JPH09216302A - Packaging material for food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep flavor or the like of food by removing vapor, water content, oil content emitted from the food by absorption by a method wherein water vapor permeability of a laminate of a nonporous thermoplastic resin film and nonwoven fabric is made at least a specific value. SOLUTION: This packaging material for food is obtained wherein for example, polyester as thermoplastic resin is made into a film by a melt extrusion method, and the non-porous polyester film is laminated on nonwoven fabric by thermal adhesion, and they re monoaxially stretched thereafter. Further, its water vapor permeability is at least 1,000g/(m<2> .day). When the nonwoven fabric is laminated on a food side, stickiness of the food is prevented by absorbing water content, and oil content which are emitted from the food, and deterioration of flavor is prevented. Furthermore, by forming a webbed structure wherein a filmy product is formed at a confounding point on the food surface side of the nonwoven fabric under a state wherein single fibers are fusion welded to each other, the water content and oil content which are once absorbed are prevented from flowing backward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a food packaging material that absorbs and removes steam, moisture and oil released from food and retains the flavor and the like of the food, and is particularly suitable for microwave cooking. Regarding

[0002]

2. Description of the Related Art Fast foods such as hamburgers, hot dogs and fries are eaten in a warm state at the store, or depending on the store, at the time of purchase or after taking home, reheated and cooked in a microwave oven. There is. Since these foods contain a large amount of liquid seasonings such as water and sauce, a liquid-impermeable packaging material in which polyethylene or the like is laminated on paper has been conventionally used. In addition, when cooking in a microwave oven, the generated steam and the moisture formed by condensation of the steam deteriorate the flavor of foods.Therefore, air-permeable packaging materials such as porous films and non-woven fabrics that absorb liquid are impermeable to liquids. Packaging materials laminated with films have been used.

[0003]

The liquid impermeable sheet alone deteriorates the flavor and the like of food due to water vapor and dew condensation water generated during microwave oven cooking, and the porous film contains moisture and oil released from food. May leak out of the packaging. With a packaging material having a liquid absorbing layer such as a non-woven fabric, it is not possible to remove even the water vapor generated from the food, which gives the food a moist feel.

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above problems, and as a result, have found that the above problems can be solved by a moisture permeable laminate of a nonporous thermoplastic resin film and a nonwoven fabric. Invented. That is, the present invention
A laminate of a non-porous thermoplastic resin film and a non-woven fabric,
A food packaging material having a moisture permeability of 1000 g / (m ² · day) or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Since the food packaging material of the present invention is composed of a non-porous thermoplastic resin film, water and oil released from the food will not leak out of the packaging material, and Does not stain clothes. In addition, by increasing the moisture permeability of the packaging material, water vapor generated during microwave oven cooking can escape to the outside of the packaging, and the flavor of the food can be maintained.
Therefore, the water vapor transmission rate is 1000 g / (m ² · d
ay) or more is necessary, preferably 3000 g / (m
² · day) or more. In addition, in order to prevent unnecessary drying of food after cooking, the water vapor permeability is especially 1000-2.
It is preferably in the range of 0000 g / (m ² · day), more preferably 3000 to 15000 g / (m ² · d).
The range of ay) is more preferable. In addition, the water vapor transmission rate in this invention is the water vapor transmission rate converted into per day (24 hours) by multiplying the water vapor transmission rate by the A-1 method of JIS-L-1099 by 24 times.

