ° C. or more and less than 110 ° C. , A polyethylene resin layer containing less than 1.0 part by weight, and (B layer) having a Vicat softening point of 12
With respect to 100 parts by weight of the ethylene / α-olefin copolymer (b) having a temperature of 0 ° C or more and less than 128 ° C, fine particles having an average particle size of 2 µm or more and less than 8 µm are used in an amount of 0.05 part by weight or more.
The polyethylene-based multilayer film for aerated and heat sterilized packaging comprising a polyethylene-based resin layer containing less than 50 parts by weight, and the (A layer) and the (B layer) in terms of the Vicat softening point of (C layer) and (a). For pneumatic heat sterilization packaging laminated via a resin layer composed of an ethylene / α-olefin copolymer or a mixture of ethylene / α-olefin copolymers (c) having a Vicat softening point that is large (b) and smaller than the Vicat softening point A polyethylene-based multilayer film is provided. Hereinafter, the present invention will be described in detail.

The film of the present invention has at least two or more layers. Here, layer A corresponds to the sealing layer of the air-containing heat sterilizing packaging bag, and layer B corresponds to the outer layer. The thickness ratio of each layer is preferably 1/6 or more of the total thickness. When the A layer is less than 1/6, the sealing property is poor, and when the B layer is less than 1/6, the heat resistance is poor, which is not preferable. The thickness of the film is preferably 30 μm or more and less than 100 μm, and particularly preferably 40 μm or more and less than 80 μm in the case of a raw noodle-containing packaging bag.

The ethylene / α-olefin copolymer referred to in the present invention is an ethylene-based copolymer composed of ethylene and an α-olefin having 4 to 10 carbon atoms, and the α-olefin includes butene-1 and hexene- One or more of 1,4-methylpentene-1, octene-1, decene-1 and the like can be used. These ethylene and α
The film obtained from the olefin copolymer has the features of being excellent in heat seal strength, hot tack property, foreign matter seal property, impact resistance and the like.

Ethylene used in (A layer) of the present invention
The α-olefin copolymer (a) has a Vicat softening point of 10
0 ° C or higher and lower than 110 ° C. The A layer is on the seal layer side of the aerated and heat sterilized package. Therefore, contradictory properties such as low-temperature heat-sealing property and heat resistance against heat sterilization after filling and packaging raw noodles or the like are required.
If the Vicat softening point is less than 100 ° C., the heat-sealed portion peels off during heat sterilization and eventually breaks. Also,
When the Vicat softening point is 110 ° C. or higher, the low-temperature sealing property is impaired. When the sealing temperature is increased to compensate for this, the layer B is melted and the appearance is remarkably deteriorated, and the thickness of the sealing portion is reduced. Some parts are formed, and the heat sealing strength is also reduced. This Vicat softening point has a density of 0.915 to
It can be achieved by controlling the amount to 0.927 g / cm ³ . Also,
Melt flow rate (MFR) is 0.5 to 10 g / 10
Min., And more preferably 1 to 5 g / 10 min. If it is larger than this range, the moldability with a normal T-die will be poor, and if it is smaller, the resin pressure will be high, and as a result the extrusion amount will be small, which is not preferable in production. The melt flow rate is a value determined according to JIS-K7210.

When the layer A is used as a bag, the inner surfaces thereof are opposed to each other. Therefore, it is essential to use fine particles as an antiblocking agent for the purpose of improving the opening property of the bag, that is, the opening property. The particle size and addition amount of the antiblocking agent are 0.2 parts by weight or more and less than 1.0 part by weight of fine particles having an average particle size of 5 μm or more and less than 15 μm. Can be reduced. 0.2
If the amount is less than part by weight, the opening property of the bag is insufficient, and if the amount is more than 1.0 part by weight, heat sealability and transparency deteriorate, which is not preferable.

Examples of usable fine particles include inorganic fine particles such as diatomaceous earth, silica, and zeolite, and examples of organic fine particles include polymethyl methacrylate, polystyrene, and polyamide. In particular, since organic fine particles generally have a lower hardness than inorganic fine particles, they are highly effective in improving the abrasion resistance when the films rub against each other. Therefore, it is more preferable to use organic fine particles. The shape of the fine particles is most preferably spherical in order to form effective projections on the film surface, but other shapes such as a cubic or irregular shape may be used. The decomposition start temperature of the fine particles is 250 ° C. or higher, and the higher the temperature, the better. Normal T
In the extrusion and film formation by the die method, the temperature of the molten resin is about 230 ° C.
At the time of film formation, fish eyes are generated due to gelation and decomposition odor is generated, which is not preferable in terms of safety and health.

