JPH01297243A - Heat-shrinkable composite stretched film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heat-shrinkable composite stretched film that can be suitably used for vacuum packaging raw meat and has excellent low-temperature shrinkability and finished packaging appearance.

(Prior art and its problems) As a vacuum shrink packaging film for raw meat such as chilled meat,
A composite stretched film is used in which the intermediate layer is a heat-shrinkable film using polyvinylidene chloride resin or a polyamide resin such as nylon 6, and the inner and outer layers are laminated with various resins and then stretched. The film with the above-mentioned polyamide resin as an intermediate layer has excellent strength, but even if the film is heat-shrinked after vacuum packaging raw meat, the film itself will have fine wrinkles and its adhesion to the surface of the raw meat will be poor. There was a problem with the appearance and storage of the packaged product, as drips from the raw meat were observed to migrate into the wrinkled area.

In particular, in recent years, the heating temperature during vacuum shrink packaging has been set to a lower temperature for the purpose of suppressing the growth of bacteria and reducing energy consumption. The above-mentioned problems were more likely to occur with these films.

An object of the present invention is to provide a heat-shrinkable composite stretched film with excellent shrinkage characteristics at low temperatures.

(Means for Solving the Problems) In order to achieve the above object, the composite stretched film of the present invention uses a polyamide resin having a specific composition, and the gist thereof is: an outer layer and an inner layer. is a polyolefin layer, and a polyamide resin layer is provided between the two layers. It consists of a mixture with a polyamide resin (6T/6I nylon) formed by polycondensing acid and/or isophthalic acid, and the mixing ratio of the polyamide resin is (6/66 nylon): (6T/6I nylon); 7
The heat-shrinkable composite stretched film is characterized in that the content is in the range of 0 to 95% by weight: 30 to 5% by weight.

The polyamide resin used in the intermediate layer of the composite stretched film of the present invention is mainly composed of a copolymerized polyamide resin of 6 nylon and 66 nylon (6/66 nylon), and other components include hexamethylene diamine, terephthalic acid, and/or isophthalic acid. It is a polyamide resin (6T/6I nylon) obtained by polycondensation.

The above 6/66 nylon is mainly made of 66 nylon.
A material having a nylon content of 10 to 25% by weight can be suitably used. In addition, as 6T/6I nylon, we also use Chinoku 6T) which is made by polycondensing hexamethylene diamine and terephthalic acid, 6I) which uses isophthalic acid as the acid component, and nylon which uses the above acid components in combination. can.

The mixing ratio of the above polyamide resin is 6/66 nylon 7
6T/6I nylon, which is another component, must be in the range of 5 to 30% by weight relative to 0 to 95% by weight, and if 6T/6I nylon is less than 5% by weight, the shrinkability at low temperatures cannot be improved. Moreover, if the amount exceeds 30% by weight, there is a problem that the film is likely to break during the stretching process.

The thickness of this polyamide resin layer may be in the range of 5 to 20μ, preferably 10 to 15μ; if it is less than 5I, the stretchability during film formation will be poor, and if it exceeds 20μ, the flexibility of the film will be lost, which is disadvantageous. It is.

The intermediate layer may also be a combination of the above polyamide layer and an ethylene-vinyl acetate saponified material layer in order to improve gas barrier properties, and the ethylene-vinyl acetate saponified material may have an ethylene content of 30 to 60 mol%. , or the degree of saponification is 95 mol % or more, and the layer thickness is preferably in the range of 3 to 7 μm. Furthermore, the intermediate layer can also be used in combination with other gas barrier resins or resins with other properties.

As the polyolefin used for the outer layer and the inner layer, ionomer resins, polyethylene, copolymers of ethylene and other components, such as ethylene-vinyl acetate copolymers, ethylene-propylene copolymers, etc. can be used. The thickness of the inner layer is preferably 25I or more; if it is less than 25μ, there is a drawback that the film is likely to be broken through by small bones or cartilage remaining on the surface of raw meat.