The thermoplastic resin of the non-porous thermoplastic resin film includes, for example, polyester, polyamide, polyolefin, polyurethane and the like, and polyester is particularly preferable. Preferred polyesters include compositions containing polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as main components. Examples of more preferable polyesters include compositions containing polyethylene terephthalate and polyethylene naphthalate as main components, and particularly preferable are polyester compositions containing polyethylene terephthalate as main components. Such a polyethylene terephthalate-based polyester composition has an ethylene terephthalate repeating unit content of 70% by weight or more and less than 98% by weight and a polyalkylene oxide moiety of less than 30% by weight and 2% by weight or more of the polyester molecule repeating units. Preferably there is. Further, the molecular weight of the polyalkylene oxide moiety is preferably 500 or more, and further, the polyalkylene oxide moiety is polyethylene oxide and / or
Alternatively, it is preferably composed of polytetramethylene oxide. Such polyethylene oxide moiety can be obtained by copolymerizing polyoxyethylene glycol or its ester-forming derivative,
Particularly, polyoxyethylene glycol can be preferably used. The polytetramethylene oxide portion can be obtained by copolymerizing polyoxytetramethylene glycol or an ester-forming derivative thereof, and polyoxytetramethylene glycol can be particularly preferably used. Further, other components can be further copolymerized within a range satisfying the above conditions. Such a polyester composition mainly composed of polyethylene terephthalate can be produced by a conventionally known method.
For example, a method in which a dicarboxylic acid component and a diol component are directly esterified, and then the reaction product is heated under reduced pressure to distill the diol component to cause polycondensation, or an ester of the dicarboxylic acid component. There is a method in which the forming derivative and the diol component are esterified by a transesterification reaction and then polycondensed in the same manner as above. At this time, the necessary copolymerization component is added at a necessary time.

The water vapor permeability of the present invention is 1000 g / (m ² · d)
ay) In order to obtain a food packaging material of the above, the polyester composition described above, for example, having an average molecular weight of 1000
A polyethylene terephthalate composition containing 10% by weight each of polyoxyethylene glycol and polyoxytetramethylene glycol is melt-extruded, laminated with a non-woven fabric, and stretched to make a film portion of the composition 10 μm or less. Can be easily obtained.

In order to perform printing on the food packaging material of the present invention, a printing ink receiving layer may be provided on the outer surface of the non-porous thermoplastic resin film.

The nonwoven fabric in the food packaging material of the present invention is
When laminated on the food side, it absorbs water and oil released from the food to prevent stickiness of the food and deterioration of flavor and the like. Furthermore, by forming a water-scraping structure on the food surface side of the nonwoven fabric, it is possible to prevent the once absorbed water and oil from returning to the food side. The water-scrapy structure of the nonwoven fabric surface in the present invention is a structure in which a film-like material is formed at the entanglement points where the single fibers of the nonwoven fabric are fused together. The water-like structure is formed between at least two monofilaments at the entanglement point, and the thickness of the film is smaller than the diameter of the monofilaments. The non-woven fabric in the present invention, from the viewpoint of heat sealability as a packaging material and the formation of a water-like structure, it is preferable that the single fibers are composed of synthetic fibers, preferably a non-woven fabric composed of fibers such as polyolefin, polyamide, polyester. Can be mentioned. A more preferable non-woven fabric is a non-woven fabric composed of polyester long fibers mainly composed of polyethylene terephthalate and polyethylene naphthalate, and a particularly preferable non-woven fabric composed of polyester long fibers composed mainly of polyethylene terephthalate. Examples of the polyester filaments mainly composed of polyethylene terephthalate include polyester filaments having an ethylene terephthalate repeating unit content of 70% by weight or more among the polyester molecular repeating units. Further, pulp fibers may be mixed in the non-woven fabric in order to increase the water absorption within a range that does not hinder the heat-sealing property or the formation of the water-scrapy structure.

The larger the basis weight of the nonwoven fabric, the greater the amount of water and oil absorbed, but the thicker the packaging material becomes. Therefore, the basis weight of the nonwoven fabric is 2 g / m ² to 2
A range of 00 g / m ² is preferred.

