JPS60206859A - Heat-sealable food packaging material - Google Patents

Abstract

PURPOSE:To obtain a heat-sealable packaging material which does not emit the odor of plastics when foods are sealed therewith, by providing a hot-melt adhesive layer formed by mixing at least two kinds of satd. polyester resins having specified glass transition temp. CONSTITUTION:A heat-sealable food packaging material having a hot-melt adhesive layer formed by mixing at least two kinds of satd. polyester resins in which the difference in glass transition temp. therebetween is at least 30 deg.C. Preferred substrate materials are metallic foils such as aluminum foil and heat-resistant plastic films such as polyethylene terephthalate film, and a laminate thereof or a laminate thereof with paper is used. It is desirable that one of two satd. polyester resins to be mixed with each other has a glass transition temp. of 30 deg.C or above and the other has a glass transition temp. of 0 deg.C or below. The thickness of the hot-melt adhesive layer is 5-100mu, pref. 10-30mu.

Description

Detailed Description of the Invention The present invention relates to a heat-sealable packaging material that does not produce a plastic odor when food is hermetically packaged. In a heat-sealable packaging material having laminated layers, a mixture of saturated polyester resins having a difference in glass transition temperature of 30° C. or more is used as the thermal adhesive.

Generally, when liquid or solid foods are hermetically packaged, the contents are filled and housed in a packaging container or packaging bag, and then the opening is sealed by heat sealing. In this case, the adhesive layer is the innermost layer of the eight containers and is in constant contact with the food, so if a plastic layer forms from the hot adhesive, it will transfer to the food during distribution and storage, resulting in the flavor of the food. There was a problem in writing.

Conventionally, thermoplastic synthetic resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer are mainly used as thermal adhesives in heat-sealable containers for food, especially liquid beverages such as alcohol, juice, coffee, and milk. However, these have the disadvantage that they often have an unpleasant taste when drinking because they have a very slight residual plastic odor.

As a result of research to solve the above problems, the present inventor found that saturated polyester resin has extremely low odor compared to other thermoplastic synthetic resins, and in particular, the glass transition temperature of this saturated polyester resin differs by more than 30'C. The present invention was completed based on the discovery that when at least two types are mixed, both the film formability and the heat sealability as a Wj film are improved.

That is, the present invention uses a heat-resistant plastic film, metal foil 9 paper, or a laminate thereof as a base material, and 3
This is a heat-sealable food packaging material made by laminating and adhering mixture films of at least two types of saturated polyester resins having a glass transition temperature difference of 0°C or more with or without an appropriate adhesive.

Suitable base materials in the present invention include metal foils such as aluminum foil, heat-resistant plastic films such as polyethylene terephthalate, stretched nylon, stretched or unstretched polycarbonate, polystyrene, and polyvinyl chloride; Laminated materials with paper are used.

Saturated polyester resins used as thermal adhesives include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, maleic acid derivatives, succinic acid, adipic acid,
Saturated polybasic acids such as sebacic acid, ethylene glycol, diethylene glycol, glycerin, trimethylolpropane, 1-2 propylene glycol, 1-3 butanediol.

Dipropylene glycol, 1-4 butanediol.

It is obtained by ester bonding with a polyhydric alcohol such as 1-6 hequinane di-A-l, pentaerythritol, sorbitol, neopentyl glycol, and 1-4 cyclohexane dimetatool.

In general, it is difficult for these saturated polyester resins to maintain and achieve a good balance between film-forming properties and heat-sealing properties using a single component, especially those with a glass transition temperature of 70°C or higher. Heat-sealability is extremely low, and those with a glass transition temperature of 0° C. or lower have poor film-forming properties such as blocking and curling during film formation, and cannot be used as a thermal adhesive film.

However, a mixture of as uniformly as possible a saturated polyester resin with a relatively high glass transition temperature and poor heat sealability and a saturated polyester resin with a relatively low glass transition temperature a and poor film forming properties is difficult to form into a film. It has a good balance between film formability and heat sealability.

The practical condition is that one of the at least two types of saturated polyester resins to be mixed has a glass transition temperature of 30°C.
As mentioned above, although it is desirable that the other temperature is 0° C. or lower, it is not necessarily limited to this. However, the difference in glass transition temperature between the two is at least 30°C, preferably 60°C or more.

In addition, the thermal adhesive layer formed by this is heated to 200°C.
The following heat seal [1] provides an adhesive strength of 2K (1/151 width or more) and provides sufficient sealing strength.

The appropriate thickness of the thermal adhesive layer is 5 to 100 μm, and 10 to 30 μm.
μ is the optimum value; if it is less than 5μ, the impurity sealing property will deteriorate and the sealing strength will become unstable, and if it is more than 100μ, there will be no particular improvement in sclerosis, which is economically disadvantageous.

The mixing ratio of saturated polyester resin is 1=9 to 9 by weight.
:1 is desirable, and if it is outside this range, one of the properties will be stronger, and either the film formability or the heat sealability will be poor, which is not preferable.

Examples will be shown below, but the present invention is not limited thereto.

Example 1 Saturated polyester resin 211 below! A film with a thickness of 30 mm was created by blending the following at a weight ratio of 1:1 and using the inflation method.
A packaging material was obtained by dry laminating the film onto a 40 μm thick aluminum foil using a urethane adhesive.

Saturated polyester resin (1) Acid component; Phthalic acid alcohol component: Ethylene glycol and 1-4 cyclohexanediol To (glass transition temperature); -20°C Saturated polyester resin (2) Acid component: Terephthalic acid and isophthalic acid alcohol component; Glycol and 1-4 cyc 0 hexane dimetatool T < 1: 81° C. Two sheets of this packaging material were stacked one on top of the other with the saturated polyester resin surfaces in contact and sealed on three sides, and distilled water was filled therein and sealed by heat sealing.

Heat sealing conditions: miso℃, pressure 2. Ok(]/cn?, time 1
This package was left in an atmosphere of 40° C. and 90% relative humidity for 14 days and then tested.

When a 90° peel 1111 test was conducted at a tensile rate of 00 n+m/min, the peel strength was 3. It was 15mm wide.

Next, we conducted a taste test of the stored distilled water and found that all (
I didn't notice any plastic smell or strange taste.

Note that when the saturated polyester resin (1) was used alone to form a film by inflation, blocking occurred and film formation was impossible.

Furthermore, when the saturated polyester resin (2) was formed into a film by inflation alone, sufficient adhesive strength could not be obtained even when heat-sealed at 200° C. or higher.

Example 2 A saturated polyester resin of 1919°C and a saturated polyester resin of Tg 82°C were blended at a weight ratio of 1:2, and a film with a thickness of 50μ was formed by the inflation method.
A packaging material was obtained by dry laminating a μ-thick stretched nylon film with a urethane adhesive.

When the same test as in Example 1 was conducted, the peel strength was 2.6 and 97.
The taste test results were the same as in the previous example.

Claims (1)

[Claims] 1. A heat-sealable food packaging material comprising a thermal adhesive layer containing a mixture of at least two types of saturated polyester resins having glass transition temperatures of 30° C. or more.