JP3440227B2 - Laminated stretch shrink film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated stretch shrink film, and more particularly to a heat seal as a stretch packaging or shrink packaging film mainly used for pre-packaging of retail products mainly for food. The present invention relates to a laminated stretch shrink film which is excellent in heat resistance, heat resistance, and low temperature shrinkability and has excellent shrink finish.

[0002]

2. Description of the Related Art In recent years, the demand for stretch films for packaging foods such as meats, seafood, vegetables, fruits and prepared foods has been further increasing with the expansion of supermarkets and convenience stores. Conventionally, the stretch film is most often used because the film made of plasticized polyvinyl chloride has excellent performances such as transparency and self-adhesiveness, but a large amount of plasticizer is used. As a result, the amount of water vapor permeation increases and the loss or deterioration of the packaged product is likely to occur, or the plasticizer easily migrates to the packaged product and is contaminated. Also, the film is formed during film forming or during packaging. There are problems of safety and hygiene and pollution such as generation of harmful hydrogen chloride gas at the time of fusing and further at the time of incineration.

For this reason, development of a film replacing plasticized polyvinyl chloride has been actively carried out by using polyethylene resins such as polyethylene and ethylene-vinyl acetate copolymer, polybutadiene resins and polypropylene resins. However, although the film obtained from the polyethylene-based resin or polypropylene resin has no problems of safety and health and pollution, it is not yet satisfactory as a stretch film.

On the other hand, with the diversification of items to be packaged, in the case of a lot of water such as pickles and tsukudani, the seal part is peeled off due to the adhesion of water only by the self-adhesive property, and the loss of the item to be packaged occurs. Further, there is a problem that the commercial value is lowered, and a material that can be sufficiently heat-sealed is desired. In addition, depending on the product to be packaged, there are cases in which wrinkles and tarmi remain and a sufficiently tight packaging finish cannot be obtained with only the stretchability, and a material having heat shrinkability is also desired.

Further, from the viewpoint of improving productivity and wrapping speed, the spread of automatic stretch wrapping machines, automatic stretch shrink wrapping machines, etc. in place of the hand wrap wrapping machines is remarkable together with the expansion of convenience stores and supermarkets. There is also a strong demand for improving the suitability of automatic packaging machines.

In order to solve the above-mentioned drawbacks of the stretch film, the inventors of the present invention have excellent transparency and luster, have appropriate gas permeability, have low water vapor permeability, and reduce the deterioration of the package. It has heat shrinkability and stretchability by using a polyethylene resin that does not have plasticizer migration and does not generate hydrogen chloride gas during combustion, and can be sufficiently heat-sealed with a hot plate, resulting in a good shrink-wrapping finish. For the purpose of providing a film, a multi-layer polyethylene stretch shrink film containing a specific linear low density polyethylene as a main component has been proposed (Japanese Patent Laid-Open No. 8-90737).

However, even in the above-mentioned multi-layer polyethylene stretch shrink film, the heat resistance is insufficient with respect to the suitability for an automatic packaging machine and the packaging finish, and there are the following problems. 1. For trays with a deformed bottom shape, such as raised bottom trays and trays with ribs, if the hot plate sealing temperature is raised, the film will melt above the heat resistant temperature before it can be sufficiently sealed and holes will be formed in the film. It opens (hereinafter, this state is called "burn"). 2. If the hot air temperature of the tunnel is increased to obtain a clean shrink-free finish for irregularly shaped items, burns will occur beyond the heat-resistant temperature before the finish is clean.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has a high heat resistance temperature, a wide temperature range for hot plate sealing and a wide temperature range for heat shrink tunnels, and is compatible with trays of various shapes. It is an object to provide a stretch shrink film that can be made.

[0009]

Means for Solving the Problems As a result of intensive studies to overcome the drawbacks of the above-mentioned stretch shrink film, the present inventors have drawn a laminated film of at least three layers having an inner layer made of a specific polypropylene resin. By improving the heat resistance of the film, it was possible to sufficiently heat seal the film, and it was found that a film with excellent shrinkage finish can be obtained in correspondence with trays of various shapes, and the present invention was completed. I arrived. That is, the present invention is to disperse ethylene-propylene rubber in a micron order in both surface layers composed of one or more polyethylene-based resins (A) selected from ethylene homopolymers and ethylene-based copolymers and a crystalline propylene polymer. The Vicat softening point of the polymer alloy formed is in the range of 60 to 75 ° C.
A polypropylene-based elastomer (B) having a melting peak temperature of 150 ° C. or higher measured by SC or an inner layer containing the same, and at a temperature lower than the melting point of (B) by 30 ° C. or higher,
The present invention relates to a laminated stretch shrink film which is stretched to a lengthwise and widthwise ratio of 2 or more and has a haze of 0.9% or less as measured by JIS-K7105 and is composed of at least three layers.

