JPH0450904B2 - - Google Patents

Description

[Detailed description of the invention]

(1) Industrial Application Field The present invention relates to a film for stretch packaging of foods. (2) Conventional technology In recent years, films for so-called pre-packages, in which foods such as fruits and vegetables, fresh fish, fresh meat, and side dishes are placed directly or on plastic trays and then stretch-wrapped with film, have been used for safety and health reasons. Due to these problems, the development of products using ethylene resins such as low-density polyethylene resins and ethylene-vinyl acetate copolymer resins in place of conventional polyvinyl chloride resins is being actively conducted. (3) Problems to be solved by the invention However, low-density polyethylene resin films such as low-density polyethylene resin and ethylene-butene-1 copolymer resin, which are already known for use in stretch packaging, are hard and difficult to stretch. Therefore, even if the food is stretched forcibly, it will only tear or elongate unevenly.Furthermore, the tray holding the food to be packaged will be deformed or destroyed, causing wrinkles and making it difficult to obtain the tightening force necessary for packaging. There is a problem that it is not possible to package it with commercial value. Furthermore, in the case of ethylene-vinyl acetate copolymer resin films, if the vinyl acetate content, melt flow rate, etc. are appropriately selected, the problems mentioned above with low-density polyethylene resin films can be solved; If the food to be packaged has sharp edges or if the tray on which the food is placed has sharp edges, stretching the film while wrapping may cause the film to hit these sharp corners and tear. In addition, during the logistics process for stretch packaging, if small tears occur in the film due to contact with various objects, those tears may propagate and expand to become larger tears, which may cause problems when the film is unresolved. There is a problem with wrapping it up. Furthermore, although the above-mentioned laminated film of low-density polyethylene resin film and ethylene-vinyl acetate copolymer resin film does not have the problem of being hard and difficult to stretch, it does not have the above-mentioned problem of being easily torn during packaging and distribution processes. ,
Particularly when the film thickness is reduced to 6 to 40 microns, this is not a sufficient solution. The present invention was made in view of the above-mentioned conventional problems with stretch packaging films for food products, and its purpose is to provide suitable slipperiness,
Not only does it have self-adhesiveness, sufficient thermal adhesion and transparency, but it also has excellent extensibility and flexibility.
In particular, it is an object of the present invention to provide a thin stretch packaging film having extremely excellent tear strength. (4) Means for Solving the Problems The stretch packaging film of the present invention is a random copolymer of propylene, ethylene, and an α-olefin having 4 to 8 carbon atoms; - A propylene-α-olefin random copolymer selected from random copolymers with olefins, wherein the α-olefin content in the copolymer is 4 to 19% by weight, and the melt flow rate is is 1-10g/10min of propylene-α
- Both sides of a layer with a thickness of 2 to 10 microns mainly composed of olefinic random copolymer resin with a vinyl acetate content of 5 to 25% by weight and a melt flow rate of 0.3
It is a laminated film with a thickness of 6 to 40 microns and has a three-layer structure in which layers mainly composed of ethylene-vinyl acetate copolymer resin of ~5 g/10 min are laminated. That is, the stretch packaging film of the present invention is
A layer containing an ethylene-vinyl acetate copolymer resin as a main component is laminated on both sides of a layer containing a propylene-α-olefin random copolymer resin as a main component. This propylene-α-olefin random copolymer resin includes propylene, ethylene, and α-olefin having 4 to 8 carbon atoms, such as butene-1, hexene-1, 4-methylpentene-
1, octene-1, etc., or a random copolymer of propylene and α-olefin, in which the proportion of α in these copolymers is - an olefin content of 4 to 19% by weight, preferably 4 to 19% by weight;
16% by weight, the melt flow rate at 230℃ is 1
~10g/10min, preferably 1~8g/10min of a propylene random copolymer. The propylene-α-olefin random copolymer resin is used here because conventional ethylene-α-olefin copolymer resins, for example, can be used for thin stretch packaging films such as those of the present invention. This is because the strength is inferior, and the reason why α-olefins are limited to those with carbon numbers of 4 to 8 or used in combination with ethylene is because the content is one of the requirements for a stretch packaging film with excellent tear strength. This is because the resin can be stably produced. In addition, α- of this copolymer resin
If the olefin content is less than 4% by weight, extensibility and flexibility will be insufficient, and improvement in tear strength will also be insufficient.