The above-mentioned non-woven fabrics can be manufactured by the conventionally known flash spinning method, melt blow method, spun bond method, spun lace method and the like. For example, in the melt blow method, when the molten polymer is discharged from the die, hot air is blown from a peripheral portion of the die to make the discharged polymer finer, and then sprayed onto a net conveyor arranged at an appropriate position. It is manufactured by collecting and forming a web. Since the web is sucked together with the hot air by the suction device provided on the net conveyor, it is collected before the fibers are completely solidified. That is, the fibers of the web are collected while being fused to each other.
By appropriately setting the collection distance between the base and the net conveyor, the degree of fusion of the fibers can be adjusted.
Further, by appropriately adjusting the polymer discharge amount, the hot air temperature, the hot air flow rate, the conveyor moving speed, etc., the fiber areal weight of the web and the single yarn fineness can be arbitrarily set. The fibers melt-spun are finely densified by hot air pressure, but are not stretched and solidified in a so-called non-oriented state. The thickness of the fibers is not uniform, and the web is formed in a state in which the thick fibers and the thin fibers are appropriately dispersed. Further, the polymer discharged from the die is rapidly cooled from the molten state to the room temperature atmosphere, and thus solidifies in a state close to an amorphous state.

As a method for forming a water-scrapy structure on a non-woven fabric, a method for drawing a non-woven fabric having an entanglement point where single fibers are fused to each other can be mentioned. When the number of entanglement points where the single fibers are fused to each other in the non-woven fabric is small or absent, the entanglement points where the single fibers are fused to each other can be formed by calendering the non-woven fabric with a heated calendar roll. The stretching method of the nonwoven fabric may be uniaxial stretching or biaxial stretching. The food packaging material of the present invention can be manufactured all at once by laminating the non-porous thermoplastic resin film and the nonwoven fabric and then stretching. That is, it can be produced by forming a thermoplastic resin into a film by a melt extrusion method, laminating the non-porous thermoplastic resin film and a non-woven fabric by thermal bonding, and then stretching the film at least uniaxially, preferably biaxially. . By heat-bonding the film and the non-woven fabric, no adhesive is required, and if stretched under appropriate conditions after lamination, a non-woven fabric is formed in the non-woven fabric, and at the same time the non-porous thermoplastic resin film can be stretched. The adhesive force between the non-porous thermoplastic resin film and the non-woven fabric is enhanced. Furthermore, if the film portion and the non-woven fabric portion of the food packaging material of the present invention are composed of a polyester composition mainly composed of polyethylene terephthalate, it becomes possible to collect and recycle without the need for separation, and the food packaging material can be made inexpensive. It can be manufactured and is less likely to generate scraps, which is also preferable for environmental problems.

As the melt extrusion method in the present invention, a conventionally known method can be used in which a thermoplastic resin heated and melted by a uniaxial or biaxial extruder is discharged from a slit die to a casting drum to form a film. The thickness of the film can be adjusted by adjusting the discharge rate of the molten thermoplastic resin, the slit size of the die, and the rotation speed of the casting drum. The heat adhesion between the film and the nonwoven fabric can be achieved by stacking the film and the nonwoven fabric while heating. For example, thermal bonding can be performed by sending a film and a non-woven fabric between heated rolls and applying pressure. The biaxial stretching method may be either a sequential biaxial stretching method or a simultaneous biaxial stretching method. In the sequential biaxial stretching method, generally, the stretching in the machine direction is carried out and then the stretching in the transverse direction is carried out, but the order may be reversed. Further, in carrying out biaxial stretching, the stretching ratio is not particularly limited,
Usually, about 2 to 5 times is appropriate. After biaxial stretching, it may be stretched again in the machine direction and / or the transverse direction, if necessary. Furthermore, it is preferable to heat-treat the biaxially stretched laminate, and it is preferable to perform the treatment at a temperature not higher than the melting point of the fibers constituting the nonwoven fabric for 0.5 seconds to 60 seconds.

[0014]

[Method of measuring characteristics] Each characteristic in Examples and Comparative Examples was measured by the following method.

(1) Moisture Permeability JIS-L-109, which is a moisture permeability test method for textiles.
According to the A-1 method (calcium chloride method) of 9, temperature 40
The measurement was carried out at a temperature of 90 ° C. and a relative humidity of 90%, and the measured value was multiplied by 24 to determine the water vapor transmission rate per day (24 hours).