Ethylene used in the (B layer) of the present invention
The α-olefin copolymer (b) has a Vicat softening point of 12
0 ° C or higher and lower than 128 ° C. The layer B is on the outside of the air-containing heat-sterilized package and directly touches the seal bar, so that heat resistance is required. Vicat softening point is 12
If the temperature is lower than 0 ° C., the film melts and adheres to the seal bar. This not only significantly impairs the appearance, but also creates a thinner portion in the thickness of the seal portion, and also lowers the heat seal strength. This Vicat softening point has a density of 0.938-0.
It can be achieved by setting it to 945 g / cm ³ . Further, the melt flow rate (MFR) is preferably 0.5 to 10 g / 10 minutes, more preferably 1 to 5 g / 10 minutes.

The layer B has a portion that comes into contact with a metal cylinder called a triangular plate when performing vertical sealing with, for example, a four-side seal bag making machine. When the ethylene / α-olefin copolymer (b) does not contain the anti-blocking agent, the sliding property between the film and the triangular plate is poor, and the film is scratched. Therefore, it is necessary to use a blocking resistant agent. The particle size and the amount of the anti-blocking agent
In the case of die forming, the part where the cast roll surface and the molten resin are in contact may cause poor adhesion,
A large amount is not preferred. Therefore, fine particles having an average particle diameter of 2 μm or more and less than 8 μm are contained in an amount of 0.05 part by weight or more and
It is necessary to contain less than 0 parts by weight. Examples of the fine particles that can be used include, like the A layer, inorganic fine particles such as diatomaceous earth, silica, and zeolite, and organic fine particles such as polymethyl methacrylate, polystyrene, and polyamide. Higher is more preferable. The shape is most preferably spherical in order to form effective projections on the film surface, but other shapes such as cubes and irregular shapes may be used.

According to the present invention, there is provided a three-layer film (A layer) / (C layer) / (B layer) in which the A layer and the B layer are laminated via the C layer. The C layer is required to have intermediate properties between the A layer and the B layer, and an ethylene / α-olefin copolymer having a Vicat softening point larger than the Vicat softening point of (a) and smaller than the Vicat softening point of (b), or An ethylene / α-olefin copolymer mixture (c) is used. An ethylene / α-olefin copolymer satisfying this Vicat softening point is:
It can be achieved by setting the density to 0.915 to 0.937 g / cm ³ .

When a three-layer film is used, A layer / C layer /
The thickness ratio of the B layer is preferably 1/6 or more of the total thickness of each layer. The thickness of the film is 30 μm or more and 100
A thickness of less than μm, particularly 40 μm or more and less than 80 μm, is suitable for use in aerated noodle-containing packaging.

Generally, three layers are most widely used. In this case, it is substantially unnecessary to add fine particles which are anti-blocking agents to the layer C. Therefore, it is preferable to mix only the slip agent described later in the C layer from the viewpoint of improvement in transparency or cost. When manufacturing a film, it is common to collect ears and film dust generated during film formation and slitting, but in this case, it is preferable to collect the film in the intermediate layer C.

Each layer of the multilayer film of the present invention may be mixed with another resin, for example, an ethylene / vinyl acetate copolymer, an ethylene / acrylic ester copolymer or the like, if necessary, as long as the properties of the film are not impaired. Can also be used. Further, additives such as a slip agent, an antioxidant, an antistatic agent, an ultraviolet absorber, and a coloring agent which are usually used in all the layers can be used. In particular, slip agents such as higher fatty acid amides and higher fatty acid bisamides are preferably used in the entire layer in the range of 0.02 to 0.08 parts by weight in order to improve the slipperiness. It is also possible to add a layer having various functions, for example, a gas barrier property.

The method of forming the multilayer film of the present invention is not particularly limited, and any of known air-cooled and water-cooled inflation molding, T-die film molding and the like can be used. The molding temperature is determined from the heat resistance of the organic fine particles.
It is desirable not to exceed 250 ° C. When printing is performed on the outer surface of the bag, the surface of the layer B may be subjected to a surface treatment such as a corona discharge treatment.