If it exceeds 19% by weight, it becomes difficult to obtain sufficient tightening force. Furthermore, the production of the resin itself becomes difficult. Further, if the melt flow rate is less than 1 g/10 minutes, the elongation will be small, and if it exceeds 10 g/10 minutes, the breaking strength will be small, and in both cases, extensibility becomes a problem. The propylene-α-olefin random copolymer resin may contain ethylene-propylene copolymer, ethylene-
10 to 50% by weight of resin and rubber made of butene-1 copolymer, polybutene-1, etc., ethylene-vinyl acetate copolymer resin, etc., and additives as described below can be blended. In addition, ethylene-laminated on both sides of the propylene-α-olefin random copolymer resin
The vinyl acetate copolymer resin has a vinyl acetate content of 5 to 25% by weight, preferably 10 to 20% by weight, and a melt flow rate at 190°C of 0.3 to 5 g/
10 minutes, preferably 1 to 3 g/10 minutes. If the vinyl acetate content is less than 5% by weight, extensibility and flexibility will be insufficient, and sufficient self-adhesiveness will be difficult to obtain. It becomes difficult to obtain. Also, the melt flow rate is 0.3
If it is less than g/10 minutes, the elongation will be small, and if it exceeds 5 g/10 minutes, the breaking strength will be small, and in either case, extensibility becomes a problem. The ethylene-vinyl acetate copolymer resin includes:
In order to impart appropriate slipperiness, self-adhesiveness, antifogging properties, and antistatic properties, for example, carbon atoms with a carbon number of 1 to
12, an aliphatic alcohol fatty acid ester which is a compound of an aliphatic alcohol having preferably 1 to 6 carbon atoms and a fatty acid having 10 to 22 carbon atoms, preferably 12 to 18 carbon atoms, specifically monoglycerin oleate, polyglycerin Oleate, glycerin triricinolate, glycerin acetyl ricinosheet, methyl acetyl ricinolate, ethyl acetyl ricinosheet, butylacetyl ricinosheet, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, polyethylene glycol sorbitan laurate, etc. , as well as polyalkylene ether polyols, specifically,
It is preferable to blend polyethylene glycol, polypropylene glycol, etc. in an amount of 0.5 to 10% by weight, preferably 2.5 to 5% by weight. In addition, in the present invention, the propylene-α-
The reason why we decided to laminate the layer containing the ethylene-vinyl acetate copolymer resin as the main component on both sides of the layer containing the olefin-based random copolymer resin as the main component was because of the propylene-α-olefin random copolymer resin. This is because a single-layer film made of a composite resin has poor extensibility and flexibility, and a single-layer film made of an ethylene-vinyl acetate copolymer resin has poor tear strength. The stretch packaging film of the present invention having the above structure is obtained by laminating the two types of resins using a plurality of extruders by a known method such as a coextrusion method using inflation molding or T-die molding, or an extrusion lamination method. molded. In order to obtain a film with a sufficient balance of mechanical strength such as tear strength in the longitudinal and transverse directions, a coextrusion method using inflation molding is preferred, and the blow ratio at that time is preferably 3 to 7. The thickness of the film of the present invention is 6 to 40μ, preferably 8 to 20μ, of which the layer mainly composed of propylene-α-olefin random copolymer resin is 2 to 10μ, preferably 2 to 8μ, Both surface layers each containing ethylene-vinyl acetate copolymer resin as a main component have a thickness of 2 to 15 microns, preferably 3 to 6 microns. (5) Effect The stretch packaging film of the present invention is a random copolymer of propylene, ethylene, and an α-olefin having 4 to 8 carbon atoms, or a random copolymer of ethylene and an α-olefin having 4 to 8 carbon atoms. A propylene-α-olefin random copolymer selected from polymers with an α-olefin content of 4 to 19% by weight and a melt flow rate of 1 to 19% by weight.