The general method for producing the film of the present invention is to form a film by laminating the layers by coextrusion and then stretching by the inflation method. The stretching ratio is 2.0 to 2.0 in both the longitudinal direction (direction in which the film is taken) and the transverse direction (direction perpendicular to the above direction).
It is best to stretch within the range of 3.5 times, and the stretching ratio is 2°0.
If it is less than 3.5 times, the shrinkage rate will be low and the adhesion will be poor.
If it exceeds twice that, the film tends to break during film formation, which is inappropriate. The stretching temperature can be suitably carried out within the range of 80 to 110°C.

By appropriately selecting stretching conditions within this range, the film of the present invention can achieve high shrinkage at 75°C of 30% or more in both the longitudinal and transverse directions, which is difficult to achieve with conventional polyamide composite films. be able to.

Hereinafter, the present invention will be explained by examples.

(Example) Ethylene with a vinyl acetate content of 5 mol% was used in the exception layer and inner layer.
The intermediate layer is a saponified ethylene-vinyl acetate copolymer R (4μ) with an ethylene content of 45 mol% and a saponification degree of 99 mol%, and a polyamide resin layer with the contents shown in Table 1. (12μ), laminated in a coextrusion annular die (set temperature 240°C), and then stretched by an inflation method to form a film. The stretching ratio is shown in Table 1, and the stretching temperature is set according to the optimum stretching temperature condition (N
90°C for O1-4 and 7, 130° for NO5 and 6
Obtain a tube with a folded diameter of 50 cm as C).

The obtained tube was bottom-sealed and the folded diameter was 50cn+.
A bag having a length of 60C11 was prepared, and after filling the bag with about 7 kg of chilled beef, the opening was impulse sealed and vacuum packaging was performed using a vacuum packaging machine manufactured by Multivac.

Next, each package was heat-shrinked in a hot water shower at 75°C.

Table 1 shows the evaluation results of "shrinkage rate" and "appearance" of each of the above films.

"Shrinkage rate" is calculated using a film that has been stored at 30°C for 20 days after film formation, and the length before shrinkage is L, and the film is placed in a hot water bath at a temperature of 75°C or 85°C. The length of the film after shrinkage was measured (L-L
/L) x 100.

"Appearance" was determined by observing the appearance of each of the above packages after storing them at 5°C for 43A. Good appearance with no drips or wrinkles observed (O
), and those with poor appearance due to dripping or wrinkles were rated (Δ).

*6-66Ny: A copolymer of nylon 6 and nylon 66 with a nylon 66 content of 20% by weight.

*26 T / 6 I N y ; A polyamide resin made by polycondensing hexamethylene diamine with a content of 20% by weight of 6 T nylon, terephthalic acid, and isophthalic acid.

*36-6TNy; A copolymer of 6T nylon and 6T nylon with a 6T nylon content of 10% by weight.

From Table-1, sample NOI, which is the composite film of the present invention,
It can be seen that No. 2 has excellent low-temperature shrinkability with a shrinkage rate of 30% or more at 75° C. and excellent appearance. On the other hand, 6T
NO3 with too high a mixing ratio of 6T/6I nylon has poor stretchability, and conversely, NO3 with too low a 6T/6I nylon ratio
It can be seen that O4 has poor low-temperature shrinkability. Furthermore, it can be seen that NO5°6.7, which uses different types of polyamide resins, are all inferior in low-temperature shrinkability and appearance.

(Effects of the Invention) As explained above, the heat-shrinkable composite stretched film of the present invention has excellent shrinkability at low temperatures and a good appearance, making it highly applicable in the field of vacuum packaging of raw meat. It is.

Patent applicant: Mitsubishi Plastics Co., Ltd. Agent: Patent attorney Hisami Konfuji Continuation of younger brother page 1

Claims (1)

[Claims] A composite stretched film in which the outer layer and the inner layer are polyolefin layers, and a polyamide resin layer is provided between both layers, wherein the polyamide resin layer is made of a copolymerized polyamide resin (6/66) of nylon 6 and nylon 66. (6/66 nylon): (6T/6I nylon) = 70
~95% by weight: A heat-shrinkable composite stretched film characterized in that the content is in the range of 30 to 5% by weight.