(2) Observation of water-scratched structure and measurement of film thickness After depositing platinum on a sample, the food surface side of the nonwoven fabric was observed by a scanning electron microscope. The film thickness was measured by observing the cross section of the sample,
Photographs were taken at 10 locations, the film thickness at 10 locations was measured for each cross-sectional photograph, and the film thickness at 100 locations in total was determined as the average.

(3) Intrinsic viscosity of polymer o-chlorophenol was used as a solvent. The polymer and solvent were dissolved by stirring at 160 ° C. for 15 minutes. The measurement is 2
Performed at 5 ° C.

(4) Unit weight of non-woven fabric The non-woven fabric was cut into 10 cm squares and the weight thereof was measured by a balance. The measured value was converted into the number of grams per 1 m ² . The basis weight of the non-woven fabric portion of the packaging material was measured in the same manner by removing the film portion from the packaging material and taking out only the non-woven fabric portion.

(5) Flavor of Food After packaging the food, it was cooked in a microwave oven, and the flavor of the food was judged according to the following criteria.

Good: Almost no deterioration of the flavor of the food and passed. Normal: Little deterioration of the flavor of the food and passed. Poor: The flavor of the food was deteriorated and failed.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples.

Example 1 (Polymerization of Polymer) 80.8 of dimethyl terephthalate was used.
Parts by weight, 49 parts by weight of ethylene glycol, 10 parts of polyoxyethylene glycol having an average molecular weight of 3000
Parts by weight, 10 parts by weight of polyoxytetramethylene glycol having an average molecular weight of 1000, magnesium acetate 1
0.05 parts by weight of sodium hydrate and 0.0 part of lithium acetate dihydrate
01 parts by weight and 0.03 parts by weight of antimony trioxide were charged into a reactor and melted at 150 ° C. The temperature of the reactor contents was raised from 150 ° C. to 240 ° C., methanol was distilled off, and an ester exchange reaction was carried out. After the transesterification reaction was completed, 0.03 part by weight of trimethylphosphoric acid was added, and the reaction product was transferred to the polymerization apparatus. While increasing the temperature of the contents of the polymerization apparatus from 240 ° C. to 290 ° C., the pressure inside the polymerization apparatus was reduced from atmospheric pressure to 70 Pa or less, and ethylene glycol was distilled off to carry out a polymerization reaction. After the reaction,
The reaction product was water-cooled, and a cutter was used to obtain polymer A in the form of chips. The intrinsic viscosity was 0.91.

101 parts by weight of dimethyl terephthalate,
61.3 parts by weight of ethylene glycol, 0.05 part by weight of magnesium acetate decahydrate, 0.001 part by weight of lithium acetate dihydrate, 0.03 part by weight of antimony trioxide were charged into a reactor at 150 ° C. Melted The temperature of the reactor contents was raised to 150 to 240 ° C., methanol was distilled off, and an ester exchange reaction was carried out. After the transesterification reaction was completed, 0.03 part by weight of trimethylphosphoric acid was added, and the reaction product was transferred to the polymerization apparatus. While raising the temperature of the contents of the polymerization apparatus to 240 to 290 ° C., the pressure inside the polymerization apparatus was reduced from atmospheric pressure to 70 Pa or less, and ethylene glycol was distilled off to carry out a polymerization reaction. After the reaction was completed, the reaction product was water-cooled, and a cutter was used to obtain a polymer B in the form of chips. The intrinsic viscosity was 0.60.

(Production of Nonwoven Fabric) Using a spinneret having a hole diameter of 0.25 mm and 1000 holes, the polymer B was melted at 290 ° C. and then discharged from the spinneret, and further finely fined by an air ejector and sprayed onto a net conveyor. Thus, a non-woven fabric C having a basis weight of 500 g / m ² was obtained.

