JPH0717043B2 - Food packaging bag - Google Patents

Description

TECHNICAL FIELD The present invention relates to a food packaging bag.

[Conventional technology]

BACKGROUND ART A bag made of a film such as a polyethylene film or an unstretched polypropylene film is known as a packaging bag for packaging heavy items such as root vegetables and fruits. However, these films do not have good anti-fogging property and transparency and cannot be said to be suitable for a film for food packaging.
Therefore, instead of the polyethylene film or the like, a food packaging bag using a stretched polyethylene film having good antifogging property and transparency has been proposed.

[Problems to be Solved by the Invention]

A food packaging bag using the above-mentioned conventional film made of a stretched polyethylene film has a weak fusing seal strength, so that the fusing seal portion is likely to tear when a heavy object is accommodated.

It is an object of the present invention to provide a food packaging bag having a good fusion seal strength and antifogging property.

[Means for Solving the Problems]

The food packaging bag of the present invention has the following requirements A) to E).

A) Polypropylene resin layer, ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-propylene-butene terpolymer, ethylene-vinyl acetate copolymer, ethylene- An olefin copolymer resin layer made of at least one copolymer selected from a methacrylic acid copolymer and an ethylene-methyl methacrylate copolymer is laminated, and a biaxially stretched film is formed.

B) An antifogging agent is added to the polypropylene resin layer.

C) The birefringence of the film is set to 8 × 10 ⁻³ to 15 × 10 ⁻³ .

D) The thickness of the olefin copolymer resin layer is 0.2 to 0.8 μm
Is set to.

E) Equipped with a bottom folding part and both sides of the fusing seal part.

*** The film used for the food packaging bag of the present invention is a biaxially stretched film in which an olefin copolymer resin layer is laminated on one or both sides of a polypropylene resin layer.

The polypropylene resin used in the present invention includes a polypropylene resin, an ethylene-propylene copolymer,
Examples thereof include copolymer resins of propylene and other olefins such as butene-propylene copolymer and ethylene-butene-propylene copolymer. As the polypropylene-based copolymer resin, either a random copolymer or a block copolymer may be used.
Further, the polypropylene resins may be used alone or in combination of two or more kinds.
Furthermore, homopolymers or copolymers of olefins other than propylene may be mixed. The polypropylene resin used in the present invention preferably has a polypropylene content of 80% by weight or more. The polypropylene resin has a melt flow rate (MFR) of 1
Those of -5 are preferred. Here, MFR is a value measured according to the E method of JIS-K6760.

An antifog agent is added to the polypropylene resin. Examples of the antifogging agent include N-acyl amino acids or salts thereof, anionic surfactants such as alkyl ether carboxylates, cationic surfactants such as aliphatic amine salts and aliphatic quaternary ammonium salts, carboxybetaine and imidazo. Examples thereof include amphoteric surfactants such as linium betaine and aminocarboxylic acid salts, nonionic surfactants, and fluorochemical surfactants. Among these, as the nonionic surfactant, ether type such as polyoxyethylene alkyl ether and polyoxyethylene secondary alcohol ether, ether ester type such as polyoxyethylene glycerin fatty acid ester and polyoxyethylene sorbitan fatty acid ester, polyethylene glycol Ester types such as fatty acid ester, fatty acid monoglyceride and sorbitan fatty acid ester, and other fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide and the like can be used. The above antifogging agents may be used alone or 2
You may mix and use 1 or more types. The antifogging agent is particularly preferably an amphoteric surfactant, a nonionic surfactant, or a mixture of the same kind or different kinds thereof.

The addition amount of the antifogging agent is preferably 0.1 to 1.5 parts by weight, more preferably 0.5 to 1.0 part by weight, based on 100 parts by weight of the polypropylene resin. If the amount added is less than 0.5 parts by weight, good antifogging property cannot be obtained. On the other hand, if the amount exceeds 1.5 parts by weight, the film becomes sticky, and the blocking resistance and fusing seal strength of the film deteriorate.

The polypropylene resin includes a heat stabilizer, a nucleating agent,
A third component such as an antioxidant, a lubricant, an ultraviolet absorber or the like may be added within a range that does not impair the object of the present invention.

Examples of the olefin copolymer resin used in the present invention include an olefin copolymer resin and a mixture of the olefin copolymer resin and an olefin homopolymer resin. Examples of the olefin copolymer resin include ethylene-propylene copolymer, ethylene-butene copolymer, propylene-butene copolymer, ethylene-propylene-butene terpolymer, ethylene-vinyl acetate copolymer, ethylene. At least one copolymer selected from a methacrylic acid copolymer, an ethylene-methyl methacrylate copolymer, and the like can be given. Further, as the olefin homopolymer resin mixed in these copolymers, polyethylene,
Examples thereof include polypropylene and polybutene. The pre-olefin copolymer and the olefin homopolymer may be used alone or as a mixture of two or more kinds.

