JP4535322B2 - Polyolefin-based laminated film for packaging - Google Patents

Description

  The present invention relates to a polyolefin-based laminated film for packaging with improved delamination (easy opening) and the like. The pyro-type packaging bag made of the film is effective for enclosing and packaging, for example, raw vegetable foods and heating and cooking (for example, a microwave oven) as they are.

About the laminated | multilayer film for packaging, the function required for the use is attached | subjected and it is used in many fields. Among them, for example, packaging bags for microwave ovens, packaging bags having easy opening properties even at extremely low temperatures, and easy peeling properties are also known.
In addition, as a common function of these laminated films, when some tearing action is applied to the bag, the action is relaxed at the layer corresponding to the middle part and slowly broken or stopped at the middle layer. , It does not lead to direct destruction of the base layer.

As for films relating to packaging bags for microwave ovens, for example, having an OPP film as a base material layer, a printing layer, a resin layer made of ethylene-vinyl acetate copolymer resin, etc. from one side below, an adhesive layer made of polyurethane adhesive, LLDPE A five-layer film in which a sealant layer made of a resin is sequentially laminated is known (see Patent Document 1).
On the other hand, for a film relating to a packaging bag having easy-openability or easy-release properties even at extremely low temperatures, for example, polypropylene is used as a base layer (A), and a first intermediate layer (B) (for example, made of polyolefin resin on one side) A binary propylene resin of ethylene copolymer or a ternary propylene resin of ethylene and a C _{4 to} C ₆ olefin) and a second intermediate layer (C) (for example, a C _{3 to} C ₈ olefin mainly composed of ethylene). Copolymer) and a heat seal layer (D) (for example, a blend resin of a copolymer of ethylene mainly composed of propylene and a copolymer of butene mainly composed of propylene) and a four-layer film. Is known (see Patent Document 2).

JP 2002-53184 A JP 2003-191407 A

The present invention has been found as a result of intensive studies aimed at further improving the following two points which are insufficient with the four-layer film disclosed in JP-A-2003-191407.
One of them is that the four-layer film disclosed in the Japanese Patent Laid-Open Publication No. 2001-133 is processed into a palm-type bag (pillo-type bag), and raw vegetables are encapsulated therein. It may be broken suddenly with a popping sound. The sudden destruction accompanied by the plosive sound is not preferable from the psychological viewpoint as well as the scattering of water into the microwave oven.
Two of them are that the seal temperature when processing into a palm bag is high. Depending on the type of package, it may be desirable to be able to seal at a lower temperature, even if it is sealed at a faster rate.

First, in the present invention, a layer (C), a layer (B), and a layer (A) by a polyolefin resin described below are sequentially laminated from below one side of a longitudinally and transversely stretched base layer (D) made of crystalline polypropylene. It is characterized by being a polyolefin-based laminated film for packaging.
<Polyolefin resin for layer (C)>
Ternary copolymer resin of ethylene mainly composed of propylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (B)>
Blend resin of 15 to 40 parts by mass of low density polyethylene with respect to 100 parts by mass of binary copolymer resin of ethylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (A)>
Propylene and _C 4 -C ₆ olefins and amorphous binary copolymer resin 50 to 75 wt% propylene and _C 4 -C ₆ olefin crystalline binary copolymer resin 50 to 25 wt% and of of the Blend resin

Then, a polyolefin-based laminate for packaging in which layers (C), (B) and (A) of polyolefin resin described below are sequentially laminated from below one side of the longitudinally and transversely stretched base layer (D) made of crystalline polypropylene. It is also characterized by being a film.
<Polyolefin resin for layer (C)>
Ternary copolymer resin of ethylene mainly composed of propylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (B)>
Blend resin of 15 to 40 parts by mass of low density polyethylene with respect to 100 parts by mass of binary copolymer resin of ethylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (A)>
Propylene and _C 4 -C ₆ olefins and amorphous binary copolymer resin 50 to 75 wt% propylene and _C 4 -C ₆ olefin crystalline binary copolymer resin 50 to 25 wt% and of of the relative blends resin 100 parts by weight, alone resin according to any of the olefins _C 4 -C ₆ of 5 to 45 parts by weight

  Further, the present invention is also characterized by a food packaging bag in which food is enclosed and packaged in a pillow-type packaging bag made of the above-mentioned polyolefin-based laminated film for packaging (for use).

  Since this invention is comprised as mentioned above, there exist the following effects.

