JPS6016906B2 - Laminated stretched film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminated stretched film suitable for packaging processed meat products such as hams and sausages.

In the manufacturing process of processed meat products such as hams and sausages, seasoned and aged meat (hereinafter referred to as "processed meat") is inserted into a cylindrical packaging film with excellent oxygen barrier properties such as vinylidene chloride. The processed meat is boiled for several minutes to several hours at a temperature of 8,000 to 90 degrees Celsius, and then cooled to produce the product.The film used to package this processed meat has excellent oxygen barrier properties, and retains water well even after the boiling and cooling process. The processed meat inside must be held tightly. (Hereinafter, this property will be referred to as "stress suitability.") Various films for packaging these processed meats have been developed in the past, but a film that combines both the above-mentioned barrier properties and stress suitability has not yet been released on the market. Currently, the development of such a device is awaited.

The present invention relates to a laminated stretched film that has both of the above properties, and its gist is that a thermoplastic resin with excellent oxygen barrier properties is used as an intermediate layer, and on both sides thereof,
A laminated stretched film laminated with a thermoplastic resin other than the above, wherein the laminated stretched film has a shrinkage rate of 5% or more in both the longitudinal and transverse directions at 86°C,
9/ The expansion and contraction rate of the ground under tensile stress is within ±15% in both the vertical and horizontal directions, and the contraction return rate when the stress is removed at a temperature of 2 pi○ is vertical, This is a laminated stretched film characterized by having a temperature of 1° C. or higher in both the transverse direction and the transverse direction.

This will be explained in detail below.

In the present invention, the thermoplastic resin with excellent oxygen barrier properties has an oxygen permeability coefficient (measured by Seikaken method) of 1×10-11.
Examples of resins smaller than cc/k/k/sec/kHg include polyamide, polyethylene terephthalate, saponified ethylene-vinyl acetate copolymer, and polyvinyl alcohol.

If the oxygen permeability coefficient is larger than the above value, the amount of oxygen permeation will be large, making it unsuitable for preserving processed meat. In order to satisfy the requirements (hereinafter measured by ASTM D1434), the thickness of the film used must be increased, which adversely affects other physical properties.

Other thermoplastic resins to be combined with the above thermoplastic resins include ethylene-vinyl acetate copolymer polybutene-1, crosslinked polyethylene, and the like.

By using a thermoplastic resin with excellent oxygen barrier properties as the middle layer and laminating other thermoplastic resins on both sides, it protects the resin layer from damage, water absorption, peeling, etc., and preserves the processed meat inside. etc., it is extremely advantageous.

Moreover, the shrinkage rate, expansion/contraction rate, and shrinkage return rate as used in the present invention are as follows.

The direction in which the laminated film flows is defined as the longitudinal direction, and the direction perpendicular thereto is defined as the lateral direction.

Two reference points are set in each direction at room temperature, the distance between these reference points is L, and the distance between the reference points after heating it for 5 minutes at a temperature of 85 pm without load is L. , and 5 at a temperature of 85q0 under a tensile stress of 20k9/ground.
If the distance between the above reference points after heating for 1 minute is L2, and the above tensile stress is removed at a temperature of 20:00, and the distance between the above reference points after being left at this temperature for 5 minutes is -, then shrinkage occurs. Rate = 3≠3XI.

〇(%) Stretching rate F333XI.

〇(%) Contraction return rate i-hand L3×,oo(%) It is stipulated that

Processed meat is inserted into a cylindrical laminated stretched film made of the above combination, but in order to improve work efficiency during insertion, the inner diameter of the laminated cylindrical packaging film is made larger than the outer diameter of the processed meat. After insertion, the laminated packaging film is heated and shrunk by boiling to hold the processed meat.

Therefore, the heat shrinkage rate of the laminated stretched film used is 8.
The shrinkage rate when heated for 5 minutes at a temperature of 52°C is required to be 5% or more in both the vertical and horizontal directions.