The present invention will be described in more detail below. The polyethylene-based resin (A) used in both surface layers in the present invention has a function of imparting heat-sealing property on a hot plate in an automatic packaging machine and anti-fogging property, and is a low-density polyethylene having long-chain branching. , Ethylene and propylene,
1 type or 2 types having 3 to 20 carbon atoms, preferably 4 to 8 carbon atoms, including butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, and decene-1. The melting peak temperature measured by linear low-density polyethylene and ultra-low-density polyethylene which are copolymers with the above α-olefins, amorphous or differential scanning calorimeter (hereinafter referred to as DSC) is 50 to 100. Low-crystalline ethylene and α-olefin copolymer having a temperature of 0 ° C., ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer, At least one selected from ionomer resins can be used.

Of these, linear low-density polyethylene and low-density polyethylene having a relatively low density are preferably used from the viewpoint that heat sealability at low temperatures is easily imparted, and
A linear low-density polyethylene having a relatively narrow molecular weight distribution produced by using a so-called metallocene catalyst (single-site catalyst) and the like can also be used from the viewpoint of suppressing excessive blocking and easily imparting a low-temperature heat-sealing property. The density of linear low-density polyethylene and low-density polyethylene is 0.890-
The range of 0.940 g / cm ³ is preferable, and the range of 0.
If it is less than 890 g / cm ³ , excessive blocking occurs, which is not preferable, and if it exceeds 0.940 g / cm ³ , the low-temperature heat-sealing property is deteriorated, which is not preferable. Further, the melt flow rate (hereinafter referred to as MFR, measured temperature 190
C., load 2.16 kg) is in the range of 0.1 to 10 g / 10 minutes, and if it is less than 0.1 g / 10 minutes, the workability is deteriorated, and if it exceeds 10 g / 10 minutes, excessive blocking occurs. Undesirably occurs.

Further low temperature heat sealing depending on packaging conditions
Ethylene-α-olefin copolymer
Mixed with linear low density polyethylene or low density polyethylene.
It can be used together. Ethylene used-α-
Examples of the olefin copolymer include ethylene and propylene.
Len, butene-1, pentene-1, hexene-1, 4-
Methylpentene-1, octene-1, decene-1 or
Copolymers with these mixtures may be mentioned, and preferably a copolymer
A copolymer with Ten-1 is used. Ethylene-α-o
The density of the reffin copolymer is 0.800 to 0.900 g /
cm ^Three Used in the range of 0.800 g / cm
^Three If it is less than 1, the effect of low temperature heat sealability becomes large.
However, blocking is not preferable, and 0.900 g
/ Cm^Three If it exceeds, the effect of low temperature heat sealability is small.
Unfavorable. Of ethylene-α-olefin copolymer
If the MFR is in the range of 0.1 to 20 g / 10 minutes,
If it is less than 0.1 g / 10 minutes, the workability is lowered, which is preferable.
No, there is excessive blocking when it exceeds 20 g / 10 minutes.
It is not preferable because it easily occurs. Ethylene-α-olefin
The ratio of the copolymer in both surface layers is 20 to 60 weight.
% Is preferable, and when it is 20% by weight or less, low temperature sealability is
It is not preferable because it is deficient, and if it is more than 60 wt%
The occurrence of king is severely undesirable.

Further, for both surface layers, an ethylene-vinyl acetate copolymer may be used alone or in combination with an ethylene-α-olefin copolymer. The ethylene-vinyl acetate copolymer has a vinyl acetate content of 3 to 28.
When the content is 3% by weight or less, the low-temperature sealing property and the tackiness are deteriorated, and when it is 28% by weight or more, blocking is seriously unfavorable. MFR of ethylene-vinyl acetate copolymer (190 ° C, 2.
16 kg) is used in the range of 0.3 to 10 g / 10 min. If it is less than 0.3 g / 10 min, the workability is lowered, and if it exceeds 10 g / 10 min, the stretching stability is lowered. Is not preferable.

On the other hand, in the case of a film used for applications such as a fusing and sealing type packaging machine which do not require low temperature heat sealability, a linear low density in the range of 0.92 to 0.94 g / cm ³ In the combination of polyethylene and an ethylene-α-olefin copolymer, ethylene-α-
An olefin copolymer having a surface layer ratio of 3 to 60% by weight can be used.