First, a polyolefin-based laminated film for packaging according to the present invention (hereinafter simply referred to as a laminated film).
) Is processed into, for example, a pillow-type packaging bag, in which, for example, a food containing moisture is enclosed, and even if this is cooked in a microwave oven, for example, a popping sound is generated due to an increase in internal pressure during heating. The base layer is not suddenly broken. Therefore, there is no scattering of water into the microwave oven, and it can be used as something that can be safely cooked.

When the laminated film of the present invention is processed into a pillow type packaging bag by pilling and heat sealing with, for example, a vertical pillow type packaging machine, the sealing temperature is about 75 to 13.
As low as 0 ° C. This is extremely effective both for foods to be handled and for productivity.

  In addition, even if the food-filled pillow-type packaging bag is stored frozen and opened in the frozen state, it can be opened along the seal surface (without tearing the base layer). It can also be used for storage. Further, even if the frozen bag is dropped, the main body (base layer) is not torn.

First, the base layer (D) stretched longitudinally and laterally with crystalline polypropylene, which is the base of the present laminated film, will be described.
The base layer (D) sufficiently adheres at the interface with the layer (C), supports the three layers (C), the layer (B), and the layer (A), and is appropriately handled. This is necessary for obtaining properties, scratch resistance and the like. Here, the appropriate handling property means that it is difficult to be broken by handling, or that food is easily opened or inserted when food is inserted into a pillow-type packaging bag, or that the open state is easy to maintain. Say that.

The crystalline polypropylene forming the base layer (D) is an isotactic crystalline polypropylene resin that has good moldability and can be stretched in the vertical and horizontal directions.
This is because the hardness of all three layers (C), (B) and (A) is also in the direction of softness, and this softness is firmly supported and proper handling is obtained. It is effective as Therefore, even if this is polypropylene with low crystallinity, even if it is other resin, sufficient effect is not acquired.
The degree of crystallinity of this crystalline polypropylene is exemplified by NMR pentad fraction (the isotactic pentad fraction measured by a generally known ¹³ C-nuclear magnetic resonance absorption method). 98%. This is also about 155 to 165 ° C. at the melting point.
In addition, since a brittleness etc. will be added if a too high crystalline thing is used, in such a case, a highly crystalline polypropylene is made into a main component, for example, a slightly low crystallinity, such as a polypropylene copolymer resin ( For example, it may be adjusted by blending ethylene of about 5% by mass or less or a copolymer of butene 1 (butylene). This has the effect of suppressing the deterioration of the brittleness and the adhesiveness with the layer (C).

Next, the layer (C) made of the polyolefin resin will be described.
First, the layer (C) exhibits a sufficient adhesion between the base layer (D) and the layer (B) and is laminated with a slightly weak adhesion between the layers (B).
First, when the breaking action from the layer (A) cannot be completely absorbed by the layer (B), the remaining breaking action is received completely by the layer (C), and the base layer (D) This is a layer provided to completely prevent tearing. That is, if all of the tearing operations in the layer (B) that are actively received are not performed here, it is received by the layer (C), and the base layer (D) is not broken. This layer can be said to be an auxiliary tear prevention layer for securing.

The polyolefin-based resin forming the layer (C) is a terpolymer resin of ethylene mainly composed of propylene and a C _{4 to} C ₆ olefin. Specifically, the copolymer is copolymerized with about 1 to 10% by mass of ethylene and C _{4 to} C ₆ olefins with respect to the amount of propylene. The resin in such a composition range is also crystalline and exhibits a melting point of about 80 to 95 ° C. and an MFR of about 4.5 to 6.5 g / 10 min (190 ° C., 21.18 N).
Here, C ₄ -C ₆ olefins are preferable, butene 1 (butylene) and pentene 1 are preferable, and butene 1 is more preferable. This is because as C increases, the resin becomes softer, which is not preferable.
The main component of the action of the ternary copolymer resin is as described above. In addition, the ternary copolymer resin also acts to develop an appropriate interlayer adhesion. That is, the propylene unit is the main component, so that the interlayer adhesion with the base layer (D) is the strongest, and a unit of a small amount of ethylene and a C _{4 to} C ₆ olefin is in contact with the layer (B). It acts so as to be adhered and laminated to the interlayer with a slightly low force.