[0024]

EXAMPLES Next, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these.
Table 1 shows the types of ethylene / α-olefin copolymer used.
Table 2 shows the combinations and evaluation results. In Table 2, particles having a circle in the column of fine particles indicate that the layer A is spherical fine particles of polymethyl methacrylate (Nippon Shokubai Co., Ltd., Eposter MA1010: average particle diameter of 10 μm).
m) is 0.7 parts by weight based on 100 parts by weight of the ethylene / α-olefin copolymer (a), and the B layer is made of diatomaceous earth (manufactured by Showa Chemical Industry Co., Ltd., radiolite: average particle size of 3.5 μm). -0.2 parts by weight were added to 100 parts by weight of the α-olefin copolymer (b), respectively, and a cross indicates that no fine particles were added.
Further, PE-6: PE described in the C layer of Example 4
-2 = 1: 1 indicates that the respective ethylene / α-olefin copolymers were mixed at a ratio of 1: 1. Further, in all the examples, erucamide (Diamid L-200, manufactured by Nippon Kasei) was used as a slip agent in all layers in ethylene.
0.05 parts by weight was added to 100 parts by weight of the α-olefin copolymer.

The multilayer films of all the following examples were produced by the following methods. When forming a two-layer film,
The layer A was melted and kneaded at 230 ° C. using an extruder of 50 mmφ and a layer of 50 mmφ at 230 ° C. Then, a multi-manifold type three-layer T die was used as two layers. The kneading and film forming temperature was 230 ° C., and a film having a thickness of 60 μm was obtained using the layer B as a casting roll side. At this time, the thickness ratio of the A layer / B layer was 1/4. In the case of a three-layer film, A
Layer 50mmφ, B layer 50mmφ, C layer 65mmφ
6 extruder under the same conditions as for the two-layer film
A 0 μm film was obtained. The thickness ratio of layer A / layer C / layer B was set to 1/3/1.

The evaluation method in the present embodiment is as follows. (1) Appropriate heat sealing temperature range The surface of layer A, which is the sealing surface of the obtained film, is overlapped with each other to form a sealing width of 10 mm, a sealing temperature of 70 ° C. to 5 ° C., a sealing time of 1 second, a sealing pressure of 1 second. 2.0Kg /
A single-sided heat seal was performed under the condition of cm ² , and the obtained test piece was sampled in a width of 15 mm, and subjected to a T-peeling test at a speed of 300 mm / min using a tensile tester. At that time, the temperature at which the strength was 500 g / 15 mm width or more was defined as the heat sealing start temperature. Further, the sealing temperature was further increased, and the temperature at which the test piece was fused to the seal bar was defined as the heat sealing upper limit temperature, and the value obtained by subtracting the heat sealing start temperature from the heat sealing upper limit temperature was defined as an appropriate heat sealing temperature range. The larger the range is, the more preferable the sealing conditions at the time of actual bag making and filling / packaging can be set.

(2) Evaluation of Bag Making The appearance, sealing suitability, etc., when vertical sealing was performed using a three-side seal bag making machine were observed. If no problem was observed, then ○, and if there was a problem, × was given.

(3) Suitability for heat sterilization Steamed sterilization was carried out at 94 ° C. for 30 minutes on a heat-sealed sealed packaging bag filled with raw noodles. These conditions are usually the same as the conditions for heat sterilizing raw noodles. The number of tests was 20 for each sample, and samples with no bag breaking were evaluated as ○, and samples with at least one bag breaking were evaluated as x. In addition, GP-10 which is a tube film packaging machine manufactured by General Packer Co., Ltd.
00B2 was used.

(4) Water drainage property The film subjected to the steam sterilization curls inward,
It was checked whether water could easily accumulate in the remainder of the horizontal seal. Those that hardly accumulate were rated as 、, and those that easily accumulate were rated X.

Examples 1 to 4 All of the combinations had an appropriate heat sealing temperature range, and no problems were recognized in bag making, filling of fresh noodles, steam sterilization, and drainage.

Comparative Example 1 The ethylene / α-olefin copolymer (a) used for the layer A (seal layer) was changed to one having a lower Vicat softening point than PE-6 of Example 1. The appropriate heat sealing temperature range became wide, and there was no problem in the appearance of the sealing portion. However, all the bags were broken by steam sterilization at 94 ° C. for 30 minutes.

Comparative Example 2 The ethylene / α-olefin copolymer (a) used for the layer A (seal layer) was changed to one having a lower Vicat softening point than PE-7 of Example 3. No problem was observed in the appearance of the seal part, but the steam sterilization at 94 ° C. for 30 minutes
Four of the bags broke.