In the combination of surface raw materials, low density polyethylene or a linear low density polyethylene / ethylene / butene-1 copolymer is used in order to achieve a good balance between low-temperature sealability, tackiness and blocking resistance. An ethylene-α-olefin copolymer or an ethylene-vinyl acetate copolymer is preferably used.

The polypropylene-based elastomer (B) used in the inner layer in the present invention is polymer-alloyed during the polymerization to give ethylene in the crystalline propylene polymer.
Propylene rubber is finely dispersed in the order of microns. Thereby, having a heat resistance equivalent to that of a general crystalline propylene polymer, the temperature at which heat sealing is possible,
Also, the temperature of the shrink tunnel can be increased. Furthermore, since it has excellent softness, it is easy to impart stretchability, and since it can be uniformly stretched at a temperature lower than the melting point by 30 ° C. or more, it is possible to impart excellent low-temperature shrinkability. The transparency after stacking and stretching is obviously better than that of other general polypropylene resins.

The content of the crystalline propylene polymer in the polypropylene elastomer (B) is 25 to 65% by weight. If it is 25% by weight or less, heat resistance and elastic modulus are lowered, which is not preferable. If it is 65% by weight or more, tear strength,
Impact strength and transparency decrease, which is not preferable. MFR of polypropylene elastomer (B) (230 ° C,
2.16 kg) is 0.2 to 10 g / 10 minutes, and further D
The melting peak temperature measured by SC is 150 ° C or higher,
The Vicat softening point is preferably 60 to 75 ° C. If the melting peak temperature is less than 150 ° C, the heat resistance is lowered and the film is apt to be burned, which is not preferable. When the Vicat softening point is less than 60 ° C, the strength of the film is lowered, which is not preferable, and when it exceeds 75 ° C, low temperature stretching becomes difficult, which is not preferable. In the present invention, DS
The melting peak temperature is measured by C according to JIS K7121.
The procedure was as described.

Within a range that does not hinder the purpose of the present invention,
By mixing and using a general propylene polymer and a polypropylene elastomer (B), the ratio of polypropylene and ethylene-propylene rubber is changed to improve heat resistance,
It is also possible to adjust the elastic modulus.

By mixing the polyethylene resin (A) into the inner layer containing the polypropylene elastomer (B), or by using the polyethylene resin (A) composed of at least one kind as the inner layer. , Transparency and tear strength are easy to control. In this case, the proportion of the polyethylene-based resin (A) in the inner layer containing the polypropylene-based elastomer (B) is preferably 2 to 75% by weight, and if it is 2% by weight or less, the effect of improving the tear resistance cannot be obtained. It is not preferable, and when it is 75% by weight or more, transparency and heat resistance are deteriorated, which is not preferable. Examples of the polyethylene-based resin (A) mixed in the inner layer containing the polypropylene-based elastomer (B), or the polyethylene-based resin (A) composed of at least one type used as the inner layer include:
Low-density polyethylene with long chain branch, ethylene and propylene, butene-1, pentene-1, hexene-1, 4,
-Methylpentene-1, octene-1, and decene-1 having 1 to 3 carbon atoms, preferably 4 to 8 carbon atoms
Linear low-density polyethylene and ultra-low-density polyethylene which are copolymers of one or two or more kinds of α-olefins, amorphous or have a melting peak temperature measured by DSC of 50
~ 100 ° C low crystalline ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, ethylene-aliphatic unsaturated carboxylic acid copolymer, ethylene-aliphatic unsaturated carboxylic acid ester copolymer , At least one selected from ionomer resins. Among these, linear low-density polyethylene, low-density polyethylene, and ethylene-α-olefin copolymer, which is a copolymer of ethylene and butene-1, are preferably used from the viewpoint of easily imparting transparency and tear resistance. .

In the present invention, both surface layers X made of a polyethylene resin (A) and one inner layer Y containing a polypropylene elastomer (B) are formed into three layers (X / Y /
X) can also achieve the purpose, but it is also possible to newly provide an internal layer and have a structure of three or more layers. For example, X /
In the five-layer structure of Y / X / Y / X, both surface layers X are made of a polyethylene resin having a relatively low melting point in order to provide low temperature sealing property, and the inner layer X is made of a high crystal having a relatively high strength. The use of a highly flexible polyethylene resin has the advantage that film strength and low-temperature sealability can be achieved at the same time.