(Production of packaging material for food) Polymer A was charged into a melt extrusion machine, melted at 280 ° C., and then discharged from a die onto a casting drum to form a film.
Subsequently, the film and the non-woven fabric C were superposed on each other and then continuously passed through a heating roll for thermal adhesive lamination. Then, the laminate is further guided to a stretching machine, and the laminate is longitudinally moved by a roll peripheral speed difference.
After being double-stretched, it was stretched 3.3 times in the transverse direction by a tenter system. The stretched laminate was further continuously introduced into a heat treatment apparatus and heat-treated at 200 ° C. In this way, the food packaging material D was obtained. The characteristics of the food packaging material D are shown in Tables 1, 2 and 3. Width 20c for food packaging material D
The sheet was cut into m pieces and a length of 40 cm, folded into two with the nonwoven fabric inside, and the remaining two sides were heat-sealed with one side as an opening. In this way, the food packaging material D has a width of 20 cm,
The bag was 20 cm in length.

(Microwave cooking of food) A hamburger was placed in a bag made of food packaging material D, and cooked in a microwave oven with an output of 500 W for 2 minutes. After cooking, there was no leakage of sauce from the bag, and the hamburger did not have any unpleasant dampness or deterioration in flavor, so there was no difference from the freshly prepared one. The results are shown in Table 3.

Comparative Example 1 A polyethylene terephthalate composition containing 0.2% by weight of synthetic calcium carbonate having an average particle size of 0.5 μm was polymerized by the same method as in Example 1 to obtain polymer E.
I got Food packaging material F was prepared in the same manner as in Example 1 except that polymer E was used as the film polymer.
I got Using the food packaging material F, the hamburger was cooked in the same manner as in Example 1. After cooking, the sauce did not leak from the bag, but the bread had lost its elasticity and was steamed with steam, causing the flavor to deteriorate. The results are shown in Tables 1, 2 and 3.

Comparative Example 2 Polyethylene 7 having 30 parts by weight of ground calcium carbonate having an average particle diameter of 2.0 μm and a density of 0.921 g / cm ^3.
0 parts by weight were mixed and kneaded with a twin-screw kneader. The kneaded chips were placed in an extruder and discharged from a die onto a casting drum to form a film. After that, the film was guided to a longitudinal stretching machine, stretched 3 times in the longitudinal direction, and then stretched 3 times in the transverse direction by a tenter system. Thus, a polyethylene film having holes was obtained. Next, a non-woven fabric having a basis weight of 50 g / m ² was produced by melt-blowing only the polyethylene resin, and laminated with the above-mentioned film. Thus, a food packaging material G was obtained. When the hamburger was cooked in the same manner as in Example 1, the sauce and the like leaked from the bag and the hands and the like were soiled. The results are shown in Tables 1, 2 and 3.

Examples 2 to 4 Food packaging materials were obtained in the same manner as in Example 1 except that the thickness of the film portion, the basis weight of the nonwoven fabric, the thermal adhesion, the stretching conditions, etc. were changed. Moreover, the hamburger was cooked in the same manner as in Example 1. The results are shown in Tables 1, 2 and 3.

[0030]

[Table 1]

[Table 2]

[Table 3]

[0031]

Industrial Applicability The food packaging material of the present invention absorbs and removes steam, water, and oil released from food, and retains the flavor and the like of food. Particularly suitable for microwave cooking.

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Claims (4)

[Claims] 1. A laminate of a non-porous thermoplastic resin film and a non-woven fabric, having a water vapor transmission rate of 1000 g / (m ² · day).
The packaging material for foods characterized by the above. 2. The food packaging material according to claim 1, wherein the non-woven fabric is laminated on the food side, and the non-woven fabric is provided with a water-scraping structure on the food surface side. 3. A thermoplastic resin is formed into a film by a melt extrusion method, the thermoplastic resin film and a non-woven fabric are laminated by thermal bonding, and then stretched in at least uniaxial direction. Item 4. A food packaging material according to item 2. 4. The packaging material for food according to any one of claims 1 to 3, wherein the non-porous thermoplastic resin film is a polyester film.