Comparative Example 3 The ethylene / α-olefin copolymer (a) used for the layer A (seal layer) was changed to a material having a lower Vicat softening point than PE-5 of Example 5. Although there was no problem in the appearance of the seal portion, all the bags were broken by steam sterilization at 94 ° C. for 30 minutes.

Comparative Example 4 The ethylene / α-olefin copolymer (a) used for the layer A (seal layer) was changed to a material having a higher Vicat softening point than PE-6 of Example 1. The sealing start temperature is high, and it is necessary to increase the set temperature in the bag making evaluation, and in this case, the seal appearance deteriorated.

Comparative Examples 5 and 6 The ethylene / α-olefin copolymer (b) used in the B layer (outer layer) was changed to one having a lower Vicat softening point than PE-2 of Example 1. The outside of the film tended to fuse to the seal bar, and the seal appearance was poor.

Comparative Example 7 The same procedure as in Example 1 was carried out except that the fine particles serving as the anti-blocking agent were removed from the layer B (outer layer). Although there was no problem in the sealability, etc., abrasion was observed on the outside of the film after the vertical seal bag-making. The cause was found to occur when the triangular plate (metal tube) of the four-side seal bag making machine rubs against the layer B of the film.

Comparative Example 8 The same procedure as in Example 1 was carried out except that the fine particles serving as the antiblocking agent were removed from the A layer (seal layer). Although there was no problem with the sealing properties, the inner surfaces of the films after the vertical sealing were slightly adhered. This made it difficult to open the bag when the next step of opening the bag and putting the raw noodles, and the raw noodles could not be put.

[0038]

[Table 1] PE-2,4,6,7,9 Idemitsu Petrochemical Co., Ltd. PE-1,10 Sumitomo Chemical Co., Ltd. PE-3,5,8 Mitsui Petrochemical Co., Ltd.

[0039]

[Table 2]

[0040]

As described above, the film of the present invention can omit a laminating step such as dry laminating, and can be subjected to heat sterilization after air-tight packaging of fresh noodles and the like. In addition, it has excellent heat seal temperature range, heat seal strength, heat resistance, water resistance, drainage, suitability for bag making, mechanical suitability with packaging machine, etc. It is a multilayer film and is particularly suitable for aerated packaging of raw noodles and the like.

Claims (4)

[Claims] 1. (A layer) An average particle size of 5 μm to 15 parts per 100 parts by weight of an ethylene / α-olefin copolymer (a) having a Vicat softening point of 100 ° C. or higher and lower than 110 ° C.
a polyethylene resin layer containing at least 0.2 part by weight and less than 1.0 part by weight of fine particles having a particle size of less than 0.1 μm, and an ethylene / α-olefin copolymer having a Vicat softening point of at least 120 ° C. and less than 128 ° C. For 100 parts by weight of the combined (b),
Fine particles having an average particle diameter of 2 μm or more and less than 8 μm are 0.05%
A polyethylene-based multi-layer film for aeration and heat sterilization packaging comprising a polyethylene-based resin layer containing at least 0.5 parts by weight and at least 0.5 parts by weight. 2. (A layer) An average particle size of 5 μm or more per 100 parts by weight of an ethylene / α-olefin copolymer (a) having a Vicat softening point of 100 ° C. or higher and lower than 110 ° C.
A polyethylene resin layer containing at least 0.2 part by weight and less than 1.0 part by weight of fine particles having a particle size of less than 5 μm, and an ethylene / α-olefin copolymer having a Vicat softening point of at least 120 ° C. and less than 128 ° C. Fine particles having an average particle diameter of 2 μm or more and less than 8 μm are added to 100 parts by weight of the combined (b).
(C layer) ethylene / α having a Vicat softening point greater than the Vicat softening point of (a) and less than the Vicat softening point of (b). A polyethylene-based multi-layer film for aerated and heat sterilized packaging laminated via a resin layer composed of an olefin copolymer or a mixture (c) of an ethylene / α-olefin copolymer. 3. The polyethylene-based multilayer film for aerated and heat sterilized packaging according to claim 1, wherein the fine particles contained in the (A layer) are organic. 4. A package of raw noodles, wherein the (A layer) of the polyethylene-based multi-layer film for aerated and heat sterilized packaging according to claim 1 and 2 is made into an inner surface, the fresh noodles are air-packaged and heat sterilized.