Next, the layer (B) made of the polyolefin resin will be described.
First, the layer (B) is laminated so that the adhesion between the layer (C) and the layer (C) is increased and the adhesion between the layer (A) and the layer (A) is weakened. The center for the substrate layer (D) is here received all of the breaking action from the substrate layer (D) as little as possible to the layer (C) and not to the substrate layer (D). It is a layer that can be said to be an anti-tear layer.
The meaning of not breaking here means that the base layer (D) is not broken, and the layer (B) and the layer (C) are broken (although the degree of breaking performance is different) Exfoliation).
Here, the tearing position in the layer (B), in other words, the peeling position is either the boundary surface with the layer (A), or the boundary surface with the layer (C) in the layer (B).

The polyolefin resin forming the layer (B) is a blend resin of a binary copolymer resin of ethylene and a C _{4 to} C ₆ olefin and a low density polyethylene.
Here, the binary copolymer resin is, for example, an ethylene-based resin in which ethylene is about 55 to 95% by mass and the olefin is about 45 to 5% by mass. The resin in such a composition range is, for example, a soft resin having an MFR of about 3.5 to 5.5 g / 10 min (190 ° C., 3.10 N) and a hardness (A) of about 55 to 75. In the interlaminar adhesion relationship, the copolymer resin mainly acts between the layers (C).

One low-density polyethylene has a generally known density of about 0.915 to 0.925, a melting point of about 105 to 112 ° C., and an MFR of about 2.0 to 4.5 g / 10 min (190 ° C., 3. 10N). It is softer, easier to stretch, and more resistant to impact than medium and high density.
This low density polyethylene is blended for the following reasons.
In the action of the layer (B), the interlayer adhesion between the layer (B) and the layer (A) is in a weaker laminated state with the layer (C). However, this weakness is also an interlaminar adhesion that easily breaks in a heating environment such as encapsulating raw bean sprouts in a pyro-type bag and heating it in a microwave oven, for example, handling at room temperature to about 50 ° C. It is not a weaker interlaminar adhesion force that would peel off underneath. This is not preferable because it also becomes a practical defect.
The occurrence of such a problem must be prevented, and the layer (B) and the layer (A) must be in close contact with each other with appropriate strength to be balanced from room temperature to high temperature. This low density polyethylene is a resin that effectively expresses this action. Therefore, other functions such as medium density and high density polyethylene are not sufficient.
The blend of the low density polyethylene also increases the transparency of the layer (B), that is, the transparency of the present laminated film. This is considered to be a result of acting as a nucleating agent on the binary copolymer resin to be blended.

And the said binary copolymer resin and low density polyethylene become more effective in the following blend ratio range. That is, it is 15-40 mass parts of this polyethylene with respect to 100 mass parts of this copolymer resin, Preferably it is 20-35 mass parts. If this is less than 15 parts by mass, the assisting of the breaking operation is not complete, and conversely, if it exceeds 40 parts by mass, the action of preventing the breaking operation of the binary copolymer resin that is inherently central is reduced, This is because the interlayer adhesion between the layer (A) and the layer (C) becomes worse.
The blending means is carried out by either dry blending or melt kneading. At this time, an antioxidant generally used in molding of olefin resin (for example, phenol, organic phosphite, aromatic) Addition of small amounts of amines and the like is preferred.

Next, the layer (A) made of the polyolefin resin will be described.
First, the layer (A) is a heat-seal layer in the case where the layers (A) are adhered and laminated between the layers (B) and heat-sealed together. -It also becomes a scratch-resistant layer due to contact with food when it becomes a type packaging bag. For example, when raw vegetables are enclosed and cooked in a microwave oven, It becomes a steam-resistant layer, and a peeling operation (for example, a natural peeling opening from the seal portion by an internal pressure applied by the generation of the heating steam or an artificial peeling opening at the seal portion) is performed. In this case, the operation is also transmitted in priority to the layer (B) and does not reach the layer (C).

The layer polyolefin resin forming the (A), especially propylene and C ₄ -C amorphous 2 and ₆ olefin terpolymer resin with propylene and a crystalline 2 ternary the olefin C ₄ -C ₆ It consists of a blend resin with a polymer resin. Here, amorphous and crystalline are distinguished by the presence or absence of a melting point, which is mainly determined by the copolymerization ratio of the olefin to propylene. When the copolymerization ratio of the olefin is small, it is inclined in the crystal direction, and when it is large, it is inclined in the amorphous direction.
The amorphous binary copolymer resin has a softening point (instead of having no melting point). The softening point (Vickers) is about 105 to 120 ° C., and the MFR is about 3.5 to 5.5 g / 10 min (190 ° C., 3.10 N).
One of the crystalline binary copolymer resins has a melting point of about 130 to 155 ° C, preferably 135 to 150 ° C. The MFR is about 8 to 15, preferably 10 to 14 g / 10 min (190 ° C., 21.18 N).