Particularly preferred as the olefin copolymer resin,
Mixture of ethylene-propylene copolymer and propylene-butene copolymer and ethylene-propylene-butene 3
It is a former copolymer. Particularly, those having an ethylene content of 1 to 15% by weight and a butene content of 2 to 25% by weight are preferable. The MFR of the olefin copolymer resin is preferably 6-15, more preferably 7-10. Here, the value of MFR is
It is a value measured according to the E method of JIS-K6760, like the polypropylene resin. When the MFR value is within the above range, the olefin copolymer resin and the polypropylene resin layer can be laminated more uniformly.

The above-mentioned antifogging agent may be added to the olefin copolymer resin. Further, a heat stabilizer, a nucleating agent, an antioxidant, a lubricant, an ultraviolet absorber and the like may be added within a range not impairing the object of the present invention.

Films used in food packaging bag of the present invention, a birefringence ([Delta] n) is ^{8 × 1010 -3 ~15 × 10 -3} , preferably 9 × 10
It is set to ^{-3 ~12} × 10 ^-3. When Δn is less than 8 × 10 ⁻³ , the film has a large unevenness in thickness and a weak stiffness. On the other hand, when it exceeds 15 × 10 ^-3 , the fusion-cut seal strength is low and the film has poor antifogging properties. Further, when the value of Δn is within the above range, it is easy to uniformly set the thickness of the olefin copolymer resin layer within the range described below. Incidentally, the birefringence referred to in the present invention, the longitudinal refractive index (ny) and width direction refractive index (nx) of the film is measured by an Atsube refractometer using methyl salicylate as a film mount solution, and It is obtained by the formula.

Δn = nx-ny Next, an example of a method for producing a film used for the food packaging bag of the present invention will be described. Here, the manufacturing method by the co-extrusion method will be described.

Prepare polypropylene resin and olefin copolymer resin respectively, and supply both resins to separate extruders. Then, both resins are melt-extruded at 230 to 300 ° C., wound on a cooling drum at 30 to 80 ° C., and cooled to form a laminated resin film. Then, the obtained laminated resin film
Stretched in the longitudinal direction (film forming direction) 3 to 7 times at 100 to 145 ° C,
It is a uniaxially stretched film. Further, the uniaxially stretched film is stretched 9 to 13 times in the transverse direction at 150 to 185 ° C. to produce a biaxially stretched film-forming film. The draw ratio is
The area magnification is preferably set to 35 to 60 times. The obtained bag-making film is heat-treated at a constant temperature if desired, and then both surfaces are subjected to corona discharge treatment.

The method of laminating the polypropylene resin and the olefin copolymer resin layer is not limited to the coextrusion method, and a method of uniaxially or biaxially stretching the polypropylene resin film and then extrusion laminating the olefin copolymer resin is adopted. May be done. Further, the stretching treatment of the laminated film is not limited to sequential stretching, and may be performed by simultaneous stretching.

The thickness of the film produced by the production method described above is preferably about 10 to 25 μm. Among them, the thickness of the olefin copolymer resin layer is set to 0.2 to 0.8 μm regardless of the thickness of the polypropylene resin layer. When the thickness of the olefin copolymer resin layer is less than 0.2 μm,
Good fusing seal strength and anti-fogging property cannot be obtained. On the contrary, 0.
If it exceeds 8 μm, the fusing seal strength is inferior. The thickness of the entire film and the thickness of the olefin copolymer resin layer are the values measured by observing the film with an electron microscope after dyeing the film with OsO ₄ and RuO ₄ , cutting it into ultrathin pieces.

The film used for the food packaging bag of the present invention is wound around a core material and provided in a roll form.

The food packaging bag of the present invention includes a bottom-side folded portion and both sides of the fusible seal portion. An example of the manufacturing method
A description will be given with reference to FIGS. 1A, 1B and 2.

First, as shown in FIG.
Fold it in half to obtain the state shown in Figure 1B. In this case, the folded portion 2 of the film 1 is sufficiently pressed.

Next, the folded film 1 is fused and cut at regular intervals in the longitudinal direction, as indicated by the alternate long and short dash line in FIG. 1B. The fusing can be performed using, for example, a seal bar.

The melted film 1 becomes a food packaging bag 3 as shown in FIG. In this bag 3, both ends of the original film 1 in the longitudinal direction (direction of arrow in FIG. 2) are fusion-sealed,
The folding part 2 is the bottom part. The bag 3 is used for packaging heavy items such as root vegetables such as potatoes and onions and fruits.

〔The invention's effect〕

The food packaging bag of the present invention is made of the laminated film as described above, and is provided with a bottom-side folded portion and both sides of a fusion-cut seal portion. Therefore, according to the present invention, it is possible to realize a packaging bag in which the fusing sealing property and the antifogging property are good, the side portion has high strength, and which is suitable for containing a heavy food containing moisture.