X1 / X2 / Y / X2 / X1 {X1, X2
In the constitution of polyethylene-based resin (A) having different properties from each other, low-temperature sealability can be imparted by using a polyethylene-based resin having a relatively low melting point for both surface layers X1, and both surface layers can be provided for inner layer X2 Use of at least one polyethylene resin having a higher melting peak temperature than the resin and a lower melting peak temperature than the polypropylene elastomer (B) of the inner layer Y further improves transparency and gloss, and is excellent in appearance. You can get a film.

In the present invention, scraps generated in the film manufacturing process or the like can be recovered and reused in the inner layer Y containing the polypropylene elastomer (B). In this case, the proportion of the polypropylene-based elastomer (B) in the inner layer Y is not particularly limited unless the characteristics of the film are deteriorated.

In the present invention, the antifogging property can be improved by adding a nonionic surfactant to at least one layer so that the content ratio with respect to one layer is 0.1 to 4.0% by weight. I can. The nonionic surfactant is not particularly limited as long as it is generally commercially available. For example, glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acid ester, propylene glycol. Fatty acid ester, sucrose fatty acid ester, citric acid mono (di or tri) stearyl ester, pentaerythritol fatty acid ester, trimethylolpropane fatty acid ester, polyoxyethylene glycerin fatty acid ester, polypropylene glycol fatty acid ester, polyoxyethylene alkylphenyl ether, poly Oxyethylene alkyl ether, polyoxypropylene polyoxyethylene block polymer, polyethylene glycol Polypropylene glycol, polyethylene oxide, alkyl diethanol amides, polyoxyethylene alkyl amines, ethylene oxide adducts of castor oil, one or two non-ionic surface active agent such as isopropyl alcohol
A mixture of two or more species is used. The amount of the nonionic surfactant blended in at least one layer or more is 0.1 to 4.0% by weight with respect to one layer, and if it is less than 0.1% by weight, antifogging property cannot be obtained. Even if it exceeds 4.0% by weight, the antifogging property is not improved and it is not preferable.

Further, in the present invention, by adding the tackifier (C) to at least one layer so that the content ratio with respect to all layers is 5 to 30% by weight, the tensile elastic modulus is increased and the hot plate seal is formed. It is also possible to improve the foldability when using a mold packaging machine and obtain a better hot plate seal finish. The tackifier (C) is not particularly limited as long as it is commercially available regardless of whether it is natural or synthetic. For example, rosin, rosin derivative, terpene resin, terpene phenol resin, aliphatic petroleum resin. , Acid modified C5
Petroleum resin, alicyclic petroleum resin, hydrogenated alicyclic petroleum resin,
Aromatic petroleum resin, hydrogenated aromatic petroleum resin, C5 / C9
One or more of tackifiers such as copolymer petroleum resin, styrene resin, alkylphenol resin, xylene resin and coumarone indene resin are used in combination,
Preferably, the terpene resin and the hydrogenated alicyclic petroleum resin are used alone or in combination. Since the terpene resin and the hydrogenated alicyclic petroleum resin have good compatibility with the resin used in the present invention, they improve transparency. The amount of the tackifier (C) added to at least one layer is 5 to 30% by weight, preferably 10 to 25% by weight, based on the total layers. If it is 5% by weight or less, it is not preferable because the tensile modulus is not improved.
It is not preferable because the antifogging property is lowered.

The thickness of the film of the present invention is not particularly limited, but it is preferably in the range of 5 to 30 μ, preferably 5 to 20 μ depending on the required film strength and hot plate sealing property.
The thickness of the surface layer is 1 μm considering the stability of heat sealing.
The above is preferable, the thickness ratio of each layer is such that the ratio of the layer X arranged on the surface or inside is 10 to 40%, the layer Y arranged inside, in consideration of strength as a multilayer film, stiffness, and heat resistance. Z ratio is 10-80%, 20-35%, respectively
Is preferred. In addition, the haze is preferably 0.9% or less from the viewpoint that the object to be packaged is easily identified and the commercial value is not reduced.

Naturally, additives such as lubricants, antiblocking agents, and antistatic agents are appropriately used for the purpose of providing effective effects, so long as they do not hinder the object of the present invention.

The laminated stretch shrink film of the present invention is produced by the following stretching method in order to impart sufficient low temperature shrinkability. That is, it is produced by a method in which a molten resin is extruded through an annular die, an unstretched raw fabric which has been rapidly cooled and solidified is reheated, and stretched at a temperature lower than the melting point of the polypropylene-based elastomer of the inner layer by 30 ° C. or more. The stretching ratio is 2 or more in the longitudinal and transverse directions, preferably 2.5 or more, and more preferably 3 or more. The film stretched as described above and taken out from the stretching device can be subjected to heat treatment such as heat setting and aging, if necessary. Further, a treatment such as corona discharge can be carried out for the purpose of causing the antifogging agent to bleed faster.