The amorphous binary copolymer resin in the blend resin effectively acts mainly on the lower temperature and the peeling operation in the case of heat sealing.
On the other hand, the crystalline binary copolymer resin effectively acts on better scratch resistance and steam resistance (giving appropriate heat resistance).
These effects become more effective at the next blend ratio, and are obtained as a synergistic effect. The amorphous binary copolymer resin is 50 to 75 mass%, preferably 55 to 65 mass%, and the crystalline binary copolymer resin 50 to 25 mass%, preferably 45 to 35 mass%.

  The heat seal temperature of the layer (A) by the two-type blend resin is about 10 to 20 ° C. lower than that of the four-layer film described in, for example, JP-A-2003-191407, and about 120 to 130 ° C. However, when the bag making speed is desired to be increased, heat sealing can be performed at a lower temperature, which is also effective from the bag making step.

In general, as a means for lowering the heat seal temperature, for example, a petroleum resin is often blended, but in the present invention, 5 to 45 parts by weight, preferably 15 to 15 parts by weight with respect to 100 parts by weight of the blended resin. By further blending 43 parts by mass of a single resin with any olefin of C _{4 to} C ₆ , the temperature can be lowered more effectively. This is because the seal temperature can be further lowered while maintaining the characteristics of the layer (A) of the two-type blend resin. Accordingly, the heat seal temperature decreases almost in proportion to the blend amount of the single resin and can be lowered to about 75 ° C., but it is not good that it exceeds 45 parts by mass. This is because the properties of the layer (A) by the two kinds of blends are adversely affected. If the amount is less than 5 parts by mass, the effect of reducing the temperature is not achieved.

Although it is a single resin based on any one of the C _{4 to} C ₆ olefins, preferred is C ₄ or C ₅ , more preferred C ₄ , that is, a polybutene-1 resin.
This polybutene-1 resin has a broader molecular weight range (for example, 25 to 3 million) than that of a normal polypropylene resin, and can reduce the heat seal temperature despite being crystalline. Even in this polybutene-1 resin, those having a molecular weight range corresponding to a melting point of 70 to 85 ° C. and an MFR of 3 to 5 g / 10 min (190 ° C., 21.18 N) are more preferable. Those in this range also have a lower hardness, a lower yield point (easily stretched), and an excellent wear resistance. It seems that this physical property leads to the action of maintaining the properties of the layer (A) by the two-type blend.

  The layer (A) of the above-mentioned 2-3 kinds of blend resin may be slightly blocked, but may be blocked, for example, together with PMMA fine powder, silica fine powder, etc. that are generally used as a blocking agent, and further, for example, sodium of organic acid It is safe to add a small amount of a nucleating agent such as salt or sorbitol.

As for the presence / absence of stretching in the laminated film, at least the base layer (D) needs to be stretched in the vertical and horizontal directions as described above. This is because it is necessary to obtain the above-mentioned operational effects to the maximum. The specific draw ratio is about 3 to 5.5 times in the longitudinal direction, preferably 3.5 to 5.0 times, about 7 to 13 times in the transverse direction, preferably 8.5 to 11 times. It is better to enlarge the horizontal direction.
On the other hand, the layer (C), the layer (B), and the layer (A) may be non-stretched, laterally and / or longitudinally, but preferably stretched laterally and / or longitudinally. When the stretching in the transverse and / or longitudinal direction is specifically shown, this may be in the same range as in the case of the base layer (D).
The stretching of the present laminated film is more preferably performed by positively stretching the transverse direction as a whole. With respect to the layer (C), the layer (B) and the layer (A) in the transverse direction stretching, the breaking action of the layer (B) and the layer (C) described above is more easily performed, and the layer (A ) Is also good for maintaining the heat seal strength of the comrades.

The layer thickness structure of the present laminated film is as follows.
First, the total thickness is preferably 25 to 60 μm. In each layer, the base layer (D) is thickest as 20 to 50 μm, and the layers (C) and (B) related to fracture are 1 to 2.5 μm (among those, the layer (C) is slightly thicker). The layer (A), which can also be referred to as a heat seal layer, is preferably 3 to 5 μm thicker than the layers (C) and (B). This layer thickness structure is also effective as a secondary aid for the above effect.