〔Example〕

Examples 1 and 2 As polypropylene resin, glycerin ester 0.4
% And diethanolamide 0.2% by weight, M
FR2.0 polypropylene resin was prepared. Further, as the olefin copolymer resin, a mixture of 60% by weight of an ethylene-propylene copolymer containing 4% by weight of ethylene and 40% by weight of a butene-propylene copolymer containing 20% by weight of butene (MFR = 9.0 ) Was prepared. Then, by supplying both resins to separate extruders and coextruding at 280 ° C,
An unstretched film in which both resins were laminated was manufactured.

The obtained unstretched film was stretched 4.3 times in the longitudinal direction at 136 ° C. Further, after cooling the film, it was preheated and heated to be stretched in the transverse direction 10 times at 170 ° C. to produce a biaxially stretched bag-making film. Both sides of the obtained biaxially stretched bag-making film were subjected to corona discharge treatment.

Example 3 A polypropylene resin of MFR2.5 containing 0.2% by weight of lauric acid diethanolamide and 0.4% by weight of a carboxy double-sided surfactant was prepared as a polypropylene resin. Also,
As an olefin copolymer resin, ethylene 1.5% by weight
An ethylene-propylene-butene copolymer of MFR 8.2 containing 14% by weight of butene was prepared. Then, both resins were supplied to separate extruders to produce a biaxially stretched bag-making film under the same conditions as in Example 1. However, the stretching condition in the longitudinal direction of the unstretched film was changed to 4.8 times at 130 ° C.

Comparative Example 1 Using the polypropylene resin used in Example 1, a single-layer bag-making film was produced. The stretching treatment conditions, etc.
The settings were the same as in the example.

Comparative Example 2 Using the same resin used in Example 3, a bag-making film provided with an olefin copolymer resin layer thicker than that in Example 3 was produced under the same conditions as in Example 3.

Comparative Examples 3 and 4 Using the same resin as used in Example 1, a bag-making film was produced under the same conditions as in Example 1. However, the stretching ratio in the longitudinal direction was set to 5 times.

Film characteristics such as birefringence and fusing seal strength were examined for each of the examples and comparative examples. The results are shown in Table 1. The evaluation method and criteria of the film characteristics are as follows.

Fusing seal strength 60 pieces / using a bag-making machine equipped with a fusing seal bar of 310 ℃
The bag was made in minutes, the fusing seal strength (kg / cm) of the seal portion of each obtained bag was measured, and the values were averaged. The higher the value, the better the fusing sealing property.

Surface resistivity Measured based on the surface resistivity of the film. Surface resistivity is measured according to JIS-C2330 volume resistivity test,
The electric resistance per unit area of the film. The surface resistivity (R _S ) is determined by placing the sample film between the main electrode and the counter electrode (both are circular electrodes), applying the voltage (V) between both electrodes, and the current flowing on the film surface. It was measured by determining the ratio with (I _S ) (R _S = V / I _S ). The surface resistivity was calculated by the following formula based on the obtained surface specific resistance (R _S ).

Surface resistivity = π (D + d) R _S / (D-d) In the formula, d represents the outer diameter (cm) of the main electrode, and D represents the inner diameter (cm) of the counter electrode. The surface resistivity was measured using an ultra-insulation meter (R-503 manufactured by Kawaguchi Electric Co., Ltd.) and a room temperature measurement box (P-601).

200 cc of water at 20 ° C. was placed in a 200 cc anti-fogging beaker, the beaker was sealed with a film to be tested and placed in a refrigerator at 5 ° C., and after 60 minutes, the surface condition of the film was examined.

○: Water droplets attached to the film spread well, and the entire surface of the film leaks uniformly.

X: Fine water droplets are attached to the entire film.

[Brief description of drawings]

1A and 1B are plan views showing the manufacturing process of the food packaging bag of the present invention, and FIG. 2 is a plan view of the food packaging bag manufactured in the above process. 1 ... Film. 3 ... Food packaging bag.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-2-60745 (JP, A) JP-A-1-103442 (JP, A) JP-A-63-31755 (JP, A) JP-A-53- 128685 (JP, A)

Claims (1)

[Claims] 1. A polypropylene resin layer to which an antifogging agent is added, an ethylene-propylene copolymer, an ethylene-butene copolymer, a propylene-butene copolymer, an ethylene-
A propylene-butene terpolymer, an ethylene-vinyl acetate copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylate copolymer. Is 0.2 to 0.8μ
The olefin copolymer resin layer set to m is laminated, biaxially stretched, and has a birefringence of 8 × 10 ⁻³ to 15
A bag for food packaging, which is made of a film set to × 10 ^-3 and has a bottom-side folded portion and both sides of a fusion-cut seal portion.