[0028]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Raw material resins used in Examples and Comparative Examples are shown below. A1: Linear low-density polyethylene (multi-site catalyst, density = 0.920 g / cm ³ , MFR (measurement temperature 190
C., load 2.16 kg) = 0.5 g / 10 min, melting peak temperature = 122 ° C.) A2: linear low density polyethylene (multisite catalyst, density = 0.910 g / cm ³ , MFR (190 ° C., 2.
16 kg) = 3.6 g / 10 min, melting peak temperature = 11
9 ° C.) A3: Linear low-density polyethylene (multi-site catalyst, density = 0.916 g / cm ³ , MFR (190 ° C., 2.
16 kg) = 1.2 g / 10 minutes, melting peak temperature = 12
0 ° C.) A4: ethylene-butene-1 copolymer (density = 0.88)
g / cm ³ , MFR (190 ° C., 2.16 kg) = 3.
6 g / 10 minutes, melting peak temperature = 70 ° C.) A5: ethylene-vinyl acetate copolymer (NUC-3758 manufactured by Nippon Unicar, vinyl acetate content 15% by weight, MF)
R (190 ° C., 2.16 kg) = 2.2 g / 10 minutes, melting peak temperature = 93 ° C., density = 0.94 g / cm ³ ) B1: polypropylene-based elastomer (Montel JPO
KS-081P, polypropylene content 35% by weight,
MFR (230 ° C, 2.16kg) = 0.8g / 10
Min, melting peak temperature = 165 ° C., density = 0.89 g / c
m ³ , Vicat softening point = 68 ° C.) B2: Polypropylene elastomer (Montel JPO
KS-021P, polypropylene content 55% by weight,
MFR (230 ° C, 2.16kg) = 0.8g / 10
Min, melting peak temperature = 165 ° C., density = 0.89 g / c
m ³ , Vicat softening point = 69 ° C.) B3: propylene-ethylene copolymer (MFR (230
C, 2.16 kg) = 2.6 g / 10 min, melting peak temperature = 143 ° C.) B4: isotactic polypropylene (homopolymer, MFR (230 ° C., 2.16 kg) = 15 g / 10
Min, melting peak temperature = 161 ° C., density 0.91 g / cm
³ , Vicat softening point = 150 ° C.) C1: terpene resin (softening point 125 ° C., number average molecular weight 7)
00, glass transition temperature 68 ° C.) C2: hydrogenated alicyclic resin (softening point 135 ° C., number average molecular weight 480, glass transition temperature 79 ° C.)

Further, each physical property measurement shown in this example was obtained by the following methods. (1) Haze: Measured according to JIS-K7105. (2) Gloss: Measured according to JIS-K7105. (3) 90 ° C. heat shrinkage rate A film cut into a square of 10 cm in length and width is sprinkled with talc powder, left for 15 minutes in an oven at 90 ° C., taken out and rapidly cooled, and then measured in length and width. , T
The shrinkage ratio of D was calculated. (4) Tensile elastic modulus: Measured according to JIS-K7127. (5) After putting 50 ml of water at 60 ° C. in a 100 ml beaker with antifogging property,
Cover and fix the top of the beaker with a film to prevent wrinkles. Then, the film was allowed to stand in a refrigerator at 5 ° C. for 1 hour, and the degree of cloudiness of the film was observed and evaluated according to the following criteria. ◯: No cloudiness at all. Δ: Some water droplets are attached, but the inside of the beaker is visible. X: The entire surface is cloudy and the inside of the beaker cannot be seen. (6) Suitable for pillow type automatic packaging machine 1. Fuselage-sealing type wrapping machine 200g of spaghetti is put into a polypropylene pasta tray (with a lid) having a width of 170mm, a length of 220mm, and a depth of 40mm. Omori Machine DW-00
According to 1), a packaging test was carried out at a packaging rate of 30 pieces / minute with 30 pieces, and the heat resistant temperature and appearance of the packaging machine were examined. The heat resistant temperature is the shrink tunnel setting temperature immediately before the whitening of the film or the reduction of the strength of the film starts. The heat resistant temperature was evaluated by increasing the tunnel temperature at a pitch of 5 ° C. 2. Hot plate seal type packing machine Pillow type stretch automatic packing machine equipped with hot plate seal and shrink tunnel by placing two oranges with a diameter of 5 cm on a foam polystyrene tray with width 120 mm, length 180 mm and depth 20 mm. A packaging test was carried out by (Omori Machine SP-300) to examine the heat resistant temperature. The heat resistant temperature is
The temperature of the hot plate was raised at a pitch of 5 ° C. so that the film on the bottom of the tray could be perforated.