Next, means for producing the present laminated film will be described.
There are various methods for this means.
For example, as one of the methods, first, the crystalline polypropylene of the base layer (D) is film-formed with stretching in the longitudinal and transverse directions, and the layer (C ), Layer (B), method of laminating layer (A), as the two methods, after co-extrusion of the base layer (D) and layer (C), layer (B) and layer (A), A method of simultaneously stretching in the longitudinal and transverse directions, and as the three methods, first, the base layer (D) is formed with stretching in the longitudinal direction, and (C), layer (B) and layer (A) 3 are formed on one side thereof. Examples thereof include a method of coextruding the layer and then stretching the whole in the transverse direction.
In this molding, there are a T-die method for forming in a web shape and a round die method for forming in a tube shape, but the T-die method is preferred. Hereinafter, this T-die method will be mainly described.

The molding method mentioned as the three methods will be described more specifically.
First, the steps on the apparatus are as follows.
Four single-screw screen extruders are placed online. One of them is arranged at the head for the base layer (D). A single-layer T-die is set at the discharge port of the extruder, followed by a cooling roll 1, a heating roll (for longitudinal stretching with heating), and then a longitudinal stretching roll. Next, the layer (C), the layer (B), and the layer (A) are connected to a molding process.
The crystalline polypropylene base layer (D) stretched in the machine direction is immediately sent to the forming step for the layer (C), the layer (B) and the layer (A). A three-layer T die is set at the discharge port of the three extruders for the layer (C), layer (B), and layer (A) that are waiting, then the cooling roll 2, and then (horizontal A heating zone (tunnel) in which preheating, stretching, and heat setting (for directional stretching) are performed successively, and finally a winding roll is arranged. Here, the transverse stretching is performed by a tenter.
In addition, when performing a corona discharge process to this base layer (D), a corona discharge processing machine is arrange | positioned after this heating zone.

And it shape | molds as follows by the shaping | molding process connected online.
The polyolefin resins for the base layer (D), layer (C), layer (B), and layer (A) are supplied to a heated extruder. The heating temperature of the extruder (barrel) and the T-die is 180 to 230 ° C. First, when the crystalline polypropylene of the base layer (D) is extruded from the single-layer T die, it passes through the cooling roll 1. Immediately after that, it is sent to the next heating roll (about 140 to 150 ° C.). Here, the film is stretched in the longitudinal direction. The polypropylene substrate layer (D) stretched in the machine direction is fed under the waiting layer (C), the layer (B) and the three-layer T die for the layer (A). This three-layer T die is co-extruded from the three-layer T die onto the upper surface of the base layer (D) so that the layer (C) is the bottom, the layer (B) is the middle, and the layer (A) is the top. . Here, four layers are laminated and sent to the cooling roll 2. Subsequently, it is sent to a heating zone in which preheating, transverse stretching and heat setting are continuously performed, and transverse stretching and heat setting are performed. The preheating temperature is about 165 to 180 ° C, and the stretching and heat setting is about 160 to 170 ° C. Here, the base layer (D) is changed into a four-layer film extending in the vertical and horizontal directions, and the layers (C), (B) and (A) are extended in the horizontal direction.
If corona discharge treatment, the non-laminated surface of said substrate layer (D), about 1000~2000J / ^{m 2} is irradiated.
The four-layer film that has been finally wound is preferably subjected to aging treatment (35 to 50 ° C.) for about 1 to 2 days in order to remove internal distortion and the like, rather than immediately using it.

  The four-layer film thus obtained is easily processed and used in various packaging bags with the low-temperature heat-sealing property of the layer (A). For example, in a pillow-type packaging bag, using a vertical pillow-type packaging machine, align the layers (A) with the inside facing, heat-seal the vertical and lower sides to a certain width, and form a pillow bag with an upper opening. Made in a bag. When a pillow bag with an upper opening is made, food is placed and the upper opening is heat sealed to produce a product.

The corona discharge treatment is performed on the non-laminated surface of the base layer (D) for the following reason.
In general, the outer bag layer is printed by gravure printing, but for this printing. Increases wettability, improves printing ink (water-based, oil-based) and adhesion.
Although the printed printing layer may be left as it is, a protective layer may be laminated in order to further protect this layer from damage and the like.
This protective layer is generally laminated separately in the same manner as the base layer (D), such as longitudinally and laterally stretched polypropylene and PET films. This protective layer has a thickness of about 10 to 20 μm. If the base layer (D) becomes harder than necessary, the thickness of the base layer (D) itself is adjusted to be reduced. Is good.