If the heating shrinkage rate is less than 5%, the inner diameter of the laminated packaging cylindrical film cannot have a large allowance compared to the outer diameter of the processed meat, which reduces work efficiency when inserting the processed meat. During boiling in the post-process, the shrinkage of the film is insufficient and the processed meat cannot be held tightly, which is undesirable because it tends to sag at the binding part and tends to accumulate meat stains etc. in some areas. In order to keep this processed meat tight, the expansion/contraction rate and the shrinkage return rate are important factors in addition to the contraction rate.

In order to hold the processed meat tightly, the expansion/contraction rate should be within 15% in both the vertical and horizontal directions, preferably 0 to ±10%, and the shrinkage return rate should be 1% or more in both the vertical and horizontal directions. This is a necessary factor. If the expansion/contraction ratio exceeds -15% in both the vertical and horizontal directions, the stress during boiling shrinkage of the film will be too strong and breakage will easily occur at the binding part or the weak part of the film. Films with values exceeding this value have weak stress during boiling shrinkage and may stretch locally.
Easily deformed and loses product value.

Moreover, if the shrinkage return rate is less than 1%, it will not be able to follow the shrinkage due to cooling of the processed meat that occurs in the cooling process after boiling, and the product value will be impaired. In order to increase the shrinkage return rate to 1% or more,
The combination of resins to be used, the thickness of the resin film, the thickness composition ratio, etc. should be determined as appropriate.

In order to obtain a packaging film that has excellent oxygen barrier properties and is suitable for processing processed meat, a resin with good oxygen barrier properties is used as an intermediate layer, and coextrusion with the other resins mentioned above or coextrusion of each resin is carried out. The sheet is made into a laminated sheet by a known method, and the obtained laminated sheet is stretched in the longitudinal and lateral directions at a temperature range of not less than the secondary transition point of any of those resins and not more than the melting point of each of the resins, to a product of the longitudinal and lateral stretching ratios of 2 to 5Q. Magnification ratio is 0.5
What is necessary is just to carry out biaxial stretching in the range of -2.0.

Example Nylon 6-66 copolymer (66 nylon content, 15
Mol%, melting point 198 qo, secondary dislocation point 43 qo, oxygen permeability number 2.2 x 10-11 cc, skin/disgusting, sec, same day g) and low density polyethylene (melting point 110°C, secondary dislocation point -30°C) Each resin layer was simultaneously melt-extruded from a die so that it had a laminated structure of low-density polyethylene nonylon 6-6 copolymer/low-density polyethylene, and the surface of each resin immediately after melt-extrusion was treated with ozone. The layered film was simultaneously stretched 3 times in the transverse direction and 3 times in the longitudinal direction at a temperature of 85 qC to create a laminated stretched film.

A cylindrical case was made from each of these laminated and stretched films and the processed meat was filled therein, and then boiled at a temperature of 85 qC for 2 hours and cooled with 10 qo of water.

Table 1 shows the results when they were stored for one month under conditions of 5° C. and 70% relative humidity, along with the physical properties at the time of manufacture.
(Note) Thickness) indicates the thickness of each resin layer before stretching.LDP
E is low density polyethylene, PA6-66 is nylon 6-
Each resin layer of the 66 copolymer is shown.

Claims (1)

[Claims] 1 A stretched film in which a thermoplastic resin with excellent oxygen barrier properties is used as an intermediate layer and thermoplastic resins other than those mentioned above are laminated on both sides, and the shrinkage rate of the laminated stretched film at 85°C is 5 in both the longitudinal and transverse directions. % or more, and the expansion/contraction rate under a stress of 20 kg/cm^2 at a temperature of 85°C is in the longitudinal direction,
A laminated stretched film characterized in that it is within ±15% in both the transverse direction and has a shrinkage return rate of 1° C. or more in both the longitudinal and transverse directions when the stress is removed at a temperature of 20° C.