Example 1 In a raw material resin having a compounding ratio shown in Table 1, 0.2% by weight of a nonionic surfactant polyoxyethylene (n = 20) sorbitan monopalmitate, diglycerin fatty acid ester 1.
3% of the composition for the surface layer and the composition for the core layer containing 8% by weight were added.
Each of them is melt-kneaded at 170 ° C. to 240 ° C. with a single extruder so that the thickness after stretching is 13 μm and the thickness ratio of each layer is surface layer: inner layer: surface layer = 1: 5: 1. The extrusion rate of the extruder was adjusted to push downward from the slit of the three-layer annular die maintained at 240 ° C. The diameter of the slit of the annular die is 75 mm and the slit gap is 0.8 m.
It was m. The extruded three-layered fused tubular film was attached directly below the die with an outer diameter of 76 mm
While sliding the outer surface of the cylindrical mandrel which circulates cooling water of ℃, the outside is cooled by water by passing through a water tank and cooled to room temperature and then taken off. Diameter: about 75 mm, thickness: 190
A tube-shaped unstretched film of μm was obtained. This tubular unstretched film was introduced into the tubular biaxial stretching device shown in FIG. 1 and expanded and stretched. At this time, the voltage and current of the annular infrared heater of the preheater 4 were adjusted to adjust the film temperature at the outlet of the preheater. Eight annular infrared heaters of the main heater 5 are divided into four sections to adjust the voltage and current of each heater to heat the film, and the air flowing along the bubbles from below the main heater is supplied to the low speed nip roll 2 3. Pressurized air is fed into the tubular film between the high-speed nip rolls 3, and the lengthwise direction is varied depending on the air and the peripheral speed ratio of the low-speed and high-speed nip rolls.
Bubble stretching was performed 0 times and 3.5 times in the lateral direction (area stretching ratio 14 times), and then heat treatment was performed to obtain a stretched film of about 13 μm. The stretchability was good, neither vertical movement of the stretching point nor swing of the stretching bubble was observed, nor was non-uniform stretching state such as necking observed. As shown in Table 1, the obtained film was excellent in transparency, gloss and antifogging property, and had a high heat shrinkage rate at 90 ° C. When a packaging test was performed using a pasta tray with a pillow type automatic stretch wrapping machine (fusing seal type), heat resistance was good and it was possible to raise the tunnel temperature, so the shrink finish was beautiful and practical. Was enough.

Comparative Example 1 As shown in Table 1, a laminated stretch shrink was prepared in the same manner as in Example 1 except that a mixture of two kinds of linear low density polyethylene was used for the surface layer and a propylene-ethylene copolymer was used for the inner layer. A film was produced. Drawability is good in all cases, there is no vertical movement of the drawing point or oscillation of the drawing bubble, and
Neither non-uniform stretched state such as necking was observed.
However, the obtained film was whitish and had a high heat shrinkage at 90 ° C. as shown in Table 1 and good anti-fog property, but was poor in transparency and gloss. When a packaging test was performed using a pasta tray with a pillow type automatic stretch wrapping machine (fusing seal type), the heat resistance temperature was low. It did not come to a practically satisfactory shrinkage finish.

Comparative Example 2 As shown in Table 1, a laminated stretch shrink film was produced in the same manner as in Example 1 except that linear low density polyethylene was used for the surface layer and the inner layer. The stretchability was not so good and a non-uniform stretched state such as necking was not observed, but vertical movement of the stretch point and swing of the stretch bubble occurred. As shown in Table 1, the obtained film had good transparency, glossiness and antifogging property, and had a high 90 ° C. heat shrinkage. When a packaging test was performed using a pasta tray with a pillow type automatic stretch wrapping machine (fusing seal type), the heat resistance temperature was low. It happened and the shrinkage finish was not practically satisfactory.

Example 2 With the raw material composition shown in Table 2, the surface layer raw material and the internal layer raw material were mixed with 5
The thickness ratio of each layer is melted and kneaded with an extruder of a stand, and the thickness ratio of each layer is: surface layer: inner layer (intermediate layer): inner layer (core layer): inner layer (intermediate layer): surface layer = 1: 3: 2: 3: A 13 μm-thick stretched film was obtained in the same manner as in Example 1 except that the extrusion amount was adjusted so as to obtain No. 1 and the extrusion was performed through the slit of the five-layer annular die. The stretchability was good, neither vertical movement of the stretching point nor oscillation of the stretching bubble was observed, and non-uniform stretching state such as necking was not observed. As shown in Table 2, the obtained film had good transparency, glossiness and antifogging property, and had a high 90 ° C. heat shrinkage. A pillow type stretch automatic wrapping machine (hot plate seal type) was used to perform a packaging test using a tray on which mandarin oranges were placed. As the heat-resistant temperature was high, the temperature of the hot plate could be raised, and sufficient sealing was possible. .