Hereinafter, examples will be described together with comparative examples.
In addition, the check about the presence or absence of the burst by measurement of the heat seal strength etc. in this example, the bag making of a pillow type bag, food enclosure, and microwave heating was based on the following conditions.

● Heat seal strength etc. First, layer (A) surfaces of two samples cut to 10 mm x 150 mm are put together, leaving one end, and heated for 0.5 seconds under a seal temperature of 95 ° C or 128 ° C and a pressure of 2 kg. Fuse. And the film of the one end which is not melt | fused was extended to 180 degree | times, and it peeled at normal temperature and the tension | pulling speed of 200 mm / min using the R200 type | mold strograph made by Toyo Seiki Co., Ltd., and measured the seal strength. Together with this strength measurement, the peeled state was also checked.

● Pillow type bag making, food inclusion and presence or absence of rupture due to microwave heating Width of 420mm and cut in the longitudinal direction (longitudinal stretching of the base layer D) as a sample. Using a vertical pillow type packaging machine manufactured by Kawashima Seisakusho, first, the part that becomes the spine (pillar) and the part that becomes the bottom (bottom) under the following conditions are heat-sealed to form a pillow bag with an upper opening. Next, 200 g of fresh bean sprout washed with water from the upper opening is inserted, and finally the upper part is heat-sealed. Perform this operation continuously to make a total of 100 bags.
The heat seal width of the spine part, the lower part and the upper part is 15 mm each, the sealing temperature is 128 ° C., and the upper and lower cut length (corresponding to the vertical length of the bag) is 280 mm.
A total of 100 bags are made as described above, from which 5 bags are randomly extracted, and each bag is placed in a microwave oven and heated at 500 W for 5 minutes. During that 5 minutes, carefully observe from the outside, and check for the presence of a popping sound during that time. Take out and check the tearing of the 3-way seal.

Example 1
First, the following resins were used as the resin for each layer.
<For substrate layer (D)>
Crystalline polypropylene resin (Mitsui Chemicals, Inc., grade F102C, melting point 161 ° C., Pendat fraction 95.5%)
<For layer (C)>
Propylene / ethylene / butene 1 terpolymer (Sun Allomer Co., Ltd., Variety 5C30F, MFR5.5, Melting point 130 ° C.)
<For layer (B)>
Binary copolymer resin of ethylene / butene 1 (Mitsui Chemicals, Inc., grade Tuffmer P0180, MFR 4.5, hardness A67) with respect to 100 parts by mass, low density polyethylene (Tosoh Corporation, grade Petrocene 186, MFR 3.0, melting point A blended resin chip obtained by first mixing 25 parts by mass of (111 ° C.) and then melt-kneading this.
<For layer (A)>
Amorphous propylene / butene 1 binary copolymer resin (Mitsui Chemicals, Inc., Variety Tuffmer XL106, MFR 4.3, Vicat softening point 114 ° C.) 65% by mass and crystalline propylene / butene 1 binary copolymer resin ( Sun Aroma Co., Ltd. Varieties RC215M, MFR12, melting point 143 ° C.) 35 parts by mass of dry blend resin with 100 parts by mass, PMMA antiblocking agent 0.6 parts by mass and sorbitol nucleating agent 0.5 parts by mass are dried. Blended.

Next, a manufacturing apparatus was prepared.
Four single screw extruders are lined up in the order of the base layer (D), the layer (C), the layer (B), and the layer (A). Here, the barrel temperature for the substrate layer (D) is 180-220 ° C., and for the other three layers, the temperature is heated to 120-220 ° C. A single-layer T die (temperature: 200 ° C.) is attached to the base layer D, and a single three-layer T die (temperature: 215 ° C.) is attached to the three layers for co-extrusion of three layers. . A cooling roll 1 (50 ° C.) and a longitudinal stretching heating roll are disposed between the single-layer T die and the three-layer T die, and a cooling roll 2 (temperature 40 ° C.) is provided after the three-layer T die. ) And a heating zone (175 to 165 ° C.) for preheating to transverse stretching to heat setting, an acquisition winding roll for the finally obtained stretched four-layer film is arranged.