Since a propylene-α-olefin random copolymer resin of 10 g/10 min is used, it has excellent extensibility and flexibility, and especially extremely excellent tear strength. Ethylene-vinyl acetate copolymer resin, which has excellent extensibility and flexibility and has a vinyl acetate content of 5 to 25% by weight, is laminated on both sides of the copolymer resin layer, so it has appropriate slipperiness. , has self-adhesive properties. (6) Examples Example 1 Ethylene content 3.1% by weight, propylene content
82.2% by weight, butene-1 content 14.7% by weight, 230
Propylene-ethylene-butene-1 random copolymer resin 90% by weight, melt flow rate at °C 5.0 g/10 min, butene-1 content 15% by weight, 190 °C
A resin composition consisting of 10% by weight of ethylene-butene-1 copolymer with a melt flow rate of 4.0 g/10 min was heated to 185
Meanwhile, vinyl acetate content 15% by weight, kneaded at °C.
Melt flow rate at 190°C: 2.0 g/10 min Ethylene-vinyl acetate copolymer resin 97% by weight, polyethylene glycol (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.,
A resin composition consisting of 2% by weight of PEG300) and 1% by weight of sorbitan laurate (Rikemar L300, manufactured by Riken Vitamin Co., Ltd.) was kneaded at 160°C using an extruder with a diameter of 50 mm and a L/D of 25. was fed into an annular three-layer die, and a 5μ thick layer containing propylene-ethylene-butene-1 random copolymer resin as the main component was coated on both sides with ethylene-vinyl acetate copolymer resin as the main component. The die temperature was 185℃, the blow ratio was
A stretch packaging film having the physical properties shown in the table and a total thickness of 13 μm was produced by inflation molding at a temperature of 5.0. Using this film, meat, fish, and vegetables were placed on trays made of foamed polystyrene, stretched polystyrene, and impact-resistant polystyrene, and wrapped using a stretch automatic packaging machine, A22 manufactured by Fuji Pack System Co., Ltd. However, with any of the trays, packaging can be done smoothly and stably without tearing at the tray corners, etc., and the packaging has a good commercial value with no wrinkles or looseness, excellent transparency, and a sense of tightness. It was hot. Comparative Example 1 In place of the propylene-ethylene-butene-1 random copolymer resin in Example 1, the ethylene content was 7.1% by weight, and the melt flow rate at 230°C
A stretch packaging film having the physical properties shown in Table 1 was produced in the same manner as in Example 1, except that a 1.0 g/10 minute propylene-ethylene random copolymer resin was used. When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Comparative Example 2 In place of the propylene-ethylene-butene-1 random copolymer resin in Example 1, ethylene content was 5.2% by weight, melt flow rate at 230°C
A stretch packaging film having the physical properties shown in Table 1 was produced in the same manner as in Example 1, except that a propylene-ethylene random copolymer resin of 6.1 g/10 min was used. Using this film, stretch wrapping was carried out in the same manner as in Example 1, and good results were obtained. Comparative Example 3 In place of the propylene-ethylene-butene-1 random copolymer resin in Example 1, the ethylene content was 4.4% by weight, and the melt flow rate at 230°C
A stretch packaging film having the physical properties shown in the table was produced in the same manner as in Example 1, except that a propylene-ethylene random copolymer resin of 5.3 g/10 min was used. When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Example 2 In place of the propylene-ethylene-butene-1 random copolymer resin in Example 1, propylene-hexene-1 was used with a hexene-1 content of 13.2% by weight and a melt flow rate of 1.5 g/10 min at 230°C.