Example 3 A stretched film having a thickness of 13 μm was obtained in the same manner as in Example 2 except that the raw materials for the inner layers (intermediate layer and core layer) were changed as shown in Table 2. The stretchability was good, neither vertical movement of the stretching point nor oscillation of the stretching bubble was observed, and non-uniform stretching state such as necking was not observed. As shown in Table 2, the obtained film had good transparency, glossiness and antifogging property, and had a high 90 ° C. heat shrinkage. A pillow type stretch automatic wrapping machine (hot plate seal type) was used to perform a packaging test using a tray on which mandarin oranges were placed. As the heat-resistant temperature was high, the temperature of the hot plate could be raised, and sufficient sealing was possible. .

Example 4 Surface layer and internal layer (intermediate layer and core layer) The raw materials are shown in Table 2, and the thickness ratio of each layer is as follows: surface layer: inner layer (intermediate layer): inner layer (core layer): Inner layer (middle layer): surface layer =
A stretched film having a thickness of 13 μm was obtained in the same manner as in Example 2 except that the ratio was changed to 1: 3.5: 1: 3.5: 1. The stretchability was good, neither vertical movement of the stretching point nor oscillation of the stretching bubble was observed, and non-uniform stretching state such as necking was not observed. As shown in Table 2, the obtained film has good transparency, glossiness and antifogging property, and is 90 ° C.
The heat shrinkage rate was also high. A pillow type stretch automatic wrapping machine (hot plate seal type) was used to perform a packaging test using a tray on which mandarin oranges were placed. As the heat-resistant temperature was high, the temperature of the hot plate could be raised, and sufficient sealing was possible. .

Example 5 A stretched film having a thickness of 13 μm was obtained in the same manner as in Example 4, except that the raw materials for the inner layer (intermediate layer) were changed as shown in Table 2. The stretchability was good, neither vertical movement of the stretching point nor oscillation of the stretching bubble was observed, and non-uniform stretching state such as necking was not observed. As shown in Table 2, the obtained film had good transparency, glossiness and antifogging property, and
The heat shrinkage rate at ℃ was also high. A pillow type stretch automatic wrapping machine (hot plate seal type) was used to perform a packaging test using a tray on which mandarin oranges were placed. As the heat-resistant temperature was high, the temperature of the hot plate could be raised, and sufficient sealing was possible. .
In addition, since the tensile elastic modulus is high, the foldability is particularly good,
An excellent hot plate seal finish was obtained.

Example 6 Surface layer and inner layer (intermediate layer and core layer) The raw materials are shown in Table 3, and the thickness ratio of each layer is as follows: surface layer: inner layer (intermediate layer): inner layer (core layer): Inner layer (middle layer): surface layer =
A stretched film having a thickness of 13 μm was obtained in the same manner as in Example 2 except that the ratio was changed to 1: 1: 4: 1.: 1. The stretchability was good, neither vertical movement of the stretching point nor oscillation of the stretching bubble was observed, and non-uniform stretching state such as necking was not observed. As shown in Table 3, the obtained film was particularly excellent in transparency and glossiness, had good antifogging property, and had a high heat shrinkage rate at 90 ° C. A pillow type stretch automatic wrapping machine (hot plate sealing type) was used to perform a packaging test using a tray on which mandarin oranges were placed. As a result, the heat-resistant temperature was high, so the temperature of the hot plate could be raised, so that sufficient sealing was possible.

Comparative Example 3 A non-ionic surfactant was not added, and the raw materials for the inner layers (intermediate layer and core layer) were changed as shown in Table 3, and the same method as in Example 2 was applied to prepare a film having a thickness of 13 μm. A stretched film was obtained.
The stretchability was good, there was no vertical movement of the stretching point, no oscillation of the stretching bubble, and no non-uniform stretching state such as necking was observed. However, the obtained film was whitish, and as shown in Table 3, the heat shrinkage rate at 90 ° C. was high and the antifogging property was also good, but the transparency and gloss were not good. A pillow type automatic stretch wrapping machine (heat plate seal type) was used to wrap the tangerines on a tray, and the heat resistance temperature was low, so film piercing occurred when the temperature exceeded the heat resistance temperature before sufficient sealing was possible. did.