  First, the resin for the substrate layer (D) was extruded and cooled by the above apparatus to obtain a substrate layer (D) longitudinally stretched 4.6 times at 145 ° C., and this was fed under the three-layer T die. Then, the layer (C), the layer (B), and the layer (A) are co-extruded from the three-layer T die onto the upper surface of the base layer (D) that has been fed in, and the layers are in close contact with each other. Then, a transversely stretched tenter was fed into a heating zone disposed in the center. Here, after preheating to 175 ° C., the film was transversely stretched 10 times at 165 ° C., heat-set, wound on an acquisition winding roll, and this step was completed. Finally, the product was aged by leaving it in a room at 40 ° C. for 24 hours with the obtained winding roll.

  The total thickness of the obtained four-layer film is 30 μm, of which the substrate layer (D) is 23 μm, the layer (C) is 1.5 μm, the layer (B) is 1.7 μm, and the layer (A) is 3.8 μm. Yes, there was no blocking sign on the layer (A) surface, and the back surface had high transparency (4% in haze ratio).

Three samples were taken from the front, center, and rear positions of the four-layer film, and heat sealing was performed at a heat sealing temperature of 120 ° C., and the strength was measured. The intensity of the three samples was in the range of 3.00 to 3.15 N / cm.
And the peeling (breaking) state was observed with the magnifying microscope. The peeling occurred in the longitudinal direction between the layers (A), between the layers (A) and (B), and between the layers (B) and (C) (irregularly).

(Example 2)
In Example 1, a four-layer film molded under the same conditions and subjected to final aging except that a resin obtained by blending the following polybutene 1 was used as the resin for the layer (A). Obtained.
<Resin for layer (A)>
Amorphous propylene / butene 1 binary copolymer resin (Mitsui Chemicals, Inc., Variety Tuffmer XL106, MFR 4.3, Vicat softening point 114 ° C.) 65% by mass and crystalline propylene / butene 1 binary copolymer resin ( Sun Aroma Co., Ltd., varieties RC215M, MFR12, melting point 143 ° C.) and 35 parts by mass of dry blend resin 100 parts by mass, 25 parts by mass of polybutene 1 (Mitsui Chemicals, Inc. variety BL2481, MFR 4.0, melting point 75 ° C.) , PMMA resin (anti-blocking agent) 0.6 part by mass and sorbitol nucleating agent 0.5 part by mass.

  The total thickness of the obtained four-layer film was 30 μm, of which the substrate layer (D) was 22.5 μm, the layer (C) was 1.8 μm, the layer (B) was 1.7 μm, and the layer (A) was 4. It was 0 μm, there was no blocking sign on the layer (A) surface, the back surface was smooth, and the transparency was high (4% in haze ratio).

Then, three samples were taken from the front, center, and rear positions of the four-layer film, heat sealed at a heat seal temperature of 95 ° C., and the strength was measured. The strength of the three samples was in the range of 2.95 to 3.15 N / cm.
And the peeling part was observed with the magnified microscope. The separation is irregularly in the vertical direction between the layers (A), between the layers (A) and (B), and between the layers (B) and (C), as in Example 1. It was happening.

(Comparative Example 1)
In Example 1, the resin for layer (B) was molded under the same conditions except that a low-density polyethylene was not blended and a binary copolymer resin of ethylene / butene 1 was used alone, and final aging was also performed. A four-layer film for comparison was obtained.
The thickness structure of the obtained four-layer film was the same as that in Example 1. And 3 samples were carried out like Example 1, and it heat-sealed at 128 degreeC, and measured the seal strength at normal temperature. The result is 2.5 to 2.8 N / cm, and when the peeled state is observed, layer (A) and layer (B)
Most of the layers were peeled off.
The four-layer film had a haze ratio of 7% and was not as transparent as in Examples 1 and 2.

(Comparative Example 2)
In Example 1, instead of the crystalline propylene / butene 1 binary copolymer resin used as one of the layer (A) resins, a binary copolymer resin with ethylene containing propylene as a main component (melting point) Except for using 138 ° C., the film was molded under the same conditions, and the final aging was also performed to obtain a comparative four-layer film.
The thickness structure of the obtained four-layer film was the same as that in Example 1. And 3 samples were carried out like Example 1, and it heat-sealed at 128 degreeC, and measured the seal strength at normal temperature. The result was 2.7 to 2.9 N / cm. When this was heat sealed at 140 ° C., it was 3.2 to 3.4 N / cm.