A stretch packaging film having the physical properties shown in the table was produced in the same manner as in Example 1, except that a random copolymer resin was used. When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Example 3 70% by weight of the same propylene-ethylene-butene-1 random copolymer resin used in Example 1;
A resin composition whose main component is the same ethylene-vinyl acetate copolymer resin used as the surface layer in Example 1.
A stretch packaging film having the physical properties shown in the table was produced in the same manner as in Example 1, except that a resin composition containing 30% by weight was used as the intermediate layer. When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Example 4 50% by weight of the same propylene-ethylene-butene-1 random copolymer resin used in Example 1,
Polybutene-1 (manufactured by Adeca Argus Chemical Co., Ltd.) with a melt flow rate of 1.8 g/10 min at 190°C.
WITRON0220) 42% by weight, 5% by weight of the same ethylene-butene-1 copolymer used in Example 1, 2% by weight of the same polyethylene glycol also used in Example 1, and 1% by weight of sorbitan laurate. Example 1 except that the intermediate layer was
A stretch packaging film having the physical properties shown in the table was produced in the same manner as above. When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Example 5 A stretch packaging film having the physical properties shown in the table was produced in the same manner as in Example 1, except that the same propylene-hexene-1 random copolymer resin used in Example 2 was used alone for the intermediate layer. . When this film was used for stretch wrapping in the same manner as in Example 1, good results were obtained. Comparative Example 4 Ethylene-butene-1 content 9.0% by weight, melt flow rate 2.0g/10 min at 190°C
A film with the physical properties shown in the table was produced in the same manner as in Example 1, except that a single random copolymer resin was used for the intermediate layer, and when it was stretch-wrapped, the phenomenon of occasional tearing at the tray corner was observed. Admitted. Comparative Example 5 In place of the propylene-ethylene-butene-1 random copolymer resin in Example 1, ethylene content was 2.5% by weight, melt flow rate at 230°C
A film with the physical properties shown in the table was produced in the same manner as in Example 1, except that a propylene-ethylene random copolymer resin of 8.5 g/10 min was used, and when stretch packaging was performed, the film was transparent. Not only did it have poor properties, but it was also hard and difficult to stretch, causing uneven stretching. Example 6 A resin composition consisting of 75% by weight of the propylene-ethylene-butene-1 random copolymer resin used in Example 1 and 25% by weight of polybutene-1 used in Example 4 was used for the intermediate layer. A stretch packaging film having the physical properties shown in the table was produced in the same manner as in Example 1, and stretch packaging was carried out. The results are shown in the table along with the physical properties of the film. Comparative Example 6 Comparative Example except that a resin composition consisting of 75% by weight of the propylene-ethylene random copolymer resin used in Comparative Example 5 and 25% by weight of polybutene-1 used in Example 4 was used for the intermediate layer. A stretch packaging film having the physical properties shown in the table was produced in the same manner as in 5, and stretch packaging was performed. The results are shown together with the physical properties of the film.

[Table] (7) Effects of the Invention The stretch packaging film of the present invention has appropriate slipperiness and self-adhesiveness, as well as sufficient thermal adhesiveness and transparency, as well as extensibility and It has excellent flexibility and, even though it is thin, has excellent tear strength.

Claims (1)

[Claims] 1 Propylene, ethylene and carbon number 4-8
A propylene-α-olefin random copolymer selected from a random copolymer with α-olefin of α-olefin content in the polymer is 4 to 19% by weight
Then, a layer containing 5 to 25% by weight of vinyl acetate was applied on both sides of a layer with a thickness of 2 to 10μ mainly composed of a propylene-α-olefin random copolymer resin with a melt flow rate of 1 to 10 g/10 minutes. A stretch packaging film having a three-layer structure laminated with layers mainly composed of ethylene-vinyl acetate copolymer resin having a melt flow rate of 0.3 to 5 g/10 minutes, and having a thickness of 6 to 40 μm.