Comparative Example 4 A non-ionic surfactant was not added, and the raw materials for the inner layers (intermediate layer and core layer) were changed as shown in Table 3, and the same method as in Example 2 was applied to obtain a 13 μm thick film. A stretched film was obtained.
The stretchability was good, there was no vertical movement of the stretching point, no oscillation of the stretching bubble, and no non-uniform stretching state such as necking was observed. However, the obtained film was whitish, and as shown in Table 3, the heat shrinkage rate at 90 ° C. was high and the antifogging property was also good, but the transparency and gloss were not good. A pillow type automatic stretch wrapping machine (heat plate sealing type) was used to wrap the tangerines on a tray. The heat resistant temperature was low, and the film exceeded the heat resistant temperature and pierced the film before it could be sufficiently sealed. did.

[0040]

[Table 1] Heat resistant temperature: Tunnel temperature

[0041]

[Table 2] Heat resistance temperature = hot plate seal upper limit temperature

[0042]

[Table 3] Heat resistance temperature = hot plate seal upper limit temperature

[0043]

As described above, according to the present invention, particularly as a film for stretch packaging or shrink packaging mainly used for pre-packaging of retail products, which is mainly used for foods, "heat-sealing property, heat resistance, It has excellent low-temperature shrinkability, good transparency, and excellent shrinkage finish. "A laminated stretch shrink film consisting of at least three layers having both surface layers made of polyethylene resin and an inner layer containing polypropylene elastomer is Provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a tubular biaxial stretching device used in Examples and Comparative Examples.

[Explanation of symbols]

1. Unstretched raw 2. Low speed nip roll 3. High speed nip roll 4. Preheater 5. Main heater 6. Cooling air ring 7. Folding roll

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-9-254338 (JP, A) JP-A-10-272747 (JP, A) JP-A-9-154479 (JP, A) JP-A-6- 256539 (JP, A) JP 2000-280407 (JP, A) JP 2000-62113 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (9)

(57) [Claims] 1. One or more polyethylene resins (A) selected from ethylene homopolymers and ethylene copolymers.
And the Vicat softening point is in the range of 60 to 75 ° C., and the melting peak temperature measured by DSC is 15
Polymer alloyed polypropylene-based elastomer (B) in which ethylene-propylene rubber is dispersed in a crystalline propylene polymer at 0 ° C. or higher in the order of micron
Or, having an inner layer containing it, the melting point of (B) is 30 ° C.
JIS-K stretched at least twice the length and width at low temperature
Laminated stretch shrink film consisting of at least three layers having a haze measured by 7105 of 0.9% or less. 2. The inner layer comprises 98 to 25% by weight of a polypropylene elastomer (B) and a polyethylene resin (A).
The laminated stretch shrink film according to claim 1, which is a mixture of 2 to 75% by weight. 3. A polyethylene resin (A) constituting both surface layers comprises 40 to 97% by weight of low-density polyethylene having a density of 0.920 to 0.940 g / cm ³ , and 0.80.
Ethylene-α- with a density of 0 to 0.900 g / cm ^3.
Consisting of a mixture of 60 to 3% by weight of olefin copolymer,
The laminated stretch shrink film according to claim 1. 4. The laminated stretch shrink film according to claim 1, wherein the polyethylene-based resin (A) constituting both surface layers comprises an ethylene-vinyl acetate copolymer having a vinyl acetate content of 3 to 28% by weight. . 5. The inner layer comprises three or more layers in which a layer made of a polyethylene resin (A) is sandwiched between polypropylene elastomer (B) or a layer containing the same.
5. The laminated stretch shrink film according to any one of 4 to 4. 6. The inner layer comprises three or more layers in which a layer made of a polypropylene elastomer (B) is sandwiched between layers containing a mixture of a polyethylene resin (A) and a polypropylene elastomer (B). The laminated stretch shrink film according to any one of 1 to 4. 7. A polyethylene resin (A) in which the inner layer is a layer containing a mixture of a polyethylene resin (A) and a polypropylene elastomer (B) and is different from both surface layer components.
The laminated stretch shrink film according to any one of claims 1 to 4, which is composed of three or more layers sandwiched between the layers. 8. The laminate according to claim 1, wherein the nonionic surfactant is blended in at least one layer such that the content ratio with respect to one layer is 0.1 to 4% by weight. Stretch shrink film. 9. The content ratio to all layers is 5 to 30% by weight.
The laminated stretch shrink film according to any one of claims 1 to 8, wherein the tackifier (C) is blended in at least one layer such that