(Example 3) (Experiment with a bag including a comparative example)
Using the four-layer films obtained in Examples 1 and 2 and Comparative Examples 1 and 2, the presence or absence of rupture due to the making of pyro-type bags, the inclusion of food, and the heating in a microwave oven was checked. The results for each bag were as follows. However, in Comparative Example 2, a bag sealed at a sealing temperature of 140 ° C. was used.

<In the case of Example 1>
After about 1.5 minutes after heating, it swelled greatly, and in about 2.2 to 2.2 minutes, the swell suddenly deflated without any bursting sound. Heating was continued for another 5 minutes. In the meantime, the bulge gradually decreased, but the bulge and deflation were repeated. I took it out and saw it torn. The center portion of the vertical heat seal portion was mainly broken and peeled off, and the base layer (D) had no such thing as a tear or crack.
In addition, there was no abnormality such as wrinkles or whitish throughout the bag.

<In the case of Example 2>
Heating was performed in the same manner as in Example 1. In about 1.9 minutes after heating, the swelling swelled suddenly without any bursting sound. Thereafter, the swelling and deflation were repeated in the same manner as in Example 1 (although the swelling was smaller than in Example 1). I took it out and saw it torn. Mainly the vertical heat seal part was wide open. Of course, the substrate layer (D) was not broken or cracked at all, but wrinkles were generated on the inner surface of the bag.

<In the case of Comparative Example 1>
Heating was performed in the same manner as in Example 1. After 1.3 minutes from the heating, it was taken out and the seal portion was observed. Not only the vertical seal portion but also the upper and lower seal portions were peeled off.

<In the case of Comparative Example 2>
Heating was performed in the same manner as in Example 1. The swelling suddenly deflated about 3 minutes after heating. The wilting did not sound like a plosive sound, but accompanied by a fine sound. After 4 minutes, it was taken out and the seal part was observed. Not only the vertical seal portion but also the upper and lower seal portions were partially peeled off. Although there was no influence on the base layer (D), the inner surface of the bag became slightly but whitish and some wrinkles were observed.
In addition, the raw cooking time of the raw bean sprouts was about 2.5 minutes, and the crunchy feeling remained and it was just a good time to eat.

In addition, using the four-layer film in Examples 1 and 2, a pillow-type bag is made in the same manner, and the body of scallops is enclosed in this, and it is rapidly frozen at −20 ° C. From the height of 1 m, It dropped on the concrete and checked for breakage resistance against cryogenic temperatures.
As a result, there was no damage such as cracks or tears in the heat seal parts as well as the bag body.

Claims (3)

For packaging, characterized in that a layer (C), a layer (B), and a layer (A) of a polyolefin resin described below are laminated in sequence from one side of a base layer (D) that is vertically and horizontally stretched with crystalline polypropylene. Polyolefin-based laminated film.
<Polyolefin resin for layer (C)>
Ternary copolymer resin of ethylene mainly composed of propylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (B)>
Blend resin of 15 to 40 parts by mass of low density polyethylene with respect to 100 parts by mass of binary copolymer resin of ethylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (A)>
Propylene and _C 4 -C ₆ olefins and amorphous binary copolymer resin 50 to 75 wt% propylene and _C 4 -C ₆ olefin crystalline binary copolymer resin 50 to 25 wt% and of of the Blend resin For packaging, characterized in that a layer (C), a layer (B), and a layer (A) of a polyolefin resin described below are laminated in sequence from one side of a base layer (D) that is vertically and horizontally stretched with crystalline polypropylene. Polyolefin-based laminated film.
<Polyolefin resin for layer (C)>
Ternary copolymer resin of ethylene mainly composed of propylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (B)>
Blend resin of 15 to 40 parts by mass of low density polyethylene with respect to 100 parts by mass of binary copolymer resin of ethylene and C _{4 to} C ₆ olefin <Polyolefin resin for layer (A)>
Propylene and _C 4 -C ₆ olefins and amorphous binary copolymer resin 50 to 75 wt% propylene and _C 4 -C ₆ olefin crystalline binary copolymer resin 50 to 25 wt% and of of the relative blends resin 100 parts by weight, alone resin according to any of the olefins _C 4 -C ₆ of 5 to 45 parts by weight A food packaging bag, wherein a food is enclosed and packaged in a pillow-type packaging bag made of the polyolefin-based laminated film for packaging according to any one of claims 1 and 2 .